2,687 research outputs found

    Consensus with Ternary Messages

    Full text link
    We provide a protocol for real-valued average consensus by networks of agents which exchange only a single message from the ternary alphabet {-1,0,1} between neighbors at each step. Our protocol works on time-varying undirected graphs subject to a connectivity condition, has a worst-case convergence time which is polynomial in the number of agents and the initial values, and requires no global knowledge about the graph topologies on the part of each node to implement except for knowing an upper bound on the degrees of its neighbors

    An Alloy Verification Model for Consensus-Based Auction Protocols

    Full text link
    Max Consensus-based Auction (MCA) protocols are an elegant approach to establish conflict-free distributed allocations in a wide range of network utility maximization problems. A set of agents independently bid on a set of items, and exchange their bids with their first hop-neighbors for a distributed (max-consensus) winner determination. The use of MCA protocols was proposed, e.g.e.g., to solve the task allocation problem for a fleet of unmanned aerial vehicles, in smart grids, or in distributed virtual network management applications. Misconfigured or malicious agents participating in a MCA, or an incorrect instantiation of policies can lead to oscillations of the protocol, causing, e.g.e.g., Service Level Agreement (SLA) violations. In this paper, we propose a formal, machine-readable, Max-Consensus Auction model, encoded in the Alloy lightweight modeling language. The model consists of a network of agents applying the MCA mechanisms, instantiated with potentially different policies, and a set of predicates to analyze its convergence properties. We were able to verify that MCA is not resilient against rebidding attacks, and that the protocol fails (to achieve a conflict-free resource allocation) for some specific combinations of policies. Our model can be used to verify, with a "push-button" analysis, the convergence of the MCA mechanism to a conflict-free allocation of a wide range of policy instantiations

    Noisy Rumor Spreading and Plurality Consensus

    Full text link
    Error-correcting codes are efficient methods for handling \emph{noisy} communication channels in the context of technological networks. However, such elaborate methods differ a lot from the unsophisticated way biological entities are supposed to communicate. Yet, it has been recently shown by Feinerman, Haeupler, and Korman {[}PODC 2014{]} that complex coordination tasks such as \emph{rumor spreading} and \emph{majority consensus} can plausibly be achieved in biological systems subject to noisy communication channels, where every message transferred through a channel remains intact with small probability 12+ϵ\frac{1}{2}+\epsilon, without using coding techniques. This result is a considerable step towards a better understanding of the way biological entities may cooperate. It has been nevertheless be established only in the case of 2-valued \emph{opinions}: rumor spreading aims at broadcasting a single-bit opinion to all nodes, and majority consensus aims at leading all nodes to adopt the single-bit opinion that was initially present in the system with (relative) majority. In this paper, we extend this previous work to kk-valued opinions, for any k≥2k\geq2. Our extension requires to address a series of important issues, some conceptual, others technical. We had to entirely revisit the notion of noise, for handling channels carrying kk-\emph{valued} messages. In fact, we precisely characterize the type of noise patterns for which plurality consensus is solvable. Also, a key result employed in the bivalued case by Feinerman et al. is an estimate of the probability of observing the most frequent opinion from observing the mode of a small sample. We generalize this result to the multivalued case by providing a new analytical proof for the bivalued case that is amenable to be extended, by induction, and that is of independent interest.Comment: Minor revisio

    Ribosome-messenger recognition in the absence of the Shine-Dalgarno interactions

    Get PDF
    AbstractIn an attempt to understand how Escherichia coli ribosomes recognize the initiator codon on mRNAs lacking the Shine-Dalgamo (SD) sequence, we have studied 30S initiation complex formation in extension inhibition (toeprinting) experiments using (-SD)mRNAs which are known to be reliably translated in E. coli: the plant viral messenger A1MV RNA 4 and two chimaeric mRNAs coding for β-glucuronidase (GUS) and bearing the 5'-untranslated sequence of TMV RNA Ω or the Ω-derived sequence (CAA)n as 5'-leaders. Ribosomal protein Sl and IF3 have been found to be indispensable for translational initiation. Protein S1 appears to be a key recognition element. S1 binds to sequences within the leaders of (-SD)mRNAs thus providing their affinity to E. coli ribosomes
    • …
    corecore