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Technical reports and papers

Author:
Andy Harter, Andy Hopper, Pete Steggles, Andy Ward, Paul Webster
Title:
The Anatomy of a Context-Aware Application
Abstract:
We describe a sensor-driven, or sentient, platform for context-aware computing that enables applications to follow mobile users as they move around a building. The platform is particularly suitable for richly equipped, networked environments. The only item a user is required to carry is a small sensor tag, which identifies them to the system and locates them accurately in three dimensions. The platform builds a dynamic model of the environment using these location sensors and resource information gathered by telemetry software, and presents it in a form suitable for application programmers. Use of the platform is illustrated through a practical example, which allows a user s current working desktop to follow them as they move around the environment.

Keywords: Mobile computing, sentient computing, context-aware computing, location sensors, resource monitoring, middleware, spatial indexing, CORBA, visualisation, HCI

Reference:
  • Wireless Networks, Vol. 8, pp. 187-197
  • Technical Report 2002.2
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2002.2.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2002.2.ps.gz
Author:
Maurice Wilkes
Title:
A Personal Revisitation of Neural Nets
Reference:
  • Technical Report 2002.1
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2002.1.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2002.1.ps
Author:
David Riddoch, Steve Pope, Kieran Mansley
Title:
VIA over the CLAN Network
Abstract:
The Virtual Interface Architecture is an industry standard for high performance networking in system-area networks, and the same model is proposed for Infiniband. Existing implementations suffer from high complexity, and scaling to higher bandwidths and large numbers of endpoints is likely to be problematic.

We present a novel implementation of VIA that consists of a thin software layer over the CLAN network. Performance of CLAN VIA is comparable with native solutions. The software implementation is highly flexible: we show that performance optimisations and extensions to the standard are easy to add.

The CLAN network has a very simple network model with very low overhead, that we believe scales well to very high bandwidths and large numbers of endpoints. These desirable properties are thus inherited by CLAN VIA.

Reference:
  • Technical Report 2001.14
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.14.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.14.ps.gz
Author:
Glenford Mapp
Title:
Is IPv6 The Key to a Global Network Infrastructure ?
Abstract:
When IPv6 was devised, it was seen as an enhancement of IPv4, providing extra bits for addressing, etc. The world has moved on and new technologies, including mobile phones, ATM backbones, GPS systems and residential network access have now become ubiquitous.

There is a need to define a global network infrastructure to make all these services operate seamlessly and yet be compatible with systems based on IPv4.

This talk examines proposed enhancements to IPv6 to allow it to become a key part of a new Global Network Infrastructure

Reference:
  • IPv4 to IPv6 Migration, 10-11 September 2001 Sheraton Hotel, Stockholm
  • Technical Report 2001.13
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.13.pdf
Author:
Frank Hoffmann, James Scott, Mike Addlesee, Glenford Mapp, Andy Hopper
Title:
Data Transport on the Networked Surface
Abstract:
Networked Surfaces are surfaces such as desks which provide network connectivity to specially augmented de-vices, for example handheld computers. When the devices are physically placed on top of the surface, they can connect to different kinds of services mainly, but not exclusively to send and receive data. This paper discusses challenges in implementing Net-worked Surfaces, paying particular attention to data flow issues, focusing on how the various software and hardware entities comprising the Surface interact to transport data to and from objects. Keywords: Mobile Networking, Sentient Computing
Reference:
  • Technical Report 2001.12
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.12.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.12.ps.gz
Author:
David Scott, Richard Sharp
Title:
Abstracting Application-Level Web Security
Abstract:
Application-level web security refers to vulnerabilities inherent in the code of a web-application itself (irrespective of the technologies in which it is implemented or the security of the web-server/back-end database on which it is built). In the last few months application-level vulnerabilities have been exploited with serious consequences: hackers have tricked e-commerce sites into shipping goods for no charge, usernames and passwords have been harvested and confidential information (such as addresses and credit-card numbers) has been leaked.

In this paper we investigate new tools and techniques which address the problem of application-level web security. We (i) describe a scalable structuring mechanism facilitating the abstraction of security policies from large web-applications developed in heterogenous multi-platform environments; (ii) present a tool which assists programmers develop secure applications which are resilient to a wide range of common attacks; and (iii) report results and experience arising from our implementation of these techniques.

Reference:
  • Technical Report 2001.11
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.11.ps.gz
Author:
Diego Lspez de Ipiqa, Sai-Lai Lo
Title:
Sentient Computing for Everyone
Abstract:
Sentient Computing gives perception to computing systems so that they can detect, interpret and respond to changing aspects of user contexts. The location attribute of a user's context is of special interest because it makes human-computer interactions more natural. In the last few years, several sophisticated indoor location technologies, which can track user whereabouts, have been developed. However, they are yet to be widely adopted because of their high cost and complexities in deployment, configuration and maintenance. This paper describes a novel vision-based software location system, known as TRIP, whose low-cost, off-the-shelf hardware requirements and easy deployment features overcome other systems' limitations. Nevertheless, in order to foster the deployment of "sentient spaces" that bring services to users wherever they are or about to move to, a location system must also be accompanied by the middleware to facilitate user-bound software service activation, migration and deactivation. LocALE addresses this issue by providing a CORBA-based solution that deals with heterogeneous object lifecycle and location control. Some distributed applications combining TRIP's and LocALE's capabilities are presented to demonstrate that Sentient Computing can be made readily available for everyone and everywhere.
Reference:
  • To appear in Proceedings of the The Third IFIP WG 6.1 International Working Conference on Distributed Applications and Interoperable Systems (DAIS'2001), Krakow, Poland. September 17 - 19, 2001
  • Technical Report 2001.10
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.10.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.10.ps.gz
Author:
Diego Lspez de Ipiqa, Sai-Lai Lo
Title:
LocALE: a Location-Aware Lifecycle Environment for Ubiquitous Computing
Abstract:
The LocALE (Location-Aware Lifecycle Environment) framework provides a simple management interface for controlling the lifecycle of CORBA distributed objects. It supports mechanisms for the remote construction, movement, removal and recovery of heterogeneous software objects in a location domain, i.e. a group of hosts on a network within a given physical area. Client applications use LocALE to intelligently control their required services' location and relocation in the network. LocALE offers load-balancing, automatic activation, and fault-tolerance facilities for the services whose lifecycles it controls. It provides the middleware necessary for the efficient implementation of location-aware mobile applications in richly equipped network environments. LocALE's infrastructure has been tested with the development of several follow-me applications that dynamically move with their users as they change location. For illustration, two of these follow-me LocALE-enabled applications are described.
Reference:
  • Proceedings of the 15th IEEE International Conference on Information Networking (ICOIN-15), Beppu City, Japan. January 31 - February 2, 2001 (received ICOIN-15's best student paper award)
  • Technical Report 2001.9
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.9.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.9.ps.gz
Author:
Mike Addlesee, Rupert Curwen, Steve Hodges, Joe Newman, Pete Steggles, Andy Ward, Andy Hopper
Title:
Implementing a Sentient Computing System
Abstract:
Sentient computing systems, which can change their behavior based on a model of the environment they construct using sensor data, may hold the key to managing tomorrow s device-rich mobile networks.
Reference:
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.8.pdf
Author:
James Weatherall, Alan Jones
Title:
Ubiquitous Networks and their Applications (Available soon)
Reference:
Author:
James ''Wez'' Weatherall & David Scott
Title:
Mobile Computing with Python
Abstract:
This paper describes MoPy, a port of the Python 1.5.2 interpreter to the Psion 5/Epoc32 platform and Koala, a CORBA-style Object Request and Event Broker implemented natively in Python. While primarily a direct POSIX-based port of the standard Python interpreter, MoPy also adds thread, socket and serial support for the Psion platform. The Koala ORB is designed particularly with MoPy in mind and aims to support interoperation of devices over the low-power Prototype Em-bedded Network. The low-power requirements of PEN impose severe bandwidth and latency penalties to which conventional RPC technologies are not typically well suited.
Reference:
  • Proceedings of the 9th International Python Conference, March 2001
  • Technical Report 2001.6
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.6.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.6.ps.gz
Author:
Gray Girling
Title:
Interaction Support in a Kernel for the Embedded Environment
Abstract:
As any other systems, those produced for an embedded environment are better developed when specified and implemented in a modular fashion. This paper outlines some infrastructural abstractions that allow the interaction of a wide range of system components; and goes on to describe their implementation optimised for the simplicity of typical embedded applications in a kernel for a component-based operating system. At the same time it explores the extent to which these abstractions can apply to a standard model of computational elements in the Open Distributed Processing environment. It is argued that designing code to use the proposed abstractions may help to extend its utility beyond application to specific embedded systems. Finally, some examples of the practical use of such an infrastructure are described.
Reference:
  • Technical Report 2001.5
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.5.pdf
Author:
Maurice Wilkes
Title:
The Memory Gap and the Future of High Performance Memories
Reference:
  • Technical Report 2001.4
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.4.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.4.ps.gz
Author:
David Riddoch, Steve Pope
Title:
A Low Overhead Application/Device-driver Interface for User-level Networking
Abstract:
Recent user-level network interfaces have placed an increasing proportion of their functionality in hardware, in order to provide an efficient user-level interface. The performance of such systems is significantly better than that of traditional network architectures, but comes at a cost; namely increasing complexity of the hardware, reduced flexibility and limited scalability.

In this paper we present a technique that reduces the overhead of the application/device-driver interface, hence shifting the tradeoff towards a soft implementation. We show how this technique is used to improve the performance of the CLAN user-level network interface. Results given show that the performance of this interface exceeds that of other technologies that provide a direct user-level interface to the hardware, whilst retaining the flexibility and simplicity of a software interface.

Reference:
  • 2001 International Conference on Parallel and Distributed Processing Techniques and Applications
  • Technical Report 2001.3
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.3.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.3.ps.gz
Author:
Joseph Newman, David Ingram, Andy Hopper
Title:
Augmented Reality in a Wide Area Sentient Environment
Abstract:
Augmented Reality (AR) both exposes and supplements the user's view of the real world. Previous AR work has focussed on the close registration of real and virtual objects, which requires very accurate real-time estimates of head position and orientation. Most of these systems have been tethered and restricted to small volumes. In contrast, we have chosen to concentrate on allowing the AR user to roam freely within an entire building. At AT&T Laboratories Cambridge we provide personnel with AR services using data from an ultrasonic tracking system, called the Bat system, which has been deployed building-wide.

We have approached the challenge of implementing a wide-area, in-building AR system in two different ways. The first uses a head-mounted display connected to a laptop, which combines sparse position measurements from the Bat system with more frequent rotational information from an inertial tracker to render annotations and virtual objects that relate to or coexist with the real world. The second uses a PDA to provide a convenient portal with which the user can quickly view the augmented world. These systems can be used to annotate the world in a more-or-less seamless way, allowing a richer interaction with both real and virtual objects.

