A wireless radio channel measurement method based on smart metasurface

Abstract

The application discloses a wireless channel measurement method based on an intelligent metasurface RIS, and relates to the technical field of wireless channel measurement.The method comprises the following steps: setting the RIS as a transmitting antenna to construct a wireless channel based on the RIS; selecting and building an experimental scene; transmitting a signal by a transmitting end; setting the code of the RIS; collecting a receiving signal by a receiving end; moving the receiving end to a next measuring point, resetting the code of the RIS and collecting a receiving signal until the receiving signals of all measuring points are collected; obtaining the response of a measuring system; obtaining a channel impulse response; and analyzing the characteristics of the RIS wireless channel.The RIS wireless channel measurement method based on the application can collect high-precision channel data, further extract key channel parameters, analyze channel characteristics, help to deeply understand the regulation effect of the RIS on the channel, and provide strong support for RIS system performance evaluation and deployment strategy making.

Description

Technical Field

[0001] This invention relates to the field of radio channel measurement technology, and in particular to a radio channel measurement method based on a smart metasurface. Background Technology

[0002] The rapid development of wireless communication technology necessitates innovative solutions to address the challenges posed by increasingly complex channel environments. Reconfigurable Intelligent Surfaces (RIS) offer advantages such as low power consumption and ease of deployment. Importantly, they can reconstruct the wireless channel environment by manipulating electromagnetic waves, creating electromagnetic fields with controllable amplitude, phase, and polarization parameters. This significantly improves the performance of wireless communication systems, making RIS a potential technology for future wireless communication systems.

[0003] As the foundation of wireless communication systems, the characteristics of the channel directly determine the system's performance and design strategy. A wireless propagation channel is the channel between transmitting and receiving antennas, considering only antenna radiation parameters. A radio channel encompasses both transmitting and receiving antennas and the wireless propagation channel; in addition to antenna radiation parameters, antenna circuit parameters must also be considered. With the increase in the number of antenna elements and the decrease in element spacing, the antenna becomes inseparable from the communication environment, becoming part of it. Current research on channels mainly focuses on wireless propagation channels. However, with the widespread application of technologies such as RIS (Radio Reduction Interchange) and VMI (Very Large Scale Infrared) systems, there is an urgent need for in-depth research on radio channels that include both antenna parameters and transmitting / receiving antenna radiation parameters.

[0004] The Reflector Array (RIS) possesses the ability to dynamically adjust the phase and amplitude of its reflector elements according to external environmental conditions, creating a high degree of coupling between it and the propagation environment. Studying it solely from the perspective of the propagation channel is insufficient to fully reveal the deep interaction between the RIS's control mechanism and the environment. Treating the RIS as a transmitting antenna, by changing its amplitude, phase, and other parameters, the antenna parameters are altered, thus combining the antenna with the wireless propagation channel to construct the RIS radio channel. RIS radio channel measurement is fundamental to analyzing its characteristics. Different RIS beam orientations have varying impacts on the radio channel's characteristics. Current research on RIS channel measurement and characteristic analysis primarily focuses on the propagation channel, lacking specific methods for measuring the RIS radio channel. Therefore, researching RIS radio channel measurement methods is of significant practical importance for RIS radio channel characteristic analysis, communication system design, and performance analysis. Summary of the Invention

[0005] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies and provide a radio channel measurement method based on intelligent metasurfaces. This method provides relevant measurements and characteristic analysis of RIS radio channels, thereby enabling a better understanding and modeling of RIS radio channel characteristics. By changing the receiver's position and RIS coding, channel data is acquired. Combined with environmental configuration, channel characteristic analysis is performed on relevant parameters, leading to a better understanding of the RIS radio channel. This invention is applicable to channel measurements in typical indoor scenarios.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A radio channel measurement method based on a smart metasurface, according to the present invention, includes:

[0008] Step S1: Set the RIS as the transmitting antenna to construct a radio channel based on the smart metasurface RIS;

[0009] Step S2: Set up the experimental scenario, set up the measurement route, and set up multiple measurement points on the measurement route. The RIS code of each measurement point is different.

