CN102820903A - Method suitable for self-adaption matching filter under large frequency deviation wireless channel - Google Patents
Method suitable for self-adaption matching filter under large frequency deviation wireless channel Download PDFInfo
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- CN102820903A CN102820903A CN2012102457718A CN201210245771A CN102820903A CN 102820903 A CN102820903 A CN 102820903A CN 2012102457718 A CN2012102457718 A CN 2012102457718A CN 201210245771 A CN201210245771 A CN 201210245771A CN 102820903 A CN102820903 A CN 102820903A
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Abstract
The invention belongs to the field of wireless chain data, relates to a rapid capturing and synchronizing method of a related data chain, and particularly relates to a method suitable for a self-adaption matching filter under a large frequency deviation wireless channel. At present, the search is conducted in a three-dimensional space of a phase and a frequency, and finally, the rapid capture and synchronization can be achieved. The method comprises the steps that an input signal x (k) passes through a self-adaption folding matching filter to obtain an output signal y (k), the coefficient Wn (k) of the filter can be adjusted dynamically in a self-adaption manner by reutilizing the difference of the input signal y (k) and an ideal output signal d (k); the coefficient of the each filter is shown by multiple bits, wherein the most significant digit is a sign bit; and the input signal x (k) and the coefficient Wn (k) are firstly subjected to signed number multiplication and then are subjected to addition/subtraction and delay unit calculation. Compared with the prior art, the rapid capturing and synchronizing method has the advantage that the signals can be captured rapidly and effectively under the large frequency deviation communication environment.
Description
Technical field
The invention belongs to wireless data chain field, relate to catching fast and method for synchronous of a kind of related data chain, especially a kind ofly be applicable to adaptive matched filter method under the big frequency deviation wireless channel.
Background technology
In wireless communications environment; The large scale decline that the multipath effect of channel produces causes very communication quality and seriously influences; And direct sequence spread spectrum skill has overcome multipath effect to a certain extent, and this also is one of direct sequence spread spectrum skill reason of being widely used in wireless data chain field.Generally adopted folding matched filter algorithm to catching of Direct Sequence Spread Spectrum Signal at present, this algorithm capture time is short, and resource utilization is high, if there is not bigger frequency deviation influence in system, capture effect is outstanding.Folding matched filter structure is as shown in Figure 2; Be characterized in that spreading code is stored in the pseudo-code register of 1bit according to 1 or 0; The data input rate is all identical with spread-spectrum code rate with calculating output result, and symbol period of system-computed can capture the correlation peak of pseudo-code in theory.But when having big frequency deviation (frequency deviation is greater than 1/2 of data symbol), this matched filter can't operate as normal, promptly catches failure.
But in some application scenario, receive like gps signal, the big frequency deviation that Doppler frequency shift produces will be very serious to the influence of communication, if do not take measures, the wireless data catenary system can't operate as normal.In order to solve this difficult problem; With the GPS receiver is that the receiver system of representative has adopted the two-dimensional FFT operation based on phase place and frequency; But adopt the method need carry out the division of " frequency well " to frequency deviation region, actually on frequency domain carried out the subregion search, this just greatly reduces system acquisition and synchronous time; With the GPS receiver is example, its catch with lock in time with second level be unit.It is thus clear that the GPS acquisition algorithm is applicable to catching of continuous signal, if communication mode is the burst communication pattern, signal sending time is very brief, has bigger frequency deviation influence again, and this existing method can't be accomplished the task of catching.
Summary of the invention
The object of the present invention is to provide the catching method under a kind of communication environment that is applicable to high dynamically big frequency deviation, in phase place and frequency two-dimensional space, search for simultaneously, finally reach and catch fast and synchronous purpose.
The technical scheme that the present invention adopted is:
A kind ofly be applicable to adaptive matched filter method under the big frequency deviation wireless channel; Input signal x (k) obtains exporting signal y (k) through adaptive folded matched filter, utilizes output signal y (k) and ideal to export the adjustment filter coefficient W of the difference dynamic self-adapting of signal d (k) again
n(k); Each filter coefficient representes that with many bits wherein highest order is a sign bit; Said input signal x (k) and coefficient W
n(k) carry out the signed number multiplying earlier, add/subtract computing and delay unit computing again.
