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Dr Chang Ge


My publications

Publications

Ge C, Sun Z, Wang N (2012) A survey of power-saving techniques on data centers and content delivery networks,IEEE COMMUNICATIONS SURVEYS & TUTORIALS 15 (3) pp. 1334-1354 IEEE
How to reduce power consumption within individual data centers has attracted major research efforts in the past decade, as their energy bills have contributed significantly to the overall operating costs. In recent years, increasing research efforts have also been devoted to the design of practical powersaving techniques in content delivery networks (CDNs), as they involve thousands of globally distributed data centers with content server clusters. In this paper, we present a comprehensive survey on existing research works aiming to save power in data centers and content delivery networks that share high degree of commonalities in different aspects. We firstly highlight the necessities of saving power in these two types of networks, followed by the identification of four major power-saving strategies that have been widely exploited in the literature. Furthermore, we present a high-level overview of the literature by categorizing existing approaches with respect to their scopes and research directions. These schemes are later analyzed with respect to their strategies, advantages and imitations. In the end, we summarize several key aspects that are considered to be crucial in effective power-saving schemes. We also highlight a number of our envisaged open research directions in the relevant areas that are of significance and hence require further elaborations.
Ge C, Sun Z, Wang N, Xu K, Wu J (2014) Energy Management in Cross-Domain Content Delivery Networks: A Theoretical Perspective.,IEEE Transactions on Network and Service Management 11 (3) 3 pp. 264-277
In a content delivery network (CDN), the energy cost is dominated by its geographically distributed data centers (DCs). Generally within a DC, the energy consumption is dominated by its server infrastructure and cooling system, with each contributing approximately half. However, existing research work has been addressing energy efficiency on these two sides separately. In this paper, we jointly optimize the energy consumption of both server infrastructures and cooling systems in a holistic manner. Such an objective is achieved through both strategies of: 1) putting idle servers to sleep within individual DCs; and 2) shutting down idle DCs entirely during off-peak hours. Based on these strategies, we develop a heuristic algorithm, which concentrates user request resolution to fewer DCs, so that some DCs may become completely idle and hence have the opportunity to be shut down to reduce their cooling energy consumption. Meanwhile, QoS constraints are respected in the algorithm to assure service availability and end-to-end delay. Through simulations under realistic scenarios, our algorithm is able to achieve an energy-saving gain of up to 62.1% over an existing CDN energy-saving scheme. This result is bound to be near-optimal by our theoretically-derived lower bound on energy-saving performance.
Ge C, Wang N, Skillman SM, Foster G, Cao Y (2016) QoE-Driven DASH Video Caching and Adaptation at 5G Mobile Edge,Proceedings of the 3rd ACM Conference on Information-Centric Networking pp. 237-242
In this paper, we present a Mobile Edge Computing (MEC) scheme for enabling network edge-assisted video adaptation based on MPEG-DASH (Dynamic Adaptive Streaming over HTTP). In contrast to the traditional over-the-top (OTT) adaptation performed by DASH clients, the MEC server at the mobile network edge can capture radio access network (RAN) conditions through its intrinsic Radio Network Information Service (RNIS) function, and use the knowledge to provide guidance to clients so that they can perform more intelligent video adaptation. In order to support such MECassisted DASH video adaptation, the MEC server needs to locally cache the most popular content segments at the qualities that can be supported by the current network throughput. Towards this end, we introduce a two-dimensional user Quality-of-Experience (QoE)-driven algorithm for making caching / replacement decisions based on both content context (e.g., segment popularity) and network context (e.g., RAN downlink throughput). We conducted experiments by deploying a prototype MEC server at a real LTE-A based network testbed. The results show that our QoE-driven algorithm is able to achieve significant improvement on user QoE over 2 benchmark schemes
Ge C, Wang N, Sun Z (2012) Optimizing Server Power Consumption in Cross-Domain Content Distribution Infrastructures,IEEE International Conference on Communications pp. 2628-2633
Optimizing server?s power consumption in content distribution infrastructure has attracted increasing research efforts. The technical challenge is the tradeoff between server power consumption and the content service capability on both the server and the network side. This paper proposes and evaluates a novel approach that optimizes content servers? power consumptions in large-scale content distribution platforms across multiple ISP domains. Specifically, our approach strategically puts servers to sleep mode without violating load capacities of virtual content delivery links and active servers in the infrastructure. Such a problem can be formulated into a nonlinear programming model. The efficiency of our approach is evaluated in a content distribution topology covering two real interconnected domains. The simulation has shown that our approach is capable of reducing servers? power consumptions by up to 62.2%, while maintaining the actual service performance in an acceptable scope.
