Professor Barry Evans

Professorial Research Fellow

Email:
Phone: Work: 01483 68 9131
Room no: 17 CII 02

Further information

Publications

Highlights

  • Kasparis C, Beaudonnet M, Gyftodimos E, Evans BG. (2010) 'Gradient projection decoding of LDPC codes and algorithmic variations'. IET COMMUNICATIONS, 4 (2), pp. 223-233.
  • Du HF, Evans BG, Chlamtac I. (2009) 'QoS-AWARE ADAPTATION FOR SATELLITE MULTIMEDIA BROADCASTING VIA HIERARCHICAL PACKET SCHEDULING'. IEEE WIREL COMMUN, 16 (3), pp. 60-68.

    Abstract

    With the unique broadcast nature and ubiquitous coverage of satellite networks, the synergy between satellite and terrestrial networks provides opportunities for delivering wideband services to a wide range of audiences over extensive geographical areas. This article concerns the optimization techniques pertinent to packet scheduling to facilitate multimedia content delivery over the satellite with a return channel via a terrestrial network. We propose a novel hierarchical packet scheduling scheme that allocates the resources at different parts of the network in response to network dynamics and link variations while under the system power/resource constraints. Simulations prove that the HPS scheme can effectively improve the end-to-end performance and resource utilization with desirable scalability and fairness features.

  • Awoseyila AB, Kasparis C, Evans BG. (2009) 'Robust Time-domain Timing and Frequency Synchronization for OFDM Systems'. IEEE T CONSUM ELECTR, 55 (2), pp. 391-399.

    Abstract

    A robust and efficient technique for frame/symbol timing and carrier frequency synchronization in OFDM systems is presented. It uses a preamble consisting of only one training symbol with two identical parts to achieve reliable timing and frequency accuracy in the time-domain, over a wide-frequency estimation range which can be up to half of the signal sampling frequency. Also, it has a loti, complexity which is adaptive to the degree of channel distortion. Computer simulations in the Rayleigh fading ISI channel show that the proposed method achieves superior performance to existing techniques in terms of timing and frequency accuracy. Also, its operation in the time-domain helps to achieve faster synchronization convergence(1).

  • Fan L, Du H, Mudugamuwa U, Evans BG. (2008) 'A Cross-Layer Delay Differentiation Packet Scheduling Scheme for Multimedia Content Delivery in 3G Satellite Multimedia Systems'. IEEE TRANSACTIONS ON BROADCASTING, 54 (4), pp. 806-815.

Journal articles

  • Butash T, Evans B. (2016) 'IJSCN special issue on Ka band and high throughput satellites'. INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, 34 (4), pp. 459-460.
  • Aliu OG, Mehta M, Imran MA, Karandikar A, Evans B. (2015) 'A new cellular-automata-based fractional frequency reuse scheme'. IEEE Transactions on Vehicular Technology, 64 (4), pp. 1535-1547.

    Abstract

    © 1967-2012 IEEE.A fundamental challenge in orthogonal-frequency-division-multiple-access (OFDMA)-based cellular networks is intercell interference coordination, and to meet this challenge, various solutions using fractional frequency reuse (FFR) have been proposed in the literature. However, most of these schemes are either static in nature, dynamic on a large time scale, or require frequent reconfiguration for event-driven changes in the environment. The significant operational cost involved can be minimized with the added functionality that self-organizing networks bring. In this paper, we propose a solution based on the center of gravity of users in each sector. This enables us to have a distributed and adaptive solution for interference coordination. We further enhance our adaptive distributed FFR scheme by employing cellular automata as a step toward achieving an emergent self-organized solution. Our proposed scheme achieves a close performance with strict FFR and better performance than SFR in terms of the edge user's sum rate.

  • Maleki S, Chatzinotas S, Evans B, Liolis K, Grotz J, Vanelli-Coralli A, Chuberre N. (2015) 'Cognitive spectrum utilization in Ka band multibeam satellite communications'. IEEE Communications Magazine, 53 (3), pp. 24-29.

    Abstract

    © 2015 IEEE.Multibeam satellite networks in Ka band have been designed to accommodate the increasing traffic demands expected in the future. However, these systems are spectrum limited due to the current spectrum allocation policies. This paper investigates the potential of applying cognitive radio techniques in satellite communications (SatCom) in order to increase the spectrum opportunities for future generations of satellite networks without interfering with the operation of incumbent services. These extra spectrum opportunities can potentially amount to 2.4 GHz of bandwidth in the downlink and 2 GHz of bandwidth in the uplink for high density fixed satellite services (HDFSS).

  • Liu X, Evans BG, Moessner K. (2015) 'Energy-efficient sensor scheduling algorithm in cognitive radio networks employing heterogeneous sensors'. IEEE Transactions on Vehicular Technology, 64 (3), pp. 1243-1249.

    Abstract

    © 2013 IEEE.We consider, in this paper, the maximization of throughput in a dense network of collaborative cognitive radio (CR) sensors with limited energy supply. In our case, the sensors are mixed varieties (heterogeneous) and are battery powered. We propose an ant colony-based energy-efficient sensor scheduling algorithm (ACO-ESSP) to optimally schedule the activities of the sensors to provide the required sensing performance and increase the overall secondary system throughput. The proposed algorithm is an improved version of the conventional ant colony optimization (ACO) algorithm, specifically tailored to the formulated sensor scheduling problem. We also use a more realistic sensor energy consumption model and consider CR networks employing heterogeneous sensors (CRNHSs). Simulations demonstrate that our approach improves the system throughput efficiently and effectively compared with other algorithms.

  • Mathiopoulos PT, Candreva EA, Awoseyila AB, Dalakas V, Tarchi D, Evans BG, Vanelli-Coralli A, Corazza GE. (2015) 'Performance improvement techniques for the DVB-RCS2 return link air interface'. International Journal of Satellite Communications and Networking, 33 (5), pp. 371-390.

    Abstract

    Copyright © 2015 John Wiley & Sons, Ltd.Summary This paper presents performance improvement techniques for the second-generation digital video broadcast return channel via satellite air interface, which can be used for supporting future demands for Tbit/s traffic requirements. In particular, we have investigated minimum-shift keying (MSK) type of continuous phase modulation (CPM) waveforms by considering both single-carrier and multi-carrier transmission and single-amplitude and multi-amplitude signals, which improve the spectral efficiency. In addition, we consider frame timing and synchronization techniques, which make synchronization more accurate and robust. Our research has shown that the MSK single-carrier frequency-division multiple access (SC-FDMA) outperforms the quadrature phase-shift keying SC-FDMA in terms of resilience to distortion with the performance gap increasing when the amplifier shows a milder distortion. The performance of a multi-amplitude CPM scheme, based upon the superposition of two single-amplitude MSK signals at the radio frequencies level, is also investigated. In comparison with other equivalent linear modulation schemes, performance evaluation results have been shown that the proposed multi-amplitude CPM scheme significantly improves the spectral efficiency in the presence of adjacent channel interference. Finally, we have proposed a viable and efficient methodology, which enables reliable and accurate timing and frequency synchronization for the SC-FDMA satellite return link. This involves a combination of global positioning system (GPS)-based pre-compensation of differential timing between user terminals, preamble detection in an integrated random access channel, and user channel frequency estimation based on repetitive symbols in the time domain.

  • Mathiopoulos PT, Candreva EA, Awoseyila AB, Dalakas V, Tarchi D, Evans BG, Vanelli-Coralli A, Corazza GE. (2015) 'Performance improvement techniques for the DVB-RCS2 return link air interface'. INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, 33 (5), pp. 371-390.
  • Tang W, Thompson, P, Kyrgiazos A, Evans BG. (2015) 'Extending the Usable Ka-Band Spectrum for FSS Satellite Systems by using a FS Database'. International Journal on Advances in Telecommunications, 8 (3 & 4), pp. 121-141.

    Abstract

    Broadband access by satellite in Ka-band will become constrained by spectrum availability. In this context, the European Union (EU) FP7 project CoRaSat is examining the possible spectrum extension opportunities that could be exploited by a database approach in Ka-band via the use of cognitive mechanisms. The database approach utilizing spectrum scenarios between Fixed Satellite Services (FSS), Fixed Services (FS) and Broadcast Satellite Service (BSS) feeder links are considered. Database statistics for several EU countries are also provided for database analysis. Interference in the downlink scenarios are evaluated by the database approach using real databases and propagation models. The importance of using correct terrain profiles and accurate propagation models are shown. For the case of BSS interference to the FSS downlink (17.3-17.7GHz) it is demonstrated that in the UK an area of less than 2% is adversely affected. FS interference into the FSS downlink 17.7- 19.7GHz is shown for the UK to only affect a small percentage of the band at any location. Some initial preliminary findings when considering earth stations on moving platforms are also presented. It is concluded that by using a database approach to allocate frequencies it is possible to use most of the band across different locations for satellites services in the shared Ka-band.

  • Kyrgiazos A, Evans BG, Thompson P. (2014) 'On the Gateway diversity for high throughput broadband satellite systems'. IEEE Transactions on Wireless Communications, 13 (10), pp. 5411-5426.

    Abstract

    © 2014 IEEE.This paper addresses the Smart Gateway diversity scheme to be employed in future High Throughput Satellite Systems (HTS) at Ka, Q/V bands or above. The availability of a network of N gateways is presented with P redundant and with N active multiplexed gateways. A new time switched architecture is compared with the more conventional frequency division system for the N-active scheme but retaining transparent satellite transponders. In addition, resource allocation algorithms are compared, end to end, which maximize the throughput and balance the traffic amongst the user beams for gateways links degraded by rain. The time switched gateway approach allows simplifies satellite payloads and reduced ground segment size and hence cost.

  • Sohail A, Al-Imari M, Xiao P, Evans BG. (2014) 'Theoretical Analysis of Power Saving In Cognitive Radio with Arbitrary Inputs'. IEEE Transactions on Vehicular Technology,
    [ Status: Accepted ]

    Abstract

    In Orthogonal Frequency Division Multiplexing (OFDM) based cognitive radio systems, power optimization algorithms have been evaluated to maximize the achievable data rates of the Secondary User (SU). However, unrealistic assumptions are made in the existing work, i.e. a Gaussian input distribution and traditional interference model that assumes frequency division multiplexing modulated Primary User (PU) with perfect synchronization between the PU and the SU. In this paper, we first derive a practical interference model by assuming OFDM modulated PU with imperfect synchronization. Based on the new interference model, the power optimization problem is proposed for the Finite Symbol Alphabet (FSA) input distribution (i.e., M-QAM), as used in practical systems. The proposed scheme is shown to save transmit power and to achieve higher data rates compared to the Gaussian optimized power allocation and the uniform power loading schemes. Furthermore, a theoretical framework is established in this paper to estimate the power saving by evaluating optimal power allocation for the Gaussian and the FSA input. Our theoretical analysis is verified by simulations and proved to be accurate. It provides guidance for the system design and gives deeper insights into the choice of parameters affecting power saving and rate improvement.

  • Sohail A, Al-Imari M, Xiao P, Evans BG. (2014) 'Theoretical Analysis of Power Saving in Cognitive Radio with Arbitrary Inputs'. IEEE Transactions on Vehicular Technology,

    Abstract

    In Orthogonal Frequency Division Multiplexing (OFDM) based cognitive radio systems, power optimization algorithms have been evaluated to maximize the achievable data rates of the Secondary User (SU). However, unrealistic assumptions are made in the existing work, i.e. a Gaussian input distribution and traditional interference model that assumes frequency division multiplexing modulated Primary User (PU) with perfect synchronization between the PU and the SU. In this paper, we first derive a practical interference model by assuming OFDM modulated PU with imperfect synchronization. Based on the new interference model, the power optimization problem is proposed for the Finite Symbol Alphabet (FSA) input distribution (i.e., M-QAM), as used in practical systems. The proposed scheme is shown to save transmit power and to achieve higher data rates compared to the Gaussian optimized power allocation and the uniform power loading schemes. Furthermore, a theoretical framework is established in this paper to estimate the power saving by evaluating optimal power allocation for the Gaussian and the FSA input. Our theoretical analysis is verified by simulations and proved to be accurate. It provides guidance for the system design and gives deeper insights into the choice of parameters affecting power saving and rate improvement.

  • Kyrgiazos A, Evans B, Thompson P, Mathiopoulos PT, Papaharalabos S. (2014) 'A terabit/second satellite system for European broadband access: A feasibility study'. International Journal of Satellite Communications and Networking, 32 (2), pp. 63-92.

    Abstract

    SUMMARYThis paper presents a feasibility study for a fixed broadband access High Throughput Satellite terabit/second system by considering appropriate state-of-the-art communication technologies. For the investigated system model, DVB-S2 and DVB-RCS2 are assumed as the air interfaces for the forward and return link, respectively. The performance of DVB-S2 and DVB-RCS2 Adaptive Coding and Modulation is examined along with potential extensions of these standards. For example, the performance of very low rate DVB-RCS turbo codes are investigated and their performance is evaluated. In addition, a performance comparison for M-ary (M=16, 32, 64) constellations in the presence of a linear and a high power amplifier non-linear channel is carried out. Various frequency reuse schemes and different antenna models are also considered, and their performance is analyzed and evaluated. It is demonstrated that, by using the Q/V (40/50 GHz) bands for the gateways and the Ka (20-30 GHz) band for the user terminals, around 20 gateways and 200 beams are required to provide with the proposed satellite system terabit/second capacity. The obtained performance evaluation results have shown that the forward link is limited by noise rather than interference, whereas the return link is interference limited. Additionally, some further aspects of the system design in relation with the total number of gateways and the payload are discussed. Copyright © 2014 John Wiley & Sons, Ltd. This paper presents a feasibility study for a fixed broadband access High Throughput Satellite terabit/second system by considering appropriate state-of-the-art communication technologies. It is demonstrated that, by using the Q/V bands for the gateways and the Ka band for the user terminals, around 20 gateways and 200 beams are required to provide with the proposed satellite system terabit/second capacity. Additionally, some further aspects of the system design in relation with the total number of gateways and the payload are discussed. Copyright © 2014 John Wiley & Sons, Ltd.

  • Jeannin N, Castanet L, Radzik J, Bousquet M, Evans B, Thompson P. (2014) 'Smart gateways for terabit/s satellite'. International Journal of Satellite Communications and Networking, 32 (2), pp. 93-106.

    Abstract

    SUMMARY To reach the terabit per second of throughput, telecommunication satellites cannot make use of frequency below Ka band only. Therefore, the use of broad portion of the spectrum available at Q/V (40/50 GHz) band is foreseen for the feeder link. This study presents the evaluation of performances of different macro-diversity schemes that may allow mitigating the deep fades experienced at Q/V bands by introducing cooperation and a limited redundancy between the different gateways of the system. Two different solutions are firstly described. The performances resulting from the use of those assumptions are derived in a second stage. Copyright © 2014 John Wiley & Sons, Ltd. This paper describes macro-diversity solutions to mitigate the effect of the propagation impairments for the feeder links of high throughput satellite. Preliminary performance assessments are performed on two possible designs. Copyright © 2014 John Wiley & Sons, Ltd.

  • Jeannin N, Castanet L, Radzik J, Bousquet M, Evans B, Thompson P. (2014) 'Smart gateways for terabit/s satellite'. INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, 32 (2), pp. 93-106.

    Abstract

    To reach the terabit per second of throughput, telecommunication satellites cannot make use of frequency below Ka band only. Therefore, the use of broad portion of the spectrum available at Q/V (40/50 GHz) band is foreseen for the feeder link. This study presents the evaluation of performances of different macro-diversity schemes that may allow mitigating the deep fades experienced at Q/V bands by introducing cooperation and a limited redundancy between the different gateways of the system. Two different solutions are firstly described. The performances resulting from the use of those assumptions are derived in a second stage.

  • Pérez-Trufero J, Evans B, Kyrgiazos A, Dervin M, Garnier B, Baudoin C. (2014) 'High throughput satellite system with Q/V-band gateways and its integration with terrestrial broadband communication networks'. 32nd AIAA International Communications Satellite Systems Conference, ICSSC 2014,

    Abstract

    Satellite broadband systems will play a key role in reducing the Digital Divide by complementing terrestrial networks in the delivery of superfast broadband in remote and rural areas. We present the system architecture, sizing and performance assessment of a next generation High Throuhgput Satellite system with Q/V-band gateways targeting the 2020 timeframe. In addition, we present a novel optimisation framework for the design of the backbone network interconnecting the satellite gateways with national PoPs in the serviced countries, which takes into account the impact in costs an payload constraints.

  • Mehta M, Rane N, Karandikar A, Imran MA, Evans BG. (2014) 'A self-organized resource allocation scheme for heterogeneous macro-femto networks'. Wireless Communications and Mobile Computing,
    [ Status: Accepted ]

    Abstract

    This paper investigates the radio resource management (RRM) issues in a heterogeneous macro-femto network. The objective of femto deployment is to improve coverage, capacity, and experienced quality of service of indoor users. The location and density of user-deployed femtos is not known a-priori. This makes interference management crucial. In particular, with co-channel allocation (to improve resource utilization efficiency), RRM becomes involved because of both cross-layer and co-layer interference. In this paper, we review the resource allocation strategies available in the literature for heterogeneous macro-femto network. Then, we propose a self-organized resource allocation (SO-RA) scheme for an orthogonal frequency division multiple access based macro-femto network to mitigate co-layer interference in the downlink transmission. We compare its performance with the existing schemes like Reuse-1, adaptive frequency reuse (AFR), and AFR with power control (one of our proposed modification to AFR approach) in terms of 10 percentile user throughput and fairness to femto users. The performance of AFR with power control scheme matches closely with Reuse-1, while the SO-RA scheme achieves improved throughput and fairness performance. SO-RA scheme ensures minimum throughput guarantee to all femto users and exhibits better performance than the existing state-of-the-art resource allocation schemes. © 2014 John Wiley & Sons, Ltd.

