Wireless Two-way Relay Cooperative Communication System Beam Forming And Power Allocation Algorithms

Relay based cooperavtive communication technique has three main advantages:provide cooperation diversity gain, improve the communication quality at the cell edge of the cellular system, and increase the coverage area of BS (base station) and reduce blind area of BS. As two-way protocol can greatly increase the spectral efficiency compared to one-way relay, it has recently attracted a large amount of attention and become one of the key technologies for the next generation of wireless communication system. In view of this, we mainly research the two-way relay systems based on amplify and forward (AF), including beamforming, capacity region analysis and the power allocation. The main research contents are as follows:1) For the relay system with two single-antenna users and one multi-antenna relay, first two relay beamforming schemes, zero forcing (ZF) algorithm and generalized power iteration (GPI) algorithm are compared, and then the beamforming at Capacity boundary of the system is realized through a convex optimization method. The simulation results show that, the GPI algorithm and convex optimization are better than ZF in rate. Furthermore, ZF is sensitive with the number of antennas and the correlation coefficient of channel.2) In the case of the MIMO two-way relay systems, the ZF and minimum mean square error (MMSE) transceive filters are given the sum rate maximization is obtained by using gradient descent (GD) algorithm; Finaly, a power allocation (PA) scheme is proposed. Simulation results show that:the GD can achieve the same sum-rate performance as the GPI, and the proposed PA scheme is0.3to0.5bit larger in sum rate than equal PA.3) In distributed two-way relay systems, the MSE-based asymptotically optimal cooperate relay (MSEAOCR) scheme, the minimizing power (MP), and the SNR balancing are realized. Simulation results show:the MP achieves the best performance of sum rate among three algorithms, the MSEAOCR is worse than the MP; although the SNR balancing algorithm is not good at low SNR regiont, the performance of the SNR balancing approaches the MP and finally reach the same performance as the MP as SNR increases; although the sum rate performance of distributed two-way relay system is worse than that of the centralized two-way relay system, but it has lower complexity.