597 research outputs found
Network emulation focusing on QoS-Oriented satellite communication
This chapter proposes network emulation basics and a complete case study of QoS-oriented Satellite Communication
Reducing energy consumption in mobile ad-hoc sensor networks
PhD ThesisRecent rapid development of wireless communication technologies and portable mobile devices such as tablets, smartphones and wireless sensors bring the best out of mobile computing, particularly Mobile Ad-hoc Sensor Networks (MASNETs). MASNETs
are types of Mobile Ad-hoc Networks (MANETs) that are designed to consider energy
in mind because they have severe resource constraints due to their lack of processing power, limited memory, and bandwidth as in Wireless Sensor Networks (WSNs).
Hence, they have the characteristics, requirements, and limitations of both MANETs
and WSNs. There are many potential applications of MASNETs such as a real-time
target tracking and an ocean temperature monitoring. In these applications, mobility
is the fundamental characteristic of the sensor nodes, and it poses many challenges
to the routing algorithm. One of the greatest challenge is to provide a routing algorithm that is capable of dynamically changing its topology in the mobile environment
with minimal consumption of energy. In MASNETs, the main reason of the topology
change is because of the movement of mobile sensor nodes and not the node failure due
to energy depletion. Since these sensor nodes are limited in power supply and have low
radio frequency coverage, they easily lose their connection with neighbours, and face diffi culties in updating their routing tables. The switching process from one coverage
area to another consumes more energy. This network must be able to adaptively alter
the routing paths to minimize the effects of variable wireless link quality, topological
changes, and transmission power levels on energy consumption of the network. Hence,
nodes prefer to use as little transmission power as necessary and transmit control packets as infrequently as possible in energy constrained MASNETs. Therefore, in this
thesis we propose a new dynamic energy-aware routing algorithm based on the trans-
mission power control (TPC). This method effectively decreases the average percentage
of packet loss and reduces the average total energy consumption which indirectly pro-
long the network lifetime of MASNETs. To validate the proposed protocol, we ran
the simulation on the Avrora simulator and varied speed, density, and route update
interval of mobile nodes. Finally, the performance of the proposed routing algorithm
was measured and compared against the basic Ad-hoc On-demand Distance Vector
(AODV) routing algorithm in MASNETs.The Ministry of Education of Malaysia:
The Universiti Malaysia Sarawak
Supporting Cyber-Physical Systems with Wireless Sensor Networks: An Outlook of Software and Services
Sensing, communication, computation and control technologies are the essential building blocks of a cyber-physical system (CPS). Wireless sensor networks (WSNs) are a way to support CPS as they provide fine-grained spatial-temporal sensing, communication and computation at a low premium of cost and power. In this article, we explore the fundamental concepts guiding the design and implementation of WSNs. We report the latest developments in WSN software and services for meeting existing requirements and newer demands; particularly in the areas of: operating system, simulator and emulator, programming abstraction, virtualization, IP-based communication and security, time and location, and network monitoring and management. We also reflect on the ongoing
efforts in providing dependable assurances for WSN-driven CPS. Finally, we report on its applicability with a case-study on smart buildings
Estudo do IPFS como protocolo de distribuição de conteúdos em redes veiculares
Over the last few years, vehicular ad-hoc networks (VANETs) have been the
focus of great progress due to the interest in autonomous vehicles and in
distributing content not only between vehicles, but also to the Cloud. Performing
a download/upload to/from a vehicle typically requires the existence
of a cellular connection, but the costs associated with mobile data transfers
in hundreds or thousands of vehicles quickly become prohibitive. A VANET
allows the costs to be several orders of magnitude lower - while keeping the
same large volumes of data - because it is strongly based in the communication
between vehicles (nodes of the network) and the infrastructure.
The InterPlanetary File System (IPFS) is a protocol for storing and distributing
content, where information is addressed by its content, instead of
its location. It was created in 2014 and it seeks to connect all computing
devices with the same system of files, comparable to a BitTorrent swarm
exchanging Git objects. It has been tested and deployed in wired networks,
but never in an environment where nodes have intermittent connectivity,
such as a VANET. This work focuses on understanding IPFS, how/if it can
be applied to the vehicular network context, and comparing it with other
content distribution protocols.
In this dissertation, IPFS has been tested in a small and controlled network
to understand its working applicability to VANETs. Issues such as neighbor
discoverability times and poor hashing performance have been addressed.
To compare IPFS with other protocols (such as Veniam’s proprietary solution
or BitTorrent) in a relevant way and in a large scale, an emulation platform
was created. The tests in this emulator were performed in different times of
the day, with a variable number of files and file sizes. Emulated results show
that IPFS is on par with Veniam’s custom V2V protocol built specifically for
V2V, and greatly outperforms BitTorrent regarding neighbor discoverability
and data transfers.
