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Layered Division Multiplexing: Basic

Conce ts A lication Scenarios andPerformanceIEEE BTS LECTURE

. ,

IEEE Broadcast Technology Society Distinguished Lecturer

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IEEE Broadcast Technolo Societ

The IEEE Broadcast Technology Society (BTS) is

one of the technical societies & councils ou can

join as an IEEE member.

entertainment to audiences worldwide and on the go

BTS now has about 2,000 members and chapters worldwide,

s onsors technical eriodicals rovides su ort for technical meetin s

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S eaker

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S eaker

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S eaker

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A enda

Introduction

Layered Division Multiplexing

System technical highlights Results

Prototypes

Conclusions

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Introduction

Layered Division Multiplexing (LDM), which grew out from the Cloud-Txn (*) concept, is a

.

(*)

Cloud

Transmission:

Y.Wu etal,Cloudtransmission:Anewspectrumreusefriendlydigitalterrestrialbroadcasting

transmissionsystem.Broadcasting, IEEETransactionsOn58(3),pp.329337.2012.

It has been proposed as a Physical Layer technology to theATSC 3.0 next gen. DTV standard

In short, the main goal is to develop a terrestrial DTV PHY Layer thatis: Simple to build, Flexible and Efficient, With backward

compa e u ure ex ens on

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Introduction

Conventional FDM/TDM

single-decker bus.

is like a double-decker bus, morecapacity with the same foot print in

c anne .

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Introduction

It also provides flexibili ty for future growth: multi-decker bus, or adaptive-decker bus, with full backward

.

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A enda

Introduction Layered Division Multiplexing

Basic Concepts

System Architecture

.

System technical highlights

Prototypes

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Basic Conce t

Use of spectrum overlay techniques to

transmit multi le data streams in one RF

channel with different robustness and datacapacity for different services and

reception environmentsInjection

LevelStream A

100% of RF bandwidth and 100% of the time are

used to transmit the multi-layered signals

Stream B

-

efficiency and flexible use of the spectrum

Si nal cancellation is used to retrieve the robust

RFChannel BWupper layer signal first, cancel it from the receivedsignal, and then start the decoding of lower layer

signal

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Basic Conce t

The upper layer (UL) needs to be ultra-robust: Limited Data Rate

The lower layer (LL) wil l carry a high data rate:

Required for multiple HD and UHD services to fixed or portable

terminals

Injected from 3 to 6 dB below the upper layer signal

-

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Basic Conce t

The upper layer (UL) needs to be ultra-robust

The lower layer (LL) wil l carry a high data rate:

Required for multiple HD and UHD services to fixed or portable

terminals

Injected from 3 to 6 dB below the upper layer signal

-

More layers could be added later as network extension for new

The network is scalable and can be implemented progressively It is backward compatible for future extension

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Basic Conce t

10m directional antennaS/N = -1 dB

Upper layer por table reception:

1.5m Omni-directional antenna,

S/N = -0.5 dB

1.5m Omni-directional antenna,

S/N = +2 dB

DTV Tx

Lower layer fixed reception:

10m directional antenna,S/N = +19 dB

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A enda


Basic Concepts

System Architecture

.


Prototypes

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S stem Architecture

Preamble Preamble

UL payloadGI UL payloadGI

Max. 250 ms Max. 250 ms

LL payloadGI LL payloadGI

The Upper and Lower layer share some parameters:

FFT Size GI length

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S stem Architecture: Transmitter

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S stem Architecture: Transmitter

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S stem Architecture: Receiver

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S stem Architecture: Receiver

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A enda


Basic Concepts

System Architecture

.


Prototypes

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Capacity Examples: Case I Mobile + Fixed 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% Capacity

Data rate SNR Data rate SNR Data rate SNR Data rate SNR

layer 3.1 Mbps

QPSK 1/4-1.0 dB

Low layer w. -4 dB injection

Low-rate.

