WO2018133644A1

WO2018133644A1 - Direct path extraction method and device

Info

Publication number: WO2018133644A1
Application number: PCT/CN2017/119586
Authority: WO
Inventors: 向平叶
Original assignee: 中兴通讯股份有限公司
Priority date: 2017-01-17
Filing date: 2017-12-28
Publication date: 2018-07-26
Also published as: CN108337197A; CN108337197B

Abstract

Provided are a direct path extraction method and a device. The method comprises: receiving, by a base station, a positioning reference signal from a terminal; utilizing, by the base station, the positioning reference signal and a local positioning reference signal to perform channel estimation to obtain a channel estimation value; determining, by the base station, an energy window of the channel estimation value and the energy distributed in the energy window by using the channel estimation value; and determining, by the base station, a direct path according to the energy distributed in the energy window, and extracting the direct path.

Description

Direct path extraction method and device

Technical field

The present disclosure relates to the field of wireless positioning, for example, to a direct path extraction method and apparatus.

Background technique

With the development of the mobile Internet, people's demand for positioning and navigation functions will become higher and higher. Outdoor positioning technology represented by Global Positioning System (GPS) and Beidou has been widely used, but in complex indoor or closed environments, such as large waiting rooms, large venues, stadiums, large office buildings, underground mines, etc. The scene, due to the occlusion of the signal, causes severe attenuation and still cannot be located. In these complex indoor environments, indoor positioning of the communication system base station can be utilized.

The positioning method based on the triangulation principle of Time of Arrival (TOA) and Time Difference of Arrival (TDOA) is a commonly used positioning technique. By measuring the signal transmission delay value between the base station and the terminal, and then according to The signal transmission delay value estimates the actual distance between the base station and the terminal, thereby locating the location of the terminal.

In the positioning system, the time model based on wireless signal propagation is greatly affected by multipath in the indoor complex environment. After multipath interference, the measured signal transmission delay between the base station and the terminal will have a large error, resulting in a large error. The positioning accuracy is greatly reduced.

In the related art, the correlation of the training sequence is often used to detect the earliest arrival path, and the TOA is determined by searching the receiving end for the correlation spectrum peak of the received signal and the local reference training sequence. This method is only applicable to the case where there is a direct path and the direct path is the strongest. However, in a densely populated cell in a city, wireless signal transmission conditions are poor, and multipath interference is severe at this time, and the error of the TOA positioning method is large.

Summary of the invention

The present disclosure provides a direct path extraction method and apparatus for solving a problem of large errors caused by multipath interference in a complex environment by finding a direct path in a multipath signal.

The present disclosure provides a direct path extraction method, including:

The base station receives the positioning reference signal from the terminal;

The base station performs channel estimation by using the positioning reference signal and the local positioning reference signal to obtain a channel estimation value;

Determining, by the base station, the energy window of the channel estimation value and the energy distributed in the energy window by using the channel estimation value;

The base station determines a direct path according to energy distributed in the energy window, and extracts the direct path.

Optionally, the base station performs channel estimation by using the positioning reference signal and the local positioning reference signal, and obtaining the channel estimation value includes:

The base station performs least square channel estimation on the positioning reference signal and the local positioning reference signal to obtain a channel estimation value.

Optionally, the determining, by the base station, the energy window of the channel estimation value and the energy distributed in the energy window by using the channel estimation value, including:

Performing interpolation processing on the channel estimation value by the base station to obtain an interpolated channel estimation value;

The base station performs a frequency domain to time domain transform process on the interpolated channel estimation value to obtain a channel estimation value in a time domain;

The base station calculates the energy distributed in the energy window and the energy window by using the channel estimation value of the time domain.

Optionally, the calculating the energy distributed in the energy window and the energy window comprises:

Determining, by the base station, a coefficient for calculating the energy window according to the channel estimation value, and calculating a front window and a rear window according to the coefficient used for calculating the energy window, by using the front window and the Adding back windows to obtain the energy window;

The base station obtains energy distributed in the energy window by multiplying a channel estimation value of the time domain with a conjugate of a channel estimation value of the time domain.

