Performance of Quadrature OFDM System in Rayleigh Fading Channels

الملخص

This paper uses the Divide-and-Conquer DFT/IDFT computation approach instead of direct computation approach in OFDM system introducing a proposed system called Quadrature OFDM (Q-OFDM). The use of this approach introduces a multi sub-channels each have a set of subcarriers orthogonal with each other in two orthogonal coordinates. This arrangement leads to decrease the probability that all subcarriers in a sub-channel see deep fading. Furthermore, this approach reduces the computational complexity and reducing peak-to-average power ratio problem which are common problems in common OFDM systems especially when large number of carriers is used. The performance of the Q-OFDM system has been tested and compared with conventional OFDM system in AWGN, flat fading and selective fading channels. The results show that the performance of Q-OFDM is superior that conventional OFDM especially for high values of SNR. A maximum gain of 5 dB gain in SNR has been obtained in both AWGN and flat fading channels in Q-OFDM system over the conventional one. While 3 dB maximum gain has been obtained for the case of selective fading channel.