CN108882171A - A kind of personnel's trace tracking method based on CSI - Google Patents
A kind of personnel's trace tracking method based on CSI Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/02—Services making use of location information
- H04W4/029—Location-based management or tracking services
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/02—Services making use of location information
- H04W4/021—Services related to particular areas, e.g. point of interest [POI] services, venue services or geofences
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/30—Services specially adapted for particular environments, situations or purposes
- H04W4/33—Services specially adapted for particular environments, situations or purposes for indoor environments, e.g. buildings
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W64/00—Locating users or terminals or network equipment for network management purposes, e.g. mobility management
- H04W64/006—Locating users or terminals or network equipment for network management purposes, e.g. mobility management with additional information processing, e.g. for direction or speed determination
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Abstract
The present invention provides a kind of personnel's trace tracking method based on CSI extracts CSI signal value；What is represented at the maximum value of frequency spectrum function is the highest point of image；Since the element carrier frequency and spread speed of signal are it is known that doppler velocity can be obtained；Redundant points processing is removed to obtained moving point using smoothing algorithm, the position of moving point is determined with the improved three side location algorithm based on least square method again, judge structure algorithm in term of reference, if in term of reference, then the obtained point in scope of activities is handled, enough points is acquired and simulates the track of personnel indoors.All moving points of indoor occupant can be depicted as trace image and intuitively shown by the trace tracking method, realize the tracking and positioning more accurate to indoor occupant.
Description
Technical field
The invention belongs to internet of things field, are related to a kind of tracking, in particular to a kind of personnel's rail based on CSI
Mark tracking.
Background technique
An important component of the location technology as general fit calculation and Internet of Things, by more and more extensive concern.
Global Satellite Navigation System（Global Navigation Satellite System, GNSS）It is risen in terms of outdoor accurate positioning
Key effect, but indoors under environment, multipath effect that GNSS is showed in communication process due to signal dissipates
It penetrates, the characteristics such as diffraction, makes it that can not play the advantage of its high accuracy positioning again.Currently based on CSI Study of location
Certain achievement is achieved, or even has had reached the positioning accuracy of meter level or sub-meter grade.
Since 2010, the Massachusetts Institute of Technology, Stanford University, University of Washington, Hong Kong University of Science and Thchnology, Tsinghua University etc.
Colleges and universities have all carried out a large amount of research to CSI aware application system.Occur：It is realized using commercial WI-FI without people in canyon
Member's tracking, realization is also able to achieve very high positioning accuracy in the case where packet loss, delay, but does not account for multi-human tracking, reality
When tracking, multipath effect influence problem.Use software radio（USRP）The gesture identification of entire Experimental Area is realized, and
Doppler frequency shift is detected using FFT.Virtual touch screen is constructed using RFID, and carries out fine granularity tracking using AoA information.
WiDraw provides the thinking that position is determined using phase information using AoA information well, but needs Wi-Fi transmitter in ring
All directions are covered in border.And influenced in the actual environment by multipath effect, implement that there are certain difficulty.Additionally mention
Going out many acoustics solutions for gesture identification and gesture tracking, they usually utilize the Doppler frequency shift in sonic-frequency band,
And accuracy is further increased using inertial sensors such as accelerometer and gyroscopes, but unresolved multipath effect is to gesture identification
The influence of effect.
Summary of the invention
The object of the present invention is to provide a kind of personnel's trace tracking method based on CSI is realizing the same of high position precision
When, eliminate influence of the multipath effect to gesture recognition effect.
To achieve the above object, the technical scheme adopted by the invention is that：A kind of personnel track following side based on CSI
Method specifically carries out according to the following steps：
Step 1：Extract CSI signal；
Step 2：Using Music algorithm estimating Doppler frequency displacement, then estimate AOA frequency spectrum, so that it is determined that personnel positions whether
In preset range；
Step 3：Redundant points processing is removed to the moving point that step 2 obtains using smoothing algorithm, then with based on least square
The improved three side location algorithm of method determines the position of moving point, structure algorithm is judged in term of reference, if in reference model
In enclosing, then 4 are entered step；
Step 4：The obtained point in scope of activities is handled, enough points is acquired and simulates the rail of personnel indoors
Mark.
