Calculating number of cells

Question

A particular city has area of 1300 square miles which is covered by the cellular system using the seven cell reuse pattern. Every cell has a radius of the 4 miles and city has 40 MHz spectrum having a full duplex channel bandwidth of 60KHz. Find:

a)  Number of cells within the service area.
b)  Number of channels per cell.
c)  Total number of subscribers which can be served.

Answer 1

a)  Radius of cell = 4 miles
Area covered by cell = 50 square miles.
For 7 cells reuse pattern 
Area covered by the cluster = 7*50 = 350 square miles.
Thus, no. of cells needed to cover the 1300 square miles is 28.

b) No. of channels per cell = total no. of channels/no. of cells in the cluster
Available frequency = 40MHz
Channel bandwidth = 60 KHz
Number of channels available = 40 MHz/60KHz = 666 channels
Number of channels per cell = 666/7= 95 channels per cell.

c) Total number of the subscriber which can be served =666*4 = 2664 subscribers.