An analysis of IPFS’ performance in a real scenario was also conducted, using
a subset of STCP’s vehicular network in Oporto, with the support of
Veniam. Results from these tests show that IPFS can be used as a content
dissemination protocol, showing it is up to the challenge provided by a
constantly changing network topology, and achieving throughputs up to 2.8
MB/s, values similar or in some cases even better than Veniam’s proprietary
solution.Nos últimos anos, as redes veiculares (VANETs) têm sido o foco de grandes
avanços devido ao interesse em veículos autónomos e em distribuir conteúdos,
não só entre veículos mas também para a "nuvem" (Cloud). Tipicamente,
fazer um download/upload de/para um veículo exige a utilização
de uma ligação celular (SIM), mas os custos associados a fazer transferências
com dados móveis em centenas ou milhares de veículos rapidamente se
tornam proibitivos. Uma VANET permite que estes custos sejam consideravelmente
inferiores - mantendo o mesmo volume de dados - pois é fortemente
baseada na comunicação entre veículos (nós da rede) e a infraestrutura.
O InterPlanetary File System (IPFS - "sistema de ficheiros interplanetário")
é um protocolo de armazenamento e distribuição de conteúdos, onde a informação
é endereçada pelo conteúdo, em vez da sua localização. Foi criado
em 2014 e tem como objetivo ligar todos os dispositivos de computação num
só sistema de ficheiros, comparável a um swarm BitTorrent a trocar objetos
Git. Já foi testado e usado em redes com fios, mas nunca num ambiente
onde os nós têm conetividade intermitente, tal como numa VANET. Este
trabalho tem como foco perceber o IPFS, como/se pode ser aplicado ao
contexto de rede veicular e compará-lo a outros protocolos de distribuição
de conteúdos.
Numa primeira fase o IPFS foi testado numa pequena rede controlada, de
forma a perceber a sua aplicabilidade às VANETs, e resolver os seus primeiros
problemas como os tempos elevados de descoberta de vizinhos e o fraco desempenho
de hashing.
De modo a poder comparar o IPFS com outros protocolos (tais como a
solução proprietária da Veniam ou o BitTorrent) de forma relevante e em
grande escala, foi criada uma plataforma de emulação. Os testes neste emulador
foram efetuados usando registos de mobilidade e conetividade veicular
de alturas diferentes de um dia, com um número variável de ficheiros e
tamanhos de ficheiros. Os resultados destes testes mostram que o IPFS está
a par do protocolo V2V da Veniam (desenvolvido especificamente para V2V
e VANETs), e que o IPFS é significativamente melhor que o BitTorrent no
que toca ao tempo de descoberta de vizinhos e transferência de informação.
Uma análise do desempenho do IPFS em cenário real também foi efetuada,
usando um pequeno conjunto de nós da rede veicular da STCP no Porto,
com o apoio da Veniam. Os resultados destes testes demonstram que o
IPFS pode ser usado como protocolo de disseminação de conteúdos numa
VANET, mostrando-se adequado a uma topologia constantemente sob alteração,
e alcançando débitos até 2.8 MB/s, valores parecidos ou nalguns
casos superiores aos do protocolo proprietário da Veniam.Mestrado em Engenharia de Computadores e Telemátic
Using Cooja for WSN Simulations: Some New Uses and Limits
International audienceThe Cooja/MSPSim network simulation framework is widely used for developing and debugging, but also for performance evaluation of WSN projects.We show in this paper that Cooja is not limited only to the simulation of the Contiki OS based systems and networks, but can also be extended to perform simulation experiments of other OS based platforms, especially that with RIOT OS.Moreover, when performing our own simulations with Cooja and MSPSim, we observed timing inconsistencies with identical experimentations made on actual hardware. Such inaccuracies clearly impair the use of the Cooja/MSPSim framework as a performance evaluation tool, at least for time-related performance parameters.We will present in this paper, as our contributions: On the one hand, how to use Cooja with projects not related to Con-tiki OS; On the other hand, the detailed results of our investigations on the inaccuracy problems, as well as the consequences of this issue, and give possible leads to fix or avoid it
A Java application to display temperature, humidity and luminosity in a Wireless Sensor Network
The aim of this thesis is to develop a Java application, using Android platform, to display in a mobile device the values taken by a Wireless Sensor Network (WSN). For this purpose, in this papers, firstly I give a general vision of what the Wireless Sensor Networks are. In particular, I wished to provide a comprehensive analysis of the main component of the WSN: the
sensor node. I describe its hardware and software structural. The second part of the thesis is dedicated to the implementation of the application. It is listed which software were useful to the development and it explained how the application has been built. In the last part of the thesis it is shown the graphical result of the work obtainedope
- …