Quadrature OFDMA systems based on layered FFT structure
Quadrature OFDMA systems based on layered FFT structure
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DOI：
10.1109/tcomm.2009.03.060620
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发表时间：
2009-03
影响因子：
8.3
通讯作者：
Jian Zhang;Lin Luo;Zhenning Shi
中科院分区：
文献类型：
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作者：
Jian Zhang;Lin Luo;Zhenning Shi
在当前OFDMA系统中，由于子载波数量多，产生了峰值平均功率比（PAPR）高、载波频偏（CFO）敏感和用户终端复杂性高等三大问题。在本文中，基于层状FFT结构的创新概念，我们提出了一种新的正交OFDMA （Q-OFDMA）系统来克服这些问题。特别是，该系统可以实现与传统OFDMA系统相同的保护间隔开销和相同的带宽占用，同时降低了PAPR，提高了CFO鲁棒性和频率分集。Q-OFDMA系统还保证了下行链路接收器的低复杂性。研究了预定义和自适应用户数据速率的参数配置。对Q-OFDMA和OFDMA的误码率性能进行了理论比较，并通过仿真结果进行了验证。结果表明，当信噪比（SNR）高于信道条件下的阈值时，Q-OFDMA系统可以获得比OFDMA更好的性能，并且由于Q-OFDMA系统具有较大的频率分集，因此采用最小均方误差均衡器等先进均衡器可以显著降低该阈值。
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 Q-OFDMA 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.