Dynamic digital communication system control

• US 20030086514A1
• Filed: 06/08/2001
• Published: 05/08/2003
• Est. Priority Date: 06/01/2001
• Status: Active Grant

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Inventors: Ginis, Georgios, Cioffi, John M., Zeng, Chaohuang, Yu, Wei
• Granted Patent: US 7,158,563 B2
• Time in Patent Office: Days
• US Class Current: 375/346
• CPC Class Codes: H04B 1/10 Means associated with receiver for limiting or suppressing noise or interference
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 1/1081 Reduction of multipath noise by equalising H04B7/005
• CPC Class Codes: H04B 15/00 Suppression or limitation of noise or interference by means associated with receiver H04B1/10
• CPC Class Codes: H04B 2001/1045 Adjacent-channel interference
• CPC Class Codes: H04B 3/32 Reducing cross-talk, e.g. by compensating
• CPC Class Codes: H04B 3/46 Monitoring; Testing
• CPC Class Codes: H04B 3/466 Testing attenuation in combination with at least one of group delay and phase shift
• CPC Class Codes: H04B 3/487 Testing crosstalk effects
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0037 Inter-user or inter-terminal allocation
• CPC Class Codes: H04L 5/0044 allocation of payload
• CPC Class Codes: H04L 5/0046 Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04L 5/0094 Indication of how sub-channels of the path are allocated
• CPC Class Codes: H04L 7/0016 correction of synchronization errors
• CPC Class Codes: H04M 11/062 using different frequency bands for speech and other data

Abstract

Methods, apparatus and systems for dynamically controlling a digital communication system, such as a DSL system, collect information about digital communication lines in the system and adaptively and/or dynamically determine line and signal characteristics of the digital communication lines, including interference effects. Based on the determined characteristics and the desired performance parameters, operation of the digital communication lines is adjusted to improve or otherwise control the performance of the system. The collection and processing of information may be performed by a party that is not a user in the system. This independent party also may control operational characteristics and parameters of the system. The invention can be used to eliminate or reduce signal interference such as crosstalk that can be induced on communication lines in systems such as DSL systems. Specific iterative power allocation and vectored transmission techniques and apparatus are disclosed.

Claims

1. A method of controlling a digital communication system having a plurality of communication lines on which signals are transmitted and received, the signals being affected by interference during transmission, each of the communication lines being used by a user and having at least one transmitter and at least one receiver, the method comprising the steps of:

collecting information about line, signal and interference characteristics of the communication lines;

creating a model of the line, signal and interference characteristics of the communication lines;

synchronizing transmissions of signals between transmitters and receivers;

processing signals using the model to remove interference from signals.

2. The method of claim 1 wherein the digital communication system is a DSL system.

3. The method of claim 1 wherein the step of processing signals using the model is performed prior to transmission of a signal.

4. The method of claim 1 wherein the step of processing signals using the model is performed after reception of the signals.

5. The method of claim 1 wherein the step of synchronizing transmissions of signals comprises using block transmission and reception.

6. The method of claim 1 wherein the interference affecting transmission of signals includes crosstalk from communication lines adjacent the communication line on which the signal is sent.

7. The method of claim 1 wherein the digital communication system uses discrete multitone transmission and the step of processing signals using the model to remove interference from signals is done on a tone by tone basis.

8. The method of claim 1 wherein the step of processing signals using the model to remove interference from signals comprises canceling crosstalk interference in signals by QR decomposition.

9. The method of claim 1 wherein the step of collecting information about line, signal and interference characteristics of the communication lines is performed by a party other than one of the users.

10. The method of claim 1 wherein each user is permitted to transmit and receive signals using a data rate and wherein the step of processing signals using the model to remove interference from signals comprises maximizing a weighted sum of the data rates of the users.

11. The method of claim 10 wherein the step of maximizing the weighted sum of the data rates of the users comprises allocating energy to each user for transmission of signals.

12. The method of claim 1 wherein the signals are sent using a plurality of frequencies and further wherein the step of processing signals using the model to remove interference from signals comprises dynamically adjusting the frequencies used to send the signals.

13. A method of controlling a digital communication system having a plurality of communication lines, each of the communication lines being used by a user, wherein the total power a user can use in the system is limited by a power constraint, the method comprising the steps of:

assigning the total power constraint for each user an initial value;

determining a competitively optimal data rate for each user, comprising the steps of;

determining a power allocation within the total power constraint of each user by iteratively allowing each user to optimize its power allocation; and

determining the competitively optimal data rate for each user based on the determined power allocation for the user;

evaluating the competitively optimal data rate for each user, comprising the steps of;

comparing the competitively optimal data rate of a user with a target rate for the user;

increasing the power constraint for a user if the competitively optimal data rate of the user is less than the target rate for the user;

decreasing the power constraint for the user if the competitively optimal data rate of the user exceeds the target rate for the user by at least a prescribed variance;

maintaining the power constraint for the user if the competitively optimal data rate of the user is equal to the target rate for the user; and

maintaining the power constraint for the user if the competitively optimal data rate of the user exceeds the target rate for the user by less than the prescribed variance.

14. The method of claim 13 wherein the steps of determining a competitively optimal data rate for each user and evaluating the power constraint for each user are repeated until no power constraint is increased or decreased.

15. The method of claim 13 wherein the digital communication system is a DSL system.

16. The method of claim 13 wherein the total power allowed each user is allocated among a plurality of frequencies.

17. The method of claim 13 performed by a single entity.

18. The method of claim 13 performed by the users in a distributed fashion.

19. The method of claim 13 wherein crosstalk interference is injected into the communication line of a user by at least one of the lines of another user and further wherein the crosstalk interference is considered by a user in the step of determining the power allocation of the user.

20. The method of claim 13 wherein each user uses a modem having a power limit and wherein the power constraint of a user will not be increased to a level greater than the modem power limit irrespective of the competitively optimal data rate of the user.