Radio Cell Planning

Calculation of required number of BTSs

• This leads to the following calculations:
• Frequencies per cell = 24 / 12 = 2
• Traffic channels per cell = 2 x 8 - 2 (control channels) = 14 TCH
• Traffic per cell = 14 TCH with a 2% GOS implies 8.2 Erlangs per cell
• The number of subscribers per cell = 8.2E / 25mE = 328 subscribers per cell
• If there are 10,000 subscribers then the number of cells needed is 10,000 / 328 = 30 cells.
• Therefore, the number of three sector sites needed is 30 /3=10

Part of Erlang’s B Table

Example 1

A cell has 500 Sub, how many TRX’s are needed to serve the subscribers

taking into account that the generated traffic per subscriber is 25 mE and

the GoS is 0.02

Solution:

Generated traffic in the cell:

500 * 25mE = 12.5 Er

From Erlange B table n= 20 TCH

Number of TRX = 3.

Example 2

A cell has 4 TRX ,how many subscribers can be served taking into account the previous assumptions.