Ge C, Wang N, Foster G, Wilson M (2017) Towards QoE-assured 4K Video-on-Demand Delivery through Mobile Edge Virtualization with Adaptive Prefetching,IEEE Transactions on Multimedia 19 (10) pp. 2222-2237 IEEE
Internet video streaming applications have been
demanding more bandwidth and higher video quality, especially
with the advent of Virtual Reality (VR) and Augmented
Reality (AR) applications. While adaptive streaming protocols
like MPEG-DASH (Dynamic Adaptive Streaming over HTTP)
allows video quality to be flexibly adapted, e.g., degraded when
mobile network condition deteriorates, this is not an option if the
application itself requires guaranteed 4K quality at all time. On
the other hand, conventional end-to-end TCP has been struggling
in supporting 4K video delivery across long-distance Internet
paths containing both fixed and mobile network segments
with heterogeneous characteristics. In this paper, we present a
novel and practically-feasible system architecture named MVP
(Mobile edge Virtualization with adaptive Prefetching), which
enables content providers to embed their content intelligence
as a virtual network function (VNF) into the mobile network
operator?s (MNO) infrastructure edge. Based on this architecture,
we present a context-aware adaptive video prefetching scheme
in order to achieve QoE-assured 4K video on demand (VoD)
delivery across the global Internet. Through experiments based
on a real LTE-A network infrastructure, we demonstrate that
our proposed scheme is able to achieve QoE-assured 4K VoD
streaming, especially when the video source is located remotely
in the public Internet, in which case none of the state-of-the-art
solutions is able to support such an objective at global Internet
scale.
Qian P, Wang N, Oh B, Ge C, Tafazolli R Optimization of Webpage Downloading Performance with Content-aware Mobile Edge Computing,MECOMM '17 Proceedings of the Workshop on Mobile Edge Communications pp. 31-36 Association for Computing Machinery (ACM)
With increased complexity of webpages nowadays, computation
latency incurred by webpage processing during downloading operations
has become a newly identified factor that may substantially
affect user experiences in a mobile network. In order to tackle this issue,
we propose a simple but effective transport-layer optimization
technique which requires necessary context information dissemination
from the mobile edge computing (MEC) server to user devices
where such an algorithm is actually executed. The key novelty in
this case is the mobile edge?s knowledge about webpage content
characteristics which is able to increase downloading throughput
for user QoE enhancement. Our experiment results based on a real
LTE-A test-bed show that, when the proportion of computation
latency varies between 20% and 50% (which is typical for today?s
webpages), the downloading throughput can be improved up to
34.5%, with reduced downloading time by up to 25.1%
Ge Chang, Wang Ning, Chai W, Hellwagner H (2018) QoE-Assured 4K HTTP Live Streaming via
Transient Segment Holding at Mobile Edge
,
IEEE Journal on Selected Areas in Communications (J-SAC) 36 (8) pp. 1816-1830 IEEE
HTTP-based live streaming has become increasingly
popular in recent years, and more users have started generating
4K live streams from their devices (e.g., mobile phones) through
social-media service providers like Facebook or YouTube. If the
audience is located far from a live stream source across the global
Internet, TCP throughput becomes substantially suboptimal
due to slow-start and congestion control mechanisms. This is
especially the case when the end-to-end content delivery path
involves radio access network (RAN) at the last mile. As a result,
the data rate perceived by a mobile receiver may not meet the
high requirement of 4K video streams, which causes deteriorated
Quality-of-Experience (QoE). In this paper, we propose a scheme
named Edge-based Transient Holding of Live sEgment (ETHLE),
which addresses the issue above by performing context-aware
transient holding of video segments at the mobile edge with
virtualized content caching capability. Through holding the
minimum number of live video segments at the mobile edge cache
in a context-aware manner, the ETHLE scheme is able to achieve
seamless 4K live streaming experiences across the global Internet
by eliminating buffering and substantially reducing initial startup
delay and live stream latency. It has been deployed as a virtual
network function at an LTE-A network, and its performance has
been evaluated using real live stream sources that are distributed
around the world. The significance of this paper is that by
leveraging virtualized caching resources at the mobile edge, we
address the conventional transport-layer bottleneck and enable
QoE-assured Internet-wide live streaming services with high data
rate requirements.
