Exact BERs for M-QAM with MRC and channel estimation errors in Rician channels

In this paper, we study the effect of imperfect channel estimation (ICE) on the performance of M-level quadrature amplitude modulation (M-QAM) with maximum ratio combining (MRC) and pilot-symbol assisted modulation (PSAM) in generalized Rician fading channels. Via a novel formulation of the bit error rate (BER) of M-QAM in terms of the distribution of new decision variables, we derive the exact BER of M-QAM with MRC diversity and channel estimation errors. Our new result is valid for both square and rectangular M-QAM, arbitrary linear channel estimators, and unbalanced and correlated diversity branches in Rician fading. Using our new results, we evaluate the performance of minimum mean square error (MMSE)- and sinc-interpolator-based channel estimators with PSAM, and present some interesting findings.