US6404803B1
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PN code acquisition with adaptive antenna array and adaptive threshold for CDMA wireless communications
Assignee: Buffalo Patents LLC
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Filing: 2000-10-24
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Granted: 2002-06-11
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Expires: 2020-10-24
Abstract
Abstract A pseudonise (PN) code acquisition scheme employs all elements of a smart antenna array and an adaptive threshold. The basic structure is the combination of a conventional PN correlation searcher, an adaptive beamformer, and an adaptive threshold setting circuit. During each observation interval, the adaptive beamformer adaptively updates the weight vector for the smart antenna elements using the accumulated received signal despread with trial PN code phase error as input, preferably at the chip rate. A spatially correlated signal is then formed by weighting an accumulated value of the signal received by each antenna in the array over the observation period with the corresponding final weight of smart antenna weight vector as calculated by the adaptive beamformer. This spatially correlated signal is then compared to a threshold to determine whether PN code acquisition has occurred. In preferred embodiments, an adaptive threshold setting algorithm is employed to adapt to varying environment for efficient PN code acquisition. The adaptive threshold setting circuit accumulates the signal received by each element over the observation period, multiplies the accumulated values by the updated weight vector and combines the weighted values to an average estimated power. The average estimated power is then employed to scale a fixed reference threshold to create the adaptive threshold.
Inventors
- 👤 Bing Wang
- 👤 Hyuck M. Kwon
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 10:59
CPC Classifications
H; H04; H04B; H04B15/00; H04B1/00; H04B1/69; H04B1/707; H04B1/7073; H04B1/7075; H04B1/70755; H01; H01Q; H01Q3/00; H01Q3/26; H01Q3/2605; H04B7/00; H04B7/02; H04B7/04; H04B7/08; H04B7/0837; H04B7/0842; H04B7/0848; H04B7/086
Claims Analysis
Total Claims: 60
Claim 1
Independent Claim
138 words
A method for acquiring a pseudo-noise (PN) code comprising the steps of: accumulating despread samples obtained from a plurality of elements in a smart antenna array at a sampling rate, the samples being despread using a PN code shifted by a trial PN code phase error, separate accumulations being maintained for each element; updating an antenna array weight vector based on the accumulated despread samples; forming a spatially correlated signal by weighting the accumulated despread samples from each element with a corresponding weight from the updated antenna array weight vector and combining the weighted samples; comparing the spatially correlated signal to a threshold to determine whether PN code acquisition has been achieved; and selecting a new trial PN code phase error and repeating the accumulating, updating, forming and comparing steps if PN code acquisition has not been achieved.
Claim 2
Independent Claim
138 words
A method for acquiring a pseudo-noise (PN) code comprising the steps of: accumulating despread samples obtained from a plurality of elements in a smart antenna array at a sampling rate, the samples being despread using a PN code shifted by a trial PN code phase error, separate accumulations being maintained for each element; updating an antenna array weight vector based on the accumulated despread samples; forming a spatially correlated signal by weighting the accumulated despread samples from each element with a corresponding weight from the updated antenna array weight vector and combining the weighted samples; comparing the spatially correlated signal to a threshold to determine whether PN code acquisition has been achieved; and selecting a new trial PN code phase error and repeating the accumulating, updating, forming and comparing steps if PN code acquisition has not been achieved.
Claim 3
Dependent Claim
16 words
The method of claim 1 , wherein the sampling rate is equal to a chip rate.
Claim 4
Dependent Claim
16 words
The method of claim 1 , wherein the sampling rate is faster than a chip rate.
Claim 5
Dependent Claim
18 words
The method of claim 1 , wherein the updating step is performed using a least mean square algorithm.
Claim 6
Dependent Claim
19 words
The method of claim 1 , wherein the updating step is performed using a normalized least mean square algorithm.
Claim 7
Dependent Claim
11 words
The method of claim 1 , wherein the threshold is fixed.
Claim 8
Dependent Claim
11 words
The method of claim 1 , wherein the threshold is adaptive.
Claim 9
Dependent Claim
17 words
The method of claim 7 , wherein the adaptive threshold is determined based upon an estimated power.
Claim 10
Dependent Claim
62 words
The method of claim 8 , wherein the process of estimating the power includes the steps of accumulating received signals that have not been despread from each element to form a plurality of spread accumulated signals, weighting each spread accumulated signal from each element by a corresponding weight from the updated antenna array weight vector, and combining the weighted spread accumulated signals.
Claim 11
Dependent Claim
18 words
The method of claim 9 , further comprising the step of averaging the combined weighted spread accumulated signal.
Claim 12
Dependent Claim
30 words
The method of claim 1 , wherein the accumulating step is performed for a number of samples that is one less than the number of samples in an observation period.
Claim 13
Dependent Claim
21 words
The method of claim 1 , wherein the updating step is performed at a rate approximately equal to the sampling rate.
Claim 14
Dependent Claim
30 words
The method of claim 12 , wherein the updating step is performed for a number of samples that is two less than the number of samples in an observation period.
