CN113068127B - Positioning method of NB-IoT terminal - Google Patents
Positioning method of NB-IoT terminal Download PDFInfo
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Abstract
The invention provides a positioning method of an NB-IoT terminal, which solves the problem of low positioning precision of the NB-IoT terminal in the prior art and comprises the following steps: establishing an NB-IoT terminal positioning system; the NB-IoT application terminal sends a positioning request to an NB-IoT positioning server; the NB-IoT positioning server respectively interacts positioning data and positioning configuration information with the NB-IoT terminal and the NB-IoT base station, estimates the coordinates of the NB-IoT terminal, confirms whether the propagation path between each NB-IoT base station participating in positioning and the NB-IoT terminal is a line-of-sight propagation path or a non-line-of-sight propagation path, and selects the most appropriate reference base station; and finally, jointly referring to the plane coordinates of the base station and the estimated coordinates of the NB-IoT terminal, and calculating the final coordinates of the NB-IoT terminal. The invention greatly improves the positioning precision of the NB-IoT terminal under the existing configuration of the NB-IoT.
Description
Technical Field
The invention relates to the technical field of communication of the Internet of things, in particular to a positioning method of an NB-IoT terminal.
Background
The application of narrowband Internet of Things (NB-IoT) in location tracking and positioning is very wide, and many commercial applications and public services rely on location information of NB-IoT terminals. The outdoor equipment generally adopts a GPS positioning system, but the NB-IoT terminal mostly works indoors, and the GPS signal is too fast to be used for positioning calculation of the NB-IoT terminal indoors due to signal fading. The 3GPP protocol defines a related NB-IoT terminal location technology, and the location principle is to obtain NPRS characteristics including Signal strength (RSSI), Signal Arrival Time (TOA), and Signal Arrival Angle (AOA) through interacting Narrowband location Reference signals (NPRS) between the NB-IoT terminal and the NB-IoT base station according to a plurality of NB-IoT base stations whose Reference coordinate positions are already established and known, and obtain a sending and receiving Time Difference (TDOA) based on the TOA, and the NB-IoT location requirement can be realized by studying corresponding algorithms through the above Signal characteristics.
In the prior art, there are several methods for positioning an NB-IoT terminal: the positioning algorithm based on the received signal strength RSSI is based on signal transmission loss, namely, the calculation is carried out after the transmission power and the received power are measured, the positioning algorithm does not need to install extra equipment on nodes, the realization is simpler, but the positioning accuracy is lower, the reliability is poorer, the positioning algorithm cannot be applied to all working environments, the RSSI value is greatly influenced by various obstacles in the propagation process, and the RSSI positioning algorithm can only be used as a positioning auxiliary method; the positioning algorithm based on the signal arrival angle AOA senses the arrival direction of a signal sent by terminal equipment through a base station, calculates the relative position or angle between a receiving terminal and the base station, and calculates the position of the terminal to be positioned by utilizing a triangulation method or other methods, but the algorithm needs a special antenna array to measure the signal arrival angle, and the special antenna array has higher cost, is not suitable for the requirement of low-cost construction of the Internet of things, and increases the investment budget; the TOA/TDOA positioning algorithm is a method for positioning by using time difference, the positioning accuracy depends on the signal resolution error of the signal propagation time, the NB-IoT system standard sampling rate is 1.92MHz, the time resolution is 520ns, the transmission corresponding distance resolution is 156 meters, and the positioning accuracy is still not high.
Chinese patent CN111343584A published in 26.6.2020 provides a method for positioning NB-loT terminals and a server. The method comprises the following steps: a server receives a positioning request sent by an NB-loT terminal which does not have a satellite positioning function or cannot have the satellite positioning function, wherein the positioning request carries an identifier of a cell where the NB-loT terminal is located; the server inquires a longitude and latitude coordinate database of the cell according to the identification of the cell carried in the positioning request to obtain longitude and latitude coordinates corresponding to the identification of the cell, wherein the longitude and latitude coordinate database of the cell is obtained by the server according to the longitude and latitude coordinates which are obtained by at least one terminal with a satellite positioning function based on the satellite positioning function and are sent at different moments; and the server sends a positioning response to the NB-loT terminal, the positioning response carries the longitude and latitude coordinates corresponding to the cell identifier, so that the positioning accuracy of the NB-loT terminal is improved, but the longitude and latitude coordinates of the cell where the NB-loT terminal is located are directly used as the coordinates of the NB-loT terminal, and the positioning accuracy is low.
Disclosure of Invention
The invention provides a positioning method of an NB-IoT terminal, aiming at overcoming the defect of low positioning accuracy of the prior art on the NB-IoT terminal, which can improve the positioning accuracy of the NB-IoT terminal under the existing configuration of the NB-IoT.
