Systems and methods for positioning and messaging of reserved tones for peak-to-average ratio (PAR) reduction in DSL systems

1. A method for reducing peak-to-average power ratio (PAR) in a digital subscriber line (DSL) system having a passband for signal communication, the passband comprising a MEDLEY set of tones and a set of upper frequency tones having higher frequencies than the MEDLEY set of tones, the method comprising:

performing a startup procedure for DSL session having a handshake phase and a transceiver training phase; and

using PAR reserved tones (PRT) to reduce PAR, wherein the handshake phase comprises

determining a plurality of the set of upper frequency tones for PAR reduction;

reserving the plurality of the set of upper frequency tones as PRT; and

transmitting an upper frequency index based on the plurality of the set of upper frequency tones, and

wherein the transceiver training phase comprises

obtaining bits-per-tone values for all tones; and

determining a revised plurality of upper frequency tones for PAR reduction; and

wherein the method further comprises performing a second startup sequence having a second handshake phase, wherein the second handshake phase comprises:

reserving the revised plurality of upper frequency tones as PRT; and

transmitting a second upper frequency index based on the revised plurality of upper frequency tones.

2. The method of claim 1 wherein the handshake phase further comprises:

estimating a coarse loop length estimate; and

wherein the determining a plurality of the set of upper frequency tones comprises determining a rate loss based on the coarse loop length estimate.

3. The method of claim 1 wherein the transceiver training phase further comprises

obtaining bits-per-tone values for all tones; and

determining a further revised plurality of upper frequency tones for PAR reduction;

wherein the method further comprises performing a third startup sequence having a third handshake phase if the further revised plurality of upper frequency tones differs from the plurality of the set of upper frequency tones, wherein the third handshake phase comprises:

reserving the further revised plurality of upper frequency tones as PRT; and

transmitting a third upper frequency index based on the further revised plurality of upper frequency tones.

4. A method for reducing PAR in a digital subscriber line (DSL) system having a passband for signal communication, the passband comprising a MEDLEY set of tones and a set of upper frequency tones having higher frequencies than the MEDLEY set of tones, the method comprising:

performing a startup procedure for a DSL session having a handshake phase and a transceiver training phase; and

using PRT to reduce PAR, wherein the handshake phase comprises

determining the plurality of in-medley tones for PAR reduction, wherein in-medley tones reside in the MEDLEY set of tones in the passband; and

reserving the plurality of in-medley tones as PRT;

wherein the transceiver training phase comprises:

suppressing power transmission for the plurality of in-medley tones, and

wherein the transceiver training phase further comprises

obtaining bits-per-tone values for all tones; and

determining a revised plurality of in-medley tones for PAR reduction; and

wherein the method further comprises performing a second startup sequence having a second handshake phase and a second transceiver training phase, wherein the second handshake phase comprises:

reserving the revised plurality of in-medley tones as PRT;

wherein the second transceiver training phase comprises: suppressing power transmission for the revised plurality of in-medley tones.

5. The method of claim 4 wherein the handshake phase further comprises:

determining a plurality of the set of upper frequency tones for PAR reduction;

reserving the plurality of the set of upper frequency tones as additional PRT;

determining an upper frequency index based on the plurality of the set of upper frequency tones; and

transmitting the upper frequency index.

6. The method of claim 4 wherein the handshake phase further comprises:

estimating a coarse loop length estimate; and

wherein the determining a plurality of the set of upper frequency tones comprises determining a rate loss based on the coarse loop length estimate.

7. The method of claim 4 , wherein the training phase further comprises:

estimating a fine loop length estimate;

estimating a bits-per-tone value for all tones in the MEDLEY set; and

wherein determining a plurality of in-medley tones is based on the fine loop length estimate and the bits-per-tone values.

