Method and apparatus for reducing interference within a communication system

• US 7,221,722 B2
• Filed: 02/27/2003
• Issued: 05/22/2007
• Est. Priority Date: 02/27/2003
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Vook, Frederick W., Thomas, Timothy A.
• Primary Examiner(s): TRAN, KHANH C
• Application Number:
  US10/375,438
• Publication Number:
  US 20040184570A1
• Time in Patent Office: 1,545 Days
• Field of Search: 375/285, 375346-350, 375147-148, 375/260, 375/267, 455/132, 455/135, 455/137, 455/134, 455/273, 455/273.1, 455/279.1, 455/63.1, 455/65, 455/67.13, 455/447, 455/296, 370/210, 370/335, 370/337, 370/347, 370/208, 370/343
• US Class Current: 375/346
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

A method for reducing interference within a communication system is provided herein. The method comprising the steps of receiving a signal y(n), where y(n) comprises a desired signal, s(n), and a co-channel interfering signal, i(n), wherein s(n) and i(n) are not time-synchronized, converting y(n) into a frequency-domain signal Y(k), calculating a weight vector W(k), wherein W(k) is based on s(n) and i(n), and additionally based on a time offset T existing between s(n) and i(n), and applying W(k) to Y(k) in order to equalize the desired signal, s(n), and reduce co-channel interference i(n).

Claims

1. An apparatus for reducing interference within a communication system, the apparatus comprising:

an antenna receiving a signal y(n), where y(n) comprises a desired signal, s(n), and a co-channel interfering signal, i(n), wherein s(n) and i(n) are not time-synchronized;

a transformer for transforming y(n) into a frequency-domain signal Y(k);

a weight calculator outputting a weight vector W(k), wherein W(k) is based on s(n) and i(n), and additionally based on a time offset T existing between s(n) and i(n); and

a signal combiner applying W(k) to Y(k) in order to reduce co-channel interference i(n), wherein W(k) is additionally based on a spatial correlation matrix of the desired signal on a subcarrier k, R_d(k), wherein W(k) is additionally based on a spatial correlation matrix of the interferer on subcarrier k, R_I(k), wherein W(k) is additionally based on a spatial correlation matrix of noise, R_E(k), and wherein W(k)=(R_d(k)+R_I(k)+R_E(k))<sup>−

1</sup>p(k), wherein p(k) is an M×

1 crosscorrelation vector.

2. The apparatus of claim 1 wherein the weight calculator further comprises:

logic circuitry utilized to calculate correlation matrices R_d(k) and R_I(k);

logic circuitry utilized to calculate the crosscorrelation matrix p(k);

logic circuitry utilized to calculate noise correlation matrix R_E(k); and

logic circuitry used to calculate W(k).

3. An apparatus comprising:

logic circuitry utilized to calculate a spatial correlation matrix of a desired signal on a sub carrier k, R_d(k);

logic circuitry utilized to calculate a spatial correlation matrix of an interferer on the subcarrier k, R_I(k);

logic circuitry utilized to calculate on a spatial correlation matrix of noise, R_E(k); and

logic circuitry used to calculate a weighting vector W(k) to be applied to a received signal, the weighting vector W(k) being based on R_d(k), R_I(k), and R_E(k), wherein W(k)=(R_d(k)+R_I(k)+R_E(k))<sup>−

1</sup>p(k), wherein p(k) is an M×

1 crosscorrelation vector.

4. A method for reducing interference within a communication system, the method comprising the steps of:

calculating a spatial correlation matrix of the desired signal on subcarrier k, R_d(k);

calculating a spatial correlation matrix of the interferer on subcarrier k, R_I(k);

calculating a spatial correlation matrix of the noise, R_E(k); and

calculating a weighting vector W(k) to be applied to a received signal to reduce interference, the weighting vector W(k) being based on R_d(k), R_I(k), and R_E(k)), wherein W(k)=(R_d(k)+R_I(k)+R_E(k))<sup>−

1</sup>p(k), wherein p(k) is an M×

1 crosscorrelation vector.

5. A method for reducing interference within a communication system, the method comprising the steps of:

receiving a signal y(n), where y(n) comprises a desired signal, s(n), and a co-channel interfering signal, i(n), wherein s(n) and i(n) are not time-synchronized;

converting y(n) into a frequency-domain signal Y(k);

calculating a weight vector W(k), wherein W(k) is based on s(n) and i(n), and additionally based on a time offset T existing between s(n) and i(n); and

applying W(k) to Y(k) in order to reduce co-channel interference i(n), wherein the step of calculating W(k) comprises the step of calculating W(k) based on a spatial correlation matrix of the desired signal on a subcarrier k, R_d(k), wherein the step of calculating the weight vector W(k) comprises the step of calculating W(k)=(R_d(k)+R_E(k))<sup>−

1</sup>p(k), wherein p(k) is an M×

1 crosscorrelation vector.

6. The method of claim 5 the step of calculating W(k) comprises the step of calculating W(k) based on a spatial correlation matrix of noise, R_E(k).

7. A method for reducing interference within a communication system, the method comprising the steps of:

receiving a signal y(n), where y(n) comprises a desired signal, s(n), and a co-channel interfering signal, i(n), wherein s(n) and i(n) are not time-synchronized;

converting y(n) into a frequency-domain signal Y(k);

calculating a weight vector W(k), wherein W(k) is based on s(n) and i(n), and additionally based on a time offset T existing between s(n) and i(n); and

applying W(k) to Y(k) in order to reduce co-channel interference i(n), wherein the step of calculating W(k) comprises the step of calculating W(k) based on a spatial correlation matrix of the desired signal on a subcarrier k, wherein the step of calculating W(k) comprises the step of calculating W(k)=(R_d(k)+R_I(k)+R_E(k))<sup>−

1</sup>p(k), wherein p(k) is an M×

1 crosscorrelation vector.

8. The method of claim 7 wherein the step of calculating W(k) comprises the step of calculating W(k) based on a spatial correlation matrix of the interferer on subcarrier k, R_I(k).