Digital signal transmission system using frequency division multiplex

A many-carrier frequency-division-multiplex transmitter, comprising:

• input means for receiving a digital data stream for transmission;
• means coupled to the input means for modulating a plurality of carriers with respective bits of the digital data by a modulation method which carries the information in the phase or amplitude of the individual carriers to provide a plurality of first modulated signals;
• first transform means coupled to the modulating means for reversibly transforming the first modulated signals from the frequency domains to the time domain to provide first time domain signals;
• means coupled to the first transform means for limiting the first time domain signals to limit their amplitude or power to provide limited time domain signals;
• second transforms means coupled to the limiting means for inversely transforming the limit time domain signals into a plurality of second modulated signals in the frequency domain;
• means coupled to the second transform means for adjusting the phase and/or amplitude of some of the second modulated signals to provide a plurality of adjusted signals;
• and
• third transform means coupled to the adjusting means for transforming the adjusting signals from the frequency domain to the time domain to provide second time domain signals for transmission.

A method of transmitting a digital data stream on a many-carrier frequency-division-multiplex signal, comprising the steps of:

• modulating a plurality of carriers with respective bits of the digital data to provide a plurality of modulated signals;
• reversibly encoding the modulated signals by an encoding function to provide encoded signals;
• subjecting the encoded signals to a predetermined function to provide modified encoded signals;
• decoding the modified encoded signals to provide decoded signals;
• adjusting at least some of the decoded signals to conform more closely with the modulated signals and provide adjusted signals;
• and
• recording the adjusted signals by the said encoding function to provide encoded output signals for transmission.

Apparatus for transmitting a digital data stream on a many-carrier frequency-division-multiplex signal, comprising:

• input means for receiving a digital data stream for transmission;
• means coupled to the input means for modulating a plurality of carriers with respective bits of the digital data to provide a plurality of modulated signals;
• encoding means coupled to the modulating means for reversibly encoding the modulated signals by an encoding function to provide encoded signals;
• means coupled to the encoding means for subjecting the encoded signals to a predetermined function to provide modified encoded signals;
• decoding means coupled to the function subjecting means for decoding the modified encoded signals to provide decoded signals;
• means coupled to the decoding means for adjusting at least some of the decoded signals to conform more closely with the modulated signals and provide adjusted signals;
• and
• recoding means coupled to the adjusting means for recoding the adjusted signals by the said encoding function to provide encoded output signals for transmission.