August 2004

Benoit Denis, CEA/LETI STMicroelectronicsSlide 1

doc.: IEEE 802.15-04/418r0

Submission

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Submission Title: UWB Localization TechniquesDate Submitted: 10 August 2004Source: Benoit Denis Company: CEA/LETI, STMicroelectronicsAddress: 17 rue des Martyrs, F 38054 Grenoble cedex 9, FRANCE (CEA/LETI) 39 ch. du Champ des Filles CH - 1228 Plan-les-Ouates, SWITZERLAND (STMicroelectronics)Voice:(33)(0)4 38 78 58 11, FAX: (33)(0)4 38 78 51 59, E-Mail:denisbe@chartreuse.cea.fr

Re: TG4a Ranging Subcommittee Time-of-Arrival Algorithms

Abstract: This document describes classical UWB TOA ranging / localization algorithms

Purpose: In support of TG4a Ranging Subcommittee work.

Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.

August 2004

Benoit Denis, CEA/LETI STMicroelectronicsSlide 2

doc.: IEEE 802.15-04/418r0

Submission

UWB Localization Techniques

Benoît DENIS benoit.denis@cea.fr M17

M14

L09

L01

M21

L06M27

M15

M12

M20M13

M28

M25

M23M29

M26

L04

L03

M24

M16

M11

M18M30

L10L07L02

M19

M22

L08

Fusing Accurate Positioning Capabilities and Digital

Communications

August 2004

Benoit Denis, CEA/LETI STMicroelectronicsSlide 3

doc.: IEEE 802.15-04/418r0

Submission

Time Of Arrival (TOA) & Two Way Ranging (TWR)

Terminal B

Request

Prescribed Protocol

Delay and/or Processing

Time

To

TReply

T1

Terminal A TX/RX

Terminal B RX/TX

TOF TOF

cTd

TTTT

AOFAB

AOF

.~~2

1~Reply01

TOF EstimationTerminal A

August 2004

Benoit Denis, CEA/LETI STMicroelectronicsSlide 4

doc.: IEEE 802.15-04/418r0

Submission

Time Of Arrival (TOA) & Two Way Ranging (TWR)

B

BAAAOFAOF

TTT

12

1~ Reply

Main Limitations / Impact of Clock Drift on Perceived Time

Range estimation is affected by :

•Relative clock drift between A and B

•Clock accuracy in A and B

•Prescribed response delay

Is the frequency offset relative to the nominal ideal frequency 0f0. f

Relaxing constraints on clock accuracy by

•Performing fine drift estimation/compensation

•Benefiting from cooperative transactions (estimated clock ratios…)

•Adjusting protocol durations (time stamp…)

August 2004

Benoit Denis, CEA/LETI STMicroelectronicsSlide 5

doc.: IEEE 802.15-04/418r0

Submission

MAC resources for a double DEV2PNC TWR Transaction

TOF

Request (Medium Access)

T2’

T2

PNC’s TOF Estimate

Acknowledgement

Transmitting to DEV PNC’s TOF

Estimate

TOF

DEV’s TOF Estimate

Receiving PNC’s TOF Estimate

MCTA (Slotted Aloha)

TOF

PNC

DEV

RefDEV

RefPNC

T1’

T1

Beacon Detection

Ex : DEV2PNC Ranging in the 802.15.3 Scenario

•Time stamp (fixed retransmission times T’)

•Beacon synchronization (PNC2DEV)

•Association procedure in MCTA slots Imm-ACK or Dly-ACK (PNC2DEV) & Association Request (DEV2PNC)

DEV-ADEV-C

DEV-B PNC•Relative clock drift DEV / PNC available

•Correction of DEV’s Time Offset (propagation delay from PNC)

PicoNet Synchronization

August 2004

Benoit Denis, CEA/LETI STMicroelectronicsSlide 6

doc.: IEEE 802.15-04/418r0

Submission

Time Of Arrival (TOA) & One Way Ranging (OWR)

Terminal

A

Terminal B

Request

To

Terminal A TX

Terminal B RX

TOF

TOF Estimation

Isochronous

Isochronous

T1

cTd

TTT

BOFAB

BOF

.~~

~01

TOF Estimation

If Terminals are synchronized to a common clock, direct

OWR can be used for Ranging

August 2004

Benoit Denis, CEA/LETI STMicroelectronicsSlide 7

doc.: IEEE 802.15-04/418r0

Submission

DEV-A

MAC resources for a single DEV2DEV OWR Transaction Guaranteed Time Slots in the CTA can be used between isochronous DEVs (i.e. with common reference start times)