Reference:
  • To appear in the Proceedings of the 2nd International Symposium on Augmented Reality (ISAR 2001)
  • Technical Report 2001.2
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.2.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.2.ps.gz
Author:
Chris Town, David Sinclair
Title:
Ontological Query Language for Content Based Image Retrieval
Abstract:
This paper discusses the design and implementation of the oquel query language for content based image retrieval. The retrieval process takes place entirely within the ontological domain defined by the syntax and semantics of the user query. Since the system does not rely on the pre-annotation of images with sentences in the language, the format of text queries is highly flexible. The language is also extensible to allow for the definition of higher level terms such as ``cars'', ``people'', ``buildings'', etc. on the basis of existing language constructs. Images are retrieved by deriving an abstract syntax tree from of a textual user query and probabilistically evaluating it by comparing the composition and perceptual properties of salient image regions in light of the query. The matching process utilises automatically extracted image segmentation and classification information and can incorporate any other feature detection mechanisms (such as face recognisers) or context-dependent knowledge available at the time the query is processed.
Reference:
  • 2001 IEEE Workshop on Content-based Access of Image and Video Libraries
  • Technical Report 2001.1
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.1.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2001.1.ps.gz
Author:
Tim Edmonds, Antony Rowstron, Andy Hopper
Title:
Using Time Encoded Terrain Maps for Cooperation Planning
Abstract:
This paper describes a novel adaptation and use of Terrain Mapping and Optimal Path Planning to fuse large and diverse time varying data sets into a common structure used for path extraction. The method described uses a system of map distortion and manipulation to encode anticipated future states of the environment into a single map. By doing so, it effectively encodes time into the map, allowing paths to be planned incorporating short term accuracy and an approximate long term path which accounts for anticipated movement of obstacles in the environment. The path is refined with recalculation as progress is made along the path. An application of the technique in cooperation planning for multiple physical agents is presented in the context of the RoboCup Robot Football Competition.
Reference:
  • Advanced Robotics, Volume 13, No. 8, pp. 719--792, 2000
  • Technical Report 2000.16
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.16.pdf
Author:
Alan Jones, Andy Hopper
Title:
The Prototype Embedded Network (PEN)
Abstract:
This paper describes a prototype low-power wireless link designed for embedding into everyday objects. After a brief description of the hardware platform, we discuss protocols for discovery and long-term rendezvous, contrasting our approach with master based approaches. The protocols are presented as examples drawn from a larger family of interoperable protocols which may be important to cover the broad range of applications for this sort of network. We then describe some of the applications built using PEN, and add some observations on spectrum costs, and future designs.
Reference:
  • To appear in Computer Networks
  • Technical Report 2000.15
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.15.pdf
Author:
Chris Town, David Sinclair
Title:
Content Based Image Retrieval using Semantic Visual Categories
Abstract:
This paper demonstrates an approach to content based image retrieval founded on the semantically meaningful labelling of images by high level visual categories. The image labelling is achieved by means of a set of trained neural network classifiers which map segmented image region descriptors onto semantic class membership terms. It is argued that the semantic terms give a good estimate of the salient features which are important for discrimination in image retrieval. Furthermore, it is shown that the choice of visual categories such as grass or sky which mirror high level human perception allows the implementation of intuitive and versatile query composition interfaces and a variety of image similarity metrics for content based retrieval.
Reference:
  • A shortened version of this paper is being submitted to ICCV2001 (International Conference on Computer Vision, July 2001)
  • Technical Report 2000.14
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.14.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.14.ps.gz
Author:
Gray Girling, Jennifer Li Kam Wa, Paul Osborn, Radina Stefanova
Title:
The Design and Implementation of a Low Power Ad Hoc Protocol Stack
Abstract:
Low power consumption is a key design metric for wireless network devices that have limited battery energy. The problem of reducing power consumption needs to be addressed at every level of system design. This paper investigates the issues of designing low power protocols in the context of the PEN system, a mobile ad hoc network developed at AT&T Laboratories Cambridge. It describes the ad hoc protocols that have been implemented, outlining both the design of individual protocols and the structure of the overall stack. The power-relevant mechanisms from the various protocols are collated in a summary.
Reference:
  • Proceedings of the IEEE Wireless Communications and Networking Conference, September 2000, Chicago
  • Technical Report 2000.13
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.13.pdf
Author:
Gray Girling, Jennifer Li Kam Wa, Paul Osborn, Radina Stefanova
Title:
The PEN Low Power Protocol Stack
Abstract:
Low power consumption is a key design metric for wireless network devices that have limited battery energy. The problem of reducing power consumption needs to be addressed at every level of system design. This paper investigates the issues of designing low power protocols in the context of the PEN system, a mobile ad hoc network developed at the AT&T Laboratories Cambridge. It describes the ad hoc protocols that have been implemented, outlining both the design of individual protocols and the structure of the overall stack. A summary of the lessons in low power design that were learnt is provided
Reference:
  • Proceedings of the 9th IEEE International Conference on Computer Communications and Networks, October 2000, Las Vegas
  • Technical Report 2000.12
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.12.pdf
Author:
J.N. Weatherall
Title:
The R2 Low-Power Messaging and Rendezvous Layer
Abstract:
Recent advances in microprocessor and wireless technologies have created scope for a new class of device - the tetherless computer. Tetherless computers encompass not only those devices traditionally regarded as computers but also other electronic household devices. Tetherless computing may even extend, as will be illustrated, to networking non-electronic home items. The R2-Layer provides a simple yet flexible low-power rendezvous and messaging interface suitable for tetherless devices.
Reference:
  • Proceedings of SIGOPS European Workshop, September 2000
  • Technical Report 2000.11
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.11.pdf
Author:
Timothy J. Mills, David Pye, David Sinclair, Kenneth R. Wood
Title:
Shoebox: A Digital Photo Management System
Abstract:
This paper reports recent work at AT&T to develop a system for the management of personal digital photograph collections. Shoebox, the resulting software package, provides a range of browsing and searching facilities, utilising spoken annotations and image content to enable both semantically similar and visually similar images to be retrieved. We report on the design of the system, the construction of a test collection, and the evaluation of its searching facilities. The results show that audio annotation is an effective means of retrieval for photographs, which significantly out-performs image content-based techniques.
Reference:
  • Technical Report 2000.10
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.10.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.10.ps.gz
Author:
James Scott, Frank Hoffman, Mike Addlesee, Glenford Mapp, Andy Hopper
Title:
Networked Surfaces: A New Concept in Mobile Networking
Abstract:
Networked Surfaces are surfaces which provide network connectivity to specially augmented objects, when these objects are physically placed on top of the surface. When an object (e.g. a notebook computer) connects, a handshaking protocol assigns functions such as data or power transmission to the various conducting paths that are established. This paper describes the position occupied by this concept in the world of networking, presents an overview of the technology used in its realisation, describes the current prototype implementation, and outlines the potential implications of its introduction.
Reference:
  • Technical Report 2000.9
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.9.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.9.ps.gz
Author:
Frank Stajano, Ross Anderson
Title:
The Grenade Timer: Fortifying the Watchdog Timer Against Malicious Mobile Code
Abstract:
Systems accepting mobile code need protection from denial of service attacks staged by the guest program. While protected mode is the most general solution, it is not available to the very low-cost microcontrollers that are common in embedded systems.

In this paper we introduce the grenade timer, an evolution of the watchdog timer that can place a hard upper bound on the amount of processor time that guest code may consume. Unlike its predecessor, it is resistant to malicious attacks from the software it controls; but its structure remains extremely simple and maps to very frugal hardware resources.

Reference:
  • Proceedings of 7th International Workshop on Mobile Multimedia Communications (MoMuC 2000), Waseda, Tokyo, Japan, 23-26 October 2000.
  • Technical Report 2000.8
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.8.pdf
Author:
David Riddoch, Steve Pope, Derek Roberts, Glenford Mapp, David Clarke, David Ingram, Kieran Mansley, Andy Hopper
Title:
Tripwire: A Synchronisation Primitive for Virtual Memory Mapped Communication
Abstract:
Existing user-level network interfaces deliver high bandwidth, low latency performance to applications, but are typically unable to support diverse styles of communication and are unsuitable for use in multiprogrammed environments. Often this is because the network abstraction is presented at too high a level, and support for synchronisation is inflexible.

In this paper we present a new primitive for in-band synchronisation: the Tripwire. Tripwires provide a flexible, efficient and scalable means for synchronisation that is orthogonal to data transfer.

We describe the implementation of a non-coherent distributed shared memory network interface, with Tripwires for synchronisation. This interface provides a low-level communications model with gigabit class bandwidth and very low overhead and latency. We show how it supports a variety of communication styles, including remote procedure call, message passing and streaming.

Reference:
  • Proceedings of the 4th International Conference on Algorithms and Architectures for Parallel Processing. Hong Kong, December 2000
  • Journal of Interconnection Networks Vol.2 No.3 September 2001
  • Technical Report 2000.7
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.7.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.7.ps.gz
Author:
Alan Mycroft, Richard Sharp
Title:
The FLaSH Project: Resource Aware Synthesis of Declarative Specifications
Abstract:
The FLaSH project concerns the development of a hardware synthesis system based around the idea of mapping a high-level functional specification language, SAFL, into hardware using sophisticated compiler technology.

The system has two phases: first we transform SAFL programs using meaning-preserving transformations to choose the area-time position (e.g. by resource duplication/sharing, specialisation, pipelining) while remaining a high-level specification. After this the FLaSH compiler maps the resultant SAFL program into hardware in a resource-aware manner, that is we map separate functions into separate functional units; functions which are called twice now become shared functional units - accessed by multiplexers and possibly arbiters. The current compiler outputs hierarchical RTL Verilog.

The first phase is user-guided. The second is completely automatic - it uses optimising compiler technology to insert arbiters for shared functional units and to insert intermediate registers (both on an `only when needed' basis). We justify SAFL as both amenable to transformation and facilitating an efficient translation to hardware.

The current compiler has been used to implement a small commercial processor; we achieve similar gatecounts to two previous RTL and netlist specifications but with around one tenth the source code.

Reference:
  • Technical Report 2000.6
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.6.ps.gz
Author:
Frank Stajano
Title:
Il falsario contro il crittologo: sicurezza per la lotteria informatizzata (The Forger vs. the Cryptologist: Security Issues for the Computerised Lottery)
Abstract:
We present the main security issues for a lottery system using a hypothetical sequence of attacks, defenses and counterattacks. Cryptologic techniques are introduced where appropriate and the case of a fully digital lottery scenario is also examined.
Reference:
  • Proceedings of the 40th conference of the Italian Statistical Society, Florence, Italy, April 2000. Invited paper
  • Technical Report 2000.5
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.5.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.5.ps.gz
Author:
Frank Stajano
Title:
The Resurrecting Duckling -- What Next?
Abstract:
In the context of the security of wireless ad hoc networks, we previously explored the problem of secure transient association between a master and a slave device in the absence of an online authentication server. We introduced the Resurrecting Duckling security policy model to address this problem. Master-slave relationships, however, do not exhaust the range of interesting interactions. We therefore extend the Duckling model to also cover relationships between peers.
Reference:
  • Proceedings of the 8th International Workshop on Security protocols, Cambridge, UK, April 2000,
  • To be published in the Lecture Notes in Computer Science series, Springer-Verlag
  • Technical Report 2000.4
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.4.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.4.ps.gz
Author:
Richard Sharp, Alan Mycroft
Title:
The FLaSH Compiler: Efficient Circuits from Functional Specifications
Abstract:
In previous work we have outlined the design of a functional language, SAFL, and argued that it is well suited to hardware description and synthesis. Unlike conventional high-level synthesis languages, SAFL specifications capture explicitly resource allocation, variable binding and scheduling. This paper is concerned with the details of the FLaSH compiler: an optimising silicon compiler which translates SAFL specifications to RTL Verilog suitable for simulation or synthesis. We describe a number of high-level optimisation and analysis techniques which find novel application in the field of hardware-synthesis. In particular, we believe our approach to compiling function definitions into shared resources could be applied advantageously in existing industrial silicon compilers.
Reference:
  • Technical Report 2000.3
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.3.ps.gz
Author:
Sheng Feng Li, Mark Spiteri, John Bates, Andy Hopper
Title:
Capturing and Indexing Computer-based Activities with Virtual Network Computing
Abstract:
In this paper, we present a new technique to capture and index computer-based activities, without hindering natural human-computer interactions. This technique is based on the Virtual Network Computing (VNC) technology, which is an ultra-thin-client/server computing model that separates the display interface from the application logic in windowing systems. The server executes all the applications and the client simply presents the frame buffer updates to the user and accepts user input. We record the frame buffer updates for work review, and store the user and system events as potential indices into the recording.
Reference:
  • Proceedings of the 2000 ACM Symposium on Applied Computing, Como, Italy, Vol 2. Pages 601-603, March 19-21, 2000
  • Technical Report 2000.2
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.2.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.2.ps.gz
Author:
Sheng Feng Li, Quentin Stafford-Fraser, Andy Hopper
Title:
Integrating Synchronous and Asynchronous Collaboration with Virtual Networking Computing
Abstract:
The trend in computing models has changed from thin-client (text terminals) to thick-client (graphics terminals) to standalone personal computing (PCs), and then back to thick-client (client/server applications) and thin-client (Web-based applications) again. This trend is now leading us to the so-called stateless-client computing, which is an ultra-thin-client model that frees the client completely from preserving any application state. This paper explains how we integrate synchronous and asynchronous sharing of workspace with VirtualNetwork Computing, a stateless-client computing technology developed at the AT&T Laboratories Cambridge. Experiments and applications have demonstrated that our collaborative system is feasible for operation in current and future computing environment.
Reference:
  • Proceedings of the First International Workshop on Intelligent Multimedia Computing and Networking, Atlantic City, USA, Vol. 2, Pages 717-721, February 27-March 3, 2000
  • Technical Report 2000.1
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.1.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.2000.1.ps.gz
Author:
Tim Edmonds, Steve Hodges, Andy Hopper
Title:
An Adaptive Thin-Client Robot Control Architecture
Abstract:
This paper describes an architecture and runtime system to implement distributed control and data processing applications in a thin-client manner, suitable for implementing a thin-client mobile robotics system. The system varies control fidelity and locality to adapt a control application to changes in Quality of Service availability and processing resources using a cost benefit model. An example application is presented in which the architecture is used to implement the distributed control of an inverted pendulum over a shared network. Performance results are compared with non-adaptive distributed control approaches.
Reference:
  • In proceedings: International Conference on Real-Time Computing Systems and Applications, Hong Kong, December 1999
  • Technical Report 1999.13
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.13.pdf
Author:
Andy Hopper
Title:
The Royal Society Clifford Paterson Lecture, 1999, Sentient Computing
Abstract:
Sentient computing is the proposition that applications can be made more responsive and useful by observing and reacting to the physical world. It is particularly attractive in a world of mobile users and computers.

The paper presents a classification and quantification of sensor information together with a description of a method for altering the behaviour of arbitrary terminal devices. It also presents a framework for ``programming with space'' which can associate space-related events with actions. Consideration is given to the applications made possible by such systems.

