Research Project Title
The Information Theory of Cognitive Radio

Principal Investigator
Pramod Viswanath

Unit # 29
Project Overview

The question we are investigating is: What is the optimal scheme for the cognitive radio to use, from the standpoint of maximum jointly achievable rates of reliable communication for the two users?

The question we propose to answer is: What is the communication scheme that the cognitive radio should employ in order to guarantee optimal performance in the sense of maximum achievable rates of reliable communication for both the primary and cognitive
user? In seeking an answer to this question, we hope to leverage the recent discovery of
optimal coding schemes for MIMO downlink channels. In particular, the cognitive
radio’s codeword could be designed based upon the knowledge of the primary user’s
codeword to effectively null the interference caused by the primary user at receiver 2,
while simultaneously boosting the reception quality of the primary user at receiver 1. We
propose to investigate the optimality and feasibility of such communication schemes as
well as their potential impact on the future design of networked cognitive radio systems.

Specifically, we are studying two communication scenarios: the cognitive uplink radio channel and the cognitive interference radio channel. In the first scenario, all the communication is directed towards the nearest base-station while in the second scenario, the primary and cognitive users wish to communicate to different target destinations. Our aim is to quantify, in both of these scenarios, the trade-off between operating the cognitive radio in stealth mode, whereby the cognitive radio does not use its side-information to aid the primary user, and cooperative mode, in which the primary user stands to actually benefit, in terms of quality of service, from the presence of the cognitive user in its vicinity. We propose to study the fundamental limits on the performance of such cognitive radio systems, and derive practical design guidelines for their deployment.