1. Considerations on the MAC issue of BAN
January 2007
doc.: IEEE
September/2007
Considerations on the MAC issue of BAN
Bin Zhen, Huan-bang Li and Ryuji Kohno
National Institute of Information and Communications Technology (NICT)
Zhen, Li and Kohno
Carlos Cordeiro, Philips

2. Outline IEEE 1073 requirements Comparison of medical SN and general SN
January 2007
doc.: IEEE
September/2007
Outline
IEEE 1073 requirements
Comparison of medical SN and general SN
Design principles of MAC
Conclusion
Zhen, Li and Kohno
Carlos Cordeiro, Philips

3. IEEE 1073 over MBAN HL7 Application presentation Session Transport
January 2007
doc.: IEEE
September/2007
IEEE 1073 over MBAN
HL7
ISO model
Application
Medical device data language
P1073.1
presentation
Device application profile
P x
Session
Transport
Transport profile
Network
P x
Data link
MBAN
(PHY/MAC)
Physical
P x
Zhen, Li and Kohno
Carlos Cordeiro, Philips

4. IEEE 1073 RF wireless group Guidelines chapters
January 2007
doc.: IEEE
September/2007
IEEE 1073 RF wireless group
Guidelines chapters
Wireless medical device use case
Technology overview, analysis and constraints
Device data characterization
QoS requirements
Wireless service model
Risk management and security
Interference and coexistence
Conformance and interoperability
Medical device data classifications
Alarms
Waves (real-time and near RT)
Parameters (RT and non-RT)
Charting (parameters and wave snippet)
Control and status
History and archival/log
Medical device QoS parameters
Reliability
Latency
Priority
Bandwidth
Data rate
Continuous vs. intermittent/burst
Zhen, Li and Kohno
Carlos Cordeiro, Philips

5. IEEE 1073 QoS parameters Data type Bandwidth Priority Reliability
January 2007
doc.: IEEE
September/2007
IEEE 1073 QoS parameters
Data type
Bandwidth
Priority
Reliability
Latency
Alarm/alert
Low (64 bytes), intermittent
highest
High 3s
RT-waves
High ( bps/channel), continuous
RT or CS= 3s
RT parameters
Low-medium, continuous
Non-RT parameters
Low (20 bytes), intermittent
Non-RT events
Low-medium, intermittent
Medium
PoC: 3s, CS: 3s
Controls
Low, intermittent
high
PoC: 3s, CS: 5s
History/ archive
High, burst, intermittent
Low
Medium high
push: 3s, pull: 5s
Web browsing
3-5s
Zhen, Li and Kohno
Carlos Cordeiro, Philips

6. Analysis of 1073 QoS requirements
January 2007
doc.: IEEE
September/2007
Analysis of 1073 QoS requirements
Priority and real time
Alarm/alert is the top priority
We do not have history/archive traffic in BAN
Questions
Why control is low priority?
Is the 3 seconds latency too long?
The listed QoS parameters are not suitable for artificial sensing, i.e. cochlear, retina.
Zhen, Li and Kohno
Carlos Cordeiro, Philips

7. Medical sensor networks (for BAN)
January 2007
doc.: IEEE
September/2007
Comparisons
Medical sensor networks (for BAN)
General WSN
Common features
Limited resources: battery, computation, memory, energy efficiency (reception consumes more than transmission)
Diversity coexistence environment
Dynamic network scale, plug-and-play, low/modest data rate, heterogeneous devices ability, dense distribution
Medical sensor/
actuator
Single function device (for medical reasons)
Multi-function device
Lightweight sensors (wearable and implant, space and power limited)
Versatile (underwater) sensors
Fast relative movement in small range
Rare or slow movement in large range
device lifetime,
days, <10 years
network lifetime and device lifetime
Months, <10 years
Safe (low electromagnetic expose) and quality first (lifetime for implant sensor)
Cost sensitive
Dependability
Reliability (first), guaranteed QoS
expected QoS, redundancy-based reliability
Strongly security, (except emergency)
Required security
Zhen, Li and Kohno
Carlos Cordeiro, Philips

8. Medical sensor networks (for BAN)
January 2007
doc.: IEEE
September/2007
Comparisons (cont.)
Medical sensor networks (for BAN)
General WSN
Networking
Small scale star network (<1e3 nodes)
Large scale hierarchical network (<1e6 nodes)
no redundancy in device (limited body/interest/effect area)
redundant distribution
Deterministic node distribution
Random node distribution
Traffic
Periodical RT (dominant), burst (priority)
Burst (dominant), periodical
Unidirectional traffic
Unidirectional and bidirectional traffic
Low/modest duty cycle
Low duty cycle (typical)
M:1 communication
M:1 or point-point communication
Frequency
Specific medical channel (clean, narrow band, licensed by rule)
ISM band for part of applications
ISM band (narrow/wide band, noise)
Channel
Body surface or through body
Dynamic fading channel (body movement)
Obstacle is unknown
Zhen, Li and Kohno
Carlos Cordeiro, Philips

