Optimal Power Control over Fading Cognitive Radio Channels by Exploiting Primary User CSI
Abstract
This paper is concerned with spectrum sharing for mobile wireless communication, where a secondary user or cognitive radio (CR) link communicates using the same bandwidth that is originally allocated to an existing primary user link. It is assumed that the secondary transmitter has perfect channel state information (CSI) on the channels from it to both the primary and secondary receivers (as usually assumed in literature) as well as the channel from the primary transmitter to primary receiver (a new assumption made for the first time). With the known primary user CSI, we study the optimal power control for the secondary user fading channel to maximize its ergodic capacity subject to the constraint that the average capacity loss of the primary link due to the secondary transmission is kept below some certain threshold. It is seen that the proposed power-control policy is superior than the existing schemes in literature that apply the average interference-power constraint at the primary receiver as a common means to protect the primary transmission. Simulation results show that under certain channel conditions, there exist great potentials to improve substantially the CR link capacity using the proposed power-control policy that exploits the primary user CSI.Keywords
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