English

Abstract

The most favorable technique for high speed data transmission is Multicarrier Code Division Multiple Access. The MC-CDMA signals, which are characterized through PAPR, which can reduce the efficiency of the system. In this paper, we have to reduce the PAPR of an MC-CDMA system using PTS (Partial Transmit Sequence) through suboptimal combination algorithms (BPSO&BFO), which uses binary phase factors, for different number of subcarriers and for different length of sub blocks of PTS. I. I n tro d uct io n Mainly, the transmission of multi-carrier is to divide the entire bandwidth into smaller bandwidths. Each bandwidth with a different sub-carrier frequency, such that each of these narrow- band signals is protected from frequency selective fading and the data-rates are improved as compared to single-carrier system as we say that the total bandwidth can be increased significantly.MC-CDMA is a combination of both OFDM and CDMA that can provide protection from frequency selective fading and time dispersion. The CDMA part that provides both multiple access ability as well as spread each user signal over the frequency domain provide protection cover from the impact of frequency selective fading. The OFDM provides spreading across time domain of each spreading code's chip which decreases the effect of inter-symbol interference. So that we are able to get high data rate for transmission purpose. As we see, MC-CDMA is a powerful technique which has multiple accesses, but not free from problem. MC-CDMA signal has large peak to average ratio (PAPR) which largely limits its applications. High PAPR values causes a critical problem to the power amplifier (PA) used at transmitter. The efficiency performance of power amplifier decreases as PAPR increases. At transmitter side, the signal suffers from non-linear distortion. At receiver side, it degrades Bit Error Rate performance. This implements the use of power amplifier with large linear range so that the cost increases. Therefore it is necessary to reduce the impact of PAPR by means of PAPR reduction schemes. PTS is one of them most suitable probabilistic distortion less technique due to its less complexity.