A spectrum sensing and transmission model for secondary users in cognitive radios

An analysis of spectrum sensing and transmission of a secondary user sharing a channel with a licensed primary user is presented. The primary user access patterns are modeled as an on-off Markov process. A five state Markov model is derived to describe the performance of a secondary user that aims to utilize the channel during its idle state. Assuming perfect knowledge of the primary user access patterns, the model is analyzed with respect to the size of a back-off counter chosen when the channel is sensed busy and the size of the window allocated for secondary transmission when the channel is sensed idle. An analytical region is derived for the secondary users to operate in while the primary channel is free.