Researches On Interference Cancellation And Coexistence For Ultra Wideband Wireless Communication Systems

Ultra wideband (UWB) radio is a novel wireless communication technology, to which more and more attentions have been paid. UWB wireless communications techniques have many merits, including an extremely simple radio architecture, low-cost design, large processing gain, low power, fine time resolution, which make UWB radio an key role for medium and short range high rate wireless communications in future. And it will have a broad application prospect in wireless communication field.We firstly survey the history and the research status of UWB radar & communications. And the characteristics of the UWB radio signal are analyzed, comparing to some traditional radio. A variety of concentrated problems and fundamental questions are listed. And the main research contents of this thesis are pointed out. Then we introduce the basic modulation schemes of UWB impulse radio and the channel model used for simulation widely.We analyze the BER performance of time-hopping pulse position modulation (TH-PPM) and time-hopping pulse amplitude modulation (TH-BPM) in the deterministic multipath model. And point out that there are unbalanced bit error rate for different transmitted data symbol of UWB TH-PPM while using the conventional receiver architecture, since there is inter-path interference for TH-PPM. Aiming at the unbalanced bit error rate, two solutions are proposed. One is dynamics threshold of RAKE for different channel environment; the other is balance encoding the transmitted data symbol. It is shown by theoretical analysis and computer simulation that these two methods can solve the unbalanced bit error rate of traditional TH-PPM. Comparing with dynamic threshold method, the balance encoding scheme can be implemented more easily, and is more robust to the channel time variant characteristics, the channel estimation of RAKE receiver and the combination techniques.We evaluate the anti-jamming performance of different UWB radio systems. For the modulation scheme with local correlation receiver, we analyze the system parameters impact to anti-jamming performance of UWB system. And we propose the method of system parameters selection to improve the anti-jamming performance. For the differential-demodulation-like TR-UWB system, we investigate the method to improve the performance in AWGN. We analyze that the conventional TR-UWB receiver is not fit for demodulation while single-tone interference is present. And we propose several methods to improve the anti-jamming performance of TR-UWB, including weighting the delay-product result of receiver, averaging multiple reference pulses of TR-UWB received signal. It is shown that the proposed methods can improve the anti-jamming performance efficiently by theoretical analysis and computer simulation.The general closed formula of power spectrum density (PSD) for multi-user aggregate pulsed UWB radio is given, which is the theoretical base for optimizing PSD design of UWB radio. We investigate the main system parameters impact to the PSD of UWB aggregate signals. Based on the proposed PSD of UWB radio, we study the coexistence between the UWB and conventional direct sequence spread spectrum (DSSS). And the in-band interference power of time division-synchronous CDMA (TD SCDMA) is investigated as function of UWB system parameters while the UWB signal and TD SCDMA are overlapped in frequency domain. The BER performance of conventional DSSS system impacted by the UWB radio is analyzed.