ADAPTIVE TEXT COMPRESSION TO ENHANCE A MODEM

Abstract

The design of a coding system is described and evaluated in the context of a computer-to-terminal modem connection. Unlike other compression problems, it is hard to characterise the kinds of information that may require processing. For this reason the system uses an adaptive Markov model, in conjuction with arithmetic coding. The compression performance improves with available memory. Two techniques for storing the Markov model are described. Experimental results are reported for a variety of sample texts. It is shown that effective line speeds can be at least doubled, and in some cases tripled, using less than 64 Kbytes of memory.