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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: Mitsubishi-electrics-time-hopping-impulse-radio-standards-presentation Date Submitted: November 15, 2004 Source: Andreas F. Molisch et al., Mitsubishi Electric Research Laboratories - PowerPoint PPT Presentation
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Molisch et al., Preliminary ProposalSlide 1
doc.: 15-05-0005-02-004a
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: Mitsubishi-electrics-time-hopping-impulse-radio-standards-presentation Date Submitted: November 15, 2004Source: Andreas F. Molisch et al., Mitsubishi Electric Research LaboratoriesAddress MERL, 201 Broadway Cambridge, MA, 02139, USA Voice: +1 617 621 7558, FAX: +1 617 621 7550 , E-Mail: Andreas.Molisch@ieee.org
Re: [Response to Call for Proposals]
Abstract:
Purpose: [Proposing a PHY-layer interface for standardization by 802.15.4a]
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.
Molisch et al., Preliminary ProposalSlide 2
doc.: 15-05-0005-02-004a
Submission
Ultra WideBand
Mitsubishi Electric Proposal
Impulse Radio
A. F. Molisch, Z. Sahinoglu, P. Orlik, J. ZhangMitsubishi Electric Research Lab
M. Z. WinMassachusetts Institute of Technology
S. GeziciPrinceton University
Y. G. LiGeorgia Tech University
Molisch et al., Preliminary ProposalSlide 3
doc.: 15-05-0005-02-004a
Submission
Contents
– Proposal overview – Goals
– Impulse radio basics
– Proposed hybrid modulation
– Physical-layer details
– Simulation results
– Ranging
– Summary and conclusions
Molisch et al., Preliminary ProposalSlide 4
doc.: 15-05-0005-02-004a
Submission
Goals• Provide a system that can work with different
modulation and detection methodsAllows trade-offs among transmitter and receiver
complexity/cost/performance Works with a variety of signaling (modulation) methods
and pulse shapesEnables different receiver structures: coherent,
differential, incoherent
• Propose concrete system based on optimized technologies for impulse radio transceivers
• Share ideas with other 4a members in the hope of working together.
Molisch et al., Preliminary ProposalSlide 5
doc.: 15-05-0005-02-004a
Submission
Impulse Radio Basics
Molisch et al., Preliminary ProposalSlide 6
doc.: 15-05-0005-02-004a
Submission
Time Hopping Impulse Radio (TH-IR)
Ts
Tc
Tf
+1
-1
• Each symbol represented by sequence of very short pulses
• Each user uses different sequence (Multiple access capability)
•Bandwidth mostly determined by pulse shape
Molisch et al., Preliminary ProposalSlide 7
doc.: 15-05-0005-02-004a
Submission
TH-IR Coherent RAKE Receiver
Rake ReceiverFinger Np
AGC
Rake ReceiverFinger 2
Rake ReceiverFinger 1
SummerConvolutional Decoder Data
Sink
Optimum receiver for multipath channels
Molisch et al., Preliminary ProposalSlide 8
doc.: 15-05-0005-02-004a
Submission
Transmitted Reference
Ts
TcTf
Td
+1
-1
•First pulse serves as template for estimating channel distortions
•Second pulse carries information
•Drawback: Waste of 3dB energy on reference pulses
reference
data
Molisch et al., Preliminary ProposalSlide 9
doc.: 15-05-0005-02-004a
Submission
Transmitted Reference Receiver – Differentially Coherent
Td
0
Convolutional Decoder
Advantage: Simple receiver
Molisch et al., Preliminary ProposalSlide 10
doc.: 15-05-0005-02-004a
Submission
Proposal – Hybrid TR and TH-IR Modulation
Molisch et al., Preliminary ProposalSlide 11
