  A noncooperative game theoretical approach for analysing opportunistic
spectrum access (OSA) in cognitive radio (CR) environments is proposed. New
concepts from game theory are applied to spectrum access analysis in order to
extract rules of behaviour for an emerging environment. In order to assess OSA
scenarios of CRs, two oligopoly game models are reformulated in terms of
resource access: Cournot and Stackelberg games. Five CR scenes are analysed:
simultaneous access of unlicensed users (commons regime) with symmetric and
asymmetric costs, with and without bandwidth constraints and sequential access
(licensed against unlicensed). Several equilibrium concepts are studied as game
solutions: Nash, Pareto and the joint NashPareto equilibrium. The latter
captures a game situation where players are non-homogeneous users, exhibiting
different types of rationality, Nash and Pareto. This enables a more realistic
modelling of interactions on a CR scene. An evolutionary game equilibrium
detection method is used. The Nash equilibrium indicates the maximum number of
channels a CR may access without decreasing its payoff. The Pareto equilibrium
describes a larger range of payoffs, capturing unbalanced as well as equitable
solutions. The analysis of the Stackelberg modelling shows that payoffs are
maximised for all users if the incumbents are Nash oriented and the new
entrants are Pareto driven.
