Test 1: Co-channel interference at the mobile unit
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Transcript of 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
• Increasing the separation between two co-channel cells
• Using directional antennas at the base station
• Lowering the antenna heights at the base station.
Reduction of Co-channel Interference by Means of a Notch in the Tilted Antenna Pattern
A seven-cell cellular configuration
Antenna Pattern
Vertical Beamwidth
Horizontal Beamwidth
33°,45°,65°,85°
A typical pattern for a directional antenna of 120° beamwidth
(a) Azimuthal pattern of 8-dBdirectional antenna
A typical pattern for a directional antenna of 120° beamwidth
(b) Vertical pattern of 8-dB directional antenna
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
Mechanical Downtilting
Mechanical Downtilt
Mechanical Downtilt
The Effect of Mechanically Downtilting Antenna on the Coverage Pattern
Vertical antenna pattern of a 120° directional antenna
Notch appearing in tilted antenna pattern
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
Antenna ParametersMechanical Downtilt Electrical Downtilt
• HBW gets bigger
• Causes gain reduction
• HBW remains the same
• But can’t adjust downtilt (fixed)
Suggested Method for Reducing Interference
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.