Transcript Project: IEEE P802.15 Working Group for Wireless Personal Area Networks...

August 2004
doc.: IEEE 802.15-04/418r0
Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: UWB Localization Techniques
Date Submitted: 10 August 2004
Source: Benoit Denis Company: CEA/LETI, STMicroelectronics
Address: 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:[email protected]
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.
Submission
Slide 1
Benoit Denis, CEA/LETI STMicroelectronics
August 2004
doc.: IEEE 802.15-04/418r0
UWB Localization
Techniques
L03 M26
M22
M21
M24
Benoît DENIS
[email protected]
M16
M19
L08
M29
M23 M13
M20
M30
M18
L02 L07
L10
M11
M14
M17
M12
M25
L09
M27
L01
L06
M15
L04
M28
Fusing Accurate Positioning
Capabilities and Digital
Communications
Submission
Slide 2
Benoit Denis, CEA/LETI STMicroelectronics
August 2004
doc.: IEEE 802.15-04/418r0
Time Of Arrival (TOA) & Two Way Ranging (TWR)
T1
To
Terminal A
TX/RX
Terminal B
RX/TX
TOF
Terminal
A
Prescribed
Protocol
Request
Delay and/or
Processing
Terminal
Time
B
Submission
TOF
TReply
TOF Estimation

1
~
TOF A  T1  T0   TReply
2
~
~
d AB  TOF A .c
Slide 3

Benoit Denis, CEA/LETI STMicroelectronics
August 2004
doc.: IEEE 802.15-04/418r0
Time Of Arrival (TOA) & Two Way Ranging (TWR)
Main Limitations / Impact of Clock Drift on Perceived Time
TReply  A   B 
~
TOF A  TOF A 1   A  
21   B 
. f 0 Is the frequency offset relative to the nominal ideal frequency
f0
Range estimation is affected by :
•Relative clock drift between A and B
•Clock accuracy in A and B
•Prescribed response delay
Relaxing constraints on clock accuracy by
•Performing fine drift estimation/compensation
•Benefiting from cooperative transactions (estimated clock ratios…)
•Adjusting protocol durations (time stamp…)
Submission
Slide 4
Benoit Denis, CEA/LETI STMicroelectronics
August 2004
doc.: IEEE 802.15-04/418r0
Ex : DEV2PNC Ranging in the 802.15.3 Scenario
MAC resources for a double DEV2PNC TWR Transaction
•Beacon synchronization (PNC2DEV)
DEV-C
DEV-A
•Association procedure in MCTA slots
Imm-ACK or Dly-ACK (PNC2DEV) & Association Request (DEV2PNC)
•Time stamp (fixed retransmission times T’)
DEV-B
•Relative clock drift DEV / PNC available
PNC
•Correction of DEV’s Time Offset (propagation delay from PNC)
RefPNC
RefDEV
Transmitting to
DEV PNC’s TOF
Estimate
PNC’s TOF Estimate
T2’
T1
PNC
TOF
TOF
TOF
DEV
T1’
Beacon
Detection
PicoNet Synchronization
Submission
T2
DEV’s TOF
Estimate
Request
(Medium Access)
Acknowledgement
Receiving
PNC’s TOF
Estimate
MCTA (Slotted Aloha)
Slide 5
Benoit Denis, CEA/LETI STMicroelectronics
August 2004
doc.: IEEE 802.15-04/418r0
Time Of Arrival (TOA) & One Way Ranging (OWR)
To
T1
If Terminals are synchronized
to a common clock, direct
OWR can be used for Ranging
Terminal A
TX
Isochronous
Terminal B
RX
TOF
Terminal
A
TOF Estimation
Request
TOF Estimation
~
TOF B  T1  T0 
~
~
d AB  TOF B .c
Terminal
B
Isochronous
Submission
Slide 6
Benoit Denis, CEA/LETI STMicroelectronics
August 2004
doc.: IEEE 802.15-04/418r0
Ex : DEV2DEV Ranging in the 802.15.3 Scenario
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
RefPNC+ DEV-A’s Estimate
of TCA
Ts
RefPNC
RefPNC+
2Ts
DEV-B
DEV-A
TAB
DEV-B
TCA
DEV-B’s Estimate
of TAB
TBC
DEV-C’s
Estimate of TBC
DEV-C
Slot 1
Slot 2
Slot 3
CTA
Submission
Slide 7
Benoit Denis, CEA/LETI STMicroelectronics
August 2004
doc.: IEEE 802.15-04/418r0
Time Of Arrival (TOA) & One Way Ranging (OWR)
Main Limitations / Impact of Synchronization and Clock Drifts
on Perceived Time
~
TOF B  TOF 1   B    synchro
f 0 Is the frequency offset relative to the nominal ideal frequency f 0
Range estimation is affected by :
•Clock accuracy
•Uncertainty on the reference start times (synchronization)
Requirements
•Achieving fine synchronization between terminals prior to ranging
Submission
Slide 8
Benoit Denis, CEA/LETI STMicroelectronics
August 2004
doc.: IEEE 802.15-04/418r0
Positioning from TOA
3 anchors with known positions (at
least) are required to retrieve a 2Dposition from 3 TOAs
d1 
d2 
d3 
x
x
x
A1
 xM
A2
 xM
A3
 xM
  y
  y
  y
2
A1
 yM
(xA2,yA2)



