Two-dimensional contract theory in Cognitive Radio networks

While the spectrum resource of modern society is more and more insufficient, Cognitive Radio, which allows the Secondary Users (unlicensed users, SU) to access the licensed spectrum, is a promising solution to make the utilization of spectrum resource more efficient. Among many different paradigms of cognitive radio, market-driven spectrum trading has been proved to be an efficient way to deal with Cognitive Radio problems. In this paper, we consider the problem of spectrum trading with single primary user (PU) who has multiple spectra selling his idle spectra to multiple SUs in multiple types. Since there is only one PU, so it is a monopoly market, in which the PU sets the prices, powers and time for the spectrum he sells, just as a monopolist. SUs as customers choose the spectrum with exact price, power and time to buy. We model it as a two-dimensional power-time-price contract which is much different from the usual contract because the time could either be a strategy that an SU could decide to choose itself or a type which is not decided by SUs. We first discuss the situation in which the time is set as the strategy and we will prove that it can derive a feasible contract with some conditions. Then we will discuss the second situation in which the time is set as a type. In this situation, because the SU has two kinds of types, so it´s difficult to make it become a feasible contract, however we will provide a solution to deal with this problem.