Abstract-A primary functionality of wireless sensor networks (WSNs) is transporting the information acquired by the sensors as per the desired application requirements. The diverse applications supported by WSNs also stipulate a diverse range of reliability requirements for the transport of various information types. The continuous variation of application requirements and dynamic operational perturbations complicates the design of a generic solution for information transport in WSNs. In this paper, we present a new framework for generic information transport (GIT), which considers varied application requirements and evolvable network conditions in WSNs. GIT manages the information and utilizes a probabilistic approach to ensure tunable reliability of information transport. The GIT framework is distributed in nature and performs its operations locally. The simulation results validate the tunability of the GIT framework. In some setups GIT achieves up to 4-5 times reduction in number of transmissions compared to existing approaches.

A prominent functionality of a Wireless Sensor Network (WSN) is environmental monitoring. For this purpose the WSN creates a model for the real world by using abstractions to parse the collected data. Being cross-layer and application-oriented, most of WSN research does not allow for a widely accepted abstraction. A few approaches such as database-oriented and publish/subscribe provide acceptable abstractions by reducing application dependency and hiding communication details. Unfortunately, these approaches ignore the spatial correlation of sensor readings and still address single sensor nodes. In this work we present a novel approach based on a "world model" that exploits the spatial correlation of sensor readings and represents them as a collection of regions called maps. Maps are a natural way for the presentation of the physical world and its physical phenomena over space and time. Our Map-based World Model (MWM) abstracts from low-level communication issues and supports general applications by allowing for efficient event detection, prediction and queries. In addition our MWM unifies the monitoring of physical phenomena with network monitoring which maximizes its generality. Using two case studies we highlight the simplicity and also the versatility of the proposed architecture. From our approach we deduce a general modeling and design methodology for WSNs. Categories and Subject Descriptors General TermsWorld model, design paradigm, global and local view

Abstract

Distributed mobile transactions utilize commit protocols to achieve atomicity and consistent decisions. This is challenging as mobile environments are typically characterized by frequent perturbations such as network disconnections and node failures. On one hand environmental constraints on mobile participants and wireless links may increase the resource blocking time of fixed participants. On the other hand frequent node and link failures complicate the design of atomic commit protocols by increasing both the transaction abort rate and resource blocking time. Hence, the deployment of classical commit protocols (such as two-phase commit) does not reasonably extend to distributed infrastructure-based mobile environments driving the need for perturbation-resilient commit protocols.In this paper, we comprehensively consider and classify the perturbations of the wireless infrastructure-based mobile environment according to their impact on the outcome of commit protocols and on the resource blocking times. For each identified perturbation class a commit solution is provided. Consolidating these sub-solutions, we develop a family of fault-tolerant atomic commit protocols that are tunable to meet the desired perturbation needs and provide minimized resource blocking times and optimized transaction commit rates. The framework is also evaluated using simulations and an actual testbed deployment.

Abstract-The support of distributed atomic transactions in mobile ad-hoc networks (MANET) is a key requirement for many mobile application scenarios. Atomicity is a fundamental property that ensures that all nodes decide a consistent outcome. As MANETs are characterized by frequent perturbations due to network partitioning and the fragility of nodes, providing atomicity is challenging. Existing protocols that ensure strict atomicity in MANETs are either bound to specific mobility pattern or based on building blocks such as consensus or group membership, not allowing arbitrary partitions or requiring exact knowledge about the members of a partition. These assumptions limit the deployment of these protocols to very restricted MANET scenarios, and may lead to poor commit rate, high message overhead or blocking related to intolerably long Commit/Abort decision times.In this paper, we present the first Partition-Tolerant Atomic Commit protocol (ParTAC) for MANETs which does not rely on consensus or group partition membership. As a consequence, ParTAC supports a significantly wider range of mobility patterns and partitioning scenarios than existing protocols. To reduce Commit/Abort decision times and prevent the protocol from blocking, ParTAC follows a best-effort strategy by defining a lifetime for every transaction after which the transaction is aborted. Further, we introduce a new coordination strategy based on a flexible pre-selection of multiple coordinators among the participating nodes. Thus, the failure of a single coordinator can be tolerated in the presence of network partitioning. Moreover, transactions can be aborted by any coordinator based on lifetime expiration. ParTAC is evaluated using simulations to demonstrate the performance of the protocol in terms of commit rate, message efficiency and Commit/Abort decision time.

No abstract

No abstract

In the expanding e-society, mobile embedded systems are increasingly used to support transactions such as for banking or database applications. Such systems entail a range of heterogeneous entities - both the devices and the networks connecting them. While these systems are exposed to frequent and varied perturbations, the support of atomic distributed transactions is still a fundamental requirement to achieve consistent decisions. Guaranteeing atomicity and high performance in traditional fixed wired networks is based on the assumption that node and link failures occur rarely. This assumption is often not supported in current and upcoming mobile environments where the heterogeneity and mobility often result in link and node failures as a dominant operational scenario. In order to continue guaranteeing strict atomicity while providing for high efficiency (low resource blocking time of transaction participants and message overhead) and acceptable commit rate, transactional fault-tolerance techniques need to be revisited perhaps at the cost of transaction execution time. In this paper, we provide a comprehensive classification of perturbations for a wide range of mobile environments including infrastructure-based, ad-hoc, and hybrid environments. We also investigate the impact of these perturbations on the design of mobile transactions. In particular we argue for the delay-awareness of mobile transactions to allow for the fault-tolerance mechanisms to ensure resilience to the various and frequent perturbations.