CN111366890B - Method and system for direction finding of mobile phone based on wifi - Google Patents
Method and system for direction finding of mobile phone based on wifi Download PDFInfo
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- CN111366890B CN111366890B CN201811589448.6A CN201811589448A CN111366890B CN 111366890 B CN111366890 B CN 111366890B CN 201811589448 A CN201811589448 A CN 201811589448A CN 111366890 B CN111366890 B CN 111366890B
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- 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
- G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
- G01S3/02—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using radio waves
- G01S3/14—Systems for determining direction or deviation from predetermined direction
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/0413—MIMO systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2602—Signal structure
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/06—Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
Abstract
The invention discloses a method and a system for direction finding of a mobile phone based on wifi. The method comprises the following steps: generating a wifi hotspot through a preset wireless access device, and broadcasting induction information to a preset range; the target mobile phone is induced to feed back direction finding data information to the wireless access equipment through the induction information; and monitoring direction-finding data information fed back by the target mobile phone by using an antenna array of the wireless access equipment, and calculating the direction of arrival of the target mobile phone according to an MUSIC algorithm so as to carry out direction finding on the target mobile phone. The invention induces the target mobile phone to automatically feed back the direction-finding data information to the wireless access equipment under the condition of not accessing a wifi hotspot, and monitors the direction-finding data information fed back by the target mobile phone by adopting the antenna array, so that the dependence on the wifi signal can be reduced, the MUSIC algorithm has better performance on the aspects of direction-finding positioning precision and multi-path interference elimination, and the direction-finding calculation can be effectively carried out on the target mobile phone.
Description
Technical Field
The invention relates to the technical field of mobile phone direction finding, in particular to a mobile phone direction finding method and system based on wifi.
Background
At present, wireless fidelity (wifi) has been widely used as a wireless data communication method, and there is a strong demand for using wifi signals to perform direction finding and positioning on mobile devices.
The existing wifi positioning technology is mainly divided into two positioning methods, namely a propagation model method and a position fingerprint method, and the propagation model method is more widely applied due to the fact that manpower and material resources are relatively saved.
However, the above method relies on the position information of the Access Point (AP for short) and an accurate signal transmission loss model on the path, and is poor in applicability to different scenes and poor in positioning and direction finding effects.
Disclosure of Invention
In order to solve the problems in the prior art, the embodiment of the invention provides a method and a system for direction finding of a mobile phone based on wifi. The technical scheme is as follows:
in one aspect, an embodiment of the present invention provides a wifi-based method for direction finding of a mobile phone, where the method includes:
generating a wifi hotspot through a preset wireless access device, and broadcasting induction information to a preset range;
when the target mobile phone enters a preset range, the target mobile phone is induced to feed back direction-finding data information to the wireless access equipment through the induction information;
the antenna array of the wireless access equipment is utilized to monitor the direction-finding data information fed back by the target mobile phone, and the direction of arrival of the target mobile phone is calculated according to a Multiple Signal Classification (MUSIC) algorithm so as to carry out direction finding on the target mobile phone.
In the above wifi-based direction finding method for a mobile phone according to the embodiment of the present invention, the generating a wifi hotspot through a preset wireless access device and broadcasting induction information to a preset range includes:
the method comprises the steps of generating an HS2.0 hotspot through preset wireless access equipment, and broadcasting a beacon data packet to a preset range, wherein the beacon data packet is used for inducing a target mobile phone to continuously feed back an ANQP data packet under the condition that the target mobile phone is not accessed to the hotspot.
In the wifi-based direction finding method for a mobile phone according to the embodiment of the present invention, the antenna array includes a plurality of uniform linear antennas configured based on a Multiple-Input Multiple-Output (MIMO) technology,
the method for monitoring the direction-finding data information fed back by the target mobile phone by using the antenna array of the wireless access equipment and calculating the direction of arrival of the target mobile phone according to the MUSIC algorithm so as to carry out direction finding on the target mobile phone comprises the following steps:
acquiring Orthogonal Frequency Division Multiplexing (OFDM) signals in direction-finding data information monitored by each antenna in an antenna array, and acquiring corresponding time domain sample data;
and calculating the direction of arrival of the target mobile phone relative to the antenna array by utilizing an MUSIC algorithm according to the acquired time domain sample data.
