Spreading factor detector
First Claim
1. A method for estimating a spreading factor in a receiver of a variable spreading factor CDMA system, comprising:
- inputting a received signal into a plurality of matched filters, each matched filter having a unique spreading factor, de-spreading the received signal with a spreading code corresponding to the spreading factor and outputting a plurality of de-spread signals;
calculating a mean power for each of the plurality of output de-spread signals; and
estimating a spreading factor of the received signal based on the calculated mean power.
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Abstract
A method for determining whether a zero rate or non-zero rate transmission has occurred, in a variable spreading factor CDMA system, which provides the solution to the problem of de-spreading received signals with incorrect spreading codes and reducing processing delays, is presented. The method utilizes information determined from the received signals, which include control and data channel information, to determine whether a zero rate or non-zero rate transmission has occurred, and generating the correct spreading factor based on that determination. The method is based in a spreading factor detector, which is subsequently able to be utilized in several types of multiple access interference cancellation receivers, which utilize interference cancellation techniques.
77 Citations
21 Claims
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1. A method for estimating a spreading factor in a receiver of a variable spreading factor CDMA system, comprising:
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inputting a received signal into a plurality of matched filters, each matched filter having a unique spreading factor, de-spreading the received signal with a spreading code corresponding to the spreading factor and outputting a plurality of de-spread signals;
calculating a mean power for each of the plurality of output de-spread signals; and
estimating a spreading factor of the received signal based on the calculated mean power. - View Dependent Claims (2)
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3. A method for estimating a spreading factor in a receiver of a variable spreading factor CDMA system, comprising:
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inputting a received signal into a plurality of matched filters, each matched filter having a unique spreading factor and de-spreading the received signal with a spreading code corresponding to the spreading factor, and outputting a plurality of de-spread signals;
calculating an absolute amplitude for each of the plurality of de-spread signals;
calculating a matched filter integrand, MFAIX, for each of the plurality of de-spread signals;
calculating a matched filter difference, MFDX, for each pair of adjacent matched filters; and
estimating a spreading factor of the received signal based on the matched filter difference, MFDX. - View Dependent Claims (4, 5, 6)
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7. A method for determining whether a zero rate transmission has occurred in a wide band code division multiple access communications system, comprising:
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calculating a first threshold value;
calculating a likelihood ratio;
comparing the first threshold value to the likelihood ratio; and
determining a non-zero rate transmission has occurred if the likelihood ratio is greater than or equal to the first threshold value, or determining that a zero rate transmission has occurred if the likelihood ratio is less than the first threshold value. - View Dependent Claims (8, 9, 10, 11, 13, 14, 15, 16, 18, 19, 20)
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12. A method for determining whether a zero rate transmission has occurred in a wide band code division multiple access communications system, comprising:
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calculating a second threshold value, λ
2;
calculating a first test statistic, T1(r);
comparing the second threshold value to the first test statistic; and
determining a non-zero rate transmission has occurred if the first test statistic is greater than or equal to the second threshold value, or determining that a zero rate transmission has occurred if the first test statistic is less than the second threshold value.
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17. A method for determining whether a zero rate transmission has occurred in a wide band code division multiple access communications system, comprising:
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calculating a third threshold value, λ
3;
calculating a second test statistic, T2(r);
comparing the third threshold value to the second test statistic; and
determining a non-zero rate transmission has occurred if the second test statistic is greater than or equal to the third threshold value, or determining that a zero rate transmission has occurred if the second test statistic is less than the third threshold value.
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21. A spreading factor detector, for use in a wideband code division multiple access communications system, comprising:
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a de-scrambler, with an input connected to a received baseband signal, and a real signal output, and an imaginary signal output;
a SIR processor, with an input connected to the imaginary signal output, and a plurality of SIR processor outputs;
a plurality of matched filters, each matched filter having an input connected to the real signal output, and a matched filter output;
a non-zero rate spreading factor detector having a plurality of inputs connected to the plurality of matched filter outputs, and a plurality of non-zero rate spreading factor detector outputs; and
a zero rate spreading factor detector having a plurality of inputs connected to the plurality of non-zero rate spreading factor detector outputs and the plurality of SIR processor outputs, and an estimated spreading factor output signal.
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Specification