Tobias Zimmer

A Location Model for Communicating and Processing of Context

Abstract: Location is one of the most important elements of context in ubiquitous computing. In this paper we describe a location model, a spatial-aware communication model and an implementation of the models that exploit location for processing and communicating context. The location model presented describes a location tree, which contains human-readable semantic and geometric information about an organisation and a structure to describe the current location of an object or a context. The proposed system is dedicated to work not only on more powerful devices like handhelds, but also on small computer systems that are embedded into everyday artefact (making them a digital artefact). Model and design decisions were made on the basis of experiences from three prototype setups with several applications, which we built from 1998 to 2002. While running these prototypes we collected experiences from designers, implementers and users and formulated them as guidelines in this paper. All the prototype applications heavily use location information for providing their functionality. We found that location is not only of use as information for the application but also important for communicating context. In this paper we introduce the concept of spatial-aware communication where data is communicated based on the relative location of digital artefacts rather than on their identity.

The particle computer system

This paper presents a sensor-based, networked embedded system, referred to as the particle computer system. It is comprised of tiny wireless sensor nodes, capable of communication with each other, as well as connectivity with backend, PC-based systems, thereby facilitating software development and data analysis in an integrated systems package. The core design principles of the sensor nodes enable operation in very mobile settings and truly ad-hoc, peer-to-peer interoperation without the intervention of a master or explicit middleware layer. The two main system properties highlighted in this paper are: 1) information distribution to all components within the system and 2) the usage of a common communication language in all system components. This language has been proprietarily developed for the particle system and is known as ConCom. As a result of these system properties, we have found the particle system to be very extensible and applicable in many everyday scenarios. The paper presents insights to the implementation of the particle computer system, including software development and data analysis capabilities, and the overall system integration.

AwareCon: Situation Aware Context Communication

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, as it features 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.

Collaborative sensing in a retail store using synchronous distributed jam signalling

The retail store environment is a challenging application area for Pervasive Computing technologies. It has demanding base conditions due to the number and complexity of the interdependent processes involved. We present first results of an ongoing study with dm-drogerie markt, a large chemists retailer, that indicate that supporting product monitoring tasks with novel pervasive technology is useful but still needs technical advances. Based on this study, we uncover problems that occur when using identification technology (such as RFID) for product monitoring. The individual identification struggles with data overload and inefficient channel access due to the high number of tags involved. We address these problems with the concept of Radio Channel Computing, combining approaches from information theory, such as the method of types and multiple access adder channels. We realise data pre-processing on the physical layer and significantly improve response time and scalability. With mathematical formulation, simulations and a real world implementation, we evaluate and prove the usefulness of the proposed system.

Inexpensive and automatic calibration for acceleration sensors

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.

Towards a better understanding of context attributes

The use of context as an input is one of the major characteristics of ubiquitous computing systems. We look into the structural and the systematic features of context in ubiquitous computing environments and their possible influence on context computing and the design of context-aware applications. We give a definition regarding an understanding of context and how it is derived at a systematic level. Context interaction is investigated by a consumer-producer schema that models the exchange of context among artefacts. Validity, relevance, reliability and context history are identified and discussed as relevant systematic attributes of context.

The uPart experience: building a wireless sensor network

This paper presents an experience report illustrating the design of the uPart tiny low-power sensor network platform: from the analysis phase over the definition of the application, design and construction of hardware, the implementation of the software and network to the application set-up. uPart sensor nodes were given away in the conference badge to 500 voluntary attendees of the Ubicomp 2005. In our demo application, uParts were able to recognize activities of attendees of the Ubicomp 2005 conference. Design was carried out under serve time and budget restrictions. The paper focuses on reporting design decisions and presents technical details of uPart hardware, firmware and applications. It also shows first qualitative experiences with the run of the system at the conference. The outcome of the paper is a general meta-guideline for designing sensor network systems under similar conditions.

Using a Context Quality Measure for Improving Smart Appliances

Many ubicomp appliances require the recognition of context. Existing context systems do not provide information about the quality of the context recognized to the appliance at runtime. In this paper we propose the first context quality system which gives quantitative measures, the context quality measure (CQM), in real time. The CQM can be used by application to improve decision quality when interpreting context values. Our Fuzzy Inference System based approach considers the context detection algorithm as a black-box. It is therefore able to give generalized independet context quality measures and is applicable as an add-on to any context recognition system. A first practical implementation shows a gain of 33% in context detection quality in tested application scenarios.

The uPart experience: The uPart experience

This paper presents an experience report illustrating the design of the uPart tiny low-power sensor network platform: from the analysis phase over the definition of the application, design and construction of hardware, the implementation of the software and network to the application set-up. uPart sensor nodes were given away in the conference badge to 500 voluntary attendees of the Ubicomp 2005. In our demo application, uParts were able to recognize activities of attendees of the Ubicomp 2005 conference. Design was carried out under serve time and budget restrictions. The paper focuses on reporting design decisions and presents tech-nical details of uPart hardeware, firmware and applications. It also shows first qualitative experiences with the run of the system at the conference. The outcome of the paper is a general meta-guideline for designing sensor network systems under similar conditions.This paper presents an experience report illustrating the design of the uPart tiny low-power sensor network platform: from the analysis phase over the definition of the application, design and construction of hardware, the implementation of the software and network to the application set-up. uPart sensor nodes were given away in the conference badge to 500 voluntary attendees of the Ubicomp 2005. In our demo application, uParts were able to recognize activities of attendees of the Ubicomp 2005 conference. Design was carried out under serve time and budget restrictions. The paper focuses on reporting design decisions and presents tech-nical details of uPart hardeware, firmware and applications. It also shows first qualitative experiences with the run of the system at the conference. The outcome of the paper is a general meta-guideline for designing sensor network systems under similar conditions.

AwareOffice: Integrating Modular Context-Aware Applications

Developing valuable context-aware applications is at the centre of research in Ubicomp. In this paper we want to describe our experience over the last years in designing and developing such applications and in integrating them to build homogeneous Ubicomp environments. We introduce the concept of modular integration of context-aware application by presenting the AwareOffice TecO’s test bed for all kinds of context-aware applications form the office domain. We will show how we can easily build new applications by simply exploiting the modularity of our system. Therefore we introduce some base applications of the AwareOffice in some detail and show how to build more complex applications by modularly integrating them.