Research On The Interference Suppression Of The Chirp And OCC Based UWB System

Ultra-wideband (UWB) technology is a good candidate for high data rate and short range wireless communications and has attracted considerable interests since FCC approved the spectrum occupation for UWB technology in2002. UWB technology has inherent capabilities to offer low transmission power and the other advantages, such as, low cost, very good multipath immunity and easy to implement, etc. These characteristics make UWB technology in wireless communication, radar, accurate positioning, and other fields to be a very broad application prospects, especially in the field of indoor short range wireless communication and gradually becomes the main possible candidates for the physical layer of wireless personal area network (WPAN). Due to the huge bandwidth of the UWB technology, it inevitable be affected by the narrowband systems within the shared spectrum, therefore, the research on UWB wireless communication system are of great significance to the development of wireless communication technology. The main work of this thesis is utilizing adaptive algorithm, characteristic function (CF) analysis method, the Chirp pulse and orthogonal complementary codes (OCC) and other technology to analyze the UWB system in interference environment.This thesis contains three parts:In the first part, the basic theory of UWB technology is introduced in detail. This thesis first introduces the basic theory of UWB technology which mainly includes the following aspects of content:firstly, we expatiate on the definition, advantages and development application prospect of UWB theology. At the same time, the time-frequency characteristics of typical pulses that UWB system commonly used are analyzed. Then, signal modulation and multi-access methods are carefully studied. Finally, we briefly describe the modeling of UWB IEEE802.15.3a indoor propagation wireless channels and standard channel model of UWB system.In second part, we also go into traditional Chirp waveforms and different NBI models, study the performance of UWB system suppression under narrowband interference (NBI) based on nonlinear Chirp pulse. Then the adaptive conjugate gradient (CG) algorithm is applied to UWB system, it can better reduce the influence of NBI in the UWB communication system. Simulation results demonstrate that utilizing the characteristics of the CG algorithm and its corresponding adaptive filter, we realize the NBI suppression and obtain the low cost and more practical UWB pulse design for a kind of optional proposes. In complex indoor wireless communication environment which needs exact analysis of narrowband interference, it is necessary to study the performance of UWB system in the aspects of the NBI suppression under multipath channel. This thesis studies the performance of characteristic function (CF) method based Chirp-UWB systems under multipath channel, and deduces the bit error rate (BER) formula of the Chirp-UWB system. Simulation results show that the presented CF method is more close to the actual performance of the system than the traditional Gaussian approximation method, and the accuracy of the system is improved.The third part, according to the exist multiple access interference (MAI) in addition to the multipath interference (MI) and NBI in UWB system, this paper provides UWB design and analysis based on complete complementary codes (OCC). First the correlation properties of spreading sequences, the definition of OCC, the serial OCC based UWB system and OS modulation based UWB system implementation scheme are introduced in detail. Then Chirp pulse is applied to the OCC based UWB system to improve the MAI and NBI suppression performance. In order to improve the rate and communication performance of the system, then we puts forward the parallel OCC UWB scheme, this scheme have both the advantages of MB-OFDM and IR-UWB, and the chirp signal is produced by SAW device, therefore the implementation of this theme is simple. Simulation results demonstrate that the UWB system can suppress NBIs and MAI simultaneously. At last, the research work in this thesis which has been accomplished is summarized and the future work is prospected.