Spectrum decision in GSM band using a fuzzy logic controller

In this paper we explore the possibility of exploiting underutilized channels in the GSM bands, by means of secondary use of spectrum. The secondary (unlicensed) users are the nodes of an overlay cognitive ad-hoc network, which opportunistically transmits in data channels left unused by the primary (licensed) system. The focus is on the feasibility of the proposed approach, so that we consider a system level simulator based on a realistic GSM network deployed in the city of Bologna. In this context we propose a fuzzy-based approach to select the most appropriate frequency carrier for secondary usage, and we evaluate the impact that the operation of the secondary users has on the performances of the primary system. In addition, we study the performances that can be obtained by the secondary system under the condition of marginal interference to the primary system. We will show that the use of fuzzy logic, makes the secondary usage of spectrum a valid approach to increase the operator´s spectrum efficiency.