En av hörnstenarna inom Industri 4.0 och den moderna anslutningen på fabriksgolvet är användningen av standardiserade kommunikationsprotokoll. Med utvecklingen av kommunikation idag och dess användning i industrier blir behovet av att överföra information snabbt mer akut. I denna avhandling har etablerade IIoT-kommunikationsprotokoll utvärderats för deras prestanda för dataöverföringshastighet mellan system. De analyserade kommunikationsprotokollen är OPC-UA, MQTT, AMQP och ROS. Testmiljön för att utvärdera protokollen består av två datorer som är anslutna via en switch. Testerna består av att skicka tre typer av data, en bild i form av en bytearray, en JSON-fil och heltal. Resultaten av testet kommer att jämföras genom att se hur snabbt protokollen kan skicka dessa typer av data samtidigt. Resultaten kommer sedan att analyseras för att föreslå ett lämpligt protokoll för ett distributionssystem som skickar dessa typer av data. / One of the cornerstones of Industry 4.0 and the state-of-the-art industrial shop floor connectivity is the use of standardized communication protocols. With the development of communications today and its use in industries, the need to transfer information quickly becomes more urgent. In this thesis common IIoT communication protocols have been evaluated for their performance for data transfer rate between systems. The communication protocols that are analyzed are OPC-UA, MQTT, AMQP, and ROS. The test bench for evaluating the protocols is made up of two computers connected by a switch. The tests consist of sending three types of data, an image in the form of a bytearray, a JSON file and integers. The results of the test will be compared by seeing how fast the protocols can send these types of data concurrently. The results will then be analyzed to propose a suitable protocol for a distributed system sending these types of data.

La diversité croissante des différents agents constituant les réseaux de communication actuels ainsi que la capacité accrue des technologies concurrentes dans l’environnement réseau a conduit à la prise en compte d’une nouvelle approche distribuée de la gestion du réseau. Dans cet environnement réseau évolué, le besoin en accroissement de la bande passante et en ressources rares, s’oppose à la réduction de la consommation énergétique globale.Dans notre travail nous nous intéressons à l’application de mécanismes distribués et de méthodes d’apprentissages visant à introduire d’avantage d’autonomie dans les réseaux hétérogènes, mobiles en particulier, tout en améliorant les performances par rapport aux débits et à la qualité de service. Notre étude se concentre principalement sur l’élaboration de mécanismes distribués stochastiques et énergétiquement efficaces en profitant des capacités de calcul de tous les agents et entités du réseau. Divers outils de la théorie des jeux nous permettent de modéliser et d’étudier différents types de systèmes dont la complexité est induite par la grande taille, l’hétérogénéité et le caractère dynamique des interconnexions. Plus spécifiquement, nous utilisons des outils d’apprentissage par renforcement pour aborder des questions telles que l’attachement distribué des utilisateurs permettant une gestion dynamique, décentralisée et efficace des ressources radio. Nous combinons ensuite les procédures de sélection d’accès à des méthodes d’optimisation distribuées du type gradient stochastique, pour adresser le problème de coordination des interférences intercellulaires (ICIC) dans les réseaux LTE-A. Cette approche se base sur un contrôle de puissance dynamique conduisant à une réutilisation fractionnaire des fréquences radios. Par ailleurs nous adressons dans les réseaux décentralisés non-hiérarchiques, plus précisément les réseaux tolérants aux délais (DTNs), des méthodes décentralisées liées à la minimisation du délai de transmission de bout en bout. Dans ce cadre nous nous intéressons, en outre des équilibres de Nash, à la notion d’équilibre évolutionnairement stables dans différents contextes de jeux évolutionnaires, jeux évolutionnaires décisionnels markoviens et jeux de minorité. Enfin, la majeure partie du travail effectué se rattachant aux tests et validations par simulations,nous présentons plusieurs éléments d’implémentations et d’intégrations liés à la mise en place de plateformes de simulations et d’expérimentations / Growing diversity of agents in current communication networks and increasing capacitiesof concurrent technologies in the network environment has lead to the considerationof a novel distributed approach of the network management. In this evolvednetwork environment the increasing need for bandwidth and rare channel resources,opposes to reduction of the total energy consumption.This thesis focuses on application of distributed mechanisms and learning methodsto allow for more autonomy in the heterogeneous network, this in order to improveits performances. We are mainly interested in energy efficient stochastic mechanismsthat will operate in a distributed fashion by taking advantage of the computationalcapabilities of all the agents and entities of the network. We rely on application ofGame theory to study different types of complex systems in the distributed wirelessnetworks with dynamic interconnectivity.Specifically, we use the stochastic reinforcement learning tools to address issuessuch as, distributed user-network association that allows achieving an efficient dynamicand decentralized radio resource management. Then, we combine access selectionprocedures with distributed optimization to address the inter-cells interferencescoordination (ICIC) for LTE-advanced networks using dynamic power control and designof fractional frequency reuse mechanisms. Moreover we address in non-hierarchicalnetworks, more precisely in Delay Tolerant Networks (DTNs), decentralized methodsrelated to minimization of the end-to-end communication delay. In this framework weare interested, in addition to Nash equilibrium, to the notion of evolutionary stableequiliria in the different context of Evolutionary Games, Markov Decision EvolutionaryGames and Minority Games. As the major parts of our work includes testing andvalidations by simulations, eventually we present several implementations and integrationsmaterials for edition of simulation platforms and test beds

