The Experts below are selected from a list of 5475 Experts worldwide ranked by ideXlab platform
Brian L Mark - One of the best experts on this subject based on the ideXlab platform.
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online parameter estimation for temporal spectrum sensing
2015Co-Authors: Brian L Mark, Y EphraimAbstract:We develop a computationally efficient online parameter estimation algorithm for temporal spectrum sensing of a cognitive radio channel using a hidden bivariate Markov model. The online estimator is based on a block-recursive parameter estimation algorithm developed by Ryden for hidden Markov models. This approach requires the score function only. We develop an efficient method for computing the score function recursively and extend Ryden's approach to hidden bivariate Markov models. The advantage of the hidden bivariate Markov model over the hidden Markov model is its ability to characterize non-geometric state sojourn time distributions, which can be crucial in spectrum sensing. Based on the hidden bivariate Markov model, an estimate of the future state of the primary user can be obtained, which can be used to reduce Harmful Interference and improve channel utilization. Moreover, the online estimator can adapt to changes in the statistical characteristics of the primary user. We present numerical results that demonstrate the performance of temporal spectrum sensing using the proposed online parameter estimator.
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estimation of maximum Interference free power level for opportunistic spectrum access
2009Co-Authors: Brian L Mark, Ahmed O. NasifAbstract:We consider a scenario in which frequency agile radios opportunistically share a fixed spectrum resource with a set of primary nodes. We develop a collaborative scheme for a group of frequency agile radios to estimate the maximum power at which they can transmit on a given frequency channel, without causing Harmful Interference to the primary receivers. The proposed scheme relies on signal strength measurements taken by a group of frequency agile radios, which are then used by a target node to characterize the spatial size of its perceived spectrum hole in terms of the maximum permissible transmit power. We derive an approximation to the maximum Interference-free transmit power using the Cramer-Rao bound on localization accuracy. We present numerical results to demonstrate the effectiveness of the proposed scheme under a variety of scenarios.
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an analytical performance model of opportunistic spectrum access in a military environment
2008Co-Authors: Shensheng Tang, Brian L MarkAbstract:In an opportunistic spectrum sharing system, secondary users equipped with cognitive radios opportunistically access spectrum that is not being used by the primary users, i.e., the licensed spectrum users, without causing Harmful Interference to the primary users. We present an analytical performance model of opportunistic spectrum access in a military environment consisting of a group of secondary users sharing a set of channels with primary users in a coverage area. A secondary user occupying a given channel detects when a primary user accesses the channel and then either moves to another idle channel or is placed in a virtual queue where it waits until either a channel becomes available or a maximum waiting time is reached. Using a two-dimensional Markov model, we derive expressions for the blocking probabilities and reconnection probability and evaluate the performance metrics under a range of parameter settings.
Michael J Medley - One of the best experts on this subject based on the ideXlab platform.
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cross layer routing and dynamic spectrum allocation in cognitive radio ad hoc networks
2010Co-Authors: Lei Ding, Tommaso Melodia, Stella N Batalama, John D Matyjas, Michael J MedleyAbstract:Throughput maximization is one of the main challenges in cognitive radio ad hoc networks, where the availability of local spectrum resources may change from time to time and hop by hop. For this reason, a cross-layer opportunistic spectrum access and dynamic routing algorithm for cognitive radio networks is proposed, which is called the routing and dynamic spectrum-allocation (ROSA) algorithm. Through local control actions, ROSA aims to maximize the network throughput by performing joint routing, dynamic spectrum allocation, scheduling, and transmit power control. Specifically, the algorithm dynamically allocates spectrum resources to maximize the capacity of links without generating Harmful Interference to other users while guaranteeing a bounded bit error rate (BER) for the receiver. In addition, the algorithm aims to maximize the weighted sum of differential backlogs to stabilize the system by giving priority to higher capacity links with a high differential backlog. The proposed algorithm is distributed, computationally efficient, and has bounded BER guarantees. ROSA is shown through numerical model-based evaluation and discrete-event packet-level simulations to outperform baseline solutions, leading to a high throughput, low delay, and fair bandwidth allocation.
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rosa distributed joint routing and dynamic spectrum allocation in cognitive radio ad hoc networks
2009Co-Authors: Lei Ding, Tommaso Melodia, Stella N Batalama, Michael J MedleyAbstract:Throughput maximization is one of the main challenges in cognitive radio ad hoc networks, where local spectrum resources may change from time to time and hop-by-hop. For this reason, a cross-layer opportunistic spectrum access and dynamic routing algorithm for cognitive radio networks is proposed, called ROSA (ROuting and Spectrum Allocation algorithm). Through local control actions, ROSA aims at maximizing the network throughput by performing joint routing, dynamic spectrum allocation, scheduling, and transmit power control. Specifically, the algorithm dynamically allocates spectrum resources to maximize the capacity of links without generating Harmful Interference to other users while guaranteeing bounded BER for the receiver. In addition, the algorithm aims at maximizing the weighted sum of differential backlogs to stabilize the system by giving priority to higher-capacity links with high differential backlog. The proposed algorithm is distributed, computationally efficient, and with bounded BER guarantees. ROSA is shown through discrete-event packet-level simulations to outperform baseline solutions leading to a high throughput, low delay, and fair bandwidth allocation.