[0010] Step S3: The transmitting end transmits a signal;

[0011] Step S4: Set the RIS encoding;

[0012] Step S5: The receiving end acquires the received signal;

[0013] Step S6: Move the receiver to the next measurement point and repeat steps S4 and S5 until all the received signals from all measurement points have been collected.

[0014] Step S7: Obtain the response of the measurement system;

[0015] Step S8: Based on the response of the measurement system obtained in step S7 and the received signal collected in step S5, obtain the channel impulse response.

[0016] Step S9: Based on the channel impulse response obtained in step S8, analyze the path loss, delay spread (DS), and delay power spectral density of the RIS radio channel.

[0017] As a further optimization of the radio channel measurement method based on smart metasurfaces described in this invention, step S2 includes:

[0018] Step S201: Place the transmitter and RIS according to the measurement environment, and adjust the placement angle of the RIS;

[0019] Step S202: Connect the RF output line of the transmitter to the feed antenna of the RIS;

[0020] Step S203: Set up a measurement route with multiple measurement points along the route. Each measurement point is distinguished by a serial number, and place the receiving end at the first measurement point.

[0021] Step S204: Adjust the beam pointing direction of the RIS to align with the measurement route.

[0022] As a further optimization of the radio channel measurement method based on smart metasurfaces described in this invention, step S3 includes:

[0023] Step S301: For the vector signal transceiver at the transmitting end, set the center frequency, sampling rate, and signal bandwidth, and select the pre-designed signal;

[0024] Step S302: For the upconverter at the transmitting end, set the local oscillator signal frequency and the amplification power of the built-in power amplifier;

[0025] Step S303: Set the vector signal transceiver at the transmitter to transmit signals.

[0026] As a further optimization of the radio channel measurement method based on smart metasurfaces described in this invention, step S4 includes:

[0027] Step S401: Determine the RIS encoding based on the distance between the receiver and the RIS;

[0028] Step S402: Transmit the encoding to the FPGA of the RIS to change the encoding state of each RIS unit.

[0029] As a further optimization of the wireless channel measurement method based on intelligent metasurface described in this invention, step S5 includes: setting the parameters of the downconverter at the receiving end, setting the parameters of the vector signal transceiver at the receiving end, and acquiring the received signal.

[0030] As a further optimization of the radio channel measurement method based on smart metasurfaces described in this invention, step S5 is as follows:

[0031] Step S501: For the downconverter at the receiving end, set the local oscillator signal frequency and the amplification power of the built-in power amplifier;

[0032] Step S502: For the vector signal transceiver at the receiving end, set the center frequency, signal bandwidth, and signal acquisition time, and start acquiring the received signal;

[0033] Step S503: Ensure that the GPS antennas at both the transmitting and receiving ends are operational during the data acquisition process, and that the rubidium clock accuracy is greater than 10. -13 s.

[0034] As a further optimization of the radio channel measurement method based on a smart metasurface described in this invention, step S7 includes:

[0035] Step S701: The RF output interface of the transmitter's inverter is connected to the first antenna of the receiver's antenna array through a signal attenuator to acquire the direct-connect signal;

[0036] Step S702: Obtain the response of the receiving switch box using a vector network analyzer;

[0037] Step S703: Reconstruct the impulse response of the measurement system, including the channel, based on the direct-connect signal and the switch box response. .

