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
Horizontal Beamwidth
33°,45°,65°,85°

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