Author: Shaodan Ma

Publisher: Open Dissertation Press

Published: 2017-01-27

Total Pages:

ISBN-13: 9781361469330

This dissertation, "Semi-blind Signal Detection for MIMO and MIMO-OFDM Systems" by Shaodan, Ma, 馬少丹, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled "Semi-Blind Signal Detection for MIMO and MIMO-OFDM Systems" Submitted by Ma Shaodan for the degree of Doctor of Philosophy at The University of Hong Kong in May 2006 MIMO (Multiple Input Multiple Output) and MIMO-OFDM (Orthogonal Frequency Division Multiplexing) systems have attracted a lot of research interest in recent years due to their potential for future high speed wireless communications. This thesis focuses on the problem of signal detection and proposes three semi-blind algorithms for MIMO, MIMO-OFDM with short cyclic prefix (CP), and MIMO- OFDM without CP, respectively. A three-step semi-blind Rake-based multi-user detection technique is proposed for quasi-synchronous MIMO systems. The first step separates the multi-user multi-path signal vector into multi-user single-path signal vectors based on second-order statistics (SOS) of the received signals. A simple estimation method is proposed in the second step to estimate the time delays with the aid of pilots. The third step combines multiple multi-user single-path signal vectors for signal detection. System performance is improved by time diversity and only the upper bounds of the channel length and the time delays are required. Simulation results show that the proposed technique achieves good performance and is not sensitive to over-estimation of the maximum channel length and the maximum time delay. A MIMO-OFDM system with short CP is next considered for higher bandwidth efficiency and a time domain semi-blind signal detection algorithm is proposed. A new system model in which the i th received OFDM symbol is left shifted by J samples is introduced. Based on some structural properties of the new system model, an equalizer is designed using SOS of the received signals to cancel most of the inter- symbol interference (ISI). The transmitted signals are then detected from the equalizer output. In the proposed algorithm, only 2P ( P is the number of transmit antennas/users in MIMO-OFDM systems) columns of the channel matrix need to be estimated, and channel length estimation is unnecessary. In addition, the proposed algorithm is applicable irrespective of whether the channel length is shorter than, equal to or longer than the CP length. Simulation results verify the effectiveness of the proposed algorithm, and show that it outperforms the existing ones in all cases. Finally, in order to further improve bandwidth efficiency, a MIMO-OFDM system without CP is considered and a two-step semi-blind signal detection algorithm is proposed. The algorithm is based on some structural properties derived from shifting the received OFDM symbols. The first step cancels inter-carrier interference (ICI) and ISI with an equalizer designed using SOS of the shifted received OFDM symbols. The second step involves signal detection from the equalizer output in which the signals are still corrupted with multi-antenna interference (MAI). In the proposed algorithm, precise knowledge of the channel length is unnecessary and only one pilot OFDM symbol is utilized to estimate the required channel state information. Simulation results show that the proposed algorithm achieves comparable performance to algorithms for standard MIMO-OFDM systems and it is robust against channel length overestimation. The number of words: 460 DOI: 10.5353/th_b3684656 Subjects: Signal detection Algorithms MIMO systems Orthogonal