Hyperexponential approximation of channel idle time distribution with implication to secondary transmission strategy

Channel idle time distribution (CITD) based secondary transmission strategies have been studied intensively in the literature. The performance of secondary devices are limited by the presumed CITD. But none of them provides a reasonable characterization of the CITD in reality. In this paper, we carefully examine the feature of the CITD using large amount of channel idle time data collected in various WLAN networks. It is demonstrated that the CITD can be well approximated by hyperexponential densities. Based on the estimated density, we propose a novel multiple-shot transmission strategy which takes advantage of the hyperexponential feature of the CITD. This strategy achieves at least twice the increase for the data we examine in average secondary access time compared to conventional transmission strategies.