Moby Dick

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Moby Dick

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On-line publications
(2002 - 2001 – 2000 – 1999 – 1998 – 1997 - 1996, …. )

 

The publications sorted by subject can be found here.

2002

·         Influences of Rake receiver/Turbo decoder parameters on energy consumption and Quality
Smit L.T., Smit G.J.M., Havinga P.J.M., Hurink J.L., Broersma H., Proceedings World Wireless Congress, San Francisco, Delson group Inc. ISBN 1529-2592, pp 175-181, May 2002.

·         A reconfigurable function array architecture for 3G and 4G wireless terminals
Heysters P.M., Bouma H., Smit J., Smit G.J.M., Havinga P.J.M., Proceedings World Wireless Congress, San Francisco, Delson group Inc. ISBN 1529-2592, pp 399-405, May 2002.

·         Energy Efficient TCP
Donckers L., Havinga P.J.M., Smit G.J.M., Smit L.T., Proceedings 2nd Asian International Mobile Computing conference (AMOC2002), Malaysia, ACM Sigmobile, ISBN 983-40633-1-8, pp 18-28, May 2002.

·         WCRP – A WAP based multi-vehicle Personal Navigation Service
Gorter J., Gorter O., de Keijzer A., Speekenbrink D.G., Havinga P.J.M., Smit G.J.M., Heysters P.M., Proceedings 2nd Asian International Mobile Computing conference (AMOC2002), Malaysia, ACM Sigmobile, ISBN 983-40633-1-8, pp 69-75, May 2002.

·         MIRAI Architecture for Heterogeneous Network
G. Wu, P. Havinga, and M. Mizuno, IEEE Communications Magazine, February 2002

·         Enhancing Energy Efficient TCP by Partial Reliability
Donckers L., Havinga P.J.M., Smit G.J.M, Smit L.T., 13th IEEE International Symposium on Personal, indoor and mobile radio communications (PIMRC'2002), Lisboa, Portugal, September 15-18, 2002.

·         Dynamic Reconfiguration in Mobile Systems
Smit G.J.M., Havinga P.J.M., Smit L.T., Heysters P.M., Rosien M., 12th International Conference on Field Programmable Logic and Application, Montpellier, September 2002.

·         Max-Log-MAP Mapping on an FPFA
Heysters P.M., Smit L.T., Smit G.J.M., Havinga P.J.M., Proceedings of International Conference on Engineering of Reconfigurable Systems and Algorithms (ERSA '02) Las Vegas, June 2002

2001

·         Architectures for Ubiquitous Computing
G.J.M. Smit, P.J.M. Havinga, J. Scholten: PT Embedded Systems, Vol.3 dossier 2002, pp. 8-11, Ten Hagen & Stam Uitgevers, ISSN 1389-1905, December 2001

·         Wireless Internet over Heterogeneous Wireless Networks
G. Wu, P. Havinga, and M. Mizuno, IEEE GLOBECOM’01, pp. 1759-1765, San Antonio, Nov. 2001.

·         Parameter Selection At Run-Time To Optimize Energy Efficiency
Lodewijk T. Smit, Gerard J.M. Smit, Paul J.M. Havinga
PROGRESS 2001, proceedings 2nd workshop on Embedded Systems, pp. 227-236, ISBN 90-73461-27-X, Veldhoven, the Netherlands, October 2001.
Energy efficiency is vital for a mobile terminal. In this paper we investigate how to choose the right parameter settings at run-time so that the energy consumption is minimized while satisfying the required level of service. To use a real world example, the energy consumption of a third generation telephone WCDMA downlink receiver with turbo decoding forward error correction is considered. A trade-off is made between the number of fingers of a rake receiver and the number of iterations of the turbo decoder. A simulation environment is constructed to simulate the system. In this paper we present graphs, with which the trade-off can be easily made.

·         Reconfigurable System Design: The Control Part
Paul M. Heysters, Henri Bouma, Jaap Smit, Gerard J.M. Smit, Paul J.M. Havinga
PROGRESS 2001, proceedings 2nd workshop on Embedded Systems, pp. 89-94, ISBN 90-73461-27-X, Veldhoven, the Netherlands, October 2001.
Advancement in low-power hand-held multimedia systems requires exploration of novel system architectures. In conventional computer architectures, an increase in processing power also implies an increase in energy consumption. In a mobile system this results in a shorter operating-time. Limiting the generality of an architecture can improve its energy efficiency. However, application specific architectures have a number of drawbacks and are too restricted. Therefore, an application domain specific architecture is proposed. As part of an application domain specific architecture for the digital signal-processing domain, the Field Programmable Function Array (FPFA) was conceived. The FPFA is a reconfigurable device with a data-path that can be configured to implement a number of DSP algorithms energy efficiently. The flexibility in the FPFA results in a data-path that requires many control signals. To reduce the vast amount of control signals, the FPFA control-path uses a combination of configuration registers and vertical microprogramming.

