Real-Time Systems. Design Principles for Distributed Embedded Applications. Herman Kopetz. Second Edition (811374), страница 92
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A consumer can carry a special monitoring tag that alerts the carrierwhenever a clandestine reading attack is detected. The monitoring tag transformsa clandestine reading action to an open reading action and thus exposes the hiddenadversary.Denial of Service. A denial of service attack tries to make a computer systemunavailable to its users. In any wireless communication scenario, such as an RFIDsystem or a sensor network, an adversary can jam the ether with high-power signalsof the appropriate frequency in order to interfere with the communication of thetargeted devices.
In the Internet, an adversary can send a coordinated burst ofservice requests to a site to overload the site such that legitimate service requestscannot be handled any more (see also Sect. 6.2.2 on botnets).Some RFID tags support – as a privacy enhancement mechanism – the functionality to put a tag into a sleep mode or to permanently kill a tag. An adversary can usethis functionality to interfere with the proper operation of the service.Example: At an automated supermarket checkout an RFID reader determines the purchased goods by reading the RFID tags of the items in the shopping cart.
If an adversarydisables some tags, the respective items will not be recognized and don’t appear on the bill.13.5Wireless Sensor NetworksRecent progress in the field of Micro-Electro-Mechanical Systems (MEMS), lowpower microelectronics, and low-power communication has made it possible tobuild small integrated smart objects, called sensor nodes, that contain a sensor, amicrocontroller and a wireless communication controller. A sensor node can acquirea variety of physical, chemical, or biological signals to measure properties of itsenvironment. Sensor nodes are resource constrained. They are powered either by asmall battery or by energy harvested from its environment, have limited computational power, a small memory, and constrained communication capabilities.In order to monitor and observe a phenomenon, a number (from few tens tomillions) of sensor nodes are deployed, either systematically or randomly, in asensor field to form an ad hoc self-organizing network – a wireless sensor network(WSN).
The WSN collects data about the targeted phenomenon and transmits thedata via an ad-hoc multi-hop communication channel to one or more base stationsthat can be connected to the Internet.Points to Remember321After a sensor node is deployed in a sensor field, it is left on its own and relies onits self-organizing capabilities. At first, it must detect its neighbors and establishcommunication.
In the second phase, it must learn about the arrangement in whichthe nodes are connected to each other, the topology of nodes, and build up ad-hocmulti-hop communication channels to a base station. In case of the failure of anactive node, it must reconfigure the network.Wireless sensor networks can be used in many different applications such asremote environment monitoring, surveillance, medical applications, ambient intelligence, and in military applications. The utility of a wireless sensor network is inthe collective emergent intelligence of all active sensor nodes, not the contributionof any particular node.A sensor network is operational as long as a minimum number of nodes is activeand the connectivity of the active nodes to one of the base stations is maintained.
Inbattery-powered sensor networks, the lifetime of the network depends on the energycapacity of the batteries and the power-consumption of a node. When a sensor nodehas depleted its energy supply, it will cease to function and cannot forwardmessages to its neighbors any more. Energy conservation is thus of utmost importance in sensor networks. The design of the nodes, the communication protocols,and the design of the system and application software for sensor networks areprimarily determined by this quest for energy efficiency and low cost.Recently, attempts are made to use the RFID infrastructure for the interconnection of autonomous low-cost RFID-based sensor nodes [Bha10].
These sensornodes operate without a battery and harvest the energy either from the environmentor the electromagnetic radiation emitted by the RFID reader. This technology hasthe potential to produce long-lasting, low-cost ubiquitous sensor nodes that mayrevolutionize many embedded applications.Points to RememberlllAccording to the IoT vision, a smart planet will evolve, where many of theeveryday things around us have an identity in cyberspace, acquire intelligence,and mash-up information from diverse sources.The Electronic Product Code (EPC) is a unique identifier for the naming ofevery physical smart object on the planet.
This is more ambitious than theforerunner, the optical bar code, which assigns a unique identifier only to aclass of objects. The EPC is managed by the international organization EPCglobal.A composite object requires its own UID that is only loosely related to the UIDsof its constituent parts. The different names, UID, object type name, and objectrole name must be introduced at the level of composite objects as well. Since acomposite object can be an atomic unit at the next level of integration, the namespace must be built up recursively.322lllllll13 Internet of ThingsThe division of work between a smart object and the cloud will be determined, toa considerable degree, by energy considerations.
