ATSC 3.0 Backward Compatible SFN In-Band Distribution Link andIn-Band Inter-Tower Wireless Network for Backhaul, IoT, and Datacasting

Communications Research Centre – Canada

Electronics and Telecommunications Research Institute – South Korea

Merrill Weiss Group LLC – United States

University of the Basque Country - Spain

Presented by Yiyan Wu, CRC Canada

NAB Show Express BEITC’2020

May 13-14, 2020 2

Outline

• Motivation

• ATSC 3.0, Single Frequency Network (SFN), andLayered-Division Multiplexing (LDM)

• In-Band Distribution Links (IDL) in ATSC 3.0: Challenges and Solutions

• Bi-Directional Inter-Tower Communications (ITC)

• Conclusions

3

Motivation

• To achieve robust mobile service delivery in ATSC 3.0, use ofSingle-Frequency-Networks (SFNs) becomes necessary

• Significant costs for deploying new SFN transmitters are to install & operate Studio-to-Transmitter Links (STLs)

• With many more low power transmitters being deployed, STL cost quickly becomes unaffordable

• A capable, scalable, and cost-effective STL solution is needed for fast & economical deployment of ATSC 3.0 SFN transmitters

• Wireless In-Band Distribution Link (IDL) is a cost- and spectrally-efficient alternative to existing fiber & microwave solutions

4

Single Frequency Network

• Single Frequency Networks (SFNs) offer high spectral efficiency in

delivering regional services over large geographic areas

• SFNs significantly reduce total transmission power compared to existing

single-transmitter operations

• In an SFN, all transmitters emit the same signal, frequency-locked, with

controlled relative signal emission times

• With robust signal configurations, broadcasters can deliver different

signals from adjacent SFN transmitters, permitting local services as an

extended use of the traditional SFN

5

ATSC 3.0 SFN

There are cost & availability issues to install and operate SFN STL

• Dedicated microwave links:

(1) Spectrum often scarce

(2) Installation often costly

• Fiber links:

(1) Expensive construction

(2) Rental costs often high

• Satellite:

(1) Expensive space segment

Exciter

Tx-B

ATSC 3.0

GatewayATSC 3.0

ExciterSTL

Tx-A

Exciter

Tx-C

Exciter

Tx-D

STL

STL

STL

CL

EL

CL

EL

CL

EL

CL

EL

User

Device

User

Device

User

Device

User

Device

Solution: Wireless In-Band Distribution Links (IDL)

6

ATSC 3.0 Service Capacity

Robust Mobile Service

Fixed Service

Extra capacity can be used for In-Band Distribution Link,

supplemental down-link, and other emerging services

IDL

Robust Mobile Service

Fixed High-Data Rate Service

Core Layer (CL): Up to 3×720p/30FPS or 8×480p/30FPS

2.5 – 5 Mbps

Next Gen-TV with LDM in a 6 MHz channel

Enhanced Layer (EL): Up to 8×720p/60FPS or 4×1080p/60FPS

16 – 20 Mbps

Time/Frequency

Time/Frequency

ATSC 3.0 with LDM and IDL

There are cost & availability issues to install and operate SFN STL

7

ATSC 3.0 In-Band Distribution Link

Service capacity loss to enable IDL:

• About 30% EL capacity at beginning

• Can be reduced to around 20%, and

• Further reduced to about 10%

Capacity loss reduced by advanced signal processing algorithms at remote transmitters

Tower-to-tower propagation and high gain Rx antennas allow the use of high-order

modulation (1k/4k-QAM) and high coding Rate (12/15 or 13/15) for IDL transmission

8

IDL with TDM vs LDM Examples

IDL (%)MBS

[Mbps]FBS

[Mbps]STL

[Mbps]

STL-SISOTDM 33% 2.6 10.7 13.4

LDM-EL 41% 4.0 9.5 13.5

STL-MIMOTDM 20% 3.2 12.8 16.0

LDM-EL 24% 4.0 12.1 16.1

No IDL 0% 4.0 16.0 0

• An ATSC 3.0 system with two 720p mobile services in CL and four 1080p fixed services in EL

• Using LDM avoids any performance loss in CL capacity

• With advanced IDL receiver, EL capacity loss from using LDM compared to TDM becomes negligible.