[0038] As a further optimization of the radio channel measurement method based on a smart metasurface described in this invention, in step S8, the transmitted signal is denoted as... The response of the measurement system is denoted as The impulse response of the channel is denoted as Direct signal for:

[0039] (1)

[0040] in, Represents the convolution of signals;

[0041] The received signal acquired in step S5 for:

[0042] (2)

[0043] Performing a Fourier transform (FFT) on equations (1) and (2) yields:

[0044]

[0045]

[0046] in, The channel transfer function represents the direct-connected signal. The channel transfer function represents the received signal. , and They represent , and The variables obtained after FFT The channel impulse response is obtained by inverse Fourier transform (IFFT). :

[0047] .

[0048] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0049] (1) By treating the RIS as a reconfigurable transmitting antenna and adjusting the electromagnetic parameters of its reflecting elements to change the antenna parameters, the antenna radiation characteristics can be flexibly controlled, thereby forming an integrated coupling with the propagation channel to construct a RIS radio channel. This method can not only measure the channel response of the RIS under different beam directions, but also further analyze the channel characteristics, thus revealing the RIS's ability to control the channel characteristics.

[0050] (2) The method proposed in this invention has good adaptability and scalability, and can provide reliable data support and modeling basis for the deployment and optimization of RIS in various indoor communication scenarios. It is especially suitable for channel measurement, modeling and performance evaluation research of future wireless communication systems. This method has important theoretical guiding value and engineering reference significance for the research of key technologies such as RIS system design, network deployment strategy and beam scheduling mechanism. Attached Figure Description

[0051] Figure 1 This is a flowchart illustrating a radio channel measurement method based on a smart metasurface provided in Embodiment 1 of the present invention.

[0052] Figure 2 This is the measurement route diagram in Embodiment 1 of the present invention;

[0053] Figure 3 This is the path loss versus distance curve in Embodiment 1 of the present invention;

[0054] Figure 4 The cumulative distribution function (CDF) curve of the delay spread in Embodiment 1 of the present invention;

[0055] Figure 5 This is the time delay power spectral density curve in Embodiment 1 of the present invention. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0057] Example 1:

[0058] This embodiment provides a radio channel measurement method based on a smart metasurface. The process of this method is as follows: Figure 1 As shown, it includes:

[0059] Step S1: Use the RIS as a transmitting antenna to construct a radio channel based on the smart metasurface RIS;

[0060] Step S2: Select and build the experimental scenario;

[0061] Specifically, in this embodiment, step S2 includes the following steps:

[0062] Step S201: Select the indoor measurement scenario. The measurement environment mainly consists of metal walls, glass walls, glass doors, and metal pillars. The measurement route is close to the metal wall, with a distance of 1 m between the measurement route and the wall. No one is walking in the hall during the measurement. Place the transmitter next to the glass door, and place the RIS on the table. Adjust the placement angle of the RIS.

[0063] Step S202: Connect the RF output line of the transmitter to the feed antenna of the RIS;

[0064] Step S203: As Figure 2 As shown, a route is selected, and 20 measurement points are chosen along this route. Each measurement point is distinguished by a serial number, and the receiver is placed at the first measurement point. The distance between any two measurement points is 1.6 m, and the distance between the RIS center and the first measurement point is also 1.6 m. The RIS feed antenna is perpendicular to the RIS array, and the signal is incident perpendicularly to the RIS array, so the incident angle is 0°, and the reflection angles are set to 30° and 45°.

[0065] Step S204: Adjust the beam angle of the RIS to align with the measurement path, and fix the positions of the transmitter and the RIS.

[0066] Step S3: The transmitter transmits a signal;

[0067] Specifically, in this embodiment, step S3 includes the following steps:

[0068] Step S301: For the vector signal transceiver at the transmitting end, make the following settings: center frequency set to 3.5GHz, sampling rate set to 300 MHz, signal bandwidth set to 200 MHz;

[0069] Step S302: For the upconverter at the transmitting end, make the following settings: set the local oscillator signal frequency to 12.25GHz and the built-in power amplifier to 35dB;

[0070] Step S303: Select a pre-designed signal and transmit it;

[0071] Step S304: After double frequency conversion, the upconverter outputs a 28 GHz radio frequency signal.

