Outage probability of a coded BPSK system in Rayleigh fading channels

Performance of digital transmission is usually measured in terms of the average probability of bit error. In fading channels, the signal amplitude can exhibit erratic behavior and an average performance measure may not be meaningful. An alternative measure of performance under these conditions is the probability of outage. The authors define the probability of outage as a natural extension of the definition used for both analog and uncoded digital communications in fading channels. For coded signals, the fading must be averaged over all the symbols in the codeword. For properly interleaved signals and i.i.d. Rayleigh fade statistics, the average must be performed over a chi-squared variate. The probability of outage, defined as the probability that the decoded bit error rate exceeds a specified threshold, is monotonic with the probability that the chi-squared variate is less than a specified threshold. The authors derive upper and lower bounds on the outage probability for both soft and hard decision decoding for convolutionally encoded binary phase shift keying in a flat Rayleigh fading channel. These bounds are consistent with the results of simulations, which are also presented in the paper