Reference:
  • The Clifford Paterson Lecture, 1999 Sentient computing, Phil. Trans. R. Soc. Lond. A (2000) 358, 2349-2358
  • Technical Report 1999.12
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.12.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.12.ps.gz
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.12.doc
Author:
Rupert Curwen, Andy Hopper, Pete Steggles, Andy Ward
Title:
Sentient Computing
Abstract:
The integration of Active Bats and other sensors is made possible by using an object model of the environment. Together with an API for programming with spatial relationships, they enable a style of programming called sentient computing.
Reference:
  • Technical Report 1999.13 (video)
Video:
http://www-lce.eng.cam.ac.uk/pub/videos/qsif-200/spirit-qsif-200.mpg
Author:
Raymond Liao, Martin Brown, Glenford Mapp, Ian Wassell
Title:
The Cambridge Wireless Broadband Trial
Abstract:
In this paper, we present a system overview of the Cambridge Wireless Broadband Trial which is being deployed in the Cambridge City area in the UK. The trial network is intended to serve as a testbed for research into new paradigms for wireless communications, and will provide an infrastructure for research on home networks. After a brief discussion of the network provisioning methods required to make the network operational, we present some preliminary measurement results. We then identify potential performance issues and propose some possible solutions as future work.
Reference:
  • 1999 IEEE International Workshop on Mobile Multimedia Communications(MomuC'99), 15-17th November 1999, San Diego, CA USA
  • Technical Report 1999.11
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.11.pdf
Author:
Frank Stajano
Title:
Python in Education: Raising a Generation of Native Speakers
Abstract:
Primarily because of its young age, Python is still a language that people only discover after having digested a few others: while many of its users love it enthusiastically, almost nobody is a native speaker of it, in the sense of having been exposed to it before any other.

As computer literacy evolves from desirable to necessary for people from all backgrounds, computer professionals and academics are responsible for taking a long-term view on how best to educate the next few generations of computer users. Form shapes contents, so the influence of a clean yet expressive first language in establishing good mental models and programming habits should not be underestimated.

This paper discusses how Python, with its high level of abstraction and judicious balance of simplicity, conciseness and versatility, is an excellent choice to introduce the fundamental ideas of the art of programming.

Reference:
  • To appear in the Proceedings of the 8th International Python Conference
  • Technical Report 1999.10
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.10.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.10.ps.gz
Author:
Steve Hodges, Dave Crosby, Antony Rowstron, Ben Bradshaw, Tim Edmonds, Andy Hopper, Steve Lloyd, Jian Wang
Title:
Building and integrating a goalkeeper robot for the small-size RoboCup competition
Abstract:
This paper details the design and development of a highly specialised goalkeeping robot for use in the RoboCup small-size league, and its integration into the Cambridge University Robot Football Team (RFT). The goalkeeper described is novel in its shape, in its use of CO2 as a power source, and in its ability to actually catch the ball and subsequently 'kick' it out at high speed. The last of these attributes also means that the goalkeeper has to coordinate with the rest of the team much more than it would otherwise have to.

The Cambridge RFT came top of their group and subsequently fourth overall in the Paris 1998 RoboCup small-size league. In the later stages of the competition the goalkeeper proved highly valuable, and enabled extended periods of play. Although it is difficult to provide empirical data to show the skill of a given team, or the effectiveness of its individual players, descriptions of the goalkeeper in use in a penalty shoot-out, and whilst in play against the CMU '98 team in the semi-final are provided.

Reference:
  • Proceedings of the RoboCup Workshop, PRICAI '98 (The 5th Pacific Rim International Conference on Artificial Intelligence), Singapore, November 1998, pp. 145-154
  • Technical Report 1999.9
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.9.pdf
Author:
Dave Crosby, Steve Greaves, Andy Hopper
Title:
A Theoretical Analysis of Multiple Diffraction in Urban Environments for Wireless Local Loop Systems
Abstract:
The simulation technique of Walfisch is used to examine multiple diffraction in wireless local loop systems. The simulations results show that the average propagation characteristic is described by a two slope model. In the immediate vicinity of the basestation the propagation loss is found to have a distance dependence of 20 dB per decade. At greater distances the slope increases to approximately 40 dB per decade. The distance at which the slope changes value is derived by considering the probability of Fresnel zone blockage.
Reference:
  • Proceedings 9th Virginia Tech/MPRG Symposium on Wireless Personal Comms, June 2-4, 1999 Balcksburg,Virginia
  • Technical Report 1999.8
Text:
Not currently available in electronic form
Author:
Andy Harter, Andy Hopper, Pete Steggles, Andy Ward, Paul Webster
Title:
The Anatomy of a Context-Aware Application
Abstract:
We describe a platform for context-aware computing which enables applications to follow mobile users as they move around a building. The platform is particularly suitable for richly equipped, networked environments. The only item a user is required to carry is a small sensor tag, which identifies them to the system and locates them accurately in three dimensions. The platform builds a dynamic model of the environment using these location sensors and resource information gathered by telemetry software, and presents it in a form suitable for application programmers. Use of the platform is illustrated through a practical example, which allows a user's current working desktop to follow them as they move around the environment.
Reference:
  • Proceedings of the 5th Annual ACM/IEEE International Conference on Mobile Computing and Networking (Mobicom '99), Seattle, Washington, USA, August 15 - 20 1999
  • Technical Report 1999.7
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.7.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.7.ps.gz
Author:
Sheng Feng Li, Quentin Stafford-Fraser, Andy Hopper
Title:
Frame-buffer on Demand: Applications of Stateless Client Systems in Web-based Learning
Abstract:
The growth of the Internet and the World Wide Web has changed the way people areeducated, and distance learning is amongst the most promising fields of new Webapplications built from existing services with supporting infrastructures. Inthis paper, we introduce a number of new applications built from StatelessClient Systems to assist the learning of computer-based activities. StatelessClient Systems separate the display interface from the application logic inwindowing systems. They embed a client/server architecture, where the serverexecutes all the applications and the client simply presents the frame buffersor screen images to the user and accepts user input. We seamlessly introduce aproxy server into the client/server architecture and create tools that enableteachers and students to record, replay, operate and share computer-based worksessions. The concepts and the systems for distance learning can be easilyextended to generic collaborative work.
Reference:
  • Proceedings of the 5th International Conference on Information Systems Analysis and Synthesis (ISAS'99), Orlando, Florida, 31 July - 3 August, 1999
  • Technical Report 1999.6
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.6.ps.gz
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.6.pdf
Author:
James Weatherall, Andy Hopper
Title:
Predator: A Distributed Location Service and Example Applications
Abstract:
This paper introduces a simple distributed location service, suitable for deployment on a wide variety of heterogeneous platforms and which is scalable to cope with location forwarding on a global scale. Also described are two existing applications of the Predator location service, in particular to support of a wireless-via-wired routing service for low-power mobile devices, suitable for deployment both in-building and over a wide area.
Reference:
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.5.ps.gz
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.5.pdf
Author:
Frank Stajano, Ross Anderson
Title:
The Cocaine Auction Protocol: On The Power of Anonymous Broadcast
Abstract:
Traditionally, cryptographic protocols are described as a sequence of steps, in each of which one principal sends a message to another. It is assumed that the fundamental communication primitive is necessarily one-to-one, so protocols addressing anonymity tend to resort to the composition of multiple elementary transmissions in order to frustrate traffic analysis.

This paper builds on a case study, of an anonymous auction between mistrustful principals with no trusted arbitrator, to introduce ``anonymous broadcast'' as a new protocol building block. This primitive is, in many interesting cases, a more accurate model of what actually happens during transmission. With certain restrictions it can give a particularly efficient implementation technique for many anonymity-related protocols.

Reference:
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.4.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.4.ps.gz
Author:
David Sinclair
Title:
Voronoi seeded colour image segmentation
Abstract:
The goal of the segmentation scheme presented is to combine edge and region information to achieve a stable segmentation. The segmentation scheme presented is designed to operate on general home and stock photographs, it returns a comprehensive region-based description of the visual content of an image (including a distinction between smooth and textured regions and a description of the internal properties of the later).

A colour edge detector is presented, where hue difference is weighted more heavily than brightness difference. Seed points for region growing are derived from the colour edge image as the peaks in the associated Voronoi image. Regions are grown using gates on pixel colour relative to region central colour and region edge pixel colour. This permits regions to encompass shading gradients. Image edges act as hard barriers during region growing. A discrete feature based texture model is derived and then used to unify groups of smaller regions into extended textured regions.

The segmentation scheme is designed to facilitate image retrieval and has been tested on a corpus of over 40000 images and has been found to be robust.

Keywords: image segmentation, colour edge detection, textured region properties, region based image retrieval.

