US5692006A
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Adaptive despreader
Assignee: Qualcomm Inc
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Filing: 1995-07-31
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Granted: 1997-11-25
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Expires: 2015-07-31
Abstract
Abstract A method and apparatus for adaptively despreading a direct sequence spread spectrum signal. The direct sequence spread spectrum signal is provided to a transversal filter. The output of the filter is demodulated to provide a soft symbol. The soft symbol is provided to an error corrector which generates an error corrected version of the soft symbol, referred to as a hard symbol. The value of the hard symbol is subtracted from the soft symbol to generate an error symbol. The error symbol is then used to compute tap values of the transversal filter by an LMS algorithm.
Inventors
- 👤 Arthur Ross
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 19:02
CPC Classifications
H; H04; H04B; H04B1/00; H04B1/69; H04B1/707; H04B1/7097; H04B1/711; H04L; H04L25/00; H04L25/02; H04L25/03; H04L25/03006; H04L25/03012; H04L25/03019; H04L25/03038; H04L2025/0335; H04L2025/03375; H04L2025/03433; H04L2025/03439; H04L2025/03445; H04L2025/03471; H04L2025/03477; H04L2025/03592; H04L2025/03598; H04L2025/03611; H04L2025/03617
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
150 words
An adaptive despreader comprising: transversal filter means for receiving input samples and for filtering said input samples in accordance with a set of adaptive filter tap values to provide filtered chip values wherein said adaptive tap values are updated in accordance with a re-spread error signal; de-spreading means for receiving said filtered chip values and de-spreading said filtered chip values in accordance with a direct sequence spread spectrum format to provide a first estimated symbol and for generating a second estimated symbol in accordance with a predetermined decision format; error calculator means for receiving said first estimated signal and said second estimated signal and for generating an error signal in accordance with said first estimated signal and said second estimated signal; spreading means for receiving said error signal and for spread spectrum spreading said error signal in accordance with a predetermined spread spectrum format to provide said re-spread error signal.
Claim 2
Dependent Claim
150 words
An adaptive despreader comprising: transversal filter means for receiving input samples and for filtering said input samples in accordance with a set of adaptive filter tap values to provide filtered chip values wherein said adaptive tap values are updated in accordance with a re-spread error signal; de-spreading means for receiving said filtered chip values and de-spreading said filtered chip values in accordance with a direct sequence spread spectrum format to provide a first estimated symbol and for generating a second estimated symbol in accordance with a predetermined decision format; error calculator means for receiving said first estimated signal and said second estimated signal and for generating an error signal in accordance with said first estimated signal and said second estimated signal; spreading means for receiving said error signal and for spread spectrum spreading said error signal in accordance with a predetermined spread spectrum format to provide said re-spread error signal.
Claim 3
Dependent Claim
17 words
The apparatus of claim 1 wherein said transversal filter means is an finite impulse response (FIR) filter.
Claim 4
Dependent Claim
51 words
The apparatus of claim 1 wherein said de-spreading means comprises: symbol estimator means for generating a first symbol estimate in accordance with said filtered chip values; and hard decision means for generating a hard symbol estimate in accordance with said first symbol estimate in accordance with a predetermined hard decision format.
Claim 5
Dependent Claim
14 words
The apparatus of claim 3 wherein said hard decision means comprises a comparator circuit.
Claim 6
Dependent Claim
14 words
The apparatus of claim 3 wherein said hard decision means comprises a Viterbi decoder.
Claim 7
Dependent Claim
57 words
The apparatus of claim 3 wherein said de-spreading means further comprises: pseudo random sequence generator means for generating a pseudo random sequence; and multiplier means for receiving said multiplying said filtered chip values and for receiving said pseudo random sequence and for multiplying said filtered chip values by said pseudo random sequence to provide a product sequence.
Claim 8
Dependent Claim
25 words
The apparatus of claim 1 wherein said transversal filter means updates said tap values in accordance with a least means square (LMS) tap adaptation format.
Claim 9
Dependent Claim
20 words
The apparatus of claim 6 wherein said symbol estimator is for integrating said product sequence to provide a de-spread sequence.
Claim 10
Dependent Claim
27 words
The apparatus of claim 8 wherein said symbol estimator means is further for mapping said de-spread sequence to a second sequence according to a predetermined mapping format.