  • Alsedairy T, Qi Y, Imran A, Imran MA, Evans B. (2014) 'Self organising cloud cells: a resource efficient network densification strategy'. TRANSACTIONS ON EMERGING TELECOMMUNICATIONS TECHNOLOGIES, 26 (8), pp. 1096-1107.
  • Kyrgiazos A, Evans B, Thompson P, Dervin M, Baudoin C, Garnier B. (2014) 'Gateway diversity for a future high throughput satellite system'. 32nd AIAA International Communications Satellite Systems Conference, ICSSC 2014,
  • Tarchi D, Guidotti A, Icolari V, Vanelli-Coralli A, Sharma SK, Chatzinotas S, Malekil S, Evans B, Thompson P, Tang W, Grotz J. (2014) 'Technical challenges for cognitive radio application in satellite communications'. Proceedings of the 2014 9th International Conference on Cognitive Radio Oriented Wireless Networks and Communications, CROWNCOM 2014, , pp. 136-142.

    Abstract

    During the last years, spectrum scarcity has become one of the major issues for the development of new communication systems. Cognitive Radio (CR) approaches have gained an ever increasing attention from system designers and operators, as they promise a more efficient utilization of the available spectral resources. In this context, while the application of CRs in terrestrial scenarios has been widely considered from both theoretical and practical viewpoints, their exploitation in satellite communications is still a rather unexplored area. In this paper, we address the definition of several satellite communications scenarios, where cognitive radio techniques promise to introduce significant benefits, and we discuss the major enablers and the associated challenges. © 2014 ICST.

  • Maleki S, Chatzinotas S, Sharma SK, Guidotti A, Tarchi D, Vanelli-Coralli A, Tang W, Evans BA, Grotz J, Liolis K, Krause J, Chuberre N. (2014) 'Cognitive radio for Ka band satellite communications'. 32nd AIAA International Communications Satellite Systems Conference, ICSSC 2014,

    Abstract

    The satellite communication data traffic is increasing dramatically over the coming years. High throughput multibeam satellite networks in Ka band are potentially able to accommodate the upcoming high data rate demands. However, there is only 500 MHz of exclusive band for download and the same amount for upload. This spectrum shortage impose a barrier in order to satisfy the increasing demands. Cognitive satellite communication in Ka band is considered in this paper in order to potentially provide an additional 4.4 GHz bandwidth for downlink and uplink fixed-satellite-services. In this way, it is expected that the problem of spectrum scarcity for future generation of satellite networks is alleviated to a great extent. The underlying scenarios and enabling techniques are discussed in detail, and finally we investigate the implementation issues related to the considered techniques.

  • Kyrgiazos A, Evans B, Thompson P, Mathiopoulos PT, Papaharalabos S. (2014) 'A terabit/second satellite system for European broadband access: A feasibility study'. International Journal of Satellite Communications and Networking,

    Abstract

    This paper presents a feasibility study for a fixed broadband access High Throughput Satellite terabit/second system by considering appropriate state-of-the-art communication technologies. For the investigated system model, DVB-S2 and DVB-RCS2 are assumed as the air interfaces for the forward and return link, respectively. The performance of DVB-S2 and DVB-RCS2 Adaptive Coding and Modulation is examined along with potential extensions of these standards. For example, the performance of very low rate DVB-RCS turbo codes are investigated and their performance is evaluated. In addition, a performance comparison for M-ary (M=16, 32, 64) constellations in the presence of a linear and a high power amplifier non-linear channel is carried out. Various frequency reuse schemes and different antenna models are also considered, and their performance is analyzed and evaluated. It is demonstrated that, by using the Q/V (40/50GHz) bands for the gateways and the Ka (20-30GHz) band for the user terminals, around 20 gateways and 200 beams are required to provide with the proposed satellite system terabit/second capacity. The obtained performance evaluation results have shown that the forward link is limited by noise rather than interference, whereas the return link is interference limited. Additionally, some further aspects of the system design in relation with the total number of gateways and the payload are discussed. © 2014 John Wiley & Sons, Ltd.

  • Sohail A, Al-Imari M, Xiao P, Evans B. (2013) 'Cognitive Radio Systems: Multicarrier Modulation and Power Allocation Challenges'. Journal of Electrical & Electronic Systems, 3 (1), pp. 1-6.

    Abstract

    The rapid development of modern communication services results in high data rate requirements from the end user. It is challenging to meet high data rate requirements because of prevailing issues such as spectrum scarcity and spectrum underutilization due to fixed spectrum assignment policy. Cognitive Radio (CR), being the enabler of dynamic spectrum management techniques, has the capability to tackle these issues by proficiently implementing spectrum sharing schemes using Multicarrier Modulation (MCM) techniques. In CR system, where the Primary User (PU) and the Secondary User (SU) co-exist in the same frequency band, mutual interference (i.e., from SU to PU and vice versa) is a limiting factor on the achievable capacity of both the PU and the SU. Power allocation in MCM based CR systems aims to dynamically control the transmit power on each subcarrier of the SU in order to reduce the mutual interference. Furthermore, combining multiple antennas with MCM is regarded as a very attractive solution for the CR communications to effectively enhance data rate without demanding additional bandwidth and transmit power.

  • Jalili B, Dianati M, Evans BG, Moessner K. (2013) 'Collaborative radio resource allocation for the downlink of multi-cell multi-carrier systems'. IET COMMUNICATIONS, 7 (5), pp. 430-438.
  • Thompson PT, Evans BG, Walsh M, Cronin M. (2013) 'Results of simultaneous low elevation Ku-band propagation effects at two sites in southern England'. Space Communications, 22 (2-4), pp. 99-110.

    Abstract

    This paper reports on satellite beacon measurements at 12.7 GHz from late October 2010 until the end of June 2012 at two geographically separated Arqiva Teleport sites in Southern England in order to obtain propagation data to be used in operational decision making and improvement of the scientific understanding of such effects. These sites operate at very low elevation angles (4.1 and 5.3 degrees) and therefore experience significant propagation effects. Measurements are on-going to achieve meaningful long term statistics, however there is value in comparing the results obtained at both sites over the common period of measurement data to date (approximately 20 months). The measurements are performed at 1/2 second intervals and statistical analysis applied. A primary objective of this work is to assess the influence of tropospheric scintillation and consequently the paper will focus on this with the addition of some lesser material on rain fade effects. The measurements and analysis have been performed as a collaborative effort between Arqiva and staff who work at the University of Surrey. It is emphasised that the primary objective of this work is to assess the influence of tropospheric scintillation and rain attenuation from an operational perspective and to a lesser extent from an academic viewpoint. © 2009-2013 - IOS Press and the authors. All rights reserved.

  • Aliu OG, Mehta M, Imran MA, Karandikar A, Evans BG. (2013) 'A cellular automata approach towards self organisation in wireless cellular networks'. 19th European Wireless Conference, EW 2013,

    Abstract

    This paper gives an introduction to a key tool that can help provide various self organised solutions in wireless cellular networks. We begin by describing the need for self organised networks and the challenges associated with it. An introduction to cellular automata theory is then given with an easy to follow example. We provide an analysis of such solutions and discuss its stability and convergence criterion. Finally, we formulate a specific problem for Inter-Cell Interference Coordination (ICIC), describing how the cellular automata approach can be applied to achieve ICIC. In addition, we discuss the prospective use case of applying cellular automata in achieving energy efficiency in heterogeneous networks. This paper will serve as a guide for anyone willing to develop self organising solutions in wireless cellular networks. © VDE VERLAG GMBH.

  • Liu X, Evans BG, Moessner K. (2013) 'Comparison of reliability, delay and complexity for standalone cognitive radio spectrum sensing schemes'. IET Communications, 7 (9), pp. 799-807.

    Abstract

    The ability to reliably and autonomously identify unused frequency bands plays an extremely important role in cognitive radio networks. Relying on the spectrum sensing, ongoing licensed operation must not be compromised and the secondary spectrum usage efficiency should be maintained. Thus, it is critical to ensure that the confidence level of the estimated signal status satisfies the primary user's requirement, while keeping the delay and computational complexity to a minimum. This study provides a comprehensive comparison in terms of performance, reliability and complexity of standalone sensing schemes for various cognitive radio application areas. The authors first give some new results on reliability performance, and then evaluate the sensing time required to achieve the target performance. Finally, the authors compare the computational complexity of various sensing approaches by calculating the number of arithmetic operations required by each approach. © The Institution of Engineering and Technology 2013.

  • Liolis K, Schlueter G, Krause J, Zimmer F, Combelles L, Grotz J, Chatzinotas S, Evans B, Guidotti A, Tarchi D, Vanelli-Coralli A. (2013) 'Cognitive radio scenarios for satellite communications: The CoRaSat approach'. 2013 Future Network and Mobile Summit, FutureNetworkSummit 2013,

    Abstract

    This paper presents initial results of the recently kicked-off FP7 ICT STREP project "CoRaSat" (Cognitive Radio for Satellite Communications) [1]. Focus is put on the preliminary identification of the scenarios which are suitable for the applicability of Cognitive Radio technology over Satellite Communications (SatCom). The considered frequency bands include Ka-band, Ku-band, C-band and S-band, where regulatory and coordination constraints exist. An initial mapping of broadband and narrowband SatCom use cases on each identified scenario is also provided. Moreover, several challenges associated to the applicability of Cognitive Radio over SatCom in the identified scenarios are presented, which form the basis of the market/business, regulatory, standardization and technological framework of CoRaSat. Furthermore, ongoing and future work of the CoRaSat project is outlined. © 2013 Authors.

  • Kyrgiazos A, Evans B, Thompson P. (2013) 'Dynamic resource allocation for a future satellite system employing an time switched payload'. 31st AIAA International Communications Satellite Systems Conference, ICSSC 2013,

    Abstract

    The continuous increase of traffic demands for satellite networks has resulted in the consideration and use of higher bands such as Ka (20/30 GHz) and Q/V (40/50 GHz) bands. Additionally, it is foreseen that the traffic demands will be unevenly distributed. Recent studies 1 argue that more than 200 user beams at Ka band and more than 25 active gateways at Q/V bands are required in order to satisfy demands by 2020. The non-uniform traffic demand distribution can be accommodated with flexible bandwidth allocation (Beam Hopping). But considering that the feeder links operate at Q/V bands, they are subject to severe precipitation fades. As each gateway will carry very high capacity, it is essential to ensure very high availabilities for the feeder links. In an effort to reduce the total number of gateways in the system, the concept of Smart gateways has emerged which dictates that a user beam is served by a pool of gateways instead of just one. In this paper, we consider that each user beam is served by a number of gateways via time multiplexing. This architecture is consistent with beam hopping (on the user side) and the payload architecture resembles the already implemented Satellite Switched TDMA (SS-TDMA). The rationale for this system is to introduce more flexibility not only to the user side but also in the feeder links, and reduce the total number of gateways in the system while minimising the capacity losses and ensuring the necessary feeder link availability. A framework which takes into account the atmospheric conditions of each gateway and the traffic demands of the beams, decides the number of time slots that each gateway uplink is connected to a user beam is proposed allowing a match to the instantaneous user demands with the offered capacity of the gateways. The scheduling of the switching matrix is discussed, as now it depends also on the predefined beam hopping sequence. The results are presented for a hypothetical scenario, and the improvements provided by this architecture are presented along with the impact on the system design.

  • Kyrgiazos A, Evans B, Thompson P. (2013) 'Irregular beam sizes and non-uniform bandwidth allocation in HTS multibeam satellite systems'. 31st AIAA International Communications Satellite Systems Conference, ICSSC 2013,

    Abstract

    Current HTS multibeam satellite systems assume a uniform offered traffic per beam, but it is foreseen that future traffic demands will be highly uneven over the coverage area. Then imbalances result in some user beams being overprovisioned whilst others are under provisioned resulting in lower satisfaction for user traffic demands. One of the major challenges in designing a future broadband satellite system is how to increase the operators revenue and cope with the uneven traffic demands simultaneously. In the literature, it has been proposed to overcome these imbalances either by applying non-uniform bandwidth distribution (in the frequency domain or beam hopping in the time domain) or by engineering the beam sizes such as to balance the traffic demands over the beams. In this paper, we propose a joint optimisation of non-uniform bandwidth allocation and non-uniform beam sizes to better match the traffic demands, increase the total useful capacity and utilise the limited space resources more efficiently. The proposed method is applied for a hypothetical traffic scenario over Europe, where a maximum number of 200 user beams is assumed. Only the forward direction is studied herein. The DVB-S2 air interface is considered. A transparent payload is considered, where the user links operate in Ka-band. The results of the forward link are presented and compared with a uniform design and a case with only non-uniform bandwidth allocation. The improvements due the joint optimisation are presented, and the implications to the system design are discussed.

  • Awoseyila AB, Evans BG, Kim HW. (2013) 'Frequency sharing between satellite and terrestrial in the 2GHZ MSS band'. 31st AIAA International Communications Satellite Systems Conference, ICSSC 2013,

    Abstract

    Simultaneous frequency sharing in integrated satellite and terrestrial networks can help to achieve increased network capacity based on an efficient reuse of frequency resources in a way that minimizes interference. In this paper, we investigate the use of the 2GHz MSS frequency allocation for satellite and terrestrial mobile services based on LTE. Results show that uplink frequency sharing is not feasible due to the predominant terrestrial interference into the satellite service. On the other hand, downlink frequency sharing is feasible for pedestrian microcells and vehicular macrocells but not for the wider rural cells. In this regard, a satellite multimedia broadcast service can be deployed simultaneously with twoway terrestrial mobile service in urban and suburban areas. Furthermore, dynamic radio resource allocation combined with interference coordination can be used to optimize performance throughout the integrated network.

  • Kyrgiazos A, Thompson P, Evans B. (2013) 'Gateway diversity via flexible resource allocation in a multibeam SS-TDMA System'. IEEE Communications Letters, 17 (9), pp. 1762-1765.

    Abstract

    This letter addresses the problem of gateway diversity for a future broadband multibeam satellite system. A system architecture which employs a Satellite Switched TDMA payload is considered in an effort to introduce more flexibility and reduce the total number of gateways in the system while minimising the capacity losses and ensuring the necessary feeder link availability. Herein, an architecture and a framework based on assignment of a number of time slots that each gateway uplink is connected to a user beam is proposed allowing a match to the user demands with the offered capacity of the gateways. Three resource allocation schemes are proposed, which take into account the uplink propagation conditions and the users demands. One of the proposed schemes attempts to maximise the throughput and the others attempt to balance the traffic amongst beams, are tested under a scenario where four feeder uplinks are used to serve four user beams. Rain models are applied to generate precipitation fades, and the schemes performance is examined in terms of loss of capacity. © 1997-2012 IEEE.

  • De Silva V, Shi X, Evans B, Trufero JP, Peters G. (2013) 'Designing a QoE aware intelligent home gateway for future smart homes'. 2013 Future Network and Mobile Summit, FutureNetworkSummit 2013,

    Abstract

    The future smart homes will be equipped with a variety of devices that are connected to the internet to provide a multitude of services to consumers. An adequate and reliable broadband connection is a must to support smart home services such as E-Health, home automation, smart energy management and seamless usage of multimedia. To realize such advanced networked applications, especially for households in geographical areas that are unserved or underserved with broadband connectivity, the European Union's 7th Framework Programme funded the BATS integrated project (Broadband Access via integrated Terrestrial and Satellite systems). The main objective of the BATS project is to integrate satellite and terrestrial networks to provide broadband connectivity to households through a home gateway. The envisaged home gateway is intelligent such that it is able to determine in real time the QoS requirements of applications and accordingly make routing decisions to optimize Quality of Experience (QoE) of the end user. In this paper we introduce future smart home applications and devices that would benefit from the BATS concept and discuss the different aspects of designing an intelligent home gateway that is both QoE aware and standard compliant. © 2013 Authors.

  • Ijaz A, Awoseyila AB, Evans BG. (2012) 'Signal-to-noise ratio estimation algorithm for advanced DVB-RCS systems'. IEEE Transactions on Broadcasting, 58 (4), pp. 603-608.

    Abstract

    This paper presents a signal-to-noise ratio (SNR) estimation algorithm for advanced Digital Video Broadcasting - Return Channel via Satellite (DVB-RCS) systems using adaptive coding and modulation (ACM) in the reverse link of broadband satellite systems. Due to the absence of a repetitive pilot symbol structure, SNR estimation has to be performed using the fixed symbol preamble data. Moreover, sporadic nature of data traffic on the return link causes variation in interference level from slot to slot and, therefore, the estimation has to be done within one traffic slot duration. Hence, it becomes necessary to use a combination of data-aided (DA) and decision-directed (DD) algorithms so as to make use of traffic data. A non-data-aided (NDA) estimator that was previously proposed by the authors for binary phase shift keying (BPSK) and QPSK schemes is extended to 8-PSK in a decision directed manner. This estimator shows improved performance over existing estimators. The inherent bias of DD approach at low values of SNR is reduced by using a hybrid approach, i.e. using the proposed estimator at moderate/high values of SNR and the moments-based estimator (M2M4) at low values of SNR. Overall improved performance of the proposed hybrid estimator, in terms of accuracy and complexity, makes it an attractive choice for implementing ACM in advanced DVB-RCS systems.

  • Ijaz A, Awoseyila AB, Evans BG. (2012) 'Signal-to-Noise Ratio Estimation Algorithm for Advanced DVB-RCS Systems'. IEEE Transactions on Broadcasting,

    Abstract

    This paper presents a signal-to-noise ratio (SNR) estimation algorithm for advanced Digital Video Broadcasting-Return Channel via Satellite (DVB-RCS) systems using adaptive coding and modulation (ACM) in the reverse link of broadband satellite systems. Due to the absence of a repetitive pilot symbol structure, SNR estimation has to be performed using the fixed symbol preamble data. Moreover, sporadic nature of data traffic on the return link causes variation in interference level from slot to slot and, therefore, the estimation has to be done within one traffic slot duration. Hence, it becomes necessary to use a combination of data-aided (DA) and decision-directed (DD) algorithms so as to make use of traffic data. A non-data-aided (NDA) estimator that was previously proposed by the authors for binary phase shift keying (BPSK) and QPSK schemes is extended to 8-PSK in a decision directed manner. This estimator shows improved performance over existing estimators. The inherent bias of DD approach at low values of SNR is reduced by using a hybrid approach, i.e., using the proposed estimator at moderate/high values of SNR and the moments-based estimator (M M ) at low values of SNR. Overall improved performance of the proposed hybrid estimator, in terms of accuracy and complexity, makes it an attractive choice for implementing ACM in advanced DVB-RCS systems.

