Capacity analysis for UWB systems with power controlled terminals under power and coexistence constraints

Ultra-wideband (UWB) wireless technology will play a key role in the future beyond third generation wireless. systems guaranteeing very high bit rates availability, low power consumption, low costs and location capabilities. The worldwide acceptance of UWB technology is mainly related to coexistence issues with other existing narrowband and wideband systems sharing the spectrum with UWB. To this aim regulatory bodies imposed restrictions on UWB transmissions so implicitly limiting its system capacity intended as the number of users that can be served for a specified link outage probability. In this work the problem of calculation of UWB system capacity subject to power and coexistence constraints is analyzed. The problem is first formulated and a semi-analytical method for solving it is presented. The proposed procedure is then applied to a study case considering the coexistence between an UWB network located inside a building and outdoor fixed wireless systems. It is observed that power and coexistence constraints can lead to a significant under-utilization of the available UWB system capacity. The capacity-coexistence tradeoff is also discussed. In general, it can be observed that depending on the relative, position between the UWB devices and the victim receiver, coexistence requirements may result to be more restrictive than power limitations and the UWB system can be limited by coexistence rather than by self-interference.