Power, Sensing Time, and Throughput Tradeoffs in Cognitive Radio Systems: A Cross-Layer Approach

Cognitive radio has the ability to listen to the wireless channel, detect the vacant spectrum bands, and make use of them. However, the sensing ability of this smart radio may not be perfect which may induce interference to the primary system. One of the main challenges in cognitive communication lies therefore in striking a balance between the conflicting goals of minimizing the interference to the primary system and maximizing the performance of the secondary one. In this paper, we formulate a cross-layer optimization problem to design the sensing time and optimize the transmit power in order to maximize the cognitive system throughput while keeping the interference to the primary user under a threshold constraint. We study the impact of sensing time and power adaptation on the performance of the cognitive radio system. Through numerical analysis, we find that optimizing the transmit power of the cognitive user and the sensing time play an important role in maximizing the system throughput.