atsc m/h synchronization based on gps (epoch)€¦ · an atsc system time generator (stg) is a...

ATSC M/H Synchronization based on GPS (Epoch)

Overview

ATSC S stem Time O er ie• ATSC System Time Overview• Potential Enhanced Applications ATSC M/H• Conclusions

Rosum Corporation Confidential

Who We Are

Rosum• Founded by original GPS

Rohde & Schwarz• Broadcast equipment

f tarchitects

• Provider of timing and location

manufacturer: – M/H Exciters– M/H Multiplexers and

solutions using broadcast TV

• Dual-use technology supporting

Encoders – M/H Test & Measurement

gy pp gcommercial and public safety applications

• Initially introduced concept of System Time

Rosum Corporation Confidential 3

What is System Time?

• ATSC System Time creates a direct relationship between GPS and ATSC emissions

• GPS is commonly used as a timing and frequency calibration reference in broadcast and communications networks: examples include T-DMB, DVB-H, WiMAX, CDMA and MediaFLOCDMA and MediaFLO

• Potentially can be used to enhance ATSC M/Hy


Why is a Precision Time Reference Important?

• Enhanced system performance: supports enhanced handoff; enables diversity (frequency, physical, time); supports both MFNs and SFNs

• Minimal investment: One GPS receiver at transmitter, can be implemented with new equipment for ATSC M/H

• Interoperability: Supports potential interoperability with non-ATSC networks (WiMAX, FLO etc)( , )

• Extensibility: Provides platform for future applications; also aligned with SMPTE and EBU Task Force on Synchronizationwith SMPTE and EBU Task Force on Synchronization


M/H System Block (review)

M/H Pre-Processor“Studio”

M/H Post-Processor“Transmitter”


Simplified System Block

STL


M/H Frame is a virtual “Container”

“C i ” & l

Mobile / Handheld “Essence”

“Container” & select“Essence” can be

synchronized across stations


Content , metadata, etc across stations(Network)

M/H Slot Position (Tightly Synchronized VSB Frame)

M/H Slots are mapped to consecutive portions of VSB Data fields:1 M/H Slot = ½ VSB Data field M/H slots are offset 37 packets relative to half data field boundaries

Transmit Order

M/H slots are offset 37 packets relative to half data field boundariesSynchronous relationship so receivers can discover physical layer

37 packet offset Field sync (Positive PN63)

Se

4 828 Symbols

156 TS packetsM/H Sl t #0

OrderTransmit

Order

37 packet offset

Data+FEC

Field sync (Negative PN63)

egment

24.2msp

Slot #0

M/H Slot #1

M/H

156 TS packets

156 TS packets

Data+FEC

Sync

24.2msSlot #2

M/H Slot #3

156 TS packets

156 TS packets


Effective M/H Turbo Code Block

M/H R i d d l tM/H Receiver depends on placementof M/H Data in known positions VSB FrameTo locate correct Symbols


Defining ATSC System Time (Epoch)

1PPMF1PPMF ((1 Pulse Per M/H Frame) = Time beginning of 1 Pulse Per M/H Frame) = Time beginning of M/H VSB Frame should be emitted M/H VSB Frame should be emitted

Air Interface DTV AntennaAir Interface DTV Antenna


ATSC System Time MetricsATSC System Time Metrics

# VSB Frames M/H (MPH) Frame = 20 # VSB Frames M/H (MPH) Frame = 20

GPS / ATSC Epoch = Jan 6, 1980 00:00:00 UTCGPS / ATSC Epoch = Jan 6, 1980 00:00:00 UTC

# Symbols per M/H Frame = 10,416,640 Symbols# Symbols per M/H Frame = 10,416,640 Symbols

# Packets (M/H Frame) = 12,480 # Packets (M/H Frame) = 12,480

“Integer Relationship”

ATSC System Time = # M/H Frames since Epoch ATSC System Time = # M/H Frames since Epoch

1PPMF = 1 Pulse per M/H Frame1PPMF = 1 Pulse per M/H Frame


ATSC M/H ATSC M/H New Reference SignalNew Reference Signal

An ATSC System Time Generator (STG) is a device that generates a frequency reference signal (such as 10 MHz), a 1 pulse per M/H frame (1 PPMF) reference signal, and a counter representing ATSC ST.

1PPMF1PPMF11 PPulse PPer MM/H FFrame

( )( )(NEW)(NEW)


Technical Advantage• All data in every M/H frame will have a simple timing relationship relative to

ATSC ST and the 1PPMF reference signal

Some facts about ATSC System Time• Some facts about ATSC System Time– ATSC ST is uniform and monotonically increasing– There are no leap seconds or any other adjustments to worry about, ever– There is an exact integer relationship between GPS Time and ATSC ST givenThere is an exact integer relationship between GPS Time and ATSC ST given

by:

• Since all synchronization is nominally referenced relative to ATSC ST and the 1 PPMF signal, there are no “sliding time references” or “wrap-around” cases to deal with. This avoids some of the ambiguity that can arise when using a non-ATSC li d ti i f lik l d (1 PPS) hi h i ht taligned timing reference like a one pulse per second (1 PPS) which might occur at

an awkward time within an M/H frame

• This globally defined timing reference is valid for both SFNs and MFNs.


g y g

Applications that will benefit• Channel Change (Consumer Experience)• Handoff / Roaming (Regional Area)• Handoff / Roaming (Regional Area)• Diversity Techniques (Local Area)

– Frequency– Frequency – Time– Transmitter (SFN)( )

• New SFN Architectures• Positioning ServicesPositioning Services


Channel Change Improvement


Broadcast Applications: Handoff, Diversity

Placeholder for R&SPlaceholder for R&S

(Wide Regional Area)


Duopoly (Local Area)