Reference:
  • Technical Report 1999.3
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.3.ps.gz
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.3.pdf
Author:
Frank Stajano, Ross Anderson
Title:
The Resurrecting Duckling: Security Issues for Ad-hoc Wireless Networks
Abstract:
In the near future, many personal electronic devices will be able to communicate with each other over a short range wireless channel. We investigate the principal security issues for such an environment. Our discussion is based on the concrete example of a thermometer that makes its readings available to other nodes over the air. Some lessons learned from this example appear to be quite general to ad-hoc networks, and rather different from what we have come to expect in more conventional systems: denial of service, the goals of authentication, and the problems of naming all need re-examination. We present the resurrecting duckling security policy model, which describes secure transient association of a device with multiple serialised owners.
Reference:
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.2.pdf,
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.2.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.2b.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.2b.ps.Z
Author:
Sheng Feng Li, Quentin Stafford-Fraser, Andy Hopper
Title:
Applications of Stateless Client Systems in Collaborative Enterprises
Abstract:
We exploit and extend the so-called stateless client systems to support individuals in cooperative work. Stateless client systems are the software tools that separate the display interface from the application logic in windowing systems. They embed a client/server architecture, where the server executes all applications and the client simply presents the frame buffers or screen images to the user and accepts user input. By providing these stateless clients with suitable coordination mechanism, we enable geographically separated users to share workspaces and applications in a work session. And by recording the messages flowing between the client and the server, we enable temporally separated users to search for and playback previous work sessions to share knowledge and experience.
Reference:
  • The First International Conference on Enterprise Information Systems (ICEIS'99), Setubal, Portugal, March 27-30, 1999.
  • Technical Report 1999.1
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.1.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1999.1.ps.Z
Author:
Andy Hopper
Title:
DART Shoebox
Abstract:
The DART project builds systems which allow indexing and retrieval of multimedia from large archives. In this example application we applied DART technology to the problem of the storing and finding pictures in personal photographic collections. Speech annotations are attached to the photos. The speech is then automatically recognised so that photos can be searched for and retrieved using keywords. Image content can also be used to retrieve photos from the archive.
Reference:
  • Technical Report 1998.18 (video)
Video:
http://www-lce.eng.cam.ac.uk/pub/videos/qsif-200/shoebox-qsif-200.mpg
Author:
Andy Ward
Title:
Ultrasonic Location Sensing
Abstract:
Small, wearable devices known as Active Bats and ceiling-mounted ultrasonic sensors are used to follow the time-varying 3D position of people and objects in a building.
Reference:
  • Technical Report 1998.17 (video)
Video:
http://www-lce.eng.cam.ac.uk/pub/videos/qsif-200/bat-qsif-200.mpg
Author:
Tristan Richardson, Quentin Stafford-Fraser
Title:
Virtual Network Computing
Abstract:
VNC is a remote display system which allows you to view a computing 'desktop' environment not only on the machine where it is running, but from anywhere on the Internet and from a wide variety of machine architectures.
Reference:
  • Technical Report 1998.16 (video)
Video:
http://www-lce.eng.cam.ac.uk/pub/videos/qsif-200/vnc-qsif-200.mpg
Author:
D. Pye, N. Hollinghurst, T. Mills, K. Wood
Title:
Audio Visual segmentation for content based retrieval
Abstract:
This paper reports recent work at ORL on segmentation of digital audio/video recordings. Firstly, we described an audio segmentation algorithm that partitions a soundtrack into manageably sized segments for speech recognition. Secondly, we present an algorithm for detecting camera shotbreak locations in the video. The output of these two algorithms is combined to produce a semantically meaningful segmentation of audio/video content, appropriate for information retrieval. We report the success of the algorithms in the context of television news retrieval.
Reference:
  • the international conference on spoken language processing (ICSLP 98), Sydney, Australia, December 98.
  • Technical Report 1998.15
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1998.15.pdf
Author:
M. V. Wilkes
Title:
CMOS Workstations and Servers---How Far Can Evolution and Innovation Take Us?
Reference:
  • Keynote Address delivered at the Conference on Parallel Architectures and Compilation Techniques (PACT) held in Paris on October 12-18 1998.
  • Technical Report 1998.14
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1998.14.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1998.14.pdf
Author:
S. F. Li, Andy Hopper
Title:
What You See Is What I Saw: Applications of Stateless-Client Systems in Asynchronous CSCW
Abstract:
In stateless-client systems, the application processing takes place in the server, only changes to the user interface are sent to the client. Our paper will focus on how we make use of the stateless-client systems to support asynchronous CSCW on the World-wide Web by recording the changes to the user interface during a work session and replaying the session for any collaborative participant who is temporally separated. The recorded medium is a stream of rectangles containing pixel data of the user interface. Experiments show that the new lossless medium in general consumes less storage space than required by an equivalent lossy MPEG video.
Reference:
  • The Fourth Joint Conference on Information Sciences (JCIS'98), Research Triangle Park, North Carolina, Oct. 23-28, 1998
  • Technical Report 1998.13
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1998.13.ps.gz
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1998.13.pdf
Author:
S. F. Li, Andy Hopper
Title:
A Framework to Integrate Synchronous and Asynchronous Collaboration
Abstract:
In this research paper, we describe a framework for asynchronous as well as synchronous collaboration by extending ORL's Virtual Network Computing system. The framework provides facilities to transfer screen images or frame buffers of the on going CSCW session to remote users, allowing the available participants to share the view and the control of the session simultaneously, and to record the screen images or frame buffers for the absent participants to retrieve and playback the seesion at a later stage, with VCR-like controls.
Reference:
  • IEEE Seventh International Workshop on Enabling Technologies: Infrastructure for Collaborative Enterprises (WET ICE'98), Stanford University, June 17-19, 1998
  • Technical Report 1998.12
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1998.12.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1998.12.pdf
Author:
M.P. Sellars, S.D. Greaves, J. Porter, Andy Hopper, W.J. Fitzgerald
Title:
Fast Start-up Equalizer for Radio ATM
Abstract:
High speed TDMA wireless networks require high data rate efficiency and fast turnaround times. In dispersive multipath channels, an equalizer is needed to remove ISI from the signal. The equalizer may be trained more quickly if its taps are preloaded with initial values. This paper describes a power ratio approximation method which produces estimates for the initial tap values. Simulation results demonstrate that these estimates are sufficiently accurate to considerably reduce the equalizer settling time. The performance and complexity of the method is compared with existing methods for calculating the initial tap values, and shown to offer advantages for high speed systems.
Reference:
  • proceedings of COMSIG'98 (IEEE South African Symposium on Communications and Signal Processing), Cape Town, South Africa
  • Technical Report 1998.11
Author:
John Naylon, Damian Gilmurray, John Porter, Andy Hopper
Title:
Low Latency Handover in a Wireless ATM LAN
Abstract:
The micro- and pico-cellular architectures proposed for wireless ATM LANs lead to wireless terminals frequently changing their point of attachment to the network. Because ATM connections have QoS guarantees which must be maintained, handover must be as seamless as possible. We present a novel architecture and protocol which primarily aims to keep the interruption period due to handover low, rather than seeking to keep the process entirely lossless. We compare the trade-offs made with those in other schemes from the literature and give quantitative results from an implementation of our scheme on a 10Mbps prototype wireless ATM LAN.
Reference:
  • IEEE Journal on Selected Areas in Communications, Vol. 16, No 6, pp 909--921
  • Technical Report 1998.10
Author:
Frank Stajano
Title:
The SMS server, or why I switched from Tcl to Python
Abstract:
The SMS server is a system that allows mobile users to access information on their fixed computer facilities through the short message facility of GSM cellphones. Writing a versatile and extensible SMS server in Python, with interfaces to the cellphone on one side and to the Internet on the other, has been an interesting and enjoyable experience. This paper examines some Python programming issues and techniques used in implementing the server and distils some experience-based insights about the relative strengths and weaknesses of this remarkable programming environment when compared to the author's previous weapon of choice in the realm of scripting.
Reference:
  • Proceedings of the 7th International Python Conference, Houston, Texas, USA, November 1998.
  • Technical Report 1998.9
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1998.9.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1998.9.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.1998.9.html/index.html
Author:
P J Steggles, P M Webster, A C Harter
Title:
The Implementation of a Distributed Framework to support 'Follow Me' Applications
Abstract:
This paper describes a framework for supporting `Follow Me' applications; that is, applications that adapt their behaviour to best serve a mobile user. The framework is based around a 3-tier architecture comprising a centralised database, a middle layer of parallel object servers and a collection of distributed clients. Some clients gather information from the environment, and are long running. Other clients are the mobile applications, which must respond rapidly to environmental changes. As all these applications are in daily use, robustness and availability are key requirements. The framework uses on-demand loading of CORBA objects and is sufficiently flexible and scalable to be applied to a wide variety of other application areas.
Reference:
  • Technical Report 98.8
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.98.8.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.98.8.pdf
Author:
S J Hodges, S Pope, D E Roberts, G E Mapp, Andy Hopper
Title:
Remoting Peripherals using Memory-Mapped Networks
Abstract:
Memory-mapped networks such as Scalable Coherent Interconnect (SCI) and Memory Channel offer a new method for constructing network peripherals by remoting a host's IO bus. This paper details our experiences from building such an endpoint, and examines how greater support may be provided.
Reference:
  • Technical Report 98.7
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.98.7.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.98.7.pdf
Author:
S. Pope, S. J. Hodges, G. E. Mapp, D. E. Roberts, Andy Hopper
Title:
Enhancing Distributed Systems with Low-Latency Networking
Abstract:
Recently several network technologies which support user-level communication between processes using a shared-memory interface have become available. These technologies offer very low latency, high bandwidth communication by eliminating the need for software protocol stacks. Whilst there has been much research on the use of such networks in the context of parallel computing, relatively little work has been done on their suitability for distributed applications. This paper describes the work undertaken to integrate the Scalable Coherent Interface (SCI) interconnect with the standard NFS server and a CORBA 2.0 compliant ORB over Linux. It is shown that impressive performance increases can be achieved without modification to either the operating system or the distributed application.
Reference:
  • Parallel and Distributed Computing and Networks (PDCN98) Brisbane, Queensland, Australia, December 1998.
  • Technical Report 98.6
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.98.6.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.98.6.pdf
Author:
S Pope, S Lo
Title:
The Implementation of a Native ATM Transport for a High Performance ORB
Abstract:
The paper describes the design and implementation of omniTransport, a lightweight, user level transport protocol which has been tailored for the asymmetric communication requirements of a CORBA 2.0 compliant ORB, omniORB2. The protocol is shown to interwork with omniORB2 and has outperformed a leading in-kernel TCP implementation.
Reference:
  • Technical Report 98.5
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.98.5.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.98.5.pdf
Author:
S Lo, S Pope
Title:
The Implementation of a High Performance ORB over Multiple Network Transports
Abstract:
This paper describes the implementation of a high performance Object Request Broker (ORB)-- omniORB2. The discussion focuses on the experience in achieving high performance by exploiting the protocol and other characteristics of the CORBA 2.0 specification. The design is also highly adaptable to a variety of network transports. The results of running the ORB over TCP/IP, shared memory, Scalable Coherent Interface (SCI) and ATM Adaptation Layer 5 (AAL5) are presented. In both null calls and bulk data transfers, the performance of omniORB2 is significantly better than other commercial ORBs.
Reference:
  • Technical Report 98.4
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.98.4.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.98.4.pdf
Author:
Frank Stajano, Alan Jones
Title:
The Thinnest Of Clients: Controlling It All Via Cellphone
Abstract:
The "thin client" paradigm aims to give users access to central resources through inexpensive and easily deployed computing systems. But, however 'thin' the client hardware, mobile users in the field still have the burden of carrying it. To alleviate this problem, we decided to adopt as our client a piece of hardware that many mobile users already carry with them anyway: the cellphone. This paper presents our experience in researching, implementing, deploying and using a system whereby users, wherever they are, can query and control their personalised computing resources and services by typing short messages on the keypad of their cellphone. Our system has been deployed and in use for over a year and has given us valuable insights on how to design and build a personal information service.
Reference:
  • ACM Mobile Computing and Communications Review vol 2 no 4, October 1998
  • Technical Report 98.3
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.98.3.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.98.3.pdf
Author:
Frank Stajano
Title:
A Gentle Introduction to Relational and Object-Oriented Databases
Reference:
  • Technical Report 98.2
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.98.2.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.98.2.pdf
Author:
Tristan Richardson, Quentin Stafford-Fraser, Kenneth R. Wood, Andy Hopper
Title:
Virtual Network Computing
Abstract:
VNC is an ultra-thin client system based on a simple, open, platform-independent display protocol. It achieves mobile computing without requiring the user to carry any hardware
Reference:
  • IEEE Internet Computing, Vol. 2, No. 1, Jan/Feb 1998, pp 33-38
  • Technical Report 98.1
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.98.1.pdf
Author:
Michael D. Addlesee, Alan Jones, Finnbar Livesey, Ferdinando Samaria
Title:
The ORL Active Floor
Abstract:
In this article a novel type of sensor system called the Active Floor is presented that allows the time varying spatial weight distribution of the active office environment to be captured. The properties of the Active Floor are described, showing that it differs substantially from other commonly encountered sensor systems. Furthermore, classification of the footstep signature of a number of individuals is attempted by application of the hidden Markov model technique.
Reference:
  • IEEE Personal Communications, Vol. 4, No. 5, October 1997, pp 35-41
  • Technical Report 97.10
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.97.11.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.97.11.pdf
Author:
Andy Ward, Alan Jones, Andy Hopper
Title:
A New Location Technique for the Active Office
Abstract:
Configuration of the computing and communications systems found at home and in the workplace is a complex task that currently requires the attention of the user. Recently, researchers have begun to examine computers that would autonomously change their functionality based on observations of who or what was around them. By determining their context, using input from sensor systems distributed throughout the environment, computing devices could personalize themselves to their current user, adapt their behaviour according to their location, or react to their surroundings. The authors present a novel sensor system, suitable for large scale deployment in indoor environments, which allows the locations of people and equipment to be accurately determined. We also describe some of the context-aware applications which might make use of this fine-grain location information.
Reference:
  • IEEE Personal Communications, Vol. 4, No. 5, October 1997, pp 42-47
  • Technical Report 97.10
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.97.10.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.97.10.pdf
Author:
Frazer Bennett, David Clarke, Joseph B. Evans, Andy Hopper, Alan Jones, David Leask
Title:
Piconet - Embedded Mobile Networking
Abstract:
Piconet is a general purpose, low powered, ad-hoc radio network. It provides a base level of connectivity to even the simplest of sensing and computing objects. It is our intention that a full range of portable and embedded devices may make use of this connectivity. This paper outlines the Piconet system, under development at the AT&T Laboratories Cambridge (ORL). We discuss the motivation for providing this low-level 'embedded networking', and describe our experiences of building such a system. We conclude with a commentary of some of the implications that power-saving, and other considerations central to Piconet, have on the design of the system.
Reference:
  • IEEE Personal Communications, Vol. 4, No. 5, October 1997, pp 8-15
  • Technical Report 97.9
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.97.9.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.97.9.pdf
Author:
Glenford Mapp, Steve Pope, Andy Hopper
Title:
The Design and Implementation of a High-Speed User-Space Transport Protocol
Abstract:
Audio and video are fast becoming an integral part of new computing environments. These media have transport requirements which differ from the normal bursty computer traffic. There is therefore a need to explore transport protocols that can provide different qualities of service. User-space implementations of such protocols are particularly interesting because they can be easily tested and refined. This paper discusses the design and implementation of a high-speed user-space protocol called A1. Its preliminary performance in an ATM environment is presented and compared with an efficient kernel implementation of TCP/IP.
Reference:
  • Globecom'97, Phoenix, Arizona, 4th-8th November 1997 Volume 3 pp 1958-1962
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.97.8.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.97.8.pdf
Author:
Subir Biswas, Andy Hopper
Title:
An Agent-Based Signaling Architecture for Supporting Mobility in Radio ATM Networks
Abstract:
The paper presents a signaling architecture for supporting mobility in radio asynchronous transfer mode (ATM) networks. A new concept of mobile software agent, known as 'representative', is used for insulating fixed network entities from the effects of user mobility. It is shown that, depending on the physical locations of the mobile terminals, their representatives can be used for distributing the mobility management load within the fixed backbone network. This paper describes a location and a representative management scheme followed by a novel connection caching strategy which is used for implementing a family of low-latency and scalable ATM connection handovers. A prototype implementation of the proposed architecture and the associated experimental results are also presented to demonstrate the feasibility and performance of this agent-based signaling scheme.
Reference:
  • International Journal of Communication Systems, Vol. 10, 87-101 (1997)
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.97.7.ps.Z
Author:
Steve Young, Jonathan Foote, Gareth Jones, Karen Sparck-Jones, Martin Brown
Title:
Acoustic Indexing for Multimedia Retrieval and Browsing
Abstract:
This paper reviews the Video Mail Retrieval (VMR) project at Cambridge University and ORL. The VMR project began in September 1993 with the aim of developing methods for retrieving video documents by scanning the audio soundtrack for keywords. The project has shown, both experimentally and through the construction of a working prototype, that speech recognition can be combined with information retrieval methods to locate multimedia documents by content. The final version of the VMR system uses pre-computed phone lattices to allow extremely rapid word spotting and audio indexing, and statistical information retrieval (IR) methods to mitigate the effects of spotting errors. The net result is a retrieval system that is open-vocabulary and speaker-independent, and which can search audio orders of magnitude faster than real time.
Reference:
  • Proceedings of ICASSP 97, Munich, April 1997
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.97.6.ps.Z
Author:
Maurice V. Wilkes, Andy Hopper
Title:
The Collapsed LAN: a Solution to a Bandwidth Problem?
Reference:
  • Computer Architecture News vol 25 No 3 July 1997
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.97.5.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.97.5.pdf
Author:
David Sinclair
Title:
Image parsing for image retrieval from large image data bases: from coloured image to coloured regions
Abstract:
This paper gives details of a series of low level image processing routines which successfully break an image into a set of coloured regions. The first stage in the process is multi-scale edge detection. A fixed set of different sized kernels are used with the results being put into a single 'edgeness' image. A fixed lower threshold is applied to the edgeness image. A non-maximum suppression step is then applied. The histogram of edge strength in the non-max-suppressed image is used to set the high threshold for a hysteresis edge tracking routine. Points in the non-max-suppressed image above the high threshold are used as seed points to grow edges with the full edgeness image being used as the search domain. The edge growing algorithm therefore suffers less from the topological damage resulting from non-maximum suppression. A saliency filter is used to reject short crinkled edge chains. The second stage in the process uses the edge image to generate a series of Voronoi peaks. These are used as seed points for dilation type region growing. As the regions are grown the edgeness image is used to give a simple integrated measure of distance from a Voronoi centre. Pixels are then assigned membership in the 'nearest' centre. Regions are not permitted to grow through edges in the edge image. A merging step is then applied to amalgamate regions with large non-edge shared boundary. The mean colour of each region is evaluated and the regions then form nodes in a graph.
