116 research outputs found
Performance analysis of a Master/Slave switched Ethernet for military embedded applications
Current military communication network is a generation
old and is no longer effective in meeting the emerging
requirements imposed by the next generation military embedded applications. A new communication network based upon Full Duplex Switched Ethernet is proposed in this paper to overcome these limitations. To allow existing military subsystems to be easily supported by a Switched Ethernet network, our proposal consists in keeping their current centralized communication scheme by using an optimized master/slave transmission control on Switched Ethernet thanks to the Flexible Time Triggered (FTT) paradigm. Our main objective is to assess the performance
of such a proposal and estimate the quality of service we
can expect in terms of latency. Using the Network Calculus formalism, schedulability analysis are determined. These analysis are illustrated in the case of a realistic military embedded application extracted from a real military aircraft network, to highlight the proposal's ability to support the required time constrained communications
Worst-case response time of aperiodc message in WorldFIP and its improvement in real-time capability
Analysis of time delays in scheduled and unscheduled communication used in process automation
This paper introduces a network model for analysing the time delays of scheduled and unscheduled communication services among field devices used in process automation. The proposed model is implemented by configuring multiple control loops of real-time field devices into a network. The consensus of the network is designed using segment checkerTM simulation software. The simulated network of the field devices is re-configured for the proposed network model by mapping virtually. Every device is treated as a node in the network model and the real-time data is accessed. The time delays recorded for both scheduled and unscheduled communication of field-bus topology in simulation environment and the performance is compared with scheduled communication delay. The better bandwidth utilization and assignment of field device is achieved by introducing the unscheduled communication time delays in the network. It helps in the improvement of network capacity by accommodating more devices and reduces the commissioning cost
Intrusion detection for in-vehicle communication networks: An unsupervised kohonen SOM approach
The diffusion of embedded and portable communication devices on modern vehicles entails new security risks since in-vehicle communication protocols are still insecure and vulnerable to attacks. Increasing interest is being given to the implementation of automotive cybersecurity systems. In this work we propose an efficient and high-performing intrusion detection system based on an unsupervised Kohonen Self-Organizing Map (SOM) network, to identify attack messages sent on a Controller Area Network (CAN) bus. The SOM network found a wide range of applications in intrusion detection because of its features of high detection rate, short training time, and high versatility. We propose to extend the SOM network to intrusion detection on in-vehicle CAN buses. Many hybrid approaches were proposed to combine the SOM network with other clustering methods, such as the k-means algorithm, in order to improve the accuracy of the model. We introduced a novel distance-based procedure to integrate the SOM network with the K-means algorithm and compared it with the traditional procedure. The models were tested on a car hacking dataset concerning traffic data messages sent on a CAN bus, characterized by a large volume of traffic with a low number of features and highly imbalanced data distribution. The experimentation showed that the proposed method greatly improved detection accuracy over the traditional approach
Analysis of Real-Time Capabilities of Dynamic Scheduled System
This PhD-thesis explores different real-time scheduling approaches to effectively utilize industrial real-time applications on multicore or manycore platforms. The proposed scheduling policy is named the Time-Triggered Constant Phase scheduler for handling periodic tasks, which determines time windows for each computation and communication in advance by using the dependent task model
Aeronautical Engineering: A special bibliography, supplement 60
This bibliography lists 284 reports, articles, and other documents introduced into the NASA scientific and technical information system in July 1975
Sobre a aplicação de técnicas de controlo em redes industriais com falhas
Doutoramento em Engenharia EletrotécnicaThe performance of real-time networks is under continuous improvement as
a result of several trends in the digital world. However, these tendencies not
only cause improvements, but also exacerbates a series of unideal aspects
of real-time networks such as communication latency, jitter of the latency
and packet drop rate.
This Thesis focuses on the communication errors that appear on such realtime
networks, from the point-of-view of automatic control. Specifically, it
investigates the effects of packet drops in automatic control over fieldbuses,
as well as the architectures and optimal techniques for their compensation.
