7th Lincs Scientific Highlight - LINCS Annual Workshop with its Scientific Committee

“Can Aloha Achieve Implicit Admission Control?”, by Fabien Mathieu (Inria).
Adaptive Aloha protocols allow several transmitting stations to share the same communication channel, with each transmitter managing its transmissions using an internal state. They form the basis of many networks, including 802.11 networks. In this presentation, we consider a discrete-time scenario where ? “saturated” stations always have to transmit. Using a geometric decay model, we give a new stability condition based on the notion of ambient noise and propose formulas for approximating the behavior. However, comparing these results with simulations shows that for large ? the stable/instable distinction loses its meaning, as only a transient regime is visible at reasonable time scales. In this transient regime, we observe a form of implicit admission control: if ? is too large, some of the stations are in “frozen” states, allowing the others a reasonable access to the channel.