Question

1) What is the total bandwidth required to combine 25 voice signals using frequency- division multiplexing? Please answer it carefully and take your time, let's get it right the first time.

Answer 1

Let B be the bandwidth of each voice signal (Hz).

There are 25 voice signals. Then total bandwidth requirement for this is 25*B Hz.

But, to avoid interference we also need guard bands in between two voice signals. So, for 25 voice signals 24 guard bands are required.

Let G be the bandwidth requirement for one guard band.

Then total bandwidth requirement will be 25*B + 24*G.

Arrangement will be like this:

B1-G-B2-G-B3-G-B4-G- ..........G-B24-G-B25.

Channels are separated by guard bands to avoid interference of one signal by its neighboring signal, for example if one signal is in the range 10 kHz -20 kHz and there is another signal in range 20 kHz - 30 kHz then these two will interfere with each other. Hence, a guard band is needed to be introduced between them in this situation let 10 kHz. Then arrangement will be

1st signal - 10 - 20 khz

Guard band - 20 - 30 khz

2nd signal - 30 - 40 khz