Firstly, a new approach to address the problems that rise in virtue of such
packet drops, is proposed. This novel approach is based on the simultaneous
transmission of several values in a single message. Such messages can
be from sensor to controller, in which case they are comprised of several
past sensor readings, or from controller to actuator in which case they are
comprised of estimates of several future control values. A series of tests
reveal the advantages of this approach.
The above-explained approach is then expanded as to accommodate the
techniques of contemporary optimal control. However, unlike the aforementioned
approach, that deliberately does not send certain messages in
order to make a more efficient use of network resources; in the second case,
the techniques are used to reduce the effects of packet losses.
After these two approaches that are based on data aggregation, it is also
studied the optimal control in packet dropping fieldbuses, using generalized
actuator output functions. This study ends with the development of a new
optimal controller, as well as the function, among the generalized functions
that dictate the actuator’s behaviour in the absence of a new control
message, that leads to the optimal performance.
The Thesis also presents a different line of research, related with the output
oscillations that take place as a consequence of the use of classic co-design
techniques of networked control. The proposed algorithm has the goal of
allowing the execution of such classical co-design algorithms without causing
an output oscillation that increases the value of the cost function. Such
increases may, under certain circumstances, negate the advantages of the
application of the classical co-design techniques. A yet another line of research, investigated algorithms, more efficient than
contemporary ones, to generate task execution sequences that guarantee
that at least a given number of activated jobs will be executed out of
every set composed by a predetermined number of contiguous activations.
This algorithm may, in the future, be applied to the generation of message
transmission patterns in the above-mentioned techniques for the efficient
use of network resources. The proposed task generation algorithm is better
than its predecessors in the sense that it is capable of scheduling systems
that cannot be scheduled by its predecessor algorithms.
The Thesis also presents a mechanism that allows to perform multi-path
routing in wireless sensor networks, while ensuring that no value will be
counted in duplicate. Thereby, this technique improves the performance of
wireless sensor networks, rendering them more suitable for control applications.
As mentioned before, this Thesis is centered around techniques for the
improvement of performance of distributed control systems in which several
elements are connected through a fieldbus that may be subject to packet
drops. The first three approaches are directly related to this topic, with the
first two approaching the problem from an architectural standpoint, whereas
the third one does so from more theoretical grounds. The fourth approach
ensures that the approaches to this and similar problems that can be found
in the literature that try to achieve goals similar to objectives of this Thesis,
can do so without causing other problems that may invalidate the solutions
in question. Then, the thesis presents an approach to the problem dealt
with in it, which is centered in the efficient generation of the transmission
patterns that are used in the aforementioned approaches.Em resultado de várias tendências que têm afetado o mundo digital, o desempenho
das redes de comunicação em tempo-real está continuamente a
ser melhorado. No entanto, tais tendências não só introduzem melhorias,
como também introduzem uma série de não idealidades, tais como a
latência, o jitter da latência de comunicação e uma maior probabilidade de
perda de pacotes.
Esta tese tem o seu cerne em falhas de comunicação que surgem em tais
redes, sob o ponto de vista do controlo automático. Concretamente, são
estudados os efeitos das perdas de pacotes em redes de controlo, bem como
arquitecturas e técnicas óptimas de compensação das mesmas.
Primeiramente, ´e proposta uma nova abordagem para colmatar os problemas
que surgem em virtude de tais perdas. Essa nova abordagem ´e baseada
no envio simultâneo de vários valores numa única mensagem. Tais mensagens
podem ser de sensor para controlador, caso em que as mesmas são
constituídas por um conjunto de valores passados, ou de controlador para
actuador, caso em que tais mensagens contˆem estimativas de futuros valores
de controlo. Uma série de testes revela as vantagens de tal abordagem.
A abordagem acima explanada ´e seguidamente expandida de modo a acomodar
o controlo óptimo. Contudo, ao contrário da abordagem acima
apresentada, que passa pelo não envio deliberado de certas mensagens com
vista a alcançar um uso mais eficiente dos recursos de rede; no presente
caso, as técnicas são usadas para reduzir os efeitos da perda de pacotes.