• Using 2x2 MIMO could reduce the capacity required by IDL

MBS: Mobile Broadcast Service FBS : Fixed Broadcast Service

9

Transmitter Timing Control in IDL

• RL-Rx antenna receives both forward signal (FWS) from the main transmitter (Tx-A) and loopback signal (LBS) from the secondary SFN transmitter (Tx-B) antenna

Tx-A

Tx-B

10

IDL Implementation Challenges

(a)

FBS

MBS (MBS+FBS)-

STL

EL

CL

FBS

MBS Training

Sequence

(b)

EL

CL

• RL-Rx antenna receives both forward signal (FWS) from the main transmitter Tx-A and loopback signal (LBS) from the SFN transmitter (Tx-B) transmit antenna

• LBS could be much stronger than FWS

RL-Rx

Exciter

Signal

Isolation

Tx-A

Tx-B

MBS + FBS + STL

11

Loopback Signal Isolation

To reduce the LBS power at the IDL receiver antenna:

• Increase Tx-Rx antenna spacing

• Install LBS signal blocking

• Design Rx antenna directivity

• Avoid LBS signal reflections on nearby obstacles

12

Loopback Signal Cancellation

• The received signal:

• Since the LBS signal (XLBS) is known, the key to achieving good LBS cancellation is to obtain accurate LBS channel estimate : HLBS

0

RL STL FWS LBS LBSY k X k H k X k H k

N k

13

LBS Cancellation : LOS Channel

• This is a typical scenario

• Mean square error (MSE) of the channel estimates, equivalent to the residual LBS power level relative to the original level, for LBS levels of 0, 10, 20, and 30 dB above FWS signal

• 2D-Windowing

• SNR of FWS with residual LBS after cancellation is always over 40 dB –irrelevant to loop back signal level

Even for a high-throughput STL signal with SNR threshold of 35 dB, the residual LBS

introduces little impact on the STL signal detection

14

LBS Cancellation : Multipath Channel

• This is a worst-case scenario

• MSE of residual LBS power level relative to the original level, for LBS of 0, 10, 20, and 30 dB above FWS signal

• 2D-Wiener channel estimator

• SNR of FWS with residual LBS after cancellation is always over 30 dB: irrelevant to loop back signal level

For a STL signal with SNR threshold of 25 dB, the residual LBS introduces little impact on the

STL signal detection

15

IDL Receiver Dynamic Range

• The IDL receiver needs to have sufficient dynamic range to cancel LBS and detect IDL signal.

• For example, when

• LBS/FWS = 30 dB

• IDL detection SNR = 25 dB

• the required dynamic range is 55~60 dB

16

LBS vs FWS Signal Strength

• Fc = 473 MHz

• Free space propagation

• LBS antenna pattern attenuation: 20 dB

• No blocking

Example,

• PTx-A = PTx-B = 50 dBm

• IDL Tx-Rx distance = 5 km

• LB Tx-Rx = 50 m for PFWA = PLBS at RL_Rx

• LB Tx-Rx < 10 m is sufficient with LBS

cancellation of 25 dB

17

A Case Study in Ottawa

• A measurement campaign was carried out in Ottawa area to evaluate the feasibility of implementing IDL

• Existing DTV tower is used as the Master Transmitter (Tx-A), located on top of mountain Camp Fortune, Chelsea, Quebec, with an antenna height above sea level of 360 meters

18

A Case Study in OttawaCh. Ch. #

Fc[MHz]

HTx*

[m]Tx ERP[dBm]

Global Toronto

14 473 169.1 81.6

TVO 24 533 130.9 79.8

CBC Ottawa 25 539 197.8 84.9

Tele-Quebec 30 569 141.3 84.8

Radio Canada

33 587 197.8 83.8

V-Tele 34 593 141.3 74.8

19

A Case Study in Ottawa

• For all test points, the received FWS signal power is higher than -60 dBm

• Some test points have a remote antenna height of only 10 meters

• For all test points, the LBS over FWS power ratio is less than 30 dB, even for testing points of 100 km away

