CN107343315B - Positioning system and method based on wireless local area network multi-frequency point combined measurement - Google Patents

Positioning system and method based on wireless local area network multi-frequency point combined measurement Download PDF

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CN107343315B
CN107343315B CN201710673807.5A CN201710673807A CN107343315B CN 107343315 B CN107343315 B CN 107343315B CN 201710673807 A CN201710673807 A CN 201710673807A CN 107343315 B CN107343315 B CN 107343315B
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wireless access
access point
user
point
frequency
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CN107343315A (en
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张舜卿
徐树公
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Jiangsu Hengxin Technology Co Ltd
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Beijing Transpacific Technology Development Ltd
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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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/0257—Hybrid positioning
    • G01S5/0268—Hybrid positioning by deriving positions from different combinations of signals or of estimated positions in a single positioning system
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/08—Position of single direction-finder fixed by determining direction of a plurality of spaced sources of known location
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/10—Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements, e.g. omega or decca systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/10—Small scale networks; Flat hierarchical networks
    • H04W84/12—WLAN [Wireless Local Area Networks]

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
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Abstract

A positioning system and method based on wireless local area network multi-frequency point combined measurement includes: a joint estimation unit, a user equipment and a plurality of wireless access points, wherein: each wireless access point receives and processes signals transmitted by user equipment on a plurality of frequency points by changing the angle of the antenna, estimates the arrival angle and the propagation time of the signals through time offset compensation and signal reconstruction, estimates the position of the user equipment relative to the wireless access point, and transmits the relative position information back to the joint estimation unit; the joint estimation unit estimates the accurate geographic position of the user equipment by combining the pre-stored information and updates the geographic position of the user in time; according to the invention, on the premise of not additionally increasing the deployment cost of the wireless access points, the problem that the traditional positioning method cannot accurately position is solved through the joint measurement of a plurality of frequency points of a plurality of wireless access points, and a good foundation is laid for other applications of the subsequent wireless local area network based on the user position.

Description

Positioning system and method based on wireless local area network multi-frequency point combined measurement
Technical Field
The invention relates to a technology in the field of wireless local area network positioning, in particular to a positioning system and a positioning method based on wireless local area network multi-frequency point combined measurement, which can be used for occasions of broadband multi-frequency and multi-antenna networks with a plurality of indoor and outdoor user positioning requirements, such as cellular networks, Internet of things, vehicle networking, smart power grids, smart home networks and the like.
Background
With the rapid development of the mobile internet, the application of the Wireless local area network (WiFi) is more and more extensive, and the number of Access Points (APs) is also increased explosively from the original computer connected to the internet to the function of providing interconnection and internet data Access for a series of computer devices including mobile phones, tablet computers, smart appliances, and the like. From the standard, the wireless local area network physical layer communication is evolved from the original IEEE 802.11a/b/g to the new version including the current 802.11n/ac, and the transmission speed, the number of simultaneously supported users and the anti-interference capability are greatly improved.
In addition to wireless transmission, wireless local area networks have also emerged as an indoor and outdoor user location application that utilizes access point location to facilitate subsequent user location information-based applications. However, in the current positioning application based on the wireless local area network, there still exist a lot of problems, especially how to improve the positioning accuracy of the user. On one hand, the signals transmitted by the wireless local area network access points (hereinafter referred to as wireless access points) often need to be reflected and scattered by complex indoor and outdoor environments, and the propagation paths are complex, and on the other hand, the actual measurement results of the user propagation channels are also influenced because the interference environments of the current wireless local area networks are complex.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a positioning system and a positioning method based on wireless local area network multi-frequency point joint measurement, which realize accurate estimation of user positions and measurement of geographical positions of user equipment by carrying out relevant processing analysis and joint estimation on signals received by different receiving antennas, and have low deployment cost and no need of hardware updating.
The invention is realized by the following technical scheme:
the invention relates to a positioning system based on wireless local area network multi-frequency point combined measurement, which comprises: a joint estimation unit, a user equipment and a plurality of wireless access points, wherein: each wireless access point receives and processes signals transmitted by the user equipment on a plurality of frequency points by changing the angle of the antenna, estimates the position of the user equipment relative to the wireless access point, and transmits the relative position information back to the joint estimation unit; the joint estimation unit estimates the accurate geographic position of the user equipment by combining the pre-stored information and updates the geographic position of the user in time.