Thomas W Hazlett - One of the best experts on this subject based on the ideXlab platform.
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exactitude in defining rights radio spectrum and the Harmful Interference conundrum
2013Co-Authors: Thomas W HazlettAbstract:In the century since the Radio Act of 1912 initiated U.S. spectrum allocation rules, a precise definition of “Harmful Interference”—the control of which forms the rationale for regulation—has eluded policymakers. In one sense, that result is unsurprising; rights are always defined incompletely. In another sense, however, the regulatory system is dysfunctional, severely limiting the productive use of spectrum while locked down in yearslong border disputes. These disagreements have, in turn, triggered calls to develop brighter lines and fuller engineering specifications of Harmful Interference. However, this emphasis on exact definitions is misguided. Spectrum use rights generate more robust market development when they feature technically fuzzy borders but are awarded in economically efficient bundles. The key ingredients are (a) exclusive, flexible rights; (b) frequency borders set via standardized edge emission limits; (c) large bundles of complementary rights that limit fragmentation; and (d) fluid secondary trading that allows mergers to end border disputes by eliminating borders. Regulators should focus less on delineating precise Interference contours, and instead expeditiously distribute standard bandwidth rights to economically responsible agents, taking care to avoid undue fragmentation (and tragedy of the anticommons). Many episodes illustrate these lessons, including those involving reallocation of the broadcast TV band, the emergence of HD radio, the Nextel/public safety “spectrum swap,” and the ongoing WCS/SDARS dispute. Each instance reveals that economic incentives, not engineering complexity, drive—or block—productive coordination of radio spectrum use. © 2013 Thomas W. Hazlett and Sarah Oh. All Rights Reserved. † Professor of Law and Economics, George Mason University School of Law; FCC Chief Economist, 1991–1992. This Article follows from a presentation on Creating Efficient Spectrum Property, Towards an Economic Definition of “Harmful Interference” in Radio Transmissions, Presentation at the Conference on Spectrum Markets: Challenges Ahead, Kellogg School of Management, Northwestern University (June 2–3, 2011). The author thanks Brent Skorup for excellent research assistance. †† Research Fellow, Information Economy Project. Ph.D. Student in Economics, George Mason University; J.D. George Mason University; B.S. Stanford University, Management Science & Engineering. 0227-0340_HAZLETT_081313_WEB (DO NOT DELETE) 8/13/2013 5:00 PM 228 BERKELEY TECHNOLOGY LAW JOURNAL [Vol. 28:227
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exactitude in defining rights radio spectrum and the Harmful Interference conundrum
2012Co-Authors: Thomas W HazlettAbstract:In the century since the Radio Act of 1912 initiated U.S. spectrum allocation rules, a precise definition of “Harmful Interference” – the control of which forms the rationale for regulation – has eluded policymakers. In one sense, that result is unsurprising; rights are always defined incompletely. In another sense, however, the regulatory system is dysfunctional, severely limiting the productive use of spectrum while locked down in years-long border disputes. These disagreements have, in turn, triggered calls to develop brighter lines and fuller engineering specifications of “Harmful Interference.” Yet, spectrum use rights featuring technically fuzzy borders, awarded in economically efficient bundles, generate robust market development. The key ingredients are (a) exclusive, flexible use rights; (b) frequency borders set via standardized edge emission limits; (c) large bundles of complementary rights, limiting fragmentation; and (d) fluid secondary trading, allowing mergers to end border disputes by eliminating borders. Regulators should focus less on delineating precise Interference contours, and instead expeditiously distribute standard bandwidth rights to economically responsible agents, taking care to avoid undue fragmentation (and tragedy of the anti-commons). These lessons are illustrated in many episodes, including those involving reallocation of the broadcast TV band, the emergence of HD radio, the Nextel/public safety “spectrum swap,” and the ongoing WCS/SDARS dispute. Each instance reveals that economic incentives, not engineering complexity, drives productive coordination of radio spectrum use – or blocks it.
Lei Ding - One of the best experts on this subject based on the ideXlab platform.
