Chuan Heng Foh

Dr Chuan Heng Foh


Senior Lecturer

Biography

Biography

Chuan Heng Foh received his M.Sc. degree from Monash University, Australia in 1999 and Ph.D. degree from the University of Melbourne, Australia in 2002. After his PhD, he spent 6 months as a Lecturer at Monash University in Australia. In December 2002, he joined Nanyang Technological University, Singapore as an Assistant Professor until 2012. He is now a Senior Lecturer at the University of Surrey. His research interests include protocol design and performance analysis of various computer networks including wireless local area and mesh networks, mobile ad hoc and sensor networks, 5G networks, and data center networks.

He has authored or co-authored over 100 refereed papers in international journals and conferences. He actively participates in IEEE conference and workshop organization, including the International Workshop on Cloud Computing Systems, Networks, and Applications (CCSNA) where he is a steering member. He is an Associate Editor for IEEE Access, IEEE Wireless Communications, International Journal of Communications Systems, and a Guest Editor for various International Journals. Currently, he is the Vice-Chair (Europe/Africa) of IEEE Technical Committee on Green Communications and Computing (TCGCC) and the Chair of Special Interest Group on Green Data Center and Cloud Computing under TCGCC. He is a senior member of IEEE.

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My publications

Publications

Qureshi J, Foh CH, Cai J (2010) An efficient network coding based retransmission algorithm for wireless multicast, IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC
Retransmission based on packet acknowledgement (ACK/NAK) is a fundamental error control technique employed in IEEE 802.11-2007 unicast network. However the 802.11-2007 standard falls short of proposing a reliable MAC-level recovery protocol for multicast frames. In this paper we propose a latency and bandwidth efficient coding algorithm based on the principles of network coding for retransmitting lost packets in a single-hop wireless multicast network and demonstrate its effectiveness over previously proposed network coding based retransmission algorithms. ©2009 IEEE.
Fang S, Yu Y, Foh CH, Aung KMM (2013) A loss-free multipathing solution for data center network using software-defined networking approach, IEEE Transactions on Magnetics 49 (6) pp. 2723-2730
Conventional Ethernet protocols struggle to meet the scalability and performance requirements of data centers. Viable replacements have been proposed for data center ethernet (DCE): link-layer Multipathing (MP) is deployed to replace spanning tree protocol (STP) and thus improve network throughput; end-to-end link-layer congestion control (CC) is proposed to better guarantee loss-free frame delivery for Ethernet. However, little work has been done to incorporate MP and CC to offer a more comprehensive solution for DCE. In this paper, we propose a two-tier solution by integrating our dynamic load balancing Multipath (DLBMP) scheme with CC. Instead of using two separate parameters, i.e., path load and buffer level, to trigger MP and CC, our solution only needs to monitor path load metric to manage MP and CC in an integrated way. Different from a single CC mechanism, which generates congestion notifications from network core, our integrated CC can make use of link load information in access switches which directly inform sources to control their traffic admission. To minimize overhead and accelerate update, SDN techniques are employed in our implementation, which decouples routing intelligence from data transmission. Hence, data sources can react more rapidly to congestion and network can be guaranteed with loss-free delivery. In addition, our MP scheme is further improved by introducing application-layer flow differentiation. With such a fine flow differentiation (FFD) mechanism, traffic can be more evenly distributed along multipaths, resulting in better bandwidth utilization. Simulation results show that our combined solution can further improve network throughput with FFD mechanism and guarantee loss-free delivery with integrated CC. © 1965-2012 IEEE.
Yu Y, Aung KMM, Tong EKK, Foh CH (2010) Dynamic load balancing multipathing in data center ethernet, Proceedings - 18th Annual IEEE/ACM International Symposium on Modeling, Analysis and Simulation of Computer and Telecommunication Systems, MASCOTS 2010 pp. 403-406
Currently implemented Spanning Tree Protocol (STP) cannot meet the requirement of a data center due to its poor bandwidth utilization and lack of multipathing capability. In this paper, we propose a layer-2 multipathing solution, namely dynamic load balancing multipathing (DLBMP), for data center Ethernets. With DLBMP, traffic between two communication nodes can be spread among multiple paths. The traffic load of all paths is continuously monitored so that traffic split to each path can be dynamically adjusted. In addition, per-flow forwarding is preserved to guarantee in-order frame delivery. Computer simulations show that DLBMP gives much better performance as compared to STP due to its multipathing and dynamic load balancing capability. © 2010 IEEE.
Li J, Andrew LLH, Foh CH, Zukerman M, Neuts MF (2006) Meeting connectivity requirements in a wireless multihop network, IEEE Communications Letters 10 (1) pp. 19-21
This paper investigates the connectivity probability of 1-dimensional ad hoc networks in which nodes have random, non-identically distributed locations, this leads to optimization of the number of nodes required. An empirical approach is used. We fit a parametric distribution to the CDF of the maximum distance between adjacent nodes. Special and extreme cases which are not covered by the empirical approach are treated separately. © 2006 IEEE.
Zhang K, Fu CP, Foh CH, Ode M, Zhang JL (2008) Fluid-based modeling of TCP veno, GLOBECOM - IEEE Global Telecommunications Conference pp. 5075-5079
This paper makes use of the fluid-based approach to model the throughput of TCP Veno flow over wired/wireless networks. A generalized formula is derived between Veno's throughput and its window evolution parameters, packet loss rate and round-trip time. Simulation experiments and real network measurements are conducted to validate the accuracy of this model. © 2008 IEEE.
Lu H, Foh CH, Wen Y, Cai J (2012) Optimizing content retrieval delay for LT-based distributed cloud storage systems, GLOBECOM - IEEE Global Telecommunications Conference pp. 1920-1925
Among different setups of cloud storage systems, fountain-codes based distributed cloud storage system provides reliable online storage solution through placing coded content fragments into multiple storage nodes. Luby Transform (LT) code is one of the popular fountain codes for storage systems due to its efficient recovery. However, to ensure high success decoding of fountain codes based storage, retrieval of additional fragments is required, and this requirement introduces additional delay, which is critical for content retrieval or downloading applications. In this paper, we show that multiple-stage retrieval of fragments is effective to reduce the content-retrieval delay. We first develop a delay model for various multiple-stage retrieval schemes applicable to our considered system. With the developed model, we study optimal retrieval schemes given the success decodability requirement. Our numerical results demonstrate that the content-retrieval delay can be significantly reduced by optimally scheduling packet requests in a multi-stage fashion. © 2012 IEEE.
Liu G, Wong KJ, Lee BS, Seet BC, Foh CH, Zhu L (2003) PATCH: A novel local recovery mechanism for mobile ad-hoc networks, IEEE Vehicular Technology Conference 58 (5) pp. 2995-2999
On-demand routing protocol is an important category of the current ad-hoc routing protocols, in which a route between a communicating node pair is discovered only on demand. However, due to the dynamic and mobile nature of the nodes, intermediate nodes in the route tend to lose connection with each other during the communication process. When this occurs, an end-to-end route discovery is typically performed to establish a new connection for the communication. Such route repair mechanism causes high control overhead and long packet delay. In this paper, we propose a Proximity Approach To Connection Healing (PATCH) local recovery mechanism, which aims to reduce the control overhead and achieve fast recovery when route breakage happens. It is shown that PATCH is simple, robust and effective. We present simulation results to illustrate the performance benefits of using PATCH mechanism.
Yang M, Fu J, Lu Y, Cai J, Foh CH (2014) An adaptive multi-layer low-latency transmission scheme for H.264 based screen sharing system, Proceedings - IEEE International Symposium on Circuits and Systems pp. 2153-2156
Virtual screen system is becoming an essential part in the mobile cloud computing platform. However, designing a low-latency interactive communication for the high-resolution screen content is still challenging due to the network dynamics and the unique characteristics of screen content. In this paper we propose a H.264 based low-latency screen sharing system. To achieve high play-out frame rate, we decouple the low-latency screen content communication problem into two parts, a scalable H.264 based encoding and an optimal scalable stream transmission scheduling. By leveraging the unique characteristics of screen content, a multi-layer scalable video encoding scheme is designed to achieve a certain error resilience while keeping good video coding efficiency. In the transmission scheduling module, an optimal frame skipping policy is proposed to schedule the frames in the buffer to maximize the play-out frame rate. In the performance evaluation, we simulate our system in both one-hop end-to-end topology and two-hop proxy-based topology. The simulation results show that the proposed scheme achieves much better performance on frame rate and average delay, especially in the low bandwidth condition. © 2014 IEEE.
Zhang Q, Foh CH, Seet BC, Fong ACM (2010) Applying spring-relaxation technique in cellular network localization, IEEE Wireless Communications and Networking Conference, WCNC
This paper presents a simple solution suitable for the mandatory localization function for E-911 services specified by FCC. Our solution introduces zero-length spring technique to compute the estimated location based on received signal strength (RSS). The introduced zero-length spring concept permits a less detailed path loss model to use without significant impact to the location estimation. We show the stability of our algorithm by illustrating the convergence of the estimated locations computed by the algorithm. We then demonstrate with simulation the accuracy of the estimation with various settings, and compare this accuracy with two candidate localization techniques. ©2010 IEEE.
Foh CH, Cai J, Qureshi J (2010) Collision codes: Decoding superimposed BPSK modulated wireless transmissions, 2010 7th IEEE Consumer Communications and Networking Conference, CCNC 2010
The introduction of physical layer network coding gives rise to the concept of turning a collision of transmissions on a wireless channel useful. In the idea of physical layer network coding, two synchronized simultaneous packet transmissions are carefully encoded such that the superimposed transmission can be decoded to produce a packet which is identical to the bitwise binary sum of the two transmitted packets. This paper explores the decoding of superimposed transmission resulted by multiple synchronized simultaneous transmissions. We devise a coding scheme that achieves the identification of individual transmission from the synchronized superimposed transmission. A mathematical proof for the existence of such a coding scheme is given. ©2010 IEEE.
Lu H, Lu F, Cai J, Foh CH (2013) LT-W: Improving LT Decoding With Wiedemann Solver, IEEE TRANSACTIONS ON INFORMATION THEORY 59 (12) pp. 7887-7897 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Lu X, Zhang K, Foh CH, Fu CP (2014) SSthreshless Start: A Sender-Side TCP Intelligence for Long Fat Network,
Measurement shows that 85% of TCP flows in the internet are short-lived flows
that stay most of their operation in the TCP startup phase. However, many
previous studies indicate that the traditional TCP Slow Start algorithm does
not perform well, especially in long fat networks. Two obvious problems are
known to impact the Slow Start performance, which are the blind initial setting
of the Slow Start threshold and the aggressive increase of the probing rate
during the startup phase regardless of the buffer sizes along the path. Current
efforts focusing on tuning the Slow Start threshold and/or probing rate during
the startup phase have not been considered very effective, which has prompted
an investigation with a different approach. In this paper, we present a novel
TCP startup method, called threshold-less slow start or SSthreshless Start,
which does not need the Slow Start threshold to operate. Instead, SSthreshless
Start uses the backlog status at bottleneck buffer to adaptively adjust probing
rate which allows better seizing of the available bandwidth. Comparing to the
traditional and other major modified startup methods, our simulation results
show that SSthreshless Start achieves significant performance improvement
during the startup phase. Moreover, SSthreshless Start scales well with a wide
range of buffer size, propagation delay and network bandwidth. Besides, it
shows excellent friendliness when operating simultaneously with the currently
popular TCP NewReno connections.
Fang S, Yu Y, Foh CH, Aung KMM (2012) A loss-free multipathing solution for data center network using software-defined networking approach, 2012 Digest APMRC - Asia-Pacific Magnetic Recording Conference: A Strong Tradition. An Exciting New Look!
Conventional Ethernet protocols struggle to meet the scalability and performance requirements of data centers. Viable replacements have been proposed for Data Center Ethernet (DCE): link-layer multipathing (MP) is deployed to replace Spanning Tree Protocol (STP) and thus improves network throughput; end-to-end link-layer congestion control (CC) is proposed to better guarantee loss-free frame delivery for Ethernet. However, little work has been done to incorporate MP and CC to offer a more comprehensive solution for DCE. In this paper, we propose a two-tier solution by integrating our Dynamic Load Balancing MultiPath (DLBMP) scheme with CC. Instead of using two separate parameters, i.e. path load and buffer level, to trigger MP and CC, our solution only needs to monitor path load metric to manage MP and CC in an integrated way. Different from a pure CC mechanism, which generates notifications from network core, our integrated CC can make use of link load information in edge switches which directly inform sources to control traffic admission. To minimize overhead and accelerate update, Software-Defined Networking (SDN) techniques are employed in our implementation, which decouples routing intelligence from data transmission. Hence, data sources can react more rapidly to congestions and network can be guaranteed with loss-free delivery. In addition, our MP scheme is further improved by introducing application-layer flow differentiation. With such a fine flow differentiation (FFD) mechanism, traffic can be more evenly distributed along multipaths, resulting in better bandwidth utilization. Simulation results show that our combined solution can further improve network throughput with FFD mechanism and guarantee loss-free delivery with integrated CC. © 2012 DSI.
Tran Q, Tantra JW, Foh CH, Tan AH, Yow KC, Qiu D (2006) Wireless indoor positioning system with enhanced nearest neighbors in signal space algorithm, IEEE Vehicular Technology Conference pp. 2355-2359
With the rapid development and wide deployment of wireless Local Area Networks (WLANs), WLAN-based positioning system employing signal-strength-based technique has become an attractive solution for location estimation in indoor environment. In recent years, a number of such systems has been presented, and most of the systems use the common Nearest Neighbor in Signal Space (NNSS) algorithm. In this paper, we propose an enhancement to the NNSS algorithm. We analyze the enhancement to show its effectiveness. The performance of the enhanced NNSS algorithm is evaluated with different values of the parameters. Based on the performance evaluation and analysis, we recommend some guidelines on optimizing the parameters of our proposed enhanced algorithm. © 2006 IEEE.
