SIGNAL TO NOISE RATIO MARGIN EQUALIZATION IN SYSTEMS WITH CODED MODULATION

1 . A method, comprising:

measuring a respective signal-to-noise-ratio (SNR) margin for each respective tone in a multicarrier channel;

determining a plurality of tone groups by, for each tone group, grouping at least one tone with a relatively high SNR margin with at least one tone with a relatively low SNR margin to form a tone group; and

communicating ordering information describing the plurality of tone groups to a transmitter, wherein the transmitter is configured to load bits for transmission by way of the tones based at least on the ordering information.

2 . The method of claim 1 , wherein the tones are assigned respective integer tone indices and the grouping comprises, until all tones have been grouped:

selecting, from tones having even indices, first tone having a minimum SNR margin;

selecting, from tones having odd indices, a second tone having a maximum SNR margin;

grouping the first tone with the second tone to form a new tone group; and

eliminating the first tone and the second tone from consideration.

3 . The method of claim 1 , further comprising:

for each tone in each tone group, determining a number of bits allocated to the tone based at least on the SNR margin for the tone; and

communicating allocation information describing the determined number of bits allocated to each tone to the transmitter, wherein the transmitter loads bits for transmission by way of the tones based at least on the allocation information.

4 . The method of claim 1 , further comprising forming the plurality of tone groups in a manner that equalizes a group SNR margin amongst the tone groups.

5 . The method of claim 4 , further comprising determining the group SNR for each group based at least on a square root of a product of the SNR margin for a first tone in the tone group and the SNR margin for a second tone in the tone group.

6 . The method of claim 1 , further comprising, after communicating the ordering information to the transmitter:

measuring a second SNR margin for each tone; and

when a threshold based at least on SNR margin is met:

determining a second plurality of tone groups by, for each tone group, grouping at least one tone with a relatively high second SNR margin with at least one tone with a relatively low second SNR margin to form a new tone group; and

communicating second ordering information describing the plurality of new tone groups to the transmitter.

7 . The method of claim 6 , further comprising determining whether the threshold is met by:

determining a group SNR margin for each tone group based at least on the second SNR margin for each tone;

identifying, from amongst the group SNR margins for the tone groups, a minimum group SNR margin and a maximum group SNR margin;

comparing the minimum group SNR margin to a minimum threshold;

determining that the threshold has been met when the minimum group SNR margin is less than the minimum threshold;

comparing the maximum group SNR margin to a maximum threshold; and

determining that the threshold has been met when the maximum group SNR margin is less than the maximum threshold.

8 . A transceiver, comprising:

a receiver comprising determination circuitry configured to:

measure a respective signal-to-noise-ratio (SNR) margin for each respective tone in a multicarrier channel;

determine a plurality of tone groups by, for each tone group, grouping at least one tone with a relatively high SNR margin with at least one tone with a relatively low SNR margin to form a tone group; and

a transmitter configured to transmit tone ordering information describing the plurality of tone groups to a second transceiver, wherein the second transceiver is configured to load bits for transmission to the receiver based at least on the ordering information.

9 . The transceiver of claim 8 , wherein the tones are assigned respective integer tone indices and the determination circuitry is configured to, until all tones have been grouped:

select, from tones having even indices, first tone having a minimum SNR margin;

select, from tones having odd indices, an second tone having a maximum SNR margin;

group the first tone with the second tone to form a new tone group; and

eliminate the first tone and the second tone from consideration.

10 . The transceiver of claim 8 , wherein:

the determination circuitry is further configured to for each tone in each tone group, determine a number of bits allocated to the tone based at least on the SNR margin for the tone; and

the transmitter is configured to transmit allocation information describing the determined number of bits allocated to each tone to the transceiver, wherein the transceiver loads bits for transmission to the receiver by way of the tones based at least on the allocation information.

11 . The transceiver of claim 8 , wherein the determination circuitry is further configured to form the plurality of tone groups in a manner that equalizes a group SNR margin for each tone group.

