Throughput-Efficient Spectrum Access in Cognitive Radio Networks: A Coalitional Game Theoretic Approach

Throughput-Efficient Spectrum Access in Cognitive Radio Networks: A Coalitional Game Theoretic Approach

Raza Umar, Wessam Mesbah
DOI: 10.4018/978-1-4666-6571-2.ch017
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Cognitive radio based on dynamic spectrum access has emerged as a promising technology to meet the insatiable demand for radio spectrum by the emerging wireless applications. In this chapter, the authors address the problem of throughput-efficient spectrum access in Cognitive Radio Networks (CRNs) using Coalitional Game-theoretic framework. They model the problem of joint Coalition Formation (CF) and Bandwidth (BW) allocation as a CF game in partition form with non-transferable utility and present a variety of algorithms to dynamically share the available spectrum resources among competing Secondary Users (SUs). First, the authors present a centralized solution to reach a sum-rate maximizing Nash-stable network partition. Next, a distributed CF algorithm is developed through which SUs may join/leave a coalition based on their individual preferences. Performance analysis shows that the CF algorithms with optimal BW allocation provides a substantial gain in the network throughput over existing coalition formation techniques as well as the simple cases of singleton and grand coalition.
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Cognitive radio (CR) technology provides a smart solution to spectrum scarcity problem by allowing unlicensed users to access licensed frequency bands under stringent operating constraints. In CR terminology, the users with legacy rights on the usage of specific part of the spectrum are called primary users (PU) while the term secondary users (SU) is reserved for low-priority un-licensed users which are equipped with a cognitive capability to exploit this spectrum without being noticed by PU. The practical implementation of CRNs is facing many challenges and conflicting requirements such as PU protection and SU rate maximization, as identified by Akyildiz et al. (2006). While the last decade of research activities has focused on enhancing spectrum sensing (SS) performance (Umar and Sheikh, 2012), or more recently on jointly optimizing the spectrum sensing and spectrum access parameters (Khan et al., 2010), (Hao et al., 2012) as a means of improving the secondary network throughput, their scope has proven to be limited after the FCC ruling (FCC, 2010) which obviated the SS requirement in CRNs. As a result, there has been a dire need to explore stand-alone efficient spectrum access schemes in a competitive environment where SUs do not solely rely on SS performance for their throughput improvement.

Hence, this chapter presents an efficient strategy to dynamically share the available spectrum resources among competing SUs under the assumption that available spectrum opportunities are known a priori. The task of obtaining information about the real time spectrum occupancy by the primary users, and ultimately identifying secondary spectrum usage opportunities, is termed as spectrum sensing, and has been extensively discussed in literature (Yucek and Arslan, 2009, Wang and Ray, 2011, Axell et al., 2012, Umar and Sheikh, 2013). The overall performance of a CRN is influenced by the sensitivity and specificity of the underlying sensing mechanism (Yucek and Arslan, 2009, Umar and Sheikh, 2012), such that any error in the spectrum sensing either result in the interference with the primary transmissions or causes a reduced secondary network throughput. The impact of sensing errors on the performance of CRN has been well investigated in the literature (Khan et al., 2010Hao et al., 2012, Saad et al. 2012), however, how to efficiently share the available spectrum resources among the competing SUs, is comparatively less-explored in analyzing the achievable performance of CRNs. Hence, this chapter primarily focuses on the throughput-efficient spectrum access in CRNs.

Key Terms in this Chapter

Secondary Coordinator (SC): A master controller that is typically present in an infrastructure based network.

Network Partition / Coalition Structure: A set of non-overlapping coalitions that span all the players in the network.

Cognitive Radio (CR)/Secondary User: An intelligent reconfigurable unlicensed (with no legacy rights for the use of spectrum) device that can interact with its radio environment and update its transmission parameters (in software) on the run to optimally benefit from the available radio resources.

Coordinated Coalition Formation Game: A centralized approach to organize distributed CRs wherein a CF algorithm is executed at SC.

Nash Stable Network Partition: A network partition is said to be Nash stable if no player finds an incentive (rate improvement) to leave its coalition.

Coalition: A group of players (SUs).

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