A method and system for measuring parameters of a wireless communication channel

Abstract

The application discloses a wireless communication channel parameter measurement method and system, comprising the following steps: obtaining a sending signal based on a PN sequence of a wireless transmitting end; obtaining an influence of a channel impulse response based on the sending signal; performing convolution on the sending signal and the influence of the channel impulse response to obtain a receiving signal; obtaining autocorrelation outputs of different channels based on the receiving signal and the PN sequence; and obtaining path loss of the channel based on the autocorrelation outputs of the different channels. Compared with the traditional channel measurement activity using a special channel measurement instrument or a VNA, the device cost is greatly reduced, the manpower and material resources cost of the measurement activity is low, and a large amount of channel data can be obtained according to different experimental schemes.

Description

Technical Field

[0001] This application belongs to the field of wireless communication technology, specifically relating to a method and system for measuring wireless communication channel parameters. Background Technology

[0002] With the rapid development of wireless communication technology, the requirements for communication speed and spectrum utilization are gradually increasing, making high-speed and high-quality communication an inevitable trend. Throughout the communication process, the wireless channel is undoubtedly one of the most crucial components, and its impact on communication largely depends on the propagation environment. Different environments, such as urban, suburban, and indoor environments, produce different responses to signal propagation, posing a significant challenge to building reliable communication systems. Therefore, successfully designing and optimizing wireless communication systems requires understanding channel characteristics and their impact on communication signals.

[0003] Channel measurement is a crucial method for studying and understanding the characteristics of wireless channels. Through channel measurements, information about the propagation characteristics of wireless channels can be obtained, such as link gain parameters (received power, path loss), link time angle parameters (power delay spectrum), and link spatial angle parameters (AOA, DOA). After acquiring this channel characteristic data, analysis and processing of the data are beneficial for subsequent channel modeling, thereby enabling better establishment and optimization of wireless communication systems.

[0004] There has been considerable research in channel measurement. For example, J. Huang proposed a millimeter-wave time-domain channel detector to conduct millimeter-wave MIMO channel measurements in multiple scenarios across campuses using the 28, 32, and 39 GHz bands. C. Umit Bas used a signal generator and VNA to measure O2I channels, studying path loss, delay spread, and angle spread at indoor and outdoor Rx locations in two different types of buildings. Ebrahimizadeh, Javad used Ray Tracing simulation experiments to measure real-world street canyon scenarios in the millimeter-wave band. Y. Wang built a channel detection system based on USRP equipment and used directional and omnidirectional antennas to measure the 4.9, 5.2, and 5.8 GHz bands in a campus IoT scenario. Current problems include the high cost and inconvenient deployment of traditional channel measurement instruments, and the limited accuracy of data obtained through simulation methods such as Ray Tracing, which cannot accurately reflect the characteristics of the real environment. Summary of the Invention

[0005] This application provides a method and system for measuring wireless communication channel parameters to solve the problems of high cost and inconvenient deployment of traditional channel measurement hardware, as well as the poor accuracy of RayTracing simulation measurement data.

[0006] To solve the above-mentioned technical problems, this application adopts the following technical solution: a method for measuring wireless communication channel parameters, comprising the following steps:

[0007] The transmitted signal is obtained based on the PN sequence of the wireless transmitter;

[0008] Based on the transmitted signal, the impact on the channel impulse response is obtained;

[0009] The received signal is obtained by convolving the effects of the transmitted signal and the channel impulse response.

[0010] Based on the received signal and the PN sequence, the autocorrelation output of different channels is obtained;

[0011] The path loss of a channel is obtained based on the autocorrelation output of different channels.

[0012] Furthermore, the method for acquiring the transmitted signal includes:

[0013] Based on formula (1), the transmitted signal is obtained; where formula (1) is:

[0014] x(t)=∑ n x[n]p(t-nT s (1);

[0015] Where x(t) is the transmitted signal, x[n] is the original PN sequence, and n represents the number of channels.

