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Optimization scheme with pre-processing for cooperative relay multicast networks in cellular system

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The Journal of china Universities of posts and telecommunications 2011年第3期18卷 16-21页

作者： WANG Cheng-jin li xi ZHANG lin ji hong key laboratory Of universal wireless Communication Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China

For cooperative relay multicast networks, the general cross-layer optimization approaches converge to the global optimal value slowly because of the large quantity of relay terminals. However, the mobility of relay terminals requires quick converging optimization strategies to refresh the relay links frequently. Based on the capacity analysis of multiple relay channels, an improved cross-layer optimization scheme is proposed to resolve this problem, in which the bound of the relay selecting region is determined as a pre-processing. Utilizing the primal-dual algorithm, a cross-layer framework with pre-processing optimizes both the relay terminal selection and power allocation with quick convergence. The simulation results prove the effectiveness of the proposed algorithm.

关键词： cooperative relay cross-layer optimization pre-processing multicast

Scalable peer-to-peer resource discovering scheme for wireless self-organized networks

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The Journal of china Universities of posts and telecommunications 2009年第2期16卷 47-52,57页

作者： li xi ji hong key laboratory of universal wireless communications Minisa-y of Education Beijing University of Posts and Telecommunications Beijing 100876 China

Peer-to-peer technologies have attracted increasing research attention with fruitful protocols and applications proposed for wired networks. As to mobile environments, there are currently no mature deployments. A novel resource managing and discovering protocol, Cheer, is proposed to realize scalable and effective peer-to-peer lookup in wireless self-organized networks. Cheer resolves the topologies mismatch problem between peer-to-peer overlay networks and actual nodes distribution, allowing for frequent nodes membership changes. With specially designed resource storage table, Cheer also supports multikey and fuzzy lookup. Its hybrid architecture and improved routing scheme based on small-world theory may realize effective lookup routing. Theoretical analysis and simulation results both prove that Cheer makes using peer-to-peer applications in large-scale self-organized mobile networks feasible and promising.

关键词： peer-to-peer small-world resource discovering

Cross-layer scheduling with fairness for multi-user OFDM system:a restless bandit approach

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The Journal of china Universities of posts and telecommunications 2011年第4期18卷 25-30页

作者： GE Wen-dong ji hong li xi key laboratory of universal wireless communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China

In OFDM-based System such as long term evolution （LTE）, the scheduling scheme plays an essential role in not only improving the capacity of system, but also guarantee the fairness among the user equipments （UEs）. However, most existing work about scheduling only considers the current throughput in physical layer. Thus in this paper, a cross-layer scheduling with fairness based on restless bandit （CSFRB） scheme with the ＇indexability＇ property is proposed for the multi-user orthogonal frequency-division multiplexing （OFDM） system to minimize the distortion in the application layer, to maximize the throughput and to minimize the energy consumption in the physical layer. The scheduling problem is firstly established as a restless bandit problem, which is solved by the primal-dual index heuristic algorithm based on the first order relaxation with low complexity, to yield the CSFRB scheme. AdditionaUy, this scheme is divided into offiine computation and online selection, where main work will be finished in former one so as to decrease the complexity further. Finally, extensive simulation results illustrate the significant performance improvement of the proposed CSFRB scheme compared to the existing one in different scenarios.

关键词： multi-user OFDM scheduling cross-layer design restless bandits

MEC-Assisted Flexible Transcoding Strategy for Adaptive Bitrate Video Streaming in Small Cell Networks

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china communications 2021年第2期18卷 200-214页

作者： Chunyu liu Heli Zhang hong ji xi li School of Information and Communication Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China key laboratory of universal wireless communications Ministry of Education(Beijing University of Posts and Telecommunications)Beijing 100876China

Adaptive bitrate video streaming(ABR)has become a critical technique for mobile video streaming to cope with time-varying network conditions and different user ***,there are still many problems in achieving high-quality ABR video streaming over cellular *** Edge Computing(MEC)is a promising paradigm to overcome the above problems by providing video transcoding capability and caching the ABR video streaming within the radio access network(RAN).In this paper,we propose a flexible transcoding strategy to provide viewers with low-latency video streaming services in the MEC networks under the limited storage,computing,and spectrum *** to the information collected from users,the MEC server acts as a controlling component to adjust the transcoding strategy flexibly based on optimizing the video caching placement ***,we cache the proper bitrate version of the video segments at the edge servers and select the appropriate bitrate version of the video segments to perform transcoding under jointly considering access control,resource allocation,and user *** formulate this problem as a nonconvex optimization and mixed combinatorial ***,the simulation results indicate that our proposed algorithm can ensure a low-latency viewing experience for users.

