Method for processing a signal coming from a transmission channel

Patent metadata

Field	Value
Publication number	US-9985688-B2
Application number	US-201615042326-A
Country	US
Kind code	B2
Filing date	Feb 12, 2016
Priority date	Jul 9, 2015
Publication date	May 29, 2018
Grant date	May 29, 2018

Abstract

A method is for processing a channel analog signal coming from a transmission channel. The method may include converting the channel analog signal into a channel digital signal, and detecting a state of the transmission channel based on the channel digital signal to detect whether the transmission channel is, over an interval of time, one or more of linear and time invariant and linear and cyclostationary.

First claim

That which is claimed is:

1. A method for processing a channel analog signal coming from a transmission channel, the method comprising:
detecting, during a detection phase, a state of the transmission channel based on a channel digital signal from an analog to digital conversion of the channel analog signal to determine whether the transmission channel is, over an interval of time, linear and time invariant (LTI) or linear and cyclostationary; and
generating a first signal based on determining whether the transmission channel is, over the interval of time, LTI or linear and cyclostationary, wherein the channel analog signal includes a plurality of frames, each frame comprising a plurality of symbols; and wherein the detection phase is carried out during reception of a frame, the detected state of the transmission channel being valid for a duration of the frame, and wherein the detection phase comprises:
performing a plurality of channel estimations respectively using a plurality of reference symbols of the frame to generate a plurality of transfer functions of the transmission channel, and
determining a phase difference between a pair of transfer functions, the detecting of the state comprising a comparison of an absolute value of the phase difference with a threshold, the transmission channel being LTI when the absolute value of the phase difference is less than or equal to the threshold and being linear and cyclostationary when the absolute value of the phase difference is greater than the threshold.

2. The method according to claim 1 , wherein the detection phase is carried out during reception of each frame, the detected state of the transmission channel detected during reception of a current frame being valid for a duration of the current frame.

3. The method according to claim 1 , wherein the channel analog signal is from a digital to analog conversion of an initial digital signal, and wherein when a sampling frequency of the channel digital signal is different from a sampling frequency of the initial digital signal, performing the plurality of channel estimations comprises:
estimating a plurality of base transfer functions respectively based upon the plurality of reference symbols of the frame, and
correcting the plurality of base transfer functions with a phase shift corresponding to a shift in sampling frequency between the channel digital signal and the initial digital signal.

4. The method according to claim 1 , wherein the plurality of reference symbols of the frame extends in time over a duration equal to or greater than a cyclostationary period; and wherein each pair of transfer functions is respectively associated with a pair of reference symbols separated in time by a period longer than a limiting period of time corresponding to a minimum number of reference symbols.

5. The method according to claim 4 , wherein a limiting number of reference symbols is 6.

6. The method according to claim 1 , wherein the detection phase comprises:
determining a plurality of phase differences respectively between a plurality of pairs of transfer functions;
averaging absolute values of the plurality of phase differences to generate a mean phase difference; and
comparing the mean phase difference with the threshold, the transmission channel being LTI when the mean phase difference is less than or equal to the threshold and being linear and cyclostationary when the mean phase difference is greater than the threshold.

7. The method according to claim 1 , wherein the plurality of reference symbols of the frame corresponds to a plurality of known symbols of the frame, the plurality of reference symbols being decoded without knowing a transfer function of the transmission channel.

8. The method according to claim 7 , wherein each channel estimation is based upon a received decodable symbol and comprises:
decoding of the received decodable symbol;
re-encoding of the received decodable symbol to generate a re-encoded symbol; and
determining the transfer function of the transmission channel based upon the re-encoded symbol and the received decodable symbol.

9. The method according to claim 7 , wherein each frame comprises a preamble sequence, a header following the preamble sequence, and a payload following the header; and wherein the plurality of reference symbols is in the header and the payload.

10. The method according to claim 9 , further comprising:
when the transmission channel is linear and cyclostationary for a duration of the frame,
generating a sequence of N transfer functions of the transmission channel respectively associated with N successive time slices, a duration of the N successive time slices being equal to a cyclostationary period of the transmission channel, and
decoding at least some symbols of a frame using, for each of the at least some symbols, a transfer function associated with a successive time slice including a respective symbol.

11. The method according to claim 10 , wherein generating the sequence of N transfer functions comprises generating an initial sequence of M transfer functions respectively associated with M successive reference symbols of each frame, the M successive reference symbols covering a period of time equal to or greater than the cyclostationary period, the N transfer functions being based upon the M transfer functions.

12. The method according to claim 11 , wherein the initial sequence of M transfer functions is generated during the detection phase.

13. The method according to claim 11 , wherein M is equal 15; wherein N is equal to 7; and wherein the sequence of N transfer functions is averages taken two by two of fourteen successive transfer functions of the initial sequence of M transfer functions.

14. The method according to claim 11 , wherein decoding of symbols following a last reference symbol uses, successively and cyclically, the sequence of N transfer functions.

15. The method according to claim 14 , wherein when the duration of the N successive time slices is different from the cyclostationary period, the decoding of the symbols following the last reference symbol also periodically comprises a shift of transfer function in the successive and cyclical use of the sequence of N transfer functions.

16. The method according to claim 14 , wherein the channel analog signal is conveyed via power-line communication, the cyclostationary period of the transmission channel being half of a period of an alternating current flowing on an electrical power line; wherein a reference signal is delivered at each zero crossing of the alternating current; and wherein a value of the cyclostationary period of the transmission channel is reset based upon an occurrence of the reference signal.

17. The method according to claim 1 , wherein the channel analog signal is modulated based upon an orthogonal frequency-division multiplexing (OFDM) modulation.

18. The method according to claim 1 , wherein the transmission channel comprises an electrical power line, the channel analog signal being conveyed via power-line communication; and wherein a cyclostationary period of the transmission channel is half of a period of an alternating current flowing on the electrical power line.

19. The method according to claim 18 , wherein the channel analog signal is based upon a power-line communication (PLC) PLC-G3 standard.

20. The method according to claim 1 , wherein the threshold is 0.75 radians.

21. The method according to claim 1 , further comprising, when the transmission channe

Assignees

• St Microelectronics Rousset

Inventors

• Demaj Pierre
• Bouvet Yoann

Classifications

• H04L27/2647

  Arrangements specific to the receiver only (equalisation H04L27/01) · CPC title

• H04L25/0224

  using sounding signals · CPC title

• H04B2203/5495

  having measurements and testing channel · CPC title

• H04B3/544 Primary

  Setting up communications; Call and signalling arrangements · CPC title

• H04B3/466

  Testing attenuation in combination with at least one of group delay and phase shift · CPC title