DSL rate adaptation
View Patent ↗A method for enhancing the bit rate and/or margin at which quadrature amplitude modulation (QAM) communication is performed includes the steps of varying a spectral allocation and constellation size with which communication is performed, so as to define a combination of spectral allocation and constellation size at which the bit rate and/or margin are enhanced. The spectral allocation can be varied by varying a stop frequency thereof, while maintaining a substantially constant start frequency, so as to mitigate undesirable high frequency content of the bandwidth. Alternatively, both start and stop frequencies may be varied.
1. A method for data communication over a transmission channel, comprising:
(a) evaluating, by a communications transceiver, a channel response characteristic with respect to a constellation size and a single carrier having an adjustable center frequency of a transmission signal;
(b) varying, by the communications transceiver, the adjustable center frequency of the transmission signal;
(c) determining, by the communications transceiver, a maximum spectral allocation for the transmission channel for which a signal-to-noise ratio is less than a predetermined value;
(d) re-evaluating, by the communications transceiver, the channel response characteristic with respect to the varied center frequency; and
(e) determining, by the communications transceiver, an optimal constellation size and optimal center frequency responsive to at least one of an optimum bit rate and an optimum noise margin.
2. The method of claim 1 , wherein step (b) comprises:
(b)(i) varying a stop frequency of a spectral allocation of the transmission signal while maintaining a substantially constant start frequency of the spectral allocation.
3. The method of claim 1 , wherein the transmission channel is a single QAM channel.
4. The method of claim 1 , further comprising:
(f) varying the constellation size by encoding a signal in conformance with a plurality of discrete constellation sizes and determining a maximum constellation size at which a single QAM communication occurs without exceeding a predetermined bit error rate.
5. The method of claim 4 , wherein step (f) comprises:
(f)(i) varying the constellation size while maintaining a substantially constant spectral allocation; and repeating the constellation size varying step at a plurality of different discrete spectral allocations.
6. The method of claim 1 , wherein step (b) comprises:
(b)(i) varying the spectral allocation while maintaining a constant constellation size; and
(b)(ii) repeating the center frequency varying step for a plurality of different discrete constellation sizes.
7. A method for enhancing a potential channel response characteristic of a transmission channel, comprising:
(a) varying, by a communications transceiver, a center frequency and a constellation size of the transmission channel;
(b) determining, by the communications transceiver, the potential channel response characteristic associated with the center frequency and the constellation size; and
(c) defining, by the communications transceiver, a combination of the center frequency and the constellation size at which the potential channel response characteristic is enhanced.
8. The method of claim 7 , wherein step (a) comprises:
(a)(i) varying a start frequency and a stop frequency thereof.
9. The method of claim 8 , wherein step (a)(i) comprises:
(a)(i)(A) varying the start frequency and the stop frequency in discrete increments.
10. The method of claim 8 , wherein step (a)(i) comprises:
(a)(i)(A) sweeping the start frequency and the stop frequency in a continuous manner.
11. The method of claim 7 , wherein the channel performs quadrature amplitude modulated (QAM) communication.
12. The method of claim 7 , wherein step (c) comprises:
(c)(i) defining the combination of the center frequency and the constellation size at which a bit rate is enhanced.
13. The method of claim 7 , wherein step (c) comprises:
(c)(i) defining the combination of the center frequency and the constellation size at which a margin at which quadrature amplitude modulated (QAM) communication is performed is enhanced.
14. The method of claim 7 , wherein step (a) comprises:
(a)(i) utilizing a plurality of different constellation sizes so as to determine a maximum constellation size at which communication occurs.
15. The method of claim 7 , wherein step (a) comprises:
(a)(i) utilizing a plurality of different constellation sizes so as to determine a maximum constellation size at which communication occurs without exceeding a predetermined bit error rate (BER).
16. The method of claim 7 , wherein step (a) comprises:
(a)(i) varying the constellation size while maintaining a constant center frequency and repeating this step for a plurality of different center frequencies.
17. The method of claim 7 , wherein step (a) comprises:
(a)(i) varying the center frequency while maintaining a constant constellation size for a plurality of different constellation sizes.
18. A system for data communication over a transmission channel, comprising:
means for evaluating a channel response characteristic with respect to a constellation size and a single carrier having an adjustable center frequency of a transmission signal;
means for varying the adjustable center frequency of the transmission signal;
means for determining a maximum spectral allocation for the transmission channel for which a signal-to-noise ratio is less than a predetermined value;
means for re-evaluating the channel response characteristic with respect to the varied center frequency; and
means for determining an optimal constellation size and an optimal center frequency responsive to at least one of an optimum bit rate and an optimum noise margin.
19. The system of claim 18 , wherein means for varying the adjustable center frequency comprises:
means for varying a stop frequency of spectral allocation of the transmission signal while maintaining a substantially constant start frequency of the spectral allocation.
20. The system of claim 18 , further comprising:
means for varying the constellation size by encoding a signal in conformance with a plurality of discrete constellation sizes; and
means for determining a maximum constellation size at which a single QAM communication occurs without exceeding a predetermined bit error rate.
21. The system of claim 20 , wherein the means for varying the constellation size comprises:
means for varying the constellation size while maintaining a substantially constant spectral allocation; and
means for repeating the varying of the constellation size at a plurality of different discrete spectral allocations.
22. The system of claim 18 , means for varying the adjustable center frequency of the transmission signal comprises:
means for varying the spectral allocation while maintaining a constant constellation size; and
means for repeating the center frequency varying step for a plurality of different discrete constellation sizes.
23. A system for enhancing a potential channel response characteristic of a transmission channel, comprising:
means for varying a center frequency and a constellation size of the transmission channel;
means for determining the potential channel response characteristic associated with the center frequency and the constellation size; and
means for defining a combination of the center frequency and the constellation size at which the channel response characteristic is enhanced.
24. The system of claim 23 , wherein the means for varying the center frequency and constellation size comprises:
means for varying a start frequency and a stop frequency thereof.
25. The system of claim 24 , wherein the means for varying the center frequency and constellation size comprises:
means for varying the start frequency and the stop frequency in discrete increments.
26. The system of claim 24 , wherein the means for varying the center frequency and the constellation size comprises:
means for sweeping the start frequency and the stop frequency in a continuous manner.
27. The system of claim 23 , wherein the channel performs quadrature amplitude modulated (QAM) communication.
28. The system of claim 23 , wherein the means for defining the combination of the center frequency and the constellation size comprises:
means for defining the combination of the center frequency and the constellation size at which a bit rate is enhanced.
29. The system of claim 23 , wherein the means for defining the combination of the center frequency and the constellation size comprises:
means for defining the combination of the center frequency and the constellation size at which a margin at which quadrature amplitude modulated (QAM) communication is performed is enhanced.
30. The system of claim 23 , wherein the means for varying the center frequency and the constellation size comprises:
means for utilizing a plurality of different constellation sizes so as to determine a maximum constellation size at which communication occurs.
31. The system of claim 23 , wherein the means for varying the center frequency and the constellation size comprises:
means for utilizing a plurality of different constellation sizes so as to determine a maximum constellation size at which communication occurs without exceeding a predetermined bit error rate (BER).
32. The system of claim 23 , wherein the means for varying the center frequency and the constellation size comprises:
means for varying the constellation size while maintaining a constant center frequency and repeating this step for a plurality of different center frequencies.
33. The system of claim 23 , wherein the means for varying the center frequency and the constellation size comprises:
means for varying the center frequency while maintaining a constant constellation size for a plurality of different constellation sizes.