Question

Consider a synchronous TDM system in which 6 input channels are multiplexed into a 125-microsecond output frame. Each output frame includes exactly four bits from each input source, plus one synch bit per frame.

a) What is the size of each output frame in bits?
b) What is the total bit rate of the output line?
c) Suppose we would like to replace one of the input sources with a new source that has a data rate of 24 Kilobits per seconds. Calculate how many extra bits must be stuffed for this source in each output frame

Answer 1

In a synchronous TDM system, each output frame has a size of 25 bits and the total bit rate of the output line is 200,000 bits per second. To replace an input source with a data rate of 24 Kilobits per second, 20 extra bits must be stuffed in each output frame.

Step-by-step explanation:

a) The size of each output frame can be calculated by multiplying the number of input sources (6) by the number of bits from each input source (4), and then adding 1 synch bit. Therefore, the size of each output frame is (6 * 4) + 1 = 25 bits.

b) The total bit rate of the output line can be calculated by dividing the size of each output frame (25 bits) by the duration of each frame (125 microseconds), and then multiplying by 10^6 to convert from microseconds to seconds. Therefore, the total bit rate is (25 / 125) * 10^6 = 200,000 bits per second.

c) To calculate the number of extra bits that must be stuffed for the new source with a data rate of 24 Kilobits per second, we need to find the difference between the data rate of the new source and the data rate of each input source.

The difference is 24 Kilobits per second minus 4 Kilobits per second (data rate of each input source). Therefore, the number of extra bits that must be stuffed for the new source in each output frame is (24 - 4) = 20 bits.