Em seguida são estudadas abordagens de controlo óptimo que em situações
de perda de pacotes empregam formas generalizadas da aplicação de valores
de saída. Este estudo culmina com o desenvolvimento de um novo
controlador óptimo, bem como a função, entre as funções generalizadas
do funcionamento do actuador, que conduz o sistema a um desempenho óptimo. É
também apresentada uma linha de investigação diferente, relacionada com a oscilação da saída que ocorre em consequência da utilização de técnicas e algoritmos clássicos de co-desenho de controlo e redes industriais. O algoritmo
proposto tem como finalidade permitir que tais algoritmos clássicos
possam ser executados sem causar oscilações de saída, oscilações que por
sua vez aumentam o valor da função de custo. Tais aumentos da função
do custo, podem, em certas circunstâncias, por em causa os benefícios da
aplicação das técnicas de co-desenho clássico. Numa outra linha de investigação, foram estudadas formas, mais eficientes
que as contemporâneas, de geração de sequências de execuções de tarefas
que garantam que pelo menos um dado número de tarefas activadas
serão executadas por cada conjunto contíguo composto por um número
predefinido de activações. Esta técnica poderá, no futuro, ser aplicada na
geração dos padrões de envio de mensagens que ´e empregue na abordagem
de utilização eficiente dos recursos de rede acima referida. A técnica proposta
de geração de tarefas é melhor que as anteriores no sentido em que
a mesma é capaz de escalonar sistemas que não são escalonáveis pelas
técnicas clássicas.
A tese também apresenta um mecanismo que permite fazer o encaminhamento
multi-caminho em redes de sensores sem fios com falhas sem
causar a contagem em duplicado. Assim sendo a mesma técnica melhora
o desempenho das redes de sensores sem fios, tornando as mesmas mais
maleável as necessidades do controlo aum´atico em redes sem fios.
Como foi referido acima, a tese foca-se em t´ecnicas de melhoria de desempenho
de sistemas de controlo distribu´ıdo em que os v´arios elementos
de controlo encontram-se interligados por meio de uma rede industrial que
pode estar sujeita a perda de pacotes. As primeiras três abordagens cingemse
a este tema, sendo que primeiras duas olham para o problema sob um
ponto de vista arquitetural, enquanto que a terceira olha sob um ponto de
vista mais teórico. A quarta abordagem garante que outras propostas que
podem ser encontradas na literatura e que visam atingir resultados semelhantes
aos que se pretendem atingir nesta tese, possam fazˆe-lo sem causar
outros problemas que invalidem as soluções em questão. Seguidamente, é
apresenta-se uma abordagem ao problema proposto nesta tese que foca-se
na geração eficiente de padrões para subsequente utilização nas abordagens
acima referidas. E por fim, apresentar-se-a uma técnica de optimização do
funcionamento de redes sem fios que promete melhorar o controlo em tais
redes
Design of static intercell interference coordination schemes for realistic lte-based cellular networks
Today, 3.5 and 4G systems including Long Term Evolution (LTE) and LTE-Advanced
(LTE-A) support packet-based services and provide mobile broadband access for
bandwidth-hungry applications. In this context of fast evolution, new and challenging
technical issues must be e ectively addressed. The nal target is to achieve a
signi cant step forward toward the improvement of the Quality of Experience (QoE).
To that end, interference management has been recognized by the industry as a key
enabler for cellular technologies based on OFDMA. Indeed, with a low frequency
reuse factor, intercell interference (ICI) becomes a major concern since the Quality of
Service (QoS) is not uniformly delivered across the network, it remarkably depends on
user position. Hence, cell edge performance is an important issue in LTE and LTE-A.
Intercell Interference Coordination (ICIC) encompasses strategies whose goal
is to keep ICI at cell edges as low as possible. This alleviates the aforementioned
situation. For this reason, the novelties presented in this Ph.D. thesis include not
only developments of static ICIC mechanisms for data and control channels, but
also e orts towards further improvements of the energy e ciency perspective.
