Performance of Orthogonal Space-Time Coded MCPM System in Nonlinear Channel

This paper investigates the effect of nonlinear power amplifiers (NLPA) on orthogonal space-time coded multi-level continuous phase modulation (OST-MCPM) transmission systems with two transmit antennas. The maximum likelihood sequence detection (MLSD) is applied to OST-MCPM systems. Simple upper bound of the pair-wise error probability (PWEP) is derived to evaluate the achievable diversity gain in nonlinear multiple input multiple output (MIMO) channel. Pre-distortion circuit is applied to decrease the effect of nonlinear amplifier. The frame error rate (FER) performance of this algorithm in nonlinear MIMO channel were simulated and compared with those with linear amplification over Rayleigh fading channels. MATLAB simulation results show that the system in nonlinear channel has the same diversity gain as the system with linear amplifier. The degradation of FER performance in nonlinear channel is larger for higher modulation level for the MLSD algorithm. And the predistorter can compensate the influence accurately and rapidly.