Relying on Safe Distance to Ensure Consistent Group Membership in Ad Hoc Networks

The design of ad hoc mobile applications often requires the availability of a consistent view of the application state among the participating hosts. Such views are important be- cause they simplify both the programming and verification tasks. Essential to constructing a consistent view is the abil- ity to know what hosts are within proximity of each other, i.e., form a group in support of the particular application. In this paper we propose a protocol that allows hosts within communication range to maintain a consistent view of the group membership despite movement and frequent discon- nections. The novel features of this protocol are its reliance on location information and a conservative notion of logical connectivity that creates the illusion of announced discon- nection. Movement patterns and delays are factored in the policy that determines which physical connections are sus- ceptible to disconnection. An implementation of the protocol in Java is available for testing.