CN112815947A - Indoor positioning system and method based on terminal cluster - Google Patents
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Abstract
The invention discloses an indoor positioning system and method based on a terminal cluster, aiming at the indoor positioning system based on the terminal cluster, comprising: indoor access node TtAnd a plurality of terminals QpP is terminal number, T is node number, and at least four nodes T not on the same plane1、T2、T3And T4The node is a base station around the environment to be positioned and uses a terminal Q1Any terminal to be positioned in a plurality of terminals in the representation area, namely a terminal Q1A device with read-write function; the positioning method comprises the following steps: (S100) the node transmits information in a two-level precoding manner; (S200) terminal Q1For received data from node TtDetecting the signal of (a); (S300) to the terminal Q1And carrying out three-dimensional space position estimation. The method can provide good positioning service for a plurality of terminals simultaneously, improves the positioning efficiency of the indoor positioning system, effectively overcomes inter-cluster interference and intra-cluster interference in the terminal cluster, and improves the positioning accuracy.
Description
Technical Field
The invention relates to an indoor positioning method, in particular to an indoor positioning system and method based on a terminal cluster.
Background
With the rapid increase of data services and multimedia services, people's demands for positioning are increasing, and especially in complex indoor environments, such as airport halls, supermarkets, libraries, underground parking lots and the like, it is often necessary to determine the indoor position information of the mobile terminal or its holder, facilities and articles. Most current positioning algorithms are only researched for a wireless two-dimensional network, however, in practical application, a wireless network node is often in a three-dimensional environment, three-dimensional position information of a mobile terminal needs to be provided in the situations, and currently, researchers provide many indoor positioning solutions based on radio frequency identification.
For example, chinese patent CN201710697495.1, which uses beam scanning to realize positioning, uses multiple antenna tags, and combines beam scanning to realize indoor positioning. However, the downward inclination angle of the antenna in the vertical direction in the two-dimensional beam is fixed, and only the spatial domain resource in the horizontal direction is utilized, so that the energy convergence is not high enough, and the coverage range is limited.
The multi-user multi-input multi-output technology fully utilizes the space freedom degree provided by the multi-antenna and effectively improves the average throughput of the system in a time-frequency resource multiplexing mode. When the base station adopts a uniform linear array structure, the downward inclination angle of the wave beam is fixed, and the wave beam forming can be carried out only in a horizontal two-dimensional plane; it can distinguish users at different horizontal angles, but cannot distinguish two users at the same horizontal angle and different distances.
Chinese patent CN201811108110.4 discloses an indoor multi-user positioning method based on three-dimensional beams, which uses three-dimensional beam scanning for positioning, but this method uses a uniform scanning mode based on region, does not consider environmental physical characteristics of the scanning region, and its positioning accuracy is low.
Disclosure of Invention
The invention aims to provide an indoor positioning system and method based on a terminal cluster, which can provide good positioning service for a plurality of terminals simultaneously, improve the positioning efficiency of the indoor positioning system, effectively overcome inter-cluster interference and intra-cluster interference in the terminal cluster and improve the positioning accuracy.
In order to achieve the above object, the present invention provides an indoor positioning method based on a terminal cluster, the method aiming at an indoor positioning system based on a terminal cluster, comprising: indoor access node TtAnd a plurality of terminals QpP is terminal number, T is node number, and at least four nodes T not on the same plane1、T2、T3And T4The node is a base station around the environment to be positioned and uses a terminal Q1Any terminal to be positioned in a plurality of terminals in the representation area, namely a terminal Q1A device with read-write function; the indoor positioning method comprises the following steps:
(S100) the node transmits information in a two-stage precoding manner: any one node TtSetting the total number of terminals in the coverage area as K, and setting the node TtThe terminals in the coverage area are divided into N terminal clusters, and the number of the terminals of the q cluster is set as Kq,q∈[1,2,…,N]And is andthrough node T1,T2,T3,T4The terminals respectively perform two-stage precoding-based transmission, and the nodes T1,T2,T3,T4The transmitted information includes: id and location information of the node;