• Earlier simulation results show that a simple LBS cancellation could provide > 30 dB STL signal SNR

20

Inter-Tower Communications

• Bi-directional Inter-Tower Communication (ITC) links can be realized between adjacent broadcast towers, as an extension of IDL technology

• Each tower can broadcast A/V/data services, while receiving information from other towers for relay, backhaul, and broadcasting

• ITC Use Cases include:

• Fault-tolerant IDL network

• Network O&M: requiring remote towers sending back diagnostic information

• Internet of Things (IoT) applications that collect device information

• Connected vehicle applications that collect real-time traffic information

• Other datacasting applications with an uplink

21

Inter-Tower Communications• TV service fixed/handheld reception has low Rx antenna height

that has small coverage area, due to terrain and structure blockage

• Broadcast tower can mount high Rx antenna reaching much farther

• Full-duplex transmission: broadcast/multi-cast out, unicast-in on the same frequency

Tower1 Tower2 Distance

50m 50m 50 km

200m 50m 75 km

200m 200m 100 km

500m 250m 135 km

IDL/ICT

SFN & Localized services

IDL/ICT

SFN & Localized services

22

Inter-Tower Communications

There are three different signals:

• A/V/Datacasting services to mobile/fixed terminals using LDM

• IDL Link: 1-way, high data rate, high SNR for spectrum efficiency

• ITC link: 2-way communications among towers

ITC Network can also run on multi-frequency environment (no signal cancellation required)

(a) IDL & ITC on EL with LDM

PLP of Mobile Broadcast

PLP Fixed Broadcast

CL

EL

PLP of Mobile Broadcast

PLP Fixed Broadcast

CL

EL

IDL PLP

IDL PLPITC

PLP

ITC

PLP

(b) IDL & ITC with TDMtime time

PLP – Physical Layer Pipe

23

ITC Datacasting for Localized IoTD1(t)

• Different cells can broadcast different data (localized services)

• Some cells can operate as SFN if desired

• LDM can be used to achieve tiered service and improve spectrum efficiency

• Robust transmission mode can be used to improve the reception in overlapping areas

Different Rx antennas needed at head-end

D2(t)

D3(t)

D4(t)

D5(t)

24

ITC SummarySFN Broadcast In-band Distribution Inter-Tower Network

• Improve service quality for

mobile, handheld, and

indoor receptions

• Allow new services: IoT,

connected car, datacasting

• One-to-many timely

services for large rural

areas for traffic map

update, weather

conditions, emergency

warning

• Different services in different cells

• Eliminate studio-to-transmitter

link spectrum requirement

• Reduce broadcast operating

costs

• Spectrum sharing and re-use

• Scalable & reconfigurable network embedded in a

broadcast system

• Broadcast network cue & control that do not rely

on other telecom infrastructure – surviving

emergency and nature disaster

• Backhaul data among towers: IoT, connected cars,

datacasting, etc.

• Full-Duplex Transmission: Transmission and

receiving on the same frequency – improving

spectrum efficiency

• Dynamic Spectrum Re-Use and Sharing + LDM:

Converging Broadcast and Wireless Services

• Inter-Tower Network can work under SFN, OCR, or Multi-Frequency Network environments

25

Conclusions

• A wireless in-band distribution (IDL) technology offers a cost and spectral efficiency

solution for future broadcast systems, in which distribution data is delivered to new SFN

transmitters in the same ATSC 3.0 waveform as service data is delivered to the public

• Assigning a special PLP for STL data allows a completely backward-compatible solution

• Layered-division multiplexing is an ideal choice for IDL to deliver STL data in EL, taking

advantage of the extra capacity it brings

• Different IDL signal configurations are available for different capacity-complexity trade-offs

• IDL could be extended to an Inter-Tower Communication (ITC) technology to implement

an independent inter-tower network on top of the broadcast network

• IDL/ITC are enabling technologies to deliver new datacasting services in future DTV

26

Thank you

Questions …

yiyan.wu@canada.ca

27

28