Research Trends in Wireless Body Area Networks: From On ......Wireless localization for healthcare...

04/04/2014

Research Trends in Wireless Body Area Networks: From On-Body to Body -to-Body

Cooperation

Mickael MAMAN, Benoit DENIS, Raffaele D’ERRICO,

CEA-LETI, Grenoble, France

© CEA. All rights reserved

Research Trends in Wireless Body Area Networks: From On-Body to Body-to-Body Cooperation | 2

� The IEEE 802.15.6 (TG6) task group has been established to

provide an international standard for BANs.

� Design of both contention-based (e.g. CSMA/CA, Aloha, etc.) and time division-

based (e.g. TDMA) MAC protocols, and Physical layers (Narrowband, UWB and

Human Body Communications)

� The target functional requirements of this BANs standard are summarized:

� Intra/Inter BANs coexistence issues have not been solved out yet.

Context



BAN applications (1)

� Wireless localization for healthcare

� Future health management systems need precise/reliable localization

and long-term tracking in daily-life environments

� More ergonomic, less intrusive and reactive monitoring, prevention and

rescue systems (e.g. Physical rehab at home, assisted mobility, finding

people)

Doctors control progresses in your physical rehab

remotely

Grand-Pa’s felt down in the kitchen

Christine has travelled 10.6kms this week by foot



BAN applications (2)

� Wireless localization for Wellness, Fitness and Personal sports

� Monitor & capture in real-time and/or analyse offline the user’s mobility

and gesture

� Optimize and secure the user’s performance

� Enable self-learning of the good practice/gesture with quantified

feedback (e.g. martial arts, skating);

http://spoonphone.com/en/

Training with location-enabled smartphones as “personal coaches ”

Assessing (individual and collective) performance v s. physical risk



Challenges� BANs extension to cooperative Body-to Body Networks



Challenges



BAN channels

� 4 BANs communication categories :

� In-Body

• In-Body to In-Body

• In-Body to On-Body

• In-Body to Off-Body

� On-Body to On-Body

� On-Body to Off-Body

� Body-to-Body



In-Body channel

� At least one node is located inside the human body and it should

communicate with one or more devices either in, on or off the

body.



On-Body Channel

� All the nodes placed on the human body� Directly stitched on the skin, � Integrated into textile and

worn by the subject, � Packed into different

wearable/portable objects.

� Dynamic Channel� Channel gain

(by scenario)� Long term fading

(shadowing)� Short term fading

(multi-path)



(On-to-) Off-Body channel

� At least one of the devices placed

outside the human body, located

everywhere in a general area

playing the role of a gateway or

an access point. External Gateway

RX

TX

Rx1:Left Hip

Rx2:Heart

Rx3:Right Ear

Height: 1.2m

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-90

-85

-80

-75

-70

-65

-60

-55

-50

-45

-40

Time [s]

Cha

nnel

Gai

n [d

B]

Anechoic Chamber - Top Loaded Monopole - Dynamic LOS - Rx Ear

Walk 1Walk 2Walk 3Walk 4Walk 5Fit Ear

LOS NLOS

0 45 90 135 180 225 270 315 360-90

-85

-80

-75

-70

-65

-60

-55

-50

-45

-40

Angle [°]

Cha

nnel

Gai

n [d

B]

Shadowing Effect - Anechoic Chamber - Top Loaded Monopole - Rx Heart

Dynamic Circular Data, Rx HeartShadowing Effect, Rx HeartStatic Circular Data, Rx HeartMean Value, Rx Heart

� Dynamic Channel� Channel gain

(distance dependent)� Shadowing

(body masking effect)� Short term fading

(multi-path)



Body-to-Body channel

� At least two nodes are

placed on different subjects

0 45 90 135 180 225 270 315 360-110

-100

-90

-80

-70

-60

-50

-40

-30

α [°]P

(dr, α

) [dB

]

G0(d

r,α) for d

r=1m

G0(d

r,α) for d

r=3m

G0(d

r,α) for d

r=5m

G0(d

r,α) for d

r=7m

P(dr,α) for d

r=1m

P(dr,α) for d

r=3m

P(dr,α) for d

r=5m

P(dr,α) for d

r=7m

SubBSubA

α = [0° ÷ 360°]

1 2 3 4 5 6 7 8-110

-100

-90

-80

-70

-60

-50

-40

d [m]

P(d

, α=0

°) [d

B]

Walk 1Walk 2Walk 3

G0(d,α=0°)|

dB

SubBSubAd

SubASubA SubBSubBSubA SubB

� Dynamic Channel

� Channel gain

(distance dependent

according to the scenario)

� Shadowing

(multiple body

masking effect)

� Short term fading

(multi-path)



Challenges



� MAC specification requires specific BAN investigations and optimizations due to the closeness of the human body and its environment.

� BANs peculiar channel characteristics:

� Propagation losses not directly proportional to Tx-Rx distance

� Different shadowing conditions due to human body motion

� The star topology is unstable for BANs

� To face to broken/weak links existence, 3 approaches are possible:

� Increase transmission power

� Retransmit when the channel is better (to prevent fast fading)

� Take advantage of other nodes and asking them for acting as relays (to prevent shadowing effect) Cooperation

Robust On-Body communications (1)



75%

80%

85%

90%

95%

100%

Taux

de

succ

ès

Classique (Direct) Relayage (Double Hop) Combinaison (Combined)

Pourcentage de paquets de données correctement reçus avec le MotionPod

Direct Double Hop Combined

Suc

cess

Rat

e

� Retransmission No systematic PER improvement

� Spatial diversity through cooperation Enhanced PER & power performances

� Benefits of relaying functionalities and protocols implemented on complete platforms.