(S200) terminal Q1For received data from node TtDetecting the signal of (a);
(S300) to the terminal Q1And (3) carrying out three-dimensional space position estimation: obtaining terminal Q through RSSI distance loss model1And T1、T2、T3And T4A distance l between1、l2、l3And l4Respectively with node T1、T2、T3And T4As the center of a circle, a distance of l1、l2、l3And l4Four balls for the radius, said terminal Q1In the space area enclosed by the four balls; re-estimating with four nodes T1、T2、T3And T4Coordinate (x) of1,y1,z1)、(x2,y2,z2)、(x3,y3,z3) And (x)4,y4,z4) Triangular pyramid circumscribed sphere center coordinate (x) as vertexOuter cover,yOuter cover,zOuter cover) The intersection points of the connecting lines of the four sphere centers and the triangular pyramid external sphere center and the sphere are determined, and the total four inner intersection points G are determinedtT is 1,2,3,4, and has the coordinate of (x)gt,ygt,zgt) And calculating the weighted mass center of the four intersection points as a terminal Q1Position coordinates of (d), mutAs a weighting factor, then terminal Q1The position coordinates of (a) are:
in step (S100), the method for the node to transmit information in the two-stage precoding scheme includes:
(S110) dividing the terminal clusters based on the mahalanobis distance minimum criterion: according to any two terminals QcAnd QdOf the channel covariance matrix of (a) is determined by the mahalanobis distance d (Q) between the channel covariance matrices of (a)c,Qd) And an empirical value dSetting upDetermining the division of the terminal cluster: if d (Q)c,Qd)≤dThreshold valueThen terminal QcAnd QdDivided into a same terminal cluster for use inRepresents;
(S120) estimating precoding from the terminal cluster: for terminal clusterThe estimation is based on the channel covariance matrixTwo-stage precoding of cq;
(S130) secondary precoding transmission based on terminal clustering: node TtThe original signal S is weighted by the secondary precoding and mapped to the corresponding antenna port, and the transmitted signal is: c. Cq·s。
In step (S120), the method for estimating precoding from a terminal cluster includes:
(S121) estimating outer layer precoding: according to the maximum trace of the channel covariance matrix, the outer precoding c is obtainedq, outerThe method comprises the following steps:
in the formulas (5), (6) and (7), the upper corner mark is used for solving the conjugation transpose; tr () represents the trace of the matrix; c. CiIs a precoding codeword; w3DIs a precoding codebook;as a node TtTo the aggregate channel among all terminals in the qth cluster, where Ht,q1As a node TtChannel to 1 st terminal of qth cluster, Ht,q2As a node TtChannel to the 2 nd terminal of the qth cluster, Ht,qKqAs a node TtTo cluster q, KqA channel of each terminal;for aggregating channelsThe channel covariance matrix of (a) is determined,for aggregating channelsThe dimension(s) of (a) is,is a channel covariance matrix corresponding to the terminal cluster other than the q cluster, argmax]C represents the time when the latter expression is maximizediValue selection, which means that the code word with the maximum objective function value is selected in the codebook as the outer precoding cq, outer;
(S122) estimating inner layer precoding: setting aggregated channelsThe equivalent channel formed by the outer layer precoding of the q-th cluster terminal is as follows:using equivalent channelsTo eliminate intra-cluster interference, then:
(S123) obtaining a secondary precoding according to the outer layer precoding and the inner layer precoding, comprising:
cq=cq, outer·cq, inner (9)。
Preferably, in step (S110), dividing the terminal cluster based on the mahalanobis distance minimum criterion includes:
(S111) estimating arbitrary two terminals QcAnd QdOf the channel covariance matrix of (a) is determined by the mahalanobis distance d (Q) between the channel covariance matrices of (a)c,Qd) And an empirical value dSetting upDetermining the division of the terminal cluster: if d (Q)c,Qd)≤dThreshold valueThen terminal QcAnd QdDivided into the same terminal cluster
In the formulae (1) and (2), RcRepresents terminal QcOf the channel covariance matrix, RdRepresents terminal QdThe upper index indicates the conjugate transpose, the upper index-1 indicates the inversion, rowqIs terminal QqChannel H ofqQ is c or d;
(S112) forRepresenting clusters of terminalsCenter point Y ofc+dCorresponding channel, terminal clusterIs a virtual terminal, thenAs a node TtTo the virtual terminalAggregate channels of, andHt,cas a node TtTo terminal clusterMiddle terminal QcChannel of (1), Ht,dAs a node TtTo terminal clusterMiddle terminal QdEstimating a virtual terminalAnd QeOf the channel covariance matrix ofAnd an empirical value dSetting upDetermining the division of the terminal cluster: if it isThen the terminalAnd QeDivided into a same terminal cluster, terminal Qc、QdAnd QeBelong to the same terminal cluster;
in the formulae (3) and (4),representing virtual terminalsThe channel covariance matrix of (a); reRepresents terminal QeOf the channel covariance matrix, ReObtained by the formula (2).