&ldquo / Numerically Controlled&rdquo / (NC) machine tools, which are automatically operated by encoded (digital) commands, are capable of machining components with quality and quantity. Manufacturing industry heavily depends on these machines. Many different control architectures have been adapted in today&rsquo / s CNC technology. Centralized control system is quite popular in industry due to its ease of implementation. If the number of controlled axes on a CNC machine tool (&gt / 3), increases so does the computational burden on the central processors. Hence, more powerful processors are needed. An alternative architecture, which is not commonly used in CNC technology, is the decentralized (distributed) control. In this topology, the tasks handled by the distributed controllers that are interconnected to each other by a communication network. As the need arises, a new controller can be added easily to the network without augmenting the physical configuration. Despite its attractive features, this architecture has not been fully embraced by the CNC industry. Synchronization among the axes in the coordinated motion is proven to be quite challenging. In this thesis, alternative distributed controller architecture was proposed for CNC machine tools. It was implemented on a 3-axis CNC milling machine. Open-loop control performance was investigated under various conditions. Different communication protocols along with different physical communication interfaces and a number of controller hardware were devised. An industry-standard network (RS-485) was set up by interconnecting these distributed controllers. Different data transmission protocols were devised in order to establish appropriate communication methods. Also, computer software (a.k.a. graphical user interface), which can coordinate the interconnected controllers, interpret NC part programs and generate reference position data for each axis, was designed within the scope of this thesis.

Wireless multimedia sensor networks (WMSNs) are networks of interconnected devices that allow retrieving video and audio streams, still images, and scalar data from the environment. In a densely deployed WMSN, there exists correlation among the observations of camera sensors with overlapped coverage areas, which introduces substantial data redundancy in the network. In this dissertation, efficient communication schemes are designed for WMSNs by leveraging the correlation of visual information observed by camera sensors. First, a spatial correlation model is developed to estimate the correlation of visual information and the joint entropy of multiple correlated camera sensors. The compression performance of correlated visual information is then studied. An entropy-based divergence measure is proposed to predict the compression efficiency of performing joint coding on the images from correlated cameras. Based on the predicted compression efficiency, a clustered coding technique is proposed that maximizes the overall compression gain of the visual information gathered in WMSNs. The correlation of visual information is then utilized to design a network scheduling scheme to maximize the lifetime of WMSNs. Furthermore, as many WMSN applications require QoS support, a correlation-aware QoS routing algorithm is introduced that can efficiently deliver visual information under QoS constraints. Evaluation results show that, by utilizing the correlation of visual information in the communication process, the energy efficiency and networking performance of WMSNs could be improved significantly.

In this thesis, we consider a vector Gaussian multiple access channel (MAC) with users demanding reliable communication at specific (Shannon-theoretic) rates. The objective is to assign vectors and powers to these users such that their rate requirements are met and the sum of powers received is minimum. We identify this power minimization problem as an instance of a separable convex optimization problem with linear ascending constraints. Under an ordering condition on the slopes of the functions at the origin, an algorithm that determines the optimum point in a finite number of steps is described. This provides a complete characterization of the minimum sum power for the vector Gaussian multiple access channel. Furthermore, we prove a strong duality between the above sum power minimization problem and the problem of sum rate maximization under power constraints. We then propose finite step algorithms to explicitly identify an assignment of vectors and powers that solve the above power minimization and sum rate maximization problems. The distinguishing feature of the proposed algorithms is the size of the output vector sets. In particular, we prove an upper bound on the size of the vector sets that is independent of the number of users. Finally, we restrict vectors to an orthonormal set. The goal is to identify an assignment of vectors (from an orthonormal set) to users such that the user rate requirements is met with minimum sum power. This is a combinatorial optimization problem. We study the complexity of the decision version of this problem. Our results indicate that when the dimensionality of the vector set is part of the input, the decision version is NP-complete.

