Down-link throughput with opportunistic feedback, multi-user and diversities in Rayleigh fading environments

This paper studies throughput of wireless systems employing opportunistic feedback, multi-user, selection combining (SC) and maximal ratio combining (MRC) diversities for transmission in Rayleigh fading environments. The first contribution of this paper is the employment of an arbitrary average branch signal-to-noise ratio (SNR) Ω which is shown to improve system throughput under specific conditions. The effects of SC and MRC on system throughput are studied with new and detailed throughput expressions for both schemes are derived and validated. Performance comparisons between SC and MRC are also made under several scenarios by varying important parameters. It is also shown that (i) MRC outperforms SC under outage and normal operating conditions as expected, (ii) the proposed system outperforms a well-known system for large values of diversity order L and (iii) for L = 1, the proposed system can be correctly reduced to other systems reported in the open literature which validates the current work.