Ge Chang, Wang Ning, Selinis Ioannis, Cahill Joe, Kavanagh Mark, Liolis Konstantinos, Politis Christos, Nunes Jose, Evans Barry, Rahulan Yogaratnam, Nouvel Nivedita, Boutin Mael, Desmauts Jeremy, Arnal Fabrice, Watts Simon, Poziopoulou Georgia (2019) QoE-Assured Live Streaming via Satellite Backhaul in 5G Networks,IEEE Transactions on Broadcasting IEEE
Satellite communication has recently been included
as one of the key enabling technologies for 5G backhauling,
especially for the delivery of bandwidth-demanding enhanced
mobile broadband (eMBB) applications in 5G. In this paper,
we present a 5G-oriented network architecture that is based
on satellite communications and multi-access edge computing
(MEC) to support eMBB applications, which is investigated in
the EU 5GPPP Phase-2 SaT5G project. We specifically focus on
using the proposed architecture to assure Quality-of-Experience
(QoE) of HTTP-based live streaming users by leveraging satellite
links, where the main strategy is to realise transient holding and
localization of HTTP-based (e.g., MPEG-DASH or HTTP Live
Streaming) video segments at 5G mobile edge while taking into
account the characteristics of satellite backhaul link. For the very
first time in the literature, we carried out experiments and systematically
evaluated the performance of live 4K video streaming
over a 5G core network supported by a live geostationary satellite
backhaul, which validates its capability of assuring live streaming
users? QoE under challenging satellite network scenarios.
Wang Ning, Nouwell Nivedita, Ge Chang, Evans Barry, Rahulan Yogaratnam, Boutin Mael, Desmauts Jeremy, Liolis Konstantinos, Politis Christos, Votts Simon, Poziopoulou Georgia (2018) Satellite Support for Enhanced Mobile Broadband Content Delivery in 5G,Proceedings of 2018 IEEE International Symposium on Broadband Multimedia Systems and Broadcasting (BMSB 2018) pp. 1-6 Institute of Electrical and Electronics Engineers (IEEE)
Satellite communication has recently been included as one of the enabling technologies for 5G backhauling, in particular for the delivery of bandwidth-demanding enhanced mobile broadband (eMBB) application data in 5G. In this paper we introduce a 5G-oriented network architecture empowered by satellite communications for supporting emerging mobile video delivery, which is investigated in the EU 5GPPP Phase 2 SAT5G Project. Two complementary use cases are introduced, including (1) the use of satellite links to support offline multicasting and caching of popular video content at 5G mobile edge, and (2) real-time prefetching of DASH (Dynamic Adaptive Streaming over HTTP) video segments by 5G mobile edge through satellite links. In both cases, the objective is to localize content objects close to consumers in order to achieve assured Quality of Experiences (QoE) in 5G content applications. In the latter case, in order to circumvent the large end-to-end propagation delay of satellite links, testbed based experiments have been carried out to identify specific prefetching policies to be enforced by the Multiaccess computing server (MEC) for minimizing user perceived disruption during content consumption sessions.
Ge Chang, Wang Ning, Selinis Ioannis, Cahill Joe, Kavanagh Mark, Liolis Konstantinos, Politis Christos, Nunes Jose, Evans Barry, Rahulan Yogaratnam, Nouvel Nivedita, Boutin Mael, Desmauts Jeremy, Arnal Fabrice, Watts Simon, Poziopoulou Georgia (2019) QoE-Assured Live Streaming via Satellite Backhaul in 5G Networks,IEEE Transactions on Broadcasting 65 (2) pp. 381-391 Institute of Electrical and Electronics Engineers (IEEE)
Satellite communication has recently been included as one of the key enabling technologies for 5G backhauling, especially for the delivery of bandwidth-demanding enhanced mobile broadband (eMBB) applications in 5G. In this paper, we present a 5G-oriented network architecture that is based on satellite communications and multi-access edge computing to support eMBB applications, which is investigated in the EU 5GPPP phase-2 satellite and terrestrial network for 5G project. We specifically focus on using the proposed architecture to assure quality-of-experience (QoE) of HTTP-based live streaming users by leveraging satellite links, where the main strategy is to realize transient holding and localization of HTTP-based (e.g., MPEG-DASH or HTTP live streaming) video segments at 5G mobile edge while taking into account the characteristics of satellite backhaul link. For the very first time in the literature, we carried out experiments and systematically evaluated the performance of live 4K video streaming over a 5G core network supported by a live geostationary satellite backhaul, which validates its capability of assuring live streaming users' QoE under challenging satellite network scenarios.