In the above wifi-based method for direction finding of a mobile phone according to an embodiment of the present invention, the obtaining of the OFDM signal in the direction finding data information monitored by each antenna in the antenna array includes:
detecting whether an OFDM signal is received through any antenna in the antenna array;
when one antenna receives OFDM signals, clock synchronization adjustment is carried out on the OFDM signals received by all the antennas in the antenna array;
and after the clocks are synchronized, confirming the OFDM signals of other antennas according to the OFDM signal acquired by one antenna.
In the above wifi-based direction finding method for a mobile phone according to the embodiment of the present invention, the method further includes:
decoding the received direction-finding data information, acquiring a Media Access Control Address (MAC Address for short) of the wireless Access equipment, and positioning the target mobile phone by combining the direction of arrival of the target mobile phone.
On the other hand, the embodiment of the invention provides a mobile phone direction finding system based on wifi, which comprises:
the wireless access equipment is used for producing wifi hotspots and broadcasting the induction information to a preset range;
the target mobile phone is used for feeding back direction-finding data information to the wireless access equipment according to the induction information when entering a preset range;
the antenna array is loaded on the wireless access equipment, connected with the wireless access equipment and used for monitoring direction-finding data information fed back by the target mobile phone;
and the wireless access equipment is used for calculating the direction of arrival of the target mobile phone according to the MUSIC algorithm so as to carry out direction finding on the target mobile phone.
In the wifi-based direction finding system for the mobile phone according to the embodiment of the present invention, the wireless access device is further configured to generate a hotspot of HS2.0, and broadcast a beacon packet to a preset range, where the beacon packet is used to induce the target mobile phone to continuously feed back the ANQP packet without accessing the hotspot.
In the wifi-based direction finding system for the mobile phone, which is provided by the embodiment of the invention, the antenna array comprises a plurality of uniform linear antennas arranged based on the MIMO technology,
the wireless access equipment is also used for acquiring OFDM signals in the direction finding data information received by each antenna in the antenna array and acquiring corresponding time domain sample data;
the wireless access equipment is also used for calculating the arrival direction of the target mobile phone relative to the antenna array according to the acquired time domain sample data and by utilizing an MUSIC algorithm.
In the above wifi-based direction finding system for a mobile phone according to the embodiment of the present invention, the wireless access device is further configured to detect whether any antenna in the antenna array receives an OFDM signal;
the wireless access equipment is also used for carrying out clock synchronization adjustment on signals received by the antenna array when one antenna receives OFDM signals;
the wireless access equipment is also used for confirming the OFDM signals of other antennas according to the OFDM signals acquired by one antenna after clock synchronization.
In the wifi-based mobile phone direction-finding system in the embodiment of the present invention, the wireless access device is further configured to decode the received direction-finding data information, obtain an MAC address of the wireless access device, and position the target mobile phone in combination with the direction of arrival of the target mobile phone.
In the wifi-based direction finding system for the mobile phone according to the embodiment of the present invention, the wireless access device supports a hot spot of HS 2.0.
The technical scheme provided by the embodiment of the invention has the following beneficial effects:
generating a wifi hotspot through a preset wireless access device, and broadcasting induction information to a preset range; when the target mobile phone enters a preset range, inducing the target mobile phone to access the wifi hotspot through the induction information, and feeding back direction-finding data information to the wireless access equipment; and monitoring direction-finding data information fed back by the target mobile phone by using an antenna array of the wireless access equipment, and calculating the direction of arrival of the target mobile phone according to an MUSIC algorithm so as to carry out direction finding on the target mobile phone. Therefore, the target mobile phone can be induced by the induction information to automatically feed back direction-finding data information to the wireless access equipment under the condition of not accessing a wifi hotspot for direction-finding use of the target mobile phone; meanwhile, the antenna array is adopted to monitor the direction-finding data information fed back by the target mobile phone, so that the dependence on wifi signals can be reduced, the MUSIC algorithm has better performance on the aspects of direction-finding positioning precision and multi-path interference elimination, and the direction-finding calculation can be effectively carried out on the target mobile phone.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a flowchart of a wifi-based direction-finding method for a mobile phone according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a wifi-based mobile phone direction-finding system according to a second embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Example one
The embodiment of the invention provides a mobile phone direction finding method based on wifi, which is suitable for direction finding of a mobile phone in a wifi environment, and referring to fig. 1, the method can comprise the following steps:
and step S11, generating wifi hot spots through preset wireless access equipment, and broadcasting induction information to a preset range.
