CN103353589A - Phase-based effective indoor positioning method - Google Patents

Phase-based effective indoor positioning method Download PDF

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CN103353589A
CN103353589A CN2013102886116A CN201310288611A CN103353589A CN 103353589 A CN103353589 A CN 103353589A CN 2013102886116 A CN2013102886116 A CN 2013102886116A CN 201310288611 A CN201310288611 A CN 201310288611A CN 103353589 A CN103353589 A CN 103353589A
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phase
label
signal
frequency
card reader
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CN103353589B (en
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马永涛
刘开华
赵阳
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Tianjin University
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Abstract

The invention relates to phase-based effective indoor positioning method, belonging to the field of signal processing. The method comprises that cosine wave forms are selected for emission signals, an AM mode is used for modulation, and whole-cycle ambiguity is eliminated by adding subcarriers; a full-phase FFT (Fast Fourier Transform) method is used to accurately extract phase values in corresponding frequencies from the emission signals; reference labels are uniformly laid in a scene, and signal phase differences of multiple readers and a single reference label are calculated one by one; for each reader, an optimal reference label whose phase difference is most similar to that of an objected label is searched; a line-of-sight distance between the optimal reference label and the corresponding reader is calculated and used as the line-of-sight distance between the objected label and the reader; line-of-sight distances from the objected label to all the readers are obtained; and positioning is carried out. The phase-based effective indoor positioning method can improve precision in positioning a moving object in a complex indoor environment.

Description

A kind of effective indoor orientation method based on phase place
Technical field
The invention belongs to the contactless automatic identification field based on REID (RFID Radio Frequency Identification), particularly for the orientation problem under the indoor multi-path environment.
Background technology
Along with the development of wireless communication technology, people are also more and more urgent for the demand of wireless location service, especially under the indoor environment of complexity, and such as hospital, mine, the environment such as storage.Utilize REID that target is positioned, so just can under noncontact, efficient prerequisite, guarantee staff's safety and the accuracy of logistic track.But the influence factor of indoor signal is more, and traditional location technology can not satisfy the requirement of bearing accuracy under the indoor environment, and therefore, the indoor positioning technology has very high researching value.
In general, localization method can be divided into two classes: a kind of method that is based on range finding, or be called geometric method; Another kind is based on the method for non-range finding, or is called statistic law.Telemetry is mainly utilized the geometric relationship of distance between card reader and target labels, and the method by least square positions; The method of non-range finding is not considered range information, but by obtain the positioning result on the statistical significance from the angle that minimizes evaluated error.Signal measurement information commonly used in the location technology has, time of arrival (Time of Arrival (TOA)), time of arrival poor (Time Difference of Arrival (TDOA)), the angle of arrival (Direction of Arrival (DOA)), the energy intensity (Received Signal Strength (RSS)) that arrives phase place (phase of arrival (POA)) and receive.These information namely can be mixed use again separately as position reference information, and these information are all more commonly used in distance-finding method, but generally adopt RSS as reference information in non-distance-finding method.
Studies show that in a large number these metrical informations have the advantages and disadvantages of self, in the method based on TOA and TDOA, require multipath signal can divide in time domain, this has just introduced the research of ultra-broadband signal; Based on present study more of the method for DOA, have benefited from the development of array signal process technique; Subject matter based on the POA method is that complete cycle fuzzy, namely can't record the in the air complete cycle issue of process of signal, and feasible solution is to introduce the concept of subcarrier signal in the document at present.As for the method based on RSS, because the nonlinear relationship of energy and distance, relatively more classical is exactly to introduce reference label at present, obtains the locating information of target by the degree of approximation that compares reference label and tag energy undetermined.
