1 Doc: IEEE 15-05-0383-03-004 19 July 2005 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: [Non-coherent ranging results with a-priori knowledge of noise variance] Date Submitted: [24 June 2005] Source: [Ismail Guvenc, Zafer Sahinoglu, Andy Molisch, Philip Orlik, Mitsubishi Electric] Contact: Zafer Sahinoglu Voice:[+1 617 621 7588, E-Mail: [email protected]] Abstract: [This document provides performance results of non- coherent ranging receivers, under the assumption that noise variance is accurately estimated and available a-priori] Purpose: [To help objectively evaluate ranging proposals under consideration] 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.
Transcript
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Doc: IEEE 15-05-0383-03-004a19 July 2005
Project: IEEE P802.15 Working Group for Wireless Personal Area Networks Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)(WPANs)
Submission Title: [Non-coherent ranging results with a-priori knowledge of noise variance]Date Submitted: [24 June 2005]Source: [Ismail Guvenc, Zafer Sahinoglu, Andy Molisch, Philip Orlik, Mitsubishi Electric]Contact: Zafer SahinogluVoice:[+1 617 621 7588, E-Mail: [email protected]]Abstract: [This document provides performance results of non-coherent ranging
receivers, under the assumption that noise variance is accurately estimated and available a-priori]
Purpose: [To help objectively evaluate ranging proposals under consideration]
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.
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Doc: IEEE 15-05-0383-03-004a19 July 2005
Outline
• Signal waveforms• Receiver architectures• Simulations• Summary• Recommendations
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Objective
• Study feasibility of non-coherent ranging• Evaluate ranging performance of various proposals
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Signal Parameters
Signal Energy ConditionerChannel
Characteristics
Signal Energy Collector
Signal
TOAEstimate
Signal Energy Edge Detector
Generic Architecture for Ranging
• Received signal energy is collected• Energy vector is processed to suppress noise artifacts and enhance signal containing
parts• Edge detection is performed
channel
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4 pulses
One Bit
Always EmptyAlways Empty Always Empty
4-pulses
Option-III (Ternary Sequences)
…………………………
1 2 3 314 5 6 7 8 30
Pulse Repetition Interval ~ 62.5ns
Option-IV (Pulse PPM)
Tp = 4ns
Tf = ~125ns
PRP ± TH
Option-I (Burst PPM) The Other Bit
Proposed System Parameters (With Same # Pulses per unit time)
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Technical Differences and CommonalitiesPulse OOK (option-III) Burst PPM (option-I) Pulse OOK (option-IV)
Energy Integration period (for ranging)
2~4ns 2~4ns 2~4ns
Type of receiver that can receive this Common signaling preamble
Coherent, differential & energy detector
Coherent, differential & energy detector
Coherent, energy detector
Symbol Duration 2us 2us 2us
Pulses per symbol 16 16 16
Pulses per microsecond 8 8 8
Edge per symbol 16 4 16
# of edges per us 8 2 8
Power per pulse P P P
Peak to Side Lobe Ratio (PSLR) - periodic
0 (at the cost of increased noise variance)
N/A 1/N
Peak Signal to Interference Ratio 6dB N/A 3dB
Zero Correlation Zone (periodic) Yes (symbol wide) N/A Yes (fraction of a symbol)
Noise Variance (noise only region) in 2us of preamble
32 Units 4 Units 16 Units
Noise Floor Level 1 Unit (16+, 15- in the bipolar correlation
template)
4 Units 16 Units
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Energy Detection Receiver Architectures
TOA Estimator
BPF
( )2
LPF / 2-4ns
integrator
ADC
1D to 2D Conversion
Length-3 Vertical Median or Minimum Filtering
Removes interference
2D to 1D Conversion with Energy Combining
Energy image generation
"Path-arrival dates" table
1D to 2D Conversion
Assumption path synchronization
Matrix
Filtering + Assumption/path
selectionTime base 1-2ns accuracy
Time stamping
Analog comparator
Sliding Correlator
Energy combining across symbols
interference suppression
1D-2D Conversion
2D-1D Conversion
Energy image generation
Bipolar template
MERL
I2R
FT R&D
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LOS Before and After Square-Law
• A 500MHz pulse (4ns duration) is passed through a channel sampled at 8GHz
• Received signal energy is collected at 4ns intervals• Strong LOS is lost
