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In this paper, we analyze the spectrum occupancy in cognitive radio networks (CRNs) using different machine learning techniques. Both supervised techniques [naive Bayesian classifier (NBC), decision trees (DT), support vector machine (SVM), linear regression (LR)] and unsupervised algorithms [hidden Markov model (HMM)] are studied to find the best technique with the highest classification accuracy (CA). A detailed comparison of the supervised and unsupervised algorithms in terms of the computational time and the CA is performed. The classified occupancy status is further utilized to evaluate the blocking probability of secondary user for future time slots, which can be used by system designers to define spectrum-allocation and spectrum-sharing policies. Numerical results show that SVM is the best algorithm among all the supervised and unsupervised classifiers. Based on this, we proposed a new SVM algorithm by combining it with a firefly algorithm (FFA), which is shown to outperform all the other algorithms. [ABSTRACT FROM PUBLISHER]

Cognitive radio (CR) has been proposed to improve spectrum efficiency by taking advantage of the vacancies in primary channels. Since the frequency range of operation is very wide in a CR network (CRN) and, usually, CRs cannot scan all the channels simultaneously, one of the fundamental tasks for a CR is the channel selection strategy, which directly impacts its performance. In this paper, we present a distributed polynomial time algorithmic framework for computing channel strategies in a CRN with no assumption on the distribution followed by the primary users' channel occupancy. For a secondary user (SU), the upper bound on the gap between the expected profit obtained at each time slot by using the global optimal strategy and the expected profit by using our algorithm is guaranteed to be arbitrarily small when the time horizon is sufficiently large. We also prove an upper bound on the gap between the expected profit by using any strategy sequence and the expected profit by using our strategy sequence. [ABSTRACT FROM PUBLISHER]