  • Ijaz A, Awoseyila AB, Evans BG. (2012) 'Signal-to-noise ratio estimation algorithm for adaptive coding and modulation in advanced DVB-RCS systems'. IET Communications, 6 (11), pp. 1587-1593.

    Abstract

    This paper presents a signal-to-noise ratio (SNR) estimation algorithm for advanced digital video broadcastingreturn channel via satellite (DVB-RCS) systems using adaptive coding and modulation (ACM). Due to the absence of a repetitive pilot symbol structure, SNR estimation has to be performed using the fixed symbol preamble data. Moreover, sporadic nature of data traffic on the return link causes variation in interference level from slot to slot and, therefore, the estimation has to be done within one traffic slot duration. Hence, it becomes necessary to use a combination of data-aided and decision-directed (DD) algorithms so as to make use of traffic data. A non-data-aided estimator that was previously proposed by the authors for binary and quadrature phase shift keying schemes is extended to 8-PSK in a decision directed manner. The inherent bias of DD approach at low values of SNR is reduced by using a hybrid approach, that is, using the proposed estimator at moderate/high values of SNR and the moments-based estimator (M2M4) at low values of SNR. Overall improved performance of the proposed hybrid estimator, in terms of accuracy and complexity, makes it an attractive choice for implementing ACM in advanced DVB-RCS systems.

  • Afelumo O, Awoseyila AB, Evans BG. (2012) 'Simplified evaluation of APSK error performance'. Electronics Letters, 48 (14), pp. 886-888.

    Abstract

    An analytical evaluation of the performance of amplitude phase shift keying constellations in additive white Gaussian noise is performed and an expression to approximate the error probability is presented. The expression accounts for a number of symbols, equal to the number of concentric rings in the constellation. It is shown to significantly reduce the computational complexity associated with previously known error performance expressions, while closely predicting the error rates in the relevant signal-to-noise ratio range.

  • Afelumo O, Awoseyila AB, Evans BG. (2012) 'Simplified evaluation of APSK error performance'. Electronics Letters, 48 (14), pp. 886-888.

    Abstract

    An analytical evaluation of the performance of amplitude phase shift keying constellations in additive white Gaussian noise is performed and an expression to approximate the error probability is presented. The expression accounts for a number of symbols, equal to the number of concentric rings in the constellation. It is shown to significantly reduce the computational complexity associated with previously known error performance expressions, while closely predicting the error rates in the relevant signal-to-noise ratio range. © 2012 The Institution of Engineering and Technology.

  • Zhou J, Li Y, Evans B. (2012) 'Antenna selection for multiple-input and single-output cognitive radio systems'. IET COMMUNICATIONS, 6 (8), pp. 917-930.
  • Aliu OG, Imran A, Imran MA, Evans B. (2012) 'A Survey of Self Organisation in Future Cellular Networks'. IEEE COMMUNICATIONS SURVEYS AND TUTORIALS, 15 (1), pp. 336-361.
  • Oredope A, Frassetto G, Evans B. (2012) 'An evaluation of vertical handovers in LTE networks'. Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 7277 LNCS, pp. 198-207.

    Abstract

    One of the key requirements of the LTE core network is to provide seamless mobility and session continuity at the IP layer across multiple access networks - 3GPP and non-3GPP. Although this can be achieved in LTE networks using Proxy Mobile IPv6 (PMIPv6), two key limitations still exists - handover latency and high packet loss. In this paper, we provided our proposed, designed and implemented novel protocol known as Proxy Mobile IPv6 Plus (PMIPv6+) aimed at addressing handover latency while reducing signaling traffic in the current standardized PMIPv6 implementations. Our experimental tests and performance analysis shows that PMIPv6+ reduces handover latency by 50% while also reducing the packet loss by almost 95% as compared to legacy PMIPv6. © 2012 Springer-Verlag.

  • Jalili B, Dianati M, Evans BG, Mehta M, Karandikar A. (2012) 'Interference evaluation for distributed collaborative radio resource allocation in downlink of LTE systems'. IEEE Vehicular Technology Conference,

    Abstract

    Collaboration among neighbouring eNBs in radio resource allocation, in the absence of a centralized control unit, is one of the challenges raised from the flat architecture suggested for the Long Term Evolution (LTE) networks. This paper investigates the system performance of a collaborative resource allocation scheme, in a scenario that consists of two tiers of collaborative Regions (CoR), and considers the gain achieved from the eNB collaboration and performance degradation due to the interference from neighbouring eNBs. Our results indicate that interference introduced from the cells outside the collaborating cluster can have significant impact on the system performance. However, Monte Carlo simulation based performance analysis demonstrates the effectiveness of collaborative resource allocation among adjacent eNBs for the LTE networks. © 2012 IEEE.

  • Jalili B, Mehta M, Dianati M, Karandikar A, Evans BG. (2012) 'Interference evaluation for distributed collaborative radio resource allocation in downlink of LTE systems'. IEEE Vehicular Technology Conference,

    Abstract

    Collaboration among neighbouring eNBs in radio resource allocation, in the absence of a centralized control unit, is one of the challenges raised from the flat architecture suggested for the Long Term Evolution (LTE) networks. This paper investigates the system performance of a collaborative resource allocation scheme, in a scenario that consists of two tiers of collaborative Regions (CoR), and considers the gain achieved from the eNB collaboration and performance degradation due to the interference from neighbouring eNBs. Our results indicate that interference introduced from the cells outside the collaborating cluster can have significant impact on the system performance. However, Monte Carlo simulation based performance analysis demonstrates the effectiveness of collaborative resource allocation among adjacent eNBs for the LTE networks. © 2012 IEEE.

  • Khan AH, Imran MA, Evans BG. (2012) 'Iterative turbo beamforming for orthogonal frequency division multiplexing-based hybrid terrestrial-satellite mobile system'. IET Communications, 6 (2), pp. 157-164.

    Abstract

    In the context of orthogonal frequency division multiplexing (OFDM)-based systems, pilot-based beamforming (BF) exhibits a high degree of sensitivity to the pilot sub-carriers. Increasing the number of reference pilots significantly improves BF performance as well as system performance. However, this increase comes at the cost of data throughput, which inevitably shrinks due to transmission of additional pilots. Hence an approach where reference signals available to the BF process can be increased without transmitting additional pilots can exhibit superior system performance without compromising throughput. Thus, the authors present a novel three-stage iterative turbo beamforming (ITBF) algorithm for an OFDM-based hybrid terrestrial-satellite mobile system, which utilises both pilots and data to perform interference mitigation. Data sub-carriers are utilised as virtual reference signals in the BF process. Results show that when compared to non-iterative conventional BF, the proposed ITBF exhibits bit error rate gain of up to 2.5 dB with only one iteration.

  • Evans BG, Khan A, Imran MA. (2012) 'Semi-adaptive beamforming for ofdm based hybrid terestrial-satellite mobile satellite'. IEEE Trans Wireless Communications, 11 (10), pp. 3424-3433.
  • Evans BG, Thompson PT, Corazza GE, Vanelli-Coralli A, Candreva EA. (2011) '1945-2010: 65 Years of Satellite History From Early Visions to Latest Missions'. PROCEEDINGS OF THE IEEE, 99 (11), pp. 1840-1857.
  • King PR, Brown TWC, Kyrgiazos A, Evans BG. (2011) 'Empirical-stochastic LMS-MIMO channel model implementation and validation'. Antennas and Propagation, IEEE Transactions on, 60 Article number 2 , pp. 606-614.
  • Ijaz A, Awoseyila AB, Evans BG. (2011) 'Low-complexity time-domain SNR estimation for OFDM systems'. Electronics Letters, 47 (20), pp. 1154-1156.

    Abstract

    A low-complexity signal-to-noise ratio (SNR) estimation algorithm for orthogonal frequency division multiplexing (OFDM) systems in frequency-selective fading channels is proposed. The estimator is based on a conventional preamble having two identical parts. It uses the correlation of the received signal samples to estimate signal power while noise power is estimated using the difference between received samples. Simulation results show that the proposed estimator is robust to the channel's frequency selectivity and its attained accuracy and reduced complexity make it an attractive choice for current wireless OFDM systems.

  • Ijaz A, Awoseyila A, Evans BG. (2011) 'Low-complexity time-domain SNR estimation for OFDM systems'. ELECTRONICS LETTERS, 47 (20), pp. 1154-1155.
  • Zhu M, Awoseyila A, Evans BG. (2011) 'Low-complexity time-domain channel estimation for OFDM systems'. ELECTRONICS LETTERS, 47 (1), pp. 60-61.
  • Zhu M, Awoseyila AB, Evans BG. (2011) 'Low Complexity Time-Domain Channel Estimation for OFDM Systems'. Electronics Letters, 47 (1), pp. 60-62.

    Abstract

    A low-complexity time-domain channel estimation scheme for orthogonal frequency division multiplexing (OFDM) is proposed in the presence of timing synchronisation error. It uses training symbols (preamble) to estimate the channel impulse response where the degradation caused by synchronisation error can be compensated for by an optimisation mechanism. The proposed scheme can be easily integrated with the existing near-ideal synchronisation technique. Simulation results in quasistatic channels show that the proposed method achieves near-ideal accuracy with a complexity much lower than that of the MMSE.

  • Lutz E, Evans B, Vanelli-Coralli A, De Cola T, Giambene G. (2011) 'SatNEx phase III - Satellite communication network of experts'. Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, 71, pp. 175-185.

    Abstract

    SatNEx is a European Network of Experts for satellite communications, coordinated by the German Aerospace Center DLR. The first two phases of SatNEx were funded by the EU from 2004 to 2009. The third phase, SatNEx-III, comprises 17 partners and is funded by ESA from 2010 to 2013. A core team consisting of DLR, University of Surrey, and University of Bologna is coordinating the SatNEx-III research activities. Specific research tasks are contracted to partners in the frame of annual "Call-off Orders". © Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2011.

  • Awoseyila AB, Evans BG, Kim HW. (2011) 'On achieving optimum C/I in satellite-terrestrial frequency sharing networks'. 29th AIAA International Communications Satellite Systems Conference 2011, ICSSC-2011,

    Abstract

    Frequency sharing in satellite-terrestrial cellular networks can help to achieve increased capacity. However, it has the undesirable effect of generating increased interference due to the introduction of satellite-terrestrial interference paths. In this paper we investigate the factors affecting the carrier-to-interference power ratio (C/I) and the possibilities of achieving an optimum C/I in these networks. It is shown that a proper scaling of some relevant parameters such as EIRP and cell size would help to achieve C/I values comparable to those achievable in satellite-only and terrestrial-only cellular networks. © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

  • Oredope A, Dianati M, Evans B, Budhiraja R, Ramamurthi B. (2011) 'Deploying IP multimedia subsystem (IMS) services over next generation networks (NGNs): The IU-ATC integrated test bed'. Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST, 46, pp. 727-735.

    Abstract

    The IP Multimedia Subsystem (IMS) is the Third Generation Partnership Project's (3GPP) standardized service platform that enables the deployment of rich and personalized services over fixed and mobile networks whilst allowing end-users ubiquitous access to services such as voice, video, presence and online gaming anytime and anywhere. However, the delivery of these services to the end-users is highly dependent on the available or preferred access network which could range from fixed broadband access to mobile 4G connections. Although the IMS was initially developed as the core network for Third Generation (3G) systems, it has now been adopted as the service platform for the Long Term Evolution (LTE) and System Architecture Evolution (SAE). As this transition of 3G to 4G and beyond evolves, there is an immediate need for a research testbed that facilitates the research, development and early trials of the integration of these technologies. This has motivated us to integrate the IMS based Advanced Next Generation Network (ANGN) testbed at the University of Surrey (UniS), U.K. with the 4G Access Network Testbed at IIT Madras, India via an academic transnational network link to form a fully functional telecommunications mobile network. In this paper, we discuss the rationales, motivations and objectives behind the integrated testbed whilst also investigating how it can be extended to support 4G and future technologies such as LTE/SAE and WiMAX. The testbed as a whole plays a key as role in the future of IMS development as it provides a fully functional platform similar to commercial networks for researchers to investigate and demonstrate the feasibility of their proposal in a realistic environment. © Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2011.

  • Bousquet M, Radzik J, Jeannin N, Castanet L, Thompson P, Evans B. (2011) 'Broadband access terabit/s satellite concepts'. 29th AIAA International Communications Satellite Systems Conference 2011, ICSSC-2011,

    Abstract

    This paper aims at presenting different concepts for a broadband access satellite. A hybrid system using Q/V-bands on the feeder links and Ka-band on the user links has been considered. European coverage with a large number of beams allows a large frequency reuse factor depending on the number of colors of the cluster pattern. The use of Q/V band for the feeder links requires site diversity to counteract the strong tropospheric fading occurring at Q/V band and to obtain acceptable link availability. The paper gives an overview of the various trade-offs for frequency-reuse scenarios, size and number of beams, number of gateways, site diversity options and gateway handover. © 2011 by Prof. Michel Bousquet. Published by the American Institute of Aeronautics and Astronautics, Inc.

  • Evans B, Thompson P. (2010) 'Key issues and technologies for a terabit/s satellite'. 28th AIAA International Communications Satellite Systems Conference, ICSSC 2010,

    Abstract

    In this paper we investigate the next but one generation of fixed satellite systems and the technological challenges that face this generation which we define as operational by 2020. Various technologies and architectures are presented with a view to identifying the most promising to pursue. © 2010 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

  • Ijaz A, Awoseyila A, Evans B. (2010) 'SNR estimation for ACM in DVB-RCS satellite systems'. 28th AIAA International Communications Satellite Systems Conference, ICSSC 2010,
  • Awoseyila AB, Evans BG, Zhu M. (2010) 'Low complexity time-domain channel and delay spread estimation for OFDM systems'. IEEE Transactions on Consumer Electronics, 56 (4), pp. 2170-2177.

    Abstract

    A low complexity time-domain channel estimation scheme for OFDM systems is presented. It uses a training symbol (preamble) to estimate the channel impulse response (CIR) in the presence of timing synchronization errors. Its computational complexity is much lower than that of the popular MMSE technique and this can be further reduced if there is prior knowledge of the channel delay spread. Consequently, channel delay spread estimation is also addressed by using threshold setting on the optimized CIR. Computer simulations show that the proposed scheme achieves near-ideal accuracy in quasi-static channels.

  • Makaratat K, Brown TWC, Stavrou S, Evans B. (2010) 'Complex correlation on linear array angle-of-arrival estimation measurement of ultra wideband propagation channels'. IET MICROWAVES ANTENNAS & PROPAGATION, 4 (9), pp. 1354-1369.
  • Ijaz A, Awoseyila AB, Evans BG. (2010) 'Improved SNR estimation for BPSK and QPSK signals'. ELECTRONICS LETTERS, 45 (16), pp. 858-859.
  • Mansor MF, Brown TWC, Evans BG. (2010) 'Satellite MIMO Measurement With Colocated Quadrifilar Helix Antennas at the Receiver Terminal'. IEEE Antennas and Wireless Propagation Letters, 9, pp. 712-715.
  • Awoseyila AB, Evans BG. (2010) 'Improved time diversity for LTE over satellite using split multicode transmission'. ELECTRONICS LETTERS, 46 (10), pp. 729-U94.
  • Kasparis C, Beaudonnet M, Gyftodimos E, Evans BG. (2010) 'Gradient projection decoding of LDPC codes and algorithmic variations'. IET COMMUNICATIONS, 4 (2), pp. 223-233.
  • Zhu M, Awoseyila A, Evans BG. (2010) 'Low complexity time-domain channel and delay spread estimation for OFDM systems'. IEEE Transactions on Consumer Electronics, 56 (4), pp. 2170-2177.

    Abstract

    A low complexity time-domain channel estimation scheme for OFDM systems is presented. It uses a training symbol (preamble) to estimate the channel impulse response (CIR) in the presence of timing synchronization errors. Its computational complexity is much lower than that of the popular MMSE technique and this can be further reduced if there is prior knowledge of the channel delay spread. Consequently, channel delay spread estimation is also addressed by using threshold setting on the optimized CIR. Computer simulations show that the proposed scheme achieves near-ideal accuracy in quasi-static channels.

  • Lattanzi F, Giambene G, Acar G, Evans B. (2010) 'Admission control and handover management for high-speed trains in vehicular geostationary satellite networks with terrestrial gap-filling'. INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, 28 (1), pp. 1-27.
  • Sali A, Karim HA, Acar G, Evans B, Giambene G. (2010) 'Multicast link adaptation in reliable transmission over geostationary satellite networks'. Wireless Personal Communications, 62 (4), pp. 759-782.

    Abstract

    The exploitation of fluctuating channel conditions in link adaption techniques for unicast transmission has been shown to provide large system capacity gains. However, the problem of choosing transmission rates for multicast transmission has not been thoroughly investigated. In this paper, we investigate multicast adaptive techniques for reliable data delivery in GEO satellite networks. An optimal multicast link adaptation is proposed with the aim to maximise terminal throughput whilst increasing resource utilization and fairness in the face of diverse channel conditions. Via simulation results and theoretical analysis, the proposed algorithm has shown to outperform other alternative multicast link adaptation techniques especially when the terminals are in vigorous channel conditions.

  • Goulianos A, Brown TWC, Stavrou S, Evans BG. (2010) 'Power Delay Profile Modelling on the UWB Off-Body Propogation Channel'. IET Journal on Microwaves, Antennas and Propogation, 4 (1), pp. 62-71.

    Abstract

    This study presents a statistical power delay profile (PDP) model for the evaluation and design of ultra wideband (UWB) off-body communication systems. The analysis is based on extensive real-body measurements carried out in the frequency range between 3.5 and 6.5 GHz. Due to the dependence of the radio propagation channel on the body region (i.e. front, side and back), we gradually develop separate stochastic tapped-delay-line models for each body region. Based on the newly estimated parameters, channel simulation methods are provided for each of the proposed models. Finally, several comparisons between the empirical data and the simulations results are presented, by means of key properties of the recorded PDP profiles.