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Submission
Motivation
• Different applications require different performance
• Vendors want to differentiate themselves• 802.15.4 already has different device types
• We provide proposal that allows trade-offs among complexity/capability/cost and performance– Enables simple receivers without penalizing more complex
ones
Molisch et al., Preliminary ProposalSlide 12
doc.: 15-05-0005-02-004a
Submission
Heterogeneous Network Architectures
Coherent Rx
Differential Rx
Modulation supports homogenous and
heterogeneous network architectures
Longer range when both transceivers are coherent
Molisch et al., Preliminary ProposalSlide 13
doc.: 15-05-0005-02-004a
Submission
Proposed Transmitter
Pulse Gen.TH Seq
BPSK symbol mapper
BPSK symbol mapper
Delay
Central Timing Control
Multiplexe
r
Td
0
Rake ReceiverFinger Np
Rake ReceiverFinger 2
Rake ReceiverFinger 1
Summer
One Transmitter Enables Multiple Receiver Types
Molisch et al., Preliminary ProposalSlide 14
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Submission
Ts
Proposed Transmitter Structure – Sample Waveform
+1 -1 +1 -1 +1 -1
-1 -1 +1 +1 -1 -1
0 0 1 1 0 0 1
b0 b4b3b2b1 b5b-1
Tx Bits
Reference Polarity
Data Pulse Polarity
Molisch et al., Preliminary ProposalSlide 15
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Submission
Physical Layer Details
Molisch et al., Preliminary ProposalSlide 16
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Submission
Proposed Transmitted Reference Receiver – Differentially Coherent
Td
0
MatchedFilter
Convolutional Decoder
•Addition of Matched Filter prior to delay and correlate operations improves output signal to noise ratio and reduces noise-noise cross terms
SNR of decision statistic
Molisch et al., Preliminary ProposalSlide 17
doc.: 15-05-0005-02-004a
Submission
Proposed RAKE -- Coherent Receiver
Rake ReceiverFinger Np
Demultiplexer Rake ReceiverFinger 2
Rake ReceiverFinger 1
Summer
Channel Estimation
Convolutional Decoder Data
Sink
Sequence Detector
• Addition of Sequence Detector – Proposed modulation may be viewed as having memory of length 2• Main component of Rake finger: pulse generator• A/D converter: 3-bit, operating at symbol rate• No adjustable delay elements required
Molisch et al., Preliminary ProposalSlide 18
doc.: 15-05-0005-02-004a
Submission
Channel Estimation
• Swept delay correlator
• Principle: estimating only one channel sample per symbol. Similar concept as STDCC channel sounder of Cox (1973).
• Sampler, AD converter operating at SYMBOL rate (1.2 MHz)
• Requires longer training sequence
• Two-step procedure for estimating coefficients:– With lower accuracy: estimate at which taps energy is significant
– With higher accuracy: determine tap weights
• “Silence periods”: for estimation of interference
Molisch et al., Preliminary ProposalSlide 19
doc.: 15-05-0005-02-004a
Submission
Multiple Access
• Multiple access:– Combination of pulse-position-hopping and polarity
hopping for multiple access
– More degrees of freedom for design of good hopping sequence than pure pulse-position-hopping
– Short or long hopping sequences possible
• Long hopping sequence == period of sequence > Number of frames in a symbol.
Molisch et al., Preliminary ProposalSlide 20
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Submission
Spectral Shaping & Interference Suppression (Optional)
• Basis pulse: use simple pulse shape gaussian, raised cosine, chaotic, etc.
