Performance improvement of Q-OFDMA systems using low complexity approach

Quadrature Orthogonal Frequency Division multiple access (Q-OFDMA) has been renowned as a promising technique which provides a solution to the high PAPR (Peak to average power ratio), sensitivity to carrier frequency offset (CFO) problem and design complexity as introduced by the normal OFDMA systems. Exploiting this Q-OFDMA systems on the Multi-Input Multi-Output (MEMO) architecture, leads to a remarkable improvement in achievable rates. A critical part of this technology is to design the full-rate diversity codes for two transmit and two receive antennas. This paper endeavours to identify key factors and trade-offs issues associated with designing Q-OFDMA systems. We proposed a Space Time Block Codes and spatial multiplexing technique as well as low complexity detection methods for more than 2×2 antennas at the cost of low complexity. This performs well for different fading channel environments and improves the overall system performance such as diversity gain, SNR (Signal to Noise Ratio), Coding gain and BER (bit error rate. The proposed scheme can be easily applied in OFDMA and Single-Carrier Frequency Division Multiple Access (SC-FDMA) by adjusting the parameters of Q-OFDMA.