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N E T W O R K E D S U R F A C E S James Scott and Frank Hoffmann {jws22, fh215}@cam.ac.uk. The Laboratory for Communications Engineering In the Engineering Department at Cambridge University Founded 2 years ago after move from Computer Lab Professor Andy Hopper is the main man

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N e t w o r k e d s u r f a c e s james scott and frank hoffmann jws22 fh215 @cam ac uk l.jpg

N E T W O R K E DS U R F A C E SJames Scott and Frank Hoffmann{jws22, fh215}@cam.ac.uk


Introduction l.jpg

The Laboratory for Communications Engineering

In the Engineering Department at Cambridge University

Founded 2 years ago after move from Computer Lab

Professor Andy Hopper is the main man

James Scott and Frank Hoffmann

2nd year PhD students, both supervised by Andy Hopper

From Computer Science and Electronics backgrounds respectively

Advisors at AT&T Labs: Glenford Mapp and Mike Addlesee

Introduction

James

Frank

Andy

Glenford

Mike


Networked surfaces l.jpg

Provide network connectivity using physical surfaces

Such as desks, floors, etc.

All devices are surface-bound due to gravity: lets make use of this!

No 'plug', no special position/alignment required

Provides near-total mobility for non-wearable devices

Uses precise “topology” of metal pads to achieve this

Supports a range of services

Ethernet-style inter-computer networks

Slower serial busses for peripherals

Power

Other devices

Networked Surfaces


A wired wireless compromise l.jpg

Wireless:

Mobility

Lower bandwidth

Interference between users

A Wired/Wireless Compromise

Wired:

  • High bandwidth

  • Dedicated connections

  • Inconvenient for mobile users


Example app networked desk l.jpg

Get rid of “spaghetti” behind desks

and of need for trunking everywhere

Eliminates possibility of mis-wiring

Novices don’t want to know what a “serial port” is

c.f. Ubiquitous Computing

Power provided as low voltage DC

With current limiting hardware

No danger to humans

Even more important: no danger to circuitry!

Most devices do not use mains-level AC anyway

Example App: Networked Desk


System architecture l.jpg

F U N C T I O N B U S S E S

T I L E C O N T R O L B U S

Handshaking

Object

e.g.

Palm Pilot

Computer

Keyboard

Mobile phone

etc

Surface

Manager

(keeps track

of objects,

allocates

resources,

controls tiles)

Tile

Controller

Object

Controller

Tile

Controller

To other

networks

System Architecture

  • Distributed architecture  scalability


Prototype l.jpg
Prototype

Surface Pads

Power for Tile Controllers

Tile Controller

Function Busses

Object Pads

Tile Control Bus

Object Controller

PCI Interface to PC acting as Surface Manager


Topology l.jpg
Topology

  • Arrangement of metal pads with:

    • Rectangular strips on Surface

    • Circular pads, themselves in a circle, on Object

  • Connects regardless of object location

    • proven mathematically and in computer simulations

  • Minimises number of pads required

    • and hence the amount of controlling circuitry

  • Could be implemented invisibly

    • conducting paints, novel materials...


  • Handshaking l.jpg
    Handshaking

    • “Handshaking” = finding and connecting new objects

      • Distributed on surface-side to tile controllers

  • Object asks for functions from the surface

    • E.g. high speed data bus, low speed data bus, power

    • Different surfaces might have different functions available

  • When connection is finalised,tile and object controllers play no further role

    • And therefore do not have to “understand” the signals sent on the busses


  • Surface busses l.jpg
    Surface Busses

    • All busses must be true multi-drop

      • i.e. not Ethernet, which nowadays is hubbed

  • Low speed devices are catered for with I2C

    • RS-232 data can be packaged easily over I2C, using the handshaking mP

  • High speed bus uses B-LVDS differential modulation

    • Differential scheme better for signal quality in noisy environment

  • Multiple B-LVDS busses are provided

    • this provides more bandwidth, and allows QoS to be supported


  • Data transport l.jpg

    Low bandwidth devices: Present as “virtual” serial ports

    e.g. Palm Pilot, keyboard, modem

    High bandwidth devices: Will have TCP/IP stacks

    But TCP performs badly in presence of disconnection

    It wrongly assumes losses are due to congestion, and backs off

    Could modify TCP to include “Disconnected” state

    Instead, make link layer “smart”, by re-sending packets on behalf of TCP when connections are re-established

    “Kicks” TCP into action, without waiting for exponential timeout

    Saves having to re-implement TCP for every object

    Mobile IP/IPv6 can handle movement between surfaces

    Data Transport


    Conclusions finally l.jpg

    Prototypes are currently at systems integration stage

    Using microprocessors and FPGA’s for quick, flexible hardware implementation

    Preliminary results show object discovery and connection in ~ 300ms, and LVDS bus speeds ~ megabits

    Advantages

    Mobility

    Convenience

    Ubiquity

    Conclusions (Finally)

    • Disadvantages

      • Cost

      • Sensitive to movement once connected

      • Not suitable for power-hungry devices


    Question time faq below l.jpg

    Q: Your diagram/statement on slide X is wrong

    A: Well done for catching the deliberate error

    Q: Will it work?

    A: Yes

    Q: Back that up

    A: Next question please

    Question Time! (FAQ Below)


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