CN107341424A - A kind of precise phase computational methods based on the estimation of RFID multipaths - Google Patents
A kind of precise phase computational methods based on the estimation of RFID multipaths Download PDFInfo
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- G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
- G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
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- G06K7/10019—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers.
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- G06K7/10079—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers. the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions
- G06K7/10089—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers. the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions the interrogation device using at least one directional antenna or directional interrogation field to resolve the collision
- G06K7/10099—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers. the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions the interrogation device using at least one directional antenna or directional interrogation field to resolve the collision the directional field being used for pinpointing the location of the record carrier, e.g. for finding or locating an RFID tag amongst a plurality of RFID tags, each RFID tag being associated with an object, e.g. for physically locating the RFID tagged object in a warehouse
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- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
- G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
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- G06K7/10316—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves using at least one antenna particularly designed for interrogating the wireless record carriers
- G06K7/10356—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves using at least one antenna particularly designed for interrogating the wireless record carriers using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas
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Abstract
The invention discloses a kind of precise phase computational methods based on the estimation of RFID multipaths, find out the internal relation for receiving phase between multichannel, and assess the ratio for receiving to be influenceed by multipath effect in phase data.Because the influence of multipath effect is unknown, the radio frequency shift of RFID hardware, the movement of people, and some uncontrollable factors etc. we can not obtain real phase value.Therefore these influences are assessed by measuring the degree of scatter of receiving phase, and concludes therefrom that real possible phase value.The present invention need not have particular/special requirement to hardware, it is not required that existing commercial agreement be modified, the present invention supports to obtain more accurate phase value from existing system completely, even in the indoor environment of multipath generally existing.
Description
Technical field
The invention belongs to radio frequency identification (RFID) technical field, and in particular to a kind of essence based on the estimation of RFID multipaths
True phase calculation method.
Background technology
REID (RFID) is prevalent in as in many applications such as retail business, supermarket, logistics, storage.In recent years
Come, Many researchers concern RFID applications, for example position, human body active perception, trajectory track etc..In such applications, phase
Value enjoy high praise and it is particularly useful.Because phase can reflect the change of fine granularity label position.Movement for label
Object can be using its continuous phase value come tracing path.Equally, in recent years, in indoor environment generally existing multipath effect
Cause the attention of large quantities of researchers.For example static reflex source, such as cement wall have been estimated in some researchs, and attempt to cut down surrounding
The influence of environment.Other some researchs reach their target using the characteristics of multipath effect.In addition, part is studied
Multipath effect can be eliminated or cut down in the indoor environment of complexity, and its core views is to assess multipath and then reject impacted
Data.However, having a strong impact on due to indoor multipath, many research work all in the less environment of a multipath or
Collected in one predefined region comprising the training data including phase.These deficiencies can be to influence related work in reality
In application.For example, when experiment scene is deployed in a narrow region, a people walks at random between reader and label
When dynamic, the phase value of label can be had a strong impact on by multipath reflection signal.
Existing RFID much studies the phase that make use of signal, introduces the significant direction of two comparisons, is label respectively
Trajectory track positions and human body behavior perceives.
Label track tracing and positioning：Due to occupying middle critical positions in the signal, phase is often used in marking as characteristic value
Sign trajectory track positioning.Based on hyperbola：Some researchers build hyp side by using the phase that receives of target labels
Method is so as to positioning the position of label.Work different from the past, this method can determine that target in the case of not needing anchor tag
The coordinate of label.But the degree of accuracy of the method depends on how to collect the accurate phase information of target labels, to ensure result
Accurate the method must work under the weaker environment of a multipath effect.Method based on hologram：I.e. by comparing instruction
Practice the phase of label and test label.This method is accurate in spacing smaller (13cm) in the environment of multipath effect generally existing
True rate is up to 86%.However, the method needs to assess the data by multipath effect and assigns a low weight to it, thus
Influence can be brought on the accuracy of whole method.Except the method for above-mentioned two tag location, concern label is compared in some researchs
Trajectory track.For example, some researchs follow the trail of the track of mobile tag based on hologram, and it can accurately find out the position of label
Put, accuracy can reach Centimeter Level.Compare regrettably, these work are required for being influenceed by multipath effect at one smaller
Environment in work.
Human body behavior perceives：Phase purposes in human body behavior perception is also quite varied.It is well known that mobile people couple
The communication of RFID reader and label is influential.Some scholar's research receive phase and the relation of human body behavior, for example,
Some work can carry out the mobile object of tracking through walls independent of any equipment, it can collect in advance some reference datas and
Eliminate the influence that stationary body (such as furniture) causes multipath effect；Also some work can be by analyzing the commodity of label
The purchasing habits of customer are inferred by the change of phase during movement.
In addition to RFID fields, other field such as Wi-Fi, 60G, sound etc. have similar algorithmic technique.However, by
Limited in itself in by RFID communication protocol and passive passive label, these algorithmic techniques can not all be used directly in RFID system
In.In sound, it is thus proposed that a kind of distance measurement method based on phase, this method can be estimated to be moved by what hand introduced
State vector.But because of the transmission speed based on sound and based on RFID, frequency and Protocol Design gap are bigger, this method
It can not directly apply in commercial RFID device.And Wi-Fi and some similar techniques, that is, 60G, send and receive all to exist
More sub-channels similarly hereinafter walk progress, and in same environment.Some Wi-Fi business machine can assess present channel
Parameter and calculate possible phase value.