[0072] Step S4: Set the RIS encoding;

[0073] Specifically, in this embodiment, step S4 includes the following steps:

[0074] Step S401: Determine the RIS encoding based on the distance between the receiver and the RIS board;

[0075] Step S402: Transmit the encoding to the RIS FPGA via a laptop to change the encoding state of each RIS unit;

[0076] Step S5: The receiving end acquires the received signal;

[0077] Specifically, in this embodiment, step S5 includes the following steps:

[0078] Step S501: For the downconverter at the receiving end, make the following settings: set the local oscillator signal frequency to 12.25GHz and the built-in power amplifier to 35dB;

[0079] Step S502: For the vector signal transceiver at the receiving end, make the following settings: center frequency set to 3.5GHz, signal bandwidth set to 200 MHz, signal acquisition time set to 2 s, and start acquiring the received signal;

[0080] Step S503: Ensure that the GPS antennas at both the transmitting and receiving ends are operational during the data acquisition process, and that the rubidium clock accuracy is greater than 10. -13 s.

[0081] Step S6: Determine whether all measurement points have completed signal acquisition;

[0082] Specifically, in this embodiment, step S6 includes the following steps:

[0083] Step S601: If there are still measurement points where signal acquisition has not been completed, move the receiver to the next measurement point; otherwise, complete the signal acquisition and proceed to step S7.

[0084] Step S602: Repeat steps S4 and S5 until all measurement points have been acquired.

[0085] Step S7: Obtain the response of the measurement system;

[0086] Specifically, in this embodiment, step S7 includes the following steps:

[0087] Step S701: The RF output interface of the transmitter's inverter is connected to the first antenna of the receiver's antenna array through a signal attenuator to acquire the direct-connect signal;

[0088] Step S702: Acquire the response of the receiving switch box using a vector network analyzer;

[0089] Step S703: Reconstruct the response of the measurement system, including the channel, based on the direct-connect signal and the switch box response. .

[0090] Step S8: Obtain the channel impulse response;

[0091] Specifically, in this embodiment, let the transmitted signal be denoted as The response of the measurement system is denoted as The impulse response of the channel is denoted as The direct-connect signal can then be represented as:

[0092]

[0093] in This represents the convolution of the signal. The acquired received signal can be represented as:

[0094]

[0095] Performing an FFT using the two formulas yields:

[0096]

[0097]

[0098] in, The channel transfer function represents the direct-connected signal. The channel transfer function represents the received signal. , and They represent , and The variables obtained after FFT The channel impulse response can be obtained through IFFT:

[0099]

[0100] Step S9: Analyze the characteristics of the RIS radio channel;

[0101] Specifically, in this embodiment, the path loss, delay spread, and delay power spectral density of the RIS radio channel are analyzed.

[0102] The method in this embodiment is used to perform RIS radio channel measurements, and the channel characteristics are analyzed after obtaining the channel impulse response. Figure 3 The curves showing the path loss as a function of distance at RIS reflections of 30° and 45° are presented. It can be seen that the path loss obtained by measuring the RIS radio channel using the method proposed in this invention fits well with the floating intercept (FI) path loss model. Figure 4 and Figure 5 The time delay spread and time delay power spectral density of metal reflection at 30° and 45° and RIS reflection at 30° and 45° are shown respectively. It can be seen that the time delay spread of RIS reflection is smaller than that of metal reflection, and RIS can reduce the multipath effect in the wireless channel.

[0103] In summary, the radio channel measurement method based on smart metasurfaces established in this invention supports the measurement of radio channels combining RIS and wireless channels. By adjusting the RIS coding, it supports the extension to measuring channels with different beam reflection directions of the RIS, which has guiding significance for RIS wireless communication systems and RIS deployment.

[0104] Any aspects of this invention not described in detail are well-known to those skilled in the art.