[0016] Furthermore, methods for obtaining the influence of channel impulse response include:

[0017] Based on formula (2), the influence of the channel impulse response is obtained; where formula (2) is:

[0018]

[0019] Where h(t) represents the influence of the channel impulse response; A l τ represents amplitude information, and τ1 represents delay information.

[0020] Furthermore, the method for acquiring the received signal includes:

[0021] Based on formula (3), the received signal is obtained; where formula (3) is:

[0022]

[0023] Where y(t) is the received signal.

[0024] Furthermore, methods for obtaining the autocorrelation outputs of different channels include:

[0025] Based on formula (4), the autocorrelation output of the PN sequence is obtained; where formula (4) is:

[0026]

[0027] Where c[n] is the delayed sequence relative to the original sequence;

[0028] Based on formula (5), the autocorrelation outputs after filtering through different channels are obtained; where formula (5) is:

[0029]

[0030] Among them, R cy [m] represents the autocorrelation output.

[0031] Furthermore, methods for obtaining the path loss of the channel include...

[0032] The power delay spectrum of the multipath is obtained based on the autocorrelation output after filtering through different channels.

[0033] Based on the power delay spectrum of multipath and peak search algorithm, channel noise is eliminated and the received power is obtained;

[0034] Based on formula (6), the path loss is calculated; where formula (6) is:

[0035] L = P t +G USRP-T +G t +G r +G USRP-R -L sys -P r (6);

[0036] Where Pt is the device's transmit power, and G USRP-T T and G USRP-R These are the RF gains of the USRP device's transmitter and receiver, respectively, G t With G r Here, Pr represents the transmitting antenna gain and the receiving antenna gain, and L represents the received power. sys It is system loss.

[0037] One technical solution adopted in this application is: a wireless communication channel parameter measurement system, comprising:

[0038] A wireless transmitter used to generate a PN sequence and transmit signals.

[0039] A wireless receiver is connected in communication with a wireless transmitter. The wireless receiver is used to receive and convert the transmitted signal into a received signal.

[0040] The simulation software is set up at both the wireless transmitter and the wireless receiver. The simulation software is used to calculate the signal parameters of the transmitted and received signals.

[0041] Furthermore, the wireless transmitter includes:

[0042] The first computer was used to run simulation software and calculate signal parameters;

[0043] A first USRP is connected to a first computer, wherein the first USRP generates a PN sequence and generates a transmit signal;

[0044] A first antenna is connected to a first USRP, wherein the first antenna is used to transmit signals;

[0045] A first clock positioning component is connected to a first USRP, wherein the first clock positioning component is used to obtain the location information and time information of the wireless transmitter.

[0046] A first resonator is connected to a first USRP, wherein the first resonator is used to filter and amplify the transmitted signal;

[0047] The first power supply component is used to supply power to other components.

[0048] The wireless receiver includes:

[0049] The second computer is used to run simulation software and calculate signal parameters;

[0050] The second USRP is connected to the second computer, and the second USRP is used to analyze and sample the transmitted signal;

[0051] The second antenna is connected to the second computer, and the second antenna is used to receive transmitted signals.

[0052] The second clock positioning component is connected to the second USRP, wherein the second clock positioning component is used to obtain the location information and time information of the wireless receiver.

[0053] The second resonator is connected to the second USRP, and the second resonator is used to filter, amplify and frequency convert the transmitted signal;

[0054] The second power supply unit is used to supply power to other components.

[0055] The beneficial effects of this application are as follows: Compared with traditional channel measurement activities using dedicated channel measurement instruments or VNAs, this application significantly reduces equipment costs, lowers the manpower and material costs of measurement activities, and allows for flexible deployment to acquire a large amount of channel data according to different experimental schemes. Compared with acquiring a large amount of channel data using simulation software via RayTracing, this application obtains measurement data in a real physical environment, taking into account the influence of various environmental factors, resulting in higher measurement data accuracy. Attached Figure Description

[0056] Figure 1 This is a flowchart illustrating an embodiment of the wireless communication channel parameter measurement method of this application;

