Research On Optimal Scheduling Algorithm In Relay Enhanced OFDMA System

With the rapid development of modern wireless communication system, peoplebring up the higher and stricter requirements to coverage of cell-edge users, networkthroughput, cost of facilities and transmission rate for the next generation wirelesscommunication system．As one of the key technologies for the fourth generation mobilecommunication system, the relay technology can effectively solve a series ofchallenging problems that Orthogonal Frequency Division Multiple Access (OFDMA)system faced, which greatly enhances its overall performance. Therefore, the relaytechnology incorporated with OFDMA in the wireless communication system hasreceived high degree of attention and considerable recognition in academics andindustry, which is becoming one of the develop trends of wireless communicationsystem.In OFDMA based relay enhanced cellular networks, the introduce of relaytechnology makes the demand of frequency spectra resource in system further increasedand the level of complexity of resource schedule enhanced. Therefore, rational resourcescheduling and allocation became a challenging hot issue，and further discussion andinvestigation about the new resource scheduling have important research value andpractical significance.First, for relay cooperation system, optimal power allocation aimed at systemcapability maximization is mainly researched, meanwhile, a selective coordinationstrategy is presented, which can provide diversity gain and improve bandwidth utilityefficiency. In addition, the influence of relay location on system performance isdiscussed, and joint optimization for relay location and power allocation scheme isobtained.Secondly, resource scheduling algorithms for OFDMA system are researched.Three kinds of classical sub-carrier scheduling are studied, which is Round Robin, maxC/I and Proportional Fair. And Proportional Fair can make the whole system reach thebest state by simulation analysis.At last, resource scheduling algorithms for relay enhanced OFDMA system arestudied emphatically. According to the process of resources scheduling, we willresearch on both sub-carrier scheduling and power allocation. First, several kinds of sub-carrier scheduling algorithms are studied. One hand, simulation results verify thatrelay enhanced cellular system outperform the traditional networks significantly, on theother hand, considering the tradeoff between the system throughput and user fairness,Partial Proportional Fair can make the whole system reach the best state. And secondly,after sub-carrier scheduling, the power allocation strategy is researched simply.