Τα τελευταία χρόνια εξελίξεις στην τεχνολογία της μικροηλεκτρονικής και των ψηφιακών επικοινωνιών έκαναν δυνατή τη δημιουργία αυτόνομων μικροσκοπικών συσκευών, εξοπλισμένων με αισθητήρες, επεξεργαστή και δυνατότητα ασύρματης επικοινωνίας, που ονομάζονται μικροαισθητήρες. Τα ασύρματα δίκτυα μικροαισθητήρων αποτελούνται από ένα μεγάλο πλήθος μικροαισθητήρων που τοποθετούνται (συνήθως με τυχαίο τρόπο) σε μία περιοχή ενδιαφέροντος προκειμένου να μετρήσουν την τιμή ενός μεγέθους ενδιαφέροντος. Λόγω των περιορισμένων δυνατοτήτων των συσκευών, τόσο σε υπολογιστικούς πόρους, μνήμη και εμβέλεια επικοινωνίας όσο και κυρίως σε αποθέματα ενέργειας, είναι αναγκαία η ανάπτυξη πρωτοκόλλων επικοινωνίας που λαμβάνουν υπόψη τους περιορισμούς αυτούς. Στο παρόν κείμενο παρουσιάζουμε νέα πρωτόκολλα για ασύρματα δίκτυα μικροαισθητήρων. Τα πρωτόκολλα καλύπτουν πολλές σημαντικές πτυχές του προβλήματος της επικοινωνίας σε αυτή την κατηγορία δικτύων, όπως είναι η αποτελεσματική διάδοση δεδομένων, η αποφυγή συγκρούσεων και η εξοικονόμηση ενέργειας. Ο σχεδιασμός τέτοιων πρωτοκόλλων απαιτεί ανάπτυξη και χρήση μη τετριμμένων αλγοριθμικών τεχνικών, όπως είναι η προσαρμοστικότητα, η ικανοποίηση \\\\EN{trade-offs}, η ετερογένεια του δικτύου ως σχεδιαστικό εργαλείο κλπ. Η ανάλυση των πρωτοκόλλων γίνεται με την διεξαγωγή εξαντλητικών πειραμάτων προσομοίωσης μεγάλης κλίμακας και την μέτρηση της απόδοσής τους σε συγκεκριμένες μετρικές. Οι επιδόσεις των πρωτοκόλλων αξιολογούνται σε σύγκριση με ευρέως αποδεκτά αντίστοιχα πρωτόκολλα που έχουν προταθεί στη διεθνή βιβλιογραφία. / In recent years, advances in technology in the areas of microelectronics and digital communications made possible the creation of tiny autonomous devices, that are equipped with sensors, a processor and wireless communication capabilities, which are called sensors. Wireless sensor networks are comprised of a large number of sensor devices which are deployed (usually in a random manner) in an area of interest, in order to measure the value of a condition. Due to the limited capabilities of the devices, in processing, memory, communication range and mostly energy supplies, it is necessary to develop communication protocols that take into account these limitations. In this work we present new protocols for wireless sensor networks. Our protocols cover many important aspects of the problem of efficient communication in this type of networks, such as efficient data propagation, collision avoidance and energy conservation. The design of such protocols requires the development and use of non-trivial algorithmic techniques, such as adaptation, satisfaction of trade-offs, using the heterogeneity of the network as a design tool etc. The analysis of the protocols is performed by conducting thorough, large scale simulation experiments and measuring their performance in various metrics. The performance of the protocols is evaluated in comparison to well known widely accepted protocols proposed in the international literature.