Reference:
  • Technical Report 97.4
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.97.4.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.97.4.pdf
Author:
Glenford Mapp, Steve J Hodges
Title:
Qos-Based Transport
Abstract:
This paper looks at transport services required by applications and proposes using a QoS vector to specify all transport requirements. These ideas have been pursued in the design and development of a new transport protocol called A1. Preliminary performance results for A1 over ATM are presented and compared with an efficient kernel implementation of TCP/IP.
Reference:
  • Proceedings of IFIP Fifth International Workshop on Quality of Service, CTR, Columbia University, New York, May 1997
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.97.3.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.97.3.pdf
Author:
Noha Adly, Pete Steggles, Andy Harter
Title:
SPIRIT: a Resource Database for Mobile Users
Abstract:
Users of computer systems need continuous access to information and services, but, as they move around in a richly equipped, networked environment, the available hardware resources change; software systems must adapt to these changes, offering location-aware personalisation and control. The SPIRIT project (SPatially Indexed Resource Identification and Tracking) is building a resource database which integrates the configuration data for heterogeneous networked hardware and software with fine-grained location data for users and equipment, allowing software to dynamically configure and reconfigure itself as users move around the networked environment. The ultimate goal of the project is to make it seem to users as though an application knows as much about the physical environment as they do. This paper describes the architecture of the SPIRIT database and provides an overview of some of its client applications.
Reference:
  • Proceedings of ACM CHI'97 Workshop on Ubiquitous Computing, Atlanta, Georgia, March 1997
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.97.2.ps.Z
Author:
Frank Stajano, Tom Blackie
Title:
AMIE - Advanced Multimedia Integrated Environment
Abstract:
The objective of the AMIE project was to research, develop and demonstrate an advanced environment for co-operative and distributed multimedia applications which would be integrated into an enterprise wide information technology system. A major design goal was to develop generic sub-system components which could be quickly and easily re-configured and integrated to address many different multimedia application and systems scenarios. The health care arena was chosen as an excellent demonstration for the capabilities of such a system, as it offered a demanding environment with a plethora of data modalities. An application area was identified where specific needs of a group of real users within a cardiology department were addressed. The culmination of the project was a three-month pilot field trial (later extended to four months) where the system was used in an operational role. This richly illustrated CD describes the aims and achievements of the project at various levels of detail, from a general overview of the system to technical papers and highlights of business exploitation opportunities. The documentation is presented as web pages and contains local links to, among other items, multimedia slide shows and MPEG movies showing the system in action.
Reference:
  • Technical Report 97.1 (CD ROM)
CD ROM:
CD-ROM available on request
Text:
http://www-lce.eng.cam.ac.uk/amie/
Author:
Andy Hopper
Title:
Network Computer Architectures
Abstract:
Network computers can present a simpler and more manageable interface to the user. The ATM network computer developed at our lab was a stateless device which combined a pen interface with a network-remoted windowing system. It was also a high-bandwidth networked multimedia display. In contrast a purely software development, the Virtual Network Computer, requires only a Web browser to interact with a windowing system running back at base.
Reference:
  • Technical Report 96.10 (video)
Video:
http://www-lce.eng.cam.ac.uk/pub/videos/qsif-200/nca-qsif-200.mpg
Title:
Video Mail Retrieval
Abstract:
The large collections of video mail which accumulated during the Pandora and later the Medusa projects suggested a difficult retrieval problem. The Video Mail Retrieval project showed that it was practical to use a speech recognition system in combination with traditional text-based techniques to achieve useful retrieval rates. Video.
Reference:
  • Technical Report 96.9 (video)
Video:
http://www-lce.eng.cam.ac.uk/pub/videos/qsif-200/vmr-qsif-200.mpg
Author:
Andy Hopper
Title:
Modular Networked Multimedia
Abstract:
This video features new applications made possible by the Medusa approach of delivering large numbers of ATM multimedia streams to the desktop.
Reference:
  • Technical Report 96.8 (video)
Video:
http://www-lce.eng.cam.ac.uk/pub/videos/qsif-200/mnm-qsif-200.mpg
Author:
Martin Brown
Title:
Supporting User Mobility
Abstract:
The availability of wireless network connections to laptop computers and PDA's has created interest in the issues surrounding mobile computing. However, enabling users to be genuinely mobile in their work requires more than a wireless connection. Distributed system services are needed to support the locating of people, equipment and software objects, and, especially for mobile multimedia applications, network transport protocols which can adapt to a wide range of networking conditions must be developed. This paper reviews some important mobility issues, looks at some of the systems requirements raised by user mobility, and describes some practical experiences with mobile applications at AT&T Laboratories Cambridge
Reference:
  • Proceedings of the IFIP'96 Conference, Mobile Communications, Canberra, Australia, September 1996 (Invited Paper), Chapman and Hall
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.96.7.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.96.7.pdf
Author:
Martin Brown, Jonathan Foote, Gareth Jones, Karen Sparck-Jones, Steve Young
Title:
Open-Vocabulary Speech Indexing for Voice and Video Mail Retrieval
Abstract:
This paper presents recent work on a multimedia retrieval project at Cambridge University and Olivetti Research Limited (ORL). We present novel techniques that allow extremely rapid audio indexing, at rates approaching several thousand times real time. Unlike other methods, these techniques do not depend on a fixed vocabulary recognition system or on keywords that must be known well in advance. Using statistical methods developed for text, these indexing techniques allow rapid and efficient retrieval and browsing of audio and video documents. This paper presents the project background, the indexing and retrieval techniques, and a video mail retrieval application incorporating content-based audio indexing, retrieval, and browsing.
Reference:
  • Proceedings of the Fourth ACM International Multimedia Conference, Boston, November 1996 (Best Paper Award),
  • Readings in Multimedia Computing and Networking, Eds. Kevin Jeffay and HongJiang Zhang, Morgan Kaufman Publishers, 2002
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.96.6.ps.Z
Author:
John Porter, Andy Hopper, Damian Gilmurray, Oliver Mason, John Naylon, Alan Jones
Title:
The ORL Radio ATM System, Architecture and Implementation
Abstract:
This paper presents a solution to the problem of connectivity of portables to an ATM wired network in the in-building environment. The approach to the support of ATM reduces the mobility load on the wired ATM network and is compatible with standard signalling protocols. The system is pico-cellular with a large number of base stations. The base stations are designed to be deployed in large numbers each covering a short range with partially overlapping coverages. This increases the aggregate throughput and reduces some of the problems specific to a radio physical layer. The MAC layer is optimised to provide efficient use of bandwidth and support guarantees for ATM traffic classes. An experimental prototype system based on low-cost fixed ATM switches and software controlled base stations has been developed and is outlined.
Reference:
  • Technical Report 96.5
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.96.5.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.96.5.pdf
Author:
Feng Shi, Andy Hopper
Title:
A Network Striped Storage System for Video on Demand
Abstract:
This research advocates the architecture of using the switched network as the interconnect among the loosely coupled storage devices for large scale video on demand(VOD) servers. The article proposes a flexible and scalable network striped distributed storage system framework to exploit the above architecture. Quality of Service(QoS) and implementation issues are also discussed in the end.
Reference:
  • Collected Abstracts from the 6th International Workshop
  • on Network and Operating System Support for Digital
  • Audio and Video (NOSSDAV'96), Zushi, Japan, April 1996
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.96.4.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.96.4.pdf
Author:
Brendan Murphy, Glenford Mapp
Title:
Integrating Multimedia Streams into a Distributed Computing System
Abstract:
Continuous media, such as audio and video, are quickly becoming an integral part of distributed computing environments. A shortcoming of such environments is their lack of support for continuous flows of information. What is missing is the notion of an on-going communication activity with an associated quality of service. This paper describes a model for integrating multimedia flows into a distributed computing system. The model permits explicit bindings to be established between type-checked stream interfaces. The stream binding is represented in the computational model as a first-class object which encapsulates configuration rules and QoS attributes. An operational interface supplied by the binding object allows other objects within the system to manage the binding, to renegotiate QoS parameters, to control the flows across the binding, and to register interest in stream events such as flow reports and communication errors. The in-band stream interface is an abstract C++ wrapper around transport mechanisms that include intra-host IPC and network transport protocols such as TCP and XTP. A prototype implementation of this model is described using the Common Object Request Broker Architecture (CORBA). The implementation environment comprises a local area ATM network with directly attached multimedia peripherals and general purpose workstations.
Reference:
  • Proceedings of Multimedia Computing and Networking, San Jose, CA, USA, January 1996
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.96.3.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.96.3.pdf
Author:
Kenneth R. Wood, Tristan Richardson, Frazer Bennett, Andy Harter, Andy Hopper
Title:
Global Teleporting with Java: Towards Ubiquitous Personalised Computing
Abstract:
Previous work has described Teleporting, an approach to mobile computing in which it is the user's personal application environment which is mobile rather than the hardware on which the applications run. In this paper we describe an extended teleporting system which makes the user's environment available on any machine in the world running a Java-compliant web browser. We present some preliminary experimental results together with discussions of security and performance issues.
Reference:
  • Presented and demonstrated at Nomadics '96, San Jose, USA, March 1996.
  • Technical Report 96.2
Reference:
  • (Japanese) $B!JF|K\8lLu!K(B $B;}$AJb$+$J$$%b%P%$%k!&%3%s%T%e!<%F%#%s%0(B $B%V%i%&%6$K<+J,$N4D6-$r8F$S=P$9(B $B%1%K%9!&(BR$B!&%&%C%I(B, $B%H%j%9%?%s!&%j%A%c!<%I%=%s(B, $B%U%l%$%6!&%Y%M%C%H(B, $B%"%s%G(B%# $B!&%O!<%?!<(B, $B%"%s%G%#!&%[%C%Q(B!< $BF|7P%3%s%T%e!<%?JL:}(B $B%=%U%H%&%(%"3+H/$N:G?75;(B=Q pp79-87, $BF|7P(BBP$B
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.96.2.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.96.2.pdf
Author:
Ferdinando Samaria, Harold Syfrig, Alan Jones, Andy Hopper
Title:
Enhancing Network Services through Multimedia Data Analysers
Abstract:
This paper summarises our experience of using data analysers to enhance network multimedia services. Analysers are categorised based on their location with respect to the network. The location is determined by balancing bandwidth requirements and computational complexity. Various applications are described where analysers are used to enhance aspects of the service provided. Details of the multimedia environment are given, followed by an overview of the analyser architecture and examples of analyser-enhanced applications. The paper is concluded by indicating directions of future development.
Reference:
  • Proceedings of ACM Multimedia'96, 4th International MultiMedia Conference and Exhibition, Boston, USA, November 1996
  • Technical Report 96.1
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.96.1.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.96.1.pdf
Author:
Glenford Mapp
Title:
Preliminary Performance Evaluation of SandiaXTP on ATM at ORL
Abstract:
With the deployment of high speed networks based on ATM, multimedia systems are quickly becoming an integral part of distributed computing environments. Protocols which can transport multimedia data are essential for the success of this new enterprise. XTP is one such protocol. In this paper we examine the issues involved in porting SandiaXTP to the ORL's ATM environment and assess its performance using some preliminary tests.
Reference:
  • Proceedings of PROMS '95, Second Workshop on Protocols for Multimedia Systems, Salzburg, Austria, October 1995
  • Technical Report 95.10
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.95.10.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.95.10.pdf
Author:
Subir Biswas, Andy Hopper
Title:
A Representative Based Architecture for Handling Mobility in Connection Oriented Radio Networks
Abstract:
This paper presents a connection management architecture tuned for handling mobility in a radio network environment. A new concept of per roaming entity software agent, known as mobile representative, is used for insulating fixed network entities from the effects of user mobility. It is shown that mobile representatives can be used for distributing mobility management within fixed backbone network, depending on the instantaneous physical locations of mobile terminals. This paper describes a representative management architecture followed by a novel connection caching strategy which is used for achieving low-latency and scalable connection handovers.
Reference:
  • Proceedings of ICUPC '95, International Conference on Universal Personal Communications, Tokyo, Japan, November 1995
  • Technical Report 95.9
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.95.9.ps.Z
Author:
Martin Brown, Jonathan Foote, Gareth Jones, Karen Sparck-Jones, Steve Young
Title:
Automatic Content-Based Retrieval of Broadcast News
Abstract:
This paper presents current work on a video retrieval project at Cambridge University and Olivetti Research Limited (ORL). We show that statistical methods developed for text retrieval are also effective for retrieving and browsing multimedia documents. These methods allow rapid retrieval of news broadcasts by information content determined from teletext subtitles. Information retrieval results for experiments performed on a large archive of news broadcasts are presented. This is made possible by the ORL Medusa system, which allows practical recording, storage, and playback of tens of gigabytes of multimedia data. This work is a step towards practical retrieval of multimedia documents, where the information content is determined from speech recognition performed on the audio soundtrack. We describe the project background, the ORL Medusa multimedia system, and retrieval application, as well as the news broadcast corpus and methods of browsing the retrieved news stories.
Reference:
  • Proceedings of the Third ACM International Multimedia Conference, San Francisco, November 1995
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.95.8/index.html
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.95.8.ps.Z
Author:
Tristan Richardson
Title:
Teleporting - Mobile X Sessions
Abstract:
This paper examines issues involved in making an X session mobile. A mobile X session is one which is not fixed to a particular X display, but can be materialised on demand at any suitable display. The Teleporting System developed at Olivetti Research Laboratory (ORL) is a tool for experiencing mobile X sessions. It provides a familiar, personalised way of making temporary use of X displays as the user moves from place to place. When linked to location facilities such as those provided by the Olivetti Active Badge System the traditional log-in process can be almost entirely eliminated, allowing the nomadic user to easily make use of computing resources which are to hand.
Reference:
  • Proceedings Ninth Annual X Technical Conference, Boston MA, January 1995
  • Technical Report 95.7
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.95.7.html/paper.html
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.95.7.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.95.7.pdf
Author:
Frazer Bennett, Andy Hopper
Title:
Developments in Networked Multimedia
Abstract:
This paper discusses developments in multimedia applications and systems from a network-oriented point of view. We highlight the different generations of network that have been used as substrates for multimedia experiments, focusing particularly on two systems that we have developed. Finally, we look forward to a third generation of network, the subject of more recent attention, which we hope will make ubiquitous, mobile, networked multimedia applications possible.
Reference:
  • Proceedings NEC Research Symposium in Multimedia Computing, June 1995
  • Technical Report 95.6
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.95.6.ps.Z
Author:
Frank Stajano, Rob Walker
Title:
Taming the Complexity of Distributed Multimedia Applications
Abstract:
The Medusa environment for networked multimedia uses Tcl to compose applications out of low-level processing blocks called modules. A medium-sized application such as a two way multi-stream videophone already uses around one hundred interworking modules, running in parallel on several host machines. This paper shows how we overcome the inherent complexity of such applications: to deal with parallelism we use a multi-threaded library hidden behind a single-threaded Tcl interpreter; to build higher order components than the modules we use the object oriented extension [incr Tcl]; and to exploit the variety of available input and output devices we adopt the Model-View-Controller paradigm.
Reference:
  • Proceedings of the 1995 Usenix Tcl/Tk Workshop, Toronto, July 1995
  • Technical Report 95.5
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.95.5.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.95.5.pdf
Author:
David Clarke
Title:
The Medusa Video Brick: An ATM Camera
Abstract:
This technical report describes the Medusa Video Brick, which is an ATM peripheral for the capture of video. The Video Brick supports multiple concurrent streams of video at different qualities, and connects directly to the Olivetti Research ATM network without requiring the presence of any host workstation.
Reference:
  • Technical Report 95.4
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.95.4.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.95.4.pdf
Author:
Alan Chaney, Ian Wilson, Andy Hopper
Title:
The Design and Implementation of a RAID-3 Multimedia File Server
Abstract:
The Olivetti Research Laboratory has developed an experimental system based on intelligent peripherals connected directly to an ATM network. As well as multimedia modules (e.g. audio and video) the system also includes a directly connected RAID-3 storage server called the 'Disc Brick'. This paper describes the architecture of the Disc Brick, and discusses some of the hardware and software issues raised by its design. It also presents measurements taken from a Disc Brick in operation, and discusses how the observations relate to the original design objectives. Finally, the paper attempts to evaluate the Disc Brick as part of ORL's family of directly connected peripherals.
Reference:
  • Proceedings of 5th International Workshop on Network and Operating System Support for Digital Audio and Video (NOSSDAV'95), Durham NH, USA, April 1995
  • Technical Report 95.3
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.95.3.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.95.3.pdf
Author:
Ferdinando Samaria, Andy Harter
Title:
Parameterisation of a Stochastic Model for Human Face Identification
Abstract:
Recent work on face identification using continuous density Hidden Markov Models (HMMs) has shown that stochastic modelling can be used successfully to encode feature information. When frontal images of faces are sampled using top-bottom scanning, there is a natural order in which the features appear and this can be conveniently be modelled using a top-bottom HMM. However, a top-bottom HMM is characterised by different parameters, the choice of which has so far been based on subjective intuition. This paper presents a set of experimental results in which various HMM parameterisations are analysed.
Reference:
  • Proceedings of 2nd IEEE Workshop on Applications of Computer Vision, Sarasota FL, December 1994
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/paper.95.2.ps.Z
Author:
Tony Heap, Ferdinando Samaria
Title:
Real-Time Hand Tracking and Gesture Recognition Using Smart Snakes
Abstract:
This paper gives architecture and implementation details of a hand tracking and gesture recognition system which has been developed at Olivetti Research Limited as an application for the Medusa distributed multimedia environment. The system uses live 15-bit colour video from a networked camera, runs in real time (25 frames/sec on a DEC Alpha), and copes well with background clutter. Tracking is achieved using the 2D deformable Active Shape Models (smart snakes) of Cootes and Taylor, and a genetic algorithm is used to perform an initial global image search. The Point Distribution Model used for both snakes and genetic algorithms provides a generic and flexible model that can be used to track any 2D deformable object.
Reference:
  • Technical Report 95.1
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.95.1.ps.Z
Author:
Mike Addlesee, Chris Turner, Andy Hopper
Title:
Displaying the Future
Reference:
  • 4th International Scientific Conference on Work with Display Units, Milan, October 1994
  • Technical Report 94.13
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.13.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.13.pdf
Author:
Andy Hopper
Title:
The Medusa Applications Environment
Abstract:
The Platform - The Medusa project aims to provide a rich multimedia environment for the desktop user. It is based on hardware which utilises ATM communications technology as the basic interconnect both for computers and multimedia peripherals such as cameras, microphones and other devices. The speed of the ATM fabric is sufficiently high (100Mbps at the link level) that the networking does not present a bottleneck. Small 4x4 and 8x8 ATM switches are used to implement the network in the local area. This is compatible with wide-area ATM networks and will make it possible to extend this approach.

