15.02.23.ehu ldm tutorial · single layer tdm/fdm system multi-layer transmission system mobile and...
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Layered Division Multiplexing: A technique to make flexible use of the broadcast
spectrum
Pablo Angueira < [email protected]>Cristina Regueiro <[email protected]>Jon Montalban <[email protected]>
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Jon Montalban [email protected]. Communications EngineeringUniversity of the Basque Country
Bilbao, Spain
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Who we areWho we are
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Research Activity
11 Professors
Research Activity
11 Professors
4 PhD students
3 Post Docs
3 Engineers contracted
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Research ActivityResearch Activity
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AgendaAgenda
Introduction
Layered Division Multiplexing Layered Division Multiplexing Basic Concepts
System Architecture
LDM vs TDM/FDM
System highlightsSystem highlights New LDPC Coding Algorithms
Signal Cancellation and Channel Estimation
Doppler Influence
PAPR
Results: Computer Simulations
Laboratory
Fi ld T t
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Field Tests
Conclusions
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Introduction
Layered Division Multiplexing (LDM), which grew out from the Cloud‐Txnh h h f h
Introduction
(*) concept, is a research project to enhance the capacity of the new generation broadcasting systems.
It has been proposed as a Physical Layer technology to the ATSC 3 0 Next It has been proposed as a Physical Layer technology to the ATSC 3.0 Next Generation Digital TV standard.
Cooperation project between CRC Canada, ETRI Korea and EHU Spain.p p j , p
In short, the main goal is to develop a terrestrial DTV PHY Layer that is:
Simple to build Simple to build
Flexible and Efficient use of the spectrum
With backward compatible future extension With backward compatible future extension
(*) Cloud Transmission: Y. Wu, B. Rong, K. Salehian and G. Gagnon.
Cl d i i A f i dl di i l i l
Layered Division Multiplexing (LDM) Tutorial – UPV/EHU ‐ DVB TM Geneva, Oct 2014 6
Cloud transmission: A new spectrum‐reuse friendly digital terrestrial broadcasting transmission system. Broadcasting, IEEE Transactions On 58 (3), pp. 329‐337. 2012.
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AgendaAgenda
Introduction
Layered Division Multiplexing Layered Division Multiplexing Basic Concepts
System Architecture
LDM vs TDM/FDM
System highlights New LDPC Coding Algorithms New LDPC Coding Algorithms
Injection Ranges Impact
Signal Cancellation and Channel Estimation
Doppler Influence
PAPR
Results: Computer Simulations
Laboratory
Fi ld T t
Layered Division Multiplexing (LDM) Tutorial – UPV/EHU ‐ DVB TM Geneva, Oct 2014 7
Field Tests
Conclusions
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Layered Division Multiplex: Concept
Use of spectrum overlay technology to
Layered Division Multiplex: Concept
Use of spectrum overlay technology to transmit multiple data streams in one RF channel with different robustness and data capacity for different services and reception I j ticapacity for different services and reception environments
100% f RF b d id h d 100% f h
InjectionLevel Stream A
100% of RF bandwidth and 100% of the time are used to transmit the multi‐layered signals (hierarchical spectrum re‐use) for
t ffi i d fl ibl f thspectrum efficiency and flexible use of the spectrum Stream BRF
Channel BW
Signal cancellation is used to retrieve the robust upper layer signal first, cancel it from the received signal, and then start the d d f l l l
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decoding of lower layer signal
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Layered Division Multiplex: Concept
The upper layer (UL) needs to be ultra‐robust (Cloud Transmission)
Layered Division Multiplex: Concept
pp y ( ) ( )
Thus, a high data rate lower layer (LL) transmission system is a must:
Required for multiple HD and UHD services to fixed or portable terminalsterminals
Injected from 3 to 6 dB below the upper layer signal
DTV‐T2/NGH can be used as the lower layer system DTV‐T2/NGH can be used as the lower layer system
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Layered Division Multiplex: Concept
The upper layer (UL) needs to be ultra‐robust (Cloud Transmission)
Layered Division Multiplex: Concept
pp y ( ) ( )
Thus, a high data rate lower layer (LL) transmission system is a must:
Required for multiple HD and UHD services to fixed or portable terminalsterminals
Injected from 3 to 6 dB below the upper layer signal
DTV‐T2/NGH can be used as the lower layer system
More layers could be added later as network extension for new
DTV‐T2/NGH can be used as the lower layer system
services
The network is scalable and can be implemented progressively
b k d bl f f
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It is backward compatible for future extension
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LDM 2‐Layer System Coverage (outdoor)
Robust mobile upper layer (S/N_thr= ‐1 dB, 2.5 Mbps, 720p)
LDM 2 Layer System Coverage (outdoor)
High‐data rate lower layer (S/N_thr = +19 dB, 24 Mbps, UHDTV or multi‐HDTV)
Upper layer fixed reception:10m directional antenna10m directional antennaS/N = ‐1 dB
Upper layer portable reception:1 5m Omni directional antenna1.5m Omni‐directional antenna,S/N = ‐0.5 dB
Upper la er mobile receptionUpper layer mobile reception: 1.5m Omni‐directional antenna,S/N = +2 dB
Lower layer fixed reception:10m directional antenna,S/N = +19 dB
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AgendaAgenda
Introduction
Layered Division Multiplexing Layered Division Multiplexing Basic Concepts
System Architecture
LDM vs TDM/FDM
System highlights New LDPC Coding Algorithms New LDPC Coding Algorithms
Injection Ranges Impact
Signal Cancellation and Channel Estimation
Doppler Influence
PAPR
Results: Computer Simulations
Laboratory
Fi ld T t
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Field Tests
Conclusions
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LDM System Architecture: Frame StructureLDM System Architecture: Frame Structure
bl bl
UL payloadGI UL payloadGI
Preamble Preamble
LL payloadGI LL payloadGI
Max. 250 ms Max. 250 ms
• The Upper and Lower layer share some parameters:
• FFT SizeFFT Size
• GI length
• Preamble
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• Maximum frame size ≤ 250ms
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LDM System Architecture: Transmitter StructureLDM System Architecture: Transmitter Structure
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LDM System Architecture: Transmitter (DVB‐T2 Alike)LDM System Architecture: Transmitter (DVB T2 Alike)
Freq. Int’lFEC1Bit‐Int’l1
Mapper1Cell‐Int’l
FramingTime‐Int’l
Injection LevelFEC2
Bit‐Int’l2
Mapper2
Pilot Insert.
