On the Throughput of Ad-Hoc Networks using Connectivity Graphs

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Under distributed decision-making (a.k.a. social learning), several agents cooperate according to a communication graph to solve a classification task. A traditional assumption in social learning is that the spatial dependence across the agents’ data is not available, while each individual agent is assumed to know a local model encoding the marginal distribution of its personal data. Recent work shows that, when some joint parametric model is available to describe the spatial dependence, the theory of copul

Centrality indices, such as closeness and eccentricity, are key to identifying influential nodes within a network, with applications ranging from social and biological networks to communication and transportation systems. However, computing these indices for every node in large graphs is computationally prohibitive due to the need for solving the All-Pairs Shortest Path (APSP) problem. This paper introduces a framework for approximating closeness and eccentricity centrality by selecting a sequence of strate

We design and evaluate a traffic anonymization protocol for wireless networks, aiming to protect against computationally powerful adversaries. Our protocol builds on recent key-generation techniques, that leverage intrinsic properties of the wireless together with standard coding techniques. We show how to exploit the security properties of such keys to design a Tor-like anonymity network, without making any assumptions about the computational capabilities of an adversary. Our analysis and evaluation on sim

Processing large graphs is an important part of the big-data problem. Recently a number of scale-up systems such as X-Stream, Graphchi and Turbograph have been proposed for processing large graphs using secondary storage on a single machine. The design and evaluation of these systems however have focused on physical machines. We expect that a natural evolution of such systems is to the cloud where a virtual machine would run the graph processing algorithm and access the graph from secondary storage remotely

We present a structured Quantize-Map-and- Forward (QMF) scheme for cooperative communication over wireless networks, that employs LDPC ensembles for the node operations and message-passing algorithms for decoding. We demonstrate through extensive simulation results over the full- duplex parallel relay network, that our scheme, with no transmit channel state information, offers a robust performance over fading channels and achieves the full diversity order of our network at moderate SNRs.

Traditionally, spatial analysis of point pattern has been mostly focused on Euclidean space. As many human related phenomena take place on a network, the assumption of a continuous isotropic space fails to describe events which actually occur on a one-dimensional subset of this space. Thus, recently, researchers have begun integrating network structure constraints to study point patterns. The focus of this report is primarily aimed at the integration of the network structure constraints in studying the firs

Numerous methods have been developed for inference of gene regulatory networks from expression data, however, their strengths and weaknesses remain poorly understood. Accurate and systematic evaluation of these methods is hampered by the difficulty of constructing adequate benchmarks and the lack of tools for a differentiated analysis of network predictions on such benchmarks. Here, we present the new version (3.0) of GeneNetWeaver (GNW), an open-source tool for in silico benchmark generation and performanc

Most papers addressing consensus in wireless ad hoc networks adopt system models similar to those developed for wired networks. These models are focused towards node failures while ignoring link failures, and thus are poorly suited for wireless ad hoc networks. The recently proposed HO model does not have this drawback. The paper shows that an existing algorithm and the HO model can be used for multi-hop wireless ad hoc networks, if extended with an adequate communication layer. The description of the commu

We present an architecture for implementing a wireless physical layer in a packet-based network simulator. We have integrated this architecture in the popular ns-2 network simulator and used it to implement an impulse-radio ultra-wide band (IR-UWB) physical layer. Contrary to the current wireless physical layer implementation of ns-2, in our case a packet is fully received by our physical layer before being delivered to the MAC layer. A packet detection and timing acquisition model has been implemented. Fur

The throughput of wireless networks is known to scale poorly when the number of users grows. The rate at which an arbitrary pair of nodes can communicate must decrease to zero as the number of users tends to infinity, under various assumptions. One of them is the requirement that the network is fully connected: the computed rate must hold for any pair of nodes of the network. We show that this requirement can be responsible for the lack of throughput scalability. We consider a two-dimensional network of ext

