CN115913408B

CN115913408B - Antenna phase error correction method, device, base station and storage medium

Info

Publication number: CN115913408B
Application number: CN202310015302.5A
Authority: CN
Inventors: 潘孟冠; 齐望东; 刘鹏; 黄永明; 刘升恒; 郑旺; 李晓东
Original assignee: Network Communication and Security Zijinshan Laboratory
Current assignee: Network Communication and Security Zijinshan Laboratory
Priority date: 2023-01-06
Filing date: 2023-01-06
Publication date: 2023-05-23
Anticipated expiration: 2043-01-06
Also published as: CN115913408A

Abstract

The application relates to an antenna phase error correction method, an antenna phase error correction device, a base station and a storage medium. The method comprises the following steps: acquiring positioning signals of the same terminal at different positions, and acquiring a frequency domain response matrix of a wireless channel according to the positioning signals; obtaining a path fading coefficient of a direct path in the positioning signal according to the frequency domain response matrix; obtaining phase differences among antenna array elements according to path fading coefficients of direct paths; and obtaining an antenna phase error estimated value according to the phase difference among the antenna array elements, and realizing antenna phase error correction according to the antenna phase error estimated value. The method can be applied to a multipath environment, avoids system deployment in a darkroom, and has lower correction cost and shorter time consumption, and the real response of the antenna in the current environment can be obtained due to the fact that the antenna phase error measurement and estimation are realized on site after the deployment is completed, so that the correction precision and the array direction finding precision are improved.

Description

Antenna phase error correction method, device, base station and storage medium

Technical Field

The present disclosure relates to the field of wireless communications technologies, and in particular, to a method and apparatus for correcting an antenna phase error, a base station, and a storage medium.

Background

Along with the rapid development of the industrial Internet, the Internet of things and the Internet of vehicles, high-precision positioning becomes an indispensable key support service for mobile terminals such as intelligent robots, unmanned vehicles and the like. When the terminal is positioned, the positioning precision is required to be improved according to the measured parameters, the positioning error is reduced, and the positioning error is corrected.

In the conventional art, for active correction of antenna phase errors in a positioning system, angle dependent phase errors are considered. However, when measuring the phase curve, the influence of multipath signals is not considered, so that when calculating, the phase curve needs to be measured in a non-reflective microwave darkroom or in a hollow outdoor environment, the cost is high, time and labor are wasted, and the practicability is low.

Disclosure of Invention

In view of the foregoing, it is desirable to provide an antenna phase error correction method, apparatus, base station, computer-readable storage medium, and computer program product that can be implemented based on multipath signals.

In a first aspect, the present application provides a method for antenna phase error correction. The method comprises the following steps:

acquiring positioning signals of the same terminal at different positions, and acquiring a frequency domain response matrix of a wireless channel according to the positioning signals;

Obtaining a path fading coefficient of a direct path in the positioning signal according to the frequency domain response matrix;

obtaining phase differences among antenna array elements according to path fading coefficients of direct paths;

and obtaining an antenna phase error estimated value according to the phase difference among the antenna array elements, and realizing antenna phase error correction according to the antenna phase error estimated value.

In one embodiment, obtaining a path fading coefficient of a direct path in a positioning signal according to a frequency domain response matrix includes:

and determining the number of paths in the positioning signal according to the frequency domain response matrix, determining the direct paths in all paths of the positioning signal, and obtaining the path fading coefficients of the direct paths. In one embodiment, determining the number of paths in the positioning signal according to the frequency domain response matrix, determining the direct paths in all paths of the positioning signal, and obtaining the path fading coefficient of the direct paths includes:

based on the frequency domain response matrix, combining the path propagation delay and the path fading coefficients of all paths to construct a log likelihood function;

and solving the log-likelihood function to obtain the path fading coefficient of each path.

In one embodiment, the resolving the log likelihood function to obtain a path fading coefficient of each path includes:

And carrying out iterative computation on the log likelihood function by adopting an expected maximization algorithm until the difference between the results of two adjacent iterative computation is smaller than a set value, thereby obtaining a path fading coefficient.

In one embodiment, determining the number of paths in the positioning signal according to the frequency domain response matrix, determining the direct paths in all paths of the positioning signal, and obtaining the path fading coefficient of the direct paths includes:

solving the log likelihood function to obtain path propagation delay of each path;

and determining the direct paths in all paths of the positioning signal according to the path propagation delay.

In one embodiment, obtaining the phase difference between the antenna elements according to the path fading coefficient of the direct path includes:

according to the path fading coefficient of the direct path, combining an antenna array structure, compensating phase rotation caused by path difference among antenna array elements, and obtaining an updated path fading coefficient of the direct path;

extracting the phase of the updated direct path fading coefficient;

and obtaining the phase difference among the antenna array elements according to the phase in the updated direct path fading coefficient.

In one embodiment, obtaining an antenna phase error estimation value according to a phase difference between antenna array elements, and implementing antenna phase error correction according to the antenna phase error estimation value includes:

Acquiring phase differences among a plurality of antenna array elements through acquiring positioning signals for a plurality of times;

obtaining an antenna phase error estimated value according to the phase difference among a plurality of antenna array elements;

and determining a phase error function through the phase difference estimated value among the antenna array elements, and realizing antenna phase error correction according to the phase error function.

In a second aspect, the present application further provides an antenna phase error correction device. The device comprises:

the acquisition unit is used for acquiring positioning signals of the same terminal at different positions and acquiring a frequency domain response matrix of the wireless channel according to the positioning signals;

the computing unit is used for obtaining a path fading coefficient of a direct path in the positioning signal according to the frequency domain response matrix;

the determining unit is used for obtaining the phase difference between the antenna array elements according to the path fading coefficient of the direct path;

and the correction unit is used for obtaining an antenna phase error estimated value according to the phase difference among the antenna array elements and realizing antenna phase error correction according to the antenna phase error estimated value.