• Drawbacks:– Possible loss of power compared to FCC-allowed power– Strong radiation at 2.45 and 5.2 GHz
frequency (Hz)
Monocycle, 5th derivative of gaussian pulse
Power spectral density of the monocycle
10
log
10|P
(f)|
2 d
B
Molisch et al., Preliminary ProposalSlide 21
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Submission
Linear Pulse Combination
• Solution: linear combination of delayed, weighted pulses– Adaptive determination of weight and delay
– Number of pulses and delay range restricted
– Can adjust to interferers at different distances
(required nulldepth) and frequencies
• Weight/delay adaptation in two-step procedure• Initialization as solution to quadratic optimization problem (closed-
form)
• Refinement by back-propagating neural network
• Matched filter at receiver good spectrum helps coexistence and interference suppression
Molisch et al., Preliminary ProposalSlide 22
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Submission
Spectral Shaping & Polarity Scrambling
Td = 10 ns
Td = 20 ns
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
x 1010
-220
-210
-200
-190
-180
-170
-160
-150
-140
-130
-120
W/ Polarity ScramblingW/O Polarity Scrambling
Molisch et al., Preliminary ProposalSlide 23
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Submission
Adaptive frame duration
• Advantage of large number of pulses per symbol:– Smaller peak-to-average ratio
– Increased possible number of SOPs
• Disadvantage:– Increased interframe interference
– In TR: also increased interference from reference pulse to data pulse
• Solution: adaptive frame duration– Feed back delay spread and interference to transmitter
– Depending on those parameters, TX chooses frame duration
Molisch et al., Preliminary ProposalSlide 24
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Submission
Parameters
• Modulation & coding– Hybrid-impulse radio (slides 12-13)– Pulse shape – 5th derivative gaussian (0.5 ns pulse width)– Symbol rate 1.21 Msym/sec– Td = 20nsec; 20 frames/symbol– Rate ½ convolutional code
• Constraint length = 7• polynomial [117, 115]octal
• Receivers– Matched filter differential receiver (slide 16)
• Filter matched to reference pulse sequence– Coherent RAKE (slide 17)
• 10 fingers with MR combining• Length 2 sequence detector
• Channel model version 7 was used for all results will update with version 8 at march meeting
Molisch et al., Preliminary ProposalSlide 25
doc.: 15-05-0005-02-004a
Submission
PER Performance Coherent Reception (CM1 & AWGN)
608 Kbps, Td = 20ns, 20 Frames per symbol,
10 RAKE fingers
Molisch et al., Preliminary ProposalSlide 26
doc.: 15-05-0005-02-004a
Submission
PER Performance Differential Reception (CM1 & AWGN)
608 Kbps, Td = 20ns, 20 Frames per symbol
Modified Match Filter Differential Receiver
Molisch et al., Preliminary ProposalSlide 27
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Submission
SOP PER Performance Coherent Reception (CM1)
608 Kbps, Td = 20ns, 20 Frames per symbol, Reference distance = 58 meters
10 RAKE fingers used in receiver
7 meter separation distance
Molisch et al., Preliminary ProposalSlide 28
doc.: 15-05-0005-02-004a
Submission
SOP PER Performance Differential Reception (CM1)
608 Kbps, Td = 20ns, 20 Frames per symbol, reference distance = 23 meters
Modified Match Filter Differential Receiver
8 meter separation distance
Molisch et al., Preliminary ProposalSlide 29
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Submission
Link BudgetParameter
Differential Rx Coherent Rx
Throughput (Rb) 608 K b/s 608 Kb /s
Average Tx power ( TP ) -4.3 dBm -4.3 dBm
Tx antenna gain ( TG ) 0 dBi 0 dBi
maxmin' fff c : geometric center frequency of
waveform ( minf and maxf are the -10 dB edges
of the waveform spectrum)
5.73GHz 5.73GHz
Path loss at 1 meter ( )/4(log20 '101 cfL c
)
8103c m/s
47.6 dB 47.6 dB
Path loss at d m ( )(log20 102 dL ) 29.54 dB at d=30 meters
29. 54 dB at d=30 meters
Rx antenna gain ( RG ) 0 dBi 0 dBi
Rx power ( 21 LLGGPP RTTR (dB)) -81.4 dBm -81 .4 dBm
Average noise power per bit ( )(log*10174 10 bRN )
-11 6.2 dBm -116 .2 dBm
Rx Noise Figure Referred to the Antenna Terminal ( FN )1
7 dB 7 dB
Average noise power per bit ( FN NNP ) -109 .2 dBm -109.2 dBm
