We analyze the local delay of cognitive radio ad hoc networks in which secondary nodes are overlaid with a pair of primary nodes. Supposing slotted ALOHA multiple access is adopted by secondary nodes, we derive the closed-form expression of the local delay by modeling the channel occupied by primary nodes as continuous-time Markov on-off process. Furthermore, we obtain the asymptotic local delay for two special cases: large and small primary traffic. We theoretically prove that the local delay increases with the increasing primary packet arrival rate and decreases with the increasing primary packet departure rate. Numerical and simulation results show that the local delay could be approximated to be the result obtained with significant primary traffic in most cases, which is the steady of the channel idle state. Keywords Local delay Cognitive radio networks Overlay Slotted ALOHA
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