The pre-stored information comprises: antenna angle information and geographic location information for the wireless access point.
The signal includes a pilot signal or other reference signal and is known in advance by the wireless access point.
The processing comprises the following steps: and calculating the real-time state information of a transmission channel between the user equipment and the wireless access point according to the received signals, thereby estimating and eliminating the time offset between the wireless access point and the user.
The wireless access point is provided with a user arrival angle and propagation time estimation unit, can estimate at multiple frequency points, and comprises the following steps: the system comprises a user signal receiving module, a user time bias estimation module, a user time bias compensation module, a user signal reconstruction module and an arrival angle and propagation time estimation module which are connected in sequence, wherein: after receiving the signal transmitted by the user, the user signal receiving module estimates the time offset of the received signal by the user time offset estimation module, and eliminates the time offset by the user time offset compensation module, and the eliminated information is reconstructed by the user signal reconstruction module and then transmitted to the arrival angle and propagation time estimation module for estimation of the arrival angle and propagation time.
The joint estimation unit may be disposed at a wireless access point or a remote server.
The joint estimation unit is provided with a joint information processing module of the arrival angle and the propagation time of the multi-access point user, and comprises: and the multi-frequency point signal arrival angle and propagation time receiving module and the multi-frequency point arrival angle and propagation time joint estimation and decision module are connected.
The arrival angle and propagation time estimation module of the wireless access point is connected with the multi-frequency point signal arrival angle and propagation time receiving submodule through a return network.
The backhaul network may be a wireless connection or a physical connection (including an associated communication protocol carried over a physical connection) via a wired medium.
The invention relates to a positioning method based on the system, wherein each wireless access point receives signals sent by user equipment on a plurality of frequency points, and estimates the arrival angle and the propagation time of the signals through time offset compensation and signal reconstruction, so as to estimate the position of a user relative to the wireless access point, and sends the estimated position information to a joint estimation unit, and the joint estimation unit estimates the accurate geographic position of the user equipment by combining pre-stored information and updates the geographic position in time.
Technical effects
Compared with the prior art, the method solves the problem of accurately positioning the position of the user through the signal reception of the multi-frequency point multi-wireless access point in a complex indoor environment, realizes the measurement and channel estimation of the multi-frequency point signal and the joint estimation of the multi-frequency point signal so as to determine the geometric relationship between the wireless access point and the user, and determines the specific position of the user and further realizes the tracking of the geographic position of the user through the geometric relationship between the plurality of wireless access points and the user; the method has the advantages of realizing accurate wireless local area network user positioning measurement, supporting the timely tracking of the user position, supporting the large-scale wireless local area network user positioning measurement, controlling the network burden and further realizing the user clustering positioning.
Drawings
FIG. 1 is a schematic view of a positioning system;
FIG. 2 is a schematic layout view of the embodiment 1;
FIG. 3 is a flowchart of a positioning method according to embodiment 1;
FIG. 4 is a schematic diagram of a joint estimation method;
in the figure, a is a schematic diagram of weight estimation; b is a schematic diagram of position information estimation;
FIG. 5 is a schematic layout diagram of embodiment 2.
Detailed Description
Example 1
As shown in fig. 1 and 2, the present embodiment includes: a joint estimation unit, a user equipment and three wireless access points 1, 2, 3, wherein: the three wireless access points receive and process signals transmitted by the user equipment on two frequency points by changing the angle of the antenna, namely, observe a transmission channel of the user equipment, estimate the position of the user equipment relative to the wireless access point, and transmit relative position information back to the joint estimation unit; the joint estimation unit estimates the accurate geographic position of the user equipment by combining the pre-stored information and updates the geographic position of the user in time.
The antenna may be a single receiving antenna or a plurality of receiving antennas.
The pre-stored information comprises: antenna angle information and geographic location information for the wireless access point.
The processing comprises the following steps: and calculating the real-time state information of a transmission channel between the user equipment and the wireless access point according to the received signals, thereby estimating and eliminating the time offset between the wireless access point and the user.