Aforesaid a kind of adaptive matched filter method under the big frequency deviation wireless channel that is applicable to, wherein: adopt the least-square methods update coefficients, renewal equation is:
W
n(k+1)＝W
n(k)+2μe(k)x(k)
Wherein, W
n(k) be the coefficient of folding matched filter, x (k) is the input signal of folding matched filter, and e (k) is the difference of output valve and ideal value, and μ is a convergence factor.
Aforesaid a kind of adaptive matched filter method under the big frequency deviation wireless channel that is applicable to, wherein: said coefficient W
n(k) initial value is 1 or-1.
Aforesaid a kind of adaptive matched filter method under the big frequency deviation wireless channel that is applicable to; Wherein: said desirable output signal d (k) computational methods are: spreading factor N multiply by the optimum sampling value of input signal x (k), and said x (k) optimum sampling value is maximum signed number.
The invention has the beneficial effects as follows:
(1) method that the present invention is proposed is applied to the data chainning system, and the data chainning system adopts the Direct-Spread system, can realize that maximum frequency deviation is 5 times of information symbol rate, catches and is not more than 10ms lock in time.
(2) this algorithm is compared with present other algorithms, and it is moderate to have the algorithm difficulty, and resource overhead is less, catches with synchronous fast, is easy to the characteristics that FPGA realizes.
(3) through adopting folding matched filter, and represent each coefficient of filter, make the coefficient that folds matched filter and pseudo noise code and frequency have correlation simultaneously, complete successfully the task of catching with many bits.
Description of drawings
Fig. 1 is a kind of system schematic that is applicable to adaptive matched filter method under the big frequency deviation wireless channel that the present invention proposes;
Fig. 2 is common folding matched filter structural representation;
Fig. 3 is the folding matched filter structural representation of a kind of improvement that is applicable to that the adaptive matched filter method is adopted under the big frequency deviation wireless channel that the present invention proposes;
Fig. 4 is to the figure as a result of method convergence emulation.
Embodiment
A kind of be applicable to that the adaptive matched filter method is introduced under the big frequency deviation wireless channel below in conjunction with accompanying drawing and embodiment to provided by the invention:
As shown in Figure 1; A kind ofly be applicable to adaptive matched filter method under the big frequency deviation wireless channel; Input signal x (k) obtains exporting signal y (k) through adaptive folded matched filter, utilizes output signal y (k) and ideal to export the adjustment filter coefficient W of the difference dynamic self-adapting of signal d (k) again
n(k); Each coefficient representes that with many bits wherein highest order is a sign bit; Said input signal x (k) and coefficient W
n(k) carry out the signed number multiplying, add/subtract computing and delay unit computing again.
As shown in Figure 2; The coefficient of existing folding matched filter is compared with common filter (like narrow band filter, formed filter etc.); Coefficient is different, and this is because the coefficient of folding matched filter is to be used for carrying out convolution algorithm with pseudo noise code, promptly has correlation with pseudo noise code.But (promptly code0 among the figure code1...) only stores simple 1 or 0 1bit pseudo-code to the pseudo-code register, lacks the correlation with frequency.
Therefore, make the folding original pseudo-code register of matched filter will no longer store simple 1 or 0 1bit pseudo-code, but storage have certain bit wide, the variable coefficient W of numerical value
n(k), as shown in Figure 3.Wherein, each coefficient representes that with many bits highest order is a sign bit; And input signal x (k) no longer carries out XOR with pseudo noise code, but carries out computing according to the signed number multiplication.
In order under big frequency deviation, to capture correct pseudo-code correlation peak, need the difference dynamic self-adapting adjustment filter coefficient W with desirable output signal d (k) according to filter output signal y (k)
n(k), finally reach the minimum result of error signal, this moment, matched filter output was pseudo-code correlation peak, acquisition success.
