Research On Radio Resource Allocation Policies In MIMO-OFDM Systems

With the users'growing demand of wireless multimedia service, wireless communication and network technologies are experiencing a significant rapid development, and supporting multi-media traffics, improving spectrum utilization and guaranteeing multi-cell coverage have become the technical requirements of fourth generation (4G) mobile communication systems. As MIMO and OFDM have been adopted as the key physical layer techniques for 4G wireless communication systems, research on the radio resource allocation polices and intercell interference management schemes in MIMO-OFDM systems are valuable and applicable to meet different user's variety of services requirements and improve the reliability of wireless links, guarantee multi-cell network performance.Therefore, some in-depth and systematical research on QoS-guaranteed radio resource allocation scheme for 4G systems is proposed in this thesis. Some creative contributions have been achieved, which include optimal resource allocation polices of multi-user scenario in OFDMA/SDMA systems, low complexity packet scheduling in space-time-frequency resource domain and inter-cell interference coordination. The contents of thesis are presented as follows:Firstly, based on utility functional resource allocation framework, this paper considers the scheduling and resource allocation problem for downlink OFDMA/SDMA systems with the objective to maximize the system capacity and guarantee each user's QoS requirements, and then gives the detail proof of the equivalent optimal policy. Moreover, a low complexity algorithm based on signal space theory is proposed for practical implementation. The proposed algorithm assigns the corresponding space-frequency subchannel with maximum marginal utility, and considers the delay factor in utility function to efficiently handle the real time service. Simulation results show that the proposed algorithm is able to better attain the tradeoff between system throughput and QoS requirement to employ different utility functions.To deal with the co-channel interference management problem in multi-cell OFDMA system, inter-cell interference coordination is a promising approach. Firstly, existing interference coordination schemes are compared to deduce the scheme design direction. In order to solve the load balance problem in multi-cell and complex exchange signal in future flat network architecture, a spectrum pool based and distributed semi-static interference coordination scheme is proposed, which can be carried out conflict-free decision distributedly with local information and adapt to the flat network architecture. Simulation results show that, the proposed scheme can improve the cell edge throughput effectively with system performance guarantee, also reduce the signaling overhead.A summary is given at the end, where the future research directions related to this thesis are also pointed out.