Wireless communication channel parameter measurement method and system

Abstract

The invention discloses a wireless communication channel parameter measurement method and system, and the method comprises the following steps: obtaining a transmission signal based on a PN sequence of a wireless transmitting end; obtaining the influence of the channel impulse response based on the sending signal; carrying out convolution on the influence of the sending signal and the channel pulse response to obtain a receiving signal; obtaining self-correlation outputs of different channels based on the received signal and the PN sequence; and obtaining the path loss of the channel based on the self-correlation output of different channels. Compared with a traditional channel measurement activity using a special channel measurement instrument or a VNA, the device cost is greatly reduced compared with the special channel measurement instrument, the manpower and material resource cost of the measurement activity is low, and a large amount of channel data can be flexibly obtained according to different experimental schemes.

Description

Technical Field

[0001] The present application belongs to the field of wireless communication technology, and specifically relates to a method and system for measuring wireless communication channel parameters. Background Art

[0002] With the rapid development of wireless communication technology, the requirements for communication speed and spectrum utilization are gradually increasing, so it is a general trend to achieve high-speed and high-quality communication. In the entire communication process, the wireless channel is undoubtedly one of the most core parts. The impact of the wireless channel on communication depends largely on the propagation environment in which the communication occurs. Different environments, such as cities, suburbs, and indoors, have different responses to signal propagation, which poses a severe challenge to building a reliable communication system. Therefore, the successful design and optimization of wireless communication systems requires understanding the channel characteristics and their impact on communication signals.

[0003] Channel measurement is an important means to study and understand the characteristics of wireless channels. Through channel measurement, we can obtain information about the propagation characteristics of wireless channels, such as link gain parameters (received power, path loss), link time angle parameters (power delay spectrum) and link space angle parameters (AOA, DOA). After measuring and obtaining these channel characteristic data, analyzing and processing the data is conducive to subsequent channel modeling, so as to better establish and optimize wireless communication systems.

[0004] At present, there have been many studies on channel measurement. For example, J. Huang proposed a millimeter wave time domain channel detector to measure millimeter wave MIMO channels in 28, 32 and 39 GHz frequency bands and multiple scenarios on campus. C. Umit Bas used a signal generator and VNA to measure the O2I channel and studied the path loss, delay spread and angle spread of indoor and outdoor Rx positions in two different types of buildings. Ebrahimizadeh and Javad used the Ray Tracing simulation experiment method to measure the real street canyon scene in the millimeter wave frequency band. Y. Wang built a channel detection system based on USRP devices and used directional antennas and omnidirectional antennas to measure the 4.9, 5.2 and 5.8 GHz frequency bands in the campus Internet of Things scenario. The current problems are that the use of traditional channel measurement instruments and equipment for actual measurement is costly and inconvenient to arrange. The data obtained by simulation methods such as Ray Tracing is limited in accuracy and cannot accurately reflect the characteristics of the real environment. Summary of the invention

[0005] The present application provides a wireless communication channel parameter measurement method and system to solve the problem that the traditional channel measurement hardware measurement cost is too high and inconvenient to provide and the technical problem that the RayTracing simulation measurement measurement data has poor accuracy.

[0006] To solve the above technical problems, a technical solution adopted by the present application is: a method for measuring wireless communication channel parameters, comprising the following steps:

[0007] Based on the PN sequence of the wireless transmitter, a transmission signal is obtained;

[0008] Based on the transmitted signal, obtain the impact of the channel impulse response;

[0009] Convolve the transmitted signal and the influence of the channel impulse response to obtain the received signal;

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

[0011] Based on the autocorrelation outputs of different channels, the path loss of the channel is obtained.

[0012] Further, the method for obtaining the sending signal includes:

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

[0014] x(t)=∑ n x[n]p(t-nT s ) (1);

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

[0016] Further, the method for obtaining the influence of the channel impulse response includes:

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

[0018]

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

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

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

[0022]

[0023] Among them, y(t) is the received signal.

[0024] Further, the method for obtaining the autocorrelation outputs of different channels includes:

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

[0026]

[0027] Among them, c[n] is the delayed sequence relative to the original sequence;

[0028] Based on formula (5), the autocorrelation output after filtering of different channels is obtained; wherein formula (5) is:

[0029]

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

[0031] Further, the method for obtaining the path loss of the channel includes:

[0032] Based on the autocorrelation output after filtering of different channels, the power delay spectrum of multipath is obtained;

[0033] Eliminate channel noise and obtain received power based on multipath power delay spectrum and peak search algorithm;

[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 transmission power, G USRP-T T and G USRP-R are the RF gains of the USRP device’s transmitter and receiver, respectively. t With G r is the antenna gain of the transmitting end and the receiving end, Pr is the received power, L sys is the system loss.

