High Accuracy Distance Measurement for Bluetooth Based on Phase Ranging

GCT Semiconductor, Inc.TTA - Workshop 2019
High Accuracy Distance Measurement for Bluetooth
Based on Phase Ranging
Ealwan Lee
GCT Semiconductor, Inc.
Session : De-facto Standard Development Organization #3
May 24, 2019 (11:40 am ~ 12:00 pm)
2019 ICT 표준화포럼/전문가 합동워크숍

1/23
Table of Contents
❑ Introduction
◆ Scope of the presentation(HADM)
◆ Use case of HADM
❑ Phase Ranging Method adopted in HADM
◆ Phase Shift Measurement
✓ Analogy : Vernier scale, Moiré pattern,
◆ Active Reflector
❑ IPR issues and History of Phase Ranging
◆ ATMEL
◆ Handover from 802.15.4 to Bluetooth
❑ Implementation issues : non-FRAND IPR
❑ Forecasting on the HADM technology
❑ Bluetooth Standardization Activity
◆ Discussion of HADM at Core Specification WG.
❑ Summary
❑ Acknowledgment
[ pp. 4 ~ 10 ]
[ pp. 11 ~ 15 ]
[ p. 22 ]
[ p. 23 ]
[ p. 2 ]
[ p. 16 ]
[ pp. 19 ~ 21 ]
[ pp. 17 ~ 18 ]
[ p. 3 ]

2/23
Introduction
❑ LBS(Location Based Service) feature in Bluetooth Low Energy
◆ 4.x (4.0, 4.1, 4.2) since Dec 2009
✓ Separate physical channel assigned for broadcast(advertisement) channel
 fast scan and connection became available.
✓ Proximity based service
 beacon service
◆ 5.1 (Released as of Jan 2019) : 6.0 in ICT Standardization Strategy Map(2019)
✓ Half of long-waited Madrid version is related suddenly without LE audio feature.
✓ Direction Finding Feature for AoA(Angle-of-Arrival) and AoD(Angle-of-Departure)
◆ Milan version (5.2 or 6.0?)
◆ Sydney version (6.0 or 6.1?)
✓ HADM, RP
❑ HADM : High-Accuracy-Distance-Measurement
◆ consists of
✓ Phase Ranging with Secure QTE(Quick Tone Exchange)
✓ ToF(Time-of-Flight)
◆ Use cases
✓ Positioning
✓ Relay attack Protection
http://www.tta.or.kr/data/reporthosulist_view.jsp?kind_num=5&hosu=2019

3/23
Use Cases of HADM(not limited to Phase Ranging Method)
❑ Indoor Positioning
◆ Asset Tracking
✓ ATP(Asset Tracking Profile) under formal IOP
◆ Way Finding
✓ IPS-1.1(Indoor Positioning Service Enhancement)
✓ IPP(Indoor Positioning Profile) = IPS-1.1 + CTES(Constant Tone Extension Service)
❑ Relay Attack Protection : Accurate and Invulnerable Proximity service
◆ RSSI-only based system cannot protect SARA(Signal Amplification Relay Attack).
◆ Competition against 802.15.4z(UWB-like EIR based ranging)
✓ distance bounding(one of the PHY layer protection) can be easily implemented in 802.15.4z.
An amplifier for key-to-car(UHF)
as a man-in-the-middle
An amplifier for car-to-key(LF)
Wake-up
d1
1
d2
2
d3
3
RSSI(distance)-only
direction(angle)-only
direction+
(precise) distance
key fob

4/23
Methods of Positioning : Improvement by HADM
❑ Trilateration : Distance
◆ RSS (Received Signal Strength)
✓ Precision is lost as the distance gets longer.
◆ ToF (Time of Flight) : RTT(Round-Trip Time/Delay)
✓ Precision is proportional to the band-width of the pulse signal
✓ Ideal for wide-band signal standard : UWB(802.15.4z), WiFi(802.11az)
◆ Phase Ranging : Interferometry
✓ A (narrow-band) tone signal is used.
❑ Triangulation : Angle
◆ AoA, AoD
✓ Now available with v5.1
✓ multi-antenna, still multi devices are required
RSS(logscale)
distance(linear)
Madridversion
Sydney version :
- a single device with multi-antenna for positioning
- a single device with a single antenna for ranging-only.
BLE (2MHz or 1MHz)
frequency
fc
UWB (> 500MHz or fc /5)
WiFi(20, 40, 80, 160 MHz)
∆𝒓 𝟏 = ∆𝒓 𝟐
∆𝒓 𝟏
∆𝒓 𝟐
∆𝒅 𝟏 ∆𝒅 𝟐
∆𝒅 𝟏 < ∆𝒅 𝟐

