| Developing indoor technologies including wireless multimedia personal area networks (WPANs) requires high-rate systems capable of supporting multiple users (piconets) with variable rates. These requirements motivate the design of multiband ultra-wideband systems for their simplicity in handling frequency selectivity, agility in coping with interference, scalability in providing multi-rate operation, and their low cost. Compared to baseband UWB radios, the MultiBand OFDM ultra-wide band system has obtained widespread approval in short-range wireless links. This article emphasises on researches on the MB-OFDM ultra-wide band system and multiple access technology.Compared with direct-sequence UWB (DS-UWB) system, the . MB-OFDM ultra-wide band system is more suitable in high-rate wireless communications. This article discusses the key technologies of MBOA Physical Layer Proposal, as well as IEEE803.15.3a standard ultra-wide band channel model. And then it builds the OFDM ultra-wide band system model in Matlab. After setting up system parameters according to MBOA standard Proposal, the article analyses the simulation results.How to assign the effective channel to multiusers in order to obtain the high system capacity, namely, the UWB multiple access(MA) technology, is one of the key technologies of UWB system. Shortly after the first UWB radio appeared, time-hopping (TH) spreading codes were advocated to enable multiple access in impulse radio (IR) UWB systems. Subsequently, direct-sequence (DS) and hybrid DS-TH were proposed to facilitate IR-MA. OFDM-based MA has been studied extensively in the context of non-UWB wireless communications. We could design the multiple access of WPAN based on the superiority in the frequency range of MB-OFDM ultra-wide band. In order to compare the performance of several multiple access methods, this article derives a unifying OFDM-based MB-UWB system framework, considering all subbands. Then it proves how existing FH-OFDM proposals fit with this framework. This article proposes a multiple access based on cross-band OFDM UWB system, combined with the OFDM UWB system structure. In theory, the cross-band OFDM UWB system achieves the frequency diversity and stands against the narrowband interference. The OFDMA subcarrier allocation has also guaranteed MUI (multiuser interference) elimination. Finally simulations in Matlab confirm the advantage of the multiple-access scheme based on cross-band OFDM UWB system. |
