An Asymptotic Study of Hierarchical Diversity Receptions Over Rician Channels With Arbitrary Correlation

Hybrid-selection maximal-ratio combining (HS/MRC) is a useful diversity reception technique to reduce the number of radio frequency chains, and this diversity scheme has been well studied. However, past studies on HS/MRC have often ignored the significant insertion loss associated with hardware implementation of HS/MRC. Therefore, we consider a special class of two-stage diversity receptions known as hierarchical diversity with low insertion loss. The asymptotic error rate performances of hierarchical selection-combining MRC (SC-MRC) and hierarchical selection-combining equal-gain combining are studied for Rician fading channels with arbitrary correlation. Based on our asymptotic analysis, it is shown that, for a practical number of antenna branches, SC-MRC will suffer, at most, 0.6-dB performance losses with respect to HS/MRC; however, SC-MRC will incur significantly less insertion loss. Based on closed-form asymptotic error expressions, we also study unique transmission properties of two-stage diversity receptions over Rician channels with arbitrary branch correlation.