Phase-free channel parameter extraction method

Abstract

The invention discloses a phase-free channel parameter extraction method, which comprises the following steps of: recovering phase response by utilizing Hilbert transform by acquiring scalar frequency response measured on a plurality of antenna units; carrying out direct path calibration by combining a prior direct path distance, an angle of arrival and array geometric information so as to reconstruct a complex channel response of each antenna unit; and finally, extracting a channel power angle delay spectrum through an array angle of arrival estimation algorithm and inverse discrete Fourier transform, and obtaining angle and time delay information of a wireless channel. The method overcomes the limitation that phase information must be obtained in a traditional channel measurement system, is suitable for scenes where phases are difficult to obtain such as an unmanned aerial vehicle platform and a millimeter wave / terahertz frequency band, and remarkably reduces the complexity and cost of the system.

Description

TECHNICAL FIELD

[0001] The present application relates to a phaseless channel parameter extraction method, belonging to the technical field of wireless communication and channel measurement. BACKGROUND

[0002] It is very important to know the wideband spatial channel distribution, i.e. the Power Angle Delay Profile (PADP), in wireless channel characterization. PADP is usually extracted from the complex Channel Frequency Response (CFR) measured on a multi-antenna array system or a directional scanning antenna system. Inverse Discrete Fourier Transform (IDFT) of the CFR in the delay domain can obtain the Channel Impulse Response (CIR), i.e. the delay information is extracted. The angular domain information can be extracted by using beamforming algorithm on the CFR recorded on multiple antenna elements. However, the measurement of complex signals becomes more and more difficult. It is necessary to use expensive and complex measuring instruments to obtain accurate phase information in the millimeter wave (mmWave) and terahertz (THz) frequency bands. In addition, complex signal measurement devices, such as Vector Network Analyzer (VNA), require a radio frequency cable connection between the transmitter (TX) and the receiver (RX) to ensure the synchronization of phase and frequency, but this is difficult to achieve in many scenarios, such as antenna measurement using a drone. The high integration of transceiver design also makes it impossible to directly use the radio frequency cable to connect the antenna port to measure the phase. Therefore, the method of obtaining the wideband channel spatial distribution based on the scalar frequency response (SFR) can be expected to solve the problem of phase acquisition.

[0003] The phase recovery method based on Hilbert transform has been proved to be able to reconstruct the complex CFR from the SFR by using the amplitude-phase transformation relationship existing under certain channel conditions. This method is only applicable to the scenario where there is a Line of Sight (LOS). Some scholars have applied it to the antenna pattern reconstruction and various channel scene characterization in non-ideal environments, and have achieved good results. Some scholars have further studied the mathematical conditions that the channel must satisfy for this method. However, these studies are limited to single antenna scenarios, and no method has been developed to extract wideband spatial channel parameters based on this method combined with multi-antenna systems. In addition, the problem of absolute delay loss of the LOS path existing in this method has not been solved. SUMMARY

[0004] The technical problem solved by the present application is to provide a phaseless channel parameter extraction method, which calibrates the LOS path by using the prior knowledge of the LOS path distance and the array geometry layout of the angle of arrival, so as to recover the absolute time delay lost by the LOS path.

[0005] The present application solves the above technical problem by adopting the following technical scheme: A phaseless channel parameter extraction method, the method comprising: For a multi-antenna system comprising a transmitting antenna and a receiving antenna array having a plurality of antenna elements, measuring the distance and angle between the transmitting antenna and the center of the receiving antenna array, and recording the geometry layout of the receiving antenna array; Measuring the scalar frequency response of the transmitting antenna to each antenna element in the receiving antenna array, and performing Hilbert transform on the scalar frequency response by using a phase recovery algorithm based on Hilbert transform to obtain a preliminary reconstructed channel frequency response; According to the distance and angle between the transmitting antenna and the center of the receiving antenna array, and the geometry layout of the receiving antenna array, performing direct path calibration on the preliminary reconstructed channel frequency response to obtain a reconstructed channel frequency response; Based on the reconstructed channel frequency response, using an array angle of arrival estimation algorithm to estimate the multipath angle of arrival information, and using inverse discrete Fourier transform to estimate the multipath time delay information.

