801 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
Improving the communication reliability of body sensor networks based on the IEEE 802.15.4 protocol
Body sensor networks (BSNs) enable continuous monitoring of patients anywhere, with minimum constraints to daily life activities. Although the IEEE 802.15.4 and ZigBee® (ZigBee Alliance, San Ramon, CA) standards were mainly developed for use in wireless sensors network (WSN) applications, they are also widely used in BSN applications because of device characteristics such as low power, low cost, and small form factor. However, compared with WSNs, BSNs present some very distinctive characteristics in terms of traffic and mobility patterns, heterogeneity of the nodes, and quality of service requirements. This article evaluates the suitability of the carrier sense multiple access–collision avoidance protocol, used by the IEEE 802.15.4 and ZigBee standards, for data-intensive BSN applications, through the execution of experimental tests in different evaluation scenarios, in order to take into account the effects of contention, clock drift, and hidden nodes on the communication reliability. Results show that the delivery ratio may decrease substantially during transitory periods, which can last for several minutes, to a minimum of 90% with retransmissions and 13% without retransmissions. This article also proposes and evaluates the performance of the BSN contention avoidance mechanism, which was designed to solve the identified reliability problems. This mechanism was able to restore the delivery ratio to 100% even in the scenario without retransmissions.Fundação para a Ciência e a Tecnologia (FCT
Towards efficient coexistence of IEEE 802.15.4e TSCH and IEEE 802.11
A major challenge in wide deployment of smart wireless devices, using
different technologies and sharing the same 2.4 GHz spectrum, is to achieve
coexistence across multiple technologies. The IEEE~802.11 (WLAN) and the IEEE
802.15.4e TSCH (WSN) where designed with different goals in mind and both play
important roles for respective applications. However, they cause mutual
interference and degraded performance while operating in the same space. To
improve this situation we propose an approach to enable a cooperative control
which type of network is transmitting at given time, frequency and place.
We recognize that TSCH based sensor network is expected to occupy only small
share of time, and that the nodes are by design tightly synchronized. We
develop mechanism enabling over-the-air synchronization of the Wi-Fi network to
the TSCH based sensor network. Finally, we show that Wi-Fi network can avoid
transmitting in the "collision periods". We provide full design and show
prototype implementation based on the Commercial off-the-shelf (COTS) devices.
Our solution does not require changes in any of the standards.Comment: 8 page
Goodbye, ALOHA!
©2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.The vision of the Internet of Things (IoT) to interconnect and Internet-connect everyday people, objects, and machines poses new challenges in the design of wireless communication networks. The design of medium access control (MAC) protocols has been traditionally an intense area of research due to their high impact on the overall performance of wireless communications. The majority of research activities in this field deal with different variations of protocols somehow based on ALOHA, either with or without listen before talk, i.e., carrier sensing multiple access. These protocols operate well under low traffic loads and low number of simultaneous devices. However, they suffer from congestion as the traffic load and the number of devices increase. For this reason, unless revisited, the MAC layer can become a bottleneck for the success of the IoT. In this paper, we provide an overview of the existing MAC solutions for the IoT, describing current limitations and envisioned challenges for the near future. Motivated by those, we identify a family of simple algorithms based on distributed queueing (DQ), which can operate for an infinite number of devices generating any traffic load and pattern. A description of the DQ mechanism is provided and most relevant existing studies of DQ applied in different scenarios are described in this paper. In addition, we provide a novel performance evaluation of DQ when applied for the IoT. Finally, a description of the very first demo of DQ for its use in the IoT is also included in this paper.Peer ReviewedPostprint (author's final draft
Beacon scheduling in cluster-tree IEEE 802.15.4/ZigBee 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 report tackles this
problem, unveils the ambiguities regarding the use of the cluster-tree topology and proposes two collisionfree
beacon frame scheduling schemes
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
A Suitable MAC Protocol for Transmit-Only Sensor Nodes in a Housing Community Wireless Network
This paper investigates the development of a suitable Medium Access Control (MAC) protocol for a housing community wireless network that consists of both wireless infrastructural mesh nodes and wireless sensor nodes. In this network, transmit-only sensor nodes are employed in order to obtain a low cost, easy to deploy and low power solution. However, such sensor nodes have no way of verifying successful data transfer and it is, therefore, imperative that the associated MAC protocol provides a high level of confidence for transferring this data. In this paper, we examine methods of packaging and transmitting sensor node data in order to obtain such a MAC protocol for the aforementioned housing community wireless network. Microchipâs rfPIC is used as the platform for the sensor node. Some preliminary analysis and results are presented within
A Suitable MAC Protocol for Transmit-Only Sensor Nodes in a Housing Community Wireless Network
This paper investigates the development of a suitable Medium Access Control (MAC) protocol for a housing community wireless network that consists of both wireless infrastructural mesh nodes and wireless sensor nodes. In this network, transmit-only sensor nodes are employed in order to obtain a low cost, easy to deploy and low power solution. However, such sensor nodes have no way of verifying successful data transfer and it is, therefore, imperative that the associated MAC protocol provides a high level of confidence for transferring this data. In this paper, we examine methods of packaging and transmitting sensor node data in order to obtain such a MAC protocol for the aforementioned housing community wireless network. Microchipâs rfPIC is used as the platform for the sensor node. Some preliminary analysis and results are presented within
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