  • Awoseyila AB, Evans BG. (2010) 'Link performance of LTE vs. WiMAX for satellite mobile broadband'. 28th AIAA International Communications Satellite Systems Conference, ICSSC 2010,

    Abstract

    In this paper, we investigate and compare the performance of the IEEE mobile WiMAX and the 3GPP LTE terrestrial air interfaces over GEO satellite links with amplifier nonlinearity and mobile wideband fading, in order to have an insight into which would be a better candidate for ubiquitous mobile broadband delivery. Both air-interfaces are compared in terms of achievable single-link capacities for a 5MHz channel. Link-level computer simulations are also carried out to establish their block-error-rate performance. Although both standards share a lot of similarity, simulation results show that they can differ in performance as a result of their subcarrier multiplexing schemes and the variants of OFDMA implemented. © 2010 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

  • Ijaz A, Awoseyila A, Evans BG. (2009) 'Improved SNR Estimation Technique for BPSK and QPSK Signals'. Electronics Letters, 45 (16), pp. 858-859.

    Abstract

    A novel non-data-aided SNR estimation technique for BPSK and QPSK modulations in complex additive white Gaussian noise (AWGN) is proposed. It uses the constant amplitude property of in-phase and quadrature components of these modulations to achieve an improved performance. Its complexity is shown to be lower while its accuracy supersedes the popular moments-based estimator, approaching closely to the Cramer-Rao lower bound.

  • Goulianos AA, Brown TWC, Evans BG, Stavrou S. (2009) 'Wideband Power Modeling and Time Dispersion Analysis for UWB Indoor Off-Body Communications'. IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, 57 (7), pp. 2162-2171.
  • Du HF, Evans BG, Chlamtac I. (2009) 'QoS-AWARE ADAPTATION FOR SATELLITE MULTIMEDIA BROADCASTING VIA HIERARCHICAL PACKET SCHEDULING'. IEEE WIREL COMMUN, 16 (3), pp. 60-68.

    Abstract

    With the unique broadcast nature and ubiquitous coverage of satellite networks, the synergy between satellite and terrestrial networks provides opportunities for delivering wideband services to a wide range of audiences over extensive geographical areas. This article concerns the optimization techniques pertinent to packet scheduling to facilitate multimedia content delivery over the satellite with a return channel via a terrestrial network. We propose a novel hierarchical packet scheduling scheme that allocates the resources at different parts of the network in response to network dynamics and link variations while under the system power/resource constraints. Simulations prove that the HPS scheme can effectively improve the end-to-end performance and resource utilization with desirable scalability and fairness features.

  • Awoseyila AB, Kasparis C, Evans BG. (2009) 'Robust Time-domain Timing and Frequency Synchronization for OFDM Systems'. IEEE T CONSUM ELECTR, 55 (2), pp. 391-399.

    Abstract

    A robust and efficient technique for frame/symbol timing and carrier frequency synchronization in OFDM systems is presented. It uses a preamble consisting of only one training symbol with two identical parts to achieve reliable timing and frequency accuracy in the time-domain, over a wide-frequency estimation range which can be up to half of the signal sampling frequency. Also, it has a loti, complexity which is adaptive to the degree of channel distortion. Computer simulations in the Rayleigh fading ISI channel show that the proposed method achieves superior performance to existing techniques in terms of timing and frequency accuracy. Also, its operation in the time-domain helps to achieve faster synchronization convergence(1).

  • Du H, Fan L, Evans BG. (2009) 'Efficient packet scheduling for heterogeneous multimedia provisioning over broadband satellite networks: An adaptive multidimensional QoS-based design'. INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, 27 (1), pp. 53-85.
  • Du H, Huang X, Liang J, Liu J, Evans BG, Chlamtac I. (2009) 'Cross-layer quality-driven adaptation for scheduling heterogeneous multimedia over 3G satellite networks'. Wireless Networks, 16 (4), pp. 1-14.

    Abstract

    Wireless networks are experiencing a paradigm shift from focusing on the traditional data transfer to accommodating the rapidly increasing multimedia traffic. Hence, their scheduling algorithms have to concern not only network-oriented quality-of-service (QoS) profiles, but also application-oriented QoS targets. This is particularly challenging for satellite multimedia networks that lack fast closed-loop power control and reliable feedbacks. In this paper, we present a cross-layer packet scheduling scheme, namely Hybrid Queuing and Reception Adaptation (HQRA), which performs joint adaptations by considering the traffic information and QoS targets from the applications, the queuing dynamics induced from the network, as well as the end-to-end performance and channel variations from respective users. By jointly optimizing multiple performance criteria at different layers, the scheme enjoys quality-driven, channel-dependant, and network-aware features. HQRA can well accommodate return link diversity and the imperfect feedbacks, whilst ensuring robustness in highly heterogeneous and dynamic satellite environments. We evaluate its performance over diverse network and media configurations in comparison with the state-of-the-art solutions. We observe noticeable performance gains on application-oriented QoS, bandwidth utilization, and objective video quality, together with favorable fairness and scalability measures.

  • Fan L, Du H, Mudugamuwa U, Evans BG. (2008) 'A Cross-Layer Delay Differentiation Packet Scheduling Scheme for Multimedia Content Delivery in 3G Satellite Multimedia Systems'. IEEE TRANSACTIONS ON BROADCASTING, 54 (4), pp. 806-815.
  • Awoseyila AB, Kasparis C, Evans BG. (2008) 'Improved Preamble-Aided Timing Estimation for OFDM Systems'. IEEE COMMUNICATIONS LETTERS, 12 (11), pp. 825-827.
  • Kalama M, Acar G, Evans B, Isoard A. (2008) 'VoIP over DVB-RCS satellite systems: Trial results and the impact of adaptive speech coding using cross-layer design'. COMPUTER NETWORKS, 52 (13), pp. 2461-2472.
  • Awoseyila A, Kasparis C, Evans B. (2008) 'Improved single frequency estimation with wide acquisition range'. Electronics Letters, 44 (3), pp. 245-247.

    Abstract

    An improved method for estimating the frequency of a single complex sinusoid in complex additive white Gaussian noise is proposed. The method uses a modified version of the weighted linear predictor to achieve optimal accuracy at low/moderate SNR while retaining its speed and wide acquisition range. Consequently, it has an advantage over known methods that use the weighted phase averager since they suffer from an increased threshold effect at frequencies approaching the full estimation range.

  • Awoseyila AB, Kasparis C, Evans BG. (2008) 'Improved single frequency estimation with wide acquisition range'. ELECTRONICS LETTERS, 44 (3), pp. 245-246.
  • Kasparis C, King P, Evans BG. (2007) 'Doppler spectrum of the multipath fading channel in mobile satellite systems with directional terminal antennas'. IET COMMUNICATIONS, 1 (6), pp. 1089-1094.
  • Du H, Fan L, Mudugamuwa U, Evans BG. (2007) 'A cross-layer packet scheduling scheme for multimedia broadcasting via satellite digital multimedia broadcasting system'. IEEE COMMUNICATIONS MAGAZINE, 45 (8), pp. 94-101.
  • Liang L, Fan L, Du H, Sun Z, Evans BG, Selier C, Chuberre N, Fitch M, Cole M, Boivin T, Bunout E. (2007) 'Network architecture and radio resource management for Satellite Digital Multimedia Broadcast system'. IEEE AEROSPACE AND ELECTRONIC SYSTEMS MAGAZINE, 22 (7), pp. A7-A16.
  • Du H, Fan L, Evans BG. (2007) 'Novel radio resource allocation strategy for multimedia content delivery over satellite multicast/broadcast systems'. COMPUTER COMMUNICATIONS, 30 (8), pp. 1870-1889.
  • Papaharalabos S, Sweeney P, Evans BG, Mathiopoulos PT, Albertazzi G, Vanelli-Coralli A, Corazza GE. (2007) 'Modified sum-product algorithms for decoding low-density parity-check codes'. IET COMMUNICATIONS, 1 (3), pp. 294-300.
  • Kasparis C, Evans BG. (2007) 'Gradient projection decoding of LDPC codes'. IEEE COMMUNICATIONS LETTERS, 11 (3), pp. 279-281.
  • Papaharalabos S, Sweeney P, Evans BG. (2007) 'SISO algorithms based on Max-Log-MAP and Log-MAP turbo decoding'. IET COMMUNICATIONS, 1 (1), pp. 49-54.
  • Sali A, Acar G, Evans BG. (2007) 'A channel-aware scheduler with feedback implosion suppression in reliable multicast data transmission over geostationary satellite networks'. 25th AIAA International Communications Satellite Systems Conference,

    Abstract

    In this paper, we propose a channel-aware scheduling algorithm and feedback implosion suppression (FIS) technique that exploits reported Channel State Information (CSI) through the return link from a subset of users in a multicast group for reliable multicast delivery over a geostationary satellite network. Reliability is guaranteed via a MFTP-like transport protocol that retransmits lost segments to the group. The deployed scheduling mechanism uses CSI collected from group members before making a decision as to whether or not to transmit a data segment in the forward link. As such, the algorithm aims at avoiding unfavourable channel conditions to reduce the forward link resources that would be wasted in retransmission. However, the users' feedback collected from a large pool would result in the feedback implosion problem. Hence, we propose a FIS technique to complement the CSI collection policy to reduce traffic implosion in the return link as well as reducing the probability to transmit unnecessary CSI values. A change detection scheme run at the users' terminal is implemented using rectangular sliding test window to update a smoothed CSI value depending on its discrepancies with a nominal model from a reference window. The scheduling algorithm together with the CSI collection and FIS policies aims to reduce file transfer delay (FTD) by trading off total number of CSI updates in the face of L-band mobile satellite channel conditions. © 2007 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

  • Chai WK, Pavlou G, Evans B. (2007) 'Providing proportional loss differentiation over bandwidth on demand satellite networks'. 25th AIAA International Communications Satellite Systems Conference,

    Abstract

    Next generation Internet requires the capability of providing quality of service (QoS) with service differentiation. Broadband satellite networks as an integral part of the global broadband network infrastructure are moving towards the same goal of providing service differentiation. Due to the unique properties of the space environment, providing service differentiation in satellite networks has additional challenges such as long propagation delay. In this paper, we present an innovative profile-based probabilistic dropping scheme for the provision of relative loss differentiation in a geostationary (GEO) bandwidth on demand (BoD) satellite network which follows the DVB-RCS standard, approved and published by ETSI for interactive broadband satellite network. The network is structured to support a finite number of ordered service classes. We adopt the proportional differentiated service (PDS) model which strikes a balance between the strict QoS guarantee of Integrated Services (IntServ) and softer QoS guarantee of Differentiated Services (DiffServ) to provide proportional loss differentiation to different priority classes. Our scheme controls the loss rates by computing the appropriate packet drop probability based on the congestion level within each satellite terminal (ST) independent of operating condition of other terminals and without requiring a central controller or monitor. Unlike previous proposals designed for terrestrial and wireless networks where the correct differentiation is only achieved locally on per-hop basis (i.e. the queues for different classes must be co-located in a node sharing a common buffer and communication channel), our scheme is able to maintain network-wide proportional loss even though the queues are physically distributed. Additionally, in the design of our solution, we ensure simplicity of the algorithm to minimize overhead incurred in the satellite network and also intra- and inter-node differentiation consistency. We extend the ns-2 simulator with the BoD capability analogous to the DVB-RCS system in which STs first request for resources (i.e. time slots) and only start transmitting packets following the reception of burst time plan (BTP). We implement our loss differentiation algorithm and attach it to each ST. Simulation results show that the scheme is able to achieve the PDS model in a heterogeneous ST environment. Our results also suggest that the predictability property of the PDS model may be violated if the service

  • Awoseyila AB, Kasparis C, Evans BG. (2007) 'Carrier Synchronization for DVB-S2 systems in a Rician mobile environment'. 25th AIAA International Communications Satellite Systems Conference,

    Abstract

    The second generation standard for Digital Video Broadcasting via Satellite (DVB-S2) which was designed for fixed terminals is being considered for the delivery of broadband services to mobile platforms (such as airplanes, ships and trains). In this paper, we investigate the existing frequency synchronization algorithms that were proposed for DVB-S2 fixed terminals, in the specified mobile environment. Based on the simulation results obtained, a new algorithm is proposed to enhance frequency synchronization performance for DVB-S2 in the mobile channel. © 2007 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

  • Awoseyila AB, Kasparis C, Evans BG. (2007) 'Low-complexity frequency estimator for DVB-S2 and burst transmissions at low SNR'. 25th AIAA International Communications Satellite Systems Conference,

    Abstract

    A simple method for frequency estimation of a PSK-modulated carrier in complex additive white Gaussian noise is proposed. Although this feedforward pilot-aided technique is sub-optimal in terms of the Cramer-Rao bound (CRB) for one pilot field, its performance greatly improves (in comparison to some established methods) when used over consecutive pilot fields. At low signal-to-noise ratios (SNR) where there is an inherent use of averaging over consecutive pilot fields to achieve the required estimation accuracy, this method achieves a similar speed and accuracy to Luise and Reggiannini (L&R)'s method for fine frequency recovery but with a significantly lower complexity. It also provides a competitive speed and accuracy for coarse frequency offset estimation without a threshold region as associated with Kay's method. Simulations have been run based on the DVB-S2 standard (with all examined methods benefiting from the averaging over multiple pilot fields) and the results are presented. © 2007 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

  • Acar G, Lattanzi F, Evans B. (2007) 'DVB-RCS mobility management in vehicular satellite networks'. 25th AIAA International Communications Satellite Systems Conference,

    Abstract

    This article focuses on link and network-layer mobility issues in vehicular DVB-RCS satellite networks. The article presents a discussion on these topics before proposing a position-based spotbeam handover mechanism in some detail. The mechanism relies on regular position updates being available at mobile terminals. The NCC is responsible for making spotbeam handover decisions according to handover need information from mobile terminals with the objective to balance the load and maximise the overall utilisation. Particular emphasis has been placed on signalling issues. Backwardcompatible, light-weight, add-on mechanisms are crucial for commercial viability of a mobile DVB-RCS. Similarly, accurate modelling of existing DVB-RCS signalling mechanisms is necessary to attain useful conclusions regarding the performance of new handover mechanisms. The article briefly presents our ns-based DVB-RCS simulator and presents the performance analyses of our spotbeam handover mechanism in terms of failure rate and delay for. © 2007 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

  • Skoutaridis P, Kasparis C, Evans BG. (2007) 'Adaptive coding and modulation for vehicular satellite communications'. 25th AIAA International Communications Satellite Systems Conference,

    Abstract

    This paper presents the findings of an effort to establish the performance of ACM as defined in the DVB-S2 standard, in the context of vehicular satellite communications. The effects of multipath fading as well as rain attenuation and the high round trip delays associated with geostationary satellite systems are discussed. Performance results have been obtained by means of link level simulations. The work has been curried out under the FP6 project MOWGLY whose objective is the design, testing and implementation of a prototype system for broadband satellite communications to aircraft, maritime vessels and high speed trains. © 2007 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

  • Kalama M, Acar G, Evans BG, Mourgues S, Donny C, Planells M. (2007) 'Cross-layer design and assessment of TCP congestion control protocols over future broadband satellite systems'. 25th AIAA International Communications Satellite Systems Conference,

    Abstract

    Adaptation of TCP for satellite links has been the subject of many research studies in the last decade. In many such studies, Performance Enhancing Proxies (PEPs) and modified TCP congestion control algorithms have been reported to considerably improve TCP performance over satellite systems. In parallel to Transport layer developments, Link layer mechanisms as well as satellite hardware design are also evolving, providing more reliable transmission and higher capacity utilisation. Under the new light of these evolutions, this paper presents a simulation campaign, comparing the performance of different TCP variants over a satellite network using PEPs. The second contribution of this paper is the performance assessment of a novel TCP congestion control mechanism based on cross-layer design. Cross-layer adaptation is a relatively new idea in network design, based on the vertical integration of protocol layers. Simulation results for this mechanism demonstrate the strong relationship between the Transport and Link layers and illustrate the benefits of joint analysis and design. © 2007 by University of Surrey.

  • Du H, Fan L, Evans BG. (2007) 'Cross-layer joint priority packet scheduling scheme for multimedia QoS provisioning in satellite broadcast/multicast systems'. 25th AIAA International Communications Satellite Systems Conference,

    Abstract

    The design of efficient radio resource management (RRM) strategy has become a key technique for the next-generation wireless systems to provision multimedia data services at appropriate QoS. In this paper, the authors propose a novel cross-layer joint priority (CLJP) packet scheduling scheme for QoS provisioning of multimedia traffic in satellite broadcast/multicast systems. The scheme considers both the application and transport layers' QoS requirements and RLC layer's queuing status into MAC layer packet scheduling decisions, aiming at guaranteeing diverse QoS demands and achieving efficient resource allocation subject to power/resource constraints. In comparison with existing schemes, the simulation results prove that the proposed scheme achieves better QoS and fairness, and enhances the throughput/channel utilisation. © 2007 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

  • Bousquet M, Castanet L, Vanelli-Coralli AA, Giambene G, Evans B, Corazza GE, Davoli F, Ferro E, Lutz E, Morlet C, Rumeau R, Sheriff R, Donner A. (2007) 'Air interface research activities within SatNEx, the European satellite communications Network of Excellence'. 25th AIAA International Communications Satellite Systems Conference,

    Abstract

    SatNEx has brought together 24 partners from European research organizations and academia to form a pan-European research network. A major objective of SatNEx is to rectify the fragmentation in satellite communications research by bringing together leading European academic research organizations in a durable way. The paper presents the organization of the Network of Excellence and the "Air Interface" research activities. © 2007 by Prof. Michel Bousquet.

