G-MAC: Geographical group MAC for event-driven wireless sensor networks

This paper proposes geographical group MAC (G-MAC) for event-driven wireless sensor networks. G-MAC is a hybrid MAC protocol combined with the contention-based and contention-free MAC protocols. Collision avoidance is one major task in the contention-based MAC protocols. Collision is much significant as a channel is shared by a large number of contending hosts. If it is possible to reduce the number of contending hosts, collisions could be decreased. This is a basic idea of the proposed G-MAC. By diving the area covered by the sensing hosts into the multiple geographical groups and by separating the channel access time for each group, it could reduce the number of contending hosts. Also, G-MAC needs the time synchronization and channel access scheduling for the separating groups to avoid the interference with others. Simply to say, the proposed G-MAC works on the contention-based channel access for the hosts within a group, but operates on the contention-free channel access among the groups. Computer simulation is conducted to study the effects of the number of groups on collision, packet loss and delay. This paper presents that the proposed G-MAC has the superior performance of collision avoidance and packet loss compared to the contention-based MAC protocols.