8. A method for reducing PAR in a digital subscriber line (DSL) system having a passband for signal communication, the passband comprising a MEDLEY set of tones and a set of upper frequency tones having higher frequencies than the MEDLEY set of tones, the method comprising:

performing a startup procedure for a DSL session having a handshake phase and a transceiver training phase; and

using PRT to reduce PAR, wherein the handshake phase comprises

determining the plurality of in-medley tones for PAR reduction, wherein in-medley tones reside in the MEDLEY set of tones in the passband; and

reserving the plurality of in-medley tones as PRT;

wherein the transceiver training phase comprises:

suppressing power transmission for the plurality of in-medley tones, and

wherein the transceiver training phase further comprises

obtaining bits-per-tone values for all tones; and

determining a revised plurality of upper frequency tones for PAR reduction; and

wherein the method further comprises

performing a second startup sequence having a second handshake phase, wherein the second handshake phase comprises:

reserving the revised plurality of upper frequency tones as additional PRT; and

transmitting a second upper frequency index based on the revised plurality of upper frequency tones.

9. The method of claim 4 wherein the determining the plurality of in-medley tones comprises subdividing all tones based on each tone's power spectral density constraints.

10. A method for reducing PAR in a digital subscriber line (DSL) system having a passband for signal communication, the passband comprising a MEDLEY set of tones and a set of upper frequency tones having higher frequencies than the MEDLEY set of tones, the method comprising:

performing a startup procedure for a DSL session having a handshake phase and a transceiver training phase; and

using PRT to reduce PAR, wherein the handshake phase comprises

determining a plurality of the set of upper frequency tones and in-medley tones for PAR reduction, wherein in-medley tones reside in the MEDLEY set of tones in the passband;

reserving the plurality of upper frequency tones and in-medley tones as PRT; and

transmitting information indicative of the plurality of the set of upper frequency tones and in-medley tones in a vendor discretionary field, and

wherein the transceiver training phase further comprises

obtaining bits-per-tone values for all tones; and

determining a revised plurality of upper frequency tones and in-medley tones for PAR reduction; and

wherein the method further comprises performing a second startup sequence having a second handshake phase, wherein the second handshake phase comprises:

reserving the revised plurality of upper frequency tones and in-medley tones as PRT; and

transmitting information indicative of the revised plurality of upper frequency tones and in-medley tones in a vendor discretionary field.

11. The method of claim 10 wherein the vendor discretionary field is transmitted in a mode select and/or capabilities list message during the handshake phase.

12. The method of claim 10 wherein the determining the plurality of in-medley tones comprises subdividing all tones based on each tone's power spectral density constraints.

13. The method of claim 10 , wherein the second handshake phase begins by receiving a long capabilities list/request (CLR) message thereby skipping initial steps in the second handshake phase.

14. The method of claim 10 , wherein the second handshake phase begins by receiving a mode select message thereby skipping initial steps in the second handshake phase.

15. The method of claim 10 , wherein the second handshake phase begins by receiving a mode request message thereby skipping initial steps in the second handshake phase.

16. The method of claim 10 , wherein the second startup sequence proceeds to the channel analysis phase.

17. A system for DSL communications having reduced PAR comprising:

a symbol mapper;

an inverse fast Fourier transform (IFFT) receiving symbols from the symbol mapper and generating a time-domain signal from the symbols;

a PAR tone indicator coupled to the mapper and the IFFT;

a time-domain compensation signal generator controlled by the PAR tone indicator that generates a time-domain compensation signal;

an additive mixer which mixes the time-domain signal and the time-domain compensation signal into an output signal;

a digital to analog converter which converts the output signal into an analog signal; and

startup logic which is configured to reserve PRT used by the PAR tone indicator by performing a startup procedure for a DSL session having a handshake phase and a transceiver training phase,

wherein the handshake phase comprises

determining the plurality of in-medley tones for PAR reduction, wherein in-medley tones reside in the MEDLEY set; and

reserving the plurality of in-medley tones as PRT;

wherein the transceiver training phase comprises:

suppressing power transmission for the plurality of in-medley tones.

18. The system of claim 17 , further comprising a passband for signal communication, the passband comprising a MEDLEY set of tones and a set of upper frequency tones having higher frequencies than the MEDLEY set of tones, and wherein the handshake phase comprises

determining a plurality of upper frequency tones for PAR reduction;

reserving the plurality of the set of upper frequency tones as PRT; and

transmitting an upper frequency index based on the plurality of upper frequency tones.

