Abstract
Ph.D. (Electrical & Electronic Engineering)
In the ideal communication system no noise is present and error free communication is
possible. In practice, however, several factors influence the correctness of· the
communication. One of the most important of these factors is the synchronization of the
message. Synchronization techniques form an integral part of data communication systems
and without synchronization no comprehensible message can be received.
An example of a communication system in which synchronization errors occur is the
plesiochronous communication network which is used in many telephone networks [49,50].
A common problem with the use of the multiplexers in such a network is that output pulses
may occur that do not contain valid data, due to minor discrepancies in the clock frequencies
of the incoming signals. These inserted bits are termed ''justification bits" and their presence
is signaled over the link by the justification control bits or stuffing control bits, which are
included in the frame [49 and 50]. Synchronization of the network is dependent, among other
factors, on the correct decoding of the stuffing control bits.
Synchronization at the receiver can also be lost when the frame markers are not recognizable
due to errors on the channel...