| Though the 3rd Generation of the mobile communication technology (3G) is proved capable to meet the needs of fast data transmission and broadband multimedia service, it's not the case when it comes to fast data transmission with extensive coverage, high quality and low cost of manufacture or multimedia service with high resolution. The ultrawideband technology is a communication mode based on narrow pulse spread spectrum technology. Compared to traditional communication technologies, this ultrawideband one is independent of carrier circuit or mixer circuit. As a result of its characteristics, such as fast transmission speed, high confidentiality, little manufacturing cost and low power consumption, 3G could get its application in the field of mobile communication, so as to not only provide more perfect and more diversified multimedia service satisfying the communication requirement with given bandwidth, but also indicate an effective solution to the short supply of the spectrum resource. As an important part in the research into the characteristics of ultrawideband pulse, the selection of the pulse waveform has an direct influence on the performance of the overall ultrawideband system. Therefore, it's worthy to study into the pulse waveform.With the research background of the ultrawideband technology introduced, the significance of the research is then illustrated. With a literature review prepared, the main research contents is designated, according to the existing research findings, and the technology route is also made, as a direction of the subsequent research works.Up to now, there are kinds of realization plans of the ultrawideband technology. Three typical plans are analyzed and compared by overall system performance, including cost of implementation and error rate, so as to reveal the internal relationship between the waveform designation of the ultrawideband pulse and the corresponding system implementation. Waveforms of common ultrawideband pulses are analyzed, such as Rayleigh Pulse, Sine Guass Pulse, Hermite multinomial Pulse, Pulse based on approximate prolate spheroidal wave function, and Pulse based on wavelet function. With these common waveforms simulated in Matlab, the main influential factor and evaluating indicator is given according to the results of the simulation, and a combined ultrawideband pulse waveform is proposed.The influence of the ultrawideband pulse waveform to the overall system performance is related to the modulation mode. Based on the analysis of TH-PPM and TH-BPSK, two kinds of modulation modes of ultrawideband pulses, the signal to interference and noise ratios and bit error rates are found by simulation and compared. It's proposed a quantitative analysis method for the pulse waveform designation problem in different modulation modes.The optimal designation problem of pulse waveforms is studied intergrated with the model of ultrawideband communicational channel. It's specially studied the performance of different ultrawideband pulse signals based on multipath channel model, and the error performances of various pulses are analyzed and compared by simulation in Matlab. The process and steps of the optimal waveform designation is explained, taking Guass pulse as an example, and it's determined the key parameters of the optimal model with the pulse width and the differential order as in the Guass pulse as well. |
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