Specifically, the step S11 can be implemented as follows:
generating an HS2.0 hotspot through preset wireless access equipment, and broadcasting a beacon data packet to a preset range, wherein the beacon data packet is used for inducing the target mobile phone to continuously feed back the ANQP data packet under the condition that the target mobile phone is not accessed to the hotspot.
In this embodiment, ANQP (Access Network Query Protocol) is an efficient Network Access Protocol based on wifi 802.11u Protocol. Hotspot2.0 (namely HS2.0) is developed by wifi alliance and wireless bandwidth alliance, aiming at realizing seamless traffic handover between cellular mobile network and wifi network when the mobile device supporting HS2.0 enters into HS2.0 coverage area, without user selection of wifi SIID and input of authentication key, to provide better bandwidth and QoS, and reduce traffic load of cellular mobile network. Hotspot2.0 adopts an IEEE 802.11u protocol to realize communication between the mobile device and the Hotspot, and supports automatic network discovery, authorization and access right assignment.
In this embodiment, a wireless network hotspot based on an 802.11a/b/g/n/u wireless local area network communication protocol is established through a wireless access device (i.e., a wireless access point), and a beacon packet (i.e., induction information) with hotspot2.0 information is broadcast to the air, so that an ANQP packet can be automatically and continuously fed back to the wireless access device for direction finding use (in a common scenario, in a case of no connection to a hotspot, the number of packets sent by a mobile phone is small and cannot meet the positioning requirement).
And step S12, when the target mobile phone enters the preset range, the target mobile phone is induced by the induction information to feed back the direction-finding data information to the wireless access equipment.
In this embodiment, the target mobile phone is a target to be direction-found by the mobile phone direction-finding method, and when entering a wifi hotspot generated by the wireless access device, the target mobile phone is induced by the induction information, and automatically feeds back an ANQP data packet (i.e., direction-finding data information) to the wireless access device without accessing the hotspot.
And step S13, monitoring direction-finding data information fed back by the target mobile phone by using the antenna array of the wireless access equipment, and calculating the direction of arrival of the target mobile phone according to the MUSIC algorithm so as to carry out direction finding on the target mobile phone.
In the present embodiment, the Direction Of Arrival (DOA) estimation is also called spectral estimation (spectral estimation) or Angle Of Arrival (Angle Of Arrival) estimation. There are many possible propagation paths and angles of arrival for a source. If several transmitters are operating simultaneously, each source forms a potential multipath component at the receiver. Therefore, it is important for the receiving antenna to estimate the arrival angles, in order to estimate which transmitter is working and the direction of the transmitter, in short, the direction of the incoming wave from the target transmitter is estimated by using the own radar; the physical principle is the principle of linear propagation of electromagnetic waves. The position of the radiation source is estimated by measuring the direction of arrival or angle of arrival of the radiation signal.
It should be noted that the MUSIC algorithm is a method based on the spatial decomposition of matrix features. Geometrically, the observation space of signal processing can be decomposed into a signal subspace and a noise subspace, which are obviously orthogonal. The signal subspace consists of the eigenvectors corresponding to the signals in the data covariance matrix received by the array, and the noise subspace consists of the eigenvectors corresponding to all the minimum eigenvalues (noise variances) in the covariance matrix. A signal spectrum function can be constructed according to the obtained noise subspace, and the incidence direction of the signal can be obtained through spectrum peak searching.
In the embodiment, the antenna array is adopted to monitor the direction-finding data information fed back by the target mobile phone, so that the dependence on wifi signals can be reduced, the MUSIC algorithm has better performance on the aspects of direction-finding positioning precision and multi-path interference elimination, and the direction-finding calculation can be effectively carried out on the target mobile phone.
Specifically, the antenna array includes a plurality of uniform linear antennas arranged based on MIMO technology. The above step S13 can be implemented as follows:
a, obtaining an OFDM signal received by each antenna in the antenna array, and obtaining corresponding time domain sample data.