Based on a comprehensive review of the state of the art, a set of research
opportunities were identi ed. To be precise, the need for
exible performance
evaluation methods and optimization frameworks for static ICIC strategies. These
mechanisms are grouped in two families: the schemes that de ne constraints on the
frequency domain and the ones that propose adjustments on the power levels. Thus,
Soft- and Fractional Frequency Reuse (SFR and FFR, respectively) are identi ed as
the base of the vast majority of static ICIC proposals.
Consequently, during the rst part of this Ph.D. thesis, interesting insights into
the operation of SFR and FFR were identi ed beyond well-known facts. These
studies allow for the development of a novel statistical framework to evaluate the
performance of these schemes in realistic deployments. As a result of the analysis, the
poor performance of classic con gurations of SFR and FFR in real-world contexts
is shown, and hence, the need for optimization is established. In addition, the
importance of the interworking between static ICIC schemes and other network
functionalities such as CSI feedback has also been identi ed. Therefore, novel CSI
feedback schemes, suitable to operate in conjunction with SFR and FFR, have been
developed. These mechanisms exploit the resource allocation pattern of these static
ICIC techniques in order to improve the accuracy of the CSI feedback process. The second part is focused on the optimization of SFR and FFR. The use of
multiobjective techniques is investigated as a tool to achieve e ective network-speci c
optimization. The approach o ers interesting advantages. On the one hand, it allows
for simultaneous optimization of several con
icting criteria. On the other hand, the
multiobjective nature results in outputs composed of several high quality (Pareto
e cient) network con gurations, all of them featuring a near-optimal tradeo
between the performance criteria. Multiobjective evolutionary algorithms allow
employing complex mathematical structures without the need for relaxation, thus
capturing accurately the system behavior in terms of ICI. The multiobjective
optimization formulation of the problem aims at achieving e ective adjustment of
the operational parameters of SFR and FFR both at cell level and network-wide.
Moreover, the research was successfully extended to the control channels, both the
PDCCH and ePDCCH.
Finally, in an e ort to further improve the network energy e ciency (an aspect
always considered throughout the thesis), the framework of Cell Switch O (CSO),
having close connections with ICIC, is also introduced. By means of the proposed
method, signi cant improvements with respect to traditional approaches, baseline
con gurations, and previous proposals can be achieved. The gains are obtained in
terms of energy consumption, network capacity, and cell edge performance.Actualmente los sistemas 3.5 y 4G tales como Long Term Evolution (LTE) y
LTE-Advanced (LTE-A) soportan servicios basados en paquetes y proporcionan
acceso de banda ancha m ovil para aplicaciones que requieren elevadas tasas de
transmisi on. En este contexto de r apida evoluci on, aparecen nuevos retos t ecnicos
que deben ser resueltos e cientemente. El objetivo ultimo es conseguir un salto
cualitativo importante en la experiencia de usuario (QoE). Con tal n, un factor
clave que ha sido reconocido en las redes celulares basadas en Orthogonal Frequency-
Division Multiple Access (OFDMA) es la gesti on de interferencias. De hecho, la
utilizaci on de un factor de reuso bajo permite una elevada e ciencia espectral pero
a costa de una distribuci on de la calidad de servicio (QoS) que no es uniforme en la
red, depende de la posici on del usuario. Por lo tanto, el rendimiento en los l mites
de la celda se ve muy penalizado y es un problema importante a resolver en LTE
y LTE-A.
La coordinaci on de interferencias entre celdas (ICIC, del ingl es Intercell Interfe-
rence Coordination) engloba las estrategias cuyo objetivo es mantener la interferencia
intercelular (ICI) lo m as baja posible en los bordes de celda. Esto permite aliviar
la situaci on antes mencionada. La contribuci on presentada en esta tesis doctoral
incluye el dise~no de nuevos mecanismos de ICIC est atica para los canales de datos y
control, as como tambi en mejoras desde el punto de vista de e ciencia energ etica.
A partir de una revisi on completa del estado del arte, se identi caron una serie
de retos abiertos que requer an esfuerzos de investigaci on. En concreto, la necesidad
de m etodos de evaluaci on
exibles y marcos de optimizaci on de las estrategias de
ICIC est aticas. Estos mecanismos se agrupan en dos familias: los esquemas que
de nen restricciones sobre el dominio de la frecuencia y los que proponen ajustes
en los niveles de potencia. Es decir, la base de la gran mayor a de propuestas ICIC
est aticas son la reutilizaci on de frecuencias de tipo soft y fraccional (SFR y FFR,
respectivamente).
