A Game Theoretic Approach for Medium Access of Open Spectrum in Cognitive Radios

Abstract

The requirement of additional spectrum for the ever increasing demand to support the various Quality of Service requirements (QoS) in wireless systems is of primary interest to the research community since the unlicensed spectrum is reaching its limit and regulatory changes to provide portions from licensed bands are complicated and usually take a long time. In this work, we discuss the medium access control of open spectrum for spectrum agile radios that use spectrum opportunistically, also referred to as cognitive radios. Spectrum agile radios operate in parts of the spectrum that is originally licensed to other radio services. They identify the parts of the spectrum that is unused, coordinate its usage and release it when it is required by the licensed radio system. In this work, the problem of spectrum allocation is shown to be similar to the load balancing problem in distributed computer systems, and the problem of spectrum sharing is formulated as a non-cooperative game. We propose a non-cooperative load balancing algorithm, referred here as Spectrum Load Balancing (SLB) algorithm, and is applied to spectrum agile radio system. The game has a Nash equilibrium and SLB converges to this equilibrium. In this work, the capability of SLB to support QoS in the presence of other competing cognitive networks is evaluated via simulations and compared with the Spectrum Load Smoothing (SLS) algorithm.