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TECHNICAL ASPECTS IN CHANNEL PLANNING FOR DIGITAL TERRESTRIAL TELEVISION BROADCASTING IN NIGERIA

TECHNICAL ASPECTS IN CHANNEL PLANNING FOR DIGITAL TERRESTRIAL TELEVISION BROADCASTING IN NIGERIA. GBENGA-ILORI, A.O. DEPARTMENT OF ELECTRICAL AND ELECTRONIC ENGINEERING FEDERAL UNIVERSITY OF TECHNOLOGY, AKURE, ONDO-STATE, NIGERIA. biodun732000@yahoo.com. WHY DIGITAL BROADCASTING?.

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TECHNICAL ASPECTS IN CHANNEL PLANNING FOR DIGITAL TERRESTRIAL TELEVISION BROADCASTING IN NIGERIA

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  1. TECHNICAL ASPECTS IN CHANNEL PLANNING FOR DIGITAL TERRESTRIAL TELEVISION BROADCASTING IN NIGERIA GBENGA-ILORI, A.O. DEPARTMENT OF ELECTRICAL AND ELECTRONIC ENGINEERING FEDERAL UNIVERSITY OF TECHNOLOGY, AKURE, ONDO-STATE, NIGERIA. biodun732000@yahoo.com

  2. WHY DIGITAL BROADCASTING? • Consistent service quality with improved immunity to noise • Near error-free picture and sound propagation within the range of performance • Lower operating costs through the use of compression technology • Efficient use of the spectrum; small re-use distance • Lower transmitter power required compared with analogue counterpart

  3. KEY OBJECTIVES IN CHANNEL PLANNING • To minimize or avoid interference and disruption to analogue television reception. • To identify a number of channels that can be used for digital services at sufficient e.r.p. levels to achieve the same level of coverage from the same transmitting sites as analogue services

  4. CONSTRAINTS • The suitability of existing transmission facilities; and • The population of existing receive antennas

  5. TYPES OF INTERFERENCE • Digital-to-analogue Interference • Digital-to-digital interference

  6. DIGITAL-TOANALOGUE INTERFERENCE • Degree of degradation on analogue services from digital services • Digital spectrum characteristic is similar to Gaussian noise • Effect of CCI is to raise the noise thresholds of analogue receivers • Overall effect is reduction in picture grade

  7. DIGITAL-TO-DIGITAL INTERFERENCE • Degree of degradation to digital service from a digital service • The effect is to increase the system’s susceptibility as the modulation levels are increase. • However, higher modulation levels allows very sophisticated error-management schemes

  8. DIGITAL CHANNEL PLANNING METHODOLOGY • Propagation prediction methods • Station Information • Establishment of the size of analogue coverage areas • Establishment of the size of digital coverage areas • Protection ratio

  9. Proper propagation prediction methods using information from a terrain data bank are needed

  10. STATION INFORMATION • Name • Channel Number • Frequency of operation • Location • ERP • Antenna Height • Polarisation

  11. SIZE OF ANALOGUE COVERAGE AREAS • Need for analogue coverage area to estimate digital service e.r.p. • Impact of co-channel interference on analogue services • Impact of adjacent channel interference on analogue services

  12. CO-CHANNEL INTERFERENCE Ta Tb Ra Rb Dm Dt Figure1: Protection Ratio Parameters

  13. PROTECTION RATIO PARAMETERS Rp = Dt - (Ra + Rb) Dm Rp - Protection ratio Dt - Line of sight distance between two co-channel transmitter Dm - Limiting Distance between them Ra - Service range of transmitter A Rb - Service range of transmitter B

  14. LEVELS OF PROTECTION Dt - (Ra + Rb) = 1 Dm Dt - (Ra + Rb) > 1 Dm Dt - (Ra + Rb) < 1 Dm

  15. SIZE OF DIGITAL COVERAGE AREASMORE COMPLICATED; WHY? • Maximum e.r.p. can be largest value which does not cause unacceptable interference • Polarization may be the same with existing analogue service or orthogonal • Planning to choose required standard

  16. REQUIRED PROTECTION RATIO • UNWANTED ANALOG UNWANTED DIGITAL LOWER ADJACENT CHANNEL -37dB -30dB CO-CHANNEL +20dB +3dB Wanted Digital UPPER ADJACENT CHANNEL -38dB -30dB -30dB -46dB IMAGE CHANNEL FIGURE 2: DIGITAL PROTECTION RATIO

  17. THE SITUATION IN NIGERIA • 42 CO-CHANNEL VHF STATIONS • 22 CO-CHANNEL UHF STATIONS • NUMBER INCLUDE PROPOSED ANALOGUE TELEVISION STATIONS

  18. LEVEL OF PROTECTION AGAINST CO-CHANNEL INTERFERENCE IN VHF TELEVISION STATIONS IN NIGERIA.

  19. LEVEL OF PROTECTION AGAINST CO-CHANNEL INTERFERENCE IN UHF TELEVISION STATIONS IN NIGERIA

  20. PREFERENTIAL TELEVISION CHANNEL FOR DIGITAL TELEVISION IN NIGERIA Not preferred for digital television because of co-channel interference CH 5 - 12 VHF BAND III Not preferred for digital television because of co-channel interference CH 28 - 35 UHF BAND IV Preferred for digital transmission since it is relatively free from CCI CH 36 - 69 UHF BAND V

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