earticle

영어

In this paper, we present a dynamic spectrum access strategy to reduce the average overall system time of secondary users (SUs) in multi-channel cognitive radio networks. Before transmitting a packet, SU senses the spectrum environment. If there are free channels in the system, SU randomly selects one for transmitting. If all the channels are busy, we consider a probability-based spectrum selection scheme in which the access channel is chosen based on the predetermined probabilities for saving the sensing power and reducing the overall system time of SU. When the transmission of SU is preempted by the primary user (PU), SU will stay on the operating channel and retransmit the whole data after PU leaves the channel. SU may undergo multiple interruptions before finishing a successful transmission. The interruptions and retransmissions inevitably increase the overall system time of SU. We propose an analytical model by applying the preemptive repeat identical priority M/G/1 queueing theory. Based on the model, we obtain the overall system time expression of SU packets under different spectrum environment and find the optimal distribution vector for the probability-based spectrum access scheme to minimize the average overall system time for SU.