19-02-2011, 04:22 PM
submitted by:
Ramhari Bhapkar
Anup Gholkar
Abhijeet Kumbhojkar
[attachment=8858]
CO CHANNEL INTERFERENCE REDUCTION IN GSM
Introduction to Cellular Systems
Solves the problem of spectral congestion and user capacity.
Offer very high capacity in a limited spectrum without major technological changes.
Reuse of radio channel in different cells.
Enable a fix number of channels to serve an arbitrarily large number of users by reusing the channel throughout the coverage region.
Frequency Reuse
Each cellular base station is allocated a group of radio channels within a small geographic area called a cell.
Neighbouring cells are assigned different channel groups.
By limiting the coverage area to within the boundary of the cell, the channel groups may be reused to cover different cells.
Keep interference levels within tolerable limits.
Frequency reuse or frequency planning seven groups of channel from A to G
Co-channel Interference and System Capacity
To reduce co-channel interference, co-channel cell must be separated by a minimum distance.
When the size of the cell is approximately the same
co-channel interference is independent of the transmitted power
co-channel interference is a function of
R: Radius of the cell
D: distance to the centre of the nearest co-channel cell
For a hexagonal geometry
Q = D/R = √3N
A small value of Q provides large capacity
A large value of Q improves the transmission quality - smaller level of co-channel interference
A trade-off must be made between these two objectives
Improving Capacity in Cellular System
Methods for improving capacity in cellular systems
– Cell Splitting: subdividing a congested cell into smaller cells.
– Sectoring: directional antennas to control the interference and frequency reuse.
Reducing cochannel interference
Increasing the separation between two cochannel cells
Using directional antennas at the base station
lowering the antenna heights at the base station.
The use of directional antennas in each cell can serve two purposes:
- further reduction of cochannel interference
- increasing the channel capacity when thetraffic increases.
Cell Sectoring
Decrease the co-channel interference and keep the cell radius R unchanged
– Replacing single omni-directional antenna by several directional
antennas
– Radiating within a specified sector
Ramhari Bhapkar
Anup Gholkar
Abhijeet Kumbhojkar
[attachment=8858]
CO CHANNEL INTERFERENCE REDUCTION IN GSM
Introduction to Cellular Systems
Solves the problem of spectral congestion and user capacity.
Offer very high capacity in a limited spectrum without major technological changes.
Reuse of radio channel in different cells.
Enable a fix number of channels to serve an arbitrarily large number of users by reusing the channel throughout the coverage region.
Frequency Reuse
Each cellular base station is allocated a group of radio channels within a small geographic area called a cell.
Neighbouring cells are assigned different channel groups.
By limiting the coverage area to within the boundary of the cell, the channel groups may be reused to cover different cells.
Keep interference levels within tolerable limits.
Frequency reuse or frequency planning seven groups of channel from A to G
Co-channel Interference and System Capacity
To reduce co-channel interference, co-channel cell must be separated by a minimum distance.
When the size of the cell is approximately the same
co-channel interference is independent of the transmitted power
co-channel interference is a function of
R: Radius of the cell
D: distance to the centre of the nearest co-channel cell
For a hexagonal geometry
Q = D/R = √3N
A small value of Q provides large capacity
A large value of Q improves the transmission quality - smaller level of co-channel interference
A trade-off must be made between these two objectives
Improving Capacity in Cellular System
Methods for improving capacity in cellular systems
– Cell Splitting: subdividing a congested cell into smaller cells.
– Sectoring: directional antennas to control the interference and frequency reuse.
Reducing cochannel interference
Increasing the separation between two cochannel cells
Using directional antennas at the base station
lowering the antenna heights at the base station.
The use of directional antennas in each cell can serve two purposes:
- further reduction of cochannel interference
- increasing the channel capacity when thetraffic increases.
Cell Sectoring
Decrease the co-channel interference and keep the cell radius R unchanged
– Replacing single omni-directional antenna by several directional
antennas
– Radiating within a specified sector