Methods, devices and systems of supporting discontinuous operation in communication systems using vectoring
Methods, devices and systems of supporting discontinuous operation in communication systems using vectoring Methods, devices and techniques are disclosed where vectoring is adapted to lines becoming inactive and active, for example in a discontinued operation. In some embodiments, the vectoring is modified based on already present coefficients.
1. A method, comprising:
transmitting signals over a plurality of lines in a discontinuous operation mode in a time division duplex (TDD) operation, wherein, on any of the plurality of lines, symbols are transmitted only when user data is available for transmission during a transmission opportunity of a TDD frame, and wherein any one of the plurality of lines is powered off when no data is available for transmission on that one of the plurality of lines during the transmission opportunity of the TDD frame,
reducing crosstalk of the plurality of lines in a vectored group by vectoring, wherein an effective number of lines in the vectored group changes when any of the plurality of lines are powered off in the discontinuous operation mode, thereby resulting in a change of composition of the vectored group, and
modifying the crosstalk reduction based on previous crosstalk reduction in case of the change of composition of the vectored group in the discontinuous operation mode.
2. The method of claim 1 , wherein reducing the crosstalk comprises at least one of a crosstalk precompensation prior to transmitting via the lines of the vectored group or a crosstalk equalization after receiving signals from the lines of the vectored group.
3. The method of claim 1 , wherein modifying the crosstalk reduction comprises performing the crosstalk reduction in a case, where only a subset of lines from a set of lines are active based on crosstalk reduction coefficients for a case where all lines of the set of lines are active.
4. The method of claim 3 , wherein the crosstalk reduction coefficients comprise at least one of precoder coefficients and equalization coefficients.
5. The method of claim 3 , wherein, for a case where one line of the set of lines is deactivated, crosstalk is precompensated according to
x ai =P ia T ·u a −P di ·P ad T ·u a
wherein x ai is a signal sent on active line a, P is a precompensation matrix, i indicates an inactive line and u a is a vector of data signals to be sent on the active lines.
6. The method of claim 3 , wherein, for a case where one line of the set of lines is deactivated, crosstalk is precompensated according to
x a =P aa u a −P da ·P dd −1 ·P ad ·u a
wherein for matrix inversion an approximation according to
[
P
dd
-
1
]
ij
≈
{
-
p
dd
ij
for
i
≠
j
p
dd
ij
for
i
=
j
is used, wherein x a is a vector of signals sent on active lines, P is a precompensation matrix, and u a is a vector of data signals to be sent on the active lines.
7. The method of claim 3 , wherein, for a case where one line of the set of lines is deactivated, crosstalk is precompensated according to
x a =P f aa ·u mod a +( H aa −1 ·H ad )· P f da ·u mod a
wherein H is the channel matrix, wherein the precoding is a nonlinear precoding, wherein x a is a vector of signals sent on active lines, P is a precompensation matrix, and u a is a vector of data signals to be sent on the active lines.
8. The method of claim 3 , wherein, for a case where one line of the set of lines is deactivated, crosstalk is cancelled according to
û a =G aa y a −G da ·G dd −1 ·G ad ·y a ,
wherein û a is a corrected received signal, y a is a received and G is an equalization matrix for a case when all lines of the set are active.
9. The method of claim 1 , further comprising performing a power allocation update.
10. The method of claim 9 , wherein the update is performed based on a scale factor.
11. A device, comprising:
a plurality of transceivers configured to transmit signals over a plurality of lines in a discontinuous operation mode in a time division duplex (TDD) operation, wherein, on any of the plurality of lines, symbols are transmitted only when user data is available for transmission during a transmission opportunity of a TDD frame, and wherein any one of the plurality of lines is powered off when no data is available for transmission on that one of the plurality of lines, and
a crosstalk reduction circuit operably coupled to the plurality of transceivers, and adapted to reduce crosstalk of a plurality of lines associated with the plurality of transceivers in a vectored group by vectoring, wherein an effective number of lines in the vectored group changes when any of the plurality of lines are powered off in the discontinuous operation mode, thereby resulting in a change of composition of the vectored group, and to modify the crosstalk reduction based on previous crosstalk reduction in case of the change of composition of the vectored group in the discontinuous operation mode.