Optionally, the determining, by the base station, the direct path according to the energy distributed in the energy window includes:

The base station multiplies a maximum peak energy in the energy window by a threshold coefficient to obtain a threshold energy for determining a direct path;

The base station searches for a first energy path in the energy window that is greater than the threshold energy as the direct path.

The present disclosure also provides a direct path extraction device, including:

a receiving module, configured to receive a positioning reference signal from the terminal;

a channel estimation module, configured to perform channel estimation by using the positioning reference signal and the local positioning reference signal to obtain a channel estimation value;

An energy calculation module configured to determine an energy window of the channel estimation value and an energy distributed in the energy window by using the channel estimation value;

The direct path extraction module is configured to determine a direct path according to the energy distributed in the energy window, and extract the direct path.

Optionally, the channel estimation module is configured to perform least square channel estimation on the positioning reference signal and the local positioning reference signal to obtain a channel estimation value.

Optionally, the energy calculation module includes:

An interpolation submodule configured to perform interpolation processing on the channel estimation value to obtain an interpolated channel estimation value;

An Inverse Discrete Fourier Transform (IDFT) sub-module, configured to perform frequency domain to time domain transform processing on the interpolated channel estimation value to obtain a channel estimation value in a time domain;

An energy window determining submodule, configured to calculate energy distributed in the energy window and the energy window by using channel estimation values in the time domain;

Wherein, the IDFT is an inverse discrete Fourier transform.

Optionally, the energy window determining submodule is configured to determine a coefficient used to calculate the energy window according to the channel estimation value, and calculate a front window according to the coefficient used to calculate the energy window. a rear window, the energy window is obtained by adding the front window and the back window, and then multiplying a channel estimation value of the time domain by a conjugate of a channel estimation value of the time domain to obtain The energy distributed in the energy window.

Optionally, the direct path extraction module is configured to multiply a maximum peak energy in the energy window by a threshold coefficient, obtain a threshold energy for determining a direct path, and search for energy in the energy window to be greater than the threshold. The first energy path of energy is taken as the direct path.

The present disclosure also provides a computer readable storage medium storing computer executable instructions for performing any of the methods described above.

The present disclosure also provides a direct path extraction device including one or more processors, a memory, and one or more programs, the one or more programs being stored in the memory when being one or more The above method is executed when the processor executes.

The present disclosure also provides a computer program product comprising a computer program stored on a non-transitory computer readable storage medium, the computer program comprising program instructions, when the program instructions are executed by a computer, Having the computer perform any of the methods described above.

The direct path extraction method and device provided by the present disclosure can determine and extract a direct path according to the energy distribution in the energy window, can effectively approximate the signal transmission delay value of the true direct path, and improve the accuracy of the wireless positioning.

DRAWINGS

FIG. 1 is a block diagram of a direct path extraction method according to an embodiment.

2 is a block diagram of a direct path extraction device according to an embodiment.

FIG. 3 is a block diagram of a direct path extracting device according to another embodiment.

4 is a flow chart of delay calculation provided by an embodiment.

FIG. 5 is a schematic diagram showing the hardware structure of a direct path extracting device according to an embodiment.

detailed description

1 is a block diagram of a direct path extraction method provided by an embodiment. As shown in FIG. 1, the steps include:

Step 110: The base station receives a positioning reference signal from the terminal. The positioning reference signal may be a Sounding Reference Signal (SRS) or a Demodulation Reference Signal (DMRS).

Step 120: The base station performs channel estimation by using the positioning reference signal and the local positioning reference signal to obtain a channel estimation value.

In an embodiment, the base station obtains a channel estimation value by performing Least Square (LS) channel estimation on the received positioning reference signal and the local positioning reference signal, and the channel estimation value is a channel estimation value in the frequency domain.

Step 130: The base station uses the channel estimation value to determine an energy window of the channel estimation value and energy distributed in the energy window.