[0006] As a further preferred scheme of the present application, the specific steps of the method are as follows: Step 1, deploying a multi-antenna system comprising a transmitting antenna and a receiving antenna array having a plurality of antenna elements, recording the geometry layout of the receiving antenna array; Step 2, using a phaseless measurement device to measure the scalar frequency response of the transmitting antenna to each antenna element in the receiving antenna array , , and measuring the distance and angle , including the elevation angle and the azimuth angle ; Step 3, for the measured on the first antenna element in the receiving antenna array, using a phase recovery algorithm based on Hilbert transform to reconstruct the phase information thereof, and calculating the preliminary reconstructed channel frequency response according to and the phase information; Step 4, according to the distance , angle and geometry layout information of the receiving antenna array to the preliminary reconstructed channel frequency response performing direct path calibration to calculate the reconstructed channel frequency response ; Step 5, traversing steps 3-4 to obtain the reconstructed channel frequency response of all antenna units of the receiving antenna array, using an array angle of arrival estimation algorithm to estimate the angle of arrival information of the multipath, and using an inverse discrete Fourier transform to estimate the time delay information of the multipath, to finally obtain a channel power angle time delay spectrum.

[0007] Compared with the prior art, the technical scheme of the present application has the following technical effects: 1. Compared with the conventional phase recovery algorithm based on Hilbert transform, the present application can use only the phaseless data sampling of the multi-antenna array to perform channel measurement, complete the reconstruction of the CFR, and realize the joint estimation of the time domain and angle domain information of the multipath channel.

[0008] 2. The present application only needs a power measurement device to measure the channel SFR, and provides a phaseless channel response reconstruction and parameter estimation algorithm for many scenarios where the phase is difficult to obtain, and has the characteristics of simple algorithm, easy implementation and low hardware cost. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a flowchart of a phaseless channel parameter extraction method of the present application; Figure 2 is an indoor scene layout diagram of an embodiment of the present application; Figure 3 is a schematic diagram of a TX-RX experiment setup in the embodiment; Figure 4 is a reference CIR directly measured by the VNA in the embodiment; Figure 5 is a reconstructed CIR obtained by using the phaseless channel parameter extraction method proposed in the present application in the embodiment; Figure 6 is a reference PADP calculated by using the VNA to directly measure in the embodiment; Figure 7 is a PADP obtained by using the phaseless channel parameter extraction method proposed in the present application in the embodiment. DETAILED DESCRIPTION

[0010] The embodiments of the present application will be described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be interpreted as a limitation of the present application.

[0011] This invention proposes a phase-free channel parameter extraction method to reconstruct the phase-dependent channel parameter (PADP) in a low-os (LOS) scenario using the channel frame rate (SFR) measured by a multi-antenna system. The method includes: First, measuring the SFR of the channel using a multi-antenna system, recording the distance and angle from the transmit antenna to the center of the receive antenna array, and recording the geometric layout of the receive antenna array; next, applying a phase retrieval algorithm based on Hilbert transform to the SFR measured on each antenna element of the multi-antenna system to obtain a preliminary reconstructed channel frame rate (CFR); then, performing direct path calibration on the preliminary reconstructed CFR based on the distance and angle from the transmit antenna to the center of the receive antenna array and the array geometry to obtain the reconstructed CFR; finally, using the reconstructed CFR, employing an array angle-of-arrival (AOA) estimation algorithm and IDFT to estimate multipath AOA information and time delay information. The antenna elements of the receive antenna array are omnidirectional antennas.

[0012] In the following embodiments, the experimental setup is as follows: Figure 2 As shown, the experiment was conducted in an indoor setting. For simplicity, this experiment considers measuring a 2D multipath channel (without elevation dimension) using a Uniform Circular Array (UCA), but the principle applies to other antenna arrays and 3D multipath channels. The measured channel must be in a scenario where a LOS path exists and the following conditions are met: , Among them, subscript This indicates the LOS path, therefore Indicates the complex amplitude of the LOS path. Represents the complex amplitude of a non-direct path. The imaginary unit satisfies , used to represent the phase factor in a complex exponential term, The frequency variable represents the operating frequency of the measurement.

[0013] TX is a broadband omnidirectional biconical antenna, and RX is formed by placing the same broadband omnidirectional biconical antenna on a turntable along the radius... The horizontal circumference, with The rotation angle is measured in steps, with a total of 720 steps, rotating the virtual UCA clockwise. Before the experiment, the distance between the center of the transmit antenna (TX) and the center of the UCA was measured to be 5m, and the angle between the center of the transmit antenna and the center of the receive antenna array was measured to be... With the center of the array as the origin, the first... The angular position of each antenna element is , ,like Figure 3As shown. The experiment was conducted in the 28-30 GHz frequency band, with 750 frequency points sampled for each virtual antenna element. A VNA was used to measure the Channel Response Rate (CFR) as a reference result, and the modulus of the measured CFR was used to obtain the Channel Response Rate (SFR) for channel response reconstruction.

