ATSC M/H Synchronization based on GPS (Epoch)€¦ · An ATSC System Time Generator (STG) is a...
Transcript of 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
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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
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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
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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
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M/H System Block (review)
M/H Pre-Processor“Studio”
M/H Post-Processor“Transmitter”
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Simplified System Block
STL
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M/H Frame is a virtual “Container”
“C i ” & l
Mobile / Handheld “Essence”
“Container” & select“Essence” can be
synchronized across stations
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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
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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
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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
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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
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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)
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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.
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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
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Channel Change Improvement
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Broadcast Applications: Handoff, Diversity
Placeholder for R&SPlaceholder for R&S
(Wide Regional Area)
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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
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M/H Frames
Regional Broadcast Autonomous Roaming
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System Time Distributed Transmission (A/110)
System timey
GPS
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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
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A4Site 13 Sit
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All transmitters synchronized by:– M/H Frame Cadence derived from GPS (ATSC Epoch)
– All exciters use inherent M/H Trellis Coder Initialization for Sync
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All exciters use inherent M/H Trellis Coder Initialization for Sync
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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
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Adjacent Markets with Overlapping Contours
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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
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• 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
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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
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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
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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
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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
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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
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