19. The system of claim 18 , further comprising

a loop length estimator and wherein the handshake phase further comprises:

estimating a fine loop length estimate by the loop length estimator;

estimating a bits-per-tone value for all tones in the MEDLEY set; and

wherein determining a plurality of upper frequency tones is based on the coarse loop length estimate and the bits-per-tone values.

20. The system of claim 18 , further comprising a loop length estimator and wherein the handshake phase further comprises:

estimating a coarse loop length estimate by the loop length estimator; and

wherein the determining a plurality of upper frequency tones comprises determining a rate loss based on the coarse loop length estimate.

21. The system of claim 17 wherein the handshake phase further comprises

determining a plurality of upper frequency tones for PAR reduction;

reserving the plurality of the set of upper frequency tones as PRT; and

transmitting an upper frequency index based on the plurality of upper frequency tones.

22. The system of claim 17 wherein the determining the plurality of in-medley tones comprises subdividing all tones based on each tone's power spectral density constraints.

23. The system of claim 17 , further comprising a passband for signal communication, the passband comprising a MEDLEY set of tones and a set of upper frequency tones having higher frequencies than the MEDLEY set of tones, and wherein the handshake phase comprises

determining a plurality of the set of upper frequency tones and in-medley tones for PAR reduction;

reserving the plurality of the set of upper frequency tones and in-medley tones as PRT; and

transmitting information indicative of the plurality of upper frequency tones and in- medley tones in a vendor discretionary field.

24. The system of claim 23 , wherein the vendor discretionary field is transmitted in a mode select and/or capabilities list message during the handshake phase.

25. A system for DSL communications having reduced PAR comprising:

a symbol mapper;

an inverse fast Fourier transform (IFFT) receiving symbols from the symbol mapper and generating a time-domain signal from the symbols;

a PAR tone indicator coupled to the mapper and the IFFT;

a time-domain compensation signal generator controlled by the PAR tone indicator that generates a time-domain compensation signal;

an additive mixer which mixes the time-domain signal and the time-domain compensation signal into an output signal;

a digital to analog converter which converts the output signal into an analog signal;

startup logic which is configured to reserve PRT used by the PAR tone indicator by performing a startup procedure for a DSL session having a handshake phase and a transceiver training phase; and

bit-loading values logic;

wherein the PAR tone indicator determines a revised plurality of upper frequency tones and/or a revised plurality of in-medley tones based on bits-per-tone values for all tones obtained from the bit-loading values logic during the transceiver training phase; and

wherein startup logic is further configured to reserve PRT used by the PAR tone indicator by performing a second startup procedure for a DSL session having a handshake phase.

26. The system of claim 25 wherein the second handshake phase comprises:

reserving the revised plurality of upper frequency tones as PRT; and

transmitting a second upper frequency index based on the revised plurality of upper frequency tones.

27. The system of claim 25 wherein the second handshake phase begins by transmitting a mode request message thereby skipping initial steps in the second handshake phase.

28. The system of claim 25 wherein the second startup sequence comprises:

a second transceiver training phase;

wherein the second handshake phase comprises: reserving the revised plurality of in-medley tones as PRT;

wherein the second transceiver training phase comprises: suppressing power transmission for the revised plurality of in-medley tones.

29. The system of claim 28 wherein the second handshake phase comprises:

reserving the revised plurality of upper frequency tones as additional PRT; and

transmitting a second upper frequency index based on the revised plurality of upper frequency tones.

30. The system of claim 25 , wherein the second handshake phase comprises:

reserving the revised plurality of upper frequency tones and in-medley tones as PRT; and

transmitting information indicative of the plurality of upper frequency tones and in-medley tones in a second vendor discretionary field.

31. The system of claim 30 wherein the second vendor discretionary field is transmitted in a mode select and/or capabilities list message during the second handshake phase.

32. The system of claim 25 , wherein the second handshake phase begins by transmitting a long CLR message thereby skipping initial steps in the second handshake phase.

33. The system of claim 25 , wherein the second handshake phase begins by receiving a mode select message thereby skipping initial steps in the second handshake phase.

34. The system of claim 25 , wherein the second startup sequence proceeds to the channel analysis phase.