The wireless access points are provided with user arrival angle and propagation time estimation units, and can perform estimation on multiple frequency points, and the estimation comprises the following steps: the system comprises a user signal receiving module, a user time bias estimation module, a user time bias compensation module, a user signal reconstruction module and an arrival angle and propagation time estimation module which are connected in sequence, wherein: after receiving the signal transmitted by the user, the user signal receiving module estimates the time offset of the received signal by the user time offset estimation module, and eliminates the time offset by the user time offset compensation module, and the eliminated information is reconstructed by the user signal reconstruction module and then transmitted to the arrival angle and propagation time estimation module for estimation of the arrival angle and propagation time.
The joint estimation unit may be disposed at a wireless access point or a remote server.
The joint estimation unit is provided with a joint information processing module of the arrival angle and the propagation time of the multi-access point user, and comprises: and the multi-frequency point signal arrival angle and propagation time receiving module and the multi-frequency point arrival angle and propagation time joint estimation and decision module are connected.
And the signal arrival angle and propagation time estimation module of the wireless access point is connected with the multi-frequency point signal arrival angle and propagation time receiving submodule through a return network.
The backhaul network may be a wireless connection, or a physical connection (including a related communication protocol carried on the physical connection) through a wired medium, so as to ensure reliable communication between the wireless access point and the joint estimation unit.
The three wireless access points all have two commonly used frequency points of 2.4GHz and 5GHz for access. For convenience of description, it is assumed that two frequency points have a direct path and a reflected path, respectively.
As shown in fig. 3, the present embodiment relates to a positioning method based on the above system, which includes the following steps:
step 1, the user equipment transmits a signal S for measuring the real-time state of a channel transmitted between the user equipment and the wireless access point.
The signal S includes a pilot signal or other reference signal for measuring the channel quality, and is known in advance by the wireless access point, so that the wireless access point can calculate the real-time status of the channel between the wireless access point and the user according to the known signal.
For each wireless access point and each frequency point (such as the wireless access point 1, the frequency point 1), a pilot frequency or other reference signals S transmitted by a user is received first, and real-time state information H of a transmission channel between the user equipment and the wireless access point is estimated. In practical systems, the pilot or other reference signal S for a user is typically transmitted simultaneously with the data transmission signal, and therefore introduces substantially no additional communication overhead.
And 2, adjusting the antenna angle of each wireless access point, receiving the signals through a user signal receiving module, and estimating real-time state information H of a transmission channel between the user equipment and the wireless access point according to the signals.
For example, for a common received signal y ═ Hs + w (w is noise), the wireless access point may estimate the corresponding channel real-time status information H according to a known pilot or other reference signal s (e.g., H ═ y/s).
Due to the existence of noise, the estimated real-time channel state information H may have a certain difference from the true value, but does not affect the positioning idea of this embodiment.
And 3, each wireless access point carries out time offset estimation and time offset compensation to obtain channel state information H' after time offset is eliminated.
Because the sampling frequencies of the user equipment and each wireless access point cannot be completely consistent, certain time offsets exist for signals received by different wireless access points and different frequency points. The time offset will vary from one wireless access point to another and from one frequency point to another, and needs to be eliminated.
The time offset estimation method comprises a minimum absolute error method, a least square method and other traditional signal estimation methods.
The minimum absolute error method specifically comprises the following steps:
s1: and obtaining a phase matrix P corresponding to the channel state information H.
S2: solving for satisfaction according to the phase matrix P
Figure GDA0001399802350000041
Is given by the minimum time offset T. Wherein P (i, j) represents the phase information of the channel state information on the ith antenna and the jth subcarrier, fcI and J represent the maximum number of antennas and the number of subcarriers, respectively, for the bandwidth of the subcarriers.
S3: according to the time offset information, phase compensation is adopted for the original channel state information H to eliminate the time offset, and the channel state information H' after the time offset is eliminated is obtained:
Figure GDA0001399802350000042
and 4, each wireless access point carries out signal reconstruction on the channel state information H' of the frequency point 1 obtained after the time offset is eliminated.
The signal reconstruction means that: respectively expanding the channel state information H' obtained after eliminating the time offset according to the dimensions of the sub-channels and the antenna serial numbers, so that the expanded channel state information
Figure GDA0001399802350000043
The dimensionality is at least larger than the number of independent channels between the wireless access point and the user, and the correspondingly expanded channel state information is found out
Figure GDA0001399802350000044
The feature vector a (θ, τ) of the column vector.
