CBA 2004 Technical Presentation

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CBA 2004
KEITH.LARSON_at_fcc.gov FCC Media Bureau
[phone]

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GOOD MORNING !
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Todays Topic Technical Aspects of Digital LPTV
Report and Order

• Protected Contours Power Limits
• Interference Protection
• Out-of-Channel Emissions
• Transmitter Certification
• Modification of Equipment

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Digital Protected Signal Contours and Current ERP
Limits
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Signal Coverage
UHF station 300 feet above average terrain
15,000 watts
51 dBu
F(50,90)
X
26 mi
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Interference Protection
Best prediction modeling for ensuring protection

Fully account for terrain features and the RF
environment
Permits other means of interference avoidance to
maximize channel availability
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Digital Station Interference Prediction Analysis
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D/U Signal Strength Ratios

• For no predicted interference
• D - U gt Interference Threshold

Desired Signal Strength (D)
D and U are expressed in field strength units of
dBu (decibels above 1 microvolt per meter)
Undesired Signal Strength (U)
D U expressed in decibels
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Adopted D/U Interference Thresholds

• D/U values for different channel relationships
  between protected and potentially interfering
  stations
• Except for adjacent channel interference from
  digital stations, apply 73.623(c) of DTV rules
• Examples for co-channel protection
• Digital protecting digital 15 dB
• Digital protecting analog 34 dB

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D/U Ratios for Interference From First Adjacent
Channel Stations
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Contour Protection Methodology

D - U gt Threshold value? Where U is the
predicted strength of the proposed station.
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Adopted Use of the DTV Prediction Methodology for
Digital LPTV, TV Translator and Class A Stations

• OET Bulletin 69
• Longely-Rice Propagation

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Establish grid over protected contour
DTV Interference Prediction Method
(Simplified illustration)
FCC(50,90) 51 dBu (UHF digital LPTV)
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Identify Good Cells Longley-Rice Field
Strength of Desired Signal Exceeds Noise-limited
Value (e.g., 41 dBu for UHF)
L-R (50,90)P
P
gt 41 dBu


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Check Good Cells for Interference
(Longley-Rice)
Signal Strength of Potentially Interfering
Station (U)

(D - U) gt Threshold ?
P


Signal Strength of Protected Station at Pth Cell
( D )
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D/U Adjusted for Affects of Receiving Antenna
Suppression
D/U D/Uuncorrected antenna suppression gt
Threshold?
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Determine Cell Populations From
Census Data
Obtain service population by adding populations
of good cells (i.e., signal above noise-limited
value and no predicted interference)
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OET Bulletin 69 DTV Methodology Predicts Service
Population
Proposed Station
X
Bad Cells - masking interference from another
station
Service Area (Population)
Bad Cells signal is terrain-blocked
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Permitted Service Population Reductions
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Need to Tailor Assumed Vertical Antenna Pattern
in Table 8. of OET 69 Model for Typical Antennas
Used by LPTV Stations
ERPMAX 10 kW
Assumed vertical relative field 0.110
for F gt 6 degrees
6 º
F

ERP (6º 121 watts)
1000 feet
10 miles
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Assumed Vertical Antenna Pattern

• As temporary measure, will double values in Table
  8 of OET Bulletin 69 up to a value of 1.00
• FCC open to a revised procedure if more realistic
  assumed vertical field strength values are
  proposed

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Applicants for analog LPTV, TV translator or
Class A stations may use either the contour
overlap or OET Bulletin 69 DTV approach without
need for a rule waiver
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Other Available Means for Channel Finding
Interference Agreements
Co-located adjacent channel operation
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Transmission Issues
Require FCC Certification of New Digital LPTV and
TV Transmitters
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Key Transmitter Performance Criteria for
Certification

• Produces output signal that can be satisfactorily
  viewed on receivers designed for FCC DTV
  transmission standard
• Does not exceed the maximum rated digital
  average power output under any condition
• Out-of-channel emissions at output terminals
  (including all output filtering) meet the
  attenuation requirements of the simple mask
• Local oscillator frequency of RF upconverter must
  be maintained within 10 kHz