MISO IFFT GIPAPR Preamble D/AInsert.
Upper Layer BICM
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Lower Layer BICM
Common Modules
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LDM System Architecture: ReceiverLDM System Architecture: Receiver
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LDM System Architecture: Receiver
Common for LDM
LDM System Architecture: Receiver
Sync & Timing Clock Recovery
Tuner IF & Down Converter A-D Converter
OFDM Demo& Equalization
Time De-Int’l
AGC
Stream A
Delay
Stream A Decoder
Data buffer
+ Bit to Cell Mapping
Data + FECUpper Layer BICM
Lower Layer BICM
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Stream B Decoder Stream B Common Modules
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AgendaAgenda
Introduction
Layered Division Multiplexing Layered Division Multiplexing Basic Concepts
Physical Structure
LDM vs TDM/FDM
System highlights New LDPC Coding Algorithms New LDPC Coding Algorithms
Injection Ranges Impact
Signal Cancellation and Channel Estimation
Doppler Influence
PAPR
Results: Computer Simulations
Laboratory
Fi ld T t
Layered Division Multiplexing (LDM) Tutorial – UPV/EHU ‐ DVB TM Geneva, Oct 2014 18
Field Tests
Conclusions
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LDM vs TDM/FDM: Capacity Gain
High S/N environment
LDM vs TDM/FDM: Capacity GainP
ower
Multi-layer transmission systemSingle layer TDM/FDM system
Mobile and fixed services work well for both systems
y yg y y
y
Single layer system wastes channel capacity LDM improves spectrum efficiency
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Only part of time (TDM) or RF channel (FDM) used 100% time, 100% RF channel
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LDM vs TDM/FDM: Capacity Gain
Low S/N environment
LDM vs TDM/FDM: Capacity GainP
ower
Multi-layer transmission systemSingle layer TDM/FDM system
Only mobile services work
y yg y y
Single layer system wastes channel capacity
Only part of time (TDM) or RF channel (FDM) used
LDM improves spectrum efficiency
100% time, 100% RF channel
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Use case I: Mobile ReceptionUse case I: Mobile Reception
( ) ( )LDM (two layers) vs. DVB‐T2+NGH (single layer)8 MHz RF Channel
LDM System Mobile 50% Capacity Mobile 33.3% Capacity Mobile 25% Capacityy p y p y p y
Upperlayer
(Robust‐mod)
Data rate SNR Data rate SNR Data rate SNR Data rate SNR3.1 MbpsQPSK 1/4
‐1.0 dB2.5 MbpsQPSK 2/5
‐0.2 dB2.6 MbpsQPSK 2/3
3.1dB2.5 MbpsQPSK 4/5
4.7dB
Low layer w. ‐4 dB injection Fixed(T2) 50% Fixed(T2) 66.7% Fixed(T2) 75%
Low‐rate17.5 Mbps16QAM 2/3
14.4 dB18.1 Mbps256QAM2/3
17.8 dB18.2 Mbps64QAM 2/3
13.5 dB18.3 Mbps64QAM 3/5
12.0 dB
26 3 Mbps 27 2 Mbps 27 2 MbpsMid‐rate
26.3 Mbps64QAM 2/3
19.0 dB ‐ N/A27.2 Mbps256QAM 3/4
20.0 dB27.2 Mbps256QAM 2/3
17.8 dB
High‐rate32.9 Mbps64QAM 5/6
22.3 dB ‐ N/A ‐ N/A34 Mbps
256QAM 5/622.0 dB
All SNR power levels are referenced to the total RF in‐band power (of all layers)LDM: 16K FFT, GI= 1/16, P12,2. TDM: Fixed 32K FFT, GI = 1/32, P24,4; Mobile 8K FFT, GI = 1/8, P6,2.
