18 research outputs found
Proposition and validation of an original MAC layer with simultaneous medium accesses for low latency wireless control/command applications
Control/command processes require a transmission system with some
characteristics like high reliability, low latency and strong guarantees on
messages delivery. Concerning wire networks, field buses technologies like FIP
offer this kind of service (periodic tasks, real time constraints...).
Unfortunately, few wireless technologies can propose a communication system
which respects such constraints. Indeed, wireless transmissions must deal with
medium characteristics which make impossible the direct translation of
mechanisms used with wire networks. The purpose of this paper is to present an
original Medium Access Control (MAC) layer for a real time Low Power-Wireless
Personal Area Network (LP-WPAN). The proposed MAC-layer has been validated by
several complementary methods; in this paper, we focus on the specific
Simultaneous Guaranteed Time Slot (SGTS) part
Wireless Networked Control System using IEEE 802.15.4 with GTS
International audienceIn this paper, the suitability of wireless sensor networks for networked control loop is shown. As the non beacon-enabled mode of IEEE 802.15.4/ZigBee does not ensure the stability for the control loop since non mechanism can prevent the perturbation coming from other applications sharing the same network, we investigate the beacon-enabled mode using the Guaranteed Time Slot (GTS) mechanism and show it is suitable
Zigbee over tinyos: Implementation and experimental challenges
The IEEE 802.15.4/Zigbee protocols are a promising technology for Wireless
Sensor Networks (WSNs). This paper shares our experience on the implementation and
use of these protocols and related technologies in WSNs. We present problems and
challenges we have been facing in implementing an IEEE 802.15.4/ZigBee stack for
TinyOS in a two-folded perspective: IEEE 802.15.4/ZigBee protocol standards
limitations (ambiguities and open issues) and technological limitations (hardware and
software). Concerning the former, we address challenges for building scalable and
synchronized multi-cluster ZigBee networks, providing a trade-off between timeliness
and energy-efficiency. On the latter issue, we highlight implementation problems in terms
of hardware, timer handling and operating system limitations. We also report on our
experience from experimental test-beds, namely on physical layer aspects such as
coexistence problems between IEEE 802.15.4 and 802.11 radio channels
An IEEE 802.15.4 based adaptive communication protocol in wireless sensor network : application to monitoring the elderly at home
International audienceMonitoring behaviour of the elderly and the disabled living alone has become a major public health problem in our modern societies. Among the various scientific aspects involved in the home monitoring field, we are interested in the study and the proposal of a solution allowing distributed sensor nodes to communicate with each other in an optimal way adapted to the specific application constraints. More precisely, we want to build a wireless network that consists of several short range sensor nodes exchanging data between them according to a communication protocol at MAC (Medium Access Control) level. This protocol must be able to optimize energy consumption, transmission time and loss of information. To achieve this objective, we have analyzed the advantages and the limitations of WSN (Wireless Sensor Network) technologies and communication protocols currently used in relation to the requirements of our application. Then we proposed a deterministic, adaptive and energy saving medium access method based on the IEEE 802.15.4 physical layer and a mesh topology. It ensures the message delivery time with strongly limited collision risk due to the spatial reuse of medium in the two-hop neighbourhood. This proposal was characterized by modelling and simulation using OPNET network simulator. Finally we implemented the proposed mechanisms on hardware devices and deployed a sensors network in real situation to verify the accuracy of the model and evaluate the proposal according to different test configurations
H-NAMe: a hidden-node avoidance mechanism for wireless sensor networks
The hidden-node problem has been shown to be a major
source of Quality-of-Service (QoS) degradation in Wireless
Sensor Networks (WSNs) due to factors such as the limited
communication range of sensor nodes, link asymmetry and the
characteristics of the physical environment. In wireless
contention-based Medium Access Control protocols, if two
nodes that are not visible to each other transmit to a third
node that is visible to the formers, there will be a collision –
usually called hidden-node or blind collision. This problem
greatly affects network throughput, energy-efficiency and
message transfer delays, which might be particularly
dramatic in large-scale WSNs. This paper tackles the hiddennode
problem in WSNs and proposes H-NAMe, a simple yet
efficient distributed mechanism to overcome it. H-NAMe
relies on a grouping strategy that splits each cluster of a WSN
into disjoint groups of non-hidden nodes and then scales to
multiple clusters via a cluster grouping strategy that
guarantees no transmission interference between overlapping
clusters. We also show that the H-NAMe mechanism can be
easily applied to the IEEE 802.15.4/ZigBee protocols with
only minor add-ons and ensuring backward compatibility
with the standard specifications. We demonstrate the
feasibility of H-NAMe via an experimental test-bed, showing
that it increases network throughput and transmission success
probability up to twice the values obtained without H-NAMe.
