Adaptive Time-Sharing and Power Allocation for Cognitive Radio Fading Broadcast Channels

In this contribution, we address the resource allocation problem in cognitive radio (CR) broadcast channels (BC) when the radio resources are shared between the primary user of the spectrum band and the CR-BC secondary network. Specifically, we propose utilizing spectrum sensing information about the primary´s activity at the secondary base station for an efficient allocation of the resources, namely, transmission time and power, to the secondary users. For this purpose, we assume that the spectrum sensing information, obtained using spectrum-aware sensors deployed in the secondary transmission range, and secondary channel side information, are available at the CR-BC secondary transmitter and receivers. Based on this information, we obtain an optimal time and power allocation policy to maximize the achievable capacity of fading cognitive radio broadcast channels, where the spectrum-sharing requirements are specified by appropriate constraints on the average received-interference at the primary receiver and on the peak transmit-power of the secondary base station. Finally, we sustain our theoretical results by numerical and simulation analysis.