www.wiserban.eu

WiserBAN –

Smart miniature low-power wireless

microsystem for Body Area Networks

Riccardo Cavallari

Stefan Mijovic

riccardo.cavallari@unibo.it

stefan.mijovic@unibo.it

Aim is to develop a BAN protocol architecture that:

• provides optimized power consumption while providing support for identified application requirements

• supports coexistence and as much as possible cooperation and compliance with other BAN/PAN protocol architectures.

MAC protocol

MAC protocol: Architecture

MAC protocol: Implementation

INITIALIZED

READY

mac_init(mac_extended_address_t address)

All statesMLME_RESET_REQUEST

COORDINATOR

SYNCHRONIZATION

MLME_TDMA_START_REQUEST (*)

MLME_SYNC_REQUEST (**)

MLME_RESET_REQUEST

SYNCHRONIZED

MLME_BEACON_NOTIFY_INDICATION

ASSOCIATED

MLME_ASSOCIATE_CONFIRM

MLME_DISASSOCIATE_CONFIRM

LPL

All states but INITIALIZED

MLME_LPL_START_REQUEST

(*) This transition implies the channel selection procedure through energy detection.

(**) This transition implies the Passive/Active scan procedure.

SYNCHRONIZATION LOST

MLME_SYNC_LOSS_INDICATION

MLME_SYNC_LOSS_INDICATION

MLME_SYNC_REQUEST

MLME_TDMA_START_REQUEST

LOW POWER DEVICE

REDUCED FUNCTION DEVICE

FULL FUNCTION DEVICE

Synchronous MAC

High traffic applications

MAC protocol: Superframe mode

802.15.6 Slotted ALOHA

802.15.4 CSMA/CA

802.15.6 CSMA/CA

Beaco

n

Inactive(Sleep)

ACKPOLL

(Indicators)

CAP(CSMA/CA

orSlotted ALOHA)

CFP(TDMA)

RELAYING

Beaco

n

MAC protocol: LPL mode

Asynchronous MAC

Low traffic, low energy applications

P P

TX

ON

IDLE

RX

ON

IDLE

Ton Tw

t

t

P P

P

A

C

K

ACK

DataFrame

DataFrame

T1

Tdata

= TX

= RX

A

C

K

ACK

SleepActive

MAC protocol: Frames example - Data

Preamble

4 Bytes

Pattern

4 Bytes

Length

1 Byte

PSDU

0-255 Bytes

CRC

2 Bytes

BAN ID

4 Bytes

Frame Type

½ Byte

Addressing mode

½ Byte

Destination

address

Short

1 Byte Source

address

Short

1 Byte Frame

SpecificLong

4 Bytes

Long

4 Bytes

Acknowledgement

policy

½ Byte

Relaying policy

½ Byte

Sequence number

1 Byte

MPDU

0-242 Bytes

Manufacturer ID

1 Byte

Device ID

1 Byte

Audio samples

14 Bytes

Average packet delay

Packet lost rate

Throughput

Energy consumption

Performance Evaluation Metrics

Experimental Platform

IcyCom platform (CSEM)• Tailored for WBAN applications

• 863-928 MHz transceiver (MSK modulation)

• 32-bit icyflex1 DSP/MCU @ 3.2 MHz

• Low voltage operation down to 1V

• Low continuous Rx current: 2.5 mA

• Data rate of 200 kbps

• 96 kB low leakage SRAM

• I2C, I2S, SPI, UART and GPIO

• GNU development tools (gcc)

Implementation and tests of the superframe with

Slotted ALOHA within the CAP portion

3 end devices + 1 coordinator

Experimental Setup

RightHip

RightEar

LeftEar

Remote Control

802.15.6 Slotted Aloha

TCAP =60 ms

Beacon

Superframe (SF), 75 ms

Beacon

t

Inactive

`

RC

1

2

3

Experimental Results

IEEE 802.15.6 Slotted ALOHA

0 10 20 30 40 50 60 70 80 90 1000.016

0.018

0.02

0.022

0.024

0.026

0.028

0.03

Payload Size [Byte]

Dela

y [

s]

on table 10 dBm

on body -20 dBm

Slotted ALOHA protocol

CAP duration = 60 ms

Slotted Aloha: Average Delay

0 10 20 30 40 50 60 70 80 90 1000

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

Payload Size [Byte]

PLR

on body -22 dBm

on table 10 dBm

Slotted Aloha: PLR

Slotted ALOHA protocol

CAP duration = 60 ms

Experimental Results

IEEE 802.15.6 CSMA/CA

CSMA/CA

Star topology composed of 3 EDs and one Coordinator.

