Performance improvement of ultra-wideband wireless communication systesm based on the design of modulators and pilot patterns

Abstract

In this thesis, we deal with the performance improvement of UWB wireless communication systems. Our main objectives are 1) to investigate the design considerations and features of UWB communication systems caused by band spectrum and target applications and 2) to design UWB communication systems which can support improved performance under the pre-described design considerations and features. To reach the objective, we are focusing on the design of modulator which can support high data rate and inherent processing and diversity gain (chapter 3); pilot insertion scheme for channel estimation and providing other advantages without the degradation of bandwidth efficiency (chapter 4 and 5); and design of preamble for improved synchronization performance (chapter 6). As a modulator, we propose multi-coded pulse position modulation (MC-PPM) scheme. Multi-coding scheme, which uses several orthogonal codes simultaneously, is combined with PPM in order to achieve variable and high data rate and processing gain guaranteeing the advantages of PPM schemes. In addition, we also propose multi-coded bi-orthogonal PPM (MC-BPPM) scheme which is the extended version of MC-PPM in order to increase data rate by using pulse polarity. For a pilot insertion scheme, we propose an hidden pilot scheme and its application to single band direct sequence UWB (DS-UWB) and multi-band orthogonal frequency division multiplexing UWB (OFDM-UWB) systems. The hidden pilot sequence, which uses a fraction of the informative sequence``s transmitting power as pilot information, is utilized for channel estimation and aiding multi-user interference (MUI) suppression in DS-UWB system; channel estimation, frequency diversity gain combined with multi-coding scheme and peak-toaverage power ration (PAPR) reduction in OFDM-UWB system guaranteeing higher bandwidth efficiency (no use of resources just for pilots). Finally, we de-sign the preamble signal in order to increase synchronization performance in the UW...