Capacity analysis of Correlated Rayleigh Fading Channels at low average signal to noise ratios for Selection Combining Diversity

In this paper, we derive Capacity per unit bandwidth (Spectrum Efficiency) of Correlated Rayleigh Fading Channels under Selection Combining Diversity at Low average SNRs. This paper provides closed-form expressions for Spectrum efficiency among M diversity branches under different adaptation policies, like (i) Optimal Power and Rate Adaptation (OPRA) policy, (ii) Optimal Rate Adaptation (ORA) policy (iii) Channel Inversion with Fixed Rate (CIFR) policy, and (iv) Truncated channel Inversion with Fixed Rate (TIFR) policy with Selection Combining diversity. Upper bound capacities for OPRA and ORA policies have been derived and plotted. Analytical results show accurately that OPRA policy provides the highest capacity over other adaptation policies. The outage probability for the correlated case at low average SNRs is also derived, plotted and analyzed in detail in this work.