wireless body area networks for ambulatory health monitoring
TRANSCRIPT
Wireless body area networksfor ambulatory health monitoring
with prototype demonstration
August 25, 2006
Chris A. [email protected]
Electrical and Computer Engineering Department University of Alabama in Huntsville
Outline
� Introduction
� Proposed Solution
� WBAN Prototype
� WBAN Wireless Communications
� Embedded Software
� Personal Server Application
� Demonstration
� Conclusions
Motivation
� Healthcare is the Largest Segment of US Economy� $1.8 Trillion in 2004 (15% of GDP)
� $200 Million Informal Care Givers
� $4178 per capita (50% more than the next nearest nation)- US is less than 10th in life expectancy
- US is 26th in infant mortality rates
� Pending Crisis� Retiring Baby Boomers
� Elderly is the Largest Growing Age Group
� 45 million Uninsured
Motivation
� Current Healthcare Systems are Centralized, Focused on Reacting to Illness
� We are in need of Distributed Systems, Focused on Proactive Wellness Management
Healthcare Spending by Category
Drugs
15%
Diagnostic
4%
Treatments,
Hospital Stays,
and Rehabilitation
81%
Tobacco 18.1%
Poor diet and physical inactivity 16.0%
Alcohol consumption 3.5%
Microbial agents 3.1%
Toxic agents 2.3%
Motor vehicles 1.8%
Firearms 1.2%
Causes of Death in the US in 2000
Ambulatory Health Monitoring
� Wearable Systems For Health Monitoring
�Close monitoring of Vital Signs
�Quantitative Feedback
�Computer Assisted Rehabilitation
� Holter Monitors
�Data Recorders ( < 24 hours)
�Post-session Analysis
� Telemedicine Systems
CardioLabs
� Ambulatory Heart Monitoring
� Event-based Recorders
�Loop Recorders (32 min)
�Patient Presses “event”button during episode
� Data Extracted for Post-Analysis
CardioNet
� Mobile Cardiac Outpatient Telemetry (MCOT)
� Wireless Sensor and Wireless Monitor
� Heartbeat by Heartbeat Monitoring
� Arrythmia event detection
Heart Rate Monitors
� Polar Electro, Suunto, Timex, Reebok,…
� Integration into Fitness Equipment
� Real-time Heart rate
� Some “Journal” capabilities
ActiWatch
� Cambridge Neurotechnology
� Actigraphy
� Single Axis Accelerometer
� Clinical Research� Sleep / Wake Patterns
� Sleep Disorders
� Periodic Leg Movement (PLMS)
� Infant Monitoring
Body Media (bodyBugg)
� Multi-modal sensing� Single axis-accelerometer (motion)� (2) Temperature Sensors (heat flux)� Galvanic Skin Response (GSR)
� Upload Data using USB� Calorie Consumption Estimation
� Proprietary Algorithms � Clinically tested
CodeBlue
� Harvard University, Boston University School of Management, and Boston Medical Center, 10Blade (start-up)
� Real-time Triage, Disaster Relief� Pulse Oximeters, ECG, accelerometers
Outline
� Introduction
� Proposed Solution
� WBAN Prototype
� WBAN Wireless Communications
� Embedded Software
� Personal Server Application
� Demonstration
� Conclusions
Proposed Solution
� Wireless Body Area Network (WBAN) for Ambulatory Health Monitoring
� Mobility
� Increased Quality of Life
� Multimodal Physiological Monitoring
� Hierarchical Multi-tier Telemedicine System
System Architecture
User2
nc
InternetInternet
Tier 1:WBAN
A A
AE
Tier 2:PS
Tier 3:MS
WBAN
WWAN(GPRS)
Emergency
Informal
caregiver
Healthcare
provider
UserN
Medical
Server
WWANWLAN
WLAN(Wi-Fi)
…
User2User1 UserN…
ZigBee or
Bluetooth
User1
Outline
� Introduction
� Proposed Solution
� WBAN Prototype
� WBAN Wireless Communications
� Embedded Software
� Personal Server Application
� Demonstration
� Conclusions
WBAN Prototype - Goals
� Implement a Working WBAN� Activity Monitor / Motion Sensor
� ECG Sensor
� Network Coordinator
� Personal Server
� Explore Challenges � Sensor Fusion
� On-Sensor Processing
� Communications
� Power Efficiency
Hardware Architecture - Tmote Sky
TI MSP430 Microcontroller
10
-pin
h
eade
r6-p
inhe
ade
r
UART[0] 2
I2C[0] 2
GPIO 2
ADC[0-3] 2
ADC[6-7] 2
GPIO 2