The eigenvector is a function of an arrival angle theta and a propagation time tau, and is used for channel state information H 'of 10 subcarriers with 4 antennas'
Figure GDA0001399802350000051
Signal reconstruction is performed in case the number of independent channels is greater than 5:
Figure GDA0001399802350000052
generated feature vector
Figure GDA0001399802350000053
Wherein:
Figure GDA0001399802350000054
is the phase shift caused by propagation delay; phi ═ e-j2πDsin(θ)f/cIs the phase shift due to the arrival angle, D is the distance between adjacent receiving antennas, and f is the frequency of the transmitted signal.
Step 5, each wireless access point reconstructs the channel state information according to the signal
Figure GDA0001399802350000055
And a characteristic vector a (theta, tau), and the signal arrival angle theta and the propagation time tau of the user equipment are preliminarily estimated.
The preliminary estimation refers to: estimating the arrival angle theta and the propagation time tau sample of each sampling point by adopting a traditional multidimensional signal estimation method such as an orthogonal subspace method or a maximum likelihood method, carrying out clustering operation according to the compactness of the samples, and resolving the most possible arrival angle theta and the propagation time tau of each independent channel between the wireless access point and the user equipment by taking the sample cluster as a unit.
Since there may be multiple propagation paths corresponding to the same channel state information
Figure GDA0001399802350000061
A number of estimated arrival angle theta and propagation time tau values may be obtained. Channel state information of frequency point 1 in actual system
Figure GDA0001399802350000062
A plurality of samples will be obtained as the data transmission time continues and, therefore, a plurality of samples of the angle of arrival θ and the propagation time τ will be generated accordingly.
The orthogonal subspace method specifically comprises the following steps:
s1: determining positive definite matrix
Figure GDA0001399802350000063
The value of (c).
S2: and decomposing the eigenvalue of the normal matrix X, and finding out the eigenvector y corresponding to the eigenvalue when the eigenvalue is smaller than the threshold.
S3: all the obtained feature vectors are combined into an orthogonal subspace matrix Y.
S4: finding out the corresponding values of theta and tau when M (theta, tau) obtains an extreme value according to the feature vector a (theta, tau) and the orthogonal subspace matrix Y, wherein:
Figure GDA0001399802350000064
and 6, each wireless access point transmits the estimated result back to the joint estimation unit through a return network, namely a connecting network between the connecting wireless access point and the joint estimation unit.
The feedback means that: the wireless access point 1 respectively calculates a weight value for each independent channel of the frequency point 1 according to a preset weight function, selects a path with the maximum weight value as a direct path, and obtains the arrival angle theta 'and the propagation time tau' of the direct path of the frequency point 1 for transmission, so that different weights are set for information returned by different wireless access points in the return process.
The wireless access point 2 and the wireless access point 3 adopt the same steps to transmit the arrival angle theta 'and the propagation time tau' of the respective direct paths to the joint estimation unit.
The weighting function may be a weighted sum function of variables such as the number of samples, the sample propagation time, the angle of arrival and randomness of the propagation time (e.g., variance, standard deviation), the sample duration, etc.
And 7, carrying out joint estimation on the geographic position of the user equipment by the joint estimation unit.
As shown in fig. 4, the joint estimation refers to: the joint estimation unit selects a reference arrival angle theta 'and propagation time tau' for each wireless access point 1, 2, 3 (the selected standard can be the direct path with the shortest propagation time in each frequency point), and calculates the weight of the direct paths of other frequency points; and then, calculating the position information of the user equipment by combining the weight of each frequency point path on each wireless access point, the prestored antenna angle information of the wireless access point and the geographical position information of each wireless access point, wherein the method specifically comprises the following steps:
Figure GDA0001399802350000065
wherein: the specific definitions of the variables are: m is the serial number of the wireless access point, n is the serial number of the frequency point, xmAnd ymI.e. the coordinate position of the mth wireless access point. Like
Figure GDA0001399802350000066
And
Figure GDA0001399802350000067
respectively the propagation delay and the arrival angle of the user equipment to the mth wireless access point through wireless propagation on the nth frequency point,
Figure GDA0001399802350000071
is the weight corresponding to the propagation path.