Tracking of the present invention is first handled the CSI signal extracted with smoothing algorithm, forms enhanced CSI
Algorithm；Enhanced CSI algorithm is to compare the value size of previous CSI and current CSI value, to reduce mobile personnel
The kinetic energy of target fluctuates, and recycles improved three sides positioned centroid algorithm to determine each moving point, all moving points are drawn
Trace image is made intuitively to show, realizes the tracking and positioning more accurate to indoor occupant.
Detailed description of the invention
Fig. 1 is multiple snapshot schematic diagrames in each CSI sample frequency domain taken in tracking of the present invention.
Fig. 2 is the basic schematic diagram of trilateration.
Specific embodiment
The following describes the present invention in detail with reference to the accompanying drawings and specific embodiments.
CSI is the channel state information for measuring channel situation（Channel State Information）, belong to PHY layer,
Decoded subcarrier under ofdm system.CSI is fine-grained physical message, more sensitive to environment, so being applied to
The fields such as action recognition, gesture identification, keystroke identification, tracking.Firstly the need of the reception power for knowing tested node, to emit section
Then point signal power utilizes distance of the signal propagation attenuation model conversion between node, finally again with improved as reference
Trilateration algorithm can simply determine the position of unknown node.Pass between the transmission power and reception power of wireless signal
System can use formula（1）It indicates,
P R =P T /r n （1）
Formula（1）In,P R It is the reception power of wireless signal；P T It is the transmission power of wireless signal；rBe between transmitting unit with connect
Receive the distance of unit；nIt is propagation factor, since nlos environment is influenced by multipath effect than view distance environment big, causes to propagate
The factor is larger, to make the reception power of wireless signal become smaller, so propagation factor numerical values recited depends on radio signal propagation
Environment.
To formula（1）Both sides take logarithm, obtain formula（2）,
10×nlgr=10lg(P T / P R ) （2）
The transmission power of nodeP T Be it is known, transmission power is substituted into formula（2）, obtain formula（3）,
10lg P R =A-nlgr （3）
Formula（3）In 10lg P R It is the expression formula that received signal power is converted to dBm, can be directly write as formula（4）,
P R (dBm) = A-10×nlgr（4）
Formula（4）InARepresent unit of transfer's distance（1m）When, required power.
Formula（4）InP R (dBm) it is exactly CSI constant；AWithnNumerical value determine received signal strength and signal transmission distance
Relationship between.
Because the signal attenuation degree of each reference point is different, only one propagation factornValue do not have it is general
Property, it is also difficult to illustrate its accuracy.So by formula（4）Obtain formula（5）,
n i =-(CSI i -A)/( 10×lgr i ) （5）
Pass through formula（5）One group can be found outn i Valuen 1, n 2, n 3,…n n；Then the average value of this group of number is sought, as required
Propagation factor.
Multipath transmisstion is exactly in the indoor environment with a pair of of transmitter and receiver, and signal is not only passed along direct path
It broadcasts, but also exists by other objects（Such as people）The phenomenon that blocking reflection with wall, so that received signal is at receiver
The superposition of signal from all paths.When a people moves in the environment, the length in path is different by the reflection signal of people
And correspondingly change, this is that carrier frequency Doppler-shifted reflection signal is caused to change, carrier frequency such as formula（6）It is shown：
f Doppler =f(v path /c) （6）
Formula（6）In,fIt is the original carrier frequency of signal；v path It is the speed of change in path length；cIt is Wi-Fi signal in air
In spread speed.
But when people when moving, introduce Doppler's Wi-Fi signal frequency conversion it is only several for 5GHz channel
Ten hertz, it is clear that it is very difficult that fine granularity, so small Doppler carrier shift, which carries out detection,.
In acquisition, packet loss and delay as caused by time ambient noise and interference easily cause status information
It cannot normally send, receive sample data packet.In order to solve these problems, how to be obtained using Wi-Fi equipment accurately how general
Strangling frequency displacement estimation becomes key, and the invention proposes one to obtain accurate Doppler frequency transfer based on the algorithm of MUSIC
The algorithm of estimation.