It is more serious that multipath disturbs the impact on indoor position accuracy, this is because the barrier of indoor placement, the pedestrian walks about, ground, the meetings such as wall cause reflection to signal, and the impacts such as scattering are so that the los path between echo signal and reader is covered, and arrive reader by different obstructed paths, then cause larger positioning error.But it is very difficult directly obtaining the direct projection path, and under complex environment owing to the reason direct projection paths such as barrier exist sometimes, so there is implementation barrier in the scheme based on the los path location in the practical application.In addition, owing to having noise in the signal communication environments, there is error in signal measurement information with the corresponding relation between the signal propagation distance, can introduce the error that can not eliminate for next step position fixing process.
Summary of the invention
The direct projection path that exists for current indoor positioning technology be difficult to extract and environment in have the problem of the noise effect that is difficult to eliminate, the present invention proposes a kind of indoor orientation method based on phase place.The method can finely must be eliminated the impact that multipath disturbs, and the dynamic environment factor is had good robustness, thus obtain preferably bearing accuracy and this algorithm fairly simple, easily realize.Technical scheme of the present invention is as follows:
A kind of indoor positioning algorithm based on phase place comprises the following steps:
1) transmit and select the cosine wave (CW) form, modulation system is the AM mode, and it is fuzzy to eliminate complete cycle by the method for adding subcarrier, and establishing subcarrier frequency is f 0, transmitter, phase is
Figure BDA00003492828500029
, receiving phase is
Figure BDA000034928285000210
, for overclocking carrier wave f c, make transmitter, phase be
Figure BDA000034928285000211
, receiving phase is
Figure BDA000034928285000212
, modulation level is A, and the receiving end additional noise is z, and the bandpass sampling frequency is f s, then distribute and penetrate burst s (n) and acknowledge(ment) signal sequence r (n):
s(n)＝[cos(2πnf 0/f s+
Figure BDA00003492828500025
)+A]·cos(2πnf c/f s+
Figure BDA00003492828500026
)
r(n)＝[cos(2πnf 0/f s+ )+A]·cos(2πnf c/f s+ )+z；
2) introduce two subcarrier numeral angular frequency 0=2 π f 0/ f sWith overclocking carrier wave numeral angular frequency c=2 π f c/ f s, then distribute and penetrate burst s (n) and acknowledge(ment) signal sequence r (n) is:
Figure BDA00003492828500021
3) utilize the whole phase FFT transform method, accurately extract phase value under the middle corresponding frequencies that transmits according to following criterion:
A) calculating respectively the rear signal frequency f of modulation is f c-f 0, f cAnd f c+ f 0The time at sample frequency f sThe spectral line sequence number k=[(f-[f/f of middle correspondence s] * f s) * N/f s], wherein, hits is N, [] expression rounds;
B) in phase spectrum according to f c-f 0, f cAnd f c+ f 0Three signal frequencies spectral line sequence number separately finds three phase values under the frequency, is respectively
Figure BDA000034928285000213
With
Figure BDA000034928285000214
, note by abridging and be
Figure BDA000034928285000215
If,
Figure BDA000034928285000216
, then
Figure BDA000034928285000217
C) With Also need satisfy:
Figure BDA00003492828500023
α∈(2,3)
β∈(1,2)；
4) then transmit return through label after the phase difference calculating formula be
Figure BDA00003492828500024
5) in scene, evenly lay reference label, according to 1) to 4) process ask for one by one the phase differential of signal between each card reader merchandiser one reference label;
6) for each card reader, seek with target labels and have the optimal reference label of close phase difference value, namely select reference label by nearest neighbor method;
7) calculate los path distance between this optimal reference label and corresponding card reader, and with the los path distance of this los path distance as target labels and this card reader;
8) repeating step 6) and 7), until travel through all card reader, obtain the los path distance of target labels and all card reader;
9) utilize the method for least square can obtain final positioning result.
