Multi-path birth and death modeling method based on wireless channel simulator

Abstract

The invention relates to a multipath birth and death modeling method based on a wireless channel simulator, which comprises the following steps of: acquiring multipath number and phase information in adjacent scenes, judging whether the multipath number of the adjacent scenes is consistent and whether phase difference exists in the phases of the adjacent scenes, and if the multipath number of the adjacent scenes is not consistent, executing the step of modeling; determining the number of the multiple paths in the scene with the maximum number of the multiple paths in all the scenes; and enabling scenes except the scene with the maximum multipath number to realize the consistency of the multipath number of all the scenes in a zero padding manner, if a phase difference exists between phases of adjacent scenes, determining that the last sampling point of channel impact response of the previous scene in the adjacent scenes corresponds to a phase sequence of all the multipath, taking the phase sequence as an initial phase in the next scene, and taking the initial phase as an initial phase in the next scene. And for the scenes with different multipath numbers, the multipath numbers of all the scenes are consistent in a zero padding manner. The change of the multipath number caused by scene change is simulated based on the simulation instrument, the relative speed change of the transmitting end and the receiving end is realized, and the simulation scene of the wireless channel simulation instrument is enriched.

Description

Technical Field

[0001] The invention belongs to the technical field of multipath birth and death modeling, and in particular relates to a multipath birth and death modeling method based on a wireless channel simulator. Background Art

[0002] Multipath generation and death refers to the dynamic propagation environment in which multipath signals suddenly appear or disappear in an outdoor wireless channel. This is usually caused by the change of the propagation scene. In the laboratory, the wireless channel simulator can simulate the multipath generation and death process to test the receiver's resistance to the sudden disappearance or sudden appearance of multipath signals.

[0003] The traditional method of simulating the birth and death of multipath in wireless channel simulators is generally to use multiple pure direct-view paths and randomly adjust the delays of these paths through the simulator. Figure 1 As shown, for the five pure direct-view paths, the delays before the transition are 1ns, 3ns, 4ns, 5ns and 7ns respectively, and the delays after the transition are 2ns, 3ns, 5ns, 7ns and 8ns respectively.

[0004] The switching of communication scenarios will lead to dynamic changes in wireless channels. For example, when a terminal enters an indoor environment from an outdoor environment, the wireless channel will generally switch from a LOS scenario to a NLOS scenario, which means that the number of multipaths may change. When a car enters a parking lot, not only the number of multipaths changes, but also the running speed. Traditional multipath generation and death simulation methods cannot reflect the above changes.

[0005] Therefore, how to improve the traditional simulation method of multipath generation and death in the wireless channel emulator, so as to simulate the change of multipath number caused by scene change based on the emulator, and at the same time realize the relative speed change between the transmitting and receiving ends, and enrich the simulation scene of the wireless channel emulator, is a technical problem that needs to be solved urgently. Summary of the invention

[0006] The purpose of the present invention is to provide a multipath birth and death modeling method based on a wireless channel emulator, which is used to improve the traditional simulation method of multipath birth and death in the wireless channel emulator, so as to simulate the change of the number of multipaths caused by the scene change based on the emulator, and at the same time realize the relative speed change between the transmitting and receiving ends, thereby enriching the simulation scene of the wireless channel emulator.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] A multipath birth and death modeling method based on a wireless channel simulator, characterized in that it comprises the following steps:

[0009] S1: Obtain the number and phase information of multipaths in adjacent scenes, determine whether the number of multipaths in adjacent scenes is consistent and whether there is a phase difference in the phases of adjacent scenes. If the number of multipaths in adjacent scenes is inconsistent, execute step S2; if there is a phase difference in the phases of adjacent scenes, execute step S4;

[0010] S2: Determine the number of multipaths N in the scene with the largest number of multipaths among all scenes max,path ;

[0011] S3: divide the scenes other than the scene with the largest number of multipaths into N max,path Based on this, the number of multipaths in all scenarios is made consistent by padding with zeros;

[0012] S4: Determine the phase sequence of all multipaths corresponding to the last sample point of the previous scene channel impulse response in the adjacent scene θ1 = [θ1, θ1, ... θ N1 ], where N1 represents the number of multipaths in the previous scene;

[0013] S5: Take θ1 as the initial phase in the next scenario, and use N max,path Based on this, the number of multipaths in all scenarios is made consistent by padding with zeros.