Zhang L, Gao D, Foh CH, Yang D, Gao S (2014) A survey of abnormal traffic information detection and transmission mechanisms in VSNs, International Journal of Distributed Sensor Networks 2014
With the continuously increasing number of vehicles, particularly in cities, there are more and more abnormal traffic events occurring on road, which easily cause road congestion. In vehicular sensor networks (VSNs), with the intervehicle cooperative communication, vehicle nodes can detect the abnormal traffic events and disseminate the related information to the interesting vehicles or persons. This paper gives out a survey of the abnormal traffic information detection and transmission mechanisms in VSNs. Firstly, we overview the origin, characteristic, and application of VSNs. Meanwhile, the definition and features of traffic abnormal information are also introduced and presented. Then, we put more energy on elaborating the existing information detection and transmission mechanisms based on VSNs. Finally, the challenges and problems are discussed. © 2014 Lingjuan Zhang et al.
Banerjee A, Foh CH, Yeo CK, Lee B-S (2012) Performance improvements for network-wide broadcast with instantaneous network information., J. Network and Computer Applications 35 3 pp. 1162-1174
Li J, Andrew LL, Foh CH, Zukerman M, Chen HH (2009) Connectivity, coverage and placement in wireless sensor networks., Sensors (Basel) 9 (10) pp. 7664-7693
Wireless communication between sensors allows the formation of flexible sensor networks, which can be deployed rapidly over wide or inaccessible areas. However, the need to gather data from all sensors in the network imposes constraints on the distances between sensors. This survey describes the state of the art in techniques for determining the minimum density and optimal locations of relay nodes and ordinary sensors to ensure connectivity, subject to various degrees of uncertainty in the locations of the nodes.
Foh CH, Tantra JW (2007) Comments on the paper 'Analysis of collision probabilities for saturated IEEE 802.11 MAC protocol', Electronics Letters 43 (10)
The present authors would like to point out that the observation where the channel collision probability depends on whether the channel was busy or idle discussed by Kuan and Dimyati has been reported earlier by the present authors, Foh and Tantra. © The Institution of Engineering and Technology 2007.
Fang S, Li H, Foh CH, Wen Y, Aung KMM (2012) Energy optimizations for data center network: Formulation and its solution, GLOBECOM - IEEE Global Telecommunications Conference pp. 3256-3261
Data center consumes increasing amount of power nowadays, together with expanding number of data centers and upgrading data center scale, its power consumption becomes a knotty issue. While main efforts of this research focus on server and storage power reduction, network devices as part of the key components of data centers, also contribute to the overall power consumption as data centers expand. In this paper, we address this problem with two perspectives. First, in a macro level, we attempt to reduce redundant energy usage incurred by network redundancies for load balancing. Second, in the micro level, we design algorithm to limit port rate in order to reduce unnecessary power consumption. Given the guidelines we obtained from problem formulation, we propose a solution based on greedy approach with integration of network traffic and minimization of switch link rate. We also present results from a simulation-based performance evaluation which shows that expected power saving is achieved with tolerable delay. © 2012 IEEE.
Foh CH, Zhang Y, Ni Z, Cai J, Ngan KN (2007) Optimized cross-layer design for scalable video transmission over the IEEE 802.11e networks, IEEE Transactions on Circuits and Systems for Video Technology 17 (12) pp. 1665-1678
A cross-layer design for optimizing 3D wavelet scalable video transmission over the IEEE 802.11e networks is proposed. A thorough study on the behavior of the IEEE 802.11e protocol is conducted. Based on our findings, all timescales rate control is developed featuring a unique property of soft capacity support for multimedia delivery. The design consists of a macro timescale and a micro timescale rate control schemes residing at the application layer and the network sublayer respectively. The macro rate control uses bandwidth estimation to achieve optimal bit allocation with minimum distortion. The micro rate control employs an adaptive mapping of packets from video classifications to appropriate network priorities which preemptively drops less important video packets to maximize the transmission protection to the important video packets. The performance is investigated by simulations highlighting advantages of our cross-layer design. Copyright © 2007 IEEE.
Zhu W, Gao D, Foh CH (2015) An Efficient Prediction-Based Data Forwarding Strategy in Vehicular Ad Hoc Network, INTERNATIONAL JOURNAL OF DISTRIBUTED SENSOR NETWORKS ARTN 128725 HINDAWI PUBLISHING CORPORATION
Wu J, Foh CH, Siew CK, Zukerman M (2013) Recurrent Leaky Bucket, IEEE SIGNAL PROCESSING LETTERS 20 (12) pp. 1244-1248 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Tantra JW, Foh CH, Mnaouer AB (2005) Throughput and delay analysis of the IEEE 802.11e EDCA saturation, IEEE International Conference on Communications 5 pp. 3450-3454
In this paper, we introduce a simple model for the enhanced distributed channel access (EDCA) mechanism under saturation condition. This model captures the operation of the AIFS and contention window differentiation of the EDCA mechanism. Using this model, we analyze the throughput and delay performance of EDCA. The results of our analytical model are then verified using simulations. © 2005 IEEE.
Shi H, Arumugam RV, Foh CH, Khaing KK (2013) Optimal disk storage allocation for multitier storage system, IEEE Transactions on Magnetics 49 (6) pp. 2603-2609
The current storage system is facing the bottleneck of performance due to the gap between fast CPU computing speed and the slow response time of hard disk. Recently a multitier hybrid storage system (MTHS) which uses fast flash devices like a solid-state drive (SSD) as the one of the high performance storage tiers has been proposed to boost the storage system performance. In order to maintain the overall performance of the MTHS, optimal disk storage assignment has to be designed so that the data migrated to the high performance tier like SSD is the optimal set of data. In this paper we proposed a optimal data allocation algorithm for disk storage in MTHS. The data allocation problem (DAP) is to find the optimal lists of data files for each storage tier in the MTHS to achieve maximal benefit values without exceeding the available size of each tier. We formulate the DAP as a special multiple choice knapsack problem (MCKP) and propose the multiple-stage dynamic programming (MDP) to find the optimal solutions. The results show that the MDP can achieve improvements up to 6 times compared with the existing greedy algorithms. © 1965-2012 IEEE.
Foh CH, Zukerman M (2000) CSMA with reservations by interruptions (CSMA/RI): a novel approach to reduce collisions in CSMA/CD., IEEE Journal on Selected Areas in Communications 18 9 pp. 1572-1580
Lu H, Cai J, Foh CH (2010) Joint unequal loss protection and LT coding for layer-coded media delivery, GLOBECOM - IEEE Global Telecommunications Conference
Rateless codes such as LT codes have become more and more popular due to their abilities to handle varying channel conditions without much feedback. However, rateless codes have the drawback of unable to provide intermediate outputs when delivering layer-coded media content. Although some methods have been proposed to produce intermediate outputs based on adjusting the distribution of LT codes, they are typically content-dependent and unable to guarantee that a more important layer can always be decoded before the decoding of a less important layer. In this paper, we propose a simple joint unequal loss protection (ULP) and LT coding (ULP-LT) scheme for layered media delivery, where different numbers of FEC are allocated to different layers to guarantee the priority and LT codes are used to deal with varying channel conditions. Simulation results show that with a small amount of overhead allocated to ULP, the ULP-LT scheme can produce good intermediate performance while still enjoying the nice features provided by LT codes. ©2010 IEEE.
Guo T, Cai J, Foh CH, Zhang Y (2008) Improving Videophone Transmission over Multi-Rate IEEE 802.11e Networks., ICC pp. 3258-3262 IEEE
Xia W, Wen Y, Foh CH, Niyato D, Xie H (2015) A Survey on Software-Defined Networking, IEEE Communications Surveys and Tutorials 17 (1) pp. 27-51
© 1998-2012 IEEE.Emerging mega-trends (e.g., mobile, social, cloud, and big data) in information and communication technologies (ICT) are commanding new challenges to future Internet, for which ubiquitous accessibility, high bandwidth, and dynamic management are crucial. However, traditional approaches based on manual configuration of proprietary devices are cumbersome and error-prone, and they cannot fully utilize the capability of physical network infrastructure. Recently, software-defined networking (SDN) has been touted as one of the most promising solutions for future Internet. SDN is characterized by its two distinguished features, including decoupling the control plane from the data plane and providing programmability for network application development. As a result, SDN is positioned to provide more efficient configuration, better performance, and higher flexibility to accommodate innovative network designs. This paper surveys latest developments in this active research area of SDN. We first present a generally accepted definition for SDN with the aforementioned two characteristic features and potential benefits of SDN. We then dwell on its three-layer architecture, including an infrastructure layer, a control layer, and an application layer, and substantiate each layer with existing research efforts and its related research areas. We follow that with an overview of the de facto SDN implementation (i.e., OpenFlow). Finally, we conclude this survey paper with some suggested open research challenges.
Banerjee A, Foh CH, Yeo CK, Lee BS (2011) Multi-rate broadcasting: Analysis and design of stateless algorithms, IEEE Vehicular Technology Conference
We look at the problem of network wide broadcast using the multi-rate feature of a wireless ad hoc network. Existing research has primarily focused on achieving minimum latency by construction of minimum weight connected dominating sets (WCDS) based on neighbourhood information. In this paper, we are interested in stateless multi-rate broadcasting algorithms in which nodes determine their broadcasting behaviour based on neighbourhood transmissions. The primary contribution of this paper is that we show how broadcast effectiveness at different data rates are related and how this relationship can be used to optimize algorithm design. We propose three stateless broadcasting algorithms and demonstrate the performance improvements achievable. Our simulation results show that significant benefits can be obtained in terms of minimizing both the number of forwarding nodes as well as the broadcast latency. © 2011 IEEE.
Gao D, Cai J, Foh CH, Lau CT, Ngan KN (2008) Improving WLAN VoIP capacity through service differentiation, IEEE Transactions on Vehicular Technology 57 (1) pp. 465-474
Voice over Internet protocol (VoIP) is one of the most important applications for IEEE 802.11 wireless local area networks (WLANs). For network planners who deploy VoIP over WLANs, one of the important issues is the VoIP capacity. Directly implementing VoIP over infrastructure WLANs will create the bottleneck problem at the access point (AP). In this paper, we propose the use of the service differentiation provided by the new IEEE 802.11e standard to solve the bottleneck problem and improve voice capacity. In particular, we propose the allocation of a higher priority access category (AC) to the AP while allocating lower priority AC to mobile stations. We develop a simple Markov chain model, which considers the important enhanced distributed channel access (EDCA) parameters and the channel errors under saturation and nonsaturation conditions. Based on the developed analytical model, we analyze the performance of VoIP over EDCA. By appropriately selecting the EDCA parameters, we are able to differentiate the services for the downlink and uplink. The experimental results are very promising. With the adjustment of only one EDCA parameter, we improve the VoIP capacity by 20%-30%. © 2008 IEEE.
Foh CH, Zhang Y, Ni Z, Cai J (2007) Scalable Video Transmission over the IEEE 802.11e Networks Using Cross-Layer Rate Control., ICC pp. 1760-1765 IEEE
Foh CH, Lee BS (2004) A closed form network connectivity formula for one-dimensional MANETs, IEEE International Conference on Communications 6 pp. 3739-3742
In this paper, a closed form network connectivity formula for a one-dimensional Mobile Ad hoc Network (MANET) is developed. Precisely, we derive the probability that a MANET is fully connected given a certain number of nodes randomly and uniformly placed along a path between a source and destination pair. This formula is particularly useful in the process of design and deployment of a MANET. The formula also provides a critical constraint function to the problem of network optimization. It formulates the relationship between the number of mobile nodes required for a particular MANET given a desired network connectivity probability. An approximation is employed to achieve the final closed form expression. The approximation is then tested by simulation to show the accuracy of our formula under practical network conditions.
Duan J, Gao D, Yang D, Foh CH, Chen HH (2014) An energy-aware trust derivation scheme with game theoretic approach in wireless sensor networks for IoT applications, IEEE Internet of Things Journal 1 (1) pp. 58-69
© 2014 IEEE.Trust evaluation plays an important role in securing wireless sensor networks (WSNs), which is one of the most popular network technologies for the Internet of Things (IoT). The efficiency of the trust evaluation process is largely governed by the trust derivation, as it dominates the overhead in the process, and performance of WSNs is particularly sensitive to overhead due to the limited bandwidth and power. This paper proposes an energy-aware trust derivation scheme using game theoretic approach, which manages overhead while maintaining adequate security of WSNs. A risk strategy model is first presented to stimulate WSN nodes' cooperation. Then, a game theoretic approach is applied to the trust derivation process to reduce the overhead of the process. We show with the help of simulations that our trust derivation scheme can achieve both intended security and high efficiency suitable for WSN-based IoT networks.
Foh CH, Zukerman M (2000) Improving the Efficiency of CSMA using Reservations by Interruptions., ICC (1) pp. 144-148
Banerjee A, Foh CH, Yeo CK, Lee BS (2010) A network lifetime aware cooperative MAC scheme for 802.11b wireless networks, 2010 7th IEEE Consumer Communications and Networking Conference, CCNC 2010
Cooperative communication techniques have earlier been applied to design of the IEEE 802.11 medium access control (MAC) and shown to perform better. High rate stations can help relay packets from low-rate stations resulting in better throughput for the entire network. However, this also involves additional energy costs on the part of the relay which can result in reducing the network lifetime. We propose a cooperative MAC protocol NetCoop with the objective of maximizing the network lifetime and achieving high throughput. Based on this design, we also propose a flexible strategy which allows cooperation to be achieved using more than one relay. We show that this can achieve at least as good throughput as that of single relay cooperation while maintaining a high network lifetime. ©2010 IEEE.