Two traffic schemes:

Performance evaluated:• Average delay

• Packet loss rate (PLR)

• Throughput

C

ED1

ED2

ED3

`

RC

1

2

3

B B

t

B

Packet generation

Periodic, T = 75 ms (SF duration )

B B

t

B

Packet generation

Random(0,T)T=[20,30,50,100,200] ms

CSMA/CA: Average Delay

0 20 40 60 80 100 120 140 160 180 20020

25

30

35

40

45

Data Payload [Bytes]

Mean D

ela

y [

ms]

UP 3 - 0 RTX

UP 5 - 0 RTX

UP 7 - 0 RTX

UP 3 - 1 RTX

UP 5 - 1 RTX

UP 7 - 1 RTX

Higher UP value leads to lower delay

Average delay for a network composed of three nodes with different UP values. 0 and 1 re-transmissions

Coord

UP 3

UP 5

UP 7

0 10 20 30 40 50 60 70 80 90 1000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Data Payload [Bytes]

Packet

Loss R

ate

UP5 - 0 RTX

UP5 - 1 RTX

UP5 - 2 RTX

UP3 - 0 RTX

UP3 - 1 RTX

UP3 - 2 RTX

CSMA/CA: PLR

PLR increase by increasing UP

PLR is flat because CAP is long enough to fit all the transmissions

UP

50 100 150 200 25020

40

60

80

100

120

140

Offered load [kbit/s]

Thro

ughput

[kbit/s

]

0 RTX

1 RTX

Ideal

CSMA/CA: Throughput

N: number of devices in the network.

T: packet generation period.

Nrx: average number of correctly received packets in the period T.

Lp and Lh: payload and header sizes respectively.

Throughput deviates from the ideal case because of:

The presence of the header,

Collisions,

Hardware limitations.

Experimental Results

All together…

Protocol Comparison: Average Delay

Protocol Comparison: PLR

Experimental Results

Low-Power-Listening MAC

Low-Power-Listening MAC

Star topology composed of 1,2 or 3 EDs and one Coordinator.

Traffic:

C

ED1

ED2

ED3

`

RC

1

2

3

LPL: Energy Consumption

50 75 100

0.1

0.2

0.3

0.4

0.5

Tw [ms]

Ave

rag

e e

ne

rgy c

on

su

me

d p

er

pa

cke

t [m

J/p

acke

t]

RX, 20 Bytes

RX, 60 Bytes

RX, 100 Bytes

TX, 20 Bytes

TX, 60 Bytes

TX, 100 BytesReceiver

Transmitter

LPL: Average Delay

50 75 100

40

50

60

Tw [ms]

Avera

ge p

acket

dela

y [

ms]

100 Bytes

60 Bytes

20 Bytes

LPL: Throughput

0 50 100 150 200 250 300 350 400

100

200

300

400

Offered load [kbit/s]

Th

rou

gh

pu

t [k

bit/s

]

Ideal MAC

LPL peer-to-peer

LPL Star 2 TX

LPL Star 3 TX

0 10 20 30 40 50 60 70 80 90 1000

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Payload size [Byte]

PLR

Packet Loss Rate

link 1: right ear

link 2: left ear

link 3: heart

link 4: left hip

average

Measurement Results: PLR for each link

CSMA/CA Body shadowing: PLR

LeftHip

Heart

RightEar

LeftEar

Remote Control

WiserBAN after three years: SiP

First functional 2D-SiP for implantable devices. Left: 2D-SiP after assembly and Right: 2D-SiP

after embedding. The final size of the 2D-SiP is 4.2mmx4.3mmx0.77mm.

First chips are coming out…

WiserBAN after three years: SiP

2D-SiP on characterization board3D SiP. From bottom down: SoC, piezo and antenna modules

3D SIP close-up

WiserBAN after three years: Antennas

Photographs of the first L-antenna prototypes

Radiation pattern of the L-antenna near human head

New design of the micro SD antenna

Directivity pattern for the smartphone scenario

WiserBAN after two years: Antennas

Passive micro-SD antenna for WBAN remote control node Active frequency agile dipole antenna for ITE hearing aid

Loop antenna integrated in cochlea implant

WiserBAN after three years: Radio

Info

For more information:

www.wiserban.eu

…public documents public deliverables