This paper presents you the basic principle of OFDM(Orthogonal Frequency Division Multiplexing)and where it excels based on OFDM system , following with the prospective of wireless mobile communication. After a brief introduction to OFDM principle , it mainly focuses on the effect of OFDM system under different channels and with different system realizations on the Bit Error Rate (BER). It mainly includes two kinds of channels: the AWGN channel and the Rayleigh fading. In the latter, we compare the BER with two different system realizations: one with Guard Intervals(GI), and the other without GI. Based on the theoretical analysis, making use of MATLAB to simulate the performance of OFDM. The result of computer simulation are also discussed.
Key Words : OFDM, AWGN, Rayleigh fading , BER ,GI , Simulation.