In this embodiment, the MIMO technology is to use a plurality of transmitting antennas and receiving antennas at a transmitting end and a receiving end, respectively, so that signals are transmitted and received through the plurality of antennas at the transmitting end and the receiving end, thereby improving communication quality. The multi-antenna multi-transmission multi-receiving system can fully utilize space resources, realizes multi-transmission and multi-reception through a plurality of antennas, can improve the system channel capacity by times under the condition of not increasing frequency spectrum resources and antenna transmitting power, and shows obvious advantages. In this embodiment, the antenna array may be integrated with the wireless access device, and the MIMO technology is used to improve the communication quality and improve the direction finding accuracy.
OFDM (i.e., orthogonal frequency division multiplexing), the main idea is: the channel is divided into a plurality of orthogonal sub-channels, the high-speed data signal is converted into parallel low-speed sub-data streams, and the parallel low-speed sub-data streams are modulated to be transmitted on each sub-channel. The orthogonal signals can be separated by using correlation techniques at the receiving end, which can reduce mutual interference between the sub-channels. One major advantage of OFDM systems is that orthogonal subcarriers can be modulated and demodulated using a fast fourier transform (FFT/IFFT). For N-point IFFT operation, N ^2 complex multiplications need to be implemented, and the complex multiplication of the common 2-based IFFT algorithm is only (N/2) log2N, so that the operation complexity can be reduced remarkably.
In this embodiment, after acquiring the OFDM signal of each antenna in the antenna array and thus acquiring the time domain sample data of each antenna, the arrival angle of the direction finding data information sent by the target mobile phone is calculated by using the MUSIC algorithm, thereby positioning the target mobile phone.
Alternatively, the step a may be implemented as follows:
a1, detecting whether receiving OFDM signal through any antenna in the antenna array.
In this embodiment, one antenna in the antenna array is used to detect whether there is an OFDM packet in the current signal, and according to the Preamble (i.e. Preamble) in IEEE 802.11a/g ERP-OFDM PPDU, which starts with 10 short symbols, each symbol has a length of 16, a delay correlation algorithm is used to detect the data packet.
a2, when there is one antenna to receive OFDM signal, making clock synchronization adjustment to the signal received by the antenna array.
In this embodiment, the purpose of clock synchronization is to determine the starting position of the first OFDM symbol, so that the cyclic prefix is correctly removed and the samples for FFT in the symbol are extracted in the subsequent processing.
a3, after clock synchronization, confirming the OFDM signals of other antennas according to the OFDM signals acquired by one antenna.
In this embodiment, after clock synchronization, according to the starting position of the OFDM symbol of the current antenna, the OFDM symbol positions of other antennas are the same, wifi signal Preamble (i.e., Preamble) data of the antenna array is taken, and the data length of each antenna is 320 time domain sample points.
And b, calculating the direction of arrival of the target mobile phone relative to the antenna array according to the acquired time domain sample data and by utilizing an MUSIC algorithm.
The following takes wifi working band 2.4G as an example, and specifically describes how to calculate the angle of arrival through the MUSIC algorithm.
After packet detection (i.e., OFDM signal detection) and clock synchronization, the first 20us of the received signal (as shown in the direction-finding frame format) may be used for direction finding. And performing IFFT on the long and short symbols of the received signal to a time domain respectively. These symbols are then concatenated to form a sequence xp(t), D is 0,. M is the antenna number.
D mutually uncorrelated target echo signals in the space are set to be incident to receiving array elements of the antenna array, and the azimuth angles of the D mutually uncorrelated target echo signals are respectively theta1,θ2,...,θDAnd the number D of the incident signals is less than the array element number M of the antenna array. In general, the output vector of the antenna array at the receiving end is represented as:
X(t)＝AS(t)+N
where x (T) ═ x1(T), … xm (T) ] T is a superimposed signal of signals received by M antenna elements and noise. S (T) ([ s1(T), … sd (T)) ] T is the transmitted signal, and in our application scenario, there is only one target, so D ═ 1.
A(θ)＝[a(θ1),a(θ2),...a(θD)]TIs a matrix formed by the steering vectors of the antenna array, wherein a (theta) is the steering vector and is related to the arrangement mode of the antenna array.
