Explain the frequency reuse distance in cellular radio system

2. Explain the frequency reuse distance in cellular radio system.

Frequency reuse distance: The minimum distance which allows the same frequency to be reused will depend on many factors, such as the number of co-channel cells in the vicinity of the center cell, the type of geographical terrain contour, the antenna height and the transmitted power at each cell site. The frequency reuse distance can be determined from

Where K is the frequency reuse pattern shown in Fig.3, then

If all the cell sites transmit the same power, then K increases and the frequency reuse distance D increases. This increased D reduces the chance that co channel interference may occur.Theoretically, a large K is desired. However, the total number of allocated channels is fixed. When K is too large, the number of channels assigned to each of K cells becomes small. It is always true that if the total number of channels in K cells is divided as K increases, trunking inefficiency results. The same principle applies to spectrum inefficiency: if the total numbers of channels are divided into two network systems serving in the same area, spectrum inefficiency increases.

Obtaining the smallest number K involves estimating co channel interference and selecting the minimum frequency reuse distance D to reduce co channel interference. The smallest value of K is K = 3, obtained by setting i = 1, j = 1 in the equation.