Cognitive Radio Networks with the RESTART Retransmission Strategy and Limited Reconnections

In cognitive radio networks (CRNs) based on spectrum overlay sharing, the connection of a secondary user fails when a primary user arrives and there is not idle channels. Retransmissions of interrupted secondary sessions may lead the system towards an unstable condition. Therefore, it is important to develop mechanisms to alleviate performance degradation due to reconnected secondary sessions. To the best of the authors´ knowledge, mechanisms based on limiting the number of reconnections for reducing failure rate have been neither analyzed nor evaluated in the literature. In this paper, limiting the maximum number of reconnections in CRNs with RESTART retransmission strategy for delay tolerant traffic is evaluated as a mechanism to reduce the negative impact of retransmissions and to widen the conditions under which system stability can be achieved. Numerical results show that limiting reconnections is an effective mechanism to alleviate performance degradation due to connection failure. Also a tradeoff between the call completion probability and the supported offered traffic load that can be controlled by varying either the number of reserved channels or the number of allowed retransmission is observed.