dt-wban: disruption tolerant wireless body area networks · felix büsching | dt-wbans in...

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Felix Büsching, Maximiliano Bottazzi, Wolf-Bastian Pöttner, and Lars [email protected]

DT-WBAN: Disruption Tolerant Wireless Body Area Networks in Healthcare Applications

Felix Büsching | DT-WBANs in Healthcare Applications | 2

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Interplanetary Communication

Radio CommunicationDirect (LOS) not possibleDynamic SystemNever continuous end-to-endDisruption Tolerance needed


Disruption Tolerant Networks (DTN)

Store-Carry-Forward PrincipleHandle delays and disruptionsCarry data through time and

space … and vice versa


Summary: Interplanetary Communication – e.g. Mars Rover “Curiosity”

AimCollect data, transfer it to earthChallengesHarsh environmentHuge delaysNo continuous end-to-end connectionSolutions: Store – Carry – Forward Delay-Tolerant Networking Architecture (RFC 4838)Bundle Protocol Specification (RFC 5050)


DT-WBAN: Disruption Tolerant Wireless Body Area Networks

What is a DTN?How do DTNs work?Motivation & Use Case: Long Term MonitoringMultiple Scenarios Covered Sensors and Data RatesOpportunity for DTNs?! Experiments & Evaluations


Health and Activity Monitoring

Sensors for vital parametersECGBlood pressureAcceleration Temperature, Air Pressure

Long term monitoring – todayData is either Stored on memory card or Transmitted wirelessly to base station


Drawbacks of Local Storage and Wireless Transmission

Local Storage (Body Device)Robust, but Limited capacity Interaction required (exchange cards)No remote configuration possible

Constant Wireless Transmission to SinkComfortable Data available in “realtime” Remote configuration, but

Unstable linksData loss


Summary: Wireless Monitoring in Health Care

AimCollect data, … , transfer it somehow to physicianChallengesHarsh environment (elderly)Huge delaysOften disrupted connectionSolutions Look up!


Opportunity for DTN techniques

Adopt “Store – Carry – Forward” Principle Store – while “on the road”Carry – data home Forward – to base station at home

Implicit SynchronizationNo data get’s lost Seamless handover from “online” to “offline”


Health & Activity MonitoringMultiple SensorsCover huge periodsWithout data loss

Fall DetectionBased on Accelerometer Data Instant alarm by base stationWithin communication range

Additional Benefit: One Sensor Supporting Multiple Scenarios

d


Health & Activity MonitoringNo lost data Implicit Synchronization

Online Fall DetectionNormal functionWithin range of base station

Combined Use Case

d>d



What is a DTN?How do DTNs work?Motivation & Use Case: Long Term MonitoringMultiple Scenarios Covered Sensors and Data RatesOpportunity for DTNs?! Experiments & Evaluations


3 Limiting Factors for DTN Usage

PersonGenerator data rate, 𝐷𝐷𝑔𝑔𝑔𝑔𝑔𝑔 Stored data capacity, 𝑆𝑆𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓

Network Transmission throughput, goodput, 𝐷𝐷𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔

𝑫𝑫𝒈𝒈𝒈𝒈𝒈𝒈 < 𝑫𝑫𝒈𝒈𝒈𝒈𝒈𝒈𝒈𝒈


Generated Data: Expected Data Rates

Typical Sensors

Sensor Dmin Dmax Dtyp Configuration f. Dtyp

Accelerometer 3 Bit/s 124 800 Bit/s 1 500 Bit/s 10 Bit, 50 Hz, 3 axisGyroscope 4 800 Bit/s 38 400 Bit/s 9 600 Bit/s 16 Bit, 200 Hz, 3 axisAir Pressure + Temp. 35 Bit/s 4 392 Bit/s 70 Bit/s 19 Bit + 16 Bit, 2 HzPulse 8 Bit/s 32 Bit/s 16 Bit/s 8 Bit, 2 HzEKG 800 Bit/s 96 000 Bit/s 8 400 Bit/s 14 Bit, 200 Hz, 3 Channel

