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Detection and channel estimation for MIMO-OFDM wireless communications.

机译：MIMO-OFDM无线通信的检测和信道估计。

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摘要

Orthogonal frequency division multiplexing (OFDM) transforms a frequency selective channel into a large set of individual frequency non-selective narrowband channels, which is suited for a multiple-input multiple-output (MIMO) structure that re quires a frequency non-selective characteristic at each channel when the transmission rate is high enough to make the whole channel frequency selective. Therefore, a MIMO system employing OFDM, denoted MIMO-OFDM, is able to achieve high spectral efficiency. However, the adoption of multiple antenna elements at the transmitter for spatial transmission results in a superposition of multiple transmitted signals at the receiver weighted by their corresponding multipath channels and makes the reception more difficult. This imposes a real challenge on how to design a practical system that can offer a true spectral efficiency improvement.; In this dissertation, we couple spatial transmission technology with data detection and channel estimation algorithm design to improve spectral efficiency at the physical layer for MIMO-OFDM wireless communications. In the MIMO-OFDM structure, either a space-time coded OFDM signal is sent over two antenna elements (AEs) exploiting spatial diversity, or an independent OFDM signal is sent over each of AEs utilizing spatial multiplexing. A data detection algorithm, QRD-M algorithm, is proposed to obtain a spectrally-efficient and computationally-efficient solution. The QRD-M algorithm combines advantages of both the QR decomposition (QRD) and the M-algorithm to attain a comparable performance with the maximum likelihood (ML) algorithm but reduces the computational complexity. To further improve the computational efficiency, an adaptive complexity QRD-M (AC-QRD-M) algorithm is proposed in which a different number of searching branches are assigned to individual subcarriers. The idea is to perform adaptive tree search by distinguishing strong and weak subcarriers.; Coupled tightly with spatial transmission and data detection, accurate channel estimation is indispensable to reliable communication. With the assumption of a static channel over a packet, a space-time block coded algorithm operates on two training symbols to estimate channel coefficients, and an EM-based algorithm works on one training symbol to iteratively estimate the channels in the ML sense. In a scenario of fast-fading channels, a decision-directed Kalman filter (KF) solution is proposed for joint estimation of channel coefficients, which is robust even at large normalized Doppler spreads. Iterative channel estimation through a non-decision-directed approach using Kalman filters is studied to further improve the estimation.; Signal models and algorithms for spatial transmission, data detection, and channel estimation are derived, developed and simulated. Based on the results, a performance improvement is obtained through the cooperation of spatial transmission, data detection and channel estimation.
机译：正交频分多路复用（OFDM）将频率选择信道转换为一大组单独的频率非选择窄带信道，适用于需要在以下位置具有频率非选择特性的多输入多输出（MIMO）结构每个通道在传输速率足够高时都可以使整个通道具有选择性。因此，采用表示为MIMO-OFDM的OFDM的MIMO系统能够实现高频谱效率。然而，在发送器处采用多个天线元件进行空间发送会导致在接收器处多个发送信号被其相应的多径信道加权而叠加，并使接收更加困难。这给如何设计一个可以真正提高光谱效率的实用系统带来了真正的挑战。本文将空间传输技术与数据检测和信道估计算法设计相结合，以提高物理层的MIMO-OFDM无线通信频谱效率。在MIMO-OFDM结构中，或者在两个利用空间分集的天线单元（AE）上发送空时编码的OFDM信号，或者利用空间复用在每个AE上发送独立的OFDM信号。提出了一种数据检测算法QRD-M算法来获得频谱有效和计算有效的解决方案。 QRD-M算法结合了QR分解（QRD）和M算法的优点，以达到与最大似然（ML）算法相当的性能，但降低了计算复杂度。为了进一步提高计算效率，提出了一种自适应复杂度QRD-M（AC-QRD-M）算法，其中将不同数量的搜索分支分配给各个子载波。想法是通过区分强和弱子载波来执行自适应树搜索。与空间传输和数据检测紧密结合，准确的信道估计对于可靠的通信必不可少。假设数据包上有静态信道，则空时分组编码算法将对两个训练符号进行操作以估计信道系数，而基于EM的算法将对一个训练符号进行操作以从ML角度迭代地估计信道。在信道快速衰落的情况下，提出了一种针对判决系数的卡尔曼滤波器（KF）解决方案，用于信道系数的联合估计，即使在较大的标准化多普勒扩展下，该解决方案也很健壮。研究了使用卡尔曼滤波器的非决策定向方法进行的迭代信道估计，以进一步改善估计。推导，开发和仿真了用于空间传输，数据检测和信道估计的信号模型和算法。根据结果​​，通过空间传输，数据检测和信道估计的协作可以获得性能上的提高。

著录项

  • 作者

    Yue, Jiang.;

  • 作者单位

    Southern Methodist University.;

  • 授予单位 Southern Methodist University.;
  • 学科 Engineering Electronics and Electrical.
  • 学位 Ph.D.
  • 年度 2005
  • 页码 139 p.
  • 总页数 139
  • 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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