[0105] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for measuring radio channels based on smart metasurfaces, characterized in that, include: Step S1: Set the RIS as the transmitting antenna to construct a radio channel based on the smart metasurface RIS; Step S2: Set up the experimental scenario, set up the measurement route, and set up multiple measurement points on the measurement route. The RIS code of each measurement point is different. Step S3: The transmitting end transmits a signal; Step S4: Set the RIS encoding; Step S5: The receiving end acquires the received signal; Step S6: Move the receiver to the next measurement point and repeat steps S4 and S5 until all the received signals from all measurement points have been collected. Step S7: Obtain the response of the measurement system; Step S8: Based on the response of the measurement system obtained in step S7 and the received signal collected in step S5, obtain the channel impulse response. Step S9: Based on the channel impulse response obtained in step S8, analyze the path loss, delay spread (DS), and delay power spectral density of the RIS radio channel.

2. The radio channel measurement method based on a smart metasurface according to claim 1, characterized in that, Step S2 includes: Step S201: Place the transmitter and RIS according to the measurement environment, and adjust the placement angle of the RIS; Step S202: Connect the RF output line of the transmitter to the feed antenna of the RIS; Step S203: Set up a measurement route with multiple measurement points along the route. Each measurement point is distinguished by a serial number, and place the receiving end at the first measurement point. Step S204: Adjust the beam pointing direction of the RIS to align with the measurement route.

3. The radio channel measurement method based on a smart metasurface according to claim 1, characterized in that, Step S3 includes: Step S301: For the vector signal transceiver at the transmitting end, set the center frequency, sampling rate, and signal bandwidth, and select the pre-designed signal; Step S302: For the upconverter at the transmitting end, set the local oscillator signal frequency and the amplification power of the built-in power amplifier; Step S303: Set the vector signal transceiver at the transmitter to transmit signals.

4. The radio channel measurement method based on a smart metasurface according to claim 1, characterized in that, Step S4 includes: Step S401: Determine the RIS encoding based on the distance between the receiver and the RIS; Step S402: Transmit the encoding to the FPGA of the RIS to change the encoding state of each RIS unit.

5. The radio channel measurement method based on a smart metasurface according to claim 1, characterized in that, Step S5 includes: setting the parameters of the downconverter at the receiving end, setting the parameters of the vector signal transceiver at the receiving end, and acquiring the received signal.

6. The radio channel measurement method based on a smart metasurface according to claim 1, characterized in that, Step S5 is as follows: Step S501: For the downconverter at the receiving end, set the local oscillator signal frequency and the amplification power of the built-in power amplifier; Step S502: For the vector signal transceiver at the receiving end, set the center frequency, signal bandwidth, and signal acquisition time, and start acquiring the received signal; Step S503: Ensure that the GPS antennas at both the transmitting and receiving ends are operational during the data acquisition process, and that the rubidium clock accuracy is greater than 10. -13 s.

7. The radio channel measurement method based on a smart metasurface according to claim 1, characterized in that, Step S7 includes: Step S701: The RF output interface of the transmitter's upconverter is connected to the first antenna of the receiver's antenna array through a signal attenuator to acquire the direct-connect signal; Step S702: Obtain the response of the receiving switch box using a vector network analyzer; Step S703: Reconstruct the impulse response of the measurement system, including the channel, based on the direct-connect signal and the switch box response. .

8. The radio channel measurement method based on a smart metasurface according to claim 1, characterized in that, In step S8, the transmitted signal is denoted as The response of the measurement system is denoted as The impulse response of the channel is denoted as Direct signal for: （1）； in, Represents the convolution of signals; The received signal acquired in step S5 for: （2）； Performing a Fourier transform (FFT) on equations (1) and (2) yields: ； ； in, The channel transfer function represents the direct-connected signal. The channel transfer function represents the received signal. , and They represent , and The variables obtained after FFT The channel impulse response is obtained by inverse Fourier transform (IFFT). : 。

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