Closed-form approximation of Coded BER in QAM-based BICM Faded Transmission

In this paper we develop closed-form approximations for the coded BER in bit-interleaved coded modulation (BICM) transmission over Rayleigh fading channels. To obtain the desired expressions we apply the so-called saddle point approximation and use analytical forms of the probability density functions (PDF) of the reliability metrics. Numerical examples illustrate the accuracy of the proposed method.