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LDM: 16K FFT, GI 1/16, P12,2. TDM: Fixed 32K FFT, GI 1/32, P24,4; Mobile 8K FFT, GI 1/8, P6,2.
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Use case II: Indoor ReceptionUse case II: Indoor Reception
( l ) ( l l )LDM (two layers) vs. DVB‐T2+NGH (single layer)8 MHz RF Channel
LDM System Mobile 50% Capacity Mobile 33.3% Capacity Mobile 25% Capacityy p y p y p y
Upperlayer
(Robust‐mod)
Data rate SNR Data rate SNR Data rate SNR Data rate SNR5.46 MbpsQPSK 6/15
2.7 dB5.46 MbpsQPSK 2/5
4.7 dB5.46 Mbps16QAM 2/3
8.9 dB5.55 Mbps64 QAM 3/5
12.0dB
Low layer w. ‐4 dB injection Fixed(T2) 50% Fixed(T2) 66.7% Fixed(T2) 75%
Low‐rate17.5 Mbps16QAM 2/3
14.4 dB18.1 Mbps256QAM2/3
17.8 dB18.2 Mbps64QAM 2/3
13.5 dB18.3 Mbps64QAM 3/5
12.0 dB
Mid26.3 Mbps
19 0 dB N/A27.2 Mbps
20 0 dB27.2 Mbps
17 8 dBMid‐rate26.3 Mbps64QAM 2/3
19.0 dB ‐ N/A27.2 Mbps256QAM 3/4
20.0 dB27.2 Mbps256QAM 2/3
17.8 dB
High‐rate32.9 Mbps64QAM 5/6
22.3 dB ‐ N/A ‐ N/A34 Mbps
256QAM 5/622.0 dB
All SNR power levels are referenced to the total RF in‐band power (of all layers)LDM: 16K FFT, GI= 1/16, P12,2. TDM: Fixed 32K FFT, GI = 1/32, P24,4; Mobile 8K FFT, GI = 1/8, P6,2.
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LDM: 16K FFT, GI 1/16, P12,2. TDM: Fixed 32K FFT, GI 1/32, P24,4; Mobile 8K FFT, GI 1/8, P6,2.
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LDM vs TSM GainLDM vs TSM Gain
LDM vs TDM: MOBILE SERVICE GAIN (AWGN)
50% 33.3% 25%
3 1 Mb 0 8 dB 4 1 dB 5 7 dB3.1 Mbps 0.8 dB 4.1 dB 5.7 dB
5.46 Mbps 2.0 dB 6.2 dB 9.3 dB
LDM vs TDM: HIGH‐CAPACITY GAIN (AWGN)
50% 67.7% 75%
17.5 Mbps 3.4 dB ‐ 0.9 dB ‐2.4 dB
26 3 Mb N/A 1 dB 1 2 dB26.3 Mbps N/A 1 dB ‐1.2 dB
24.6 Mbps N/A N/A ‐0.3 dB
LDM gain between 4-8 dB
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Key Technical Issues to solve
A t ti d d iti ti t f th U
Key Technical Issues to solve
A strong error correction code and error mitigation system for the Upper layer that can achieve a negative SNR value, closer to the Shannon limit, and save power. A rate compatible LDPC code optimized for low coding rate;
Closer to the Shannon limit at low coding rate;
It can be truncated to higher rate code for power saving and low latencyIt can be truncated to higher rate code for power saving and low latency decoding.
A good signal cancelation scheme th t i i i th ll ti A good signal cancelation scheme that can minimize the cancellation errors which makes a high data rate lower layer viable. Low‐complex channel estimation and equalization algorithms.