In order to solve the technical problems and achieve the technical effects, the technical scheme of the invention is as follows:
the invention provides a positioning method of an NB-IoT terminal, which comprises the following steps:
s1: establishing an NB-IoT terminal positioning system, wherein the system comprises n NB-IoT base stations, an NB-IoT terminal, an NB-IoT positioning server and an NB-IoT application terminal;
s2: the NB-IoT application terminal sends an NB-IoT terminal positioning request to an NB-IoT positioning server;
s3: the NB-IoT positioning server sends a positioning capability request to an NB-IoT terminal and confirms the positioning capability of the NB-IoT terminal;
s4: the NB-IoT positioning server sends a positioning data request to the NB-IoT terminal after confirming the positioning capability of the NB-IoT terminal; after the NB-IoT terminal receives the positioning data request, the positioning data is returned to the NB-IoT positioning server;
s5: after the NB-IoT positioning server receives the positioning data, the NB-IoT positioning server sends a positioning configuration information request to an NB-IoT base station; after receiving the positioning configuration information request, the NB-IoT base station returns the positioning configuration information to an NB-IoT positioning server;
s6: the NB-IoT positioning server estimates the coordinates of the NB-IoT terminal according to the received positioning data and the positioning configuration information to obtain the estimated coordinates of the NB-IoT terminal;
s7: the NB-IoT positioning server confirms whether the propagation path between each NB-IoT base station participating in positioning and the NB-IoT terminal is a line-of-sight propagation path or a non-line-of-sight propagation path based on the positioning configuration information and the estimated coordinates of the NB-IoT terminal;
s8: the NB-IoT positioning server selects a reference base station according to the propagation path between the NB-IoT base station and the NB-IoT terminal, and confirms the plane coordinate of the reference base station;
s9: and the NB-IoT positioning server takes the plane coordinates of the reference base station as reference coordinates, combines the estimated coordinates of the NB-IoT terminal, calculates the final coordinates of the NB-IoT terminal, and sends the final coordinates to the NB-IoT application terminal to complete the positioning of the NB-IoT terminal.
Preferably, in step S3, the specific method for the NB-IoT positioning server to send the positioning capability request to the NB-IoT terminal to confirm the positioning capability thereof is as follows: after an NB-IoT positioning server sends a positioning capability request to an NB-IoT terminal, the NB-IoT terminal returns a positioning capability response to the NB-IoT positioning server.
Preferably, after the NB-IoT terminal receives the positioning data request in step S4, the method further includes:
s4.1: the NB-IoT terminal sends NPRS positioning signals to n NB-IoT base stations, wherein n is larger than or equal to 3;
s4.2: the NB-IoT base station reports NPRS positioning signals and records communication time T i And signal strength RSSI i Then, sending a return signal to the NB-IoT terminal; wherein T is i Indicating the communication time of the NB-IoT terminal for sending the NPRS positioning signal to the ith NB-IoT base station, RSSI i Signal strength representing NPRS positioning signals sent by the NB-IoT terminal to the ith NB-IoT base station, i ═ 1, 2, …, n;
s4.3: after the NB-IoT terminal receives the return signal, the NPRS positioning signal sending and receiving time difference Tdoa is calculated i (ii) a Wherein Tdoa i The transmission and reception time difference of the NB-IoT terminal to transmit the NPRS positioning signal to the ith NB-IoT base station is represented, i is 1, 2, …, n;
s4.4: the NB-IoT terminal calculates the obtained sending and receiving time difference Tdoa i Transmitted as positioning data to an NB-IoT positioning server.
Preferably, in S5, the positioning configuration information includes the number of the NB-IoT base station, the cell number, the frequency point number, and the GPS coordinate.
Preferably, in S6, when the NB-IoT positioning server estimates the coordinates of the NB-IoT terminal according to the positioning configuration information, it needs to convert the NB-IoT base station GPS coordinates in the positioning configuration information into plane coordinates. The process of estimating the coordinates of the NB-IoT terminal is based on the distance between the NB-IoT terminal and the NB-IoT base station, which is necessary to translate the NB-IoT base station GPS coordinates to planar coordinates.
Preferably, the specific method for converting the plane coordinates is as follows:
carrying out Gaussian projection on the GPS coordinates of the NB-IoT base station by taking a reference ellipsoid of WGS-84 as a reference, and unifying the GPS coordinates into a Beijing 54 coordinate system, a Xian 80 coordinate system or a local arbitrary coordinate system through forced coordinate conversion, such as similarity transformation, affine transformation, complete quadratic polynomial transformation and the like to obtain the plane coordinates of the NB-IoT base station.
Preferably, in S6, a specific method for obtaining the estimated coordinates of the NB-IoT terminal is:
let the estimated coordinates of the NB-IoT terminals be (x) 0 ，y 0 ) The plane coordinate of the ith NB-IoT base station is (x) i ，y i ) The planar coordinate of the jth NB-IoT base station is (x) j ，y j ) The NPRS positioning signals are transmitted to the ith NB-IoT base station and the jth NB-IoT base station by the NB-IoT terminal with the transmission and reception time difference of Tdoa ij Then NB-IoT terminal sends NPRS positioning signal to ith NB-IoT base station and jth NB-IoT base station with propagation distance difference delta d ij ：
Δd ij ＝c*Tdoa ij
Wherein c represents a radio wave propagation speed; calculated by the above formula (x) 0 ，y 0 ) I.e. the estimated coordinates of the NB-IoT terminal.