Minimum E b/N 0 (S) 12 dB 6 dB
Implementation Loss 2 (I) 3 dB 3 dB
Link Margin ( ISPPM NR ) 12.8 dB 18 .8 dB
Proposed Min. Rx Sensitivity Level 3 -94 .2 dBm - 100 .2 dBm
Molisch et al., Preliminary ProposalSlide 30
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Submission
Narrowband Interference
802.11a In-Band Tone
In-Band Modulated Tone
Coherent <1m <1m <1m
Differential <1m <1m <1m
DUT is operating in CM1
Molisch et al., Preliminary ProposalSlide 32
doc.: 15-05-0005-02-004a
Submission
Two Step Ranging Algorithm
• Step-I: – Estimate rough TOA of the incoming signal in a time
window by detecting received signal energy
• Step-II:– Determine the arrival time of the first signal path by
using hypothesis testing (change detection)
3.6MHz
Molisch et al., Preliminary ProposalSlide 33
doc.: 15-05-0005-02-004a
Submission
Step-I: Energy Detection
TRF =531.14ns TRB = 26.56ns
1 2 … NB 1 2 … NB 1 2 … NBi =
1 2 N1j =
Y2,1 Y2,2 Y2,N1
2|)(| tr 2|)(| tr 2|)(| tr
Y2Y1 YNB
Block Decision Mechanism
Block decision
Step-II
i = Ranging Block index
j = Ranging Frame index
k
bk̂
Molisch et al., Preliminary ProposalSlide 34
doc.: 15-05-0005-02-004a
Submission
Step-II: Chip Detection
• TOA is estimated at chip resolution– Once a ranging block is detected, the chips in that block plus M1 extra chips
prior to the ranging block (to prevent errors due to multipath) are searched
– Correlations of the received signal with time delayed versions of a template signal are considered
– Correlation output is obtained over multiple symbol duration to have a sufficient SNR
– Solution of first arriving path found by hypothesis testing methods on zi
r(t), received signal
s(t-TC), shifted template signal
FC
C
TNiT
iT
2
(.) zi
Molisch et al., Preliminary ProposalSlide 35
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Submission
Ranging System Settings
Notations and Terms Definition Value in Simulations
Tf Pulse repetition interval, frame 531.135 ns
Nb Number of blocks within a Tf 20
Nc Number of chips within a Tf 1000
TH{} Time hopping sequence in chips {h1, ...., h5}
POL{} Polarity codes {p1, ..., p5}
N1 Number of frames in the 1st-step 50
N2 Number of frames in the 2nd-step
30
winshift search back interval in #of chips 5
BW Bandwidth 7.5GHz
Chip duration Duration of a chip in samples 11 samples
Sample Period Sampling interval 4.8285e-11
Wave propagation speed Speed of radio wave 3e8
C Number of correlators 10
Molisch et al., Preliminary ProposalSlide 36
doc.: 15-05-0005-02-004a
Submission
Ranging Results
• AWGN
Round Trip ranging error (with no drift compensation)
– ~16cm (0.088ms), no clock drift
– ~19cm (1ppm)
– ~27cm (4ppm)
– ~42cm (10ppm)
– ~121cm (40ppm)
Molisch et al., Preliminary ProposalSlide 37
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Submission
Ranging Results
• Residential LOSTrue Distance (m) One-way ranging
error (confidence)
25m 8cm (97%)
30m 8cm (~90%)
39m 8cm (73%) 136cm(80%)
55m 8cm (60%) 136cm(%78)
Molisch et al., Preliminary ProposalSlide 38
doc.: 15-05-0005-02-004a
Submission
Two-way Ranging Protocol
• Developed for transceivers that can first detect the coarse TOA of a signal and then determine the offset (error) of the coarse estimation
• No need to transmit extra information to correct the timing offset or the processing delay
• Each node switches between receive and transmit mode every T seconds until the ranging is complete
Molisch et al., Preliminary ProposalSlide 39
doc.: 15-05-0005-02-004a
Submission
Conventional Two-way Ranging Protocol
Enhanced Two-way Ranging Protocol
TOA estimation error
TOA estimation error
T
Second transmission may help filter out clock drifts, if the Tx has a more reliable clock
Molisch et al., Preliminary ProposalSlide 40
doc.: 15-05-0005-02-004a
Submission
Acquisition
• The first step of the TOA estimation algorithm is also suitable for acquisition– For block level acquisition, select the highest energy block index
– For refining to the chip level, select the highest correlator output index
Molisch et al., Preliminary ProposalSlide 41
doc.: 15-05-0005-02-004a
Submission
Summary and Conclusions
• Impulse radio based standards proposal– UWB signaling achieves accurate ranging.