In a third aspect, the present application also provides a computer device. The computer device comprises a memory and a processor, the memory stores a computer program, and the processor executes the computer program to realize the following steps:

In a fourth aspect, the present application also provides a computer-readable storage medium. The computer readable storage medium having stored thereon a computer program which, when executed by a processor, performs the steps of:

In a fifth aspect, the present application also provides a computer program product. The computer program product comprising a computer program which, when executed by a processor, performs the steps of:

The antenna phase error correction method, the device, the base station, the storage medium and the computer program product send positioning signals to the base station at different terminal positions through terminals with known positions, and process the received mixed signals of all paths of different positions including direct paths and reflected paths at the base station to obtain a frequency domain response matrix of a wireless channel; obtaining a path fading coefficient of the direct path extracted from the positioning signal according to the frequency domain response matrix; obtaining phase differences among antenna array elements according to path fading coefficients of direct paths; and obtaining an antenna phase error estimated value according to the phase difference among the antenna array elements, and realizing antenna phase error correction according to the antenna phase error estimated value. Compared with the traditional method for measuring the phase error curve of the active experiment in the microwave darkroom, the method can be applied to the multipath environment to realize the accurate estimation of the phase error of the antenna by acquiring the path fading coefficient of the direct path. According to the method, the antenna phase error measurement and estimation are realized on site after deployment is completed, so that errors introduced in the deployment process can be taken into consideration, the obtained error wireless can reflect the real response of the antenna in the current environment, and the correction precision of the antenna phase error and the array direction finding precision are improved.

Drawings

FIG. 1 is a diagram of an application environment of an antenna phase error correction method according to one embodiment;

FIG. 2 is a flow chart of a method of antenna phase error correction in one embodiment;

FIG. 3 is a schematic diagram of a positioning system configuration in one embodiment;

FIG. 4 is a flowchart of an antenna phase error correction method according to another embodiment;

FIG. 5 is a flow chart of a method of computing a frequency response matrix in one embodiment;

FIG. 6 is a flow chart of generating an antenna phase error function in one embodiment;

FIG. 7 is a diagram of an experimental configuration of antenna phase error correction in one embodiment;

FIG. 8 is a graph comparing antenna phase error function estimates with collected data estimates in one embodiment;

FIG. 9 is a diagram of an experimental configuration of antenna phase error correction and AoA estimation according to another embodiment;

FIG. 10 is a graph of the result of an empirical cumulative distribution function of AoA estimation errors in one embodiment;

FIG. 11 is a block diagram of an antenna phase error correction device in one embodiment;

fig. 12 is an internal structural diagram of a base station in one embodiment.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.

The antenna phase error correction method provided by the embodiment of the application can be applied to an application environment shown in fig. 1. Wherein the terminal 102 communicates with the base station 104. The base station 104 acquires positioning signals of the same terminal at different positions, and acquires a frequency domain response matrix of a wireless channel according to the positioning signals; the base station 104 obtains a path fading coefficient of a direct path in the positioning signal according to the frequency domain response matrix; the base station 104 obtains the phase difference between the antenna array elements according to the path fading coefficient of the direct path; the base station 104 obtains an antenna phase error estimated value according to the phase difference between the antenna array elements, and realizes antenna phase error correction according to the antenna phase error estimated value.

The terminal 102 may be, but not limited to, various personal computers, notebook computers, smart phones, tablet computers, internet of things devices, and portable wearable devices, where the internet of things devices may be smart speakers, smart televisions, smart air conditioners, smart vehicle devices, and the like. The portable wearable device may be a smart watch, smart bracelet, headset, or the like. The base station 104 may be a macro base station, a micro base station, a remote radio, a repeater, an indoor distribution system, or the like.

In one embodiment, as shown in fig. 2, an antenna phase error correction method is provided, and the method is applied to the base station 104 in fig. 1 for illustration, and includes the following steps:

Step 202: and acquiring positioning signals of the same terminal at different positions, and acquiring a frequency domain response matrix of the wireless channel according to the positioning signals.

The positioning system comprises a terminal and a base station, wherein an antenna is arranged on the base station, and the terminal is in the coverage range of the antenna of the base station. In the positioning system of this embodiment, positioning signals are respectively transmitted to the base station at different positions through the same terminal, and the position of the terminal is calibrated at the position of each positioning signal. The base station estimates the antenna phase error from the positioning signal.

The frequency domain response matrix of the wireless channel is obtained by performing signal processing on the positioning signal. When the frequency domain response matrix of the wireless channel is obtained according to the positioning signal, the received positioning signal is subjected to data processing such as filtering to obtain a positioning signal sequence, then the frequency domain receiving positioning signal matrix is obtained through a method such as fourier transform, and then the channel estimation is performed according to the frequency domain receiving positioning signal matrix and the transmitting positioning signal sequence to obtain the frequency domain response matrix of the wireless channel between the terminal and the base station. The wireless channel frequency domain response matrix may be calculated using a Least Squares (LS) channel estimator when performing channel estimation. For the frequency domain response matrix, the radio frequency channel error in the matrix can be corrected by the radio frequency channel correction coefficient, and the embodiment calculates an antenna phase error function according to the corrected frequency domain response matrix.

Step 204: and obtaining a path fading coefficient of the direct path in the positioning signal according to the frequency domain response matrix.

