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Qing Zhao - One of the best experts on this subject based on the ideXlab platform.

  • Power control in cognitive radio networks: how to cross a multi-lane highway
    IEEE Journal on Selected Areas in Communications, 2009
    Co-Authors: Wei Ren, Qing Zhao, Ananthram Swami
    Abstract:

    We consider power control in cognitive radio networks where secondary users identify and exploit instantaneous and local Spectrum opportunities without causing unacceptable interference to primary users. We qualitatively characterize the impacts of the transmission power of secondary users on the occurrence of Spectrum opportunities and the reliability of Opportunity detection. Based on a Poisson model of the primary network, we quantify these impacts by showing that (i) the probability of Spectrum Opportunity decreases exponentially with the transmission power of secondary users, where the exponential decay constant is given by the traffic load of primary users; (ii) reliable Opportunity detection is achieved in the two extreme regimes in terms of the ratio between the transmission power of secondary users and that of primary users. Such analytical characterizations allow us to study power control for optimal transport throughput under constraints on the interference to primary users. Furthermore, we reveal the difference between detecting primary signals and detecting Spectrum opportunities, and demonstrate the complex relationship between physical layer Spectrum sensing and MAC layer throughput. The dependency of this PHY-MAC interaction on the application type and the use of handshake signaling such as RTS/CTS is also illustrated.

  • Power Control in Cognitive Radio Networks: How to Cross a Multi-Lane Highway
    arXiv: Networking and Internet Architecture, 2008
    Co-Authors: Wei Ren, Qing Zhao, Ananthram Swami
    Abstract:

    We consider power control in cognitive radio networks where secondary users identify and exploit instantaneous and local Spectrum opportunities without causing unacceptable interference to primary users. We qualitatively characterize the impact of the transmission power of secondary users on the occurrence of Spectrum opportunities and the reliability of Opportunity detection. Based on a Poisson model of the primary network, we quantify these impacts by showing that (i) the probability of Spectrum Opportunity decreases exponentially with respect to the transmission power of secondary users, where the exponential decay constant is given by the traffic load of primary users; (ii) reliable Opportunity detection is achieved in the two extreme regimes in terms of the ratio between the transmission power of secondary users and that of primary users. Such analytical characterizations allow us to study power control for optimal transport throughput under constraints on the interference to primary users. Furthermore, we reveal the difference between detecting primary signals and detecting Spectrum opportunities, and demonstrate the complex relationship between physical layer Spectrum sensing and MAC layer throughput. The dependency of this PHY-MAC interaction on the application type and the use of handshake signaling such as RTS/CTS is illustrated.

  • low complexity approaches to Spectrum Opportunity tracking
    International Conference on Cognitive Radio Oriented Wireless Networks and Communications, 2007
    Co-Authors: Qing Zhao, Bhaskar Krishnamachari, Keqin Liu
    Abstract:

    We consider opportunistic Spectrum access under design constraints imposed at both node and link levels. First, hardware and energy limitations at node level may prevent a secondary user from sensing all the channels in the Spectrum simultaneously. A channel selection strategy is thus necessary to track the time-varying Spectrum opportunities. Second, sensing errors are inevitable. A secondary user needs to decide, based on imperfect sensing outcomes, whether to access the sensed channel and how to update its statistical knowledge of Spectrum dynamics for better tracking in the future. Third, a secondary transmitter and its intended receiver need to hop synchronously in the Spectrum in order to communicate. When a dynamic Opportunity tracking strategy is used where the channel selection depends on the sensing history, achieving this synchrony is nontrivial in the absence of a dedicated control channel and in the presence of sensing errors. These practical constraints significantly complicate the design of opportunistic Spectrum access, and the optimal performance requires the joint design of the Spectrum sensor, Opportunity tracking strategy, and Spectrum access decisions. The focus of this paper is on developing low-complexity approaches for opportunistic Spectrum access. We show that under certain conditions on the Spectrum dynamics, simple myopic strategies can provide optimal performance for the joint design of Spectrum sensor, Opportunity tracking, and Opportunity exploitation. We also propose an alternate low-complexity indexing strategy for other conditions that takes into account the expected time to channel availability.

  • Spectrum Opportunity and interference constraint in opportunistic Spectrum access
    International Conference on Acoustics Speech and Signal Processing, 2007
    Co-Authors: Qing Zhao
    Abstract:

    In this paper, we study two important concepts in opportunistic Spectrum access: Spectrum Opportunity and interference constraint. We aim to provide a certain level of rigor to these seemingly intuitive terms central to opportunistic Spectrum access. Their implications in Spectrum Opportunity detection and transmission power control of secondary users are discussed.