INGA Wireless Sensor Node Designed for human activity monitoring IEEE 802.15.4 radio interfaceMicro-SD card slot

Accelerometer 3 Bit/s 124 800 Bit/s 1 500 Bit/s 10 Bit, 50 Hz, 3 axis


Benefit: Implicit Synchronization

Storage fills when disruption occurs 𝑆𝑆𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 = 𝑡𝑡𝑔𝑔𝑓𝑓𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 � 𝐷𝐷𝑔𝑔𝑔𝑔𝑔𝑔Synchronization time depends on fill level and data rates

𝑡𝑡𝑑𝑑𝑠𝑠𝑔𝑔𝑠𝑠 = 𝑆𝑆𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝐷𝐷𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔−𝐷𝐷𝑔𝑔𝑔𝑔𝑔𝑔

AssumptionsAccelerometer 3 axis, 50 Hz, 10 Bit 1500 Bit/s IEEE802.15.4 radio DTN implementation on INGA50 KBit/s DTN goodput

tdisrupt tsync Sfill

1 second 0.03 seconds < 200 Byte1 minute 1.86 seconds < 12 KByte1 hour < 2 minutes < 1 MByte1 day < 45 minutes < 17 MByte1 month < 5.2 hours < 500 MByte1 year < 11.5 days < 6 GByte


General Solution

Special solution 𝑆𝑆𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 = 𝑡𝑡𝑔𝑔𝑓𝑓𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 � 𝐷𝐷𝑔𝑔𝑔𝑔𝑔𝑔

𝑡𝑡𝑑𝑑𝑠𝑠𝑔𝑔𝑠𝑠 = 𝑆𝑆𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝐷𝐷𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔−𝐷𝐷𝑔𝑔𝑔𝑔𝑔𝑔

Combine

𝑡𝑡𝑑𝑑𝑠𝑠𝑔𝑔𝑠𝑠 = 𝑑𝑑𝑔𝑔𝑓𝑓𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑�𝐷𝐷𝑔𝑔𝑔𝑔𝑔𝑔𝐷𝐷𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔−𝐷𝐷𝑔𝑔𝑔𝑔𝑔𝑔

Substitute

η = 𝐷𝐷𝑔𝑔𝑔𝑔𝑔𝑔𝐷𝐷𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔

𝑡𝑡𝑑𝑑𝑠𝑠𝑔𝑔𝑠𝑠 = 𝜂𝜂�𝑑𝑑𝑔𝑔𝑓𝑓𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑1−𝜂𝜂

Synchronization time dependsDuration of DisruptionRatio Generated data Throughput


36,36

111,34 400 900 3600 108001440032400

68400

356400

0

5.000

10.000

15.000

20.000

0

50000

100000

150000

200000

250000

300000

350000

400000

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1

Use

d St

orag

e [K

Byte

]

Sync

hron

isat

ion

Tim

e [s

]

η

1 Hour Disruption

Storage

Synchronization after 1 Hour Disruption, different η

Generation: 1.5 KBit/sGoodput: 50 Kbit/sSynced in : < 2 min.Storage: < 1 MB

Generation: 49,5 KBit/sGoodput: 50 Kbit/sSynced in : < 100 days Storage: < 23 MB

Generation: 25 KBit/sGoodput: 50 Kbit/sSynced in : 1 hr.Storage: < 12 MB


Summary: Opportunity for DTNs?!

