1. November 2004
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Enhancement of Ranging & Positioning by Combining TOA & TDOA]
Date Submitted: [21 July, 2005]
Source: [Kwan-Ho Kim(1), Sungsoo Choi(1), Youngjin Park(1), Hui-Myoung Oh(1), Yoan Shin(2),
Won Cheol Lee(2), and Ho-In Jeon(3)] Company: [(1)Korea Electrotechnology Research Institute(KERI), (2)Soongsil University(SSU), and (3)Kyung-Won University(KWU)]
Address: [(1)665-4, Naeson 2-dong, Euiwang-City, Kyunggi-do,Republic of Korea (2) 1-1, Sangdo-5-dong, Dongjak-Gu, Seoul, Republic of Korea (3)San 65, Bok-Jeong-dong, Seongnam, Republic of Korea]
Voice:[(1) , (2) , (3) ], FAX: [(1) , (2) , (3) ],
Re: []
Abstract: [This document proposes proposal for the IEEE alternate PHY standard.]
Purpose: [Final Proposal for the IEEE a standard]
Notice: This document has been prepared to assist the IEEE P 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 P
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

2. Enhancement of Ranging & Positioning by Combining TOA & TDOA
November 2004
Enhancement of Ranging & Positioning by Combining TOA & TDOA
KERI-SSU-KWU
Republic of Korea
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

3. Contents Introduction Signal waveforms
November 2004
Contents
Introduction
Signal waveforms
Energy Detection Receiver Architecture
Enhancement Ranging and Positioning based on TOA and TDOA Method
Simulation results
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

4. November 2004
Introduction
KERI, SSU, and KWU proposed a Ranging and Positioning Scheme based on SORP.
SORP provides a low power, low cost, non-coherent ranging and positioning.
It, however, suffers from the clock drift error due to many number of signal transmission.
Ternary codes with Time Hopping for the provision of SOP supportability has been adopted for our simulation
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

5. Signal waveform using Ternary code
November 2004
Signal waveform using Ternary code
Ranging Preamble can be constructed by repeating ternary code
TOA information is obtained accumulation across PRI
Integrator integrates over the 1.5 ns
60ns
1920ns
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

6. Signal waveform using TH & Ternary code
November 2004
Signal waveform using TH & Ternary code
To mitigate SOP interference, each piconet is assigned a different time hopping sequence.
Ex) Piconet 1 =
In addition to ‘0’, the number of 32 ternary code is used.
60ns
1920ns
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

7. First Energy Detection Receiver Architecture
November 2004
First Energy Detection Receiver Architecture
RER
ADC
Accumulator
BPF
( )2
LPF/
Integrator
Window Buffers
Accumulator
offset
DC level
estimator
Sliding
Correlator
Coarse/Fine
Timing Detector
ToA Information
Energy detector yields an energy signal w.r.t received signal.
Analog LPF operates to provide the DC offset.
DC bias existing on the input to ADC is removed.
RER(Ranging Error Reduction) may reduce the noise suppression and eliminate the uncertainty of the first path arrival.
Fine ranging can be provided by the estimated TOA through comparator with the predetermined threshold.
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

8. Energy Detection Receiver Architecture
November 2004
Energy Detection Receiver Architecture
Integrator integrates over the 1.5ns
Sliding Correlator 1 : In the initialization process, the transmitted TH code is estimated by using the sliding correlation of TH mask.  Alleviates the problem of SOP interference
Sliding Correlator 2 : Estimate the first arrival time by performing the correlation.
Sliding
Correlator 2
Energy
Combining
ToA
Estimator
BPF
( )2
LPF/
Integrator
ADC
1D  2D
1D  2D
Rearrange
Sliding
Correlator 1
TH code
detection
2D  1D
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

9. Initialization process to find TH code
November 2004
Initialization process to find TH code
TH mask set
ADC
1D  2D
Sliding
Correlator
2D  1D
TH code 획득
Preamble length 1 2 3 M
M+1
M+2
M+3
M+K
SFD
Payload 1 2 N
1D  2D Th
Tpri
TH mask set
N = 4 M = K = 12
2D  1D
Acquire corresponding TH code
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