Foh CH, Wei L, He B, Cai J (2015) Towards Efficient Resource Allocation for Heterogeneous Workloads in IaaS Clouds, IEEE Transactions on Cloud Computing. IEEE
Infrastructure-as-a-service (IaaS) cloud technology has attracted much attention from users who have demands on large
amounts of computing resources. Current IaaS clouds provision resources in terms of virtual machines (VMs) with homogeneous
resource configurations where different types of resources in VMs have similar share of the capacity in a physical machine (PM).
However, most user jobs demand different amounts for different resources. For instance, high-performance-computing jobs require
more CPU cores while big data processing applications require more memory. The existing homogeneous resource allocation
mechanisms cause resource starvation where dominant resources are starved while non-dominant resources are wasted. To overcome
this issue, we propose a heterogeneous resource allocation approach, called skewness-avoidance multi-resource allocation (SAMR), to
allocate resource according to diversified requirements on different types of resources. Our solution includes a VM allocation algorithm
to ensure heterogeneous workloads are allocated appropriately to avoid skewed resource utilization in PMs, and a model-based
approach to estimate the appropriate number of active PMs to operate SAMR. We show relatively low complexity for our modelbased
approach for practical operation and accurate estimation. Extensive simulation results show the effectiveness of SAMR and the
performance advantages over its counterparts.
Qureshi J, Cai J, Foh CH (2011) Cooperative Retransmissions through Collisions., ICC pp. 1-5 IEEE
Zhang J, Seet B-C, Lie T-T, Foh CH (2013) Opportunities for Software-Defined Networking in Smart Grid, 2013 9TH INTERNATIONAL CONFERENCE ON INFORMATION, COMMUNICATIONS AND SIGNAL PROCESSING (ICICS) IEEE
Foh CH, Tantra JW (2005) Comments on IEEE 802.11 saturation throughput analysis with freezing of backoff counters., IEEE Communications Letters 9 2 pp. 130-132
Duan J, Gao D, Foh CH, Zhang H (2013) TC-BAC: A trust and centrality degree based access control model in wireless sensor networks, Ad Hoc Networks 11 (8) pp. 2675-2692
Access control is one of the major security concerns for wireless sensor networks. However, applying conventional access control models that rely on the central Certificate Authority and sophisticated cryptographic algorithms to wireless sensor networks poses new challenges as wireless sensor networks are highly distributed and resource-constrained. In this paper, a distributed and fine-grained access control model based on the trust and centrality degree is proposed (TC-BAC). Our design uses the combination of trust and risk to grant access control. To meet the security requirements of an access control system with the absence of Certificate Authority, a distributed trust mechanism is developed to allow access of a trusted node to a network. Then, centrality degree is used to assess the risk factor of a node and award the access, which can reduce the risk ratio of the access control scheme and provide a certain protection level. Finally, our design also takes multi-domain access control into account and solves this problem by utilizing a mapping mechanism and group access policies. We show with simulation that TC-BAC can achieve both the intended level of security and high efficiency suitable for wireless sensor networks. © 2013 Elsevier B.V. All rights reserved.
Banerjee A, Tantra JW, Foh CH, Yeo CK, Lee BS (2010) A service/device differentiation scheme for contention-tone-based wireless LAN protocol, IEEE Transactions on Vehicular Technology 59 (8) pp. 3872-3885
A contention-tone-based wireless local area network (WLAN) protocol uses out-of-band signaling for contention resolution to achieve efficient medium access. It is shown that such a protocol can operate at near-optimal channel utilization in the medium access control (MAC) layer. This paper addresses the service differentiation design aspect of a contention-tone-based WLAN protocol. In particular, service and device differentiation schemes are proposed to fulfill a particular quality of service (QoS) for data packet transmissions for contention-tone-based WLANs. Our analysis shows that our design not only provides bandwidth differentiation that matches that specified in the IEEE 802.11e standard but operates at near-optimal channel utilization as well. Our design also incorporates device differentiation to eliminate the access-point bottleneck problem in WLANs. Analytical and simulation results confirm the performance advantages of our design. © 2006 IEEE.
Foh CH, Zukerman M, Tantra JW (2007) A markovian framework for performance evaluation of IEEE 802.11, IEEE Transactions on Wireless Communications 6 (4) pp. 1276-1285
A new approach for modeling and performance analysis of the IEEE 802.11 medium access control (MAC) protocol is presented. The approach is based on the so-called system approximation technique, where the protocol service time distribution of the IEEE 802.11 MAC protocol is studied and approximated by an appropriate phase-type distribution, leading to the construction of a versatile queueing model which is amenable to analysis and, at the same time, general enough to allow for bursty arrival process as well as key statistical characteristics of the protocol operations. The versatility of the model is demonstrated by considering Markov modulated and on/off arrival processes as well as various data frame size distributions. The accuracy of the analytical results is verified by simulation. © 2007 IEEE.
Mnaouer AB, Foh CH, Chen L (2011) A Generic Polymorphic Unicast Routing Protocol for vehicular ad hoc networks, Wireless Communications and Mobile Computing
In this work, we present a new generic polymorphic routing protocol tailored for vehicular ad hoc networks (VANETs). Similar to the case of mobile ad hoc networks, the routing task in VANETs comes under various constraints that can be environmental, operational, or performance based. The proposed Polymorphic Unicast Routing Protocol (PURP) uses the concept of polymorphic routing as a means to describe dynamic, multi-behavioral, multi-stimuli, adaptive, and hybrid routing, that is applicable in various contexts, which empowers the protocol with great flexibility in coping with the timely requirements of the routing tasks. Polymorphic routing protocols, in general, are equipped with multi-operational modes (e.g., grades of proactive, reactive, and semi-proactive), and they are expected to tune in to the right mode of operation depending on the current conditions (e.g., battery residue, vicinity density, traffic intensity, mobility level of the mobile node, and other user-defined conditions). The objective is commonly maximizing and/or improving certain metrics such as maximizing battery life, reducing communication delays, improving deliverability, and so on. We give a detailed description and analysis of the PURP protocol. Through comparative simulations, we show its superiority in performance to its peers and demonstrate its suitability for routing in VANETs. © 2011 John Wiley & Sons, Ltd.
Zhang CL, Fu CP, Yap M-T, Foh CH, Wong KK, Lau CT, Lai MK (2004) Dynamics comparison of TCP Veno and Reno., GLOBECOM pp. 1329-1333 IEEE
Foh CH, Andrew LLH, Wong E, Zukerman M (2004) FULL-RCMA: a high utilization EPON., IEEE Journal on Selected Areas in Communications 22 8 pp. 1514-1524
Foh CH, Zukerman M (2001) Performance evaluation of IEEE 802.11, IEEE Vehicular Technology Conference 2 (53ND) pp. 841-845
This paper analyzes the performance of IEEE 802.11 MAC protocol under a disaster scenario. The performance is measured in terms of the recovery time and the throughput of the protocol when a network disaster occurs. To make the problem amenable to analysis, some approximations are used, and a new technique to collapse a very large state space is introduced. The analytical results are found to agree with simulations.
Gao D, Foh CH, Seet B-C, Yang OWW (2015) Wireless Vehicular Sensor and Ad Hoc Networks 2015, INTERNATIONAL JOURNAL OF DISTRIBUTED SENSOR NETWORKS ARTN 257146 HINDAWI PUBLISHING CORPORATION
Tantra JW, Foh CH, Tinnirello I, Bianchi G (2007) Out-of-band signaling scheme for high speed wireless LANs, IEEE Transactions on Wireless Communications 6 (9) pp. 3256-3267
In recent years, the physical layer data rate provided by 802.11 Wireless LANs has dramatically increased thanks to significant advances in the modulation and coding techniques employed. However, previous studies show that the 802.11 MAC operation, namely the Distributed Coordination Function (DCF), represents a limiting factor: the throughput efficiency drops as the channel bit rate increases, and a throughput upper limit does indeed exist when the channel bit rate goes to infinite high. These findings indicate that the performance of the DCF protocol will not be efficiently improved by merely increasing the channel bit rate. This paper shows that the DCF performance may significantly benefit from the adoption of two separate physical carriers: one devised to manage the channel access contention, and another devised to deliver information data. We propose a scheme, referred to as Out-of-Band Signaling (OBS), designed to reuse (and remain backward compatible with) the existing 802.11 medium access control (MAC) specification. Performance evaluation of OBS is carried out through analytical techniques validated via extensive simulation, for both saturation and statistical traffic conditions. Numerical results show that OBS improves the throughput/delay performance, and provides better bandwidth usage compared with the in-band signaling technique employed by DCF. © 2007 IEEE.
Zhang K, Fu CP, Man Z, Foh CH (2007) Queue dynamics analysis of TCP Veno with RED, IEEE Wireless Communications and Networking Conference, WCNC pp. 3027-3031
In this paper, we aim to study the queue dynamics of TCP Veno with RED in the wired-wireless heterogeneous networks. We first develop a fluid-flow model of TCP Veno with RED over heterogeneous network, and then use the classical linear feedback control theory to analyze it. Analysis results reveal the relationship between the RED queue oscillation and the network parameters. We use simulation tool to validate our analysis, and show how to stabilize the router queue and improve the co-existence of TCP Veno with TFRC. © 2007 IEEE.
Fang S, Kanagavelu R, Lee BS, Foh CH, Aung KMM (2013) Power-efficient virtual machine placement and migration in data centers, Proceedings - 2013 IEEE International Conference on Green Computing and Communications and IEEE Internet of Things and IEEE Cyber, Physical and Social Computing, GreenCom-iThings-CPSCom 2013 pp. 1408-1413
In this paper, we propose a power-efficient solution for virtual machine placement and migration in a fat tree data center network. This solution reduces power consumption as well as job delay by aggregating virtual machines to a few hyper visors and migrating communicating parties to close locations. In this work, we consider OpenFlow as the implementation protocol. In an OpenFlow environment, a centralized controller oversees job loads, virtual machine requirements and hardware availability. Given observation of such global knowledge, the OpenFlow controller can schedule jobs and distribute virtual machines accordingly. As jobs change and flows shift, the OpenFlow controller dynamically adjusts virtual machine assignments by aggregating virtual machines to close locations in order to save energy. With this placement and migration proposal, more jobs can operate concurrently with close sources and destinations of flows, thus both job and flow delay can be reduced. © 2013 IEEE.
Korki M, Hosseinzadeh N, Vu HL, Moazzeni T, Foh CH (2011) A channel model for power line communication in the smart grid, 2011 IEEE/PES Power Systems Conference and Exposition, PSCE 2011
Although Power Line Communication (PLC) is not a new technology, its use to support communication with low rate on low voltage (LV) distribution networks is still the focus of ongoing research. In this paper, we propose a PLC channel modeling method based on the bottom-up approach for LV PLC in a narrow, low frequency band between 9 kHz and 490 kHz. We employ the model to derive the transfer function of a typical LV PLC network, which is comprised of two common cable types (copper cables and aluminum conductor steel reinforced). We then investigate the multipath effect of the LV PLC in the studied low frequency bandwidth using numerical computations. Our simulation results based on the proposed channel model show an acceptable performance between neighboring nodes, in terms of bit error rate versus signal to noise ratio, which enables communication required for smart grid applications. Furthermore, we show that data transmission beyond one-hop communication in LV PLC networks will have to rely on upper layer protocols. © 2011 IEEE.
Mnaouer AB, Chen L, Foh CH, Tantra JW (2007) OPHMR: An optimized polymorphic hybrid multicast routing protocol for MANET, IEEE Transactions on Mobile Computing 6 (5) pp. 503-514
We propose in this paper an optimized, polymorphic, hybrid multicast routing protocol for MANET. This new polymorphic protocol attempts to benefit from the high efficiency of proactive behavior (in terms of quicker response to transmission requests) and the limited network traffic overhead of the reactive behavior, while being power, mobility, and vicinity-density (in terms of number of neighbor nodes per specified area around a mobile node) aware. The proposed protocol is based on the principle of adaptability and multibehavbral modes of operations. It is able to change behavior in different situations in order to improve certain metrics like maximizing battery life, reducing communication delays, improving deliverability, etc. The protocol is augmented by an optimization scheme, adapted from the one proposed for the Optimized Link State Routing protocol (OLSR) in which only selected neighbor nodes propagate control packets to reduce the amount of control overhead. Extensive simulations and comparison to peer protocols demonstrated the effectiveness of the proposed protocol in improving performance and in extending battery power longevity. © 2007 IEEE.
Gao D, Chen P, Foh CH, Niu Y (2011) Hop-distance relationship analysis with quasi-UDG model for node localization in wireless sensor networks., EURASIP J. Wireless Comm. and Networking 2011 pp. 99-99
Foh CH, Zukerman M (2002) A Novel and Simple MAC Protocol for High Speed Passive Optical LANs., NETWORKING 2345 pp. 467-478 Springer
Foh CH, Zukerman M (2001) Performance comparison of CSMA/RI and CSMA/CD with BEB., ICC pp. 2670-2675 IEEE
Foh CH, Tantra JW, Cai J, Lau CT, Fu CP (2007) Modeling hop length distributions for reactive routing protocols in one dimensional MANETs, IEEE International Conference on Communications pp. 3882-3886
In mobile ad hoc networks (MANETs), packets hop from a source to a series of forwarding nodes until they reach the desired destination. Defining the hop length to be the distance between two adjacent forwarding nodes, we observe that the two adjacent forwarding nodes tend to be farther away from each other with a higher probability in a one-dimensional MANET. We derive the probability density functions for the hop lengths to confirm our observation. Applying the developed results, we further formulate the relationship between the mean number of hops and the distance between the source and the destination. © 2007 IEEE.
