Download - cell splitting and sectoring
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Power point presentationon
cell splitting and sectoring
:SHWETANSHU GUPTA
MIET (342/08)
MADE BY:
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CELL?
LARGER AREA DIVIDED INTO SMALL NO. OF AREAS
SHAPE IS HEXAGONAL
EACH WITH ITS OWN BASE STATION AND SET OF FREQUENCIES.
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Why hexagonal cell ?
circular
square
hexagonal
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FREQUENCY REUSE
Each cell is assigned a part of the available frequency spectrum.
same part of the frequency spectrum more than once. This is called frequency reuse. 1
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Reuse Distance
For hexagonal cells
reuse distance---
D= R.√3N Reuse factor---
D/R= √3N
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Channel capacity?
C = MKN = MS
C= capacity
M= number of clusters
K= allotted channel to a cell
N= no of cells in a cluster.
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Why cell splitting and sectoring?
As users increases channel capacity decreases.
Techniques are needed to provide extra channels.
cell splitting and sectoring increases capacity.
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Cell splitting
The process of subdividing a congested cell into smaller cell.
Each with its own base station and a corresponding reduction in antenna height.
leads to increase in capacity
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Limitations:
Handoffs are more frequent. Channel assignments become difficult. All cells are not split simultaneously so
special care have to be taken for proper allocation of problem.
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Umbrella approach:
Handoff issues must be addressed so that high speed and low speed traffic can be accommodated simultaneously.
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Cell sectoring:
To overcome some limitations like co-channel interference, cell sectoring is done.
Involves replacing an omni- directional antenna at the base station by several directional antennas,
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Different sectors:
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Advantages:
It improves S/I ratio. It reduces interference which increases
capacity. It enables to reduce the cluster size and
provides an additional freedom in assigning channels.
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Limitations:
Increased number of antennas at each base station.
Decrease in trunk efficiency. Loss of traffic. Since sectoring reduces the coverage area
of a particular group of channels, the number of handoffs increases as well.
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