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

In 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.