Lu H, Foh CH, Cai J (2012) Scalable data dissemination protocol for wireless sensor networks, IEEE International Conference on Networks, ICON pp. 471-476
Opportunistic wireless transmission is a technique offering collaboration of simultaneous flows to achieve error resilient transmissions. In this paper, we introduce the use of opportunistic wireless transmission for data diffusion which deals with the all-to-all data dissemination in a wireless sensor network. Our design turns the network infrastructure into a single fountain encoder where source packets arrive from each sensor node and these packets are encoded while flooding throughout the entire network to all nodes. Simulation and analysis are carried out showing that our proposed opportunistic data diffusion achieves efficient and error resilient all-to-all data dissemination. The results confirm that our solution offers not only efficient and reliable all-to-all data dissemination over lossy wireless links, but also scalability to large networks. © 2012 IEEE.
Fang S, Foh CH, Mi K, Aung M (2010) Differentiated ethernet congestion management for prioritized traffic, IEEE International Conference on Communications
This paper proposes and studies a differentiated congestion control for Ethernet congestion management. Following the popular approach that uses a cooperation of an Additive Increase and Multiplicative Decrease (AIMD) based rate limiter and Explicit Congestion Notification (ECN) active queue management to combat the congestion in Ethernet, the proposal considers differentiated AIMD settings for rate limiters to achieve congestion control differentiation for traffic of different priorities. We illustrate that while the operation of AIMD and ECN are independent, by using different AIMD settings, we can achieve differentiated control of bandwidth utilization. We provide an analysis and its numerical results showing the effectiveness of this method. Our proposed method is also implemented in OMNET++ simulator with results showing the effectiveness of bandwidth ratio differentiation. ©2010 IEEE.
Qureshi J, Foh CH, Cai J (2013) Primer and Recent Developments on Fountain Codes, CoRR abs/1305.0918
Yu Y, Fang S, Aung KMM, Foh CH, Li H, Zhu Y (2014) A layer 2 multipath solution and its performance evaluation for data center ethernets, International Journal of Communication Systems 27 (11) pp. 2555-2576
© 2013 John Wiley & Sons, Ltd.Data Center Ethernet is likely to be deployed as the communication infrastructure for future data centers, which carries multiple types of traffic with very different characteristics and handling requirements. Conventional Spanning Tree Protocol (STP) cannot meet the requirement of a Data Center Ethernet framework because of its poor bandwidth utilization and lack of multipathing capability. In this paper, we propose a layer 2 multipathing solution, namely optimized dynamic load-balancing multipathing (ODLBMP), to be deployed in Data Center Ethernet. Our proposed method utilizes all available links and ports for frame delivery and can split traffic of a communication pair along multiple paths. In ODLBMP, the traffic loads of all paths are continuously monitored so that traffic assigned to each path can be dynamically adjusted to avoid path/link over-utilization. Per-flow forwarding is observed in ODLBMP to guarantee the in-order delivery, which is important for most storage traffic. In addition, ODLBMP finely differentiates flows from application perspective so it has more flexibility in traffic splitting and route selection, and achieves better multipath load balancing. Computer simulations show that our proposed algorithm performs better than other compared algorithms, including STP, Transparent Interconnection of Lots of Links, and DLBMP, in all simulation scenarios in terms of frame delivery ratio and network throughput.
Tantra JW, Foh CH, Lee BS (2003) An efficient scheduling scheme for high speed IEEE 802.11 WLANs, IEEE Vehicular Technology Conference 58 (4) pp. 2589-2593
The emergence of high speed WLANs, such as the IEEE 802.1 la and IEEE 802.11g, has provided an alternative solution for mobile users to access a network in addition to the popular IEEE 802.11b solution. Although the channel data rate of those emerging high speed WLANs is five times higher than that of 802.11b, some recent studies have shown that the throughput of IEEE 802.11 drops as the channel data rate increases, and the throughput upper limit do exist when the channel data rate goes to infinite high. These findings indicate that the performance of a WLAN will not be efficiently improved by merely increasing the channel data rate. In this paper, we propose a new protocol scheme that makes use of an out-of-band signaling (OBS) technique. The proposed scheme provides better bandwidth usage compared to the in-band signaling technique in the existing scheme and is compatible with the existing IEEE 802.11 standard.
Foh CH, Lu H, Wen Y, Cai J (2016) Delay-Optimized File Retrieval under LT-Based Cloud Storage, IEEE Transactions on Cloud Computing IEEE
Fountain-code based cloud storage system provides reliable
online storage solution through placing unlabeled content blocks
into multiple storage nodes. Luby Transform (LT) code is one of the
popular fountain codes for storage systems due to its efficient recovery.
However, to ensure high success decoding of fountain codes
based storage, retrieval of additional fragments is required, and this
requirement could introduce additional delay. In this paper, we show
that multiple stage retrieval of fragments is effective to reduce the fileretrieval
delay. We first develop a delay model for various multiple
stage retrieval schemes applicable to our considered system. With
the developed model, we study optimal retrieval schemes given
requirements on success decodability. Our numerical results suggest
a fundamental tradeoff between the file-retrieval delay and the target
probability of successful file decoding, and that the file-retrieval delay
can be significantly reduced by optimally scheduling packet requests
in a multi-stage fashion.
Gao D, Cai J, Foh CH (2008) Medium access cooperations for improving VoIP capacity over hybrid 802.16/802.11 cognitive radio networks, Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 4982 LNCS pp. 889-900
There are some existing works that study the coexistence of 802.16 and 802.11 networks. However, not many of them consider the resource allocation issues in the case of delivering traffic between mobile stations and Internet users through an access point (AP) and a base station (BS) which operate at the same frequency band. In this paper, we design a cooperation mechanism for 802.16 and 802.11 to share the same medium with adaptable resource allocation. The adaptiveness in resource allocation in our design eliminates the potential inefficiency from the cooperation due to bandwidth bottleneck. Targeting VoIP applications, we propose a simple approach for the adaptation that optimizes the resource allocation not only between the IEEE 802.11 AP and the stations but also between the IEEE 802.16 BS and the IEEE 802.11 AP. Numerical results show significant improvement in voice capacity. © 2008 Springer-Verlag Berlin Heidelberg.
Qureshi J, Foh CH, Cai J (2011) Joint Network Coding for Interfering Wireless Multicast Networks, Arxiv
Interference in wireless networks is one of the key-capacity limiting factor.
The multicast capacity of an ad- hoc wireless network decreases with an
increasing number of transmitting and/or receiving nodes within a fixed area.
Digital Network Coding (DNC) has been shown to improve the multicast capacity
of non-interfering wireless network. However recently proposed Physical-layer
Network Coding (PNC) and Analog Network Coding (ANC) has shown that it is
possible to decode an unknown packet from the collision of two packet, when one
of the colliding packet is known a priori. Taking advantage of such collision
decoding scheme, in this paper we propose a Joint Network Coding based
Cooperative Retransmission (JNC- CR) scheme, where we show that ANC along with
DNC can offer a much higher retransmission gain than that attainable through
either ANC, DNC or Automatic Repeat reQuest (ARQ) based retransmission. This
scheme can be applied for two wireless multicast groups interfering with each
other. Because of the broadcast nature of the wireless transmission, receivers
of different multicast group can opportunistically listen and cache packets
from the interfering transmitter. These cached packets, along with the packets
the receiver receives from its transmitter can then be used for decoding the
JNC packet. We validate the higher retransmission gain performance of JNC with
an optimal DNC scheme, using simulation.
Lim TM, Tantra JW, Foh CH, Lee B-S (2004) Out-of-band polling scheme for QoS support in wireless LANs., Int. J. Communication Systems 17 6 pp. 643-661
Chen L, Mnaouer AB, Foh CH (2006) An optimized polymorphic hybrid multicast routing protocol (OPHMR) for Ad Hoc networks, IEEE International Conference on Communications 8 pp. 3572-3577
We propose in this paper, an optimized, polymorphic, hybrid multicast routing protocol for MANET. The protocol proposed is based on the principle of adaptability and multibehavioral modes of operations. It is able to change behavior in different situations in order to improve certain metrics like maximizing battery life, reducing communication delays, improving deliverability, etc. This new polymorphic protocol attempts to benefit of the high efficiency of proactive behavior and the low cost of network traffic of the reactive behavior, while being power, mobility and vicinity density aware. The protocol is augmented by an optimization scheme, adapted from the one proposed for the optimized link state routing protocol (OLSR) in which only selected neighbor nodes propagate control packets to reduce the amount of control overhead. Extensive simulations and comparison to peer protocols demonstrated the effectiveness of the proposed protocol in improving performance and in extending battery power longevity. © 2006 IEEE.
Shi H, Arumugam RV, Foh CH, Khaing KK (2012) Optimal disk storage allocation for multi-tier storage system, 2012 Digest APMRC - Asia-Pacific Magnetic Recording Conference: A Strong Tradition. An Exciting New Look!
The current storage system is facing the bottleneck of performance due to the gap between fast CPU computing speed and the slow response time of hard disk. Recently multi-tier hybrid storage system (MTHS) which uses fast flash devices like solid state drive (SSD) as the one of the high performance storage tiers has been proposed to boost the storage system performance. In order to maintain the overall performance of the MTHS, optimal disk storage assignment has to be designed so that the data migrated to the high performance tier like SSD is the optimal set of data. In this paper we proposed a optimal data allocation algorithm for disk storage in MTHS. The data allocation problem (DAP) is to find the optimal lists of data files for each storage tier in the MTHS to achieve maximal benefit values without exceeding the available size of each tier. We formulate the DAP as a special multiple choice knapsack problem (MCKP) and propose the multiple-stage dynamic programming (MDP) to find the optimal solutions. The results show that the MDP can achieve improvements up to 6 times compared with the existing greedy algorithms. © 2012 DSI.
Dhananjayan A, Seow KT, Foh CH (2013) Lyapunov stability analysis of load balancing in datacenter networks, 2013 IEEE Globecom Workshops, GC Wkshps 2013 pp. 912-916
Modern datacenters are becoming increasingly complex, with datacenter networks (DCN's) built to meet the data transmission demands of densely interconnected nodes of server hosts and switches. Load balancing in DCN's - to balance the bandwidth utilization among the DCN links - is indispensable for network stability as well as for meeting important objectives such as maximizing throughput and minimizing latency. Simulation has been the de facto empirical method for investigating the stability of DCN's under load balancing policies. To complement simulation with analytical insights into load balancing stability of DCN's, in this paper, we present an application of the qualitative version of the Lyapunov stability theory for load balancing DCN's modeled as discrete-event systems. The general Lyapunov control theory states that a controlled system is stable if there exists a function on the state space of the system, called the Lyapunov function, whose value is non-increasing along any execution trajectory of the system. Analytically proving the existence of such a Lyapunov function is sufficient to verify that the DES model representing a class of DCN's under a load balancing policy is stable. We illustrate the utility of our approach by investigating the stability of a class of DCN's configured in a fat-tree topology under a specific load balancing policy. Our work represents the first step towards a general qualitative stability theory for the policy design of load balancing algorithms for DCN's. © 2013 IEEE.
Gao D, Foh CH, Cai J, Zhang H (2010) Channel resource allocation for VoIP applications in collaborative IEEE 802.11/802.16 networks, Eurasip Journal on Wireless Communications and Networking 2010
Collaborations between the IEEE 802.11 and the IEEE 802.16 networks operating in a common spectrum offers dynamic allocate bandwidth resources to achieve improved performance for network applications. This paper studies the bandwidth resource allocation of collaborative IEEE 802.11 and IEEE 802.16 networks. Consider delivering data packets between mobile stations and Internet users through an access point (AP) of the IEEE 802.11 network and a base station (BS) of the IEEE 802.16 network operating on a common frequency band, we analyze their medium access control (MAC) protocols, frame structures, and design a cooperation mechanism for the IEEE 802.11 and the IEEE 802.16 networks to share the same medium with adaptive resource allocation. Based on the mechanism, an optimized resource allocation scheme is proposed for VoIP applications. An analytical model is developed for the study to show significant improvements in voice capacity for our optimized resource allocation scheme. Copyright © 2010 Deyun Gao et al.
Zhang Y, Foh CH, Cai J (2008) An On-Off Queue Control Mechanism for Scalable Video Streaming over the IEEE 802.11e WLAN., ICC pp. 4958-4962 IEEE
Zhang Q, Foh CH, Seet BC, Fong ACM (2012) Variable elasticity spring-relaxation: Improving the accuracy of localization for WSNs with unknown path loss exponent, Personal and Ubiquitous Computing 16 (7) pp. 929-941
Wireless sensor network is a key enabling technology for Ambient Intelligence, where location information is crucial for many applications. RSS-based ranging localization takes advantage of its low cost and low complexity, but it has an infeasible assumption of an accurate path loss exponent of the physical environment. In this paper, we study the impact of path loss exponent accuracy on the localization accuracy. We formulate the relationship between the path loss exponent estimate and localization error, and found the localization error of exponential order which we call the error magnification effect. By our in-depth investigation, we propose a passive and an active measures to suppress the error magnification effect, where the passive measure stabilizes the localization error of the spring-relaxation algorithm (SR), and the active measure introduces variable elasticity into the SR algorithm to cancel off the exponential ranging error. The combination of both measures forms our localization solution called variable elasticity spring-relaxation (VESR) localization. We conduct extensive simulation experiments to show the effectiveness of VE-SR in suppressing the error magnification effect in various experiment setup. For a wide variety of physical environments, VE-SR offers location estimation with an average accuracy of no more than 10% of transmission range. © Springer-Verlag London Limited 2011.
