Simulation Study of OFDM, COFDM and Mimo-OFDM System

Abstract

Orthogonal frequency division Multiplexing (OFDM) is a popular method for high data-rate wireless transmission. It converts a frequency selective channel into a set of parallel flat fading subchannels,which makes the receiver simpler. Thereby, the bandwidth of the sub-carriers becomes small compared with the coherence bandwidth of the channel, which allows simple equalization. The BER curve of OFDM is compared with the single carrier 16-QAM systems. The BER curve for COFDM using differential encoding method is also discussed. OFDM may be combined with multiple antennas at both Transmitter and Receiver, resulting a MIMO-OFDM system. In this paper, various channel estimation methods of MIMO-OFDM system using MMSE and LS are discussed. Also, in this, the effect of various Doppler frequencies on the normalized channel estimation is discussed. Finally, the normalized channel estimation versus no. of iteration by using multiple antennas (same or different) at both the access points is discussed.