[0014] To further illustrate the present invention, the method of the present invention will be introduced below based on the experimental setup example described above.

[0015] like Figure 1 As shown, the specific steps are as follows: 1. Use a vector network analyzer to measure the CFR of all antenna elements from TX to RX, and measure the distance and angle between the centers of TX and RX, i.e., the distance of the direct path. The angle between the transmitting antenna and the center of the receiving antenna array ; 2. Take the modulus of the CFR recorded on all cells to obtain the SFR, and perform a Hilbert transform on the SFR to obtain the preliminary reconstructed channel frequency response. As shown in the following formula: .

[0016] 3. Perform direct path calibration on all initially reconstructed CFRs to obtain the reconstructed CFR, i.e. As shown in the following formula: ; Based on known UCA array geometry and distance data and angle data The first UCA can be calculated The distance between each antenna element and TX , The distance between the center of the receiving antenna array and the transmitting antenna. The azimuth angle of the transmitting antenna relative to the center of the receiving antenna array. The radius of the receiving antenna array, For the first The angle of each element relative to the center of the receiving antenna array The speed of light is used to calculate... At this point, the CFRs on all antenna elements have been reconstructed from the SFRs through Hilbert transform phase recovery and direct path calibration.

[0017] 4. An array angle of arrival estimation algorithm is applied to the reconstructed CFR. In this embodiment, the classic beamforming algorithm is used, and the expression is as follows: , in, Is assigned to the first complex weights of the antenna elements, represents the scanning angle. Subsequently, the PADP can be calculated by applying IDFT to the above equation, which is expressed as follows: , wherein, is the number of frequency sampling points, is a frequency discrete sampling form of is the frequency at the th frequency sampling point, is the time delay information. Similarly, the same array angle of arrival estimation and IDFT calculation are performed on the CFR measured directly using the VNA as the reference PADP.

[0018] The CIR measured directly using the VNA and the reconstructed CIR are shown in Figure 4 and Figure 5 , respectively, showing that the reconstruction result and the measurement result have high consistency. The reference PADP and the reconstructed PADP result are shown in Figure 6 and Figure 7 , respectively. The LOS path and the six reflection paths can be observed in the reconstructed PADP, which is basically consistent with the reference result. In the PADP graph, due to the limitation of the classical beamforming algorithm, the joint sidelobe effect will appear in the delay domain and the angle domain, which can be solved by using a higher precision angle estimation algorithm.

[0019] Although the method of the present application is described by taking a single transmitting antenna-multiple receiving array as an example, the principle thereof can be extended to a multiple transmitting-multiple receiving system. For each channel of the transmitting antenna and the receiving array, the amplitude and phase reconstruction based on the Hilbert transform and the direct path calibration process can be independently performed, so as to realize the multipath parameter estimation of the multiple antenna system.

[0020] In the embodiments, the method of the present application is described by taking a system structure of a single antenna at the transmitting end and a multiple antenna array at the receiving end as an example, for illustrating the implementation process of the amplitude and phase reconstruction based on the Hilbert transform and the multipath parameter estimation. It should be understood that the method of the present application has universality and is not limited to the above-mentioned system structure. According to the reciprocity principle of the wireless channel, when the propagation environment and the system geometry remain unchanged, the functions of the transmitting end and the receiving end can be interchanged. Therefore, when the system structure is a multiple antenna array at the transmitting end and a single antenna at the receiving end, the method of the present application is also applicable. At this time, the scalar frequency response corresponding to each transmitting antenna can be regarded as the array measurement data, and the Hilbert transform phase recovery and the direct path calibration steps are sequentially performed, so as to realize the reconstruction of the channel complex response and the estimation of the multipath parameters.

[0021] Based on the same inventive concept, the embodiment of the present application provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor executes the computer program to implement the steps of the foregoing phaseless channel parameter extraction method.

[0022] Based on the same inventive concept, the embodiment of the present application provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the steps of the foregoing phaseless channel parameter extraction method.

[0023] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) containing computer-usable program code.

[0024] The present application is described with reference to flowcharts and / or block diagrams of the method, device (system) and computer program product according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing apparatus to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing apparatus generate a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 means for performing the functions specified in the flowchart

[0025] These computer program instructions can also be stored in a computer-readable memory capable of guiding a computer or other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer-readable memory produce a product comprising instruction means, which implements the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 means for performing the functions specified in the flowchart

[0026] These computer program instructions can also be loaded into a computer or other programmable data processing apparatus, so that a series of operation steps are performed on the computer or other programmable data processing apparatus to produce a computer-implemented process, so that the instructions executed on the computer or other programmable data processing apparatus provide a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1steps of the functions specified in the one or more blocks.

