Method, apparatus and computer program product providing widely linear interference cancellation for multi-carrier systems

US 20070026833A1
Filed: 07/31/2006
Published: 02/01/2007
Est. Priority Date: 08/01/2005
Status: Abandoned Application

First Claim

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1. A method comprising:

receiving a multi-carrier signal comprising a plurality of subcarriers; and

performing widely linear (WL) processing on the received signal.

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Abstract

A method is provided. The method includes: receiving a multi-carrier signal that includes a plurality of subcarriers; and performing widely linear (WL) processing on the received signal.

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35 Claims

1. A method comprising:
- receiving a multi-carrier signal comprising a plurality of subcarriers; and
  
  performing widely linear (WL) processing on the received signal.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
- - 2. The method of claim 1, wherein the multi-carrier signal comprises an orthogonal frequency division multiplexed (OFDM) signal.
  - 3. The method of claim 1, wherein the received multi-carrier signal comprises a signal modulated using conjugate symmetric modulation.
  - 4. The method of claim 3, wherein a time domain received signal in baseband form is denoted as:
    - y _k =h _k ⊕
      
      s _k +n _k and wherein in-phase and quadrature parts of the received signal are collected and stacked in vector format as;
      
      $[\begin{matrix} ℜ y_{k} \\ ?? y_{k} \end{matrix}] = [\begin{matrix} ℜ h_{k} \\ ?? h_{k} \end{matrix}] \otimes s_{k} + [\begin{matrix} ℜ n_{k} \\ ?? n_{k} \end{matrix}]$ which has a vector form;
      
      {tilde over (y)}_k={tilde over (h)}_k⊕
      
      s_k+ñ
      
      _k.
  - 5. The method of claim 4, wherein a frequency domain received signal is denoted as:
    - {tilde over (y)}(f_k)={tilde over (h)}(f_k)x(f_k)+ñ
      
      (f_k), wherein elements of the denoted frequency domain received signal are complex valued and exhibit conjugate symmetry, wherein an information carrying symbols pair [x(f_k),x*(N−
      
      f_k)] is combined using an un-biased minimum mean-squared error (MMSE) scheme such that;
      
      $z (f_{k}) = \frac{1}{2} {\tilde{h}}^{†} (f_{k}) R_{\tilde{n} \tilde{n}}^{- 1} (f_{k}) [\tilde{y} (f_{k}) + {\tilde{y}}^{*} (N - f_{k})] for k = 1, \dots, \frac{N}{2} - 1$ where MMSE weights are applied after combing conjugate symmetric parts.
  - 6. The method of claim 3, wherein WL filtering is applied to complex and complex-conjugate replicas such that:
    - y(f_k)=h(f_k)x(f_k)+n(f_k) where
      y(f_k)≅
      
      [y(f_k),y*(N−
      
      f_k)]′
      
      , h(f_k)≅
      
      [h(f_k),h*(N−
      
      f_k)]′
      
      , n(f_k)≅
      
      [n(f_k),n*(N−
      
      f_k)]′
      
      .
  - 7. The method of claim 6, wherein a conjugate symmetric symbol pair [x(f_k), x*(N−
    - f_k)] is combined such that;
      
      $\overline{z} (f_{k}) = \frac{1}{2} {\tilde{h}}^{†} (f_{k}) R_{\tilde{n} \tilde{n}}^{- 1} (f_{k}) \overline{y} (f_{k}) for k = 1, \dots, \frac{N}{2} - 1,$ where R_nn^−
      
      1(f_k) denotes a WL noise correlation matrix and z(f_k) denotes a scalar decision variable used to generate bit wise soft decisions.
  - 8. The method of claim 1, wherein the received multi-carrier signal comprises a signal modulated using Pulse Amplitude Modulation (PAM).
  - 9. The method of claim 8, wherein the WL processing comprises a Discrete Fourier Transform (DFT), wherein an output of the DFT comprises:
    - y(f_k)=h(f_k)a(f_k)+n(f_k), wherein in-phase and quadrature parts of the received signal are collected such that;
      
      $[\begin{matrix} ℜ y (f_{k}) \\ ?? y (f_{k}) \end{matrix}] = [\begin{matrix} ℜ h (f_{k}) \\ ?? h (f_{k}) \end{matrix}] s_{k} + [\begin{matrix} ℜ n (f_{k}) \\ ?? n (f_{k}) \end{matrix}]$ which has a compact vector form;
      
      {hacek over (y)}(f_k)={hacek over (h)}(f_k)a(f_k)+{hacek over (n)}(f_k).
  - 10. The method of claim 9, wherein linear minimum mean squared error (LMMSE) symbol estimates are provided such that:
    - {hacek over (z)}(f_k)={hacek over (h)}†
      