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AgendaAgenda
Introduction Layered Division Multiplexing
Basic Concepts
Physical Structurey
LDM vs TDM/FDM
System highlightsN LDPC C di Al i h New LDPC Coding Algorithms
Injection Ranges Impact
Signal Cancellation and Channel Estimation
Doppler Influence
PAPR
Non Uniform Constellations Non‐Uniform Constellations
Latency & Complexity
Results
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A Rate Compatible LDPC CodeA Rate Compatible LDPC Code
LDPC Parity Check MatrixLDPC Parity Check Matrix (PCM) Structure fully compatible with DVB Code PCMCode PCM
The code is optimized pin the range of R < 0.5
It is very close to the Shannon limit (< 1 dB)
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AgendaAgenda
Introduction Layered Division Multiplexing
Basic Concepts
Physical Structurey
LDM vs TDM/FDM
System highlightsN LDPC C di Al i h New LDPC Coding Algorithms
Injection Ranges Impact
Signal Cancellation and Channel Estimation
Doppler Influence
PAPR
Non Uniform Constellations Non‐Uniform Constellations
Latency & Complexity
Results
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Injection levels Impact: Some ExamplesInjection levels Impact: Some Examples
Upper layer Lower layerUpper layer only
Injection level UL Min. SNRLower layer
onlyLL Min. SNR
SNR = ‐3.4dB
3 1 Mb
‐3 dB ‐0.5 dB SNR=6.2 dB
11 2 Mb
11.0 dB‐4 dB ‐1 0 dB 11 7 dB3.1 Mbps
R = ¼ QPSK
11.2 Mbps
R = 1/2 16QAM
4 dB 1.0 dB 11.7 dB‐5 dB ‐1.5 dB 12.4 dB
SNR = ‐3.4dB ‐3 dB ‐0.5 dB SNR=13.4dB 18.2 dB
3.1 Mbps
R = ¼ QPSK
26.3 Mbps
R = 2/3 64QAM
‐4 dB ‐1.0 dB 18.9 dB‐5 dB ‐1.5 dB 19.6 dB
SNR = ‐3 4dB ‐3 dB ‐0 5 dB SNR=18 1dB 22 9 dBSNR 3.4dB
3.1 Mbps
R = ¼ QPSK
3 dB 0.5 dB SNR 18.1dB
35.1 Mbps
R= 2/3 256QAM
22.9 dB‐4 dB ‐1.0 dB 23.6 dB‐5 dB ‐1.5 dB 24.3 dB
There is a tradeoff between injection level and required SNR threshold for d di b th th U d L L
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decoding both the Upper and Lower Layers
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AgendaAgenda
Introduction Layered Division Multiplexing
Basic Concepts
Physical Structurey
LDM vs TDM/FDM
System highlightsN LDPC C di Al i h New LDPC Coding Algorithms
Injection Ranges Impact
Signal Cancellation and Channel Estimation
Doppler Influence
PAPR
Non Uniform Constellations Non‐Uniform Constellations
Latency & Complexity
Results
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A two layered systemA two layered system
U L Si l S(U) + L L Si l S(L)
Total Signal Power
Upper Layer Signal S(U) + Lower Layer Signal S(L)
Upper Layer Signal S(U)
InjectionLevel Δ
Lower Layer Signal S(L)
Pilot Signals
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A two layered system : Rx Input
M lti th Di t ti [S(U) + S(L)] + N i
A two layered system : Rx Input
Multipath Distortion[S(U) + S(L)] + NoiseTotal Signal Power
Upper Layer Signal S(U)
Injection
Lower Layer Signal S(L)
Signal S(U)Level Δ
Pilot Signals
Noise
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A two layered system : after equalization
S(U) + S(L) + (Channel Estimation Error) + Noise
A two layered system : after equalization
S(U) + S(L) + (Channel Estimation Error) + Noise
Total Signal Power
Upper Layer Signal S(U)
Injection
Lower Layer Signal S(L)
Signal S(U)Level Δ
Pilot Signals
ColouredNoise ChannelNoise Channel
EstimationError
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A two layered system : after equalization
S(U) + S(L) + (Channel Estimation Error) + Noise
A two layered system : after equalization
S(U) S(L) (Channel Estimation Error) NoiseChannel Estimation Error is the Signal Cancellation Error
Lower Layer Signal S(L)
Pilot Signals
ColouredNoise ChannelNoise Channel
EstimationError
• The lower layer signal has significantly boosted pilots. Good for equalization.
Layered Division Multiplexing (LDM) Tutorial – UPV/EHU ‐ DVB TM Geneva, Oct 2014 33
The lower layer signal has significantly boosted pilots. Good for equalization.• Channel estimation error should be much lower than the “noise”.
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Cancellation ErrorCancellation Error
• There is only a main noise sources that can lead to aycancellation error:
Channel estimation error
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Channel Estimation Performance Analysis
Pilot‐Aided Channel Estimation and Decision‐Directed
Channel Estimation Performance Analysis
Channel Estimation in 0 dB Single‐Echo channels with different echo delays.
Focus on:• Signal cancellation performance vs. echo delay;Signal cancellation performance vs. echo delay;• Pilot Aided 3rd order interpolation (PA‐Cinterp); • Pilot Aided DFT interpolation (PA‐DFTF);
D i i Di d DFT Fil i (DD DFTF)• Decision Directed DFT Filtering (DD‐DFTF).
Montalban, J.; Bo Rong; Yiyan Wu; Liang Zhang; Angueira, P.; Velez, M., "Cloud Transmission frequency domain cancellation," Broadband Multimedia Systems and Broadcasting (BMSB), 2013 IEEE International Symposium on , vol., no., pp.1,4, 5‐7 June 2013
Montalban, J.; Angulo, I.; Vélez, M.; Angueira, P.; Regueiro, C.; Yiyan Wu; Liang Zhang; Li., W. Error Propagation in the Cancellation Stage for a Multi‐Layer Signal Reception, " Broadband Multimedia Systems and Broadcasting (BMSB), 2013 IEEE International Symposium on , vol., no.,
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pp.1,4, 25‐27 June 2014
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Signal Cancellation in 0dB Echo Channels
Ch l C ditiNMSE
Signal Cancellation in 0dB Echo Channels
Channel Condition 2D‐CUBIC 2D‐DFT DD‐DFTSNRLL(dB) Tap fdTu
0 dB Echo (D=1/4GI) 10 40 0 ‐34.0 ‐33.0 ‐35.0
0 dB Echo (D=7/8GI) 10 40 0 ‐18.0 ‐32.5 ‐32.5
0 dB E h (D 7/8GI) 10 80 0 35 5 35 50 dB Echo (D=7/8GI) 10 80 0 ‐ ‐35.5 ‐35.5
0 dB Echo (D=7/8GI) 20 40 0 ‐ ‐40.0 ‐32.5
2D‐DFT PA channel estimation provides very accurate channel estimation.
