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Test 1: Co-channel interference at the mobile unit

Test 1: Co-channel interference at the mobile unit. Test 2: Co-channel interference at the cell site. Lowering the Antenna Height. ( a )  on a high hill. ( b )  in a valley. In a Forested Area. Reduction of Co-channel interference in a cellular mobile system.

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Test 1: Co-channel interference at the mobile unit

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  1. Test 1: Co-channel interference at the mobile unit

  2. Test 2: Co-channel interference at the cell site

  3. Lowering the Antenna Height (a) on a high hill (b) in a valley

  4. In a Forested Area

  5. Reduction of Co-channel interference in a cellular mobile system • Increasing the separation between two co-channel cells • Using directional antennas at the base station • Lowering the antenna heights at the base station.

  6. Reduction of Co-channel Interference by Means of a Notch in the Tilted Antenna Pattern A seven-cell cellular  configuration

  7. Antenna Pattern 33°,45°,65°,85° Horizontal Beamwidth Vertical Beamwidth

  8. A typical pattern for a directional antenna of 120° beamwidth (a) Azimuthal pattern of 8-dBdirectional  antenna

  9. A typical pattern for a directional antenna of 120° beamwidth (b) Vertical pattern of 8-dB  directional antenna

  10. Antenna Tilting • In general, the vertical pattern of an antenna radiates the main energy towards the horizon • Only that part of the energy which is radiated below the horizon can be used for the coverage of the sector • Downtiltingthe antenna limits the range by reducing the field strength in the horizon

  11. Mechanical Downtilting

  12. Mechanical Downtilt

  13. Mechanical Downtilt

  14. The Effect of Mechanically Downtilting Antenna on the Coverage Pattern Vertical antenna pattern  of a 120°  directional  antenna

  15. Notch appearing in tilted antenna pattern

  16. Mechanical Downtilting • is the down tilt angle • d1 is the length of the upper antenna-mounting arm • d2 is the length of the lower antenna-mounting arm • h is the distance between d1 and d2

  17. Antenna Parameters Mechanical Downtilt Electrical Downtilt • HBW gets bigger • Causes gain reduction • HBW remains the same • But can’t adjust downtilt (fixed)

  18. Suggested Method for Reducing Interference

  19. Umbrella-pattern Effect • Antenna in which the waves are guided downward in all directions from a central pole or tower to the ground, somewhat like the ribs of an open umbrella. 

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