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.