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In this thesis, the investigation into the optimization of low speed communication protocols for narrow band networks will be presented. The main focus will be on analysing commonly used low speed communication protocols and investigate an alternative to these protocols to provide an optimized low speed narrow band network that provides better performance at high and low channel utilization. A study of existing low speed communication networks within the field of water supply has been used to identify the most appropriate protocols to be included in the analysis. The analysis of each protocol discussed includes the development of a simulation and theoretical model, with parameters based on those obtained from implemented communication networks focusing on the parameters used within the Namib water supply scheme of NamWater in Namibia. Of the currently implemented contention protocols, the non-persistent Carrier Sense Multiple Access (CSMA) protocol is implemented the most. Current models used for modelling these protocols make use of various assumptions. These models have been expanded to provide a more accurate representation of the non-persistent CSMA model. The Round Robin Polling (RRP) protocol is another well known protocol used within the telemetry industry and has also been modelled as an alternative to the non-persistent CSMA model. The Adaptive Tree Walk (ATW) protocol has been identified as the limited contention protocol to be modelled as a possible alternative to the conventional methods used. A new model has been developed for modelling this protocol by making use of the same strategies and tools used in the modelling of the non-persistent CSMA and RRP protocols. The Simulation modelling has been developed by making use of DESMO-J, an Object Orientated Simulation API based in Java, developed by the Faculty of Informatics at the University of Hamburg. DESMO-J has been chosen as an alternative to the more traditional simulation languages due to its complete documentation, support structures, ease of use and flexibility. All theoretical models have been implemented in Matlab. / AFRIKAANSE OPSOMMING: In hierdie tesis sal die ondersoek na die optimering van laespoed protokolle vir kommunikasie oor nouband netwerke voorgelê word. Die hoof fokus is op die analise van algemene laespoed kommunikasie protokolle en die ondersoek van alternatiewe wat ’n meer optimale laespoed nouband netwerk sal lewer deur beter werkverigting by lae en hoë kanaalverkeer. ’n Studie van praktiese laespoed nouband netwerke in die veld van waterverspreiding word gebruik om die mees algemene protokolle te identifiseer wat in die analise ingesluit moet word. Die analise van die protokolle sluit in teoretiese en simulasie modelle, met parameters soos geidentifiseer uit die studie van ‘n praktiese netwerk, naamlik die Namib waterverspreidingskema van NamWater in Namibië. Die ’Non-persistent Carrier Sense Multiple Access’ en ’Round Robin Polling’ protokolle is geidentifiseer as dié wat meeste geimplementeer word. Die werkverigting van die protokolle is geanaliseer deur gebruik te maak van teoretiese en simulasie modeleringstegnieke. Huidige modelle van die CSMA protokol is gebaseer op sekere aannames. Hierdie aannames word aangepas en verbeter vir implementering van die teoretiese model. Die model word ook verder uitgebrei om beter resultate te lewer oor ’n groter parameterstel. Die ’Adaptive Tree Walk’ protokol is geidentifiseer as ’n moontlike optimale protokol en word gemodeleer en vergelyk teen die CSMA en RRP protokolle se werkverigting. Die simulasiemodelle is ontwikkel deur gebruik te maak van die DESMO-J sagteware, soos ontwikkel as ’n Java program-koppelvlak deur die Universiteit van Hamburg se Fakulteit van Informatika. DESMO-J is gekies as ’n alternatief vir die meer tradisionele simuleringstale omrede goeie dokumentasie, maklike gebruik en buigbaarheid. Alle teoretiese modelering is uitgevoer in Matlab.