N (T) ([ n1(T), … nm (T)) ] T is the noise vector superimposed on the signal in the surrounding environment. The covariance matrix of the antenna array output vector x (t) can be expressed as:
R＝E[XXH]＝ARSAH+σ2I
as can be seen from the foregoing analysis, D of the M eigenvalues are correlated with the target echo signal, and are respectively equal to the matrix ARSAHAll characteristic values of (a) are respectively equal to σ2The remaining M-D eigenvalue magnitudes are σ2。
The space of the antenna array element output signal is divided into signal subspaces
Noise subspace
Column vector and noise subspace of directional vector matrix A of antenna receiving array
Are orthogonal to each other, i.e.
The resulting spatial spectrum function P (θ) is then constructed as:
in the formula
Is that
Vector 2 norm.
And enabling the P (theta) to obtain the theta corresponding to the maximum point to be the required direction angle of the target, namely if D targets are incident at different direction angles, the P (theta) has D maximum points.
The following is a description of the implementation steps of the MUSIC algorithm:
1. covariance matrix for sampled data
And (6) estimating. One cycle of sampling is called a snapshot. If the number of snapshots is N, N data vectors x (N) are obtained, where N is 1, 2. Independent of each other, there are
2. Will be provided with
Carrying out characteristic value decomposition;
3. sorting the eigenvalues obtained by decomposition from large to small, and determining the number n of the minimum eigenvaluesECalculating nEMinimum eigenvalue lambdaD+1,...,λM. A noise subspace is obtained which is composed of the noise feature vectors.
4. Completing the spectrum peak search to obtain the value of space spectrum P (theta)
In the above equation, θ corresponding to the D maximum values obtained by P (θ) is the direction of the target echo signal, i.e. the estimated target azimuth.
Optionally, referring to fig. 1, the method may further include:
and step S14, decoding the received direction finding data information, acquiring the MAC address of the wireless access equipment, and positioning the target mobile phone by combining the direction of arrival of the target mobile phone.
In this embodiment, the MAC address (i.e., the MAC address), which is an address used to identify the location of the device on the network. After the direction of arrival of the target mobile phone relative to the antenna array is determined, the target mobile phone can be further positioned by combining the MAC address of the wireless access equipment.
In this embodiment, the direction-finding method for the mobile phone uses the MIMO technology and the OFDM technology in the wifi 802.11n protocol, estimates based on the MUSIC algorithm, and uses the beacon data packet to excite the target mobile phone to automatically and continuously return the ANQP data packet without accessing a hot spot, thereby implementing the positioning and direction-finding of the target mobile phone.
In the embodiment of the invention, wifi hotspots are generated through the preset wireless access equipment, and the induction information is broadcasted in the preset range; when the target mobile phone enters a preset range, the target mobile phone is induced to feed back direction-finding data information to the wireless access equipment through the induction information; and monitoring direction-finding data information fed back by the target mobile phone by using an antenna array of the wireless access equipment, and calculating the direction of arrival of the target mobile phone according to an MUSIC algorithm so as to carry out direction finding on the target mobile phone. Therefore, the target mobile phone can be induced by the induction information to automatically feed back direction-finding data information to the wireless access equipment under the condition of not accessing a wifi hotspot for direction-finding use of the target mobile phone; meanwhile, the antenna array is adopted to monitor the direction-finding data information fed back by the target mobile phone, so that the dependence on wifi signals can be reduced, the MUSIC algorithm has better performance on the aspects of direction-finding positioning precision and multi-path interference elimination, and the direction-finding calculation can be effectively carried out on the target mobile phone.
Example two
The embodiment of the present invention provides a wifi-based mobile phone direction-finding system, which executes the method described in the first embodiment, and referring to fig. 2, the system may include: wireless access equipment 100, target mobile phone 200 and antenna array 300.
And the wireless access equipment 100 is used for producing wifi hotspots and broadcasting the induction information to the preset range.
In this embodiment, a wireless network hotspot based on an 802.11a/b/g/n/u wireless local area network communication protocol is established through a wireless access device (i.e., a wireless access point), and a beacon packet (i.e., induction information) with hotspot2.0 information is broadcast to the air, so that an ANQP packet can be automatically and continuously fed back to the wireless access device for direction finding use (in a common scenario, in a case of no connection to a hotspot, the number of packets sent by a mobile phone is small and cannot meet the positioning requirement).
And the target mobile phone 200 is configured to feed back direction-finding data information to the wireless access device according to the guidance information when the target mobile phone enters the preset range.
