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Cooperation and Learning in Multiuser Opportunistic Spectrum Access
"... Abstract — We consider how two secondary users should interact to maximize their total throughput in a twochannel sensingbased opportunistic spectrum access network where spectrum opportunities are time varying and spatially inhomogeneous. By modeling the occupancy of the primary users as discrete ..."
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Abstract — We consider how two secondary users should interact to maximize their total throughput in a twochannel sensingbased opportunistic spectrum access network where spectrum opportunities are time varying and spatially inhomogeneous. By modeling the occupancy of the primary users as discretetime Markov chains, we obtain the optimal dynamic coordination policy using a partially observable Markov decision process (POMDP) solver. We also develop several tractable approaches a cooperative multiuser approach based on explicit communication between the secondary users, a learningbased approach involving use of collision feedback information, and a singleuser approach based on uncooperative independent decisions. As a baseline we consider the static partitioning policy where both users are allocated a single channel of their own. Simulations comparing the performance of these strategies yield several interesting findings: that significant improvements over static partitioning are possible with the optimal scheme; that the cooperative multiuser approach shows nearoptimal performance in all cases; that there are scenarios when learning through collision feedback can be beneficial; and that the singleuser approach generally shows poor performance. I.
Asymptotic optimality for distributed spectrum sharing using bargaining solutions
 IEEE Trans. Wireless Commun
, 2009
"... Abstract—Recent studies on spectrum usage reveal poor utilization, both spatially and temporally. Opportunistic use of licensed spectrum while limiting interference to primary users can enhance spectrum reuse and provide orders of magnitude improvement in available channel capacity. This calls for ..."
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Cited by 12 (2 self)
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Abstract—Recent studies on spectrum usage reveal poor utilization, both spatially and temporally. Opportunistic use of licensed spectrum while limiting interference to primary users can enhance spectrum reuse and provide orders of magnitude improvement in available channel capacity. This calls for spectrum sharing protocols that are dynamic, exible, and efcient, in addition to being fair to end users. We employ cooperative game theory to address the opportunistic spectrum access problem. Specically, we develop a gametheoretic model to analyze a scenario in which nodes in a wireless network seek to agree on a fair and efcient allocation of spectrum. First, we show that in high interference environments, the utility space of the game is nonconvex, making certain optimal allocations unachievable with pure strategies. To mitigate this, we show that as the number of channels available increases, the utility space approaches convexity, thereby making optimal allocations achievable with pure strategies. Second, by comparing and analyzing three bargaining solutions, we show that the Nash Bargaining Solution achieves the best tradeoff between fairness and efciency, using a small number of channels. Finally, we develop a distributed algorithm for spectrum sharing that is general enough to accomodate nonzero disagreement points, and show that it achieves allocations reasonably close to the Nash Bargaining Solution. Index Terms—Dynamic spectrum access, cooperation, game theory, radio resource management, Nash bargaining solution. I.
Cooperative profit sharing in coalition based resource allocation in wireless networks
 in Proc. of IEEE INFOCOM, (Rio de Janeiro
, 2009
"... Abstract—We consider a network in which several service providers offer wireless access service to their respective subscribed customers through potentially multihop routes. If providers cooperate, i.e., pool their resources, such as spectrum and base stations, and agree to serve each others ’ cust ..."
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Cited by 9 (4 self)
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Abstract—We consider a network in which several service providers offer wireless access service to their respective subscribed customers through potentially multihop routes. If providers cooperate, i.e., pool their resources, such as spectrum and base stations, and agree to serve each others ’ customers, their aggregate payoffs, and individual shares, can potentially substantially increase through efficient utilization of resources and statistical multiplexing. The potential of such cooperation can however be realized only if each provider intelligently determines who it would cooperate with, when it would cooperate, and how it would share its resources during such cooperation. Also, when the providers share their aggregate revenues, developing a rational basis for such sharing is imperative for the stability of the coalitions. We model such cooperation using transferable payoff coalitional game theory. We first consider the scenario that locations of the base stations and the channels that each provider can use have already been decided apriori (spectrum pooling game). We show that the optimum cooperation strategy, which involves the allocations of the channels and the base stations to mobile customers, can be obtained as solutions of convex optimizations. We next show that if all providers cooperate, there is always an operating point that maximizes the providers’ aggregate payoff, while offering each such a share that removes any incentive to split from the coalition. Next, we show that when the providers can choose the locations of their base stations and decide which channels to acquire, the above results hold in important special cases. Finally, we examine cooperation when providers do not share their payoffs, but still share their resources so as to enhance individual payoffs. We show that, in the spectrum pooling game, if all providers cooperate, there is always a joint action that fetches payoffs such that no subset of providers would break away from the coalition. I.
