Blind classification of modulation scheme of an interfering signal

Patent metadata

Field	Value
Publication number	US-2018176051-A1
Application number	US-201715849584-A
Country	US
Kind code	A1
Filing date	Dec 20, 2017
Priority date	Dec 21, 2016
Publication date	Jun 21, 2018
Grant date	—

Abstract

A technique for wireless signal processing performed at a receiver in a wireless network includes receiving, by a wireless receiver, an orthogonal frequency division multiplexing (OFDM) signal on a shared downlink channel from the wireless network, wherein the OFDM signal includes contribution from a serving cell signal and at least one interfering signal, obtaining an estimate of the serving cell signal, calculating a residual signal by subtracting the estimate of the serving cell signal from the OFDM signal, generating a whitened residual signal by whitening the residual signal, obtaining an estimate of a modulation scheme of the at least one interfering signal by performing a likelihood-based blind classification on the whitened residual signal, and performing further receiver-side processing of the serving cell signal using the estimate of the modulation scheme of the at least one interfering signal.

First claim

What is claimed is:

1 . A method of wireless signal processing performed at a receiver in a wireless network, comprising:
receiving, by a wireless receiver, an orthogonal frequency division multiplexing (OFDM) signal on a shared downlink channel from the wireless network, wherein the OFDM signal includes contribution from a serving cell signal and at least one interfering signal; obtaining an estimate of the serving cell signal; calculating a residual signal by subtracting the estimate of the serving cell signal from the OFDM signal; generating a whitened residual signal by whitening the residual signal; obtaining an estimate of a modulation scheme of the at least one interfering signal by performing a likelihood-based blind classification on the whitened residual signal; and performing further receiver-side processing of the serving cell signal using the estimate of the modulation scheme of the at least one interfering signal.

2 . The method of claim 1 , wherein the likelihood-based blind classification is performed by performing an empirical search procedure over a plurality of modulation scheme hypotheses.

3 . The method of claim 2 , wherein the performing the empirical search procedure comprises:
formulating an objective function; and minimizing a value of the objective function.

4 . The method of claim 3 , wherein the formulating the objective function includes:
formulating the objective function over a number of received OFDM symbols.

5 . The method of claim 3 , wherein the minimizing the value of the objective function includes:
performing QR decomposition of a channel matrix.

6 . The method of claim 3 , wherein the minimizing the value of the objective function includes:
evaluating, for a number of candidate symbol estimates, corresponding values of the objective function; and selecting a candidate symbol estimate that results in a least value of the objective function.

7 . The method of claim 6 , wherein the number of candidate symbol estimates are processed for constellation estimation using a fixed sphere decoding technique.

8 . The method of claim 7 , wherein a radius parameter for the fixed sphere decoding technique is between 0.3 and 0.4.

9 . The method of claim 1 , wherein the obtaining the estimate of the modulation scheme is performed using a search procedure that uses pre-calculated lookup tables indicative of a modulation scheme.

10 . The method of claim 1 , wherein the blind classification is implemented in a frequency domain on a per physical resource block (PRB) granularity of transmission.

11 . The method of claim 1 , wherein the blind classification is implemented in a time domain on a per transmission time interval granularity.

12 . A wireless receiver apparatus, comprising:
a receiver circuit that receives an orthogonal frequency division multiplexing (OFDM) signal on a shared downlink channel from a wireless network, the OFDM signal including contribution from a serving cell signal and at least one interfering signal; and a processor that processes the received OFDM signals by:
obtaining an estimate of the serving cell signal;
calculating a residual signal by subtracting the estimate of the serving cell signal from the OFDM signal;
generating a whitened residual signal by whitening the residual signal;
obtaining an estimate of a modulation scheme of the at least one interfering signal by performing a likelihood-based blind classification on the whitened residual signal; and
performing further receiver-side processing of the serving cell signal using the estimate of the modulation scheme of the at least one interfering signal.

13 . The apparatus of claim 12 , wherein the likelihood-based blind classification is performed by performing an empirical search procedure over a plurality of modulation scheme hypotheses, and wherein the performing the empirical search procedure comprises formulating an objective function and minimizing a value of the objective function.

14 . The apparatus of claim 13 , wherein the formulating the objective function includes formulating the objective function over a number of received OFDM symbols.

15 . The apparatus of claim 13 , wherein the minimizing the value of the objective function includes performing QR decomposition of a channel matrix.

16 . A method of wireless signal processing performed at a receiver in a wireless network, comprising:
receiving a signal that includes a desired signal, which carries information intended to be received, and an interfering signal, which is an undesired signal superimposed on the desired signal; obtaining a residual signal by subtracting the desired signal from the received signal; and determining a modulation scheme of the interfering signal using a likelihood calculation procedure based on certain constellation points of a first candidate modulation scheme having minimum distances from constellation points of the residual signal and based on corresponding constellation points of a second candidate modulation scheme closest to the constellation points of the first candidate modulation scheme.

17 . The method of claim 16 , wherein the likelihood calculation procedure is performed by using an empirical search procedure over a plurality of modulation scheme hypotheses.

18 . The method of claim 16 , wherein the determining the modulation scheme of the interfering signal is performed using a search procedure that uses pre-calculated lookup tables indicative of a modulation scheme.

19 . The method of claim 16 , wherein the determining the modulation scheme of the interfering signal includes:
searching for constellation points that minimize an Euclidean distance between the constellation points of the residual signal and the first candidate modulation scheme; selecting, for the second candidate modulation scheme, constellation points closest to the constellation points of the first candidate modulation scheme; calculating a likelihood for each candidate modulation scheme; and selecting the modulation scheme having the maximum likelihood.

20 . The method of claim 19 , before calculating the likelihood, further comprising:
selecting, for a third candidate modulation scheme, constellation points obtained using a fixed sphere decoding technique based on the constellation points of at least one of the first and second candidate modulation schemes.

Assignees

• Zte Corp
• Zte Canada Inc

Inventors

• Qian Xing
• Zhao Lijuan
• Zhan Junling

Classifications

• H04L27/2647

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

• H04B7/0417

  Feedback systems · CPC title

• H04L1/0048 Primary

  in conjunction with detection of multiuser or interfering signals, e.g. iteration between CDMA or MIMO detector and FEC decoder (for spatial equalizer H04L25/03286) · CPC title

• H04L27/0012 Primary

  arrangements for identifying the type of modulation · CPC title

• H04J11/005

  of intercell interference · CPC title