Tantra JW, Foh CH, Tinnirello I, Bianchi G (2006) Analysis of the IEEE 802.11e EDCA under statistical traffic, IEEE International Conference on Communications 2 pp. 546-551
Many models have been proposed to analyze the performance of the IEEE 802.11 distributed coordination function (DCF) and the IEEE 802.11e enhanced distributed coordination function (EDCA) under saturation condition. To analyze DCF under statistical traffic, Foh and Zukerman introduce a model that uses Markovian Framework to compute the throughput and delay performance. In this paper, we analyze the protocol service time of EDCA mechanism and introduce a model to analyze EDCA under statistical traffic using Markovian Framework. Using this model, we analyze the throughput and delay performance of EDCA mechanism under statistical traffic. © 2006 IEEE.
Zhang Y, Ni Z, Foh CH, Cai J (2005) Improving scalable video transmission over IEEE 802.11e networks, Proceedings of SPIE - The International Society for Optical Engineering 6015
Providing a certain quality of service (QoS) for multimedia transmissions over a noisy wireless channel has always been a challenge. The IEEE 802.11 standardization dedicates a working group, group e, to investigate and propose a solution for enabling IEEE 802.11 networks to provide multimedia transmissions with certain QoS supports. As drafted in the latest draft release, the IEEE 802.11e working group proposes the use of contention based mechanism to achieve the transmissions of prioritized traffic, which in turn provides a framework to support multimedia transmissions over IEEE 802.11 networks. However, such a contention based priority scheme does not deliver a strong QoS capability. In this paper, we first study the characteristics of the IEEE 802.11e network. For all the four defined priorities of IEEE 802.11e, we first investigate their capacity characteristics. We then design a resource allocation technique to better utilize the bandwidth and improve the performance of video transmissions. Our design uses a QoS mapping scheme according to the IEEE 802.11e protocol characteristics to deliver scalable video. In addition, we design an appropriate cross-layer video adaptation mechanism for the scalable video that further improves the video quality combining with our proposed resource allocation technique. We have evaluated our proposed technique via simulations (NS2). We use PSNR as our video quality measures. Our results show improvement in video quality and resource usage when our proposed technique is implemented.
Seet B-C, Liu G, Lee B-S, Foh CH, Wong KJ, Lee K-K (2004) A-STAR: A Mobile Ad Hoc Routing Strategy for Metropolis Vehicular Communications., NETWORKING 3042 pp. 989-999 Springer
Foh CH, Liu G, Lee B-S, Seet B-C, Wong KJ, Fu CP (2005) Network connectivity of one-dimensional MANETs with random waypoint movement., IEEE Communications Letters 9 1 pp. 31-33
Yang M, Gao M, Foh CH, Cai J (2015) Hybrid Collision-Free Medium Access (HCFMA) Protocol for Underwater Acoustic Networks: Design and Performance Evaluation, IEEE Journal of Oceanic Engineering 40 (2) pp. 292-302
© 1976-2012 IEEE.Underwater acoustic channels are typically characterized by long propagation delay, time-varying multipath, as well as very limited bandwidth, thus making it very challenging to develop efficient underwater medium access control (MAC) protocols. In this paper, we propose a new MAC protocol for underwater acoustic networks (UANs), called the hybrid collision-free medium access (HCFMA) scheme. The operation of the HCFMA scheme is based on the combination of the multichannel technique, the channel reservation mechanism, and the juggling-like stop-and-wait (JSW) transmission scheme. With the multichannel technique, the exchange of control signaling and data transmission can be separated, consequently, increasing the throughput of the network. The channel reservation mechanism which is carried out by the temporarily chosen control nodes guarantees no collision in data transmission. This is different from those whose channel reservations rely on a dedicated central controller. The JSW scheme provides an error-control mechanism during data transmission. Together, these approaches greatly improve the performance of UAN in throughput and delay. This paper describes the operation of the HCFMA scheme and analyzes its performance. We further conduct simulation to validate our analytical results. Our results show encouraging throughput and delay performance compared with other popular solutions, especially under heavy load conditions.
Tantra J, Foh C (2006) Achieving near maximum throughput in IEEE 802.11 WLANs with contention tone, IEEE Communications Letters 10 (9) pp. 658-660
Future wireless local area networks (WLANs) promise bit rates higher than 100 Mbps. Previous research by Xiao et al. reported that the current IEEE 802.11 medium access control (MAC) protocol does not scale well to high bit rate channels. In this letter, we propose an enhancement that uses contention-tone transmitted on a separate narrow band signaling channel. The proposed contention tone mechanism avoids more than 96% of transmission collisions, hence achieving near to the theoretical maximum throughput of a WLAN MAC protocol. © 2006 IEEE.
Qureshi J, Foh CH, Cai J (2009) An efficient network coding based retransmission algorithm for wireless multicast., PIMRC pp. 691-695 IEEE
Yang M, Cai J, Wen Y, Foh CH (2011) Complexity-rate-distortion evaluation of video encoding for cloud media computing, ICON 2011 - 17th IEEE International Conference on Networks pp. 25-29
Cloud computing provides a promising solution to cope with the increased complexity in new video compression standards and the increased data volume in video source. It not only saves the cost of too frequent equipment upgrading but also gives individual users the flexibilities to choose the amount of computing according to their needs. To facilitate cloud computing for real-time video encoding, in this paper we evaluate the amount of computing resource needed for H.264 and H.264 SVC encoding. We focus on evaluating the complexity-rate- distortion (C-R-D) relationship with a fixed encoding process but under different external configuration parameters. We believe such an empirical study is meaningful for eventually realizing real-time video encoding in an optimal way in a cloud environment. © 2011 IEEE.
Zhang Q, Foh CH, Seet B-C, Fong ACM (2011) RSS ranging based Wi-Fi localization for unknown path loss exponent, GLOBECOM - IEEE Global Telecommunications Conference
Localization of mobile phones is important to location-based mobile services, but achieving good location estimation of mobile phones is difficult especially in environment whose path loss exponent is unknown. In this paper, we present a Wi-Fi localization solution specifically designed for dense WLANs with unknown path loss exponent. In order to leverage between the computational cost and localization accuracy, our solution establishes a neighbor selection scheme based on the Voronoi diagram to identify a subset of Access Points (APs) to participate in localization. It considers the identified subset of APs and a mobile phone to be located as a mass-spring system. Provided with information of known coordinates of APs, the solution estimates the path loss exponent of the physical environment, infers inter-distances between APs and the mobile phone from Wi-Fi signals received, and implements spring relaxation algorithm to approximate the geographical location of the mobile phone, where this location estimation is fed back to refine the estimated exponent iteratively. Extensive simulation results confirm that our solution is able to provide location estimation with an attractive average accuracy of below 2 m in a typical Wi-Fi setup. © 2011 IEEE.
Guo T, Cai J, Gao M, Foh CH (2011) Dynamic scheduling of a mixture of scalable IPTV and VoD traffic over wireless home networks, Proceedings of the 10th International Conference on Mobile and Ubiquitous Multimedia, MUM'11 pp. 123-126
Unlike most of the existing studies on video streaming over WLANs, which usually focus on only one type of video streams, either stored videos or live videos, in this paper we propose a dynamic scheduling method for transmitting a mixture of live and stored videos over WLANs. In particular, we dynamically estimate the future IPTV traffic information based on the past. Our proposed dynamic scheduling algorithm allows VoD traffic to be transmitted not only at a later time but also in advance so as to provide more flexibility to serve the overall traffic to achieve a better QoS. The ns-2 simulations verify the effectiveness of the proposed approach. © 2011 ACM.
Yang M, Gao M, Foh CH, Cai J (2014) Hybrid Collision-Free Medium Access (HCFMA) Protocol for Underwater Acoustic Networks: Design and Performance Evaluation, IEEE Journal of Oceanic Engineering
Underwater acoustic channels are typically characterized by long propagation delay, time-varying multipath, as well as very limited bandwidth, thus making it very challenging to develop efficient underwater medium access control (MAC) protocols. In this paper, we propose a new MAC protocol for underwater acoustic networks (UANs), called the hybrid collision-free medium access (HCFMA) scheme. The operation of the HCFMA scheme is based on the combination of the multichannel technique, the channel reservation mechanism, and the juggling-like stop-and-wait (JSW) transmission scheme. With the multichannel technique, the exchange of control signaling and data transmission can be separated, consequently, increasing the throughput of the network. The channel reservation mechanism which is carried out by the temporarily chosen control nodes guarantees no collision in data transmission. This is different from those whose channel reservations rely on a dedicated central controller. The JSW scheme provides an error-control mechanism during data transmission. Together, these approaches greatly improve the performance of UAN in throughput and delay. This paper describes the operation of the HCFMA scheme and analyzes its performance. We further conduct simulation to validate our analytical results. Our results show encouraging throughput and delay performance compared with other popular solutions, especially under heavy load conditions.
Foh CH, Zukerman M (2002) A new technique for performance evaluation of random access protocols, IEEE International Conference on Communications 4 pp. 2284-2288
A new technique is proposed for performance evaluation of random access protocols. This technique is based on the idea that the service probability distribution of a particular random access protocol can be described by a phase-type distribution. By modeling the service probability distribution of a protocol into a phase-type distribution, the performance of the protocol can be evaluated using an equivalent Continuous Time Markov Chain. In this paper we demonstrate the applicability of the technique to performance evaluation of the IEEE 802.3 and the IEEE 802.11 MAC protocols. Furthermore, we provide an example of performance evaluation of a MAC protocol subject to bursty traffic models such as the Markov Modulated Poisson Process. The accuracy the results are verified by simulation.
Qureshi J, Foh CH, Cai J (2012) Optimal solution for the index coding problem using network coding over GF(2)., SECON pp. 209-217 IEEE
Zhang Y, Ni Z, Foh CH, Cai J (2007) Retry limit based ULP for scalable video transmission over IEEE 802.11e WLANs, IEEE Communications Letters 11 (6) pp. 498-500
We investigate the packet loss behavior in the IEEE 802.11e wireless local area networks (WLANs) under various retry limit settings. Considering scalable video traffic delivery over the IEEE 802.11e WLANs, our study shows the importance of adaptiveness in retry limit settings for the Unequal Loss Protection (ULP) design. Based on the study, we present a simple yet effective retry limit based ULP which adaptively adjusts the retry limit setting of the IEEE 802.11e medium access control protocol to maintain a strong loss protection for critical video traffic transmission. The simulation results illustrate significant advantages in the delivered video quality for our proposed design. © 2007 IEEE.
Fang S, Foh CH, Aung KMM (2011) Differentiated congestion management of data traffic for data center Ethernet, IEEE Transactions on Network and Service Management 8 (4) pp. 322-333
This paper aims at designing a congestion and priority solution for Ethernet congestion management. Following the popular approach that uses a cooperation of an Additive Increase and Multiplicative Decrease (AIMD) based rate limiter and Explicit Congestion Notification (ECN) active queue management to combat congestions in Ethernet, the proposal considers differentiated AIMD settings for rate limiters to achieve congestion control differentiation for traffic of different priorities. We illustrate that while the operations of AIMD and ECN are independent, by using different AIMD settings, we can achieve differentiated control of bandwidth utilization. We develop a control theoretic analytical model to study the effectiveness of our proposed method. Moreover, we implement our proposed method in OMNET++ simulator to conduct simulation experiments. Our analytical and simulation results both indicate the effectiveness of bandwidth ratio differentiation. © 2011 IEEE.
Qureshi J, Foh CH, Cai J (2014) Online XOR packet coding: Efficient single-hop wireless multicasting with low decoding delay, Computer Communications 39 pp. 65-77
In this paper we present a cross-layer solution to the problem of unreliability in IEEE 802.11 wireless multicast network, where an Access Point (AP) is multicasting a data file to a group of receivers over independent wireless erasure channels. We first present a practical scheme for collecting feedback frames from the receivers by means of simultaneous acknowledgment (ACK) frames collision. Based on these feedback frames, we design an online linear XOR coding algorithm to retransmit the lost packets. Through simulation results we first show that our proposed coding algorithm outperforms all the existing XOR coding algorithms in terms of retransmission rate. We further show that our proposed coding algorithm has the lowest average decoding delay of all the known network coding schemes. XOR coding and decoding only requires addition over GF(2), hence it enjoys lower encoding and decoding computational complexities. Because of these features such an online XOR coding algorithm is also of interest for delay-sensitive applications such as multicast audio video (AV) streaming, and in battery constrained devices such as smartphones. © 2013 Elsevier B.V. All rights reserved.
Tantra JW, Foh CH, Qiu D (2006) On Link Reliability in Wireless Mobile Ad Hoc Networks., VTC Fall pp. 1-5 IEEE
Guo T, Cai J, Foh CH (2011) Scalable video adaptation in wireless home networks with a mixture of IPTV and VoD users, GLOBECOM - IEEE Global Telecommunications Conference
In this paper, we propose a scalable video adaptation mechanism to improve the overall quality of service (QoS) in wireless home networks with a mixture of IPTV and VoD users. Unlike most of the existing studies on video streaming over WLANs, which usually focus on only one type of video streams, either stored videos or live videos, here we consider a mixture of live and stored videos. We make use of the pre-buffering time of VoD users in the rate adaptation for both IPTV and VoD users so as to achieve an overall optimal QoE for all the users. In addition, we employ the standard H.264 SVC and consider a practical multi-rate scenario, where the physical data rate of a wireless user is determined according to its distance to the access point (AP). The corresponding multi-rate multi-queue MAC-layer throughput is analyzed so as to accurately estimate the bandwidth for the video streaming. The ns-2 simulations verify the effectiveness of the proposed scalable video adaptation. © 2011 IEEE.