Spectrum sharing games on the interference channel
 in Proc. IEEE Intl. Conf. on Game Theory for Networks (Gamenets
, 2010
"... Abstract—In this paper, we address the problem of spectrum sharing where competitive operators coexist in the same frequency band. First, we model this problem as a strategic noncooperative game where operators simultaneously share the spectrum according to the Nash Equilibrium (N.E). Given a set o ..."
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Cited by 9 (4 self)
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Abstract—In this paper, we address the problem of spectrum sharing where competitive operators coexist in the same frequency band. First, we model this problem as a strategic noncooperative game where operators simultaneously share the spectrum according to the Nash Equilibrium (N.E). Given a set of channel realizations, several Nash equilibria exist which renders the outcome of the game unpredictable. For this reason, the spectrum sharing problem is reformulated as a Stackelberg game where the first operator is already being deployed and the secondary operator follows next. The Stackelberg equilibrium (S.E) is reached where the best response of the secondary operator is taken into account upon maximizing the primary operator’s utility function. Finally, we assess the goodness of the proposed distributed approach by comparing its performance to the centralized approach. I.
Spectrum sharing in multipleantenna channels: A distributed cooperative game theoretic approach,”
 IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications,
, 2008
"... I. ABSTRACT We consider a cognitive radio scenario in which two (or more) operators providing services in the same area wish to share the same licensed band of spectrum. This scenario differs from the classical cognitive setup with a primary and a secondary operators, as both operators here are ins ..."
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Cited by 6 (0 self)
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I. ABSTRACT We consider a cognitive radio scenario in which two (or more) operators providing services in the same area wish to share the same licensed band of spectrum. This scenario differs from the classical cognitive setup with a primary and a secondary operators, as both operators here are instead on an equal footing. The operators face the choice of competition or cooperation in the way they choose their transmission parameters (here beamforming vectors) to communicate with their respective users. We build on interesting recently published work II. INTRODUCTION Interference mitigation is a central problem in cognitive radio. We consider here the problem of independent operators sharing one identical band in the same geographical area, thus creating interference to one another. This context is different from the traditional cognitive setup where some hierarchy is respected between a primary operator and a secondary operator sharing the band. In our scenario, there is no hierarchy as both operators seek to maximize the rate experienced by their own users by the choice of transmission parameters, at the cost of creating and receiving interference to/from the other party. In our paper, we consider multipleantenna transmitters and the choice of a transmission parameter (from the base to the terminal) is limited to the choice of a beamforming vector, subject to a transmit power constraint. However other type of transmission parameters could also be considered such as power level, modulation/coding, subcarrier assignement etc. As the the operators (and their users) have the selfish goal of maximizing their own performance, this results in a conflict situation between the transmitterreceiver pairs. Game theory has been a popular tool for years for analysing optimization problems with conflicting objectives by independent players A game where some form of trust is established between players for the sake of maximizing their utilities jointly is referred to as a cooperative game. Such games have been brought up recently in the wireless networking literature Although mainly heuristic in nature, this algorithm finds some theoretical justification in the recently published literature. [5] and
Sharing Rewards in Cooperative Connectivity Games
"... We consider how selfish agents are likely to share revenues derived from maintaining connectivity between important network servers. We model a network where a failure of one node may disrupt communication between other nodes as a cooperative game called the vertex Connectivity Game (CG). In this ga ..."
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Cited by 5 (4 self)
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We consider how selfish agents are likely to share revenues derived from maintaining connectivity between important network servers. We model a network where a failure of one node may disrupt communication between other nodes as a cooperative game called the vertex Connectivity Game (CG). In this game, each agent owns a vertex, and controls all the edges going to and from that vertex. A coalition of agents wins if it fully connects a certain subset of vertices in the graph, called the primary vertices. Power indices measure an agent’s ability to affect the outcome of the game. We show that in our domain, such indices can be used to both determine the fair share of the revenues an agent is entitled to, and identify significant possible points of failure affecting thereliabilityofcommunicationinthenetwork. Weshowthatingeneralgraphs,calculating theShapleyandBanzhafpowerindicesis#Pcomplete, butsuggestapolynomialalgorithm for calculating them in trees. We also investigate finding stable payoff divisions of the revenues in CGs, captured by the game theoretic solution of the core, and its relaxations, the ǫcore and least core. We show a polynomial algorithm for computing the core of a CG, but show that testing whether an imputation is in the ǫcore is coNPcomplete. Finally, we show that for trees, it is possible to test for ǫcore imputations in polynomial time. 1.
