39 research outputs found
Latency Optimization in Smart Meter Networks
In this thesis, we consider the problem of smart meter networks with data collection to a central point within acceptable delay and least consumed energy. In smart metering applications, transferring and collecting data within delay constraints is crucial. IoT devices are usually resource-constrained and need reliable and energy-efficient routing protocol. Furthermore, meters deployed in lossy networks often lead to packet loss and congestion. In smart grid communication, low latency and low energy consumption are usually the main system targets. Considering these constraints, we propose an enhancement in RPL to ensure link reliability and low latency. The proposed new additive composite metric is Delay-Aware RPL (DA-RPL). Moreover, we propose a repeaters’ placement algorithm to meet the latency requirements. The performance of a realistic RF network is simulated and evaluated. On top of the routing solution, new asynchronous ordered transmission algorithms of UDP data packets are proposed to further enhance the overall network latency performance and mitigate the whole system congestion and interference. Experimental results show that the performance of DA-RPL is promising in terms of end-to-end delay and energy consumption. Furthermore, the ordered asynchronous transmission of data packets resulted in significant latency reduction using just a single routing metric
Upgrading the Power Grid Functionalities with Broadband Power Line Communications: Basis, Applications, Current Trends and Challenges
This article reviews the basis and the main aspects of the recent evolution of Broadband Power Line Communications (BB-PLC or, more commonly, BPL) technologies. The article starts describing the organizations and alliances involved in the development and evolution of BPL systems, as well as the standardization institutions working on PLC technologies. Then, a short description of the technical foundation of the recent proposed technologies and a comparison of the main specifications are presented; the regulatory activities related to the limits of emissions and immunity are also addressed. Finally, some representative applications of BPL and some selected use cases enabled by these technologies are summarized, together with the main challenges to be faced.This work was financially supported in part by the Basque Government under the grants IT1426-22, PRE_2021_1_0006, and PRE_2021_1_0051, and by the Spanish Government under the grants PID2021-124706OB-I00 and RTI2018-099162-B-I00 (MCIU/AEI/FEDER, UE, funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”)
A new coupling solution for G3-PLC employment in MV smart grids
This paper proposes a new coupling solution for transmitting narrowband multicarrier power line communication (PLC) signals over medium voltage (MV) power lines. The proposed system is based on an innovative PLC coupling principle, patented by the authors, which exploits the capacitive divider embedded in voltage detecting systems (VDS) already installed inside the MV switchboard. Thus, no dedicated couplers have to be installed and no switchboard modifications or energy interruptions are needed. This allows a significant cost reduction of MV PLC implementation. A first prototype of the proposed coupling system was presented in previous papers: it had a 15 kHz bandwidth useful to couple single carrier PSK modulated PLC signals with a center frequency from 50–200 kHz. In this paper, a new prototype is developed with a larger bandwidth, up to 164 kHz, thus allowing to couple multicarrier G3-PLC signals using orthogonal frequency division multiplexing (OFDM) digital modulation. This modulation ensures a more robust communication even in harsh power line channels. In the paper, the new coupling system design is described in detail. A new procedure is presented for tuning the coupling system parameters at first installation in a generic MV switchboard. Finally, laboratory and in-field experimental test results are reported and discussed. The coupling performances are evaluated measuring the throughput and success rate in the case of both 18 and 36 subcarriers, in one of the different tone masks standardized for the FCC-above CENELEC band (that is, from 154.6875–487.5 kHz). The experimental results show an efficient behavior of the proposed coupler allowing a two-way communication of G3-PLC OFDM signals on MV networks
Communication technology selection method for smart energy metering based on analytic hierarchy process
As new communication technologies continue to emerge and the integration of these
technologies into the modernization of the electricity grid becomes increasingly necessary,
a variety of communication protocols and combinations are being explored for their
potential use in the smart grid domain. However, given the multitude of technological
possibilities available, choosing the optimal technology capable of adequately addressing
the communication requirements of the intelligent grid remains a challenge for utilities.