16QAM 2/314.4 dB

Mid-rate26.3 Mbps

64QAM 2/319.0 dB

High-rate

32.9 Mbps

64QAM 5/6 22.3 dB

power eve s are re erence o e o a n- an power o a ayers

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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layer 3.1 Mbps

QPSK 1/4-1.0 dB

2.5 Mbps

QPSK 2/5-0.2 dB

Low layer w. -4 dB injection Fixed(T2) 50%

Low-rate.

16QAM 2/314.4 dB

.

256QAM2/317.8 dB

Mid-rate26.3 Mbps

64QAM 2/319.0 dB - N/A

High-rate

32.9 Mbps

64QAM 5/6 22.3 dB - N/A



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layer 3.1 Mbps

QPSK 1/4-1.0 dB

2.5 Mbps

QPSK 4/5

4.7

dB

Low layer w. -4 dB injection Fixed(T2) 75%

Low-rate.

16QAM 2/314.4 dB

.

64QAM 3/512.0 dB

Mid-rate26.3 Mbps

64QAM 2/319.0 dB

27.2 Mbps

256QAM 2/317.8 dB

High-rate

32.9 Mbps

64QAM 5/6 22.3 dB

34 Mbps

256QAM 5/6 22.0 dB



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layer 3.1 Mbps

QPSK 1/4-1.0 dB

2.5 Mbps

QPSK 2/5-0.2 dB

2.6 Mbps

QPSK 2/33.1dB

2.5 Mbps

QPSK 4/5

4.7

dB

Low layer w. -4 dB injection Fixed(T2) 50% Fixed(T2) 66.7% Fixed(T2) 75%

Low-rate.

16QAM 2/314.4 dB

.

256QAM2/317.8 dB

.

64QAM 2/313.5 dB

.

64QAM 3/512.0 dB

Mid-rate26.3 Mbps

64QAM 2/319.0 dB - N/A

27.2 Mbps

256QAM 3/420.0 dB

27.2 Mbps

256QAM 2/317.8 dB

High-rate

32.9 Mbps

64QAM 5/6 22.3 dB - N/A - N/A

34 Mbps

256QAM 5/6 22.0 dB



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Capacity Examples: Case II Indoor + Fixed Reception




layer 5.46 Mbps

QPSK 6/152.7 dB

5.46 Mbps

QPSK 2/54.7 dB

5.46 Mbps

16QAM 2/38.9 dB

5.55 Mbps

64 QAM 3/5

12.0

dB


Low-rate.

16QAM 2/314.4 dB

.

256QAM2/317.8 dB

.

64QAM 2/313.5 dB

.

64QAM 3/512.0 dB

Mid-rate26.3 Mbps

64QAM 2/319.0 dB - N/A

27.2 Mbps

256QAM 3/420.0 dB

27.2 Mbps

256QAM 2/317.8 dB

High-rate

32.9 Mbps

64QAM 5/6 22.3 dB - N/A - N/A

34 Mbps

256QAM 5/6 22.0 dB



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Capacity Examples: Case II Indoor + Fixed Reception




layer 5.46 Mbps

QPSK 6/152.7 dB

5.46 Mbps

QPSK 2/54.7 dB

5.46 Mbps

16QAM 2/38.9 dB

5.55 Mbps

64 QAM 3/5

12.0

dB


Low-rate.

16QAM 2/314.4 dB

.

256QAM2/317.8 dB

.

64QAM 2/313.5 dB

.

64QAM 3/512.0 dB

Mid-rate26.3 Mbps

64QAM 2/319.0 dB - N/A

27.2 Mbps

256QAM 3/420.0 dB

27.2 Mbps

256QAM 2/317.8 dB

High-rate32.9 Mbps

64QAM 5/622.3 dB - N/A - N/A

34 Mbps

256QAM 5/622.0 dB



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LDM vs TDM/FDM: Gain

LDM vs TDM: MOBILE SERVICE GAIN (AWGN)

50% 33.3% 25%

3.1 Mbps 0.8 dB 4.1 dB 5.7 dB

. ps . . .