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Emission Masks
Total Average Channel Power
47 dB down
71 dB
71 dB
76 dB
76 dB
3
3
0.5 MHz
-0.5 MHz
6 MHz
- 6 MHz
6 MHz Channel
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Emission Resolution Bandwidth

• Standard bandwidth of 500 kHz
• Results from any alternate bandwidth should be
  converted to equivalent results from 500 kHz
  bandwidth
• A (dB) Aalternative 10 log (BWalternative
  /500)

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GPS Protection From 2nd and 3rd Harmonic Emissions

• RNSS frequency bands 1164-1215 MHz, 1215-1240
  MHz and 1559-1610 MHz
• Affects only TV channels 22-24, 32-36, 38, and
  65-69
• For FCC certification, transmitter must employ
  filtering that attenuates harmonic emissions in
  the RNSS bands by at least 85 dB

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GPS Protection From 2nd and 3rd Harmonic Emissions

• External filter with at least 85 dB attenuation
  in the RNSS bands may be field-installed on an
  existing transmitter
• Field measurements of the second or third
  harmonic output of transmitters so equipped are
  not required

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Modification of Transmission Systems

• Permit modification of existing analog equipment
  for digital transmissions (e.g., final RF
  amplifiers)
• FCC certificated manufacturer field modification
  kits
• Custom modifications

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Modification of Transmission Systems

• For custom modifications, transmitter must be
  performance-tested and station licensee must
  certify compliance with transmitter certification
  requirements

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• To obtain FCC documents go to www.fcc.gov
• For digital translator/LPTV Notice of Proposed
  Rule Making (NPRM)
• On the FCC home page click ltBureaus and Officesgt
  and then ltMediagt
• Scroll to headlines for 10/03/03 and click on
  link for the NPRM

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Thanks! Questions?
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CBA 2004
KEITH.LARSON_at_fcc.gov FCC Media Bureau
[phone]

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Use of Carrier Frequency Offset by Analog
Stations

fv
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Frequency Offset Operation

• Co-channel D/U ratio of 45 dB where analog
  stations operate without 10 kHz offsets or on
  same offset
• Ratio of 28 dB between stations operating on
  different offsets (a huge difference)

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Effect of Offset Relationship
102 mi
Protected Signal Contour
With offset
x
10 kW/500 ft co-channel stations
Interfering Signal Contour without offset
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New Offset Policy Consider the Following
Situation

• A proposed analog station fails to protect an
  existing co-channel LPTV or translator stations
  operating without a frequency offset
• If the proposed station could protect the
  existing station if both operated with different
  offsets, then
• FCC would direct the existing station, at its
  expense, to operate with a frequency offset

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Check Each Good Cell for raw Interference
Interfering Station (U)

U L-R (50,10)
P
(D - U)raw gt Threshold Standard?


D L-R (50, 90)
Desired Station DTV ( D )
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Cell Interference Accounting for Receiving
Antenna Suppression
g antenna cos (???
Interfering Station (U)
F/B lesser of - 20 log (g)
or 14 dB
D/U D/Uraw F/B
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OET Bulletin 69 DTV Prediction Methodology
Protects Service Population
Protected Station
Proposed Station
X
Bad Cells- Interference from another source
Bad Cells No service, signal is terrain-blocked
Service Area (Population)
Proposed Station Cannot Reduce Service Population
by more than 0.5
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DTV Service Area
shadowed
NTSC IX
DTV IX
NTSC DTV IX
DTV Service
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Modification of Transmission Systems

• Digital output power may not exceed 25 of
  previous peak sync NTSC output power
• For custom modifications, transmitter must be
  performance-tested and station licensee must
  certify compliance with transmitter certification
  requirements

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Digital Low Power TV and TV Translator Rules and
Policies

• IEEE Broadcast Symposium September 13, 2004

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Digital LPTV and TV Translator Rules
Keith Larson Media Bureau, FCC
[phone] Keith.Larson _at_fcc.gov