Preferably, the weighting factor μtTaking the reciprocal of the maximum characteristic root of the channel covariance matrix as:
λ1as a node T1To terminal Q1Channel H of1,1The maximum characteristic root of the covariance matrix of (a) is:
λ2as a node T2To terminal Q1Channel H of2,1The maximum characteristic root of the covariance matrix of (a) is:
λ3as a node T3To terminal Q1Channel H of3,1The maximum characteristic root of the covariance matrix of (a) is:
λ4as a node T4To terminal Q1Channel H of4,1The maximum characteristic root of the covariance matrix of (a) is:
in the formula, argmax [ eig () ] represents taking the largest characteristic root in ().
Preferably, in step (S300), the terminal Q is paired1A method for performing three-dimensional spatial position estimation, comprising:
(S310) verifying four nodes T1、T2、T3And T4Are not in the same planeThe above step (1);
(S320) estimating a terminal Q using a distance loss model1To four nodes T1、T2、T3And T4A distance of l1、l2、l3And l4;
(S330) establishing a three-dimensional spherical equation set: with node T1、T2、T3And T4Coordinate (x) of1,y1,z1)、(x2,y2,z2)、(x3,y3,z3) And (x)4,y4,z4) Are the centers of the spheres and are respectively represented by1、l2、l3And l4Spherical equation for radius, is:
(S340) estimating the circumscribed spherical center coordinates of the triangular pyramid having the coordinates of the four nodes as vertexes as the decentration coordinates (x)Outer cover,yOuter cover,zOuter cover) Then, there are:
(S350) 4 inner intersection points of the connecting lines of the four sphere centers and the triangular pyramid outer sphere center and the spherical surface are obtained, the reciprocal of the maximum characteristic root of the channel covariance matrix is used as a weighting factor, and the mass center of the 4 intersection points is obtained as a terminal Q1Position coordinates of (2):
centre of sphere (x)1,y1,z1) To the heart (x)Outer cover,yOuter cover,zOuter cover) Equation of the connecting line:
centre of sphere (x)2,y2,z2) To the heart (x)Outer cover,yOuter cover,zOuter cover) Equation of the connecting line:
centre of sphere (x)3,y3,z3) To the heart (x)Outer cover,yOuter cover,zOuter cover) Equation of the connecting line:
centre of sphere (x)4,y4,z4) To the heart (x)Outer cover,yOuter cover,zOuter cover) Equation of the connecting line:
the equations (10) and (14) are solved simultaneously to obtain two intersection points g1、g2Get g1、g2Middle distance of other three (x)2,y2,z2)、(x3,y3,z3) And (x)4,y4,z4) The intersection point of the sphere centers is the inner intersection point and is marked as
The equations (11) and (15) are solved simultaneously to obtain two intersection points g3、g4Get g3、g4Middle distance of other three (x)1,y1,z1)、(x3,y3,z3) And (x)4,y4,z4) The intersection point of the sphere centers is the inner intersection point and is marked as
The equations (12) and (16) are solved simultaneously to obtain two intersection points g5、g6Get g5、g6Middle distance of other three (x)1,y1,z1)、(x2,y2,z2) And (x)4,y4,z4) The intersection point of the sphere centers is the inner intersection point and is marked as
The equations (13) and (17) are solved simultaneously to obtain two intersection points g7、g8Get g7、g8Middle distance of other three (x)1,y1,z1)、(x2,y2,z2) And (x)3,y3,z3) The intersection point of the sphere centers is the inner intersection point and is marked as
Another object of the present invention is to provide an indoor positioning system based on a terminal cluster, the indoor positioning system comprising: indoor access node TtAnd a plurality of terminals QpP is terminal number, T is node number, and at least four nodes T not on the same plane1、T2、T3And T4The node is a base station around the environment to be positioned and uses a terminal Q1Any terminal to be positioned in a plurality of terminals in the representation area, namely a terminal Q1A device with read-write function; any terminal Q to be positioned in indoor positioning system1The positioning is carried out by the method.
The indoor positioning system and method based on the terminal cluster have the following advantages:
the method of the invention is based on the terminal cluster with the minimum Mahalanobis distance, can provide good positioning service for a plurality of terminals simultaneously, and improves the positioning efficiency of the indoor positioning system. Meanwhile, inter-cluster interference and intra-cluster interference in the terminal cluster can be effectively overcome by adopting two-stage precoding, and the positioning accuracy is improved. The space sphere weighted centroid method based on the channel covariance matrix fully utilizes channel information between each node and a terminal, and is more targeted to channel environments (including topographic features, surrounding buildings and the like), so that the service quality is improved.
