Performance Evaluation of MRC Systems Over Sub-Terahertz MFTR Fading Channels

We analyze the outage probability (OP), ergodic capacity (EC), and average bit error probability (ABEP) of L-branch diversity systems using maximal-ratio-combining (MRC) over Multi-cluster-Fluctuating-Two-Ray (MFTR) fading channels, a model well-suited for sub-terahertz bands. We derive exact OP, EC, and ABEP expressions. For this latter metric, we assume M-ary quadrature amplitude modulation (M-QAM), and we also perform its asymptotic analysis to obtain the coding gain and diversity order. Unlike previous works for simpler fading models, our expressions retain consistent complexity regardless of the number of MRC branches and depend on functions available in standard mathematical software. The results show that coding gain relies on fading distribution parameters, L, and M. Meanwhile, diversity order is determined by multiplying L with the number of multipath clusters in the MFTR model.