System and method for selecting parameters for compressing coefficients for nodescale vectoring
In general, the present invention relates to methods and systems for optimizing the precoder coefficient compression parameters for reducing the storage and other demands on a vectored DSL system. Embodiments of the invention can be implemented in conjunction with various existing coefficient compression techniques such as quantization of coefficients and decimation in frequencies. According to certain aspects, the compression parameters (e.g. Golomb modulus and quantization level) are selected for each of a plurality of macrobands so as to optimize the overall data rate of the system for any given channel condition. According to further aspects, the compression parameters are computed to ensure that the compressed coefficients for all macrobands do not exceed the available memory allocated for storing the coefficient data.
1. A method performed by a processor for optimizing coefficient data for a vectored DSL system, comprising:
identifying a plurality of macrobands in the vectored DSL system;
selecting respective coefficient data compression parameters for each of the macrobands, wherein the coefficient data compression parameters specify parameters of one or more data compression schemes used to compress coefficient data from an original number of bits to a lower compressed non-zero number of bits;
evaluating performance of the vectored DSL system with the selected coefficient data compression parameters; and
optimizing the selecting of the respective coefficient data compression parameters in accordance with a desired system performance as determined by the evaluating, wherein the optimized coefficient data compression parameters of a first one of the macrobands are different than the optimized coefficient data compression parameters of a second one of the macrobands;
storing the optimized coefficient data compression parameters in a vectoring module.
2. The method according to claim 1 , further comprising:
identifying a total available size of the coefficient data,
wherein selecting coefficient data compression parameters is performed such that compressed coefficient data for all of the plurality of macrobands does not exceed the total available size.
3. The method according to claim 1 , wherein evaluating performance includes identifying a corresponding channel condition.
4. The method according to claim 1 , wherein the coefficient data compression parameters include a Golomb modulus.
5. The method according to claim 1 , wherein the coefficient data compression parameters include a quantization level.
6. The method according to claim 1 , further comprising:
performing the evaluating and optimizing for a plurality of different channel conditions; and
storing optimal coefficient data compression parameters in a lookup table indexed by the plurality of different channel conditions.
7. The method according to claim 6 , further comprising:
determining a current channel condition,
wherein selecting includes looking up the current channel condition in the lookup table.
8. The method according to claim 6 , wherein the channel conditions comprise electrical length.
9. The method according to claim 6 , further comprising:
identifying a total available size for the lookup table; and
quantizing possible coefficient data compression parameters and channel conditions in accordance with the total available size.
10. The method according to claim 1 , wherein the desired system performance is an overall maximum data rate of both upstream and downstream communications in the vectored DSL system.
11. The method according to claim 1 , wherein the desired system performance is an overall maximum data rate of one of upstream and downstream communications in the vectored DSL system.
12. The method according to claim 1 , further comprising:
computing far end crosstalk (FEXT) coefficients for a current channel condition;
compressing the FEXT coefficients using the selected coefficient data compression parameters; and
storing the compressed FEXT coefficients.
13. The method according to claim 12 , wherein compressing includes frequency decimation and difference coding.
14. The method according to claim 13 , wherein the difference coding uses a Golomb modulus obtained from the selected coefficient data compression parameters.
15. The method according to claim 12 , wherein compressing includes quantization.
16. The method according to claim 15 , wherein the quantization uses a quantization level obtained from the selected coefficient data compression parameters.
17. The method according to claim 1 , wherein each macroband consists of an upstream or downstream macroband in a DSL system bandplan.
18. The method according to claim 1 , wherein the coefficient data compression parameters comprise both quantization and Golomb modulus parameters.
19. A method performed by a processor for optimizing coefficient data for a vectored DSL system, comprising:
identifying a plurality of macrobands in the vectored DSL system;
selecting respective coefficient data compression parameters for each of the macrobands;
evaluating performance of the vectored DSL system with the selected coefficient data compression parameters; and
optimizing the selecting of the respective coefficient data compression parameters in accordance with a desired system performance as determined by the evaluating;
performing the evaluating and optimizing for a plurality of different channel conditions; and
storing optimal coefficient data compression parameters in a lookup table indexed by the plurality of different channel conditions, wherein the channel conditions comprise a sum of mapped differences.
20. A vectored DSL system comprising:
a vectoring control entity (VCE);
one or more processors configured for optimizing coefficient data for the vectored DSL system, the optimizing comprising:
identifying a plurality of macrobands in the vectored DSL system;
selecting respective coefficient data compression parameters for each of the macrobands, wherein the coefficient data compression parameters specify parameters of one or more data compression schemes used to compress coefficient data from an original number of bits to a lower compressed non-zero number of bits;
evaluating performance of the vectored DSL system with the selected coefficient data compression parameters; and
optimizing the selecting of the respective coefficient data compression parameters in accordance with a desired system performance as determined by the evaluating, wherein the optimized coefficient data compression parameters of a first one of the macrobands are different than the optimized coefficient data compression parameters of a second one of the macrobands;
storing the optimized coefficient data compression parameters in a vectoring control entity.