In the obtained frequency domain response matrix signals, signals generated by reflection of signals transmitted by the terminal, such as walls, posts, water pipes, metal equipment and the like, are generated based on multipath effects besides positioning signals transmitted by the terminal. In this embodiment, for this case, the positioning signal is first processed to obtain a path fading parameter of the direct path in the positioning signal, and then the antenna phase error is calculated based on the path fading coefficient of the direct path, so as to implement antenna phase error estimation. For example, the path fading coefficients of all paths may be obtained according to the positioning signal, and then the path fading coefficients of the direct paths in the positioning signal may be obtained.

Step 206: and obtaining the phase difference among the antenna array elements according to the path fading coefficient of the direct path.

And extracting the phase of the acquired path fading coefficient of the direct path to obtain the phase of the direct path fading coefficient. And then calculating the phase difference between each array element of the antenna array and the reference array element according to the phase in the path fading coefficient.

Step 208: and obtaining an antenna phase error estimated value according to the phase difference among the antenna array elements, and realizing antenna phase error correction according to the antenna phase error estimated value.

The estimated value of the antenna phase error is an estimated value obtained by calculating according to the phase difference among antenna array elements which are repeatedly measured for a plurality of times, and the estimated accuracy of the phase error can be improved through the phase difference obtained by repeatedly measuring for a plurality of times. When the antenna phase error estimated value is calculated, a filter can be used for removing abnormal values in the repeated measured sequence, or the antenna phase error value is estimated in an average value mode, and the abnormal values can be removed again, and error estimation is carried out through the average value.

In the antenna phase error correction method, positioning signals of the same terminal at different positions are obtained, a frequency domain response matrix of a wireless channel is obtained according to the positioning signals, a path fading coefficient of a direct path in the positioning signals is obtained according to the frequency domain response matrix, a phase is extracted through the path fading coefficient of the direct path, a phase difference between antenna array elements is obtained through calculation, an antenna phase difference estimated value is obtained, an antenna phase error function is obtained according to the antenna phase difference estimated value, and correction of an antenna phase error is achieved.

The method is based on a positioning system, can realize the calculation of the antenna phase error in the field environment with complex multipath, avoids the step of precisely measuring the antenna phase error by utilizing a microwave dark room, obviously reduces the correction cost of the antenna phase error, and improves the practicability of an AOA (Angle of Arrival) technology in a wireless positioning system.

In one embodiment, obtaining a path fading coefficient of a direct path in a positioning signal according to a frequency domain response matrix includes: and determining the number of paths in the positioning signal according to the frequency domain response matrix, determining the direct paths in all paths of the positioning signal, and obtaining the path fading coefficients of the direct paths.

As described above, the positioning signal includes, in addition to the signal transmitted by the terminal, a signal reflected by a wall or the like due to multipath effects, and the total number of paths included in the positioning signal is estimated. Illustratively, the number of all paths in the corresponding positioning signal of the channel frequency domain response matrix may be estimated according to the AIC criterion (Akaike Information Criteria, red-pool information criterion) or the MDL (Minimum Description Length ) criterion of the Akaike information theory.

When determining the path fading coefficients of the direct paths, the path fading coefficients of all paths of the positioning signal can be calculated first, then the direct paths in all paths of the positioning signal are determined, and the path fading coefficients corresponding to the direct paths are obtained through extracting direct path data in the path fading coefficients of all paths.

According to the embodiment, the path fading coefficient of the direct path in the positioning signal is obtained through calculation and processing of the multipath signal, the antenna phase can be obtained through the path fading coefficient of the direct path, the antenna phase error value is estimated based on the antenna phase fading coefficient, and the antenna phase error correction is carried out.

In one embodiment, determining the number of paths in the positioning signal according to the frequency domain response matrix, determining the direct paths in all paths of the positioning signal, and obtaining the path fading coefficients of the direct paths includes: based on the frequency domain response matrix, combining the path propagation delay and the path fading coefficients of all paths to construct a log likelihood function; and solving the log-likelihood function to obtain the path fading coefficient of each path.

Obtaining a time delay matching vector function through the path propagation time delay; the frequency domain response vector is represented by a time delay matching vector function, a path fading coefficient, and a noise component, and the constructed function may be a log likelihood function. And solving the log likelihood function to obtain path propagation delay and path fading coefficients on all paths.

In one embodiment, resolving the log likelihood function to obtain path fading coefficients for each path includes: and carrying out iterative computation on the log likelihood function by adopting an expected maximization algorithm until the difference between the results of two adjacent iterative computation is smaller than a set value, thereby obtaining a path fading coefficient.

For the log likelihood function, the direct solving operation amount is large, and an EM (Expectation-Maximization) algorithm can be adopted for quick solving. The channel frequency domain response vector of the present embodiment is referred to as a non-perfect signal in the EM algorithm, while the signal separate for each path plus the respective noise is referred to as a perfect signal in the EM algorithm.

In the EM algorithm, a process of obtaining a complete signal from an incomplete signal is referred to as an Expectation process, and a process of solving a maximum likelihood solution from a complete signal is referred to as a Maximization process. The EM algorithm iteratively performs the estimation and Maximization solutions until the estimated results of two adjacent iterations do not change significantly, then the result of the last iteration is the output of this embodiment.

According to the embodiment, multipath resolution and estimation of the fading initial phase of multipath arrival receiving antennas are realized through an EM algorithm, so that multipath interference is reduced, and estimation of the phase error of an array antenna can be realized in a complex multipath environment.

In one embodiment, determining the number of paths in the positioning signal according to the frequency domain response matrix, determining the direct paths in all paths of the positioning signal, and obtaining the path fading coefficients of the direct paths includes: solving the log likelihood function to obtain path propagation delay of each path; and determining the direct paths in all paths of the positioning signal according to the path propagation delay.