Synchronization “Essence and Containers”

Satellite“Regional

GPS

NTP SRegional Essence” NTP Server

M/HExciter

Station“Local

Essence”

STLM/H Mux

M/H Virtual Containers


M/H Frames

Regional Broadcast Autonomous Roaming


System Time Distributed Transmission (A/110)

System timey

GPS


Novelty: Novelty: First Time ever SFN with Re-Mux on Network Edge is possible

New SFN Architecture With National Content OverlayNew SFN Architecture With National Content Overlay

Multi‐Beam Satellite

Save $$ and satellite BW

A1 B3 C2D1D 4

A4A1 B3 C2D1D 4

A4Site 13 Sit

B1

C1D3

A2

A3B5

C4

A5

B7

C 7

D6

A9D8

C 8

B9

B 11

C10A12

B1

C1D3

A2

A3B5

C4

A5

B7

C 7

D6

A9D8

C 8

B9

B 11

C10A12

St diSt di

Site 3

Site 2

3 SiteM/H SFN

B2B4

C 3

A15

D2

B6

C5

B8

D 7

C 8

B10

D 9

C11

A11

B1 2C12

D11

A8

B2B4

C 3

A15

D2

B6

C5

B8

D 7

C 8

B10

D 9

C11

A11

B1 2C12

D11

A8

StudioStudioSite 2

All transmitters synchronized by:– M/H Frame Cadence derived from GPS (ATSC Epoch)

– All exciters use inherent M/H Trellis Coder Initialization for Sync

C6

A6 C9

A7D1 0

A10

C13

D12

A13

A14

D5

C6

A6 C9

A7D1 0

A10

C13

D12

A13

A14

D5Local Station SpotSpot--beambeam (Local Content < 19.39 Mbps ATSC M/H TS)

All exciters use inherent M/H Trellis Coder Initialization for Sync


D1 3D1 3CONUSCONUS National Content (Mobile)Site n Re‐Mux (National + Local) 19.39 Mbps M/H TS is Broadcast

New InterNew Inter--Market RoamingMarket Roaming

Multi‐Beam SatelliteATSC M/H System Time (GPS)Common Essence Sync

to System Time

A1 B3 C2D1D 4

A4A1 B3 C2D1D 4

A4

y

B1

C1D3

A2

A3B5

C4

A5

B7

C 7

D6

A9D8

C 8

B9

B 11

C10A12

B1

C1D3

A2

A3B5

C4

A5

B7

C 7

D6

A9D8

C 8

B9

B 11

C10A12

Market

Market

B2B4

C 3

A15

D2

B6

C5

B8

D 7

C 8

B10

D 9

C11

A11

B1 2C12

D11

A8

B2B4

C 3

A15

D2

B6

C5

B8

D 7

C 8

B10

D 9

C11

A11

B1 2C12

D11

A8

MarketC

tB

A

C6

A6 C9

A7D1 0

A10

C13

D12

A13

A14

D5

C6

A6 C9

A7D1 0

A10

C13

D12

A13

A14

D5

Adjacent Markets with Overlapping Contours


D1 3D1 3

Seamless Roaming and Frequency DiversitySFN to SFN or MFN SFN to SFN or MFN possible with System time

Adjacent Markets with Overlapping Contours

TV based Positioning is a natural complement

The broadcast TV infrastructure is highly correlated with population density, and offsets many of GPS’ vulnerabilities

• High Power1MW ERP

L F

• Low Power500W from 20,000 km

• Low Frequency50-750 MHz

• Frequency DiversityWide 6MHz channels,

,

• High Frequency1.6 GHz

• No Frequency

• Horizontal SignalsLess attenuation from walls than roofs

multiple channels per towerDiversity

• Narrow Bandwidth1 MHz


• Vertical Signals • Robust InfrastructureSupports EAS, Katrina survivor,backup power

Rosum TV-Positioning Today

• Rosum currently uses reference infrastructure to tell the receiver what signals to expect

Device measures TV signals in the areasignals in the area

Regional Monitor Unit (reference station) for aiding information Rosum Location &

Timing Server


NegativeRequires Back Channel

TV-Positioning in ATSC-M/H

• Supports autonomous positioning for unconnected devices (PMPs etc)• No ancillary inputs required for location determination• Overall system more robust

ATSC-M/H broadcasts

• Overall system more robust

TV-positioning utilizes signals 128 dBm-128 dBm

Device autonomouslyDevice autonomously calculates its position


Requires No Back Channel

TV-Positioning in GPS-Unavailable Environments

Midtown Manhattan, lobby level Senate Hart Building, Washington DC

Propagation of TV enables use for positioning indoors in GPS-denied environments; wide bandwidth enables mitigation of signal multipath


Commercial Positioning & Timing Applications

• System Time enhances a variety of positioning and timing applicationspp

• Commercial applications include: – Location-based services

• Self-navigation• Friend finder• Location-enabled mobile social networks

– Location-based advertisingDRM– DRM

– TBD


Augmentation and Compensation for GPS

• GPS has three major well-documented vulnerabilities:– Poor performance indoors and in urban areasp– Susceptibility to natural RF interference– Susceptibility to manmade interference (jamming /

spoofing)

• This is a recognized threat to commercial and public• This is a recognized threat to commercial and public safety communications networks


Public Safety Positioning & Timing Applications

• Public safety / homeland security applications:– Positioning and timing for first response indoors and in urban

areas where GPS is challenged – Location-aware receivers for alerts in support of WARN Act – Timing and frequency for public safety communications networks– Timing and frequency for intelligence networks– E911


Questions

Mike SimonRohde & Schwarz

[email protected]

atsc m/h synchronization based on gps (epoch)€¦ · an atsc system time generator (stg) is a...

Documents