12 . The transceiver of claim 11 , wherein the determination circuitry is further configured to determine the group SNR for each group based at least on a square root of a product of the SNR margin for a first tone in the tone group and the SNR margin for a second tone in the tone group.

13 . The transceiver of claim 8 , wherein the determination circuitry is further configured to, after the transmitter transmits the tone ordering information to the transmitter:

measure a second SNR margin for each tone; and

when a threshold based at least on SNR margin is met:

determine a second plurality of tone groups by, for each tone group, grouping at least one tone with a relatively high second SNR margin with at least one tone with a relatively low second SNR margin to form a new tone group;

communicate second ordering information describing the plurality of new tone groups to the transmitter for transmission to the transceiver.

14 . The transceiver of claim 8 , wherein the determination circuitry is further configured to determine whether the threshold is met by:

determining a group SNR margin for each tone group based at least on the second SNR margin for each tone;

identifying, from amongst the group SNR margins for the tone groups, a minimum group SNR margin and a maximum group SNR margin;

comparing the minimum group SNR margin to a minimum threshold;

determining that the threshold has been met when the minimum group SNR margin is less than the minimum threshold;

comparing the maximum group SNR margin to a maximum threshold; and

determining that the threshold has been met when the maximum group SNR margin is less than the maximum threshold.

15 . Computer readable media having computer-executable instructions stored thereon that, when executed by a processor, cause the processor to perform corresponding functions, the instructions comprising instructions for:

measuring a respective signal-to-noise-ratio (SNR) margin for each respective tone in a multicarrier channel;

determining a plurality of tone groups by, for each tone group, grouping at least one tone with a relatively high SNR margin with at least one tone with a relatively low SNR margin to form a tone group; and

communicating ordering information describing the plurality of tone groups to a transmitter, wherein the transmitter is configured to load bits for transmission by way of the tones based at least on the ordering information.

16 . The computer readable media of claim 15 , wherein the tones are assigned respective integer tone indices and wherein the instructions for grouping comprise instructions for, until all tones have been grouped:

selecting, from tones having even indices, first tone having a minimum SNR margin;

selecting, from tones having odd indices, an second tone having a maximum SNR margin;

grouping the first tone with the second tone to form a new tone group; and

eliminating the first tone and the second tone from consideration.

17 . The computer readable media of claim 15 , wherein the instructions further comprise instructions for:

for each tone in each tone group, determining a number of bits allocated to the tone based at least on the SNR margin for the tone; and

communicating allocation information describing the determined number of bits allocated to each tone to the transmitter, wherein the transmitter loads bits for transmission by way of the tones based at least on the allocation information.

18 . The computer readable media of claim 15 , wherein the instructions comprise instructions for forming the plurality of tone groups in a manner that equalizes a group SNR margin for each tone group.

19 . The computer readable media of claim 18 , wherein the instructions comprise instructions for determining the group SNR for each group based at least on a square root of a product of the SNR margin for a first tone in the tone group and the SNR margin for a second tone in the tone group.

20 . The computer readable media of claim 15 , wherein the instructions comprise instructions for, after communicating the ordering information to the transmitter:

measuring a second SNR margin for each tone; and

when a threshold based at least on SNR margin is met:

determining a second plurality of tone groups by, for each tone group, grouping at least one tone with a relatively high second SNR margin with at least one tone with a relatively low second SNR margin to form a new tone group; and

communicating second ordering information describing the plurality of new tone groups to the transmitter.

21 . The computer readable media of claim 20 , wherein the instructions for determining whether the threshold is met comprise instructions for:

determining a group SNR margin for each tone group based at least on the second SNR margin for each tone;

identifying, from amongst the group SNR margins for the tone groups, a minimum group SNR margin and a maximum group SNR margin;

comparing the minimum group SNR margin to a minimum threshold;

determining that the threshold has been met when the minimum group SNR margin is less than the minimum threshold;

comparing the maximum group SNR margin to a maximum threshold; and

determining that the threshold has been met when the maximum group SNR margin is less than the maximum threshold.