Advanced Receiver Design for Quadrature OFDMA Systems

Quadrature orthogonal frequency division multiple access (Q-OFDMA) systems have been recently proposed to reduce the peakto-average power ratio (PAPR) and complexity, and improve carrier frequency offset (CFO) robustness and frequency diversity for the conventional OFDMA systems. However, Q-OFDMA receiver obtains frequency diversity at the cost of noise enhancement, which results in Q-OFDMA systems achieving better performance than OFDMA only in the higher signal-to-noise ratio (SNR) range. In this paper, we investigate various detection techniques such as linear zero forcing (ZF) equalization, minimum mean square error (MMSE) equalization, decision feedback equalization (DFE), and turbo joint channel estimation and detection, for Q-OFDMA systems to mitigate the noise enhancement effect and improve the bit error ratio (BER) performance. It is shown that advanced detections, for example, DFE and turbo receiver, can significantly improve the performance of Q-OFDMA.