Optimizing transmission and reception techniques for ultra wide-band communication systems

Abstract

This thesis deals with the optimization and study of transmission and reception techniques for ultra wide-band (UWB) communication systems. More specifically, this thesis introduces a novel technique for high data rate transmission in UWB communications systems considering the limited bandwidth modulated and modified Hermite pulse (LB-MMHP) set of different orders for each user in order to reduce various interferences. The LB-MMHP set is composed of pseudo-orthogonal pulses that have both good auto-correlation characteristics in all orders and low cross-correlation characteristics between different orders. The LB-MMHP pulses maintain their orthogonality without significantly changing their pulse bandwidth for any pulse order used. The Data is transmitted using MN-ary biorthogonal pulse position amplitude modulation (BPPAM) at a rate of many pulses per symbol. Multiple access capability is achieved using spread spectrum time hopping (TH). The Multi-user interference (MUI) and inter symbol interference (ISI) can be reduced effectively in a multi-user system. The performance of the proposed system is evaluated over multipath fading channels. Numerical and simulation results show that the proposed UWB system has significant performance improvements in terms of interference suppression and the advantage of low transceiver complexity. Furthermore, the thesis investigates the use of opportunistic UWB networks which can be efficiently applied to collect data through sensors employed for preserving environment. The high-precision positioning capabilities of UWB technology, based on its operation of ultra short data bearing pulses, can be a reliable solution. Most of the positioning techniques are based on time-of-arrival (ToA) of the first path which can be effectively estimated when the probability of early detection (PoED) is known. In this thesis, the PoED of UWB positioning sensor network subject to narrowband interference (NBI) modeled with Nakagami-m distribution is evaluated. The derived closed-form approximative expression of the PoED has remarkable accuracy in comparison to the existing semi-infinite series expression. The derived closed-form approximative expression is an easily handling finite sum that can be easily evaluated by any standard commercial mathematical software package. However, the tight lower and upper closed form bounds for the PoED are derived. Numerical and simulation results are shown to validate the analytical derivations.