In this embodiment, the target mobile phone is a target to be direction-found by the above-mentioned mobile phone direction finding method, and when entering into a wifi hotspot range produced by the wireless access device, the target mobile phone is induced by the induction information, and automatically feeds back an ANQP data packet (i.e. direction finding data information) to the wireless access device without accessing the hotspot.
The antenna array 300 is loaded on the wireless access device 100 and connected with the wireless access device 100, and is used for monitoring direction-finding data information fed back by the target mobile phone.
The wireless access device 100 is further configured to calculate a direction of arrival of the target cell phone according to the MUSIC algorithm, so as to perform direction finding on the target cell phone.
In the present embodiment, the Direction Of Arrival (DOA) estimation is also called spectral estimation (spectral estimation) or Angle Of Arrival (Angle Of Arrival) estimation. There are many possible propagation paths and angles of arrival for a source. If several transmitters are operating simultaneously, each source forms a potential multipath component at the receiver. Therefore, it is important for the receiving antenna to estimate the arrival angles, in order to estimate which transmitter is working and the direction of the transmitter, in short, the direction of the incoming wave from the target transmitter is estimated by using the own radar; the physical principle is the principle of linear propagation of electromagnetic waves. The position of the radiation source is estimated by measuring the direction of arrival or angle of arrival of the radiation signal.
It should be noted that the MUSIC algorithm is a method based on the spatial decomposition of matrix features. Geometrically, the observation space of signal processing can be decomposed into a signal subspace and a noise subspace, which are obviously orthogonal. The signal subspace consists of the eigenvectors corresponding to the signals in the data covariance matrix received by the array, and the noise subspace consists of the eigenvectors corresponding to all the minimum eigenvalues (noise variances) in the covariance matrix. A signal spectrum function can be constructed according to the obtained noise subspace, and the incidence direction of the signal can be obtained through spectrum peak searching.
In the embodiment, the antenna array is adopted to monitor the direction-finding data information fed back by the target mobile phone, so that the dependence on wifi signals can be reduced, the MUSIC algorithm has better performance on the aspects of direction-finding positioning precision and multi-path interference elimination, and the direction-finding calculation can be effectively carried out on the target mobile phone.
Specifically, the wireless access device 100 further has a hotspot where HS2.0 is generated, and broadcasts a beacon packet to a preset range, where the beacon packet is used to induce the target mobile phone to continuously feed back the ANQP packet without accessing the hotspot.
In this embodiment, ANQP (Access Network Query Protocol) is an efficient Network Access Protocol based on 802.11u Protocol in wifi. Hotspot2.0 (namely HS2.0) is developed by wifi alliance and wireless bandwidth alliance, aiming at realizing seamless traffic handover between cellular mobile network and wifi network when the mobile device supporting HS2.0 enters into HS2.0 coverage area, without user selection of wifi SIID and input of authentication key, to provide better bandwidth and QoS, and reduce traffic load of cellular mobile network. Hotspot2.0 adopts an IEEE 802.11u protocol to realize communication between the mobile device and the Hotspot, and supports automatic network discovery, authorization and access right assignment.
In this embodiment, a wireless network hotspot based on an 802.11a/b/g/n/u wireless local area network communication protocol is established through a wireless access device (i.e., a wireless access point), and a beacon packet (i.e., induction information) with hotspot2.0 information is broadcast to the air, so that an ANQP packet can be continuously fed back to the wireless access device automatically for direction finding use (in a common scenario, in a case of not connecting to a hotspot, the number of packets sent by a mobile phone is small, and the number of packets required for positioning cannot be reached) without accessing the hotspot by a target mobile phone.
In particular, the antenna array comprises a plurality of uniform linear antennas arranged based on MIMO technology.
The wireless access device 100 is further configured to obtain the OFDM signal received by each antenna in the antenna array, and obtain corresponding time-domain sample data.
In this embodiment, the MIMO technology is to use a plurality of transmitting antennas and receiving antennas at a transmitting end and a receiving end, respectively, so that signals are transmitted and received through the plurality of antennas at the transmitting end and the receiving end, thereby improving communication quality. The multi-antenna multi-transmission multi-receiving system can fully utilize space resources, realizes multi-transmission and multi-reception through a plurality of antennas, can improve the system channel capacity by times under the condition of not increasing frequency spectrum resources and antenna transmitting power, and shows obvious advantages. In this embodiment, the antenna array may be integrated with the wireless access device, and the MIMO technology is used to improve the communication quality and improve the direction finding accuracy.