Different from aforementioned technology, RFID system be only capable of in a channel by an antenna in the same time and
One label is communicated.In other words, different passive passive labels can not share same channel.In addition, multipath effect exists
Lasting change in communication process, data expected from neither one refer to.These limit to brings to phase estimation and calculating
Many problems.To sum up, art methods can practicality, actual deployment, the degree of accuracy and other in terms of all exist or it is big or
The problem of small.
The content of the invention
In order to solve the problems of the prior art, the present invention proposes that a kind of precise phase based on the estimation of RFID multipaths calculates
Method, interference of the existing multipath effect to phase value can be overcome, accurately to calculate pure phase value.
In order to realize the above object the technical solution adopted in the present invention is：Comprise the following steps：
1) reader antenna collects the phase data of target labels, receiving phase β；
2) row vector decomposition and angular transformation are entered to the phase data of collection：
Vector is decomposed with the relation after angular transformation：
Wherein, β is receiving phase, and θ is pure phase, and α is multipath effect phase, and θ ' is the pure phase after angular transformation
Position, β ' are that receiving phase, α ' after angular transformation is multipath effect phase after angular transformation, k0Integer is represented, Z is integer
Collection；
3) pure phase theta and mirror image phase are establishedRelation： Represent integer,Value is by tan α '
Determine；
4) mirror image phase is solved according to following equationValue：
For the multipath variable in channel n,To jump to from n n+1 receiving phase value added, β when channelnTo be every
The receiving phase of individual channel, n=1,2,3 ... N；
5) according to the pure phase theta that step 3) is established and mirror image phaseRelation, and step 4) solve mirror image phaseValue counter release pure phase value.
Reader antenna travels through N number of channel, and N is more than or equal in 5 seconds data of each channel collection in the step 1)
3, obtain receiving phase β.
K in the step 2)0There is following relation：
Wherein, m ∈ Z.
Multipath variable in the step 4) in channel nIncluding static multipath and dynamic multi-path, static multipath represents quiet
Reflecting properties in the case of state, dynamic multi-path represent to be influenceed by mobile object.
According to mirror image phase in the step 4)Solution formula obtain matrix equation：AN×(N+2)·x(N+2)×1=bN×1,
Wherein AN×(N+2)It is coefficient matrix, x(N+2)×1It is unknown matrix of variables, bN×1Represent the receiving phase of matrix：
Wherein, ()TRepresent transposed matrix；
Then the solution of matrix equation is expressed as：
X=ξ0+c1·ξ1+c2·ξ2
Wherein ξ0It is particular solution, ξ1And ξ2It is general solution, c1And c2It is ξ respectively1And ξ2Coefficient.
Needed the receiving phase β of all channels in the solution procedure of effective solution of the matrix equationnIt is adjusted to one
On fit line, the fit line linear equation after adjustment is yn=kn+d, and need to meet following condition：
Wherein, ωnIt is channel n weight, k is slope, and d is intercept；
Utilize the sample average error σ of receiving phase in channel nnTo represent dispersion：
Wherein,The sample in each channel is represented,It is the average of t sample；
Then defining weight equation is：
When sample number t is sufficiently large, have：
So as to obtain fit line according to weight equation.
The slope k of the fit line and intercept d calculating process：
Formula is minimized firstInIt is as follows to obtain partial derivative：
Then make above formula be equal to 0 and solve to obtain：
The formula x=ξ0+c1·ξ1+c2·ξ2Middle coefficient c1And c2Solved by following equation：
Wherein, yiAnd yN+1-iFor the random selection group point on fit line.
Compared with prior art, the present invention receives the internal relation of phase between finding out multichannel, and assesses and receive phase
The ratio influenceed in data by multipath effect.Because the influence of multipath effect is unknown, the radio frequency shift of RFID hardware, the shifting of people
Move, and some uncontrollable factors etc. cause that real phase value can not be obtained, therefore by measuring the scattered journey of receiving phase
Spend to assess these influences, and conclude therefrom that real possible phase value.The present invention need not have particular/special requirement to hardware,
Modified also without to existing commercial agreement, the present invention supports to obtain more accurate phase from existing system completely
Value, even in the indoor environment of multipath generally existing.Present invention extraction from the environment by multipath effect obtains real
Phase value, it is not necessary to disposed in advance to label, equipment, it is not required that training dataset, this is significantly improved the present invention's
Practicality.Secondly, the perfect compatible existing RFID commercializations agreement of the present invention, and hardware need not be modified.Therefore, this hair
The bright middleware that can be easy to easily as application system carrys out work.As a result show, this method is in open area environment
And error is all very low in the environment of multipath generally existing.The present invention is only by reader and the relative distance of target labels
Can calculates the real phase value in the environment of multipath generally existing, even if mobile object in this environment be present, gram
Interference of the existing multipath effect to phase value is taken, accurately to calculate pure phase value.
Further, due in environment indoors receiving phase had a long way to go with desired value, influenceed seriously by multipath effect.Cause
This, the present invention is flexible to multipath effect estimation accurately to calculate pure phase, and the present invention draws a square by analogizing
Battle array equation, in order to obtain effective solution of matrix equation, the receiving phase of all channels is adjusted on a fit line, and is passed through
Define weight equation and receive the influence of phase outlier to cut down, weight equation can help to obtain more suitably fit line and more
Good estimated result.