  • Micro Scanning Probe Array Memory (μSPAM)
    Mathieu Bolks, Ferdy Hanssen, Leon Abelmann, Paul Havinga, Pieter Hartel, Pierre Jansen, Cock Lodder, Gerard Smit
    PROGRESS 2001, proceedings 2nd workshop on Embedded Systems, pp. 17-26, ISBN 90-73461-27-X, Veldhoven, the Netherlands, October 2001.
    The design for a new type of non-volatile mass storage memory is discussed. This new design, based on scanning probe techniques, combines the low volume and power consumption of the FlashRAM, with the high capacity of the hard disk. The small form factor of the device makes it an excellent candidate for mass storage in handheld embedded systems. Its hierarchical architecture allows us to make a trade-off between data-rate, access time and power consumption. The power consumption scales linearly with the desired data-rate, and is expected to be lower than what can be achieved with competing technologies.
  • Resource Management for Seamless Mobile Services
    Havinga P.J.M., Vognild L., Smit G.J.M, Wu G.
    The fourth international symposium on wireless personal multimedia communications (WPMC), September 2001
    The seamless provisioning of services and applications across heterogeneous wireless systems will play a key role in future communication systems. While each individual enabling wireless technology is advanced and stable, or is expected to become mature in the near future, a framework for enabling the management of this heterogeneous infrastructure efficiently and user-friendly, does not exist yet. We address these challenges within the SMART project with the invention of a novel architecture for seamless provision of mobile services over heterogeneous wireless networks. The SMART architecture is scalable, is able to use the available resources efficiently (like network, energy, and money), and makes the heterogeneous network transparent to, but nevertheless under control of the user. User-friendliness, security, and efficiency are the key goals of the architecture. In SMART all these issues are being dealt with in an integrated, coherent way.
  • Mobile Multimedia Systems
    P.J.M. Havinga, G.J.M. Smit
    Chapter 15 of     “Electronic Business and Education, Recent Advances in Internet Infrastructures” (edited by Wendy Chin, Frédéric Patricelli, Veljko Milutinovic), Kluwer Academic Publishers, Boston, ISBN 0-7923-7508-4, August 2001.
  • The SMART project: Exploiting the Heterogeneous Mobile World
    Havinga P.J.M., Smit G.J.M, Wu G., Vognild L.
    session on "Wireless Internet: Protocols and Applications" as part of the 2nd International Conference on Internet Computing, (invited), Las Vegas, USA, June 2001.
  • Energy efficient TCP
    Donckers L.
    Master’s thesis University of Twente, department of Computer Science    , May 2001
    This thesis describes the design of an energy-efficient transport protocol for mobile wireless communication. We first describe the metrics used to measure the energy efficiency of transport protocols. These metrics were used to study the performance of TCP/IP on wireless links carefully. Four problem areas are defined that prevent TCP/IP from reaching high levels of energy efficiency. For these problem areas, solutions are proposed and their feasibility is examined. The results of this study were used to design E2TCP. A simulation model of this proposed energy-efficient transport protocol has been implemented and was subject to a thorough evaluation. The results show that E2TCP not only has a higher energy efficiency than TCP/IP, but it also manages to outperform TCP/IP on more traditional performance metrics: throughput and latency.
  • Energy management for dynamically reconfigurable heterogeneous mobile systems
    Havinga P.J.M., Smit L.T., Smit G.J.M., Bos M., Heysters P.M.
    10th Heterogeneous Computing Workshop, San Francisco, USA, April 2001
    Dynamically reconfigurable systems offer the potential for realising efficient systems as well as providing adaptability to changing system requirements. Such systems are suitable for future mobile multimedia systems that have limited battery resources, must handle diverse data types, and must operate in dynamic application and communication environments. We propose an approach in which reconfiguration is applied dynamically at various levels of a mobile system, whereas traditionally, reconfigurable systems mainly focus at the gate level only. The research performed in the CHAMELEON project aims at designing such a heterogeneous reconfigurable mobile system. The two main motivations for the system are 1) to have an energy-efficient system, while 2) achieving an adequate Quality of Service for applications.
  • QoS scheduling for energy-efficient wireless communication
    Havinga P.J.M., Smit G.J.M.
    International Conference on Information Technology: Coding and Computing (ITCC2001), special session on recent advances in wireless networking and communications (invited), Las Vegas, USA, April 2-4, 2001
    In this paper we present a QoS scheduler that assigns the bandwidth over the wireless channel such that the amount of energy spend by the mobile is minimized, while maintaining the Quality of Service of the connections. Energy efficiency is an important issue for mobile computers since they must rely on their batteries. We have designed and implemented an energy-efficient architecture and MAC protocol for wireless multimedia traffic. The scheduling is based on two mechanisms, 1) a short term transmission frame scheduling that concatenates uplink and downlink traffic of one mobile, and 2) a long-term scheduling, that tries to collect traffic as much as possible within the QoS requirements of the connections. The result is that the transceiver can be in a low-power operating mode for an extended period of time and that the number of operating mode transitions is reduced.
  • Architecture of Multimedia Integrated network by Radio Access Innovation (MIRAI)
    G. Wu, P. J. M. Havinga, and M. Mizuno
    IEICE Tech. Report, March 2001.
  • Wireless Internet on Heterogeneous Networks
    Havinga P.J.M., Wu G.
    workshop on Mobile Communications in Perspective, Enschede, the Netherlands, February 2001.
    The wide proliferation of wireless systems and the use of software radio technologies enables the employment of a heterogeneous network. In this concept services are delivered via the network that is most efficient for that service. The solution is based on a common core network that interconnects access points of various wireless access points. A mobile host can apply multiple different access networks simultaneously to increase capacity or efficiency. A basic access network, separated from other wireless access networks, is used as a means for wireless system discovery, signaling and paging. Quality of Service is of prominent importance due to the heterogeneous environment and the characteristics of the wireless channel. This paper describes the concepts of our architecture, and presents an overview of the architecture.
  • Energy-efficient wireless networking for multimedia applications
    Havinga P.J.M., Smit G.J.M.
    Wireless Communications and Mobile Computing, Wiley, 2001.
    In this paper we identify the most prominent problems of wireless multimedia networking and present several state-of-the-art solutions with a focus on energy efficiency. Three key problems in networked wireless multimedia systems are 1) the need to maintain a minimum quality of service over time-varying channels, 2) to operate with limited energy resources, and 3) to operate in a heterogeneous environment. We identify two main principles to solve these problems. The first principle is that energy efficiency should involve all layers of the system. Second, Quality of Service is an essential mechanism for mobile multimedia systems not only to give users an adequate level of service, but also as a tool to achieve an energy-efficient system. Due to the dynamic wireless environment, adaptability of the system will be a key issue in achieving this.

