METHOD AND APPARATUS FOR CANCELLING IMPULSE NOISE IN DSL SYSTEMS
The present invention generally relates to an impulse noise canceller for DSL systems. According to certain aspects, embodiments of the invention provide a dual sensor receiver to deal with the impulse noise effectively. The second sensor can be incorporated by either a common mode or unused differential port. Alternatively a power line sensor can also act as a sensor. According to certain additional aspects, embodiments of the invention provide various alternative implementations of an impulse noise canceller within a DSL receiver. According to still further aspects, embodiments of the invention provide methods for selectively training an impulse noise canceller in the various implementations.
1 . An apparatus comprising:
a receiver coupled to receive a data signal of a wireline communication system;
a sensor that is coupled to not receive the data signal and is configured to produce a sensor signal that represents noise affecting the received data signal; and
an impulse noise canceller that cancels impulse noise affecting the received data signal based on the sensor signal.
2 . An apparatus according to claim 1 , wherein the sensor is configured to receive a common mode signal corresponding to a differential mode signal comprising the data signal.
3 . An apparatus according to claim 1 , wherein the receiver is coupled to a twisted pair line of the wireline communication system and the sensor is coupled to an unused twisted pair line of the wireline communication system.
4 . An apparatus according to claim 1 , wherein the sensor is coupled to a powerline that is separate from the wireline communication system.
5 . An apparatus according to claim 1 , wherein the receiver includes a slicer for determining a value associated with a symbol of the data signal, and wherein the impulse noise canceller is trained based on a slicer error of the slicer.
6 . An apparatus according to claim 1 , wherein the data signal comprises a plurality of tones, and wherein the impulse noise canceller cancels noise on each of the plurality of tones independently.
7 . An apparatus according to claim 6 , wherein the impulse noise canceller includes a coefficient for each of the plurality of tones.
8 . An apparatus according to claim 1 , wherein the impulse noise canceller includes a coefficient that is trained in an optimization process during a duration of the impulse noise.
9 . An apparatus according to claim 8 , wherein the optimization process comprises an MMSE criteria computed on FFT outputs corresponding to the sensor signal.
10 . An apparatus according to claim 8 , wherein the receiver includes a slicer for determining a value associated with a symbol of the data signal, and wherein optimization processes comprises an MMSE criteria computed on a slicer error associated with the slicer.
11 . An apparatus according to claim 8 , wherein training of the coefficient is performed selectively in portions of the duration of the impulse noise.
12 . An apparatus according to claim 11 , wherein the selection of the portions is determined based on an Useful Signal Power to Instantaneous Noise Power ratio (UINR) compared to a given threshold.
13 . An apparatus according to claim 11 , wherein the selection of the portions is determined based on a projected instantaneous power of the impulse noise against a given threshold.
14 . An apparatus according to claim 11 , wherein the selection of the portions is determined based on a modulus of the sensor signal obtained at a FFT output multiplied by a modulus of an estimate of the coefficient and compared against a minimum distance.
15 . An apparatus according to claim 11 , wherein the selection of the portions is determined based on characteristics of the impulse noise observed by the receiver or the sensor.
16 . An apparatus according to claim 1 , wherein the impulse noise canceller is applied conditionally during a duration of the impulse noise based on a conditional application process.
17 . A method comprising:
receiving a data signal of a wireline communication system;
producing, by a sensor that is coupled to not receive the data signal, a sensor signal that represents noise affecting the received data signal; and
cancelling impulse noise affecting the received data signal based on the sensor signal.
18 . A method according to claim 17 , wherein the data signal comprises a plurality of tones, and wherein cancelling includes cancelling noise on each of the plurality of tones independently.
19 . A method according to claim 17 , further comprising training a coefficient that is used during cancelling in an optimization process during a duration of the impulse noise.
20 . An apparatus according to claim 19 , wherein training of the coefficient is performed selectively in portions of the duration of the impulse noise.