Rateless codes aided coherent M‐ary PSK systems in the presence of receiver imperfections and Rician fading

Abstract

ABSTRACTIn this paper, we study the bit error rate (BER) and the symbol error probability (SEP) performance for a rateless coded M‐ary phase‐shift keying (MPSK) system in a situation where stochastic phase error, quadrature error and in‐phase–quadrature (I–Q) gain mismatch take place all concurrently over a Rician fading channel. Similar scenario has been considered before by Djordjevic et al. for quasi‐cyclic low‐density parity‐check (QC‐LDPC) codes, but the effect of I–Q gain mismatch is not correctly modeled, because the Gaussian noise components in I and Q paths are assumed to have the same variance. By taking two different Gaussian noise variances into consideration, precise expressions are derived for the SEP of a coherent MPSK system under the aforementioned condition (with the stochastic phase error depicted by Tikhonov distribution), thus providing a baseline to evaluate the merits of the proposed rateless coded system and that of QC‐LDPC codes. The validity of the rateless coded system is substantiated by simulation results. It is observed that rateless codes outperform QC‐LDPC codes even the I–Q gain mismatch is modeled in the same way as Djordjevic's work when the target BER is lower than 10−2. Copyright © 2011 John Wiley & Sons, Ltd.