The UWB Pulse Design Of Direct Sequence Ultra-Wideband System

As the ultra-wideband technology can share spectrum resources with other communications systems,the ultra-wideband technology caused the extensive attention when the FCC permitted the Ultra-Wideband technology for civilian applications in February 2002.The first problem of Ultra-wideband technology to solve is to avoid interference with other communications systems.And the basic standard estimating interference is that the radiation energy of system must meet the FCC's radiation limit.The pulse shape of Ultra-Wideband System determines the energy radiation of pulse-mode UWB system.For this reason,this paper studies on pulse shape of the pulse-mode ultra-wideband system.It researches the UWB pulse shape design according FCC spectrum mask,from the time-domain to frequency domain,and frequency domain to the time-domain design points of view.It also researches the affect of UWB pulse on the ultra-wideband system performance in order to evaluate the UWB pulse and guide the design of ultra-wideband pulse.The main work and research results are as follows.1.The study of realization technology of ultra-widebandIt studies the working principles of IR-UWB,DS-UWB and MB-UWB,and analysis their technical characteristics.Then,The system cost,power consumption, interference,bit error rate of the three ultra-wideband are analyzed and compared.It establishes the UWB system scheme for this article which is direct sequence spread spectrum,BPM modulation ultra-wideband system with frequency shifting.The research results concluded that:DS-UWB and MB-UWB suitable for high-speed communications;IR-UWB is not applicable to high-speed communications but imaging systems and ground-penetrating radar.Compared with MB-UWB,DS-UWB is simpler,lower error rate,adaptive FCC's radiation restrictions better.2.UWB pulse study based on time-domainIt discusses the basic design principles of Ultra-Wideband pulse.It studies on time-domain characteristics and frequency-domain characteristics of existing pulses, analyses whether they meet the FCC spectrum mask,discusses the algorithms of optimizing and combining pulse to best match with the FCC spectrum mask.Based on the front research results,it designs two ultra-wideband pulses,single-Gaussian pulse and Gaussian-combination pulse,in accordance with the optimization and combination algorithms for the direct sequence ultra-wideband system.The two pulses are easy to realization and have high frequency spectrum utilization as opposed to the previous ultra-wideband pulse.3.UWB pulse study based on frequency-domainIt studies the UWB pulse design from frequency domain to the time-domain design point of view.It proposes a new ultra-wideband design method,direct frequency-domain method.It designs two UWB pulse,the square-root raised cosine pulse and raised cosine pulse,for the direct sequence UWB system according to the new method.The two designed pulses have better Spectrum utilization,less interference to other communication systems,more secret than the existing ultra-wideband pulses.This indicates that the direct frequency-domain method is fine.4.UWB pulse study based on system performance Scholtz pulse,It analyses the AWGN channel model and UWB wireless multi-path channel model recommended by the IEEE,and constructs the direct sequence ultra-wideband system model.It realize the system bit error rate simulation using Scholtz pulse,the single-Gaussian pulse,the combination-Gaussian pulse,the approximate prolate spheroidal wave pulse,the square raised root cosine pulse,and raised root cosine pulse in the AWGN,CM1,CM2,CM3,and CM4 channel.The results show that the bit error rate of single-user direct sequence ultra-wideband system using six kind of pulses is not very different.Then,it researches and simulates the performance of multi-user direct sequence ultra-wideband system.It first derives bit error rate formula of the multi-user direct sequence ultra-wideband system.The bit error rate formula indicates that the Multi-user interference MUI is determined by the number of users,data bit rate,and auto-correlation function of the pulse.Through analyzing MUI of the six pulses System,it obtains the conclusion that combination-Gaussian pulse,raised cosine pulse,and square root raised cosine pulse have strong resistance on MUI,and Scholtz pulse has weak resistance on MUI. It establishes the multi-user direct sequence ultra-wideband system model,simulates bit error rate of multi-user system using different pulse,and obtains the multi-user capacity of six pulses.Combination-Gaussian pulse,and raised cosine pulse have big multi-site capacity,Scholtz pulse has small multi-site capacity.According to the results of the performance simulation,the designed four pulses by this paper,the single-Gaussian pulse,the combination-Gaussian pulse,the raised cosine pulse,and the square root raised cosine pulse can be used to direct sequence ultra-wideband system.Considering the interference to other systems,the bit error rate performance,multi-site capacity,difficulty to achieve,the raised cosine pulse is best.