In an embodiment, the base station may perform frequency domain to time domain transform processing on the channel estimation value, obtain a channel estimation value in a time domain, and calculate an energy window and the energy channel by using the channel estimation value in the time domain. The energy distributed in the energy window. The base station determines a coefficient for calculating an energy window according to the channel estimation value, and calculates a front window and a rear window according to the coefficient for calculating an energy window, by using the front window and the rear window The windows are summed to obtain an energy window, and the energy distributed in the energy window is obtained by multiplying the channel estimate of the time domain by its conjugate.

In an embodiment, before performing the transform processing from the frequency domain to the time domain, the base station performs interpolation processing on the channel estimation values in the frequency domain to obtain an interpolated channel estimation value in the frequency domain.

Step 140: The base station determines a direct path according to the energy distributed in the energy window, and extracts the direct path.

In one embodiment, the base station multiplies the maximum peak energy in the energy window by a threshold coefficient, obtains a threshold energy for determining a direct path, and searches for a first energy in the energy window that is greater than the threshold energy. The diameter is used as a direct path. That is to say, the base station takes the first energy in the energy window that is greater than the energy of the threshold energy as the direct path.

That is to say, in order to eliminate the influence of multipath interference on the wireless positioning in the wireless positioning system, the present embodiment can eliminate the multipath interference by multipath separation and finding the direct path in the multipath interference. In one embodiment, before measuring the signal transmission delay value, the frequency domain channel estimation interpolation method is first used, then the IDFT operation is performed to improve the time domain channel estimation resolution, and finally, according to the distribution characteristics of the multipath energy in the time domain, The corresponding threshold is determined, and the direct path is extracted by using the characteristic of the direct path arrival time, which is equivalent to changing the multipath environment into a line-of-sight environment to improve the positioning accuracy.

It will be understood by those skilled in the art that all or part of the steps of the foregoing embodiments may be implemented by a program to instruct related hardware, and the program may be stored in a computer readable storage medium. , including steps 110 to 140. The storage medium may be a non-transitory storage medium or a transitory storage medium. The non-transitory storage medium may include: Read-Only Memory (ROM)/Random Access Memory (RAM), a magnetic disk, an optical disk, and the like.

FIG. 2 is a block diagram of a direct path extracting apparatus according to an embodiment. As shown in FIG. 2, the method includes a receiving module 21, a channel estimating module 22, an energy calculating module 23, and a direct path extracting module 24.

The receiving module 21 is configured to receive a positioning reference signal from the terminal. The positioning reference signal may be a Sounding Reference Signal (SRS) or a Demodulation Reference Signal (DMRS).

The channel estimation module 22 is configured to perform channel estimation on the received reference signal and the local positioning reference signal to obtain a channel estimation value. In one embodiment, LS channel estimation is performed on the two signals to obtain a channel estimation value, which is a channel estimation value in the frequency domain.

The energy calculation module 23 is configured to determine an energy window of the channel estimate and an energy distributed in the energy window using the channel estimate.

The direct path extraction module 24 is configured to determine the direct path threshold and the direct path extraction. That is, the direct path extraction module 24 determines the direct path based on the energy distributed in the energy window and extracts the direct path. In one embodiment, the maximum peak energy in the energy window is multiplied by a threshold coefficient to obtain a threshold energy for determining the direct path, and the first energy path in the energy window of the search that is greater than the threshold energy is used as the direct path.

During the terminal positioning using the wireless communication network, the positioning in the complex environment is subject to multipath interference, resulting in a large error in the wireless positioning. By the method of extracting the direct path in this embodiment, the direct path of the multipath signal can be found, thereby The path environment is transformed into a line-of-sight environment to improve the accuracy of indoor positioning methods such as TOA and TDOA.

3 is a block diagram of a direct path extracting device according to another embodiment of the present application. As shown in FIG. 3, compared with the embodiment shown in FIG. 2, the energy calculating module 23 may include: an interpolation submodule 231, an IDFT submodule 232, and energy. Window determination module 233.

The interpolation sub-module 231 is configured to perform an interpolation operation on the frequency domain channel estimation, that is, the interpolation sub-module 231 performs interpolation processing on the channel estimation value in the frequency domain output by the channel estimation module 22 to obtain an interpolated channel estimation value.

