Implementation of a Novel Concatenated FEC by RS and Irregular Turbo Codes on OFDM Systems

Code Division Multiple Access (CDMA) performs well in a multi-cellular environment where a single frequency is used in all cells. Code Division Multiple Access (CDMA) has severe problems associated with multipath and Channel news. One possible problem is that the receiver may require a very large dynamic range in order to handle the large signal strength variation among users. Due to that the Bit Error Rate (BER) is getting increased. Moreover due to the addition of uncontrollable random channel noise degrade the performance of the receiver. The multipath problems give inter symbol interference. This can be reduced by Orthogonal Frequency Division Multiplexing (OFDM) technique. More work could be done on investigating suitable techniques for doing OFDM promises to be a suitable modulation technique for high capacity wireless communications and will become increasing important in the future as wireless networks become more relied on. In order to increase the wireless network performance, this study has concentrated on OFDM with a novel forward error correction by data transmission with Quadrature Phase Shift Keying (QPSK) as modulation techniques. Here an FEC scheme by concatenation of Reed Solomon (RS) and the Irregular Turbo code is implemented in OFDM. The simulation results show that the system BER performance is decreased with this technique, when compared to the system having Forward Error Correction (FEC) by RS code alone and irregular turbo code alone.