关键词： mobile edge computing adaptive bi-trate video streaming flexible transcoding strategy ADMM

Balanced energy-efficient relay selection scheme in wireless mobile relay networks

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High Technology Letters 2010年第3期16卷 235-240页

作者： liu Wei ji hong li xi key laboratory of universal wireless communications Ministry＂ of Education Beijing University of Posts and Telecommunications Beijing 100876 P.R. China

In order to resolve the relay selection problem in wireless mobile relay networks （WMRNs）, a novel balanced energy-efficient mobile relay selection scheme is proposed in this paper. Compared with traditional counter-based algorithm, distance and energy consumption are considered from network respect to provide a better network lifetime performance in the proposed scheme. Also, it performs well when nodes move freely at high speed. A random assessment delay （RAD） mechanism is added to avoid collisions and improve transmission efficiency. Simulation results reveal that, the proposed scheme has advantages in prolonging network lifetime, balancing energy compared with existing counter-based scheme. consumption and reducing the total energy consumption

关键词： relay network lifetime energy-efficient wireless mobile relay network (WMRN) random assessment delay(RAD)

Handover improvement based on cost function and user fairness for cellular relay enhanced LTE networks

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High Technology Letters 2011年第3期17卷 299-304页

作者： Chen Muqiong ji hong li xi key laboratory of universal wireless communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 P. R. China

In order to optimize handover target selection and achieve better handover performance in cellular relay networks under the long term evolution （LTE） system, a novel handover measurement and decision scheme based on cost function is proposed in the paper. The relay-enhanced network provides user equipment （UE） multiple handover choices from neighbor base stations or relays. This may result in different overhead, resource utility and traffic load which attaches importance to proper handover schemes. Compared with traditional handover measurement and decision schemes, the proposed scheme adopts reference signal receiving quality （RSRQ） in the measurement stage and uses a modified signal cost function considering signal overhead in different handover types and expected long-term throughput of UE. Besides, UE fairness and sector resource utilization are taken into account as well. Theory analysis and simulation results prove that the proposed scheme can enhance cell throughput, decrease handover delay and signal overhead, and improve UE fairness.

关键词： handover relay cost function fairness

Coalition-based downlink resource allocation for LTE system with divide-and-conquer approach

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The Journal of china Universities of posts and telecommunications 2012年第6期19卷 1-5页

作者： GAO xiang li xi ji hong li Yi key laboratory of universal wireless communications Ministry of EducationBeijing University of Posts and Telecommunications

To take advantage of the multiuser diversity resulted from the variation in channel conditions among the users, it has become an interesting and challenging problem to efficiently allocate the resources such as subcarriers, bits, and power. Most of current research concentrates on solving the resource-allocation problem for all users together in a centralized way, which brings about high computational complexity and makes it impractical for real system. Therefore, a coalitional game framework for downlink multi-user resource allocation in long term evolution （LTE） system is proposed, based on the divide-and-conquer idea. The goal is to maximize the overall system data rate under the constraints of each user＇s minimal rate requirement and maximal transmit power of base station while considering the fairness among users. In this framework, a coalitional formation algorithm is proposed to achieve optimal coalition formation and a two-user bargaining algorithm is designed to bargain channel assignment between two users. The total computational complexity is greatly reduced in comparison with conventional methods. The simulation results show that the proposed algorithms acquire a good tradeoff between the overall system throughout and fairness, compared to maximal rate and max-min schemes.

关键词： LTE resource allocation divide-and-conquer coalitional game bargaining solution

Resource allocation for load balancing and fairness improvement in relay-assisted OFDMA cellular

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High Technology Letters 2011年第4期17卷 377-382页

作者： Zhang Hailong ji hong li xi key Lab of universal wireless communications Ministry of EducationBeijing University of Posts and Telecommunications Beijing 100876 P.R.China

A resource allocation scheme with the considerations of user fairness and load balancing is proposed in orthogonal frequency division multiple access （OFDMA）-based relay networks. The optimal resource allocation scheme is formulated mathematically to maximize the minimum achievable rate among all user equipments （UEs） for fairnegs improvement. The optimal problem has been proved to be N-P-hard and it is prohibitive to find the optimal solution for its computational complexity. Accordingly, this paper proposes a suboptimal scheme which considers not only user fairness but also load balancing among base stations （BS） and relay stations （RSs） during resource allocation procedure. The suboptimal scheme takes the traffic load of access nodes （BS and RSs） into consideration to balance the system traffic load, which would prevent them from overloading and throughput degradation. Simulation results show that the suboptimal scheme performs similarly to the optimal solution and can enhance the system fairness and load balancing performance significantly compared with the traditional schemes.

关键词： radio resource allocation relay fairness load balancing orthogonal frequency division multiple access (OFDMA)

Adaptive minimum bit feedback for sum-rate analysis in multi-user distributed antenna systems

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The Journal of china Universities of posts and telecommunications 2013年第2期20卷 32-36页

作者： ZHANG xiao-liang ji hong li xi key laboratory of universal wireless communications Ministry of Education Beijing University of Posts and Telecommunications

The paper mainly studies the sum-rate performance of limited feedback （LFB） block-diagonalization （BD） in multi-user distributed antenna system （DAS）. As the channel state information （CSI） fed back to base station （BS） is limited, multi-user interference （MUI） is caused inevitably because of the quantization error. Considering the influence of the MUI to the capacity of DAS, we propose a parameter of effective sum-rate ratio （ESRR） to denote the capacity offset under the condition of the BS can get perfect CSI and limited CSI first, then we confirm that the approximated ESRR is very close to actual ESRR got through simulations. After that, based on the approximated ESRR, an adaptive minimum bit feedback scheme which can effectively reduce the overhead of feedback channel and the complexity of the system is proposed. Simulation results show the effectiveness of the proposed scheme.

关键词： BD DAS ESRR minimum bit feedback