If the time averaging filter is doubled the cancellation residual errorIf the time averaging filter is doubled the cancellation residual error decreases by 3 dB.
For high SNR the PA channel estimation performs better than the DD.
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Signal Cancellation
1. Signal cancellation error is the same as the channel estimation error.
g
1. Existing channel estimation and equalization algorithms work well. Not need to invent new fancy algorithms.
2. Channel estimation error also related to noise level. Channel estimation error should be lower than the noise level to minimize the impact to the receiver performance
4. Pilot Added algorithms work well for high SNR cases. Decision Directed algorithms work better for low SNR cases; Two layer system is equivalent to boosting pilots by several dB (injection level) for lower channel estimation, which provides good channel estimation results.
5. Larger size FFT OFDM modulation will improve estimation performance, since for the same percentage of pilots, large FFT modulation reduces the pilot spacing (in Hz)
Layered Division Multiplexing (LDM) Tutorial – UPV/EHU ‐ DVB TM Geneva, Oct 2014 37
Hz).
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AgendaAgenda Introduction Layered Division Multiplexing
Basic Concepts
Physical Structure
LDM vs TDM/FDMLDM vs TDM/FDM
System highlights New LDPC Coding Algorithms
Injection Ranges Impact
Signal Cancellation and Channel Estimation
Doppler Influencepp
PAPR
Non‐Uniform Constellations
L t & C l it Latency & Complexity
Results
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Doppler Noise for different FFT sizesDoppler Noise for different FFT sizes
D bl h FFT i5
Signal Contributions
Double the FFT size, the Doppler noise increase by 6 dB.
0
For 16K FFT, the Doppler noise is about
-10
-5
)
Rx Power (2K)
ICI Noise (2K)Rx Power(4K)
16K FFT
Doppler noise is about ‐10 dB.
20
-15 P
ow
er (
dB
m) Rx Power(4K)
ICI Noise(4K)
Rx Power(8K)
ICI Noise(8K)
Rx Power(16K)ICI Noise(16K)
8K FFT
If the UL layer SNR is ‐3 dB, the ‐10 dB Doppler noise is 13 dB
-25
-20Gaussian Noise
4K FFT
Doppler noise is 13 dB below the noise threshold and will have very limited 0 50 100 150 200 250
-35
-30
2K FFT
Layered Division Multiplexing (LDM) Tutorial – UPV/EHU ‐ DVB TM Geneva, Oct 2014 39
have very limited impact.
0 50 100 150 200 250 Symbol Number
150 Hz Doppler shift
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Example: LDM UL 16K for MobileExample: LDM UL 16K for Mobile
20LDM UL (=-5 dB), TI=200ms, 16K, TU-6, ATSC-3. Ideal CSI
16
18
UL: QPSK 7/15; =-5dB
UL: QPSK 6/15; =-5 dB
UL: QPSK 5/15; =-5 dB
12
14
min
8
10 SN
Rm
4
6
LDM UL 16K can go up to 260 km/h for the CR=5/15 (4 5 Mbps) with a 3 dBmargin
0 50 100 150 200 250 3002
V (km/h)
Layered Division Multiplexing (LDM) Tutorial – UPV/EHU ‐ DVB TM Geneva, Oct 2014 40
LDM UL 16K can go up to 260 km/h for the CR=5/15 (4.5 Mbps) with a 3 dBmargin
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Example: LDM UL 32K for MobileExample: LDM UL 32K for Mobile
18
20LDM UL, LL-5dB, TI-100ms, 32k, QPSK, TU, ATSC-3 LDPC, DFT-ChEst
LDM-UL, r-4/15TDM, r-8/15
14
16
tio [
dB]
TDM, r-10/15TDM, r-12/15
8
10
12
nal t
o N
oise
Rat
4
6
8
Sig
n
3 dBThreshold
95 km/h
0 20 40 60 80 100 120 140 1602
Vehicle speed [km/h]
Threshold135km/h
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AgendaAgenda Introduction Layered Division Multiplexing
Basic Concepts
Physical Structure
LDM vs TDM/FDMLDM vs TDM/FDM
System highlights New LDPC Coding Algorithms
Injection Ranges Impact
Signal Cancellation and Channel Estimation
Doppler Influencepp
PAPR
Non‐Uniform Constellations
L t & C l it Latency & Complexity
Results
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PAPR on LDM systemsPAPR on LDM systems
100
PAPR : SL system with 4K-point FFT (Oversampling L=4)
16-QAM (SL)
PAPR : SL system with 4K-point FFT (Oversampling L=4)
16-QAM (SL)
10-1
( )
ML (LL-16QAM)64-QAM (SL)
ML(LL-64QAM)
256-QAM (SL)
ML(LL-256QAM)Theor. 1
16 QAM (SL)
ML (LL-16QAM)64-QAM (SL)
ML(LL-64QAM)
256-QAM (SL)
ML(LL-256QAM)Theor. 1
10-2
lity
(PA
PR
>P
AP
R0) Theor. 2
10-5
ity(
PA
PR
>P
AP
R0) Theor. 2
10-3
CC
DF
=P
rob
abil
CC
DF
=P
rob
abil
10-4
LDM and SL PAPR is about 13.2 dB with a probability below 10^‐5.
