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Journal ArticleDOI

Optimal multi-channel cooperative sensing in cognitive radio networks

01 Mar 2010-IEEE Transactions on Wireless Communications (IEEE)-Vol. 9, Iss: 3, pp 1128-1138
TL;DR: In this paper, optimal multi-channel cooperative sensing strategies in cognitive radio networks are investigated and a polynomial-complexity algorithm is proposed to solve the problem optimally.
Abstract: In this paper, optimal multi-channel cooperative sensing strategies in cognitive radio networks are investigated. A cognitive radio network with multiple potential channels is considered. Secondary users cooperatively sense the channels and send the sensing results to a coordinator, in which energy detection with a soft decision rule is employed to estimate whether there are primary activities in the channels. An optimization problem is formulated, which maximizes the throughput of secondary users while keeping detection probability for each channel above a pre-defined threshold. In particular, two sensing modes are investigated: slotted-time sensing mode and continuous-time sensing mode. With a slotted-time sensing mode, the sensing time of each secondary user consists of a number of mini-slots, each of which can be used to sense one channel. The initial optimization problem is shown to be a nonconvex mixed-integer problem. A polynomial-complexity algorithm is proposed to solve the problem optimally. With a continuous-time sensing mode, the sensing time of each secondary user for a channel can be any arbitrary continuous value. The initial nonconvex problem is converted into a convex bilevel problem, which can be successfully solved by existing methods. Numerical results are presented to demonstrate the effectiveness of our proposed algorithms.

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Citations
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Journal ArticleDOI
TL;DR: Detection performance of an energy detector used for cooperative spectrum sensing in a cognitive radio network is investigated over channels with both multipath fading and shadowing and can be extended to channels with Nakagami-m multipath fades and lognormal shadowing as well.
Abstract: Detection performance of an energy detector used for cooperative spectrum sensing in a cognitive radio network is investigated over channels with both multipath fading and shadowing. The analysis focuses on two fusion strategies: data fusion and decision fusion. Under data fusion, upper bounds for average detection probabilities are derived for four scenarios: 1) single cognitive relay; 2) multiple cognitive relays; 3) multiple cognitive relays with direct link; and 4) multi-hop cognitive relays. Under decision fusion, the exact detection and false alarm probabilities are derived under the generalized "k-out-of-n" fusion rule at the fusion center with consideration of errors in the reporting channel due to fading. The results are extended to a multi-hop network as well. Our analysis is validated by numerical and simulation results. Although this research focuses on Rayleigh multipath fading and lognormal shadowing, the analytical framework can be extended to channels with Nakagami-m multipath fading and lognormal shadowing as well.

512 citations


Cites background from "Optimal multi-channel cooperative s..."

  • ...Data fusion: Each cognitive user simply amplifies the received signal from the primary user and forwards to the fusion center [2], [4], [16]....

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Journal ArticleDOI
TL;DR: An overview of recent research achievements of including spectrum sensing, sharing techniques and the applications of CR systems is provided.
Abstract: Cognitive radio (CR) can successfully deal with the growing demand and scarcity of the wireless spectrum. To exploit limited spectrum efficiently, CR technology allows unlicensed users to access licensed spectrum bands. Since licensed users have priorities to use the bands, the unlicensed users need to continuously monitor the licensed users' activities to avoid interference and collisions. How to obtain reliable results of the licensed users' activities is the main task for spectrum sensing. Based on the sensing results, the unlicensed users should adapt their transmit powers and access strategies to protect the licensed communications. The requirement naturally presents challenges to the implementation of CR. In this article, we provide an overview of recent research achievements of including spectrum sensing, sharing techniques and the applications of CR systems.

259 citations


Cites methods from "Optimal multi-channel cooperative s..."

  • ...In a multi-channel system based on linear CSS, the optimal value of the decision threshold, gc, and sensing time, τ, are obtained by maximizing the throughput of the SU system for a given detection probability [49]....

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Journal ArticleDOI
TL;DR: This paper formulate the joint spectrum sensing and access problem as an evolutionary game and derive the evolutionarily stable strategy (ESS) that no one will deviate from, and design a distributed learning algorithm for the secondary users to converge to the ESS.
Abstract: Many spectrum sensing methods and dynamic access algorithms have been proposed to improve the secondary users' opportunities of utilizing the primary users' spectrum resources. However, few of them have considered to integrate the design of spectrum sensing and access algorithms together by taking into account the mutual influence between them. In this paper, we propose to jointly analyze the spectrum sensing and access problem by studying two scenarios: synchronous scenario where the primary network is slotted and non-slotted asynchronous scenario. Due to selfish nature, secondary users tend to act selfishly to access the channel without contribution to the spectrum sensing. Moreover, they may take out-of-equilibrium strategies because of the uncertainty of others' strategies. To model the complicated interactions among secondary users, we formulate the joint spectrum sensing and access problem as an evolutionary game and derive the evolutionarily stable strategy (ESS) that no one will deviate from. Furthermore, we design a distributed learning algorithm for the secondary users to converge to the ESS. With the proposed algorithm, each secondary user senses and accesses the primary channel with the probabilities learned purely from its own past utility history, and finally achieves the desired ESS. Simulation results shows that our system can quickly converge to the ESS and such an ESS is robust to the sudden unfavorable deviations of the selfish secondary users.

