On Cooperative Transmit Diversity In Wireless Network

Multiple Input-Multiple Output (MIMO) technology is a significant breakthrough in wireless communications, which can greatly improve the system capacity and spectral efficiency. However, due to the limitation in size, power or hardware complexity, antenna array is not exercisable to implement for mobile devices. Hence, cooperative diversity has been proposed to overcome the difficulty. In cooperative communication systems, each mobile terminal has one or more partners. By sharing each other's single antenna, cooperative diversity constitutes virtual MIMO system, so that the spatial diversity can be realized in single-antenna mobile terminals.In this thesis, a study has been made of the scheme for and the optimization of resources allocation in cooperative diversity. A bandwidth efficient cooperative technique is proposed. Moreover, resource utilization efficiency is further increased by introducing the adjustable power allocation factor. The main work of this thesis can be summarized as follows:Firstly, focusing on the typical two-user cooperation, a fixed relaying cooperative system based on 16-HPSK is proposed. The end-to-end bit error rate is derived when each user employs 16-HPSK modulation, which theoretically proves that the proposed scheme has higher spectrum efficiency compared to that based on orthogonal modulation. Simulation results verify the correctness of the theory.Secondly, in order to avoid the power inefficiency when the users fail to cooperate, a selective relaying cooperative system based on 16-HPSK is proposed. Compared with the formal fixed relaying scheme, this scheme is more adaptive to channel, and thus can improve the resource utilization efficiency.Finally, in allusion to the lack of adaptivity to channel in equal power allocation scheme, the adjustable power allocation factor is introduced, and the optimal power allocation schemes for both the fixed relaying and selective relaying cooperative system based on 16-HPSK are investigated. Simulation results suggest that, compared with the equal power allocation scheme, the optimal power allocation scheme can improve the cooperative gain, dominating by the quality of channel between different users.