[0014] Preferably, when the terminal speeds of adjacent scenes are inconsistent, the multipath generation and death caused by the switching of adjacent scenes is processed through the following specific process:

[0015] S21: Assume that the half-wavelength sampling density is ρ, which represents the number of sampling points on the half-wavelength length during the modeling process, and the interval between two sampling points is d. Where λ represents the wavelength;

[0016] S22: Establish the Doppler formula:

[0017]

[0018] Among them, f center is the center frequency, v represents the terminal running speed, and Ω is the incoming wave angle;

[0019] according to

[0020] S23:

[0021] t0 represents the sampling time between two sample points. Substitute into the formula In, get

[0022] make

[0023] S24:

[0024] represents the baseband sampling rate,

[0025] It is expressed as:

[0026]

[0027] in, Indicates the maximum Doppler shift.

[0028] Preferably, when the terminal velocity remains unchanged, the maximum Doppler shift f d,max constant.

[0029] Preferably, in a multipath generation and death scenario with different motion speeds, the baseband sampling rate F s The channel impulse response of the adjacent scenes with inconsistent multipath numbers or phase differences is calculated. The formula for calculating the channel impulse response is:

[0030]

[0031] Among them, ρ1 represents the half-wavelength sampling density of the scene before multipath birth and death, ρ2 represents the half-wavelength sampling density of the scene after multipath birth and death, v1 is the terminal velocity of the scene before multipath birth and death, and v2 is the terminal velocity of the scene after multipath birth and death.

[0032] Preferably, two adjacent scenarios are established through channel modeling: the density of half wavelength in the first scenario is set to 16, and the moving speed is 3km / h; the density of half wavelength in the second scenario is set to 8, and the moving speed is 6km / h. The baseband sampling rates of the two scenarios are consistent, and the multipaths are spliced. As the terminal speed increases, the channel jitter experienced increases.

[0033] The beneficial effects of the present invention include:

[0034] The multipath birth and death modeling method based on the wireless channel emulator provided by the present invention obtains the number and phase information of multipaths in adjacent scenes, determines whether the number of multipaths in adjacent scenes is consistent and whether there is a phase difference in the phases of adjacent scenes. If the number of multipaths in adjacent scenes is inconsistent, the number of multipaths in the scene with the largest number of multipaths in all scenes is determined; the scenes other than the scene with the largest number of multipaths are filled with zeros to achieve the consistency of the number of multipaths in all scenes. If there is a phase difference in the phases of adjacent scenes, the phase sequence of all multipaths corresponding to the last sample point of the channel impulse response of the previous scene in the adjacent scene is determined, and the phase sequence is used as the initial phase in the next scene, and the number of multipaths in all scenes is made consistent by filling zeros for scenes with inconsistent numbers of multipaths. Based on the simulation of the change in the number of multipaths caused by the change in the scene by the emulator, the relative speed change between the transmitting and receiving ends is achieved, and the simulation scenes of the wireless channel emulator are enriched. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of traditional multipath birth and death.

[0036] Figure 2 The following is a schematic diagram of multipath zero filling in different scenarios.

[0037] Figure 3 Schematic diagram of phase discontinuity when splicing two adjacent scenes (LOS-LOS).

[0038] Figure 4 Schematic diagram of the amplitude-frequency response of phase discontinuity noise in adjacent multipath birth and death scenarios.

[0039] Figure 5 Schematic diagram of the amplitude response of adjacent scenes spliced ​​at different speeds. DETAILED DESCRIPTION

[0040] The following is combined with Figure 1 to Figure 5 The present invention is further described in detail:

[0041] Example 1

[0042] A multipath birth and death modeling method based on a wireless channel simulator, characterized in that it comprises the following steps:

[0043] S1: Obtain the number and phase information of multipaths in adjacent scenes, determine whether the number of multipaths in adjacent scenes is consistent and whether there is a phase difference in the phases of adjacent scenes. If the number of multipaths in adjacent scenes is inconsistent, execute step S2; if there is a phase difference in the phases of adjacent scenes, execute step S4;

[0044] S2: Determine the number of multipaths N in the scene with the largest number of multipaths among all scenes max,path ;

