927 research outputs found
An Approximate Inner Bound to the QoS Aware Throughput Region of a Tree Network under IEEE 802.15.4 CSMA/CA and Application to Wireless Sensor Network Design
We consider a tree network spanning a set of source nodes that generate
measurement packets, a set of additional relay nodes that only forward packets
from the sources, and a data sink. We assume that the paths from the sources to
the sink have bounded hop count. We assume that the nodes use the IEEE 802.15.4
CSMA/CA for medium access control, and that there are no hidden terminals. In
this setting, starting with a set of simple fixed point equations, we derive
sufficient conditions for the tree network to approximately satisfy certain
given QoS targets such as end-to-end delivery probability and delay under a
given rate of generation of measurement packets at the sources (arrival rates
vector). The structures of our sufficient conditions provide insight on the
dependence of the network performance on the arrival rate vector, and the
topological properties of the network. Furthermore, for the special case of
equal arrival rates, default backoff parameters, and for a range of values of
target QoS, we show that among all path-length-bounded trees (spanning a given
set of sources and BS) that meet the sufficient conditions, a shortest path
tree achieves the maximum throughput
Wireless industrial monitoring and control networks: the journey so far and the road ahead
While traditional wired communication technologies have played a crucial role in industrial monitoring and control networks over the past few decades, they are increasingly proving to be inadequate to meet the highly dynamic and stringent demands of today’s industrial applications, primarily due to the very rigid nature of wired infrastructures. Wireless technology, however, through its increased pervasiveness, has the potential to revolutionize the industry, not only by mitigating the problems faced by wired solutions, but also by introducing a completely new class of applications. While present day wireless technologies made some preliminary inroads in the monitoring domain, they still have severe limitations especially when real-time, reliable distributed control operations are concerned. This article provides the reader with an overview of existing wireless technologies commonly used in the monitoring and control industry. It highlights the pros and cons of each technology and assesses the degree to which each technology is able to meet the stringent demands of industrial monitoring and control networks. Additionally, it summarizes mechanisms proposed by academia, especially serving critical applications by addressing the real-time and reliability requirements of industrial process automation. The article also describes certain key research problems from the physical layer communication for sensor networks and the wireless networking perspective that have yet to be addressed to allow the successful use of wireless technologies in industrial monitoring and control networks
Exploiting programmable architectures for WiFi/ZigBee inter-technology cooperation
The increasing complexity of wireless standards has shown that protocols cannot be designed once for all possible deployments, especially when unpredictable and mutating interference situations are present due to the coexistence of heterogeneous technologies. As such, flexibility and (re)programmability of wireless devices is crucial in the emerging scenarios of technology proliferation and unpredictable interference conditions.
In this paper, we focus on the possibility to improve coexistence performance of WiFi and ZigBee networks by exploiting novel programmable architectures of wireless devices able to support run-time modifications of medium access operations. Differently from software-defined radio (SDR) platforms, in which every function is programmed from scratch, our programmable architectures are based on a clear decoupling between elementary commands (hard-coded into the devices) and programmable protocol logic (injected into the devices) according to which the commands execution is scheduled.
Our contribution is two-fold: first, we designed and implemented a cross-technology time division multiple access (TDMA) scheme devised to provide a global synchronization signal and allocate alternating channel intervals to WiFi and ZigBee programmable nodes; second, we used the OMF control framework to define an interference detection and adaptation strategy that in principle could work in independent and autonomous networks. Experimental results prove the benefits of the envisioned solution
Droplet: A New Denial-of-Service Attack on Low Power Wireless Sensor Networks
In this paper we present a new kind of Denial-of-Service attack against the PHY layer of low power wireless sensor networks. Overcoming the very limited range of jamming-based attacks, this attack can penetrate deep into a target network with high power efficiency. We term this the Droplet attack, as it attains enormous disruption by dropping small, payload-less frame headers to its victim's radio receiver, depriving the latter of bandwidth and sleep time. We demonstrate the Droplet attack's high damage rate to full duty-cycle receivers, and further show that a high frequency version of Droplet can even force nodes running on very low duty-cycle MAC protocols to drop most of their packets
Fast Desynchronization For Decentralized Multichannel Medium Access Control
Distributed desynchronization algorithms are key to wireless sensor networks
as they allow for medium access control in a decentralized manner. In this
paper, we view desynchronization primitives as iterative methods that solve
optimization problems. In particular, by formalizing a well established
desynchronization algorithm as a gradient descent method, we establish novel
upper bounds on the number of iterations required to reach convergence.
Moreover, by using Nesterov's accelerated gradient method, we propose a novel
desynchronization primitive that provides for faster convergence to the steady
state. Importantly, we propose a novel algorithm that leads to decentralized
time-synchronous multichannel TDMA coordination by formulating this task as an
optimization problem. Our simulations and experiments on a densely-connected
IEEE 802.15.4-based wireless sensor network demonstrate that our scheme
provides for faster convergence to the steady state, robustness to hidden
nodes, higher network throughput and comparable power dissipation with respect
to the recently standardized IEEE 802.15.4e-2012 time-synchronized channel
hopping (TSCH) scheme.Comment: to appear in IEEE Transactions on Communication
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
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
Performance enhancement of IEEE 802.15.4 by employing RTS/CTS and frame concatenation
IEEE 802.15.4 has been widely accepted as the de facto standard for wireless sensor networks (WSNs). However, as in their current solutions for medium access control (MAC) sub-layer protocols, channel efficiency has a margin for improvement, in this study, the authors evaluate the IEEE 802.15.4 MAC sub-layer performance by proposing to use the request-/clear-to-send (RTS/CTS) combined with frame concatenation and block acknowledgement (BACK) mechanism to optimise the channel use. The proposed solutions are studied in a distributed scenario with single-destination and single-rate frame aggregation. The throughput and delay performance is mathematically derived under channel environments without/with transmission errors for both the chirp spread spectrum and direct sequence spread spectrum physical layers for the 2.4 GHz Industrial, Scientific and Medical band. Simulation results successfully verify the authors’ proposed analytical model. For more than seven TX (aggregated frames) all the MAC sub-layer protocols employing RTS/CTS with frame concatenation (including sensor BACK MAC) allow for optimising channel use in WSNs, corresponding to 18–74% improvement in the maximum average throughput and minimum average delay, together with 3.3–14.1% decrease in energy consumption.info:eu-repo/semantics/publishedVersio
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