In multiagent surveillance missions, a group of agents monitors some points of interest to provide situational awareness. For agents with local communication capabilities, one way to transmit the surveillance information to a base is streaming by the instantaneous data via multihop communications over a connected network. However, a connected communication network may become disconnected if some agents leave the surveillance area (for example, for refueling). This paper presents a locally applicable, efficient, and scalable strategy that guarantees a connected communication network between the base and the agents in the face of any agent removal. The proposed decentralized strategy is based on a sequence of local replacements, which are initiated by the agent leaving the network. It is shown that the replacement sequence always ends with the relocation of an agent, for which the absence from its current position does not disconnect the network. Furthermore, the optimality (that is, the minimum number of r...
In this paper, we present a decentralized recovery mechanism to maintain network connectivity in arbitrary agent removal. The replacement control problem has been initially introduced in @cite_36 , and replacements by minimum degree neighbors have been presented as a solution. Here, we generalize the connectivity maintenance scheme as the message passing strategy, and we show that this method maintains connectivity even in the case of agents sharing minimum amount of information, i.e. only node IDs. Moreover, we show that utilizing @math -criticality information in the message passing strategy significantly improves the optimality of the solution.
@cite_36
2313205331 2118941026 2950479988 2141327408
Connectivity is a fundamental property in many networked systems for communication and coordination among the agents. Removal of any agent from a network may destroy its connectivity. In order to maintain the connectivity of mobile networked systems in agent loss, one can design a robust network topology such that the network is tolerant to a finite number of agent losses, and or develop a control strategy, such that the network reconfigures itself until the connectivity requirements are satisfied. In this paper, we introduce a decentralized control scheme based on a sequence of replacements, each of which occurs between an agent and one of its neighbors. The proposed scheme always maintains the graph connectivity, and it does not rely on any gathering of global information either a priori or at the intermediate steps of a mission. Moreover, the proposed scheme does not cause any increase in the total number of edges and the maximum node degree in a graph, thus it assures no increase in the overall communication cost due to the topological changes. In this study, we validate the control strategy by means of an analytical proof and simulation results. In order to accomplish cooperative tasks, multi-robot systems are required to communicate among each other. Thus, maintaining the connectivity of the communication graph is a fundamental issue. Connectivity maintenance has been extensively studied in the last few years, but generally considering only kinematic agents. In this paper we will introduce a control strategy that, exploiting a decentralized procedure for the estimation of the algebraic connectivity of the graph, ensures the connectivity maintenance for groups of Lagrangian systems. The control strategy is validated by means of analytical proofs and simulation results. Consider a scenario of broadcasting a common content to a group of cooperating wireless nodes that are within proximity of each other. Nodes in this group may receive partial content from the source due to packet losses over wireless broadcast links. We further consider that packet losses are different for different nodes. The remaining missing content at each node can then be recovered, thanks to cooperation among the nodes. In this context, the minimum amount of time that can guarantee a complete acquisition of the common content at every node is referred to as the completion time. It has been shown that instantly decodable network coding (IDNC) reduces the completion time as compared to no network coding in this scenario. Yet, for applications such as video streaming, not all packets have the same importance and not all users are interested in the same quality of content. This problem is even more interesting when additional, but realistic constraints, such as strict deadline, bandwidth, or limited energy are added to the problem formulation. We assert that direct application of IDNC in such a scenario yields poor performance in terms of content quality and completion time. In this paper, we propose a novel Content-Aware IDNC scheme that improves content quality and network coding opportunities jointly by taking into account significance of each packet towards the desired quality of service (QoS). Our proposed Content-Aware IDNC maximizes the quality under the completion time constraint, and minimizes the completion time under the quality constraint.We demonstrate the benefits of Content-Aware IDNC through simulations. A distributed control law that guarantees connectivity maintenance in a network of multiple mobile agents is presented. The control law, which lets the agents perform formation manoeuvres, respects sensor limitations by allowing each agent to only take into account agents within its sensing radius. In contrast to previous approaches to the problem, the proposed control law does not attain infinite values whenever an edge of the communication graph tends to be lost. This is achieved via the use of decentralised navigation functions, which are bounded potential fields. The navigation functions are defined to take into account the connectivity maintenance objective. The authors first treat the case of connectivity maintenance for a static communication graph and then extend the result to the case of dynamic graphs. The results are illustrated on a formation control problem.