2000

  • Energy-efficient TDMA medium access control protocol scheduling
    Havinga P.J.M., Smit G.J.M.
    proceedings Asian International Mobile Computing Conference (AMOC 2000), Nov. 2000.
    In this paper we study the energy efficiency and channel efficiency of TDMA MAC protocol scheduling mechanisms. Most MAC protocols are based on phase grouping that basically has three phases in a frame: uplink, downlink and reservation. We propose a new mechanism in which we have multiple uplink and downlink phases. These phases are grouped per mobile in a frame. Although this has a negative effect on the capacity of the channel, it allows the mobile to turn the power off from the wireless interface for a longer period. We made this choice since in a mobile multimedia environment it is more important that connections have a certain QoS, than highest possible bandwidth. We present an analysis in which these two basic mechanisms are compared in respect to bandwidth efficiency and energy efficiency. We have developed and implemented a novel MAC protocol based on mobile grouping that provides Quality of Service (QoS) support for diverse traffic types.
  • Mapping the SISO Module of the Turbo Decoder to a FPFA
    G. Smit, P. Heysters, P. Havinga, L. Smit, J. Dilessen, J. Huisken
    proceedings Second International Symposium on Mobile Multimedia Systems & Applications (MMSA2000), November 2000.
    In the CHAMELEON project a reconfigurable systems-architecture, the Field Programmable Function Array (FPFA) is introduced. FPFAs are reminiscent to FPGAs, but have a matrix of ALUs and lookup tables instead of Configurable Logic Blocks (CLBs). The FPFA can be regarded as a low power reconfigurable accelerator for an application specific domain. In this paper we show how the SISO (Soft Input Soft Output) module of the Turbo decoding algorithm can be mapped on the reconfigurable FPFA.
  • Exploring Energy-Efficient Reconfigurable Architectures for DSP Algorithms
    Heysters P.M., Smit J., Smit G.J.M., Havinga P.J.M.
    proceedings PROGRESS 2000 workshop, pp. 37-46, ISBN 90-73461-22-7, Oct. 2000.
    Future hand-held multimedia terminals require a very high performance on a very small energy budged. Such devices can only be realized if their entire system is energy cognisant. In this paper a reconfigurable systems-architecture for mobile multimedia systems is introduced. The Field Programmable Function Array (FPFA) is discussed in detail. Several digital signal processing algorithms are discussed and applied on the FPFA. Also, the power radius theory about low-power design is introduced.
  • Run-time Energy Management for Mobiles
    Smit L.T., Smit G.J.M. and Havinga P.J.M.
    proceedings PROGRESS 2000 workshop, pp. 107-112, ISBN 90-73461-22-7, Oct. 2000.
    Due to limited energy resources, mobile computing requires an energy efficient architecture. The dynamic nature of a mobile environment demands an architecture that allows adapting to (quickly chan in conditions. The mobile has to adapt dynamically to new circumstances in the best suitable manner. The hardware and software architecture should be able to support such adaptability and minimize the energy consumption by making resource allocation decisions at run-time. To make these decisions effective, a tradeoff has to be made between computation, communication and initialization costs (both time and energy). This paper describes our approach to construct a model that supports taking such decisions.
  • Channel Communication and Reconfigurable Hardware
    Bos M., Havinga P.J.M., Smit G.J.M.
    proceedings PROGRESS 2000 workshop, pp. 11-14, ISBN 90-73461-22-7, Oct. 2000.
    Many applications can be structured as a set of processes or threads that communicate via channels. These threads can be executed on various platforms (e.g. general purpose CPU, DSP, FPGA, etc). In our research we apply channels as a basic communication mechanism between threads in a reconfigurable system. The research involves providing system level functions to describe the setup of communicating threads, which may now either run timeshared on a general CPU or in dynamically-setup special purpose logic that runs on reconfigurable hardware. The use of channels and threads running in both software and hardware, will be made transparent for the application level programmers by the system level functions. By first describing the threads and how they are connected and then letting the operating system decide on ’geograph-ical’ placement of the threads and buffers, multiprogram-ming will be supported and programs will be able to run on different setups of hardware (i.e. different amount of CPUs or available programmable logic). This is an ongoing work, the paper is a collection of thoughts, which lead to a first setup of rudimentary support functions in the operating system.
  • Reconfiguration in mobile multimedia systems
    Smit G.J.M., Havinga P.J.M., Bos M., Smit L.T., Heysters P.M.
    proceedings PROGRESS 2000 workshop, pp. 95-106, ISBN 90-73461-22-7, Oct. 2000.
    Dynamically reconfigurable systems offer the potential for realising efficient systems as well as providing adaptability to changing system requirements. Such systems are suitable for future mobile multimedia systems that have limited battery resources, must handle diverse data types, and must operate in dynamic application and communication environments. We propose an approach in which reconfiguration is applied dynamically at various levels of a mobile system, whereas traditionally, reconfigurable systems mainly focus at the gate level only. The research performed in the CHAMELEON project aims at designing such a heterogeneous reconfigurable mobile system. The two main motivations for the system are 1) to have an energy-efficient system, while 2) achieving an adequate Quality of Service for applications.
  • Lessons learned from the design of a mobile multimedia system in the MOBY DICK project
    G.J.M. Smit, P.J.M. Havinga
    HUC2k, Bristol, UK, September 2000
    The research performed in the MOBY DICK project is about designing a mobile multimedia system. This paper discusses the approach made in the MOBY DICK project to solve some of the problems involved, discusses its contributions, and accesses what was learned from the project.
  • Mapping of DSP Algorithms on Field Programmable Function Arrays
    Paul M. Heysters, Jaap Smit, Gerard J.M. Smit, Paul J.M. Havinga
    FPL2000, August 2000
    This position paper discusses reconfigurability issues in low-power hand-held multimedia systems. A reconfigurable systems-architecture is introduced, with a focus on a Field Programmable Function Array (FPFA). Application domain specific algorithms determine the granularity of FPFA processor tiles. Several algorithms are discussed and mapped onto a FPFA processor tile.
  • Moby Dick, on the design of a Swiss army knife of computing
    P.J.M. Havinga, G.J.M. Smit
    International Conference on Advances in infrastructure for Electronic Business, Science, and Education on the internet (SSGRR 2000), L'Aquila, Italy, August, 2000
    Recent advances in wireless networking technology and the exponential development of semiconductor technology have engendered a new paradigm of computing, called personal mobile computing or ubiquitous computing. This offers a vision of the future with a much richer and more exciting set of architecture research challenges than extrapolations of the current desktop architectures. In particular, these devices will have limited battery resources, will handle diverse data types, and will operate in environments that are insecure, dynamic and which vary significantly in time and location. The research performed in the MOBY DICK project is about designing such a mobile multimedia system. This paper discusses the approach made in the MOBY DICK project to solve some of these problems, discusses its contributions, and accesses what was learned from the project.
  • Energy efficient adaptive wireless network design
    P.J.M. Havinga, G.J.M. Smit, Martinus Bos
    The Fifth Symposium on Computers and Communications (ISCC'00), Antibes, France, July 3-7, 2000
    Energy efficiency is an important issue for mobile computers since they must rely on their batteries. We present an energy-efficient highly adaptive architecture of a network interface and novel data link layer protocol for wireless networks that provides Quality of Service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations are necessary to achieve energy efficiency and an acceptable quality of service. The paper provides a review of ideas and techniques relevant to the design of an energy efficient adaptive wireless network. In our approach we apply adaptability through all layers of the protocol stack, and provide feedback to the applications. In this way the applications can adapt the data streams, and the network protocols can adapt the communication parameters. We present an overview of the techniques we have applied for our wireless system.
  • Mobile Multimedia Systems
    P.J.M. Havinga
    Ph.D. thesis University of Twente, February 2000, ISBN 90-365-1406-1
    The research presented in this thesis addresses the design of an architecture for a mobile multimedia handheld computer. Energy efficiency and Quality of Service is important for these systems. We show that the key to energy efficiency will be achieved in the design of the higher layers of the system, its system architecture, its operating system, and the entire network. Of special importance in this are the communication channels. Quality of Service is used not only to give users an adequate level of service, but also as a tool to achieve an energy efficient system.
    Specific contributions of the research described in this thesis are the design of an energy-efficient architecture for mobile multimedia systems and a reconfigurable connection switch, as well as the design of crucial wireless network functions (i.e. MAC protocol, adaptable network interface, and a model for adaptable error-correction) that are energy efficient and can support multimedia traffic.
  • Moby Dick, het ontwerp van een Digitale Kameraad (in Dutch)
    P.J.M. Havinga, G.J.M. Smit
    I/O Vivat, May 2000, Vol. 16-3, ISSN 1389-0468.
    Zullen de zaktelefoon en de mobiele computer uitgroeien tot een Digitale Kameraad waarmee je betaalt, de voordeur opent, jezelf identificeert en luistert naar muziek tijdens het joggen? Dit is een vraag waar het MOBY DICK project zich mee bezig houdt. In het MOBY DICK project van het cluster Embedded Systemen wordt onderzoek gedaan aan dergelijke systemen.
  • Energy efficient wireless ATM design
    P.J.M. Havinga, G.J.M. Smit, Martinus Bos
    ACM/Baltzer Journal on Mobile Networks and Applications (MONET), Special issue on Wireless Mobile ATM technologies, Vol. 5, No 2., 2000
    We present an architecture for wireless ATM and a novel MAC protocol that achieves a good energy efficiency of the wireless interface of the mobile and provides QoS support for diverse traffic types. The scheduler of the base station is responsible for providing the required QoS to connections on the wireless link and to minimise the amount of energy spent by the mobile. The main principles used are to avoid unsuccessful actions, to minimise the number of transitions, and to synchronise the mobile and the base-station. We will show that considerable amounts of energy can be saved using these principles. In the protocol the actions of the mobile are minimised. The base-station with plenty of energy performs actions in courtesy of the mobile. We have paid much attention in reducing the cost for a mobile of just being connected. The protocol is able to provide near-optimal energy efficiency (i.e. energy is spent for the actual transfer only) for a mobile within the constraints of the QoS of all connections in a cell, and only requires a small overhead.
  • Design techniques for low-power systems
    P.J.M. Havinga, G.J.M. Smit
    (Journal of Systems Architecture, Vol. 46, Iss. 1, 2000)
    Portable products are being used increasingly. Because these systems are battery powered, reducing power consumption is vital. In this report we give the properties of low power design and techniques to exploit them on the architecture of the system. We focus on: minimizing capacitance, avoiding unnecessary and wasteful activity, and reducing voltage and frequency. We review energy reduction techniques in the architecture and design of a hand-held computer and the wireless communication system, including error control, sys tem decomposition, communication and MAC protocols, and low power short range networks.

