Embedded Internet System Architectures

Today, using computers is a daily thing for many people over the world. We use computers to for example communicate, read news, search for sport-events, correspond with e-mail, participate in meetings, and download the latest polyphonic ring tones for our mobile phones. This digital world is often distinguished from the outside world, or the physical world. 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 controlling actuators. Combining those sensor and actuators with wireless networking capabilities enables a new paradigm to for example scientists, medical personnel, and engineers to observe physical phenomena and react to it. The world of networking sensors is vast and covers aspects such as communication protocols, ubiquitous computing environments, embedded operating systems, embedded system designs, security, low-power operations, location-awareness, and middleware issues etc. At Luleå University of Technology, EISLAB, the development of various applications requires a platform, in terms of both hardware and software, to form a network of wireless nodes. A platform that is intelligent and accessible over the Internet opens new possibilities for system fault detection, 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. The focus has been on a collection of small, battery-operated, and autonomous wireless networking nodes. The thesis makes contribution to the area by exploring and elaborating the possibilities of making those resource limited nodes accessible over the public Internet. First, a small wireless networking sensor unit accessible from devices in close proximity is presented. The generic architecture enables the rapid development of various applications, adaptable to different usage scenarios. Second, an architecture (and the implementation of the architecture) is presented where devices like simple sensors become accessible as nodes on the public Internet. The architecture enables direct access to collected measurements and events from the physical world. Third, it is shown that a small spontaneous network of mobile nodes can be established, even though the resources on the nodes are very limited. The nodes do not have to be user operated and can selfestablish a connection with an appropriate access point. 4 THESIS INTRODUCTION