212 citations

Journal ArticleDOI
14 Feb 2014
TL;DR: This paper provides an in-depth analysis on the recent advancements in multiband spectrum sensing techniques, their limitations, and possible future directions to improve them.
Abstract: Cognitive radio has been widely considered as one of the prominent solutions to tackle the spectrum scarcity. While the majority of existing research has focused on single-band cognitive radio, multiband cognitive radio represents great promises toward implementing efficient cognitive networks compared to single-based networks. Multiband cognitive radio networks (MB-CRNs) are expected to significantly enhance the network's throughput and provide better channel maintenance by reducing handoff frequency. Nevertheless, the wideband front-end and the multiband spectrum access impose a number of challenges yet to overcome. This paper provides an in-depth analysis on the recent advancements in multiband spectrum sensing techniques, their limitations, and possible future directions to improve them. We study cooperative communications for MB-CRNs to tackle a fundamental limit on diversity and sampling. We also investigate several limits and tradeoffs of various design parameters for MB-CRNs. In addition, we explore the key MB-CRNs performance metrics that differ from the conventional metrics used for single-band-based networks.

143 citations

Journal ArticleDOI
TL;DR: An optimal wideband spectrum sensing framework which identifies secondary transmission opportunities over multiple nonoverlapping narrowband channels is presented and it is demonstrated that the problem can be solved by convex optimization if certain practical constraints are applied.
Abstract: An optimal wideband spectrum sensing framework which identifies secondary transmission opportunities over multiple nonoverlapping narrowband channels is presented. The framework, which is referred to as multiband sensing-time-adaptive joint detection, improves the overall secondary user performance while protecting the primary network and keeping the harmful interference below a desired low level. Considering a periodic sensing scheme, the detection problem is formulated as a joint optimization problem to maximize the aggregate achievable secondary throughput capacity given a bound on the aggregate interference imposed on the primary network. It is demonstrated that the problem can be solved by convex optimization if certain practical constraints are applied. Simulation results attest that the proposed wideband spectrum sensing framework achieves superior performance compared to contemporary frameworks. An efficient iterative algorithm which solves the optimization problem with much lower complexity compared to other numerical methods is presented. It is established that the iteration-complexity and the complexity-per-iteration of the proposed algorithm increases linearly as the number of optimization variables (i.e., the number of narrowband channels) increases. The algorithm is evaluated via simulation and is shown to obtain the optimal solution very quickly and efficiently.

128 citations

References
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Book
01 Mar 2004
TL;DR: In this article, the focus is on recognizing convex optimization problems and then finding the most appropriate technique for solving them, and a comprehensive introduction to the subject is given. But the focus of this book is not on the optimization problem itself, but on the problem of finding the appropriate technique to solve it.
Abstract: Convex optimization problems arise frequently in many different fields. A comprehensive introduction to the subject, this book shows in detail how such problems can be solved numerically with great efficiency. The focus is on recognizing convex optimization problems and then finding the most appropriate technique for solving them. The text contains many worked examples and homework exercises and will appeal to students, researchers and practitioners in fields such as engineering, computer science, mathematics, statistics, finance, and economics.

33,341 citations

Journal ArticleDOI
Simon Haykin1
TL;DR: Following the discussion of interference temperature as a new metric for the quantification and management of interference, the paper addresses three fundamental cognitive tasks: radio-scene analysis, channel-state estimation and predictive modeling, and the emergent behavior of cognitive radio.
Abstract: Cognitive radio is viewed as a novel approach for improving the utilization of a precious natural resource: the radio electromagnetic spectrum. The cognitive radio, built on a software-defined radio, is defined as an intelligent wireless communication system that is aware of its environment and uses the methodology of understanding-by-building to learn from the environment and adapt to statistical variations in the input stimuli, with two primary objectives in mind: /spl middot/ highly reliable communication whenever and wherever needed; /spl middot/ efficient utilization of the radio spectrum. Following the discussion of interference temperature as a new metric for the quantification and management of interference, the paper addresses three fundamental cognitive tasks. 1) Radio-scene analysis. 2) Channel-state estimation and predictive modeling. 3) Transmit-power control and dynamic spectrum management. This work also discusses the emergent behavior of cognitive radio.

