Monday, November 5, 2012

Cell Splitting - Mobile Computing : [BE - IT/Comp]

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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.

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1 comment:

  1. Can you exolain the procedure of cell splitting with a numerical or practical example that Hw a
    cell can be split into micro cells?