Correlated diversity versus simple block coding on frequency-selective fading channels

Forward error correction (FEC) coding is a well-known method that can be used to improve the performance of communication on wireless fading channels. The authors investigate the performance of combined diversity and FEC coding strategies. For block coding to be effective, bit errors in each code word should be independent. To render the channel memoryless, perfect bit interleaving is assumed. That is, bit errors in the code word are assumed to be independent. The authors analyze the performance of MDPSK on frequency-selective Rayleigh fading channels using two branch postdetection equal gain (EG) combining. Both the effects of correlation between the two diversity branches and the effects of cochannel interference on the BER performance are investigated. The interferers are assumed to be MDPSK modulated signals with same symbol rate as that of the desired signal, but with random symbol timing offsets relative to the desired signal. The cochannel interference contribution is represented by a Gaussian noise whose mean and variance are equal to the mean and variance of the sum of the interfering signals