Preferably, in S7, determining whether the propagation path between each NB-IoT base station and the NB-IoT terminal is a line-of-sight propagation path or a non-line-of-sight propagation path by using a least square method, specifically including:
let the planar coordinate of the ith NB-IoT base station be (x) i ，y i ) The estimated coordinates of the NB-IoT terminal are (x) 0 ，y 0 ) Then the distance from the NB-IoT terminal to the ith NB-IoT base station is:
wherein c represents the propagation velocity of radio waves, T i Representing the communication time of the NB-IoT terminal for sending the NPRS positioning signal to the ith NB-IoT base station;
coordinate (x) of NB-IoT terminal by adopting least square method 0 ，y 0 ) Performing error estimation to obtain least square optimization value min (L) of NB-IoT terminal coordinates n {x 0 ，y 0 })：
For n NB-IoT base stations, excluding any one NB-IoT base station, the remaining (n-1) NB-IoT base stations again use least squares to coordinate (x) NB-IoT terminals 0 ，y 0 ) Performing error estimation to obtain least square optimization value min (L) of NB-IoT terminal coordinates excluding one NB-IoT base station n-1 {x 0 ，y 0 })：
Mixing min (L) n-1 {x 0 ，y 0 }) and min (L) n {x 0 ，y 0 }) if min (L) n-1 {x 0 ，y 0 })＜min(L n {x 0 ，y 0 }) confirming that the excluded NB-IoT base station and the NB-IoT terminal are the line-of-sight propagation path, otherwise confirming that the excluded NB-IoT base station and the NB-IoT terminal are the non-line-of-sight propagation path;
and respectively excluding each NB-IoT base station by using the method, and confirming whether the propagation path between each NB-IoT base station and each NB-IoT terminal is a line-of-sight propagation path or a non-line-of-sight propagation path.
Since the NB-IoT terminal receives the NPRS positioning signals returned from the plurality of NB-IoT base stations, the positioning signal reception time difference error is affected by the propagation environment, and there may be a line-of-sight propagation path and a non-line-of-sight propagation path, and it is necessary to distinguish the line-of-sight propagation path from the non-line-of-sight propagation path.
Preferably, in S8, the specific method for selecting the reference base station is as follows:
if the propagation path between the NB-IoT base station and the NB-IoT terminal has a line-of-sight propagation path, selecting the NB-IoT base station with the propagation path corresponding to the line-of-sight propagation path as a reference base station;
if the propagation path between each NB-IoT base station and each NB-IoT terminal is a non-line-of-sight propagation path, calculating the weight of each NB-IoT base station by using a weighting method, and selecting the NB-IoT base station with the largest weight as a reference base station, namely:
NB-IoT terminal RSSI i The sending and receiving time difference Tdoa is obtained by multiplying the numerical values sequenced from large to small by a first weight i And (3) according to the numerical value, the NB-IoT base station with the largest weight value after the two items of addition are selected as a reference base station by multiplying the second weight value in the sequence from small to large:
max(α 1 *RSSI i +α 2 *Tdoa i )
wherein alpha is 1 Is a first weight, α 2 Is the second weight.
Under the condition of the line-of-sight propagation path, the positioning accuracy of the CHAN algorithm is high, so that an NB-IoT base station corresponding to the line-of-sight propagation path is selected as a reference base station; and when the line-of-sight propagation path does not exist, the NB-IoT base station with the largest weight value is selected as the reference base station by an RSSI and TDOA weighting method, so that the positioning accuracy is improved.
Preferably, in S9, the CHAN algorithm is used to calculate the final coordinates of the NB-IoT terminal, and the specific method is as follows:
let the plane coordinates of the reference base station be the reference coordinates (x) k ，y k ) Combining estimated coordinates (x) of NB-IoT terminals 0 ，y 0 ) And the plane coordinates (x) of the ith NB-IoT base station i ，y i ) Calculating the distance difference delta d between the NB-IoT terminal and the ith NB-IoT base station and the reference base station ik ：
Wherein d is i Representing the distance of the NB-IoT terminal from the ith NB-IoT base station, d k Indicating the distance from the NB-IoT terminal to the reference base station, i ≠ k, which is simplified as follows:
wherein x is ik Is the difference between the abscissa of the ith NB-IoT base station and the abscissa of the reference base station, x ik ＝x i -x k ；y ik Is the difference between the ordinate of the ith NB-IoT base station and the ordinate of the reference base station, y ik ＝y i -y k ；
Setting auxiliary variables
Then there is a matrix D ═ a × h, where a and h are both determinants,
the residual function of matrix D ═ A × h is L i (x i ，y i ) (x) when the absolute value of the modulus of the residual function vector is minimum is calculated by the least square method 0 ，y 0 ) Is taken as (x) * ，y * ) As final coordinates of NB-IoT terminal:
(x * ，y * )＝argmin(L i (x i ，y i ) T L i (x i ，y i ))＝argmin((D-A*h) T (D-A*h))
wherein argmin (x) is a function for obtaining the value of a variable when the target function is the minimum value, L i (x i ，y i ) T Is the residual function L i (x i ，y i ) The transpose function of (1).