� Relaying mechanisms Same performance with a lower transmission power.

Save energy & less pollute the other surrounding communications (BAN Coexistence)

Robust On-Body communications (2)



� An adaptive and low-power communication protocols for Body Area Networks� Unique : a common protocol architecture for several applications

� Generic as much as possible.

� Flexible (Network size, topology, communication…)

� Adapted to Body Area Networks

� Guaranteeing good QoS (reliability, latency,…)

• Several MACs supporting different traffics.

• Dynamic and Automatic relaying mechanisms mitigating the

shadowing impact on PER

� Optimized low power consumption for a long autonomy

� Providing network functionalities (association, self-organizing, data

collection…)

� Transparent for the application thanks to several profiles

• Autonomously and dynamically adaptive

• Trade off between QoS and energy consumption

• Adapted to several applications

• Adapted to heterogeneous traffics

0 1

4

3

2

Innovating functionalities design



Ex. of implementation & prototyping (1)� A BAN of heterogeneous modules

� The motional (e.g. 3D accelerometer, 3D magnetometer and 3D gyrometer)

and emotional (e.g. microphone) sensors

� 868 MHz Radio SoC

� Adaptive and low-power communication protocol

� Several application profiles for:

• Robotics based rehabilitation

• Daily life physical activity monitoring

• Gaming

Wear-A-BAN project node with textile antenna Microphone node

Central node

Coordinator



� Protocols extension to fit with more application requirements.

� 2 different MAC protocols:

• Low Power Listening-based (LPL), used for low energy consuming, aperiodic

and loose traffic

• Superframe-based MAC, useful for periodic traffic and streaming

� Management of 3 different PHY Layers:

• 802.15.4-like PHY (MSK with spreading) with a bit rate of 250 kbit/s

• Bluetooth-LE PHY (GMSK) with a bit rate of 1 Mbit/s.

• Proprietary PHY (MSK without spreading) with a bit rate of 2 Mbit/s

� Definition of new profiles

� Dynamic selection of the best solution depending on the application

requirements

� Trade off between the QoS and Energy consumption in real time

depending on the environment conditions and users activities and needs

Ex. of implementation & prototyping (2)



Application

Low Power Listening MAC

WiserBAN Chip

SoC Application

Abstraction Layer

Specific platform driver

Generic implementationTDMA MAC

(Superframe)

PHY 1: 15.4 250kbit/s

PHY 2: BTLE 1Mbit/s

PHY 3: 15.4 2Mbit/s

Logical Link Control Layer

SPI

SoC

Embedded Application

Ex. of implementation & prototyping (3)



Coexistence and interoperability

� IEEE 802.15.6 BAN = Pico-area network with a coordinator.

When multiple BANs are co-located, no ability to stop transmission of

others and generation of interference

� Coexistence algorithm should ensure independently or cooperatively

communications without severe interference

� Share whole spectrum into non overlapping sets (cooperation)

• Time resource sharing

• Time offset

Limitation of total throughput and adapted to low duty cycle

� Isolated BAN minimizing the probability of collision

• CSMA/CA & LBT

• Frequency band selection

� Coexistence interference mitigation with transmission in common slots

• Time hopping which change frame-by-frame the time slot (better performance that

totally separating BAN on time)

• Fixed combination of sensor pairs



Challenges



Wireless localization for healthcare &

wellness� Current research axes for robust, scalable and privacy-aware

localization services� Location-enabled, low-cost and low-consumption integrated radio technologies

� Relevant models and algorithms supporting obstruction of radio links and usage conditions

� Opportunistic cooperation between mobile units or agents

� Cross-layer protocol design

� Privacy-preserving

� Hybrid data fusion (heterogeneous multi-standard radio contexts and/or inertial units)

� Mobility learning Mobility learning out of collected past traces

Low-power low data rate ranging-enabled

tags (IR-UWB)Algorithms & protocols

for cooperative localization



� Individual and collective navigation over large scale indoor

trajectories in a heterogeneous WBAN Context.

� Different cooperation scenarios have been considered, involving on-body and

body-to-body links on top of off-body links with respect to fixed infrastructure

anchors.

� Cooperative EKF formulation adapted to BAN and body shadowing mitigation.

Ex. of BAN-based navigation (1)

5

87

6

9

1211

10

1

43

2

� Scenario:

� 3 WBANs of 4 nodes each

� Infrastructure anchors: 4

� Room: 20mx20m

� Speed: 1 m/sec

� Refreshment rate: 30 ms



Ex. of BAN-based navigation (2)

Cooperative vs Non Cooperative scenarios/

different PER Over Off-Body links

� The potential and the benefits of cooperative schemes to

improve both localization precision and robustness.

Cooperative vs Non Cooperative

scenarios



Conclusions

� Most of WBAN research on close-to-body communications

� New requirements imposed by coexistence and collective

mobility suggest to exploit body-to-body cooperation.

� Remaining challenges:

� Coexistence and interoperability towards the ”Man” integration into the

numerical world (e.g. smart cities and social networks).

� Motion capture:

• Latency in mesh On-Body network topologies under realistic MAC

constraints.

• The mitigation of radio obstructions due to body shadowing.

• The design of suitable ranging enabled receivers or detection algorithms.

� BAN-based group navigation:

• The selection of additional cooperative Body-to-Body links in heterogeneous

contexts, from energy consumption, computational complexity and link

quality perspectives.

Thanks for your

attentionMickael MAMAN

CEA-Leti Minatec [email protected]

Research Trends in Wireless Body Area Networks: From On ......Wireless localization for healthcare...

Documents

Transcript of Research Trends in Wireless Body Area Networks: From On ......Wireless localization for healthcare...