O uso de técnicas de cópia-zero e desvio do sistema operacional permitem a diminuição da latência de comunicação e o aumento da largura de banda. Menores latências e maiores larguras de banda contribuem para que o desempenho das aplicações paralelas seja mais alto, bem como torna-as mais escaláveis. Protocolos de comunicação que utilizam-se destas técnicas são conhecidos como protocolos de comunicação em nível de usuário. Baseado nas experiências de outros grupos de pesquisa na implementação de bibliotecas de comunicação e bibliotecas de programação paralelas sobre VIA e na experiência do GPPD na implementação da biblioteca DECK, este texto apresenta a implementação das primitivas DECK sobre o padrão VIA, o qual é classificado como sendo um protocolo de nível de usuário. O objetivo desta dissertação é implementar o DECK sobre VIA evitando qualquer cópia intermediária na comunicação de uma mensagem, atingindo assim cópia-zero. Dentre as bibliotecas de comunicação sobre VIA, DECK/VIA foi a única biblioteca que teve o compromisso ser totalmente livre de cópias intermediárias, embora houvesse que forçar um sincronismo na comunicação para manter este compromisso. Para a implementação do DECK/VIA, utilizou-se a implementação VI-GM de VIA para redes Myrinet. A biblioteca DECK/VIA demonstrou uma latência de 86.85 μs e uma largura de banda máxima de 205 Mbytes/s, 82% da banda nominal da rede Myrinet. Para validar a biblioteca foi executada a aplicação FT do pacote NPB. Apresenta-se comparações destes resultados frente aos resultados obtidos pela execução da mesma aplicação no DECK/GM, para redesMyrinet e DECK/TCP, para redes Ethernet. Constatou-se que mesmo com uma camada a mais de software e realizando todas as comunicações em três vias em virtude do handshake, DECK/VIA conseguiu valores de speedup bastante próximos de DECK/GM e de DECK/TCP para Gigabit Ethernet, superando os valores de DECK/TCP para Fast Ethernet. Conclui-se que o ideal na implementação de bibliotecas de programação paralela é encontrar uma solução balanceada entre a busca pelo desempenho e a manutenção da semântica original da biblioteca. O trabalho contribuiu com um survey de diversas soluções encontradas por outros grupos no desenvolvimento de bibliotecas de comunicação, que pode servir de guia para outros pesquisadores no desempenho da mesma tarefa. Também contribui com a introdução de um algoritmo para prevenção de deadlocks causados por comunicações síncronas. / Techniques like zero-copy and operating system bypass can decrease communication latency and increase bandwidth. Smaller latencies and greater bandwidths contribute for better performance in parallel applications and became them more scalables as well. Communication protocols using these techiniques are known as user-level communication protocols. Based on experiences from another research groups implementing communication libraries and parallel programming libraries over VIA and experience from GPPD implementing DECK, the text presents the implementation of DECK primitives over VIA standard, which is classified as an user-level protocol. The goal of this master’s thesis is implement DECK over VIA avoiding any intermediate copy between the data source and destination, reaching zero-copy. DECK/VIA is the unique library among all libriaries over VIA here studied totally free of intermediate copies, although a synchronous behavior was forced to keep this compromise. VI-GM, an implementation of VIA for Myrinet networks was used to implement DECK/VIA library. The implementation of DECK/VIA has shown a one-way latency of 86.85 μs and a maximum bandwidth of 205 Mbytes/s, 82% of nominal bandwidth of Myrinet network. To validate the library, the FT application from NPB was executed. Their results were compared with the results obtained with DECK/GM, for Myrinet networks and DECK/TCP, for Ethernet networks. Even with one additional software layer and doing all communication using a handshake, DECK/VIA reaches speedup values very closer of DECK/GMand DECK/TCP on Gigabit Ethernet and was better than DECK/TCP on Fast Ethernet. When implementing parallel programming libraries, we concluded the ideal solution is that meets the good balance between the quest for performance and the keeping of original library’s semantics. This work contibutes with a survey of communication libraries development, their problems and their solutions, which can guide others researchers performing the same task. Also it contributes with an algorithm to prevent deadlocks caused by synchonism.

Made available in DSpace on 2016-06-02T19:05:17Z (GMT). No. of bitstreams: 1 DissRPBM.pdf: 1011856 bytes, checksum: 715ebb8b484f0962fc766a3efbebb601 (MD5) Previous issue date: 2006-05-31 / Financiadora de Estudos e Projetos / EPCGlobal communication protocol for RFID (Radio Frequency Identification) does not ensure security and privacy for its system users. This fact makes possible several kinds of security problems on RFID technology usage justifying that security mechanisms should be added to communication protocol preserving the existing standards. This work proposal is based on communication authentication usage making use of low-cost cryptography with the TEA algorithm. The proposed mutual authentication mechanism was specified and proved using BAN logic. All protocol specification has considered the EPCGlobal standard for Class 1 tags as base adding security and privacy extensions to data communication to get protection against several attacks. The results from this work include an authentication protocol formal specification with cryptography allowing this way the protocol standardization using as base the current Class 1 protocol. / O protocolo de comunicação para a Identificação por Radiofreqüência (RFID- Radio Frequency Identification), definido como padrão pela EPCGlobal, não oferece mecanismos para a garantia de segurança e privacidade aos usuários do sistema. Esta característica possibilita a presença de diversos tipos de problemas no emprego da tecnologia justificando que novos mecanismos de segurança sejam incorporados diretamente ao protocolo de comunicação, preservando os padrões existentes. A proposta deste trabalho baseia-se na utilização de autenticação da comunicação com emprego de criptografia de baixo custo utilizando o algoritmo TEA. O mecanismo de autenticação mútua proposto foi especificado e validado com lógica BAN. Toda a especificação do protocolo considerou o padrão EPCGlobal para tags Classe 1 como base, adicionando extensões visando combater as possibilidades de ataques relacionados à segurança e privacidade na comunicação dos dados. Os resultados obtidos com este trabalho incluem a especificação formal de um protocolo de autenticação com criptografia, permitindo a padronização deste protocolo baseado no padrão para tags Classe 1 e preservando a especificação padrão base.