Drawings
Fig. 1 is a flowchart of an indoor three-dimensional positioning method based on a terminal cluster according to the present invention.
Fig. 2 is a flowchart of a method for transmitting information by a node in a two-stage precoding manner according to the present invention.
Fig. 3 is a flowchart of a method for selecting a terminal in a terminal cluster according to the present invention.
Fig. 4 is a positioning block diagram of the method of the present invention.
Fig. 5 is a schematic diagram of terminal clusters partitioned based on mahalanobis distance minimum criterion according to the present invention.
Fig. 6 is a schematic diagram of terminal clustering-based two-stage precoding transmission.
Fig. 7 is a schematic diagram of a spatial sphere weighted centroid method based on a channel covariance matrix.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
An indoor positioning method based on a terminal cluster is shown in fig. 4, which is a positioning block diagram of the method of the present invention, and the indoor positioning system based on the terminal cluster aimed by the method comprises: indoor access node TtAnd a plurality of terminals QpP is terminal number, T is node number, and at least four nodes T not on the same plane1、T2、T3And T4The node is a base station around the environment to be positioned and uses a terminal Q1Any terminal to be positioned in a plurality of terminals in the representation area, namely a terminal Q1The device has read-write function. As shown in fig. 1, a flowchart of an indoor three-dimensional positioning method based on a terminal cluster according to the present invention is shown, and the positioning method includes:
(S100) the node transmits information in a two-stage precoding manner: any one node TtSetting the total number of terminals in the coverage area as K, and setting the node TtThe terminals in the coverage area are divided into N terminal clusters, and the number of the terminals of the q cluster is set as Kq,q∈[1,2,…,N]And is andthrough node T1,T2,T3,T4The terminals respectively perform two-stage precoding-based transmission, and the nodes T1,T2,T3,T4The sent information comprises the id, the position information and the like of the node;
(S200) terminal Q1For received data from node TtThe signal of (2) is detected: in actual detection, assume terminal Q1Receiving T1、T2、T3And T4Separating the signals of the four nodes from the signals of the four nodes, and then processing the signals;
(S300) to the terminal Q1And (3) carrying out three-dimensional space position estimation: obtaining terminal Q through RSSI distance loss model1And each node Tt(t is 1,2,3,4) distance lt(T is 1,2,3,4), and each node T is a node Tt(t is 1,2,3,4) as the center of circle and a distance lt(t is 1,2,3,4) four spheres are obtained as radii, and the actual terminal Q is obtained1In the space area enclosed by the four balls; re-estimating with four nodes T1、T2、T3And T4Coordinate (x) of1,y1,z1)、(x2,y2,z2)、(x3,y3,z3) And (x)4,y4,z4) Triangular pyramid circumscribed sphere center coordinate (x) as vertexOuter cover,yOuter cover,zOuter cover) (ii) a Then, the intersection points of the connecting lines of the four sphere centers and the triangular pyramid external sphere center and the sphere are calculated, and the total four inner side intersection points GtT is 1,2,3,4, and has the coordinate of (x)gt,ygt,zgt) And calculating the weighted mass center of the four intersection points as a terminal Q1Position coordinates of (d), mutAs a weighting factor, then terminal Q1The position coordinates of (a) are:
in step (S100), the method for transmitting information by a node in a two-stage precoding manner, referring to fig. 2, includes:
(S110) terminal clusters are divided based on the mahalanobis distance minimum criterion
FIG. 5 is a schematic diagram of a terminal cluster divided based on the Mahalanobis distance minimum criterion, T1The nodes are represented by other marks, the terminals in different clusters are distinguished by different marks, the cross is the center of a terminal cluster or the position of a virtual terminal, a dotted line represents a connecting line between the terminal and the center point of the cluster, the total number K of the terminals in the graph is 10, the number Q of the terminal clusters is 3, the number of the terminals in the 1 st cluster, the number of the terminals in the 2 nd cluster and the number of the terminals in the 3 rd cluster are respectively 3, 5 and 2, and the number is respectively marked as the terminal clusterAnd
by terminal clusterFor an example, a method for selecting a terminal in a terminal cluster is described, with reference to fig. 3, specifically as follows:
(S111) terminal Q1Of the channel covariance matrix R1And terminal Q2Of the channel covariance matrix R2Mahalanobis distance d (Q) therebetween1,Q2) The method comprises the following steps:
in the formulas (1) and (2), the upper corner mark indicates the conjugation transpose, the upper corner mark-1 indicates the inversion, and row indicatesqIs terminal QqChannel H ofqQ is 1 or 2.
