Coding for the correction of synchronization errors

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..