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