      (f_k)R_{{hacek over (n)}{hacek over (n)}}^−
      
      1(f_k){hacek over (y)}(f_k).
  - 11. The method of claim 1, wherein the received multi-carrier signal comprises a signal modulated using Quadrature Amplitude Modulation (QAM).
  - 12. The method of claim 11, wherein the WL processing comprises a Discrete Fourier Transform (DFT), wherein a frequency domain output of the DFT comprises:
    - y(f_k)=h(f_k)b(f_k)+n(f_k), wherein in-phase and quadrature parts of the received signal in a frequency domain are collected such that;
      
      $[\begin{matrix} y_{I} (f_{k}) \\ y_{Q} (f_{k}) \end{matrix}] = [\begin{matrix} h_{I} (f_{k}) & - h_{Q} (f_{k}) \\ h_{Q} (f_{k}) & h_{I} (f_{k}) \end{matrix}] [\begin{matrix} b_{I} (f_{k}) \\ b_{Q} (f_{k}) \end{matrix}] + [\begin{matrix} n_{I} (f_{k}) \\ n_{Q} (f_{k}) \end{matrix}]$ which has a vector-matrix form;
      
      y(f_k)=H(f_k)b(f_k)+n(f_k).
  - 13. The method of claim 12, wherein QAM symbols are recovered using a ML/MAP decoder that minimizes a distance term, wherein the distance term comprises:
    - d(f_k)=e(f_k)R_nn^−
      
      1(f_k)e(f_k), wherein the candidate symbol e(f_k) comprises;
      
      e(f_k)=y(f_k)−
      
      H(f_k){circumflex over (b)}(f_k)
  - 14. The method of claim 1, wherein performing widely linear (WL) processing on the received signal comprises:
    - splitting the received signal into a real part and an imaginary part;
      
      applying a Discrete Fourier Transform (DFT) to the real part and the imaginary part, wherein outputs of the DFT comprise an in-phase branch signal and a quadrature branch signal;
      
      applying a whitening filter to the in-phase branch signal and the quadrature branch signal; and
      
      demodulating an output of the whitening filter.
  - 15. The method of claim 14, wherein the whitening filter comprises a pre-whitening filter utilizing Choleski factorization of a noise correlation matrix.
  - 16. The method of claim 1, wherein performing widely linear (WL) processing on the received signal comprises:
    - applying a Discrete Fourier Transform (DFT) to the received signal;
      
      splitting an output of the DFT into a real part and an imaginary part;
      
      applying a whitening filter to the real part and the imaginary part; and
      
      demodulating an output of the whitening filter.
  - 17. The method of claim 1, wherein performing widely linear (WL) processing on the received signal comprises:
    - applying a Discrete Fourier Transform (DFT) to the received signal, wherein outputs of the DFT comprise a complex part of the signal and a complex-conjugate part of the signal;
      
      applying a conjugate symmetry operation to the complex part and the complex-conjugate part;
      
      applying a whitening filter to outputs of the conjugate symmetry operation; and
      
      demodulating an output of the whitening filter.
  - 18. The method of claim 1, wherein performing widely linear (WL) processing on the received signal comprises:
    - applying a Discrete Fourier Transform (DFT) to the received signal, splitting an output of the DFT into a complex part of the signal and a complex-conjugate part of the signal;
      
      applying a conjugate symmetry operation to the complex part and the complex-conjugate part;
      
      applying a whitening filter to outputs of the conjugate symmetry operation; and
      
      demodulating an output of the whitening filter.
  - 19. The method of claim 1, wherein the multi-carrier signal comprises one of an Ultra-Wideband (UWB) signal or a Wireless Local Area Network (WLAN) signal.

20. A computer program product comprising program instructions embodied on a tangible computer-readable medium, execution of the program instructions resulting in operations comprising:
- inputting a received multi-carrier signal comprising a plurality of subcarriers; and
  
  performing widely linear (WL) processing on the received signal.
- View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28)
- - 21. The computer program product of claim 20, wherein the multi-carrier signal comprises a signal modulated using conjugate symmetric modulation, wherein a time domain received signal in baseband form is denoted as:
    - y_k=h_k⊕
      
      s_k+n_k, wherein in-phase and quadrature parts of the received signal are collected and stacked in vector format as;
      
      $[\begin{matrix} ℜ y_{k} \\ ?? y_{k} \end{matrix}] = [\begin{matrix} ℜ h_{k} \\ ?? h_{k} \end{matrix}] \otimes s_{k} + [\begin{matrix} ℜ n_{k} \\ ?? n_{k} \end{matrix}]$ which has a vector form;
      
      {tilde over (y)}_k={tilde over (h)}_k⊕
      
      s_k+ñ
      
      _k.
  - 22. The computer program product of claim 21, wherein a frequency domain received signal is denoted as:
    - {tilde over (y)}(f_k)={tilde over (h)}(f_k)x(f_k)+ñ
      