[0027] The above embodiments are only to illustrate the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the present application.

Claims

1. A method for extracting phaseless channel parameters, characterized in that, The method includes: For a multi-antenna system including a transmitting antenna and a receiving antenna array with several antenna elements, the distance and angle between the transmitting antenna and the center of the receiving antenna array are measured, and the geometric layout of the receiving antenna array is recorded. The scalar frequency response of each antenna element in the transmit-to-receive antenna array is measured, and the scalar frequency response is transformed by a phase recovery algorithm based on Hilbert transform to obtain the preliminary reconstructed channel frequency response. Based on the distance and angle between the transmitting antenna and the center of the receiving antenna array, as well as the geometric layout of the receiving antenna array, the preliminary reconstructed channel frequency response is calibrated by direct path calibration to obtain the reconstructed channel frequency response. Based on the reconstructed channel frequency response, an array angle of arrival estimation algorithm is used to estimate multipath angle of arrival information; at the same time, inverse discrete Fourier transform is used to estimate multipath delay information.

2. The method for extracting phase-free channel parameters according to claim 1, characterized in that, The specific steps of the method are as follows: Step 1, Deployment includes transmitting antenna and having A multi-antenna system with a receiving antenna array of individual antenna elements, recording the geometric layout of the receiving antenna array; Step 2: Measure the scalar frequency response of each antenna element in the transmitting antenna to receiving antenna array using a phase-free measurement device. , And measure the distance between the transmitting antenna and the center of the receiving antenna array. and angle , Including pitch angle and azimuth ; Step 3, for the first in the receiving antenna array Measured on each antenna element The phase information is reconstructed using a phase retrieval algorithm based on Hilbert transform. The channel frequency response is initially reconstructed by calculating the phase information. ; Step 4, based on distance ,angle The geometric layout information of the receiving antenna array contributes to the initial reconstruction of the channel frequency response. Perform direct path calibration and calculate the reconstructed channel frequency response. ; Step 5: Traverse steps 3-4 to obtain the channel frequency response reconstructed by all antenna elements of the receiving antenna array. Use the array angle of arrival estimation algorithm to estimate the multipath angle of arrival information. At the same time, use the inverse discrete Fourier transform to estimate the multipath delay information. Finally, obtain the channel power angle delay spectrum.

3. The method for extracting phase-free channel parameters according to claim 1, characterized in that, The channel measurement scenario for the multi-antenna system must have a direct path and meet the following conditions: ， Among them, subscript Indicates the direct path. The complex amplitude represents the path of the direct beam. Represents the complex amplitude of a non-direct path. , For the total number of paths, The imaginary unit, For frequency variables, For the first The propagation delay of the multipath components.

4. The method for extracting phaseless channel parameters according to claim 1, characterized in that, The antenna elements in the receiving antenna array are all omnidirectional antennas.

5. The method for extracting phase-free channel parameters according to claim 2, characterized in that, In step 3, the channel frequency response is initially reconstructed. The expression is as follows: ， in, The imaginary unit, This represents the Hilbert transform operation. Represents the natural logarithm operation.

6. The method for extracting phase-free channel parameters according to claim 2, characterized in that, In step 4, the reconstructed channel frequency response The expression is as follows: ， in, The imaginary unit, This represents the Hilbert transform operation. Represents the natural logarithm operation. For frequency variables, The time delay compensated for during direct path calibration. , For the receiving antenna array The distance between each antenna element and the transmitting antenna It is the speed of light.

7. The method for extracting phase-free channel parameters according to claim 2, characterized in that, In step 5, an array angle of arrival estimation algorithm is used to estimate the multipath angle of arrival information, as shown in the following expression: ， The inverse discrete Fourier transform is used to estimate the multipath delay information, as shown in the following expression: ， in, Indicates assignment to the first The complex weights of each antenna element, The imaginary unit, For frequency variables, This represents the number of frequency sampling points. for The frequency discrete sampling form, For the first The frequency at each frequency sampling point Indicates the scanning angle. This is time delay information.

8. A computer device comprising a memory, a processor, and a computer program stored in the memory and capable of running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the phaseless channel parameter extraction method as described in any one of claims 1 to 7.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the phaseless channel parameter extraction method as described in any one of claims 1 to 7.

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