This is due, on the one hand, to the fact that different intelligent grid applications have
different qualitative and quantitative communication requirements. Moreover, on the
other hand, each technology has advantages and disadvantages concerning its performance
characteristics in such requirements. This work uses the AHP (Analytic Hierarchy Process)
methodology to select the wireless technology that presents the best performance
characteristics concerning determined requirements. For this, a computational algorithm
was developed in the Matlab programming environment, through which criteria such
as data rate, latency, range, security, reliability, and interoperability were compared to
select the best technological alternative among Wi-Fi, ZigBee, Z-Wave, and Bluetooth.
Data collected from the literature review, with the performance characteristics of these
technologies, were applied in a single case study simulating the practical implementation
of this work. Among the analyzed criteria, simulations demonstrated that Wi-Fi was the
winning technology alternative with 32.353%, followed by Z-Wave with 29.865% in second
place, and ZigBee and Bluetooth were ranked third and fourth with 25.255% and 12.527%,
respectively. In addition, sensitivity analysis shows how the AHP methodology can be a
feasible alternative to assist decision-making in the smart grid domain.À medida que novas tecnologias de comunicação continuam a surgir e a integração destas
tecnologias na modernização da rede elétrica se torna cada vez mais necessária, uma
variedade de protocolos e combinações de tecnologias de comunicação vem sendo explorados
para a sua potencial utilização no domínio da rede inteligente. No entanto, dada a multiplicidade
de possibilidades tecnológicas disponíveis, a escolha da melhor tecnologia capaz
de responder, adequadamente, aos requisitos de comunicação da rede elétrica inteligente
continua sendo um desafio para diferentes atores interessados. Isto se deve, por um lado, ao
fato de diferentes aplicações de rede inteligente terem diferentes requisitos de comunicação,
quer sejam quantitativos ou qualitativos. Além disso, por outro lado, cada tecnologia tem
vantagens e desvantagens relacionadas com as suas características de desempenho em
tais requisitos. Este trabalho, portanto, utiliza a metodologia AHP (Analytic Hierarchy
Process) para selecionar a tecnologia sem fios que apresenta as melhores características
de desempenho relativamente a determinados requisitos. Para tal, foi desenvolvido um
algoritmo computacional no ambiente de programação Matlab, através do qual critérios
tais como taxa de dados, latência, alcance, segurança, confiabilidade e interoperabilidade
foram comparados para selecionar a melhor alternativa tecnológica entre Wi-Fi, ZigBee,
Z-Wave e Bluetooth. Os dados coletados na revisão de literatura, com as características de
desempenho destas tecnologias, foram aplicados num único estudo de caso simulando a
implementação prática deste método em ambiente residencial. Dentre os critérios analisados,
as simulações demonstraram que o Wi-Fi foi a alternativa tecnológica vencedora
com 32,353%, seguido pelo Z-Wave com 29,865% em segundo lugar, e ZigBee e Bluetooth
ficaram em terceiro e quarto lugar com 25,255% e 12,527%, respectivamente. Além disso,
a análise de sensibilidade, dos resultados, mostra como a metodologia AHP pode ser uma
alternativa viável para auxiliar na tomada de decisões no domínio da rede inteligente
Cross-layer energy efficiency of plc systems for smart grid applications
Though opinions are still divided over the specific choices of technology for
smart grid, there is a consensus that heterogeneous communications network
is most appropriate. Power line communication (PLC) is promising because
it is readily available and it aligns with the natural topology of power distribution
network. One of the emerging realities is that the communication
system enabling smart grid must be energy-efficient. This thesis employs a
cross-layer approach to address energy efficiency of PLC networks in different
smart grid scenarios.
At network layer, this work exploits the topology of a PLC-enabled advanced
metering infrastructure (AMI) to improve the probability of successful
packet delivery across the network. The technique, termed AMI clustering,
leverages the traditional structure of the low voltage (LV) network by organising
the smart meters into clusters and locally aggregating their readings.
Improvement in packet delivery inherently reduces energy wastage.