LDM vs TDM: HIGH-CAPACITY GAIN (AWGN)

.

17.5 Mbps 3.4 dB - 0.9 dB -2.4 dB

-. .

24.6 Mbps N/A N/A -0.3 dB

LDM gain between 4-8 dB

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LDM vs TDM/FDM: Ca acit Gain

High S/N environment

P

ower

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

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LDM vs TDM/FDM: Ca acit Gain

Low S/N environment

P

ower

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

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A enda

Introduction


Basic Concepts

System Architecture

.


Prototypes

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Im act of In ection on Thresholds

InjectionLevel

Stream A

The injection level provides an

remains constant

additional tool for broadcasters to

configure the coverage area.

Stream B

Higher injection levels provide more

emphasis on the fixed services

There is a tradeoff between injection level and required SNR

Channel BW emphasis on the mobile/portable services

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Im act of In ection on Thresholds

Upper layeronly

Injection level UL Min. SNR Lower layeronly

LL Min. SNR

-3 dB -0.5 dB 11.0 dB - .

3.1 Mbps

R = QPSK

.

11.2 Mbps

R = 1/2 16QAM

-4 dB -1.0 dB 11.7 dB

-5 dB -1.5 dB 12.4 dB

= - .

3.1 Mbps

R = 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

3.1 MbpsR = QPSK

- - . SNR=18.1dB

35.1 MbpsR= 2/3 256QAM

.

-4 dB -1.0 dB 23.6 dB

-5 dB -1.5 dB 24.3 dB

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Ke Enablin Technolo ies

that can achieve a negative SNR value, closer to the Shannon limit, and savepower.

Closer to the Shannon limit at low coding rate;

It can be truncated to higher rate code for power saving and low latencydecoding.

goo s gna cance a on sc eme a can m n m ze e cance a on

errors which makes a high data rate lower layer viable. Low-complex channel estimation and equalization algorithms.

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A enda

Introduction

Layered Division Multiplexing System technical highlights

New LDPC Coding Algorithms

Signal Cancellation and Channel Estimation

Do ler Influence Non-Uniform Constellations

Latency & Complexity

Results

Prototypes

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A rate com atible LDPC code

LDPC Parity Check Matrix (PCM)

Structure full com atible with DVB

Code PCM

of R < 0.5

It is very close to the Shannon limit

(< 1 dB)

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Cancellation in a two la ered s stem

Total Signal Power

pper ayer gna + ower ayer gna

Lower Layer

pper ayer

Signal S(U)Injection

Level

Signal S(L)

Pilot Signals

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Total Signal PowerMultipath Distort ion[S(U) + S(L)] + Noise

Upper Layer


Level

Signal S(L)

Pilot Signals

Noise

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S(U) + S(L) + (Channel Estimation Error) + Noise Total Signal Power

Upper Layer


Level

Signal S(L)

Pilot Signals

Noise

Channel

EstimationError

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

Channel Estimation Error is the Signal Cancellation Error

Lower La erSignal S(L)

Pilot Signals

Noise Channel

EstimationError

. .

Channel estimation error should be much lower than the noise.

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Cancellation Error

=

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Pilot-Aided Channel Estimation and Decision-Directed Channels ma on n ng e- c o c anne s w eren ec o e ays.

Signal cancellation performance vs. echo delay;

Pilot Aided 3rd

order interpolation (PA-Cinterp); Pilot Aided DFT interpolation (PA-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.; Vlez, M.; Angueira, P.; Regueiro, C.; Yiyan Wu; Liang Zhang; Li., W. Error Propagation in the Cancellation Stage for a Multi-" - , , , ., ., . , , -

June 2014

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1. Signal cancellation error is the same as the channel estimation error.

. .

need to invent new fancy algorithms.

3. 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

. .

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

prov es goo c anne es ma on resu s.

5. Larger size FFT OFDM modulation will improve estimation performance,since for the same ercenta e of ilots lar e FFT modulation reduces the ilot

spacing (in Hz).