5/23
Phase Ranging : Phase Shift Measurement + Active Reflector
❑ Phase Shift = Phase difference between carriers with different frequency
❑ min f (Channel spacing of Bluetooth LE) = 2 MHz => d = 75m.
◆ Phase shift folds with the periodicity of 75m(w/ round-trip path of active reflection).
◆ Is 75 m enough for indoor positioning?
✓ Typical range of BLE ~ 10 m : seems to be enough
❑ Weak to interferer, multi-path channel.
Initiator
(Tx)
Reflector
(Rx)
Initiator
(Rx)
Reflector
(Tx)
Initiator
(Tx)
Reflector
(Rx)
Initiator
(Rx)
Reflector
(Tx)
f1
f2= f1+f
1
2=1+
𝒅 =
𝒄
𝟒𝝅
∙
∆∅
∆𝒇
distance
phase

6/23
Analogy of Phase Shift Measurement (1/2) : Vernier Scale
❑ Vernier Scale
◆ A visual aid for accurate measurement reading between two graduation markings
◆ https://en.wikipedia.org/wiki/Vernier_scale
◆ Devices : Vernier Caliper
❑ Vernier Delay Line for Time Difference Amplification in Integrated Circuit Design
◆ Vernier Delay Line based TDC(Time-to-Digital Converter)
main
Vernier
Read-out : 10.02 mm
Vernier Constant : 0.01 mm = 1 - 9/10 mm

7/23
Analogy of Phase Shift Measurement (2/2) : Moiré pattern
❑ Aliasing caused by similar patterns(including frequencies)
◆ Can be seen in 2D and 1D
◆ https://en.wikipedia.org/wiki/Moir%C3%A9_pattern#Geometrical_approach
❑ Hold your smartphone camera near(not too close) the notebook screen.
◆ If the resolution of camera and display gets comparable, Moiré pattern will appear.
Moiré effect in photos
𝒅 =
𝒑
𝟐
∙
𝒑
𝜹𝒑
The period of pattern is
amplified by the factor of
(p/dp)

8/23
QTE for HADM(High Accuracy Distance Measurement)
❑ QTE = Quick Tone Exchange
◆ Frequency offset compensation in the initial stage
❑ Multi(2+) Carrier Phase Ranging Technique for Vernier Scaling
◆ To cope with Interferer, frequency selective channel.
Reflector
Frequency
of a tone signal
Transmitter
(Initiator/
Reflector)
Frequency Error
Measurement
Antenna
in either side of
Initiator/
Reflector
#0
Initiator Initiator
1st Phase Measurement
#0 #1 #2 #3 #0 #1 #2 #3
n-th Phase Measurement
ReflectorInitiator
#0 #1 #2 #3 #0 #1 #2 #3
Tx Rx
Frequency
compensation

9/23
Packet Format modified for Direction Finding in Bluetooth v5.1
❑ CTE(Constant Tone Extension) is appended after the CRC.
◆ No CTE is allowed in legacy advertisement channel(Ch #37, #38, #39)
◆ Flag for the CTE presence is different between
✓ Advertisement channel : Used for AoD.
✓ Data channel : Used for AoA.
❑ Switching of RF antenna is required in either side.
Preamble
(1 ~2 octets, 8 µs)
Access Address
(4 octets)
PDU
(2 ~ 258 octets)
CRC
(3 octets)
PDU header
(2 octets)
payload
(1 ~ 256 octets)
Advertisement channel
Packet type
= AUX_SYNC_IND
(Available only in 5.x)
Data channel PDU header
(2 ~ 3 octets)
payload
(1 ~ 256 octets)
MIC
(4 octets)
AoD :
AoA :
Connectionless
multi-antenna in Tx(beacon)
Connected
multi-antenna in Rx(locator)
Extended header flag
CP : CTE Present
CTE
(16 ~ 160 µs)

