635 research outputs found
On the capacity of cluster-tree ZigBee networks
Modeling the fundamental performance limits of
Wireless Sensor Networks (WSNs) is of paramount importance
to understand their behavior under worst-case conditions and
to make the appropriate design choices. In that direction this
paper contributes with an analytical methodology for modeling
cluster-tree WSNs where the data sink can either be static or
mobile. We assess the validity and pessimism of analytical model
by comparing the worst-case results with the values measured
through an experimental test-bed based on Commercial-Off-
The-Shelf (COTS) technologies, namely TelosB motes running
TinyOS
Dimensioning and worst-case analysis of cluster-tree sensor networks
Modeling the fundamental performance limits of Wireless Sensor Networks (WSNs) is of paramount
importance to understand their behavior under the worst-case conditions and to make the appropriate
design choices. This is particular relevant for time-sensitive WSN applications, where the
timing behavior of the network protocols (message transmission must respect deadlines) impacts
on the correct operation of these applications. In that direction this paper contributes with a
methodology based on Network Calculus, which enables quick and efficient worst-case dimensioning
of static or even dynamically changing cluster-tree WSNs where the data sink can either
be static or mobile. We propose closed-form recurrent expressions for computing the worst-case
end-to-end delays, buffering and bandwidth requirements across any source-destination path in a
cluster-tree WSN. We show how to apply our methodology to the case of IEEE 802.15.4/ZigBee
cluster-tree WSNs. Finally, we demonstrate the validity and analyze the accuracy of our methodology
through a comprehensive experimental study using commercially available technology, namely
TelosB motes running TinyOS
EMMON - EMbedded MONitoring
Despite the steady increase in experimental deployments, most of research work on WSNs has focused only on
communication protocols and algorithms, with a clear lack of effective, feasible and usable system architectures,
integrated in a modular platform able to address both functional and non–functional requirements. In this paper, we
outline EMMON [1], a full WSN-based system architecture for large–scale, dense and real–time embedded monitoring
[3] applications. EMMON provides a hierarchical communication architecture together with integrated middleware and
command and control software. Then, EM-Set, the EMMON engineering toolset will be presented. EM-Set includes a
network deployment planning, worst–case analysis and dimensioning, protocol simulation and automatic remote
programming and hardware testing tools. This toolset was crucial for the development of EMMON which was designed
to use standard commercially available technologies, while maintaining as much flexibility as possible to meet specific
applications requirements. Finally, the EMMON architecture has been validated through extensive simulation and
experimental evaluation, including a 300+ nodes testbed
Optimal and quasi-optimal energy-efficient storage sharing for opportunistic sensor networks
This paper investigates optimum distributed storage techniques for data preservation, and eventual dissemination, in opportunistic heterogeneous wireless sensor networks where data collection is intermittent and exhibits spatio-temporal randomness. The proposed techniques involve optimally sharing the sensor nodes' storage and properly handling the storage traffic such that the buffering capacity of the network approaches its total storage capacity with minimum energy. The paper develops an integer linear programming (ILP) model, analyses the emergence of storage traffic in the network, provides performance bounds, assesses performance sensitivities and develops quasi-optimal decentralized heuristics that can reasonably handle the problem in a practical implementation. These include the Closest Availability (CA) and Storage Gradient (SG) heuristics whose performance is shown to be within only 10% and 6% of the dynamic optimum allocation, respectively
An efficient genetic algorithm for large-scale transmit power control of dense and robust wireless networks in harsh industrial environments
The industrial wireless local area network (IWLAN) is increasingly dense, due to not only the penetration of wireless applications to shop floors and warehouses, but also the rising need of redundancy for robust wireless coverage. Instead of simply powering on all access points (APs), there is an unavoidable need to dynamically control the transmit power of APs on a large scale, in order to minimize interference and adapt the coverage to the latest shadowing effects of dominant obstacles in an industrial indoor environment. To fulfill this need, this paper formulates a transmit power control (TPC) model that enables both powering on/off APs and transmit power calibration of each AP that is powered on. This TPC model uses an empirical one-slope path loss model considering three-dimensional obstacle shadowing effects, to enable accurate yet simple coverage prediction. An efficient genetic algorithm (GA), named GATPC, is designed to solve this TPC model even on a large scale. To this end, it leverages repair mechanism-based population initialization, crossover and mutation, parallelism as well as dedicated speedup measures. The GATPC was experimentally validated in a small-scale IWLAN that is deployed a real industrial indoor environment. It was further numerically demonstrated and benchmarked on both small- and large-scales, regarding the effectiveness and the scalability of TPC. Moreover, sensitivity analysis was performed to reveal the produced interference and the qualification rate of GATPC in function of varying target coverage percentage as well as number and placement direction of dominant obstacles. (C) 2018 Elsevier B.V. All rights reserved
Collision-free beacon scheduling mechanisms for IEEE 802.15.4/Zigbee cluster-tree wireless sensor networks
The recently standardized IEEE 802.15.4/Zigbee
protocol stack offers great potentials for ubiquitous and pervasive
computing, namely for Wireless Sensor Networks (WSNs).
However, there are still some open and ambiguous issues that turn
its practical use a challenging task. One of those issues is how to
build a synchronized multi-hop cluster-tree network, which is
quite suitable for QoS support in WSNs. In fact, the current IEEE
802.15.4/Zigbee specifications restrict the synchronization in the
beacon-enabled mode (by the generation of periodic beacon
frames) to star-based networks, while it supports multi-hop
networking using the peer-to-peer mesh topology, but with no
synchronization. Even though both specifications mention the
possible use of cluster-tree topologies, which combine multi-hop
and synchronization features, the description on how to effectively
construct such a network topology is missing. This paper tackles
this problem, unveils the ambiguities regarding the use of the
cluster-tree topology and proposes two collision-free beacon
frame scheduling schemes. We strongly believe that the results
provided in this paper trigger a significant step towards the
practical and efficient use of IEEE 802.15.4/Zigbee cluster-tree
networks
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