  • Papaharalabos S, Sweeney P, Evans BG, Mathiopoulos PT. (2006) 'Improved performance SOVA turbo decoder'. IEE PROCEEDINGS-COMMUNICATIONS, 153 (5), pp. 586-590.
  • Papaharalabos S, Sweeney P, Evans BG. (2006) 'Constant log-MAP decoding algorithm for duo-binary turbo codes'. ELECTRONICS LETTERS, 42 (12), pp. 709-710.
  • Wood L, Pavlou G, Evans B. (2001) 'Effects on TCP of routing strategies in satellite constellations'. March 2001 Edition. IEEE Communications Magazine, 39 (3), pp. 172-181.

    Abstract

    The authors introduce the types of satellite constellation networks, and examine how overall performance of TCP communications carried across such a network can be affected by the choice of routing strategies used within the network.

  • Cruickshank HS, Pan H, Sun Z, Evans BG, Bodin J. (1998) 'THESEUS terminal-access to broadband networks for European stock exchanges'. ELECTRONICS & COMMUNICATION ENGINEERING JOURNAL, 10 (6), pp. 289-296.
  • Sun Z, Ors T, Evans B. (1998) 'ATM-over-satellite demonstration of broadband network interconnection'. COMPUTER COMMUNICATIONS, 21 (12), pp. 1090-1101.
  • Ors T, Sun Z, Evans B. (1997) 'Meshed VSAT satellite network architecture using an on-board ATM switch'. IEEE International Performance, Computing & Communications Conference, Proceedings, , pp. 208-214.

    Abstract

    This paper proposes a meshed Very Small Aperture Terminal (VSAT) satellite communications network which uses an On Board Processing (OBP) satellite with spot beams and cell switching capabilities. A novel approach is used for maximizing the bandwidth utilization of the satellite by performing statistical multiplexing on-board the satellite. MF-TDMA is used as satellite multiple access protocol since it takes advantage of the flexibility and statistical multiplexing capabilities of ATM. Finally, the cell loss resulting from the limited bandwidth of the satellite link can be prevented by effective traffic control functions. A preventive control scheme has been used for this purpose. The Leaky Bucket (or Generic Cell Rate Algorithm) used as Usage Parameter Control (UPC) controls the source traffic parameters for conformance with the traffic contract. Furthermore a rate-based flow control is used to control ABR services. The results of the performance analysis of the proposed system indicate that a high increase in satellite bandwidth utilization can be achieved, compared to circuit-switched satellite systems.

  • Sun Z, Ors T, Cruickshank H, Evans B. (1996) 'Implementation of ATM over satellite for broadband services'. IEEE Colloquium (Digest), (224)

    Abstract

    It has been recognised that satellites can play very important role in supporting B-ISDN services based on ATM technology. There have been several projects to exploit ATM over satellite for broadband services since 1992. These include the European RACE II CATALYST project which developed a satellite ATM demonstrator and the EPSRC project which studied the interconnection of Broadband ATM Islands via satellite. In a broadband network environment, ATM over satellite can be used for inter-network connections as transit link and for terminal access as access link. For transit link a small number of earth stations require a high bit rate link. Static bandwidth reservation based on estimated fixed rates provide a simple solution. However for terminal access a large number of terminals require low bit rate links. Since the traffic is expected to have large fluctuations, a dynamic reservation system is a more efficient but complex solution. Dynamic reservation Time Division Multiple Access (TDMA) appears to be the best solutions, as it takes advantage of the flexibility and statistical multiplexing capabilities of ATM and supports all traffic classes. The paper shows that ATM over satellite can implement a flexible and efficient bandwidth resource management mechanisms which allows the satellite link to be configured to meet the requirements of broadband services from low bit rate to high bit rate. © 1996 The Institution of Electrical Engineers. Printed and published by the IEE.

  • Sun Z, COAKLEY F, Evans B. (1995) 'SATELLITE ATM FOR BROAD-BAND ISDN'. TELECOMMUNICATION SYSTEMS, 4 (1-2), pp. 119-131.
  • Sun Z, Coakley F, Evans B. (1995) 'Implementation of ATM via satellite for B-ISDN'. IEE Conference Publication, (403 /1), pp. 137-142.

    Abstract

    Advance in digital signal processing and telecommunication technologies has lead to the development of ATM and B-ISDN. Satellite communications systems can play an important role in the development of the initial experimental systems and also in the fully developed networks due to their features of flexible wide coverage, independent of ground distances and geographical constrains, multiple access and multipoint broadcast. This paper presents an implementation structure of ATM via satellite and its capabilities of supporting B-ISDN based on a demonstration system developed within the RACE CATALYST project.

  • Sun Z, Komisarczuk P, Coakley F, Evans BG. (1994) 'Traffic management in satellite ATM bridge'. IEE Colloquium (Digest), (78)

    Abstract

    The paper presents the studies of traffic management in the satellite ATM bridge based on RACE II RACE project - CATALYST R2074. The project aims to develop satellite ATM bridge that can support the future B-ISDN services for satellite communications. An ATM bridge can interconnect the ATM network and the existing networks as well as DQDB, FDDI, Ethernet networks. The current interfaces have different bit rates, thus the need to control traffic and manage the resources on the bridge to prevent overload and preserve the quality of the services on the satellite. The satellite ATM bridge will be used in the initial interconnections of B-ISDN islands and the development of B-ISDN for mobile telecommunications and direct broadcast services.

Conference papers

  • Mohamed A, Evans B, Shamsuddeen M. (2018) '5g new radio and fixed satellite services co-existance in mm-wave band'. Ka and Broadband Communications, Navigation and Earth Observation Conference Proceedings of the 24th Ka and Broadband Communication Conference, Niagara Falls, Canada, October 15 - 18, 2018, Niagara Falls, Canada: 24th Ka and Broadband Communication Conference
    [ Status: Accepted ]

    Abstract

    This paper investigates the 28 GHz band sharing between fixed satellite services (FSS) and fifth generation (5G) new radio (NR) cellular system. In particular, it focuses on modelling a sharing scenario between the uplink of the FSS system and the uplink of the 5G NR enhanced mobile broadband (eMBB) cellular system. Such a scenario could generate interference from the FSS terminals towards the 5G base station, known as next generation Node-B (g-NodeB). We provide detailed interference modelling, sharing constraint derivations and performance analysis under realistic path loss models and antenna radiation patterns based on the latest system characteristics of the third generation partnership project (3GPP) 5G NR Release 15. Several scenarios for seamless coexistence of the two systems are considered by evaluating the efficiency and the signal-to-interference-plus-noise ratio (SINR) at the NR g-NodeB, and using the block error rate (BLER) as a sharing constraint. A single FSS terminal is considered and the impact of several parameters, such as the distance to the g-NodeB and FSS elevation angle, on the g-NodeB spectrum efficiency are evaluated. In addition, the impact of the g-NodeB antenna array size on reducing the FSS/g-NodeB protection distance is evaluated and a dynamic beam steering is proposed to minimise the protection distance.

  • Imran MA, Zhang J, Evans B, Zhang X. (2016) 'Green Hybrid Satellite Terrestrial Networks: Fundamental Trade-off Analysis'. Nanjing, China: 2016 IEEE 83rd Vehicular Technology Conference
    [ Status: Accepted ]

    Abstract

    With the worldwide evolution of 4G generation and revolution in the information and communications technology (ICT) field to meet the exponential increase of mobile data traffic in the 2020 era, the hybrid satellite and terrestrial network based on the soft defined features is proposed from a perspective of 5G. In this paper, an end-to-end architecture of hybrid satellite and terrestrial network under the control and user Plane (C/U) split concept is studied and the performances are analysed based on stochastic geometry. The relationship between spectral efficiency (SE) and energy efficiency (EE) is investigated, taking consideration of overhead costs, transmission and circuit power, backhaul of gateway (GW), and density of small cells. Numerical results show that, by optimizing the key parameters, the hybrid satellite and terrestrial network can achieve nearly 90% EE gain with only 3% SE loss in relative dense networks, and achieve both higher EE and SE gain (20% and 5% respectively) in sparse networks toward the future 5G green communication networks.

  • Zhang J, Evans B, Imran MA, Zhang X, Wang W. (2015) 'Performance Analysis of C/U Split Hybrid Satellite Terrestrial Network for 5G Systems'. IEEE 2015 IEEE 20TH INTERNATIONAL WORKSHOP ON COMPUTER AIDED MODELLING AND DESIGN OF COMMUNICATION LINKS AND NETWORKS (CAMAD), Guildford, ENGLAND: IEEE 20th International Workshop on Computer Aided Modelling and Design of Communication Links and Networks (CAMAD), pp. 97-102.
  • Onireti OS, Evans B, Spathopoulos T, Imran MA. (2015) 'THE ROLE OF SATELLITES IN 5G'. France: European Association for Signal Processing (EURASIP) 2015

    Abstract

    The next generation of mobile radio communication systems—so called 5G—will provide some major changes to those generations to date. The ability to cope with huge increases in data traffic at reduced latencies and improved quality of user experience together with major reduction in energy usage are big challenges. In addition future systems will need to embody connections to billions of objects—the so called Internet of Things (IoT) which raise new challenges. Visions of 5G are now available from regions across the World and research is ongoing towards new standards. The consensus is a flatter architecture that adds a dense network of small cells operating in the millimetre wave bands and which are adaptable and software controlled. But what place for satellites in such a vision? The paper examines several potential roles for satellite including coverage extension, content distribution, providing resilience, improved spectrum utilisation and integrated signalling systems.

  • Thompson P, Evans B. (2015) 'Analysis of Interference between Terrestrial and Satellite Systems in the Band 17.7 to 19.7 GHz'. IEEE 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATION WORKSHOP, London, UNITED KINGDOM: IEEE International Conference on Communication Workshop, pp. 1669-1674.
  • Guidotti A, Icolari V, Tarchi D, Vanelli-Coralli A, Sharma SK, Lagunas E, Maleki S, Chatzinotas S, Grotz J, Krause J, Corbel E, Evans B, Thompson P. (2015) 'Spectrum Awareness and Exploitation for Cognitive Radio Satellite Communications'. IEEE 2015 EUROPEAN CONFERENCE ON NETWORKS AND COMMUNICATIONS (EUCNC), Paris, FRANCE: European Conference On Networks And Communications (EuCNC), pp. 16-20.
  • Evans B, Thompson P, Lagunas E, Sharma SK, Tarchi D, Icolari VR. (2015) 'Extending the Usable Ka Band Spectrum for Satellite Communications: The CoRaSat Project'. SPRINGER WIRELESS AND SATELLITE SYSTEMS (WISATS 2015), Univ Bradford, Norcroft Ctr, Bradford, ENGLAND: 7th International Conference on Wireless and Satellite Systems (WiSATS) 154, pp. 119-132.
  • Dimitrov S, Privitera N, Suffritti R, Boccolini G, Awoseyila AB, Evans BG. (2015) 'Spectrally Efficient Waveforms for the Return Link in Satellite Communication Systems'. IEEE 2015 EUROPEAN CONFERENCE ON NETWORKS AND COMMUNICATIONS (EUCNC), Paris, FRANCE: European Conference On Networks And Communications (EuCNC), pp. 6-10.
  • Tang W, Thompson P, Evans B. (2015) 'Frequency Sharing between Satellite and Terrestrial Systems in the Ka Band: A Database Approach'. IEEE 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), London, ENGLAND: IEEE International Conference on Communications (ICC), pp. 867-872.
  • Evans B, Onireti O, Spathopoulos T, Imran M. (2015) 'THE ROLE OF SATELLITES IN 5G'. IEEE 2015 23RD EUROPEAN SIGNAL PROCESSING CONFERENCE (EUSIPCO), Nice, FRANCE: 23rd European Signal Processing Conference (EUSIPCO), pp. 2756-2760.
  • Dimitrov S, Erl S, Barth B, Jaeckel S, Kyrgiazos A, Evans BG. (2015) 'Radio Resource Management Techniques for High Throughput Satellite Communication Systems'. IEEE 2015 EUROPEAN CONFERENCE ON NETWORKS AND COMMUNICATIONS (EUCNC), Paris, FRANCE: European Conference On Networks And Communications (EuCNC), pp. 175-179.
  • Wang N, Gao Y, Evans B. (2015) 'Database-augmented Spectrum Sensing Algorithm for Cognitive Radio'. IEEE 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), London, ENGLAND: IEEE International Conference on Communications (ICC), pp. 7468-7473.
  • Benfatto D, Privitera N, Suffritti R, Awoseyila A, Evans BG, Dimitrov S. (2014) 'On Acquisition and Tracking Methods for SC-FDMA over Satellite'. IEEE 2014 7TH ADVANCED SATELLITE MULTIMEDIA SYSTEMS CONFERENCE AND THE 13TH SIGNAL PROCESSING FOR SPACE COMMUNICATIONS WORKSHOP (ASMS/SPSC), Livorno, ITALY: 7th Advanced Satellite Multimedia Systems Conference / 13th Signal Processing for Space Communications Workshop (ASMS/SPSC), pp. 352-359.
  • Kyrgiazos A, Evans B. (2014) 'Gateway Diversity for Q/V Feeder Links: Requirements, Characteristics, and Challenges'. IEEE 2014 7TH ADVANCED SATELLITE MULTIMEDIA SYSTEMS CONFERENCE AND THE 13TH SIGNAL PROCESSING FOR SPACE COMMUNICATIONS WORKSHOP (ASMS/SPSC), Livorno, ITALY: 7th Advanced Satellite Multimedia Systems Conference / 13th Signal Processing for Space Communications Workshop (ASMS/SPSC), pp. 323-330.
  • Mohamed A, Lopez-Benitez M, Evans B. (2014) 'Ka-band satellite terrestrial coexistence: A statistical modelling approach'. Ka and Broadband Communications, Navigation and Earth Observation Conference Proceedings of 20th Ka and Broadband Communications, Navigations and Earth Observation Conference. Salerno, Italy, Salerno, Italy: 20th Ka and Broadband Communications, Navigations and Earth Observation Conference

    Abstract

    Cognitive radio (CR) is a potentially promising solution to the spectrum crunch problem that faces both future terrestrial and satellite systems. This paper discusses the applicability of CR in satellite/terrestrial spectrum sharing scenarios by modelling interference relations between these systems. It analyses the relative impact of several design parameters that can be tuned in order to reach a particular interference target. A realistic path loss model is considered and gain patterns of directional antennas are taken into account which are found to be efficient in minimising the interference. A generic model that is not restricted to particular systems is developed, and typical parameters are used to analyse the co-existence feasibility in a realistic sharing scenario. The results show that both satellite and terrestrial systems could potentially operate in the same band without degrading each other’s performance if appropriate considerations are taken into account and an appropriate design of the interfering system is carried out.

  • Ng UY, Kyrgiazos A, Evans B. (2014) 'Interference Coordination for the Return Link of a Multibeam Satellite System'. IEEE 2014 7TH ADVANCED SATELLITE MULTIMEDIA SYSTEMS CONFERENCE AND THE 13TH SIGNAL PROCESSING FOR SPACE COMMUNICATIONS WORKSHOP (ASMS/SPSC), Livorno, ITALY: 7th Advanced Satellite Multimedia Systems Conference / 13th Signal Processing for Space Communications Workshop (ASMS/SPSC), pp. 366-373.
  • Sohail A, Al-Imari M, Xiao P, Evans B. (2013) 'Optimum Power Allocation for OFDM Based Cognitive Radio Systems With Arbitrary Input Distributions'. IEEE Dresden, Germany: IEEE VTC2013 Spring
  • Alsedairy T, Imran M, Qi Y, Evans B. (2013) 'Energy-effcient dynamic deployment architecture for future cellular systems'. IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, , pp. 3111-3116.

    Abstract

    There is a need to develop energy-effcient adaptive systems for future telecommunication networks. While traffc varies at different times, the power consumption of the radio access network does not scale with it effectively. To make signif-cant energy savings, a dynamic deployment approach is required to allow the system to operate in an energy-effcient mode with respect to traffc load. By deploying small base stations within the area of a conventional macro station, we are able to reduce energy consumption while maintaining QoS. This paper proposes an energy-effcient dynamic deployment architecture based on fuzzy-logic. The algorithm aids in the decision of the architecture layout deployment. Moreover, by implementing the proposed adaptive energy-effcient algorithm, the network gains fexibility that can increase coverage or throughput throughout the same network by adapting its operation to source its requirements better and change them when new requirements arise. © 2013 IEEE.

  • Sohail A, Al-Imari M, Xiao P, Evans B. (2013) 'Optimum Power Allocation for OFDM Based Cognitive Radio Systems With Arbitrary Input Distributions'. IEEE Dresden, Germany: IEEE 77th Vehicular Technology Conference (VTC), pp. 1-5.

    Abstract

    In the literature, optimal power assuming Gaussian input has been evaluated in OFDM based Cognitive Radio (CR) systems to maximize the capacity of the secondary user while keeping the interference introduced to the primary user band within tolerable range. However, the Gaussian input assumption is not practical and Finite Symbol Alphabet (FSA) input distributions, i.e., M-QAM are used in practical systems. In this paper, we consider the power optimization problem under the condition of FSA inputs as used in practical systems, and derive an optimal power allocation strategy by capitalizing on the relationship between mutual information and minimum mean square error. The proposed scheme is shown to save transmit power in a CR system compared to its conventional counterpart, that assumes Gaussian input. In addition to extra allocated power, i.e., power wastage, the conventional power allocation scheme also causes nulling of more subcarriers, leading to reduced transmission rate, compared to the proposed scheme. The proposed optimal power algorithm is evaluated and compared with the conventional algorithm assuming Gaussian input through simulations. Numerical results reveal that for interference threshold values ranging between 1 mW to 3 mW, the transmit power saving with the proposed algorithm is in the range between 55-75%, 42-62% and 12-28% whereas the rate gain is in the range between 16.8-12.4%, 13-11.8% and 3-5.8% for BPSK, QPSK and 16-QAM inputs, respectively.

  • Sohail A, Al-Imari M, Xiao P, Evans B. (2013) 'Optimal Power Allocation for MIMO-OFDM Based Cognitive Radio Systems with Arbitrary Input Distributions'. IEEE London, UK: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), pp. 1909-1913.

