Performance of multi-antenna relay based cooperative spectrum sensing in cognitive radio network

In this paper, we analyse the performance of infrastructure-based fixed relay with multi-antenna in cognitive radio. We derive the mathematical expression for detection probability of single cooperative relay system over Rayleigh fading channel. Relay and fusion centre may perform either selection combining or maximal ratio combining of the signals. Effect of number of relay antennas for all four combinations of combining schemes has been analysed and as expected, increase in relay diversity improves the sensing performance. This is because, on installing more number of receiving antennas on the relay, it’s participation increases, so the detection performance also improves. In the non-cooperative system also, the performance improves on increasing the diversity order but on the other hand, this increment imposes burden on the fusion centre. Whereas in multi-antenna cooperative relay system, the burden of relay gets transferred on relay node and the fusion centre takes advantage of increased diversity order of relay. For cooperative spectrum sensing, we have used soft decision combining scheme in which secondary users send their test statistics calculated from their local observations.

本文针对认知无线电（cognitive radio）场景下搭载多天线（multi-antenna）的基础设施型固定中继系统的性能展开分析。本文推导了瑞利衰落信道（Rayleigh fading channel）下单协作中继系统的检测概率数学表达式。中继节点与融合中心（fusion centre）可对接收信号执行选择合并（selection combining）或最大比合并（maximal ratio combining）操作。本文分析了四种合并方案组合下中继天线数量对系统性能的影响，结果符合预期：中继分集度的提升可改善频谱感知性能。究其原因，在中继节点部署更多接收天线可提升其协作参与度，进而改善检测性能。在非协作系统中，提升分集阶数（diversity order）同样可改善系统性能，但该操作会额外增加融合中心的计算负担。而在多天线协作中继系统中，该计算负担被转移至中继节点，融合中心则可借助中继提升后的分集阶数获得性能增益。针对协作频谱感知（cooperative spectrum sensing）任务，本文采用了软判决合并（soft decision combining）方案，该方案中次级用户（secondary users）会发送基于本地观测值计算得到的检验统计量（test statistics）。