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This paper presents a group communication system for mobile devices, called MobileGCS. Mobile communication is slow, expensive and suffers from occasionally disconnections, especially when users are in movement. MobileGCS is based on SMS and enables group communication despite these restrictions. It provides all primitives needed for a chat application and handles process failures. As mobile communication is expensive, MobileGCS is designed for small message overhead and, additionally, exploits SMS based message relaying to handle short-term disconnections. In this work, we present the group maintenance service and the multicast service of MobileGCS. In order to distribute the overhead of failure discovery over all processes we introduce the concept of a circle of responsibility for failure detection. We discuss informally that MobileGCS can handle the most common failures while keeping the message overhead very low. |
