Question 5

An analog cellular system has a total of 33 MHz of bandwidth and uses
two 25-kHz simplex (one-way) channels to provide full duplex voice
and 
control channels. 

a) What is the number of channels available per cell for a 
frequency
reuse factor of 

(1) 4 cells 
 (2) 7 cells 
 and (3) 12
cells? 



Given,
Total bandwidth of the system = 33 MHz = 33000 kHz
Bandwidth of each channel = 25 kHz
Total bandwidth of the channel = 25*2 kHz = 50 kHz

We have,
Total available channels = bandwidth of system/bandwidth of channels
i.e. 33000 kHz / 50 kHz
= 660

Now,
When number of cells (N) = 4,
Channel per cell = 660/4 = 165

When N = 7,
Channel per cell = 660/7 = 95

When N = 12,
Channel per cell = 660/12 = 55


b) Assume that 1 MHz is dedicated to control channels but that 
only
one control channel is needed per cell. Determine a reasonable
distribution of control channels and voice channels in each cell for
the three frequency reuse factors of part (a).

Dedicated bandwidth to control channels = 1 MHz = 1000 kHz
Therefore,
No of control channels = dedicated bandwidth/bandwidth of channel
i.e. 1000 kHz/ 50 kHz
= 20
And,
No of voice channels = 660 – 20 = 640

When N = 4,
No of control channels per cell = 20/4 = 5
No of voice channels per cell = 165 – 5 = 160
When N = 7,
No of control channels per cell = 20/7 = 3 (approximately)
No of voice channels per cell = 95 – 3 = 92
When N = 12,
No of control channels per cell = 20/12 = 2 (approximately)
No of voice channels per cell = 55 – 2 = 53