Failure location in transparent optical networks is difficult because of the large amount of alarms that a failure can trigger and because of corrupted alarms. One problem that network operators often face is how to set the thresholds in monitoring devices. Setting the thresholds low results in false alarms, whereas setting them high presents the risk of missing a significant degradation in network performance because of missing alarms. In this work, we study the time complexity of the failure location prob

We propose a novel detection method for non-coherent synchronization (signal acquisition) in multi-access UWB impulse radio (IR) networks. It is designed to solve the IUI (Inter-User Interference) that occurs in some ad-hoc networks where concurrent transmissions are allowed with heterogeneous power levels. In such scenarios, the conventional detection method, which is based on correlating the received IR signal with a Template Pulse Train (TPT), does not always perform well. Our proposal has similar comple

We consider the problem of bootstrapping self-organized mobile ad hoc networks (MANET), i.e. reliably determining in a distributed and self- organized manner the services to be offered by each node when neither the identity nor the number of the nodes in the network is initially available. To this means we define a variant of the traditional consensus problem, by relaxing the requirement for the set of participating processes to be known by all at the beginning of the computation. This assumption captures t

Multi-hop hybrid networks can help providing both high bandwidth and broad coverage for wireless data networks. We focus on CSMA/CA-based networks and take IEEE 802.11 as a concrete example. We show that the three fundamental operations of synchronization, routing and energy saving can be implemented in an integrated way. Our integrated solution is based on the periodic computation of a broadcast tree among the nodes reporting to the same Access Point, starting from the Access Point itself. We use the nodes

In this paper we present Scalable Position-Based Multicast (SPBM), a multicast routing protocol for ad-hoc networks. SPBM uses the geographic position of nodes to provide a highly scalable group membership scheme and to forward data packets with a very low overhead. SPBM bases its multicast forwarding decision on whether there are group members located in a given direction or not, allowing for a hierarchical aggregation of group members contained in geographic regions: the larger the distance between a regi

This paper addresses the problem of building scalable semantic overlay networks. Our approach follows the principle of data independence by separating a logical layer, the semantic overlay for managing and mapping data and metadata schemas, from a physical layer consisting of a structured peer-to-peer overlay network for e±cient routing of messages. The physical layer is used to implement various functions at the logical layer, including attribute-based search, schema management and schema mapping managemen

When striving for reliability, multicast protocols are most commonly designed as deterministic solutions. Such an approach seems to make the reasoning about reliability guarantees (traditionally binary "all-or-nothing"- like) in the face of packet losses and/or node crashes. It is however precisely this determinism that tends to become a limiting factor when aiming at both reliability and scalability, particularly in highly dynamic networks, e.g., ad hoc networks. Gossip-based multicast protocols appear to

Several misbehavior detection and reputation systems have been proposed for mobile ad-hoc networks, relying on direct network observation mechanisms, so-called watchdogs. While these approaches have so far only been evaluated in simulations and restricted to selfish packet dropping, we are interested in the capabilities of a watchdog detection component in a real network. In this paper we present our test-bed implementation of misbehavior detection. Following an evaluation of both the feasibility and detect

A cellular hardware implementation of a spiking neural network with run-time reconfigurable connectivity is presented. It is implemented on a compact custom FPGA board which provides a powerful reconfigurable hardware platform for hardware and software design. Complementing the system, a CPU synthesized on the FPGA takes care of interfacing the network with the external world. The FPGA board and the hardware network are demonstrated in the form of a controller embedded on the Khepera robot for a task of obs

This paper provides a quantative comparison of the efficiency of the self-organized construction processes of the P-Grid and FreeNet peer-to-peer systems. Starting from a defined, realistic network topology we simulate the construction of their access structures and measure the incurred message load and memory usage for routing tables. Besides these results our experimental setup may also be used as a starting point for defining a standard test and evaluation suite for P2P systems.

On the Throughput of Ad-Hoc Networks using Connectivity Graphs

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Self-organized construction of distributed access structures: A comparative evaluation of P-Grid and FreeNet