Cognitive Power Allocation for Multicarrier Based Ultra Wide Band (UWB) Wireless Systems

This thesis presents a study of Distributed Cognitive Power Allocation for multicarrier based Ultra Wide Band (UWB) wireless systems in a point to point configuration as a way of reducing the coexistence interference for low power emission wireless systems in close proximity, as well as combating the increased path loss and fading at longer range by means of a Distributed Cognitive Power Allocation (DCPA) scheme.

The Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) standard for Ultra Wide Band (UWB) wireless data communication is used as the basis in this research. A novel gradient power allocation is developed for channel sharing and partitioning among multiple user with no direct information exchange. A novel game strategy is used to assist the gradient power allocation and guide the behaviour of the homogenous users in order to acquire their target data rate. We show the superiority of our game based approach in terms of convergence and power efficiency through the comparison between our Game based and iterative water-filling based approaches. The strength of our scheme is also gained from a theoretical proof of convergence (demonstrating of the existence of a Nash Equilibrium).

Performance analysis is carried out for both frequency selective and frequency none selective channels. Also, performance is evaluated for both interference dominated and noise dominated environments, where the severe interference is caused by the homogenous systems deployed in close vicinity. It is shown that the achievable target date rate is largely constrained by the interference while the performance is not impaired by frequency selective channel in terms of convergence and convergent speed.

The methodology is adapted for an extended range scenario, where the protection of the licensed user (Primary user) is taken into consideration as well as the target data rate requirement. A new performance measure called the Power Impact Factor is used to quantify the impact of the power allocation scheme compared with the FCC spectrum mask. This measure is used to quantify the interference generated by cognitive UWB devices in relation to the existing agile services.