Performance of OFDM SYSTEM under High Doppler Spread

It is necessary to consider fast varying channel for Orthogonal Frequency Division Multiplexing (OFDM) system when OFDM symbols are transmitted over a frequency selective time varying fading channel. The time variations of channel during one OFDM symbol destroy the orthogonality of different subcarriers and result Inter Carrier Interference (ICI), which results in degradation of system performance. To solve this problem, the OFDM symbols are designed in such a way so that the performance degradation caused by ICI can be avoided. A simple and efficient technique is proposed to design the OFDM symbols based on eigen values of time varying channel. This method is described as Channel Matched OFDM (CMOFDM). Performance comparison between conventional OFDM and proposed matched filter based CMOFDM receiver structure under the same channel conditions are provided. The system performance is measured in terms of BER. The results show that the new technique is better over the conventional OFDM receiver in suppressing ICI in OFDM system. General Terms Performance, Design, Theory.