Subject: Mobile Computing

Difficulty: Medium

Marks: 4 Marks

Methods for improving coverage area in cellular systems

Cell Splitting:

• It is the process of subdividing a congested cell into smaller cells, each with its own base station and a corresponding reduction in antenna height and transmitter power.
• Cell splitting increase the capacity of the cellular system since it increases the number of times that channels are reused. By defining new cells which have a smaller radius than the original cells and by installing these smaller cells (microcells) between the existing cell, capacity increases due to additional channels/ unit area.
• An example of cell splitting is shown below the base station are placed in corners of the cells, and area served by base station A is assumed to be saturated with traffic.
• New base stations are therefore needed in the region to increases the number of channels in the area and to reduce the area served by the single base station.

Cell Sectoring:

• It is a method to increase capacity is to keep the cell radius unchanged and seek methods to decrease D/R ratio.
• Sectoring increases SIR, so that the cluster size may be reduced. First the SIR is improved using directional antennas, then capacity improvement is achieved by reducing the number of cell in the cluster; thus increasing the frequency reuse.
• To achieve this, it is necessary to reduce the relative interference without decreasing the transmit power.

There are two types of sectoring in a cell

1. 3 Sectors $120^0$ each

2) 2. 6 Sectors $60^0$ each