Coordinated Broadcast-based Request-Reply and Group Management for Tightly-Coupled Wireless Systems

摘要

As the domain of cyber-physical systems continues to grow, an increasingnumber of tightly-coupled distributed applications will be implemented on topof wireless networking technologies. Some of these applications, includingcollaborative robotic teams, work in a coordinated fashion, whereby adistinguished node takes control decisions and sends commands to other nodes,which in turn perform the requested action/operation and send back areply/acknowledgment. The implementation of such interactions via reliablepoint-to-point flows may lead to a significant performance degradation due tocollisions, especially when the system operates close to the capacity of thecommunication channel. We propose a coordinated protocol which exploits thebroadcast nature of the wireless medium in order to support thisapplication-level interaction with a minimal number of message transmissionsand predictable latency. The protocol also comes with group managementfunctionality, allowing new processes to join and existing processes to leavethe group in a controlled way. We evaluate a prototype implementation overWiFi, using a simulated setup as well as a physical testbed. Our results showthat the proposed protocol can achieve significantly better performancecompared to point-to- point approaches, and remains fully predictable anddependable even when operating close to the wireless channel capacity.