Wireless Technology and System Integration in Body Area Networks for m-health Application

Transcription

1 Wireless Technology and System Integration in Body Area Networks for m-health Application Emil Jovanov Electrical and Computer Engineering Dept. University of Alabama in Huntsville 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. RMIT Sep. 2005, Melbourne, Australia 2

2 WBAN: Motivation Goal: ubiquitous and affordable healthcare Conditions: 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 RMIT Sep. 2005, Melbourne, Australia 3 WBAN design goals minimization of weight and size of sensors, user s acceptance, portability, unobtrusiveness, ubiquitous connectivity, reliability, and seamless system integration. RMIT Sep. 2005, Melbourne, Australia 4

3 Wireless technologies WLAN and WPAN technologies Bluetooth 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) RMIT Sep. 2005, Melbourne, Australia 5 Ubiquitous Health Monitoring RMIT Sep. 2005, Melbourne, Australia 6

4 WBAN Configurations MS MS MS Internet Internet Internet HS WLAN WAN HS NC PS NC WBAN PS NC WBAN WBAN Sn S S S S Sn S S S S Sn S S S S RMIT Sep. 2005, Melbourne, Australia 7 3-tier Hierarchical Organization RMIT Sep. 2005, Melbourne, Australia 8

5 Hierarchical organization Tier 1. Sensor 2. Personal server 3. Medical server Processing Power 1-10 MIPS ~ 100 MIPS ~ GIPS RAM 1-10 KB ~ 50 MB ~ GB Secondary memory KB, 1 MB (flash) ~ 1 GB ~ TB Power consumption 1-10mW proc. ~50mW comm. ~ 100 mw ~ 100 W Other Peripherals, timers, etc. WAN communication Internet connectivity RMIT Sep. 2005, Melbourne, Australia 9 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, RMIT Sep. 2005, Melbourne, Australia 10

6 ActiS: Activity Sensor RMIT Sep. 2005, Melbourne, Australia 11 ActiS: Activity Sensor ISPM Telos ADXL202 Accelerometer ADXL202 Accelerometer TI MSP430F1232 TI MSP430F149 CC2420 (ZigBee) Flash ECG Signal Conditioning USB Interface ECG electrodes ActiS as Motion Sensor RMIT Sep. 2005, Melbourne, Australia 12

7 Telos Wireless Platform 8MHz Texas Instruments 16-bit MSP430F1611 microcontroller 10KB RAM, 48KB Flash Chipcon 2420, IEEE 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 RMIT Sep. 2005, Melbourne, Australia 13 Intelligent Signal Processing Module ISPM 4MHz Texas Instruments 16-bit MSP430F1232 microcontroller (256B RAM, 8KB ROM) Multiple Dual Axis Analog Devices ADXL202 Accelerometers On-board bioamplifier (ECG, EMG) Texas Instruments INA321 Instrumentation Amp. Force resistor signal conditioning circuit Foot switch RMIT Sep. 2005, Melbourne, Australia 14

8 ZigBee network controller Wireless gateway ARM7 processor ~60MIPS proc. power 64KB RAM Compact Flash interface ZigBee wireless interface RMIT Sep. 2005, Melbourne, Australia 15 ActiS: Signal Processing Accelerometer based step recognition Vy[m/s] Alpha[rad] accy[g] Step Foot switch Step detected Time[s] RMIT Sep. 2005, Melbourne, Australia

9 Actis System Performance Tier Processing Power 1. Signal Processing Module 1 MIPS 2. Sensor Platform 1 MIPS 3. Wireless Gateway 60 MIPS 4. Personal Server ~ 100 MIPS RAM 256B 10 KB 64 KB ~ 64MB Power consumption 1 mw 3mW 60 mw ~ 300 mw RMIT Sep. 2005, Melbourne, Australia 17 System Design Issues Extremely low-power, low-weight, and small size Non-invasive and unobtrusive operation Reliable transmission using retransmissions Time-stamping for collective processing and out of order message processing Interoperability requires standardization Seamless connectivity Application specific standards for wireless communications, messaging, and system support Seamless customization, configuration, and integration Sensor placement and mounting Sensor commodization Security and Privacy Communication and data storage Effective user interfaces RMIT Sep. 2005, Melbourne, Australia 18

10 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! RMIT Sep. 2005, Melbourne, Australia 19 Mechanism for Time Synchronization Data transmitted over RF SFD Capture Timer Process Send Preamble SFD Length MAC Protocol Data Timestamp Propagation Data received over RF Preamble SFD Length MAC Protocol Data Timestamp SFD Capture Timer Synchronize local time (TinyOS) Network Coordinator RMIT Sep. 2005, Melbourne, Australia 20

11 Power Consumption User s convenience Battery life Size and weight of batteries Battery Life Battery Capacity [mah] BL = BC / I ave 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 RMIT Sep. 2005, Melbourne, Australia 21 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 club Design issues: Battery life Latency Number of sensors RMIT Sep. 2005, Melbourne, Australia 22

12 Power efficient wireless communication - implementation Power supply current on sensor 20 Listen Transmit 15 I [ma] 10 5 Idle I [ma] Time [sec] 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 Time [sec] RMIT Sep. 2005, Melbourne, Australia 23 Personal Server program Implemented on PC/PDA Controls the network of wireless sensors Collects data from sensors Communicates with servers on higher levels of hierarchy whenever the connection is available Provides feedback and alerts to the user Stores user s inputs RMIT Sep. 2005, Melbourne, Australia 24

13 ActiS Monitor User s Info RMIT Sep. 2005, Melbourne, Australia 25 ActiS Monitor Network health and Statistics RMIT Sep. 2005, Melbourne, Australia 26

14 ActiS Monitor Network Control RMIT Sep. 2005, Melbourne, Australia 27 ActiS Monitor Symptoms RMIT Sep. 2005, Melbourne, Australia 28

15 ActiS Monitor Alerts RMIT Sep. 2005, Melbourne, Australia 29 Actis Demo RMIT Sep. 2005, Melbourne, Australia 30

16 ActiS Monitor Signals and Graphs RMIT Sep. 2005, Melbourne, Australia 31 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 RMIT Sep. 2005, Melbourne, Australia 32

17 Wireless Integration MS Database Internet Internet Gateway WLAN/ WAN PS NC Record collections Records WBAN Events Sn S S S Raw data RMIT Sep. 2005, Melbourne, Australia 33 Record Update Mechanism Raw Data File 3 File 2 File 1 Connection Made Data is written to permanent storage Update Queue Destination RMIT Sep. 2005, Melbourne, Australia 34

18 System organization - Sessions EMR Update Session 1 Update Session 2 Contiguous Data Blocks RMIT Sep. 2005, Melbourne, Australia 35 Privacy and Security Hardware encryption of wireless communications Standard security mechanisms from the personal server to the upper levels of hierarchy EMBC05 paper: Interoperability and Security in Wireless Body Area Network (WBAN) Infrastructures RMIT Sep. 2005, Melbourne, Australia 36

19 Conclusions Promising 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 RMIT Sep. 2005, Melbourne, Australia 37 Acknowledgments Aleksandar Milenkovic, Chris Otto, Corey Sanders, John Gober, Reggie McMurtrey, University of Alabama in Huntsville Piet de Groen, Bruce Johnson, Mayo Clinic Steve Warren, Kansas State University RMIT Sep. 2005, Melbourne, Australia 38