54 research outputs found
Towards Augmenting Federated Wireless Sensor Networks
AbstractEnvironmental Monitoring (EM) has witnessed significant improvements in recent years due to the great utility of Wireless Sensor Networks (WSNs). Nevertheless, due to harsh operational conditions in such applications, WSNs often suffer large scale damage in which nodes fail concurrently and the network gets partitioned into disjoint sectors. Thus, reestablishing connectivity between the sectors, via their remaining functional nodes, is of utmost importance in EM; especially in forestry. In this regard, considerable work has been proposed in the literature tackling this problem by deploying Relay Nodes (RNs) aimed at re-establishing connectivity. Although finding the minimum relay count and positions is NP-Hard, efficient heuristic approaches have been anticipated. However, the majority of these approaches ignore the surrounding environment characteristics and the infinite 3-Dimensional (3-D) search space which significantly degrades network performance in practice. Therefore, we propose a 3-D grid-based deployment for relay nodes in which the relays are efficiently placed on grid vertices. We present a novel approach, named FADI, based on a minimum spanning tree construction to re-connect the disjointed WSN sectors. The performance of the proposed approach is validated and assessed through extensive simulations, and comparisons with two main stream approaches are presented. Our protocol outperforms the related work in terms of the average relay node count and distribution, the scalability of the federated WSNs in large scale applications, and the robustness of the topologies formed
Connectivity restoration and amelioration in wireless ad-hoc networks: A practical solution
International audienceConnectivity restoration after a node failure is one of the major issues in wireless ad-hoc networks. In particular, failures can lead to a network partitioning and a huge loss of information. Therefore, a fast mechanism is needed to heal the network between the partitions. In this paper, we consider the scenario where an intermediate node failures and a mobile system is moving autonomously to restore connectivity and provide the best service. We propose a fast connectivity restoration algorithm that is based only on local information. We implement our solution on a real robotic platform and we present some experimental results using a simple case scenario
Architectures for the Future Networks and the Next Generation Internet: A Survey
Networking research funding agencies in the USA, Europe, Japan, and other countries are encouraging research on revolutionary networking architectures that may or may not be bound by the restrictions of the current TCP/IP based Internet. We present a comprehensive survey of such research projects and activities. The topics covered include various testbeds for experimentations for new architectures, new security mechanisms, content delivery mechanisms, management and control frameworks, service architectures, and routing mechanisms. Delay/Disruption tolerant networks, which allow communications even when complete end-to-end path is not available, are also discussed
Data storage solutions for the federation of sensor networks
In the near future, most of our everyday devices will be accessible via some
network and uniquely identified for interconnection over the Internet. This
new paradigm, called Internet of Things (IoT), is already starting to influence
our society and is now driving developments in many areas.
There will be thousands, or even millions, of constrained devices that will
be connected using standard protocols, such as Constrained Application Protocol
(CoAP), that have been developed under certain specifications appropriate
for this type of devices. In addition, there will be a need to interconnect
networks of constrained devices in a reliable and scalable way, and federations
of sensor networks using the Internet as a medium will be formed.
To make the federation of geographically distributed CoAP based sensor
networks possible, a CoAP Usage for REsource LOcation And Discovery (RELOAD)
was recently proposed. RELOAD is a peer-to-peer (P2P) protocol that
ensures an abstract storage and messaging service to its clients, and it relies
on a set of cooperating peers that form a P2P overlay network for this purpose.
This protocol allows to define so-called Usages for applications to work
on top of this overlay network. The CoAP Usage for RELOAD is, therefore,
a way for CoAP based devices to store their resources in a distributed P2P
overlay. Although CoAP Usage for RELOAD is an important step towards
the federation of sensor networks, in the particular case of IoT there will be
consistency and efficiency problems. This happens because the resources of
CoAP devices/Things can be in multiple data objects stored at the overlay network,
called P2P resources. Thus, Thing resource updates can end up being
consuming, as multiple P2P resources will have to be modified. Mechanisms
to ensure consistency become, therefore, necessary.
This thesis contributes to advances in the federation of sensor networks by
proposing mechanisms for RELOAD/CoAP architectures that will allow consistency
to be ensured. An overlay network service, required for such mechanisms
to operate, is also proposed.Num futuro próximo, a maioria dos nossos dispositivos do dia-a-dia estarão
acessíveis através de uma rede e serão identificados de forma única para
poderem interligar-se através da Internet. Este novo paradigma, conhecido
hoje por Internet das Coisas (IoT), já está a começar a influenciar a nossa
sociedade e está agora a impulsionar desenvolvimentos em inúmeras áreas.
Teremos milhares, ou mesmo milhões, de dispositivos restritos que utilizarão protocolos padrão que foram desenvolvidos de forma a cumprir determinadas
especificações associadas a este tipo de dispositivos, especificações essas
que têm a ver com o facto destes dispositivos terem normalmente restrições
de memória, pouca capacidade de processamento e muitos possuirem limitações
energéticas. Surgirá ainda a necessidade de interligar, de forma fiável e
escalonável, redes de dispositivos restritos.(…
LOCALIZED MOVEMENT CONTROL CONNECTIVITY RESTORATION ALGORITHMS FOR WIRELESS SENSOR AND ACTOR NETWORKS
Wireless Sensor and Actor Networks (WSANs) are gaining an increased interest
because of their suitability for mission-critical applications that require autonomous
and intelligent interaction with the environment. Hazardous application environments
such as forest fire monitoring, disaster management, search and rescue, homeland
security, battlefield reconnaissance, etc. make actors susceptible to physical damage.
Failure of a critical (i.e. cut-vertex) actor partitions the inter-actor network into
disjointed segments while leaving a coverage hole. Maintaining inter-actor
connectivity is extremely important in mission-critical applications of WSANs where
actors have to quickly plan an optimal coordinated response to detected events. Some
proactive approaches pursued in the literature deploy redundant nodes to provide fault
tolerance; however, this necessitates a large actor count that leads to higher cost and
becomes impractical. On the other hand, the harsh environment strictly prohibits an
external intervention to replace a failed node. Meanwhile, reactive approaches might
not be suitable for time-sensitive applications. The autonomous and unattended nature
of WSANs necessitates a self-healing and agile recovery process that involves
existing actors to mend the severed inter-actor connectivity by reconfiguring the
topology. Moreover, though the possibility of simultaneous multiple actor failure is
rare, it may be precipitated by a hostile environment and disastrous events. With only
localized information, recovery from such failures is extremely challenging.
Furthermore, some applications may impose application-level constraints while
recovering from a node failure.
In this dissertation, we address the challenging connectivity restoration problem while
maintaining minimal network state information. We have exploited the controlled
movement of existing (internal) actors to restore the lost connectivity while
minimizing the impact on coverage. We have pursued distributed greedy heuristics.
This dissertation presents four novel approaches for recovering from node failure. In
the first approach, volunteer actors exploit their partially utilized transmission power
and reposition themselves in such a way that the connectivity is restored. The second
approach identifies critical actors in advance, designates them preferably as noncritical
backup nodes that replace the failed primary if such contingency arises in the
future. In the third approach, we design a distributed algorithm that recovers from a
special case of multiple simultaneous failures. The fourth approach factors in
application-level constraints on the mobility of actors while recovering from node
failure and strives to minimize the impact of critical node failure on coverage and
connectivity. The performance of proposed approaches is analyzed and validated
through extensive simulations. Simulation results confirm the effectiveness of
proposed approaches that outperform the best contemporary schemes found in
literature
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