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A enda

Introduction



New LDPC Coding Algorithms

Signal Cancellation and Channel Estimation

Do ler Influence Non-Uniform Constellations

Latency & Complexity

Results

Prototypes

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5

Signal Contributions

Double the FFT size, the Dopplernoise increase by 6 dB. -5

0

For 16K FFT, the Doppler noise is

about -10 dB. -15

-10

Power(dBm)

16K FFT

8K FFT

If the UL layer SNR is -3 dB, the -

10 dB Doppler noise is 13 dB

below the noise threshold and will-25

-20

4K FFT

have very limited impact.

0 50 100 150 200 25-35

-30

Symbol Number

2K FFT

150 Hz Doppler shift

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20LDM UL (=-5 dB), TI=200ms, 16K, TU-6, ATSC-3. Ideal CSI

UL: QPSK 7/15; =-5dB

16

18: ; =-

UL: QPSK 5/15; =-5 dB

12

14

R

min

up to 260 km/h for the

CR=5/15 4.5 Mb s8

10S

with a 3 dB margin4

6

0 50 100 150 200 250 3002

V (km/h)

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16

18

20LDM UL, LL-5dB, TI-100ms, 32k, QPSK, TU, ATSC-3 LDPC, DFT-ChEst

LDM-UL, r-4/15TDM, r-8/15

TDM, r-10/15

TDM, r-12/15

12

14

o

iseRatio[dB]

6

8Signalto

0 20 40 60 80 100 120 140 1602

4

Vehicle speed [km/h]

3 dB

Threshold

135km/h

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Sync & Timing Clock RecoveryCommon

TunerIF & Down

Converter A-D ConverterOFDM Demo

& EqualizationTime De-Intl

AGC

Stream AStream A Decoder Upper Layer BICM

+

Bit to CellMapping

Data + FEC

Lower Layer BICM

Common Modules

Stream B Decoder Stream B

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Sync & Timing Clock RecoveryCommon

TunerIF & Down

Converter A-D ConverterOFDM Demo

& EqualizationTime De-Intl

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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Com lexit of LDM receivers

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

Re-modulate the decoded data and then cancel it from the received signal

Complexity mainly depend on the LDPC decoder

LDPC decoding performance of the UL must be considered

Stream A

Delay

Stream A Decoder

Data buffer

Upper Layer BICM

Lower La er BICM

+ Bit to Cell

Mapping

Data + FEC

Common Modules

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LDPC Decodin Performance of U er la er

50QPSK 4/15 & 64-QAM 10/15 (IL = -5 dB). AWGN, Rice, Rayleigh and TU-6 fading channels

QPSK 4/15 AWGN UL: QPSK+4/15

35

40

45

QPSK 4/15 Rice

QPSK 4/15 Rayleigh

QPSK 4/15 TU-6 (Doppler = 33.3 Hz)

n

LL: 64NUC+10/15,IL: -5dB

15

20

25BER

Iteratio

-0

5

10

SNR [dB]

Given LLtarget SNR of

LDPC iterations vs SNR,

iterations < 5

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LDPC Decodin Performance of U er la er

LDPC decoder complexity:

LDPC computation complexity increase < 20% (10/50, worst case)

LDM wil l 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 .

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

, , ,

(50 iteration) should be finished simultaneously

maximum 64k cells arerequired . 32k cells for current decoding + 32k cells for storing next data

If TDI = 219(512K) cells 12.5% memory increase (worst case)

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A enda

Layered Division Multiplexing System technical highlights

Results

Simulations

Lab Tests

Field Tests

Conclusions

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Simulation Confi uration

Single Layer

CONSTELATION Code Rate

(Mbps/Hz)Bit Rate (Mbps)

QPSK3/15 0.38 1.834/15 0,53 2.45

5/15 0.66 3.07

16-QAM

. .