Only one path signal is considered first：First at the t0 moment first CSI sample is collected, then again when different
Acquisition CSI sample is carved, each sample is relative to the sampling interval of first sample
Δ t1, Δ t2 ..., Δ tM.In a short sampling window, because difference CSI samples span difference in attenuation is different,
The change speed in pathv path It is considered as a constant.So the phase difference sample between i-th of CSI is, therefore, the stage
Difference between the Mth CSI sample and first CSI sample, such as formula（7）：
Formula（7）InDoppler vector and CSI sample matrix with M sample are：
Formula（8）In, n (f) is noise function.It, can be easily from the phase of CSI sample in the presence of being placed in a path signal
Doppler frequency shift is calculated in the measurement of position；In the actual conditions with multipath, the signal of multipath reaches receiver；At this point,
Formula（7）And formula（8）The CSI sample matrix of expression is indicated as：
Formula（9）In,v i It is the path change speed of i-th of path signal,It is whole M × L
Matrix Doppler frequency shift vector is the CSI in i-th of path signal of the first sampling time T0 measurement, matrix；It is noise matrix.The Doppler frequency shift of each path signal in order to obtain, this hair
Bright tracking takes multiple snapshots in each CSI sample frequency domain, as shown in Figure 1.Sending device is over the plurality of subcarriers
CSI is provided；If K is the sub-carrier number of CSI, there is the K snapshot sample of CSI.For i-th of sample, can be expressed as：
Formula（10）In, fkIt is the element carrier frequency of k-th of subcarrier；I-th of path signal in signal matrix S (f) can table
It is shown as：
Formula（11）In,It is in the first sampling time（t0）The CSI of k-th of snapshot of i-th of path signal；From all
CSI is chosen in subcarrier, to avoid the specific subcarrier of selection low signal-to-noise ratio, it is inaccurate that this may cause Doppler frequency estimation
Really；Utilize formula（9）And formula（10）, formula（11）It can be expressed as：
Formula（12）In,
With MUSIC algorithm come the Doppler frequency shift of estimated service life CSI sample；From formula（12）In, indicate that RX is：
Formula（13）In, RS is the correlation matrix of signal matrix, and I is unit matrix, and σ is the variance of noise.Correlation matrix RS has M
A characteristic value；The smallest M-L characteristic value corresponds to noise, and other feature value corresponds to L path signal；Feature vector corresponds to
The smallest M-L characteristic value constructs a noise subspaceSignal and noise subspace are orthogonal, so
Doppler velocity spectral function can be expressed as：
What is represented at the maximum value of frequency spectrum function is the highest point of image.Due to signal element carrier frequency and spread speed
Know, doppler velocity can be obtained.
Because the personnel movement track detected changes constantly in complicated indoor positioning, along with extraneous not true
The value fluctuation of the influence for determining factor, the CSI signal caused is larger, generates biggish error to personnel positioning.It is not achieved pre-
The effect of phase.But the thought of smoothing algorithm is exactly that connected CSI signal value is compared and analyzed, and removes the biggish value of fluctuation,
Experimental result is allowed to tend towards stability, the curve finally presented is smoother, realizes precise positioning.
Therefore, improved smoothing algorithm is used in the present invention staff's trace tracking method, which is divided into
Two stages：1）The estimation of distance；2）The estimation of position.
1）The estimation of distance
CSI location mechanism is made of reference mode and unknown node two parts.It is represented in two-dimensional coordinate system by fixed position
Reference mode position coordinates and the CSI value that receives of unknown node calculated, the standardization Euclidean distance both asked：
It takes out the position coordinates of reference point and is denoted as xi for the value of horizontal axis；
The CSI value for being collected into unknown node every time is denoted as yi；
The standardization Euclidean distance of the two then acquired obtains formula and is：
In order to avoid accidental error, by formula（15）Obtain formula（16）,
Data smoothing processing definition：
R est(n)It is the range of n-th of CSI smoothly estimated；
R pre(n)It is the range of the CSI of n-th of prediction；
R mea(n)It is the range of the CSI of n-th of measurement；
R rat(n)It is n-th of range ratio smoothly estimated；
R prerat(n)It is n-th of estimation range ratio；
First calculateR est(n)WithR rat(n),
R est(n)= R pre(n)+λ(R mea(n)-R pre(n)) （17）
Wherein λ, expression gain constant, Ts are the periods of variation.