The IDFT sub-module 232 is configured to convert the output of the interpolation sub-module 231 into a channel estimation time domain value (channel estimation value of the real-time domain), that is, the IDFT sub-module 232 performs the frequency domain by using the interpolated channel estimation value. The transform process to the time domain obtains the channel estimation value in the time domain.

The energy window determination sub-module 233 is configured to calculate a signal energy distribution and determine a size of the energy window, that is, the energy window determination sub-module 233 calculates the energy window and the energy distributed in the energy window by using the channel estimation value of the time domain. . In an embodiment, the energy window determination sub-module 233 is configured to determine a coefficient for calculating an energy window according to the channel estimation value, and calculate a front window and a rear window according to the coefficient for calculating the energy window, An energy window is obtained by adding the front window and the back window, and then the energy distributed in the energy window is obtained by multiplying the channel estimation value of the time domain by its conjugate.

After receiving the positioning reference signal, the direct path extracting device can perform the following steps:

Step 1: The channel estimation module performs least square channel estimation on the received positioning reference signal.

The received positioning reference signal and the local positioning reference signal are subjected to LS channel estimation, wherein the positioning reference signal is not limited to SRS and DMRS.

Step 2: The interpolation sub-module uses an interpolation method to interpolate the LS channel estimation value (ie, the channel estimation value in the frequency domain).

The interpolation method used may be a zero-padding interpolation or a cubic spline interpolation method, and the channel estimation value after interpolation may be 1024 or 2048.

Step 3: The IDFT sub-module transforms the interpolated frequency domain channel estimation value into the time domain by IDFT.

Step 4: The energy window determination sub-module calculates the energy distribution and the energy window of the time domain channel estimate.

For the positioning terminal, the time domain channel estimated energy will be an impulse response, and the time domain energy is distributed in the energy window. The energy window of this embodiment refers to the area where the signal is expected to be distributed, and the energy window is noise.

Step 5: The direct path extraction module extracts the direct path in the energy window and estimates the transmission delay.

According to the multipath characteristic, each energy path in the multipath exhibits an impulse response peak in the time domain, and the time domain energy is the superposition value of these multipath energies, and the highest energy peak is the reference signal receiving point.

In the case of a line-of-sight environment, there is only one signal peak, and the direct path is the maximum energy path. If it is a multipath environment, the direct path has the following characteristics: 1. The direct path is a peak energy point in the time domain; 2. The direct path energy is not too low, and should be higher than the maximum energy path by a certain gate. Limit (ie, threshold factor); 3. The direct path delay is smaller than the maximum energy path delay. According to these three characteristics, a reasonable threshold can be set to find the energy peak point whose delay is less than the maximum energy path and the energy exceeds the reasonable threshold (ie, the threshold energy), so that the peak energy point found is the direct path, and then according to the energy Peak point, estimated transmission delay.

In addition, referring to FIG. 5, an embodiment further provides a direct path extracting apparatus, including a processor 510 and a memory 520 storing executable instructions of the processor 510; wherein, when the processing The 510 is configured to: receive a positioning reference signal from the terminal, perform channel estimation by using the positioning reference signal and the local positioning reference signal, and obtain a channel estimation value, where the channel estimation value is a channel estimation value in a frequency domain. Performing interpolation processing on the channel estimation value in the frequency domain to obtain an interpolated channel estimation value; performing frequency domain to time domain transformation processing on the interpolated channel estimation value to obtain a channel estimation value in a time domain; Calculating, by using the channel estimation value of the time domain, an energy window and an energy distributed in the energy window; multiplying a maximum peak energy in the energy window by a threshold coefficient to obtain a threshold energy for determining a direct path; The first energy path in the energy window that searches for energy greater than the threshold energy is used as the direct path.

The memory 520 may include a storage program area and a storage data area, and the storage program area may store an operating system and an application required for at least one function. The storage data area can store data and the like created according to the use of the electronic device. Further, the memory may include, for example, a volatile memory of a random access memory, and may also include a non-volatile memory. For example, at least one disk storage device, flash memory device, or other non-transitory solid state storage device.