Location algorithm of the present invention adopted monte carlo method to carry out 2000 times emulation experiment in matlab, simultaneously, for the impact of test environment factor on locating effect, considered the noise of 10dB in the 40dB signal to noise ratio (S/N ratio) scope in receiving signal.Test scene is in 10 * 10 * 5 meters the ranged space in the emulation, has considered that three arrive paths, is respectively the direct projection path, and ground return path and metope reflection paths for simplicity, suppose that all signals all return by former road after arriving label.Number of tags to be positioned is 200, and the reference label number is 9, and the label high unity is 1 meter.Experimental result shows, under different signal to noise ratio (S/N ratio) conditions, the average bearing accuracy of this algorithm all is about 1 meter, shows thus, and this algorithm not only bearing accuracy is higher, and has good robustness.
Description of drawings
Fig. 1 is FB(flow block) of the present invention.
Fig. 2 (a) is the front spectrogram of sampling; Fig. 2 (b) is the spectrogram behind the bandpass sampling.
Fig. 3 is the positioning principle figure that utilizes reference label, and square frame (R_1, R_2, R_3, and R_4) represents four card reader that are positioned at the corner; Circle T represents target labels, and circle VT_1 represents target labels T about the virtual label of card reader R_1 symmetry, and circle VT_2 represents target labels T about the virtual label of card reader R_2 symmetry; Triangle (RT_1, RT_2and RT_3) represents reference label; Triangle RT_4 represents the position of the label to be positioned that this algorithm calculates.
Embodiment
As shown in Figure 1, the present invention includes three key steps: bandpass sampling, extract phase value and utilize the localization method of optimal reference label.
Concrete scheme is as follows:
One, bandpass sampling
The many signals that run in the reality are band flow-through signals, and the bandwidth of sort signal is often much smaller than signal center frequency.If the upper cut off frequency of bandpass signal is f H, lower limiting frequency is f L, at this moment do not need sampling frequency to be higher than twice upper cut off frequency f H, can determine sampling frequency according to the bandpass sampling theorem.
The bandpass sampling theorem: a frequency band limits is at (f L, f H) interior time-continuous signal x (t), signal bandwidth B=f H-f L, make M=f H/ B-N, N is for being not more than f here HThe maximum positive integer of/B.If sampling frequency f sSatisfy condition
2 f H m + 1 ≤ f s ≤ 2 f L m , 0 ≤ m ≤ N - 1 - - - ( 1 )
Then can be by the undistorted reconstruction original signal of sampled sequence x (t).
To signal x (t) with frequency f sAfter the sampling, the sampled signal x (nT that obtains s) frequency spectrum be that the frequency spectrum of x (t) forms through periodic extension, the continuation cycle is f s, as shown in Figure 2.In order by the undistorted reconstruction original signal of sampled sequence x (t), to select the suitable continuation cycle (namely selecting sample frequency), so that be positioned at (f L,f H) and (﹣ f H,﹣ f L) band component can aliasing not appear with the continuation component, use like this bandpass filter just can rebuild original signal by sample sequence.Because the symmetry of positive negative frequency components, we only consider (f L,f H) band component the condition of aliasing can not appear.
In the frequency spectrum of sampled signal, at (f L,f H) both sides of frequency band, two continuation spectrum components are arranged: (f H+ mf s,-f L+ mf s) and (f H+ (m+1) f s,-f L+ (m+1) f s).For fear of aliasing, the band component after the continuation should satisfy
-f L+mf s≤f L (2)
-f H+(m+1)f s≥f H(3)
Composite type (2) and formula (3) and arrangement obtain
2 f H m + 1 ≤ f s ≤ 2 f L m - - - ( 4 )
Here m is a positive number more than or equal to zero.If m gets zero, then above-mentioned condition turns to
f s≥2fH(5)
At this moment be actually and bandpass signal is regarded as low-pass signal sample.
M obtains larger, and the sample frequency that then meets formula (4) can be lower.But m has a upper limit, because f s≤ 2f L/ m, and for fear of aliasing, the continuation cycle is greater than the signal bandwidth of twice, i.e. f s〉=2B.
