Selection Combining of Signals with Different Modulation Levels in Nakagami-m Fading

Conventionally, the BER analysis of selection combining schemes is performed under the assumption that the signals to be combined belong to the same modulation level. This is not necessarily the case in cooperative relaying, where the source and relay may use different modulation levels. Recently, a closed-form BER expression was derived for selection combing of signals with different modulation levels, under the assumption that the source-relay, source-destination, and relay-destination links are all modeled as Rayleigh fading channels. In this letter, we extend the analysis to the asymmetric Nakagami-m fading channel, which is a more versatile channel model. We derive the closed-form BER expression which is expressed in terms of elementary functions. The derived BER expression generalizes many existing expressions in the literature. Simulation results are also presented to confirm the accuracy of the derived results.