Power spectrum control method for communication channels limited by disturbers and apparatus for performing such a method
View Patent ↗A method for determining at least one operational transmit power S n k over a communication channel (L n ) coupled to a disturbance causing transceiver (n) for at least one tone (k), comprises the steps of provision of at least one reference victim communication channel (L ref ) for representing at least one reference victim for all victim communication channels which are degraded by cross-talk interferences by said communication channel (L n ), and maximizing the data rate (R ref ) over said at least one reference victim communication channel (L ref ) under the constraint that the data rate over said communication channel (L n ) achieves a target rate (R n target ) without exceeding a power constraint (P n max ).
1. A method for determining at least one operational transmit power Snk over a communication channel the method comprising:
providing at least one reference victim communication channel for representing at least one reference victim for all victim communication channels which are degraded by cross-talk interferences by said communication channel;
determining a maximum data rate over said at least one reference victim communication channel under a constraint that a data rate over said communication channel achieves a target rate without exceeding a power constraint;
providing at least one disturbance causing transceiver communicatively coupled to the communication channel and communicatively between a central office and a customer premises equipment;
determining a maximum data rate over said communication channel by maximizing a function based on the determined maximum data rate over said at least one reference victim communication channel, a number of bits allocated to a tone associated with the disturbance causing transceiver and a power associated with the disturbance causing transceiver; and
determining the at least one operational transmit power Snk based on the determined maximum data rate over said communication channel.
2. The method according to claim 1 , wherein said communication channel coupled to said disturbance causing transceiver (n) is part of a plurality of communication channels coupled to a plurality of disturbance causing transceivers, and
said providing step provides said at least one reference victim communication channel such that said at least one reference victim communication channel is used in common for all communication channels of said plurality.
3. The method according to claim 1 , wherein a plurality of communication channels correspond to wires bundled in a common binder.
4. The method according to claim 1 , wherein said step of determining the maximum data rate over said at least one reference victim channel taking into account constraints, by maximizing the following function J(S k n ) with respect to S k n :
J
(
S
k
n
)
=
log
2
(
1
+
h
k
ref
s
k
ref
Γ
k
ref
(
x
k
ref
,
n
s
k
n
+
σ
k
ref
)
)
+
w
n
log
2
(
1
+
h
k
n
s
k
n
Γ
k
n
σ
k
n
)
-
λ
n
s
k
n
wherein
S k n represents the power spectral density of tone k on communication channel n coupled to disturbance causing transceiver n,
S k ref represents the power spectral density of tone k on the at least one reference victim channel,
h k n represents the channel characteristic of communication channel n,
h k ref represents the channel characteristic of said at least one reference victim channel,
σ k n represents the overall noise on communication channel n,
σ k ref represents the background noise on the at least one reference victim channel,
x k ref,n represents either the real, or an approximation for the real or the worst case cross talk transfer function between communication channel n and the at least one reference victim channel, for tone k,
w n represents a first optimization variable for line n,
λ n represents a second optimization variable for line n,
Γ k ref represents the SNR gap for tone k for the at least one reference victim communication channel to achieve a predefined bit error rate, and
Γ k n represents the SNR gap for tone k for disturbance causing transceiver n to achieve a predefined bit error rate.
5. The method according to claim 4 , wherein said step of maximizing said equation with respect to the power spectral density S k n for tone k on disturber line n, is performed for all tones k.
6. The method according to claim 5 , wherein said maximizing steps are followed by updating said first optimization variable w n , such that the constraint that the data rate R n over said communication channel achieves a target rate R n target is obtained by the following equation:
R
n
=
∑
k
log
2
(
1
+
h
k
n
s
k
n
Γ
k
n
σ
k
n
)
≥
R
target
n
.
7. The method according to claim 5 , wherein said maximizing steps are followed by updating said second optimization variable λ n such that the overall power P n on said communication channel complies with said power constraint P n max via the following equation:
P
n
=
∑
k
s
k
n
≤
P
max
n
.
8. The method according to claim 7 , wherein the steps of maximizing said equation for all tones k, updating said first optimization variable and updating said second optimization variable are repeated until convergence is obtained.
9. The method according to claim 8 , wherein the steps of maximizing said equation for all tones k, updating said first optimization variable and updating said second optimization variable are iterated over all communication channels of said plurality of communication channels until convergence is obtained.