Therefore
m ≤ 2 f L f s ≤ 2 f L 2 B = f L B - - - ( 6 )
Because N is for being not more than f HTherefore the maximum positive integer of/B is not more than f LThe maximum positive integer of/B is N-1, therefore 0≤m≤N-1 is arranged.
In sum, undistorted recovery original signal x (t), sample frequency f sShould satisfy
2 f H m + 1 ≤ f s ≤ 2 f L m , 0 ≤ m ≤ N - 1 - - - ( 7 )
Two, extract phase value
The main policies of whole phase FFT (All-phase FFT) conversion is for input sample x (0), and all length that consideration comprises sampling point x (0) is a kind of novel analysis of spectrum mode of the sequence truncation situation of N.For the extraction of respective phase value in the phase spectrum after the whole phase FFT conversion, the present invention has designed three criterions:
1) owing to after signal is carried out bandpass sampling, the frequency spectrum of the sampled signal that obtains is the periodic extension of original signal frequency spectrum, and the continuation cycle is f sIn order in spectral amplitude, to search out the rear corresponding spectral line of signal frequency f of modulation, in order in phase spectrum, find corresponding phase value, utilize formula (8) that signal spectrum k is limited in the hits N.
k＝[(f-[f/f s]×f s)×N/f s] (8)
Wherein, [] expression rounding operation.
2) f and frequently c+ f 0Corresponding phase value
Figure BDA00003492828500044
Should be greater than difference frequency term f c-f 0Corresponding phase value
Figure BDA00003492828500045
If less than, then be
Figure BDA000034928285000413
Add 2 π, namely
Figure BDA00003492828500046
Figure BDA00003492828500047
(9)
3) by technical scheme 2) as can be known, and a frequency f c+ f 0Corresponding phase value
Figure BDA00003492828500048
With difference frequency term f c-f 0Corresponding phase value
Figure BDA00003492828500049
Should equal in theory 2 times f after the addition cCorresponding phase value
Figure BDA000034928285000410
But because the impact of noise so that
Figure BDA000034928285000411
Strictly do not equal
Figure BDA000034928285000412
Revise according to formula (10) accordingly.
Figure BDA00003492828500043
α∈(2,3)
β∈(1,2) (10)
Can obtain accurately phase estimation value after adjusting according to above three criterions, make huge contribution for improving bearing accuracy.
Three, utilize the localization method of optimal reference label
At present reference label relatively is common in the localization method based on signal received energy information, and the present invention utilizes the signal phase information of reference label to position, and has obtained more accurately locating effect.Owing to being nonlinear relationship between energy and the distance, and be linear relationship between phase differential and the distance, phase differential more can embody the distance relation between label and the card reader, be that the close label of phase differential has more close propagation distance, so the present invention adopt phase differential as the foundation of selecting the optimal reference label.
There is one virtual label VT_1 in target labels T among Fig. 3 about the hypothesis on location of card reader R_1 symmetry, then to arrive the propagation distance of target labels T and virtual label VT_1 be identical to the signal that sends of card reader, therefore, the phase difference value of expression card reader R_1 and label T distance should equal card reader and virtual label VT_1 phase difference value in theory.Because virtual label not necessarily exists in practice, if but reference label is arranged very near virtual label, in Fig. 3, reference label RT_1 is very near virtual label VT_1, so the phase difference value of reference label under card reader R_1 should also be very near the phase difference value of label T.In addition, reference label RT_3 is near target labels T in physical distance, and therefore, the phase difference value of reference label RT_3 also is relatively near the phase difference value of target labels T, but not as the phase difference value of reference label RT_1 more approaching.Therefore, if only consider whether immediate principle of phase difference value, the optimal reference label of finally selecting is RT_1, at this moment, reference label RT_1 is the most approaching with the battle-sight range of target labels T and identical card reader about the battle-sight range of card reader R_1, because the location aware of reference label RT_1, battle-sight range is easy to obtain, and therefore supposes that this battle-sight range is exactly the battle-sight range of target labels and card reader R_1.By that analogy, obtain the battle-sight range of target labels T and all card reader, the recycling least square method just can estimate the position of target labels.
