Decorrelation and Orthogonalization of Correlated Diversity Branches for HS/MRC Diversity

Four hybrid selection maximum ratio combining (HS/MRC) diversity schemes over correlated Ricean fading channels are investigated. In particular, the correlated diversity branches are either decorrelated or orthogonalized prior to diversity combining. The optimum time-invariant selection of diversity branches prior to MRC as well as conventional HS/MRC are also considered. The average bit error rate (BER) performance of these four diversity combining schemes is obtained using the Prony approximation method and using computer simulations. Numerical results indicate that decorrelation and orthogonalization of the correlated branches prior to diversity combining can restore some of the diversity gain lost due to the correlation between branches. This is observed especially for the case of a strong line-of-sight fading component, and for small numbers of selected branches in HS/MRC diversity where the signal-to-noise ratio (SNR) improvement can be as large as 2 dB.