10. The method according to claim 1 , wherein the data rate over said at least one reference victim communication channel is maximized taking into account an additional power spectrum constraint.
11. An apparatus for determining at least one operational transmit power Snk over a communication channel coupled to a disturbance causing transceiver for at least one tone, said apparatus comprising:
a network element configured to provide at least one reference victim communication channel for representing at least one reference victim for all victim communication channels which are degraded by cross-talk interferences from said communication channel, mad
the network element further configured to determine a maximum data rate over said at least one reference victim communication channel under a constraint that a data rate over said communication channel achieves a target rate without exceeding a power constraint,
the network element further configured to provide at least one disturbance causing transceiver communicatively coupled to the communication channel and communicatively between a central office and a customer premises equipment,
the network element further configured to determine a maximum data rate over said communication channel by maximizing a function based on the determined maximum data rate over said at least one reference victim communication channel, a number of bits allocated to a tone associated with the disturbance causing transceiver and a power associated with the disturbance causing transceiver, and
the network element further configured to determine the at least one operational transmit power Snk based on the determined maximum data rate over said communication channel.
12. The apparatus according to claim 11 , wherein said communication channel coupled to said disturbance causing transceiver is part of a plurality of communication channels coupled to a plurality of disturbance causing transceivers, and
said at least one reference victim communication channel is used in common for all communication channels of said plurality of communication channels.
13. The apparatus according to claim 11 , wherein a plurality of communication channels correspond to wires bundled in a common binder.
14. The apparatus according to claim 11 , wherein said network element is further configured to determine the maximum data rate of said at least one reference victim communication channel taking into account the constraints, by maximizing the following function J(S k n ) with respect to S k n :
J
(
S
k
n
)
=
log
2
(
1
+
h
k
ref
s
k
ref
Γ
k
ref
(
x
k
ref
,
n
s
k
n
+
σ
k
ref
)
)
+
w
n
log
2
(
1
+
h
k
n
s
k
n
Γ
k
n
σ
k
n
)
-
λ
n
s
k
n
wherein
S k n represents the power spectral density of tone k on communication channel n coupled to disturbance causing transceiver n,
S k ref represents the power spectral density of tone k on the at least one reference victim channel,
h k n represents the channel characteristic of communication channel n,
h k ref represents the channel characteristic of said at least one reference victim channel,
σ k n represents the overall noise on communication channel n,
σ k ref represents the background noise on the at least one reference victim channel,
x k ref,n represents either the real, or an approximation for the real or the worst case cross talk transfer function between communication channel n and the at least one reference victim channel, for tone k,
w n represents a first optimization variable for line n,
λ n represents a second optimization variable for line n,
Γ k ref represents the SNR gap for tone k for the at least one reference victim communication channel to achieve a predefined bit error rate, and
Γ k n represents the SNR gap for tone k for disturbance causing transceiver n to achieve a predefined bit error rate.
15. The apparatus according to claim 14 , wherein said network element is further configured to optimize said equation for all tones k.
16. The apparatus according to claim 15 , wherein said network element is further configured to update said first optimization variable w n , such that the constraint that the data rate R n over said communication channel achieves a target rate R n target is obtained by complying to the following equation:
R
n
=
∑
k
log
2
(
1
+
h
k
n
s
k
n
σ
k
n
)
≥
R
target
n
.
17. The apparatus according to claim 15 , wherein said network element is further configured to update said second optimization variable λ n such that the overall power on said communication channel complies with said power constraint via the following equation:
P
n
=
∑
k
s
k
n
≤
P
max
n
.
18. The apparatus according to claim 14 , wherein said network element is further configured to repeat said optimizations and said updates until convergence is obtained.
19. The apparatus according to claim 18 , wherein said network element is further configured to perform said optimizations and said updates, iteratively for all communication channels of said plurality of communication channels until convergence is obtained.
20. The apparatus according to claim 11 , wherein said network element is further configured to maximize the data rate over said at least one reference victim communication channel taking into account an additional power spectrum constraint.
21. The method according to claim 1 , comprising:
providing a at least one characteristic associated with said at least one victim reference channel and said at least one tone;
providing a background noise associated with the at least one tone;
providing a cross-talk between said at least one reference victim communication channel and said communication channel and associated with said at least one tone; and
determining said maximum data rate over said at least one reference victim communication channel based on said characteristic, said background noise and said crosstalk.