An Adaptive TDMA Protocol for Soft Real-Time Wireless Communication among Mobile Autonomous Agents

Abstract

Interest on using mobile autonomous agents has been growing, recently, due to their capacity to cooperate for diverse purposes, from rescue to demining and security. Such cooperation typically requires the exchange of state data that is time sensitive and thus, applications should be aware of temporal data coherency. In order to provide such information a real-time communications protocol must be used to prevent unbounded latency of message delivery. This is, however, not a trivial task when using wireless links because of their poor reliability properties, exhibiting high bit error rates, omissions and inconsistencies. This paper describes such a communication protocol that adapts itself to the current conditions of the medium attempting to deliver an adequate timeliness while using the least bandwidth. The protocol operates over IEEE 802.11 networks in both managed and ad-hoc modes and it is fully distributed. It has been developed within the framework of the CAMBADA project at the University of Aveiro, Portugal, which aims at developing a robotic soccer team. This paper describes the protocol and presents some preliminary experimental results. 1. Introduction and