[0045] S3: divide the scenes other than the scene with the largest number of multipaths into N max,path Based on this, the number of multipaths in all scenarios is made consistent by padding with zeros;

[0046] S4: Determine the phase sequence of all multipaths corresponding to the last sample point of the previous scene channel impulse response in the adjacent scene θ1 = [θ1, θ1, ... θ N1 ], where N1 represents the number of multipaths in the previous scene;

[0047] S5: Take θ1 as the initial phase in the next scenario, and use N max,path Based on this, the number of multipaths in all scenarios is made consistent by padding with zeros. Figure 2 , Figure 2There are three scenarios, among which the scenario with the largest number of multipaths among all the scenarios has the largest number of multipaths N max,path =3, the third path of scene 1 and the second and third paths of scene 3 are padded with zeros respectively. After the padded with zeros, the three scenes form a unified scene with a total of three paths.

[0048] When there is a phase difference between the multipaths of adjacent scenes, direct splicing will cause phase discontinuity, which may seriously affect the demodulation of the receiver. Figure 3 As shown in the figure, after the adjacent scenes are spliced ​​together, the amplitude-frequency response of the spliced ​​scene is plotted as follows: Figure 4 As shown in the figure, although the amplitudes of the two are consistent after splicing, the phase discontinuity at the splicing point will affect the noise frequency domain impulse response. Therefore, the phase sequence of all multipaths corresponding to the last sample point of the previous scene channel impulse response in the adjacent scene is determined as θ1=[θ1,θ1,…θ N1 ], where N1 represents the number of multipaths in the previous scene; θ1 is used as the initial phase in the next scene; if there is a problem of inconsistent number of multipaths in adjacent scenes, the scene with inconsistent number of multipaths is replaced by N max,path Based on this, the number of multipaths in all scenarios is made consistent by padding with zeros.

[0049] From the perspective of signal processing, the switching between the two scenarios will cause changes in the number of multipaths and phase discontinuity caused by the splicing of channel modeling scenarios. To this end, by determining the number of multipaths in the scenario with the largest number of multipaths among all scenarios, the remaining scenarios are based on the number of multipaths in the scenario with the largest number of multipaths among all scenarios by padding with zeros to achieve consistency in the number of multipaths in all scenarios.

[0050] Example 2

[0051] On the basis of Example 1, when the terminal speeds of adjacent scenes are inconsistent, the multipath generation and death caused by the switching of adjacent scenes is processed through the following specific process:

[0052] S21: Assume that the half-wavelength sampling density is ρ, which represents the number of sampling points on the half-wavelength length during the modeling process, and the interval between two sampling points is d. Where λ represents the wavelength;

[0053] S22: Establish the Doppler formula:

[0054]

[0055] Among them, f center is the center frequency, v represents the terminal running speed, and Ω is the incoming wave angle;

[0056] according to

[0057] S23:

[0058] t0 represents the sampling time between two sample points. Substitute into the formula In, get

[0059] make

[0060] S24:

[0061] represents the baseband sampling rate,

[0062] It is expressed as:

[0063]

[0064] in, Indicates the maximum Doppler shift.

[0065] Example 3

[0066] Based on Example 1 or Example 2, when the terminal speed remains unchanged, the maximum Doppler frequency shift f d,max In a multipath birth and death scenario with different moving speeds, the baseband sampling rate F s The channel impulse response of the adjacent scenes with inconsistent multipath numbers or phase differences is calculated. The formula for calculating the channel impulse response is:

[0067]

[0068] Among them, ρ1 represents the half-wavelength sampling density of the scene before multipath birth and death, ρ2 represents the half-wavelength sampling density of the scene after multipath birth and death, v1 is the terminal velocity of the scene before multipath birth and death, and v2 is the terminal velocity of the scene after multipath birth and death.

[0069] See also Figure 5 , through channel modeling, two adjacent scenarios are set up: the density of the first half wavelength is set to 16, and the moving speed is 3km / h, and the density of the second half wavelength is set to 8, and the moving speed is 6km / h. The baseband sampling rate of the two scenarios is consistent, and the multipath is spliced. As the terminal speed increases, the channel jitter experienced increases. Figure 5 It can be seen that as the speed increases, the channel jitter experienced becomes more severe, while conforming to the multipath birth and death design that realizes different speed scenarios with the same baseband sampling rate.

