Design and Evaluation of Self Organizing, Collision Free MAC Protocol for Distributed Cognitive Radio Networks

A cognitive radio network has a high promise to improve spectrum utilization, through exploitation of spectrum holes from the primary network. However, in a distributed environment, employing contention based random access, collisions and unattempted slots result in waste of the discovered holes. This waste is even costlier for a CRN as resources are consumed in finding the holes. In this paper, we have proposed a self-organizing distributed CR-MAC protocol so that the contention is not required for medium access, thereby, minimizing the waste of opportunity due to collisions or for being left idle in random access, consequently, improving the spectral efficiency. This is achieved by organizing and queuing the active secondary users through a timer value and directing them in an orderly fashion to use the discovered holes. The proposed scheme successfully assigns a channel to more than 99% of the secondary users in less than 5% of the idle slots from the primary network, compared to that required in contention based random access schemes.