Research On New Modulation Methods And RAKE Receiver In UWB Communication System

The research on Ultra-Wideband (UWB) communication technology receives more attention in recent years. UWB technology has broad application prospects because of the features of simple device infrastructure, lower transmission power, higher processing gain and data rate, hidden performance, multi-path resolution capability, etc. UWB pulse wireless communication is the new exploration for the use of radio spectrum which spreads nanosecond-level narrow pulse over a very wide frequency spectrum of several GHz. It is a powerful support for wireless communication technology.In this paper, the theoretical bases for UWB communication technology are analyzed systematically. At the beginning, it introduces the development, application, standards, research status and the Gaussian pulse shape of UWB technology in wireless communication. The UWB multiple access technology is researched. The importance and necessity of time-hopping spread spectrum technology are analyzed. The basic and new UWB modulation techniques are presented and the UWB signal structures of a variety of pulse modulations are given. The path loss model and multi-path model of IEEE 802.15.3a channel model are researched, and the basic principles and generalstructure of RAKE receiver are studied. The error probability and capacity of TH-BPPM (Time-Hopping biorthogonal pulse position modulation) UWB system are investigated. We consider BPPM over additive white Gaussian (AWGN) channels for a single-user system and multi-user environments. The derivation is also used in TH-PPAM UWB system that gets the error probability and capacity formulas. The simulation analysis for TH-BPPM UWB system and TH-PPAM UWB system over the above two cases are considered. The numerical results are presented illustrate and verify the capacity, error probability expressions .These results show that the error probability and capacity are affected by the ary modulation index, signal to noise radio (SNR), distance and the number of users.At the last part of this paper, the single-user TH-BPPM UWB system and TH-PPAM UWB system which using RAKE receiver over IEEE 802.15.3a channel are discussed. The performance of All RAKE (ARake), Partial RAKE (PRake) and Selective RAKE (SRake) are simulated. The results show that the receiving performance of TH-PPAM over CM1 channel is the best, the performance of SRake is superior to PRake. The results also show that the lager fingers of correlator, the better receiving performance.