Accurate Performance Approximations for MRC Over Log-Normal Fading Channels

Average channel capacity (ACC) and average symbol error probability (ASEP) are key metrics for evaluating wireless communication reliability under fading. This paper derives simple, low-complexity approximations for ASEP and ACC for maximal-ratio combining (MRC) receivers subject to log-normal (LN) fading, using a second-order Taylor series expansion of LN probability density function transforms. An asymptotic expression for ACC in the high-SNR regime is also provided. Numerical results show close agreement with exact solutions, while runtime comparisons demonstrate significantly reduced computational complexity compared to existing methods, making the proposed framework suitable for ultra-low latency wireless systems.