10 10.5 11 11.5 12 12.5 13 13.5 14
PAPR0[dB]
13.18 13.2 13.22 13.24 13.26 13.28 13.3 13.32 13.34
Layered Division Multiplexing (LDM) Tutorial – UPV/EHU ‐ DVB TM Geneva, Oct 2014 43
LDM and SL PAPR are within 0.05 dB margin.
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PAPR on LDM systemsPAPR on LDM systems
PAPR is mostly affected by the FFT length PAPR is mostly affected by the FFT length.
h bi i f h ll i There is not big impact for the constellation size or type.
LDM PAPR is the same as in a regular OFDMLDM PAPR is the same as in a regular OFDM
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AgendaAgenda Introduction Layered Division Multiplexing
Basic Concepts
Physical Structure
LDM vs TDM/FDMLDM vs TDM/FDM
System highlights New LDPC Coding Algorithms
Injection Ranges Impact
Signal Cancellation and Channel Estimation
Doppler Influencepp
PAPR
Non‐Uniform Constellations
L t & C l it Latency & Complexity
Results
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Non‐Uniform Contellations on LDM
LDM (two layers) vs. TDM (single layer, baseline code, no pre‐amble)
Non Uniform Contellations on LDM
8 MHz RF Channel (‐4 dB Lower Layer Injection)
LDM SystemUpperl
Data rate SNR Data rate SNR2 6 Mb 2 6 Mblayer
(robust‐mod)2.6 MbpsQPSK 3/15
‐2.1 dB2.6 MbpsQPSK 3/15
‐2.1 dB
Low layer with ‐4 dB injection
Low‐rate18.2 Mbps64NUQ 7/15
14.5 dB18.2 Mbps64Q 7/15
15.0 dB64NUQ 7/15 64Q 7/15
Mid‐rate1(hardware)
26.3 Mbps64NUQ 10/15
18.5 dB26.3 Mbps64Q 10/15
19.0 dB
Mid‐rate231.5 Mbps
256NUQ 9/1521.1 dB
31.5 Mbps256Q 9/15
22.0 dB256NUQ 9/15 256Q 9/15
High‐rate38.7 Mbps
256NUQ 11/1524.4 dB
38.7 Mbps256Q 11/15
25.2 dB
NuQAM gain is mantained in LDM
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AgendaAgenda Introduction Layered Division Multiplexing
Basic Concepts
Physical Structure
LDM vs TDM/FDMLDM vs TDM/FDM
System highlights New LDPC Coding Algorithms
Injection Ranges Impact
Signal Cancellation and Channel Estimation
Doppler Influencepp
PAPR
Non‐Uniform Constellations
L t & C l it Latency & Complexity
Results
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Latency and complexity of LDM receiversLatency and complexity of LDM receivers
Sync & Timing Clock Recovery
Tuner IF & Down Converter A-D Converter
OFDM Demo& Equalization
Time De-Int’l
Common for LDM
AGC
Stream A
Delay
Stream A Decoder
Data bufferUpper Layer BICM
+ Bit to Cell Mapping
Data + FECLower Layer BICM
Common Modules
Layered Division Multiplexing (LDM) Tutorial – UPV/EHU ‐ DVB TM Geneva, Oct 2014 48
Stream B Decoder Stream B
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Complexity of LDM receiversComplexity of LDM receivers
Sync & Timing Clock Recovery
Tuner IF & Down Converter A‐D Converter
OFDM Demo& Equalization
Time De‐Int’l
Common for LDM
AGC
• A large part of the circuits can be shared (tuner, sync, IF, ADC, AGC, OFDM demodulator,
equalizer, time deinterleaver etc.)
• Clearly no complexity increase in common parts.