Judging the Mahalanobis distance d (Q)1,Q2) And dThreshold valueTo thereby determine whether to put the terminal Q on1And terminal Q2Divided into the same terminal clusterdThreshold valueFor set empirical values (e.g. taken as 0.3 units): when d (Q)1,Q2)≤dThreshold valueThen form terminal cluster
(S112) forRepresenting clusters of terminalsCenter point Y of1+2Corresponding channel, visible terminal clusterIs a virtual terminal and is a terminal with a plurality of terminals,as a node T1To the virtual terminalAggregate channels of, andH1,11as a node T1To terminal clusterMiddle terminal Q1Channel of (1), H1,12As a node T1To terminal clusterMiddle terminal Q2Channel of (2), then virtual terminalOf the channel covariance matrix R1+2And terminal Q3Of the channel covariance matrix R3Mahalanobis distance between, is:
in the formula (4), row1+2As a virtual terminalOf aggregated channelsDimension, row of3Is terminal Q3Channel H of3Dimension (d) of (a).
Judging the Mahalanobis distanceAnd dThreshold valueThe size of (2): when in useThen form terminal cluster
(S120) estimating precoding from a cluster of terminals
And aiming at the terminal cluster, estimating two-stage precoding based on a channel covariance matrix, wherein the outer-layer precoding is used for eliminating the interference among clusters, and the inner-layer precoding is used for eliminating the interference in the clusters. The method for estimating precoding according to the terminal cluster comprises the following steps:
(S121) estimating outer layer precoding: according to the maximum trace of the channel covariance matrix, the outer precoding c is obtainedq, outerThe method comprises the following steps:
in the formula, the upper corner mark is used for solving conjugate transpose, tr () represents the trace of solving matrix, ciFor precoding code words, W3DIn order to be a precoding codebook, a precoding codebook is selected,as a node TtAggregated channels between all terminals up to the qth cluster, where Ht,q1As a node TtChannel to 1 st terminal of qth cluster, Ht,q2As a node TtChannel to qth cluster 2 nd terminal, …, Ht,qKqAs a node TtTo cluster q, KqA channel of each terminal;for aggregating channelsThe channel covariance matrix of (a) is determined,for aggregating channelsThe dimension(s) of (a) is,channel covariance matrices corresponding to other terminal clusters except the qth cluster,c represents the time when the latter expression is maximizediValue selection, which means that the code word with the maximum objective function value is selected in the codebook as the outer precoding cq, outer。
(S122) estimating inner layer precoding
Setting aggregated channelsThe equivalent channel formed by the outer layer precoding of the q-th cluster terminal is as follows:using equivalent channelsTo eliminate intra-cluster interference, then:
(S123) obtaining a secondary precoding according to the outer layer precoding and the inner layer precoding, comprising:
cq=cq, outer·cq, inner (9)
In the same way, the corresponding terminal cluster is obtainedAndthe precoding of (c) is: c. C2And c3。
(S130) Secondary Pre-coded Transmission based on terminal clustering
FIG. 6 is a schematic diagram of two-stage precoding transmission based on terminal clustering, for a terminal clusterRespectively adopting two-stage precoding mode to transmit information, i.e. adopting correspondent precoding c1、c2And c3In particular node T1The original signal S is weighted by the secondary precoding and mapped to the corresponding antenna port, i.e. the transmitted signal is: c. C1·s,c2·s,……,c3S, in which only terminal clusters are given to avoid aliasingEmission legend of (1).
(S300) the terminal performs three-dimensional spatial position estimation
As shown in fig. 7, a schematic diagram of a spatial sphere weighted centroid method based on a channel covariance matrix, a method for a terminal to perform three-dimensional spatial position estimation includes:
(S310) verifying four nodes TtThe coordinates of (t ═ 1,2,3,4) are not on the same plane
Determining a unique triangular pyramid by the four coordinates, and further determining a unique mobile terminal position coordinate; in fact, four nodes T1、T2、T3And T4Are pre-arranged and not on the same plane.
