Dynamic spectrum access in WLAN channels: empirical model and its stochastic analysis

In this work we are concerned with dynamically sharing the spectrum in the time-domain by exploiting whitespace between the bursty transmissions of a primary user, represented by an 802.11b-based wireless LAN (WLAN). For deriving such schemes we need to establish a model of the WLAN's medium access as to predict its behavior accurately. Moreover, a balance between accuracy and complexity needs to be struck as to render the model useful in practice. We emphasize that our model is based on actual measurements at 2.4GHz using a vector signal analyzer. We have shown previously that a semi-Markov model is a viable approach for modeling the busy/idle durations. In the present paper we extend our results by (i) expanding the measurement setup and looking at more realistic traffic scenarios, (ii) providing a better approximation to the distribution of the idle durations, and (iii) fitting a phasetype approximation to arrive at a computationally simpler description. The goodness-of-fit of the proposed models is evaluated using the Kolmogorov-Smirnov test.