The hardware modules available are ATM video, ATM audio, ATM LCD tile, ATM disc brick and DEC Alpha workstations. The video module can accommodate four camera heads and can provide images at six different sizes for each. The audio module has four bidirectional channels and a range of sampling frequencies up to 48KHz. The display tile is based on a 640x480 active matrix display. The disc brick uses RAID-3 technology and provides 8Gbytes of storage.

The system has been deployed in the laboratory and some two hundred modules and switches are available for experimentation. For the time being, raw video is being used to make easier the development of applications which incorporate the use of agents.

The software platform consists of two components; an object oriented applications environment, and the applications themselves written in a scripting language called Tcl/Tk. The applications environment is a peer-to-peer architecture which uses active object to represent information sources, sinks, data converters and so on. Data can flow from module to module on connections between them. Connections between modules are simple, reliable and unbuffered. More complex connections are represented by special intermediate modules. Modules for providing basic agent features are available, ranging from simple motion and sound observers to gesture, speech and face recognition components. Applications can be prototyped rapidly and different combinations of features evaluated with ease.

Applications - Applications include a media server which simultaneously provides many channels at many sizes for viewing on a workstation or display tile.

A multi-way video phone uses four video streams and an audio stream between the corresponding parties. The cameras are used to provide head and shoulder and more general views into an office. Views of documents are available from a rostrum camera above the desk. Four microphones and speakers provide hands-free audio to any part of the office. In a conversation, all video streams are sent to the recipient who can choose what to watch at the largest size. Additionally, the streams can be sent to an agent which suggests or controls the way sizes are allocated to views. The decision is a combination of the amount of motion, where in the field of view the motion is taking place, together with some hysteresis to prevent flicking between scenes. It also incorporates the user's options on a per-application and per-office basis. When two corresponding parties operate in this way a total of 30 streams are sent across the ATM network.

The video mail application records all views so that subsequently the recipient can choose which (one or many) to view. This presents a high load on the storage system because each view must be recorded at maximum size as at that it is not known how it will be subsequently presented.

Finally, a hand tracker is shown where a two-stage algorithm starts by searching for a hand in a scene, and, having found it, draws an outline and attempts some gesture recognition.

The Medusa system is currently being used to develop a variety of algorithms suitable for use by agents ranging from simple ones which can provide ubiquitous service to all clients to complex ones which are invoked as required.

