“Performance Analysis of Turbo Coded OFDM for Wireless Transmission over Fading Multipath Channel”

Abstract

OFDM is a good multicarrier modulation technique to overcome multipath fading and Inter symbol Interference (ISI). In this modulation technique, the data stream to be transmitted is divided into several lower rate data streams each being modulated on a subcarrier. ISI is eliminated by inserting a small interval known as the guard time interval into OFDM symbols. In order to combat the multipath fading and eliminate ISI almost completely, the length of the guard time interval is chosen to exceed the channel delay spread. The reduction of error rate in transmitting digital data is another major problem. Forward Error Correction (FEC) code can be used for this purpose. Convolutional code is a good FEC code but for better performance Turbo Code can be used as error correction code. Turbo codes have been widely considered to be the most powerful error control code of practical significance. The combination of OFDM and turbo coding with recursive decoding allows these codes to achieve near Shannon’s limit performance. This thesis is based on performance analysis of Turbo Coded OFDM system. First we analyze uncoded OFDM system and then apply convolutional code as FEC code and later Turbo code as FEC code. We compare and analyze the performance of uncoded OFDM system with convolutional coded and Turbo coded OFDM system.