1999

  • Reconfigurable Mobile Multimedia Systems
    G.J.M. Smit, Martinus Bos, Paul J.M. Havinga, Jaap Smit
    (ProRISC workshop on Circuits, Systems and Signal Processing, ProRISC'99, pp. 431-436, November 1999)
    This paper discusses reconfigurability issues in low-power hand-held multimedia systems, with particular emphasis on energy conservation. We claim that a radical new approach has to be taken in order to fulfill the requirements - in terms of processing power and energy consumption - of future mobile applications. A reconfigurable systems-architecture in combination with a QoS driven operating system is introduced that can deal with the inherent dynamics of a mobile system. We present the preliminary results of studies we have done on reconfiguration in hand-held mobile computers: by having reconfigurable media streams, by using reconfigurable processing modules and by migrating functions.
  • Single shared memory space architecture for less power
    M. Bos, Paul J.M. Havinga, G.J.M. Smit
    (ProRISC workshop on Circuits, Systems and Signal Processing, ProRISC'99, pp. 43-48, November 1999)
    Virtual Memory and Hardware Memory Pro-tection are so common now that they are even used in hand-held devices that do not include any secondary storage to swap to. As most handhelds depend on batteries for their power supply, it seems worth investigating an architecture without these expensive pieces of hardware. New type safe languages may allow dropping the memory protection hard-ware as well. This paper describes the first investigations done in this direction. Both benefits and drawbacks are described and ways to minimize the drawbacks are inves-tigated.
  • Octopus - an energy-efficient architecture for wireless multimedia systems
    P.J.M. Havinga, G.J.M. Smit
    (ProRISC workshop on Circuits, Systems and Signal Processing, ProRISC'99, pp. 185-192, November 1999)
    Multimedia computing and mobile computing are two trends that will lead to a new application domain in the near future. However, the technological challenges to establishing this paradigm of computing are non-trivial. Personal mobile computing offers a vision of the future with a much richer and more exciting set of architecture research challenges than extrapolations of the current desktop architectures. In particular, these devices will have limited battery resources, will handle diverse data types, and will operate in environments that are insecure, dynamic and which vary significantly in time and location. The approach we made to achieve such a system is to use autonomous, adaptable modules, interconnected by a switch rather than by a bus, and to offload as much as work as possible from the CPU to programmable modules that is placed in the data streams. A reconfigurable internal communication network switch called Octopus exploits locality of reference and eliminates wasteful data copies.
  • Chameleon - reconfigurability in hand-held multimedia computers
    Gerard J.M. Smit, Martinus Bos, Paul J.M. Havinga, Sape J. Mullender, Jaap Smit
    (Handheld and Ubiquitous Computing, HUC'99, September 1999)
    In this paper a reconfigurable systems-architecture in combination with a QoS driven operating system is introduced that can deal with the inherent dynamics of future mobile systems. We claim that a radical new approach has to be taken in order to fulfill the requirements - in terms of processing power and energy consumption - of future mobile applications.
  • Octopus: embracing the energy efficiency of handheld multimedia computers
    Paul J.M. Havinga, Gerard J.M. Smit
    (ACM/IEEE Mobicom, August 1999)
    In the MOBY DICK project we develop and define the architecture of a new generation of mobile hand-held computers called Mobile Digital Companions. The Companion has an unconventional architecture that saves energy by using system decomposition at different levels of the architecture and exploits locality of reference with dedicated, optimised modules. A reconfigurable internal communication network switch called Octopus exploits locality of reference and eliminates wasteful data copies. The switch is implemented as a simplified ATM switch and provides Quality of Service guarantees and enough bandwidth for multimedia applications. We have built a testbed of the architecture, of which we will present performance and energy consumption characteristics.
  • Energy efficiency of error correction on wireless systems
    Paul J.M. Havinga
    (IEEE Wireless Communications and Networking Conference, September 1999)
    Since high error rates are inevitable to the wireless environment, energy efficient error control is an important issue for mobile computing systems. We have studied the energy efficiency of two different error correction mechanisms and have measured the efficiency of an implementation in software. We will show that it is not sufficient to concentrate on the energy efficiency of error control mechanisms only, but the required extra energy consumed by the wireless interface should be incorporated as well. A model is presented that can be used to determine an energy efficient error correction scheme of a minimal system consisting of a general-purpose processor and a wireless interface. This model can be used to adapt the error correction parameters, such that the system is energy efficient. As an example we have determined these error correction parameters on two systems with a WaveLAN interface.
  • Energy efficient wireless ATM design
    P.J.M. Havinga, G.J.M. Smit, Martinus Bos
    (wmATM'99, June 2-4 1999)
    We present an architecture for wireless ATM and a novel MAC protocol that achieves a good energy efficiency of the wireless interface of the mobile and provides QoS support for diverse traffic types. The scheduler of the base station is responsible for providing the required QoS to connections on the wireless link and to minimise the amount of energy spent by the mobile. The main principles used are to avoid unsuccessful actions, to minimise the number of transitions, and to synchronise the mobile and the base-station. We will show that considerable amounts of energy can be saved using these principles. In the protocol the actions of the mobile are minimised. The base-station with plenty of energy performs actions in courtesy of the mobile. We have paid much attention in reducing the cost for a mobile of just being connected. The protocol is able to provide near-optimal energy efficiency (i.e. energy is spent for the actual transfer only) for a mobile within the constraints of the QoS of all connections in a cell, and only requires a small overhead.
  • Implementation of a wireless ATM transceiver using reconfigurable logic
    G.J.M. Smit, P.J.M. Havinga, Marcel van Opzeeland, Remco Poortinga
    (wmATM'99, June 2-4 1999)
    In this paper we present the design, implementation and realization of a receiver for a wireless nano-cellular ATM network using a small Field Programmable Gate Array. The network is designed for an office environment. The method used for transmitting data, at the rate of 1Mbps, is Differential Phase Shift Keying (DPSK) on a 3 MHz carrier using near-field RF. It uses differential coherent detection to demodulate the received signal. A matched filter combined with a notch filter reduces the bit error rate. A MAC protocol for this network that is suitable for multimedia traffic is implemented in a micro-controller. The system has been demonstrated in a setup where uncompressed video frames (320x200x6) were transmitted at a rate of 4 frames per second.

