Dirk Pesch

A testbed for evaluating human interaction with ubiquitous computing environments

Core to ubiquitous computing environments are adaptive software systems that adapt their behavior to the context in which the user is attempting the task the system aims to support. This context is strongly linked with the physical environment in which the task is being performed. The efficacy of such adaptive systems is thus highly dependent on the human perception of the provided system behavior within the context represented by that particular physical environment and social situation. However, effective evaluation of human interaction with adaptive ubiquitous computing technologies has been hindered by the cost and logistics of accurately controlling such environmental context. This paper describes TATUS, a ubiquitous computing simulator aimed at overcoming these cost and logistical issues. Based on a 3D games engine, the simulator has been designed to maximize usability and flexibility in the experimentation of adaptive ubiquitous computing systems. We also describe how this simulator is interfaced with a testbed for wireless communication domain simulation.

Influence of Predicted and Measured Fingerprint on the Accuracy of RSSI-based Indoor Location Systems

WLAN indoor location that is based on received signal strength indication (RSSI) technique needs extensive calibration to build a signal fingerprint. Re-calibration is also needed if there is a major change in the propagation environment. The use of propagation models to predict signal fingerprint becomes an interesting preposition. This paper will investigate the influence of predicted fingerprint on the accuracy of indoor location. They include empirical propagation models (i.e. one-slope model and multi-wall model) and a semi-deterministic model. A framework for indoor location with the nearest-neighbour and particle filter are developed to evaluate predicted and measured fingerprints. In order to take advantage of environment description, a map-filtering technique is also elaborated.

AvroraZ: extending Avrora with an IEEE 802.15.4 compliant radio chip model

This paper presents AvroraZ, an extension of the Avrora emulator -- The AVR Simulation and Analysis Framework -- which allows the emulation of the Atmel AVR microcontroller based sensor node platforms with IEEE 802.15.4 compliant radio chips thus allowing emulation of sensor nodes such as Crossbows MicaZ. AvroraZ is based on design, implementation and verification of several extensions to Avrora: the address recognition algorithm, an indoor radio model, the clear channel assessment (CCA) and link quality indicator (LQI) of the IEEE 802.15.4 standard. We have AvroraZ and demonstrated its correctness in emulating MicaZ code.

A Survey on Web Services in Telecommunications

This article presents a survey of service-oriented architecture and Web services within telecommunications. Telecommunications over the past few years has been in a state of constant flux, with shifts in regulations, increased competition, and technological progress. The article describes these forces in detail and shows that the need for successful adoption of SOA within telecommunication has become a major agenda item for the majority of telecommunication network operators. The article then proceeds to describe SOA and its key enablers in telecommunications - Web services, event-driven architectures, Parlay X/ECMA specifications, and the enterprise service bus.

A wireless sensor network design tool to support building energy management

The physical location of sensor nodes strongly influences the performance of the network from the perspective of accurate data sensing and reliable communication. Therefore deployment planning can be regarded as an essential stepping stone to producing a viable network infrastructure. The research presented in this paper aims to assist the deployment of a Building Management System relying on wireless sensors and actuators. This is accomplished by the development of a WSN design and optimization software tool to support designers and system integrators when undertaking the difficult task of WSN deployment for building energy management.

Duty cycle learning algorithm (DCLA) for IEEE 802.15.4 beacon-enabled wireless sensor networks

The current specification of the IEEE 802.15.4 standard for beacon-enabled wireless sensor networks does not define how the fraction of the time that wireless nodes are active, known as the duty cycle, needs to be configured in order to achieve the optimal network performance in all traffic conditions. The work presented here proposes a duty cycle learning algorithm (DCLA) that adapts the duty cycle during run time without the need of human intervention in order to minimise power consumption while balancing probability of successful data delivery and delay constraints of the application. Running on coordinator devices, DCLA collects network statistics during each active duration to estimate the incoming traffic. Then, at each beacon interval uses the reinforcement learning (RL) framework as the method for learning the best duty cycle. Our approach eliminates the necessity for manually (re-)configuring the nodes duty cycle for the specific requirements of each network deployment. This presents the advantage of greatly reducing the time and cost of the wireless sensor network deployment, operation and management phases. DCLA has low memory and processing requirements making it suitable for typical wireless sensor platforms. Simulations show that DCLA achieves the best overall performance for either constant and event-based traffic when compared with existing IEEE 802.15.4 duty cycle adaptation schemes.

