Slotted Aloha in a cognitive radio environment with capture effects

Slotted Aloha is an effective random access protocol and can also be an important element of more advanced media access protocols. This paper investigates slotted Aloha in a cognitive radio environment where one access point provides services for both primary users and secondary users. Considering packet capture effects in a Rayleigh fading channel, we present the mathematic derivations of system throughput and average delay for primary users and secondary users. In order to minimize the interference from secondary users to primary users, higher transmission power levels are assumed for primary users.