1998

  • Low cost & fast turnaround: reconfigurable graph-based execution units
    J. Smit, M. Stekelenburg, C.E. Klaassen, S. Mullender, G. Smit, P. Havinga
    (7th BELSIGN workshop, 1998)
    New devices with the efficiency of full-custom designs and the programmability of FPGAs will ease many aspects of the design of complex systems, without the high cost of mask production. The possibility of in-circuit programming and even dynamic reconfiguration offers great advantages over the traditional design approach. One instance of a fully programmable architecture which offers a platform for rapid prototyping, quick market and application evaluation, is introduced in the form of a field programmable function array (FPFA). The design of such a device is extremely challenging as the aspects of physical design for speed and low-power, the construction of an ALU which is optimal for as many applications as possible, as well as highly efficient mappings of algorithms, are extremely important for a successful device which suits many applications. This paper introduces the reader with the concept of reprogrammable devices with graph-based execution of arithmetic expressions, the corresponding principles of operation, the aspects of low-power operation of the proposed design, the corresponding physical design of the ALU, algorithmic mappings of systems on a chip and the performance aspects compared to other architectures and implementations.
  • Battery-powered Distributed Systems
    P.J.M. Havinga, A. Helme, S.J. Mullender, G.J.M. Smit, J. Smit
    (eighth ACM SIGOPS European Workshop on Support for Composing Distributed Applications, 7-10 September 1998, Sintra, Portugal, http://www.acm.org/sigops/EW98/papers.html)
    Mobile personal computers will be a vital technology for making electronic information processing available to people on the move. This paper reports ongoing work on Moby Dick, a research project that addresses fundamental issues in the architecture, design and implementation of low-power hand-held computers, with particular emphases on energy conservation and security.
  • Overview of the Moby Dick project
    (1st Euromicro summer school on mobile computing, August 1998)
    The Moby Dick project focuses on developing theories, architectures and applications for a new generation of hand-held computers. The combination of an intelligent information system and a location system enables many new types of applications, such as admission control, digital chequebook, paging, and an automatic diary that keeps track of where you were and with whom. The design challenges lie primarily in the creation of a single architecture that allows the integration of security functions, externally offered services, personality, and communication. In the architecture, Quality of Service (QoS) is no longer a networking issue alone, but a framework to model integration and integrated management of all the system services and applications in the Pocket Companion.
  • The Pocket Companion's architecture
    P.J.M. Havinga, G.J.M. Smit
    (1st Euromicro summer school on mobile computing, August 1998)
    The Pocket Companion is a small personal portable computer with wireless communication facilities. The typical use of the Pocket Companion induces a number of requirements concerning security, performance, energy consumption, communication and size. The energy consumption due to the increasing demand for performance and functionality will be the limiting factor for its capabilities. Therefore reducing energy consumption plays a crucial role in the architecture. Communication, and particularly wireless communication, is essential for the system to support electronic transactions. Such a system requires a good security infrastructure not only for safeguarding personal data, but also to allow safe transactions.