The arrival angle θ 'and the propagation time τ' of the reference may be: the reference frequency point of the wireless access point 1 is frequency point 1, the reference frequency point of the wireless access point 2 is frequency point 2, and the reference frequency point of the wireless access point 3 is frequency point 1. The joint estimation unit determines the direct path of the wireless access point 1 frequency point 1, the wireless access point 2 frequency point 2 and the wireless access point 3 frequency point 1 as a reference, and calculates the weight of the direct path of the wireless access point 1 frequency point 2, the wireless access point 2 frequency point 1 and the wireless access point 3 frequency point 2, specifically:
when the direct path of frequency point 1 is taken as a reference, i.e.
Figure GDA0001399802350000072
Then for the direct path of frequency point n, the angle of arrival of the reference should be
Figure GDA0001399802350000073
The weight corresponding to the direct path of the frequency point n is:
Figure GDA0001399802350000074
β is used for unifying the dimensions of angle and propagation time, and for balancing the influence of angle error and propagation delay error on position estimation, and can be calibrated by equipment test in a practical system.
And step 8, the joint estimation unit updates and releases the user position, namely the joint estimation unit stores the calculated user position information in a mapping table related to the user geographical position information and transmits the user position information to the related wireless access point and the user equipment, so that the geographical position information of the related user can be sent to the user or other demanders according to a request.
The mapping table includes information that uniquely identifies the user, such as the address of media access control of the user equipment or the internet protocol address, information of a wireless access point to which the user belongs, and information about the geographical location of the user.
Example 2
As shown in fig. 5, the present embodiment includes two wireless access points 1 and 2, and each wireless access point has three frequency points of 2.4GHz, 5GHz, and 60GHz for access. For convenience of description, it is assumed that three frequency points have a direct path and a reflected path respectively.
The arrival angle θ 'and the propagation time τ' of the reference may be: the reference frequency point of the wireless access point 1 is frequency point 1, and the reference frequency point of the wireless access point 2 is frequency point 2. And the joint estimation unit determines the direct paths of the frequency point 1 of the wireless access point 1 and the frequency point 2 of the wireless access point 2 as a reference, and calculates the weights of the direct paths of the frequency points 2 and 3 of the wireless access point 1 and the frequency points 1 and 3 of the wireless access point 2.
In the embodiment, the multiple wireless access points estimate the arrival angle and the propagation time of the user equipment in multiple directions at multiple frequency points, so that the direct path between the user and the wireless access points can be determined more accurately, and the problem of inaccurate direct path estimation caused by reflection, scattering or signal interference in the prior art is solved. In addition, because the multi-frequency point measurement is adopted for each wireless access point, an additional observation point aiming at a direct path is added, and a weight reference is provided for the joint estimation of the joint calculation unit on the user position, so that important information is provided for the accurate joint measurement of a plurality of wireless access points.
In the embodiment, information is measured mainly through pilot frequency or other reference signals transmitted by a user, so that in the actual deployment process, the positioning system can analyze the position of the user while the user performs data transmission, and no additional reference signal or communication flow is needed. Therefore, the positioning system can estimate the change condition of the user equipment position in time, and the user position can be tracked in time.
For a large-scale wireless local area network, the embodiment can estimate the user position according to the user signals detected by different wireless access points, and the wireless access points which do not receive the user signals only need to consider no consideration when calculating the user position, and do not need to additionally change the position estimation algorithm. Therefore, the positioning method has good adaptability and can be suitable for network architectures of different scales, in particular for user positioning measurement of large-scale wireless local area networks.
The embodiment can measure the channel and the position between the user and the wireless access point through the pilot frequency or other reference signals transmitted when the user and the wireless access point carry out data communication, and does not need additional wireless network communication burden. And the communication between the wireless access point and the joint estimation unit is only the arrival angle and the propagation time of the direct path on different frequency points of the user, so the actual burden of the network is controllable. Meanwhile, the joint estimation unit can collect the information of arrival angles and propagation times of different users reaching different wireless access points, and can perform user clustering according to related information so as to further provide the capability of user clustering positioning.
The method used by the embodiment only needs to add a user arrival angle and propagation time estimation module and a multi-access point user arrival angle and propagation time joint information processing module which are respectively realized by software to the wireless access point and the joint estimation unit, and does not need to add any hardware or software update to the user equipment end, so that the method has lower deployment cost and good user equipment compatibility.