Moreover, when the logic instructions in memory 520 described above can be implemented in the form of software functional units and sold or used as separate products, the logic instructions can be stored in a computer readable storage medium. The technical solution of the present disclosure may be embodied in the form of a computer software product, which may be stored in a storage medium, and includes a plurality of instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) All or part of the steps of the method described in this embodiment are performed.

A person skilled in the art can understand that all or part of the process of implementing the above embodiment method can be completed by a computer program indicating related hardware, and the program can be stored in a non-transitory computer readable storage medium. When executed, a flow of an embodiment of the method as described above may be included. FIG. 4 is a flowchart of a delay calculation according to an embodiment. The present embodiment is applicable to an indoor positioning technology based on a triangulation principle, and performs frequency domain interpolation on channel estimation of a positioning reference signal to improve resolution of a time domain channel estimation. And extracting the direct path from the multipath signal, measuring the signal transmission delay value of the direct path between the base station and the terminal, and then estimating the actual distance between the base station and the terminal according to the signal transmission delay value. The steps of extracting the direct path to improve the positioning accuracy in this embodiment include:

Step 101: A User Equipment (UE) sends a positioning reference signal to all indoor positioning base stations. The positioning reference signal may be an uplink SRS signal or a DMRS signal.

Step 102: The base station receives the positioning reference signal of the UE, and assumes that the frequency domain data useful for the received SRS is Y(k), and extracts the direct path through the following steps 103_1 to 103_7 and measures an accurate transmission delay value.

Step 103_1: Perform a least squares estimation on the frequency domain data Y ^{(u, p)} (k) of each receiving channel p of the user u (ie, UE)

Where k is the positioning reference signal subcarrier index, and X ^{(u, p)} (k) is the local pilot sequence base sequence (corresponding to the local positioning reference signal).

Step 103_2: Perform zero-padding interpolation on the LS estimation value, where M is the frequency domain point of the SRS, and N is the total number of points after zero padding, and N=1024.

Step 103_3: Estimating the frequency domain channel

Transform to the time domain,

Step 103_4: Calculate the channel impulse response window. The effective channel impulse response window L _W includes the front window L _fore and the rear window L _post , L _w =L _fore +L _post , and the front window length may take L _fore =[0.5L _c ～0.8L _c ], the rear window may take L _post = [0.2L _c ~ 0.5L _c ]; L _c is the coefficient used to calculate the energy window,

M is

The frequency domain points, the regular cyclic prefix (Cyclic Prefix, CP), l _cp = 144, when the CP is extended, l _cp = 512.

Step 103_5: Calculate the time domain signal power p ^(u,p) (n) (the energy of the instantaneous domain channel estimate), and the formula is as follows:

p ^(u,p) (n)=h ^(u,p) (n)*conj(h ^(u,p) (n)).

Among them, conj () represents the conjugate function.

Step 103_6: Multipath separation finds a direct path, and searches for a corresponding position exceeding the maximum peak energy multiplied by the threshold thr in the time domain channel estimation window length L _w , and the formula is as follows:

among them,

Indicates the position function, left means to find the first element of the set, and thr is the corresponding threshold.

103_7 step of: determining the position estimate in accordance with the time delay T _a (u), a first delay value is calculated on the port T _a (u, p), the following formula:

Then, the delay value of each port is averaged to obtain a signal transmission delay value T _a (u) between the base station and the terminal, and the formula is as follows:

Where P is the number of ports, that is, the number of receiving channels.

According to the direct path extraction technology provided by the embodiment, when the positioning service is performed by using the communication network, in order to overcome the multipath effect caused by the complex environment, when measuring the transmission delay value between the terminal and the base station, the multipath signal is separated. The direct-radiation signal is used to estimate the time delay using the direct-path signal, which is equivalent to simplifying the multi-path environment into the line-of-sight environment, eliminating the error caused by multipath, and finally applying the triangulation scheme to calculate the position of the positioning terminal.