2
2
A2
 yM
2
A3
 yM
2
2
Anchor 2
Anchor 1
(xA1,yA1)
Specific Positioning
Algorithms
Estimated Position
Measurements
~ ~ ~
d1 , d 2 , d3
Submission
Mobile
(xm,ym)
Anchor 3
(xA3,yA3)
~
xM , ~
yM
Slide 9
Benoit Denis, CEA/LETI STMicroelectronics
August 2004
doc.: IEEE 802.15-04/418r0
Time Difference Of Arrival (TDOA) & One Way Ranging (OWR)
Mobile
TX
TDOA Estimation
TOA Estimation
To
Anchor 1
RX
Anchor 1
TOF,1
Info
T2
T1
Isochronous
Anchor 2
RX
TOF,2
T2
Anchor 3
RX
Mobile
Info
T3
TOF,3
T3
Anchor 2
Anchor 3
Passive Location
TOA Estimation
T1 , T2 , T3
Submission
Info
T2
Info
T3
Isochronous
TDOA Estimation
~
~
~
T21  T1  T2  d 21  T21.c
~
~
~
T23  T3  T2  d 23  T23.c
Slide 10
Benoit Denis, CEA/LETI STMicroelectronics
August 2004
doc.: IEEE 802.15-04/418r0
Positioning from TDOA
Anchor 3
3 anchors with known
positions (at least) are
required to find a 2D-position
from a couple of TDOAs
(xA3,yA3)
Anchor 2
(xA2,yA2)
Mobile
Estimated Position
Measurements
~ ~
d32 , d31
d 32 
d 31 
x
x
Submission
~
xM , ~
yM
Specific Positioning
Algorithms
A3
 xM
A3
 xM
  y
  y
(xm,ym)
A3
 yM
A3
 yM
2
2


2
2


x
x
A2
 xM
A1
 xM
Slide 11
Anchor 1
  y
  y
2
A2
2
A1
 yM
 yM


(xA1,yA1)
2
2
Benoit Denis, CEA/LETI STMicroelectronics
August 2004
doc.: IEEE 802.15-04/418r0
Ex. of Possible Embodiment for TDOA/OWR based Systems
Serial Data Link
+ Timing Ref
Clock
RF RX &
Timing Pulse
Processor
RF RX &
Timing Pulse
Processor
Tag
RF RX &
Timing Pulse
Processor
Tag
Tag
Asynchronous
Tags to be
localized
Known Fixed
Locations
Tag
Tag
Tag
RF RX &
Timing Pulse
Processor
Base Control
Unit
Short Transmitted Packets + Asynchronous TX Tags = Infrequent Packet Collisions
Submission
Slide 12
Benoit Denis, CEA/LETI STMicroelectronics
August 2004
doc.: IEEE 802.15-04/418r0
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
Submission
Slide 13
Benoit Denis, CEA/LETI STMicroelectronics
August 2004
doc.: IEEE 802.15-04/418r0
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
Submission
Slide 14
Benoit Denis, CEA/LETI STMicroelectronics