Seet B-C, Zhang Q, Foh CH, Fong ACM, Gonzalez A (2009) Hybrid RF mapping and ranging based localization for wireless sensor networks, Proceedings of IEEE Sensors pp. 1387-1391
In this paper, we propose a hybrid approach to the wireless sensor network (WSN) localization problem. The proposed approach harnesses the strengths of two techniques: RF mapping and cooperative ranging, to overcome the potential weaknesses in one another. The idea is to first allow every node to obtain an initial estimate of its own position in a neighbor-independent way using a coarse-grained RF map acquired with minimal efforts. Then each node iteratively refines its own position through distance ranging to each of its neighbors, irregardless of their positions with respect to itself. Through simulation performance experiments, we show the potential of this hybrid approach as a practical localization system for WSN that can achieve reasonable localization accuracy without significant deployment efforts. ©2009 IEEE.
Qureshi J, Cai J, Foh CH (2011) Cooperative Retransmissions Through Collisions, International Conference on Communications
Interference in wireless networks is one of the key capacity-limiting
factors. Recently developed interference-embracing techniques show promising
performance on turning collisions into useful transmissions. However, the
interference-embracing techniques are hard to apply in practical applications
due to their strict requirements. In this paper, we consider utilising the
interference-embracing techniques in a common scenario of two interfering
sender-receiver pairs. By employing opportunistic listening and analog network
coding (ANC), we show that compared to traditional ARQ retransmission, a higher
retransmission throughput can be achieved by allowing two interfering senders
to cooperatively retransmit selected lost packets at the same time. This
simultaneous retransmission is facilitated by a simple handshaking procedure
without introducing additional overhead. Simulation results demonstrate the
superior performance of the proposed cooperative retransmission.
Wong D, Seow KT, Foh CH, Kanagavelu R (2013) Towards reproducible performance studies of datacenter network architectures using an open-source simulation approach, GLOBECOM - IEEE Global Telecommunications Conference pp. 1373-1378
In datacenter network (DCN) research, one key challenge is to reproduce the relative performances of different scalable DCN architectures in an unbiased and transparent way. Adequately addressing this challenge will support the validation of performance studies, and this is fundamental to building a strong research foundation and making wise datacenter investment decisions. In addressing this challenge, this paper presents the NTU-DSI-DCN initiative with a DCN simulation module based on an open-source platform called ns-3, on which the performance models of DCN topologies can be developed and made open source to support independent reproducibility of their performances. Advantages of the framework include the following: (1) it is low cost, (2) it provides transparent performance benchmarks of known DCN architectures and (3) it enables unbiased comparative performance simulations of DCN architectures, without the tedium of developing existing DCN models from scratch. In realizing this NTU-DSI-DCN initiative, the open-source performance models of the Fat tree and the BCube architectures have been implemented on the ns-3 platform. A comparative performance study between Fat tree and BCube is reported, along with a performance reproducibility study of Fat tree. The documentation and source codes for our simulation setups are publicly available at http://code.google. com/p/ntu-dsidcn/. In continually adding new DCN architectural models or their variants in future work, the NTU-DSI-DCN is a promising initiative that can evolve into a well-documented open-source simulation platform supporting quality research in DCNs. © 2013 IEEE.
Zhou B, Fu CP, Zhang K, Lau CT, Foh CH (2006) An enhancement of TCP veno over light-load wireless networks, IEEE Communications Letters 10 (6) pp. 441-443
This letter observes that TCP Veno behaves conservatively over light-load wireless networks. A new variable, congestion loss rate, is introduced into Veno's algorithm. It helps Veno deal with random loss more intelligently, by keeping its congestion window increasing if the link load is in light state. The simulation results demonstrate that, such enhancement can improve Veno's throughput up to 60% without any fairness or friendliness sacrificed. © 2006 IEEE.
Wei L, He B, Foh CH (2014) Towards multi-resource physical machine provisioning for IaaS clouds, 2014 IEEE International Conference on Communications, ICC 2014 pp. 3469-3474
Virtualization has been an enabling technology for IaaS (Infrastructure as a Service) Clouds. Physical machine (PM) provisioning is a key problem for IaaS cloud providers on their resource utilization and quality of service to users. Proper provisioning is able to ensure the service quality while conserving unnecessary power consumption from over-provisioned PMs. However, the effectiveness of PM provisioning in current IaaS providers such as Amazon and Rackspace is severely limited by that they offer virtual machines with proportional resource provisioning on different resource types (including CPU, memory and disk etc). Such a rigid offering cannot satisfy diversified user applications in the cloud, and can cause significant over-provision on PMs in order to satisfy users' requirement on all resource types. This paper argues a more flexible approach that IaaS providers should offer virtual machines with flexible combinations on multiple resource types. We further formulate the problem of multiple resource virtual machine allocations for IaaS clouds, and develop analytical models to predict the suitable number of PMs while satisfying a predefined quality-of-service requirement. Experiments show that the proposed approach can significantly increase the resource utilization, with a reduction on the number of active PMs by 27% on average. © 2014 IEEE.
Li J, Foh CH, Andrew LLH, Zukerman M (2008) Sizes of minimum connected dominating sets of a class of wireless sensor networks, IEEE International Conference on Communications pp. 332-336
We consider an important performance measure of wireless sensor networks, namely, the least number of nodes, N, required to facilitate routing between any pair of nodes, allowing other nodes to remain in sleep mode in order to conserve energy. We derive the expected value and the distribution of N for single dimensional dense networks. ©2008 IEEE.
Liu G, Lee B-S, Seet B-C, Foh CH, Wong KJ, Lee K-K (2004) A Routing Strategy for Metropolis Vehicular Communications., ICOIN 3090 pp. 134-143 Springer
Gao D, Foh CH, Vu H, Miao G (2014) Wireless Vehicular Sensor and Ad Hoc Networks, INTERNATIONAL JOURNAL OF DISTRIBUTED SENSOR NETWORKS ARTN 769067 HINDAWI PUBLISHING CORPORATION
Scalia L, Tinnirello I, Tantra JW, Foh CH (2006) Dynamic MAC Parameters Configuration for Performance Optimization in 802.11e Networks., GLOBECOM IEEE
Zhang Q, Foh CH, Seet BC, Fong AC (2010) Location estimation in wireless sensor networks using spring-relaxation technique., Sensors (Basel) 10 (5) pp. 5171-5192
Accurate and low-cost autonomous self-localization is a critical requirement of various applications of a large-scale distributed wireless sensor network (WSN). Due to its massive deployment of sensors, explicit measurements based on specialized localization hardware such as the Global Positioning System (GPS) is not practical. In this paper, we propose a low-cost WSN localization solution. Our design uses received signal strength indicators for ranging, light weight distributed algorithms based on the spring-relaxation technique for location computation, and the cooperative approach to achieve certain location estimation accuracy with a low number of nodes with known locations. We provide analysis to show the suitability of the spring-relaxation technique for WSN localization with cooperative approach, and perform simulation experiments to illustrate its accuracy in localization.
Mnaouer AB, Foh CH, Chen L (2013) A Generic Polymorphic Unicast Routing Protocol for vehicular ad hoc networks, Wireless Communications and Mobile Computing 13 (14) pp. 1295-1308
In this work, we present a new generic polymorphic routing protocol tailored for vehicular ad hoc networks (VANETs). Similar to the case of mobile ad hoc networks, the routing task in VANETs comes under various constraints that can be environmental, operational, or performance based. The proposed Polymorphic Unicast Routing Protocol (PURP) uses the concept of polymorphic routing as a means to describe dynamic, multi-behavioral, multi-stimuli, adaptive, and hybrid routing, that is applicable in various contexts, which empowers the protocol with great flexibility in coping with the timely requirements of the routing tasks. Polymorphic routing protocols, in general, are equipped with multi-operational modes (e.g., grades of proactive, reactive, and semi-proactive), and they are expected to tune in to the right mode of operation depending on the current conditions (e.g., battery residue, vicinity density, traffic intensity, mobility level of the mobile node, and other user-defined conditions). The objective is commonly maximizing and/or improving certain metrics such as maximizing battery life, reducing communication delays, improving deliverability, and so on. We give a detailed description and analysis of the PURP protocol. Through comparative simulations, we show its superiority in performance to its peers and demonstrate its suitability for routing in VANETs. © 2011 John Wiley & Sons, Ltd.
Zhou B, Fu CP, Lau CT, Foh CH (2007) An enhancement of TFRC over wireless networks, IEEE Wireless Communications and Networking Conference, WCNC pp. 3021-3026
TFRC is TCP-Friendly Rate Control protocol with TCP Reno's throughput equation based. It is designed to mainly provide optimal service for unicast multimedia flow operating in the best-effort Internet environment. However, due to Reno's significant performance degradation in wireless networks, TFRC has also led to unavoidable performance suffering from wireless links due to the poor performance of Reno throughput. This paper proposes an enhancement of TFRC based on the differentiating method used in TCP Veno. Specifically, it utilizes Veno's state differentiator to distinguish congestion losses and non-congestion losses during transmission. By discounting the impact of those non-congestion losses on the throughput calculation, it can effectively alleviate the throughput degradation caused by wireless links. The simulation results have shown that, our proposal can achieve throughput improvement up to 70% as compared to the original TFRC. Meanwhile, it maintains other merits of the original TFRC, such as sending rate smoothness, fairness, and TCP-friendliness. © 2007 IEEE.
Banerjee A, Foh CH, Yeo CK, Lee BS (2011) Exploiting wireless broadcast advantage as a network-wide cache, International Conference on Wireless and Mobile Computing, Networking and Communications pp. 490-497
Existing literature has looked to exploit wireless broadcast advantage (WBA) in order to optimize the performance of a wide variety of network operations. In this paper, we obtain a measure of WBA in a multihop scenario. We consider that all nodes in the network store and propagate implicitly received information from neighbourhood transmissions, resulting in the creation of a distributed cache, which we term broadcast cache. We obtain a lower bound on the growth of the broadcast cache in terms of the fewest set of transmissions in the network, which we define as the minimum set of non-altruistic transmissions. Subsequently, we use our results to obtain feasibility conditions that determine whether WBA can be effectively utilized depending on flow requirements. © 2011 IEEE.
Lu X, Zhang K, Fu CP, Foh CH (2010) A sender-side TCP enhancement for startup performance in high-speed long-delay networks, IEEE Wireless Communications and Networking Conference, WCNC
Many previous studies have shown that traditional TCP slow-start algorithm suffers performance degradation in high-speed and long-delay networks. This paper presents a sender-side enhancement, which makes use of TCP Vegas congestion-detecting scheme to monitor the router queue, and accordingly refines slow-start window evolution by introducing a two-phase approach to probe bandwidth more efficiently. Moreover, it achieves good fairness of bandwidth utilization in coexistence of multiple connections. Simulation results show that, compared with traditional slow-start and many other enhancements, it is able to significantly improve the startup performance without adversely affecting coexisting TCP connections. ©2010 IEEE.
Seet BC, Zhang Q, Foh CH, Fong ACM (2012) Hybrid RF mapping and Kalman filtered spring relaxation for sensor network localization, IEEE Sensors Journal 12 (5) pp. 1427-1435
An accurate and low-cost hybrid solution to the problem of autonomous self-localization in wireless sensor networks (WSN) is presented. The solution is designed to perform robustly under challenging radio propagation conditions in mind, while requiring low deployment efforts, and utilizing only low-cost hardware and light-weight distributed algorithms for location computation. Our solution harnesses the strengths of two approaches for environments with complex propagation characteristics: RF mapping to provide an initial estimate of each sensor's position based on a coarse-grain RF map acquired with minimal efforts; and a cooperative light-weight spring relaxation technique for each sensor to refine its estimate using Kalman filtered inter-node distance measurements. Using Kalman filtering to pre-process noisy distance measurements inherent in complex propagation environments, is found to have significant positive impacts on the subsequent accuracy and the convergence of our spring relaxation algorithm. Through extensive simulations using realistic settings and real data set, we show that our approach is a practical localization solution which can achieve sub-meter accuracy and fast convergence under harsh propagation conditions, with no specialized hardware or significant efforts required to deploy. © 2012 IEEE.
Korki M, Hosseinzadeh N, Vu HL, Moazzeni T, Foh CH (2011) Impulsive noise reduction of a narrowband power line communication using optimal nonlinearity technique, Australasian Telecommunication Networks and Applications Conference, ATNAC 2011
In this paper, we propose an optimal Clipping/Blanking nonlinearity technique for impulsive noise reduction in narrowband (9 kHz-490 kHz) PLC system. This optimal technique is based on the minimum bit error rate (BER) search. For our simulation, we have derived the transfer function of a typical low voltage (LV) PLC network using the common bottom-up approach and scattering matrix method. Our simulation results, in terms of BER versus signal to noise ratio (SNR), show that the proposed technique improves the BER performance of the narrowband PLC system. © 2011 IEEE.
Yang M, Wen Y, Cai J, Foh CH (2012) Energy minimization via dynamic voltage scaling for real-time video encoding on mobile devices, IEEE International Conference on Communications pp. 2026-2031
This paper investigates the problem of minimizing energy consumption for real-time video encoding on mobile devices, by dynamically configuring the clock frequency in the CPU via the dynamic voltage scaling (DVS) technology. The problem can be formulated as a constrained optimization problem, whose objective is to minimize the total energy consumption of encoding video contents while respecting a real-time delay constraint. Under a probabilistic workload model, we obtain closed-form solutions for both the optimal clock frequency configuration and the resulted minimum energy. We also compare the optimal solution with a brute force flat frequency configuration. Numerical results indicate that our derived optimal solution outperforms the brute-force approach significantly. Moreover, we apply the optimal solution for real-time H.264/AVC video encoding application. Our numerical results suggest that an energy saving of 10%-20% can be achieved, compared to the flat clock frequency scheduling. © 2012 IEEE.