Brief description of the drawings
Fig. 1 is the structural representation of the present invention；
Fig. 2 a are backscattering idealized model schematic diagram, and Fig. 2 b are the backscattering model signal for existing influence factor
Figure；
Fig. 3 a are the confirmatory analysis figure of experiment one, and Fig. 3 b are the confirmatory analysis figure of experiment two, and Fig. 3 c experiments three are tested
Card property analysis chart；
Fig. 4 a are the vector relations figure of Signal averaging, and Fig. 4 b are the vector relations figure for decomposing reflected signal；
Fig. 5 is receiving phase schematic diagram；
Fig. 6 is fit line and receiving phase schematic diagram.
Embodiment
The present invention is further explained with reference to specific embodiment and Figure of description.
Referring to Fig. 1, the present invention is divided into two parts, Part I, the relation of mixed-phase β and pure phase theta is carried out
Modeling；Part II, pure phase theta is calculated from the model having been built up.Key step is as follows：
1) target labels phase data is collected：Reader antenna faces target labels, in 5 seconds numbers of each channel collection
According to traveling through N number of channel, N need to be more than or equal to 3, and during RFID communication, it is a series of radiofrequency signals that reader, which receives signal,
Superposition, mainly includes：The signal of diameter line-of-sight signal and Ambient, because in practice, reflection is uncontrollable, this will give final
Receiving phase β brings a random error α, due to mutual aliasing between signal, so that final receive phase beta and be expected pure
Net phase theta has significant difference；
2) row vector decomposition and angular transformation are entered to the phase data of collection：Decomposed by vector, by phase caused by multipath
Position α be transformed to only a phase theta related to pure phase theta ', be converted to new form by vectorial, in this case, will most terminating
Receive the sum that phase beta is converted to two simple scalars；
3) by calculating and analyzing, the pure phase theta of vector and the mirror image phase of scalar are establishedBetween contact, obtain
Pure phase theta and certain mirror image phase bridge, that is, scalar phase
4) by mirror image phaseLinear Equations are substituted into other dependent phases to solve, and solve the value of mirror image phase,
In order to obtain pure phase, pass through calculatingTo assess pure phase probable value, the multipath variable defined in channel n is Include the influence of multipath effect under quiescent conditions and current intelligence, wherein static multipath
The reflecting properties under quiescent conditions, such as wall, ceiling, furniture etc. are represented, and dynamic multi-path is influenceed by the object moved, example
Such as mobile robot, the people of walking etc., when channel jumps to n+1 from n, receiving phase value added isReceive signal to exist
Phase beta in channel nnThree parts sum is represented as, i.e. multipath variable isWith mirror image phaseSum, in this situation
Under, the phase beta of each channel can be represented, and ideally, receive phase substantially all on straight line y '；
5) the pure phase theta that step 3) is established and mirror image phase are passed throughBetween relation, it is counter to release the big of pure phase theta
It is small：Have a long way to go, influenceed seriously by multipath effect, it should to multipath effect with desired value due to receiving phase in environment indoors
Estimate flexible accurately to calculate pure phase theta, a matrix equation is drawn by analogizing, in order to obtain matrix equation
Effectively solution, by the receiving phase β of all channelsnIt is adjusted on a line, and receives phase by defining weight equation to cut down
The influence of outlier, weight equation can help to obtain more suitably fit line and more preferable estimated result, the slope k of fit line
With intercept d's and and desired valueGap can calculate, next build two extra equations and carry out solution formula and obtained by matrix equation
Effective solution of the non-secondly system of linear equations gone out, the structure of formula 1 is relevant with the slope of fit line, and formula 2 is fitted by defining
Point y on linenWith receiving phase βnGap (i.e. residual error Sn) relation draw.
Referring to Fig. 2 a, the idealized model of RFID reader and passive passive label backscatter communication.Reader
Antenna sends radiofrequency signal, carries out backscattering by label, and finally received by reader antenna.Entirely propagation distance is
2d, the sighting distance of twice antenna and label.In this path, the phase information of signal is different.Except the rotation of distance, day
The circuit of line and the reflection characteristic of label can all produce extra deflection to phase, be defined as θAAnd θT.The reception of final label
Signal phase includes three parts, as follows：
θ=(θD+θA+θT)mod2π (1)
Wherein θDIt is because phase place change caused by the change of signal propagation distance.It depends on current transmission frequency f：
λ represents wavelength, and c is the light velocity.Different from multi channel wireless system, most of RFID systems only allow their read
Device is read to be communicated with label in a channel, such as ImpinJ R420.Reader can jump in the state of frequency-hopping mode
Communicated to another channel.According to explanation, the working frequency range of commercial 16 channels of reader is 860-960MHz.
Except frequency and propagation distance, phase may be influenceed by other extra factors in practice, such as multipath is imitated
Should.As shown in Figure 2 b, may be impacted in some places by the radiofrequency signal of tag backscatter, and change itself originally
Propagation path.When their final northern reader antennas receive, these ripples may be overlapped from the perspective of reader
Form a new rf wave.As shown in Figure 2 b, finally by the signal of reader receiving by diameter line-of-sight signal and reflected signal
Two parts are formed.In most cases, it is only necessary to which what pure phase value was namely calculated by formula (1), this only takes
Certainly in line-of-sight signal.
In reality, multipath effect is generally existing.Roof, cement wall, other objects in furniture and surrounding environment
All it is good reflecting medium, the present invention is verified with three experiments.