[0057] Figure 2 This is a schematic diagram of an embodiment of the wireless communication channel parameter measurement system of this application;

[0058] Figure 3 This is a hardware platform system block diagram of an embodiment of the wireless communication channel parameter measurement system of this application;

[0059] Figure 4 This is a GRC flow diagram of the software platform of an embodiment of the wireless communication channel parameter measurement system of this application;

[0060] Figure 5 This is a path loss model fitting diagram of an embodiment of the wireless communication channel parameter measurement system of this application;

[0061] Figure 6 This is a thermal distribution diagram of the field strength in a classroom scene according to an embodiment of the wireless communication channel parameter measurement system of this application;

[0062] Figure 7 This is a comparison chart of the measured data of the wireless communication channel parameter measurement system of this application and the simulation data of the traditional Ray Tracing method. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments.

[0064] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0065] See Figure 1 , Figure 1 This is a flowchart illustrating an embodiment of the wireless communication channel parameter measurement method of this application. The method includes:

[0066] Step S1. Obtain the transmitted signal based on the PN sequence of the wireless transmitter.

[0067] Specifically, the purpose of processing the measurement data is to obtain the effect of the channel impulse response (CIR). In the channel measurement experiments of this application, the wireless channel is assumed to be a time-invariant (LTI) system.

[0068] First, a PN sequence is generated, and then pulse-shaping filtering is performed using an RRC filter to obtain the transmitted signal x(t); based on formula (1), the transmitted signal is obtained; where formula (1) is:

[0069] x(t)=∑ n x[n]p(t-nT s (1);

[0070] Where x(t) is the transmitted signal, x[n] is the original PN sequence, and n represents the number of channels.

[0071] Step S2. Based on the transmitted signal, obtain the impact of the channel impulse response.

[0072] Specifically, the transmitted signal is then sent, and the multipath CIR effect of the transmitted signal in the channel is h(t). Based on formula (2), the influence of the channel impulse response is obtained; where formula (2) is:

[0073]

[0074] Where h(t) represents the influence of the channel impulse response; A l τ represents amplitude information, and τ1 represents delay information.

[0075] Step S3. Convolve the effects of the transmitted signal and the channel impulse response to obtain the received signal.

[0076] Specifically, the signal y(t) received by the receiver is the convolution of the transmitted signal and the channel response, thus obtaining the received signal.

[0077] Based on formula (3), the received signal is obtained; where formula (3) is:

[0078]

[0079] Where y(t) is the received signal.

[0080] Step S4. Based on the received signal and the PN sequence, obtain the autocorrelation output of different channels;

[0081] Specifically, because the PN sequence itself has good autocorrelation characteristics, formula (4) is obtained to obtain the autocorrelation output of the PN sequence; where formula (4) is:

[0082]

[0083] Where c[n] is the delayed sequence relative to the original sequence.

[0084] The received signal y(t) is down-converted and sampled by AD to become a discrete digital signal y[m] which enters the USRP device. After passing through the same RRC filter as the transmitter, the filtered signal is input to the autocorrelation module of the PN sequence to obtain formula (5), and the autocorrelation output after filtering for different channels is obtained; where formula (5) is:

[0085]

[0086] Among them, R cy [m] represents the autocorrelation output.

[0087] Step S5. Obtain the path loss of the channel based on the autocorrelation output of different channels.

[0088] Specifically, step S5 includes:

[0089] Step S51. Obtain the power delay spectrum of the multipath based on the autocorrelation output after filtering of different channels.

[0090] Specifically, the output after the above calculations yields the autocorrelation peak of the multipath path, which contains amplitude information A. l With delay information τ l Based on this, the power delay spectrum (PDP) of the multipath can be calculated.

[0091] Step S52. Based on the power delay spectrum of the multipath and the peak search algorithm, eliminate channel noise and obtain the received power.

