EnablingfirmwareupdatesoverLPWAN

JanJongboom|DeveloperEvangelist|Arm

TechSymposia2017

©2017ArmLimited2

©2017ArmLimited3

Wait,what...LPWAN?Po

wer

con

sum

ptio

n /

Band

wid

th

Range

IoTsweetspot

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Picktwo

High bandwidth Low power

Long range

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Manychoices...

10yearsbatterylife,10kmrange

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LPWANPhysicscrash-course©2017ArmLimited

©2017ArmLimited7

Highlinkbudget

TX

P (dBm)

RX

DerivedfromworkbyThomasTelkamp

TXPow

er

Conn

ectorloss

Antenn

again

Conn

ectorloss

Antenn

again

RXPow

er

Pathlossandfading

14

0

-100

Receiversensitivity

©2017ArmLimited7

Highlinkbudget

RX

DerivedfromworkbyThomasTelkamp

TXPow

er

Conn

ectorloss

Antenn

again

Conn

ectorloss

Antenn

again

RXPow

er

Pathlossandfading

Receiversensitivity-137dBm

14dBm151dB

mlinkbud

get

©2017ArmLimited8

Linkbudget

Wi-Fi

Unlicensed LPWAN

Licensed LPWAN

TXPower RXSensitivity Linkbudget

20.5 dBm -75 dBm 95.5dBm

14 dBm -137 dBm 151dBm

23 dBm -129 dBm 152dBm

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Theoreticalmaximuminfreespace

2.4GHz,with95.5dBmlinkbudget:550meters

915MHz,with151dBmlinkbudget:850,000meters

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Unfortunately...wedon'tliveinfreespace

Attenuation Reflection and diffraction Fresnel zone

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BasedonTokyo-modelforcalculatingrealisticpathloss

Picture by Moyan Brenn: https://commons.wikimedia.org/wiki/File:Tokyo_(16043023330).jpg©2017ArmLimited

Hatamodel

Large city (250 bps)

Large city (1,760 bps)

Suburb (250 bps)

TXheight RXheight Range

0.1 m 40 m 4km

0.1 m 40 m 2.5km

0.1 m 40 m 9km

Suburb (250 bps) 1 m 100 m 13km

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Aggressivesleeping

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Transmitaslittleaspossible

Nogatewaypinning

Nokeep-alive

NB-IoT:200mW

Sigfox:25mW

https://www.flickr.com/photos/pheezy/5875298232

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ListenaslittleaspossibleRXconsumption:9mA

500mAh/9mA/24h=2.31days

2.31days!==10years

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Relayingdatabacktodevice

TX RX TX RX TX RX

LoRaWAN Class A, LTE-M Power Save Mode, Sigfox

RX TXRX

LoRaWAN Class B, LTE-M EdRX

RX RX

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Tinypackets

NoIProutinginpackets

Securityinmessage,notintransportlayer

NoTLShandshakes(6messages,6.5Kdata)

Small13-14byteheader

Everybytecounts!

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IoTdeploymentstarget10yearslifetimeBut 10 years is a really long time!

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©2017ArmLimited©2017ArmLimited

Howto

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Naiveapproach

TX RX TX RX TX RX

Firmwarefragment

Veryinefficient!

Device 1

TX RX TX RX TX RX

Device 2

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Betterapproach

RX

Manyfirmwarefragments

Device 1

Device 2

RX

Device N

RX

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But...howdowedothis?

1. Instructdevicestouseanewsetofkeys(sameforeveryone).

2. Instructdevicestowakeupatthesametime.

3. Gatewaycantransmittoalldeviceswithonemessage.

Problem:lowQoSanduni-directional

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Settingupthedevice

DeviceAddress:0xCF32AB09MulticastKey:9310E28FA291...

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Settingupthedevice

Packetsize:204bytesPacketcount:491Padding:16bytes

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Startingmulticastsession

Frequency:924.525MHzDatarate:220bytes/sec

Timetostart:812secafterULevent13

ULCounter|RTC----------------15|78114|70413|62312|491...

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DealingwithlowQoS

CRChashoffirmware(sentwithdevice'sowncredentials)

OK!

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DealingwithlowQoS

CRChashoffirmware(sentwithdevice'sowncredentials)

OK!

Forwarderrorcorrection

http://www.inference.phy.cam.ac.uk/mackay/gallager/papers/ldpc.pdf

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Speed

220bytespersecondinrealworldscenario(2.5KMrangeincities)

180KBFirmwaresize,30KBwithDeltaupdates

Transmissioncosts3m30s@15mAcurrent

https://www.reddit.com/r/Eyebleach/comments/68r4rt/tortoise_taxi/

©2017ArmLimited©2017ArmLimited

SecurityPicturebyYuriSamoilovhttps://www.flickr.com/photos/yusamoilov/13334048894

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Linklayersecurityisnotenough

Firmware manifest Containsfirmwarehash

ContainsmanufactureranddeviceclassID

Signedwithprivatekey

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Separatetrustedandnon-trustedcode

(Notyetimplemented)

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Bootloadersupport

NewinMbedOS5.5

Bootloaderverifiesintegrity,preferablyinnon-writableflash

Tamper-proofsecureelementtoprotectkeys

https://os.mbed.com/blog/entry/firmware-updates-mbed-5-flashiap/

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Caveatshttp://www.totalprosports.com/wp-content/uploads/2013/04/first-pitch-fail-baseball-fail-gifs.gif

©2017ArmLimited©2017ArmLimited

Networkcongestion

Sendingalotofdatahasnegativeeffectonnetwork

Higherdatarateisbetter

RXsensitivityisuselesswhensomeonescreamsnexttoyou

Spreadspectrumhelpsagainstnarrowbandinterference

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SpectrumregulationsinEU

Unlicenseddoesnotmeanunregulated

1%dutycyclein868MHzband,exceptat869.525MHz

Downside:it'stheRX2channel

Round-robinbetweengateways

Driveovertositeanddeploytemporarygateway

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USisbothbetterandworse

Better

Worse

Nodutycycle

Widerchannels(500KHzvs.125KHz)

Faster

400ms.dwelltime

915MHzbandisusedforalotofotherstuff,lowerQoS

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Currentstate

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Referenceimplementation

Multi-TechxDot(Cortex-M3,32KRAM)

LoRaWAN1.02

mbedOS5.5

NetworkserverbyTheThingsNetwork

©2017ArmLimited40

Client+bootloader

Opensource

Apache2.0

AvailableonGitHub

Verylittlesecurity!

SecurebootloaderandcryptographicallysecureupdateserviceavailableaslicensableIPfromArm.

©2017ArmLimited©2017ArmLimited

Reference implementation:

https://github.com/ArmMbed/fota-lora-radio

Demo:http://bit.ly/lora-update-demo

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Recap

1. LPWANsareawesome!

2. Securefirmwareupdatesarenecessity

3. FirmwareupdatesoverLPWANdeemedimpossible...Buttheyarenot!

ThankYou!Danke!Merci!

!�����!Gracias!Kiitos!감사합니다धन्यवाद

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http://bit.ly/lora-update-demojan.jongboom@arm.com

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