By solving the log-likelihood function, the path propagation delay can also be obtained. In all paths of the positioning signal, one direct-of-sight (LOS) and several reflected paths (NLOS) are included. And selecting the shortest path of the path propagation delay from the path propagation delay and path fading coefficients calculated by all paths as the direct path, and obtaining the path fading coefficient corresponding to the direct path.

In one embodiment, obtaining the phase difference between the antenna elements according to the path fading coefficient of the direct path includes: according to the path fading coefficient of the direct path, combining an antenna array structure, compensating phase rotation caused by path difference among antenna array elements, and obtaining an updated path fading coefficient of the direct path; extracting the phase of the updated direct path fading coefficient; and obtaining the phase difference among the antenna array elements according to the phase in the updated direct path fading coefficient.

When the phase difference between the antenna array elements is calculated through the fading coefficients of the direct paths, the obtained fading coefficients of the direct paths are updated, and the phase rotation caused by the path difference between the antenna array elements is compensated by combining the antenna array structure, so that updated path fading coefficients of the direct paths are obtained. And extracting phases from the updated direct path fading coefficients, and calculating the phase difference among the array elements according to the phases in the direct path fading coefficients.

In one embodiment, obtaining an antenna phase error estimate from a phase difference between antenna elements, and implementing antenna phase error correction from the antenna phase error estimate includes: acquiring phase differences among a plurality of antenna array elements through acquiring positioning signals for a plurality of times; obtaining an antenna phase error estimated value according to the phase difference among a plurality of antenna array elements; and determining a phase error function through the phase difference estimated value among the antenna array elements, and realizing antenna phase error correction according to the phase error function.

In order to improve the estimation accuracy of the phase error, the phase difference obtained by repeated measurement is comprehensively utilized to calculate the estimated value of the phase error of the antenna. For the phase difference obtained by repeated calculation, the abnormal value in the sequence can be removed through a median filter, and then the phase difference estimated value obtained by repeated measurement of the average value of the data sequence after median filtering is obtained.

And calculating the phase error function of each array element of the antenna array according to the phase difference estimated value, and further obtaining the phase error function of the whole antenna array. And correcting the phase error of the antenna in the positioning system according to the calculated phase error function.

In the calculation of the phase error function, the median filter may be used to remove the outlier in the data first, and then the method such as cubic spline interpolation, polynomial fitting or local regression algorithm may be used to implement the estimation of the phase error function.

Fig. 3 is a schematic diagram of a positioning system configuration, where the positioning system shown in fig. 3 includes a base station and a mobile terminal, the mobile terminal respectively transmits positioning signals at different positions within a coverage area of an antenna array of the base station, and the positioning system accurately calibrates a position of the terminal at each position where the positioning signals are transmitted, and the calibration method may be a high-precision position measurement mode such as a total station, a laser radar or a differential global navigation satellite system (Global Navigation Satellite System, GNSS) signal.

As shown in fig. 3, in one embodiment, the base station uses the multi-channel positioning signals received by the antenna array to estimate the phase error, and the antenna phase error correction method is as shown in fig. 4, and includes the following steps:

step 410: and receiving positioning signals of the same terminal at different positions, and acquiring a frequency domain response matrix of the wireless channel according to the positioning signals.

Step 420: and obtaining an antenna phase error function according to the frequency domain response matrix, and correcting the antenna phase error through the antenna phase error function.

As shown in fig. 5, in step 410, receiving positioning signals of the same terminal at different positions, and obtaining a frequency domain response matrix of a wireless channel according to the positioning signals includes the following steps:

step 502: and receiving the positioning signal sets sent by the same terminal at different positions.

In order to better measure the phase error in the coverage area of the antenna array of the base station, the position of the terminal covers the coverage area of the antenna array, and the measuring position does not need equal angular spacing.

Assume that the number of antenna elements of a base station receiving antenna array isNThe set of angles measured by the array is expressed as

At each measurement angle, the base station configuring the array antenna receives the multi-channel positioning reference signal. Will be at the measuring angle- >

The received positioning signal is recorded as a function +.>

Wherein, set->

Representing real space, +.>

Representing plural spaces->

Representing a complex space of dimension N x 1. The set of positioning signals received at all measurement angles is denoted +.>

. The method of the present embodiment achieves an estimation of the antenna phase error based on the received set of positioning signals.

In one embodiment, the angular separation of the measured terminal positioning signals ranges from 3 degrees to 8 degrees, taking into account the continuity of the phase error curve.

Step 504: and processing the acquired positioning signal set to obtain a positioning signal sequence.

For received positioning signals in a positioning signal set

Processing radio frequency and intermediate frequency signals, including signal filtering, down-conversion, extraction, etc., and ADC (Analog-Digital conversion) to obtain baseband receiving and positioning signal sequence->

. The present embodiment does not limit the processing method and steps for the positioning signal, and the corresponding processing module may be set in the receiver of the base station of the positioning system.

Step 506: and performing time-frequency conversion on the positioning signal sequence to obtain a frequency domain receiving positioning signal matrix.

Receiving a positioning signal sequence for a baseband

And performing time-frequency transformation to obtain a frequency domain receiving positioning signal matrix. Illustratively, the time-frequency transformation may be accomplished by an FFT (Fast Fourier Transform ).

For a wideband positioning system, the positioning signal transmitted by the terminal is a wideband positioning signal occupying a certain bandwidth, and the bandwidth of the positioning signal is set asBFrequency of thenBandwidth occupied by domain signalsBCan be divided intoMA sub-band. When the time-frequency transformation is implemented by means of FFT,Mis the number of FFT points, and the frequency domain received data can be arranged asM×NA matrix of dimensions, expressed as

Receiving a positioning signal in the frequency domainM×NIn the matrix, the firstnColumn indicates the firstnReceived by a receiving channelMAnd (5) maintaining the frequency domain data vector.