  • Spectrum Opportunity Detection: How Good Is Listen-before-Talk?
    2007 Conference Record of the Forty-First Asilomar Conference on Signals Systems and Computers, 2007
    Co-Authors: Qing Zhao, Wei Ren, Ananthram Swami
    Abstract:

    We consider Spectrum Opportunity detection in cognitive radio networks for Spectrum overlay. We highlight the differences between detecting primary signals and detecting Spectrum opportunities. We show that besides noise and fading, the geographic distribution and traffic pattern of primary users have significant impact on the performance of Spectrum Opportunity detection. A necessary and sufficient condition for the equivalence between primary signal detection and Spectrum Opportunity detection is obtained, and the performance of listen-before- talk in a Poisson primary network with uniform traffic pattern is analyzed. Furthermore, we study the translation from the physical layer Opportunity detection performance to the MAC layer performance. This issue is crucial in examining the impact of sensing errors on the design of higher layers and in choosing the optimal operating characteristics of the Spectrum sensor. We demonstrate the complex dependency of the relationship between PHY and MAC on the applications and the use of MAC handshaking signaling such as RTS/CTS.

Ananthram Swami - One of the best experts on this subject based on the ideXlab platform.

  • Power control in cognitive radio networks: how to cross a multi-lane highway
    IEEE Journal on Selected Areas in Communications, 2009
    Co-Authors: Wei Ren, Qing Zhao, Ananthram Swami
    Abstract:

    We consider power control in cognitive radio networks where secondary users identify and exploit instantaneous and local Spectrum opportunities without causing unacceptable interference to primary users. We qualitatively characterize the impacts of the transmission power of secondary users on the occurrence of Spectrum opportunities and the reliability of Opportunity detection. Based on a Poisson model of the primary network, we quantify these impacts by showing that (i) the probability of Spectrum Opportunity decreases exponentially with the transmission power of secondary users, where the exponential decay constant is given by the traffic load of primary users; (ii) reliable Opportunity detection is achieved in the two extreme regimes in terms of the ratio between the transmission power of secondary users and that of primary users. Such analytical characterizations allow us to study power control for optimal transport throughput under constraints on the interference to primary users. Furthermore, we reveal the difference between detecting primary signals and detecting Spectrum opportunities, and demonstrate the complex relationship between physical layer Spectrum sensing and MAC layer throughput. The dependency of this PHY-MAC interaction on the application type and the use of handshake signaling such as RTS/CTS is also illustrated.

  • Power Control in Cognitive Radio Networks: How to Cross a Multi-Lane Highway
    arXiv: Networking and Internet Architecture, 2008
    Co-Authors: Wei Ren, Qing Zhao, Ananthram Swami
    Abstract:

    We consider power control in cognitive radio networks where secondary users identify and exploit instantaneous and local Spectrum opportunities without causing unacceptable interference to primary users. We qualitatively characterize the impact of the transmission power of secondary users on the occurrence of Spectrum opportunities and the reliability of Opportunity detection. Based on a Poisson model of the primary network, we quantify these impacts by showing that (i) the probability of Spectrum Opportunity decreases exponentially with respect to the transmission power of secondary users, where the exponential decay constant is given by the traffic load of primary users; (ii) reliable Opportunity detection is achieved in the two extreme regimes in terms of the ratio between the transmission power of secondary users and that of primary users. Such analytical characterizations allow us to study power control for optimal transport throughput under constraints on the interference to primary users. Furthermore, we reveal the difference between detecting primary signals and detecting Spectrum opportunities, and demonstrate the complex relationship between physical layer Spectrum sensing and MAC layer throughput. The dependency of this PHY-MAC interaction on the application type and the use of handshake signaling such as RTS/CTS is illustrated.

  • Spectrum Opportunity Detection: How Good Is Listen-before-Talk?
    2007 Conference Record of the Forty-First Asilomar Conference on Signals Systems and Computers, 2007
    Co-Authors: Qing Zhao, Wei Ren, Ananthram Swami
    Abstract:

    We consider Spectrum Opportunity detection in cognitive radio networks for Spectrum overlay. We highlight the differences between detecting primary signals and detecting Spectrum opportunities. We show that besides noise and fading, the geographic distribution and traffic pattern of primary users have significant impact on the performance of Spectrum Opportunity detection. A necessary and sufficient condition for the equivalence between primary signal detection and Spectrum Opportunity detection is obtained, and the performance of listen-before- talk in a Poisson primary network with uniform traffic pattern is analyzed. Furthermore, we study the translation from the physical layer Opportunity detection performance to the MAC layer performance. This issue is crucial in examining the impact of sensing errors on the design of higher layers and in choosing the optimal operating characteristics of the Spectrum sensor. We demonstrate the complex dependency of the relationship between PHY and MAC on the applications and the use of MAC handshaking signaling such as RTS/CTS.