9. Star network topology Wearable BAN Bedside BAN January 2007
doc.: IEEE
September/2007
Star network topology
headset
Blood pressure, temperature, ECG
Pacemaker
Capsule endoscope
Drug deliver
Access point
Access point
Wearable BAN
Bedside BAN
Zhen, Li and Kohno
Carlos Cordeiro, Philips

10. Star network topology (cont.)
January 2007
doc.: IEEE
September/2007
Star network topology (cont.)
Single hop network
Medical sensors and actuators do not forward message
Long distance communication is pushed to coordinator
Medical sensor/actuator
No redundancy in network distribution
Deterministic network position
Zhen, Li and Kohno
Carlos Cordeiro, Philips

11. Medical sensor traffic
January 2007
doc.: IEEE
September/2007
Medical sensor traffic
Periodical traffic
Waveform
ECG, EEG, EMG, bio-sound, aspiration
Image
capsule endoscope, neur-stimulation
Data
Glucose, body temperature, pulse rate, blood lactic acid, expiration, blood pressure, SpO2, joint angle (in ICU, ward and operation room)
On-demand traffic
Drip infusion, insulin pump
Glucose, body temperature, pulse rate, blood lactic acid, expiration, blood pressure, SpO2, joint angle
for diagnosis
Event-based traffic (alarm)
Fall, vital emergency
Zhen, Li and Kohno
Carlos Cordeiro, Philips

12. Medical sensor traffic (cont.)
January 2007
doc.: IEEE
September/2007
Medical sensor traffic (cont.)
Dominant traffics are periodical data
Unidirectional data stream
Sensing data from medical sensor to coordinator (uplink direction)
Command from coordinator to medical actuator (downlink direction)
Single function device
Zhen, Li and Kohno
Carlos Cordeiro, Philips

13. Requirements from IEEE 1073
January 2007
doc.: IEEE
September/2007
Requirements from IEEE 1073
Scalability
Connection sensing
blacklist
Interrupt from medical sensor
to allow service request prior to next schedule polling time
Flow control
Usually a function in application layer
Zhen, Li and Kohno
Carlos Cordeiro, Philips

14. 15.4’s drawback for medical applications
January 2007
doc.: IEEE
September/2007
15.4’s drawback for medical applications
Noisy channel environment
No connection sensing
Distributed MAC
No QoS guarantee
Not reliable enough for “life critical data”
No interrupt support in beacon-enabled mode
Zhen, Li and Kohno
Carlos Cordeiro, Philips

15. Design targets of MBAN Dependable and durable network Constraints
January 2007
doc.: IEEE
September/2007
Design targets of MBAN
Dependable and durable network
Reliability and QoS
Lifetime
Security and safety
Scalability
Constraints
Limited resources, i.e. memory, computation and battery
Noisy and fading channel
Coexistence
High density of piconets
Zhen, Li and Kohno
Carlos Cordeiro, Philips

16. January 2007
doc.: IEEE
September/2007
MAC framework of MBAN
Unified MAC mechanism for wearable BAN and implant BAN
Traffic classification for QoS
Alarm/life critical
Real time
Best effort
Unidirectional data (not forwarded data)
Sleep mode to save power
Blacklist channel
Zhen, Li and Kohno
Carlos Cordeiro, Philips

17. New channel features Not very clear channel model until now
January 2007
doc.: IEEE
September/2007
New channel features
Not very clear channel model until now
Implant channel
Strong attenuation
Wearable channel
Channel scan mechanism
Simple energy detection might be not enough
Who and how to do it?
Zhen, Li and Kohno
Carlos Cordeiro, Philips

18. Traffic classification
January 2007
doc.: IEEE
September/2007
Traffic classification
Every sensing data must be classified first before transmit
Even data from the same source can be classified into different categories.
When body temperature is over 40ºC, it is life critical. Otherwise, it is non-life critical
Traffic classification in e is statistic
Sensing data
MAC mapping
Alarm
Traffic classifier
transmit
Real time
Best effort
Zhen, Li and Kohno
Carlos Cordeiro, Philips

19. Mapping traffic priority to MAC
January 2007
doc.: IEEE
September/2007
Mapping traffic priority to MAC
ALOHA
Higher transmission probability for priority traffic
CSMA
Fewer backoff step for priority traffic
TDMA
More allocated time slots for priority traffic (in case of error)
FDMA and CDMA
seems not to be suitable for BAN
Zhen, Li and Kohno
Carlos Cordeiro, Philips

20. January 2007
doc.: IEEE
September/2007
Flow control
Typically it is pushed to application layer to simplify PHY/MAC design
An MAC interface
Radio resource definition
Zhen, Li and Kohno
Carlos Cordeiro, Philips

21. Conclusion No redundancy in medical SN Alarm traffic (top priority)
January 2007
doc.: IEEE
September/2007
Conclusion
No redundancy in medical SN
Vital signals are typically position dependent
Limited available area
Alarm traffic (top priority)
Random and priority access
Security for alarm transmission
Medical traffic pattern
Periodical data, on-demand data, and event-driven data
Dominant traffics are periodical
Unidirectional traffic (no forwarding traffic)
New MAC features
High reliability for any sensor
Unified mechanism for wearable and implantable networks
Flow control
Zhen, Li and Kohno
Carlos Cordeiro, Philips