General requirementGenerated data < throughputLong disruptions require huge amount of storage SD cards can handle this: 128 GB microSD available 20 years of accelerometer data 4 month of 12-channel ECG (500 Hz, 16 bit)

Throughput depends on used sensorWill work for all mentioned using slow 802.15.4 radio

Sensor Dmin Dmax Dtyp Configuration f. Dtyp

Accelerometer 3 Bit/s 124 800 Bit/s 1 500 Bit/s 10 Bit, 50 Hz, 3 axisGyroscope 4 800 Bit/s 38 400 Bit/s 9 600 Bit/s 16 Bit, 200 Hz, 3 axisAir Pressure + Temp. 35 Bit/s 4 392 Bit/s 70 Bit/s 19 Bit + 16 Bit, 2 HzPulse 8 Bit/s 32 Bit/s 16 Bit/s 8 Bit, 2 HzEKG 800 Bit/s 96 000 Bit/s 8 400 Bit/s 14 Bit, 200 Hz, 3 Channel



What is a DTN?How do DTNs work?Motivation & Use Case: Long Term MonitoringMultiple Scenarios Covered Sensors and Data RatesOpportunity for DTNs?!Experiments & Evaluations


System Setup

1 PC 1 Human

Transport Protocols µDTNUDP

• Acceleration• Pressure• Temperature• Channel

characteristics

2 INGA Wireless Sensor Nodes


Lab evaluation of transport protocol

Base Station

Node 2

Node 1

Evaluated System

data sampling source coding bundle

generation MAC framing channel coding modulation

demodulationchannel decodingde-framingbundle

decompositiondata

formattingUART

UART dataparsing

Fall detection

DB access

radio transmission

serial EIA-232 transmission


Lab Evaluation: µDTN

3,63

11,69

44,9544,57

90,76

97,38

66,161,91

50

55

60

65

70

75

80

85

90

95

100

0

5

10

15

20

25

30

35

40

45

50

0 20 40 60 80 100

Dur

chsa

tz [B

undl

e/s]

Dur

chsa

tz [k

Bit/s

]

Bundle Size [Byte]

Throughput [kbit/s]

Bundle/s


µDTN Application Layer Throughput

33,79

26,62

16,38

8,19

4,10

0

5

10

15

20

25

30

35

40

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64

Goo

dput

[kBi

t/s]

Bundle/s

88 Byte / Bundle64 Byte / Bundle32 Byte / Bundle16 Byte / Bundle 8 Byte / Bundle


System Evaluation of Transport Protocol: UDP

51,4649,03

35,65

18,19

9,214,77

0

10

20

30

40

50

60

0 16 32 48 64 80 96 112 128

Goo

dput

[kBi

t/s]

Paket/s

93 Byte / Paket88 Byte / Paket64 Byte / Paket32 Byte / Paket16 Byte / Paket8 Byte / Paket

Receiver Limitation Sender Limitation


System Setup

1 PC 1 Human

• Acceleration• Pressure• Temperature• Channel

Characteristics

2 INGA Wireless Sensor Nodes

Transport Protocols µDTNUDP

Bottleneck!


Synchronization: Channel Characteristics vs. Storage Fill Level


Conclusion

Similar requirements in space and healthcareDemand of robust and reliable communicationHandle delays and disruptions

Use standards, wherever applicable DTN & Bundle Protocol at least “RFC-Status”

Use DTNs … … in long term monitoring applications if throughput > generated data

… to combine online and offline scenarios and achieve implicit synchronization

Thanks for your attention! Felix Büsching, [email protected]

µDTN-Source Code:www.ibr.cs.tu-bs.de/projects/mudtn


Discovery

AgentRouting

Custody

Function CallEvent

Storage

Redundancy Report

modular

Services

Convergence

PHY-Layer

MAC-Layer

static


Disruption and Synchronization Time for Different η ϵ {0.01..0.99}

0,01

0,1

1

10

100

1000

10000

100000

1000000

10000000

100000000

1E+09

1E+10

1 10 100 1000 10000 100000 1000000 10000000 100000000

Sync

hron

osat

ion

Tim

e [s

]

Disruption Time [s]

η = 0.99η = 0.75η = 0.5η = 0.1η = 0.01

1 min 10 min 1 h 8 h 1 d 1 wk 1 mo 1 yr

1 min

1 sec

10 min

1 h

8 h1 d

1 wk

1 mo

1 yr

dt-wban: disruption tolerant wireless body area networks · felix büsching | dt-wbans in...

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