Open Access

Achievable Rates and Scaling Laws for Cognitive Radio Channels

EURASIP Journal on Wireless Communications and Networking20072008:896246

DOI: 10.1155/2008/896246

Received: 30 May 2007

Accepted: 23 October 2007

Published: 20 November 2007

Abstract

Cognitive radios have the potential to vastly improve communication over wireless channels. We outline recent information theoretic results on the limits of primary and cognitive user communication in single and multiple cognitive user scenarios. We first examine the achievable rate and capacity regions of single user cognitive channels. Results indicate that at medium SNR (0–20 dB), the use of cognition improves rates significantly compared to the currently suggested spectral gap-filling methods of secondary spectrum access. We then study another information theoretic measure, the multiplexing gain. This measure captures the number of point-to-point Gaussian channels contained in a cognitive channel as the SNR tends to infinity. Next, we consider a cognitive network with a single primary user and multiple cognitive users. We show that with single-hop transmission, the sum capacity of the cognitive users scales linearly with the number of users. We further introduce and analyze the primary exclusive radius, inside of which primary receivers are guaranteed a desired outage performance. These results provide guidelines when designing a network with secondary spectrum users.

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Authors’ Affiliations

(1)
School of Engineering and Applied Sciences, Harvard University

Copyright

© Natasha Devroye et al. 2008

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.