US Patent 7230735 Forward link text compression in satellite messaging

A method of transmitting communication information employing a coding scheme being defined by a character set. The characters of the character set are encoded into codewords of a sequence of bits, the codewords being of varying length. The characters are divided into at least two categories. The categories may be a first category of shifted characters and a second category of unshifted characters. Where a shifted character is encountered during encoding a shift codeword is inserted in the sequence of bits. This allows each category to use overlapping codewords. Then the sequence is converted to ASCII characters to be transmitted.