Advanced Receiver Design for Quadrature OFDMA Systems

Quadrature orthogonal frequency division multiple access (Q-OFDMA) systems have been recently proposed to reduce the peak-to-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

Advanced Receiver Design for Quadrature OFDMA Systems

Abstract Quadrature orthogonal frequency division multiple access (Q-OFDMA) systems have been recently proposed to reduce the peak-to-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.</p

Advanced Receiver Design for Quadrature OFDMA Systems

Quadrature orthogonal frequency division multiple access (Q-OFDMA) systems have been recently proposed to reduce the peak-to-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

Quadrature OFDMA Systems Based on Layered FFT Structure

In current OFDMA systems three major problems arise due to the large number of subcarriers, including high peak to average power ratio (PAPR), sensitivity to carrier frequency offset (CFO), and high complexity in users terminals. In this paper, based on an innovative concept of layered FFT structure, we propose novel Quadrature OFDMA (Q-OFDMA) systems which can overcome these problems. In particular, the proposed systems can achieve the same guard-interval overhead and same bandwidth occupation to conventional OFDMA systems, while with reduced PAPR and improved CFO robustness and frequency diversity. Q-OFDMA systems also promise low complexity in downlink receivers. Parameter configuration is investigated for both predefined and adaptive users data rates. Theoretical comparison of bit error rate (BER) performance between QOFDMA and OFDMA is conducted, and validated by simulation results. It is shown that Q-OFDMA systems could achieve better performance than OFDMA when signal to noise ratio (SNR) is above a threshold depending on the channel condition, and advanced equalizers, such as minimum mean square error equalizer, can significantly decrease this threshold due to the large frequency diversity in Q-OFDMA systems

Space-time block code and spatial multiplexing design for Quadrature-OFDMA systems

To alleviate the high peak-to-average power ratio (PAPR), high complexity in user terminal and sensitivity to carrier frequency offset (CFO) problems in current orthogonal frequency division multiple access (OFDMA) systems, a Quadrature OFDM (Q-OFDMA) system has been recently proposed in the single-input single-output environment. In this paper we study the realization of multi-input multi-output (MIMO) diversity- and multiplexing- oriented methods for Q-OFDMA systems. An Alamouti-like space-time block code (STBC) and simple detection for spatial multiplexing (SM) for Q-OFDMA systems are constructed, both zero forcing (ZF) and minimum mean square error (MMSE) equalizers are investigated. The proposed STBC is a full diversity scheme, which encodes in intermediate domain and decodes in frequency domain. Analytical and empirical results demonstrate that the Q-OFDMA systems can be implemented flexibly and efficiently in a MIMO framework, and 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.10 page(s

Space-time block code and spatial multiplexing design for quadrature-OFDMA systems

To alleviate the high peak-to-average power ratio (PAPR), high complexity in user terminal and sensitivity to carrier frequency offset (CFO) problems in current orthogonal frequency division multiple access (OFDMA) systems, a Quadrature OFDM (Q-OFDMA) system has been recently proposed in the single-input single-output environment. In this paper we study the realization of multi-input multi-output (MIMO) diversity-and multiplexing-oriented methods for Q-OFDMA systems. An Alamouti-like space-time block code (STBC) and simple detection for spatial multiplexing (SM) for Q-OFDMA systems are constructed, both zero forcing (ZF) and minimum mean square error (MMSE) equalizers are investigated. The proposed STBC is a full diversity scheme, which encodes in intermediate domain and decodes in frequency domain. Analytical and empirical results demonstrate that the Q-OFDMA systems can be implemented flexibly and efficiently in a MIMO framework, and 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. © 2012 IEEE