[0037] A technical solution adopted by the present application is: a wireless communication channel parameter measurement system, comprising:

[0038] The wireless transmitter is used to generate a PN sequence and transmit a signal;

[0039] A wireless receiving end is connected to the wireless transmitting end for communication, wherein the wireless receiving end is used to receive the transmitted signal and convert it into a received signal;

[0040] The simulation software is arranged at the wireless transmitting end and the wireless receiving end, wherein the simulation software is used to calculate the signal parameters of the transmitted signal and the received signal.

[0041] Furthermore, the wireless transmitter includes:

[0042] A first computer, used to run simulation software and calculate signal parameters;

[0043] A first USRP is connected to the first computer, wherein the first USRP is used to generate a PN sequence and a transmission signal;

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

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

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

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

[0048] The wireless receiver includes:

[0049] A second computer, used to run the simulation software and calculate the signal parameters;

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

[0051] A second antenna connected to the second computer, wherein the second antenna is used to receive the transmitted signal;

[0052] A second clock positioning component is connected to the second USRP, wherein the second clock positioning component is used to obtain location information and time information of the wireless receiving end;

[0053] A second resonator is connected to the second USRP, wherein the second resonator is used to filter, amplify and frequency convert the transmission signal;

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

[0055] The beneficial effects of the present application are: compared with the traditional channel measurement activities using dedicated channel measurement instruments or VNA, the present application firstly greatly reduces the equipment cost compared with the dedicated channel measurement instruments, and secondly, the measurement activities have low manpower and material costs, and can flexibly obtain a large amount of channel data according to different experimental schemes. Compared with using simulation software to obtain a large amount of channel data through the RayTracing method, the present application obtains measurement data in a real physical environment, taking into account the influence of various factors in the environment, and the measurement data has higher accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a flowchart of an embodiment of a method for measuring wireless communication channel parameters of the present application;

[0057] Figure 2 It is a structural diagram of an embodiment of a wireless communication channel parameter measurement system of the present application;

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

[0059] Figure 4 It is a GRC flow chart of the software platform of the wireless communication channel parameter measurement system of the present application;

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

[0061] Figure 6 It is a classroom scene field intensity thermal distribution diagram of an embodiment of a wireless communication channel parameter measurement system of the present application;

[0062] Figure 7 It is a comparison chart of the measured data of the wireless communication channel parameter measurement system of the present application and the simulation data of the traditional Ray Tracing method. DETAILED DESCRIPTION

[0063] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with specific embodiments.

[0064] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments of the following disclosure.

[0065] See also Figure 1 , Figure 1 1 is a flow chart of an embodiment of a method for measuring wireless communication channel parameters of the present application. The method comprises:

[0066] Step S1. Based on the PN sequence of the wireless transmitter, a transmission signal is obtained.

[0067] Specifically, the purpose of processing the measurement data is to obtain the influence of the channel impulse response (CIR). In the channel measurement experiment of the present application, the wireless channel is considered to be a time-invariant (LTI) system.

[0068] First, a PN sequence is generated, and then a pulse shaping filter is used to obtain a transmission signal x(t). Based on formula (1), the transmission signal is obtained. Formula (1) is:

[0069] x(t)=∑ n x[n]p(t-nT s ) (1);

[0070] Among them, 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 influence of the channel impulse response.

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

[0073]

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

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

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

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

[0078]

[0079] Among them, 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 a good autocorrelation characteristic, formula (4) is obtained to obtain the PN sequence autocorrelation output; wherein, formula (4) is:

[0082]

[0083] Among them, c[n] is the delayed sequence relative to the original sequence.

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

[0085]

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

[0087] Step S5: Based on the autocorrelation outputs of different channels, the path loss of the channels is obtained.

[0088] Specifically, step S5 includes:

[0089] Step S51: Based on the autocorrelation outputs after filtering of different channels, the power delay spectrum of the multipath is obtained.

[0090] Specifically, the output after the above operation can obtain the multipath autocorrelation peak, which contains the amplitude information A l With the delay information τ l , based on which the multipath power delay profile (PDP) can be calculated

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

[0092] Specifically, in order to extract the multipath component (MPC) from the PDP, a peak search algorithm is applied to set the maximum value of the possible MPC according to different measurement scenarios, and a threshold judgment 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. The formula is:

[0093]

[0094] Step S53. Calculate the path loss based on formula (6); wherein the 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 transmission power, G USRP-T T and G USRP-R are the RF gains of the USRP device’s transmitter and receiver, respectively. t With G r is the antenna gain of the transmitting end and the antenna gain of the receiving end, Pr is the received power; L sys It is the system loss, including the loss of the equipment itself and the loss of the RF cable. This part can be calculated through the direct connection equipment.