UserINT
Reset
SPI[0]
3
ST Flash1MB
CC2420 Radio2.4 GHz
IEEE 802.15.4 Compliant
SPI SPI
UART[1]
FT232MBUSB controller
RX/TX
2
CSCS
P4.4P4.2TemperatureSensor
Humidity Sensor
LightSensor
JTAG 8-pinIDC header
7JTAG
JTAG
ADC[5]
ADC[4]
I/O
TI MSP430 Microcontroller
10
-pin
h
eade
r10
-pin
h
eade
r6-p
inhe
ade
r6-p
inhe
ade
r
UART[0] 2
I2C[0] 2
GPIO 2
ADC[0-3] 2
ADC[6-7] 2
GPIO 2
UserINT
Reset
SPI[0]
3
ST Flash1MB
CC2420 Radio2.4 GHz
IEEE 802.15.4 Compliant
SPI SPI
UART[1]
FT232MBUSB controller
RX/TX
FT232MBUSB controller
RX/TX
2
CSCS
P4.4P4.2TemperatureSensor
Humidity Sensor
LightSensor
JTAG 8-pinIDC headerJTAG 8-pinIDC header
7JTAG
JTAG
ADC[5]
ADC[4]
I/O
Hardware Architecture - ISPM
� MSP430F1232 � 32KHz (ACLK) / ~4.6MHz DCO Clock (MCLK,SMCLK)
� 8KB Flash / 256B RAM
� Two (2) ADXL202 Accelerometers
� Two Analog ECG Channels
� 10-pin Tmote Sky Header
ADXL202
Accelerometer
ADXL202
Accelerometer
ECG Signal
Conditioning
TI
MSP430F1232
CC2420
(ZigBee)
Flash
USB Interface
TI
MSP430F149
TelosISPM
ECG electrodes
ADXL202
Accelerometer
ADXL202
Accelerometer
ECG Signal
Conditioning
TI
MSP430F1232
CC2420
(ZigBee)
Flash
USB Interface
TI
MSP430F149
TelosISPM
ECG electrodes
Tmote Sky
x
y
z
ActiS Sensor Nodes
� 3 axis motion detection� Step detection and gait analysis� Activity induced
Energy Estimation (AEE)
Intelligent Signal Processing Modules (ISPM)
Polar Heart Rate Monitor
ISPM for Activity / ECG
Single chip 3-axis Accelerometer
Outline
� Introduction
� Proposed Solution
� WBAN Prototype
� WBAN Wireless Communications
� Embedded Software
� Personal Server Application
� Demonstration
� Conclusions
IEEE 802.15.4 and ZigBee
� IEEE 802.15.4� LR-WPAN Access
� 250 Kbps
� CSMA-CA
� ZigBee� Network
� Application and Application Sublayer
� Security
� Star Network Topology
Power Efficient TDMA
Super Cycle
Beacon ……Slot#3Slot#2Slot#1Beacon Beacon ……Slot#3Slot#2Slot#1Beacon
Listen Tr. Listen
Time50 ms 100 ms 150 ms 1000 ms
� >90% Sensor Power from Radio� Significant Power Savings From Disabling Radio� Timeslots for Communication
� Distributed Events � Concentrated Bursts� Allows Radio to be disabled
� Extended Battery Life / Lower Weight
TDMA Means Low Power
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
superframe
� Deterministic RF timeslots
� Radio can be disabled
� Extend battery life
5 10 15 20 25 30 35 400
5
10
15
20
25
30
35
40
45
50
Channel utilization [% ]
2xAA Alkaline batteries (50gr)
Li-Ion battery (22gr) Li-Ion iPod mini battery (6gr)
Actis Processed ACC Signals
Actis Raw ACC Signals
Battery Life
Days
Typical Message Flow
NC
ACTIS_CFG_STARTMSG
ACK
ACTIS_EVENT_MASKMSGevent = HRV, R Peak
ACTIS_CALMSG
ACK
Calibration Time
ACK
Session Started
eActiS (ECG)Sensor
Personal
Server
ACTIS_EVENT_MSGevent = R Peak
Heartbeat (R peak)Detected
TIME
NC
ACTIS_CFG_STARTMSG
ACK
ACTIS_EVENT_MASKMSGevent = HRV, R Peak
ACTIS_CALMSG
ACK
Calibration Time
ACK
Session Started
eActiS (ECG)Sensor
Personal
Server
ACTIS_EVENT_MSGevent = R Peak
Heartbeat (R peak)Detected
TIME
Outline
� Introduction
� Proposed Solution
� WBAN Prototype
� WBAN Wireless Communications
� Embedded Software
� Personal Server Application
� Demonstration
� Conclusions
Embedded Software - TinyOS
� Lightweight
� Open Source
� Configuration Defined at Compile Time
� nesC (for Networked Embedded Sensors)� Component model
� Task support
� Split-phase Operation (command / event model)
Network Coordinator
� WBAN Access for Personal Server
� Network Channel Management
� Distribute Global Timing
Time Synchronization - Motivation
� TDMA
�Efficient Sharing of Communication Channels
�Timeslot Assignments
�Beacon Prediction (Maximize Radio off)
� Correlating Intra-WBAN events
�Relative timing is important
�Synchronizing start time
Time Synchronization Protocol
� Flooding Time Synchronization Protocol (FTSP)
� MAC Layer Time Stamping
