BER Reduction in OFDM with Different Modulation and Encoding Schemes

Abstract: OFDM is one of the most developing technologies in modern mobile communication. OFDM is a parallel transmission scheme, where a high – rate serial data stream is split up into a set of low – rate sub streams, each of which is modulated on a separate subcarrier. Increasing the number of parallel transmission reduces the data rate that each individual carrier must convey and that lengthens the symbol period. In present communication systems, increasing the number of users reduces the data rate that each individual carrier must convey and that lengthens the symbol period. Hence, a performance comparison of OFDM system in multipath fading and additive white Gaussian noise channels is presented. The comparison proceeds in two steps. First, design simple OFDM system. Second, a binary modulating signal is transmitted over the system and the bit error rate in multipath fading and additive white Gaussian noise channels is observed. Then first compare the performance of different modulation schemes such as Quadrature Amplitude Modulation and Quadrature Phase Shift Keying with these systems and get the best modulation schemes with less BER. Then with the combination of modulation schemes analyze the different encoding schemes such as Cyclic Redundancy Code and Reed – Solomon encoding with these systems. After that redesign the OFDM system with best encoding and modulation schemes.

Keywords: OFDM, BER, CRC, RS