Reference:
  • Proceedings of European Computer Support for Collaborative Working, Stockholm, September 1995
  • Technical Report 94.12 (video)
Video:
MPEG encoded video available
Author:
Frazer Bennett, Tristan Richardson, Andy Harter
Title:
Teleporting - Making Applications Mobile
Abstract:
The rapid emergence of mobile computers as a popular, and increasingly powerful, computing tool is presenting new challenges. This subject is already being widely addressed within the computing literature. A complementary and relatively unexplored notion of mobility is one in which application interfaces, rather than the computer on which the applications run, are able to move. The Teleporting System developed at the Olivetti Research Laboratory (ORL) is a tool for experiencing such `mobile applications'. It operates within the X Window System, and allows users to interact with their existing X applications at any X display within a building. The process of controlling the interface to the teleporting system is very simple. This simplicity comes from the use of an automatically maintained database of the location of equipment and people within the building. This paper describes the teleporting system, what it does, and how it is used. We outline some of the issues of making applications mobile that have arisen during its implementation.
Reference:
  • Proceedings of 1994 Workshop on Mobile Computing Systems and Applications, Santa Cruz, December 1994
  • Technical Report 94.11
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.11.html/paper.html
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.11.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.11.ps.Z
Author:
David Greaves, Derek McAuley, Leslie French, Eoin Hyden
Title:
Protocol and Interface for ATM LANs
Abstract:
This paper advocates local area networks using the Asynchronous Transfer Mode where data is carried in the payloads of fixed size cells. We describe the design and performance of a simple ATM host interface for inexpensive computers together with the MSNA protocol architecture. A feature of the MSNA architecture is that it can provide ATM virtual circuits directly to applications by demultiplexing to a degree normally associated with the transport layer of a protocol stack. This leads to further simplification and efficiency in end-stream implementation. We discuss implementations of the ATM adaption leyr of varying complexity, suitable for end-systems ranging from imbedded micro-controllers to Unix file servers, and discuss the appropriate place for the adaptation layer to be terminated in a multi-media workstation.
Reference:
  • Technical Report 94.10
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.10.ps.Z
Author:
Frazer Bennett, Tristan Richardson, Andy Harter, Andy Hopper
Title:
Teleporting - Making Applications Mobile
Reference:
  • Proceedings of Computer Support for Collaborative Working, Chapel Hill, Oct 1994
  • Technical Report 94.9 (video)
Video:
MPEG encoded video available
Author:
Martin Brown, Jonathan Foote, Gareth Jones, Karen Sparck-Jones, Steve Young
Title:
Video Mail Retrieval by Voice: An Overview of the Cambridge/Olivetti Retrieval System
Abstract:
This paper describes current work on a video and audio document retrieval project at Cambridge University and Olivetti Research Limited (ORL). The project seeks to integrate state-of-the-art text retrieval methos with high-performance word spotting to yield a robust and efficient video mail retrieval system. A specific goal is the development of a practical retrieval system to work with Medusa, a high-bandwidth multimedia environment in daily use. This paper describes the project background, message corpus and experiment design, and presents experimental results showing audio retrieval performance very close to that of text.
Reference:
  • Proceedings of the ACM Multimedia '94 Conference Workshop on Multimedia Database Management Systems, San Francisco, 21 Oct 1994
  • Technical Report 94.8
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.8.ps.Z
Author:
Frank Stajano
Title:
Writing Tcl Programs in the Medusa Applications Environment
Abstract:
Medusa is an applications environment for distributed multimedia which has been designed and developed at the Olivetti Research Laboratory in Cambridge, U.K. The software building blocks, or modules, are written in C++, while the applications that create networks of modules and make useful things with them are written in Tcl/Tk/TCL-DP.
Reference:
  • Proceedings of Tcl/Tk Workshop, New Orleans, June 1994
  • Technical Report 94.7
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.7.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.7.pdf
Author:
David Clarke
Title:
Video Compression for the Pandora Multimedia System
Abstract:
This document describes the video compression system used in the Olivetti Research Ltd Pandora box which was used in the Pandora distributed multimedia project. The Pandora project is described briefly, followed by a discussion of the options then available for video compression. The chosen system and its implementation is presented.
Reference:
  • Technical Report 94.6
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.6.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.6.pdf
Author:
David Clarke, Gavin Stark
Title:
Network Cards for the Pandora Multimedia System
Abstract:
A Network Interface Card is described which is used in the Olivetti Research Ltd Pandora box. The Pandora project involved the installation of a network of multimedia-equipped workstations connected to an early ATM-style network, the Cambridge Fast Ring. The architecture and function of the Pandora Box is described briefly and then the development of the Network Card is followed in more detail. This multiprocessor card uses a pair of Inmos Transputers and two custom LSI chips.
Reference:
  • Technical Report 94.5
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.5.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.5.pdf
Author:
Tristan Richardson, Frazer Bennett, Glenford Mapp, Andy Hopper
Title:
Teleporting in an X Window System Environment
Abstract:
Teleporting is the ability to redirect a windowing environment to different computer displays. This paper describes the implementation of a teleporting system developed at Olivetti Research Laboratory (ORL). We outline two particular features of the system that make it powerful. First, t operates with existing applications, which will run without any modification. Second, it incorporates sophisticated techniques of personnel and equipment location which make it simple to use. Teleporting may represent a development in attempts to achieve a ubiquitous, personalised computing environment for all
Reference:
  • IEEE Personal Communications Magazine, Vol. 1, No. 3, Third Quarter 1994, pp 6-12.
  • Technical Report 94.4
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.4.html/paper.html
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.4.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.4.pdf
Author:
Subir Biswas, Andy Hopper
Title:
Automatic Management Scheme for a Mobile Radio LAN
Reference:
  • Proceedings of the IEEE Conference on Personal Wireless Communications, Bangalore, August 1994
Text:
Not currently available in electronic form
Author:
Andy Hopper
Title:
Communications at the Desktop
Reference:
  • Computer Networks and ISDN Systems 26, July 1994
Text:
Not currently available in electronic form
Author:
Stuart Wray, Tim Glauert, Andy Hopper
Title:
The Medusa Applications Environment
Abstract:
Medusa is a peer to peer architecture for controlling networked multimedia devices. This paper describes the software model presented to the applications programmer. Active objects called modules are used to represent camera, displays, format converters and so on. Data can flow from module to module on connections between them. We introduce two key ideas: firstly, connections between modules are simple, reliable and unbuffered. More complex connections are represented by special intermediate modules. Secondly, security is provided by naming modules with inforgeable capabilities then using hierarchies of proxy modules to restrict access.
Reference:
  • Proceedings of the International Conference on Multimedia Computing and Systems, Boston MA, May 1994.
  • An extended version appeared in IEEE Multimedia, Vol. 1 No. 4, Winter 1994. pp 54-63
  • Technical Report 94.3
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.3.ps.Z
Author:
John Porter, Andy Hopper
Title:
An ATM based protocol for Wireless LANs
Abstract:
This paper presents a solution to the problem of connectivity of portables to an ATM wired network in the local area environment. A compatible ATM approach is used to provide support for multi-media traffic. Spatial re-use of a single frequency with a large number of small cells is used to increase the aggregate throughput. An experimental system based on low-cost fixed ATM switches and software controlled base stations has been developed.
Reference:
  • Technical Report 94.2
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.2.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.2.pdf
Author:
Andy Harter, Andy Hopper
Title:
A Distributed Location System for the Active Office
Abstract:
Computer and communications systems continue to proliferate in the office and home. Systems are varied and complex, involving wireless networks and mobile computers. Mobility itself introduces many new issues. However, systems are underused because the range of control mechanisms and application interfaces is too diverse. It is therefore pertinent to consider what mechanisms might allow the user to manipulate systems in simple and ubiquitous ways, and how computers can be made more aware of the facilities in their surroundings. Knowledge of the location of people and equipment within an organisation is such a mechanism. Annotating a resource database with location information allows location based heuristics for control and interaction to be constructed. This approach is particularly attractive since location techniques can be devised which are physically unobtrusive and do not rely on explicit user action. This article describes the technology of a system for locating people and equipment, and the design of a distributed system service supporting access to that information. The application interfaces which are made possible by, or benefit from this facility are presented.
Reference:
  • IEEE Network, Vol. 8, No. 1, January 1994
  • Technical Report 94.1
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.1.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.94.1.ps.Z
Author:
Andy Hopper, Andy Harter, Tom Blackie
Title:
The Active Badge System
Reference:
  • INTERCHI'93, Amsterdam, April 1993
  • Technical Report 93.7 (video)
Video:
MPEG encoded video available
Author:
David Greaves, Derek McAuley
Title:
ATM Network Services for Workstations
Abstract:
Workpackage 3 of OSI 95 was titled `New Communications Techniques' and was an evaluation of how to make use of the new communications techniques which offer services with a guaranteed quality of service, including ATM and B-ISDN. This document discusses the provision of the ATM networking services to application programs running on general purpose computing equipment which is connected to an ATM network.
Reference:
  • Document identification OSI95/B3/Book/v1
  • Technical Report 93.6
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.93.6.ps.Z
Author:
Frazer Bennett, Andy Harter
Title:
Low Bandwidth Infra-Red Networks and Protocols for Mobile Communicating Devices
Abstract:
This paper is a source of technical reference for the IR network developed at Olivetti Research and in use within Olivetti, Digital, Xerox, Bellcore and elsewhere. The scope is restricted to details of the physical communication medium and formatting of simple data packets over the medium.
Reference:
  • Technical Report 93.5
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.93.5.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.93.5.pdf
Author:
Alan Jones, Andy Hopper
Title:
Handling Audio and Video Streams in a Distributed Environment
Abstract:
Handling audio and video in a digital environment requires timely delivery of data. This paper describes the principles adopted in the design of the Pandora networked multi-media system. They attempt to give the user the best possible service while dealing with error and overload conditions. Pandora uses a sub-system to handle the multi-media peripherals. It uses transputers and associated Occam code to implement the time critical functions. Stream implementation is based on self-contained segments of data containing information for delivery, synchronisation and error recovery. Decoupling buffers are used to allow concurrent operation of multiple processing elements. Clawback buffers are used to resynchronise streams at their destinations with minimum latency. The system has proved robust in normal use, under overload, and in the presence of errors. It has been in use for a number of years. The principles involved in this design are now being used in the development of two complementary systems. One approach explodes Pandora by having the camera, microphone, speaker and display as independent units linked only by the LAN. The other approach integrates these devices as peripheral cards in a powerful workstation.
Reference:
  • Proceedings of 14th ACM Symposium on Operating System Principles, OSR, Vol 27, No 5, December 1993
  • Technical Report 93.4
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.93.4.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.93.4.pdf
Author:
Ferdinando Samaria
Title:
Face Segmentation For Identification Using Hidden Markov Models
Abstract:
This paper details work done on face processing using a novel approach involving Hidden Markov Models. Experimental results from earlier work indicated that left-to-right models with use of structural information yield better feature extraction than ergodic models. This paper illustrates how these hybrid models can be used to extract facial bands and automatically segment a face image into meaningful regions, showing the benefits of simultaneous use of statistical and structural information. It is shown how the segmented data can be used to identify different subjects. Successful segmentation and identification of face images was obtained, even when facial details (with/without glasses, smiling/non-smiling, open/closed eyes) were varied. Some experiments with a simple left-to-right model are presented to support the plausibility of this approach. Finally, present and future directions of research work using these models are indicated.
Reference:
  • Proceedings of 4th British Machine Vision Conference, Springer-Verlag, Guilford, 1993
  • Technical Report 93.3
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.93.3.ps.Z
Author:
Andy Hopper
Title:
Location Information for Simplifying Computer Networks and Communications
Reference:
  • Proceedings of the Fifteenth International Conference of Data Protection Registrars, Manchester, September 1993
Text:
Not currently available in electronic form
Author:
X.F. Jiang, Andy Hopper
Title:
Architectural Support for Multipoint Digital Video Communications
Reference:
  • Proceedings of IEEE International Conference on Communications, (ICC'93), Geneva, May 1993
Text:
Not currently available in electronic form
Contact:
Cambridge University Computer Laboratory, New Museums Site, Pembroke Street, Cambridge CB2 3QG, England
Author:
Ferdinando Samaria, Frank Fallside
Title:
Automated Face Identification Using Hidden Markov Models
Abstract:
This paper details work done on automatic face identification. A new approach to the problem was proposed involving the use of Hidden Markov Models. Initial experimental results indicated that left-to-right models with use of structural information yielded better feature extraction than ergodic models. In this paper we illustrate how these hybrid models can be used to extract facial bands and classify face images, showing the benefits of simultaneous use of statistical and structural information. Some experimental results obtained with a simple left-to-right model are presented to support the plausibility of this approach. Successful results were obtained using images with homogeneous background. We conclude indicating present and future directions of research work using these models.
Reference:
  • Proceedings of the International Conference on Advanced Mechatronics, The Japan Society of Mechanical Engineers, Japan 1993
  • Technical Report 93.2
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.93.2.ps.Z
Author:
Ferdinando Samaria, Frank Fallside
Title:
Face Identification and Feature Extraction Using Hidden Markov Models
Abstract:
This paper details work done on automatic face identification. A new approach to the problem is proposed involving the use of Hidden Markov Models. We illustrate how these models allow the automatic extraction of facial features and the classification of face images. Some experiments are presented to support the plausibility of this approach. Successful results were obtained under the constraints of homogeneous lighting and constant background.
Reference:
  • Image Processing: Theory and Applications, edited by G. Vernazza, San Remo, Elsevier 1993
  • Technical Report 93.1
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.93.1.ps.Z
Author:
Andy Hopper
Title:
Beyond 2000
Abstract:
The Active Badge was conceived, designed and prototyped at our lab between 1989 and 1992. It was the first of a series of research projects investigating mobility and location technology. This clip is taken from the Australian TV series ``Beyond 2000''.
Reference:
  • Technical Report 92.9 (video)
Video:
http://www-lce.eng.cam.ac.uk/pub/videos/qsif-200/beyond-qsif-200.mpg
Author:
Andy Hopper
Title:
The Pandora System
Reference:
  • CSCW'92, Toronto, October 1992 (video)
  • Technical Report 92.8 (video)
Video:
Not available in electronic form
Author:
David Greaves, Derek McAuley
Title:
Private ATM Networks
Abstract:
This paper advocates the use of local area networks which use 48 byte ATM cells. Hosts connected to the network are fitted with ATM interfaces and run a new protocol stack, up to the network level, which avoids multiplexing and efficiently handles the out-of-band signalling used by ATM. The private network may be WAN, MAN or LAN dimensions and contain several different network technologies, provided each is able to perform the basic function of carrying ATM cells from one point to another. The private network may be connected to the B-SIDN at one or more points.
Reference:
  • Proceedings of the 3rd International IFIP Workshop on Protocols for High Speed Networks, Stockholm, May 1992
  • Technical Report 92.7
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.92.7.ps.Z
Author:
Subir Biswas, John Porter, Andy Hopper
Title:
Performance of Multiple Access Protocols for an ATM Based Pico-Cellular Radio LAN
Reference:
  • Proceedings of 3rd IEEE International Symposium on Personal, Indoor and Mobile Communications, Boston, October 1992
Text:
Not currently available in electronic form
Author:
Andy Hopper
Title:
Digital Video on Computer Workstations
Abstract:
This paper describes the way continuous media can be used on networked digital devices. A number of architectures for incorporating digital video on a workstation are presented. These include systems which control the real-time streams but do not handle the data directly, those that send the streams through normal datapaths, and those that are particularly suited for networking of many real-time streams at once. A summary of experience with the Pandora distributed multimedia system is given, together with an outline of a new system under construction, called Medusa.
Reference:
  • Proceedings of Eurographics '92, Cambridge, England, September 1992
  • Technical Report 92.6
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.92.6.pdf
Author:
Tony King
Title:
Pandora: An Experiment in Distributed Multimedia
Abstract:
An experimental workstation is described which supports digital video and audio in a distributed environment, and which presents this functionality to the user through the medium of a video-extended implementation of the X Window System. The Pandora Workstation is built out of two quite separate parts. A standard UNIX machine (the Pandora host) brings standard hardware and software computing resources to the systems; a highly specialised processing engine (Pandora's Box) handles the high-bandwidth, time-critical, and device-dependent processing. A 50Mbit/s ATM network provides for real-time data communication within the system. Nineteen Pandora Workstations have been deployed within Olivetti Research Ltd and the Cambridge University Computer Laboratory, and are used routinely to run distributed applications including video mail, video conferencing, and real-time media delivery services.
Reference:
  • Proceedings of Eurographics '92, Cambridge, England, September 1992
  • Technical Report 92.5
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.92.5.pdf
Author:
Andy Hopper, Alan Jones, Roderick Augur, Martyn Fice, Simon Blyth, Haroon Ahmed
Title:
A Feasibility Study for the Fabrication of Planar Silicon Multichip Modules Using Electron Beam Lithography for Precise Location and Interconnection of Chips
Abstract:
A technique for fabricating multichip modules (MCM's) by mounting chips in holes etched into silicon motherboards is described. With this approach the fron faces of the chips are coplanar with the fron of the motherboard, and hence, the connections between the chips and the motherboards may be made by standard thin film processes. A method for fabricating such modules using electron beam lithography to locate the chips and to define the interconnections between the chips and the motherboard is discussed. The feasibility of the processes is demonstrated with measurements on a module designed and fabricated to test the stability of the processes.
Reference:
  • IEEE Transactions of Components, Hybrids, and Manufacturing Technology, Vol. 15, No. 1, February 1992
  • Technical Report 92.4
Text:
Not currently available in electronic form
Author:
Andy Hopper
Title:
Improving Communications at the Desktop
Abstract:
The use of two systems which improve communications at the desktop is presented. The first deals with desktop cameras attached to networked workstations (Pandora). The most popular applications are video-phone and video-mail. The second deals with location of personnel in a building using infra-red (Active Badges). The system has proved popular because by making the information available at every desktop the amount of time spent location others has been reduced. By extrapolating to newer technologies, a framework is outlined for the design of a system which makes the desktop virtual by using location information to personalise the communications environment.
Reference:
  • `Communications After 2000 AD', the Report of the Royal Society Discussion Meeting, 18/19 March 1992. Published by Chapman and Hall
  • Technical Report 92.3
Text:
Not currently available in electronic form
Author:
X.F. Jiang, Andy Hopper
Title:
Scaleable Reception and Interchange of Multi-Format Digital Video Streams
Reference:
  • Proceedings of Australian Broadband Switching and Services Symposium, Melbourne, July 1992
Text:
Not currently available in electronic form
Contact:
Cambridge University Computer Laboratory, New Museums Site, Pembroke Street, Cambridge CB2 3QG, England
Author:
Andy Hopper
Title:
The Walk-and-Wear Office
Reference:
  • Computerworld, April 20 1992
Text:
Not currently available in electronic form
Author:
Roy Want, Andy Hopper
Title:
Active Badges and Personal Interactive Computing Objects
Abstract:
This paper describes a family of Personal Active Badges developed for location of people and devices in the computer environment. Applications include location and paging of individuals as well as control of computer systems. Active Badges are one type of a range of portable computers connected to cordless communication systems that can now be made. Because of their small size and application such devices are referred to as Personal Interactive Computing Objects or PiCO's. A speculative discussion of how such devices may be used in the traditional computing environment is given.
Reference:
  • IEEE Transactions of Consumer Electronics, February 1992
  • Technical Report 92.2
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.92.2.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.92.2.pdf
Author:
Roy Want, Andy Hopper, Veronica Falcao, Jonathon Gibbons
Title:
The Active Badge Location System
Abstract:
A novel system for the location of people in an office environment is described. Members of staff wear badges that transmit signals providing information about their location to a centralised location service, through a network of sensors. The paper also examines alternative location techniques, system design issues and applications, particularly relating to telephone call routing. Location systems raise concerns about the privacy of an individual, and these issues are also addressed.
Reference:
  • ACM Transactions on Information Systems, Vol. 10, No. 1, January 1992, pp 91-102.
  • Technical Report 92.1
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.92.1.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.92.1.pdf
Author:
David Greaves, Krzysztof Zielinski
Title:
Preliminary Performance Results for CBN Half-Duplex VME Stations (V1S)
Abstract:
The CBN (Cambridge Backbone Network) offers an ATM LAN/MAN architecture based around a source release slotted ring. The current implementation operates at 512 MHz, interconnecting five sites at Olivetti Research Limited and the University of Cambridge Computer Laboratory. This paper reports performance measurements of this first implementation in terms of throughput and response time, when using the V1S CBN station interface, Motorola MVME 147 68030 CPU cards (20MHz), the MSNA (multi-service network architecture) fragmentation protocol and the Wanda micro-kernel. The purpose of this work was to identify throughput limitation in the current station interface and protocol stack, in order to guide future development.
Reference:
  • Document identification OSI95/Deliverable ORL-1 annex/V1
  • Technical Report 91.5
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.91.5.ps.Z
Author:
David Greaves, David Milway, David Garnett, Andy Hopper
Title:
Design and Implementation of an ATM Backbone Ring
Abstract:
The Cambridge Backbone Ring (CBR) is a collaborative project between Olivetti Research Limited and the University of Cambridge Computer Laboratory. The project has designed and built and experimental ring communication network for computer data, and real-time applications. The network forms a backbone facility for interconnecting groups of CFR (Cambridge Fast Ring) networks and Pandora multi-media workstations in the Cambridge area. Access control uses the empty slot protocol, using short, fixed-length cells which contain 32 bytes of payload and a 4 byte header containing the virtual circuit identifier. Although the architecture was designed for line rates of 1Gbit/second and higher, the current implementation operates at 512 MHz. Twenty-five stations have been constructed, to date. A revision incorporating the now-standard, 48 byte cells, and operating at a higher line-rate, is planned.
Reference:
  • Technical Report 91.4
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.91.4.ps.Z
Author:
Maurice V. Wilkes
Title:
Computing Perspectives
Abstract:
Columns with the following titles: Computer Security in the Business World Networks, Email, and Fax The Bandwidth Famine It's All Software Now The Rise of the VLSI Processor Software and the Programmer Revisiting Computer Security in the Business World
Reference:
  • Columns reprinted from the Communications of the ACM. April 1990 - August 1991
  • Technical Report 91.3
Text:
Not currently available in electronic form
Author:
Andy Hopper
Title:
Design and Use of High-Speed Networks in Multimedia Applications
Abstract:
This paper deals with architectures for networked multimedia systems. Such architectures are made up of both network components and multimedia device components. The networks include high speed switches and backbones for real-time stream applications as well as systems with lower capacity which provide additional facilities for different kinds of multimedia devices. The devices range from lightweight portable personal units to complex workstations. A report is given of experience from a multimedia experimental system called Pandora which places a camera on the desktop and allows many applications to be tried. An estimate of the bandwidth requirements for future systems is made by drawing on experience form the popular applications in Pandora and in the expectation of the much higher quality required by new multimedia applications.
Reference:
  • Proceedings of 3rd IFIP Conference on High Speed Networking, Berlin, March 1991
  • Technical Report 91.2
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.91.2.pdf
Author:
Maurice V. Wilkes
Title:
Progress and Research in the Computer Industry
Abstract:
The paper surveys the technical progress which has occurred in the computer industry in the recent past and the way in which the relationship between that industry and the semi-conductor industry has developed. Research in the computer industry is now dominated by software, a subject which has an intellectual basis rather than a basis in the experimental sciences. For this reason, the management of research in the computer industry presents problems of its own.
Reference:
  • Royal Society Clifford Patterson Lecture, 15 November 1990. Phil. Trans R. Soc. Lond. A(1991)334, 173-184
  • Technical Report 91.1
Text:
Not currently available in electronic form
Author:
B. Robertson, Mark Chopping, K. Zielinski, David Milway, Andy Hopper
Title:
The Metrobridge - A Backbone Network Distributed Switch
Abstract:
This paper describes the Metrobridge project - a distributed switch for connecting PC cards via a high-speed ATM-style backbone network. Initially the system architecture is outlined, then certain aspects are examined in more detail. Topics discussed include learning and routing algorithms, access/routing control, management functions, and applications.
Reference:
  • ACM Computer Communications Review, July 1991
  • Technical Report 90.3
Text:
Not currently available in electronic form
Author:
David Greaves, Dimitris Lioupis, Andy Hopper
Title:
The Cambridge Backbone Ring
Abstract:
The Cambridge Backbone Ring (CBR) is a collaborative project between Olivetti Research Limited and the University of Cambridge Computer Laboratory. The project has designed and built an experimental ring communication network for integrated computer data, voice and real-time video applications. The network is currently aimed as a backbone facility for interconnecting groups of CFR (Cambridge Fast Ring) networks in the Cambridge area. Media access control is through the empty slot technique, with transmitting stations filling multiple slots each ring revolution. The network operates on monomode optical fibre and is designed for an eventual line rate of 1000Mbit/sec. In the Backbone Ring architecture, the bandwidth of the fibre optic channel can be partitioned into a number (currently four) of TDM channels. This enables stations of varying cost and bandwidth to be attached to one network, parameterised by the number of channels a station can use concurrently. Unlike several other TDM ring projects in the literature, the Backbone Ring architecture achieves full connectivity even with the simplest type of station.
Reference:
  • Presented at IEEE Infocom 90, San Francisco 1990
  • Technical Report 90.2
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.90.2.ps.Z
Author:
Andy Hopper
Title:
Pandora - An Experimental System for Multimedia Applications
Abstract:
Pandora is a joint project between Olivetti Research Cambridge and the University of Cambridge Computer Laboratory. The project is investigating the use of multimedia workstations in a working environment with particular emphasis on digital video. It endeavours to place a camera on the desktop to make generation of multimedia documents as easy as producing text. We are aiming to produce a number of new applications as well as to provide insights into the way computer systems should be designed. The project is in three stages. In the first a peripheral, Pandora's Box, has been designed. This box can be attached to any one of a range of workstations and provides multimedia features. In the second stage a number of such systems are being deployed amongst a community of systems developers and application writers. Finally we will use the experimental system in our daily work to evaluate new applications. From the users point of view the normal workstation environment is maintained but additional features are available. This paper describes the design decisions which must be taken when incorporation video in a workstation. A description of the Pandora's Box peripheral which provides multimedia features is given. Finally the distributed system under construction is discussed.
Reference:
  • Published in Operating Systems Review, Vol 24, No.2 April 1990
  • Technical Report 90.1
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.90.1.pdf
Author:
David Greaves
Title:
The Double-slot Slotted Ring Protocol (DSR)
Reference:
  • Technical Report 89.5
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.89.5.ps.Z
Author:
Roy Want, Andy Hopper
Title:
The LAN as an Integrated Communications Environment
Reference:
  • Proceedings of Networks 89, Birmingham, England, June 1989
Text:
Not currently available in electronic form
Author:
Stuart Wray
Title:
The Interface to Pandora's Box
Abstract:
Pandora's box is a video processing peripheral for a workstation or PC. This document describes the model of Pandora's internal workings which is exposed to this host computer. The host sends requests to Pandora, and receives a reply to each one before sending the next request. Pandora can send asynchronous events to the host independently of these request-reply interactions. Pandora and the host can also asynchronously exchange data such as bit-map images and digitised audio.
Reference:
  • Technical Report 89.4
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.89.4.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.89.4.pdf
Author:
Andy Hopper, Alan Jones, Dimitris Lioupis
Title:
Multiple vs Wide Shared Bus Multiprocessors
Abstract:
In this paper, we compare the simulated performance of a family of multiprocessor architectures based on a global shared memory. The processors are connected to the memory through caches that snoop on or more shared buses in a crossbar arrangement. We have simulated a number of configurations in order to assess the relative performance of multiple versus wide bus machines, with varying amounts of prefetch. Four programs, with widely differing characteristics, were run on each configuration. The configurations that gave the best all-round results were multiple narrow buses with 4 words of prefetch
Reference:
  • Proceedings of the 16th Annual International Symposium of Computer Architecture, May 1989, Jerusalem, Israel. pp.300-306.
  • Reprinted in 'Cache and Interconnect Architectures in Multiprocessors', Kluwer Academic Publishers, 1990.
  • Technical Report 89.3
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.89.3.ps.Z
Author:
Ian D. Wilson, David Milway, Andy Hopper
Title:
Experiments in Digital Video for Workstations
Abstract:
This paper describes experimental work in the use of digital video by computer workstations. The approach is essentially practical, since the aims of the research were to gain experience with the handling of video, and to investigate some of the systems aspects of its integration into the workstation environment. The motivation for the work is explained, along with the compromises which were necessary to make the work possible. The hardware and software tools used in the experimentation are described, and the experiences gained from the first trial applications are discussed.
Reference:
  • Technical Report 89.2
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.89.2.ps.Z
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.89.2.pdf
Author:
David J. Greaves, Ian D. Wilson
Title:
Cambridge HSLAN Protocol Review
Abstract:
The Cambridge Fast Ring (CFR) local area network operates at 75 Mbit/s and forms the basis for much of out high-speed protocol research. The CFR mini-packet contains 16 bit source and destination addresses and 256 bits of data. Our current block assembly/disassembly and data-link protocol is UDL (Unison Data Link). This carries higher level protocols such as Unity RPC, local protocols for file transfer, bootstrapping etc and TCP/IP. UDL is also being used experimentally for voice, real-time video and high-speed packet switching. Unison, an Alvey collaborative project, together with Olivetti Research, has developed a CFR/UDL/RPC based protocol suite for wide-area site interconnection. This uses 2 Mbit ISDN links and an architecture for address translation at domain boundaries in the style of ATM. Without this, the sixteen bit, physical layer route identifiers would present a limitation. Protocol performance over local and wide area conditions is presented. Ongoing research is assessing UDL performance under multi-media traffic in areas such as MAC layer bridges, metropolitan area networks and workstation operating systems
Reference:
  • Proceedings of IFIP WG6.1 Workshop, IBM Ruschlikon, May 1989
  • Technical Report 89.1
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.89.1.pdf
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.89.1.ps.Z
Author:
Stuart Wray, J. Fairbairn
Title:
Non-strict Languages - Programming and Implementation
Abstract:
Non-strict evaluation improves the expressive power of functional languages at the expense of an apparent loss of efficiency. In this paper we give examples of this expressive power, taking as an example an interactive functional program and describing the programming techniques depending on non-strict evaluation which improved its design. Implementation methods for non-strict languages have delivered poor performance precisely when such programming techniques have been used. This need not be the case, however, and in the second part of the paper we describe Tim, a method of implementing non-strict languages for which the penalty for using lazy evaluation is very small.
Reference:
  • The Computer Journal, Vol.32, No.2, 1989
  • Technical Report 88.2
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.88.2.ps.Z
Author:
Andy Hopper, Roger M. Needham
Title:
The Cambridge Fast Ring Networking System
Abstract:
Local area networks have developed from slow systems operating at below 1Mbit/s to fast systems at 100Mbit/s or more. We discuss the choices facing a designer as faster speeds for networks are contemplated. The 100Mbit/s Cambridge Fast Ring (CFR) is described. The ring protocol allows one of a number of fixed size slots to be used once or repeatedly. The network design allows sets of rings to be constructed by pushing the bridge function to the lowest hardware level. Low cost and ease of use is normally achieved by design of special chips and we describe a two-chip VLSI implementation. This VLSI hardware forms the basis of a kit-of-parts from which many different network components can be constructed.
Reference:
  • IEEE Transactions on Computers, Vol. 37, No. 10, October 1988
  • Technical Report 88.1
Text:
http://www.cl.cam.ac.uk/Research/DTG/publications/public/files/tr.88.1.pdf
Author:
David Greaves, Andy Hopper
Title:
The Cambridge Backbone Network
Reference:
  • Proceedings of EPOC/LAN-88, Amsterdam, June 1988
Text:
Not currently available in electronic form
Contact:
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