wireless technology and system integration in body area networks

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Wireless Technology and System Integration inBody Area Networks for m-Health Application

Emil JovanovElectrical and Computer Engineering Dept.

University of Alabama in Huntsvillehttp://www.ece.uah.edu/~jovanov

email: [email protected]

RMIT Sep. 2005, Melbourne, Australia 22

Introduction

mHealth– special issue of IEEE Transactions on Information

Technology in Biomedicine, Dec. 2004, M-Health: Beyond Seamless Mobility and Global Wireless Health-Care Connectivity

– Mobile computing– Sensor technology– Communication technologies

WBAN – emerging integration technology– Promising technology for unsupervised, continuous,

ambulatory health monitoring – Challenge: design WBAN for extended real-time

monitoring of physiological data and events.

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WBAN: MotivationGoal: ubiquitous and affordable healthcareConditions: demographic and technology trends– Informal caregivers (1/3 in the U.S.)

Solution: 3-tier ubiquitous monitoring system– Tier 1: Wireless Body Area Network (WBAN)– Tier 2: Personal Server– Tier 3: Healthcare Provider Servers/Medical Servers

Opportunities: – Ambulatory health monitoring– Computer-assisted rehabilitation– Augmented reality systems

Long-term benefits:– Promote healthy lifestyle– Seamless integration of data into personal medical

records and research databases – Knowledge discovery through data mining


WBAN – design goals

minimization of weight and size of sensors,user’s acceptance,portability,unobtrusiveness,ubiquitous connectivity,reliability, and seamless system integration.

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Wireless technologies

WLAN and WPAN technologiesBluetooth– Widespread, cell phones/PDAs– 720 kbps– Relatively high power consumption, protocol stack

complexity ZigBee– Emerging standard– Very low power– 250 kbps

UWB– High bandwidth

Alternative solutions– MEMS resonators (100 µW)


Ubiquitous Health Monitoring

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InternetInternet

S S S S

MS

HS

PS

Sn

NCWBAN

WLAN

S S S SSn

WBAN

InternetInternet

MS

HSNC

Sn

InternetInternet

S S S S

MS

PS

WBAN

WAN

NC

WBAN Configurations


3-tier Hierarchical Organization

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Hierarchical organization

Internet connectivity

WAN communication

Peripherals, timers, etc.

Other

~ 100 W~ 100 mW1-10mW proc.~50mW comm.

Power consumption

~ TB~ 1 GB10-100 KB,1 MB (flash)

Secondarymemory

~ GB~ 50 MB1-10 KBRAM

~ GIPS~ 100 MIPS1-10 MIPSProcessingPower

3. Medical server

2. Personal server

1. SensorTier


Wireless Body Area Networks at UAH

2000: Wireless Intelligent Sensors (WISE)

2002: Distributed Wireless System for Stress Monitoring

2004: ActiS – Activity Sensor– Standard sensor platforms and

communication protocols“A wireless body area network of intelligent motion sensors for computer assisted physical rehabilitation,” Journal of NeuroEngineering and Rehabilitation, http://www.jneuroengrehab.com/content/2/1/6

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ActiS: Activity Sensor


ActiS: Activity Sensor

ADXL202Accelerometer

ADXL202Accelerometer

ECG SignalConditioning

TI MSP430F1232

CC2420(ZigBee)

Flash

USB Interface

TI MSP430F149

TelosISPM

ECG electrodes

ActiS asMotion Sensor

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Telos Wireless Platform

8MHz Texas Instruments 16-bit MSP430F1611 microcontroller – 10KB RAM, 48KB Flash

Chipcon 2420, IEEE 802.15.4 compliant wireless transceiver – Hardware link layer encryption and

authentication– 250kbps, 2.4GHz– programmable output power

Onboard antenna– Range: 50 m / 125 m

Integrated – humidity, temperature, and light sensors– ADC, DAC, DMA,Supply Voltage Supervisor

TinyOS support


Intelligent Signal Processing Module ISPM

4MHz Texas Instruments 16-bit MSP430F1232 microcontroller (256B RAM, 8KB ROM)Multiple Dual Axis Analog Devices ADXL202 AccelerometersOn-board bioamplifier (ECG, EMG) Texas Instruments INA321 Instrumentation Amp. Force resistor signal conditioning circuit– Foot switch

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ZigBee network controller

Wireless gatewayARM7 processor~60MIPS proc. power64KB RAMCompact Flash interfaceZigBee wireless interface


ActiS: Signal Processing

46 46.5 47 47.5 48 48.5 49 49.5 50 50.5 51

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Accelerometer based step recognition

Time[s]