Claim 15
Dependent Claim
32 words
The method of claim 12 , wherein the updating step is performed for a number of samples that is less than two less than the number of samples in an observation period.
Claim 16
Dependent Claim
35 words
The method of claim 14 , wherein the number of samples for which the updating step is performed is based upon a convergence rate of an algorithm used to update the antenna array weight vector.
Claim 17
Dependent Claim
21 words
The method of claim 1 , wherein the accumulating, updating, forming, comparing and selecting steps are performed at a base station.
Claim 18
Dependent Claim
21 words
The method of claim 1 , wherein the accumulating, updating, forming, comparing and selecting steps are performed at a mobile unit.
Claim 19
Dependent Claim
19 words
The method of claim 16 , wherein the base station forms part of a code division multiple access system.
Claim 20
Dependent Claim
21 words
The method of claim 16 , wherein the base station forms part of a direct sequence code division multiple access system.
Claim 21
Dependent Claim
19 words
The method of claim 17 , wherein the mobile unit forms part of a code division multiple access system.
Claim 22
Dependent Claim
21 words
The method of claim 17 , wherein the mobile unit forms part of a direct sequence code division multiple access system.
Claim 23
Dependent Claim
21 words
The method of claim 1 , wherein the accumulating, updating, forming, comparing and selecting steps are performed for a reverse link.
Claim 24
Dependent Claim
21 words
The method of claim 1 , wherein the accumulating, updating, forming, comparing and selecting steps are performed for a forward link.
Claim 25
Dependent Claim
24 words
The method of claim 1 , wherein an observation period during which samples are accumulated is constant for each iteration of the accumulating step.
Claim 26
Dependent Claim
26 words
The method of claim 1 , wherein an observation period during which samples are accumulated varies between a short observation period and a long observation period.
Claim 27
Dependent Claim
21 words
The method of claim 1 , wherein an observation period during which samples are accumulated varies between at least three periods.
Claim 28
Independent Claim
77 words
A method for calculating a threshold used to determine whether PN code acquisition has occurred, the method comprising the steps of: accumulating received signals that have not been despread from each element of a plurality of elements in an antenna array to form a plurality of separately maintained unspread accumulated signals; weighting each unspread accumulated signal from each element by a corresponding weight from an updated antenna array weight vector; and combining the weighted unspread accumulated signals.
Claim 29
Independent Claim
77 words
A method for calculating a threshold used to determine whether PN code acquisition has occurred, the method comprising the steps of: accumulating received signals that have not been despread from each element of a plurality of elements in an antenna array to form a plurality of separately maintained unspread accumulated signals; weighting each unspread accumulated signal from each element by a corresponding weight from an updated antenna array weight vector; and combining the weighted unspread accumulated signals.
Claim 30
Dependent Claim
18 words
The method of claim 27 , further comprising the step of averaging the combined weighted unspread accumulated signals.
Claim 31
Dependent Claim
29 words
The method of claim 28 , further comprising the step of repeating the accumulating, weighting, combining and averaging steps during each observation period in which the threshold is used.
Claim 32
Independent Claim
176 words
An apparatus for acquiring a pseudo-noise (PN) code comprising: a plurality of chip samplers, each chip sampler being connectable to receive a signal from a corresponding element of an antenna array, the antenna array having a plurality of elements; a plurality of despreaders, each despreader being connected to receive samples from a corresponding chip sampler; a plurality of accumulators, each accumulator being connected to receive despread samples from a corresponding despreader; an adaptive beamformer, the beamformer being connected to receive accumulated, despread samples from the accumulators, the beamformer outputting an updated antenna array weight vector; and a PN correlation searcher, the correlation searcher being connected to receive the updated antenna array vector from the beamformer and an accumulated despread sample from each of the accumulators, the correlation searcher being configured to weight accumulated samples from the accumulators by corresponding weights from the updated antenna array vector to form a spatially correlated signal, the correlation searcher further being configured to compare the spatially correlated signal to a threshold to determine whether PN code acquisition has been achieved.
Claim 33
Independent Claim
176 words
An apparatus for acquiring a pseudo-noise (PN) code comprising: a plurality of chip samplers, each chip sampler being connectable to receive a signal from a corresponding element of an antenna array, the antenna array having a plurality of elements; a plurality of despreaders, each despreader being connected to receive samples from a corresponding chip sampler; a plurality of accumulators, each accumulator being connected to receive despread samples from a corresponding despreader; an adaptive beamformer, the beamformer being connected to receive accumulated, despread samples from the accumulators, the beamformer outputting an updated antenna array weight vector; and a PN correlation searcher, the correlation searcher being connected to receive the updated antenna array vector from the beamformer and an accumulated despread sample from each of the accumulators, the correlation searcher being configured to weight accumulated samples from the accumulators by corresponding weights from the updated antenna array vector to form a spatially correlated signal, the correlation searcher further being configured to compare the spatially correlated signal to a threshold to determine whether PN code acquisition has been achieved.
Claim 34
Dependent Claim
21 words
The apparatus of claim 30 , further comprising an adaptive threshold circuit connected to supply the correlation searcher with the threshold.