Next, the adaptation layer exploits the low data rate transmission techniques
to reduce the energy requirements of PLC nodes. To achieve that, this
work developed a network model in NS-3 (an open-source network simulator)
that considers PLC transceivers as resource-constrained devices and interconnects
them to emulate home energy management system (HEMS). The model
was validated with experimental results which showed that in the home area
network (HAN), low-rate applications such as energy management can be
supported over low-power PLC networks.
Furthermore, at physical layer, this thesis proposes a more energy-efficient
multi-carrier modulation scheme than the orthogonal frequency division multiplexing
(OFDM) used in most of the current PLC systems. OFDM is widely known for its high peak-to-average-power ratio (PAPR) which degrades energy
efficiency of the systems. This thesis found that by employing vector-
OFDM (V-OFDM), power requirements of PLC transmitter can be reduced.
The results also showed the energy efficiency can be further improved by
using a dynamic noise cancellation technique such as dynamic peak-based
threshold estimation (DPTE) at the receiver.
By applying the proposed methods, packet delivery can be improved by
3% at network layer (which conserves energy) and reduced data rate can save
about 2.6014 dB in transmit power. Finally, at physical layer, V-OFDM and
DPTE can respectively provide 5.8 dB and 2.1 dB reduction in power requirements
of the PLC transceivers. These signify that if V-OFDM is combined
with DPTE, future PLC modems could benefit from energy-efficient power
amplifiers at reduced cost
Routing and Mobility on IPv6 over LoWPAN
The IoT means a world-wide network of interconnected objects based on standard communication
protocols. An object in this context is a quotidian physical device augmented with
sensing/actuating, processing, storing and communication capabilities. These objects must be
able to interact with the surrounding environment where they are placed and to cooperate with
neighbouring objects in order to accomplish a common objective. The IoT objects have also the
capabilities of converting the sensed data into automated instructions and communicating them
to other objects through the communication networks, avoiding the human intervention in several
tasks. Most of IoT deployments are based on small devices with restricted computational
resources and energy constraints. For this reason, initially the scientific community did not
consider the use of IP protocol suite in this scenarios because there was the perception that it
was too heavy to the available resources on such devices. Meanwhile, the scientific community
and the industry started to rethink about the use of IP protocol suite in all IoT devices and now
it is considered as the solution to provide connectivity between the IoT devices, independently
of the Layer 2 protocol in use, and to connect them to the Internet. Despite the use of IP suite
protocol in all devices and the amount of solutions proposed, many open issues remain unsolved
in order to reach a seamless integration between the IoT and the Internet and to provide the
conditions to IoT service widespread. This thesis addressed the challenges associated with the
interconnectivity between the Internet and the IoT devices and with the security aspects of
the IoT. In the interconnectivity between the IoT devices and the Internet the problem is how
to provide valuable information to the Internet connected devices, independently of the supported
IP protocol version, without being necessary accessed directly to the IoT nodes. In order
to solve this problem, solutions based on Representational state transfer (REST) web services
and IPv4 to IPv6 dual stack transition mechanism were proposed and evaluated. The REST web
service and the transition mechanism runs only at the border router without penalizing the IoT
constrained devices. The mitigation of the effects of internal and external security attacks
minimizing the overhead imposed on the IoT devices is the security challenge addressed in this
thesis. Three different solutions were proposed. The first is a mechanism to prevent remotely
initiated transport level Denial of Service attacks that avoids the use of inefficient and hard to
manage traditional firewalls. It is based on filtering at the border router the traffic received
from the Internet and destined to the IoT network according to the conditions announced by
each IoT device. The second is a network access security framework that can be used to control
the nodes that have access to the network, based on administrative approval, and to enforce
security compliance to the authorized nodes. The third is a network admission control framework
