Wearable Communication Part 2

Jan Beutel, Thomas von Büren, Holger Junker, Matthias Stäger

Computer Engineering and Networks Lab - Electronics LabMay 3, 2002

Computer EngineeringComputer Engineeringand Networks Laboratoryand Networks Laboratory

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May 3, 2002May 3, 2002

The Wearable Perspective

displaycontext sensor array: camera, light, microphone, GPS

distributed reconfigurable computer

body area network:wireless

communication:WLAN, GSM,

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Wireless Access Systems

Why Wireless: MobilityTarget: IP Connectivity, Compatibility

• Multi Rate/Multi System Mobile Wireless Access– UMTS– GPRS– IEEE 802.11a and IEEE 802.11b– Bluetooth

• Frontends are self-contained subsystems that are operated by commands from a host system

• Status of our work: Each system operational on IpaQ 3870, joint operation will be available in June

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Overlay Access Networking

Area Scenario

Range System Bandwidth Resources

Global 1000 km UMTS Satellite + + +

WAN 20 km GPRS/EDGE/… 473.6 kbit/sec + +

Campus 500 m IEEE 802.11 1 Mbit/sec + +

Building 100 m IEEE 802.b 11 Mbit/sec + + +

Floor 12 m IEEE 802.a 54 Mbit/sec + + + +

Room 10 m Bluetooth 768 kbit/sec + / -

PAN 1 m

Sensor 10 cm RFID/Passive bits/sec - - -

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Low Duty Cycle Concurrent Operation

Host System running Linux OS Communication Frontend B

Communication Frontend A

BAN Communication Frontend CCost/Perf TableCommand Mapping

All Interfaces disabled

Application requesting Data Transfer at Host System

Evaluation of optimal cost/performance

Init of selected Interface; Channel setup

Data Transfer

Shutdown of selected Interface

Update of Cost/Performance Table

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Benefits

• Operation in best performance mode• Scalable from 2.4 kbit/sec to n54 Mbit/sec• Quasi seamless handover• Reduction of the ON/TX duty cycles

– Best energy performance for non power optimized systems– Operation adaptive to the applications– Optimal usage of the available TX channel– Accounting for burstiness of data transfers

• Use of common protocols and applications

Example: TX of 1 Mbyte data with ACK from 10 kbit/sec data source

1. Constant transmitting of data1 sec init 71 mW + 2 sec setup 162 mW + 800 sec 151 mW = 121195 mWsec

2. 768 kbit/sec Bursts10 1 sec init 71 mW + 10 2 sec setup 162 mW + 10 1 sec 151 mW = 5460 mWsec

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Local Ad-Hoc Networking

Why Wireless: Easy Configuration, ScalabilityTarget: Better Utilization of Resources, Flexible Usage

• Very short range (sub meter)

• Medium range (meter)

Status of our work: • Prototype on Bluetooth will be used to test

setups/configurations but will not be optimal in terms of energy consumption, size, setup latency.

• First Motion Sensor Network based on I2C and serial communication in test phase.

Todo: • Research in low power, very short range data

communication

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Topology Issues

• Star topology does not work– Too many frontends– Asymmetric communication demands– Not everything will need central coordination

• Fully distributed does not work– Coordination too difficult

• Idea: Hierarchical Subsystemswith sub-controllers– Linking Units

geographically and logically

– Outsourcing processing tasks

Host System

SubSystem

SubSystem

SubSystem

Leg Motion Sensors Head Up Display

Audio System

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Demo Application 1: Audio Recording

• Wired transmission from microphone to codec• Audio preprocessing with codec logic

• Reduction to 10 kbit/sec• Buffering to allow burst transfers

• Wireless transmit with 10 packets of 64 kbits each every 65 seconds

• Temporary storage of audio data in cache file system on mobile device

• Move to fileserver storage if not accessed on mobile device

wireless link

reconfigurable

logic, inside watch

wired

microphone, attached to watch

main computing

unit, in jacket

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Demo Application 2: Motion Sensor (hj)

• Use multiple motion sensors for context awareness

• Idea: Many sensors reveal „more context“

Architecture required to combine those sensors.

Hierarchical approach makes senseI. Information content of sensors is weighted

differently

II. Reduce overall data load (minimize bandwidth requirements)

III. ...

• Map hierarchical topology to human body

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Current Development: BTnode rev2

• 8-Bit RISC CPU, 1 MIPS/MHz @ 3.6 (or 5.2) MHz

• 128 k Flash, 68 k SRAM• IO, Timer, Analog, UART, I2C

• Idle @3.6 MHz, 3.3V 6 mW

• Active @3.6 MHz, 3.3V 15 mW

• Will be used as subsystem controller

Status:• Testing of the design now• SW Kit/Drivers and Volume

production in June

61 mm

40

mm

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Parameters Influencing Communication

• Please identify the parameters important for you component/application until mid May:

– Radio Range– Frequency– Modulation– Cell Capacity– Raw Bandwidth– Data Types– Power Consumption– Duty Cycle– Setup Times– Latency– Burst Behavior– Quality of Service Guarantees