Abstract-A key challenge in operating cognitive radios (CRs) without disturbing PR transmissions. A typical measure of in a self-organizing (ad hoc) network is how to adaptively and efficiency is the achievable sum-rate of all CR pairs. It is efficiently allocate transmission powers and spectrum among CRs known that the problem of maximizing the sum-rate over a according to the surrounding environment. Most previous works multi-access interference channel subject to individual power address this issue via heuristic approaches or using centralized con-aintss anoncnvex optmizt toblemv26]. powe solutions. In this paper, we present a novel joint power/channel constraints is a non-convex optimization problem [26] . Such allocation scheme that uses a distributed pricing strategy to a problem becomes even more complicated when we allow improve the network's performance. In this scheme, the spectrum multiple CRs to share the same channel, as one must now allocation problem is modelled as a non-cooperative game. A consider the CR-to-CR interference in addition to the PR-toprice-based iterative water-filling (PIWF) algorithm is proposed, CR interference. which allows users to converge to the Nash Equilibrium (NE). Seer erence. This PIWF algorithm can be implemented distributively with Several attempts have been made to solve the aforemenCRs repeatedly negotiating their best transmission powers and tioned interference channel problem. One well-known resource spectrum. Simulation results show that the social optimality of allocation scheme, called iterative water-filling (IWF), was the NE solution is dramatically improved with our price-based first proposed in [28] , where a non-cooperative game was used strategy. Based on the orders by which CRs take actions, we study ' sequential and parallel versions of the algorithm. We show that to model the spectrum management problem with each user the parallel version converges faster than the sequential version. iteratively maximizing its own rate. This per-user optimization problem is convex and leads to a water-filling solution. For I. INTRODUCTION the two-user case, it was shown that the Nash Equilibrium The concept of cognitive radio (CR) has recently triggered (NE) exists and the IWF algorithm converges to the NE under great interest within the research community [12]. The term certain conditions. However, this NE is generally not Pareto "cognitive radio" was first coined by Mitola [17], who used it optimal [20] and may be quite inefficient in terms of the sumto refer to a reconfigurable wireless black-box that intelligently rate metric [4], [5]. This is because in a non-cooperative game, changes its communication variables in response to network each user tries to maximize its own utility function without and user needs. Mitola's definition, however, does not specify considering the overall system performance. A centralized the network architecture needed to support CR functionality. spectrum management scheme was proposed in [4]. This More recently, the FCC [9] suggested referring to any radio scheme greatly improves the system performance over the with adaptive spectrum awareness as a CR. Specifically, a CR IWF scheme by utilizing a centralized spectrum management should be able to adapt its transmission parameters to the center (SMC). However, such a centralized approach cannot surrounding environment. CRs are expected to be deployed be implemented in a distributed ad hoc CRN, where none of in both military and commercial applications. the CR users has complete knowledge of the entire CRN to Several scenarios are envisioned for operating a cognitive function as the SMC. radio network (CRN). In this paper, we focus on the role of Given the above, we are motivated to design a chanCRs in opportunistic communications. According to this role, nel/power/rate allocation scheme that overcomes the ineffiCRs are secondary users that coexist with primary radios (PRs) ciency of the classic IWF algorithm and yet can be imthat are licensed to operate over given frequency bands. PR plemented in a distributed fashion. Specifically, we provide users do not cooperate with or even provide feedback to CR incentives to CR users such that they can reach a more users. CRs continuously sense the spectrum and exploit its socially efficient NE. A commonly used incentive technique "holes" for opportunistic communications. in game theory is pricing (a thorough review is provided in One of the main challenges in an opportunistic CRN is how [13] ). Pricing techniques have previously been implemented to design an efficient and adaptive channel access scheme that in various wireless networks, including cellular networks, ad supports dynamic channel selection and power/rate allocation hoc networks, and peer-to-peer networks (e.g., [22] , [6], [27] , in a distributed (ad hoc network) environment. An efficient and [1]). In this paper, we apply pricing techniques to a design is one that tries to maximize the CRN performance distributed CRN, and propose a price-based iterative waterAuthorized licensed use limited to: National Taiwan University. Downloaded on August 17, 2009 at 03:10 from IEEE Xplore. Restrictions apply.
A joint power/channel allocation scheme is proposed in REF to improve the network performance using a distributed pricing approach.
Price-Based Spectrum Management in Cognitive Radio Networks
J. Sel. Topics Signal Processing
J. Sel. Topics Signal Processing
Computer Science