The foregoing embodiments may be modified in many different ways by those skilled in the art without departing from the spirit and scope of the invention, which is defined by the appended claims and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (7)

1. A positioning system based on wireless local area network multi-frequency point joint measurement is characterized by comprising: a joint estimation unit, a user equipment and a plurality of wireless access points, wherein: each wireless access point receives and processes signals transmitted by the user equipment on a plurality of frequency points by changing the angle of the antenna, estimates the position of the user equipment relative to the wireless access point, and transmits the relative position information back to the joint estimation unit; the joint estimation unit estimates the accurate geographic position of the user equipment by combining the pre-stored information and updates the geographic position of the user in time;
the pre-stored information comprises: antenna angle information and geographical location information of the wireless access point;
the signal comprises a pilot signal or other reference signal and is predicted by a wireless access point;
the processing comprises the following steps: calculating the real-time state information of a transmission channel between the user equipment and the wireless access point according to the received signals, thereby estimating and eliminating the time offset between the wireless access point and the user, which specifically comprises the following steps:
for a common received signal y, Hs + w, where w is noise, the wireless access point estimates corresponding channel real-time state information H according to a known reference signal s;
the estimation is as follows: each wireless access point carries out time offset estimation and time offset compensation to obtain channel state information H' after time offset is eliminated, wherein the time offset estimation method comprises a minimum absolute error method and a least square method;
the minimum absolute error method specifically comprises the following steps:
①, obtaining a phase matrix P corresponding to the channel state information H;
② solving for satisfaction according to the phase matrix P
Figure FDA0002304261560000011
A minimum time offset of T; wherein P (i, j) represents the phase information of the channel state information on the ith antenna and the jth subcarrier, fcI and J represent the maximum number of antennas and the number of subcarriers, respectively, for the bandwidth of the subcarriers;
③, according to the time offset information, performing time offset cancellation on the original channel state information H by using phase compensation to obtain the channel state information H' after time offset cancellation:
Figure FDA0002304261560000012
the elimination refers to: each wireless access point performs signal reconstruction on the channel state information H' of the frequency point 1 obtained after the time offset is eliminated, and the signal reconstruction specifically comprises the following steps: respectively expanding the channel state information H' obtained after eliminating the time offset according to the dimensions of the sub-channels and the antenna serial numbers, so that the expanded channel state information
Figure FDA0002304261560000013
The dimensionality is at least larger than the number of independent channels between the wireless access point and the user, and the correspondingly expanded channel state information is found out
Figure FDA0002304261560000014
A feature vector a (θ, τ) of the column vector;
the feature vector is related toChannel state information H 'for 10 subcarriers for 4 antennas as a function of angle of arrival theta and propagation time tau'
Figure FDA0002304261560000021
Signal reconstruction is performed in case the number of independent channels is greater than 5:
Figure FDA0002304261560000022
generated feature vector
Figure FDA0002304261560000023
Wherein:
Figure FDA0002304261560000024
is the phase shift caused by propagation delay; phi ═ e-j2πDsin(θ)f/cIs the phase shift due to the arrival angle, D is the distance between adjacent receiving antennas, f is the frequency of the transmitted signal;
the estimating of the position of the user equipment relative to the wireless access point includes: channel state information reconstructed by each wireless access point according to signals
Figure FDA0002304261560000025
And a feature vector a (θ, τ), which is used for preliminarily estimating the signal arrival angle θ and the propagation time τ of the user equipment, specifically: estimating the arrival angle theta and the propagation time tau sample of each sampling point by adopting a traditional multidimensional signal estimation method such as an orthogonal subspace method or a maximum likelihood method, performing clustering operation according to the compactness of the samples, and resolving the most possible arrival angle theta and the propagation time tau of each independent channel between a wireless access point and user equipment by taking the sample cluster as a unit;
the orthogonal subspace method specifically comprises the following steps:
s1: determining positive definite matrix
Figure FDA0002304261560000026
A value of (d);
s2: decomposing the eigenvalue of the normal matrix X, and finding out the eigenvector y corresponding to the eigenvalue when the eigenvalue is smaller than the threshold;
s3: combining all the obtained characteristic vectors into an orthogonal subspace matrix Y;
