Performance evaluation and pulse design for ultra-wideband communications

Ultra-wideband (UWB) technology is being investigated in academy and industry as a good candidate for new generation communications. In general, the performance of UWB communications is limited by channel fading and interference from other systems or user signals. This thesis contributes to the accurate bit error rate (BER) performance analysis of UWB communication systems in different transmission scenarios. It also contributes to the system design of UWB communications, specifically on pulse shaping for UWB systems.;Similar analysis is then extended to different UWB modulation schemes. Tractable expressions are derived and used to compare the performances of these systems. Unlike some previous results obtained by using the Gaussian approximation, it is shown both analytically and numerically that different schemes have different capabilities for interference suppression.;Error analysis for UWB systems operating with narrowband orthogonal frequency division multiplexing (OFDM) signals is also studied. It is found that OFDM interference significantly worsens the performance of the desired UWB signal. Some methods are expected to suppress narrowband OFDM interference. In addition, the BER performances of different UWB systems in multipath fading scenarios are examined. A realistic fading channel model is considered and the properties of several receiver structures are thoroughly examined.;Pulse shapes for UWB communications are extensively investigated. Pulse shapes proposed for UWB communications are evaluated in light of frequency emission restrictions and the BER, performances of systems using different pulses are accurately assessed. In addition, a novel pulse design paradigm is proposed to synthesize time-limited pulse shapes that meet a given frequency constraint. It is shown that the novel pulse design paradigm provides more flexibility in designing pulses for UWB communications.;A time-hopping pulse position modulation (TH-PPM) system operating in multiple access interference is first considered. A tractable analytical expression for predicting the average BER is derived using a characteristic function method. The precise BER can be obtained for a system with an arbitrary number of users using arbitrary pulse shapes with modest computational complexity. Our results are used to assess the accuracy of the Gaussian approximation, which is widely used for BER estimation.