Compared with the prior art, the technical scheme of the invention has the beneficial effects that:
according to the invention, by establishing an NB-IoT terminal positioning system, an NB-IoT application terminal sends an NB-IoT terminal positioning request to an NB-IoT positioning server; the NB-IoT positioning server firstly estimates the coordinates of the NB-IoT terminal and then determines whether the propagation path between each NB-IoT base station participating in positioning and the NB-IoT terminal is a line-of-sight propagation path or a non-line-of-sight propagation path; under the condition of different propagation paths, selecting reference base stations by different methods, ensuring that the most appropriate reference base station is selected under the condition of different propagation paths, and ensuring that the positioning accuracy is improved; and finally, jointly referring to the coordinates of the base station and the estimated coordinates of the NB-IoT terminal, and calculating the final coordinates of the NB-IoT terminal. The invention is based on the existing configuration of NB-IoT, and can greatly improve the positioning precision of the NB-IoT terminal without additionally adding hardware equipment.
Drawings
Fig. 1 is a flowchart of a positioning method of an NB-IoT terminal according to embodiment 1;
fig. 2 is an information flow diagram of the positioning method of the NB-IoT terminal according to embodiment 1.
Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the patent;
for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product;
it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
Example 1
The present embodiment provides a positioning method of an NB-IoT terminal, as shown in fig. 1 and 2, the method includes the following steps:
s1: establishing an NB-IoT terminal positioning system, wherein the system comprises n NB-IoT base stations, an NB-IoT terminal, an NB-IoT positioning server and an NB-IoT application terminal;
s2: the NB-IoT application terminal sends an NB-IoT terminal positioning request to an NB-IoT positioning server;
s3: the NB-IoT positioning server sends a positioning capability request to an NB-IoT terminal and confirms the positioning capability of the NB-IoT;
s4: the NB-IoT positioning server sends a positioning data request to the NB-IoT terminal after confirming the positioning capability of the NB-IoT terminal; after the NB-IoT terminal receives the positioning data request, the positioning data is returned to the NB-IoT positioning server;
s5: after the NB-IoT positioning server receives the positioning data, the NB-IoT positioning server sends a positioning configuration information request to an NB-IoT base station; after receiving the positioning configuration information request, the NB-IoT base station returns the positioning configuration information to an NB-IoT positioning server;
s6: the NB-IoT positioning server estimates the coordinates of the NB-IoT terminal according to the received positioning data and the positioning configuration information to obtain the estimated coordinates of the NB-IoT terminal;
s7: the NB-IoT positioning server confirms whether the propagation path between each NB-IoT base station participating in positioning and the NB-IoT terminal is a line-of-sight propagation path or a non-line-of-sight propagation path based on the positioning configuration information and the estimated coordinates of the NB-IoT terminal;
s8: the NB-IoT positioning server selects a reference base station according to the propagation path between the NB-IoT base station and the NB-IoT terminal, and confirms the plane coordinates of the reference base station;
s9: and the NB-IoT positioning server takes the plane coordinates of the reference base station as reference coordinates, combines the estimated coordinates of the NB-IoT terminal, calculates the final coordinates of the NB-IoT terminal, and sends the final coordinates to the NB-IoT application terminal to complete the positioning of the NB-IoT terminal.
The NB-IoT base station is a cellular unit in mobile communication, completes NB-IoT terminal communication and management work, and has the coverage capability of 164 dB. The NB-IoT terminal is an NB-IoT module deployed on the equipment to be positioned, communicates with the NB-IoT base station, and can send service data and positioning data information to the NB-IoT base station. The NB-IoT positioning server can perform positioning algorithm processing on the NB-IoT terminal according to positioning instruction data between the NB-IoT base station and the NB-IoT terminal; the NB-IoT positioning server can respond to the operation of positioning the NB-IoT terminal by the NB-IoT application.
Step S3, the specific method for the NB-IoT positioning server to send the positioning capability request to the NB-IoT terminal to confirm the positioning capability thereof is as follows: after an NB-IoT positioning server sends a positioning capability request to an NB-IoT terminal, the NB-IoT terminal returns a positioning capability response to the NB-IoT positioning server.
