Research On Anti-interference Transmission Techniques In Single-Carrier Frequency-Domain Equalization System

Modern wireless communications is marching towards broadband technologies with high efficiency, high capacity and high reliability. Orthogonal Frequency Division Multiplexing (OFDM) and Single-Carrier Frequency-Domain Equalization (SC-FDE), as two branches of modulation schemes for broadband wireless communications with desirable spectrum efficiency, have received extensive attention from worldwide scholars and hence become promising candidates for 4G technology. Particularly, the preferable envelope characteristics of the latter have drawn numerous focuses upon its research and applications. Meanwhile, it is equally important to enhance the ability of the receiver to combat complex electronic magnetic interferences under unknown channel conditions, hence a significant subject for research.This thesis aims at the single-input single-output SC-FDE system and analyzes several interference-induced problems that can be potentially suffered by the SC-FDE receiver. A thorough study accompanied by anti-interference solutions and simulation results is given with respect to the pre-processor of arrival detection, algorithm design of symbol timing, carrier frequency offset estimation in fading channels, and turbo FDE. This thesis is organized as follows:Chapter One gives a brief review of the history of wireless communications, followed by the main objective of this thesis.Chapter Two presents some qualitative discussion about wireless channels, as well as some quantitative analysis of the baseband impulse response model and its relevant channel functions, followed by an introduction to the wireless fading channels used for simulation in this thesis.Chapter Three examines the interference-induced problems in terms of arrival detection, symbol timing, carrier synchronization and FDE in the SC-FDE receiver. Symbol timing and FDE algorithms used in this thesis are proposed at the end of this chapter.Chapter Four addresses the problem of Narrow-Band Interference (NBI) rejection in Pseudo-random Noise (PN) correlator based arrival detection system. Five interference suppression algorithms are deduced and proposed, followed by simulation results in terms of the output of PN correlator and probability of frame detection.Chapter Five studies the problem of carrier synchronization in slow fading channels. Two Maximum Likelihood (ML) frequency estimators and two linear-model estimators are deduced and proposed, and their corresponding estimation variances are compared against the Cramer-Rao lower bound of additive white Gaussian noise channel.Chapter Six takes into account all aforementioned baseband processing modules, and examines their simulation performance from the point of view of Bit Error Rate (BER). Results indicate that the proposed frame structure combined with turbo FDE algorithm achieves a desirable BER performance for slow fading channels with limited multipath. Linear prediction and non-linear least mean squares adaptive filter prove to be two suitable approaches to NBI suppression. The ML estimator, although sensitive to Doppler shifts, is found to be able to give precise frequency offset estimation even with NBI, whereas the linear-model estimator is robust to larger Doppler shifts, but exhibits a much poorer BER performance in slow fading channels with or without NBI.