    Abstract

    In Cognitive Radio (CR) systems, the data rate of the Secondary User (SU) can be maximized by optimizing the transmit power, given a threshold for the interference caused to the Primary User (PU). In conventional power optimization algorithms, the Gaussian input distribution is assumed, which is unrealistic, whereas the Finite Symbol Alphabet (FSA) input distribution, (i.e., M-QAM) is more applicable to practical systems. In this paper, we consider the power optimization problem in multiple input multiple output orthogonal frequency division multiplexing based CR systems given FSA inputs, and derive an optimal power allocation scheme by capitalizing on the relationship between mutual information and minimum mean square error. The proposed scheme is shown to save transmit power compared to its conventional counterpart. Furthermore, our proposed scheme achieves higher data rate compared to the Gaussian optimized power due to fewer number of subcarriers being nulled. The proposed optimal power algorithm is evaluated and compared with the conventional power allocation algorithms using Monte Carlo simulations. Numerical results reveal that, for distances between the SU transmitter and the PU receiver ranging between 50m to 100m, the transmit power saving with the proposed algorithm is in the range 13-90%, whereas the rate gain is in the range 5-31% depending on the modulation scheme (i.e., BPSK, QPSK and 16-QAM) used

  • Ijaz A, Awoseyila AB, Evans BG. (2012) 'Carrier recovery and nonlinear compensation for DVB-S2 using multilevel pilots'. 2012 6th Advanced Satellite Multimedia Systems Conference, ASMS 2012 and 12th Signal Processing for Space Communications Workshop, SPSC 2012, , pp. 335-341.

    Abstract

    The current DVB-S2 standard specifies the use of constant energy level pilots for receiver synchronization and equalization algorithms. However, these are unsuitable for APSK modulations due to the nonlinear response of the satellite power amplifier. In this paper, we investigate the performance of two low-complexity techniques for nonlinear compensation in DVB-S2 systems, i.e. static predistortion and cluster based sequence equalizer (CBSE). We also propose how multilevel pilot structures, matched to each technique, can be used for carrier recovery. Simulation results are presented in terms of total degradation wherein both techniques are shown to achieve a significant improvement over the conventional system. © 2012 IEEE.

  • Kyrgiazos A, Evans B, Thompson P, Jeannin N. (2012) 'Gateway diversity scheme for a future broadband satellite system'. 2012 6th Advanced Satellite Multimedia Systems Conference, ASMS 2012 and 12th Signal Processing for Space Communications Workshop, SPSC 2012, , pp. 363-370.

    Abstract

    Future internet demands are being increased dramatically year by year. Terrestrial systems are unable to satisfy these demands in all geographical areas and thus broadband access by satellite is a key service provision platform. Considering the traffic demands, the raw capacity should approach a Terabit/s by 2020 to meet these demands. So the challenge is to reduce the cost/bit and to increase the satellite capacity from today's 10 Gbps to 1 Tbps by 2020. In order to find the available spectrum, the migration to higher bands such as Ka-band, Q/V bands is considered a neccessity. But migrating to these higher bands in order to have access to more available spectrum, we experience severe precipitation attenuation, and the feeder links that carry much more capacity are more vulnerable to these high attenuations. ACM is unable to cope with the precipitation fades in these higher bands, and single site diversity results in an excessive number of extra earth stations which is not cost effective. It is envisaged that future systems may interconnect gateways to allow traffic routing between them, a so called 'Smart Gateway diversity scheme'. This scheme is discussed and potential architectures are proposed. We evaluate the performance of such schemes in terms of their availability. © 2012 IEEE.

  • Sohail A, Xiao P, Evans BG. (2012) 'Optimal power allocation scheme under FSA constraint for OFDM based cognitive radio systems'. International Congress on Ultra Modern Telecommunications and Control Systems and Workshops, , pp. 195-200.

    Abstract

    In the literature, researchers have evaluated optimal power loading algorithms under the Zero Mean Circularly Symmetric Complex Gaussian (ZMCSCG) constraint in OFDM based CR systems. The capacity of the Secondary User (SU) is maximized while keeping the interference introduced to the Primary User (PU) band remains within tolerable range. However the drawback of such an approach is that channel capacity increases with increasing Signal to Noise Ratio (SNR), which is not applicable to a practical scenario. Therefore, we propose an optimal power loading scheme under the Finite Symbol Alphabet (FSA) constraint, (i.e., QPSK, 8-PSK, 16-QAM and 64-QAM, etc.) to achieve realistic system performance especially under the high SNR region. Subsequently, Mutual Information (MI) is derived and compared against channel capacity which reveals that in the low SNR region, they are closely related. Conversely, MI saturates in the high SNR region which indicates maximum achievable data rates for practical systems. We further evaluate channel capacity and MI by varying the interference threshold and our observation is that the saturation value of the achievable SU data rate indicated by MI changes accordingly, but total achievable data rate remains constant. On the other hand, capacity increases with increasing interference threshold. © 2012 IEEE.

  • Ijaz A, Awoseyila AB, Evans BG. (2011) 'Enhanced Channel Estimation for DVB-S2 Systems'. 29th AIAA International Communications Satellite Systems Conference
  • Jalili B, Dianati M, Evans BG. (2011) 'Distributed collaborative radio resource allocation in the downlink of OFDMA systems'. IEEE Vehicular Technology Conference,

    Abstract

    This paper investigates collaboration among neighboring Base Stations (BSs) in OFDMA based cellular networks in the absence of a centralized control unit, which is a defining characteristic of 4G wireless networks. We propose a novel scheme for collaboration between the base stations. Monte Carlo simulation based performance analysis demonstrates effectiveness of collaborative resource allocation among adjacent base stations for OFDMA systems, particularly for the users in the cell edges. © 2011 IEEE.

  • Lutz E, Evans B, Vanelli-Coralli A, De Cola T, Giambene G. (2011) 'SatNEx phase III - Satellite communication network of experts'. Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering: Personal Satellite Services, Malaga, Spain: Third International ICST Conference, PSATS 2011 71, pp. 175-185.

    Abstract

    SatNEx is a European Network of Experts for satellite communications, coordinated by the German Aerospace Center DLR. The first two phases of SatNEx were funded by the EU from 2004 to 2009. The third phase, SatNEx-III, comprises 17 partners and is funded by ESA from 2010 to 2013. A core team consisting of DLR, University of Surrey, and University of Bologna is coordinating the SatNEx-III research activities. Specific research tasks are contracted to partners in the frame of annual “Call-off Orders”.

  • Ekpe UM, Brown TWC, Evans BG. (2011) 'Channel characteristics analysis of the dual circular polarized land mobile satellite MIMO radio channel'. Proceedings - 2011 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications, APWC'11, , pp. 781-784.

    Abstract

    This paper analyses the characteristics of the dual circular polarized land mobile satellite MIMO radio channel using measured and modeled channel data. To describe the small scale fading observed in the measured channel, the model makes use of three parameters, which respectively represent the mean LOS, specular reflected and diffuse multipath signals. The model is validated by comparing the CDF plots of the received signal power and eigenvalues with that of the measured channel. Furthermore, the effects of channel correlation on the capacities of equal power allocation MIMO and dual circular polarization multiplexing (DCPM) is investigated. It is found that only the capacity of the LOS-friendly DCPM is negatively affected by a reduction in channel correlation. © 2011 IEEE.

  • Oredope A, Pham V, Evans B. (2011) 'Deploying IP Multimedia Subsystem (IMS) services in future mobile networks'. 2011 National Conference on Communications, NCC 2011,
  • Evans B, Awoseyila A. (2010) 'LTE and WiMax satellite systems:Improving FEC performance using split multicode transmission'. Cagliari, Italy: ASMS 2010
  • Evans B, Ijaz I, Awoseyila A. (2010) 'Low complexity time domain channel estimation for ofdm using training symbols'. Cagliari, Italy: ASMS 2010
  • Evans BG, Khan A, Imran M. (2010) '\ground based and on board based beamforming for hybrid terrestrial satellite mobile system'. Anahein Ca USA: 28th AIAA International satellite systems conference-ICssc-2010
  • Evans B, Thompson P. (2010) 'Key issues and technologies for a Terabit/s satellite'. Anaheim Ca USA: 28th AIAA International Communications satellite systems conference-ICSSC-2010
  • Evans BG, Khan A, Imran M. (2010) 'Preamble based adaptive beamformer for hybrid terrestrial satellite mobile systems'. Anaheim Ca USA: 28th AIAA international communications satellite systems conference-ICSSC-2010
  • Evans BG, Awoseyila A. (2010) 'Link performance of LTE versus WiMax for satellite mobile broadband'. Anaheim Ca USA: 28th AIAA international Communications satellite systems conference-ICSSC-2010
  • Ijaz A, Awoseyila A, Evans B. (2010) 'SNR estimation for ACM in DVB-RCS satellite systems'. Anaheim Ca USA: 28th AIAA International Communications satellite systems conference-ICSSC-2010
  • Alsedairy T, Imran M. (2010) 'Energy Efficiency with Adaptive Modulation and Spectrum Sharing for Cellular Systems'. Liverpool, UK : 11th Annual Postgraduate Symposium on the Convergence of Telecommunications, Networking & Broadcasting,,
  • Awoseyila A, Evans B. (2010) 'LTE and WiMAX satellite systems: Improving FEC performance using split multicode transmission'. ASMS/SPSC 2010: 2010 5th Advanced Satellite Multimedia Systems Conference and the 11th Signal Processing for Space Communications Workshop, , pp. 94-97.
  • Oredope A, Dianati M, Evans BG, Budhiraja R, Ramamurthi B. (2010) 'Deploying IP Multimedia Subsystem (IMS) Services over Next Generation Networks (NGNs): The IU-ATC Integrated Test Bed.'. Springer TRIDENTCOM, 46, pp. 727-735.
  • Luo H, Ma Y, Evans BG. (2010) 'Selective DF relaying for mobile satellite broadcasting'. IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, , pp. 2410-2414.

    Abstract

    This paper addresses mobile terminal (MT) relaying in order to improve the performance of mobile satellite broadcasting. It considers selective decode-and-forward (SDF) relaying with BICM-OFDM air interface. The BER upper bound was derived for the threshold-based SDF relaying in Rician fading channels. The suboptimal SNR threshold was then obtained by minimising this analytical upper bound. This scheme is compared in simulation with a conventional CRC and set threshold schemes. It is shown that the proposed suboptimal-SNR threshold scheme gives up to 1 dB performance gain compared to the conventional CRC-based scheme in the moderate Eb/No range (i.e., 2 dB < Eb/No < 8 dB). The proposed scheme also significantly outperforms the set threshold schemes (0 dB and 10 dB thresholds). The proposed and CRC-based schemes both offer around 2 dB performance improvement in comparison to the single link for a typical Eb/No of 10 dB. ©2010 IEEE.

  • Zhu M, Awoseyila A, Evans B. (2010) 'Low complexity time-domain channel estimation for OFDM using training symbols'. ASMS/SPSC 2010: 2010 5th Advanced Satellite Multimedia Systems Conference and the 11th Signal Processing for Space Communications Workshop, , pp. 203-207.

    Abstract

    A low complexity time domain channel estimation technique for OFDM systems is proposed. It uses training symbols to estimate the channel impulse responses (CIR) via circular cross-correlation. A CIR search window technique is also proposed to optimise the accuracy of synchronisation and channel estimation. The output of the search window can also be used for the estimation of channel delay spread. Simulation results show that the proposed method provides near-ideal accuracy with a complexity much lower than the MMSE technique. ©2010 IEEE.

  • Zhou J, Evans B. (2010) 'Sub-optimal joint beamforming on MISO cognitive radio'. Proceedings - 2010 2nd UK-India-IDRC International Workshop on Cognitive Wireless Systems, UKIWCWS 2010,

    Abstract

    In this paper, we discuss joint beamforming schemes for the downlink of a multiple input single output coexisting radio system, where both transmitters know all the channel state information. Considering the opportunistic case where both systems have equal rights to access the spectrum, we propose sub-optimal methods for several performance criteria, including sum mean squared error, continuous sum throughout, and discrete sum throughput. Simulation results show that the proposed precoding algorithms achieve the better performance trade-offs between two radio systems and increase the spectrum efficiency at the cost of full channel state information. ©2010 IEEE.

  • Khan A, Imran MA, Evans B. (2010) 'Ground based and onboard based beamforming for hybrid terrestrial-satellite mobile system'. California, USA : 28th AIAA International Communication Satellite Systems Conference (ICSSC 2010),
  • Khan A, Imran MA, Evans B. (2010) 'Preamble based Adaptive Beamformer for Hybrid Terrestrial-Satellite Mobile System'. California, USA : 28th AIAA International Communication Satellite Systems Conference (ICSSC 2010),
  • Evans B, Luo H, Ma Y. (2009) 'A spectral efficient decode and forward relaying scheme for satellite broadcast networks'. IEEE Toulouse: IWSSC
  • Evans BG, Khan A, Imran M. (2009) 'ofdm based adaptive beam forming for hybrid satellite terrestrial mobile systems and pilot re allocation'. IEEE Toulouse: IWSSC
  • Khan AH, Imran MA, Evans BG. (2009) 'OFDM based Adaptive Beamforming for Hybrid Terrestrial-Satellite Mobile System with Pilot Reallocation'. IEEE 2009 INTERNATIONAL WORKSHOP ON SATELLITE AND SPACE COMMUNICATIONS, CONFERENCE PROCEEDINGS, Univ Siena, Siena, ITALY: International Workshop on Satellite and Space Communications, pp. 201-205.
  • Evans B, Aliu O, Imran M. (2009) 'Self organised cellular networks as the future of wireless communications'. IET Liverpool UK: PGNET
  • Makaratat K, Brown TWC, Stavrou S, Evans B. (2009) 'Classification of UWB Multipath Clusters and Its Distortion Effects on Positioning Error'. 2009 3RD EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION, VOLS 1-6, Berlin, GERMANY: , pp. 191-195.

    Abstract

    Quantification of distortion effects on UWB system performances in terms of positioning error is analysed in this research. UWB multipath distorted channels are simulated in each frequency subband, over 2-11 GHz. Its characteristics are modelled corresponding to multipath clusters along the propagation paths. The classification of clusters and physics. based distortion mechanisms are generalized to be included into the simulation algorithm. Finally, distortion impacts on system performances regarding to frequency dependent characteristics and positioning errors are investigated.

  • Khan AH, Imran MA, Evans BG. (2009) 'Adaptive beamforming for OFDM based hybrid mobile satellite system'. IET Conference Publications, (552 CP)

    Abstract

    Global connectivity cannot be guaranteed by terrestrial networks due to the lack of infrastructure in rural areas. Neither can satellite networks assure this due to lack of signal penetration and capacity coverage issues in densely populated areas. To bridge this gap, we propose an Orthogonal Frequency Domain (OFDM) based hybrid architecture where users are provided service by existing mobile networks in urban areas and are served by satellite in the rural areas. In such a system terrestrial and satellite networks can reuse the portion of spectrum dedicated to each of these systems resulting in significant increase in overall capacity, wider coverage and reduced cost. This frequency reuse induces severe Co-Channel Interference (CCI) at the satellite end and our work focuses on its mitigation using OFDM based adaptive beamforming.

  • Makaratat K, Brown TWC, Stavrou S, Evans B. (2009) 'Classification of UWB Multipath Clusters and Its Distortion Effects on Positioning Error'. IEEE 2009 3RD EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION, VOLS 1-6, Berlin, GERMANY: 3rd European Conference on Antennas and Propagation, pp. 169-173.
  • Acar G, Evans B. (2009) 'Integrated vhf-satcom voice communications for air traffic services'. IET Conference Publications, (552 CP)

    Abstract

    This paper studies an integrated VHF-satellite communication network that provides Air Traffic Management (ATM) voice communications in oceanic region and remote regions. Recently, return multicast bearers are introduced in the Inmarsat SwitftBroadBand (SBB) system. These new bearers make it possible allocating a return link time slot to a group of terminals rather than individual terminals. Arbitrating access to these slots is still done within the geostationary satellite network with long propagation delays. In this paper, we propose using a VHF aeronautical ad hoc network to arbitrate return link access among a number of aircrafts that share a single SBB return multicast bearer for voice communication. The rationale behind this proposal is our desire to avoid long geostationary propagation delays during access resolution. The paper describes an integrated VHF-satellite network, proposes an access arbitration protocol, and presents its performance evaluation results.

  • Mansor MF, Brown TWC, Evans BG. (2009) 'A Dual Circularly Polarised Contrawound Quadrifilar Helix Antenna for Land Mobile Satellite MIMO Terminal'. IEEE 2009 3RD EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION, VOLS 1-6, Berlin, GERMANY: 3rd European Conference on Antennas and Propagation, pp. 1021-1025.
  • Mansor MF, Brown TWC, Evans BG. (2009) 'Mutual coupling analysis of a dual circularly polarised contrawound quadrifilar helix antenna (CQHA) in land mobile satellite (LMS) MIMO systems'. IET Conference Publications, (552 CP)

    Abstract

    Analysis of the mutual coupling and its effect on the CQHA performance in LMS MIMO system are investigated and presented in this paper. Due to the complexity of the CQHA structure, the mutual coupling effects were mainly studied using electromagnetic simulation. The effect of the separation spacing between inner and outer QHA on the mutual coupling was investigated by comparing the element isolation of CQHAs with varying outer QHA radius and fixed inner QHA radius. It can be concluded that a minimum separation of 0. 1λ is required for the isolation to be better than 15dB. The distortion of the co-polar and cross-polar radiation patterns of the CQHA due to the mutual coupling are also studied in this paper. Finally, the effect of the mutual coupling on the mean effective gain and polarisation correlation of CQHAs with varying separation spacing between inner and outer QHA were examined and its results showed that the MEG values are very much affected by mutual coupling while the polarisation and angular correlation are largely unaffected.

