脉冲位置调制光谱切片传输中英文翻译_学位论文.doc

Pulse position modulation for spectrum-sliced transmission Proponents of ultra-wideband (UWB) technology promise todeliver large amounts of data with very lowpower spectral density. The ultra-wideband radio concept is very attractive as it promises to open large amounts of spectrum to a variety of user sand at the same time it claims little interfere nice between users. Unlike conven tional wire less communications systems that are carrier based,UWB-based communications is baseband .It use sase ries of short pulses that spread thee nergy of thes ignal from near DC to a few GHz. One typical technique is to as sign a window in time and shif the position of the pulse with in that window. This is classical pulse position modulation. With band width restrictions effectively removed, UWB promises to speed upwire less data trans ferrates. Some pub lished work has addressed the issue of how many users can the UWB channel support[2][3].This work considered one type of capacity-the capacity interms on the number of users. The capacity was derived from signal-to-no is eratio (SNR)consi derations. Acer tain SNR is required to achieve a specified biterr or probability(BEP).The no is eflo or raises with the number of users. A more fund amentalty peofcapacity is the well known Shannon capacity in bits/s. Our go a list odevelopanunderstanding of thero leofvar iouspara me terso nthe Shannoncapac it yo fUWB commun ications.The well known Shannon!s form ulC=Wlog(l+SNR),where SNR is the 2 signal-to-noiseratio and Wist hechannel band width, predicts the channel capacity Cfor an additive white Gaussiannoise (AWGN) channel with continuousal uedinput sand outputs. This express iondoesnot apply to communications with PPM signals. PP mis a modul ation with discret e-valuedi nputsan dcon tinu ous-val uedoutput s.Further more,P Pmsignalsa reorthogo nal,whichi mposesa naddition alconst raintont hecapacityc alcul ations. Newcapacitycal culations arerequi red,which htakeint oaccountthes econstrai