A Novel Hierarchical Fuzzy Systems Based Cooperative Spectrum Sensing and Opportunistic Spectrum Access Techniques

Abstract

When a large number of cognitive users (CUs) are competing for the spectral resource sharing with different parameters, it is a challenging job to decide a scheduling criterion to be followed and to solve the problem of idle channel allocation. This paper proposed a novel two levels Hierarchical Fuzzy Systems based cooperative spectrum sensing (level 1) and opportunistic spectrum access (level 2). Three separate groups of hierarchical fuzzy systems has been designed to estimate the probability of presence of three primary users (PUs) in first controller level and then estimate the percentage ratio of allocating idle channels to three out of nine CUs in second controller level. To improve the performance of this system during mobility state of PUs and/or CUs, a Hopping System module is proposed. The CUs nodes dynamically coordinate their action to detect all the bands sequentially in organized manner. The results indicate that fuzzy logic can be used in cooperative spectrum sensing to provide additional flexibility in decision making. While in opportunistic spectrum access, fuzzy logic allow the CU with highest possibility of spectrum access to occupy the idle channel and improve the probability of detection in mobility state by using hopping code.