  • Luo H, Ma Y, Evans BG. (2009) 'A Spectral Efficient Decode-and-Forward Relaying Scheme for Satellite Broadcast Networks'. IEEE 2009 INTERNATIONAL WORKSHOP ON SATELLITE AND SPACE COMMUNICATIONS, CONFERENCE PROCEEDINGS, Univ Siena, Siena, ITALY: International Workshop on Satellite and Space Communications, pp. 252-256.
  • Rosati S, Awoseyila AB, Vanelli-Coralli A, Kasparis C, Corazza GE, Evans BG. (2009) 'Threshold detection analysis for OFDM timing and frequency recovery'. GLOBECOM - IEEE Global Telecommunications Conference,

    Abstract

    Some recently proposed robust methods for timedomain timing and frequency synchronization in OFDM systems incorporate the use of cross-correlation based threshold detection in their timing adjustment and joint time-frequency algorithms. In this paper, we analyze the threshold criterion used and derive its theoretical performance. This translates into a better characterization of these OFDM synchronization algorithms, leading to a closer match between design expectations and practical performance. Computer simulations show a strong agreement between theoretical predictions and numerical results.

  • Ekpe UM, Brown TWC, Evans BG. (2009) 'Unleashing the Polarisation Domain for Land Mobile Satellite MIMO Systems'. IEEE 2009 3RD EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION, VOLS 1-6, Berlin, GERMANY: 3rd European Conference on Antennas and Propagation, pp. 2199-2202.
  • Ekpe UM, Brown TWC, Evans BG. (2009) 'Unleashing the polarisation domain for land mobile satellite MIMO systems'. European Conference on Antennas and Propagation, EuCAP 2009, Proceedings, , pp. 2288-2291.

    Abstract

    This paper introduces the use of Dual Circular Polarisation Multiplexing (DCPM) for land mobile satellite communication (LMS) systems as a simpler alternative to MIMO. The conditions for switching from traditional polarisation-separated MIMO to DCPM are analysed using synthetic data and data obtained from a previous LMS measurement campaign. Metrics used for performance comparison include the channel ergodic capacity, channel correlation, and the channel cross-polar ratio (XPR). DCPM brings with it the benefits of simpler receiver based processing dependent only upon the mobile.

  • Zhu M, Kasparis C, Awoseyila A, Evans BG. (2009) 'Adaptive inter-carrier interference cancellation technique for OFDM systems'. IET Conference Publications, (552 CP)

    Abstract

    Orthogonal Frequency Division Multiplexing (OFDM) systems suffer from Inter-Carrier Interference (ICI) when the receiver is moving at a high velocity. ICI leads to significant system performance degradation and may even cause reception failure. Therefore an efficient ICI cancellation technique is required to achieve reliable reception. We investigate iterative algorithms for ICI cancellation and propose an adaptive approach to further improve system performance.

  • Ekpe UM, Brown TWC, Evans BG. (2009) 'Markov chain analysis for land mobile satellite MIMO channels'. IET Conference Publications, (552 CP)

    Abstract

    In this paper, a Markov chain analysis is performed to uncover the duration statistics of a land mobile satellite system capable of switching between MIMO and Dual Circular Polarisation Multiplexing (DCPM). Capacities have been computed using synthetic and measurement campaign data to show that DCPM is a viable alternative to MIMO and depends on the cross-polar discrimination (XPD) ratio exceeding a certain minimum value.

  • Sali A, Acar G, Evans B, Giambene G. (2009) 'A comparison of multicast adaptive techniques in reliable delivery over GEO satellite networks'. IEEE Vehicular Technology Conference,

    Abstract

    In this paper, we compare two multicast adaptive techniques for reliable data delivery in GEO satellite networks. Specifically, a channel-aware scheduling algorithm is compared with a multicast link adaptation technique, in the face of fluctuating channel conditions in downlink. The aim of the techniques is to maximise system throughput whilst increasing resource utilization. The scheduling technique is implemented within one forward bearer subtype, whereas the link adaptation mechanism considers transmission rates from a list of possible forward bearer subtypes. Simulation results are analysed and it is found that multicast link adaptation technique outperforms channel-aware scheduling algorithm, in terms of reduced session delay and retransmitted number of segments. © 2009 IEEE.

  • Lattanzi F, Acar G, Giambene G, Evans B. (2009) 'Cost-driven optimisation of a vertical handover scheme in DVB-RCS+M networks with terrestrial gap-fillers'. IET Conference Publications, (552 CP)

    Abstract

    Recently, an increasing drive towards wireless networks integration is observed. In the future, terminals are expected to host multi-mode radio interfaces that permit switching to different access technologies according to a host of factors such as topology, mobility and network congestion. This paper investigates the effects of joint satellite-terrestrial resource management on connection-level performance for high-speed trains in mobile DVB-RCS (Digital Video Broadcasting - Return Channel Satellite) systems complemented by terrestrial gap-fillers. In our study, generic terrestrial cellular networks are used to provide temporary backup capacity (vertical handover, roaming) when satellite resources are not available for handover. We developed an analytical model to derive usual network performance statistics such as new connection blocking probability, handover failure probability, and overall resource utilisation. These values are combined with an estimation of the terrestrial resources roaming expense to derive a cumulative cost function which is used to analyse the effectiveness of our probabilistic admission control policy. For each configuration, optimal design parameters are provided that minimise the cost function under a wide range of network conditions.

  • Sali A, Karim HA, Acar G, Evans B. (2009) 'Integrated adaptive approach for reliable multicast transmission over geostationary satellite networks'. 2009 International Conference on Space Science and Communication, IconSpace - Proceedings, , pp. 35-40.

    Abstract

    Multiple retransmission passes, in order to ensure bit-perfect reliability in multicast transmission, results in lower resource utilization and higher session delay. Hence, an integrated adaptive transmission via the use of a cross-layer strategy is proposed in this paper in order to increase forward and return link resource utilization. Specifically, the integration of Channel State Information (CSI) collection policies in the uplink and Channel-Aware Scheduling (CAS) in the downlink is proposed in the face of fluctuating channel conditions observed by multicast terminals. The integration approach can be mathematically represented by suppression error due to the way CSI is collected and suppressed in the return link. Particularly, the suppression error occurs since only a subset of users update their CSI values at any CSI collection instant. In relation to the analytical representation of the suppression error, the performance parameters are then verified via simulation results. From the comparison, it was found that the simulation and analytical results approach agreement at large numbers of terminals. This observation suits the multicast transmission over satellite networks which expect large numbers of terminals over wide coverage. © 2009 IEEE.

  • Quddus AU, Evans BG, Tafazolli R. (2009) 'Blind adaptive multiuser detection for code division multiple access using Cimmino's reflection method'. Proceedings of 6th International Bhurban Conference on Applied Sciences and Technology, IBCAST-2009, 2, pp. 118-120.

    Abstract

    This paper investigates adaptive implementation of the linear minimum mean square error (MMSE) detector in code division multiple access (CDMA). From linear algebra, Cimmino's reflection method is proposed as a possible way of achieving the MMSE solution blindly. Simulation results indicate that the proposed method converges four times faster than the blind least mean squares (LMS) algorithm and has roughly the same convergence performance as the blind recursive least squares (RLS) algorithm. Moreover the proposed algorithm is numerically more stable than the RLS algorithm and also exhibits parallelism for pipelined implementation. © 2009 IEEE.

  • Mansor MF, Brown TWC, Evans BG. (2009) 'A dual circularly polarised contrawound quadrifilar helix antenna for land mobile satellite MIMO terminal'. European Conference on Antennas and Propagation, EuCAP 2009, Proceedings, , pp. 1072-1076.

    Abstract

    A dual circularly polarised Contrawound Quadrifilar Helix Antenna (CQHA) is proposed for land mobile satellite MIMO systems. The CQHA is combination of two QHAs with opposite winding rotation where one is positioned inside of the other. Low return loss and isolation of the CQHA elements is achieved by varying the radius of the outer QHA while the inner QHA is fixed. Preliminary evaluation of its MIMO capability is done by calculating the mean effective gain and analysing the polarisation correlation of each QHA. A deployment configuration of two CQHAs for land mobile satellite /DVB-SH vehicular rooftop antenna is also proposed in this paper. Mean effective gain of the CQHA configuration for a complete azimuth plane is calculated by considering Gaussian Angle of Arrival model for the angular distribution of the incident waves.

  • Shi X, Lutz T, Giannakidis A, Goulianos A, Watts P, Yaici K, Evans B, Kondoz A, Petrou M, Silva SRP, de Silva S. (2008) 'The Guardian Angel Project: Using an unobtrusive Wireless Sensor Network System to Improve Health and Well-being in the 21st Century'. Montpellier, France: NT08, Ninth International Conference on the Science and Application of Nanotubes
  • Lattanzi F, Acar G, Evans B. (2008) 'Predictive reservation based Connection Admission Control for mobile DVB-RCS networks'. Proceedings of 26th AIAA International Communications Satellite Systems Conference, San Diego, USA: 26th AIAA ICSSC

    Abstract

    This paper presents a novel Connection Admission Control (CAC) strategy for vehicular DVB-RCS satellite networks. Using estimations of arriving and departing traffic in each spot-beam our proposal aims to maximize user satisfaction and minimize at the same time resource reservation. Via GPS measurements, terminals periodically estimate their time to handoff and encapsulate mobility information within signaling bursts. Upon reception of a mobility update, the NCC (Network Control Centre) is able to estimate the amount of traffic roaming around the spot-beams as well as the probabilities that active terminals will eventually handoff. As a consequence, the NCC reserves only the necessary amount of resources for handover purposes in each spot-beam in order to minimize the percentage of connections forced to termination. No overhead is introduced for the implementation of our CAC solution as it makes use of the existing DVB-RCS signaling for providing the NCC with the extra mobility parameters driving the admission control module. Through an accurate ns-2 modeling of existing DVB-RCS signaling mechanisms, we demonstrate that our lightweight CAC scheme outperforms static channel reservation schemes in terms of handover failure rate as well as traffic prediction strategies using mobility information in terms of channel utilization.

  • Lattanzi F, Acar G, Evans B. (2008) 'DVB-RCS spotbeam handover using residence time estimations in vehicular satellite networks'. 2008 4th Advanced Satellite Mobile Systems - Proceedings, ASMS 2008, , pp. 235-239.
  • Kalama M, Acar G, Evans BG, Mourgues S. (2008) 'VoIP over DVB-RCS satellite systems: A novel capacity request mechanism for improved voice activity detection'. IEEE 2008 IEEE 67TH VEHICULAR TECHNOLOGY CONFERENCE-SPRING, VOLS 1-7, Marina Bay, SINGAPORE: 67th IEEE Vehicular Technology Conference, pp. 2957-2961.
  • Du H, Evans BG. (2008) 'Adaptive QoS-aware Resource Allocation Scheme for Multimedia Broadcasting over Geostationary Satellite Networks'. IEEE 2008 IEEE INTERNATIONAL SYMPOSIUM ON A WORLD OF WIRELESS, MOBILE AND MULTIMEDIA NETWORKS, VOLS 1 AND 2, Newport Beach, CA: IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks, pp. 709-714.
  • Acar G, Evans BG. (2008) 'Impact of proactive retransmissions on forward TCP throughput over DVB-S/S2 railroad satellite links with power arches'. 2008 4th Advanced Satellite Mobile Systems - Proceedings, ASMS 2008, , pp. 29-32.
  • Janaaththanan S, Kasparis C, Evans BG. (2008) 'Improved adaptation algorithm for LUT-based pre-distorter with noisy training phase in OFDM based satellite system'. 26th AIAA International Communications Satellite Systems Conference, ICSSC,

    Abstract

    An important drawback of employing OFDM-based transmissions over non-linear satellite payloads is its sensitivity to the non-linear response of the on-board Traveling Wave Tube Amplifier (TWTA). Due to the fact that satellite systems are power limited, backing off the TWTA by a significant amount to counteract distortion is not a realistic option. Therefore amplifier linearization techniques need to be employed in order to limit the impact of the nonlinear signal distortions. In this paper, we consider Look Up Table (LUT) based pre-distortion in a 'remote linearization' scenario, i.e. where the pre-distortion sub-system for linearizing the onboard TWTA is located at the gateway's modem. In such a configuration, the training sequence at the output of the amplifier is assumed to be contaminated by AWGN. Simulation results, however, show that a noisy feedback channel heavily degrades the performance of a Secant-based algorithm that is typically used for adapting the LUT [3]. The main objective of this paper is to investigate, a modified Secant-based adaptation algorithms, which retain very low arithmetic complexity, but also provide robustness against noisy training conditions. Simulation results show that simple modifications provide significant improvement both in the link-level performance and in the reduction of out-of-band radiation. Furthermore, the results also demonstrate that the LUT pre-distorter using the modified algorithm is merely sensitive to the length of the training sequence used in the adaptation process. Copyright © 2008 by the American Institute of Aeronautics and Astronautics, Inc.

  • Skoutaridis P, Evans BG. (2008) 'Error rate based SNR estimation in the railway satellite communication environment'. IEEE 2008 IEEE 67TH VEHICULAR TECHNOLOGY CONFERENCE-SPRING, VOLS 1-7, Marina Bay, SINGAPORE: 67th IEEE Vehicular Technology Conference, pp. 994-998.
  • Sali A, Acar G, Evans B, Giambene G. (2008) 'Change detection mechanism in feedback implosion suppression algorithm for reliable transmission of multicast data over geostationary satellite network'. 26th AIAA International Communications Satellite Systems Conference, ICSSC,

    Abstract

    In this paper, we propose a channel change detection mechanism implemented at UE to support feedback implosion suppression algorithm for reliable transmission of multicast data over GEO satellite networks. In this framework, reliability is guaranteed via MFTP that retransmits lost segments to the multicast group. A channel-aware scheduling mechanism is used at the Gateway that behaves like a switch to allow downlink transmissions of MFTP packets. The scheduler uses CSI values collected from group members through the CSI collection policy before making a decision as to whether or not to transmit a multicast packet in the forward link. As such, the scheduling algorithm aims at avoiding unfavorable channel conditions to reduce the forward link resources that would be wasted for retransmissions and to allow downlink transmissions only when users are in good channel condition, in the face of L-band mobile satellite channel conditions. The integration of channel-aware scheduling algorithm and CSI collection policy aims to reduce session duration and traffic volume in the return link by updating only relevant information back to Gateway. In order to achieve this objective, change detection mechanism is proposed. The performance parameters such as change detection rate and downlink resource utilization are analyzed. Two change detection algorithms are compared; it is shown that there is a trade-off in performance, in particular between uplink signalling load and downlink resource utilization. The work presented in this paper is executed within IST SatNEx II (EU IST FP6 - Contract No. 027393), JA2330 "Radio Resource Allocation and Adaptation" activity. Copyright © 2008 by Aduwati Sali.

  • Acar G, Evans B. (2008) 'Packetised voice communications for Air Traffic Services over the INMARSAT Swiftbroadband system'. 26th AIAA International Communications Satellite Systems Conference, ICSSC,

    Abstract

    Forecasted increase in the global air traffic has prompted the EU ANASTASIA Integrated Project that investigates future satellite-based communications, navigation and surveillance technologies in civil air traffic control systems. Within the framework of ANASTASIA, we have investigated the feasibility and the performance of packetised voice communications for Air Traffic Services (ATS) over the existing Inmarsat SwiftBroadband (SBB) system in oceanic and remote regions. The study is particularly motivated by the recent introduction of the forward multicast bearers in the BGAN system within the framework of ESA-sponsored BGAN Extension Programme. We have placed significant emphasis on accuracy while analysing the impact of the existing BGAN RRM&QoS& Packetisation mechanisms on group VoIP communications. This article presents the results of our investigations at system level and performance evaluations at packet level. Copyright © 2008 by the American Institute of Aeronautics and Astronautics, Inc.

