An access strategy selection in Cognitive Radio networks and QoS provisioning

The basic notion behind Cognitive Radio (CR) is that secondary users (SU) access the under-utilized licensed spectrum of primary users (PU) in an opportunistic manner. It assuages the problem of spectrum scarcity, which is a major concern as many applications and devices nowadays are using wireless medium. Before carrying on any transmission, the SU senses the licensed spectrum and predicts whether the spectrum is preoccupied by PU. Access strategy selection is a very crucial issue for CR networks, because the SU needs to satisfy the interference constraint caused to the PU as well as the quality-of-service (QoS) requirements. In this paper the access strategies for the spectrum access, i.e., the underlay strategy and the overlay strategy have been discussed for low and high transmit power of SU transmitter. The relationship between effective capacity and the quality of service exponent has also been presented in this paper.