An infrastructure for service-oriented embedded internet systems
Sammanfattning: Embedded systems are in general designed to do some specific task, rather than be a general-purpose computer for multiple tasks. Common for embedded systems is that processing devices, sensors, transceivers, actuators, networks, and software are built into a system, encapsulated by the device it controls. Often, the development of various applications requires an embedded system that is small and lightweight, both in terms of hardware and software. Technology advances in ASIC design have enabled digital and analog components on a single chip by integrating e.g. processing, storage, and Micro-Electro-Mechanical System. The vision due to the improved miniaturization is to have self-configured, low-power, and small form-factor platforms that share resources, have access to the environment, and are deployed in an ad hoc fashion. This, together with wireless communication standards, enables ubiquitous access to information anywhere and anytime. Feeding the digital world with information, as measurements of physical phenomenon, is done by the use of sensors. Extending the control from the digital world to the physical world can be achieved by actuators. Combining those sensors and actuators with wireless networking capabilities enables a new paradigm for e.g. scientists, medical personnel, and engineers to observe physical phenomena. The world of networking sensor and actuator devices is vast and covers aspects such as energy-efficient hardware design principles, medium access protocols, routing and transport protocols, embedded operating systems, security, low-power operations, localization, data storage, mobility, and network management etc. All these areas are important for embedded systems targeting the interconnection of small devices. In the scope of this thesis, the embedded system is realized in the form of a small sensor and actuator node, a device with interfaces to measure physical phenomenon and/or affect the surrounding environment. Our primary hypothesis is that standards-based protocols and de facto standards can be utilized as the fundamental operational infrastructure of the sensor and actuator nodes. Using a universal widespread standard protocol can be advantageous in respective to a custom made solution when developing and deploying networking nodes. Today, TCP/IP is the most widespread networking protocol suite in computer communication in use. As a consequence, we show how the readily available TCP/IP protocol suite can be used as a foundation for intra/internetworking even for resource constrained sensor and actuator nodes. A platform that is intelligent and accessible over the Internet opens new possibilities for control, maintenance, and remote monitoring. In this thesis commercial off-the-shelf hardware components are used in combination with software based on standard protocols as a basis for the platform architecture. First, a small wireless networking node accessible from devices in close proximity is presented. The generic architecture enables the rapid development of various applications, adaptable to different usage scenarios. Second, it is shown that a small spontaneous network of mobile nodes can be established, even though the resources on the nodes are very limited. Third, many applications require a large number of small and lightweight nodes to cooperate. However, one of the challenges with networking sensor and actuator nodes is the distributed functionality without central control. The approach taken in this thesis was to leverage emerging technologies to model the functionality of the nodes, thus nodes are provided with the capability and mechanisms to present themselves and to discover peer nodes. Consequently, application-level interoperability is enabled by introducing service discovery techniques which have the potential to automate the discovery of nodes and required services.
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