  • Lattanzi F, Acar G, Evans B. (2008) 'Performance Study of a Lightweight DVB-RCS Handover Scheme for Vehicular GEO Networks'. IEEE 2008 INTERNATIONAL WORKSHOP ON SATELLITE AND SPACE COMMUNICATIONS, CONFERENCE PROCEEDINGS, ISAE, Toulouse, FRANCE: International Workshop on Satellite and Space Communications, pp. 216-220.
  • Azizan A, Quddus AU, Evans BG. (2008) 'Multipath interference canceller and chip-level equalizer for satellite high speed downlink packet access (S-HSDPA)'. 26th AIAA International Communications Satellite Systems Conference, ICSSC,
  • Sali A, Acar G, Evans B, Giambene G. (2008) 'Channel-Aware Scheduling Algorithms with Channel Prediction for Reliable Multicast Data Transmission over Geostationary Satellite Networks'. IEEE 2008 INTERNATIONAL WORKSHOP ON SATELLITE AND SPACE COMMUNICATIONS, CONFERENCE PROCEEDINGS, ISAE, Toulouse, FRANCE: International Workshop on Satellite and Space Communications, pp. 85-89.
  • Beaudonnet M, Kasparis C, Evans BG. (2008) 'Link between Sum-Product and gradient projection decoding of LDPC codes: An intermediate algorithm'. IEEE 2008 IEEE 67TH VEHICULAR TECHNOLOGY CONFERENCE-SPRING, VOLS 1-7, Marina Bay, SINGAPORE: 67th IEEE Vehicular Technology Conference, pp. 2902-2906.
  • Zhu M, Kasparis C, Evans BG. (2008) 'A comparison study of channel estimation techniques in OFDM based DVB-SH system'. 26th AIAA International Communications Satellite Systems Conference, ICSSC,
  • Azizan A, Quddus AU, Evans B. (2007) 'Chip Level Adaptive Equalization for Satellite High Speed Downlink Packet Access (S-HSDPA)'. Seoul, South Korea: AIAA International Communications Satellite
  • Hariyanto H, Quddus AU, Evans B. (2007) 'On-Board Linear Interference Cancellation Multiuser Detection for Uplink CDMA GEO Satellite Systems'. Seoul, South Korea: AIAA International Communications
  • Sali A, Acar G, Evans B. (2007) 'A cross-layer approach for packet scheduling in reliable multicast data transmission over geostationary satellite networks'. IEEE 2007 IEEE 65TH VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-6, Dublin, IRELAND: 65th IEEE Vehicular Technology Conference, pp. 1395-1399.
  • Sali A, Acar G, Evans B, Giambene G. (2007) 'Feedback implosion suppression algorithm for reliable multicast data transmission over geostationary satellite networks'. IEEE 2007 INTERNATIONAL WORKSHOP ON SATELLITE AND SPACE COMMUNICATIONS, IWSSC '07, CONFERENCE PROCEEDINGS, Univ Salzburg, Salzburg, AUSTRIA: International Workshop on Satellite and Space Communications, pp. 139-144.
  • Du H, Fan L, Evans BG. (2007) 'Combined delay and rate differentiation packet scheduling for multimedia content delivery in satellite broadcast/multicast systems'. IEEE 2007 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, VOLS 1-14, Glasgow, SCOTLAND: IEEE International Conference on Communications (ICC 2007), pp. 4444-4449.
  • Du H, Fan L, Evans BG. (2007) 'Adaptive multi-dimensional QoS-based packet scheduling scheme for multimedia broadcasting over geostationary satellite networks'. IEEE GLOBECOM 2007: 2007 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE, VOLS 1-11, Washington, DC: IEEE Global Telecommunications Conference (GLOBECOM 07), pp. 4613-4618.
  • Janaaththanan S, Kasparis C, Evans BG. (2007) 'Comparison of SC-FDMA and HSUPA in the return-link of evolved S-UMTS architecture'. IEEE 2007 INTERNATIONAL WORKSHOP ON SATELLITE AND SPACE COMMUNICATIONS, IWSSC '07, CONFERENCE PROCEEDINGS, Univ Salzburg, Salzburg, AUSTRIA: International Workshop on Satellite and Space Communications, pp. 56-60.
  • Evans BG, Thompson PT. (2007) 'Aspects of satellite delivered mobile TV (SDMB)'. IEEE 2007 PROCEEDINGS OF THE 16TH IST MOBILE AND WIRELESS COMMUNICATIONS, VOLS 1-3, Budapest, HUNGARY: 16th IST Mobile and Wireless Communications, pp. 1459-1463.
  • Acar G, Skoutaridis P, Kasparis C, Evans B. (2007) 'Position-based DVB-RCS spotbeam handover in vehicular geostationary satellite networks'. IEEE 2007 IEEE 65TH VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-6, Dublin, IRELAND: 65th IEEE Vehicular Technology Conference, pp. 1410-1414.
  • Chipeta M, Karaliopoulos M, Fan L, Evans BG. (2006) 'Integrating packet-level FEC with data carousels for reliable content delivery in satellite broadcast/multicast systems'. WILEY-BLACKWELL INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Siena, ITALY: International Workshop on Satellite and Space Communications 24 (6), pp. 493-520.
  • Mudugamuwa U, Evans BG. (2006) 'Impact of packet-level FEC and existing link level reliability mechanisms to deliver MBMS content over WCDMA mobile satellite systems'. JOHN WILEY & SONS LTD INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, ESA/ESTEC, Noordwijk, NETHERLANDS: Advanced Satellite Mobile System Conference 24 (2), pp. 169-184.
  • Janaaththanan S, Kasparis C, Evans BG. (2006) 'A comparison between OFDM and SC-FDE over wideband satellite downlinks'. Collection of Technical Papers - 24th AIAA International Communications Satellite Systems Conference, ICSSC, 2, pp. 1126-1132.

    Abstract

    Single Carrier Frequency Domain Equalization (SC-FDE), has recently attracted significant interest particularly in the wireless communications literature as an alternative air-interface solution to OFDM. Both SC-FDE and OFDM combat the detrimental effects of the frequency selective channel in a very efficient way; through the use of FFT/IFFT processing and parallel single-tap equalizers for each frequency bin. Despite their strong similarities, the two techniques differ in that in SC-FDE both the FFT and IFFT processing are performed at the receiving end. In the context of satellite communications, where power efficiency is a key objective, this difference translates into a much stronger resilience for SC-FDE to the non-linearity of the on-board High Power Amplifier (HPA). On the other hand the very high Peak-to-Average Power Ratio (PAPR) that characterizes OFDM signals requires employment of predistortion techniques and/or back-off. In this paper simulation results are provided, which show that SC-FDE offers some improvements to conventional OFDM in a S-UMTS downlink.

  • Acar G, Thilakawardana S, Tafazolli R, Evans B. (2006) 'Performance of Multicast File Transfer Protocol (MFTP) over geostationary satellite systems with DAMA uplinks'. Collection of Technical Papers - 24th AIAA International Communications Satellite Systems Conference, ICSSC, 1, pp. 61-74.

    Abstract

    Their inherent broadcasting capabilities over very large geographical areas make satellite systems one of the most effective vehicles for multicast service delivery. Recent advances in spotbeam antennas and high-power platforms further accentuate the suitability of satellite systems as multicasting tools. The focus of this article is reliable multicast service delivery via geostationary satellite systems. Starburst MFTP is a feedback-based multicast transport protocol that is distinct from other such protocols in that it defers the retransmission of lost data until the end of the transmission of the complete data product. In contrast to other multicast transport protocols, MFTP retransmission strategy does not interrupt the fresh data transmission with the retransmissions of older segments. Thanks to this feature, receivers enjoying favourable channel conditions do not suffer from unnecessarily extended transfer delays due to those receivers that experience bad channel conditions. Existing research studies on MFTP's performance over satellite systems assume fixed-capacity satellite uplink channels dedicated to individual clients on the return link. Such fixed-assignment uplink access mechanisms are considered to be too wasteful uses of uplink resources for the sporadic and thin feedback traffic generated by MFTP clients. Indeed, such mechanisms may prematurely limit the scalability of MFTP as the multicast client population size grows. In contrast, the reference satellite system considered in this article employs demand-assignment multiple access (DAMA) with contention-based request signalling on the uplink. DAMA MAC (Medium Access Control) protocols in satellite systems are well-known in the literature for their improved resource utilisation and scalability features. Moreover, DAMA forms the basis for the uplink access mechanisms in prominent satellite networks such as Inmarsat's BGAN (Broadband Global Area Network), and return link specifications such as ETSI DVB-RCS, However, in comparison with fixed-assignment uplink access mechanisms, DAMA protocols may introduce unpredictable delays for MFTP feedback messages on the return link. Collisions among capacity requests on the contention channel, temporary lack of capacity on the reservation channel, and random transmission errors on the uplink are the potential causes of such delays, This article presents the results of a system-level simulation analysis of MFTP over a DAMA GEO satellite system with conten

  • Skoutaridis P, Kasparis C, Evans BG. (2006) 'Simulation of DVB-S2/RCS performance in a vehicular satellite environment'. Collection of Technical Papers - 24th AIAA International Communications Satellite Systems Conference, ICSSC, 2, pp. 1104-1119.

    Abstract

    Currently there is a clear trend towards vehicular satellite systems, which are designed in high frequency bands (Ku/Ka) and support broadband data services. One such system is designed within the European project MOWGLY for broadband services provision within aeronautical, maritime and railroad environments, and which features suitably adapted DVB-S2 and DVB-RCS standards as the basic underlying communications technology. This paper presents simulation results for assessing various aspects of the performance of the DVB-S2/RCS based satellite system in different mobile environments. In particular the effects of different fading mechanisms on the Block Error Rate performance of the system is analyzed through link-level simulations. Additionally, system-level simulation results are provided that apart from complementing the link level simulations include the modeling of propagation impairments such as path loss and rain attenuation that cannot be captured in link level simulations. Copyright © 2006 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

  • Kasparis C, Evans BG. (2006) 'A cross-correlation approach for improved timing estimation in OFDM broadcasting systems'. Collection of Technical Papers - 24th AIAA International Communications Satellite Systems Conference, ICSSC, 2, pp. 1039-1048.

    Abstract

    A computationally simple cross-correlation based approach for improving timing estimation and frame detection performance in OFDM systems is proposed. The new technique requires only one pilot symbol and this can be used further for frequency-offset estimation, by employing standard available techniques. Simulation results show that the proposed approach performs more robustly relative to state-of-the-art autocorrelation based approaches. Copyright © 2006 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

  • Janaaththanan S, Kasparis C, Evans BG. (2006) 'Feasibility study of adaptive LUT-based pre-distorter for OFDM in non-linear satellite downlink channel'. IEEE Proceedings of the 2006 International Workshop on Satellite and Space Communications, Leganes, SPAIN: International Workshop on Satellite and Space Communications, pp. 126-129.
  • Du H, Fan L, Evans BG. (2006) 'Two-level channel multiplexing: A novel radio resource allocation strategy for satellite digital multimedia broadcast system'. IEEE International Conference on Communications, 10, pp. 4445-4450.

    Abstract

    Channel mapping is an important issue in the radio resource allocation scheme for the Satellite Digital Multimedia Broadcast (SDMB) system. Existing single-level channel multiplexing scheme performs well only when the bit rate of logical channel exactly matches the corresponding bit rate of the transport channel. In this paper, a novel 2-level channel multiplexing approach is proposed and developed. It performs channel multiplexing at both transport and physical channels, and applies optimised 2-stage bin-packing algorithm for the channel mapping. The results show that, in comparison with existing channel mapping schemes, our approach can require less number of transport channels, has better usage of the residual capacity on the transport channels, and can improve the total transmission capacity on the logical channels. © 2006 IEEE.

  • Fan L, Du H, Mudugamuwa U, Evans BG. (2006) 'Novel radio resource management strategy for multimedia content delivery in SDMB system'. Collection of Technical Papers - 24th AIAA International Communications Satellite Systems Conference, ICSSC, 2, pp. 1200-1207.

    Abstract

    The design of efficient radio resource management (RRM) is crucial for the multimedia content delivery in the satellite digital multimedia broadcasting (SDMB) system. In this paper, a novel packet scheduling scheme with a new power allocation algorithm has been proposed, and its performance has been evaluated via simulations. In comparison with existing schemes, the proposed strategy achieves significant performance improvement, especially on delay and jitter. Copyright © 2006 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

  • Azizan A, Quddus AU, Evans BG. (2006) 'Link level performance analysis of Satellite High Speed Downlink Packet Access (S-HSDPA)'. Collection of Technical Papers - 24th AIAA International Communications Satellite Systems Conference, ICSSC, 2, pp. 1120-1125.

    Abstract

    We investigate the physical layer performance of HSDPA via GEO satellites for use in S-UMTS and SDMB. The impact of large round trip delay on link adaptation is discussed and link-level results are presented on the performance of HARQ for a variable number of retransmissions and different categories of UE in a rich multipath urban environment with three IMRs. It is shown that the N-channel SAW HARQ protocol can significantly increase the average throughput particularly for 16-QAM but the large round trip delay also requires an increase in the number of parallel HARQ channels resulting in high memory requirements at the UE. Receive antenna diversity with varying degrees of antenna correlation is also investigated as a possible performance enhancing method. The results presented here will help in specifying the physical layer of satellite HSDPA. Copyright © 2006 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

  • Kalama M, Kluth M-P, Mourgues S, Evans B. (2006) 'Cross-layer improvement for TCP Westwood and VoIP over satellite'. IEEE Proceedings of the 2006 International Workshop on Satellite and Space Communications, Leganes, SPAIN: International Workshop on Satellite and Space Communications, pp. 204-208.
  • Sali A, Widiawan A, Thilakawardana S, Tafazolli R, Evans BG. (2005) 'Cross-layer design approach for multicast scheduling over satellite networks'. IEEE 2nd International Symposium on Wireless Communications Systems 2005 (ISWCS 2005), Univ Siena, Siena, ITALY: 2nd International Symposium on Wireless Communications Systems (ISWCS 2005), pp. 701-705.
  • Du HF, Kueh VYH, Evans BG. (2005) 'Advanced radio resource allocation strategies for satellite digital multimedia broadcast (SDMB) system'. IEEE 2nd International Symposium on Wireless Communications Systems 2005 (ISWCS 2005), Univ Siena, Siena, ITALY: 2nd International Symposium on Wireless Communications Systems (ISWCS 2005), pp. 749-753.
  • Papaharalabos S, Sweeney P, Evans BG, Albertazzi G, Vanelli-Coralli A, Corazza GE. (2005) 'Performance evaluation of a modified sum-product decoding algorithm for LDPC codes'. IEEE 2nd International Symposium on Wireless Communications Systems 2005 (ISWCS 2005), Univ Siena, Siena, ITALY: 2nd International Symposium on Wireless Communications Systems (ISWCS 2005), pp. 800-804.
  • Chipeta M, Fan L, Evans BG, Karaliopoulos M. (2005) 'Integration of small and large packet-level FEC codes with data carousels for reliable multicast transport over satellite links'. IEEE 2nd International Symposium on Wireless Communications Systems 2005 (ISWCS 2005), Univ Siena, Siena, ITALY: 2nd International Symposium on Wireless Communications Systems (ISWCS 2005), pp. 812-816.
  • Wood L, Pavlou G, Evans B. (2001) 'Managing diversity with handover to provide classes of service in satellite constellation networks'. Toulouse, France: AIAA 19th International Communication Satellite Systems Conference (ICSSC 01)

    Abstract

    The rosette satellite constellation network with intersatellite links (ISLs) presents unique properties, in providing locally separate ascending and descending network surfaces of interconnected satellites with which the ground terminal can communicate. We present a novel approach exploiting this rosette geometry, by use of control of handover and management of satellite diversity, to determine which surface a ground terminal will select for communication.

  • Chotikapong Y, Cruickshank HS, Sun Z, Evans BG. (2000) 'Network architecture and performance evaluation of broadband satellite systems'. IEEE INTERNATIONAL CONFERENCE ON NETWORKS 2000 (ICON 2000), PROCEEDINGS, NATL UNIV SINGAPORE, SINGAPORE, SINGAPORE: 8th IEEE International Conference on Networks (ICON 2000), pp. 488-488.
  • Sun Z, Cheng B, Cruickshank HS, Evans BG. (2000) 'BISANTE - Traffic evaluation tool for broadband satellite networks'. COLLECTION OF THE 18TH AIAA INTERNATIONAL COMMUNICATIONS SATELLITE SYSTEMS CONFERENCE AND EXHIBIT, TECHNICAL PAPERS, VOLS 1 AND 2, OAKLAND, CA: 18th AIAA International Communications Satellite Systems Conference and Exhibit, pp. 1090-1097.
  • Chotikapong Y, Sun Z, Ors Z, Evans BG. (2000) 'Network architecture and performance evaluation of TCP/IP and ATM over satellite'. COLLECTION OF THE 18TH AIAA INTERNATIONAL COMMUNICATIONS SATELLITE SYSTEMS CONFERENCE AND EXHIBIT, TECHNICAL PAPERS, VOLS 1 AND 2, OAKLAND, CA: 18th AIAA International Communications Satellite Systems Conference and Exhibit, pp. 747-754.
  • Ors T, Sun Z, Evans BG. (1998) 'Analysis of an adaptive random/reservation MAC protocol for ATM over satellite'. 48TH IEEE VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-3, OTTAWA, CANADA: 48th IEEE Vehicular Technology Conference (VTC 98), pp. 1523-1527.
  • Ors T, Sun Z, Evans BG. (1998) 'Analysis of a MAC protocol to guarantee QoS for ATM over satellite'. ICC 98 - 1998 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS VOLS 1-3, ATLANTA, GA: IEEE International Conference on Communications, pp. 1420-1424.
  • Ors T, Sun Z, Evans BG. (1998) 'A MAC protocol for ATM over satellite'. SIXTH IEE CONFERENCE ON TELECOMMUNICATIONS, HERIOT WATT UNIV, EDINBURGH CONFERENCE CTR, EDINBURGH, SCOTLAND: 6th IEE Conference on Telecommunications (451), pp. 185-189.
  • Ors T, Sun Z, Evans BG, Hadjitheodosiou M. (1997) 'ATM over VSAT networks using traditional bent-pipe or on-board processing satellites'. ATM NETWORKS - PERFORMANCE AND ANALYSIS, VOL. 3, ILKLEY, ENGLAND: 4th IFIP Workshop on Performance Modelling and Evaluation of ATM Networks, pp. 321-340.
  • Sun Z, KOMISARCZUK P, COAKLEY F, Evans BG. (1994) 'MODELLING THE SATELLITE BRIDGE FOR B-ISDN ISLANDS'. BROADBAND ISLANDS '94 - CONNECTING WITH THE END-USER, HAMBURG, GERMANY: 3rd International Conference on Broadband Islands - Connecting with the End-User, pp. 211-219.

Book chapters

  • Dimitrov S, Erl S, Barth B, Suffritti R, Privitera N, Boccolini G, Awoseyila A, Kyrgiazos A, Evans B, Jaeckel S, others . (2015) 'Capacity Enhancing Techniques for High Throughput Satellite Communications'. in Pillai P, Hu YF, Otung I, Giambene G (eds.) Wireless and Satellite Systems Springer International Publishing 154, pp. 77-91.

Patents

  • Awoseyila AB, Evans BG, Kasparis C. (2011) Frame timing and carrier frequency recovery for frequency selective signals. Europe: Article number 09711657.8

    Abstract

    The present invention relates to digital receivers in a frequency-selective (wideband) channel and in particular to frame/symbol timing and carrier frequency synchronization in the reception of orthogonal frequency-division multiplexing (OFDM) signals. The present invention provides a method of synchronizing a receiver to a received signal, wherein the signal includes a training symbol having two identical parts, the method including determining a degree of autocorrelation between parts of the signal at the spacing of the two identical parts, and a degree of cross-correlation between parts of the received signal and a reference copy of the training symbol, and multiplying together the autocorrelation and crosscorrelation to determine at least one of the timing and the frequency of the received signal. This may be achieved by multiplying the cross-correlation and autocorrelation directly, or by multiplying a function, which may be referred to as a timing metric, of one of them with the other, or my multiplying functions of both of them together.

  • Evans BG, Awoseyila A. (2009) IMproved ofdm demodulation/synchronisation. EU:

Reports

  • Evans BG, Thompson P, Awoseyila A, Kasparis C. (2009) ETSI-SES TR 102 662-Advanced satellite based services and architectures for beyond 3G.

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