[0092] Specifically, to extract multipath components (MPC) from the PDP, a peak search algorithm is applied, setting the maximum possible MPC values ​​based on different measurement scenarios, and a threshold decision method is used to distinguish useful signals from noise. The power of each multipath is superimposed, and the received power is obtained according to the following formula:

[0093]

[0094] Step S53. Calculate the path loss based on formula (6); wherein, formula (6) is:

[0095] L = P t +G USRP-T +G t+G r +G USRP-R -L sys -P r (6);

[0096] Where Pt is the device's transmit power, and G USRP-T T and G USRP-R These are the RF gains of the USRP device's transmitter and receiver, respectively, G t With G r Here, Pr represents the transmitting antenna gain and the receiving antenna gain, and L represents the received power. sys This refers to system losses, including the losses of the equipment itself and the losses of the RF cable. This part can be calculated by directly connecting the equipment.

[0097] See Figure 2 , Figure 2 This is a schematic diagram of an embodiment of the wireless communication channel parameter measurement system of this application. The system includes: a wireless transmitter 1, a wireless receiver 2, and simulation software. The wireless transmitter 1 is used to generate a PN sequence and transmit a signal. The wireless receiver 2 is communicatively connected to the wireless transmitter 1, and is used to receive the transmitted signal and convert it into a received signal. The simulation software is located at both the wireless transmitter 1 and the wireless receiver 2, and is used to calculate the signal parameters of the transmitted and received signals.

[0098] Wireless transmitter 1 includes:

[0099] The first computer 11 is used to run simulation software and calculate signal parameters;

[0100] The first USRP 12 is connected to the first computer 11, wherein the first USRP 12 is used to generate a PN sequence and generate a transmission signal;

[0101] The first antenna 13 is connected to the first USRP 12, wherein the first antenna 13 is used to transmit signals;

[0102] The first clock positioning component 14 is connected to the first USRP 12, wherein the first clock positioning component 14 is used to obtain the location information and time information of the wireless transmitter 1;

[0103] The first resonator 15 is connected to the first USRP 12, wherein the first resonator 15 is used to filter and amplify the transmitted signal;

[0104] The first power supply component 16 is used to supply power to other components.

[0105] Wireless receiver 2 includes:

[0106] The second computer 12 is used to run simulation software and calculate signal parameters;

[0107] The second USRP 22 is connected to the second computer 12, wherein the second USRP 22 is used to analyze and sample the transmitted signal;

[0108] The second antenna 23 is connected to the second computer 12, wherein the second antenna 23 is used to receive transmitted signals;

[0109] The second clock positioning component 24 is connected to the second USRP 22, wherein the second clock positioning component 24 is used to obtain the location information and time information of the wireless receiver 2;

[0110] The second resonator 25 is connected to the second USRP 22, wherein the second resonator 25 is used to filter, amplify and frequency convert the transmitted signal;

[0111] The second power supply component 26 is used to supply power to other components.

[0112] In one embodiment, the equipment used in the measurement process is arranged as follows: the first USRP 12 and the second USRP 22 are USRP X310 and USRP B210 devices respectively; the first antenna 13 and the second antenna 23 are composite antennas including a directional horn antenna and an omnidirectional antenna; the first clock positioning component 14 and the second clock positioning component 24 are both devices including a GPS antenna and a temperature-controlled crystal oscillator clock source; the first power supply component 16 and the second power supply component 26 are both uninterruptible power supplies (UPS); the first computer 11 and the second computer 12 are equipped with the Ubuntu system and GnuRadio software.

[0113] The USRP X310 and USRP B210 devices are powered by a UPS to provide 220V power to each component. Signal processing and data transmission are handled by software on the first computer 11 and the second computer 12. Each device is equipped with a USRP X310 with a carrier frequency range of 1MHz to 6GHz and a maximum bandwidth of 120MHz, a GPS antenna, and a Tx antenna. The hardware architecture on the Rx side is the same as that on the Tx side, except that the receiving device uses a USRP B210 with a carrier frequency range of 70MHz to 6GHz and a maximum bandwidth of 56MHz. The core devices of the measurement system are the USRP X310 and B210, which have multiple independently tunable RF ports and adjustable RF gain. By equipping the wireless transmitter and receiver with external clock sources and GPS antennas, timing information and location are obtained. When the device locks onto GPS, the frequency accuracy can be less than 5ppb, thereby reducing the impact of carrier frequency offset (CFO) and timing offset (TO) on the obtained channel impulse response (CIR).