Multi-metric routing decisions for ad hoc networks using fuzzy logic

Routing is an essential function for traffic management in ad hoc networks. Table-based routing algorithms used in proactive protocols are computationally intensive and require periodic transmission of status information amongst all network nodes. Also, routing table volume swells with network size and can be large for dense networks. Therefore to cope with possibly rapidly changing topology reactive protocols such as dynamic source routing (DSR) generate routes for unknown destination paths on an as needs be basis. So as to avoid the continual demand for route discovery in DSR, network nodes record previously determined routes in either path or link caches. A route discovery attempt can possibly result in several paths being uncovered for a single destination. As nodes often have a finite capacity path cache, it may not be possible to store all paths. So as to influence productive caching decisions a fuzzy logic system is applied to the route discovery technique to curb non-optimal network floods. This action causes a cessation in the generation of low quality routes as only paths with good routing metrics are selected for the rebroadcast of route discovery packets. Consequently, route query packets arriving at the necessary destination node, or at some intermediate node with knowledge of the destination node, generate high quality route replies. This paper presents a fuzzy logic based decision algorithm that weighs individual links as a path to the necessary destination is being constructed if this link is deemed suitable by the fuzzy logic system it is added to the path and route construction continue. The fuzzy controller is used to instruct caching decisions and to optimise route selection as only good quality links are recorded in source destination paths.

InRout - A QoS aware route selection algorithm for industrial wireless sensor networks

Wireless sensor networks are a key enabling technology for industrial monitoring applications where the use of wireless infrastructure allows high adaptivity and low cost in terms of installation and retrofitting. To facilitate the move from the current wired designs to wireless designs, concerns regarding reliability must be satisfied. Current standardization efforts for industrial wireless systems lack specification on efficient routing protocols that mitigate reliability concerns. Consequently, this work presents the InRout route selection algorithm, where local information is shared among neighbouring nodes to enable efficient, distributed route selection while satisfying industrial application requirements and considering sensor node resource limitations. Route selection is described as a multi-armed bandit task and uses Q-learning techniques to obtain the best available solution with low overhead. A performance comparison with existing approaches demonstrates the benefits of the InRout algorithm, which satisfies typical quality of service requirements for industrial monitoring applications while considering sensor node resources. Simulation results show that InRout can provide gains ranging from 4% to 60% in the number of successfully delivered packets when compared to current approaches with much lower control overhead.

Performance evaluation of SIP-based multimedia services in UMTS

With an ever increasing penetration of IP technologies and the tremendous growth in wireless data traffic, the wireless industry is evolving the mobile core networks towards IP technology. The third Generation Partnership Project (3GPP) has specified an IP multimedia sub-system (IMS) in UMTS Release 5/6, which is adjunct to the UMTS packet-switched (PS) GPRS core network. This IP-based network provides full packet call control capabilities by using the text-based Session Initiation Protocol (SIP). Initial indications, as to the signalling delay associated with SIP messages, have concerned mobile operators about the viability of SIP services over the UMTS air interface. This article provides an insight into the UMTS system performance, focusing on selected UMTS SIP-based services. Typical services with real-time requirements such as voice as well as delay-sensitive and non-sensitive applications, such as real-time chat and instant messaging services are investigated. Furthermore, the paper discusses and analyses the requirements and possible solutions for improving efficiency of SIP usage in a wireless environment through signalling protocol message compression. Results of a performance evaluation of SIP signalling scenarios are presented in terms of time delay and message overload in the system. Results show that message compression can considerably reduce SIP message transmission time on the radio access network while core network delay contributions are found to be still high.

Towards a wireless sensor platform for energy efficient building operation

Abstract Currently, the IT-support for energy performance rating of buildings is insufficient. So-called IT-platforms often “built” of an ad-hoc, inconsistent combination of off-the-shelf building management components, distributed data metering equipment and several monitoring software tools. A promising approach to achieve consistent, holistic performance data management is the implementation of an integrated, modular wireless sensor platform. This paper presents an approach of how wireless sensors can be seamlessly integrated into existing and future intelligent building management systems supporting improved building performance and diagnostics with an emphasis on energy management.