A PAPR Reduction Method using Constraint Code in Multicode CDMA System

Multicode - Code Division Multiple Access (MC-CDMA) system is very good for the several kinds of service rates with various quality of service requirement because it can affordable by assigning multiple codes and controlling the flexible capacity. However, the so many multi-code signals are summed in the time domain so that it suffers from the serious problem of high peak to average power ratio (PAPR). Therefore, the expensive linear amplifier or large input back-off is necessary to overcome the problem but it makes power consumption of high power amplifier (HPA) very poor. In this paper, we propose a new method that can reduce PAPR efficiently by constraint codes based on the opposite correlation property of the incoming information data. PAPR reduction performance depends on the length and indices of constraint codes in the MC-CDMA system. There is a trade-off between PAPR reduction and the length of constraint codes. We also study the BER improvement in AWGN channel. The simulation results show that BER performance can be very close to the linear amplifier in two cases: 1) when the exact constraint codes are used without input back-off and 2) when a few constraint codes are used with small input back-off.