10. TOA detection process Sliding windowing TH mask November 2004 ADC
ToA Estimator Th
Tpri TP
ADC
1D  2D
Sliding
Correlator
Energy
Combining
Preamble length 1 2 3 M
M+1
M+2
M+3
M+K
SFD
Payload
Acquisition
Channel sounding 1 2 N
TH mask
Sliding windowing
1symbol
2symbol
1D  2D
Energy window idex
Ternary mask
TOA Estimator
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

11. Process of SORP Scheme with TOA/TDOA [doc. 0615-01]
November 2004
Process of SORP Scheme with TOA/TDOA [doc ]
P_FFDs :
Independent
operation
Unknown
Universal Reference Time
causing T_offset
TOA measurement
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

12. More Details of SORP for Obtaining TDOAs
November 2004
Distances among the positioning FFDs are calculated from RTT measurements and known time interval T
Using observed RTT measurements and calculated distances, TOAs/TDOAs are updated
RTT12 = T + 2T12
RTT23 = T + 2T23
RTT13 = T12 + 2T + T23 + T13
T12 = (RTT12 – T)/2
T23 = (RTT23 – T)/2
T13 = (RTT13 – T12 – T23 – 2T)
RTT34 = T34 + T + T34
TOA34 = (RTT34 - T)/2
RTT24 = T23 + T + T34 + T + T24
TOA24 = (RTT24 - T23 - TOA34 - 2T)
RTT14 = T12 + T + T23 + T + T34 + T + T14
TOA14 = (RTT14 - T12 - T23 - TOA34 - 3T)
TDOA12 = TOA14 – TOA24
TDOA23 = TOA24 – TOA34
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

13. Ranging Error due to Clock Drift
November 2004
Ranging Error due to Clock Drift
tp : propagation delay
TAT
TBR
reply time(T)
Device A
Device B
to : clock drift
TAR
TBT
Assumptions :
tp : 30 ns, reply time(T) : 1 ms
Device A : +10PPM, Device B : -10PPM
tp = ((TAR – TAT) - (TBR – TBT))/2
= ((1e-3+60e-9)(1+10e-6) – (1e-3)(1-10e-6))/2
= ( e-3 – 1e e-8 + 1e-8)/2
= 40ns
Longer Reply time cause more effect due to clock drift
Timing error of 10ns causes Ranging Error of 3m.
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

14. TOA, TDOA Ranging Method(1)
November 2004
TOA, TDOA Ranging Method(1)
The ranging error due to Clock drift can be avoided by using SDS-TWR(IEEE ) and difference of long term(TT)
Ranging can be obtained by TOA and TDOA
Robust to GDOP problem
Ranging performance can be enhanced by using threshold of energy level.
TDOA Ranging(only)
TDOA & TOA Ranging
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

15. TOA, TDOA Ranging Method
November 2004 TT
RTTT_A T
TAG
TT’
Reference B
RTTA_T
Master
: TX
Beacon A
TOAT_A T’
TT’’
Reference C
mA_B
TAG
: RX
Master
Beacon B
TOAT_B
TA_B
TT’’’
Reference A
mB_C
Beacon C
TOAT_C
TA_C
TOAT_A = ((RTTT_A – T) + (RTTA_T – T’))/4
TOAT_B = (TOAT_A + T’ + TA_B) – mA_B  ’’
where, ’’ = (TT’’/TT) mA_B
TOAT_C = (TOAT_A + T’ + TA_C) – mB_C  ’’’
where, ’’’ = (TT’’’/TT) mB_C
TDOAA_B = TOAT_B – TOAT_A
TDOAA_C = TOAT_C – TOAT_A
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