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cross layer routing and dynamic spectrum allocation in cognitive radio ad hoc networks
2010Co-Authors: Lei Ding, Tommaso Melodia, Stella N Batalama, John D Matyjas, Michael J MedleyAbstract:Throughput maximization is one of the main challenges in cognitive radio ad hoc networks, where the availability of local spectrum resources may change from time to time and hop by hop. For this reason, a cross-layer opportunistic spectrum access and dynamic routing algorithm for cognitive radio networks is proposed, which is called the routing and dynamic spectrum-allocation (ROSA) algorithm. Through local control actions, ROSA aims to maximize the network throughput by performing joint routing, dynamic spectrum allocation, scheduling, and transmit power control. Specifically, the algorithm dynamically allocates spectrum resources to maximize the capacity of links without generating Harmful Interference to other users while guaranteeing a bounded bit error rate (BER) for the receiver. In addition, the algorithm aims to maximize the weighted sum of differential backlogs to stabilize the system by giving priority to higher capacity links with a high differential backlog. The proposed algorithm is distributed, computationally efficient, and has bounded BER guarantees. ROSA is shown through numerical model-based evaluation and discrete-event packet-level simulations to outperform baseline solutions, leading to a high throughput, low delay, and fair bandwidth allocation.
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rosa distributed joint routing and dynamic spectrum allocation in cognitive radio ad hoc networks
2009Co-Authors: Lei Ding, Tommaso Melodia, Stella N Batalama, Michael J MedleyAbstract:Throughput maximization is one of the main challenges in cognitive radio ad hoc networks, where local spectrum resources may change from time to time and hop-by-hop. For this reason, a cross-layer opportunistic spectrum access and dynamic routing algorithm for cognitive radio networks is proposed, called ROSA (ROuting and Spectrum Allocation algorithm). Through local control actions, ROSA aims at maximizing the network throughput by performing joint routing, dynamic spectrum allocation, scheduling, and transmit power control. Specifically, the algorithm dynamically allocates spectrum resources to maximize the capacity of links without generating Harmful Interference to other users while guaranteeing bounded BER for the receiver. In addition, the algorithm aims at maximizing the weighted sum of differential backlogs to stabilize the system by giving priority to higher-capacity links with high differential backlog. The proposed algorithm is distributed, computationally efficient, and with bounded BER guarantees. ROSA is shown through discrete-event packet-level simulations to outperform baseline solutions leading to a high throughput, low delay, and fair bandwidth allocation.
Arumugam Nallanathan - One of the best experts on this subject based on the ideXlab platform.
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enhancing the capacity of spectrum sharing cognitive radio networks
2011Co-Authors: Stergios Stotas, Arumugam NallanathanAbstract:Spectrum sharing has attracted a lot of attention in cognitive radio recently as an effective method of alleviating the spectrum scarcity problem by allowing unlicensed users to coexist with licensed users under the condition of protecting the latter from Harmful Interference. In this paper, we focus on the throughput maximization of spectrum sharing cognitive radio networks and propose a novel cognitive radio system that significantly improves their achievable throughput. More specifically, we introduce a novel receiver and frame structure for spectrum sharing cognitive radio networks and study the problem of deriving the optimal power allocation strategy that maximizes the ergodic capacity of the proposed cognitive radio system under average transmit and Interference power constraints. In addition, we study the outage capacity of the proposed cognitive radio system under various constraints that include average transmit and Interference power constraints, and peak Interference power constraints. Finally, we provide simulation results, in order to demonstrate the improved ergodic and outage throughput achieved by the proposed cognitive radio system compared to conventional spectrum sharing cognitive radio systems.
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optimal sensing time and power allocation in multiband cognitive radio networks
2011Co-Authors: Stergios Stotas, Arumugam NallanathanAbstract:Cognitive radio is an emerging technology that aims for efficient spectrum usage by allowing unlicensed (secondary) users to access licensed frequency bands under the condition of protecting the licensed (primary) users from Harmful Interference. The latter condition constraints the achievable throughput of a cognitive radio network, which should therefore access a wideband spectrum in order to provide reliable and efficient services to its users. In this paper, we study the problem of designing the optimal sensing time and power allocation strategy, in order to maximize the ergodic throughput of a cognitive radio that employs simultaneous multiband detection and operates under two different schemes, namely the wideband sensing-based spectrum sharing (WSSS) and the wideband opportunistic spectrum access (WOSA) scheme. We consider average transmit and Interference power constraints for both schemes, in order to effectively protect the primary users from Harmful Interference, propose two algorithms that acquire the optimal sensing time and power allocation under imperfect spectrum sensing for the two schemes and discuss the effect of the average transmit and Interference power constraint on the optimal sensing time. Finally, we provide simulation results to compare the two schemes and validate our theoretical analysis.