12. The device of claim 11 , wherein the crosstalk reduction circuit comprises at least one of a crosstalk precompensator to precompensate crosstalk prior to transmitting signals via the lines of the vectored group or a crosstalk equalizer to cancel crosstalk after receiving signals from the lines of the vectored group.
13. The device of claim 11 , wherein for modifying the crosstalk reduction, the crosstalk reduction circuit is adapted to perform the crosstalk reduction in a case, where only a subset of lines from a set of lines are active based on crosstalk reduction coefficients for a case where all lines of the set of lines are active.
14. The device of claim 13 , wherein the crosstalk reduction coefficients comprise at least one of precoder coefficients and equalization coefficients.
15. The device of claim 13 , wherein, for a case where one line of the set of lines is deactivated, the crosstalk reduction circuit is adapted to precompensate crosstalk according to
x ai =p ia T ·u a −p di ·p ad T ·u a
wherein x ai is a signal sent on active line a, P is a precompensation matrix, i indicates an inactive line and u a is a vector of data signals to be sent on the active lines.
16. The device of claim 13 , wherein, for a case where one line of the set of lines is deactivated, the crosstalk reduction circuit is adapted to precompensate crosstalk according to
x a =P aa u a −P da ·P dd −1 ·P ad ·u a
wherein for matrix inversion an approximation according to
[
P
dd
-
1
]
ij
≈
{
-
p
dd
ij
for
i
≠
j
p
dd
ij
for
i
=
j
is used, where x is a vector of signals sent on active lines, P is a precompensation matrix, and u a is a vector of data signals to be sent on the active lines.
17. The device of claim 13 , wherein, for a case when one line of the set of lines is deactivated, the crosstalk reduction circuit is adapted to precompensate crosstalk according to
x a =P f aa ·u mod a +( H aa −1 ·H ad )· P f da ·u mod a
wherein H is the channel matrix, wherein the precoding is a nonlinear precoding, where x is a vector of signals sent on active lines, P is a precompensation matrix, and ua is a vector of data signals to be sent on the active lines.
18. The device of claim 13 , wherein, for a case where one line of the set of lines is deactivated, the crosstalk reduction circuit is adapted to cancel crosstalk according to
û a =G aa y a −G da ·G dd −1 ·G ad ·y a ,
wherein û a is a corrected received signal, y a is a received and G is an equalization matrix for a case when all lines of the set are active.
19. The device of claim 13 , wherein the device is comprised in a distribution point.
20. A device, comprising:
a plurality of transceivers, and
a crosstalk reduction circuit operably coupled to the plurality of transceivers, and adapted to reduce crosstalk of a plurality of lines associated with the plurality of transceivers in a vectored group by vectoring, and to modify the crosstalk reduction based on previous crosstalk reduction in case of the change of composition of the vectored group,
wherein for modifying the crosstalk reduction, the crosstalk reduction circuit is adapted to perform the crosstalk reduction in a case, where only a subset of lines from a set of lines are active based on crosstalk reduction coefficients for a case where all lines of the set of lines are active, and
wherein, for a case where one line of the set of lines is deactivated, the crosstalk reduction circuit is adapted to precompensate crosstalk according to
x ai =p ia T ·u a −p di ·p ad T ·u a
wherein x ai is a signal sent on active line a, P is a precompensation matrix, i indicates an inactive line and u a is a vector of data signals to be sent on the active lines, or
wherein, for a case where one line of the set of lines is deactivated, the crosstalk reduction circuit is adapted to precompensate crosstalk according to
x a =P aa u a −P da ·P dd −1 ·P ad ·u a
wherein for matrix inversion an approximation according to
[
P
dd
-
1
]
ij
≈
{
-
p
dd
ij
for
i
≠
j
p
dd
ij
for
i
=
j
is used, where x is a vector of signals sent on active lines, P is a precompensation matrix, and u a is a vector of data signals to be sent on the active lines.