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Parameter estimation in OFDM systems for high-rate wireless communications: Blind approach.

机译：用于高速无线通信的OFDM系统中的参数估计：盲法。

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摘要

Channel estimation and carrier frequency offset (CFO) estimation are two critical issues for Orthogonal Frequency Division Multiplexing (OFDM) systems to accommodate high rate wireless communications. Conventional OFDM systems are based on sufficient cyclic prefix (CP) to facilitate simple receiver implementation, however, at the cost of significant channel utilization loss that may be the over-riding constraint for future high speed services. Thus, there exists increasing interest in OFDM systems with less CP or no CP, for which previous algorithms assuming sufficient CP may not be appropriate. This dissertation is focused on blind (i.e. non-data-aided) parameter estimation for such systems. The redundancy introduced by receive diversity or virtual carriers (VCs) are exploited to fulfill new algorithms that give the OFDM systems the potential to achieve higher channel utilization.; First, a subspace based blind channel estimator is developed for OFDM systems without CP, motivated by the resemblance of the multichannel signal model resulting from over-sampling or use of multiple receive sensors of the received OFDM signal to that in conventional single carrier system. The proposed algorithm distinguishes itself from many previously reported methods by the elimination of the CP.; Next, another source of redundancy—VC, is explored to accomplish a new blind channel estimator. The method is attractive since it is applicable to conventional OFDM systems with CP and those without CP. For the former, the exploitation of VC brings additional performance gain to the previously reported blind estimators. Further, the proposed method can be employed for non-CP systems, thereby potentially achieving higher channel utilization.; The last part of the dissertation addresses CFO estimation for OFDM systems over ISI channels. In this scenario, previous CFO estimators suffer from an irreducible error floor due to model mismatch. We introduce a modified signal model for this case. Benefited from the special structure in the OFDM signals due to the presence of CP and VCs, a novel subspace CFO estimator is proposed. The method is appealing for its low complexity by avoiding the expensive subspace decomposition computation and its higher channel utilization for the OFDM systems when keeping/decreasing the length of CP even in ISI channels.
机译：信道估计和载波频率偏移（CFO）估计是正交频分复用（OFDM）系统适应高速率无线通信的两个关键问题。常规的OFDM系统基于足够的循环前缀（CP）来促进简单的接收机实现，但是，代价是信道利用率的巨大损失，这可能是未来高速服务的首要约束。因此，在具有较少CP或没有CP的OFDM系统中，存在越来越多的兴趣，对于这些系统，假定足够的CP的先前算法可能是不合适的。本论文着重于此类系统的盲（即非数据辅助）参数估计。利用接收分集或虚拟载波（VC）引入的冗余来实现新算法，从而使OFDM系统有可能实现更高的信道利用率。首先，是由于对接收到的OFDM信号进行过采样或使用多个接收传感器而产生的多通道信号模型与常规单载波系统中的信号类似，从而为无CP的OFDM系统开发了基于子空间的盲信道估计器。所提出的算法通过消除CP使其与许多先前报道的方法脱颖而出。接下来，探索了另一种冗余源-VC，以完成新的盲信道估计器。该方法是有吸引力的，因为它适用于具有CP和不具有CP的常规OFDM系统。对于前者，VC的利用为先前报道的盲估计器带来了额外的性能提升。此外，所提出的方法可以用于非CP系统，从而潜在地实现更高的信道利用率。论文的最后一部分解决了ISI信道上OFDM系统的CFO估计问题。在这种情况下，由于模型不匹配，以前的CFO估算者将面临不可减少的误差底限。我们针对这种情况介绍了一种改进的信号模型。由于CP和VC的存在，受益于OFDM信号中的特殊结构，提出了一种新颖的子空间CFO估计器。该方法因其低复杂度而吸引人，即使在ISI信道中，即使保持/减小CP的长度，也避免了昂贵的子空间分解计算和OFDM系统较高的信道利用率。

著录项

  • 作者

    Li, Chengyang.;

  • 作者单位

    University of Washington.;

  • 授予单位 University of Washington.;
  • 学科 Engineering Electronics and Electrical.
  • 学位 Ph.D.
  • 年度 2002
  • 页码 99 p.
  • 总页数 99
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 无线电电子学、电信技术;
  • 关键词

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