Claim 35
Dependent Claim
17 words
The apparatus of claim 31 , wherein the adaptive threshold circuit comprises an average power calculator circuit.
Claim 36
Dependent Claim
102 words
The apparatus of claim 31 , wherein the adaptive threshold circuit comprises: a plurality of second accumulators, each of the second accumulators being connected to receive a square of an output of a corresponding chip sampler; a plurality of multipliers, each multiplier being connected to a respective second accumulator to receive a final accumulated value, each multiplier further being configured to weight the final accumulated value by a weight based on a corresponding weight from the updated antenna array weight vector; and an adder, the adder being connected to each of the multipliers to form a sum of outputs from the multipliers.
Claim 37
Dependent Claim
11 words
The apparatus of claim 30 , wherein the threshold is fixed.
Claim 38
Dependent Claim
18 words
The apparatus of claim 30 , wherein the chip samplers are configured to sample at a chip rate.
Claim 39
Dependent Claim
22 words
The apparatus of claim 30 , wherein the chip sampler are configured to sample at a rate faster than a chip rate.
Claim 40
Dependent Claim
16 words
The apparatus of claim 30 , wherein the adaptive beamformer employs a least mean square algorithm.
Claim 41
Dependent Claim
17 words
The apparatus of claim 30 , wherein the adaptive beamformer employs a normalized least mean square algorithm.
Claim 42
Dependent Claim
25 words
The apparatus of claim 30 , wherein the adaptive beamformer updates the antenna array weight vector at a rate approximately equal to the sample rate.
Claim 43
Dependent Claim
44 words
The apparatus of claim 39 , wherein the adaptive beamformer is configured to start updating the antenna array weight vector at a sample that is selected based on an estimated number of samples required for the adaptive beamformer to converge and a safety factor.
Claim 44
Dependent Claim
30 words
The apparatus of claim 40 , wherein the adaptive beamformer is configured to stop updating the antenna array weight vector at a second to last sample in an observation period.
Claim 45
Dependent Claim
25 words
The apparatus of claim 30 , further comprising the antenna array wherein each chip sampler is connected to the corresponding element of the antenna array.
Claim 46
Dependent Claim
15 words
The apparatus of claim 42 , wherein the antenna is located at a base station.
Claim 47
Dependent Claim
19 words
The apparatus of claim 42 , wherein the base station forms part of a code division multiple access system.
Claim 48
Dependent Claim
21 words
The apparatus of claim 42 , wherein the base station forms part of a direct sequence code division multiple access system.
Claim 49
Dependent Claim
15 words
The apparatus of claim 42 , wherein the antenna is located at a mobile unit.
Claim 50
Dependent Claim
19 words
The apparatus of claim 46 , wherein the mobile unit forms part of a code division multiple access system.
Claim 51
Dependent Claim
21 words
The apparatus of claim 46 , wherein the mobile unit forms part of a direct sequence code division multiple access system.
Claim 52
Dependent Claim
17 words
The apparatus of claim 30 , wherein the correlation searcher is configured to perform a simple search.
Claim 53
Dependent Claim
17 words
The apparatus of claim 30 , wherein the correlation searcher is configured to perform a complete search.
Claim 54
Dependent Claim
17 words
The apparatus of claim 30 , wherein the correlation searcher is configured to perform a serial search.
Claim 55
Dependent Claim
18 words
The apparatus of claim 30 , wherein the correlation searcher is configured to perform a single dwell search.
Claim 56
Dependent Claim
18 words
The apparatus of claim 30 , wherein the correlation searcher is configured to perform a dual dwell search.
Claim 57
Dependent Claim
18 words
The apparatus of claim 30 , wherein the correlation searcher is configured to perform a multiple dwell search.
Claim 58
Dependent Claim
25 words
The apparatus of claim 30 , wherein a spacing between adjacent elements in the array is approximately equal to one half of a carrier wavelength.
Claim 59
Independent Claim
124 words
An apparatus for calculating a threshold used to determine whether PN code acquisition has occurred, the apparatus comprising: a plurality of second accumulators, each of the second accumulators being connected to receive a square of an output from a corresponding chip sampler, the chip sampler being connected to receive a signal from a corresponding element in an antenna array; a plurality of multipliers, each multiplier being connected to a respective accumulator to receive a final accumulated value, each multiplier further being configured to weight the final accumulated value by a weight based on a corresponding weight from the updated antenna array weight vector; and an adder, the adder being connected to each of the multipliers to form a sum of outputs from the multipliers.
Claim 60
Independent Claim
124 words
An apparatus for calculating a threshold used to determine whether PN code acquisition has occurred, the apparatus comprising: a plurality of second accumulators, each of the second accumulators being connected to receive a square of an output from a corresponding chip sampler, the chip sampler being connected to receive a signal from a corresponding element in an antenna array; a plurality of multipliers, each multiplier being connected to a respective accumulator to receive a final accumulated value, each multiplier further being configured to weight the final accumulated value by a weight based on a corresponding weight from the updated antenna array weight vector; and an adder, the adder being connected to each of the multipliers to form a sum of outputs from the multipliers.
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