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Complexity of LDM receivers
• For a LDM receiver that decodes the high‐data rate lower layer
Complexity of LDM receivers
• First step is to correctly decode the upper layer
• Re‐modulate the decoded data
• And then cancel it from the received signalAnd then cancel it from the received signal
• Complexity mainly depend on the LDPC decoder, which should be shared for both
UL and LL decodingUL and LL decoding
• LDPC decoding performance of the UL must be considered
Stream A
Delay
Stream A Decoder
Data buffer Upper Layer BICM
+Bit to Cell Mapping
Data + FEC Lower Layer BICM
Common Modules
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Stream B Decoder Stream B
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LDPC Decoding Performance of Upper layerLDPC Decoding Performance of Upper layer
• UL: QPSK+4/15 LL: 64NUC+10/15 IL: ‐5dB
45
50QPSK 4/15 & 64-QAM 10/15 (IL = -5 dB). AWGN, Rice, Rayleigh and TU-6 fading channels
QPSK 4/15 AWGN
QPSK 4/15 Rice
UL: QPSK+4/15, LL: 64NUC+10/15, IL: 5dB
• FFT 32k for worst case assumption
30
35
40QPSK 4/15 Rayleigh
QPSK 4/15 TU-6 (Doppler = 33.3 Hz)
n
15
20
25
BE
RIteratio
0
5
10
15
All cases iterations <10
-5 0 5 10 15 20 250
SNR [dB]
Given LL target SNR of 15 dB iterations < 5LDPC iterations vs SNR
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Given LL target SNR of 15 dB, iterations < 5
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Complexity of LDM receivers
• LDPC decoder complexity:
Complexity of LDM receivers
p y Upper layer LDPC decoder: 5 (normal case) or 10 (worst case) iterations
LDPC computation complexity increase < 20% (10/50, worst case)
LDM will likely use up to 16QAM (4 bits) for UL and 1k‐QAM (10 bits) for LL, so the totalLDM will likely use up to 16QAM (4 bits) for UL and 1k QAM (10 bits) for LL, so the total
LDPC complexity increase is 20% x 4/10 = 8% referenced to the LL only case (LL must be
able to decode the highest modulation single PLP case).
Stream A
Delay
Stream A Decoder
+
Data bufferUpper Layer BICM
L L BICM+ Bit to Cell Mapping
Data + FECLower Layer BICM
Common Modules
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Stream B Decoder Stream B
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Complexity of LDM receivers
• Memory increase estimation assuming UL and LL use 64k LDPC codes
Complexity of LDM receivers
Since UL decoding (10 iteration), remapping, cancellation, and LL decoding (50 iteration)
should be finished simultaneously maximum 64k cells are required
32k cells for current decoding + 32k cells for storing next data
If TDI = 219(512K) cells 12.5%memory increase (worst case)
64k cells can be greatly reduced by smart scheduling
32k cells + α (less than 10% memory increase expected)
Stream A
Delay
Stream A Decoder
+
Data bufferUpper Layer BICM
L L BICM+ Bit to Cell Mapping
Data + FECLower Layer BICM
Common Modules
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Stream B Decoder Stream B
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Latency of LDM receivers
• LDPC decoder latency:
Latency of LDM receivers
LDPC decoder latency: When decoding LL, LDPC decoder will work in high S/N environment for the UL
Taking advantage of the truncated LDPC codes latency may be reduced up to 62 5% for theS/N threshold LL >> S/N threshold UL
Taking advantage of the truncated LDPC codes, latency may be reduced up to 62.5% for the
UL decoding
Delay due to the data buffer for performing cancellation is not longer than a FEC word
Stream A
Delay
Stream A Decoder
+
Data bufferUpper Layer BICM
L L BICM+ Bit to Cell Mapping
Data + FECLower Layer BICM
Common Modules
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Stream B Decoder Stream B
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AgendaAgenda
IntroductionLayered Division Multiplexing Layered Division Multiplexing Basic Concepts
System Architecture
LDM vs TDM/FDM
System highlights System highlights New LDPC Coding Algorithms
Signal Cancellation and Channel Estimation
Doppler Influence
Results: Computer Simulations Computer Simulations
Laboratory
Field Tests
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Conclusions
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Simulation ConfigurationSimulation Configuration
Single LayerEVP
Theoretical Analysis
LDM MultiplexingCONSTELATION Code Rate
Spectral Efficiency
(Mbps/Hz)Bit Rate (Mbps)
QPSK3/15 0.38 1.834/15 0 53 2.45
Computer Based Simulations
Single Layer
QPSK 4/15 0,53 2.455/15 0.66 3.07
16-QAM3/15 0.79 3.674/15 1.05 4.915/15 1.32 6.15
LDM
LDM
Laboratory Trials
Spectral Bit Rate
Single Layer
LDM
Const. Code Rate Efficiency
(Mbps/Hz)
Bit Rate
(Mbps)
Upper LayerQPSK 3/15 0,38 1.83QPSK 4/15 0,51 2.45
16 QAM 3/4 3 17 16 63Field Trials
Single Layer
Lower Layer
16-QAM 3/4 3.17 16.6364-QAM 2/3 4.22 22.18256-QAM 2/3 5.28 27.72