The below is a specific embodiment of the present invention:
The test scene size is 10 * 10 * 5 meters space, stochastic distribution 200 labels, evenly lay 9 reference label, all label height all are assumed to be 1 meter, four card reader are distributed near four corners of space top layer.Carrier frequency is 915Mhz, and subcarrier frequency is 2Mhz, and sample frequency is 36Mhz, and hits is 1024.The initial phase of four card reader carrier signals is respectively 70 °, 60 °, 50 °, 60 °, and the initial phase of subcarrier signal is respectively 10 °, 20 °, 30 °, 10 °, and the antenna polarization direction of card reader is vertical polarization.Experiment adopts monte carlo method to carry out 2000 experiments, and the bearing accuracy that finally obtains is about 1 meter.
Generally, the indoor positioning algorithm based on phase place of the present invention comprises the following steps:
1) signal is selected the cosine wave (CW) form, and modulation system is the AM mode, and eliminates complete cycle by the method for adding subcarrier and blur, and sequence s (n) and the acknowledge(ment) signal sequence r (n) of transmitting then can disperse.
s(n)＝[cos(2πnf 0/f s+ )+A]·cos(2πnf c/f s+
Figure BDA000034928285000520
)
r(n)＝[cos(2πnf 0/f s+
Figure BDA000034928285000521
)+A]·cos(2πnf c/f s+
Figure BDA000034928285000522
)+z
Wherein subcarrier frequency is f 0, transmitter, phase is
Figure BDA00003492828500055
, receiving phase is
Figure BDA00003492828500056
, for overclocking carrier wave f c, make transmitter, phase be
Figure BDA00003492828500057
, receiving phase is , modulation level is A, and the receiving end additional noise is z, and the bandpass sampling frequency is f s
2) introduce digital angular frequency 0=2 π f 0/ f s, ω c=2 π f c/ f s
Figure BDA00003492828500051
Figure BDA00003492828500052
3) utilize the mode of whole phase FFT (All-phase FFT) accurately to extract the phase value under the different frequency in the signal, comprise three criterions:
A) calculate respectively f c-f 0, f cAnd f c+ f 0At sample frequency f sThe spectral line sequence number of middle correspondence.Wherein hits is N, and [] expression rounds.
k＝[(f-[f/f s]×f s)×N/fs]
B) in phase spectrum, find three phase values under the frequency, be respectively With
Figure BDA000034928285000510
, for simplicity can be expressed as
Figure BDA000034928285000511
Figure BDA000034928285000512
With
Figure BDA000034928285000513
If
Figure BDA000034928285000514
Less than
Figure BDA000034928285000515
Corresponding spectral line sequence number, then:
Figure BDA000034928285000516
C)
Figure BDA000034928285000517
With
Figure BDA000034928285000518
Also need satisfy:
Figure BDA00003492828500053
α∈(2,3)
β∈(1,2)
4) phase differential was after then transmitted signal was returned through label
Figure BDA00003492828500054
5) in scene, evenly lay reference label, according to 1) to 4) process ask for one by one the phase differential of signal between each card reader merchandiser one reference label.
6) under each card reader, seek with target labels and have the optimal reference label of close phase difference value, namely nearest neighbor method is selected reference label.
7) calculate los path distance between this reference label and corresponding card reader, and with the los path distance of this battle-sight range as target labels and this card reader.
8) repeating step 6) and 7), until travel through all card reader.
9) after the los path of acquisition target labels and all card reader distance, utilize the method for least square just can obtain final positioning result.

