Cognitive Radio: An Information-Theoretic Perspective

• Published in: IEEE transactions on information theory Vol. 55; no. 9; pp. 3945 - 3958
• Main Authors: Jovicic, A., Viswanath, P.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.09.2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Base stations; Codes; Coding, codes; Cognitive radio; Communication channels; Costa precoding; Data encryption; Decoders; Decoding; Degradation; dirty-paper coding; Exact sciences and technology; FCC; Information theory; Information, signal and communications theory; Interference; interference channel; Interference channels; Interference constraints; Optimization; Radio; Radio communications; Radiocommunication specific techniques; Radiocommunications; Real time systems; Receivers; Signal and communications theory; spectral reuse; Telecommunications; Telecommunications and information theory; Wireless networks; Multiple access; Wireless telecommunication; interference channel; wireless networks; Decoding; Cognitive radio; Costa precoding; Degradation; Coding; dirty-paper coding; spectral reuse; Wireless network; Software radio; Information theory
• ISSN: 0018-9448; 1557-9654
• DOI: 10.1109/TIT.2009.2025539

In this paper, we consider a communication scenario in which the primary and the cognitive radios wish to communicate to different receivers, subject to mutual interference. In the model that we use, the cognitive radio has noncausal knowledge of the primary radio's codeword. We characterize the largest rate at which the cognitive radio can reliably communicate under the constraint that 1) no rate degradation is created for the primary user, and 2) the primary receiver uses a single-user decoder just as it would in the absence of the cognitive radio. The result holds in a ldquolow-interferencerdquo regime in which the cognitive radio is closer to its receiver than to the primary receiver. In this regime, our results are subsumed by the results derived in a concurrent and independent work (Wu , 2007). We also demonstrate that, in a ldquohigh-interferencerdquo regime, multiuser decoding at the primary receiver is optimal from the standpoint of maximal jointly achievable rates for the primary and cognitive users.