[0097] See also Figure 2 , Figure 2 The present invention is a schematic diagram of the structure of an embodiment of a wireless communication channel parameter measurement system of the present invention, the system comprising: a wireless transmitting terminal 1, a wireless receiving terminal 2 and simulation software. The wireless transmitting terminal 1 is used to generate a PN sequence and transmit a transmission signal. The wireless receiving terminal 2 is connected to the wireless transmitting terminal 1 in communication, wherein the wireless receiving terminal 2 is used to receive the transmission signal and convert it into a reception signal. The simulation software is set at the wireless transmitting terminal 1 and the wireless receiving terminal 2, wherein the simulation software is used to calculate the signal parameters of the transmission signal and the reception signal.

[0098] The wireless transmitter 1 includes:

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

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

[0101] A first antenna 13 is connected to the first USRP 12, wherein the first antenna 13 is used to transmit a signal;

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

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

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

[0105] The wireless receiving terminal 2 includes:

[0106] A second computer 12, used to run the simulation software and calculate the signal parameters;

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

[0108] A second antenna 23 connected to the second computer 12, wherein the second antenna 23 is used to receive and transmit signals;

[0109] A 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 receiving terminal 2;

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

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

[0112] In one embodiment, the devices used in the measurement process are listed 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 directional horn antennas and omnidirectional antennas; the first clock positioning component 14 and the second clock positioning component 24 both include GPS antennas and constant temperature crystal oscillator clock source devices; 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 installed with Ubuntu system and GnuRadio software.

[0113] The USRP X310 and USRP B210 devices provide 220V power support for each component through UPS, perform signal processing operations and data transmission interaction with the device through software on the first computer 11 and the second computer 12, and are 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 the hardware architecture on the Tx side, except that the receiving device uses a USRP B210 with a carrier frequency of 70MHz to 6GHz and a maximum bandwidth of 56MHz. The core devices of the measurement system are USRP X310 and B210, which have multiple independently tunable RF ports and adjustable RF gain. By equipping the wireless transmitter and receiver with an external clock source and a GPS antenna, the timing information and position are obtained. When the device is locked to 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 the wireless transmitter 1 (Tx), the PN sequence is first loaded into the USRP X310 through the PC, and then the X310 device samples it with a DAC and converts it into an analog signal. The analog baseband signal is then modulated to the set carrier frequency, filtered and amplified, and then transmitted to the Tx antenna via an RF cable for transmission. At the 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 signal is sampled by the ADC, down-converted into 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 uses GNU Radio software, where the GRC flow chart of the GNU Radio software based on the USRP sliding correlator system is as follows Figure 4 As shown in the figure, the upper and lower parts are 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 transmitted to the USRP Sink module, which 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 subsequent processing.

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

[0117] Table 1 is the channel measurement setting parameter table

[0118]

[0119] Many measurements were performed in real scenarios, including PL measurement in indoor and outdoor scenarios, field strength distribution measurement in indoor and outdoor scenarios, multipath effect measurement, etc. The received power data measured in indoor and outdoor scenarios are shown in Tables 2 and 3.

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

[0121]

[0122]

[0123] Table 3 shows the measured channel data for outdoor scenes

[0124]

[0125] The measured data is processed to obtain the measured data of path loss, and then fitted with the commonly used path loss model. The result is shown in the figure below: Figure 5 As shown in the figure, by calculating the MMSE, it can be seen that the FI model has the highest degree of fit to the measured data. At the same time, 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, it is believed that the measured data has a certain degree of accuracy. Figure 6 In the classroom scenario, the entire space was measured and a field strength thermal distribution map was drawn. Figure 7 This is a comparison chart of the received power data measured under a LOS path and the received power data simulated by the traditional RayTracing method. It can be seen from the figure that the overall received power is reduced by about 10dB from the measurement distance of 3 meters to 10 meters, which is basically consistent with the value reduced by the ray tracing method and the FSPL model theoretical value. However, the simulated data curve of ray tracing is monotonically decreasing, which does not conform to the physical law that the multipath effect caused by walls and floor obstacles in the real classroom scene affects the received signal. The measured data of the measurement system of the present application shows a fluctuating downward trend due to the destructive or constructive interference caused by the superposition of multipath effects in the real environment, which conforms to the physical law and is more accurate than the traditional simulation method.

