VoIP based Two-tier Cognitive Radio Network: Developing Implementation Techniques

Cognitive Radio Network (CRN) ensures higher utilization of spectrum by allowing secondary users to transmit in licensed frequency bands in absence of primary users. In order to reduce interference among these users, CRN imposes a maximum limit on total number of users that can be admitted in CRN. The overall user capacity is further increased by implementing VoIP based 2-tier CRN that allows another group of secondary users to transmit by exploiting silence suppression characteristics of secondary users involved in VoIP communication. The practical issues involved in designing VoIP based 2-tier CRN are discussed in this paper as it provides novel implementation design models for 2-tier CRN. Two algorithms based on message passing policy are proposed for deploying VoIP based 2-tier CRN with the aim of increasing system capacity while reducing interference among users. Detailed mathematical formulation establishes superiority of 2-tier CRN over basic CRN with 77% improvement in spectrum utilization. Performance analysis in simulation model validates the inferences drawn from mathematical model.