| Ultra-wideband (UWB) communication is a rising communication technology, where impulse radio based UWB (i.e., IR-UWB) is the most important branch. It has particular advantages in dense multipath channels. Optimal receiver can be used in IR-UWB system, but its complexity is often unceptable, where channel estimaton and synchronization are two chanlleging problems. Therefore, it is necessary to explore new technology with low complexity. This dissertatation focuses on autocorrelation UWB receiver. Besides, we analyze some basic problems in depth, such as channel capacity and spectrum characteristic, etc., The main contributions are as follows:(1)Different from the convention UWB system is usally aiming at high data rate communication over short distances, the dissertation discusses the feasibility of communication over long distances basing on information theory. The research results show that UWB also suits low speed communications over long distances under some special situations, while its superiority could be probably not remarkable as that in short distance communications. A "Two Cluster"supposition of long distance UWB channel model is proposed for ground-aircraft communication applications, Doppler effect and coherence time of UWB channel are proposed and analysised too. In addition, channel capacity the UWB system combined with MIMO are analyzed and some useful results are obtained.(2) Since the UWB system is required to have co-existence capability with other wireless systems, it is very important that its transmited signals must be seasonablly distributed in the frequency domain so as to interfere the latters as less as possible. After analyzing the distribution of the power spectral density of the Time-Hopping-UWB (i.e. TH-UWB) signals, the dissertation reveals that the conventional TH operation is not good enough to smooth the spectrum, which makes some residue existed in harmonic frequency points. In order to improve the properties of the spectrum, a novel pseudo chaotic pulse position modulation (PCPPM) is proposed based on analyzing CPPM and PCTH modulations, which has its comprehensive performance dramatically improved. It has been validated by means of performance analysis and simulation experimental results.(3) About the performance of the UWB autocorrelation receiver, the dissertation has classified them and analyzed their performance basing on the existing conclusion. The Transmission Reference(TR) and DIfferential (DIFF) receiver with PPM modulation are proposed, and their modulation mode is improved. The dissertation suggests that the Generalized-Likelihood-Radio-Test (GLRT) receiver of UWB could be regarded as a reference standard for the system performance. Moreover, the performance of all UWB autocorrelation receiver are analysised.(4) Combining MIMO with UWB is a very important way to realize high speed communications, but it could result in high complexity. The dissertation discover a fact, namely simply transmit diversity is effective in UWB, which is different from the convention narrow system. In addition, the dissertation proposes a noval scheme with low complexity receiver, called as TR-MIMO-UWB. The proposed scheme is easy to implement, and needn't channel estimation. The performance analysis shows that the scheme is feasible.(5) Basing on analysis of TDT blind timing algorithm, the dissertation proposes a Time-Shift-TDT(TS-TDT) blind timing algorithm to deal with timing synchronization for PPM-UWB, which gets synchronizing information from calculating the delay cross-correlation values by means of two correlation branches. Theoretical analysis and simulation results demonstrate that the implementation of this algorithm is of low complexity and flexible in precision control. |
