15.02.23.ehu ldm tutorial · single layer tdm/fdm system multi-layer transmission system mobile and...

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]>

Layered Division Multiplexing (LDM) Tutorial – UPV/EHU ‐ DVB TM Geneva, Oct 2014 1

Jon Montalban [email protected]. Communications EngineeringUniversity of the Basque Country

Bilbao, Spain

Who we areWho we are


Research Activity

11 Professors

Research Activity

11 Professors

4 PhD students

3 Post Docs

3 Engineers contracted


Research ActivityResearch Activity


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


Field Tests

Conclusions

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


Cloud transmission: A new spectrum‐reuse friendly digital terrestrial broadcasting transmission system. Broadcasting, IEEE Transactions On 58 (3), pp. 329‐337. 2012.

AgendaAgenda

Introduction


System Architecture

LDM vs TDM/FDM

System highlights New LDPC Coding Algorithms New LDPC Coding Algorithms

Injection Ranges Impact


Doppler Influence

PAPR


Laboratory

Fi ld T t


Field Tests

Conclusions

Layered Division Multiplex: Concept

Use of spectrum overlay technology to


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


decoding of lower layer signal


The upper layer (UL) needs to be ultra‐robust (Cloud Transmission)


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



The upper layer (UL) needs to be ultra‐robust (Cloud Transmission)


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


It is backward compatible for future extension

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


AgendaAgenda

Introduction


System Architecture

LDM vs TDM/FDM




Doppler Influence

PAPR


Laboratory

Fi ld T t


Field Tests

Conclusions

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


• Maximum frame size ≤ 250ms

LDM System Architecture: Transmitter StructureLDM System Architecture: Transmitter Structure


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


Lower Layer BICM

Common Modules

LDM System Architecture: ReceiverLDM System Architecture: Receiver


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


Stream B Decoder Stream B Common Modules

AgendaAgenda

Introduction


Physical Structure

LDM vs TDM/FDM




Doppler Influence

PAPR


Laboratory

Fi ld T t


Field Tests

Conclusions

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


Only part of time (TDM) or RF channel (FDM) used 100% time, 100% RF channel

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


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


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.


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.

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.


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.

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


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.


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



Doppler Influence

PAPR

Non Uniform Constellations Non‐Uniform Constellations

Latency & Complexity

Results


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)


AgendaAgenda


Basic Concepts

Physical Structurey

LDM vs TDM/FDM




Doppler Influence

PAPR



Results


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


decoding both the Upper and Lower Layers

AgendaAgenda


Basic Concepts

Physical Structurey

LDM vs TDM/FDM




Doppler Influence

PAPR



Results


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


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


Injection


Signal S(U)Level Δ

Pilot Signals

Noise


A two layered system : after equalization

S(U) + S(L) + (Channel Estimation Error) + Noise



Total Signal Power


Injection


Signal S(U)Level Δ

Pilot Signals

ColouredNoise ChannelNoise Channel

EstimationError





S(U) S(L) (Channel Estimation Error) NoiseChannel Estimation Error is the Signal Cancellation Error


Pilot Signals

ColouredNoise ChannelNoise Channel

EstimationError

• The lower layer signal has significantly boosted pilots. Good for equalization.


The lower layer signal has significantly boosted pilots. Good for equalization.• Channel estimation error should be much lower than the “noise”.

Cancellation ErrorCancellation Error

• There is only a main noise sources that can lead to aycancellation error:

Channel estimation error


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.,


pp.1,4, 25‐27 June 2014

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.


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)


Hz).

AgendaAgenda Introduction Layered Division Multiplexing

Basic Concepts

Physical Structure

LDM vs TDM/FDMLDM vs TDM/FDM

System highlights New LDPC Coding Algorithms



Doppler Influencepp

PAPR

Non‐Uniform Constellations

L t & C l it Latency & Complexity

Results


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


have very limited impact.

0 50 100 150 200 250 Symbol Number

150 Hz Doppler shift

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)


LDM UL 16K can go up to 260 km/h for the CR=5/15 (4.5 Mbps) with a 3 dBmargin

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



Basic Concepts

Physical Structure





Doppler Influencepp

PAPR



Results


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


LDM and SL PAPR are within 0.05 dB margin.

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



Basic Concepts

Physical Structure





Doppler Influencepp

PAPR



Results


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 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



Basic Concepts

Physical Structure





Doppler Influencepp

PAPR



Results


Latency and complexity of LDM receiversLatency and complexity of LDM receivers


Tuner IF & Down Converter A-D Converter


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


Stream B Decoder Stream B

Complexity of LDM receiversComplexity of LDM receivers


Tuner IF & Down Converter A‐D Converter


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.


Complexity of LDM receivers

• For a LDM receiver that decodes the high‐data rate lower layer


• 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



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


Given LL target SNR of 15 dB, iterations < 5


• LDPC decoder complexity:


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

+


L L BICM+ Bit to Cell Mapping


Common Modules




• Memory increase estimation assuming UL and LL use 64k LDPC codes


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

+




Common Modules



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

+




Common Modules



AgendaAgenda

IntroductionLayered Division Multiplexing Layered Division Multiplexing Basic Concepts

System Architecture

LDM vs TDM/FDM

System highlights System highlights New LDPC Coding Algorithms


Doppler Influence

Results: Computer Simulations Computer Simulations

Laboratory

Field Tests


Conclusions

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


LDM

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


Single Layer (Channel Estimation Loss)Single Layer (Channel Estimation Loss)

Mobile ChannelsStationary Channels


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


LDM (Channel Estimation Loss)(C a e st at o oss)



AgendaAgenda


System Architecture

LDM vs TDM/FDM



Doppler Influence

Results: Computer Simulations Computer Simulations

Laboratory

Field Tests


Conclusions

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


etc.

DBA – LDM (Receiver design and Implementation)DBA LDM (Receiver design and Implementation)


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


Single Layer (HW Impact)g y ( p )



LDM (HW Impact)( p )



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


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


-2 -1.5 -1 -0.5 010

-8

SNR (dB)

22 24 26 28 30

10-8

SNR (dB)

Field Test

AgendaAgenda


System Architecture

LDM vs TDM/FDM



Doppler Influence

Results:

Computer Simulationsp

Laboratory

Field Tests

C l i


Conclusions

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.


Questions?

Pablo Angueira [email protected]

Jon Montalban [email protected]

Cristina Regueiro [email protected]

http://www.ehu.es/tsr radiop // / _


15.02.23.ehu ldm tutorial · single layer tdm/fdm system multi-layer transmission system mobile and...

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