16. Comparison between proposed ranging types
November 2004
Comparison between proposed ranging types
Mode 1
Mode 2
Proposed Mode
Reference B
Reference B
Reference B
sync
sync
sync
Reference C
Reference C
TAG
TAG
TAG
Reference C
Master
Master
Master
Reference A
Reference A
Reference A
Type
Mode1
Mode2
Pro_Mode
SORP
Information for Ranging
TDOA
TDOA +TOA
TDOA+TOA
Ranging Performance in Bad GDOP
Poor
Good
The number of communication 5 7
Needed function of TAG Rx Tx
Tx, Rx
TOA or TDOA accuracy Assumption : Error due to clock offset =  Error due to clock drift =  6 9
9+3
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

17. Parameter conditions(1)
November 2004
Terms
Definition
Value in Simulations Tp
Pulse duration
2 ns Tf
Pulse repetition interval
60 ns Tb
Symbol duration
1920 ns
Sample Period
Sampling interval
0.025 ns
# of Preamble Symbols
The number of Symbols 12
Win_Bank Size
Integration size
1.5 nsec
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

18. Simulation results(1)
November 2004
- Channel Model : Residential LOS environment(CM1)
- Eb/No : 9dB
BPF
( )2
LPF/
Integrator
ADC
1D  2D
Sliding
correlator
I2R Ranging method
Sliding
correlator
1D  2D
Accumulator
Coarse TOA
Fine TOA
Proposed Ranging method
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

19. November 2004
Simulation results(2)
- Channel Model : Residential LOS Environment (CM8)
- Eb/No : 9dB
BPF
( )2
LPF/
Integrator
ADC
Sliding
correlator
Leading edge
The detection of leading edge depends on the threshold of ADC.
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

20. Parameter Conditions (2)
November 2004
Parameter Conditions (2)
4bytes
Terms
Value in Simulations tp
2 nsec th
15 nsec
tpri
60 nsec
thpri
480 nsec ts
1.92 sec
Integration length
1.5 nsec
Bandwidth
2 GHz
Sampling period
0.025 nsec
Preamble length
4bytes
The number of bit per symbol 2
Preamble
SFD
Payload 1 2 3 4 5 6 16 ts 1 2 4
thpri 1 2 3 4 5 6 8
tpri 1 2 4 th
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

21. Simulation results(1) Initialization for detecting TH code
November 2004
Simulation results(1)
Initialization for detecting TH code
TH code set
1D  2D
Sliding
Correlator 1
2D  1D
TH code
detection
BPF
( )2
LPF/
Integrator
ADC
Simulation Conditions
Clock speed : 500MHz
Channel model : CM1
Analog integration size : 1.5ns
8-ary TH code : Barker code used
Eb/No = 9dB
1D  2D
Integrate over th(15ns) and rearrange it in 2D array at thPRI (480ns)
Sliding Correlator1
Correlate the signal with TH code
2D  1D
Energy Combining
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

22. November 2004
Simulation results(2)
Process to detect leading edge using Ternary code mask
TH code
mask
Sliding
Correlator 2
Energy
Combining
ToA
Estimator
BPF
( )2
LPF/
Integrator
ADC
1D  2D
Leading edge
1D  2D
Rearrange in 2D Array at thPRI (480ns)
Sliding Correlator2
Correlate the signal with Ternary code mask
Energy
Combining
Combine them at ts.
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

23. November 2004
Conclusion (1/2)
Suggested an enhanced Ranging and Positioning Mechanism based on Energy Detection receiver.
Option I
Signal waveform : Same as I2R’s proposal
Ternary code has been used to estimate the arrival time
Could find an accurate arrival time by using noise reduction method and accumulations.
Option II
Signal waveform : Combination of Timing Hopping and Ternary Code
Robust to SOP interference.
TH code has been used to estimate the rough receiving time.
Accurate timing has been obtained by using Ternary and its correlations.
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

24. November 2004
Conclusion (2/2)
It does not guarantee a good result when the PRI is not large enough.
Combination of TOA with TDOA provided better ranging and positioning performance.
Could provide better performance for the bad GDOP case.
The performance of ranging can be enhanced to a great extent when a proper selection of threshold level can made.
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon

25. November 2004
Acknowledgment
This work has been supported partly by HNRC of IITA and TTA.
K. Kim, S. Choi, Y. Park, H. Oh, Y. Shin, W. Lee, and H. Jeon