Step S4, after the NB-IoT terminal receives the positioning data request, the method further includes:
s4.1: the NB-IoT terminal sends NPRS positioning signals to n NB-IoT base stations, wherein n is larger than or equal to 3;
s4.2: the NB-IoT base station reports NPRS positioning signals and records communication time T i And signal strength RSSI i Then, sending a return signal to the NB-IoT terminal; wherein T is i Indicating the communication time of the NB-IoT terminal to send the NPRS positioning signal to the ith NB-IoT base station, RSSI i Signal strength representing NPRS positioning signals sent by the NB-IoT terminal to the ith NB-IoT base station, i ═ 1, 2, …, n;
s4.3: after the NB-IoT terminal receives the return signal, the NPRS positioning signal sending and receiving time difference Tdoa is calculated i (ii) a Wherein Tdoa i The transmission and reception time difference of the NB-IoT terminal to transmit the NPRS positioning signal to the ith NB-IoT base station is represented, i is 1, 2, …, n;
s4.4: the NB-IoT terminal calculates the obtained sending and receiving time difference Tdoa i Transmitted as positioning data to the NB-IoT positioning server.
In order to improve the positioning accuracy of the NB-IoT terminal, the 3GPP defines a positioning narrowband reference signal NPRS for reference signal time difference measurement in the NB-IoT protocol specification, wherein the NPRS is a reference signal specially used for NB-IoT base stations to perform signal measurement on the terminal. In order to reduce interference as much as possible, the positioning sub-frame data does not contain user data, but only a small number of control signals.
In S5, the positioning configuration information includes the number of the NB-IoT base station, the cell number, the frequency point number, and the GPS coordinates.
In S6, when the NB-IoT positioning server estimates the coordinates of the NB-IoT terminal according to the positioning configuration information, it needs to convert the GPS coordinates of the NB-IoT base station in the positioning configuration information into planar coordinates. The process of estimating the coordinates of the NB-IoT terminal is based on the distance between the NB-IoT terminal and the NB-IoT base station, which is necessary to translate the NB-IoT base station GPS coordinates to planar coordinates.
The specific method for converting the plane coordinates comprises the following steps:
carrying out Gaussian projection on the GPS coordinates of the NB-IoT base station by taking a reference ellipsoid of WGS-84 as a reference, and unifying the GPS coordinates into a Beijing 54 coordinate system, a Xian 80 coordinate system or a local arbitrary coordinate system through forced coordinate conversion, such as similarity transformation, affine transformation, complete quadratic polynomial transformation and the like to obtain the plane coordinates of the NB-IoT base station.
In S6, the specific method for obtaining the estimated coordinates of the NB-IoT terminal is as follows:
let the estimated coordinates of the NB-IoT terminals be (x) 0 ，y 0 ) The plane coordinate of the ith NB-IoT base station is (x) i ，y i ) The planar coordinate of the jth NB-IoT base station is (x) j ，y j ) The NPRS positioning signals are transmitted to the ith NB-IoT base station and the jth NB-IoT base station by the NB-IoT terminal with the transmission and reception time difference of Tdoa ij Then NB-IoT terminal sends NPRS positioning signal to ith NB-IoT base station and jth NB-IoT base station with propagation distance difference delta d ij ：
Δd ij ＝c*Tdoa ij
Wherein c represents a radio wave propagation speed; calculated by the above formula (x) 0 ，y 0 ) I.e. the estimated coordinates of the NB-IoT terminal.
In S7, it is determined whether the propagation path between each NB-IoT base station and the NB-IoT terminal is a line-of-sight propagation path or a non-line-of-sight propagation path by using a least square method, which includes the following specific steps:
let the planar coordinate of the ith NB-IoT base station be (x) i ，y i ) The estimated coordinates of the NB-IoT terminal are (x) 0 ，y 0 ) And the distance from the NB-IoT terminal to the ith NB-IoT base station is as follows:
wherein c represents the propagation velocity of radio waves, T i Representing the communication time of the NB-IoT terminal for sending the NPRS positioning signal to the ith NB-IoT base station;
coordinate (x) of NB-IoT terminal by adopting least square method 0 ，y 0 ) Performing error estimation to obtain least square optimization value min (L) of NB-IoT terminal coordinates n {x 0 ，y 0 })：
For n NB-IoT base stations, excluding any one NB-IoT base station, the remaining (n-1) NB-IoT base stations again use least squares to coordinate (x) NB-IoT terminals 0 ，y 0 ) Performing error estimation to obtain least square optimization value min (L) of NB-IoT terminal coordinates excluding one NB-IoT base station n-1 {x 0 ，y 0 })：
Mixing min (L) n-1 {x 0 ，y 0 }) and min (L) n {x 0 ，y 0 }) if min (L) n-1 {x 0 ，y 0 })＜min(L n {x 0 ，y 0 }) confirming that the excluded NB-IoT base station and the NB-IoT terminal are the line-of-sight propagation path, otherwise confirming that the excluded NB-IoT base station and the NB-IoT terminal are the non-line-of-sight propagation path;
the method is used for respectively excluding each NB-IoT base station and confirming whether the propagation path between each NB-IoT base station and the NB-IoT terminal is a line-of-sight propagation path or a non-line-of-sight propagation path.
Since the NB-IoT terminal receives the NPRS positioning signals returned from the plurality of NB-IoT base stations, the positioning signal reception time difference error is affected by the propagation environment, and there may be a line-of-sight propagation path and a non-line-of-sight propagation path, and it is necessary to distinguish the line-of-sight propagation path from the non-line-of-sight propagation path.
