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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 245 (3 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.
Dynamic Spectrum Access with QoS and Interference Temperature Constraints
, 2007
"... Spectrum is one of the most precious radio resources. With the increasing demand for wireless communication, efficiently using the spectrum resource has become an essential issue. With the Federal Communications Commission’s (FCC) spectrum policy reform, secondary spectrum sharing has gained increa ..."
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Cited by 73 (0 self)
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Spectrum is one of the most precious radio resources. With the increasing demand for wireless communication, efficiently using the spectrum resource has become an essential issue. With the Federal Communications Commission’s (FCC) spectrum policy reform, secondary spectrum sharing has gained increasing interest. One of the policy reforms introduces the concept of an interference temperature—the total allowable interference in a spectral band. This means that secondary users can use different transmit powers as long as the sum of these power is less than the interference threshold. In this paper, we study two problems in secondary spectrum access with minimum signal to interference noise ratio (quality of service (QoS)) guarantee under an interference temperature constraint. First, when all the secondary links can be supported, a nonlinear optimization problem with the objective to maximize the total transmitting rate of the secondary users is formulated. The nonlinear optimization is solved efficiently using geometric programming techniques. The second problem we address is, when not all the secondary links can be supported with their QoS requirement, it is desirable to have the spectrum access opportunity proportional to the user priority if they belong to different priority classes. In this context, we formulate an operator problem which takes the priority issues into consideration. To solve this problem, first, we propose a centralized reduced complexity search algorithm to find the optimal solution. Then, in order to solve this problem distributively, we define a secondary spectrum sharing potential game. The Nash equilibria of this potential game are investigated. The efficiency of the Nash equilibria solutions are characterized. It is shown that distributed sequential play and an algorithm based on stochastic learning attain the equilibrium solutions. Finally, the performances are examined through simulations.
Two Players NonCooperative Iterative Power Control for Spectrum Sharing
"... Abstract — To cope with limited spectrum resources, inefficient spectrum usage and overcrowded wireless communication, the Federal Communications Commission’s (FCC) has introduced a new way to manage RF resources: the interference temperature model. With this model the key point is to let unlicensed ..."
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Cited by 2 (1 self)
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Abstract — To cope with limited spectrum resources, inefficient spectrum usage and overcrowded wireless communication, the Federal Communications Commission’s (FCC) has introduced a new way to manage RF resources: the interference temperature model. With this model the key point is to let unlicensed users use licensed frequencies, provided they can quantify and bound their interference toward the primary license holders. In this paper we study power control for spectrum sharing among two secondary users with interference temperature limit (ITL) at a measurement point. We model this scenario as 2player noncooperative game. The 2 players are selfish and rational and strive to maximize their own utility. The measurement point, upon violation of ITL, iteratively backs off a randomly selected secondary user. We identify the possible outcomes of this game and the conditions for the existence of unique/multiple Nash equilibria. We analyze the property of the Nash equilibria in our games, and compare their performances with the social optimal solution. Our simulation results demonstrate that the proposed solution can achieve a satisfactory performance in terms of the total transmitting rate of the two secondary users.
Realtime secondary spectrum sharing with QoS provisioning
 in Proc. IEEE CCNC’06
, 2006
"... Abstract — We study the quality of service (QoS) issue in secondary spectrum sharing subject to an interference temperature constraint. A nonlinear optimization problem with the objective to maximize the total transmitting rate of the secondary users is formulated. The nonlinear optimization is s ..."
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Abstract — We study the quality of service (QoS) issue in secondary spectrum sharing subject to an interference temperature constraint. A nonlinear optimization problem with the objective to maximize the total transmitting rate of the secondary users is formulated. The nonlinear optimization is solved efficiently using geometric programming techniques. When not all the secondary links can be supported with their QoS requirement, a reduced complexity searching algorithm is introduced to find the optimal subset of links which contains the maximum number of links with both QoS and interference temperature constraints satisfied. We also defined a secondary spectrum sharing potential game. The Nash equilibria of this potential game are reached by distributed sequential play. The efficiency of the Nash equilibria solutions is characterized. Finally, the performances of both the reduced complexity algorithm and the sequential play are examined through simulations. I.
Autonomous Distributed Power Control for Cognitive Radio Networks
 in IEEE Vehicular Technology Conference
, 2008
"... Abstract — In recent years, cognitive radio (CR) has received a great attention due to the ability to improve the spectrum utilization. It allows the secondary user (SU) in the CR network to opportunistically access the licensed spectrum of the primary user (PU). For this end, quality of service (Qo ..."