      (f_k), wherein elements of the denoted frequency domain received signal are complex valued and exhibit conjugate symmetry, wherein an information carrying symbols pair [x(f_k),x*(N−
      
      f_k)] is combined using an un-biased minimum mean-squared error (MMSE) scheme such that;
      
      $z (f_{k}) = \frac{1}{2} {\tilde{h}}^{†} (f_{k}) R_{\tilde{n} \tilde{n}}^{- 1} (f_{k}) [\tilde{y} (f_{k}) + {\tilde{y}}^{*} (N - f_{k})] for k = 1, \dots, \frac{N}{2} - 1$ where MMSE weights are applied after combing conjugate symmetric parts.
  - 23. The computer program product of claim 20, wherein the multi-carrier signal comprises a signal modulated using conjugate symmetric modulation, wherein WL filtering is applied to complex and complex-conjugate replicas such that:
    - y(f_k)=h(f_k)x(f_k)+n(f_k) where
      y(f_k)≅
      
      [y(f_k),y*(N−
      
      f_k)]′
      
      , h(f_k)≅
      
      [h(f_k),h*(N−
      
      f_k)]′
      
      , n(f_k)≅
      
      [n(f_k),n*(N−
      
      f_k)]′
      
      .
  - 24. The computer program product of claim 23, wherein a conjugate symmetric symbol pair [x(f_k), x*(N−
    - f_k)] is combined such that;
      
      $\overline{z} (f_{k}) = \frac{1}{2} {\overline{h}}^{†} (f_{k}) R_{\overline{n} \overline{n}}^{- 1} (f_{k}) \overline{y} (f_{k}) for k = 1, \dots, \frac{N}{2} - 1,$ where R_nn^−
      
      1(f_k) denotes a WL noise correlation matrix and z(f_k) denotes a scalar decision variable used to generate bit wise soft decisions.
  - 25. The computer program product of claim 20, wherein the multi-carrier signal comprises a signal modulated using Pulse Amplitude Modulation (PAM), wherein the WL processing comprises a Discrete Fourier Transform (DFT), wherein an output of the DFT comprises:
    - y(f_k)=h(f_k)a(f_k)+n(f_k), wherein in-phase and quadrature parts of the received signal are collected such that;
      
      $[\begin{matrix} ℜ y (f_{k}) \\ ?? y (f_{k}) \end{matrix}] = [\begin{matrix} ℜ h (f_{k}) \\ ?? h (f_{k}) \end{matrix}] s_{k} + [\begin{matrix} ℜ n (f_{k}) \\ ?? n (f_{k}) \end{matrix}]$ which has a compact vector form;
      
      {hacek over (y)}(f_k)={hacek over (h)}(f_k)a(f_k)+{hacek over (n)}(f_k).
  - 26. The computer program product of claim 25, wherein linear minimum mean squared error (LMMSE) symbol estimates are provided such that:
    - {hacek over (z)}(f_k)={hacek over (h)}†
      
      (f_k)R_{{hacek over (n)}{hacek over (n)}}^−
      
      1(f_k){hacek over (y)}(f_k).
  - 27. The computer program product of claim 20, wherein the multi-carrier signal comprises a signal modulated using Quadrature Amplitude Modulation (QAM), wherein the WL processing comprises a Discrete Fourier Transform (DFT), wherein a frequency domain output of the DFT comprises:
    - y(f_k)=h(f_k)b(f_k)+n(f_k), wherein in-phase and quadrature parts of the received signal in a frequency domain are collected such that;
      
      $[\begin{matrix} y_{I} (f_{k}) \\ y_{Q} (f_{k}) \end{matrix}] = [\begin{matrix} h_{I} (f_{k}) & - h_{Q} (f_{k}) \\ h_{Q} (f_{k}) & h_{I} (f_{k}) \end{matrix}] [\begin{matrix} b_{I} (f_{k}) \\ b_{Q} (f_{k}) \end{matrix}] + [\begin{matrix} n_{I} (f_{k}) \\ n_{Q} (f_{k}) \end{matrix}]$ which has a vector-matrix form;
      
      y(f_k)=H(f_k)b(f_k)+n(f_k).
  - 28. The computer program product of claim 27, wherein QAM symbols are recovered using a ML/MAP decoder that minimizes a distance term, wherein the distance term comprises:
    - d(f_k)=e(f_k)R_nn^−
      
      1(f_k)e(f_k), wherein the candidate symbol e(f_k) comprises;
      
      e(f_k)=y(f_k)−
      
      H(f_k){circumflex over (b)}(f_k).

