Abstract: OFDM is the combination of both multiplexing and modulation. In this paper, orthogonal frequency division multiplexing (OFDM) is considered for wideband transmission to mitigate intersymbol interference and enhance system capacity. The main principle of an OFDM is the insertion of Guard Intervals over a multipath fading channel, where two ways are possible; one method being Zero Padding and another being addition of Cyclic Prefix. This paper is mainly focused on the significance of cyclic prefix. Also, the combination of OFDM with MIMO is one of the most promising candidates for future communication systems, ranging from wireless LAN to broadband access, which is presently under study. This paper starts with comparisons of OFDM using QPSK and QAM on different channels, followed by modeling the MMSE estimators through a 4×4 MIMO system on MATLAB. Inthe end, results of different simulations are compared to conclude that MMSE algorithm provides comparatively better results with the implementation of MIMO-OFDM system.

Keywords: OFDM, Cyclic prefix, ISI, Orthogonality, BER, MIMO.