Performance Analysis and PAPR Reduction of Coded OFDM (with RS- CC and Turbo coding) System using Modified SLM, PTS and DHT Pre- coding in Fading Environments

In wireless communication, parallel transmission of symbols using multi carriers is used to achieve high efficiency in terms of throughput and better transmission quality. Orthogonal Frequency Division Multiplexing (OFDM) is one of the techniques for parallel transmission of information. In multipath environment the performance of orthogonal frequency division multiplexing degrades which can be improved by introducing some kind of channel coding. Coded OFDM (COFDM) is the new candidate for application such as Digital audio Broadcast (DAB) and Digital Video Broadcast (DVB(T) due to its better performance in fading environments. However high peak to average power ratio (PAPR) is a major demerit of OFDM system, it leads to increased complexity and reduced efficiency of RF amplifier circuit. In this paper Modified Selective mapping (SLM), Partial Transmit sequence (PTS) and Discrete Hartley Transform (DHT) precoding schemes are proposed for PAPR reduction, where SLM, PTS and DHT precoding schemes are used in conjunction with post clipping and filtering processes. However clipping can degrade the BER performance but the degradation in performance can be compensated by using OFDM with channel coding; here we have used Reed Solomon (RS) codes along with convolution codes (CC) used as serial concatenation and TURBO codes as parallel concatenation code for channel coding purpose. The BER performances are simulated for Additive white Gaussian (AWGN), Rayleigh, Rician and Nakagami (m=3) channels and Complementary cumulative distribution functions (CCDF) curves are simulated for modified as well as ordinary SLM, PTS and DHT precoding techniques. The COFDM system implemented here is as per IEEE 802.11a.