非对称双向中继系统中的协作多址广播传输方案设计与数据率性能分析

在双向中继系统中,2个节点通过一个半双工中继交换信息,2个方向的数据率都会受到较差链路的制约。当节点位置变化或信道衰落造成,中继两端的信道质量不对称时,这将导致系统的和数据率下降。为了弥补较差链路带来的数据率损失,提出了一种新的三时隙协作多址广播传输方案,使得信道质量较好的源节点与中继节点进行协作传输,并且各节点充分利用各链路所支持的最大数据率进行传输,从而有效提高系统容量及加权和数据率。推导出新方案的容量上界以及解码转发模式下的可达数据率域,并对时隙及功率等资源进行优化分配。仿真结果表明,在加性白高斯和瑞利衰落信道下,新方案在非对称信道下的性能都大大优于已有方案。

Cooperative multiple access broadcast transmission strategy and performance analysis in asymmetric two-way relay system

In a two-way relay system where two nodes exchange information via a half-duplex relay,the achievable data rates of both directions are limited by the weaker link.When the two-way channel is asymmetric due to relay positioning or channel fading,the sum rate of the two-way relay system will suffer from severe degradation.In order to compensate for the performance degradation caused by the weaker link,a novel three-time-slot cooperative multiple access broadcast strategy was proposed where the source node with better channel quality cooperatively transmitted with the relay node and each node transmitted at the maximum rate of each link.As a result,the weighted sum rate of the two-way relay sys-tem can be thus improved.The upper bound of the capacity for the new strategy and an achievable rate region with de-code-and-forward protocol were derived.Time slot allocation and power allocation at the relay were optimized to achieve the maximum weighted sum rate.Simulation results show that the proposed strategy outperforms existing strategies under asymmetric channel conditions both in AWGN and Rayleigh fading channels.