The Information Propagation Speed Upper Bound in Cognitive Radio Networks

The information propagation speed (IPS) of a network specifies how fast the information can be transmitted in a network. In this paper, we derive an IPS upper bound in cognitive radio networks. The upper bound is tight when the number of primary user (PU) channels is large. We discover that the IPS upper bound is determined by both the PU activity level and the transmission range of cognitive radios. When the PU activity level is below a certain threshold value, the IPS upper bound is achieved if cognitive radios transmit at their maximum transmission ranges. When the PU activity level is above the threshold, the cognitive radios have to use a smaller transmission range to reach the IPS upper bound. In addition, we also provide a numerical method for computing the threshold value of PU activity level and the optimal transmission range for achieving the IPS upper bound. The correctness of our analysis is validated by simulations. Our work can provide important insights and guidelines for optimal secondary user placement in cognitive radio networks.