Author Description

This dissertation, "Enhanced Techniques for Broadband Wireless Communications" by Bin, Xia,, 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 "Enhanced Techniques for Broadband Wireless Communications" Submitted by XIA Bin for the degree of Doctor of Philosophy at The University of Hong Kong in January 2004 This study investigates three enhanced techniques for broadband wireless communications, which aim to meet the challenge of high data rate services. They include (1) multi-level quadrature amplitude modulation (MQAM) with antenna diversity; (2) multicode code division multiple access (CDMA) with MQAM and interference cancellation and (3) orthogonal frequency and code division multiplexing (OFCDM) systems with Minimum Mean Squared Error (MMSE) or optimum detection. The first chapter of this thesis explains the challenges posed by high data rate services. In Chapter Two the performance of MQAM systems is studied. In particular, the effect of channel estimation error due to time varying fading and additive noise is analyzed. It is shown that with the antenna diversity technique, the bit error rate (BER) performance of MQAM systems improves significantly. By employing higher order QAM modulations with the help of antenna diversity, it is therefore possible to increase system throughput in low signal-to-noise ratio (SNR) cases. It is also observed that the inaccurate channel estimates limits the benefit of diversity. More accurate channel estimation can be achieved by increasing the length of the channel estimator and the amplitude of the pilot symbol, thereby improving th