Maximal-ratio eigen-combining: a performance analysis

Maximal-ratio eigen-combining (MREC) for wireless communications channels, also known as eigen-beamforming for receivers equipped with antenna arrays, integrates conventional maximum average signal-to-noise-ratio beamforming (Max-ASNR BF) and maximal-ratio combining (MRC) to provide both high average SNR in high fading correlation as well as diversity in low fading correlation. Previous studies of MREC were based on simulation or limited analysis and suggested that MREC can outperform Max-ASNR BF and MRC in terms of average error probability (AEP). A comprehensive analysis of MREC is provided for BPSK signals and Rayleigh fading, including computable AEP and outage probability (OP) expressions for perfectly known, correlated channel gains. Particular cases of these expressions apply to Max-ASNR BF and MRC. For imperfectly known channels the analysis yields a new and general AEP expression for MREC, which is specialized to estimation based on pilot-symbol-aidedmodulation (PSAM) and interpolation. In particular, this AEP expression applies to Max-ASNR BF and, for PSAM and data-independent interpolation filters, to MRC. Numerical results for antenna arrays receiving signals with angle-of-arrival dispersion and imperfectly known channel gains confirm the potential advantage of MREC over Max-ASNR BF and MRC.