An analysis of distributed and asynchronous wireless group communication mechanisms

Asynchronous group communication systems propagate updates from each group member to every other member. Contemporary users are wireless and operate from a variety of locations. Hence, we investigate the propagation performance for these users. An analysis of wireless users in academia, corporation and in a city-wide hotspot federation shows that the availability durations and the duration between sessions depends on the locale. A longer term analysis shows that the user session lengths are becoming smaller while the duration between sessions are becoming larger with significant user churn. We show that the propagation performance depends on the locale. New users incur a heavy cost in receiving updates from prior users; applications need to develop expiration mechanisms to reduce this overhead. Also, since users regularly leave the system, practical communication mechanisms need to choose their propagation periodicity in order to respond to scenarios when the user abruptly leaves the system without propagating their updates to other users.