Selection mechanism for signal combining methods

• US 6,466,558 B1
• Filed: 10/08/1999
• Issued: 10/15/2002
• Est. Priority Date: 06/14/1999
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Ling, Fuyun
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): MEHRPOUR, NAGHMEH
• Application Number:
  US09/414,125
• Time in Patent Office: 1,103 Days
• Field of Search: 370/335, 370/342, 370/334, 375/148, 375/349, 375/346, 375/343, 375/348, 375/350, 375/316, 455/137, 455/296, 455/63, 455/442, 455/501, 455/132, 455/135, 455/138
• US Class Current: 370/334
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• CPC Class Codes: H04B 1/712 Weighting of fingers for combining, e.g. amplitude control or phase rotation using an inner loop
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion

Abstract

An optimum combiner that reduces the amount of interference imposed upon a first base station by transmissions of other base stations within the same communication system. Two antennas are used to receive transmissions within a receiving station. A rake receiver is coupled to each antenna. By optimally combining the signals that are received by each independent finger of the rake receiver, interference that is correlated between a finger associated with the first antenna and a finger associated with the second antenna can be minimized with respect to the desired signal. Optimum combining requires determination of optimum combining coefficients. A max-ratio combining algorithm may be substituted for the optimal combining algorithm depending upon interference characteristics.

Claims

1. A method of computing optimal combining coefficients for a plurality of received signals, comprising the steps of:

estimating an autocorrelation matrix for the plurality of signals based on received noise and interference associated with the plurality of signals;

comparing the magnitudes of off-diagonal elements of the autocorrelation matrix with the magnitudes of diagonal elements of the autocorrelation matrix;

setting the off-diagonal elements equal to zero if the magnitudes of the off-diagonal elements are significantly less than the magnitudes of the diagonal elements; and

computing a plurality of optimal combining coefficients based on the autocorrelation matrix.

2. The method of claim 1, wherein the autocorrelation matrix comprises multiple diagonal 2×

2 submatrices each of which comprises two diagonal elements and two off-diagonal elements, and wherein the comparing step comprises the steps of squaring the magnitudes of each of the off-diagonal elements of each submatrix and multiplying the magnitudes of the diagonal elements of the same submatrix to obtain a product, and wherein the setting step comprises the step of setting the two off-diagonal elements of each submatrix equal to zero if the squared magnitude of each of the off-diagonal elements is less than a predefined fraction of the product of the diagonal elements of the same submatrix.

3. The method of claim 2, wherein the predefined fraction is significantly less than one.

4. The method of claim 2, wherein the predefined fraction is equal to one-fiftieth.

5. The method of claim 1, wherein the comparing step comprises the steps of squaring the magnitudes of each of the off-diagonal elements and, for each off-diagonal element, multiplying the magnitudes of the two diagonal elements located in either the same row or the same column as the off-diagonal element to obtain a product, and wherein the setting step comprises the step of setting each of the off-diagonal elements equal to zero if the squared magnitude of each of the off-diagonal elements is significantly less than the product of the two diagonal elements located in either the same row or the same column as the off-diagonal element.

6. The method of claim 1, wherein the comparing step comprises the steps of squaring the magnitudes of each of the off-diagonal elements and, for each off-diagonal element, multiplying the magnitudes of the two diagonal elements located in either the same row or the same column as the off-diagonal element to obtain a product, and wherein the setting step comprises the step of setting equal to zero each off-diagonal element having a squared magnitude that is significantly less than the product of the two diagonal elements located in either the same row or the same column as that off-diagonal element.