A Robust Push-To-Talk Service for Wireless Mesh Networks

Push-to-Talk (PTT) is a useful capability for rapidly deployable wireless mesh networks used by first responders. PTT allows several users to speak with each other while using a single, half-duplex, communication channel, such that only one user speaks at a time while all other users listen. Furthermore, enabling regular PSTN phone users (e.g., cell phones) to seamlessly participate in the wireless mesh PTT session is key to supporting the heterogeneous environment commonly found in such settings. This paper presents the architecture and protocol of a robust distributed PTT service for wireless mesh networks. The architecture supports any 802.11 client with SIP-based VoIP software and enables the participation of regular phones. Collectively, the mesh nodes provide the illusion of a single third party call controller, enabling clients to participate via any reachable mesh node. Each PTT group instantiates its own logical floor control manager that is highly available and resilient to mesh connectivity changes such as node crashes and recoveries and network partitions and merges. Experimental results on a fully deployed mesh network consisting of 14 mesh nodes and tens of emulated clients demonstrate the scalability and robustness of the system.