Exp 1 MC
Exp 1 MC
Exp 1 MC
Aim: To study the cellular frequency reuse concept to find the co-channel for a
particular cell.
Theory:
In mobile communication systems a slot of a carrier frequency / code in a carrier frequency is
a radio resource unit. This radio resource unit is assigned to a user in order to support a call/
session. The number of available such radio resources at a base station thus determines the
number of users who can be supported in the call. Since in wireless channels a signal is
"broadcast" i.e. received by all entities therefore once a resource is allocated to a user it
cannot be reassigned until the user finishes the call/ session. Thus the number of users who
can be supported in a wireless system is highly limited.
In order to support a large no. of users within a limited spectrum in a region the
concept of frequency reuse is used.
The signal radiated from the transmitter antenna gets attenuated with increasing distance.
At a certain distance the signal strength falls below noise threshold and is no longer
identifiable.
In this region when the signal attenuates below the noise floor the same radio resource may
be used by another transmission to send different information. In terms of cellular systems,
the same radio resource (frequency) can be used by two base stations which are sufficiently
spaced apart. In this way the same frequency gets reused in a layer- geographic area by two
or more different base station different users simultaneously.
Now what is important is to select the set of base stations which will use the same set of
radio resources/ channel of frequencies or technically the co- channel cells. In this context
the minimum adjacent set cells which use different frequencies each is called a cluster.
The cellular concept is the major solution of the problem of spectral congestion and user
capacity. Cellular radio relies on an intelligent allocation and channel reuse throughout a
large geographical coverage region.
another by geographic distances large enough to keep interference levels within tolerable
limits. The design process of selecting and allocating channel groups for all cellular base
stations within a system is called frequency reuse or frequency planning.
If a circle is chosen to represent the coverage area of a base station, adjacent circles overlaid
upon a map leave gaps or overlapping regions. A square, an equilateral triangle and a
hexagon can cover the entire area without overlap and with equal area. A cell must serve the
weakest mobiles typically located at the edge of the cell within the footprint. For a given
distance between the center of a polygon and its farthest perimeter points, the hexagon has
the largest area of the three. Thus, with hexagon, the fewest number of cells can cover a
geographic region and close approximation of a circular radiation pattern that occurs for an
Omni directional base antenna and free space propagation is possible.
Base station transmitters are situated either at the center of the cell (center-excited cells) or
at three of the six cell vertices (edge-excited cells). Normally, omnidirectional antennas are
used in center-exited cells and sectored directional antennas are used in edge-exited cells.
Practical system design considerations permit a base station to be positioned up to one-
fourth the cell radius away from the ideal location.
In this example,
N = 19 (i.e., i = 3, j = 2).
Where, i and j are non-negative integers.
To nd the nearest co-channel neighbors of a particular cell,
a. move i cells along any chain of hexagons then,
b. turn 60 degrees counter-clockwise and move j cells.
Performed Experiment:
Reuben D’souza Roll No. 46 TE-A CMPN (Batch 3)
Conclusion:
In conclusion, the experiment aimed to explore the cellular frequency reuse concept and
determine the co-channel for a specific cell within a cellular network. Through the
systematic study and analysis of frequency reuse patterns, it became evident that effective
frequency planning is essential for optimizing the utilization of available spectrum and
minimizing interference.
The experiment involved investigating the relationships between cells and identifying
suitable co-channels to enhance the overall efficiency of the cellular network. By
understanding the principles of cellular frequency reuse, it is possible to mitigate interference
issues, improve signal quality, and ultimately enhance the performance of the network.
In summary, the experiment provided valuable insights into the cellular frequency reuse
concept, shedding light on effective strategies for co-channel assignment. These findings
contribute to the broader field of telecommunications, aiding in the development of more
robust and efficient cellular networks to meet the ever-evolving demands of wireless
communication.