Performance of hierarchical diversity over correlated rician channels

We study the performance of multi-branch hierarchical combining diversity systems. Closed-form expressions are derived for asymptotic error rate and asymptotic outage probability of hierarchical selection-combining maximal-ratio combining (SC-MRC) and selection-combining equal-gain combining over Rician channels with arbitrary correlation. Comparison is made between hybrid-selection maximal-ratio combining (HS/MRC) and hierarchical SC-MRC, and it is shown that SC-MRC suffers at most 0.6 dB signal-to-noise ratio (SNR) loss with respect to HS/MRC for practical number of antennas. However, SC-MRC incurs much smaller insertion loss. Numerical results show that the analytical solutions can provide accurate estimation of error rate and outage probability in large SNR region.