On spectrum selection games in cognitive radio networks
 in Proc. IEEE GLOBECOM
"... AbstractCognitive Radio Networks aim at enhancing spectrum utilization by allowing cognitive devices to opportunistically access vast portions of the spectrum. To reach such ambitious goal, cognitive terminals must be geared with enhanced spectrum management capabilities including the detection of ..."
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Cited by 4 (2 self)
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AbstractCognitive Radio Networks aim at enhancing spectrum utilization by allowing cognitive devices to opportunistically access vast portions of the spectrum. To reach such ambitious goal, cognitive terminals must be geared with enhanced spectrum management capabilities including the detection of unused spectrum holes (spectrum sensing), the characterization of available bands (spectrum decision), the coordination with other cognitive devices in the access phase (spectrum sharing), and the capability to handover towards other spectrum holes when licensed users kick in or if a better spectrum opportunity becomes available (spectrum mobility). In this paper, a game theoretic framework is proposed to evaluate spectrum management functionalities in Cognitive Radio Networks. The spectrum selection process is cast as a noncooperative game among secondary users who can opportunistically select the "best" spectrum opportunity, under the tight constraint not to harm primary licensed users. Different quality measures for the spectrum opportunities are considered and evaluated in the game framework, including the spectrum bandwidth, and the spectrum opportunity holding time. The cost of spectrum mobility is also accounted in the analytical framework. Numerical results are reported to assess the quality of the game equilibria.
Load balancing for dynamic spectrum assignment with local information for secondary users
 In Proc. Symp. Dynamic Spectrum Access Networks (DySPAN
, 2008
"... Abstract—In this paper we study an idealized model of load balancing for dynamic spectrum allocation (DSA) for secondary users using only local information. In our model, each agent is assigned to a channel and may reassign its load in a round based fashion. We present a randomized protocol in which ..."
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Cited by 4 (2 self)
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Abstract—In this paper we study an idealized model of load balancing for dynamic spectrum allocation (DSA) for secondary users using only local information. In our model, each agent is assigned to a channel and may reassign its load in a round based fashion. We present a randomized protocol in which the actions of the agents depend purely on some cost measure (e. g., latency, inverse of the throughput, etc.) of the currently chosen channel. Since agents act concurrently, the system is prone to oscillations. We show how this can be avoided guaranteeing convergence towards a state in which every agent sustains at most a certain threshold cost (if such a state exists). We show that the system converges quickly by giving bounds on the convergence time towards approximately balanced states. Our analysis in the fluid limit (where the number of agents approaches infinity) holds for a large class of cost functions. We support our theoretical analysis by simulations to determine the dependence on the number of agents. It turns out that the number of agents affects the convergence time only in a logarithmic fashion. The work shows under quite general assumptions that even an extremely large number of users using several hundreds of (virtual) channels can work in a DSA fashion. I.
Bargaining to Improve Channel Sharing between Selfish Cognitive Radios
"... We consider a problem where two selfish cognitive radio users try to share two channels on which they each have potentially different valuations. We first formulate the problem as a noncooperative simultaneous game, and identify its equilibria. For cases where the resulting Nash equilibria are not ..."
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Cited by 1 (1 self)
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We consider a problem where two selfish cognitive radio users try to share two channels on which they each have potentially different valuations. We first formulate the problem as a noncooperative simultaneous game, and identify its equilibria. For cases where the resulting Nash equilibria are not efficient, we then propose a novel coordinated channel access mechanism that can be implemented with low overhead in a decentralized fashion. This mechanism, based on the Nash bargaining solution, guarantees full utilization of the spectrum resources while improving the utility of each user compared to the noncooperative setting. We quantify the resulting gains. Finally, we prove that riskaverse users that are willing to accept offered information at face value have no incentive to lie to each other about their valuations for the noncooperative game. However, we find that truthfulness is not guaranteed in the bargaining process, suggesting as an open problem the design of an incentive compatible mechanism for bargaining.