In S8, the specific method for selecting the reference base station is as follows:
if the propagation path between the NB-IoT base station and the NB-IoT terminal has a line-of-sight propagation path, selecting the NB-IoT base station corresponding to the propagation path as the line-of-sight propagation path as a reference base station;
if the propagation paths between each NB-IoT base station and the NB-IoT terminal are non-line-of-sight propagation paths, calculating the weight of each NB-IoT base station by using a weighting method, and selecting the NB-IoT base station with the largest weight as a reference base station, namely:
NB-IoT terminal RSSI i The values are sequenced from large to small and then multiplied by a first weight to send and receive the time difference Tdoa i And (3) according to the numerical value, the NB-IoT base station with the largest weight value after the two items of addition are selected as a reference base station by multiplying the second weight value in the sequence from small to large:
max(α 1 *RSSI i +α 2 *Tdoa i )
wherein alpha is 1 Is a first weight, α 2 Is the second weight. In the present embodiment, α 1 Is taken to be 0.35, alpha 2 Is 0.65.
Under the condition of the line-of-sight propagation path, the positioning accuracy of the CHAN algorithm is high, so that an NB-IoT base station corresponding to the line-of-sight propagation path is selected as a reference base station; and when the line-of-sight propagation path does not exist, the NB-IoT base station with the largest weight value is selected as the reference base station by an RSSI and TDOA weighting method, so that the positioning accuracy is improved.
For an NB-IoT terminal to be positioned, the NB-IoT terminal may be considered stationary and the distance between the NB-IoT terminal and different NB-IoT base stations is unchanged during the signal flow interaction time with the NB-IoT positioning server. It can be considered that, the closer to the NB-IoT terminal, the base station, the greater the RSSI value of the received NB-IoT terminal signal, that is, the greater the RSSI received by the NB-IoT base station, the closer to the NB-IoT terminal, the greater the probability that the NB-IoT base station is, and the NB-IoT base station is located at the position with the smaller radius of the NB-IoT terminal area.
In S9, the final coordinates of the NB-IoT terminal are calculated using the CHAN algorithm, and the specific method includes:
let the plane coordinates of the reference base station be the reference coordinates (x) k ，y k ) Combining estimated coordinates (x) of NB-IoT terminals 0 ，y 0 ) And the plane coordinates (x) of the ith NB-IoT base station i ，y i ) Calculating the distance difference delta d between the NB-IoT terminal and the ith NB-IoT base station and the reference base station ik ：
Wherein d is i Represents the distance of NB-IoT terminal to ith NB-IoT base station, d k Indicating the distance from the NB-IoT terminal to the reference base station, i ≠ k, which is simplified as follows:
wherein x is ik Is the difference between the abscissa of the ith NB-IoT base station and the abscissa of the reference base station, x ik ＝x i -x k ；y ik Is the difference of the ith NB-IoT base station ordinate and the reference base station ordinate, y ik ＝y i -y k ；
Setting auxiliary variables
Then there is a matrix D ═ a × h, where a and h are both determinants,
the residual function of matrix D ═ A × h is L i (x i ，y i ) (x) when the absolute value of the modulus of the residual function vector is minimum is calculated by the least square method 0 ，y 0 ) Is taken as (x) * ，y * ) As final coordinates of NB-IoT terminal:
(x * ，y * )＝argmin(L i (x i ，y i ) T L i (x i ，y i ))＝argmin((D-A*h) T (D-A*h))
wherein argmin (x) is a function for obtaining the value of a variable when the target function is the minimum value, L i (x i ，y i ) T Is the residual function L i (x i ，y i ) Is a transpose function of (a).
