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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

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

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  1. 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

  2. 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

  3. 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

  4. Wireless: Mobility Lower bandwidth Interference between users A Wired/Wireless Compromise Wired: • High bandwidth • Dedicated connections • Inconvenient for mobile users

  5. 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

  6. 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

  7. 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

  8. 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...

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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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