In summary,

1. In this embodiment, the frequency domain channel estimation of the positioning reference signal is interpolated before the direct path extraction, and the delay estimation granularity is reduced.

2. The present embodiment finds the first energy peak point of the threshold of the maximum energy path beyond the time domain channel as the direct path, effectively approximates the delay of the true direct path and improves the positioning accuracy.

Industrial applicability

Claims

A direct path extraction method includes:

The base station receives the positioning reference signal from the terminal;

The base station performs channel estimation by using the positioning reference signal and the local positioning reference signal to obtain a channel estimation value;

Determining, by the base station, the energy window of the channel estimation value and the energy distributed in the energy window by using the channel estimation value;

The base station determines a direct path according to energy distributed in the energy window, and extracts the direct path.
The method according to claim 1, wherein the base station performs channel estimation by using the positioning reference signal and the local positioning reference signal, and obtaining the channel estimation value comprises:

The base station performs least square channel estimation on the positioning reference signal and the local positioning reference signal to obtain a channel estimation value.
The method according to claim 1, wherein the base station uses the channel estimation value to determine an energy window of the channel estimation value and an energy distributed in the energy window, including:

Performing interpolation processing on the channel estimation value by the base station to obtain an interpolated channel estimation value;

The base station performs a frequency domain to time domain transform process on the interpolated channel estimation value to obtain a channel estimation value in a time domain;

The base station calculates the energy distributed in the energy window and the energy window by using the channel estimation value of the time domain.
The method of claim 3 wherein said calculating said energy window and said energy distribution in said energy window comprises:

Determining, by the base station, a coefficient for calculating the energy window according to the channel estimation value, and calculating a front window and a rear window according to the coefficient used for calculating the energy window, by using the front window and the Adding back windows to obtain the energy window;

The base station obtains energy distributed in the energy window by multiplying a channel estimation value of the time domain with a conjugate of a channel estimation value of the time domain.
The method according to any one of claims 1 to 4, wherein the determining, by the base station, the direct path according to the energy distributed in the energy window comprises:

The base station multiplies a maximum peak energy in the energy window by a threshold coefficient to obtain a threshold energy for determining a direct path;

The base station searches for a first energy path in the energy window that is greater than the threshold energy as the direct path.
A direct path extraction device includes:

a receiving module, configured to receive a positioning reference signal from the terminal;

a channel estimation module, configured to perform channel estimation by using the positioning reference signal and the local positioning reference signal to obtain a channel estimation value;

An energy calculation module configured to determine an energy window of the channel estimation value and an energy distributed in the energy window by using the channel estimation value;

The direct path extraction module is configured to determine a direct path according to the energy distributed in the energy window, and extract the direct path.
The apparatus of claim 6, wherein the channel estimation module is configured to perform least square channel estimation on the positioning reference signal and the local positioning reference signal to obtain a channel estimation value.
The apparatus of claim 7 wherein said energy calculation module comprises:

An interpolation submodule configured to perform interpolation processing on the channel estimation value to obtain an interpolated channel estimation value;

The IDFT sub-module is configured to perform frequency domain to time domain transform processing on the interpolated channel estimation value to obtain a channel estimation value in a time domain;

An energy window determining submodule, configured to calculate energy distributed in the energy window and the energy window by using channel estimation values in the time domain;

Wherein, the IDFT is an inverse discrete Fourier transform.
The apparatus of claim 8, wherein the energy window determination sub-module is configured to determine a coefficient for calculating the energy window based on the channel estimation value, and to calculate the energy window according to the Coefficients, a front window and a back window are calculated by adding the front window and the back window to obtain the energy window, and then by using the channel estimation value of the time domain and the channel estimation value of the time domain The conjugates are multiplied to obtain the energy distributed in the energy window.
The apparatus according to any one of claims 6-9, wherein the direct path extraction module is configured to multiply a maximum peak energy in the energy window by a threshold coefficient to obtain a threshold energy for determining a direct path. And searching for the first energy path in the energy window that is greater than the threshold energy as the direct path.
A computer readable storage medium storing computer executable instructions for performing the method of any of claims 1-5.