July 2005 France Telecom doc.: IEEE a Submission Slide 3 CONTENT 1.General description of the system 2.Focus on the synchronization process, including simulation results 3.Specificities for ranging applications, including first simulation results 4.Conclusion
25
July 2005 France Telecom doc.: IEEE 802. 15-05-0421- 00-004a Submiss ion Slide 1 Project: IEEE P802.15 Working Group for Wireless Personal Area Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Networks (WPANs) Submission Title: Simulation results of non-coherent reception based system proposed for the Low Rate alt-PHY (802.15.4a) Date Submitted: 15th July 2005 Source: Patricia Martigne Company: France Telecom R&D Address: 28 Chemin du Vieux Chêne – BP98 – 38243 Meylan Cedex - France Voice: +33 4 76 76 44 03 E-Mail: [email protected]Abstract: Simulation results related to low rate and ranging applications Purpose: This document shows some simulation results obtained for non-coherent receivers using UWB-IR technology as proposed by FT R&D fellows 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
Transcript
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 1
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: Simulation results of non-coherent reception based system proposed for the Low Rate alt-PHY (802.15.4a)Date Submitted: 15th July 2005Source: Patricia MartigneCompany: France Telecom R&DAddress: 28 Chemin du Vieux Chêne – BP98 – 38243 Meylan Cedex - FranceVoice: +33 4 76 76 44 03E-Mail: [email protected]: Simulation results related to low rate and ranging applications
Purpose: This document shows some simulation results obtained for non-coherent receivers using UWB-IR technology as proposed by FT R&D fellowsNotice: 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
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 2
UWB-Impulse Radio (IR) with Time-Hopping coding
non-coherent reception
Simulations performed by Patricia MARTIGNE, Benoit MISCOPEIN, Jean SCHWOERER
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 3
CONTENT
1. General description of the system2. Focus on the synchronization
process, including simulation results3. Specificities for ranging applications,
including first simulation results4. Conclusion
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 4
UWB-IR based systemImpulse-radio (IR) based:
– Very short pulses Reduced ISI– Robustness against fading– Episodic transmission (for LDR) allowing
long sleep-mode periods and energy savingTime Hopping coding:
– Multiple access management– Timing approach used for efficient
synchronization– Smoothing the spectrum
Low-complexity implementation (OOK modulation, pulse repetition for robustness of the transmitted symbol)
1. General description
2. Synchronization process
3. Ranging applications
4. Conclusion
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 5
UWB-IR based system• 8 pulses per symbol• Use of an 8-ary Time Hopping code of length 8
– Use of such a TH code combined with the band plan may allow to handle the SOP issue
– Code order and length are scalable to meet different requirements
• Main Goal : "Low cost & low consumption".– Pulses are generated in baseband.– No mixer, no VCO but pulse shaping.– Simple control logic and "reasonable" clock frequency (Crystal)
1- General description
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 7
UWB-IR Receiver• Energy detection technique rather than coherent
receiver, for relaxed synchronization constraints.
• Threshold detection (no A/D conversion).– The threshold is set by the demodulation
block at each symbol time, if needed.
• Synchronization fully re-acquired for each new packet received (=> no very accurate timebase needed).
1- General description
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 8
BPF
UWB-IR non-coherent Receiver
Time base 1-2ns accuracy
Analog comparator
LPF / 2-4ns
integrator
( )2
Time stamps
1st path detection
Synchro / demodulation :
Communication applications
Ranging applications
Reception • performs an energy detection • and creates a {thresholder , timebase} couple, in order to timestamp the threshold crossings.
1- General description
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 9
Each time the signal amplitude exceeds a given threshold, a timestamp is associated to this event and can be exploited by the digital part.
Analog signal conditioning
Digital signal
processingTime base
1- General descriptionUWB-IR non-coherent Receiver
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 10
UWB-IR non-coherent Receiver
Symbol detection
1- General description
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 11
Synchronization algorithm for non-coherent receivers
During a synchronization preamble of unmodulated symbols, the algorithm used consists in
• parsing the received timestamps,• so as to identify a known Time Hopping
sequence.
Simulations have been performed to validate the performances of such an algorithm, in terms
• of accuracy, and • of mean elapsed time in acquisition.
1. General description
2. Synchronization process
3. Ranging applications
4. Conclusion
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 12
Packet Acquisition & Synchronization
The synchronization algorithm • detects the threshold crossings, and • updates an assumption matrix, which can also be viewed as a
tree exploration
i Detected edge for t_pos(i)
i No edge detection for t_pos(i)
?
2
3
43
4
Δ1,2
Δ2,3
Δ3,4
Δ2,3 Δ3,4
=? Time base origin determination
Δi,j = Known time offset between the pulses appearance, with respect to the TH code.
