Research On Resource Allocation Via Frequency Sharing In Wireless Relay OFDM Network

Resource allocation is a major technical challenge for network performance optimization in wireless multi-hop relay networks. Most of the existing works on resource allocation either assume a hop by hop transmission framework, or adopt spatial frequency reuse among different hops. The former scheme is simple but leads to inefficient use of spectrum resource. The latter one can increase the system throughput but meanwhile also requires highly complex inter-hop interference cancellation.In this thesis, we propose a frequency sharing scheme for resource allocation in OFDM based relay networks. It enables simultaneous transmission of multiple hops without causing inter-hop interference. By carefully coordinate the sub-channel allocation and power allocation among these active hops, we are able to exploit not only the conventional frequency diversity within one hop, but also the newly introduced inter-hop diversity gain, referred to as hop diversity in this thesis.Under the proposed frequency sharing framework, we firstly study the resource allocation problem under a linear multi-hop relay OFDM network. We formulate a joint optimization problem of sub-channel assignment, power allocation and time control. After analyzing the optimal solution of the problem, we introduce a suboptimal solution with much lower complexity. Simulation results show that the proposed algorithm improves the system throughput efficiently.We then apply the frequency sharing framework to a two-hop wireless relay OFDMA network which consists of multiple users and several relays. The resource allocation problems with and without user QOS requirements are formulated. Compared with conventional hop by hop transmission, the frequency sharing framework together with efficient algorithms is shown to further enhance system performance in simulation.