Performance of a TH-PPM UWB system in different scenario environments

Ultra Wideband (UWB) communication technology has attracted considerable attention by researchers in recent years because of its appealing features and its several applications it offers in many areas (Win & Scholtz, 1998; Fontana, 2007; Ghavami et al, 2007). An UWB system is characterised by very short-duration pulses (usually on the order of a nanosecond) with a low duty cycle. It offers low power transmission, a fine path resolution and it easily supports multi-user communication (Di Benedetto, 2004). These properties make UWB technology an attractive candidate for short-range, high-speed wireless multiple access communication and ad hoc networking, with simple baseband and the capability to overlay legacy wireless systems. All this gives us many features such as wireless radar, communications, networking, imaging and positioning systems (Yang & Giannakis, 2004). Historically, UWB systems are based on impulse radio (IR) concepts. In an IR UWB system, a number of pulses are transmitted per information symbol and information is usually conveyed by the positions or the polarities of the pulses. In order that impulse radios, operating in the highly frequency range below a few GHz, do not interfere with narrowband radio systems operating in the same frequency band, the use of spread-spectrum techniques is necessary. A simple mean to spread the spectrum of these UWB pulse trains is Time Hopping (TH), with data modulation achieved in the rate of many pulses per data symbol (Win & Scholtz, 1998, a). In UWB systems, there are several basic methods of modulation but the most common impulse radio based UWB concepts are based on Pulse Position Modulation combined with Time Hopping (TH-PPM) where each pulse is delayed in advance of a regular time scale. Thereafter, we will describe this concept with further details. The study of digital communications system performance over the AWGN (Additive White Gaussian Noise) channels starts generally with statistically independent zero-mean Gaussian noise samples. Due to the Gaussian statistics of the noise samples, the probability of error can therefore be written in terms of a Q-function. There exists a set of efficient techniques for performance analysis when the system is distorted by AWGN and Rayleigh fading. We shall focus on the analytical methods that are useful in addressing the characteristics unique to UWB systems, such as the different modulation schemes and the large number of resolvable paths available to the receiver. In a UWB system rather realistic, the received pulses may overlap others causing inter-pulse 4