[0070] In summary, the multipath birth and death modeling method based on the wireless channel emulator provided by the present invention obtains the number and phase information of multipaths in adjacent scenes, determines whether the number of multipaths in adjacent scenes is consistent and whether there is a phase difference in the phases of adjacent scenes. If the number of multipaths in adjacent scenes is inconsistent, the number of multipaths in the scene with the largest number of multipaths in all scenes is determined; the scenes other than the scene with the largest number of multipaths are filled with zeros to achieve the consistency of the number of multipaths in all scenes. If there is a phase difference in the phases of adjacent scenes, the phase sequence of all multipaths corresponding to the last sample point of the channel impulse response of the previous scene in the adjacent scene is determined, and the phase sequence is used as the initial phase in the next scene, and the number of multipaths in all scenes is made consistent by filling with zeros for scenes with inconsistent numbers of multipaths. Based on the simulation of the change in the number of multipaths caused by the change in the scene by the emulator, the relative speed change between the transmitting and receiving ends is achieved, which enriches the simulation scenes of the wireless channel emulator.

Claims

1. A multipath birth and death modeling method based on a wireless channel simulator, characterized in that: The following steps are involved: S1: Obtain the number and phase information of multipaths in adjacent scenes, determine whether the number of multipaths in adjacent scenes is consistent and whether there is a phase difference in the phases of adjacent scenes. If the number of multipaths in adjacent scenes is inconsistent, execute step S2; if there is a phase difference in the phases of adjacent scenes, execute step S4; S2: Determine the number of multipaths N in the scene with the largest number of multipaths among all scenes max,path ; S3: divide the scenes other than the scene with the largest number of multipaths into N max,path Based on this, the number of multipaths in all scenarios is made consistent by padding with zeros; S4: Determine the phase sequence of all multipaths corresponding to the last sample point of the previous scene channel impulse response in the adjacent scene θ1 = [θ1, θ1, ... θ N1 ], where N1 represents the number of multipaths in the previous scene; S5: Take θ1 as the initial phase in the next scenario, and use N max,path Based on this, the number of multipaths in all scenarios is made consistent by padding with zeros.

2. The multipath birth and death modeling method based on a wireless channel emulator according to claim 1, characterized in that: When the terminal speeds of adjacent scenes are inconsistent, the following specific process is used to handle the multipath generation and death caused by the switching of adjacent scenes: S21: Assume that the half-wavelength sampling density is ρ, which represents the number of sampling points on the half-wavelength length during the modeling process, and the interval between two sampling points is d. Where λ represents the wavelength; S22: Establish the Doppler formula: Among them, f center is the center frequency, v represents the terminal running speed, and Ω is the incoming wave angle; S23： according to t0 represents the sampling time between two sample points. Substitute into the formula In, get S24： make represents the baseband sampling rate, It is expressed as: in, Indicates the maximum Doppler shift.

3. The multipath birth and death modeling method based on a wireless channel emulator according to claim 2, characterized in that: When the terminal velocity remains unchanged, the maximum Doppler frequency shift f d,max constant.

4. The multipath birth and death modeling method based on a wireless channel emulator according to claim 2, characterized in that: In a multipath birth and death scenario with different moving speeds, the baseband sampling rate F s The channel impulse response of adjacent scenes with inconsistent multipath numbers or phase differences is calculated. The formula for calculating the channel impulse response is: Among them, ρ1 represents the half-wavelength sampling density of the scene before multipath birth and death, ρ2 represents the half-wavelength sampling density of the scene after multipath birth and death, v1 is the terminal velocity of the scene before multipath birth and death, and v2 is the terminal velocity of the scene after multipath birth and death.

5. The multipath birth and death modeling method based on a wireless channel simulator according to claim 1, characterized in that: Through channel modeling, two adjacent scenarios are set up: in the first scenario, the density of half wavelength is set to 16 and the moving speed is 3km / h; in the second scenario, the density of half wavelength is set to 8 and the moving speed is 6km / h. The baseband sampling rates of the two scenarios are consistent, and the multipaths are spliced. As the terminal speed increases, the channel jitter experienced increases.

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