Relay-Assisted Cooperative Communication Networks

To facilitate the demand for a higher spectrum and power efficiency arising from the next generation mobile communication system, the introduction of relay-aided cooperative communication into the existing cellular infrastructure is considered as the most practical improvement under high rate and coverage. In comparison with the legacy cellular network, relay-aided cooperative communication network enjoys relative advantages over coverage efficiency, operation cost and transmission capacity. Transmission in relay-aided cooperative system falls into three types: the three-terminal transmission model, two-hop multi-relay parallel transmission model, and multi-hop multi-relay transmission model. For the extensive perspective of relay-aided cooperative communication in application, a profound research has been carried out in communication standards such as Worldwide Interoperability for Microwave Access (WiMAX) and Wireless World Initiative New Radio (WINNER).

Multi-hop routing for energy-efficiency enhancement in relay-assisted device-to-device communication

Financial and environment considerations present new trends in wireless network known as green communication. As one of the most promising network architectures, the device-to-device （D2D） communication should take seriously account to the energy-efficiency. Most of the existing work in the area of D2D communication only focus on the direct communication, however, the direct link D2D communication has to be limited in practice because of long distance, poor propagation medium and cellular interference, etc. A new energy-efficient multi-hop routing algorithm was investigated for multi-hop D2D system by jointly optimizing channel reusing and power allocation. Firstly, the energy-efficient multi-hop routing problem was formulated as a combinatorial optimization problem. Secondly, to obtain a desirable solution with reasonable computation cost, a heuristic multi-hop routing algorithm was presented to solve the formulated problem and to achieve a satisfactory energy-efficiency performance. Simulation shows the effectiveness of the proposed routing algorithm.

Relay Selection Scheme for AF System with Partial CSI and Optimal Stopping Theory

Relay selection for Relay Assisted(RA)networks is an economical and effective method to improve the spectrum efficiency.Relay selection performs especially well when the source node has accurate and timely Channel State Information(CSI).However,since perfect CSI knowledge is rarely available,research of relay selection with partial(statistical)CSI is of paramount importance.In this paper,relay selection for RA networks with statistical CSI is formulated as a Multiple-Decision(MD)problem.And,the cost of obtaining the CSI is also considered in the formulated problem.Two relay selection schemes,Maximal Selection Probability(MSP)and Maximal Spectrum Efficiency Expectation(MSEE),are proposed to solve the formulated MD problem under different optimal criteria assumptions based on the optimal stopping theory.The MSP scheme maximizes the probability that the Best Assisted Relay Candidate(BARC)can be selected,whereas the MSEE scheme provides the maximal expectation of the spectrum efficiency.Experimental results show that the proposed schemes effectively improve the spectrum efficiency,and the MSEE scheme is more suitable for stable communication cases.Meanwhile,the MSP scheme is more suitable for burst communication cases.

Loading-Balance Relay-Selective Strategy Based on Stochastic Dynamic Program

A Relay-Assisted （RA） network with relay selection is considered as a type of effective technology to improve the spectrum and energy efficiency of a cellular network. However, loading balance of the assisted relay node becomes an inevitable bottleneck in RA network development because users do not follow uniform distribution. Furthermore, the time-varying channel condition of wireless communication is also a major challenge for the RA network with relay selection. To solve these problems and improve the practicability of the RA network, a Loading Balance-Relay Selective （LBRS） strategy is proposed for the RA network in this paper. The proposed LBRS strategy formulates the relay selection of the RA network under imperfect channel state information assumption as a Multistage Decision （MD） problem. An optimal algorithm is also investigated to solve the proposed MD problem based on stochastic dynamic program. Numerical results show that the performance of the LBRS strategy is better than that of traditional greedy algorithm and the former is effective as an exhaustive search-based method.