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Consensus in Networked MultiAgent Systems with Adversaries
"... In the past decade, numerous consensus protocols for networked multiagent systems have been proposed. Although some forms of robustness of these algorithms have been studied, reaching consensus securely in networked multiagent systems, in spite of intrusions caused by malicious agents, or adversar ..."
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In the past decade, numerous consensus protocols for networked multiagent systems have been proposed. Although some forms of robustness of these algorithms have been studied, reaching consensus securely in networked multiagent systems, in spite of intrusions caused by malicious agents, or adversaries, has been largely underexplored. In this work, we consider a general model for adversaries in Euclidean space and introduce a consensus problem for networked multiagent systems similar to the Byzantine consensus problem in distributed computing. We present the Adversarially Robust Consensus Protocol (ARCP), which combines ideas from consensus algorithms that are resilient to Byzantine faults and from linear consensus protocols used for control and coordination of dynamic agents. We show that ARCP solves the consensus problem in complete networks whenever there are more cooperative agents than adversaries. Finally, we illustrate the resilience of ARCP to adversaries through simulations and compare ARCP with a linear consensus protocol for networked multiagent systems.
CONSENSUS ALGORITHMS OVER FADING CHANNELS
"... Consensus algorithms permit the computation of global statistics via local communications and without centralized control. We extend previous results by taking into account fading and unidirectional links in ring and random 2D topologies. We study conditions for convergence and present simulation r ..."
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Consensus algorithms permit the computation of global statistics via local communications and without centralized control. We extend previous results by taking into account fading and unidirectional links in ring and random 2D topologies. We study conditions for convergence and present simulation results to verify the analytical results in this paper. We compare the performance of consensus algorithms with a treebased (centralized) approach. Additionally, we implement a slotted ALOHA protocol and compare its performance to that under the initial assumption of perfect scheduling. I.
1 Toward ResourceOptimal Consensus over the Wireless Medium
"... Abstractâ€”We carry out a comprehensive study of the resource cost of averaging consensus in wireless networks. Most previous approaches suppose a graphical network, which abstracts away crucial features of the wireless medium, and measure resource consumption only in terms of the total number of tran ..."
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Abstractâ€”We carry out a comprehensive study of the resource cost of averaging consensus in wireless networks. Most previous approaches suppose a graphical network, which abstracts away crucial features of the wireless medium, and measure resource consumption only in terms of the total number of transmissions required to achieve consensus. Under a pathloss dominated model, we study the resource requirements of consensus with respect to three wirelessappropriate metrics: total transmit energy, elapsed time, and timebandwidth product. First we characterize the performance of several popular gossip algorithms, showing that they may be orderoptimal with respect to transmit energy but are strictly suboptimal with respect to elapsed time and timebandwidth product. Further, we propose a new consensus scheme, termed hierarchical averaging, and show that it is nearly orderoptimal with respect to all three metrics. Finally, we examine the effects of quantization, showing that hierarchical averaging provides a nearly orderoptimal tradeoff between resource consumption and quantization error. I.
CONSENSUS PROBLEMS AND THE EFFECTS OF GRAPH TOPOLOGY IN COLLABORATIVE CONTROL
, 2009
"... In this dissertation, several aspects of design for networked systems are addressed. The main focus is on combining approaches from system theory and graph theory to characterize graph topologies that result in efficient decision making and control. In this framework, modelling and design of sparse ..."
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In this dissertation, several aspects of design for networked systems are addressed. The main focus is on combining approaches from system theory and graph theory to characterize graph topologies that result in efficient decision making and control. In this framework, modelling and design of sparse graphs that are robust to failures and provide high connectivity are considered. A decentralized approach to path generation in a collaborative system is modelled using potential functions. Taking inspiration from natural swarms, various behaviors of the system such as target following, moving in cohesion and obstacle avoidance are addressed by appropriate encoding of the corresponding costs in the potential function and using gradient descent for minimizing the energy function. Different emergent behaviors emerge as a result of varying the weights attributed with different components of the potential function. Consensus problems are addressed as a unifying theme in many collaborative control problems and their robustness and convergence properties are studied. Implications of the continuous convergence property of consensus problems on their reachability and robustness are studied. The effects of link and agent faults on consen
Effect of Network Geometry and Interference on Consensus in Wireless Networks
"... Abstract We study the convergence of the average consensus algorithm in wireless networks in the presence of interference. It is wellknown that convergence of the consensus algorithm improves with network connectivity. However, from a networking standpoint, highly connected wireless networks may ha ..."
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Abstract We study the convergence of the average consensus algorithm in wireless networks in the presence of interference. It is wellknown that convergence of the consensus algorithm improves with network connectivity. However, from a networking standpoint, highly connected wireless networks may have lower throughput because of increased interference. This raises an interesting question: What is the effect of increased network connectivity on the convergence of the consensus algorithm, given that this connectivity comes at the cost of lower network throughput? We address this issue for two types of networks: regular lattices with periodic boundary conditions, and a hierarchical network where a backbone of nodes arranged as a regular lattice supports a collection of randomly placed nodes. We characterize the properties of an optimal TDMA protocol that maximizes the speed of convergence on these networks and provide analytical upper and lower bounds for the achievable convergence rate. Our results show that in a interferencelimited scenario the fastest converging interconnection topology for the consensus algorithm crucially depends on the geometry of node placement. In particular, we prove that asymptotically in the number of nodes, forming longrange interconnections improves the convergence rate in onedimensional tori, while it has the opposite effect in higher dimensions.