Qureshi J, Foh CH, Cai J (2012) Optimal solution for the index coding problem using network coding over GF(2), Annual IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks workshops 1 pp. 209-217
The index coding problem is a fundamental transmission problem which occurs in a wide range of multicast networks. Network coding over a large finite field size has been shown to be a theoretically efficient solution to the index coding problem. However the high computational complexity of packet encoding and decoding over a large finite field size, and its subsequent penalty on encoding and decoding throughput and higher energy cost makes it unsuitable for practical implementation in processor and energy constraint devices like mobile phones and wireless sensors. While network coding over GF(2) can alleviate these concerns, it comes at a tradeoff cost of degrading throughput performance. To address this tradeoff, we propose a throughput optimal triangular network coding scheme over GF(2). We show that such a coding scheme can supply unlimited number of innovative packets and the decoding involves the simple back substitution. Such a coding scheme provides an efficient solution to the index coding problem and its lower computation and energy cost makes it suitable for practical implementation on devices with limited processing and energy capacity. © 2012 IEEE.
Guo T, Cai J, Foh CH (2009) Distributed routing algorithm for low-latency broadcasting in multi-rate wireless mesh network, Proceedings of the 2009 ACM International Wireless Communications and Mobile Computing Conference, IWCMC 2009 pp. 338-342
Using the multi-rate feature of the IEEE 802.11 MAC protocol in a wireless mesh network (WMN) increases efficiency in network-wide message broadcasting. A challenging problem is to achieve minimal latency for network-wide broadcasting in a multi-rate wireless mesh network (MrWMN). The three features, including the multi-rate characteristics, the source scheduling to obtain the routing decision, and the multi-radio solution to avoid the interference, add great complexities to this research issue. In this paper, we propose a distributed source routing algorithm that exploits the multi-rate feature to achieve low latency network-wide broadcasting in WMNs. Multi-radio is utilized to resolve the interferences among neighboring nodes. Simulation results show that, compared to the existing best known results under various network settings, our approach produces lower latency for network-wide broadcasting in the MrWMN. Copyright 2009 ACM.
Tantra JW, Foh CH, Bianchi G, Tinnirello I (2004) Performance analysis of the out-of-band signaling scheme for high speed wireless LANs., GLOBECOM pp. 3002-3006 IEEE
Foh CH, Meini B, Wydrowski B, Zukerman M (2001) Modeling and performance evaluation of GPRS, IEEE Vehicular Technology Conference 3 (53ND) pp. 2108-2112
This paper provides an accurate model of the General Packet Radio Service (GPRS). GPRS is modeled as a single server queue in a Markovian environment. The queueing performance of data packets is evaluated by matrix geometric methods. The arrival process is assumed to follow a two state Markov modulated Poisson process (MMPP), and the service rate fluctuates based on voice loading. The analytical results are confirmed by simulation.
Wong EWM, Foh CH (2009) Analysis of cognitive radio spectrum access with finite user population, IEEE Communications Letters 13 (5) pp. 294-296
A new loss model for cognitive radio spectrum access with finite user population are presented, and exact solution for the model and its approximation for computation scalability are given. Our model provides the investigation of the delay performance of a cognitive radio system. We study the delay performance of a cognitive radio system under various primary traffic loads and spectrum band allocations. © 2009 IEEE.
Wei L, Cai J, Foh CH, He B (2016) QoS-aware Resource Allocation for Video Transcoding in Clouds, IEEE Transactions on Circuits and Systems for Video Technology
As the ?biggest big data?, video data streaming in the network contributes the largest portion of global traffic nowadays and in future. Due to heterogeneous mobile devices, networks and user preferences, the demands of transcoding source videos into different versions have been increased significantly. However, video transcoding is a time-consuming task and how to guarantee quality-of-service (QoS) for large video data is very challenging, particularly for those real-time applications which hold strict delay requirement such as live TV. In this paper, we propose a cloud-based online video transcoding system (COVT) aiming to offer economical and QoS guaranteed solution for online large-volume video transcoding. COVT utilizes performance profiling technique to obtain the different performance of transcoding tasks in different infrastructures. Based on the profiles, we model the cloud-based transcoding system as a queue and derive the QoS values of the system based on queuing theory. With the analytically derived relationship between QoS values and the number of CPU cores required for transcoding workloads, COVT is able to solve the optimization problem and obtain the minimum resource reservation for specific QoS constraints. A task scheduling algorithm is further developed to dynamically adjust the resource reservation and schedule the tasks so as to guarantee the QoS in runtime. We implement a prototype system of COVT and experimentally study the performance on real-world workloads. Experimental results show that COVT effectively provisions minimum number of resources for predefined QoS. To validate the effectiveness of our proposed method under large scale video data, we further perform simulation evaluation which again shows that COVT is capable to achieve economical and QoS-aware video transcoding in cloud
Banerjee A, Tantra JW, Foh CH, Yeo CK, Lee BS (2010) Controlling route discovery for efficient routing in resource-constrained sensor networks, 2010 7th IEEE Consumer Communications and Networking Conference, CCNC 2010
Existing ad-hoc network routing strategies base their operations on flooding route requests throughout the network and choosing the shortest path thereafter. However, this typically results in a large number of unnecessary transmissions, which could be expensive for resource-constrained nodes such as those in a sensor network. In this paper, we propose a new mechanism HopAlert which optimizes route establishment and packet routing by limiting the number of nodes taking part in the route discovery process while achieving a low number of hops establishment. Using analysis and simulations, we show that this results in more routes with shorter hop counts than a reactive flooding protocol such as AODV while achieving higher savings. ©2010 IEEE.
Yang M, Gao M, Foh CH, Cai J, Chatzimisios P (2011) DC-MAC: A data-centric multi-hop MAC protocol for underwater acoustic sensor networks, Proceedings - IEEE Symposium on Computers and Communications pp. 491-496
Due to the unique characteristics of long signal propagation, high error rate and low bandwidth in the underwater environment, the design of the medium access control (MAC) protocol for underwater acoustic networks poses significant challenges. The previous MAC protocols designed for flexible communication models have limited achievements in performance. In this paper, we consider a practical application and propose a data-centric multi-hop MAC protocol, called DC-MAC, to enhance the performance on throughput and average end-to-end packet transmission delay. Our design uses multi-channel strategy to limit transmission interference by creating multiple collision domains, and dynamic collision-free polling strategy to offer efficient protocol handshake. We analyze the saturation throughput performance and conduct extensive simulation experiments to study the throughput and delay performance. Comparing to slotted FAMA which is a potential MAC protocol candidate for the same environment, our results show that DC-MAC outperforms its peer. © 2011 IEEE.
Yu Z, Foh CH, Tantra JW, Lim TM, Fu CP (2004) A centralized hybrid scheme for QOS supports in high speed wireless lans, Proceedings - IEEE International Conference on Networks, ICON 2 pp. 792-796
This paper introduces a new centralized hybrid scheme for high speed wireless local area networks (WLANs), which combines the Out-of-Band Signaling (OBS), the Enhanced Distributed Coordination Function (EDCF) in IEEE 802.11 and the Deficit Round Robin (DRR) technologies to achieve better system performance for high-speed WLANs. We show via simulation that our overall system performance is higher than that of the EDCF in IEEE 802.11, and a certain quality of service and fairness are achieved. © 2004 IEEE.
Fu CP, Foh CH, Lau CT, Man Z, Lee BS (2007) Semi-Markov modeling for bandwidth sharing of TCP connections with asymmetric AIMD congestion control, GLOBECOM - IEEE Global Telecommunications Conference pp. 2014-2018
This paper presents a semi-Markov model that evaluates the performance of TCP connections with asymmetric Additive Increase and Multiplicative Decrease (AIMD) congestion control settings involved in sharing of a common drop-tail router. We study the fairness of the connections and their individual bandwidth utilizations as well as packet loss rates. We confirm that certain asymmetric AIMD settings may achieve fairness in bandwidth sharing. We also found that while connections with asymmetric AIMD settings operate at different bandwidth utilizations, they generally experience similar packet loss rate. © 2007 IEEE.
Pham MT, Seow KT, Foh CH (2014) Towards intelligent datacenter traffic management: Using automated fuzzy inferencing for elephant flow detection, International Journal of Innovative Computing, Information and Control 10 (5) pp. 1669-1685
© 2014, IJICIC Editorial Office, Inc. All rights reserved.Effective traffic management has always been one of the key considerations in datacenter design. It plays an even more important role today in the face of increasingly widespread deployment of communication intensive applications and cloud- based services, as well as the adoption of multipath datacenter topologies to cope with the enormous bandwidth requirements arising from those applications and services. Of central importance in traffic management for multipath datacenters is the problem of timely detection of elephant flows flows that carry huge amount of data so that the best paths can be selected for these flows, which otherwise might cause serious network congestion. In this paper, we propose FuzzyDetec, a novel control architecture for the adaptive detection of elephant flows in multipath datacenters based on fuzzy logic. We develop, perhaps for the first time, a close loop elephant flow detection framework with an automated fuzzy inference module that can continually compute an appropriate threshold for elephant flow detection based on current information feedback from the network. The novelty and practical significance of the idea lie in allowing multiple imprecise and possibly conflicting criteria to be incorporated into the elephant flow detection process, through simple fuzzy rules emulating human expertise in elephant flow threshold classification. The proposed approach is simple, intuitive and easily extensible, providing a promising direction towards intelligent datacenter traffic management for autonomous high performance datacenter networks. Simulation results show that, in comparison with an existing state-of-the-art elephant flow detection framework, our proposed approach can provide considerable throughput improvements in datacenter network routing.
Lee GM, Wydrowski BP, Zukerman M, Choi JK, Foh CH (2003) Performance evaluation of an optical hybrid switching system., GLOBECOM pp. 2508-2512 IEEE
Arumugam RV, Foh CH, Shi H, Khaing KK (2012) HCache: A Hybrid cache management scheme with Flash and next generation NVRAM, 2012 Digest APMRC - Asia-Pacific Magnetic Recording Conference: A Strong Tradition. An Exciting New Look!
We propose a dynamic cache control mechanism HCache for a hybrid storage device consisting of next generation non-volatile memory (NVM) like STT-MRAM/PCRAM and conventional Flash. HCache works by distributing the scarce NVM capacity among multiple applications to meet their QoS requirements. The dynamic adaptation of the cache size is based on the access pattern and cache demands of the application. This is tracked through a hit rate histogram to a simple chain of virtual LRU queue. We show that our method can achieve 14% - 46% improvement in latency compared to popular control mechanisms available in the literature. It can also lead to reduced number of QoS violations compared particularly to a PID control mechanism commonly used in many of the recent and some earlier works. © 2012 DSI.
Duan J, Gao D, Foh CH, Leung VCM (2013) Trust and risk assessment approach for access control in wireless sensor networks, IEEE Vehicular Technology Conference
When deploying wireless sensor networks (WSNs) in practical applications, access control systems can limit access to sensitive information only to trusted entities and provide a capability to resist against various attacks from malicious nodes. However, due to the characteristics of highly distributed and resource-constrained, applying conventional access control models to WSNs is significantly challenging. In this paper, a distributed and fine-grained access control model based on the trust and risk degree is proposed (TC-BAC). We first introduce a trust evaluation mechanism to meet the security requirements of access control systems. Then, a risk function is proposed to assess the behavior of nodes and evaluate the risk factor of the access. The simulation results show that TC-BAC can achieve both intended security and high efficiency of the network. Copyright © 2013 by the Institute of Electrical and Electronic Engineers, Inc.
Guo T, Foh CH, Cai J, Niyato D, Wong EWM (2011) Performance evaluation of IPTV over wireless home networks, IEEE Transactions on Multimedia 13 (5) pp. 1116-1126
The emergence of Internet Protocol Television (IPTV) has brought potentials to revolutionize personal entertainment. Streaming TV content over the highly pervasive wireless networks allows easy access to personalized entertainment. Focusing on wireless home entertainment which is one of the main driving forces of IPTV development, we develop a Markovian framework that investigates several important issues related to network capacity and streaming quality in an IEEE 802.11e enabled wireless home network. The Markovian framework captures not only the IEEE 802.11e MAC protocol performance, but also the statistical characteristics of IPTV media streams. The inclusion of these two key descriptions allows our model to be practically used in wireless home network planning and design. To deal with the complexity in the model, we apply the efficient Matrix Geometric approach to obtain numerical results. We further perform simulations with real IPTV traffic to not only validate our analytical results, but also obtain further insight to the performance. © 2006 IEEE.
Gao M, Foh CH, Cai J (2012) On the selection of transmission range in underwater acoustic sensor networks., Sensors (Basel) 12 (4) pp. 4715-4729
Transmission range plays an important role in the deployment of a practical underwater acoustic sensor network (UWSN), where sensor nodes equipping with only basic functions are deployed at random locations with no particular geometrical arrangements. The selection of the transmission range directly influences the energy efficiency and the network connectivity of such a random network. In this paper, we seek analytical modeling to investigate the tradeoff between the energy efficiency and the network connectivity through the selection of the transmission range. Our formulation offers a design guideline for energy-efficient packet transmission operation given a certain network connectivity requirement.
Qureshi J, Foh CH, Cai J (2014) Maximum Multipath Routing Throughput in Multirate Wireless Mesh Networks,
In this paper, we consider the problem of finding the maximum routing
throughput between any pair of nodes in an arbitrary multirate wireless mesh
network (WMN) using multiple paths. Multipath routing is an efficient technique
to maximize routing throughput in WMN, however maximizing multipath routing
throughput is a NP-complete problem due to the shared medium for
electromagnetic wave transmission in wireless channel, inducing collision-free
scheduling as part of the optimization problem. In this work, we first provide
problem formulation that incorporates collision-free schedule, and then based
on this formulation we design an algorithm with search pruning that jointly
optimizes paths and transmission schedule. Though suboptimal, compared to the
known optimal single path flow, we demonstrate that an efficient multipath
routing scheme can increase the routing throughput by up to 100% for simple
WMNs.
