Fractional bit rate encoding in a discrete multi-tone communication system

Abstract

Fractional bit rate encoding in a discrete multi-tone (DMT) communication environment allows the transmission of fractional bit rates, thus maximizing the use of signal-to-noise ratio (SNR) available on each of the DMT carriers, or tones, while maintaining a constant power density over the entire frequency spectrum.

1 . A system, comprising: 
 a fractional encoder configured to encode a group of data bits into a plurality of words, each word encoding a non-integer number of data bits, each word associated with one of a plurality of tones;    a constellation encoder configured to encode each word into a signal space constellation, each constellation associated with one of the plurality of tones, wherein the plurality of constellations and associated tones form a symbol; and    a multi-tone transmitter configured to transmit the constellation on its associated tone in the symbol.    
   
   
       2 . The system of  claim 1 , wherein the transmitter comprises a multi-carrier modulator.  
   
   
       3 . The system of  claim 1 , wherein the transmitter comprises a discrete multi-tone modulator.  
   
   
       4 . The system of  claim 1 , wherein the DMT transmitter is further configured to transmit all tones in the plurality at the same power and at a specified PSD with no ripple.  
   
   
       5 . The system of  claim 1 , wherein the fractional encoder further comprises a modulus converter.  
   
   
       6 . The system of  claim 1 , wherein the fractional encoder further comprises a shell mapper.  
   
   
       7 . The transceiver of  claim 6 , wherein the shell mapper lowers an overall peak factor of a combination of signal space constellations associated with the symbol.  
   
   
       8 . The transceiver of  claim 1 , wherein the fractional encoder further comprises a constellation switcher.  
   
   
       9 . The transceiver of  claim 1 , wherein each constellation is a circular signal space constellation.  
   
   
       10 . The transceiver of  claim 1 , wherein each constellation is a square signal space constellation.  
   
   
       11 . The transceiver of  claim 1 , further comprising a trellis encoder associated with the constellation encoder.  
   
   
       12 . A transceiver, comprising: 
 means for fractional encoding a group of data bits into a plurality of words, each word encoding a non-integer number of data bits, each word associated with one of a plurality of tones;    means for constellation encoding each word into a signal space constellation, each constellation associated with one of the plurality of tones, wherein the plurality of constellations and associated tones form a symbol; and    means for modulating each tone.    
   
   
       13 . The transceiver of  claim 12 , wherein the transmitter transmits tones at the same power.  
   
   
       14 . The transceiver of  claim 12 , wherein the DMT transmitter is further configured to transmit all tones in the plurality at the same power and at a specified PSD with no ripple.  
   
   
       15 . The transceiver of  claim 12 , wherein the fractional encoder further comprises a modulus converter.  
   
   
       16 . The transceiver of  claim 12 , wherein the fractional encoder further comprises a shell mapper.  
   
   
       17 . The transceiver of  claim 12 , wherein the fractional encoder further comprises a constellation switcher.  
   
   
       18 . A method comprising: 
 fractionally encoding a group of data bits into a plurality of words, each word encoding a non-integer number of data bits, each word associated with one of a plurality of tones;    encoding each word into a signal space constellation, each constellation associated with one of the plurality of tones, wherein the plurality of constellations and associated tones form a symbol; and    modulating the constellation with its associated tone in the symbol.    
   
   
       19 . The method of  claim 18 , further comprising the step of transmiting all tones at in the plurality at the same power.  
   
   
       20 . The method of  claim 18 , further comprising the step of transmiting all tones in the plurality at the same power and at a specified PSD with no ripple.