De este modo, durante la primera parte de esta tesis doctoral, se han estudiado
los aspectos m as importantes del funcionamiento de SFR y FFR, haciendo especial
enfasis en las conclusiones que van m as all a de las bien conocidas. Ello ha permitido
introducir un nuevo marco estad stico para evaluar el funcionamiento de estos
sistemas en condiciones de despliegue reales. Como resultado de estos an alisis, se
muestra el pobre desempe~no de SFR y FFR en despliegues reales cuando funcionan con sus con guraciones cl asicas y se establece la necesidad de optimizaci on. Tambi en
se pone de mani esto la importancia del funcionamiento conjunto entre esquemas
ICIC est aticos y otras funcionalidades de la red radio, tales como la informaci on que
env an los usuarios sobre el estado de su canal downlink (feedback del CSI, del ingl es
Channel State Information). De este modo, se han propuesto diferentes esquemas de
feedback apropiados para trabajar conjuntamente con SFR y FFR. Estos mecanismos
explotan el patr on de asignaci on de recursos que se utiliza en ICIC est atico para
mejorar la precisi on del proceso.
La segunda parte se centra en la optimizaci on de SFR y FFR. Se ha investigado el
uso de t ecnicas multiobjetivo como herramienta para lograr una optimizaci on e caz,
que es espec ca para cada red. El enfoque ofrece ventajas interesantes, por un lado, se
permite la optimizaci on simult anea de varios criterios contradictorios. Por otro lado,
la naturaleza multiobjetivo implica obtener como resultado con guraciones de red
de elevada calidad (Pareto e cientes), todas ellas con un equilibrio casi- optimo entre
las diferentes m etricas de rendimiento. Los algoritmos evolucionarios multiobjetivo
permiten la utilizaci on de estructuras matem aticas complejas sin necesidad de relajar
el problema, de este modo capturan adecuadamente su comportamiento en t erminos
de ICI. La formulaci on multiobjetivo consigue un ajuste efectivo de los par ametros
operacionales de SFR y FFR, tanto a nivel de celda como a nivel de red. Adem as,
la investigaci on se extiende con resultados satisfactorios a los canales de control,
PDCCH y ePDCCH.
Finalmente, en un esfuerzo por mejorar la e ciencia energ etica de la red (un
aspecto siempre considerado a lo largo de la tesis), se introduce en el an alisis global
el apagado inteligente de celdas, estrategia con estrechos v nculos con ICIC. A trav es
del m etodo propuesto, se obtienen mejoras signi cativas con respecto a los enfoques
tradicionales y propuestas previas. Las ganancias se obtienen en t erminos de consumo
energ etico, capacidad de la red, y rendimiento en el l mite de las celdas.Actualment els sistemes 3.5 i 4G tals com Long Term Evolution (LTE) i LTE-
Advanced (LTE-A) suporten serveis basats en paquets i proporcionen acc es de
banda ampla m obil per a aplicacions que requereixen elevades taxes de transmissi
o. En aquest context de r apida evoluci o, apareixen nous reptes t ecnics que
han de ser resolts e cientment. L'objectiu ultim es aconseguir un salt qualitatiu
important en l'experi encia d'usuari (QoE). Amb tal , un factor clau que ha estat
reconegut a les xarxes cel lulars basades en Orthogonal Frequency-Division Multiple
Access (OFDMA) es la gesti o d'interfer encies. De fet, la utilizaci o d'un factor de
re us baix permet una elevada e ci encia espectral per o a costa d'una distribuci o de
la qualitat de servei (QoS) que no es uniforme a la xarxa, dep en de la posici o de
l'usuari. Per tant, el rendiment en els l mits de la cel la es veu molt penalitzat i es
un problema important a resoldre en LTE i LTE-A.
