Performance of LDPC Coded MC-CDMA Downlink Sysetm with Constant Envelope Spread Sequences

This paper proposes a Low Density Parity Coding (LDPC) Coded Multicarrier Code Division Multiple Access (MC-CDMA) downlink system with constant envelope spread sequences. Unlike traditional downlink MC-CDMA systems, the Complex Quadratic Sequences (CQS), which has constant envelope in both time and frequency domains, is used as the spread sequences. The CQS helps the system decrease the Peak-to-Average Power Ratio (PAPR) and reduce the linearity requirements on the power amplifier consequently. On the other hand, the capability of CQS to mitigate Multiple Access Interference (MAI) has also been indicated. The simulations are carried out in a multi-user environment. The simulation results show that the proposed system outperforms the conventional LDPC coded MC-CDMA system in both PAPR reduction and Bit Error Rate (BER) performance.