DSL system loading and ordering
View Patent ↗Loading and ordering techniques are provided for one-sided and two-sided vectored line groups, as well as loading methodologies that also can be used on a single line, in communication systems such as Digital Subscriber Line (DSL) binders. In particular, a method for loading bits into a plurality of lines in a vectored DSL system using Discrete MultiTone (DMT) modulation is disclosed. The method iteratively determines two or more of the following sequentially: line ordering for each tone; power spectral density for the transmitted signal of each line; and bit allocation for the signal of each line. In some embodiments, line ordering may include order-swapping which may assign a first line to a first initial position, assign a second line to a second initial position, move the first line to the second initial position, and move the second line to the first initial position.
1. A method of assigning bits for a plurality of lines in a vectored Digital Subscriber Line (DSL) system using Discrete MultiTone (DMT) modulation, the method comprising:
performing a first iteration comprising the steps:
[1] determining a new user line ordering position for each of a plurality of tones in the vectored DSL system, wherein the determined new user line ordering position defines the order in which each of the plurality of lines in the vectored DSL system are decoded or precoded, and wherein the first iteration further comprises one or both of the steps:
[2] determining a power spectral density for a signal transmitted on each of the plurality of lines, and
[3] determining a bit allocation for the signal transmitted on each of the plurality of lines, when the determined new user line ordering position is different than an existing user line order;
performing an order-swapping operation on the determined new user line ordering positions, including:
re-assigning a first user's line to a first initial line position associated with a second user's line,
re-assigning the second user's line to a second initial line position associated with the first user's line,
moving the first user's line to the re-assigned first initial line position, and
moving the second user's line to the re-assigned second initial line position; and
performing one or more subsequent iterations, wherein each subsequent iteration comprises performing two or more of steps 1 through 3.
2. The method of claim 1 wherein determining the new user line ordering positions comprises at least one of the following:
determining a decoding order of the plurality of lines for each tone of a vectored DSL receiver; or
determining a precoding order of the plurality of lines for each tone of a vectored DSL transmitter.
3. The method of claim 1 wherein determining the new user line ordering positions comprises at least one of the following:
determining the same line ordering for all tones on all lines in the plurality of lines; or
determining an individual ordering for each line of the plurality of lines for each tone, wherein the orderings for lines do not have to be identical.
4. The method of claim 1 wherein the method is used in at least one of the following phases:
initialization of all of the lines in the plurality of lines; or
normal operation of all of the lines in the plurality of lines; or
a time period during which at least one line of the plurality of lines is in normal operation and at least one line of the plurality of lines is in initialization.
5. The method of claim 1 wherein moving the first user's line and moving the second user's line are performed after evaluating the performance of the vectored DSL system using the assigned first line and second line positions.
6. The method of claim 1 wherein the plurality of lines comprises:
at least one line of the vectored DSL system that is in normal operation; and
at least one line of the vectored DSL system that is being initialized.
7. The method of claim 1 wherein determining the new user line ordering position further comprises:
initially assigning to at least one line that is in initialization, an ordering position that increases a transmission rate performance of one or more other lines of the plurality of lines of the vectored DSL system; and
adjusting the ordering of the one or more other lines to achieve a targeted performance change for the vectored DSL system.
8. The method of claim 1 wherein the method is applied for an upstream DSL transmission; and
further wherein the method comprises performing an upstream power spectral density determination comprising solving a problem of minimizing a weighted energy sum given a set of user data rates.
9. The method of claim 1 wherein the method is applied for an upstream DSL transmission; and
further wherein the method comprises performing an upstream power spectral density determination comprising solving a problem of achieving a set of user data rates while satisfying an energy vector constraint.
10. The method of claim 1 wherein the method is applied for a downstream DSL transmission; and
further wherein the method comprises performing a downstream power spectral density determination comprising using a duality method based on a duality between a broadcast channel and its equivalent multiple-access channel with an iterative water-filling method that maximizes a sum of users data rates.
11. A non-transitory computer-readable storage medium having instructions stored thereon that, when executed by a processor in a vectored Digital Subscriber Line (DSL) system using Discrete MultiTone (DMT) modulation, performs a method of assigning bits for a plurality of lines in the vectored DSL system using DMT modulation, wherein the method comprises:
performing a first iteration comprising the steps:
[1] determining a new user line ordering position for each of a plurality of tones in the vectored DSL system, wherein the determined new user line ordering position defines the order in which each of the plurality of lines in the vectored DSL system are decoded or precoded, and wherein the first iteration further comprises one or both of the steps:
[2] determining a power spectral density for a signal transmitted on each of the plurality of lines, and
[3] determining a bit allocation for the signal transmitted on each of the plurality of lines, when the determined new user line ordering position is different than an existing user line order;
performing an order-swapping operation on the determined new user line ordering positions, including:
re-assigning a first user's line to a first initial line position associated with a second user's line,
re-assigning the second user's line to a second initial line position associated with the first user's line,
moving the first user's line to the re-assigned first initial line position, and
moving the second user's line to the re-assigned second initial line position; and
performing one or more subsequent iterations, wherein each subsequent iteration comprises performing two or more of steps 1 through 3.
12. The non-transitory computer-readable storage medium of claim 11 , wherein determining the new user line ordering position comprises at least one of the following:
determining a decoding order of the plurality of lines for each tone of a vectored DSL receiver; or
determining a precoding order of the plurality of lines for each tone of a vectored DSL transmitter.
13. The non-transitory computer-readable storage medium of claim 11 , wherein determining the new user line ordering positions comprises at least one of the following:
determining the same line ordering for all tones on all lines in the plurality of lines; or
determining an individual ordering for each line of the plurality of lines for each tone, wherein the orderings for lines do not have to be identical.
14. The non-transitory computer-readable storage medium of claim 11 , wherein the method is used in at least one of the following phases:
initialization of all of the lines in the plurality of lines; or
normal operation of all of the lines in the plurality of lines; or
a time period during which at least one line of the plurality of lines is in normal operation and at least one line of the plurality of lines is in initialization.
15. The non-transitory computer-readable storage medium of claim 11 , wherein moving the first user's line and moving the second user's line are performed after evaluating the performance of the vectored DSL system using the assigned first line and second line positions.
16. The non-transitory computer-readable storage medium of claim 11 , wherein the plurality of lines comprises:
at least one line of the vectored DSL system that is in normal operation; and
at least one line of the vectored DSL system that is being initialized.
17. The non-transitory computer-readable storage medium of claim 11 , wherein determining the new user line ordering position further comprises:
initially assigning to at least one line that is in initialization, an ordering position that increases a transmission rate performance of one or more other lines of the plurality of lines of the vectored DSL system; and
adjusting the ordering of the one or more other lines to achieve a targeted performance change for the vectored DSL system.
18. The non-transitory computer-readable storage medium of claim 11 , wherein the method is applied for an upstream DSL transmission; and
further wherein the method comprises performing an upstream power spectral density determination comprising solving a problem of minimizing a weighted energy sum given a set of user data rates.
19. The non-transitory computer-readable storage medium of claim 11 , wherein the method is applied for an upstream DSL transmission; and
further wherein the method comprises performing an upstream power spectral density determination comprising solving a problem of achieving a set of user data rates while satisfying an energy vector constraint.
20. The non-transitory computer-readable storage medium of claim 11 , wherein the method is applied for a downstream DSL transmission; and
further wherein the method comprises performing a downstream power spectral density determination comprising using a duality method based on a duality between a broadcast channel and its equivalent multiple-access channel with an iterative water-filling method that maximizes a sum of users data rates.