Data telecommunications system and method for transmitting compressed data
First Claim
1. Apparatus for transmitting data in a compressed form between an initiating unit of data terminal equipment and a receiving unit of data terminal equipment connected over communications lines, one of said units having a compressing modem connected between said unit and telephone lines, and the other of said units having a decompressing modem connected between said other unit and telephone lines, said apparatus comprising:
- (a) means for fetching a next data character from a data stream to be sent over communication lines;
(b) means for transmitting a compressed character code assigned to said next data character to the decompressing modem;
(c) means for incrementing a relative frequency counter for said next data character;
(d) means for comparing said relative frequency counter for said next data character to a relative frequency counter of a next more frequently occurring character;
(e) means for determining whether the relative frequency of said next data character is greater than the relative frequency of said next more frequently occurring character, and, if so, means for exchanging the compressed character codes assigned to said next data character and to said next more frequently occurring character;
(f) means for repeating the operations of means (d) through (e) until the relative frequency of said next data character is less than the relative frequency of said next more frequently occurring character or said next data character is the most frequent character; and
(g) means for repeating the operations of means (a) through (f) for next data characters and for transmitting said compressed character codes to said decompressing modem.
6 Assignments
0 Petitions
Accused Products
Abstract
Disclosed is a data compressing modem for connection to a decompressing modem over communication lines. The compressing modem receives an input data stream, and each character in the data stream is recodified with a compressed character code, the length of which is dependent on the frequency of the character in the data stream. A frequency table is maintained so that changes in the relative frequency of characters in the data stream will be recognized by the compressing modem and the compressed character codes representing such characters will be exchanged accordingly. A decompressing modem, which is connected over communication lines to the compressing modem, processes the compressed character code in a reverse order from the manner in which the compresing modem processing the codes. The decompressing modem also maintains a relative frequency table and as the relative frequencies of the various characters change, the actual characters represented by the compression codes must also change.
-
Citations
9 Claims
-
1. Apparatus for transmitting data in a compressed form between an initiating unit of data terminal equipment and a receiving unit of data terminal equipment connected over communications lines, one of said units having a compressing modem connected between said unit and telephone lines, and the other of said units having a decompressing modem connected between said other unit and telephone lines, said apparatus comprising:
-
(a) means for fetching a next data character from a data stream to be sent over communication lines; (b) means for transmitting a compressed character code assigned to said next data character to the decompressing modem; (c) means for incrementing a relative frequency counter for said next data character; (d) means for comparing said relative frequency counter for said next data character to a relative frequency counter of a next more frequently occurring character; (e) means for determining whether the relative frequency of said next data character is greater than the relative frequency of said next more frequently occurring character, and, if so, means for exchanging the compressed character codes assigned to said next data character and to said next more frequently occurring character; (f) means for repeating the operations of means (d) through (e) until the relative frequency of said next data character is less than the relative frequency of said next more frequently occurring character or said next data character is the most frequent character; and (g) means for repeating the operations of means (a) through (f) for next data characters and for transmitting said compressed character codes to said decompressing modem. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
Specification