Opportunistic channel access scheme for cognitive radio system based on residual white space distribution

We propose an opportunistic channel access scheme for cognitive radio-enabled secondary networks. In our work, we model the channel occupancy due to Primary User (PU) activity as a 2-state Alternating Renewal Process, with alternating busy and idle periods. Once a Secondary Node (SN) senses the channel idle, the proposed scheme uses the residual idle time distribution to estimate the transmission duration in the remaining idle time, subject to an acceptable PU interference constraint. The SN transmits the frames within the transmission duration without further sensing the channel, thereby reducing the average sensing overhead per transmitted frame. The analytical formulation used by the scheme does not require the SN to keep track of the start of the idle period. We validate the analytical formulations using simulations, and compare the performance of the proposed scheme with a Listen-Before-Talk (LBT) scheme.