Step 508: and carrying out channel estimation according to the frequency domain receiving positioning signal matrix and the transmitting positioning signal sequence to obtain a channel frequency domain response matrix.

And carrying out channel estimation according to the frequency domain receiving positioning signal matrix and the transmitting positioning signal sequence, and estimating a wireless channel frequency domain response CFR (Channel Frequency Response, channel frequency domain response) between the terminal and the base station. The frequency domain receiving positioning signal matrix is

The transmitted positioning signal sequence is denoted +.>

The obtained wireless channel frequency domain response matrix is expressed as +.>

。

The present embodiment is not limited to the method and steps of channel estimation, and the wireless channel frequency domain response matrix may be calculated using a least squares channel estimator, for example.

Representing the first of the frequency domain response matrices of the wireless channelmLine 1nThe elements of a column have the expression: />

（1）

In the formula (1),

matrix representing frequency domain received positioning signals>

Middle (f)mLine 1nElements of a column;x _m to at the firstmTransmitting positioning signal sequences of subbands, i.e. transmitting positioning signal sequence vectorsxIs the first of (2)mThe elements.

Step 510: and correcting the channel frequency domain response matrix through the radio frequency channel correction coefficient measurement value to obtain a corrected frequency domain response matrix.

And correcting the radio frequency channel error in the estimated channel frequency domain response matrix through the measured radio frequency channel correction coefficient.

In the positioning system, a base station serving as a receiving device measures the operating bandwidth of each radio frequency channel of the base stationBFrequency response in the willMThe number of sub-bands is equal to the number of sub-bands,Nthe RF channel frequency response of each receive channel is noted as

The matrix is the radio frequency channel correction coefficient of the base station as the receiving device.

The correction process of the wireless channel frequency domain response matrix comprises the following steps:

（2）

in the formula (2),

the operator represents dividing the corresponding elements of the two matrixes to obtain matrixes with the same dimension. Correcting by the radio frequency channel correction coefficient to obtain a corrected radio channel frequency domain response matrix expressed as +. >

。

As shown in fig. 6, step 420 of obtaining an antenna phase error function according to the frequency domain response matrix, and performing antenna phase error correction through the antenna phase error function includes the following steps:

step 602: and determining the number of paths in the positioning signal according to the frequency domain response matrix.

In the positioning system, objects such as walls, posts, water pipes, metal equipment and the like can cause reflection of positioning signals, so that the acquired wireless channel frequency domain response matrix

Not only from->

The signal components directed to the antenna array also have correlated signal components incident in other directions due to multipath propagation. The number of paths of the positioning signal is estimated through the channel frequency domain response matrix.

Illustratively, based on the channel frequency domain response matrix, the number of all paths in the positioning signal corresponding to the channel frequency domain response matrix can be estimated according to AIC criterion or MDL criterion of Akaike information theory, and the total number of paths is expressed as

。

Step 604: and calculating the path propagation delays and path fading coefficients of all paths.

And constructing a log-likelihood function according to the channel frequency domain response matrix, wherein the log-likelihood function takes path propagation delay and path fading coefficient as parameters to be estimated. And solving the log likelihood function to obtain path propagation delay and path fading coefficients on all paths.

First, assume that at an angle

Where, to wireless communicationThe track is subjected toQRepeated measurements, will beqChannel frequency domain response matrix representation obtained by secondary measurement>

. The present embodiment is independently +/for each angle>

Where (a)QThe secondary measurement results are calculated, so in the following description, they are omittedkAndqis to simplify the representation of the channel frequency domain response matrix of a measurement as

。

The multi-channel frequency domain response matrix can then be regarded as being used at the same timeNIndividual antennas for radio channelsNSecondary measurements, i.e.

Each column of the matrix can be regarded as a snap shot in space, denoted +.>

. The total number of paths estimated for the previous step +.>

The path propagation delay of each path is denoted +.>

The respective path complex fading coefficients corresponding to the received signal of each receiving channel are expressed as + ->

The method comprises the steps of carrying out a first treatment on the surface of the Will->

The propagation delays of the paths are uniformly represented as vectors +.>

，/>

The path fading coefficients are collectively expressed asNIndividual vectors

Then (1)nChannel frequency domain response vector measured by each receiving channel>

The expression of (2) is:

（3）

in the formula (3),

is the firstnNoise component on the individual receiving channels, +.>

Wherein->

A delay matching vector function representing the positioning system, the input parameter of the function being the path propagation delay +. >

The output is a delay matching vector, each element in the delay matching vector representing the phase rotation caused by the delay on each subband. For example, when the delay is +.>

The subband interval is +.>

In the time-course of which the first and second contact surfaces,delay matching vector->

Is the first of (2)mThe individual elements are expressed as:

（4）

since the path fading coefficients are complex, they are common in equation (3)

Unknown parameters, assuming noise component->

Obeying complex gaussian distribution, then taking path propagation delay and path complex fading coefficient as unknown parameters, the established log likelihood function is expressed as:

in the formula (5) of the present invention,

operator represents +.>

Norms. The maximum likelihood solution of the parameters to be solved is expressed as:

because the direct solving operation of the formula is large, the embodiment can adopt the EM algorithm to carry out quick solving. Due to channel frequency domain response vectors

By->

The individual signals are mixed, the channel frequency domain response vector of the present embodiment is referred to as an incomplete signal in the EM algorithm, and the signal separate for each path plus the respective noise is referred to as a complete signal in the EM algorithm. Will be the firstnReception channel number 1lThe signal of the strip path is denoted +.>

Then:

（7）

the relationship between the incomplete signal and the complete signal can be expressed as:

In the EM algorithm, a process of obtaining a complete signal from an incomplete signal is referred to as an Expectation process, and a process of solving a maximum likelihood solution from a complete signal is referred to as a Maximization process. The EM algorithm iteratively performs the Expectation and Maximization solutions, assuming the thpObtaining the estimated value of the unknown parameter after multiple iterations

And->

Then (1)p+The solving process of the EM algorithm of 1 iteration is as follows:

step (A): expect ion:

step (B): maximization:

since the EM algorithm is an iterative algorithm requiring iterative computation, an initial value needs to be set at the time of computation. The initial value may be set using an all-zero initialization, but all-zero initialization may result in more iterative steps required to achieve convergence. The path propagation delay can also be extracted from the inverse Fourier transform of the channel frequency domain response matrix of each receiving channel, i.e. CIR (channel impulse response ) of each channel

And path fading coefficient->

Is set to be a constant value.

Repeating the steps (A) and (B) of the EM algorithm until the estimated results of two adjacent iterations have not changed significantly, e.g. the difference between the results of the adjacent desired iterations is less than a set point, then the result of the last iteration

Which is the output of this step, represents an estimate of each path fading coefficient.

For a pair ofKAngle of observationQThe EM algorithm is executed on the channel frequency domain response matrix obtained by repeated measurement to obtain all

Path propagation delay of the paths and the paths areNPath fading coefficients on the respective receiving channels, respectively denoted as

And->

。

Step 606: and determining the direct path of the positioning signal according to the path propagation delay, and obtaining the path fading coefficient of the direct path.

In all paths, including a direct path sum

The reflection path of the strip. At->

Selecting the shortest path of path propagation delay from path propagation delay and path fading coefficients calculated by the paths as a direct path, and recording the path fading coefficient of the direct path as +.>

。

Step 608: and according to the path fading coefficient of the direct path, combining an antenna array structure, and compensating phase rotation caused by path difference among antenna array elements to obtain the updated path fading coefficient of the direct path.

In the path fading coefficient of the direct path, the phase rotation generated by the path difference between the array elements of the antenna array is removed.

Path fading coefficients observed in different channels

The phase comprises the phase error of the antenna array to be calculated; and a phase difference due to a difference in path length to each element when the signal propagates in the free space, the phase difference due to the difference in path length being related to the array type structure of the antenna array.

For ULA (Uniform Linear array, equidistant line array) the angle between the incident signal and the array normal direction is as followsθWhen the first array element is taken as the reference array element, for the firstnIndividual array elements, the path differencedThe amount of phase rotation induced is expressed as

. Therefore, the path fading coefficient of the direct path observed at each array element is +.>

Direct path fading coefficient after phase rotation quantity update is removed +.>

Expressed as:

step 610: and extracting the phase of the updated direct path fading coefficient, and calculating the phase difference among array elements according to the phase in the direct path fading coefficient to obtain an antenna phase error estimated value.

Illustratively by extracting complex numbers

Is realized for the updated direct path fading coefficient +.>

Expressed as:

（13）

taking the first array element of the antenna array as a reference array element according to the phase in the path fading coefficient

Calculating the phase difference between each array element of the antenna array and the reference array element, and expressing the phase difference as follows:

（14）

as can be obtained from the formula (14),

。

in order to improve the estimation accuracy of the phase error, the method comprehensively utilizes the angle

The position of the partQPhase difference obtained by repeated measurement

Calculate the angle->

An antenna phase error estimate at.

Illustratively, outliers in the sequence are first removed by a median filter, and for the removed outliers, the median of the data before and after the outlier is used instead. Then the average value of the data sequence after median filtering is selected as the angle

Phase difference estimation value +.>

。

Step 612: and determining a phase error function through the phase difference estimated value among the antenna array elements, and realizing antenna phase error correction according to the phase error function.

For the followingNAn antenna array of array elements, each array element corresponding to a phase error function, expressed as

. Wherein (1)>

Indicating the angular coverage of the antenna array. Recorded in the form of a vector function, which is expressed as +.>

The input parameter of the function is incidenceAngle ofθThe output isNThe phase error of each array element at the current angle. For example, when the incident angle is +>

The output of the phase error function is +.>

Wherein->

Representing a vector or matrix transpose operator.

From the phase difference estimate

Calculating the phase error function of each array element of the antenna array>

，n=1, …, N, resulting in a phase error function of the whole antenna array +.>

。

From calculated phase error function

And correcting the phase error of the antenna in the positioning system.

In one embodiment, in the calculation of the phase error function, the outliers in the data may be removed first using a median filter, and then the phase error function may be implemented using a method such as cubic spline interpolation, polynomial fitting, or local regression algorithm

Is a function of the estimate of (2). Due to->

Therefore, only estimation calculation is needed/>

And (3) obtaining the product.

In one embodiment, taking a sub-6GHz band-based 5G pico-base station indoor positioning system as an example, the effectiveness of the antenna phase error correction method is verified. In this embodiment, 5G SRS (Sounding Reference Signal ) is used as a positioning signal, the bandwidth occupied by the positioning signal is 100MHz, the adopted pico-cell is provided with four array elements ULA, the array normal direction is defined as a zero degree angle, and the angle between the incident signal and the normal is positioned asθThe coverage angle of the antenna array ranges from-60 degrees to +60 degrees.

Fig. 7 is a diagram of experimental configuration for antenna phase error estimation by collecting measured data, as shown in fig. 7, where positioning signals are collected at twenty-eight different terminal locations, and repeated one hundred times at each terminal location, as exemplified by the above example,N=4，K=28，Q=100。

in this embodiment, the phase error function of each array element in the antenna array is calculated through data estimation repeatedly measured for one hundred times, fig. 8 is a diagram showing a comparison between an estimated value of the phase error function of the antenna and an estimated value of the acquired data, where the estimated value of the phase error in the diagram is an estimated value of the phase error of the antenna based on positioning data acquired on site in an experiment, and the estimated value of the phase error function of the antenna is obtained by further performing function estimation according to the estimated value of the phase error of the antenna calculated in the above embodiment.