Made available in DSpace on 2014-12-17T14:56:04Z (GMT). No. of bitstreams: 1 CarlosAOJ.pdf: 1085948 bytes, checksum: 14c962ba5a82f983a474383c27475bb0 (MD5) Previous issue date: 2005-12-19 / One of the most important decisions to turn a substation automatic and no attended it relates to the communication media between this substation and Operation Center. Generally energy companies uses radio or optic fiber, depending of distances and infrastructure of each situation. This rule applies to common substations. Mobile substations are a particular case, therefore they are conceived for use at provisional situations, emergencies, preventive or corrective maintenance. Thus the telecommunication solution used at common substations are not applied so easily to mobile substations, due absence of infrastructure (media) or difficulty to insert the mobile substation data in existing automation network not long. The ideal media must supply covering in a great geographic area to satisfy presented requirements. The implantation costs of this big infrastructure are expensive, however a existing operator may be used. Two services that fulfill that requirements are satellite and cellular telephony. This work presents a solution for automation of mobile substations through satellite. It was successfully implanted at a brazilian electric energy concessionaire named COSERN. The operation became transparent to operators. Other gotten benefits had been operational security, quality in the supply of electric energy and costs reduction. The project presented is a new solution, designed to substations and general applications where few data should be transmitted, but there is difficulties in relation to the media. Despite the satellite having been used, the same resulted can be gotten using celullar telephony, through Short Messages or packet networks as GPRS or EDGE. / Uma das decis?es t?cnicas mais importantes para se automatizar uma subesta??o e torn?-la desassistida refere-se ao meio de comunica??o entre esta subesta??o e o Centro de Opera??es. Normalmente as empresas do setor el?trico optam por usar r?dio ou fibra ?tica, dependendo das dist?ncias e infra-estrutura dispon?vel em cada situa??o. Essa regra se aplica a subesta??es comuns. Subesta??es m?veis s?o um caso particular, pois s?o concebidas para uso em situa??es sazonais, emerg?ncias, manuten??es preventivas ou corretivas. Dessa forma, as solu??es de telecomunica??es para subesta??es comuns n?o s?o facilmente aplic?veis ?s m?veis, seja devido ? inexist?ncia de infra-estrutura (meio de comunica??o), ou ? dificuldade de inserir, em um curto espa?o de tempo, as informa??es da subesta??o m?vel numa rede de automa??o existente. Considera-se, ent?o, que para atender aos requisitos de mobilidade apresentados, o meio de comunica??o ideal deve fornecer cobertura em uma grande ?rea geogr?fica. Os custos de implanta??o de uma infra-estrutura desse porte s?o muito elevados, por?m os servi?os de uma operadora existente podem ser usados. Dois servi?os que atendem bem a esses requisitos s?o o sat?lite e a telefonia celular. Neste trabalho, ? apresentada uma solu??o para automa??o de subesta??es m?veis atrav?s de enlace via sat?lite. O projeto foi implantado na concession?ria de energia COSERN, com sucesso. A opera??o tornou-se transparente aos operadores. Outros benef?cios obtidos foram seguran?a operacional, qualidade no fornecimento de energia el?trica e redu??o de custos. A solu??o apresentada ? um projeto piloto, voltado n?o s? para subesta??es, mas para aplica??es cujo volume de dados transmitidos seja pequeno, e h? dificuldades quanto ao meio de comunica??o. Apesar do sat?lite ter sido usado, pode-se obter o mesmo resultado usando-se a telefonia celular, atrav?s de Short Messages ou via rede de comuta??o de pacotes, como o GPRS ou o EDGE.