Dual Layer Switch-and-Examine /??Selection Diversity Receivers

It is known that a selection combining (SC) diversity receiver can offer the full diversity order of an antenna array while necessitating only a single RF chain. However, a means must be provided to continuously monitor the SNR in all branches of the array. Switched diversity schemes, such as switch-and-examine (SEC), do not have this requirement but can provide performance approaching selection diversity in certain cases. This paper proposes a hybrid dual-layer approach which constitutes a compromise between SC and SEC, applicable especially to large arrays. Specifically, the array is divided into a number of groups and the switch and examine strategy is leveraged independently within each group. The group outputs are then processed in a second layer, which implements true selection diversity. By varying the number of groups for a fixed array size, various performance / complexity tradeoff points can be achieved. The performance of this architecture is analyzed herein in terms of outage probability and average bit error rate for i.i.d. Rayleigh fading. Simulation results show that performance is less than 0.5 dB away from true selection diversity when the group size is 2, implying that the number of monitored branches is reduced by half. Also, it is shown that by varying the group size, the performance gap between SC and SEC can be homogeneously spanned.