1997

  • Low power system design techniques for mobile computers
    P.J.M. Havinga, G.J.M. Smit
    (CTIT Technical report, No. 97-32, Enschede, the Netherlands, ISSN 1381-3625)
    Portable products are being used increasingly. Because these systems are battery powered, reducing power consumption is vital. In this report we give the properties of low power design and techniques to exploit them on the architecture of the system. We focus on: min imizing capacitance, avoiding unnecessary and wasteful activity, and reducing voltage and frequency. We review energy reduction techniques in the architecture and design of a hand-held computer and the wireless communication system, including error control, sys tem decomposition, communication and MAC protocols, and low power short range net works.
  • A request-TDMA multiple-access scheme for wireless multimedia networks
    G.R.J. Linnenbank, P. Venkataram, P.J.M. Havinga, S.J. Mullender, G.J.M. Smit
    (in Proceedings MoMuC-3, 1996 and in Mobile Multimedia Communications, (D. Goodman, D. Raychaudhuri, Eds.), pp. 173-180, 1997)
    This paper describes a cellular multiple-access scheme based on TDMA for multimedia communication networks. The scheme proposes an admission control of two different multimedia application stream types: real-time and non-real-time. We do not consider interference between cells. The proposed protocol, that is based on TDMA, exploits the available bandwidth fully. The throughput per mobile station is higher compared to other multiple-access protocols, it offers low latency for both real-time and non-real-time communication and the unused reserved bandwidth is reallocated for non-real-time communication. Furthermore, the throughput and latency remain stable under high loads.
  • Security functions for a file repository
    Arne Helme, Tage Stabell-Kulø
    (ACM Operating Systems Review, 31(2):3-8, 1997)
    When personal machines are incorporated into distributed systems a new mixture of threats is exposed. The security effort in the Moby Dick project is aimed at understanding how privacy can be incorporated in this new environment. Our claim is that a two-step process for authentication and authorization is required, but also sufficient. The research vehicle is a distributed file repositatory.
  • Off-line Delegation in a File Repository
    Arne Helme, Tage Stabell-Kulø
    (abstract, 1996 DIMACS Workshop on Trust Management in Networks)
    We are developing a minimal syntax with semantics for delegation tokens in a distributed file repository, and show how this can be exploited in the implementation of one-time access rights. Delegations can occur off-line, and we investigate the practical implications of this.
  • A survey of energy saving techniques for mobile computers
    G.J.M. Smit, P.J.M. Havinga
    (Moby Dick technical report, 1997)
    Portable products such as pagers, cordless and digital cellular telephones, personal audio equipment, and laptop computers are increasingly being used. Because these applications are battery powered, reducing power consumption is vital. In this report we first give a survey of techniques for accomplishing energy reduction on the hardware level such as: low voltage components, use of sleep or idle modes, dynamic control of the processor clock frequency, clocking regions, and disabling unused peripherals. System- design techniques include minimizing external accesses, minimizing logic state transitions, and system partitioning using application-specific coprocessors. Then we review energy reduction techniques in the design of operating systems, including communication protocols, caching, scheduling and QoS management. Finally, we give an overview of policies to optimize the code of the application for energy consumption and make it aware of power management functions. Applications play a critical role in the user's experience of a power-managed system. Therefore, the application and the operating system must allow a user to control the power management. Remarkably, it appears that some energy preserving techniques not only lead to a reduced energy consumption, but also to more performance.
  • Dummynet: a simple approach to the evaluation of network protocols (.gz)
    L.Rizzo
    (ACM Computer Communication Review, Jan.97)
    Network protocols are usually tested in operational networks or in simulated environments. With the former approach it is not easy to set and control the various operational parameters such as bandwidth, delays, queue sizes. Simulators are easier to control, but they are often only an approximate model of the desired setting, especially for what regards the various traffic generators (both producers and consumers) and their interaction with the protocol itself.
    In this paper we show how a simple, yet flexible and accurate network simulator - dummynet - can be built with minimal modifications to an existing protocol stack, allowing experiments to be run on a standalone system. dummynet works by intercepting communications of the protocol layer under test and simulating the effects of finite queues, bandwidth limitations and communication delays. It runs in a fully operational system, hence allowing the use of real traffic generators and protocol implementations, while solving the problem of simulating unusual environments. With our tool, doing experiments with network protocols is as simple as running the desired set of applications on a workstation.
    A FreeBSD implementation of dummynet, targeted to TCP, is available from the author. This implementation is highly portable and compatible with other BSD-derived systems, and takes less than 300 lines of kernel code.
  • An Embedded Network Simulator to Support Network Protocols (.gz)
    L.Rizzo
    (9th International Conference on Computer Performance Evaluation: Modelling Techniques and Tools, St. Malo, France, June 1997, LNCS-1245 pp.97-107, Springer Verlag)
    The development of network protocols, especially if designed for use in very large scale networks, generally requires extensive simulation and tests in operational environments to assess their performance and correctness. Both approaches have limitations: simulation because of possible lack of accuracy in modeling the system (and, especially, traffic generators), tests in operating networks because of the difficulty of setting up and controlling the experimental testbed.
    In this paper we propose to embed network simulators in operational systems, so as to get the advantages of both simulators and real testbeds. Such simulators can be built with minimal modifications to existing protocol stacks. They work by intercepting communications of the protocol layer under test and simulating the effects of finite queues, bandwidth limitations, communication delays, noisy channels. As a result, experiments can be run on a standalone system, while simulating arbitrarily complex networks. Thanks to the ability of using real traffic generators and protocol implementations, doing experiments becomes as simple as running the desired set of applications on a workstation.
    An implementation of such a simulator, targeted to TCP and compatible with BSD-derived systems, is available from the author.
  • Effective Erasure Codes for Reliable Computer Communication Protocols (.gz)
    L.Rizzo
    (ACM Computer Communication Review, Vol.27, n.2, Apr.97, pp.24-36)
    Reliable communication protocols require that all the intended recipients of a message receive the message intact. Automatic Repeat reQuest (ARQ) techniques are used in unicast protocols, but they do not scale well to multicast protocols with large groups of receivers, since segment losses tend to become uncorrelated thus greatly reducing the effectiveness of retransmissions. In such cases, Forward Error Correction (FEC) techniques can be used, consisting in the transmission of redundant packets (based on error correcting codes) to allow the receivers to recover from independent packet losses.
    Despite the widespread use of error correcting codes in many fields of information processing, and a general consensus on the usefulness of FEC techniques within some of the Internet protocols, very few actual implementations exist of the latter. This probably derives from the different types of applications, and from concerns related to the complexity of implementing such codes in software. To fill this gap, in this paper we provide a very basic description of erasure codes, describe an implementation of a simple but very flexible erasure code to be used in network protocols, and discuss its performance and possible applications. Our code is based on Vandermonde matrices computed over GF(p^r), can be implemented very efficiently on common microprocessors, and is suited to a number of different applications, which are briefly discussed in the paper. An implementation of the erasure code shown in this paper is available from the author, and is able to encode/decode data at speeds up to several MB/s running on a Pentium 133.
  • A Reliable Multicast data Distribution Protocol based on software FEC techniques (.gz)
    L. Rizzo, L. Vicisano
    (Proc. of IEEE HPCS'97, Chalkidiki, Greece, June 1997)
    Applications requiring the reliable distribution of data to groups of clients would be supported perfectly by reliable multicast protocols. In many cases, the problem of congestion control (a major research issue otherwise) does not exist because downlink bandwidth is ``owned'' or can be preallocated to a particular server by independent means, but the problems of insuring reliable data delivery to large groups, and adaptability to heterogeneous clients, still remain.