(S320) estimating a terminal Q using a distance loss model1Distance to each node
Let terminal Q1Has coordinates of (x, y, z), four nodes T1、T2、T3And T4Respectively is (x)1,y1,z1)、(x2,y2,z2)、(x3,y3,z3) And (x)4,y4,z4) Then, the terminal Q is estimated by using the distance loss model1To each node T1、T2、T3And T4Are each a distance of1、l2、l3And l4;
(S330) establishing a three-dimensional spherical equation set
Three-dimensional space with nodes T1、T2、T3And T4Coordinate (x) of1,y1,z1)、(x2,y2,z2)、(x3,y3,z3) And (x)4,y4,z4) Are the centers of the spheres and are respectively represented by1、l2、l3And l4Spherical equation for radius, is:
theoretically, the terminal Q to be positioned is obtained according to the estimation1And four nodes T1、T2、T3And T4Is a Euclidean distance l1、l2、l3And l4And solving to obtain a terminal Q to be positioned1The solution of the above equation system can be regarded as solving the intersection point of 4 spherical surfaces in space. In practical applications, the four spheres may not intersect at exactly one point due to measurement errors. For this purpose, a weighted centroid algorithm based on the intersection of the connecting line of the sphere center and the outer center and the sphere surface is used for estimation.
(S340) estimating coordinates of the center of the circumscribed sphere of the triangular pyramid having the coordinates of the four nodes as vertexes
Estimate with four nodes T1、T2、T3And T4Coordinate (x) of1,y1,z1)、(x2,y2,z2)、(x3,y3,z3) And (x)4,y4,z4) The circumscribed spherical center coordinate of a triangular pyramid having a vertex, i.e. the outer center coordinate (x)Outer cover,yOuter cover,zOuter cover) Then, there are:
(S350) determining the intersection point of the connecting line of the four sphere centers and the triangular pyramid external sphere center and the sphere4 inner intersection points are totally calculated, the reciprocal of the maximum characteristic root of the channel covariance matrix is used as a weighting factor, and the centroid of the 4 intersection points is obtained as a terminal Q1The position coordinates of (a).
Centre of sphere (x)1,y1,z1) To the heart (x)Outer cover,yOuter cover,zOuter cover) Equation of the connecting line:
centre of sphere (x)2,y2,z2) To the heart (x)Outer cover,yOuter cover,zOuter cover) Equation of the connecting line:
centre of sphere (x)3,y3,z3) To the heart (x)Outer cover,yOuter cover,zOuter cover) Equation of the connecting line:
centre of sphere (x)4,y4,z4) To the heart (x)Outer cover,yOuter cover,zOuter cover) Equation of the connecting line:
the equations (10) and (14) are solved simultaneously to obtain two intersection points g1、g2Get g1、g2Middle distance of other three (x)2,y2,z2)、(x3,y3,z3) And (x)4,y4,z4) The intersection point of the sphere centers is the inner intersection point and is marked as
The equations (11) and (15) are solved simultaneously to obtain two intersection points g3、g4Get g3、g4Middle distance of other three (x)1,y1,z1)、(x3,y3,z3) And (x)4,y4,z4) The intersection point of the sphere centers is the inner intersection point and is marked as
The equations (12) and (16) are solved simultaneously to obtain two intersection points g5、g6Get g5、g6Middle distance of other three (x)1,y1,z1)、(x2,y2,z2) And (x)4,y4,z4) The intersection point of the sphere centers is the inner intersection point and is marked as
The equations (13) and (17) are solved simultaneously to obtain two intersection points g7、g8Get g7、g8Middle distance of other three (x)1,y1,z1)、(x2,y2,z2) And (x)3,y3,z3) The intersection point of the sphere centers is the inner intersection point and is marked as
The three-dimensional weighted centroid method based on the space sphere is adopted for estimation, and the weighting factor mu1,μ2,μ3,μ4Taking the reciprocal of the maximum characteristic root of the channel covariance matrix as:
λ1as a node T1To terminal Q1Channel H of1,1The maximum characteristic root of the covariance matrix of (a) is:
λ2as a node T2To terminal Q1Channel H of2,1The maximum characteristic root of the covariance matrix of (a) is:
λ3as a node T3To terminal Q1Channel H of3,1The maximum characteristic root of the covariance matrix of (a) is:
λ4as a node T4To terminal Q1Channel H of4,1The maximum characteristic root of the covariance matrix of (a) is:
in the formula, argmax [ eig () ] represents taking the largest characteristic root in ().
Then terminal Q1The estimated value of the three-dimensional coordinates of (a) is:
while the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.