Then, compare the range of n-th of CSI value and the range of (n+1)th CSI value, such as formula（19）,
Formula（19）In,R pre(n+1)It is the range of the CSI of (n+1)th prediction；R pre(n)It is the range of the CSI of n-th of prediction；V est(n)It is the ratio of the CSI of (n+1)th prediction；T s It is the time of the ratio of the CSI of n-th of prediction.
Compare the estimation of n-th of CSI value ratio and the estimation of (n+1)th CSI value ratio, such as formula（20）,
V pre(n+1)= V est(n)（20）
By formula（20）The value of (n+1)th reference point is obtained, then by formula（5）The value of CSI is calculated, finally the CSI value after calculating
It is weighted processing, is sent to unknown node after eliminating the influence of propagation factor；
2）With the position coordinates of the Least Square Method unknown node after weighting：
The basic principle of trilateration is exactly to seek the intersection point of the circle of three known radius and the coordinate center of circle, as shown in Figure 2；But
There are errors when ranging, so three circles shown in Fig. 2（Circle A, circle B, circle C）The center of circle and this three round intersection point D connection
Line can not accurately intersect at a point.Estimated coordinates and the smallest point of actual coordinate difference in order to obtain, in tracking of the present invention
The coordinate of unknown node is estimated using the principle of least square method, still, in tracking of the present invention using weighting after
Least square method, specially：N group position coordinates are obtained firstly, measuring from actual experiment environment by position（x1,
y1）,（x2,y2）,…（xn,yn）；
Then, this n point in two-dimensional coordinate system is fitted with the curve of the center in sample data；
Then, with regression model：
In formula,e ii For sample（Xi,Yi）Error, acquire quadratic loss functionQ：
Quadratic loss function is determined by Q minimum, that is, is determinedWithThey are regarded as Q's
Function, at this point it is possible to then ask Q to two parameters to be estimated by differentiating to obtain an extreme valueWithPartial derivative：
Known according to mathematical knowledge, Function Extreme Value point is the point that partial derivative is zero, i.e. moving point position, solves formula（24）, obtain：
It solves、The position coordinates of as required moving point.
Claims (3)
1. a kind of personnel's trace tracking method based on CSI, which is characterized in that the trace tracking method specifically according to the following steps into
Row：
Step 1：Extract CSI signal；
Step 2：Using Music algorithm estimating Doppler frequency displacement, then estimate AOA frequency spectrum, so that it is determined that personnel positions whether
In preset range；
Step 3：Redundant points processing is removed to the moving point that step 2 obtains using smoothing algorithm, then with based on least square
The improved three side location algorithm of method determines the position of moving point, structure algorithm is judged in term of reference, if in reference model
In enclosing, then 4 are entered step；
Step 4：The obtained point in scope of activities is handled, enough points is acquired and simulates the rail of personnel indoors
Mark.
2. personnel's trace tracking method according to claim 1 based on CSI, which is characterized in that the step 2 is specific
For：
First at the t0 moment collects first CSI sample, then acquisition CSI sample at different times again, each sample relative to
The sampling interval of first sample is Δ t1, Δ t2 ..., Δ tM；In a short sampling window, because of difference CSI samples span
Difference in attenuation is different, so the change speed in pathv path It is considered as a constant；So the phase difference sample between i-th of CSI
Originally it is, therefore, the difference between the Mth CSI sample of stage and first CSI sample, such as formula（7）：
Formula（7）InDoppler vector and CSI sample matrix with M sample are：
Formula（8）In, n (f) is noise function；It, can be from the phase measurement of CSI sample in the presence of being placed in a path signal
Calculate Doppler frequency shift；In the actual conditions with multipath, the signal of multipath reaches receiver；At this point, formula（7）And formula
（8）The CSI sample matrix of expression is indicated as：
Formula（9）In,v i It is the path change speed of i-th of path signal,It is whole M × L squares
Battle array Doppler frequency shift vector is the CSI in i-th of path signal of the first sampling time T0 measurement, matrixIt is signal matrix；It is noise matrix；Each path signal is how general in order to obtain