First arriving energy block
Strongest energy block
First arriving and strongest path
Channel realization
Energy collection at 4ns
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Another exampleChannel realization
Energy collection at 4ns
With a search back window of 32ns, in this realization the first energy block is missed (the error was 4 energy blocks (2ns +3*4ns = 14ns)
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Fixed Search Back
• Fixed search back window length is not very efficient
p
Strongest energy block
x
First signal energy
z
Fixed search back window
t
threshold
y
First threshold crossing within 430 (TOA estimate)
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Threshold Selection
• Assume that µn and σn2 mean and the variance of the
noise respectively• Probability that a noise only sample greater than a
threshold ε is
• Probability of threshold crossing within K consecutive noise only samples
• The corresponding threshold is
)()(n
nQxP
K
n
nfa QP
)(11
nK
fan PQ /11 )1(1PFA ε
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Adaptive and Iterative Search Back
• K-iterative search back deals with K consecutive noise only blocks• As long as a cluster is detected backward, the search back continues
z
Strongest energy block
x
First signal energy
p
noise dependent thresholdy
Iterative search back
0123nn+1n+2n+3 Energy block index
Friday, April 21, 2023
Doc: IEEE 15-05-0363-01-004a
Ts3 = 2048ns*
Ts1 = Ts
4 = 512ns
TOA Ambiguity = 256ns
Observation window = 512ns
Option 3(16 pulses per 2us)
Option 1 **(16 pulses per 2us)
Option 4 (16 pulses per 2us)
* Since option-3 uses 31 chip sequences, 1984ns symbol duration is used for option-3 to have multiples of 4ns sampling duration. However, total energy used within 4ms duration are identical for all cases.** A training sequence of all 1’s are used. Random training sequence will introduce self interference that will degrade the performance.
Simulation Settings
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Results
• PFA = 0.01, TB = 4ns
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Results
• PFA = 0.005, TB = 4ns
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Results
• PFA = 0.001, TB = 4ns
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Results
• PFA = 0.05, TB = 2ns
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Results
• PFA = 0.01, TB = 2ns
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Results
• PFA = 0.005, TB = 2ns
Friday, April 21, 2023
Doc: IEEE 15-05-0363-01-004a
TransmittedTime-hoppingSequence
ACF of the TransmittedTime-hoppingSequence
Zero Correlation Zone
Received energysamples (after processed with the time-hopping code)
Multipath components
Peak
Search-back the leading edge
Leading Edge
Anomaly in Option-4
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Summary
• A-priori knowledge of noise variance improved ranging performance• Threshold is set according to the noise variance and
probability of missing a block, not according to the percentage of the highest signal energy block– This made option-4 suffered.
• Option-1 performed the best both in terms of 3ns confidence level and mean absolute error (MAE).– Increasing the sampling rate gained us 2dB
• 3ns 90% confidence level around 13dB at 2ns sampling interval• The MAE is appr. 2ns at 13dB with 2ns sampling interval
• In order to have SOP support, symbol duration should be prolonged in option-1– This lowers the achievable bit rate (<1Mbps)
• Coherent processing is faster with burst PPM
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Recommendation to the IEEE 802.15.4a TG
• Lower the bit rate from 1Mbps to 500Kbps– This will provide
• Non-coherent with option-1 with better SOP support
• Better non-coherent ranging
• Adopt option-1 waveform in preamble
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For an Even Better Ranging Performance
~512 ns
T1 (time-hopping margin)
Multipath tolerance
symbol with 0-ns time hopping
TH1
symbol with TH1 nanosecond burst time hopping
• Bursts are coarsely time-hopped• Can be integer multiples of BRI
M-chip times
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Backup Slide
• EBN0 = 22dB, Interference and desired equidistant to the receiver
• Strong SOP interference is easily suppressed by the way the image is created and by means of length-3 minimum filtering (in ranging)