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LDM
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Computer Simulations: Single LayerComputer Simulations: Single Layer
Stationary Channels (Ideal Channel Estimation)
AWGN RICE Rayleigh 0 dB Echo
QPSK4/15 -2.9 -2.7 -2 -2.35/15 -1.7 -1.5 -0.5 -0.9
16-QAM4/15 0.7 0.9 2.1 1.75/15 2.3 2.6 3.8 3.5
Mobile Channels (Ideal Channel Estimation)
5 Hz 50 Hz 75 Hz
QPSK4/15 -0.9 -0.8 -1.05/15 0.4 0.1 0.45/15 0.4 0.1 0.4
16-QAM4/15 2.8 3.2 3.55/15 4.4 4.8 5.1
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Single Layer (Channel Estimation Loss)Single Layer (Channel Estimation Loss)
Mobile ChannelsStationary Channels
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LDM (Injection Range=‐4 dB)( ject o a ge d )
Stationary Channels (Ideal Channel Estimation)
AWGN RICE Rayleigh 0 dB Echo
UL QPSK 4/15 -0.4 -0.1 1.3 0.8LL 16QAM 3/4 15 4 15 9 18 8 18 7LL 16QAM 3/4 15.4 15.9 18.8 18.7LL 64QAM 2/3 18.9 19.2 21.5 21.3LL 256QAM 2/3 23.2 23.5 25.7 25.8
Mobile Channels (Ideal Channel Estimation)
fd=5 Hz fd =50 Hz fd =75 Hz
QPSK 4/15 2 0 2 3 2 4QPSK 4/15 2.0 2.3 2.4
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LDM (Channel Estimation Loss)(C a e st at o oss)
Mobile ChannelsStationary Channels
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AgendaAgenda
IntroductionLayered Division Multiplexing Layered Division Multiplexing Basic Concepts
System Architecture
LDM vs TDM/FDM
System highlights System highlights New LDPC Coding Algorithms
Signal Cancellation and Channel Estimation
Doppler Influence
Results: Computer Simulations Computer Simulations
Laboratory
Field Tests
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Conclusions
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Lab Set UpLab Set Up
UPV/EHU SW
DEMOD
Based on a DVB‐T2 Software fi d di ( ) l fDefined Radio (SDR) platform;
Cloud transmission layer was added;;
Different channel models are tested: AWGN, Rice, Rayleigh, etc
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etc.
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DBA – LDM (Receiver design and Implementation)DBA LDM (Receiver design and Implementation)
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DBA – LDM (Receiver design and Implementation)DBA LDM (Receiver design and Implementation)
ETRI Korea has designed and constructed a first fullETRI Korea has designed and constructed a first full hardware LDM prototype
Shown in next Dec ATSC AH 32 Face to Face meetings
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Single Layer (HW Impact)g y ( p )
Mobile ChannelsStationary Channels
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LDM (HW Impact)( p )
Mobile ChannelsStationary Channels
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Field Test: Set Upp
Transmitting Site Banderas, Bilbao, Spain
BILBAOBILBAOSPAINSPAIN p
Frequency 690 MHzTransmitter ERP 35.68 dBWAntenna Type 4 Element UHF
l
SPAINSPAIN
panelTx Antenna Height 48 metersAltitude (a.g.l.) 216 metersRadiation Pattern Directive (140‐210º)( )Polarization VerticalChannel Bandwidth 6 MHz
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Simulation, Lab and Field Test ResultsS u at o , ab a d e d est esu ts
100
Upper Layer: 8K, GI=1/32, CR=1/4, QPSK, R=2.3 Mbps 10
0 Lower Layer: 8K, GI=1/32, CR=2/3, 256-QAM, R=30.1 Mbps
10-1
10-1
AWGN: Simulated
AWGN: LaboratoryField Test
10-3
10-2
10-3
10-2
Upper Layer: QPSKR=1/4, 2.3 Mbps.
10-4
BE
R
10-4
BE
R
R 1/4, 2.3 Mbps.
Lower Layer:256QAM, R=2/3,
10-6
10-5
10-6
10-5
Q , / ,30.1 Mbps8k FFT
10-7
10-7
AWGN: Simulated
AWGN: Laboratory
Field Test
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-2 -1.5 -1 -0.5 010
-8
SNR (dB)
22 24 26 28 30
10-8
SNR (dB)
Field Test
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AgendaAgenda
IntroductionLayered Division Multiplexing Layered Division Multiplexing Basic Concepts
System Architecture
LDM vs TDM/FDM
System highlights System highlights New LDPC Coding Algorithms
Signal Cancellation and Channel Estimation
Doppler Influence
Results:
Computer Simulationsp
Laboratory
Field Tests
C l i
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Conclusions
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ConclusionsConclusions
LDM is a multiplexing scheme, that can mix different serviceswith different reception conditions in one RF channel.
The main advantage is the use of the 100 % of the spectrumduring the whole transmission time.
It achieves 5 to 6 dB SNR gain when compared to TDM/FDMsystems for robust mobile/indoor reception.
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Questions?
Pablo Angueira [email protected]
Jon Montalban [email protected]
Cristina Regueiro [email protected]
http://www.ehu.es/tsr radiop // / _
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