Claims (1)

1. the indoor positioning algorithm based on phase place comprises the following steps:
1) transmit and select the cosine wave (CW) form, modulation system is the AM mode, and it is fuzzy to eliminate complete cycle by the method for adding subcarrier, and establishing subcarrier frequency is f 0, transmitter, phase is , receiving phase is
Figure FDA00003492828400016
, for overclocking carrier wave f c, make transmitter, phase be
Figure FDA00003492828400017
, receiving phase is
Figure FDA00003492828400018
, modulation level is A, and the receiving end additional noise is z, and the bandpass sampling frequency is f s, then distribute and penetrate burst s (n) and acknowledge(ment) signal sequence r (n):
s(n)＝[cos(2πnf 0/f s+
Figure FDA000034928284000117
)+A]·cos(2πnf c/f s+
Figure FDA000034928284000118
)
r(n)＝[cos(2πnf 0/f s+
Figure FDA000034928284000119
)+A]·cos(2πnf c/f s+
Figure FDA000034928284000120
)+z；
2) introduce two subcarrier numeral angular frequency 0=2 π f 0/ f sWith overclocking carrier wave numeral angular frequency c=2 π f c/ f s, then distribute and penetrate burst s (n) and acknowledge(ment) signal sequence r (n) is:
Figure FDA00003492828400011
Figure FDA00003492828400012
3) utilize the whole phase FFT transform method, accurately extract phase value under the middle corresponding frequencies that transmits according to following criterion:
A) calculating respectively the rear signal frequency f of modulation is f c-f 0, f cAnd f c+ f 0The time at sample frequency f sThe spectral line sequence number k=[(f-[f/f of middle correspondence s] * f s) * N/f s], wherein, hits is N, [] expression rounds;
B) in phase spectrum according to f c-f 0, f cAnd f c+ f 0Three signal frequencies spectral line sequence number separately finds three phase values under the frequency, is respectively
Figure FDA00003492828400019
With
Figure FDA000034928284000110
, note by abridging and be
Figure FDA000034928284000111
With
Figure FDA000034928284000112
If,
Figure FDA000034928284000113
, then
C)
Figure FDA000034928284000115
With
Figure FDA000034928284000116
Also need satisfy:
Figure FDA00003492828400013
α∈(2,3)
β∈(1,2)；
4) then transmit return through label after the phase difference calculating formula be
5) in scene, evenly lay reference label, according to 1) to 4) process ask for one by one the phase differential of signal between each card reader merchandiser one reference label;
6) for each card reader, seek with target labels and have the optimal reference label of close phase difference value, namely select reference label by nearest neighbor method;
7) calculate los path distance between this optimal reference label and corresponding card reader, and with the los path distance of this los path distance as target labels and this card reader;
8) repeating step 6) and 7), until travel through all card reader, obtain the los path distance of target labels and all card reader;
9) utilize the method for least square can obtain final positioning result.
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CN107656236A (en) * 2017-08-18 2018-02-02 天津大学 Based on acoustical signal optimization method under Support Vector data description marine environment
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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106324563A (en) * 2016-08-12 2017-01-11 中国电子进出口总公司 Multipoint passive detection all-phase signal sorting and arrival time difference measurement system
CN106324563B (en) * 2016-08-12 2019-04-02 中国电子进出口总公司 A kind of multiple spot passive detection all phase signal sorting and reaching time-difference measuring system
CN107092009A (en) * 2017-03-22 2017-08-25 深圳市西博泰科电子有限公司 A kind of indoor orientation method and device
CN107092009B (en) * 2017-03-22 2019-06-18 深圳市西博泰科电子有限公司 A kind of indoor orientation method and device
CN109387815A (en) * 2017-08-09 2019-02-26 南京理工大学 ApFFT composes angle-measuring method in sawtooth phase modulation linear system
CN107656236A (en) * 2017-08-18 2018-02-02 天津大学 Based on acoustical signal optimization method under Support Vector data description marine environment
CN109246612B (en) * 2018-08-23 2020-09-15 佛山市顺德区中山大学研究院 RFID indoor positioning algorithm based on double-label array phase difference

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