If a mobile computing device knows how it is positioned and oriented in relation to other devices nearby, then it can provide enhanced support for multi-device and multi-user interactions. Existing systems that provide position information to mobile computers are reliant on externally deployed infrastructure, such as beacons or sensors in the environment. We introduce the Relate system, which provides fine-grained relative position information to co-located devices on the basis of peer-topeer sensing, thus overcoming dependence on any external infrastructure. The system is realised as a hardware/software plug-in, using ultrasound for peer-to-peer sensing, USB to interface with standard mobile devices, and data abstraction and inferencing to map sensor data to a spatial model that maintains both quantitative and qualitative relationships. We present a set of services and applications to demonstrate the utility of the system. We report experimental results on the accuracy of the relative position and orientation estimates, and other aspects of system performance.

Abstract. Ubicomp environments impose tough constraints on networks, including immediate communication, low energy consumption, minimal maintenance and administration. With the AwareCon network, we address these challenges by prescribing an integrated architecture that differs from classical networking by featuring an awareness of the surrounding situation and context. In various settings, where AwareCon was implemented on tiny battery driven devices, we show that applications and usability of devices benefit from this approach.

Ensuring authenticity and integrity are important tasks when dealing with goods. While in the past seal wax was used to ensure the integrity, electronic devices are now able to take over this functionality and provide better, more fine grained, more automated and more secure supervision. This paper presents eSeal, a system with a computational device at its core that can be attached to a good, services in the network and a communication protocol. The system is able to control various kinds of integrity settings and to notify authenticated instances about consequent violations of integrity. The system works without infrastructure so that goods can be supervised that are only accessible in certain locations. The paper motivates the eSeal system and its design decisions, lists several types of integrity scenarios, presents the communication protocol and identifies practical conditions for design and implementation. An implementation in a business relevant scenario is presented as a proof of concept. The eSeal system, see Figure 2, consists of three conceptual layers: (1) the Contractual, (2) the Logical, and (3) the Technical.

Abstract-In this paper, we present two methods for calibration of acceleration sensors that are inexpensive, in-situ, require minimum user interaction and are targeted to a broad set of acceleration sensor applications and devices. We overcome the necessity of orthogonal axes alignment by extending existing calibration methods with a non-orthogonal axes model. Our non-orthogonal method can furthermore be used to enable automatic calibration for 1-or 2-axes accelerometers or realize a simultaneous mass-calibration of sensors with minimum effort. The influence of noise to the presented calibration methods is analysed.

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