Experiment one：A label is placed before reader, keeps the relative distance and relative position of label and antenna constant,
Whole system is moved to ten different places indoors.The phase and received signal strength (RSS) such as Fig. 3 a institutes of same label
Show, radius represents RSS value, and radian represents the angle of phase.It was found that the changing value of phase is at (105 °, 345 °).These fluctuations
May cause calculate apart from when more than 21cm error, the positioning and the influence of damaging property of trajectory track that this can be to label.
Experiment two：It is same to collect with four antennas of a reader using experiment two come the otherness of measuring apparatus
The phase and RSS values of label, this four antennas are models of the same race and are placed on same position, as a result as shown in Figure 3 b.It was found that
Even if each position and direction holding is constant, test the phase received still has difference with equipment difference.
Experiment three：The influence of mobile object is studied, the phase information of persistent collection label 10 seconds or so allows one during this period
Name volunteer's random walk in RFID system.As shown in Figure 3 c, phase value is widely distributed in the range of 2 π, in other words,
The phase information that the influence of object meeting clearly around RFID system is collected.
The present invention specifically includes following steps：
1) target labels phase data is collected：Reader antenna faces target labels, in 5 seconds numbers of each channel collection
According to traveling through N number of channel (N need to be more than or equal to 3).The pass of mixed-phase β and expected pure phase theta is illustrated in figs. 4 a and 4b
System.As it was previously stated, reader receives a series of superposition that signal is radiofrequency signals, mainly include：Diameter line-of-sight signal and environment
The signal of reflection, due in practice, reflection is uncontrollable, and this will bring a random error to final receiving phase β, i.e. α, such as
Shown in Fig. 4 a, the radiofrequency signal that reader receives is represented with polar coordinates, and vectorial radian represents the amplitude of signal, polarizing angle
Current phase is represented,Represent line-of-sight signal,Representing the superposition of all reflected signals, phase is θ and α respectively, whenWithMeet, their new signals of mutual superimposed formationAs a result show, phase beta and expected pure phase theta be have it is aobvious
Write difference.
2) row vector decomposition and angular transformation are entered to the phase data of collection：Decomposed by vector, by phase caused by multipath
Position α be transformed to only a phase theta related to pure phase theta ', new form is converted to by vectorial, as shown in fig. 4 a by vectorPoint
Solve as two parts, be respectivelyWithVectorWith vectorVertically, it is vectorialWithIt is parallel；As shown in Figure 4 b,
With vectorWithInstead of vectorWithIts polarizing angle is changed into α ' and β ', and in the case, Fig. 4 a can be closed safely
Reason ground equivalence is converted to Fig. 4 b, and the relation of polarizing angle is before and after conversion：
Compare Fig. 4 a and Fig. 4 b, find superposed signalβ, θ keep constant, because reflected signal is uncontrollable, polarizing angle α
It is unknown with β, however, after vector has been decomposed, structure α ' and θ relation is easy to calculate θ.
3) by calculating and analyzing, the pure phase theta of vector and the mirror image phase of scalar are establishedBetween contact, obtain
Pure phase theta and certain mirror image phase bridge, that is, scalar phaseResearch superposition vector beta and two component vectors
θ ', α ' relation, according to vector calculus, if two vector thetas1And θ2Superposition summation generates new vector theta3, triadic relation is such as
Under：
Wherein A1And A2Two vectorial amplitudes, vector beta ' formula it is as follows：
Formula (3) describes α ' and θ ' relation, according to triangle relation, can release：
If according to α ' of the formula (6) in θ ' replacement formulas (5), have：
It is now assumed that final phase beta can be represented asWithSum, that is,：
According to triangle relation, have：
DefinitionWithRepresent as follows：
It was found that formula (7) and formula (9) are of equal value, this, which means that, can build a pure phase vectors θ and defined
Bridge, i.e.,AndCurrent line-of-sight signal and the relation of reflected signal are represented, is called " multipath variable ", this
Outside, due toCan further it release：
Wherein m ∈ Z.
In this case, the superposition of final phase beta from two unknown vectors is converted to the sum of two simple scalars.This
Outside, the pure phase theta and the bridge of certain mirror image phase obtained, that is, a kind of scalar phaseNext, calculate mirror image
With respective phase θ value.
4) by mirror image phaseLinear Equations are substituted into other dependent phases to solve, and solve the value of mirror image phase,
In order to obtain pure phase, can calculateTo assess pure phase probable value.
The multipath variable defined in channel n isPay attention to,Comprising quiescent conditions and move
The influence of multipath effect in the case of state, that is,：
Wherein static multipath represents the reflecting properties under quiescent conditions, such as wall, ceiling, furniture etc., and dynamic multi-path
Influenceed by the object moved, such as the robot, the people of walking etc. moved.When channel jumps to n+1 from n, receive phase
Value added isPhase differenceIt is made up of three parts, including Δ θD, Δ θR, Δ θT.After changing frequency, wavelength also occurs
Respective change.Caused by as a result, a phase difference θ can be produced under reception signal same distanceD, same reader and label
Phase difference be respectively Δ θRWith Δ θT.Therefore, phase beta of the signal in channel n kinds is receivednThree parts sum can be represented as,
I.e.：
WhereinIt is the mirror image phase in first channel.In the case, the phase beta of each channel can be represented as
Under：
Above-mentioned decomposition is demonstrated by an experiment, label is individually placed in two kinds of environment, one is open region,
One is narrow region, records the phase beta received every channel respectivelyn, as shown in figure 5, in open area, multipath effect
It is more much lower than line-of-sight signal, that is,As a result show, when the channel of reader is from n+1, the change of phase is changed into
Linear, the phase difference of adjacent channel isIn other words, ideally, phase is received substantially all on straight line y '.