  • decentralized cognitive mac for dynamic Spectrum access
    First IEEE International Symposium on New Frontiers in Dynamic Spectrum Access Networks 2005. DySPAN 2005., 2005
    Co-Authors: Qing Zhao, Lang Tong, Ananthram Swami
    Abstract:

    We consider the problem of opportunistic dynamic Spectrum access (DSA) in an ad hoc network in which unlicensed secondary users communicate through channels not used by the primary users. Decentralized cognitive medium access control protocols are presented that allow secondary users to recognize Spectrum Opportunity and transmit based on a partial observation of the instantaneous Spectrum availability. Under a framework of partially observable Markov decision process (POMDP), we derive optimal and suboptimal decentralized strategies for the secondary users to decide which channel(s) to sense and access for the maximization of the overall network throughput

Maziar Nekovee - One of the best experts on this subject based on the ideXlab platform.

  • Cognitive Radio Access to TV White Spaces: Spectrum Opportunities, Commercial Applications and Remaining Technology Challenges
    2010 IEEE Symposium on New Frontiers in Dynamic Spectrum (DySPAN), 2010
    Co-Authors: Maziar Nekovee
    Abstract:

    Cognitive radio is being intensively researched as the enabling technology for secondary access to the so-called TV White Spaces (TVWS), large portions of Spectrum in theUHF/VHF bands which become available on a geographical basis after digital switchover. Both in the US, and more recently, in the UK the regulators have given conditional endorsement to this new mode of access. This paper reviews the state-of-the-art in technology, regulation and standardization of cognitive access to TVWS. It examines the Spectrum Opportunity and commercial use cases associated with this form of secondary access.

  • quantifying the tv white spaces Spectrum Opportunity for cognitive radio access
    International Conference on Communications, 2009
    Co-Authors: Maziar Nekovee
    Abstract:

    Cognitive radio is being intensively researched for opportunistic access to the so-called TV White Spaces (TVWS): large portions of the VHF/UHF TV bands which become available on a geographical basis after the digital switchover. In this paper we take a step back from the excitement surrounding TVWS, and quantitatively examine the real Spectrum Opportunity associated with this form of access. Using accurate digital TV (DTV) coverage maps together with a database of DTV transmitters, we develop a methodology for identifying TVWS frequencies at any given location in the United Kingdom. We use our methodology to investigate variations in TVWS as a function of the location and transmit power of cognitive radios, and examine how constraints on adjacent channel interference imposed by regulators may affect the results. Our analysis provides a realistic view on the Spectrum Opportunity associated with cognitive devices, and presents the first quantitative study of the availability and frequency composition of TWVS outside the United States.

  • Quantifying the Availability of TV White Spaces for Cognitive Radio Operation in the UK
    2009 IEEE International Conference on Communications Workshops, 2009
    Co-Authors: Maziar Nekovee
    Abstract:

    Cognitive radio is being intensively researched for opportunistic access to the so-called TV White Spaces (TVWS): large portions of the VHF/UHF TV bands which become available on a geographical basis after the digital switchover. Using accurate digital TV (DTV) coverage maps together with a database of DTV transmitters, we develop a methodology for identifying TVWS frequencies at any given location in the United Kingdom. We use our methodology to investigate variations in TVWS as a function of the location and transmit power of cognitive radios, and examine how constraints on adjacent channel interference imposed by regulators may affect the results. Our analysis provides a realistic view on the Spectrum Opportunity associated with cognitive devices, and presents the first quantitative study of the availability and frequency composition of TWVS outside the United States.

Wei Ren - One of the best experts on this subject based on the ideXlab platform.

  • Power control in cognitive radio networks: how to cross a multi-lane highway
    IEEE Journal on Selected Areas in Communications, 2009
    Co-Authors: Wei Ren, Qing Zhao, Ananthram Swami
    Abstract:

    We consider power control in cognitive radio networks where secondary users identify and exploit instantaneous and local Spectrum opportunities without causing unacceptable interference to primary users. We qualitatively characterize the impacts of the transmission power of secondary users on the occurrence of Spectrum opportunities and the reliability of Opportunity detection. Based on a Poisson model of the primary network, we quantify these impacts by showing that (i) the probability of Spectrum Opportunity decreases exponentially with the transmission power of secondary users, where the exponential decay constant is given by the traffic load of primary users; (ii) reliable Opportunity detection is achieved in the two extreme regimes in terms of the ratio between the transmission power of secondary users and that of primary users. Such analytical characterizations allow us to study power control for optimal transport throughput under constraints on the interference to primary users. Furthermore, we reveal the difference between detecting primary signals and detecting Spectrum opportunities, and demonstrate the complex relationship between physical layer Spectrum sensing and MAC layer throughput. The dependency of this PHY-MAC interaction on the application type and the use of handshake signaling such as RTS/CTS is also illustrated.

