Performance Analysis of Adaptive M-QAM for Rayleigh Fading Cooperative Systems

The use of constant-power, rate-adaptive M-QAM transmission with an amplify-and-forward cooperative system is proposed. The upper bound expressions are derived for the outage probability, achievable spectral efficiency, and error rate performance for the amplify-and-forward cooperative system over both independent and identically distributed (i.i.d.) and non-i.i.d. Rayleigh fading environments. The analysis is based on an accurate upper bound on the total effective signal-to- noise ratio SNR at the destination. Adaptive continuous rate M-QAM achieves a capacity that comes within a constant gap of the Shannon capacity of the channel, but adaptive discrete rate M-QAM suffers additional performance penalties.