� Skew Compensation with Linear Regression
Propagation
MAC Protocol DataLengthSFDPreamble
SFD � Capture Timer
Timestamp
MAC Protocol DataLengthSFDPreamble TimestampBeacon
Reception
SFD � Capture Timer
TimeSyncM
(FTSP Algorithm)
Process Send
Beacon Transmission
Propagation
MAC Protocol DataLengthSFDPreamble MAC Protocol DataLengthSFDPreamble
SFD � Capture Timer
TimestampTimestamp
MAC Protocol DataLengthSFDPreamble MAC Protocol DataLengthSFDPreamble TimestampTimestampBeacon
Reception
SFD � Capture Timer
TimeSyncM
(FTSP Algorithm)
Process Send
Beacon Transmission
Sensor Nodes
� Collect Physiological Data
� Process Data (Feature Extraction)
� Event Management
� Resource Management
� WBAN Communications
Feature Extraction – Step Detection
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
Acc Signal HP FilterAC Signal
∑
-+ DC Signal
Orientation
Energy
Estimator
Feature Extraction – Activity Estimation
dtaACaACaACAEEt
tzyxt ⋅++= ∫
−δ
222 )()()(
10 15 20 250
2
4
6
8
10x 10
5
10 15 20 2550
100
150
Slowwalking Running
Fastwalking SittingSitting
Sta-nding
AEE
Heart rateTime [min]
Time [min]
Feature Extraction – AEE and Heart Rate
Event Management
105 105.2 105.4 105.6 105.8 106 106.2 106.4 106.6 106.8 1070
1000
2000
105 105.2 105.4 105.6 105.8 106 106.2 106.4 106.6 106.8 1070.5
1
1.5x 10
4
105 105.2 105.4 105.6 105.8 106 106.2 106.4 106.6 106.8 1071000
2000
3000
4000
accX
accY
accZ
Heart Beat
Event Message
with Timestamp
…
Beacon
Message
…
Heart Beat Step Heart Beat Step
Frame i-1
Motion
Sensor
(TS2)
ECG
Sensor
(TS1)
TS1 TS2NC TS3
Frame i
Beacon
Message
TS1 TS2NC TS3
105 105.2 105.4 105.6 105.8 106 106.2 106.4 106.6 106.8 1070
1000
2000
105 105.2 105.4 105.6 105.8 106 106.2 106.4 106.6 106.8 1070.5
1
1.5x 10
4
105 105.2 105.4 105.6 105.8 106 106.2 106.4 106.6 106.8 1071000
2000
3000
4000
accX
accY
accZ
Heart Beat
Event Message
with Timestamp
…
Beacon
Message
…
Heart Beat Step Heart Beat Step
Frame i-1
Motion
Sensor
(TS2)
ECG
Sensor
(TS1)
TS1 TS2NC TS3TS1 TS2NC TS3
Frame i
Beacon
Message
TS1 TS2NC TS3TS1 TS2NC TS3
Resource Management – USART0
USART0
RadioC
olle
ct
Sam
ple
Rx
Ra
dio
Time
50 ms
SPI SPI
100 ms 150 ms
SPI SPI
Co
llect
Sam
ple
Co
llect
Sam
ple
Co
llect
Sam
ple
Co
llect
Sam
ple
Co
llect
Sam
ple
UART
Tx
Ra
dio
Tx
Ra
dio
Tx
Ra
dio
Tx
Ra
dio
Scheduled
Beacon
25ms
ScheduledTimeslot
SPI SPIF
lash
Op
s
Reserved
For Flash
Outline
� Introduction
� Proposed Solution
� WBAN Prototype
� WBAN Wireless Communications
� Embedded Software
� Personal Server Application
� Demonstration
� Conclusions
Personal Health Server
� Sensor Node Identification and Configuration
� Sensor Fusion
� Session File Management
� Graphical User Interface (GUI)
Outline
� Introduction
� Proposed Solution
� WBAN Prototype
� WBAN Wireless Communications
� Embedded Software
� Personal Server Application
� Demonstration
� Conclusions
Outline
� Introduction
� Proposed Solution
� WBAN Prototype
� WBAN Wireless Communications
� Embedded Software
� Personal Server Application
� Demonstration
� Conclusions
Conclusions
� Working WBAN Prototype� Custom-designed ISPM daughter cards� Off-the-shelf wireless sensor platforms� Standard IEEE 802.15.4 communications
� Original Solutions� Health monitoring specific, Power Efficient TDMA Scheme� WBAN communication protocol� On-sensor real-time signal processing
� Promising Technology� Optimal Treatment of Disease Rehabilitation� Low Cost Early Diagnosis� Encourages Wellness Management� Improved Mobility� Low Weight (Increased Compliance)
Future Research
� Validation� Security
� Hardware encryption of wireless communications� Standard security mechanisms from the personal server to the
upper levels of hierarchy
� Signal Processing� Discern category of activity� Improved Step Detection� Improve ECG Analysis
� Upper Tier Development� Integration into Electronic Medical Records (EMR)