Claims (5)
1. An indoor positioning method based on a terminal cluster is characterized in that the indoor positioning system based on the terminal cluster aimed by the method comprises the following steps: indoor access node TtAnd a plurality of terminals QpP is terminal number, T is node number, and at least four nodes T not on the same plane1、T2、T3And T4The node is a base station around the environment to be positioned and uses a terminal Q1Any terminal to be positioned in a plurality of terminals in the representation area, namely a terminal Q1A device with read-write function; the indoor positioning method comprises the following steps:
(S100) the node transmits information in a two-stage precoding manner: any one node TtSetting the total number of terminals in the coverage area as K, and setting the node TtThe terminals in the coverage area are divided into N terminal clusters, and the number of the terminals of the q cluster is set as Kq,q∈[1,2,…,N]And is andthrough node T1,T2,T3,T4The terminals respectively perform two-stage precoding-based transmission, and the nodes T1,T2,T3,T4The transmitted information includes: id and location information of the node;
(S200) terminal Q1For received data from node TtDetecting the signal of (a);
(S300) to the terminal Q1And (3) carrying out three-dimensional space position estimation: obtaining terminal Q through RSSI distance loss model1And T1、T2、T3And T4A distance l between1、l2、l3And l4Respectively with node T1、T2、T3And T4As the center of a circle, a distance of l1、l2、l3And l4Four balls for the radius, said terminal Q1In the space area enclosed by the four balls; re-estimating with four nodes T1、T2、T3And T4Coordinate (x) of1,y1,z1)、(x2,y2,z2)、(x3,y3,z3) And (x)4,y4,z4) Triangular pyramid circumscribed sphere center coordinate (x) as vertexOuter cover,yOuter cover,zOuter cover) The intersection points of the connecting lines of the four sphere centers and the triangular pyramid external sphere center and the sphere are determined, and the total four inner intersection points G are determinedtT is 1,2,3,4, and has the coordinate of (x)gt,ygt,zgt) And calculating the weighted mass center of the four intersection points as a terminal Q1Position coordinates of (d), mutAs a weighting factor, then terminal Q1The position coordinates of (a) are:
in step (S100), the method for the node to transmit information in the two-stage precoding scheme includes:
(S110) dividing the terminal clusters based on the mahalanobis distance minimum criterion: according to any two terminals QcAnd QdOf the channel covariance matrix of (a) is determined by the mahalanobis distance d (Q) between the channel covariance matrices of (a)c,Qd) And an empirical value dSetting upDetermining the division of the terminal cluster: if d (Q)c,Qd)≤dThreshold valueThen terminal QcAnd QdDivided into a same terminal cluster for use inRepresents;
(S120) estimating precoding from the terminal cluster: for terminal clusterEstimating two-stage precoding c based on channel covariance matrixq;
(S130) secondary precoding transmission based on terminal clustering: node TtThe original signal S is weighted by the secondary precoding and mapped to the corresponding antenna port, and the transmitted signal is: c. Cq·s;
In step (S120), the method for estimating precoding from a terminal cluster includes:
(S121) estimating outer layer precoding: according to the maximum trace of the channel covariance matrix, the outer precoding c is obtainedqAnd, in addition, is:
in the formulas (5), (6) and (7), the upper corner mark is used for solving the conjugation transpose; tr () represents the trace of the matrix; c. CiIs a precoding codeword; w3DIs a precoding codebook;as a node TtTo the aggregate channel among all terminals in the qth cluster, where Ht,q1As a node TtChannel to 1 st terminal of qth cluster, Ht,q2As a node TtChannel to the 2 nd terminal of the qth cluster, Ht,qKqAs a node TtTo cluster q, KqA channel of each terminal;for aggregating channelsThe channel covariance matrix of (a) is determined,for aggregating channelsThe dimension(s) of (a) is,is a channel covariance matrix corresponding to the terminal cluster other than the q cluster, argmax]C represents the time when the latter expression is maximizediValue selection, which means that the code word with the maximum objective function value is selected in the codebook as the outer precoding cqAnd, externally;
(S122) estimating inner layer precoding: setting aggregated channelsThe equivalent channel formed by the outer layer precoding of the q-th cluster terminal is as follows:using equivalent channelsTo eliminate intra-cluster interference, then:
(S123) obtaining a secondary precoding according to the outer layer precoding and the inner layer precoding, comprising:
cq=cqouter, cqInner (9).