10/23
Secure QTE (proposed by IMEC)
❑ Initial proposal of QTE used only a tone signal for the phase ranging.
◆ No device to detect the interferer.
◆ Side info on the packet can be used to protect the relay attack.
◆ Tone is prepended (not appended) to the reflector packet.
✓ To minimize the clock frequency drift.
❑ ToF can be measured simultaneously during the QTE with a switching data in the packet.
◆ ToF measurement result can be used unfold the phase ranging result limited to 75m.
Preamble
(1 ~2 octets, 8 µs)
Access Address
(4 octets)
CRC
(3 octets)
PDU
(2 ~ 258 octets)
PDU
(2 ~ 258 octets)
Secure QTE Packet from the initiator
with appended tone signal.
Secure QTE Packet from the reflector
with prepended tone signal.
PMU in
reflector
PMU in
initiator
Phase from the reflector
is used for distance measurement
if CRC is OK.
Minimize the clock frequency drift
Pouria Zand, et. al,
“A high-accuracy phase-based ranging solution
with Bluetooth Low Energy (BLE)”,
Proceedings of WCNC, Apr. 2019.
https://www.researchgate.net/publication/33
2655909_A_high-accuracy_phase-based_ran
ging_solution_with_Bluetooth_Low_Energy
_BLE

11/23
IPR issue on the Active Reflector(=Transponder)
❑ US Patent : 8,644,768 B2
◆ Inventor : Wolfram Kluge
Eric Sachse
◆ Date of Patent : Feb. 4, 2014
◆ Filed : Dec 20, 2009
◆ Priority Date : Dec 30, 2008 (DE)
System, method, and circuit for distance measurement
between two nodes of a radio network

12/23
Past Standardization Process of Phase Ranging
❑ Knocked the door of 802.15.4
◆ ATMEL
✓ https://mentor.ieee.org/802.15/documents
✓ No comments on the base document is found.
❑ Failed to be standardized.
15-09-0613-01-004f-ranging-with-ieee-802-15-4-narrow-band-phy.ppt
15-12-0651-00-004n-ranging-with-ieee-802-15-4-narrow-band-phy.pptx
15-13-0180-00-004n-integration-of-ranging-capabilities-with-phy-supporting-cmb.pptx
https://www.microchip.co
m/announcements/micro
chip-technology-inc-acqu
ires-atmel
Acquisition of ATMEL
by Microchip in 2016
System, method, and
circuit for distance me
asurement between tw
o nodes of a radio net
work
US Patent 8 644 768
Morgan Stanley
JP Morgan Chase
Wells Fargo
Patents on using
active reflector to
Phase Ranging
Pending IPR
issue on HADM
Still active
2009
2012
2013
Patent filed to EU @ DE (2008)
The inventor still works
in microchip.

13/23
Contribution of the precursors and hand-over to Bluetooth
❑ RTB : Ranging Tool Box (developed for ATMEL’s Zigbee chip set with PMU inside) : 2013
◆ Archived in the unnamed category of Microchips website
✓ http://ww1.microchip.com/downloads/en/AppNotes/Atmel-8443-RTB-Evaluation-Application-Software-Users-Guide_Application-Note_AVR2152.pdf
◆ Source is now open and can be found in github
✓ https://github.com/subpos/atmel_ranging_toolbox_zigbit
❑ Press release of IMEC on May 2018
◆ “IMEC Sets New Benchmark with 30cm Accurate and Secure Localization Solution based on Bluetooth”
✓ https://www.imec-int.com/en/articles/imec-sets-new-benchmark-with-30cm-accurate-and-secure-localization-solution-based-on-bluetooth
Photos of IMEC solution at Press Release
: single antenna
(distance measurement only)
ATMEL @ 2013

