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Breaking Spectrum Gridlock with Cognitive Radios: An Information Theoretic Perspective
, 2008
"... Cognitive radios hold tremendous promise for increasing spectral efficiency in wireless systems. This paper surveys the fundamental capacity limits and associated transmission techniques for different wireless network design paradigms based on this promising technology. These paradigms are unified b ..."
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Cited by 265 (4 self)
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Cognitive radios hold tremendous promise for increasing spectral efficiency in wireless systems. This paper surveys the fundamental capacity limits and associated transmission techniques for different wireless network design paradigms based on this promising technology. These paradigms are unified by the definition of a cognitive radio as an intelligent wireless communication device that exploits side information about its environment to improve spectrum utilization. This side information typically comprises knowledge about the activity, channels, codebooks and/or messages of other nodes with which the cognitive node shares the spectrum. Based on the nature of the available side information as well as a priori rules about spectrum usage, cognitive radio systems seek to underlay, overlay or interweave the cognitive radios ’ signals with the transmissions of noncognitive nodes. We provide a comprehensive summary of the known capacity characterizations in terms of upper and lower bounds for each of these three approaches. The increase in system degrees of freedom obtained through cognitive radios is also illuminated. This information theoretic survey provides guidelines for the spectral efficiency gains possible through cognitive radios, as well as practical design ideas to mitigate the coexistence challenges in today’s crowded spectrum.
An Achievable Region for a General Multi-terminal Network and its Chain Graph Representation
, 2012
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Geometry-based Optimal Power Control of Fading Multiple Access Channels for Maximum Sum-rate in Cognitive Radio Networks
- IEEE Trans. Wireless Commun
, 2010
"... Abstract—In this letter, a power-control scheme for maximum sum-rate is proposed for the fading multiple access channels by considering the presence of primary users. Both the av-erage transmit-power constraints and the peak interference-temperature constraints are considered. The interference cause ..."
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Abstract—In this letter, a power-control scheme for maximum sum-rate is proposed for the fading multiple access channels by considering the presence of primary users. Both the av-erage transmit-power constraints and the peak interference-temperature constraints are considered. The interference caused by cognitive users must be under a pre-specified threshold for protecting primary users. The power-control optimization is considered as a novel geometrical problem which investigates the relationship of positions of a line and a few points. At most two users transmit simultaneously for optimality and the corresponding conditions are provided for both cases. Based on the analysis, the optimal power control is given for each specific fading state. For lowering computational complexity, the power-control optimization problem is divided into two categories according to different tight constraints. Simulation results are provided for the optimal power-control performance. Index Terms—Cognitive radio, multiple access channel, power control, fading channel, capacity. I.
Sub-optimality of Treating Interference as Noise in the Cellular Uplink
- in Proc. of the 16th International ITG Workshop on Smart Antennas WSA
, 2012
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COOPERATION, COMPETITION AND COGNITION IN WIRELESS NETWORKS -- From Theory to Implementation
"... Nodes and/or clusters of a wireless network operating on the same frequency can operate using three different paradigms: 1) Competition: Traditionally, this is information theoretically casted in the framework of interference channels. 2) Cooperation: Silent transmitters/receivers can help active ..."
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Cited by 1 (0 self)
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Nodes and/or clusters of a wireless network operating on the same frequency can operate using three different paradigms: 1) Competition: Traditionally, this is information theoretically casted in the framework of interference channels. 2) Cooperation: Silent transmitters/receivers can help active transmitters/receivers in the transmission/reception of their messages, but have to extract this message from the underlying transmission or by other methods, and 3) Cognitive Radio Transmission: Some devices extract the message(s) of other transmitter(s) from their signals or by other methods, and use it to minimize interference from/to their own transmitted signals. Competition has been well-studied in the literature. Cooperation has been less studied and cognitive radio transmission has not been studied much. For the cooperative case, we demonstrate that most of the multiple-input multipleoutput (MIMO) space-time diversity gain can also be achieved through cooperative communications with single-antenna/multiple-antenna nodes when there
COGNITIVE NETWORKS ARE IMMINENT
"... [Highlights of information theoretic limits, models, and design] In recent years, the development of intelligent, adaptive wireless devices called cognitive radios, together with the introduction of secondary spectrum licensing, has led to a new paradigm in communications: cognitive networks. Cognit ..."
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[Highlights of information theoretic limits, models, and design] In recent years, the development of intelligent, adaptive wireless devices called cognitive radios, together with the introduction of secondary spectrum licensing, has led to a new paradigm in communications: cognitive networks. Cognitive networks are wireless networks that consist of several types of users: often a primary user (the primary licenseholder of a spectrum band) and secondary users (cognitive radios). These cognitive users employ their cognitive abilities to communicate without harming the primary users. The study of cognitive networks is relatively new and many questions are yet to be answered. In this article we highlight some of the recent information theoretic limits, models, and design of these promising networks.
TOPICS IN RADIO COMMUNICATIONS Limits on Communications in a Cognitive Radio Channel
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