EXTENDED SYNCHRONIZING CODEWORDS FOR BINARY PREFIX CODES

Synchronizing codewords (SC's) have been previously studied as a means to stop error propagation in variable-length codes, However, SC's ret ain one disadvantage: the symbols after the SC may be put in the wrong positions since the number of decoded symbols before the SC can be di fferent from the original number due to channel errors, Thus we propos e the idea of extended synchronizing codewords (ESC's) which can overc ome the drawback of SC's. After the decoder receives an ESC, the decod er correctly knows it is in synchronization, regardless of the precedi ng slippage, We derive some of the essential properties of ESC's and p rovide several upper bounds on the amount of overhead needed in design ing a code with an ESC.