Research And Realization Of Synchronization Techniques In Ultra-Wideband Wireless Communication System

UWB technology has become an interest research area in wireless communication, and it is considered as one of the key technologies for the next generation wireless communication. Presently, UWB wireless communication systems are classified into two main forms: non-carrier UWB system and carrier modulated UWB system. Meanwhile, carrier modulated UWB system can be implemented using many schemes, in which DS-CDMA UWB and MB-OFDM UWB are the two main ones.OFDM technology, with the merits of high bandwidth efficiency, robustness to multi-path and simplicity of equalization, is especially suitable for wideband wireless communication. In this thesis, an OFDM based UWB system is studied, emphasizing particularly on the research and realization of synchronization technologies.Following the introduction of the background knowledge of UWB and the basic principle of OFDM, synchronization technologies are analyzed in more detail. Some non-ideal effects on the performance of OFDM systems are discussed. And some typical OFDM synchronization schemes are presented.After investigating some existing synchronization schemes, a whole synchronization schemes for the OFDM based UWB system are designed. A special training sequence is used in timing synchronization which is divided into three steps: frame detecting, coarse timing synchronization and final timing synchronization. Frame detecting and coarse timing synchronization are achieved by random sequence with low PAR. An improved metric makes coarse timing synchronization better. Final timing synchronization based on complementary sequence pair is finished with timing field channel estimation accompanied. Complementary sequence pair makes calculating easier, while which is quite sensitive to frequency offset. It is proposed in the thesis that the frequency offset should be corrected according to frequency offset estimated in coarse timing synchronization step if necessary. In frequency synchronization scheme, frequency estimation is accomplished with coarse timing synchronization. The improved metric designed in coarse timing synchronization step also makes a great performance enhancement in frequency offset estimation. Weighting function by amplitude value of channel estimation in frequency domain is used in pilot based phase tracking, which is quite suitable for UWB frequency selective fading channel, having a great performance enhancement compared to traditional non-weighting pilot based phase tracking method. Performance of each synchronization step in UWB system is given in this thesis. In order to evaluate the performance of the whole synchronization schemes, the system performances with ideal and non-ideal synchronization are compared.The synchronization schemes of OFDM-UWB system proposed in this thesis can be simply realized by iterative or simple shift add and sub computation. FPGA realization flow of these proposed synchronization schemes in the UWB demo system is introduced last. Truncation of valid data and several equivalent methods of synchronization schemes implemented in FPGA realization are also presented. The result of hardware implement is consistent with the software simulation. The utilized resource of overall synchronization module and each sub-module of FPGA chip are presented. VertexII Pro70 of Xilinx company is used as the FPGA chip.