Towards a Versatile Problem Diagnosis Infrastructure for LargeWireless Sensor Networks

In this position paper, we address the issue of durable maintenance of a wireless sensor network, which will be crucial if the vision of large, long-lived sensornets is to become reality. Durable maintenance requires tools for diagnosing and fixing occurring problems, which can range from internode connectivity losses, to time synchronization problems, to software bugs. While there are solutions for fixing problems, an appropriate diagnostic infrastructure is essentially still lacking. We argue that diagnosing a sensornet application requires the ability to dynamically and temporarily extend the application on a selected group of nodes with virtually any functionality. We motivate this claim based on deployment experiences to date and propose a highly nonintrusive solution to dynamically extending a running application on a resource-constrained sensor node

Gossip-Based Dissemination of Time

Time synchronization between computers within a very large, highly dynamic network is a challenging task. Current solutions operate mostly in a hierarchical client-server mode based on a static configuration of logical connections, which tends to lack the scalability and robustness to failures.\ud \ud In this thesis, the author presents the Gossiping Time Protocol (GTP) --- an approach to time synchronization employing the theory of epidemics. GTP is a completely decentralized solution in which all the hosts form a peer-to-peer network. They gossip with each other in order to propagate accurate time. The algorithms constituting GTP have desired properties of scalability and robustness, while offering fast and quite accurate synchronization. Experimental results obtained with a prototype implementation on an emulated network of more than 64,000 hosts scattered across the machines of a wide-area cluster computer confirm the above claim

On Hierarchical Routing in Wireless Sensor Networks

Hierarchical routing (HR) has been touted as one of the major point-to-point routing techniques for large wireless sensor networks (WSNs). Yet, in contrast to numerous theoretical analyzes and high-level simulations, little work has been done to evaluate this technique in realistic WSN settings and to compare various proposed protocols. We fill this gap in this paper. Based on the analysis of a few tens of proposed HR infrastructures, we develop a framework that captures the common characteristics of the infrastructures and at the same time identifies various design points where the infrastructures differ. We then evaluate the implementation of the framework on a 60-node testbed and in TOSSIM. Our results demonstrate how HR performs in practice, how such performance diverges from high-level simulation results, and how it is affected by different design decisions in different infrastructures. Ultimately, our goal is to identify under which circumstances HR can be practical in WSNs

Using Area Hierarchy for Multi-Resolution Storage and Search in Large Wireless Sensor Networks

Abstract—We consider multi-resolution storage, a technique for providing scalable adaptive data fidelity, necessary for many applications of large wireless sensor networks (WSNs). Although the previously proposed design of multi-resolution storage, based on quad trees and geographic routing, is conceptually simple, it exhibits inherent problems if applied in real-world WSNs. To address these problems, we revisit some of the networking assumptions and propose an alternative design that employs an overlay combining area and landmark hierarchies. Simulations and initial experiments with a prototype embedded implementation indicate that our solution can be scalable and can work on real hardware, which motivates further research. I

The PL-Gossip algorithm

Many recently proposed sensornet applications require large number of sensor nodes operating over long periods of time. In contrast to the first-generation sensornet deployments, these applications involve sophisticated internode communication rather than simple tree-based data collection. The examples include network maintenance, data-centric storage, object tracking, and various query engines. If these proposals for next-generation applications are ever to become reality, we will need solutions for self-organization of very large networks. We argue that these applications need methods for organizing nodes into recursive geometric structures, for example, proximity-based hierarchies. Such structures should provide naming that facilitates amongst others, routing, multicasting, and data aggregation and fusion. This paper presents a novel algorithm for dynamically organizing nodes in a sensornet into an area hierarchy. The algorithm employs gossiping, guaranteeing predictable maintenance traffic, which is a crucial property when it comes to energy conservation. Simulations show that the algorithm scales to large networks, works well in the presence of message loss and networ

Musings Upon the Theme of Peer-to-Peer Search

Efficient search is an active topic in peer-to-peer networks. To date most of the work in this area has been oriented towards devising new algorithms. However, little has been done to understand the fundamental similarities and differences between the wide variety of proposed designs. Such an understanding would be invaluable for the architects of future decentralized systems. In order to stimulate further research in this direction, we present an overview of six example systems whose designs cover the majority of current research themes in peer-to-peer search. The diversity of the presented approaches demonstrates the breadth of the design space available. Based on these examples, we identify a number of open issues that require deeper exploration.

CONCURRENCY AND COMPUTATION: PRACTICE AND EXPERIENCE Concurrency Computat.: Pract. Exper. 2006;?:1–13 Prepared using cpeauth.cls [Version: 2002/09/19 v2.02]

management of semantic overlay network

M.: Sensor network bugs under the magnifying glass

If the vision of large, long-lived wireless sensor networks serving the society is to become reality, deployment and durable maintenance need much more attention. Both these issues require the ability to first diagnose, and then fix occurring problems. While there are solutions for fixing problems, an appropriate diagnostic infrastructure is essentially still lacking. Our position is that diagnosing a sensornet application requires the ability to dynamically and temporarily extend the application on a selected group of nodes with virtually any functionality. We propose a solution to this problem that is highly nonintrusive