  • Power Control in Cognitive Radio Networks: How to Cross a Multi-Lane Highway
    arXiv: Networking and Internet Architecture, 2008
    Co-Authors: Wei Ren, Qing Zhao, Ananthram Swami
    Abstract:

    We consider power control in cognitive radio networks where secondary users identify and exploit instantaneous and local Spectrum opportunities without causing unacceptable interference to primary users. We qualitatively characterize the impact of the transmission power of secondary users on the occurrence of Spectrum opportunities and the reliability of Opportunity detection. Based on a Poisson model of the primary network, we quantify these impacts by showing that (i) the probability of Spectrum Opportunity decreases exponentially with respect to the transmission power of secondary users, where the exponential decay constant is given by the traffic load of primary users; (ii) reliable Opportunity detection is achieved in the two extreme regimes in terms of the ratio between the transmission power of secondary users and that of primary users. Such analytical characterizations allow us to study power control for optimal transport throughput under constraints on the interference to primary users. Furthermore, we reveal the difference between detecting primary signals and detecting Spectrum opportunities, and demonstrate the complex relationship between physical layer Spectrum sensing and MAC layer throughput. The dependency of this PHY-MAC interaction on the application type and the use of handshake signaling such as RTS/CTS is illustrated.

  • Spectrum Opportunity Detection: How Good Is Listen-before-Talk?
    2007 Conference Record of the Forty-First Asilomar Conference on Signals Systems and Computers, 2007
    Co-Authors: Qing Zhao, Wei Ren, Ananthram Swami
    Abstract:

    We consider Spectrum Opportunity detection in cognitive radio networks for Spectrum overlay. We highlight the differences between detecting primary signals and detecting Spectrum opportunities. We show that besides noise and fading, the geographic distribution and traffic pattern of primary users have significant impact on the performance of Spectrum Opportunity detection. A necessary and sufficient condition for the equivalence between primary signal detection and Spectrum Opportunity detection is obtained, and the performance of listen-before- talk in a Poisson primary network with uniform traffic pattern is analyzed. Furthermore, we study the translation from the physical layer Opportunity detection performance to the MAC layer performance. This issue is crucial in examining the impact of sensing errors on the design of higher layers and in choosing the optimal operating characteristics of the Spectrum sensor. We demonstrate the complex dependency of the relationship between PHY and MAC on the applications and the use of MAC handshaking signaling such as RTS/CTS.

Marwan Krunz - One of the best experts on this subject based on the ideXlab platform.

  • Spectrum Opportunity based control channel assignment in cognitive radio networks
    Sensor Mesh and Ad Hoc Communications and Networks, 2009
    Co-Authors: Loukas Lazos, Marwan Krunz
    Abstract:

    We address the problem of dynamic assignment of coordination (control) channels in cognitive radio networks (CRNs) by exploiting time- and space-varying Spectrum opportunities. Motivated by the inherent grouping of Cognitive Radio (CR) users according to channel availability, we propose a cluster-based architecture for control-channel assignment in a CRN. CRs are grouped in the same cluster if they roughly sense similar idle channels and are within communication range, either directly or via a clusterhead. We formulate the clustering design as a maximum edge biclique problem. A distributed cluster agreement algorithm called Spectrum-Opportunity Clustering (SOC) is proposed to solve this problem. SOC provides a desirable balance between two competing factors: the set of common idle channels within each cluster and the cluster size. A large set of common idle channels within each cluster allows graceful migration from the current control channel should primary radio (PR) activity appear on that channel. Hence, SOC provides a stable network partition with respect to local coordination, with no need for frequent reclustering. Moreover, when reclustering has to be performed (due to CR mobility or PR activity), CRs agree on new clusters after the broadcast of only three messages, thus incurring low communication overhead.

  • Coordinated channel access in cognitive radio networks: A multi-level Spectrum Opportunity perspective
    Proceedings - IEEE INFOCOM, 2009
    Co-Authors: Tao Shu, Marwan Krunz
    Abstract:

    In a cognitive radio network (CRN), Spectrum opportunities should be efficiently utilized through careful coordination between cognitive radio (CR) users. In this paper, we formulate the coordinated channel access as a joint power/rate control and channel assignment optimization problem, with the objective of maximizing the sum-rate achieved by all CRs over all channels. The problem is formulated under a generalized multi-level Spectrum Opportunity framework, which reflects the microscopic spatial Opportunity available to CRs. A centralized polynomial-time approximate algorithm to the problem is developed. We prove the algorithm's correctness and show its accuracy through numerical examples.