As shown in figure 5, the phase of open area is certain substantially point-blank, agree with theory.On the other hand, it is narrow
The multipath effect in region be it is violent, in other words, multipath variableIt can not be ignored.As a result show, from the phase fluctuation of channel 1 to 16
It is very big, as shown in Fig. 5 intermediate cam shapes.Equally, receive phase in environment indoors to have a long way to go with desired value, by multipath effect shadow
Ring serious, therefore, the present invention should estimate multipath effect flexible accurately to calculate pure phase theta.
5) the pure phase theta that step 3) is established and mirror image phase are passed throughBetween relation, it is counter to release the big of pure phase theta
It is small.We can calculate from formula (14)And formula (14) being capable of class one matrix equation of release：
AN×(N+2)·x(N+2)×1=bN×1 (16)
Wherein, AN×(N+2)It is coefficient matrix, x(N+2)×1It is unknown matrix of variables, bN×1The phase that receives of matrix is represented, it is public
Formula (16) can be expressed as by detailed：
Wherein ()TTransposed matrix is represented, formula (16) is nonhomogeneous linear equation.Therefore non trivial solution can be expressed
For：
X=ξ0+c1·ξ1+c2·ξ2 (18)
Wherein, ξ0It is particular solution, ξ1And ξ2It is general solution.c1And c2It is ξ1And ξ2Coefficient.Because by the N number of equation of N+2 variable,
Solution x have unlimited kind may, in order to obtain effective solution that x arrives, it is necessary to additionally build two equations.
In order to reach this purpose, by the receiving phase β of all channelsnIt is adjusted on a line, the fit line after adjustment
Linear equation is yn=kn+d and need to meet following condition：
Wherein ωnIt is channel n weight.The influence of outlier is cut down by defining weight equation.Mobile object and people
Caused by dynamic reflective, it will produce uncontrollable and unstable error.As a result show, more serious multipath effect will cause
It is more scattered to receive phase.Utilize the sample average error σ of receiving phase in channel nnTo represent dispersion：
WhereinThe sample in each channel is represented,It is the average of t sample.Further define weight equation：
It is worth noting that all ωnAnd it is equal with the number of channel.Eliminated by weakening the weight of impacted channel dynamic
Uncontrollable error in state multipath effect.When sample number t is sufficiently large, have：
Weight equation can help us to obtain more suitably fit line and more preferable estimated result.
In order to obtain more suitable slope k and intercept d, it is necessary to minimize in formula (19)Partial derivative is as follows：
Make formula (23) be equal to 0 and solve, can obtain：
Weights omega in formula (24)n, receive phase betanAll it is known, k and d value are easy for calculating.In order to clear
The effect for seeing the method for Chu, the fit line y for receiving phase of narrow zone are as shown in Figure 6.It was found that fit line and it is expected
The straight line y ' arrived gaps.K and d another expression formula can be obtained by bringing formula (13) into formula (24)：
As above successfully solves fit line y.The slope k and intercept of fit line be d's and and desired valueGap be e1
+e2.Next, need to find the coefficient c that extra two equations come in solution formula (18)1And c2, i.e. formula 1 and formula 2.
Formula 1：
According to formula (18), θ is found,Multipath variableAll it is unknown in matrix x.It is, they can
And e1C can equally be used1And c2To represent.Therefore using the expression formula of the k in formula (25) as formula 1.
As it was previously stated, k value is not aware that.Two location variables only deposited in formula 1 are c1And c2.Pay attention to formula (18)
Have an impact to formula (26), can be utilized.
Formula 2：
As shown in fig. 6, point y on fit linenWith receiving phase βnThere is certain gap.Define every a pair of ynAnd βnError use
Residual error Sn, it is represented by：
Sn=yn-βn, n=1,2,3...N (27)
According to formula (25) ynIt can be expressed as follows：
With reference to formula (13), residual error SnIt can be represented as again：
If we can calculate total residual error of all channels, have：
Next one group of point y is randomly choosed on fit lineiAnd yN+1-iAnd sum：
Formula (30) is subtracted with formula (31), formula 2 can be obtained：
According to formula 1 and formula 2, can be easy to calculate c1And c2Value.Known variables in corresponding matrix x also may be used
To calculate.Pay attention to eachBy line-of-sight signal and the double influence of reflected signal.Because phase differenceNevertheless suffer from distance
(ΔθD) and ardware feature (Δ θRWith Δ θT) influence, the variable uniquely influenceed on pure phase theta isIt can be calculated as follows：
Value determined by tan α ', so far can calculate mirror image phaseAnd it can successfully obtain pure phase value θ.
The present invention can calculate true pure phase in indoor complex environment by assessing multipath to obtain accurate phase
Value.Practice have shown that error is all very low in open area environment and in the environment of multipath generally existing by the present invention, it is respectively
5.14cm 5.52cm.The present invention is excellent compared to the performance of conventional phase collection method, and is having situation existing for mobile object
Under also there is very high accuracy.
