Spatial User Capacity of UWB Networks with Space-Time Focusing Transmission

Space-time focusing transmission in impulse-radio ultra-wideband (IR-UWB) systems resorts to the large number of resolvable paths to reduce the inter-pulse interference as well as the multiuser interference, and to simplify the receiver design. In this paper, we study the spatial user capacity of IR-UWB systems with space-time focusing transmission where the users are randomly distributed. We will derive the power distribution of the aggregate interference and investigate the collision probability between the desired focusing peak signal and interference signals. The closed-form expressions of the upper and lower bound of the outage probability and the spatial user capacity are obtained. Analysis results reveal the connections between the spatial user capacity and various system and channel parameters such as antenna gain, frame length, path loss factor, and multipath delay spread, which provide design guidelines for IR-UWB networks.