As shown in fig. 8, the estimated phase error values of the second antenna element to the fourth antenna element are obtained by a phase error function according to the measured results of one hundred times. In the result of the estimation of the phase error function,

and +.>

Then the phase error estimate for the terminal position at the twenty-eight discrete angles is calculated based on the phase error estimate, based on the foregoing calculation steps,and obtaining by adopting a median filter and a local regression algorithm.

In one embodiment, as shown in fig. 9, an experimental configuration diagram of another embodiment of antenna phase error correction and AOA estimation performed by collecting measured data is shown, based on the foregoing antenna error phase correction method, for fifty-six terminal positions shown in fig. 9, the collected positioning data is repeatedly collected for one hundred times, the antenna phase error is compensated for the collected positioning data by respectively not performing antenna phase compensation and the antenna error phase correction method disclosed in the foregoing embodiment, the obtained empirical cumulative distribution function result of the overall AOA estimation error at the fifty-six positions is shown in fig. 10, after the antenna phase error is compensated by the antenna phase error estimation function obtained by the antenna phase correction method in accordance with the foregoing embodiment, the AOA estimation accuracy is significantly improved, and 90% of AOA estimation error is reduced from 4 degrees to about 2 degrees.

According to the embodiment, the antenna phase error is estimated and compensated according to the multipath signals in the actual positioning system, no additional facilities are needed, compared with a phase error curve measuring method for carrying out an active experiment in a microwave darkroom, the method is good in practicality, low in calculation complexity, high in accuracy and capable of remarkably reducing the correction cost of the antenna error phase, and the practicability of the AOA technology of the wireless positioning system is improved.

It should be understood that, although the steps in the flowcharts related to the embodiments described above are sequentially shown as indicated by arrows, these steps are not necessarily sequentially performed in the order indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in the flowcharts described in the above embodiments may include a plurality of steps or a plurality of stages, which are not necessarily performed at the same time, but may be performed at different times, and the order of the steps or stages is not necessarily performed sequentially, but may be performed alternately or alternately with at least some of the other steps or stages.

Based on the same inventive concept, the embodiment of the application also provides an antenna phase error correction device for realizing the antenna phase error correction method. The implementation of the solution provided by the device is similar to that described in the above method, so the specific limitation of the embodiment of the antenna phase error correction device or embodiments provided below may be referred to the limitation of the antenna phase error correction method hereinabove, and will not be repeated here.

In one embodiment, as shown in fig. 11, there is provided an antenna phase error correction apparatus including: an acquisition unit 1102, a calculation unit 1104, a determination unit 1106, and a correction unit 1108, wherein:

an obtaining unit 1102, configured to obtain positioning signals of the same terminal at different positions, and obtain a frequency domain response matrix of a wireless channel according to the positioning signals;

a calculating unit 1104, configured to obtain a path fading coefficient of the direct path in the positioning signal according to the frequency domain response matrix;

a determining unit 1106, configured to obtain a phase difference between antenna array elements according to a path fading coefficient of the direct path;

the correction unit 1108 is configured to obtain an antenna phase error estimation value according to the phase difference between the antenna array elements, and implement antenna phase error correction according to the antenna phase error estimation value.

In one embodiment, the computing unit 1104 is further configured to: and determining the number of paths in the positioning signal according to the frequency domain response matrix, determining the direct paths in all paths of the positioning signal, and obtaining the path fading coefficients of the direct paths.

In one embodiment, the computing unit 1104 is further configured to: based on the frequency domain response matrix, combining the path propagation delay and the path fading coefficients of all paths to construct a log likelihood function; and solving the log-likelihood function to obtain the path fading coefficient of each path.

In one embodiment, the computing unit 1104 is further configured to: and carrying out iterative computation on the log likelihood function by adopting an expected maximization algorithm until the difference between the results of two adjacent iterative computation is smaller than a set value, thereby obtaining a path fading coefficient.

In one embodiment, the computing unit 1104 is further configured to: solving the log likelihood function to obtain path propagation delay of each path; and determining the direct paths in all paths of the positioning signal according to the path propagation delay.

In one embodiment, the determining unit 1106 is further configured to: according to the path fading coefficient of the direct path, combining an antenna array structure, compensating phase rotation caused by path difference among antenna array elements, and obtaining an updated path fading coefficient of the direct path; extracting the phase of the updated direct path fading coefficient; and obtaining the phase difference among the antenna array elements according to the phase in the updated direct path fading coefficient.

In one embodiment, the correction unit 1108 is further configured to: acquiring phase differences among a plurality of antenna array elements through acquiring positioning signals for a plurality of times; obtaining an antenna phase error estimated value according to the phase difference among a plurality of antenna array elements; and determining a phase error function through the phase difference estimated value among the antenna array elements, and realizing antenna phase error correction according to the phase error function.

The respective modules in the above-described antenna phase error correction apparatus may be implemented in whole or in part by software, hardware, and a combination thereof. The above modules may be embedded in hardware or may be independent of a processor in the base station 104, or may be stored in software in a memory in the base station 104, so that the processor may invoke and execute operations corresponding to the above modules.

In one embodiment, a base station 104 is provided, the base station 104 being provided in a positioning system with an antenna array for communication with the outside. The internal structure of the base station can be shown in fig. 12. The base station comprises a processor, a memory, a communication interface, a display screen and an input device which are connected by a system bus. Wherein the processor of the base station is configured to provide computing and control capabilities. The memory of the base station comprises a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The computer program is executed by a processor to implement a method of antenna phase error correction.

