Performance of a cognitive p-persistent slotted Aloha protocol

This paper proposes a new analytical model for the performance of a p persistent slotted Aloha medium access protocol in a Cognitive Radio Network (CRN) composed by a single Primary user (PU) and several Secondary users (SUs) with Poisson traffic. SUs run a synchronized sensing-access operation cycle, and when they have a packet to transmit and the channel is sensed free, they access to the data slots with probability p. PU change their activity state (ON/OFF) independently of the SUs, and an energy-based sensing performance model is considered. This paper proposes a new analytical model for the SU´s delay and throughput which, contrarily to the existing models, considers the effect of the duration of the PU´s ON state in the SUs delay. The model is validated through simulations, and the optimal p value is calculated for different scenarios. Two context-aware configurations are proposed: the optimal p value when only the number of SUs is known, and when the number and load are known.