The advantages of this embodiment are:
1. in the embodiment, the RSSI and the differentiated propagation paths are adopted for auxiliary positioning, the calculation process is relatively simple, the positioning accuracy is high, and the requirement of 50-100 m positioning accuracy can be met;
2. according to the embodiment, the positioning accuracy is improved under the existing NB-IoT configuration, additional hardware equipment is not needed, the engineering practicability is higher, the universality is high, and the large-scale delivery of the Internet of things equipment is facilitated;
3, improving a CHAN algorithm when calculating the final coordinate of the NB-IoT terminal, and distinguishing the conditions of a line-of-sight propagation path and a non-line-of-sight propagation path; when the propagation path between each NB-IoT base station and each NB-IoT terminal is a non-line-of-sight propagation path, the planar coordinate of the NB-IoT base station with the largest weight is obtained by an RSSI (received signal strength indicator) and TDOA (time difference of arrival) weighting method and is used as a reference base station, and the positioning coordinate of the terminal is obtained by optimal solution calculation by using a combined positioning method and a least square method, so that the positioning accuracy is improved.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (9)
1. A method for positioning NB-IoT terminals, the method comprising the steps of:
s1: establishing an NB-IoT terminal positioning system, wherein the system comprises n NB-IoT base stations, an NB-IoT terminal, an NB-IoT positioning server and an NB-IoT application terminal;
s2: the NB-IoT application terminal sends an NB-IoT terminal positioning request to an NB-IoT positioning server;
s3: the NB-IoT positioning server sends a positioning capability request to the NB-IoT terminal and confirms the positioning capability of the NB-IoT terminal;
s4: after confirming the positioning capability of the NB-IoT terminal, the NB-IoT positioning server sends a positioning data request to the NB-IoT terminal; after the NB-IoT terminal receives the positioning data request, the positioning data is returned to the NB-IoT positioning server;
s5: after the NB-IoT positioning server receives the positioning data, the NB-IoT positioning server sends a positioning configuration information request to an NB-IoT base station; after receiving the positioning configuration information request, the NB-IoT base station returns the positioning configuration information to an NB-IoT positioning server;
s6: the NB-IoT positioning server estimates the coordinates of the NB-IoT terminal according to the received positioning data and the positioning configuration information to obtain the estimated coordinates of the NB-IoT terminal;
s7: the NB-IoT positioning server confirms whether the propagation path between each NB-IoT base station participating in positioning and the NB-IoT terminal is a line-of-sight propagation path or a non-line-of-sight propagation path based on the positioning configuration information and the estimated coordinates of the NB-IoT terminal;
s8: the NB-IoT positioning server selects a reference base station according to the propagation path between the NB-IoT base station and the NB-IoT terminal, and confirms the plane coordinates of the reference base station;
the specific method for selecting the reference base station comprises the following steps:
if the propagation path between the NB-IoT base station and the NB-IoT terminal has a line-of-sight propagation path, selecting the NB-IoT base station with the propagation path corresponding to the line-of-sight propagation path as a reference base station;
if the propagation path between each NB-IoT base station and each NB-IoT terminal is a non-line-of-sight propagation path, calculating the weight of each NB-IoT base station by using a weighting method, and selecting the NB-IoT base station with the largest weight as a reference base station, namely:
NB-IoT terminal RSSI i The sending and receiving time difference Tdoa is obtained by multiplying the numerical values sequenced from large to small by a first weight i Sorting according to numerical value from small to largeMultiplying the second weight number, and selecting the NB-IoT base station with the maximum weight value after the two items of addition as a reference base station:
max(α 1 *RSSI i +α 2 *Tdoa i )
wherein alpha is 1 Is a first weight, α 2 Is a second weight; RSSI i Indicating the Signal Strength, Tdoa, of the NPRS positioning signals sent by the NB-IoT terminal to the ith NB-IoT base station i The transmission and reception time difference of the NB-IoT terminal to transmit the NPRS positioning signal to the ith NB-IoT base station is represented, i is 1, 2, …, n;
s9: and the NB-IoT positioning server takes the plane coordinates of the reference base station as reference coordinates, combines the estimated coordinates of the NB-IoT terminal, calculates the final coordinates of the NB-IoT terminal, and sends the final coordinates to the NB-IoT application terminal to complete the positioning of the NB-IoT terminal.
2. The NB-IoT terminal positioning method according to claim 1, wherein the specific method for the NB-IoT positioning server to send the positioning capability request to the NB-IoT terminal to confirm the positioning capability thereof in step S3 is as follows: after an NB-IoT positioning server sends a positioning capability request to an NB-IoT terminal, the NB-IoT terminal returns a positioning capability response to the NB-IoT positioning server.
3. The NB-IoT terminal positioning method according to claim 2, wherein after the NB-IoT terminal receives the positioning data request in step S4, the method further comprises:
s4.1: the NB-IoT terminal sends NPRS positioning signals to n NB-IoT base stations, wherein n is larger than or equal to 3;
s4.2: the NB-IoT base station reports NPRS positioning signals and records communication time T i And signal strength RSSI i Then, sending a return signal to the NB-IoT terminal; wherein T is i Indicating the communication time of the NB-IoT terminal to send the NPRS positioning signal to the ith NB-IoT base station, RSSI i Signal strength representing NPRS positioning signals transmitted by the NB-IoT terminal to the ith NB-IoT base station, i ═ 1, 2, …, n;
s4.3: after the NB-IoT terminal receives the return signalCalculating the NPRS positioning signal sending and receiving time difference Tdoa i (ii) a Wherein Tdoa i The transmission and reception time difference of the NB-IoT terminal to transmit the NPRS positioning signal to the ith NB-IoT base station is represented, i is 1, 2, …, n;
s4.4: the NB-IoT terminal calculates the obtained sending and receiving time difference Tdoa i Transmitted as positioning data to the NB-IoT positioning server.
4. The NB-IoT terminal positioning method according to claim 3, wherein in S5, the positioning configuration information comprises NB-IoT base station number, cell number, frequency point number and GPS coordinates.
5. The NB-IoT terminal positioning method in the S6, wherein, when the NB-IoT positioning server estimates the coordinates of the NB-IoT terminal according to the positioning configuration information, the NB-IoT base station GPS coordinates in the positioning configuration information need to be converted into plane coordinates.
