Abstract
In this dissertation, we present a new look at spectrum management with quality-of-service (QoS) provisioning for wideband cognitive radio (CR) networks. To maximize the throughput performance of a CR network while maintaining the protection of primary users (PUs), the sensing time and the decision threshold for spectrum sensing must be determined appropriately. In the first part of this dissertation, we formulate an optimization problem to balance the sensing-throughput tradeoff for a CR network with wideband spectrum sensing. Our objective is to maximize the throughput of a CR user’s link under the constraint of a given target detection probability. Different from previous works, our approach adopts an objective function with a combined aggregate throughput for both possible scenarios of the CR network, thus achieving the maximum throughput performance under a given interference imposed on the primary network. Due to the nature of wireless fading channels and PU activities, it is necessary to adjust the transmission rate of a CR user according to the channel capacity. In the second part of this dissertation, we present a transmission rate control policy to satisfy QoS requirements of CR users, where no interference constraints of PUs are considered. We consider the spectrum sensing results and the statistical behaviors of Rayleigh fading channels jointly to determine a transmission rate such that the effective throughput of a CR user’s link is maximized, where the effective throughput is defined as the data rate successfully received by the destination. Simulation results demonstrate that a CR user’s link with the proposed transmission rate control policy achieves the maximum effective throughput performance under Rayleigh fading channels. Furthermore, we propose a low-latency transmission strategy for CR networks under an interference constraint of PUs. The proposed scheme dynamically regulates the transmission rate and the spectrum access policy for a CR user according to PU activities and the CR transmitter’s queue length; that is, a CR transmitter with a larger queue length will have a higher transmission opportunity such that the high-latency and buffer-overflow problems could be controlled. In the proposed scheme, two cost functions (i.e., transmit or suspend) are formulated to confine the QoS performance and the interference probability to an acceptable level; the CR user chooses the lower-cost action for spectrum access. Simulation results show that the proposed low-latency transmission control strategy achieves the maximum effective throughput performance with a low packet delay while maintaining the interference probability.