Performance Improvement of the MC-CDMA System Suitable for the High Speed Mobile Communication

초록

In this paper, we propose the PAPR reduction methods of SLM (Selected Mapping), and PTS (Partial Transmit Sequence) to decrease the nonlinear distortion and to improve the power efficiency of the nonlinear HPA (High Power Amplifier) in the multi-code CDMA system. Simulation results show that the PTS reduces the PAPR by about 2 dB while SLM can reduce by about 3 dB, compared with the original MC-CDMA when QPSK is used for 32 branches. Also, we find the BER performance of MC-CDMA (Multi-Code Division Multiple Access) system with and without predistorter in front of the HPA. When predistorter is used, 3 dB input backoff (IBO) is required in SLM method, and 5 dB IBO in PTS method to closely match with the linear amplifier. Without PAPR reduction method, more than 7 dB is required. Finally, the phase rotation factors transmitted as side information in PTS and SLM methods play an important role in the BER performance. So, we newly derive the theoretical BER equation when the effects of side information are considered in the Multi-Code CDMA communication system. We show that the simulation results get close to the theoretical results.