Study on Reliable Low-power Wireless Communication Systems Using Multiband Pulsed UWB Technlogy

本项目的目标是利用多频段脉冲超宽带(UWB)技术开发可靠的低功率无线通信。首先，从保证一定误码率性能的角度出发，对直接序列超宽带(DS/UWB)系统在多径衰落环境下的性能进行了评估；其次，研究了DS/UWB协作通信在多径信道中的性能。计算机仿真结果表明，在非视距多径信道中，与采用常规分集接收的DS/UWB系统相比，采用协作通信可以有效地提高系统的性能。第三，DS/UWB通信系统，尤其是分组通信系统的捕获性能。在无线分组传输中，捕获必须在分组中的前导持续时间内完成。在该方案中，DS/UWB分组传输采用RAKE合并和验证模式，以对抗多径衰落。根据IEEE802.15.4a多径衰落环境下的仿真结果，采用RAKE合并可以显著提高捕获概率。此外，当验证模式配备DS/UWB捕获系统时，平均捕获时间变得更短。为了在多径衰落环境下实现更快、更准确的捕获，提出了使用峰值检测和区间估计的方法。计算机仿真结果表明，在DS/UWB捕获中，峰值检测和区间估计能够准确捕获匹配滤波器输出的峰值。此外，还可以通过优化峰值检测的捕获间隔来缩短捕获时间。

The goal of this project is developing reliable low-power wireless communications by using multiband pulsed ultra wide band (UWB) technology. In this project, the following topics are investigated.First, the performance of direct sequence ultra wide band (DS/UWB) systems is evaluated under the multipath fading environment from the viewpoint of ensuring a certain level of error rate performance by using cumulative distribution function (CDF) of bit error rate.Second, performance of cooperative communications for DS/UWB in multipath channel is investigated. According to the computer simulation results, it is found that use of cooperative communications is effective to improve the performance in non line-of-sight multipath channel comparing with the use of conventional diversity reception in DS/UWB.Third topic is the acquisition performance DS/UWB communication systems, especially in packet communications. In wireless packet transmission, the acquisition must be completed in the preamble duration in the packet. In this project, RAKE combining and verification mode is employed in DS/UWB packet transmission to combat multipath fading. According to the simulation results under the IEEE802.15.4a multipath fading environment, significant improvement of acquisition probability is achieved by using RAKE combining. Also, mean acquisition time becomes shorter when the verification mode is equipped with the DS/UWB acquisition system. Also, using peak detector and interval estimation is proposed to achieve faster and more accurate acquisition in multipath fading environment. Computer simulation results show that the peak detection and interval estimation is effective to capture the accurate peak of the matched filter output in the DS/UWB acquisition. In addition, thereduction of the acquisition time is achievable by optimal design of the capturing interval for the peak detection.