Efficient Channel Search Algorithms for Cognitive Radio in a Multichannel System

In a cognitive radio (CR) network, secondary users (SUs) are allowed to opportunistically access a licensed spectrum that is not currently being occupied by primary users. This paper is concerned with the problem of how to quickly and accurately locate an unoccupied channel or determine that there is no unoccupied channel, from multiple (yet finite) candidate channels for a SU with a single detector. To design channel search algorithms, we propose a design criterion that minimizes average searching time subject to constraints on the error probabilities for a multichannel system. Relying on the proposed design criterion, we develop two efficient channel search algorithms that are based on a sequential application of the sequential probability ratio test and energy detection to the candidate channels.