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Context-aware service platforms need to establish and manage trust relationships for users to know if the user's privacy policies are being enforced and for service providers to control access to their services. Current trust solutions are not suitable for this because they do not address in an integrated manner trust issues related to identity provisioning, privacy enforcement and context information trustworthiness. In addition, due to their hierarchical and centralized design, current trust management solutions do not scale well in the ad-hoc pervasive environments in which context-aware platforms are typically deployed. In this paper we propose context-aware trust domains as a management solution for context-aware service platforms.

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Movement of wireless sensor and actuator networks and of nodes between WSANs are becoming more commonplace. However, enabling remote usage of sensory data in multiple applications, remote configuration and actuation is still a big challenge. The purpose of this paper is to analyse and describe which mobility support can best be used in different scenarios. This paper describes logistic and person monitoring scenarios, where different types of movements take place. These mobility types and their implications are categorized and analysed. Different degrees of support for these mobility types are analysed in the context of the mobility scenarios.

The Ambient middleware supports real-time monitoring and remote maintenance across the Internet via wired and mobile wireless network access technologies. Additionally, the middleware offers easy integration with third-party applications. Ambient Studio utilizes the middleware for remote WSN configuration and monitoring. The ConnectBox utilizes it to monitor and maintain WSNs remotely. This paper describes the Ambient middleware and compares its efficiency with the existing messaging protocols used for instant messaging and web services.

Mobile wireless networks need to maximize their network lifetime (defined as the time until the first node runs out of energy). In the broadcast network lifetime problem, all nodes are sending broadcast traffic, and one asks for an assignment of transmit powers to nodes, and for sets of relay nodes so that the network lifetime is maximized. The selection of a dynamic relay set consisting of a single node (the ‘master’), can be regarded as a special case, providing lower bounds to the optimal lifetime in the general setting. This paper provides a first analysis of a ‘dynamic master selection’ algorithm.

This paper presents a context-aware guidance and messaging system for large buildings and surrounding venues. Smart Signs are a new type of electronic door-and way-sign based on wireless networks. Smart Signs present in-situ personalized guidance and messages, are ubiquitous, and easy to understand. They combine the easiness of use of traditional static signs with the flexibility and reactiveness of navigation systems. The Smart Signs system uses context such as user's mobility limitations, the weather, and possible emergency situations to improve guidance and messaging. The working version of the system has been deployed and tested on the premises of the University of Twente. The first evaluation of the Smart Signs system has been based upon a scenario, in which a visitor arrives at an unfamiliar indoor space. It has shown that when using Smart Signs people tended to find their destination in an unfamiliar environment faster and with fewer errors. Furthermore, the participants expressed a high degree of satisfaction when using Smart Signs applauding the personalization of the signs as well as their efficiency in an effective ex-pression of easily understood navigational aids.

With the growing popularity of Wireless Sensor Networks (WSNs), the demand increases to perform time critical operations within such networks. A WSN is composed of sensor nodes, which contain a radio, ports for multiple sensors and a microcontroller. These sensor nodes have to provide a wide range of functionality as long as possible, while they use their scarce energy from a battery.

Currently, most wireless sensor network applications assume the presence of single-channel Medium Access Control (MAC) protocols. When sensor nodes are densely deployed, single-channel MAC protocols may be inadequate due to the higher demand for the limited bandwidth. To overcome this drawback, we propose multiple channel support for improving the performance. Our method allows the nodes to utilize new frequency channels which results in the significant increase on the number of nodes that are granted access to the wireless medium. The method requires only one half-duplex transceiver per node, which is capable of sending and receiving over distinguished frequency channels. Simulation results show that, method successfully utilizes multiple channels and increases the performance proportional to the number of available frequencies for an example single-channel MAC protocol, LMAC.

We consider the challenge of dynamically adapting services to context changes that occur in ubiquitous computing environments (e.g., changes in a user’s activity) and propose the Context-Aware Service Enabling (CASE) platform for that purpose. The CASE platform combines context-aware service discovery with service composition, acting as an enabler for the development of adaptive context-aware applications. In this paper, we illustrate the need for context-aware service discovery and composition in pervasive 4G environments and present the architecture of the CASE platform. The CASE platform enables applications to easily adapt to changes in service availability, which may result from changes in client and/or service context. We also provide an overview of the platform’s technical realization.

Positioning technology is rapidly making its way into the consumer market, not only through the already ubiquitous cell phone but soon also through small, on-board positioning devices in many means of transport and in types of portable equipment. It is thus to be expected that all these devices will start to generate an unprecedented data stream of time-stamped positions. Sooner or later, such enormous volumes of data will lead to storage, transmission, computation, and display challenges. Hence, the need for compression techniques. Previously some work has been done in data compression for GIS and mainly in line generalization area considering two dimensional data. However, time-stamped positions data do not form a line, as they are historically traced points. On the other hand, researches in compression for time series data mainly deal with one dimensional time series and are good for short time series and in absence of noise. This paper addresses the drawbacks of existing compression techniques and describes different techniques to compress short as well as lengthy stream of time-stamped positions data.

In recent years, surgical robotic tools have been introduced in the medical and environment, leading to a significant decrease in the invasiveness of most surgical procedures. Starting from robotic manipulators, these tools have evolved in a plethora of devices, ranging from robotic endoscopes to steerable needles and catheters. In this doctoral thesis, we investigate an alternative approach to robotic surgery: the development of microscopic and unethered robots capable of navigating the human vascular network and performing surgeries in hard-to-reach areas. In particular, we look at the advantages and limitations of microrobotics, proposing novel solutions to some of the main challenges in the field.