Packetized ensemble modem

Claim 1

A modem for transmitting source information and for receiving destination information in packetized format by means of an ensemble of frequencies through a communication medium having a passband comprising: a transmit modulator means adapted to impress signals containing said source information upon said communication medium and constructed from means for generating a plurality of first digital values directly representative of an ensemble of carriers whose frequencies are within said passband, means for generating second digital values from said first digital values directly representative of modulating said carriers with first unencoded orthogonal signals and encoding said carriers with said information in the form of discrete amplitude and phase deviations, said deviations defining digital data in packets upon said selected ones of said carriers, means for accurately controlling the duration of said modulating of said carriers for discrete epoch periods, means for converting said second digital values into analog signals for impression of said analog signals upon said communication medium as modulated carriers at said frequencies of said ensemble of carriers; a receive demodulator means adapted to extract said destination information from signals impressed upon said communication medium and constructed from means for generating a plurality of third digital values directly representative of analog signals received through said communication medium, said third digital values being developed by multiplying signals representative of said modulated carriers impressed upon said communication medium by a plurality of signals representative of second orthogonal signals of known amplitude and phase, means for integrating said third digital values precisely over time to determine frequency and phase of unencoded orthogonal signals substantially idential to said first orthogonal signals and generating therefrom said second orthogonal signals, means for comparing said third digital signals with fourth digital signals, said fourth digital signals representative of patterns of possible encoded data conveyed by said selected ones of said carriers to decode said destination information, and means for detecting packets of said data which have been corrupted in transmission; and means for measuring the transmission characteristics of said communication medium for each of said transmitted carriers constructed from means for transmitting selected ones of said carriers at a predetermined amplitude level and for a predetermined period, means for analyzing signal corruption caused by communication medium impairments to received carriers carrying said destination information by comparing received data patterns with known good data patterns, and means for avoiding use of at least a selected one of said carriers for transmission of data in the event said analyzing means indicates said selected one of said carriers is subject to impairments to said communication medium affecting transmission of data.