Claims (8)
1. a kind of precise phase computational methods based on the estimation of RFID multipaths, it is characterised in that comprise the following steps：
1) reader antenna collects the phase data of target labels, receiving phase β；
2) row vector decomposition and angular transformation are entered to the phase data of collection：
Vector is decomposed with the relation after angular transformation：
<mfenced open = "{" close = "">
<mtable>
<mtr>
<mtd>
<mrow>
<msup>
<mi>&beta;</mi>
<mo>&prime;</mo>
</msup>
<mo>=</mo>
<mi>&beta;</mi>
</mrow>
</mtd>
</mtr>
<mtr>
<mtd>
<mrow>
<msup>
<mi>&theta;</mi>
<mo>&prime;</mo>
</msup>
<mo>=</mo>
<mi>&theta;</mi>
</mrow>
</mtd>
</mtr>
<mtr>
<mtd>
<mrow>
<msup>
<mi>&alpha;</mi>
<mo>&prime;</mo>
</msup>
<mo>=</mo>
<mi>&theta;</mi>
<mo>+</mo>
<mfrac>
<mi>&pi;</mi>
<mn>2</mn>
</mfrac>
<mo>+</mo>
<msub>
<mi>k</mi>
<mn>0</mn>
</msub>
<mo>&CenterDot;</mo>
<mi>&pi;</mi>
<mo>,</mo>
<mi>w</mi>
<mi>h</mi>
<mi>e</mi>
<mi>r</mi>
<mi>e</mi>
<mi> </mi>
<msub>
<mi>k</mi>
<mn>0</mn>
</msub>
<mo>&Element;</mo>
<mi>Z</mi>
</mrow>
</mtd>
</mtr>
</mtable>
</mfenced>
Wherein, β is receiving phase, and θ is pure phase, and α is multipath effect phase, and θ ' is the pure phase after angular transformation, β '
It is the multipath effect phase after angular transformation for the receiving phase after angular transformation, α ', k0Integer is represented, Z is set of integers；
3) pure phase theta and mirror image phase are establishedRelation： Represent integer,Value is determined by tan α '
It is fixed；
4) mirror image phase is solved according to following equationValue：
<mfenced open = "{" close = "">
<mtable>
<mtr>
<mtd>
<mrow>
<msub>
<mover>
<mi>&alpha;</mi>
<mo>^</mo>
</mover>
<mn>1</mn>
</msub>
<mo>+</mo>
<mover>
<mi>&theta;</mi>
<mo>^</mo>
</mover>
<mo>+</mo>
<mn>0</mn>
<mo>&CenterDot;</mo>
<mi>&Delta;</mi>
<mover>
<mi>&theta;</mi>
<mo>^</mo>
</mover>
<mo>=</mo>
<msub>
<mi>&beta;</mi>
<mn>1</mn>
</msub>
</mrow>
</mtd>
</mtr>
<mtr>
<mtd>
<mrow>
<msub>
<mover>
<mi>&alpha;</mi>
<mo>^</mo>
</mover>
<mn>2</mn>
</msub>
<mo>+</mo>
<mover>
<mi>&theta;</mi>
<mo>^</mo>
</mover>
<mo>+</mo>
<mn>1</mn>
<mo>&CenterDot;</mo>
<mi>&Delta;</mi>
<mover>
<mi>&theta;</mi>
<mo>^</mo>
</mover>
<mo>=</mo>
<msub>
<mi>&beta;</mi>
<mn>2</mn>
</msub>
</mrow>
</mtd>
</mtr>
<mtr>
<mtd>
<mrow>
<msub>
<mover>
<mi>&alpha;</mi>
<mo>^</mo>
</mover>
<mn>3</mn>
</msub>
<mo>+</mo>
<mover>
<mi>&theta;</mi>
<mo>^</mo>
</mover>
<mo>+</mo>
<mn>2</mn>
<mo>&CenterDot;</mo>
<mi>&Delta;</mi>
<mover>
<mi>&theta;</mi>
<mo>^</mo>
</mover>
<mo>=</mo>
<msub>
<mi>&beta;</mi>
<mn>3</mn>
</msub>
</mrow>
</mtd>
</mtr>
<mtr>
<mtd>
<mo>...</mo>
</mtd>
</mtr>
<mtr>
<mtd>
<mrow>
<msub>
<mover>
<mi>&alpha;</mi>
<mo>^</mo>
</mover>
<mi>N</mi>
</msub>
<mo>+</mo>
<mover>
<mi>&theta;</mi>
<mo>^</mo>
</mover>
<mo>+</mo>
<mrow>
<mo>(</mo>
<mi>N</mi>
<mo>-</mo>
<mn>1</mn>
<mo>)</mo>
</mrow>
<mo>&CenterDot;</mo>
<mi>&Delta;</mi>
<mover>
<mi>&theta;</mi>
<mo>^</mo>
</mover>
<mo>=</mo>
<msub>
<mi>&beta;</mi>
<mi>N</mi>
</msub>
</mrow>
</mtd>
</mtr>
</mtable>
</mfenced>
For the multipath variable in channel n,To jump to from n n+1 receiving phase value added, β when channelnFor each channel
Receiving phase, n=1,2,3 ... N；
5) according to the pure phase theta that step 3) is established and mirror image phaseRelation, and step 4) solve mirror image phase's
Value is counter to release pure phase value.
A kind of 2. precise phase computational methods based on the estimation of RFID multipaths according to claim 1, it is characterised in that institute
Reader antenna is stated in step 1) in 5 seconds data of each channel collection, travels through N number of channel, and N is more than or equal to 3, is received
Phase beta.