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Abstract — In recent years, cognitive radio (CR) has received a great attention due to the ability to improve the spectrum utilization. It allows the secondary user (SU) in the CR network to opportunistically access the licensed spectrum of the primary user (PU). For this end, quality of service (QoS) requirements for both the PU and the SU should be guaranteed at the same time. These QoSs can be respectively translated into the interference temperature at the primary receiver and the received signaltointerferenceplusnoiseratio (SINR) of the secondary receiver. In such a CR network, a power control can increase the energy efficiency by keeping the transmission power of the SU as low as possible within the QoS requirements. In this paper, we propose an autonomous distributed power control scheme for CR networks that considers the QoS requirements of the PU and the SU simultaneously. Since the transmission power of each SU is constrained so that the interference temperature at the primary receiver caused by all SUs does not exceed the interference tolerance of the PU, the QoS requirement for the PU is always guaranteed. Through the simulation results, we demonstrate that the proposed scheme never exceed the interference tolerance of the PU. Index Terms−Cognitive radio, quality of service, power control, distributed constrained power control, generalized distributed constrained power control I.
A TwoStage Power and Rate Allocation Strategy for Secondary Users in Cognitive Radio Networks
"... Abstract — In this paper, we attempt to evaluate the optimal power and rate distribution choices for secondary users in order to maintain their quality of service (QoS) in a multichannel cognitive radio network (CRN). We assume that multiple secondary users share a single channel and multiple channe ..."
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Abstract — In this paper, we attempt to evaluate the optimal power and rate distribution choices for secondary users in order to maintain their quality of service (QoS) in a multichannel cognitive radio network (CRN). We assume that multiple secondary users share a single channel and multiple channels are simultaneously used by a single secondary user (SU) to satisfy their rate requirements. Our measures for QoS include signal to interference plus noise ratio (SINR)/bit error rate (BER) and minimum rate requirement. We propose a twostage optimization framework in order to solve for the optimal resource management strategy. In the first stage, we formulate a convex optimization problem to determine the minimum transmit power that SUs should employ in order to maintain a certain SINR. At first, the convex optimization problem is solved in a centralized manner and then we employ dual decomposition theory to derive three different distributed solutions. In the second stage, we formulate the rate distribution problem as a maximum flow problem in graph theory. We also develop a heuristic approach to determine the rate distribution. Simulation results demonstrate that optimal transmit power follows “reverse water filling ” process and rate allocation follows SINR. We also observe that the distributed solution converges to the centralized solution and rate distribution based on our proposed heuristic is close to the graph theoretic optimal solution. Index Terms — power allocation, distributed approach, rate allocation, quality of service I.
1Soft Sensing and Optimal Power Control for Cognitive Radio
"... We consider a cognitive radio system where the secondary transmitter varies its transmit power based on all the information available from the spectrum sensor. The operation of the secondary user is governed by its peak transmit power constraint and an average interference constraint at the primary ..."
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We consider a cognitive radio system where the secondary transmitter varies its transmit power based on all the information available from the spectrum sensor. The operation of the secondary user is governed by its peak transmit power constraint and an average interference constraint at the primary receiver. Without restricting the sensing scheme (total received energy, or correlation etc), we characterize the power adaptation strategies that maximize the secondary user’s SNR and capacity. We show that, in general, the capacity optimal power adaptation requires decreasing the secondary transmit power from the peak power to zero in a continuous fashion as the probability of the primary user being present increases. We find that that power control that maximizes the SNR is binary, i.e., if there is any transmission, it takes place only at the peak power level. Numerical results for common spectrum sensing schemes show that the SNR and capacity maximizing schemes can be very different. With an average transmit power constraint at the secondary radio, both the SNR and capacity optimal power control schemes are observed to be nonbinary. Further, we find that with secondary channel knowledge at the cognitive transmitter, the optimal SNR with an average transmit power constraint is unbounded. I.
ion IEEE/ACM TRANSACTIONS ON NETWORKING 1 An Economic Framework for Dynamic Spectrum Access and Service Pricing
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PricingBased PrimarySecondary User Power Control Game for Cognitive Radio Networks
, 2010
"... Abstract: In cognitive radio networks, if the license spectrum that is allocated to the primary users (PUs) is not utilized, the unutilized spectrum can be used by the secondary users (SUs). This unutilized spectrum is called spectrum hole. However, when the SUs access the spectrum hole, they becom ..."
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Abstract: In cognitive radio networks, if the license spectrum that is allocated to the primary users (PUs) is not utilized, the unutilized spectrum can be used by the secondary users (SUs). This unutilized spectrum is called spectrum hole. However, when the SUs access the spectrum hole, they become source of interference to the others primary and secondary users. Interference temperature is the model, which used to manage the amount of interference that the PU can tolerate. Therefore, efficient power control is crucial to control the interference in the cognitive radio system and promote system quality. Previous works on power control are mainly focus on the SUs SIR maximization as the QoS requirements, ignoring the Primary User (PU). In this paper, PU is considered that has a general utility function, and a linear pricing function is used for SUs utility function. Pricing is an effective tool used to reduce the potential harmful effect of the system and guarantee the PU QoS. We formulated the power control game as a noncooperative game, in which the first player is the PU. The number of SUs in the system is limited by the status of PU and its ability to achieve its QoS rather than used the interference temperature limits. The numerical results show that the proposed power control algorithm with pricing reduce the power consumed by PU and SUs terminals, and improved the utility functions of PU and SUs.