    These problems can be solved at once with the use of FEC techniques. In this paper we show the design of a Reliable Multicast data Distribution Protocol (RMDP) that we have built using these techniques, and discuss the implementation tradeoffs. Experimental results show that, albeit somewhat expensive, doing encoding/decoding in software is affordable for speeds in the Mbit/s range even on low-end PCs. Slower machines can still receive at high speed, thus optimizing network usage, by taking advantage of the fact that decoding needs not to be done in real time. Finally, our RMDP can work even without any feedback from the receivers, thus making it well suited to mobile/wireless systems.
  • Group-based Multicast and Dynamic Membership in Wireless Networks with Incomplete Spatial Coverage
    A. Bartoli
    (ACM/Baltzer Journal on Mobile Networks and Applications)
    In this paper we examine the problem of group-based multicast communication in the context of mobile computing with wireless communication technology. We propose a protocol in which group members may be mobile computers and such that the membership of the group may change dynamically. Multicasts are delivered in the same order at all group members (totally-ordered multicast). Mobile computers are resource-poor devices that communicate with a wired network through a number of spatially limited cells defining wireless links. The spatial coverage provided by wireless links may be either complete or incomplete, which makes the overall system model both general and realistic. The proposed protocol is simple and does not require any hand-off in the wired network upon movements of group members. Moreover, there is no part of the protocol requiring that group members do not move during its execution. This feature leads to mobility assumptions that are practical because they involve only the global movement of group members, e.g. assumptions of the form "a group member does not move very fast all the time".
  • A system for secure user-controlled electronic transactions
    Arne Helme
    (Ph. D. dissertation, University of Twente, 1997, ISBN 90-423-0011-6)
    This dissertation is concerned with how security functions can be integrated into a personal computer to provide a subsystem that cannot be easily compromised by untrusted applications executing on that computer. The dissertation presents an overall system architecture for secure user-controlled execution of electronic transactions. The proposed system architecture is particularly suitable for personal computers hosting applications with conflicting security requirements.
    In current open-networks transaction systems, cryptographic functions and protocols are used to protect the integrity of the data exchange. However, the ways in which the transaction services with security requirements are presented to the human users are often unprotected. In particular, many systems lack functionality to protect the integrity of the user interface. Since human users constitute the true ends of electronic-commerce transactions, the security risk is that human users may be lured into authorising dubious transactions.
    This dissertation argues that the security of end systems hosting electronic-commerce applications depends crucially on the presence of a trusted path between the human user of the system and the signing keys used to authorise statements on behalf of the user. One way to achieve this, as is argued in the dissertation, is to embed the input and output devices of the human-visible computer interface into the trusted computing base of the system and protect the integrity of the user-interface elements presented to the user.
  • Minimizing energy consumption for handheld computers in Moby Dick
    P.J.M. Havinga, G.J.M. Smit
    (Proceedings Euromicro 97, pp. 196-201, September 1997)
    In this report we propose a number of techniques to reduce energy consumption for mobile computers. We use extra dedicated low-power modules to cut on processor cycles of the main CPU, i.e. hardware and software decomposition. These modules are autonomous and can be powered down individually. Furthermore, as networking consumes a large part of a mobile system's battery resources much effort is put in reducing energy consumption in this part. We use intelligent network interfaces with a power aware network protocol, and a MAC protocol that minimizes the `on-time' of network interfaces to reduce energy. There is a direct link between QoS and energy consumption. Therefore we move power management into the QoS domain.
  • The Harpoon Security System for Helper Programs on a Pocket Companion
    G.J.M. Smit, P.J.M. Havinga, D. van Os
    (Proceedings Euromicro 97, September 1997, pp 231-238)
    In this paper we present a security framework for executing foreign programs, called helpers, on a Pocket Companion: a wireless hand-held computer. A helper program as proposed in this paper, is a service program that can migrate once from a server to a Pocket Companion or vice-versa. A helper program is convenient, provides environment awareness and allows asynchronous interaction. Moreover, helpers can be used to save processing power and to reduce communication. By migrating to the location of a resource, a helper can access the resource more efficiently. This is particularly attractive for mobile computing, where the network conditions can be poor and unreliable, and because it does not require a permanent connectivity. Security is a significant concern for helpers, as the user of a Pocket Companion receiving a piece of code for execution may require strong assurances about the helper's behaviour. The best way to achieve a high security is to use a combination of several methods. We are designing a prototype of a helper system, called Harpoon, on top of the Inferno operating system.
  • A Power Dissipation Comparison of the R-TDMA and the Slotted-Aloha Wireless MAC Protocols
    G.R.J. Linnenbank
    In this paper two wireless multiple-access protocols are compared by their power dissipation for the uplink traffic of a wireless networks. After briefly discussing the behaviour of the Slotted Aloha protocol and the R-TDMA protocol, we estimate the energy that is dissipated by the protocols to transmit a packet. We will show that for general loads, the power dissipation of the R-TDMA protocol is far less than that of the Slotted Aloha protocol.
  • An Event-Driven Wireless MAC Protocol Simulator
    George R.J. Linnenbank, Paul J.M. Havinga
    (Proceedings ICPWC 97, December 1997)
    Recently, many multiple-access (MAC) protocols have been or are being proposed for wireless networks. As most of these multiple-access protocols are designed for specific applications (such as telephony) and analyzed accordingly, the analysis results can not always be adapted to situations where each user has a dif ferent behavior. Wireless MAC protocols for data communication are not straightforward to analyse. To quickly make a reliable judgement of the usability of a MAC protocol for specific situa tions, we designed a simulator that makes it simple to implement the protocol and test it in different configurations and with differ ently behaving users. Our simulator generates a large amount of quantitative performance information that can be processed with standard graph drawing tools and an integrated trace analyzer.
  • Minimizing energy consumption for wireless computers in Moby Dick
    Paul J.M. Havinga, Gerard J.M. Smit
    (proceedings ICPWC 97, December 1997)
    Portable and hand-held computers must be careful not to waste the scarce energy resources in their batteries. More extensive and continuous use of network services will only aggravate this problem since communication consumes relatively much energy. The Pocket Companion is a hand-held device that is resource-poor, i.e. small amount of memory, limited battery life, low processing power, and connected with the environment via a network with variable connectivity. Because battery life is limited and battery weight is an important factor for the size and the weight of the Pocket Companion, energy management plays a crucial role in the architecture. In our architecture we apply several supplementary power reduction techniques on all levels of the system, including the operating system and applications. The two main themes are 1) to avoid wasteful activity, and 2) to exploit locality of reference.
    We put considerable effort in reducing energy consumption of communication interfaces. There are several ways to reduce energy consumption: e.g. by system decomposition, using hybrid networking, and by applying power aware MAC protocols.
  • QoS applied to security in mobile computing
    Terje Fallmyr, Tage Stabell-Kulø
    (submitted for publication)
    Hand-held mobile computers have the potential to become important communication tools for roaming users. As such, they will also become very personal. They will be used under a wide range of operating conditions, and tight user control will be enforced on issues like power consumption, consistency control, and trust management. Their ability to adapt will be the key to their success.
    In this paper we outline our notion and use of Quality of Service (QoS) to the design of adaptive software systems for mobile computers. They have been developed in the MobyDick and GDD projects. We do not emphasize on the provision of QoS guarantees. In stead, our notion of QoS is used to convey relevant and timely management information between service users and providers on the correct abstraction level. It structures adaptability management in the handheld machine, and it captures adaptability to changes both stemming from the hosting environment and user commands.
    As an example of how the architecture works, the importance of adaptivity of security services for personal companions are explained, and we show how our notion of QoS may realize adaptable security services.

