Carrier Frequency Offset Tracking in the IEEE 802.16e OFDMA Uplink
Carrier Frequency Offset Tracking in the IEEE 802.16e OFDMA Uplink
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DOI：
10.1109/twc.2010.101810.100376
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发表时间：
2010-12
影响因子：
10.4
通讯作者：
Pengfei Sun-;M. Morelli;Li X. Zhang
中科院分区：
文献类型：
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作者：
Pengfei Sun-;M. Morelli;Li X. Zhang
游牧无线城域网的 IEEE 802.16e 标准采用正交频分多址 (OFDMA) 作为空中接口。在这些系统中，上行链路信号和基站本地振荡器之间的残余载波频率偏移（CFO）会引起信道间干扰（ICI）以及多址干扰（MAI）。因此，准确的 CFO 估计和补偿对于避免错误率性能的严重下降是必要的。在这项工作中，我们解决了 IEEE 802.16e 上行链路中的 CFO 跟踪问题，并提出了基于最小二乘 (LS) 原理的闭环解决方案。在此过程中，我们利用了每个用户子通道中可用的一组导频音。由此产生的方案可以以可承受的复杂性实施，并且能够可靠地跟踪所有活跃用户的 CFO。与频偏补偿器配合使用时，可以有效减轻ICI和MAI，从而使信道均衡和数据检测直接进行。数值模拟用于证明在存在残余时变频率偏移的情况下所提出的解决方案的有效性。
The IEEE 802.16e standard for nomadic wireless metropolitan area networks adopts orthogonal frequency-division multiple-access (OFDMA) as an air interface. In these systems, residual carrier frequency offsets (CFOs) between the uplink signals and the base station local oscillator give rise to interchannel interference (ICI) as well as multiple access interference (MAI). Accurate CFO estimation and compensation is thus necessary to avoid a serious degradation of the error-rate performance. In this work, we address the problem of CFO tracking in the IEEE 802.16e uplink and present a closed-loop solution based on the least-squares (LS) principle. In doing so, we exploit a set of pilot tones that are available in each user's subchannel. The resulting scheme can be implemented with affordable complexity and is able to reliably track the CFOs of all active users. When used in conjunction with a frequency offset compensator, it can effectively mitigate ICI and MAI, thereby allowing channel equalization and data detection to follow directly. Numerical simulations are used to demonstrate the effectiveness of the proposed solution in the presence of residual time-varying frequency offsets.