6. The NB-IoT terminal positioning method according to claim 5, wherein the specific method for converting the plane coordinates is:
and performing Gaussian projection on the GPS coordinates of the NB-IoT base station by taking a reference ellipsoid of WGS-84 as a reference, and forcibly converting and unifying the GPS coordinates into a Beijing 54 coordinate system, a Xian 80 coordinate system or a local arbitrary coordinate system to obtain the plane coordinates of the NB-IoT base station.
7. The NB-IoT terminal positioning method of claim 6, wherein in S6, the specific method for obtaining the estimated coordinates of the NB-IoT terminal is as follows:
let the estimated coordinates of the NB-IoT terminals be (x) 0 ，y 0 ) The plane coordinate of the ith NB-IoT base station is (x) i ，y i ) The planar coordinate of the jth NB-IoT base station is (x) j ，y j ) The NPRS positioning signals are transmitted to the ith NB-IoT base station and the jth NB-IoT base station by the NB-IoT terminal with the difference of the transmission and reception time Tdoa ij Then NB-IoT terminal sends NPRS positioning signal to ith NB-The propagation distance difference between the IoT base station and the jth NB-IoT base station is delta d ij ：
Wherein c represents a radio wave propagation speed; calculated by the above formula (x) 0 ，y 0 ) I.e. the estimated coordinates of the NB-IoT terminal.
8. The NB-IoT terminal positioning method according to claim 7, wherein in S7, determining whether the propagation path between each NB-IoT base station and the NB-IoT terminal is a line-of-sight propagation path or a non-line-of-sight propagation path by using a least square method comprises:
let the planar coordinate of the ith NB-IoT base station be (x) i ，y i ) The estimated coordinates of NB-IoT terminal is (x) 0 ，y 0 ) Distance d from NB-IoT terminal to ith NB-IoT base station i Comprises the following steps:
d i ＝c*T i
wherein c represents the propagation velocity of radio waves, T i Representing the communication time of the NB-IoT terminal for sending the NPRS positioning signal to the ith NB-IoT base station;
coordinate (x) of NB-IoT terminal by adopting least square method 0 ，y 0 ) Performing error estimation to obtain least square optimization value min (L) of NB-IoT terminal coordinates n {x 0 ，y 0 })：
For n NB-IoT base stations, excluding any one NB-IoT base station, the remaining (n-1) NB-IoT base stations again use least squares to coordinate (x) NB-IoT terminals 0 ，y 0 ) Performing error estimation to obtain least square optimization value min (L) of NB-IoT terminal coordinates excluding one NB-IoT base station n-1 {x 0 ，y 0 })：
Will min (L) n-1 {x 0 ，y 0 }) and min (L) n {x 0 ，y 0 }) of the two samples, if min (L) n-1 {x 0 ，y 0 })＜min(L n {x 0 ，y 0 }) determining that the excluded NB-IoT base station and NB-IoT terminal are in a line-of-sight propagation path, otherwise determining that the excluded NB-IoT base station and the NB-IoT terminal are not in the line-of-sight propagation path;
and respectively excluding each NB-IoT base station by using the method, and confirming whether the propagation path between each NB-IoT base station and each NB-IoT terminal is a line-of-sight propagation path or a non-line-of-sight propagation path.
9. The NB-IoT terminal positioning method according to claim 8, wherein in S9, the CHAN algorithm is used to calculate final coordinates of the NB-IoT terminal, and the specific method is as follows:
let the plane coordinates of the reference base station be the reference coordinates (x) k ，y k ) Combining estimated coordinates (x) of NB-IoT terminals 0 ，y 0 ) And the plane coordinates (x) of the ith NB-IoT base station i ，y i ) Calculating the distance difference delta d between the NB-IoT terminal and the ith NB-IoT base station and the reference base station ik ：
Wherein d is i Represents the distance of NB-IoT terminal to ith NB-IoT base station, d k Indicating the distance from the NB-IoT terminal to the reference base station, i ≠ k, which is simplified as follows:
wherein x is ik For the i-th NB-IoT base station abscissa and the reference base station abscissaDifference, x ik ＝x i -x k ；y ik Is the difference between the ordinate of the ith NB-IoT base station and the ordinate of the reference base station, y ik ＝y i -y k ；
Setting auxiliary variable
Then there is a matrix D ═ a × h, where a and h are both determinants,
the residual function of matrix D ═ A × h is L i (x i ，y i ) (x) when the absolute value of the modulus of the residual function vector is minimum is calculated by the least square method 0 ，y 0 ) Is taken as (x) * ，y * ) As final coordinates of NB-IoT terminal:
(x * ，y * )＝argmin(L i (x i ，y i ) T L i (x i ，y i ))
wherein, argmin is a function of variable value when the objective function is minimum, L i (x i ，y i ) T Is the residual function L i (x i ，y i ) The transpose function of (1).
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