1 / 45

C B A 2 0 0 4

This report covers the technical aspects of digital LPTV, including interference protection and transmitter certification. It discusses the prediction modeling for ensuring protection from interference, as well as the D/U signal strength ratios for interference analysis. The report also explains the use of the DTV prediction methodology and Longley-Rice propagation for interference prediction. Additionally, it covers the criteria for FCC certification of new digital LPTV and TV transmitters.

venuti
Download Presentation

C B A 2 0 0 4

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CBA2004 KEITH.LARSON@fcc.gov FCC Media Bureau (202) 418-2607

  2. GOOD MORNING !

  3. Protected Contours & Power Limits Interference Protection Out-of-Channel Emissions Transmitter Certification Modification of Equipment Today’s Topic: Technical Aspects of Digital LPTV Report and Order

  4. Digital Protected Signal Contours and Current ERP Limits

  5. Signal Coverage UHF station: 300 feet above average terrain; 15,000 watts F(50,90) = 51 dBu 26 mi X

  6. 110010011001001111100110111101001010110010101011 • 1111010010101100101010111110 1111010010101100101010111110 11001001 10010011111001101111010010101100 10101011 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

  7. Digital Station Interference Prediction Analysis

  8. D/U Signal Strength Ratios For no predicted interference: D - U >= 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

  9. 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

  10. D/U Ratios for Interference From First Adjacent Channel Stations

  11. Proposed Station Protected Station 10 miles 10 miles U D 2 miles 2 miles Protected Contour (D) Antenna heights above average terrain (2-10 miles) Contour Protection Methodology D - U >= Threshold value? Where U is the predicted strength of the proposed station.

  12. Adopted Use of the DTV Prediction Methodology for Digital LPTV, TV Translator and Class A Stations OET Bulletin 69 Longely-Rice Propagation

  13. DTV Interference Prediction Method (Simplified illustration) Establish grid over protected contour FCC(50,90) = 51 dBu (UHF digital LPTV)

  14. 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 = > 41 dBu +

  15. Check “Good” Cells for Interference (Longley-Rice) Signal Strength of Potentially Interfering Station (U) + (D - U)> Threshold ? P * + Signal Strength of Protected Station at Pth Cell ( D )

  16. Interfering Station (U) P + *  + Desired Station DTV ( D ) Desired Station DTV ( D ) D/U Adjusted for Affects of Receiving Antenna Suppression D/U = D/Uuncorrected +antenna suppression >= Threshold?

  17. 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)

  18. 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

  19. Permitted Service Population Reductions

  20. 5 miles 74 dBu contour 10 kW directed down at 6º puts 74 dBu at 16 miles 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 Φ >= 6 degrees Φ = 6 º ERP (6º = 121 watts) 1000 feet 10 miles

  21. 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

  22. 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

  23. Other Available Means for Channel Finding Interference Agreements Co-located adjacent channel operation

  24. Transmission Issues Require FCC Certification of New Digital LPTV and TV Transmitters

  25. 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

  26. “Stringent” “Simple” Emission Masks Total Average Channel Power 47 dB down 71 dB 71 dB 76 dB 76 dB 3 3 - 6 MHz -0.5 MHz 0.5 MHz 6 MHz 6 MHz Channel

  27. 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)

  28. 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

  29. 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

  30. 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

  31. Modification of Transmission Systems • For custom modifications, transmitter must be performance-tested and station licensee must certify compliance with transmitter certification requirements

  32. 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 <Bureaus and Offices> and then <Media> • Scroll to headlines for 10/03/03 and click on link for the NPRM

  33. 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 1100101 Thanks!Questions?

  34. CBA2004 KEITH.LARSON@fcc.gov FCC Media Bureau (202) 418-2607

  35. Minus Offset (-) Plus Offset (+) - 10 kHz + 10 kHz 1.25 MHz 6 MHz TV Channel Use of Carrier Frequency Offset by Analog Stations fv

  36. 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)

  37. 52 mi Effect of Offset Relationship 102 mi Protected Signal Contour With offset x 10 kW/500 ft co-channel stations Interfering Signal Contour without offset

  38. 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

  39. Check Each Good Cell for “raw” Interference Interfering Station (U) + U: L-R (50,10) P (D - U)raw > Threshold Standard? * + D: L-R (50, 90) Desired Station DTV ( D )

  40. + P *  + Desired Station DTV ( D ) Desired Station DTV ( D ) 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

  41. 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%

  42. DTV Service Area shadowed NTSC IX DTV IX NTSC + DTV IX DTV Service

  43. 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

  44. Digital Low Power TV and TV Translator Rules and Policies IEEE Broadcast Symposium September 13, 2004

  45. Digital LPTV and TV Translator Rules Keith Larson Media Bureau, FCC (202) 418-2607 Keith.Larson @fcc.gov

More Related