It will be appreciated by those skilled in the art that the structure shown in fig. 12 is merely a block diagram of some of the structures associated with the present application and is not limiting of the computer device to which the present application may be applied, and that a particular computer device may include more or fewer components than shown, or may combine certain components, or have a different arrangement of components.

In one embodiment, a base station is provided, including a memory and a processor, where the memory stores a computer program, and the processor implements the steps of the method embodiments described above when the processor executes the computer program.

In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored which, when executed by a processor, implements the steps of the method embodiments described above.

In an embodiment, a computer program product is provided, comprising a computer program which, when executed by a processor, implements the steps of the method embodiments described above.

It should be noted that, user information (including but not limited to user equipment information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, presented data, etc.) referred to in the present application are information and data authorized by the user or sufficiently authorized by each party.

Those skilled in the art will appreciate that implementing all or part of the above described methods may be accomplished by way of a computer program stored on a non-transitory computer readable storage medium, which when executed, may comprise the steps of the embodiments of the methods described above.

Any reference to memory, database, or other medium used in the various embodiments provided herein may include at least one of non-volatile and volatile memory. The nonvolatile Memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash Memory, optical Memory, high density embedded nonvolatile Memory, resistive random access Memory (ReRAM), magnetic random access Memory (Magnetoresistive Random Access Memory, MRAM), ferroelectric Memory (Ferroelectric Random Access Memory, FRAM), phase change Memory (Phase Change Memory, PCM), graphene Memory, and the like. Volatile memory can include random access memory (Random Access Memory, RAM) or external cache memory, and the like. By way of illustration, and not limitation, RAM can be in the form of a variety of forms, such as static random access memory (Static Random Access Memory, SRAM) or dynamic random access memory (Dynamic Random Access Memory, DRAM), and the like.

The databases referred to in the various embodiments provided herein may include at least one of relational databases and non-relational databases. The non-relational database may include, but is not limited to, a blockchain-based distributed database, and the like. The processors referred to in the embodiments provided herein may be general purpose processors, central processing units, graphics processors, digital signal processors, programmable logic units, quantum computing-based data processing logic units, etc., without being limited thereto.

The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples only represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the present application. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application shall be subject to the appended claims.

Claims

1. An antenna phase error correction method, the method comprising:

obtaining phase differences among antenna array elements according to the path fading coefficients of the direct paths;

obtaining an antenna phase error estimated value according to the phase difference among the antenna array elements, and realizing antenna phase error correction according to the antenna phase error estimated value;

the obtaining the path fading coefficient of the direct path in the positioning signal according to the frequency domain response matrix comprises the following steps:

and determining the number of paths in the positioning signal according to the frequency domain response matrix, determining the direct paths in all paths of the positioning signal, and obtaining the path fading coefficients of the direct paths.

2. The method of claim 1, wherein the determining the number of paths in the positioning signal according to the frequency domain response matrix, determining a direct path among all paths of the positioning signal, and obtaining path fading coefficients of the direct path, comprises:

Constructing a log likelihood function based on the frequency domain response matrix by combining path propagation delay and path fading coefficients of all paths;

and resolving the log likelihood function to obtain the path fading coefficient of each path.

3. The method of claim 2, wherein said solving the log likelihood function for the path fading coefficients for each path comprises:

and carrying out iterative computation on the log likelihood function by adopting an expected maximization algorithm until the difference between the results of two adjacent iterative computation is smaller than a set value, thereby obtaining the path fading coefficient.

4. The method of claim 2, wherein the determining the number of paths in the positioning signal according to the frequency domain response matrix, determining a direct path among all paths of the positioning signal, and obtaining path fading coefficients of the direct path, comprises:

solving the log likelihood function to obtain the path propagation delay of each path;

and determining a direct path in all paths of the positioning signal according to the path propagation delay.

5. The method of claim 1, wherein the obtaining the phase difference between the antenna elements according to the path fading coefficient of the direct path comprises:

According to the path fading coefficient of the direct path, combining an antenna array structure, compensating phase rotation caused by path difference among antenna array elements, and obtaining an updated direct path fading coefficient;

extracting the phase of the updated direct path fading coefficient;

6. The method of claim 1, wherein the obtaining an antenna phase error estimate from the phase differences between the antenna elements and performing antenna phase error correction from the antenna phase error estimate comprises:

obtaining the antenna phase error estimated value according to the phase difference among the plurality of antenna array elements;

7. An antenna phase error correction device, the device comprising:

The calculating unit is configured to obtain a path fading coefficient of a direct path in the positioning signal according to the frequency domain response matrix, and obtain a path fading system of a direct path in the positioning signal according to the frequency domain response matrix, where the calculating unit includes: determining the number of paths in the positioning signal according to the frequency domain response matrix, determining the direct paths in all paths of the positioning signal, and obtaining the path fading coefficients of the direct paths;

the determining unit is used for obtaining the phase difference among the antenna array elements according to the path fading coefficient of the direct path;

8. The apparatus of claim 7, wherein the computing unit is further to:

based on the frequency domain response matrix, combining the path propagation delay and the path fading coefficients of all paths to construct a log likelihood function; and solving the log-likelihood function to obtain the path fading coefficient of each path.

9. A base station comprising a memory and a processor, the memory storing a computer program, characterized in that the processor implements the steps of the method of any of claims 1 to 6 when the computer program is executed.

10. A computer readable storage medium, on which a computer program is stored, characterized in that the computer program, when being executed by a processor, implements the steps of the method of any of claims 1 to 6.