Dynamic Resource Reservation and Connectivity Tracking to Support Real-Time Communication among Mobile Units
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Dynamic Resource Reservation and Connectivity Tracking to Support Real-Time Communication among Mobile Units Tullio Facchinetti Dipartimento di Informatica e Sistemistica (DIS), Universit`a di Pavia, 27100 Pavia, Italy Email: [email protected]
Giorgio Buttazzo Dipartimento di Informatica e Sistemistica (DIS), Universit`a di Pavia, 27100 Pavia, Italy Email: [email protected]
Luis Almeida Instituto de Engenharia Electr´onica e Telem´atica de Aveiro (IEETA), and Departamento de Electr´onica e Telecomunicac¸o˜es (DET), Universidade de Aveiro, 3810-193 Aveiro, Portugal Email: [email protected] Received 29 June 2004; Revised 25 April 2005 Wireless communication technology is spreading quickly in almost all the information technology areas as a consequence of a gradual enhancement in quality and security of the communication, together with a decrease in the related costs. This facilitates the development of relatively low-cost teams of autonomous (robotic) mobile units that cooperate to achieve a common goal. Providing real-time communication among the team units is highly desirable for guaranteeing a predictable behavior in those applications in which the robots have to operate autonomously in unstructured environments. This paper proposes a MAC protocol for wireless communication that supports dynamic resource reservation and topology management for relatively small networks of cooperative units (10–20 units). The protocol uses a slotted time-triggered medium access transmission control that is collision-free, even in the presence of hidden nodes. The transmissions are scheduled according to the earliest deadline first scheduling policy. An adequate admission control guarantees the timing constraints of the team communication requirements, including when new nodes dynamically join or leave the team. The paper describes the protocol focusing on the consensus procedure that supports coherent changes in the global system. We also introduce a distributed connectivity tracking mechanism that is used to detect network partition and absent or crashed nodes. Finally, a set of simulation results are shown that illustrate the effectiveness of the proposed approaches. Keywords and phrases: topology, wireless, mobile, real time, distributed network.
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INTRODUCTION
The relevance of ah hoc networking is clearly stated by several authors (e.g., [1, 2]) that present specific applications suitable for mobile ad hoc networks (MANETs). One class of applications is the interconnection of multiple robotic mobile units. Groups of such units represent an attractive solution in those situations in which the environment’s conditions are not suitable for direct human intervention. This can occur This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
in space missions, in the exploration of hazardous environment, in demining, surveillance, and civil protection [3]. In these cases
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