本文为英国赫特福德大学（作者：Fabien Delestre）的博士论文，共209页。

本文研究了在频率选择性信道下，利用空时分组编码（STBC）和空频分组编码（SFBC）对MIMO-OFDM通信系统进行信道估计和数据检测。针对STBC-OFDM系统和SFBC-OFDM系统，提出了一种新的迭代联合信道估计和信号检测技术。该算法基于空时空频编码方案中的事件处理序列，该方案首先利用导频子载波进行信道估计，然后在第二时刻利用估计信道对相邻数据子载波中的数据符号进行解码。一旦数据符号被恢复，系统将使用解码后的数据符号作为参考信号递归地执行一个新的信道估计。重复以上迭代过程，直到恢复所有MIMO-OFDM符号。此外，所提出的信道估计技术是基于最大似然（ML）方法，提供了线性、简单的实现。由于STBC和SFBC的正交性，该方法在接收端不需要任何矩阵反演进行估计和检测，因而计算效率很高。

本论文的另一个新贡献是提出了一种新的分组译码方法，该方法通过使用子载波分组进行传输数据恢复，大大缩短了处理时间。OFDM符号被分成若干组，其中分配了一组引导子载波，用于启动信道估计过程。同时对每组OFDM符号中包含的指定数据符号进行解码，以提高解码持续时间。最后，提出了一种新的混合STBC和SFBC信道估计和数据检测技术，该技术采用联合迭代和群译码方法。在这种技术中，STBC和SFBC交替用于导频和数据副载波，形成了STBC/SFBC和SFBC/STBC的不同组合。本文提出的多输入多输出正交频分复用（MIMO-OFDM）系统的所有信道估计和数据检测方法，在不同的场景下进行了广泛仿真，并对其性能进行了充分验证。

This thesis is concerned with channel estimation and data detection of MIMO-OFDM communication systems using Space-Time Block Coding (STBC) and Space-Frequency Block Coding (SFBC) under frequency selective channels. A new iterative joint channel estimation and signal detection technique for both STBC-OFDM and SFBC-OFDM systems is proposed. The proposed algorithm is based on a processive sequence of events for space time and space frequency coding schemes where pilot subcarriers are used for channel estimation in the first time instant, and then in the second time instant, the estimated channel is used to decode the data symbols in the adjacent data subcarriers. Once data symbols are recovered, the system recursively performs a new channel estimation using the decoded data symbols as pilots. The iterative process is repeated until all MIMOOFDM symbols are recovered. In addition, the proposed channel estimation technique is based on the maximum likelihood (ML) approach which offers linearity and simplicity of implementation. Due to the orthogonality of STBC and SFBC, high computation efficiency is achieved since the method does not require any matrix inversion for estimation and detection at the receiver. Another major novel contribution of the thesis is the proposal of a new group decoding method that reduces the processing time significantly via the use of sub-carrier grouping for transmitted data recovery. The OFDM symbols are divided into groups to which a set of pilot subcarriers are assigned and used to initiate the channel estimation process. Designated data symbols contained within each group of the OFDM symbols are decoded simultaneously in order to improve the decoding duration. Finally, a new mixed STBC and SFBC channel estimation and data detection technique with a joint iterative scheme and a group decoding method is proposed. In this technique, STBC and SFBC are used for pilot and data subcarriers alternatively, forming the different combinations of STBC/SFBC and SFBC/STBC. All channel estimation and data detection methods for different MIMO-OFDM systems proposed in the thesis have been simulated extensively in many different scenarios and their performances have been verified fully.

1 引言

2 空时编码概述

3 MIMO-OFDM系统

4 STBC-OFDM的联合信道估计和数据检测

5 SFBC-OFDM的联合信道估计和数据检测

6 采用OFDM的SFBC/STBC和STBC/SFBC信道估计

7 结论与未来研究展望