Resource Optimization And Schedulingalgorithms In Cooperative Relay Systems

With the development of wireless mobile communication systems, more and morenew technology is introduced. Orthogonal frequency division multiplexing (OFDM) hasbecome one of the key technologies of the future communications as OFDM can reducethe frequency selective fading and improve the spectral efficiency. Relay technologycan expand coverage and improve the system capacity. Resource allocation andscheduling program can further enhance the system performance. In this paper, westudy resource allocation and scheduling algorithms in OFDM relay systemsconsidering the user's QoS requirements.First, the research status of resource allocation and scheduling in the relay systemsis summarized and the research problem is proposed. Then, the theory of relay andOFDM is described which is theoretical basis for the paper. As a whole, resourceallocation, feedback mechanism and cross-layer scheduling is studied in depth aroundthe user QoS requirements and a variety of programs are proposed on the basis ofexisting research results.An optimal mathematical model which aims to minimize the difference betweenthe achievable rate and the expected data rate of the users is formulated inOFDMA-based relaying networks where the users have the expected rate. First, ajointing subcarrier pairing and dynamic subcarrier allocation algorithm is proposedunder average power allocation of source and relay node. Then, an improved algorithmis proposed to insure the fairness when the recourses are insufficient. Further, as the datarate of the first hop and the second hop is mismatched with the average power allocationand the power is wasted, a program saving system power is proposed without affectingthe system target.Achieving all channel information is the premise of resource allocation andscheduling. In order to reduce system feedback, a feedback mechanism with fixedthreshold based on outage probability is proposed for OFDM relay system with differentuser traffic rate. A feedback mechanism with dynamic threshold based on user trafficrate is proposed to distinguish the different user traffic rate. And this mechanism candynamically adjust user feedback threshold according to user traffic rate. In order tomeet the user traffic rate, a cross-layer scheduling criteria is further proposed whichcombines the traffic rate information of the business layer, queue status information of the MAC layer and channel state information of the physical layer. Finally, a feedbackscheduling program supporting different traffic is proposed. Feedback users are first gotthrough the feedback mechanism with dynamic threshold, and then the feedback usersare scheduled through the determined priority.