Spectrum efficiency evaluation of LMF channels under various adaptation policies with hybrid diversity schemes

A single-input multiple-output (SIMO) system with lognormal multipath fading (LMF) channel is considered in this paper. The spectrum efficiency (capacity per unit bandwidth) of a LMF channel for various adaptation policies is studied. We obtain the closed-form expressions for various adaptation policies such as (i) optimal power and rate adaptation (OPRA) policy, (ii) channel inversion with fixed rate (CIFR) policy, and (iii) truncated channel inversion with fixed rate (TIFR) policy with hybrid diversity combining techniques like hybrid maximal ratio combining (MRC)-equal gain combining (EGC), hybrid EGC-MRC, and hybrid MRC-selection combining (SC) diversity. Numerical results show that the use of hybrid diversity combining techniques improves the spectrum efficiency over stand-alone diversity combining techniques. OPRA policy that provides the highest spectrum efficiency when compared to other policies is also shown.