La coordinaci o d'interfer encies entre cel les (ICIC, de l'angl es Intercell Interfe-
rence Coordination) engloba les estrat egies que tenen com a objectiu mantenir la
interfer encia intercel lular (ICI) el m es baixa possible en les vores de la cel la. Aix o
permet alleujar la situaci o abans esmentada. La contribuci o presentada en aquesta
tesi doctoral inclou el disseny de nous mecanismes de ICIC est atica per als canals de
dades i control, aix com tamb e millores des del punt de vista d'e ci encia energ etica.
A partir d'una revisi o completa de l'estat de l'art, es van identi car una s erie de
reptes oberts que requerien esfor cos de recerca. En concret, la necessitat de m etodes
d'avaluaci o
exibles i marcs d'optimitzaci o de les estrat egies de ICIC est atiques.
Aquests mecanismes s'agrupen en dues fam lies: els esquemes que de neixen restriccions
sobre el domini de la freq u encia i els que proposen ajustos en els nivells de
pot encia. Es a dir, la base de la gran majoria de propostes ICIC est atiques s on la
reutilitzaci o de freq u encies de tipus soft i fraccional (SFR i FFR, respectivament).
D'aquesta manera, durant la primera part d'aquesta tesi doctoral, s'han estudiat
els aspectes m es importants del funcionament de SFR i FFR, fent especial emfasi en
les conclusions que van m es enll a de les ben conegudes. Aix o ha perm es introduir un
nou marc estad stic per avaluar el funcionament d'aquests sistemes en condicions
de desplegament reals. Com a resultat d'aquestes an alisis, es mostra el pobre
acompliment de SFR i FFR en desplegaments reals quan funcionen amb les seves
con guracions cl assiques i s'estableix la necessitat d'optimitzaci o. Tamb e es posa de
manifest la import ancia del funcionament conjunt entre esquemes ICIC est atics i altres funcionalitats de la xarxa radio, tals com la informaci o que envien els usuaris
sobre l'estat del seu canal downlink (feedback del CSI, de l'angl es Channel State
Information). D'aquesta manera, s'han proposat diferents esquemes de feedback
apropiats per treballar conjuntament amb SFR i FFR. Aquests mecanismes exploten
el patr o d'assignaci o de recursos que s'utilitza en ICIC est atic per millorar la precisi o
del proc es.
La segona part se centra en l'optimitzaci o de SFR i FFR. S'ha investigat l' us
de t ecniques multiobjectiu com a eina per aconseguir una optimitzaci o e ca c, que
es espec ca per a cada xarxa. L'enfocament ofereix avantatges interessants, d'una
banda, es permet l'optimitzaci o simult ania de diversos criteris contradictoris. D'altra
banda, la naturalesa multiobjectiu implica obtenir com resultat con guracions de
xarxa d'elevada qualitat (Pareto e cients), totes elles amb un equilibri gaireb e optim
entre les diferents m etriques de rendiment. Els algorismes evolucionaris multiobjectiu
permeten la utilitzaci o d'estructures matem atiques complexes sense necessitat de
relaxar el problema, d'aquesta manera capturen adequadament el seu comportament
en termes de ICI. La formulaci o multiobjectiu aconsegueix un ajust efectiu dels
par ametres operacionals de SFR i FFR, tant a nivell de cel la com a nivell de xarxa.
A m es, la recerca s'est en amb resultats satisfactoris als canals de control, PDCCH
i ePDCCH.
Finalment, en un esfor c per millorar l'e ci encia energ etica de la xarxa (un
aspecte sempre considerat al llarg de la tesi), s'introdueix en l'an alisi global l'apagat
intel ligent de cel les, estrat egia amb estrets vincles amb ICIC. Mitjan cant el m etode
proposat, s'obtenen millores signi catives pel que fa als enfocaments tradicionals i
propostes pr evies. Els guanys s'obtenen en termes de consum energ etic, capacitat de
la xarxa, i rendiment en el l mit de les cel les
Pipeline rings and integrated services rings.
Wong, Po-Choi.Summary in Chinese.Thesis (Ph.D.)--Chinese University of Hong Kong, 1989.Bibliography: leaves 156-164
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