04811357 is referenced by 132 patents and cites 7 patents.

A system and method are provided for use of a secondary channel in high speed (greater than 2400 bits per second) wire line modems to provide low speed (around 110 bits per second) non-interfering communications for control or monitoring functions. The secondary channel is used to monitor, configure and test the modems in the network using commands sent over the secondary channel. Secondary channels are also used in low duty cycle applications such as in alarms or teletype data transmission. The invention provides a spread spectrum secondary channel which occupies the same bandwidth as the primary data channel and is immune to jamming tones that would interfere with conventional frequency shift keying secondary channels. The spectrum spreading is achieved through use of the primary channel's trellis encoder. Phase shifts of 0.degree., 90.degree., 180.degree. or 270.degree. are induced depending upon the trellis state. This rotation simplifies decoding which as a result can be done in the reference system of the decoded primary trellis signals instead of the baseband equalizer reference system. The primary trellis decoder automatically resolves the 90.degree. references. There is no penalty in terms of additional circuitry or software because the transmitter spreading eliminates the need for additional rotation in the receiver which is required for non-spread signals.

Title
Secondary channel for digital modems using spread spectrum subliminal induced modulation
Application Number
7/140405
Publication Number
4811357
Application Date
January 4, 1988
Publication Date
March 7, 1989
Inventor
Edward S Zuranski
Largo
FL, US
William L Betts
St. Petersburg
FL, US
Agent
Kane Dalsimer Sullivan Kurcz Levy Eisele and Richard
Assignee
Paradyne Corporation
FL, US
IPC
H04L 27/30
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