Consider the complexity of calculating, convergence time, and convergence result's unbiasedness, the LMS of employing (lowest mean square) method, renewal equation is:
W
n(k+1)＝W
n(k)+2μe(k)x(k)
Wherein, W
n(k) be the coefficient of dynamics of folding matched filter, x (k) is the input data of folding matched filter, and e (k) is the difference of output valve and ideal value, i.e. error.μ is a convergence factor.
Step is specific as follows:
1) initialization: x (0)=w (0)=[00 ... 0]
T
2) as if k >=0, then
e(k)＝d(k)-x
T(k)W
n(k)
W
n(k+1)＝W
n(k)+2μe(k)x(k)
W
n(k) initial value is not to be changed to 0, but ± 1, this can reduce the required iterations of arrival optimal solution w0, and visible when the channel frequency deviation is 0, this filter deteriorates to common matched filter.
D (k) is the correlation peak of spreading code under the perfect condition, and the calculating of occurrence can be multiply by input data x (k) optimum sampling value for spreading factor N, x (k) optimum sampling value is similar to thinks maximum signed number in the method.Convergence factor μ is the convergence and the convergence rate of decision systems then, confirms μ=2 through emulation and actual debugging
-6Simulation result such as Fig. 4:
Can prove that through emulation being under the situation of 5 times of character rates this filter to the maximum in frequency deviation can restrain, and confirms that through the reality debugging this system capture time under the maximum frequency deviation environment satisfies system requirements fully less than 8ms in 20 symbol periods.
This method is compared with existing method, lock-on signal fast and effectively under the communication environment of big frequency deviation.
Claims (4)
1. one kind is applicable to adaptive matched filter method under the big frequency deviation wireless channel; It is characterized in that: input signal x (k) obtains exporting signal y (k) through adaptive folded matched filter, utilizes output signal y (k) and ideal to export the adjustment filter coefficient W of the difference dynamic self-adapting of signal d (k) again
n(k); Each filter coefficient representes that with many bits wherein highest order is a sign bit; Said input signal x (k) and coefficient W
n(k) carry out the signed number multiplying earlier, add/subtract computing and delay unit computing again.
2. a kind of adaptive matched filter method under the big frequency deviation wireless channel that is applicable to according to claim 1 is characterized in that: adopt the least-square methods update coefficients, renewal equation is:
W
n(k+1)＝W
n(k)+2μe(k)x(k)
Wherein, W
n(k) be the coefficient of folding matched filter, x (k) is the input signal of folding matched filter, and e (k) is the difference of output valve and ideal value, and μ is a convergence factor.
3. a kind of adaptive matched filter method under the big frequency deviation wireless channel that is applicable to according to claim 2 is characterized in that: said coefficient W
n(k) initial value is 1 or-1.
4. according to the described a kind of adaptive matched filter method under the big frequency deviation wireless channel that is applicable to of claim 1-3; It is characterized in that: said desirable output signal d (k) computational methods are: spreading factor N multiply by the optimum sampling value of input signal x (k), and said x (k) optimum sampling value is maximum signed number.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105388501A (en) * | 2015-11-05 | 2016-03-09 | 天津津航计算技术研究所 | Rapid capturing method of spaceborne Beidou communication system |
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| CN102325104A (en) * | 2011-09-08 | 2012-01-18 | 电子科技大学 | Digital baseband echo canceller |
| CN102435999A (en) * | 2011-10-26 | 2012-05-02 | 浙江理工大学 | Baseband module of GPS (global positioning system) receiver and GPS signal acquiring and tracing method |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102325104A (en) * | 2011-09-08 | 2012-01-18 | 电子科技大学 | Digital baseband echo canceller |
| CN102435999A (en) * | 2011-10-26 | 2012-05-02 | 浙江理工大学 | Baseband module of GPS (global positioning system) receiver and GPS signal acquiring and tracing method |
Non-Patent Citations (1)
| Title |
|---|
| 齐海兵: "自适应滤波器算法设计及其FPGA实现的研究与应用", 《中国优秀硕士学位论文全文数据库信息科技辑》 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105388501A (en) * | 2015-11-05 | 2016-03-09 | 天津津航计算技术研究所 | Rapid capturing method of spaceborne Beidou communication system |
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