自适应解码转发系统的增强型比例选择合并器

Enhanced scaled selection combiner for decode-and-forward systems with adaptive modulation

针对源和中继采用不同调制阶数以提高频谱效率的解码转发协作通信系统,提出了一种增强型的比例选择合并器(ESSC)。在合并信号时,ESSC通过为源-中继-目的支路设定比例系数,降低了错误传播对协作性能的影响。推导了瑞利信道下采用ESSC的解码转发系统的误比特率公式,给出了最优比例系数的计算方法。理论分析和仿真表明,ESSC能够获得接近二阶的分集增益。在此基础上,提出了一种解码转发协作系统的功率分配方案,进一步提高了协作传输的可靠性。

An Enhanced Scaled Selection Combiner（ESSC）is proposed for Decode-and-Forward（DF）cooperative networks,where different modulation levels are adopted by the source and relay nodes to improve spectral efficiency. When the ESSC is used to combine signals from different diversity branches,the source-relay-destination branch is weighted by varying scale factors.As a result,the performance degradation caused by erroneous relaying in DF networks can be effectively mitigated by ESSC.Towards this end,the Bit-Error-Rate（BER）expression is derived for DF networks using ESSC under Rayleigh fading channels,and the scale factors of the ESSC are optimized to minimize the system BER.Theoretical analysis and simulation results demonstrate that a diversity order close to two can be achieved by ESSC.Furthermore,apower allocation scheme is proposed for DF networks based on ESSC,which can further improve the performance of cooperation.