2- Synchronization process
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 13
Packet acquisition & Synchronization
The threshold level is set to detect a number of crossings consistent with the expectations (known time hopping sequence)
For any tested Channel Model, the synchronization is properly acquired
(during the Synch preamble)
Measured accuracy is around several 100s of ps.
2- Synchronization process
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 14
Time needed for synchronization2- Synchronization process
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 15
Time needed for synchronization
The synchronization is quickly acquired : in CM1 condition it is acquired in less than 2 symbol times for a
range of 50 meters in CM2, CM3 or CM5 condition it is acquired in less than 5
symbol times for a range of 30 meters
The synchronization is achievable within the 32 bytes synchronization preamble.
Simulation results
2- Synchronization process
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 16
Time accuracy during synchronization
Timing retrieval accuracy :
the tolerance window, set up for the timestamps validation, is centered around the theoretical position and is set to a width of 1.25ns
mean synchronization accuracy obtained in this simulation is 625ps
This value is precise enough to ensure a correct data demodulation
Considering that 625 ps represents a distance of 19 cm, this accuracy is fully consistent with the UWB-IR ranging capabilities.
Simulation results
2- Synchronization process
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 17
Accuracy vs. tolerance width (for CM2)
2- Synchronization process
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 18
Accuracy vs. tolerance width (for CM2)
Simulation results• CM2 model,
• 30 meter range, • several widths have been tested for the tolerance window: wt = 16, 20, 32, 40 For each width, a standard deviation has been computed. Mean elapsed time to acquire the synchronization (tsynch) as well as the related standard deviation for each window width are gathered in the table. To illustrate the tolerance window width dependance of the synchronization accuracy, each case is represented by a centered normal distribution on the figure.
When setting the window width from 2.5 ns to 1 ns, the standard deviation of the synchronization error is divided by 2 but the required time for acquisition encounters a 40 % increase.
Tslot/32 = 1.25 ns appears as an acceptable value in this case.
2- Synchronization process
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 19
Ranging applicationsOnce the synchronization is acquired, the system
may be used either for communication applications or for ranging applications (slide 8).
The latter one is particularly challenging for non-coherent receivers when accurate ranging measurements (less than 1 meter accuracy) are aimed at.
The ranging technique is based on the synchronization acquisition algorithm, aiming at detecting the direct path.
1. General description
2. Synchronization process
3. Ranging applications
4. Conclusion
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 20
BPF
UWB-IR non-coherent receiver for ranging
"Path-arrival dates" table
1D to 2D Conversion
Assumption path synchronization
Matrix
Filtering + Assumption/path
selectionTime base 1-2ns accuracy
Time stamping
Analog comparator
LPF / 2-4ns
integrator
( )2
3- Ranging applications
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 21
Leading edge detection
• Simulations have been performed for CM1 model, over a 50µs preamble (40 symbols)
• They provide the accuracy in 1st path detection obtained for a given Signal to Noise Ratio at the receiver antenna (input to the band pass filter)
• Graphs are given for a (SNR)ANT between -9,5dB and -1dB (corresponding to a Esymbol/E0 ranging from around 20dB to 28dB)
Simulation results
3- Ranging applications
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 22
Leading edge detectionSimulation
results
3- Ranging applications
1st path detection Accuracy
0
0,5
1
1,5
20 22 25 28
Esymb/N0 (dB)
Accu
racy
(ns)
CM1 - 50µs preamble
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 23
Leading edge detectionSimulation
results
3- Ranging applications
Some more simulations are on going to obtain results with other channel models to have a look at the accuracy obtained with
longer preambles (500µs, 4ms)
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 24
UWB-IR non-coherent schemes for IEEE 802.15.4a targeted applications
The proposed non-coherent reception concept• has an efficient behaviour in synchronization,
using a time-stamping process with less than 700ps accuracy (accuracy for the detection of the strongest path)
• provides 1st path-detection for ranging applications with an accuracy of typ. some hundreds of ps
• is still simple-designed, meeting 802.15.4a PAR goals of low complexity and low cost.
1. General description
2. Synchronization process
3. Ranging applications
4. Conclusion
4- Conclusion
July 2005
France Telecom
doc.: IEEE 802. 15-05-0421-00-004a
Submission
Slide 25
UWB-IR non-coherent schemes for IEEE 802.15.4a targeted applications
1. General description
2. Synchronization process
3. Ranging applications
4. Conclusion
4- Conclusion
This first set of simulations is showing the relevance of considering this kind of
UWB-IR non-coherent receivers, using Time Hopping coding,