OFDM (i.e., orthogonal frequency division multiplexing), the main idea is: the channel is divided into a plurality of orthogonal sub-channels, the high-speed data signal is converted into parallel low-speed sub-data streams, and the parallel low-speed sub-data streams are modulated to be transmitted on each sub-channel. The orthogonal signals can be separated by using correlation techniques at the receiving end, which can reduce mutual interference between the sub-channels. One major advantage of OFDM systems is that orthogonal subcarriers can be modulated and demodulated using a fast fourier transform (FFT/IFFT). For N-point IFFT operation, N ^2 complex multiplications need to be implemented, and the complex multiplication of the common 2-based IFFT algorithm is only (N/2) log2N, so that the operation complexity can be reduced remarkably.
In this embodiment, after acquiring the OFDM signal of each antenna in the antenna array and thus acquiring the time domain sample data of each antenna, the arrival angle of the direction finding data information sent by the target mobile phone is calculated by using the MUSIC algorithm, thereby positioning the target mobile phone.
The wireless access device 100 is further configured to calculate, according to the acquired time-domain sample data and by using a MUSIC algorithm, a direction of arrival of the target mobile phone with respect to the antenna array.
Further, the wireless access device 100 is further configured to detect whether the OFDM signal is received through any one of the antennas in the antenna array.
In this embodiment, one antenna in the antenna array is used to detect whether there is an OFDM packet in the current signal, and according to the Preamble (i.e. Preamble) in IEEE 802.11a/g ERP-OFDM PPDU, which starts with 10 short symbols, each symbol has a length of 16, a delay correlation algorithm is used to detect the data packet.
The wireless access device 100 is further configured to perform clock synchronization adjustment on signals received by the antenna array when there is one antenna receiving the OFDM signal.
In the present embodiment, the purpose of clock synchronization is to determine the starting position of the first OFDM symbol, so as to correctly remove the cyclic prefix and extract the samples for FFT in the symbol in the subsequent processing.
The wireless access device 100 is further configured to determine OFDM signals of other antennas according to the OFDM signal acquired by one antenna after clock synchronization.
In this embodiment, after clock synchronization, according to the starting position of the OFDM symbol of the current antenna, the OFDM symbol positions of other antennas are the same, wifi signal Preamble (i.e., Preamble) data of the antenna array is taken, and the data length of each antenna is 320 time domain sample points.
Optionally, the wireless access device 100 is further configured to decode the received direction finding data information, acquire an MAC address of the wireless access device, and locate the target mobile phone according to the direction of arrival of the target mobile phone.
In this embodiment, the MAC address (i.e., the MAC address), which is an address used to identify the location of the device on the network. After the direction of arrival of the target mobile phone relative to the antenna array is determined, the target mobile phone can be further positioned by combining the MAC address of the wireless access equipment.
In this embodiment, the direction-finding method for the mobile phone uses the MIMO technology and the OFDM technology in the wifi 802.11n protocol, estimates based on the MUSIC algorithm, and uses the beacon data packet to excite the target mobile phone to automatically and continuously return the ANQP data packet without accessing a hot spot, thereby implementing the positioning and direction-finding of the target mobile phone.
In the embodiment of the invention, wifi hotspots are generated through the preset wireless access equipment, and the induction information is broadcasted in the preset range; when the target mobile phone enters a preset range, inducing the target mobile phone to access the wifi hotspot through the induction information, and feeding back direction-finding data information to the wireless access equipment; and monitoring direction-finding data information fed back by the target mobile phone by using an antenna array of the wireless access equipment, and calculating the direction of arrival of the target mobile phone according to an MUSIC algorithm so as to carry out direction finding on the target mobile phone. Therefore, the target mobile phone can be induced by the induction information to automatically feed back direction-finding data information to the wireless access equipment under the condition of not accessing a wifi hotspot for direction-finding use of the target mobile phone; meanwhile, the antenna array is adopted to monitor the direction-finding data information fed back by the target mobile phone, so that the dependence on wifi signals can be reduced, the MUSIC algorithm has better performance on the aspects of direction-finding positioning precision and multi-path interference elimination, and the direction-finding calculation can be effectively carried out on the target mobile phone.
