Ultra-Wideband for Communications: Spatial Characteristics and Interference Suppression

Ultra-Wideband Communication is increasingly being considered as an attractive solution for high data rate short range wireless and position location applications. Knowledge of the statistical nature of the channel is necessary to design wireless systems that provide optimum performance. This thesis investigates the spatial characteristics of the channel based on measurements conducted using UWB pulses in an indoor office environment. The statistics of the received signal energy illustrate the low spatial fading of UWB signals. The distribution of the Angle of arrival (AOA) of the multipath components is obtained using a two-dimensional deconvolution algorithm called the Sensor-CLEAN algorithm. A spatial channel model that incorporates the spatial and temporal features of the channel is developed based on the AOA statistics. The performance of the Sensor-CLEAN algorithm is evaluated briefly by application to known artificial channels. UWB systems co-exist with narrowband and other wideband systems. Even though they enjoy the advantage of processing gain (the ratio of bandwidth to data rate) the low energy per pulse may cause these narrow band interferers (NBI) to severely degrade the UWB system's performance. A technique to suppress NBI using multiple antennas is presented in this thesis which exploits the spatial fading characteristics. This method exploits the vast difference in fading characteristics between UWB signals and NBI by implementing a simple selection diversity scheme. It is shown that this simple scheme can provide strong benefits in performance.