Lu F, Foh CH, Cai J, Chia L-T (2009) LT codes decoding: Design and analysis, IEEE International Symposium on Information Theory - Proceedings pp. 2492-2496
LT codes provide an efficient way to transfer information over erasure channels. Past research has illustrated that LT codes can perform well for a large number of input symbols. However, it is shown that LT codes have poor performance when the number of input symbols is small. We notice that the poor performance is due to the design of the LT decoding process. In this respect, we present a decoding algorithm called full rank decoding that extends the decodability of LT codes by using Wiedemann algorithm. We provide a detailed mathematical analysis on the rank of the random coefficient matrix to evaluate the probability of successful decoding for our proposed algorithm. Our studies show that our proposed method reduces the overhead significantly in the cases of small number of input symbols yet preserves the sim plicity of the original LT decoding process. © 2009 IEEE.
Fang S, Foh CH, Aung KMM (2012) Prompt congestion reaction scheme for data center network using multiple congestion points, IEEE International Conference on Communications pp. 2679-2683
With recent advocates on end-to-end congestion control, we still observe lack of consideration of network congestion status in literature. Since end-to-end congestion control mechanisms are capable of gathering path load information through data paths, taking advantage of this information, network systems have potential capacity to react promptly in presence of congestion, especially for paths with multiple congestion points. In this paper, we design a congestion control scheme with consideration of multiple congestion points along data paths. Using an improved ECN mechanism, our scheme tunes source rate with feedbacks collecting from ECNs. We further improve our scheme with saturation detection and congestion prediction mechanisms. Simulation results show that our scheme works effectively. We evaluate our scheme and compare it with DCTCP, a recently proposed congestion control scheme for data center. In scenarios of multiple congestion points, our scheme exhibits better performance in terms of reaction time and stability. © 2012 IEEE.
Gao D, Rao Y, Foh C, Zhang H, Vasilakos A (2017) PMNDN: Proxy Based Mobility Support Approach in Mobile NDN Environment, IEEE Transactions on Network and Service Management 14 (1) pp. 191-203
In this paper, we study the source mobility problem that exists in the current named data networking (NDN) architecture and propose a proxy-based mobility support approach named PMNDN to overcome the problem. PMNDN proposes using a proxy to efficiently manage source mobility. Besides, functionalities of the NDN access routers are extended to track the mobility status of a source and signal Proxy about a handoff event. With this design, a mobile source does not need to participate in handoff signaling which reduces the consumption of limited wireless bandwidth. PMNDN also features an ID that is structurally similar to the content name so that routing scalability of NDN architecture is maintained and addressing efficiency of Interest packets is improved. We illustrate the performance advantages of our proposed solution by comparing the handoff performance of the mobility support approaches with that in NDN architecture and current Internet architecture via analytical and simulation investigation. We show that PMNDN offers lower handoff cost, shorter handoff latency, and less packet losses during the handoff process.
Xu T, Gao D, Dong P, Foh C, Zhang H (2017) Mitigating the Table-Overflow Attack in Software-Defined Networking, IEEE Transactions on Network and Service Management 14 (4) pp. 1086-1097 Institute of Electrical and Electronics Engineers (IEEE)
Software-defined networking (SDN) is a promising network paradigm for future Internet. The centralized controller and simplified switches replace the traditional complex forwarding devices, and make network management convenient. However, the switches in SDN currently have limited ternary content addressable memory (TCAM) to store specific routing rules from the controller. This bottleneck provokes cyber attacks to overload the switches. Despite existing some countermeasures for such attacks, they are proposed based on simplified attack patterns. In this paper, we review the table-overflow attack using a sophisticated attack pattern. In the attack pattern, attack flows are targeted at their middle hops instead of endpoints. We first define potential targets in the network topology, and then we propose three specific traffic features and a monitoring mechanism to detect and locate the attackers. Further, we propose a mitigation mechanism to limit the attack rate using the token bucket model. With the control of token add rate and bucket capacity, it avoids the table overflow on the victim switch. Extensive simulations in different types of topologies and experiments in our testbed are provided to show the performance of our proposal.
Al Kiyumi R, Foh C, Vural S, Chatzimisios P, Tafazolli R (2018) Fuzzy Logic-based Routing Algorithm for Lifetime Enhancement in Heterogeneous Wireless Sensor Networks, IEEE Transactions on Green Communications and Networking 2 (2) pp. 517-532 Institute of Electrical and Electronics Engineers (IEEE)
Energy consumption of sensor nodes is a key factor affecting the lifetime of wireless sensor networks (WSNs). Prolonging network lifetime not only requires energy efficient operation, but also even dissipation of energy among sensor nodes. On the other hand, spatial and temporal variations in sensor activities create energy imbalance across the network. Therefore, routing algorithms should make an appropriate trade-off between energy efficiency and energy consumption balancing to extend the network lifetime. In this paper, we propose a Distributed Energy-aware Fuzzy Logic based routing algorithm (DEFL) that simultaneously addresses energy efficiency and energy balancing. Our design captures network status through appropriate energy metrics and maps them into corresponding cost values for the shortest path calculation. We seek fuzzy logic approach for the mapping to incorporate human logic. We compare the network lifetime performance of DEFL with other popular solutions including MTE, MDR and FA. Simulation results demonstrate that the network lifetime achieved by DEFL exceeds the best of all tested solutions under various traffic load conditions. We further numerically compute the upper bound performance and show that DEFL performs near the upper bound.
WSN applications demand prolonged network operation in which manually replenishing the scarce battery resources of sensor nodes are not usually possible. When the limited energy of sensor nodes is completely exhausted, this leads to reduced coverage and may cause network partitioning, which dramatically reduces the network lifetime. In this respect, network lifetime enhancement is considered the most critical aspect of WSN performance. Prolonging network lifetime requires mechanisms that provide energy consumption balancing (ECB) in addition to energy efficiency (EE).
This thesis investigates network lifetime maximization problem and proposes solutions to address both EE and ECB. The scope covers two separate but equally important fronts: duty cycling mechanisms and maximum lifetime routing strategies. Duty cycling significantly reduces the energy consumption of sensor nodes resulting from idle listening. Meanwhile, maximum lifetime routing schemes aim at balancing traffic loads and hence energy consumption among sensor nodes across the network.
In this regard, our contributions are in three-folds. First, a distributed sleep mechanism is proposed for the non-beacon-enabled mode of the IEEE 802.15.4 MAC protocol, to support energy-efficient operation in WSNs. In addition to achieving energy savings, our mechanism helps reshape generated traffic so that the overall channel contention is reduced. This effect in turns improves packet delivery ratio at the data sink.
Second, we propose a Control-theoretic Duty Cycle Adaptation algorithm (CDCA) to adapt nodes duty cycle based on time-varying and/or spatially non-uniform data traffic loads. The proposed mechanism is distributed; hence each node adjusts its duty cycle independently. We introduce a novel concept called virtual queue, which provides better insight into actual traffic conditions in comparison to existing schemes and prevents excessive packet drop. Using NS-3 simulation, we demonstrate the performance improvements obtained from CDCA in comparison to the state of the art. Furthermore, a stability analysis is conducted to investigate system stability conditions.
Third, we formulate the maximum lifetime routing problem as a minimax optimization problem, and numerically obtain the upper bound network lifetime. Moreover, we propose a Distributed Energy-aware Fuzzy-Logic based routing algorithm (DEFL). DEFL makes an appropriate trade-off between energy efficiency and energy consumption balancing and successfully extends the network lifetime under different network conditions. The simulation results demonstrate that DEFL outperforms all tested algorithms and performs very close to the upper bound.
Keywords: Network Lifetime Maximization, Energy Efficiency, Energy Consumption Balancing, MAC, Routing, Wireless Sensor Networks.
Future communication networks promise to provide ubiquitous high-speed services for numerous users, as such, it is envisioned that one of the key aspects of the next generation of communication network is the deployment of different types of access points, e.g. small cells (SCs), on a massive scale. Meanwhile, energy efficiency (EE) has become an important feature for designing the next generation of communication networks and offering good user experience to all users while incurring low operational cost to the operators. In this context, this thesis focuses on the design of a novel green scheduling framework for improving both the EE and user fairness in the underlay HetNet scenario.

Focusing on the user/subcarrier allocation, we design an EE-based allocation boundary which dynamically categorises users into inner area and cell-edge users. Our dynamic resource allocation boundary is updated at every scheduling interval such that it can capture the time-varying characteristics of the mobile networks, contrary to the fixed boundaries used in long-term planning schemes (e.g. fractional frequency reuse). This dynamic allocation boundary is used to design a green scheduling scheme and can improve the EE of an underlay HetNet system by up to 70% as compared to existing schemes.

Focusing on the power allocation algorithm, a low-complexity energy-efficient power allocation algorithm is designed to coordinate the macro and underlay SCs and fully exploit the transmit power reduction capability of SCs. By applying a symmetric user grouping method, it is shown that the original non-convex EE optimisation problem can be transformed into a pseudo-convex problem, where the optimal power allocation can be obtained for a given user/subcarrier allocation. This energy-efficient power allocation algorithm is further incorporated with the dynamic allocation boundary which improves the EE (up to 70%) and user fairness (up to 50%) compared to existing algorithms in the underlay HetNet.

Energy harvesting (EH), which refers to replenishing energy from the environment, is demonstrated to be a promising approach in reducing the operational expenses (OPEX) and increasing the network lifetime of emerging wireless communication technologies by eliminating the need for frequent battery replacing or recharging of wireless devices. Among various ambient energy sources, the focus of this dissertation is on wireless power transfer (WPT) considering the unique characteristic of radio frequency (RF) signals; that is, they inherently carry both information and energy. A particularly interesting scenario arises when sources support simultaneous wireless information and power transfer (SWIPT) to provide a remote, controllable, and on-demand energy source. In this context, one of the promising deployment approaches is SWIPT-enabled cognitive radio networks (CRNs), which offer significant gains in terms of spectral and energy efficiencies. One of the practical scenarios of RF-powered CRN is deploying a number of distributed cognitive sensor nodes, equipped with RF EH modules, to sense a specific area and send the sensed data to an access point while coexisting with a primary licensed network. However, exploiting the full potentials of SWIPT-enabled CRNs is subject to carefully aligning the requirements of the EH unlicensed secondary receivers (SRs) with those of the legitimate primary receivers (PRs). In light of this, the first contribution of this thesis focuses on investigating the problem of beamforming for the downlink of multi-user multiple-input single-output (MU-MISO) CRNs. With the objective of minimising the transmission power of the secondary base station (SBS), optimal and suboptimal solutions for the formulated optimisation problem are provided by jointly optimising the transmit beamforming vector at the SBS and adjusting the parameters of the energy harvesters at the SRs. It is shown that the obtained solutions are efficient in meeting the EH and quality-of-service (QoS) requirements of the SRs and the levels of interference accepted by the PRs.
Apart from SWIPT-enabled CRNs, relay-assisted SWIPT networks are envisioned to be a promising framework offering extended coverage, diversity gains, and enhanced energy efficiency. In this case, the relay network itself can benefit from the relayed transmissions in terms of saving energy, and the harvested energy can be used to charge relay nodes and extend their lifetime as compensation for their role of data forwarding. Nonetheless, a concrete performance analysis on the impact of the involved system parameters such as, the energy conversion efficiency and the location of the EH relay terminal, on the trade-off between the achievable information transfer efficiency and the harvested energy level is crucial for the successful implementation of SWIPT in this context. This inspired the research work in the next two contributions with the main focus on developing novel comprehensive analytical frameworks for the investigation and evaluation of SWIPT relaying systems. Specifically, the second contribution is dedicated to examining the application of noncoherent modulation, which is recognised as an energy efficient modulation scheme for SWIPT, due to its ability to eliminate the need of instantaneous channel state information (CSI) estimation/tracking. Through adopting a moments-based approach, novel expressions are derived for the outage probability, achievable throughput, and average symbol error rate (ASER) of dual-hop SWIPT relaying systems. Furthermore, new asymptotic analytical results are derived for the high SNR regime and are then utilised to analytically quantify the achievable diversity order. The proposed mathematical tools are demonstrated to be an accurate and efficient means by which one can conduct a thorough analysis on the system performance without the burden of Monte Carlo simulations. Finally, the third contribution focuses on SWIPT relaying systems oper
Yang Ting, Heliot Fabien, Foh Chuan Heng (2018) Energy-Efficient Boundary-enabled Scheduling in the Downlink of Multi-Carrier Multi-Access Heterogeneous Network, IEEE Transactions on Green Communications and Networking Institute of Electrical and Electronics Engineers (IEEE)
Future communication networks promise to provide
ubiquitous high-speed services for numerous users via densely
deployed small cells. They should offer good user experiences
to all the users while incurring a low operational cost to the
operators. User scheduling is a well-known approach to deliver
good user experience, and recent works further demonstrate
that it is also beneficial to improve energy efficiency (EE).
However, existing EE-based scheduling schemes tend to favor
users with good channel condition which lead to unfair user
experiences. In this paper, we introduce a new concept of resource
allocation boundary where EE and user fairness can be addressed
simultaneously. We derive the boundary that partition in an
effective manner the users into different groups. By applying an
appropriate scheduling strategy to each group of users, not only
users with poorer channel conditions can be served fairly, but
the EE of the system can be further improved. We also provide a
low-complexity energy-efficient power allocation algorithm that is
designed to fully exploit the transmit power reduction capability
of small cells. Simulation results show that our new scheduling
scheme can improve the EE and user fairness when compared
to existing approaches, i.e. by up to 63% and 56%, respectively.