• Innovative modulation technique– Admits multiple transmit waveforms– Provides framework for multiple receiver types
• Offers trade-off of cost/complexity/performance– Coherent and differentially coherent receivers suppress interference
• More users
• Innovative ways to manage spectrum– Meet FCC requirements– Improve performance in interference environment– Decrease interference to other systems
• Allows cheap implementation– All digital operations at symbol rate, not chip rate
Molisch et al., Preliminary ProposalSlide 42
doc.: 15-05-0005-02-004a
Submission
References
• Proposal content has been reviewed and published in various technical journals and conferences
– S. Gezici, F. Tufvesson, and A. F. Molisch, “On the performance of transmitted-reference impulse radio”, Proc. Globecom 2004,
– F. Tufvesson and A. F. Molisch, “Ultra-Wideband Communication using Hybrid Matched Filter Correlation Receivers“, Proc. VTC 2004 spring
– A. F. Molisch, Y. G. Li, Y. P. Nakache, P. Orlik, M. Miyake, Y. Wu, S. Gezici, H. Sheng, S. Y. Kung, H. Kobayashi, H.V. Poor, A. Haimovich,and J. Zhang, „A low-cost time-hopping impulse radio system for high data rate transmission“, Eurasip J. Applied Signal Processing, special issue on UWB
– S. Gezici, Z. Tian, G. B. Giannakis, H. Kobayashi, A. F. Molisch, H. Vincent Poor and Z. Sahinoglu, "Localization via Ultra-Wideband Radios," IEEE Signal Processing Magazine, invited paper (special issue)
– S. Gezici, E. Fishler, H. Kobayashi, H. V. Poor, and A. F. Molisch, “Performance Evaluation of Impulse Radio UWB Systems with Pulse-Based Polarity Randomization in Asynchronous Multiuser Environments”, Proc. WCNC 2004,
– S. Gezici, E. Fishler, H. Kobayashi, H. V. Poor, and A. F. Molisch, “Effect of timing jitter on the tradeoff between processing gains, Proc. ICC 2004, in press. F. Tufvesson and A. F. Molisch, “Ultra-Wideband Communication using Hybrid Matched Filter Correlation Receivers“, Proc. VTC 2004 spring
Molisch et al., Preliminary ProposalSlide 43
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Submission
References (Cont)
– Z. Sahinoglu, A. Catovic, "A Hybrid Location Estimation Scheme for Wireless Sensor Networks, IEEE ICC'04, June 2004, Paris
– S. Gezici, Z. Sahinoglu, H. Kobayashi, H. Vincent Poor, Book Chapter: Ultra Wideband Geolocation, Ultra Wideband Wireless Communications by H. Arslan and Z. N. Chen, John Wiley & Sons, Inc. , February 2005.
– S. Gezici, Z. Sahinoglu, H. Kobayashi, H. Vincent Poor, "Impulse Radio Systems with Multiple Types of UWB Pulses," submitted to ICASSP'05.
– A. Catovic, Z. Sahinoglu, "The Cramer-Rao Bounds of TOA/RSS and TDOA/RSS Location Estimation Schemes", IEEE Comm. Letters, October 2004
– H. Sheng, A. Haimovich, A. F. Molisch, and J. Zhang, “Optimum combining for time-hopping impulse radio UWB Rake receivers”, Proc. UWBST 2003, in press
– Li, Y.G.; Molisch, A.F.; Zhang, J., "Channel Estimation and Signal Detection for UWB", International Symposium on Wireless Personal Multimedia Communications (WPMC), October 2003
– Nakache, Y-P; Molisch, A.F., "Spectral Shape of UWB Signals - Influence of Modulation Format, Multiple Access Scheme and Pulse Shape", IEEE Vehicular Technology Conference (VTC), April 2003