1996

  • Survey of electronic payment methods and systems
    Paul J.M. Havinga, Gerard J.M. Smit, Arne Helme
    (Proceedings Euromedia '96, pp 180-187)
    In this paper an overview of electronic payment methods and systems is given. Electronic payment systems can be grouped into three broad classes: traditional money transactions, digital currency and credit-debit payments. Such payment systems have a number of requirements: security, acceptability, convenience, cost, privacy, durability, control, traceability, legal framework and control of encryption methods. Some requirements appear contradictory and trade-offs have to be made:
    - traceability versus anonymity,
    - on-line versus off-line,
    - dedicated tamper-resistance hardware versus only software.
    We further present an introduction to the basics of electronic money: encryption, digital signatures, anonymity, and solutions to the double spending problem for digital cash. We give a survey of payment mechanisms, that are either commercially or in a pilot version available today or have been published recently.

Project programme and deliverables

  • Moby Dick, The Mobile Digital Companion, LTR 20422, Annex I - Project Programme
    Sape J. Mullender, Paolo Corsini, Gunnar Hartvigsen
    An exiting prospect for the next decade is the deployment of a new generation of hand-held computers. Wireless computing greatly enhances the usability of these portable computing devices.
    The Moby Dick project has been a joint european project (Esprit Long Term Research 20422) to develop and define the architecture of a new generation of mobile handheld computers. Currently the research themes have focussed on: systems architecture of mobile computers, reconfigurable computing, energy efficient multimedia communication, and QoS over wireless access networks. The design challenges lie primarily in the creation of a single architecture that allows the integration of security functions (e.g. payment), externally offered services (e.g. airline ticket reservation), personality (i.e. these devices know what their owners want), and communication.
  • Final Report Section I: Results of the first phase
    This paper is section I of the final report of phase I. It shows the results achieved with regard to the project objectives. The design challenges of the Moby Dick project lie primarily in the creation of a single architecture that allows the integration of security functions, externally offered services, personality, and communication.
  • The Moby Dick architecture (deliverable II.3.1)
    Sape J. Mullender, Gerard J.M. Smit, Paul J.M. Havinga, Arne Helme, Gunnar Hartvigsen, Terje Fallmyr, Tage Stabell-Kulø, Alberto Bartoli, Gianluca Dini, Luigi Rizzo, Marco Avvenuti
    This document is deliverable II.3.1, and presents the Moby Dick architecture. The introduction outlines the main areas of use and the main characteristics of the Pocket Companion, and ends up with the overall demands we put on the architecture. In chapter 2 Quality of Service (QoS) as we use it in Moby Dick QoS is presented. It gives the foundation the adaptability used in the chapters to follow. In chapter 3 an overview of the software architecture of the Pocket Companion is presented. The security architecture of the Pocket Companion is presented in chapter 4, and the consistency architecture is presented in chapter 5. In chapter 6, the system architecture of the Pocket Companion is outlined.
  • Systems support for hybrid networks (deliverable II.3.2)
    Gunnar Hartvigsen, Dag Brattli, Tage Stabell-Kulø, Luigi Rizzo
    One objective of the Moby Dick project is to find out whether it is possible to switch seamless between radically different networking technologies with a resource poor machine like the Pocket Companion. This chapter will show that it's indeed feasible to utilize more than one network. We present a detailed technical documentation of the Software Network, which enables multihomed mobile computers to dynamic and seamless switch from one network to another. This means that all applications can keep their connections, while the computer switches from one network to another. The basic idea is to put the router into a mobile computer, enabling the computer to switch uninterrupted from one network to another. The Software Network protects applications from unwanted connectivity interrupts since connections are simply routed according to the quality of service of the mobile hosts network interfaces.
  • Digital cheque-book (deliverable II.3.3)
    Tage Stabell-Kulø, Arne Helme
    In this paper we will describe the overall design of the demonstrator and the technical details of its implementation. We start out by presenting an overview of the demonstrator as to what will be demonstrated and why this is relevant. Then we will embark on a technical description of the solution.
  • Distributed diary (deliverable II.3.4)
    Alberto Bartoli, Gianluca Dini, Marco Avvenuti
    The diary application allows a set of users, each equipped with his/her own handheld, to arrange for meetings. This application is an example of coordination among a set of mobile users and it is structured to take into account aspects peculiar of mobile computing.

 

 

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