A kind of 3. precise phase computational methods based on the estimation of RFID multipaths according to claim 1, it is characterised in that institute
State k in step 2)0There is following relation：
<mfenced open = "{" close = "">
<mtable>
<mtr>
<mtd>
<mrow>
<msub>
<mi>k</mi>
<mn>0</mn>
</msub>
<mo>=</mo>
<mn>2</mn>
<mo>&CenterDot;</mo>
<mi>m</mi>
<mo>,</mo>
<msup>
<mi>and&alpha;</mi>
<mo>&prime;</mo>
</msup>
<mo>=</mo>
<mi>&theta;</mi>
<mo>+</mo>
<mfrac>
<mi>&pi;</mi>
<mn>2</mn>
</mfrac>
<mo>,</mo>
<msup>
<mi>tan&alpha;</mi>
<mo>&prime;</mo>
</msup>
<mo>></mo>
<mn>0</mn>
</mrow>
</mtd>
</mtr>
<mtr>
<mtd>
<mrow>
<msub>
<mi>k</mi>
<mn>0</mn>
</msub>
<mo>=</mo>
<mn>2</mn>
<mo>&CenterDot;</mo>
<mi>m</mi>
<mo>+</mo>
<mn>1</mn>
<mo>,</mo>
<msup>
<mi>and&alpha;</mi>
<mo>&prime;</mo>
</msup>
<mo>=</mo>
<mi>&theta;</mi>
<mo>+</mo>
<mfrac>
<mrow>
<mn>3</mn>
<mi>&pi;</mi>
</mrow>
<mn>2</mn>
</mfrac>
<mo>,</mo>
<msup>
<mi>tan&alpha;</mi>
<mo>&prime;</mo>
</msup>
<mo><</mo>
<mn>0</mn>
</mrow>
</mtd>
</mtr>
</mtable>
</mfenced>
Wherein, m ∈ Z.
A kind of 4. precise phase computational methods based on the estimation of RFID multipaths according to claim 1, it is characterised in that institute
State the multipath variable in channel n in step 4)Including static multipath and dynamic multi-path, static multipath is represented under quiescent conditions
Reflecting properties, dynamic multi-path represent to be influenceed by mobile object.
A kind of 5. precise phase computational methods based on the estimation of RFID multipaths according to claim 1, it is characterised in that institute
State in step 4) according to mirror image phaseSolution formula obtain matrix equation：AN×(N+2)·x(N+2)×1=bN×1, wherein AN×(N+2)
It is coefficient matrix, x(N+2)×1It is unknown matrix of variables, bN×1Represent the receiving phase of matrix：
<mrow>
<msub>
<mi>A</mi>
<mrow>
<mi>N</mi>
<mo>&times;</mo>
<mrow>
<mo>(</mo>
<mrow>
<mi>N</mi>
<mo>+</mo>
<mn>2</mn>
</mrow>
<mo>)</mo>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mfenced open = "[" close = "]">
<mtable>
<mtr>
<mtd>
<mn>1</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mo>...</mo>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>1</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
</mtr>
<mtr>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>1</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mo>...</mo>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>1</mn>
</mtd>
<mtd>
<mn>1</mn>
</mtd>
</mtr>
<mtr>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>1</mn>
</mtd>
<mtd>
<mo>...</mo>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>1</mn>
</mtd>
<mtd>
<mn>2</mn>
</mtd>
</mtr>
<mtr>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
</mtr>
<mtr>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
</mtr>
<mtr>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
<mtd>
<mo>.</mo>
</mtd>
</mtr>
<mtr>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mo>...</mo>
</mtd>
<mtd>
<mn>1</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>1</mn>
</mtd>
<mtd>
<mrow>
<mi>N</mi>
<mo>-</mo>
<mn>1</mn>
</mrow>
</mtd>
</mtr>
</mtable>
</mfenced>
</mrow>
<mrow>
<msubsup>
<mi>x</mi>
<mrow>
<mi>N</mi>
<mo>+</mo>
<mn>2</mn>
<mo>&times;</mo>
<mn>1</mn>
</mrow>
<mi>T</mi>
</msubsup>
<mo>=</mo>
<mrow>
<mo>&lsqb;</mo>
<mrow>
<msub>
<mover>
<mi>&alpha;</mi>
<mo>^</mo>
</mover>
<mn>1</mn>
</msub>
<mo>,</mo>
<msub>
<mover>
<mi>&alpha;</mi>
<mo>^</mo>
</mover>
<mn>2</mn>
</msub>
<mo>,</mo>
<msub>
<mover>
<mi>&alpha;</mi>
<mo>^</mo>
</mover>
<mn>3</mn>
</msub>
<mo>,</mo>
<mo>...</mo>
<msub>
<mover>
<mi>&alpha;</mi>
<mo>^</mo>
</mover>
<mi>N</mi>
</msub>
<mo>,</mo>
<mover>
<mi>&theta;</mi>
<mo>^</mo>
</mover>
<mo>,</mo>
<mi>&Delta;</mi>
<mover>
<mi>&theta;</mi>
<mo>^</mo>
</mover>
</mrow>
<mo>&rsqb;</mo>
</mrow>
<mo>,</mo>
</mrow>
<mrow>
<msubsup>
<mi>b</mi>
<mrow>
<mi>N</mi>
<mo>&times;</mo>
<mn>1</mn>
</mrow>
<mi>T</mi>
</msubsup>
<mo>=</mo>
<mrow>
<mo>&lsqb;</mo>
<mrow>
<msub>
<mi>&beta;</mi>
<mn>1</mn>
</msub>
<mo>,</mo>
<msub>
<mi>&beta;</mi>
<mn>2</mn>
</msub>
<mo>,</mo>
<msub>
<mi>&beta;</mi>
<mn>3</mn>
</msub>
<mo>,</mo>
<mn>...</mn>
<msub>
<mi>&beta;</mi>
<mi>N</mi>
</msub>
</mrow>
<mo>&rsqb;</mo>
</mrow>
<mo>,</mo>
</mrow>
Wherein, ()TRepresent transposed matrix；
Then the solution of matrix equation is expressed as：
X=ξ0+c1·ξ1+c2·ξ2
Wherein ξ0It is particular solution, ξ1And ξ2It is general solution, c1And c2It is ξ respectively1And ξ2Coefficient.