[0114] At wireless transmitter 1 (Tx), the PN sequence is first loaded into the USRP X310 via a PC. The X310 device then samples the signal using a DAC and converts it into an analog signal. Next, the analog baseband signal is modulated to the set carrier frequency, filtered, and amplified before being transmitted to the Tx antenna via an RF cable. At wireless receiver 2 (Rx), the fading signal received by the Rx antenna is transmitted to the USRP B210 device via an RF cable for amplification, filtering, and down-conversion. Then, the intermediate frequency (IF) signal is sampled by an ADC, down-converted to a baseband digital signal, and transmitted to the PC for further processing.

[0115] The software platform uses the time-domain sliding correlator method, which has been widely used in previous channel measurement systems. This application selects GNU Radio software, and the GRC flowchart of the USRP-based sliding correlator system in GNU Radio software is shown below. Figure 4 As shown, the upper and lower parts represent the transmit and receive diagrams, respectively. The measured PN sequence is generated by an 11-bit linear feedback shift register (LFSR), passed to a root raised cosine (RRC) pulse shaping filter for filtering, and then the filtered signal is sent to the USRP's Sink module. This module can be configured with settings such as sampling rate, transmit port, and RF gain. The USRP Source module receives the fading signal, filters it through the RRC filter, and then the File Sink module saves the fading signal to a file for further processing.

[0116] The channel parameter measurement system hardware and software platform proposed in this application are as follows: Figure 3 and Figure 4 As shown in Table 1, the main parameter settings of the channel measurement system are as follows.

[0117] Table 1 shows the channel measurement settings parameters.

[0118]

[0119] Numerous measurements were performed in real-world scenarios, including power field (PL) measurements in both indoor and outdoor environments, field strength distribution measurements in both indoor and outdoor environments, and measurements of multipath effects. The received power data obtained from measurements in both indoor and outdoor environments are shown in Tables 2 and 3.

[0120] Table 2 shows the measured channel data for indoor scenarios.

[0121]

[0122]

[0123] Table 3 shows the measured channel data in outdoor scenarios.

[0124]

[0125] The measured data is processed to obtain the actual path loss data, which is then fitted with a commonly used path loss model. The results are shown in the figure below. Figure 5 As shown, the MMSE calculation shows that the FI model has the highest fit to the measured data, and the fitted PLE value is 1.99, while the PLE benchmark value of the real free space environment is 2.0, with a difference of only 0.01. Therefore, the measured data is considered to have a certain degree of accuracy. Figure 6 In a classroom setting, measurements were taken of the entire space, and a thermal distribution map of the electric field strength was drawn. Figure 7 The graph shows a comparison between the received power data obtained from actual measurements along a LOS path and the received power data obtained from simulations using the traditional RayTracing method. The graph shows that the measured power decreased by approximately 10 dB from a measurement distance of 3 meters to 10 meters, which is consistent with the theoretical decrease value of the ray tracing method and the FSPL model. However, the simulated data curve of the ray tracing method shows a monotonically decreasing trend, which does not conform to the physical law of the multipath effect caused by walls and floor obstacles in a real classroom setting affecting the received signal. In contrast, the measured data of the measurement system in this application shows a fluctuating decreasing trend due to the destructive or constructive interference caused by the superposition of multipath effects in the real environment, which conforms to physical laws and is more accurate than the traditional simulation method.

[0126] Compared to traditional channel measurement activities using dedicated channel measurement instruments or VNAs, this application offers several advantages. First, it significantly reduces equipment costs. Second, it lowers the manpower and material costs of the measurement activities and allows for flexible deployment to acquire large amounts of channel data based on different experimental schemes. Third, compared to acquiring large amounts of channel data using simulation software via RayTracing, this application obtains measurement data in a real physical environment, taking into account the influence of various environmental factors, resulting in higher measurement accuracy.

