Fast computation of coefficients for a variable delay decision feedback equalizer
First Claim
1. A method for computing Decision Feedback Equalizer (DFE) coefficients, the method comprising:
- estimating the channel response of a channel operated upon by the DFE;
formulating a solution that, when solved, will yield the DFE coefficients, wherein the solution is formulated as a least squares problem that is based upon the channel response;
solving the least squares problem to yield Feed Forward Equalizer (FFE) coefficients of the DFE coefficients, wherein solving the least squares problems includes;
selecting a delay of the DFE;
when the delay is less than or equal to a number of taps of the FFE minus one, performing a first set of operations; and
when the delay is greater than the number of taps of the FFE minus one, performing a second set of operations; and
convolving the FFE coefficients with a convolution matrix that is based upon the channel response to yield Feed Back Equalizer (FBE) coefficients of the DFE coefficients.
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Abstract
Optimal Decision Feedback Equalizer (DFE) coefficients are determined from a channel estimate by casting the DFE coefficient problem as a standard recursive least squares (RLS) problem and solving the RLS problem. In one embodiment, a fast recursive method, e.g., fast transversal filter (FTF) technique, is used to compute the Kalman gain of the RLS problem, which is then directly used to compute MIMO Feed Forward Equalizer (FFE) coefficients. The FBE coefficients are computed by convolving the FFE coefficients with the channel impulse response. Complexity of a conventional FTF algorithm may be reduced to one third of its original complexity by selecting a DFE delay to force the FTF algorithm to use a lower triangular matrix. The length of the DFE may be selected to minimize the tap energy in the FBE coefficients or to ensure that the tap energy in the FBE coefficients meets a threshold.
56 Citations
34 Claims
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1. A method for computing Decision Feedback Equalizer (DFE) coefficients, the method comprising:
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estimating the channel response of a channel operated upon by the DFE; formulating a solution that, when solved, will yield the DFE coefficients, wherein the solution is formulated as a least squares problem that is based upon the channel response; solving the least squares problem to yield Feed Forward Equalizer (FFE) coefficients of the DFE coefficients, wherein solving the least squares problems includes; selecting a delay of the DFE; when the delay is less than or equal to a number of taps of the FFE minus one, performing a first set of operations; and when the delay is greater than the number of taps of the FFE minus one, performing a second set of operations; and convolving the FFE coefficients with a convolution matrix that is based upon the channel response to yield Feed Back Equalizer (FBE) coefficients of the DFE coefficients. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method for computing Decision Feedback Equalizer (DFE) coefficients, the method comprising:
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estimating the channel response of a channel operated upon by the DFE; formulating a solution that, when solved, will yield the DFE coefficients, wherein the solution is formulated as a least squares problem that is based upon the channel response; solving the least squares problem using a Kalman gain solution to yield Feed Forward Equalizer (FFE) coefficients of the DFE coefficients using a Fast Transversal Filter (FTF) algorithm, wherein solving the least squares problems includes; selecting a delay of the DFE; when the delay is less than or equal to a number of taps of the FFE minus one, performing a first set of operations; and when the delay is greater than the number of taps of the FFE minus one, performing a second set of operations; and convolving the FFE coefficients with a convolution matrix that is based upon the channel response to yield Feed Back Equalizer (FBE) coefficients of the DFE coefficients. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 33, 34)
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32. A method for computing Decision Feedback Equalizer (DFE) coefficients, the method comprising:
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estimating the channel response of a channel operated upon by the DFE; formulating a solution that, when solved, will yield the DFE coefficients, wherein the solution is formulated as a least squares problem that is based upon the channel response; for each of a plurality of FBE delays, solving the least squares problem to yield a set of Feed Forward Equalizer (FFE) coefficients and Feed Back Equalizer (FBE) coefficients of the DFE coefficients, wherein each set of FFE coefficients and FBE coefficients corresponds to a respective FBE delay; and selecting an FBE delay and a corresponding set of FFE coefficients and FBE coefficients based upon the tap energy of the FBE coefficients of the set.
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Specification