A kind of 6. precise phase computational methods based on the estimation of RFID multipaths according to claim 5, it is characterised in that institute
Stating needs in the solution procedure of effective solution of matrix equation by the receiving phase β of all channelsnIt is adjusted on a fit line, adjusts
Fit line linear equation after whole is yn=kn+d, and need to meet following condition：
Wherein, ωnIt is channel n weight, k is slope, and d is intercept；
Utilize the sample average error σ of receiving phase in channel nnTo represent dispersion：
<mrow>
<msub>
<mi>&sigma;</mi>
<mi>n</mi>
</msub>
<mo>=</mo>
<mfrac>
<mrow>
<mi>&Sigma;</mi>
<mo>|</mo>
<msubsup>
<mi>&beta;</mi>
<mi>n</mi>
<mn>0</mn>
</msubsup>
<mo>-</mo>
<msub>
<mover>
<mi>&beta;</mi>
<mo>&OverBar;</mo>
</mover>
<mi>n</mi>
</msub>
<mo>|</mo>
</mrow>
<mi>t</mi>
</mfrac>
</mrow>
Wherein,The sample in each channel is represented,It is the average of t sample；
Then defining weight equation is：
<mrow>
<msub>
<mi>&omega;</mi>
<mi>n</mi>
</msub>
<mo>=</mo>
<mfrac>
<mrow>
<mi>N</mi>
<mo>&CenterDot;</mo>
<msub>
<mi>p</mi>
<mi>n</mi>
</msub>
</mrow>
<mrow>
<msub>
<mi>&Sigma;p</mi>
<mi>n</mi>
</msub>
</mrow>
</mfrac>
<mo>,</mo>
<mi>n</mi>
<mo>=</mo>
<mn>1</mn>
<mo>,</mo>
<mn>2</mn>
<mo>,</mo>
<mn>3</mn>
<mo>...</mo>
<mi>N</mi>
</mrow>
<mrow>
<mi>w</mi>
<mi>h</mi>
<mi>e</mi>
<mi>r</mi>
<mi>e</mi>
<mi> </mi>
<msub>
<mi>p</mi>
<mi>n</mi>
</msub>
<mo>=</mo>
<msup>
<mi>e</mi>
<mrow>
<msubsup>
<mi>&Sigma;</mi>
<mrow>
<mi>n</mi>
<mo>=</mo>
<mn>1</mn>
</mrow>
<mi>N</mi>
</msubsup>
<msub>
<mi>&sigma;</mi>
<mi>n</mi>
</msub>
<mo>-</mo>
<mi>N</mi>
<mo>&CenterDot;</mo>
<msub>
<mi>&sigma;</mi>
<mi>n</mi>
</msub>
</mrow>
</msup>
</mrow>
When sample number t is sufficiently large, have：
<mrow>
<munderover>
<mo>&Sigma;</mo>
<mrow>
<mi>n</mi>
<mo>=</mo>
<mn>1</mn>
</mrow>
<mi>N</mi>
</munderover>
<msub>
<mi>&omega;</mi>
<mi>n</mi>
</msub>
<mo>&CenterDot;</mo>
<msup>
<msub>
<mover>
<mi>&alpha;</mi>
<mo>^</mo>
</mover>
<mi>n</mi>
</msub>
<mrow>
<mi>d</mi>
<mi>y</mi>
<mi>n</mi>
<mi>a</mi>
<mi>m</mi>
<mi>i</mi>
<mi>c</mi>
</mrow>
</msup>
<mo>&ap;</mo>
<mn>0</mn>
</mrow>
So as to obtain fit line according to weight equation.
A kind of 7. precise phase computational methods based on the estimation of RFID multipaths according to claim 6, it is characterised in that institute
State the slope k of fit line and intercept d calculating process：
Formula is minimized firstInIt is as follows to obtain partial derivative：
Then make above formula be equal to 0 and solve to obtain：
<mrow>
<mfenced open = "{" close = "">
<mtable>
<mtr>
<mtd>
<mrow>
<mi>k</mi>
<mo>=</mo>
<mo>-</mo>
<mfrac>
<mrow>
<msubsup>
<mi>&Sigma;</mi>
<mrow>
<mi>n</mi>
<mo>=</mo>
<mn>1</mn>
</mrow>
<mi>N</mi>
</msubsup>
<msub>
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A kind of 8. precise phase computational methods based on the estimation of RFID multipaths according to claim 7, it is characterised in that institute
State formula x=ξ0+c1·ξ1+c2·ξ2Middle coefficient c1And c2Solved by following equation：
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Wherein, yiAnd yN+1-iFor the random selection group point on fit line.
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