DEV-A

DEV-B

RefPNC

CTA

DEV-C

RefPNC+Ts

TAB

DEV-B’s Estimate of TAB

TCA

DEV-A’s Estimate of TCA

Slot 1 Slot 2 Slot 3

TBC

DEV-C’s Estimate of TBC

RefPNC+ 2Ts

Ex : DEV2DEV Ranging in the 802.15.3 Scenario

DEV-B

August 2004

Benoit Denis, CEA/LETI STMicroelectronicsSlide 8

doc.: IEEE 802.15-04/418r0

Submission

Time Of Arrival (TOA) & One Way Ranging (OWR)

synchroBOFBOF TT 1~

Main Limitations / Impact of Synchronization and Clock Drifts on Perceived Time

Range estimation is affected by :

•Clock accuracy

•Uncertainty on the reference start times (synchronization)

Is the frequency offset relative to the nominal ideal frequency 0f0f

Requirements

•Achieving fine synchronization between terminals prior to ranging

August 2004

Benoit Denis, CEA/LETI STMicroelectronicsSlide 9

doc.: IEEE 802.15-04/418r0

Submission

Mobile (xm,ym)

Anchor 2 (xA2,yA2)

Anchor 3 (xA3,yA3)

Anchor 1 (xA1,yA1)

Positioning from TOA

3 anchors with known positions (at least) are required to retrieve a 2D-

position from 3 TOAs

22

3

222

221

33

22

11

MAMA

MAMA

MAMA

yyxxd

yyxxd

yyxxd

321

~,

~,

~ddd

Measurements Estimated Position

MM yx ~,~

Specific Positioning Algorithms

August 2004

Benoit Denis, CEA/LETI STMicroelectronicsSlide 10

doc.: IEEE 802.15-04/418r0

Submission

Time Difference Of Arrival (TDOA) & One Way Ranging (OWR)

To

Mobile TX

Anchor 1 RX

TOF,1

T1

Anchor 2 RX

TOF,2

T2

Anchor 3 RX

TOF,3

T3

Anchor 1

Anchor 2

Anchor 3

Mobile

Isochronous

Info T2

Info T3

Info T2

Info T3

TOA EstimationTDOA Estimation

cTdTTT

cTdTTT

.~~~

.~~~

23232323

21212121

TDOA Estimation

Passive Location

321 ,, TTT

TOA Estimation

Isochronous

August 2004

Benoit Denis, CEA/LETI STMicroelectronicsSlide 11

doc.: IEEE 802.15-04/418r0

Submission

Mobile (xm,ym)

Anchor 1 (xA1,yA1)

Anchor 2 (xA2,yA2)

Anchor 3 (xA3,yA3)

Positioning from TDOA

3 anchors with known positions (at least) are

required to find a 2D-position from a couple of TDOAs

2222

31

222232

1133

2233

MAMAMAMA

MAMAMAMA

yyxxyyxxd

yyxxyyxxd

3132

~,

~dd

Measurements Estimated Position

MM yx ~,~Specific Positioning Algorithms

August 2004

Benoit Denis, CEA/LETI STMicroelectronicsSlide 12

doc.: IEEE 802.15-04/418r0

Submission

Ex. of Possible Embodiment for TDOA/OWR based Systems

RF RX & Timing Pulse

Processor

RF RX & Timing Pulse

Processor

RF RX & Timing Pulse

Processor

RF RX & Timing Pulse

Processor

Serial Data Link + Timing Ref

Clock

Base Control Unit

Short Transmitted Packets + Asynchronous TX Tags = Infrequent Packet Collisions

Known Fixed Locations

Tag

Asynchronous Tags to be localized

TagTag

Tag

Tag

Tag

August 2004

Benoit Denis, CEA/LETI STMicroelectronicsSlide 13

doc.: IEEE 802.15-04/418r0

Submission

Received Signal Strength Indicator (RSSI)

Power Strength could be an alternative solution to TOA/TDOA in the UWB Context

•Lower requirements in terms of synchronization and clock precision

But•RSSI requires precise channel behavioral model•RSSI is sensitive to channel inconstancy and non-stationarity•RSSI does not benefit from UWB high resolution

August 2004

Benoit Denis, CEA/LETI STMicroelectronicsSlide 14

doc.: IEEE 802.15-04/418r0

Submission

Angle Of Arrival (AOA)

AOA could be an alternative solution to TOA/TDOA in the UWB Context

•Lower requirements in terms of synchronization and clock precision

•Two anchors are sufficient for 2D-positioning

But•UWB Arrays Antennas technology may be not mature•AOA requires precise calibration at anchor nodes•Cost increases with size and size may not be reduced•The number of elements in the array highly depends on the radio environment