2. The indoor positioning method based on terminal cluster as claimed in claim 1, wherein in the step (S110), dividing the terminal cluster based on mahalanobis distance minimum criterion comprises:
(S111) estimating arbitrary two terminals QcAnd QdOf the channel covariance matrix of (a) is determined by the mahalanobis distance d (Q) between the channel covariance matrices of (a)c,Qd) And an empirical value dSetting upDetermining the division of the terminal cluster: if d (Q)c,Qd)≤dThreshold valueThen terminal QcAnd QdDivided into the same terminal cluster
In the formulae (1) and (2), RcRepresents terminal QcOf the channel covariance matrix, RdRepresents terminal QdThe upper index indicates the conjugate transpose, the upper index-1 indicates the inversion, rowqIs terminal QqChannel H ofqQ is c or d;
(S112) forRepresenting clusters of terminalsCenter point Y ofc+dCorresponding channel, terminal clusterIs a virtual terminal, thenAs a node TtTo the virtual terminalAggregate channels of, andHt,cas a node TtTo terminal clusterMiddle terminal QcChannel of (1), Ht,dAs a node TtTo terminal clusterMiddle terminal QdEstimating a virtual terminalAnd QeOf the channel covariance matrix ofAnd an empirical value dSetting upDetermining the division of the terminal cluster: if it isThen the terminalAnd QeDivided into a same terminal cluster, terminal Qc、QdAnd QeBelong to the same terminal cluster;
3. The method of claim 1, wherein the weighting factor μ istTaking the reciprocal of the maximum characteristic root of the channel covariance matrix as:
λ1as a node T1To terminal Q1Channel H of1,1The maximum characteristic root of the covariance matrix of (a) is:
λ2as a node T2To terminal Q1Channel H of2,1The maximum characteristic root of the covariance matrix of (a) is:
λ3as a node T3To terminal Q1Channel H of3,1The maximum characteristic root of the covariance matrix of (a) is:
λ4as a node T4To terminal Q1Channel H of4,1The maximum characteristic root of the covariance matrix of (a) is:
in the formula, argmax [ eig () ] represents taking the largest characteristic root in ().
4. The method for indoor positioning based on terminal cluster according to any one of claims 1-3, characterized in that in step (S300), Q is applied to terminal1A method for performing three-dimensional spatial position estimation, comprising:
(S310) verifying four nodes T1、T2、T3And T4Are not on the same plane;
(S320) estimating a terminal Q using a distance loss model1To four nodes T1、T2、T3And T4A distance of l1、l2、l3And l4;
(S330) establishing a three-dimensional spherical equation set: with node T1、T2、T3And T4Coordinate (x) of1,y1,z1)、(x2,y2,z2)、(x3,y3,z3) And (x)4,y4,z4) Are the centers of the spheres and are respectively represented by1、l2、l3And l4Spherical equation for radius, is:
(S340) estimating the circumscribed spherical center coordinates of the triangular pyramid having the coordinates of the four nodes as vertexes as the decentration coordinates (x)Outer cover,yOuter cover,zOuter cover) Then, there are:
(S350) 4 inner intersection points of the connecting lines of the four sphere centers and the triangular pyramid outer sphere center and the spherical surface are obtained, the reciprocal of the maximum characteristic root of the channel covariance matrix is used as a weighting factor, and the mass center of the 4 intersection points is obtained as a terminal Q1Position coordinates of (2):
centre of sphere (x)1,y1,z1) To the heart (x)Outer cover,yOuter cover,zOuter cover) Equation of the connecting line:
centre of sphere (x)2,y2,z2) To the heart (x)Outer cover,yOuter cover,zOuter cover) Equation of the connecting line:
centre of sphere (x)3,y3,z3) To the heart (x)Outer cover,yOuter cover,zOuter cover) Equation of the connecting line:
centre of sphere (x)4,y4,z4) To the heart (x)Outer cover,yOuter cover,zOuter cover) Equation of the connecting line:
the equations (10) and (14) are solved simultaneously to obtain two intersection points g1、g2Get g1、g2Middle distance of other three (x)2,y2,z2)、(x3,y3,z3) And (x)4,y4,z4) The intersection point of the sphere centers is the inner intersection point and is marked as
The equations (11) and (15) are solved simultaneously to obtain two intersection points g3、g4Get g3、g4Middle distance of other three (x)1,y1,z1)、(x3,y3,z3) And (x)4,y4,z4) The intersection point of the sphere centers is the inner intersection point and is marked as
The equations (12) and (16) are solved simultaneously to obtain two intersection points g5、g6Get g5、g6Middle distance of other three (x)1,y1,z1)、(x2,y2,z2) And (x)4,y4,z4) The intersection point of the sphere centers is the inner intersection point and is marked as
5. An indoor positioning system based on a terminal cluster, the indoor positioning system comprising: indoor access node TtAnd a plurality of terminals QpP is terminal number, T is node number, and at least four nodes T not on the same plane1、T2、T3And T4The node is a base station around the environment to be positioned and uses a terminal Q1Any terminal to be positioned in a plurality of terminals in the representation area, namely a terminal Q1A device with read-write function; any terminal Q to be positioned in indoor positioning system1Localization is performed by the method according to any of claims 1-4.
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