14/23
Evaluation of the Phase Ranging (1/2)
❑ Lymberopoulos, Dimitrios, and Jie Liu, “The Microsoft
indoor localization competition: Experiences and less
ons learned,” IEEE Signal Processing Magazine vol 3
4, no. 5, pp. 125-140, 2017.5
◆ https://www.microsoft.com/en-us/research/event/microsoft
-indoor-localization-competition-ipsn-2014/
0.72m @ 2014
0.2m @ 2015
0.06m @ 2016
0.033m @ 2017

15/23
Evaluation of the Phase Ranging (2/2) : Enhancement
❑ Jacek Rapinski and Michal Smieja, “ZigBee Ranging using Phase Shift Measurements”, (2015)
◆ https://doi.org/10.1017/S0373463315000028
❑ Georg von Zengen et al, “No-Cost distance estimation using standard WSN radios”, (2016)
◆ https://doi.org/10.1109/INFOCOM.2016.7524540
❑ A frank review by a geek & blogger, Josh (2013)
◆ https://wp.josh.com/2013/05/23/first-look-at-distance-measurement-using-the-at86rf233-chip/
Set-up of Jacek’s work
Distance = Coefficient / Slope
Result of Georg’s work

16/23
Implementation Issues : Offset calibration + Others...
❑ Sources of the offset
◆ Frequency selective channel : Averaging method can be used.
◆ Intrinsic delay of the circuit
✓ Delay of the local oscillator relative to the reference frequency can be different.
❑ A similar concept in Vernier Scale
◆ https://www.miniphysics.com/how-to-read-a-vernier-caliper.html
I
Q
Zero is
not aligned.
Measurement
Phase
Calibration
Phase
RBB(f1)
RBB(f2)
RBB(f)
TBB(f) := RBB(f) * CRF(f)
TRF(f)
TRF(f1)=TRF(f2)
RRF(f)
RRF(f1)=RRF(f2)
Compensating rotator is frequency dependent.

17/23
Flash back on the Birth of Bluetooth Low Energy
❑ Wibree(the code name for Bluetooth Low Energy) was initially proposed to 802.15 TG4.
◆ Year : 2001
◆ http://grouper.ieee.org/groups/802/15/pub/2001/Jul01/
✓ 01230r1P802-15_TG4-Nokia-MAC-Proposal1.ppt
✓ 01231r2P802-15_TG4-Nokia-PHY-Proposal1.ppt
◆ A brief story can be found in ch 7 of “Essentials of short-range wireless” by Nick Hunn.
✓ 802.15.4 TG => Wibree => Bluetooth LE
✓ However, it is noted that
 Not exactly the same as that of current Bluetooth Low Energy.
 Separation of data channel and broadcast channel for fast scanning and connection.
 Tried to share the hardware resource with Bluetooth as much as possible.
❑ Release of the Bluetooth Low Energy in Bluetooth v4.0 (2009)
❑ Introduction of iBeacon by Apple(2013) made the BLE as the necessity of smartphone.
◆ Complementary function between WiFi(network) and Bluetooth(audio)
◆ A single chip implementation of WiFi and Bluetooth.
❑ What is your opinion on the destiny of the Phase Ranging in Bluetooth?
◆ It does not mean that all the Bluetooth features will succeed and survive, as in
✓ Transfer of picture : OPP(Object Push Protocol) => WiFi DirectTM => Cloud Storage.
✓ WiFi LocationTM is already is already in service since Android Oreo version.
✓ Mesh 1.0 : Flooded Forwarding - Poor network performance compared with Zigbee, Thread

18/23
Forecasting the future of HADM looking back on the history of BLE
❑ Data from “2019-Bluetooth-Market-Update.pdf”
◆ It can be obtained from https://www.bluetooth.com/bluetooth-resources/?types=report.
2009
BR/EDR
* head-set
* old smartphone
BR/EDR + LE
* recent smartphone
* TWS head-set (2 for left & right)
LE
* beacon, tag
* wearable devices
Release of Bluetooth 4.0(LE)