The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments.
It will be understood by those skilled in the art that all or part of the steps for implementing the above embodiments may be implemented by hardware, or may be implemented by a program instructing relevant hardware, where the program may be stored in a computer-readable storage medium, and the above-mentioned storage medium may be a read-only memory, a magnetic disk or an optical disk, etc.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (8)
1. A wifi-based method for direction finding of a mobile phone, the method comprising:
generating wifi hot spots through preset wireless access equipment, and broadcasting induction information to a preset range, including: generating an HS2.0 hotspot through preset wireless access equipment, and broadcasting a beacon data packet to a preset range, wherein the beacon data packet is used for inducing a target mobile phone to continuously feed back an ANQP data packet under the condition that the target mobile phone is not accessed to the hotspot;
when the target mobile phone enters a preset range, the target mobile phone is induced to feed back direction-finding data information to the wireless access equipment through the induction information;
and monitoring direction-finding data information fed back by the target mobile phone by using an antenna array of the wireless access equipment, and calculating the direction of arrival of the target mobile phone according to an MUSIC algorithm so as to carry out direction finding on the target mobile phone.
2. The method of claim 1, wherein the antenna array comprises a plurality of uniform linear antennas arranged based on MIMO technology,
the method for monitoring the direction-finding data information fed back by the target mobile phone by using the antenna array of the wireless access equipment and calculating the direction of arrival of the target mobile phone according to the MUSIC algorithm so as to carry out direction finding on the target mobile phone comprises the following steps:
acquiring OFDM signals in direction-finding data information monitored by each antenna in the antenna array, and acquiring corresponding time domain sample data;
and calculating the direction of arrival of the target mobile phone relative to the antenna array by utilizing an MUSIC algorithm according to the acquired time domain sample data.
3. The method of claim 2, wherein the obtaining the OFDM signals in the direction-finding data information heard by each antenna in the antenna array comprises:
detecting whether an OFDM signal is received through any antenna in the antenna array;
when one antenna receives OFDM signals, clock synchronization adjustment is carried out on the OFDM signals received by all the antennas in the antenna array;
and after the clocks are synchronized, confirming the OFDM signals of other antennas according to the OFDM signal acquired by one antenna.
4. The method of claim 1, further comprising:
and decoding the received direction-finding data information to acquire the MAC address of the wireless access equipment, and positioning the target mobile phone by combining the direction of arrival of the target mobile phone.
5. A wifi-based mobile phone direction-finding system, comprising:
wireless access device for produce wifi hotspot to the induced information of broadcast to predetermineeing the within range, include: generating a hotspot of HS2.0, and broadcasting a beacon data packet to a preset range, wherein the beacon data packet is used for inducing a target mobile phone to continuously feed back an ANQP data packet under the condition that the target mobile phone is not accessed to the hotspot;
the target mobile phone is used for feeding back direction-finding data information to the wireless access equipment according to the induction information when entering a preset range;
the antenna array is loaded on the wireless access equipment, connected with the wireless access equipment and used for monitoring direction-finding data information fed back by the target mobile phone;
and the wireless access equipment is used for calculating the direction of arrival of the target mobile phone according to the MUSIC algorithm so as to carry out direction finding on the target mobile phone.
6. The system of claim 5, wherein the antenna array comprises a plurality of uniform linear antennas arranged based on MIMO technology,
the wireless access equipment is also used for acquiring OFDM signals in the direction finding data information received by each antenna in the antenna array and acquiring corresponding time domain sample data;
the wireless access equipment is also used for calculating the arrival direction of the target mobile phone relative to the antenna array according to the acquired time domain sample data and by utilizing an MUSIC algorithm.
7. The system of claim 6, wherein the wireless access device is further configured to detect whether any antenna in the antenna array receives an OFDM signal;
the wireless access equipment is also used for carrying out clock synchronization adjustment on signals received by the antenna array when one antenna receives OFDM signals;
the wireless access equipment is also used for confirming the OFDM signals of other antennas according to the OFDM signals acquired by one antenna after clock synchronization.
8. The system of claim 5, wherein the wireless access device is further configured to decode the received direction-finding data message, obtain the MAC address of the wireless access device, and locate the target cell phone in combination with the direction of arrival of the target cell phone.
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