If the energy required toexecute a task locally is larger than the energy required to send the task parameters to a server in the cloud, the task is a candidate for remote processing.The autonomic management of smart objects must cover network service discovery, system configuration and optimization, diagnosis of failures and recoveryafter failures, and system adaptation and evolution.An RFID reader can act as a gateway to the Internet and transmit the objectidentity, together with the read-time and the object location (i.e., the location ofthe reader) to a remote computer system that manages a large database.The information security threats in the IoT can be classified into three groups:(1) the threats that compromise the authenticity of information, (2) the threats toprivacy caused by a pervasive deployment of IoT products, and (3) denial ofservice threats.In order to avoid clandestine reading, a tag must authenticate the reader.It is difficult for an adversary to clone physical one-way functions (POWF),because it is a thing with random characteristic physical properties that cannotbe represented by a mathematical function.
A POWF is not a construct ofcyberspace that can be copied or reconstructed.After a sensor node is deployed in a sensor field, it is left on its own and relies onits self-organizing capabilities. At first, it must detect its neighbors and establishcommunication. In the second phase it must learn about the arrangement inwhich the nodes are connected to each other, the topology of nodes, and build upad-hoc multi-hop communication channels to a base station.
In case of thefailure of an active node, it must reconfigure the network.Bibliographic NotesIn 2009, the European Union has published a Strategic Research Roadmap for theInternet of Things [Ver09] that discusses the vision of the IoT and relevant researchissues up to the year 2020 and beyond.
The excellent RFID handbook [Fin03] is avaluable reference for the RFID technology. The September 2010 special issue ofthe Proceedings of the IEEE [Gad10] is devoted to RFID technology.Review Questions and Problems13.1 What is the vision of the Internet of Things and which are the most pressingtechnical issues that must be resolved?13.2 What are the drivers for the Internet of Things?13.3 What is a smart object?13.4 Discuss the naming of smart objects! What is a UID, a type name, a rolename, or a name of a composite object?Review Questions and Problems13.513.613.713.813.913.1013.1113.1213.1313.14323Discuss the different standards for near-field communication!What is the relation between the IoT and cloud computing?Describe the MAPE-K model of an autonomic component!What are the functions of an RFID reader?What are typical parameters for low-costs RFID tags?What is the electronic product code (EPC) and what is its relation to theubiquitous optical bar code?What is a physical one-way function (POWF)? Where is it needed?What are the three main security threats in the RFID field?How is a sensor node deployed in a sensor field?Describe the self-organizing capabilities of a sensor node!Chapter 14The Time-Triggered ArchitectureOverview This final chapter puts a closing bracket around the contents of the book.It is shown by a concrete example that it is possible to integrate the differentconcepts that have been explained in the previous 13 chapters of this book into acoherent framework.
This coherent framework, the time-triggered architecture(TTA), is the result of more than 25 years of research at the Technische Universit€atWien where numerous master and PhD students have contributed their part to theinvestigations. We must also gratefully mention the many inputs from colleaguesfrom all over the world, particularly form the IFIP Working Group 10.4, thatprovided critical feedback and constructive suggestions.
At first, the research wasdriven by curiosity to get a deep understanding of the notions of real-time, simultaneity, and determinism. In the later phases, the active participation by industrybrought in the technical and economic constraints of the real world of industry andhelped to adapt the concepts. What now has the appearance of a consistent whole isthe result of many iterations and an intense interaction between theoretical insightsand practical necessities.The chapter starts with a short description of the TTA, showing some examplesof the industrial uptake and the impact of the time-triggered technology. Thefollowing section portrays the architectural style of the TTA.
The architecturalstyle explains the key principles that drive the design of an architecture. In the TTA,these principles relate to complexity management, a recursive component concept,coherent communication by a single mechanism, and concern for dependability androbustness. The architectural style is concretized in the architectural services thatform the contents of Sect. 14.3. Space does not permit to describe these services indetail. The reader is referred to other documents, starting with the book onGENESYS [Obm09] to get more in-depth information.
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