Data encoding for a communication channel supporting a subset of the characters to be transmitted

TLDR: In this paper, a subset of the recognized printable characters are designated as encoding characters for use in encoding data that includes characters not among the recognized printed characters, and each time that one of the encoding characters occurs in the input data, the byte representing that character must also be encoded.

Abstract: Characters that are not among those recognized for use in page messages are encoded using a subset of the recognized printable characters to enable the data comprising a page object to be transmitted over a paging channel. In one preferred form of the invention, a subset of the recognized printable characters are designated as encoding characters for use in encoding data that includes characters not among the recognized printable character set. Further, each time that one of the encoding characters occurs in the input data, the byte representing that character must also be encoded. To encode the characters, the byte is divided into nibbles. Each nibble is a hexadecimal digit that is encoded using one of the 16 encoding characters. If a byte of the input data repeats more than four times in succession, it is run length encoded (RLE) during the encoding process to compress the encoded data. Upon receipt, the encoded data are decoded using the same encoding characters, to recover the nibbles of each byte of the original input data. Furthermore, run length decoding is applied when a run length encoding signal character occurs in the encoded data stream. The run length encoding signal character is selected from the recognized printable character set. Using this technique, data can be sent that include characters not within the recognized printable character set and the encoded characters can be compressed to substantially reduce the amount of data transmitted as a paging object if the input data includes significant repeating characters.