Efficient Radio Resource Management Algorithms in Opportunistic Cognitive Radio Networks Athina Bourdena 1 , Evangelos Pallis 2 , Georgios Kormentzas 1 and George Mastorakis 2 1 Department of Information and Communication Systems Engineering, University of the Aegean, Samos, Greece 2 Department of Applied Informatics and Multimedia, Technological Educational Institute of Crete, Heraklion, Crete, Greece ABSTRACT Cognitive radio (CR) paradigm was introduced, towards addressing challenges, related with radio spectrum scarcity and increased needs for wireless networking services provision. In this direction, CR networks exploit novel networking architectures, as well as dynamic radio spectrum access techniques and methods, alleviating problems, regarding limited wireless networking resources and their inefficient usage/exploitation. CR terminals exploit innovative mechanisms to identify un-used parts of radio spectrum, such as TV White Spaces (TVWS) in UHF/VHF bands, following an interference-free opportunistic manner. However, introduction of CR networks creates new challenges that are highly related to the fluctuation of TVWS, as they vary over time and location, as well as issues related to diverse Quality of Service (QoS) requirements. In this context, this paper proposes two radio resource management (RRM) algorithms, enabling for the opportunistic exploitation of TVWS in a centralized cognitive radio networking architecture. Efficient administration of radio spectrum resources is achieved, by exploiting a novel RRM framework, adopted in a spectrum broker, which is in charge to effectively orchestrate the available wireless networking resources. Efficient RRM algorithms performance, as a matter of maximum-possible spectrum broker benefit and radio spectrum utilization, as well as minimum-possible spectrum fragmentation is evaluated, by considering a fixed-price and an auction-based optimization approach. Experimental tests that were conducted under controlled simulation conditions, confirmed the validity of both RRM algorithms adopted in the proposed CR networking architecture, identifying fields for further research and experimentation. KEY WORDS Opportunistic cognitive radio networks, TV White Spaces, radio resource management algorithms, spectrum broker, centralized networking architectures *Correspondence A. Bourdena, Department of Information and Communication Systems Engineering, University of the Aegean, Samos, Greece E-mail: abourdena@icsd.aegean.gr † This paper was presented in part at the 1st ACM Workshop on High Performance Mobile Opportunistic Systems (HP-MOSys 2012), 15th ACM International Conference on Modeling, Analysis and Simulation of Wireless and Mobile Systems, in cooperation with R8 IEEE Computer Society C16, Paphos, Cyprus, 21-25 October 2012. 1. INTRODUCTION Demand for radio spectrum was dramatically raised during previous years due to the ongoing growth of mobile communication services provision, creating new challenges in wireless networks resources management and administration. Important studies and reports on radio spectrum exploitation [1] (e.g. Federal Communications Commission studies) have proved that the existing “command-and-control” framework/policy is insufficient to address current demands for wireless services provision. Furthermore, other reports [2] revealed that a great number of radio spectrum blocks/resources, like TV White Spaces (TVWS) [3] is under-utilized or idle for long time periods in certain geographical areas. TVWS include VHF/UHF channels that are either released by the digital switchover process (“Spectrum/Digital Dividend”), or are completely un-used primarily at specific locations, according to frequency allocation rules and wireless networks planning principles (“Interleaved Spectrum”) [3]. In addition, dynamic spectrum access (DSA) paradigm was introduced, towards addressing vital radio spectrum utilization challenges [4], [5]. DSA is highly related with cognitive radio (CR) networks [6], [7], enabling for opportunistic exploitation of radio spectrum resources [4], [8], in CR networking architectures [9]. Towards this direction, CR networking architectures are categorized, either as centralized ones, if the decision of radio spectrum access is taken, by a central controller/module or distributed ones, in case that the decision is taken locally, by each individual frequency-agile device. Such devices have the ability to search for radio spectrum opportunities, discover potential un-exploited channels and adapt their operation parameters [10], [11]. Nevertheless, adoption of opportunistic CR networking architectures cannot be an easy process, particularly in licensed radio spectrum channels, where “command-and-control” policy prohibits