[0127] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for measuring wireless communication channel parameters, characterized in that, Includes the following steps: The transmitted signal is obtained based on the PN sequence of the wireless transmitter; Based on the transmitted signal, the influence of the channel impulse response is obtained; The received signal is obtained by convolving the effects of the transmitted signal and the channel impulse response. Based on the received signal and the PN sequence, the autocorrelation outputs of different channels are obtained; wherein, the method for obtaining the autocorrelation outputs of different channels includes: Based on formula (4), the autocorrelation output of the PN sequence is obtained; wherein, formula (4) is: （4）； in, This is a delayed sequence relative to the original sequence; Based on formula (5), the autocorrelation outputs after filtering through different channels are obtained; wherein, formula (5) is: （5）； in, This is the autocorrelation output; The path loss of a channel is obtained based on the autocorrelation output of different channels; wherein the method for obtaining the path loss of a channel includes: The power delay spectrum of the multipath is obtained based on the autocorrelation output after filtering through different channels. Based on the power delay spectrum of the multipath and the peak search algorithm, channel noise is eliminated and the received power is obtained; Based on formula (6), the path loss L is calculated; wherein, formula (6) is: （6）； Among them, P t For the device's transmission power ， and These represent the RF gains of the USRP device's transmitting and receiving ends, respectively. and For the transmitting antenna gain and the receiving antenna gain, Pr For received power, It is system loss.

2. The method according to claim 1, characterized in that, Methods for obtaining transmitted signals include: The transmitted signal is obtained based on formula (1); wherein, formula (1) is: （1）； in, In order to send a signal, The original PN sequence, This represents the number of channels.

3. The method according to claim 1, characterized in that, Methods for obtaining the influence of channel impulse response include: Based on formula (2), the influence of the channel impulse response is obtained; wherein, formula (2) is: （2） ； in, The influence of channel impulse response; For amplitude information, This is delayed information.

4. The method according to claim 3, characterized in that, Methods for acquiring received signals include: The received signal is obtained based on formula (3); wherein, formula (3) is: （3）； in, To receive signals.

5. A wireless communication channel parameter measurement system, characterized in that, A system for implementing the wireless communication channel parameter measurement method according to any one of claims 1-4, wherein the system comprises: A wireless transmitter used to generate a PN sequence and transmit signals. A wireless receiver is communicatively connected to the wireless transmitter, wherein the wireless receiver is used to receive the transmitted signal and convert it into a received signal; Simulation software is installed at both the wireless transmitter and the wireless receiver, wherein the simulation software is used to calculate the signal parameters of the transmitted and received signals.

6. The system according to claim 5, characterized in that, The wireless transmitter includes: A first computer is used to run the simulation software and calculate the signal parameters; A first USRP is connected to the first computer, wherein the first USRP is used to generate the PN sequence and generate the transmit signal; A first antenna is connected to the first USRP, wherein the first antenna is used to transmit the transmitted signal; A first clock positioning component is connected to the first USRP, wherein the first clock positioning component is used to obtain the location information and time information of the wireless transmitter; A first resonator is connected to the first USRP, wherein the first resonator is used to filter and amplify the transmitted signal; The first power supply component is used to supply power to other components.

7. The system according to claim 5, characterized in that, The wireless receiver includes: A second computer is used to run the simulation software and calculate the signal parameters; A second USRP is connected to the second computer, wherein the second USRP is used to analyze and sample the transmitted signal; A second antenna is connected to the second computer, wherein the second antenna is used to receive the transmitted signal; The second clock positioning component is connected to the second USRP, wherein the second clock positioning component is used to obtain the location information and time information of the wireless receiver; A second resonator is connected to the second USRP, wherein the second resonator is used to filter, amplify, and frequency-convert the transmitted signal; The second power supply unit is used to supply power to other components.

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