12,172 citations


"Optimal multi-channel cooperative s..." refers background in this paper

  • ...As an emerging technique to realize this idea, cognitive radio has received much attention recently, in which the secondary users are able to sense the spectrum, analyze the spectrum statistics, and adjust their transmissions according to the time-varying environment [3]....

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Book
16 Mar 2001

7,058 citations


"Optimal multi-channel cooperative s..." refers background in this paper

  • ..., the probability that, if there are no primary activities, the secondary users falsely estimate that primary users are active) [4]....

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Journal ArticleDOI
TL;DR: This paper designs the sensing duration to maximize the achievable throughput for the secondary network under the constraint that the primary users are sufficiently protected, and forms the sensing-throughput tradeoff problem mathematically, and uses energy detection sensing scheme to prove that the formulated problem indeed has one optimal sensing time which yields the highest throughput.
Abstract: In a cognitive radio network, the secondary users are allowed to utilize the frequency bands of primary users when these bands are not currently being used. To support this spectrum reuse functionality, the secondary users are required to sense the radio frequency environment, and once the primary users are found to be active, the secondary users are required to vacate the channel within a certain amount of time. Therefore, spectrum sensing is of significant importance in cognitive radio networks. There are two parameters associated with spectrum sensing: probability of detection and probability of false alarm. The higher the probability of detection, the better the primary users are protected. However, from the secondary users' perspective, the lower the probability of false alarm, the more chances the channel can be reused when it is available, thus the higher the achievable throughput for the secondary network. In this paper, we study the problem of designing the sensing duration to maximize the achievable throughput for the secondary network under the constraint that the primary users are sufficiently protected. We formulate the sensing-throughput tradeoff problem mathematically, and use energy detection sensing scheme to prove that the formulated problem indeed has one optimal sensing time which yields the highest throughput for the secondary network. Cooperative sensing using multiple mini-slots or multiple secondary users are also studied using the methodology proposed in this paper. Computer simulations have shown that for a 6 MHz channel, when the frame duration is 100 ms, and the signal-to-noise ratio of primary user at the secondary receiver is -20 dB, the optimal sensing time achieving the highest throughput while maintaining 90% detection probability is 14.2 ms. This optimal sensing time decreases when distributed spectrum sensing is applied.

2,889 citations


"Optimal multi-channel cooperative s..." refers background or methods or result in this paper

  • ...Similar to [12], the system setup is as follows....

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  • ...Similar to [12], r n (i) is assumed to be a zero mean CSCG random variable....

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  • ...Then the average throughput of channel n can be expressed [12] as Cn(k, kn, εn) = T−kδ T ( Pr(H0 n) ( 1− P f n (kn, εn) ) R n...

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  • ...This process is referred to as soft decisional cooperative spectrum sensing, and the detection probability and false alarm probability in the process are given [12] as...

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  • ...The optimal tradeoff in sensing time setting is investigated in [12][13] so as to optimally utilize the transmission opportunities in a single channel....

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Journal ArticleDOI
TL;DR: An analytical framework for opportunistic spectrum access based on the theory of partially observable Markov decision process (POMDP) is developed and cognitive MAC protocols that optimize the performance of secondary users while limiting the interference perceived by primary users are proposed.
Abstract: We propose decentralized cognitive MAC protocols that allow secondary users to independently search for spectrum opportunities without a central coordinator or a dedicated communication channel. Recognizing hardware and energy constraints, we assume that a secondary user may not be able to perform full-spectrum sensing or may not be willing to monitor the spectrum when it has no data to transmit. We develop an analytical framework for opportunistic spectrum access based on the theory of partially observable Markov decision process (POMDP). This decision-theoretic approach integrates the design of spectrum access protocols at the MAC layer with spectrum sensing at the physical layer and traffic statistics determined by the application layer of the primary network. It also allows easy incorporation of spectrum sensing error and constraint on the probability of colliding with the primary users. Under this POMDP framework, we propose cognitive MAC protocols that optimize the performance of secondary users while limiting the interference perceived by primary users. A suboptimal strategy with reduced complexity yet comparable performance is developed. Without additional control message exchange between the secondary transmitter and receiver, the proposed decentralized protocols ensure synchronous hopping in the spectrum between the transmitter and the receiver in the presence of collisions and spectrum sensing errors

1,709 citations


"Optimal multi-channel cooperative s..." refers methods in this paper

  • ...For spectrum sensing, a slotted time frame structure is widely used [8]–[11]....

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