Claim 11
Dependent Claim
13 words
The apparatus of claim 9 wherein said mapping format is a Hadamard transform.
Claim 12
Independent Claim
116 words
A method for adaptively despreading a spread spectrum signal comprising the steps of: receiving input samples; filtering said input samples in accordance with a set of adaptive filter tap values to provide filtered chip values wherein said adaptive tap values are updated in accordance with a re-spread error signal; de-spreading said filtered chip values in accordance with a direct sequence spread spectrum format to provide a first estimated symbol; generating a second estimated symbol in accordance with a predetermined decision format; generating an error signal in accordance with said first estimated signal and said second estimated signal; and spreading said error signal in accordance with a predetermined spread spectrum format to provide said re-spread error signal.
Claim 13
Independent Claim
116 words
A method for adaptively despreading a spread spectrum signal comprising the steps of: receiving input samples; filtering said input samples in accordance with a set of adaptive filter tap values to provide filtered chip values wherein said adaptive tap values are updated in accordance with a re-spread error signal; de-spreading said filtered chip values in accordance with a direct sequence spread spectrum format to provide a first estimated symbol; generating a second estimated symbol in accordance with a predetermined decision format; generating an error signal in accordance with said first estimated signal and said second estimated signal; and spreading said error signal in accordance with a predetermined spread spectrum format to provide said re-spread error signal.
Claim 14
Dependent Claim
19 words
The method of claim 11 wherein said step of filtering comprises finite impulse response (FIR) filtering said input samples.
Claim 15
Dependent Claim
48 words
The method of claim 11 wherein said step of de-spreading said filtered chip values comprises: generating a first symbol estimate in accordance with said filtered chip values; and generating a hard symbol estimate in accordance with said first symbol estimate in accordance with a predetermined hard decision format.
Claim 16
Dependent Claim
27 words
The method of claim 13 wherein said step of generating a hard symbol estimate comprises a comparing said first symbol estimate to a set of threshold values.
Claim 17
Dependent Claim
21 words
The method of claim 13 wherein said step of generating a hard symbol estimate comprises Viterbi decoding said first symbol estimate.
Claim 18
Dependent Claim
33 words
The method of claim 13 wherein said step of de-spreading further comprises: generating a pseudo random sequence; and multiplying said filtered chip values by said pseudo random sequence to provide a product sequence.
Claim 19
Dependent Claim
22 words
The method of claim 11 further comprising updating said tap values in accordance with a least means square (LMS) tap adaptation format.
Claim 20
Dependent Claim
21 words
The method of claim 16 wherein said step of de-spreading further comprises integrating said product sequence to provide a de-spread sequence.
Claim 21
Dependent Claim
26 words
The method of claim 18 wherein said step of de-spreading further comprises mapping said de-spread sequence to a second sequence according to a predetermined mapping format.
Claim 22
Dependent Claim
13 words
The method of claim 19 wherein said mapping format is a Hadamard transform.
Claim 23
Dependent Claim
76 words
An adaptive despreader comprising: transversal filter having a first input for receiving input samples and having a second input for receiving tap update values and having an output; error calculator having an input coupled to said transversal filter output and having an output for providing a spread spectrum calculated error signal; and tap update calculator having a first input coupled to said error calculator output and having an output coupled to said second transversal filter input.
Claim 24
Dependent Claim
76 words
An adaptive despreader comprising: transversal filter having a first input for receiving input samples and having a second input for receiving tap update values and having an output; error calculator having an input coupled to said transversal filter output and having an output for providing a spread spectrum calculated error signal; and tap update calculator having a first input coupled to said error calculator output and having an output coupled to said second transversal filter input.
Claim 25
Dependent Claim
55 words
The apparatus of claim 21 wherein said error calculator comprises: symbol estimator having an input and an output; decision circuit having an input coupled to said symbol estimator output; and subtractor having a first input coupled to said symbol estimator output and a second input coupled to said decision circuit output and having an output.
Claim 26
Dependent Claim
28 words
The apparatus of claim 22 wherein said error calculator further comprises a despreader having an input coupled to said transversal filter output coupled to said symbol estimator input.
References Cited (Backward Citations)
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