29. An electronic device comprising:
- a multi-carrier radio frequency receiver having an input for coupling to at least one antenna;
  
  a signal processing block coupled to an output of the receiver, wherein the signal processing block comprises a widely linear (WL) signal processing unit operable to demodulate a received multi-carrier signal; and
  
  a decoder having an input coupled to an output of the signal processing block.
- View Dependent Claims (30, 31, 32, 33)
- - 30. The electronic device of claim 29, wherein the signal processing block comprises:
    - a Discrete Fourier Transform (DFT) having an input coupled to an output of the receiver;
      
      a whitening filter having an input coupled to an output of the DFT; and
      
      a demodulator having an input coupled to an output of the whitening filter and an output coupled to an input of the decoder.
  - 31. The electronic device of claim 29, wherein the multi-carrier signal comprises a signal modulated using conjugate symmetric modulation, wherein a time domain received signal in baseband form is denoted as:
    - y_k=h_k⊕
      
      s_k+n_k, wherein in-phase and quadrature parts of the received signal (are collected and stacked in vector format as;
      
      $[\begin{matrix} ℜ y_{k} \\ ?? y_{k} \end{matrix}] = [\begin{matrix} ℜ h_{k} \\ ?? h_{k} \end{matrix}] \otimes s_{k} + [\begin{matrix} ℜ n_{k} \\ ?? n_{k} \end{matrix}]$ which has a vector form;
      
      {tilde over (y)}_k={tilde over (h)}_k⊕
      
      s_k+ñ
      
      _k.
  - 32. The electronic device of claim 29, wherein the multi-carrier signal comprises a signal modulated using Pulse Amplitude Modulation (PAM), wherein the WL signal processing unit comprises a Discrete Fourier Transform (DFT), wherein an output of the DFT comprises:
    - y(f_k)=h(f_k)a(f_k)+n(f_k), wherein in-phase and quadrature parts of the received signal are collected such that;
      
      $[\begin{matrix} ℜ y (f_{k}) \\ ?? y (f_{k}) \end{matrix}] = [\begin{matrix} ℜ h (f_{k}) \\ ?? h (f_{k}) \end{matrix}] s_{k} + [\begin{matrix} ℜ n (f_{k}) \\ ?? n (f_{k}) \end{matrix}]$ which has a compact vector form;
      
      {hacek over (y)}(f_k)={hacek over (h)}(f_k)a(f_k)+{hacek over (n)}(f_k).
  - 33. The electronic device of claim 29, wherein the multi-carrier signal comprises a signal modulated using Quadrature Amplitude Modulation (QAM), wherein the WL signal processing unit comprises a Discrete Fourier Transform (DFT), wherein a frequency domain output of the DFT comprises:
    - y(f_k)=h(f_k)b(f_k)+n(f_k), wherein in-phase and quadrature parts of the received signal in a frequency domain are collected such that;
      
      $[\begin{matrix} y_{I} (f_{k}) \\ y_{Q} (f_{k}) \end{matrix}] = [\begin{matrix} h_{I} (f_{k}) & - h_{Q} (f_{k}) \\ h_{Q} (f_{k}) & h_{I} (f_{k}) \end{matrix}] [\begin{matrix} b_{I} (f_{k}) \\ b_{Q} (f_{k}) \end{matrix}] + [\begin{matrix} n_{I} (f_{k}) \\ n_{Q} (f_{k}) \end{matrix}]$ which has a vector-matrix form;
      
      y(f_k)=H(f_k)b(f_k)+n(f_k).

34. An integrated circuit comprising a multi-carrier radio frequency receiver having an input for coupling to at least one antenna;
- a signal processing block coupled to an output of the receiver, wherein the signal processing block comprises a widely linear (WL) signal processing unit operable to demodulate a received multi-carrier signal; and
  
  a decoder having an input coupled to an output of the signal processing block.
- View Dependent Claims (35)
- - 35. The integrated circuit of claim 34, wherein the signal processing block comprises:
    - a Discrete Fourier Transform (DFT) having an input coupled to an output of the receiver;
      
      a whitening filter having an input coupled to an output of the DFT; and
      
      a demodulator having an input coupled to an output of the whitening filter and an output coupled to an input of the decoder.

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Current Assignee
Nokia Corporation
Original Assignee
Nokia Corporation
Inventors
Kuchi, Kiran

Application Number

US11/496,832
Publication Number

US 20070026833A1
Time in Patent Office

Days
Field of Search
US Class Current

455/296
CPC Class Codes

H04L 25/03299   with noise-whitening circuitry

H04L 27/2647   Arrangements specific to th...

H04L 27/26524   Fast Fourier transform [FFT...

Method, apparatus and computer program product providing widely linear interference cancellation for multi-carrier systems

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Method, apparatus and computer program product providing widely linear interference cancellation for multi-carrier systems

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