s4: finding out the corresponding values of theta and tau when M (theta, tau) obtains an extreme value according to the feature vector a (theta, tau) and the orthogonal subspace matrix Y, wherein:
Figure FDA0002304261560000031
the estimating of the precise geographical location of the user equipment includes: the joint estimation unit performs joint estimation on the geographic position of the user equipment, specifically: the joint estimation unit selects a reference arrival angle theta 'and propagation time tau' for each wireless access point 1, 2 and 3 (the selected standard is the direct path with the shortest propagation time in each frequency point), and calculates the weight of the direct paths of other frequency points; and then, calculating the position information of the user equipment by combining the weight of each frequency point path on each wireless access point, the prestored antenna angle information of the wireless access point and the geographical position information of each wireless access point, wherein the method specifically comprises the following steps:
Figure FDA0002304261560000032
wherein: the specific definitions of the variables are: m is the serial number of the wireless access point, n is the serial number of the frequency point, xmAnd ymThe coordinate position of the mth wireless access point is obtained; like
Figure FDA0002304261560000033
And
Figure FDA0002304261560000034
respectively the propagation delay and the arrival angle of the user equipment to the mth wireless access point through wireless propagation on the nth frequency point,
Figure FDA0002304261560000035
a weight for the corresponding propagation path;
the arrival angle θ 'and the propagation time τ' of the reference are: the reference frequency point of the wireless access point 1 is frequency point 1, the reference frequency point of the wireless access point 2 is frequency point 2, and the reference frequency point of the wireless access point 3 is frequency point 1; the joint estimation unit determines the direct path of the wireless access point 1 frequency point 1, the wireless access point 2 frequency point 2 and the wireless access point 3 frequency point 1 as a reference, and calculates the weight of the direct path of the wireless access point 1 frequency point 2, the wireless access point 2 frequency point 1 and the wireless access point 3 frequency point 2, specifically:
when the direct path of frequency point 1 is taken as a reference, i.e.
Figure FDA0002304261560000036
Then for the direct path of frequency point n, the angle of arrival of the reference should be
Figure FDA0002304261560000037
The weight corresponding to the direct path of the frequency point n is:
Figure FDA0002304261560000038
β is used for unifying the dimensions of angle and propagation time, and for balancing the influence of angle error and propagation delay error on position estimation, and is calibrated by equipment test in a practical system.
2. The positioning system of claim 1, wherein the wireless access point is provided with a user angle of arrival and propagation time estimation unit, and the estimation is performed at multiple frequency points, comprising: the system comprises a user signal receiving module, a user time bias estimation module, a user time bias compensation module, a user signal reconstruction module and an arrival angle and propagation time estimation module which are connected in sequence, wherein: after receiving the signal transmitted by the user, the user signal receiving module estimates the time offset of the received signal by the user time offset estimation module, and eliminates the time offset by the user time offset compensation module, and the eliminated information is reconstructed by the user signal reconstruction module and then transmitted to the arrival angle and propagation time estimation module for estimation of the arrival angle and propagation time.
3. The positioning system of claim 1, wherein the joint estimation unit is disposed at a wireless access point or a remote server.
4. The positioning system of claim 3, wherein the joint estimation unit is provided with a joint information processing module for the arrival angle and the propagation time of the multi-access-point user, and comprises: and the multi-frequency point signal arrival angle and propagation time receiving module and the multi-frequency point arrival angle and propagation time joint estimation and decision module are connected.
5. The positioning system of claim 4, wherein the angle-of-arrival and propagation time estimation module of the wireless access point is connected to the multi-frequency-point-signal angle-of-arrival and propagation time receiving sub-module through a backhaul network.
6. The location system of claim 5, wherein the backhaul network is a wireless connection and is also a physical connection via a wired medium.
7. A positioning method based on the system of any one of the preceding claims, wherein each wireless access point receives signals sent by user equipment at multiple frequency points, and estimates the arrival angle and propagation time of the signals through time offset compensation and signal reconstruction, thereby estimating the position of the user relative to the wireless access point, and sends the estimated position information to the joint estimation unit, and the joint estimation unit estimates the precise geographical position of the user equipment by combining the pre-stored information, and updates the geographical position in time.
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