Systems and Methods for Positioning and Messaging of Reserved Tones for Peak-to-Average Ratio (PAR) Reduction in DSL Systems

• US 20090310658A1
• Filed: 06/13/2008
• Published: 12/17/2009
• Est. Priority Date: 06/13/2008
• Status: Active Grant

• Current Assignee: Ikanos Communications Incorporated (Qualcomm, Inc.)
• Original Assignee: Conexant Systems Incorporated (Synaptics Incorporated)
• Inventors: Mahadevan, Amitkumar, Garg, Rahul, Duvaut, Patrick, Jethanandani, Harish
• Granted Patent: US 8,885,736 B2
• Time in Patent Office: Days
• US Class Current: 375/222
• CPC Class Codes: H04M 11/062 using different frequency bands for speech and other data

Abstract

Systems and methods for reducing the peak-to-average ratio (PAR) at the transmitter can reduce the dynamic range required in various analog components. PAR can be reduced by applying a time-domain compensation signal which reduces the magnitude of peaks in the time-domain signal prior to transmission where the time-domain compensation signals use tones that are reserved for the purpose of reducing the PAR. The reservation of these reserved tones for PAR can be implemented by altering the typical startup procedures in a digital subscriber line (xDSL) system. The use of the reserved tones to reduce the PAR can be implemented using a low complexity algorithm or using an adaptive technique.

Claims

1. A method for reducing peak-to-average power ratio (PAR) comprising:

performing a startup procedure for a digital subscriber line (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 upper frequency tones for PAR reduction;

reserving the plurality of upper frequency tones as PRT; and

transmitting an upper frequency index based on the 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 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 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.

4. The method of claim 1 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;

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

5. A method for reducing PAR 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 a 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.

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

determining a plurality of upper frequency tones for PAR reduction;

reserving the plurality of upper frequency tones as additional PRT;

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

transmitting the upper frequency index.

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

estimating a coarse loop length estimate; and

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

8. The method of claim 5, 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.

9. The method of claim 5 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.

10. The method of claim 5 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.

11. The method of claim 5 wherein the determining the plurality of in-medley tones comprises subdividing all tones based on each tone'"'"'s power spectral density constraints.

12. A method for reducing PAR 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 upper frequency tones and in-medley tones for PAR reduction;

reserving the 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 vendor discretionary field.

13. The method of claim 12 wherein the vendor discretionary field is transmitted in a mode select and/or capabilities list message during the handshake phase.

14. The method of claim 12 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.

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

16. The method of claim 14, wherein the second handshake phase begins by receiving a long capabilities list/request (CLR) message thereby skipping initial steps in the second handshake phase.

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

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

19. The method of claim 14, wherein the second startup sequence proceeds to the channel analysis phase.

20. 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.

21. The system of claim 20, wherein the handshake phase comprises

determining a plurality of upper frequency tones for PAR reduction;

reserving the plurality of upper frequency tones as PRT; and

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

22. The method of claim 21, 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.

23. The system of claim 21, 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.

24. The system of claim 20, wherein the handshake phase comprises

determining the plurality of in-medley tones for PAR reduction, wherein in-medley tones reside in a 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.

25. The system of claim 24, wherein the handshake phase comprises

determining a plurality of upper frequency tones for PAR reduction;

reserving the plurality of upper frequency tones as PRT; and

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

26. The system of claim 24 wherein the determining the plurality of in-medley tones comprises subdividing all tones based on each tone'"'"'s power spectral density constraints.

27. The system of claim 20, wherein the handshake phase comprises

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

reserving the 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 vendor discretionary field.

28. The system of claim 27, wherein the vendor discretionary field is transmitted in a mode select and/or capabilities list message during the handshake phase.

29. The system of claim 20, further comprising

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.

30. The system of claim 29 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.

31. The method of claim 29 wherein the second handshake phase begins by transmitting a mode request message thereby skipping initial steps in the second handshake phase.

32. The system of claim 29 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.

33. The system of claim 32 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.

34. The system of claim 29, 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.

35. The system of claim 34 wherein the second vendor discretionary field is transmitted in a mode select and/or capabilities list message during the second handshake phase.

36. The system of claim 29, wherein the second handshake phase begins by transmitting a long CLR message thereby skipping initial steps in the second handshake phase.

37. The system of claim 29, wherein the second handshake phase begins by receiving a mode select message thereby skipping initial steps in the second handshake phase.

38. The system of claim 29, wherein the second startup sequence proceeds to the channel analysis phase.