Gossip consensus algorithms via quantized communication

This paper considers the average consensus problem on a network of digital links, and proposes a set of algorithms based on pairwise ''gossip'' communications and updates. We study the convergence properties of such algorithms with the goal of answering two design questions, arising from the literature: whether the agents should encode their communication by a deterministic or a randomized quantizer, and whether they should use, and how, exact information regarding their own states in the update.Comment: Accepted for publicatio

Gossip Consensus Algorithm Based on Time-Varying Influence Factors and Weakly Connected Graph for Opinion Evolution in Social Networks

We provide a new gossip algorithm to investigate the problem of opinion consensus with the time-varying influence factors and weakly connected graph among multiple agents. What is more, we discuss not only the effect of the time-varying factors and the randomized topological structure but also the spread of misinformation and communication constrains described by probabilistic quantized communication in the social network. Under the underlying weakly connected graph, we first denote that all opinion states converge to a stochastic consensus almost surely; that is, our algorithm indeed achieves the consensus with probability one. Furthermore, our results show that the mean of all the opinion states converges to the average of the initial states when time-varying influence factors satisfy some conditions. Finally, we give a result about the square mean error between the dynamic opinion states and the benchmark without quantized communication

Recent advances on filtering and control for nonlinear stochastic complex systems with incomplete information: A survey

This Article is provided by the Brunel Open Access Publishing Fund - Copyright @ 2012 Hindawi PublishingSome recent advances on the filtering and control problems for nonlinear stochastic complex systems with incomplete information are surveyed. The incomplete information under consideration mainly includes missing measurements, randomly varying sensor delays, signal quantization, sensor saturations, and signal sampling. With such incomplete information, the developments on various filtering and control issues are reviewed in great detail. In particular, the addressed nonlinear stochastic complex systems are so comprehensive that they include conventional nonlinear stochastic systems, different kinds of complex networks, and a large class of sensor networks. The corresponding filtering and control technologies for such nonlinear stochastic complex systems are then discussed. Subsequently, some latest results on the filtering and control problems for the complex systems with incomplete information are given. Finally, conclusions are drawn and several possible future research directions are pointed out.This work was supported in part by the National Natural Science Foundation of China under Grant nos. 61134009, 61104125, 61028008, 61174136, 60974030, and 61074129, the Qing Lan Project of Jiangsu Province of China, the Project sponsored by SRF for ROCS of SEM of China, the Engineering and Physical Sciences Research Council EPSRC of the UK under Grant GR/S27658/01, the Royal Society of the UK, and the Alexander von Humboldt Foundation of Germany

Potential-based analysis of social, communication, and distributed networks

In recent years, there has been a wide range of studies on the role of social and distributed networks in various disciplinary areas. In particular, availability of large amounts of data from online social networks and advances in control of distributed systems have drawn the attention of many researchers to exploit the connection between evolutionary behaviors in social, communication and distributed networks. In this thesis, we first revisit several well-known types of social and distributed networks and review some relevant results from the literature. Building on this, we present a set of new results related to four different types of problems, and identify several directions for future research. The study undertaken and the approaches adopted allow us to analyze the evolution of certain types of social and distributed networks and also to identify local and global patterns of their dynamics using some novel potential-theoretic techniques. Following the introduction and preliminaries, we focus on analyzing a specific type of distributed algorithm for quantized consensus known as an unbiased quantized algorithm where a set of agents interact locally in a network in order to reach a consensus. We provide tight expressions for the expected convergence time of such dynamics over general static and time-varying networks. Following this, we introduce new protocols using a special class of Markov chains known as Metropolis chains and obtain the fastest (as of today) randomized quantized consensus protocol. The bounds provided here considerably improve the state of the art over static and dynamic networks. We make a bridge between two classes of problems, namely distributed control problems and game problems. We analyze a class of distributed averaging dynamics known as Hegselmann-Krause opinion dynamics. Modeling such dynamics as a non-cooperative game problem, we elaborate on some of the evolutionary properties of such dynamics. In particular, we answer an open question related to the termination time of such dynamics by connecting the convergence time to the spectral gap of the adjacency matrices of underlying dynamics. This not only allows us to improve the best known upper bound, but also removes the dependency of termination time from the dimension of the ambient space. The approach adopted here can also be leveraged to connect the rate of increase of a so-called kinetic-s-energy associated with multi-agent systems to the spectral gap of their underlying dynamics. We describe a richer class of distributed systems where the agents involved in the network act in a more strategic manner. More specifically, we consider a class of resource allocation games over networks and study their evolution to some final outcomes such as Nash equilibria. We devise some simple distributed algorithms which drive the entire network to a Nash equilibrium in polynomial time for dense and hierarchical networks. In particular, we show that such games benefit from having low price of anarchy, and hence, can be used to model allocation systems which suffer from lack of coordination. This fact allows us to devise a distributed approximation algorithm within a constant gap of any pure-strategy Nash equilibrium over general networks. Subsequently we turn our attention to an important problem related to competition over social networks. We establish a hardness result for searching an equilibrium over a class of games known as competitive diffusion games, and provide some necessary conditions for existence of a pure-strategy Nash equilibrium in such games. In particular, we provide some concentration results related to the expected utility of the players over random graphs. Finally, we discuss some future directions by identifying several interesting problems and justify the importance of the underlying problems

Distributed Parameter Estimation in Sensor Networks: Nonlinear Observation Models and Imperfect Communication

The paper studies distributed static parameter (vector) estimation in sensor networks with nonlinear observation models and noisy inter-sensor communication. It introduces \emph{separably estimable} observation models that generalize the observability condition in linear centralized estimation to nonlinear distributed estimation. It studies two distributed estimation algorithms in separably estimable models, the $\mathcal{NU}$ (with its linear counterpart $\mathcal{LU}$) and the $\mathcal{NLU}$. Their update rule combines a \emph{consensus} step (where each sensor updates the state by weight averaging it with its neighbors' states) and an \emph{innovation} step (where each sensor processes its local current observation.) This makes the three algorithms of the \textit{consensus + innovations} type, very different from traditional consensus. The paper proves consistency (all sensors reach consensus almost surely and converge to the true parameter value,) efficiency, and asymptotic unbiasedness. For $\mathcal{LU}$ and $\mathcal{NU}$, it proves asymptotic normality and provides convergence rate guarantees. The three algorithms are characterized by appropriately chosen decaying weight sequences. Algorithms $\mathcal{LU}$ and $\mathcal{NU}$ are analyzed in the framework of stochastic approximation theory; algorithm $\mathcal{NLU}$ exhibits mixed time-scale behavior and biased perturbations, and its analysis requires a different approach that is developed in the paper.Comment: IEEE Transactions On Information Theory, Vol. 58, No. 6, June 201