Article contributed by :
manoj@itportal.in
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We
have already studies in detail the concept of a cell, cluster, MS and the BS.
So, we will not discuss those all over again. Let us move straight into the
topic.
The concept of Cell
Splitting is quite self explanatory by its name itself. Cell splitting means to split up cells into smaller cells. The process of cell splitting is used to expand the capacity
(number of channels) of a mobile communication system. As a network grows, a
quite large number of mobile users in an area come into picture. Consider the
following scenario.
There are 100 people in a specific area. All of them
owns a mobile phone (MS) and are quite comfortable to communicate with each
other. So, a provision for all of them to mutually communicate must be made. As
there are only 100 users, a single base station (BS) is built in the middle of
the area and all these users’ MS are connected to it. All these 100 users now
come under the coverage area of a single base station. This coverage area is
called a cell. This is shown in Fig 2-1.
Fig 2-1. A single BS for 100 MS users.
But now, as time passed by, the number of
mobile users in the same area increased from 100 to 700. Now if the same BS has
to connect to these 700 users’ MS, obviously the BS will be overloaded. A
single BS, which served for 100 users is forced to serve for 700 users, which
is impractical. To reduce the load of this BS, we can use cell splitting. That
is, we will divide the above single cell into 7 separate adjacent cells, each
having its own BS. This is shown in Fig
2-2.
Fig 2-2. Single cell
split up into 7 cells
Now,
let us look into the big picture. Until now, we have discussed about cell
splitting in a small area. Now, we use this same concept to deal with large
networks. In a large network, it is not necessary to split up all the cells in
all the clusters. Certain BSes can handle the traffic well if their cells
(coverage areas) are split up. Only those cells must be ideal for cell
splitting. Fig 2-3 shows network
architecture with a few number of cells split up into smaller cells, without
affecting the other cells in the network.
Fig 2-3. Cell Splitting.
The concept of cell
splitting can further be applied to the split cells as well. That is, the split
up cells can further be split into a number of smaller cells to improve the
efficiency of the BS even more. Fig 2-4 shows a hierarchy of cell splitting.
Here, the master cells which have been split up
into smaller cells are known as macro cells. The split up cells are known as
micro cells. The innermost cells, split up by splitting the micro cells are
known as pico cells.
manoj@itportal.in
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