Resource Allocation And Protocol Design For Wireless Cooperative Systems

Cooperative communication is a promising diversity technique that has attractedsignificant research interests,where mobile nodes share their information andtransmit cooperatively,forming a virtual antenna array and thus providing diversityto combat signal fading due to multipath propagation without requirement ofadditional antennas at each node.In this dissertation,we investigate the problem that how to improve theperformance of cooperative communication under various scenarios by resourceallocation on physical layer and higher layers' protocols design.Firstly,we analyze the outage probability of two cooperative protocols,CRC-based selection decode-and-forward (CDF) and amplify-and-forward (AF),andillustrate the different impacts they suffer from modulation and coding schemes.Furthermore,considering quality of service (QoS) requirement,an extended linkadaptation (ELA) technique is proposed for transmission rate maximization.Outageprobability optimization based power allocation and adaptive modulation and codingtechnique are jointly designed to improve its performance.Simulation results showthat with the ELA,the two merits of cooperation,improved transmission rate andincreased coverage,can be further effectively enhanced.Secondly,cooperative communication is integrated with the multicarrier systems.For the AF-based multicarrier cooperative system,both the optimal and suboptimalresource allocation algorithms are proposed for bit error rate (BER) minimizationand rate maximization,respectively,utilizing joint power allocation,subcarrierreassignment design and adaptive modulation and coding techniques.Simulationresults show that the proposed BER-minimization algorithms not only reduce BEReffectively,but also improve the diversity order.In addition,with the locationinformation knowledge,the optimal BER performance can be achieved just bysetting an appropriate complexity coefficient of the suboptimal algorithm.Simulation results of the rate-maximization algorithm verify its advantage of efficient date rate improvement under very low implementation complexity.Thirdly,for the distributed wireless communication systems,cross-layeroptimization between cooperative communication on physical layer and protocoldesign on medium access control (MAC) layer is considered.We first discussvarious issues and challenges on designing an efficient cooperative MAC.Then,focusing on helper selection,a cooperative MAC based on IEEE 802.11 DCF isproposed under the scenario of single hop networks.After that,we extend our workto multihop network scenario and propose a two-hop interference model from aMAC perspective to analyze the performance of a cooperative network in term ofspatial and frequency reuse.It is found that with cooperation,a cooperative linkbenefits from less interference due to more suppressed interference sources,however,the increased number of blocked traffic nodes can degrade the network performancedue to a lower spatial frequency reuse.To verify the influence of cooperativecommunication on such networks,a cross-layer designed busy-tone basedcooperative MAC scheme is proposed.Furthermore,destination-assistedcollision-free piggyback mechanism and group-based helper contention are proposedin the new MAC scheme to solve the new hidden terminal problem caused bycooperation and to further improve the efficiency of helper selection,respectively.Simulation of the new cooperative MAC scheme is done to investigate theinfluenced factors including node density and traffic load.Last but not least,cooperation is further extended to application layer.Takinglocation problem as an example,we investigate the problem that how to make use ofcooperation between neighbor nodes to help to solve location in wireless sensornetworks (WSNs).A distributed location method called 3/2-NANDB based ondistance measurement is proposed according to the principle of minimal hardwarecost.Due to the information sharing between neighbors,3/2-NANDB cansufficiently mine redundant information among nodes,and effectively eliminate thedilemma of node's position.It ascertains the positions of the nodes having twoneighborhoods completely and a part of nodes which only have one neighborhood as well.It achieves the goals of reducing the number of nodes equipped with GPS,maximizing the number of localizable nodes in networks,extending the networks'observation area and prolonging the lifetime of WSNs.Using the node's dilemmaelimination algorithm,it also can assist other algorithms which are based on 3-NAlocation algorithm to improve their location performance.