An optimum pulse shape design for ultra-wideband systems with timing jitter

Abstract

Ultra-wideband (UWB) technology offers a promising solution to the radio frequency (RF) spectrum drought by allowing new services to coexist with current radio systems with minimal or no interference. Two crucial keys to communications success of UWB systems are pulse transmission power and timing jitter effects. Since the Federal Communications Commission (FCC) published its standard for the limitation of effective isotropic radiation power (EIRP) for UWB systems in 2002, the problem of spectrum shaping for UWB systems came to the forefront of scientific discourse. The interference of pulse transmission power to and from existing systems operating over the same frequency may reduce the advantages of UWB systems. On the other hand, timing jitter which results from the presence of non-ideal sampling clocks in practical receivers causes distortion. This distortion affects the correlation of signals at the receiver and thereby reducing the signal detection ability of UWB systems. This is a serious problem because the UWB pulse duration is very short so only small timing misalignment can severely affect the performance of a correlation detector. This dissertation presents a novel technique in designing the optimum pulse shape for UWB systems under the presence of timing jitter. The proposed pulse attains the adequate power to survive the noise floor and simultaneously provides good resistance to timing jitter. It also meets the power spectral mask restriction as prescribed by the FCC for indoor UWB systems. In addition, parameters of the proposed optimization algorithm are also investigated. Moreover, this study proposes a novel design of orthogonal pulses to improve the capacity of UWB systems. This orthogonal pulse design is based on the optimum pulse we propose. Therefore, all of the orthogonal pulses now have the same properties as the optimum proposed pulse. These properties include power spectral density (PSD) that meets the FCC spectral masks and simultaneously resists timing jitter. Additionally, each of the orthogonal pulses is mutually orthogonal to other pulses. The simulation results have demonstrated several relevant merits of the optimum proposed pulse over the previously known pulses, namely the lowest bit error rate (BER) of the optimum proposed pulse is achieved in the system with the imperfect timing jitter at room temperature. For the orthogonal pulses, the simulation results confirm the orthogonality properties of the orthogonal proposed pulses and show the advantages of the novel design over others.