that prevents IoT unauthorized nodes to communicate with IoT authorized nodes or with
the Internet, which drastically reduces the number of possible security attacks. The network
admission control was also exploited as a management mechanism as it can be used to manage
the network size in terms of number of nodes, making the network more manageable, increasing
its reliability and extending its lifetime.A IoT (Internet of Things) tem suscitado o interesse tanto da comunidade académica como
da indústria, uma vez que os campos de aplicação são inúmeros assim como os potenciais ganhos
que podem ser obtidos através do uso deste tipo de tecnologia. A IoT significa uma rede
global de objetos ligados entre si através de uma rede de comunicações baseada em protocolos
standard. Neste contexto, um objeto é um objeto físico do dia a dia ao qual foi adicionada a
capacidade de medir e de atuar sobre variáveis físicas, de processar e armazenar dados e de
comunicar. Estes objetos têm a capacidade de interagir com o meio ambiente envolvente e de
cooperar com outros objetos vizinhos de forma a atingirem um objetivo comum. Estes objetos
também têm a capacidade de converter os dados lidos em instruções e de as comunicar a outros
objetos através da rede de comunicações, evitando desta forma a intervenção humana em
diversas tarefas. A maior parte das concretizações de sistemas IoT são baseados em pequenos
dispositivos autónomos com restrições ao nível dos recursos computacionais e de retenção de
energia. Por esta razão, inicialmente a comunidade científica não considerou adequado o uso
da pilha protocolar IP neste tipo de dispositivos, uma vez que havia a perceção de que era muito
pesada para os recursos computacionais disponíveis. Entretanto, a comunidade científica e a
indústria retomaram a discussão acerca dos benefícios do uso da pilha protocolar em todos os
dispositivos da IoT e atualmente é considerada a solução para estabelecer a conetividade entre
os dispositivos IoT independentemente do protocolo da camada dois em uso e para os ligar à
Internet. Apesar do uso da pilha protocolar IP em todos os dispositivos e da quantidade de
soluções propostas, são vários os problemas por resolver no que concerne à integração contínua
e sem interrupções da IoT na Internet e de criar as condições para a adoção generalizada deste
tipo de tecnologias.
Esta tese versa sobre os desafios associados à integração da IoT na Internet e dos aspetos de
segurança da IoT. Relativamente à integração da IoT na Internet o problema é como fornecer
informação válida aos dispositivos ligados à Internet, independentemente da versão do protocolo
IP em uso, evitando o acesso direto aos dispositivos IoT. Para a resolução deste problema foram
propostas e avaliadas soluções baseadas em web services REST e em mecanismos de transição
IPv4 para IPv6 do tipo pilha dupla (dual stack). O web service e o mecanismo de transição são
suportados apenas no router de fronteira, sem penalizar os dispositivos IoT. No que concerne
à segurança, o problema é mitigar os efeitos dos ataques de segurança internos e externos
iniciados local e remotamente. Foram propostas três soluções diferentes, a primeira é um
mecanismo que minimiza os efeitos dos ataques de negação de serviço com origem na Internet e
que evita o uso de mecanismos de firewalls ineficientes e de gestão complexa. Este mecanismo
filtra no router de fronteira o tráfego com origem na Internet é destinado à IoT de acordo
com as condições anunciadas por cada um dos dispositivos IoT da rede. A segunda solução,
é uma framework de network admission control que controla quais os dispositivos que podem
aceder à rede com base na autorização administrativa e que aplica políticas de conformidade
relativas à segurança aos dispositivos autorizados. A terceira é um mecanismo de network
admission control para redes 6LoWPAN que evita que dispositivos não autorizados comuniquem
com outros dispositivos legítimos e com a Internet o que reduz drasticamente o número de
ataques à segurança. Este mecanismo também foi explorado como um mecanismo de gestão uma
vez que pode ser utilizado a dimensão da rede quanto ao número de dispositivos, tornando-a
mais fácil de gerir e aumentando a sua fiabilidade e o seu tempo de vida
Sistema Inteligente para Iluminação Pública
Esta dissertação apresenta uma proposta de melhoramento da iluminação pública. Estes sistemas têm vindo a sofrer alguma evolução tecnológica, de forma a aumentar a qualidade da iluminação e melhorar a eficiência energética. O sistema proposto além de satisfazer estes requisitos, adiciona também inteligência ao nível da luminária. Em suma, o sistema propõe capacidade de adaptação ao seu ambiente externo, possibilitando sempre o seu controlo, e fornecendo dados estatísticos e de manutenção, para uma interface de supervisão e controlo