Question

We need to use synchronous TDM and combine 20 digital sources, each of 100 Kbps. Each output slot carries 1 bit from each digital source, but one extra bit is added toeach frame for synchronization.
What is the size of an output frame in bits?
b. What is the output frame rate?
c. What is the duration of an output frame?
d. What is the output data rate?
e. What is the efficiency of the system (ratio of useful bits to the total
bits).

Answer 1

a)

Given data:

The total number of digital sources=20

Each frame output slot carries 1 bit from each digital source, but one extra bit is added to each frame for synchronization.

Then, the size of the an output frame in bits = 201+1

= 21 bits

b)

Each frame carries 1 bit from each source.

Then, the frame rate=100Kbps

=100,000 frames/s

c)

The duration of an output frame=

=

=10

d)

Output data rate= size of an output frame frame rate

= (100000 frames/s) (21 bits/frame)

=21 10⁵ bits/s

=2.110⁶ bits/s

=2.1 Mbps (since, 1Mbps=10⁶bits/s)

e)

In each frame 20 digital sources out of 21 are useful.

Therefore, the efficiency of the system=20/21

=95%