[0126] Compared with the traditional channel measurement activities using dedicated channel measurement instruments or VNA, the present application firstly has a significantly lower equipment cost than dedicated channel measurement instruments, and secondly has low manpower and material costs for measurement activities, and can flexibly obtain a large amount of channel data according to different experimental schemes. Compared with using simulation software to obtain a large amount of channel data through the RayTracing method, the present application obtains measurement data in a real physical environment, taking into account the impact of various factors in the environment, and the measurement data is more accurate.

[0127] The above description is only an embodiment of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for measuring wireless communication channel parameters, characterized in that: The following steps are involved: Based on the PN sequence of the wireless transmitter, a transmission signal is obtained; Based on the transmitted signal, obtaining an influence of a channel impulse response; Convolving the transmitted signal and the influence of the channel impulse response to obtain a received signal; Based on the received signal and the PN sequence, obtaining autocorrelation outputs of different channels; Based on the autocorrelation outputs of different channels, the path loss of the channels is obtained.

2. The method according to claim 1, characterized in that Get the method of sending signals, including: Based on formula (1), the transmission signal is obtained; wherein the formula (1) is: x(t)=∑ n x[n]p(t-nT s ) (1); Among them, x(t) is the transmitted signal, x[n] is the original PN sequence, and n represents the number of channels.

3. The method according to claim 1, characterized in that A method for obtaining the influence of a channel impulse response, comprising: Based on formula (2), the influence of the channel impulse response is obtained; wherein the formula (2) is: Where h(t) is the impact of the channel impulse response; A l is the amplitude information, and τ1 is the delay information.

4. The method according to claim 1, characterized in that: The method for obtaining a received signal comprises: Based on formula (3), the received signal is obtained; wherein the formula (3) is: Among them, y(t) is the received signal.

5. The method according to claim 1, characterized in that The method of obtaining the autocorrelation output of different channels includes: Based on formula (4), the PN sequence autocorrelation output is obtained; wherein the formula (4) is: Among them, c[n] is the delayed sequence relative to the original sequence; Based on formula (5), the autocorrelation output after filtering of different channels is obtained; wherein, the formula (5) is: Among them, R cy [m] is the autocorrelation output.

6. The method according to claim 1, characterized in that The method for obtaining the path loss of the channel includes: Based on the autocorrelation output after filtering of different channels, the power delay spectrum of multipath is obtained; Eliminate channel noise and obtain received power based on the multipath power delay spectrum and peak search algorithm; Based on formula (6), the path loss is calculated; wherein the formula (6) is: L=P t +G USRP-T +G t +G r +G USRP-R -L sys -P r (6); Where Pt is the device transmission power, G USRP-T T and G USRP-R are the RF gains of the USRP device’s transmitter and receiver, respectively. t With G r is the antenna gain of the transmitting end and the receiving end, Pr is the received power, L sys is the system loss.

7. A wireless communication channel parameter measurement system, characterized in that: include: The wireless transmitter is used to generate a PN sequence and transmit a signal; A wireless receiving end, which is in communication connection with the wireless transmitting end, wherein the wireless receiving end is used to receive the transmission signal and convert it into a reception signal; The simulation software is arranged at the wireless transmitting end and the wireless receiving end, wherein the simulation software is used to calculate the signal parameters of the transmitted signal and the received signal.

8. The system according to claim 7, characterized in that The wireless transmitting end comprises: A first computer, used for running the simulation software and calculating the signal parameters; A first USRP connected to the first computer, wherein the first USRP is used to generate the PN sequence and the transmission signal; A first antenna, connected to the first USRP, wherein the first antenna is used to transmit the transmission signal; A first clock positioning component, 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, connected to the first USRP, wherein the first resonator is used to filter and amplify the transmission signal; The first power supply component is used to supply power to other components.

9. The system according to claim 1, characterized in that The wireless receiving end comprises: A second computer, used for running the simulation software and calculating the signal parameters; a second USRP connected to the second computer, wherein the second USRP is used to analyze and sample the transmitted signal; a second antenna connected to the second computer, wherein the second antenna is used to receive the transmitted signal; A second clock positioning component, connected to the second USRP, wherein the second clock positioning component is used to obtain the location information and time information of the wireless receiving end; A second resonator, connected to the second USRP, wherein the second resonator is used to filter, amplify and frequency convert the transmission signal; The second power supply component is used to supply power to other components.

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