19/23
Recent Changes in Bluetooth Standardization Activities
❑ Number of WG Summit a year is increased from 1 to 4+.
◆ 1 WG Summit + 3 UPFs a year so far ~ 2018.
◆ UPFs(still) will probably be co-hosted with WG Summit.
❑ IOP(InterOperability Prototype) Test event is held on-demand collocated with any event.
2018
2019
Paris
1Q (UPF@NA) 2Q (UPF@Asia) 3Q (Summit Only)
Seoul
2020
Dallas Vienna
Malta
Kirkland
(office of Bluetooth-SIG)
4Q (UPF@EU)
upf62
Lisbon
NewOrleans
upf60
upf63
Berlin(upf61)
?
upf59 Discussion on
HADM @ CSWG
upf64
upf65
Vancouver

20/23
Discussion on HADM at Paris WG Summit (Mar, 2019)
❑ Contributors to the HADM in Sydney version of Core Specification.
◆ Lambda:4*
◆ IMEC*
◆ Samsung
◆ Denso
❑ Status of the Standardization Process : Corresponds to enhancement of Core Spec.
◆ NWP -> FRD -> DIPD(not available yet)
❑ Facts on the Bluetooth Standard Development Procedure
◆ https://www.bluetooth.com/specifications/working-groups/specification-development-process/
✓ New Work : NWP -> FRD -> 0.5 -> 0.7 -> 0.9 -> Validation -> ...
✓ Enhancement : FRD -> DIPD -> FIPD -> CR -> Validation -> ...
◆ Validation Phase (Unique to Bluetooth)
✓ Prototype Specification
✓ IOP : Informal IOP, Formal IOP(adopter member is allowed to join)
 IOP is for the validation of Standard Specification.
 Feedback on the
 UPF is for the cross-check of the developed product.
◆ Voting & Adoption
NWP : New Work Proposal
FRD : Function Requirement Document
DIPD : Draft Improvement Proposal Document
FIPD : Final Improvement Proposal Document
CR : Change Request
PS : Prototype Specification
IOP : Inter-Operability Prototype
UPF : UnPlugFest

21/23
UPF63 + WG Summit at Seoul in 2019 (Jun 10 ~ Jun 13, 2019)
❑ Promotional Statements
◆ GCT Semiconductor acts as a local host of UPF63.
HADM will be discussed at CSWG
(not at DFWG)

22/23
Summary
❑ Report of HADM standardization activity in Bluetooth-SIG
◆ Will be adopted in Sydney version(not Milan version) : 2~3 years will take.
◆ Application : Positioning, Relay attack Protection
❑ Introduction of Phase Ranging Used in HADM(High Accuracy Distance Measurement)
◆ Phase Shift Measurement
◆ Active Reflector
◆ ToF
❑ Introduction of Bluetooth Standardization Procedure
◆ Status of HADM in Sydney version : FRD -> DIPD
◆ Promotion of UPF63 and WG Summit(+IOP).
✓ Local host : GCT Semiconductor, Inc.
✓ The second-year(last) hosting in Seoul
❑ Purpose and Expectation of this presentation
◆ Introduction of the HADM, a hot topic, in Sydney version of Bluetooth Core specification.
◆ Archaeological finding on the research of phase ranging.
✓ Reference of the cited work will help to get more in-depth information on the phase ranging.
✓ Spreading the idea that “the positioning accuracy can be increased even with narrow-band signal.”

23/23
References and Acknowledgement
❑ 이일완, “Phase Ranging에 기반한 차세대 Bluetooth 표준의 High Accuracy Distance
Measurement”, ICT 국제표준화 전문가 표준화 보고서, 2019년 3월 27일
◆ https://expert.tta.or.kr/rep/reportView.do?selectedId=1281
❑ 이일완, “블루투스 기반 실내 측위 표준화 동향”, TTA 저널, vol. 183, 2019년 5~6월.
◆ http://tta.or.kr/data/reporthosulist_view.jsp?kind_num=1&hosu=183
❑ This slide is downloaded from
◆ https://www.slideshare.net/ealwanlee/high-accuracy-distance-measurement-for-bluetooth-base
d-on-phase-ranging
◆ It is subject to the change for future presentation or lectures.

High Accuracy Distance Measurement for Bluetooth Based on Phase Ranging

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