Modified OFDM configurations with equalization and CFO compensation for performance enhancement of OFDM communication systems using symmetry of the Fourier transform

The Orthogonal Frequency Division Multiplexing (OFDM) systems allow efficient spectrum usage and simple Frequency Domain Equalization (FDE). However, a large number of sub-carriers increases the computational complexity of the equalization process. In this paper, the conventional OFDM system is modified to enhance the Bit-Error-Rate (BER) performance or reduce the computational complexity. Also, the banded-matrix approximation is taken into account to reduce the equalization complexity. Simulation results show that the 1st proposed OFDM system based on Binary Phase Shift Keying (BPSK) can reduce the computational complexity to O(N/2) instead of O(N) compared to the conventional OFDM configuration based on the banded-matrix approximation concept. The 2nd proposed OFDM system based on BPSK requires approximately the same computational complexity of the conventional OFDM configuration and gives a Signal-to-Noise Ratio (SNR) gain of about 7.05 dB at BER = 10(-3) compared to the corresponding conventional OFDM configuration. The 3rd proposed OFDM system based on Quadrature Phase Shift Keying (QPSK) gives an SNR gain of about 4.51 dB at a BER = 10(-3) compared to the corresponding conventional OFDM configuration. The 2nd proposed OFDM system based on BPSK outperforms the different schemes in the presence of estimation errors. (C) 2020 Elsevier GmbH. All rights reserved.