We believe that the results in this paper will be quite useful in
efficiently enabling IEEE 802.15.4/ZigBee as a WSN protoco
H-NAMe: specifying, implementing and testing a hidden-node avoidance mechanism for wireless sensor networks
The hidden-node problem has been shown to be a major source of Quality-of-Service (QoS) degradation in Wireless Sensor
Networks (WSNs) due to factors such as the limited communication range of sensor nodes, link asymmetry and the characteristics
of the physical environment. In wireless contention-based Medium Access Control protocols, if two nodes that are not visible to
each other transmit to a third node that is visible to the formers, there will be a collision – usually called hidden-node or blind
collision. This problem greatly affects network throughput, energy-efficiency and message transfer delays, which might be
particularly dramatic in large-scale WSNs. This technical report tackles the hidden-node problem in WSNs and proposes HNAMe,
a simple yet efficient distributed mechanism to overcome it. H-NAMe relies on a grouping strategy that splits each cluster
of a WSN into disjoint groups of non-hidden nodes and then scales to multiple clusters via a cluster grouping strategy that
guarantees no transmission interference between overlapping clusters. We also show that the H-NAMe mechanism can be easily
applied to the IEEE 802.15.4/ZigBee protocols with only minor add-ons and ensuring backward compatibility with the standard
specifications. We demonstrate the feasibility of H-NAMe via an experimental test-bed, showing that it increases network
throughput and transmission success probability up to twice the values obtained without H-NAMe. We believe that the results in
this technical report will be quite useful in efficiently enabling IEEE 802.15.4/ZigBee as a WSN protocol
Procedimiento de diseño para minimizar el consumo de potencia y los retrasos en WSAN
ResumenActualmente existe un gran interés por el desarrollo de aplicaciones industriales utilizando redes inalámbricas, principalmente por el aumento de la flexibilidad del sistema y la disminución de los costos de implementación. Sin embargo, los retrasos y el jitter que introduce la red de comunicaciones en las aplicaciones de control, han dado lugar a que en algunos casos no se obtenga una buena correspondencia entre los resultados experimentales y los objetivos de control propuestos, esto como consecuencia del uso de modelos imprecisos para analizar y diseñar estos sistemas, métodos de validación poco elaborados y plataformas que no soportan los modelos empleados. En este trabajo se presenta un procedimiento de diseño que permite encontrar un modo de funcionamiento óptimo del sistema, que garantiza el cumplimiento de los plazos de tiempo de las aplicaciones, y minimiza el consumo de potencia y los retrasos
Recommended from our members
Analytic Conditions for Energy Neutrality in Uniformly-Formed Wireless Sensor Networks
Future deployments of wireless sensor network (WSN) infrastructures for environmental or event monitoring are expected to be equipped with energy harvesters (e.g. piezoelectric, thermal, photovoltaic) in order to substantially increase their autonomy. In this paper we derive conditions for energy neutrality, i.e. perpetual energy autonomy per sensor node, by balancing the node's expected energy consumption with its expected energy harvesting capability. Our analysis assumes a uniformly-formed WSN, i.e. a network comprising identical transmitter sensor nodes and identical receiver/relay sensor nodes with a balanced cluster-tree topology. The proposed framework is parametric to: (i) the duty cycle for the network activation; (ii) the number of nodes in the same tier of the cluster-tree topology; (iii) the consumption rate of the receiver node(s) that collect (and possibly relay) data along with their own; (iv) the marginal probability density function (PDF) characterizing the data transmission rate per node; (v) the expected amount of energy harvested by each node. Based on our analysis, we obtain the number of nodes leading to the minimumenergy harvestingrequirement for each tier of the WSN cluster-tree topology. We also derive closed-form expressions for the difference in the minimum energy harvesting requirements between four transmission rate PDFs in function of the WSN parameters. Our analytic results are validated via experiments using TelosB sensor nodes and an energy measurement testbed. Our framework is useful for feasibility studies on energy harvesting technologies in WSNs and for optimizing the operational settings of hierarchical WSN-based monitoring infrastructures prior to time-consuming testing and deployment within the application environment
A time division beacon scheduling mechanism for IEEE 802.15.4/ZigBee cluster-tree wireless sensor networks
While the IEEE 802.15.4/Zigbee protocol stack is being considered as a promising technology for low-cost low-power Wireless Sensor Networks (WSNs), several issues in their specifications are still open. One of those ambiguous issues is how to build a synchronized cluster-tree network, which is quite suitable for ensuring 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 they support 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, unveiling the ambiguities regarding the use of the cluster-tree topology and proposing a synchronization mechanism based on Time Division Beacon Scheduling to construct cluster-tree WSNs. We also propose a methodology for an efficient duty-cycle management in each router (cluster-head) of a cluster-tree WSN that ensures the fairest use of bandwidth resources. The feasibility of the proposal is clearly demonstrated through an experimental test bed based on our own implementation of the IEEE 802.15.4/Zigbee protocols. 1