Bit padding in Synchronous TDM :
"Till now we have assumed that the data rate of all the channels is the same ".
But practically it won't so. We will have to multiplex channels having different data rates.
To add the extra security level & encoding we can use bit padding as one of the proven and easiest technique existed ever.
The data rates are not integer multiple of each others. But in order to multiplex them using TDM , they need to be integer multiple of each other.
This can be achieved by a technique called 'Bit Padding'.