Research Of Resource Allocation Algorithms In Wireless Relay Networks

Along with the development of wireless networks, users require higher performance on network throughput, system capacity, user fairness, reliability and so on. However, the limited wireless resources and the fading property of wireless channel limit the performance. The introducing of relay nodes to traditional cellular networks decreases the distance between nodes and can enhance the system capacity and enlarge the coverage. Now relay has been the research hot spot.This thesis introduces the system model, network architecture and key technologies of wireless relay networks and discusses the relay selection and resource allocation in wireless relay networks.This thsis proposes a resource allocation scheme with user fairness and load balancing considerations in fixed relay networks. The optimal resource allocation scheme is formulated mathematically to maximize the minimum achievable rate among all UEs for fairness improvement. The optimal problem has been proved to be NP-hard and it is prohibitive to find the optimal solution for its computational complexity. Accordingly, a suboptimal scheme with low complexity is proposed.This thesis also proposes a cooperation scheme including relay selection and sub-frame division using hierarchical modulation (HM) to fully exploit the radio resources in cellular networks where UEs relay for each other. The relay selection procedure considers both the channel conditions and the energies left in relays to make the cooperative communications behave better. The bits of relay-aided UE and its relay (which is also a UE) are transmitted simultaneously in one sub-channel using HM to improve the utilization efficiency of sub-channels. Besides, time resources are used effectively with the sub-frame division scheme. Then the proposed scheme can improve the spectrum efficiency.In addition, a simulation platform for wireless relay networks is set up based on NS2. The model of wireless nodes in NS2 is modified, the nodes and protocol stack in line with orthogonal frequency division multiple access (OFDMA) based wireless relay networks are designed and some functions in radio resource management module are modified. OTCL scripts are written to implement the functions of adding protocol stacks, establishing connection, starting services and so on. At last, we can configure the network scenarios, execute the scripts and analyze the trace files.