4/15 1.05 4.91

5/15 1.32 6.15

Const. Code RateSpectral Efficiency

(Mbps/Hz)Bit Rate (Mbps)

QPSK 3/15 0,38 1.83

QPSK 4/15 0,51 2.45

Lower Layer

16-QAM 3/4 3.17 16.63

64-QAM 2/3 4.22 22.18256-QAM 2/3 5.28 27.72

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Com uter Simulations: Sin le La er

Stationary Channels (Ideal Channel Estimation)

AWGN RICE Rayleigh 0 dB Echo

QPSK4/15 -2.9 -2.7 -2 -2.3

5/15 -1.7 -1.5 -0.5 -0.9

16-QAM4/15 0.7 0.9 2.1 1.7

5/15 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 -1.0

5/15 0.4 0.1 0.4

16-QAM4/15 2.8 3.2 3.5

. . .

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Sin le La er Channel Estimation Loss

Stationary Channels

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LDM In ection Ran e = -4 dB

AWGN RICE Rayleigh 0 dB Echo

UL QPSK 4/15 -0.4 -0.1 1.3 0.8

LL 16QAM 3/4 15.4 15.9 18.8 18.7

LL 64QAM 2/3 18.9 19.2 21.5 21.3

LL 256QAM 2/3 23.2 23.5 25.7 25.8

Mobile Channels (Ideal Channel Estimation)

fd=5 Hz f d =50 Hz f d =75 Hz

QPSK 4/15 2.0 2.3 2.4

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LDM Channel Estimation Loss

Stationary Channels

Mobile Channels

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A enda

Introduction



Results

Simulations

Field Tests

Prototypes

Conclusions

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Lab Set U

UPV/EHUSW

DEMOD

Based on a DVB-T2 Software Defined Radio

(SDR) platform;

Upper Layer tested under different channel :

AWGN, Rice, Rayleigh, etc.

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UNIVERSITY OF THE BASQUE COUNTRYLDM RECEIVER

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Sin le La er HW Im act

Stationary Channels

Mobile Channels

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LDM HW Im act

Stationary ChannelsMobile Channels

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LDM Field TestBILBAOBILBAO

SPAINSPAIN, ,

Frequency 690 MHzTransmitter ERP 35.68 dBW

Tx Antenna Height 48 meters

Alt itude (a.g.l.) 216 meters

Radiation Pattern Directive (140-210)

Polarization Vertical

Channel Bandwidth 6 MHz

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Simulation Lab and Field Test Results

-1

100

Upper Layer: 8K, GI=1/32, CR=1/4, QPSK, R=2.3 Mbps

-1

100Low er Layer: 8K, GI=1/32, CR=2/3, 256-QAM, R=30.1 Mbps

AWGN: Simulated

AWGN: Laboratory

Field Test

10-2

10

10-2

10

10-4

10-3

BER

10-4

10-3

BER

R=1/4, 2.3 Mbps.

Lower Layer:

10-6

10-5

10-6

10-5

256QAM, R=2/3,

30.1 Mbps

8k FFT

-

10

-7

-

10

-7

AWGN: Simulated

AWGN: Laboratory

Field Test

-2 -1.5 -1 -0.5 010

-

SNR (dB)

22 24 26 28 30

10-

SNR (dB)

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A enda

Introduction



Results

Simulations

Field Tests

Prototypes

Conclusions

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UNIVERSITY OF THE BASQUE COUNTRYLDM RECEIVER

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ETRI: Electronics and TelecommunicationsResearch Istitute Korea

Shown in next Dec ATSC AH 32 Face to Face meetings and in Las VegasNabShow

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A enda

Introduction



Results

Simulations

Field Tests

Prototypes

Conclusions

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Conclusions

LDM is a multiplexing scheme, that can mix different services

with different reception conditions in one RF channel.

The main advantage is the use of the 100 % of the spectrum

ur ng e w o e transm ss on t me.

It achieves 5 to 6 dB SNR gain when compared to TDM/FDM

systems for robust mobile/indoor reception.

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A

Pablo Angueira

[email protected]

p: www.e u.es sr_ra o

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15.07.14.IEEEBTS.DL.pdf

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