Vy[m/s]Alpha[rad]accY[g]StepFoot switch

Step detected

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Actis System Performance

1 mW

256B

1 MIPS

1. Signal Processing Module

~ 300 mW60 mW3mW Power consumption

~ 64MB64 KB10 KBRAM

~ 100 MIPS60 MIPS1 MIPSProcessingPower

4. Personal Server

3. Wireless Gateway

2. SensorPlatform

Tier


System Design IssuesExtremely low-power, low-weight, and small sizeNon-invasive and unobtrusive operationReliable transmission using retransmissionsTime-stamping for collective processing and out of order message processingInteroperability requires standardization– Seamless connectivity– Application specific standards for wireless

communications, messaging, and system supportSeamless customization, configuration, and integrationSensor placement and mounting– Sensor commodization

Security and Privacy – Communication and data storage

Effective user interfaces

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Time Synchronization

Necessary for collective processing, data logging, power-efficient operation, etc.Problem:– High precision synchronization with low

frequency clocks • 32 KHz on Telos

FTSP FloodingTime synchronization protocols– Telos specific implementation at UAH– Implemented precision ~2 µS with 32KHz

crystal!


Mechanism for Time Synchronization

Propagation

MAC Protocol DataLengthSFDPreamble TimestampData received

over RF

SFD Capture Timer

Synchronize local time(TinyOS)

NetworkCoordinator

Data transmitted over RF

MAC Protocol DataLengthSFDPreamble

SFD Capture Timer

Timestamp

Process Send

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Power Consumption

User’s convenience– Battery life– Size and weight of

batteriesBattery Life– Battery Capacity [mAh] – BL = BC / Iave– For simple time keeping

and minimal processing average power is ~2.1µA, standard 750 mAh batteries will allow battery life:

– BL = 750 mAh / 2.1 µA ≈ 44 years !!!

Introducing:Apple Computers


Power efficient communication

Wireless communication requires ~ 10 times more power than processing– Turn-off radio whenever you can

Time slots– Time slot scheduling– Allow time slots for new sensors to join the

clubDesign issues:– Battery life– Latency– Number of sensors

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Power efficient wireless communication - implementation

Super cycle time in this example is 1 sec. Sensors listens at the beginning of each cycle for 50ms, and transmits its own messages (2 in this example) in predefined time slot.

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50

5

10

15

20

25

Time [sec]

I [m

A]

0.65 0.7 0.75 0.8 0.85 0.90

5

10

15

20

Time [sec]

I [m

A]

Listen Transmit

Idle

Power supply current on sensor


Personal Server program

Implemented on PC/PDAControls the network of wireless sensorsCollects data from sensors Communicates with servers on higher levels of hierarchy whenever the connection is availableProvides feedback and alerts to the userStores user’s inputs

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ActiS Monitor – User’s Info


ActiS Monitor – Network health and Statistics

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ActiS Monitor – Network Control


ActiS Monitor – Symptoms

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ActiS Monitor – Alerts


Actis Demo

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ActiS Monitor – Signals and Graphs


Software Organization

ISPM Software– Physiological sensor interface– Preprocessing of signal data– Resource constrained, no operating system

Telos Software– Developed in component framework of TinyOS– Significant signal processing – Defines Sampling Frequency– Server WBAN Communication

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Wireless Integration

Raw data

Events

MS

Internet Gateway

PS

Sn

NC

WBAN

WLAN/WAN

S S S

InternetInternet

Records

Record collections

Database


101001…..

Raw Data

Data is written to

permanent storage

File

1Fi

le 2

File

3…

Update Queue

Destination

Connection Made

Record Update Mechanism

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EMR

…Update

Session 1Update

Session 2

Contiguous Data Blocks

System organization - Sessions


Privacy and Security

Hardware encryption of wireless communicationsStandard security mechanisms from the personal server to the upper levels of hierarchyEMBC05 paper: “Interoperability and Security in Wireless Body Area Network (WBAN) Infrastructures”

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ConclusionsPromising technology for – Ambulatory monitoring– Early detection of abnormal conditions– Supervised rehabilitation

Advantages– Increased confidence and better quality of life– Promotes healthy lifestyle / health awareness– Data mining of huge research databases

• Effects of drug therapies and rehabilitation procedures

Need for standards for wireless communications, messaging, and system support


Acknowledgments

Aleksandar Milenkovic, Chris Otto, Corey Sanders, John Gober, Reggie McMurtrey, University of Alabama in HuntsvillePiet de Groen, Bruce Johnson, Mayo ClinicSteve Warren, Kansas State University

wireless technology and system integration in body area networks

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