Frequency displacement is strangled, takes multiple snapshots in each CSI sample frequency domain, sending device provides CSI over the plurality of subcarriers；If K is
The sub-carrier number of CSI has the K snapshot sample of CSI；For i-th of sample, can be expressed as：
Formula（10）In, fkIt is the element carrier frequency of k-th of subcarrier；I-th of path signal in signal matrix S (f) can indicate
For：
Formula（11）In,It is in the first sampling time（t0）The CSI of k-th of snapshot of i-th of path signal；From all
CSI is chosen in subcarrier, to avoid the specific subcarrier of selection low signal-to-noise ratio, it is inaccurate that this may cause Doppler frequency estimation
Really；Utilize formula（9）And formula（10）, formula（11）It can be expressed as：
With MUSIC algorithm come the Doppler frequency shift of estimated service life CSI sample；From formula（12）In, indicate that RX is：
Formula（13）In, RS is the correlation matrix of signal matrix, and I is unit matrix, and σ is the variance of noise；Correlation matrix RS has M
A characteristic value；The smallest M-L characteristic value corresponds to noise, and other feature value corresponds to L path signal；Feature vector corresponds to
The smallest M-L characteristic value constructs a noise subspace；Signal and noise subspace are orthogonal, so
Doppler velocity spectral function can be expressed as：
What is represented at the maximum value of frequency spectrum function is the highest point of image；Due to signal element carrier frequency and spread speed
Know, obtains doppler velocity.
3. personnel's trace tracking method according to claim 1 based on CSI, which is characterized in that flat in the step 3
Sliding algorithm：
1）The estimation of distance
The CSI value received by the position coordinates and unknown node of the reference mode of fixed position is represented in two-dimensional coordinate system
It is calculated, seeks the standardization Euclidean distance of the two：
It takes out the position coordinates of reference point and is denoted as xi for the value of horizontal axis；
The CSI value for being collected into unknown node every time is denoted as yi；
The standardization Euclidean distance of the two then acquired obtains formula and is：
In order to avoid accidental error, by formula（15）Obtain formula（16）,
Data smoothing processing definition：
R est(n)It is the range of n-th of CSI smoothly estimated；
R pre(n)It is the range of the CSI of n-th of prediction；
R mea(n)It is the range of the CSI of n-th of measurement；
R rat(n)It is n-th of range ratio smoothly estimated；
R prerat(n)It is n-th of estimation range ratio；
First calculateR est(n)WithR rat(n),
R est(n)= R pre(n)+λ(R mea(n)-R pre(n)) （17）
Wherein λ, expression gain constant, Ts are the periods of variation；
Then, compare the range of n-th of CSI value and the range of (n+1)th CSI value, such as formula（19）,
Formula（19）In,R pre(n+1)It is the range of the CSI of (n+1)th prediction；R pre(n)It is the range of the CSI of n-th of prediction；V est(n)
It is the ratio of the CSI of (n+1)th prediction；T s It is the time of the ratio of the CSI of n-th of prediction；
Compare the estimation of n-th of CSI value ratio and the estimation of (n+1)th CSI value ratio, such as formula（20）,
V pre(n+1)= V est(n)（20）
By formula（20）The value of (n+1)th reference point is obtained, then by formula（5）The value of CSI is calculated, finally the CSI value after calculating
It is weighted processing, is sent to unknown node after eliminating the influence of propagation factor；
2）With the position coordinates of the Least Square Method unknown node after weighting：
Using the least square method after weighting, estimated coordinates and the smallest point of actual coordinate difference are obtained, specially：Firstly, from
It is measured in actual experiment environment by position and obtains n group position coordinates（x1,y1）,（x2,y2）,…（xn,yn）；
Then, this n point in two-dimensional coordinate system is fitted with the curve of the center in sample data；
In formula,e ii For sample（Xi,Yi）Error, acquire quadratic loss functionQ：
Quadratic loss function is determined by Q minimum, that is, is determinedWith；WithWithFor variable, they are regarded as the letter of Q
Number, at this point it is possible to then ask Q to two parameters to be estimated by differentiating to obtain an extreme valueWithPartial derivative：
Known according to mathematical knowledge, Function Extreme Value point is the point that partial derivative is zero, i.e. moving point position, solves formula（24）, obtain：
It solves、The position coordinates of as required moving point.
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