Wireless fading channel simulation system and method for asymmetric doppler power spectrum

Abstract

The application discloses a wireless fading channel simulation system and method of asymmetric Doppler power spectrum, relates to the field of wireless channel modeling, and takes asymmetric Doppler power spectrum Gaussian I type as an example throughout the process, is based on a harmonic superposition method, and is extended so as to be suitable for forming asymmetric Doppler power spectrum and corresponding channel fading coefficients. According to the calculation results of channel parameters, the original signal at the input end is processed, the fading simulation of the signal is completed, and the signal is output by the radio frequency end. The application is based on the harmonic superposition method, has high adaptability of parallel calculation while ensuring the precision, and designs a simple parallel structure in the FPGA.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wireless channel modeling, and is a wireless fading channel simulation system and method for simulating the Doppler power spectrum of a time-varying wireless fading channel. BACKGROUND

[0002] In different communication environments, the time domain and frequency domain of a wireless signal are affected to varying degrees by the communication channel environment. Channel modeling is divided into large-scale fading and small-scale fading. Large-scale fading refers to power loss caused by electromagnetic waves in a wireless propagation path; small-scale fading refers to signal distortion caused by the multi-path characteristic and Doppler time-varying characteristic of electromagnetic waves affected by the environment.

[0003] Among them, the Doppler channel fading model is a mathematical model for the case where the transmitter and receiver have relative high-speed movement, and is also a basic element of the channel. There are many factors that cause this influence, including obstacles between the transmitter and receiver. At the same time, when the position of the obstacle changes or the position of the receiver relative to the transmitter moves, the degree of channel fading of the signal reaching the receiver is also different. Common Doppler power spectrum is modeled into symmetric and asymmetric Doppler power spectrum. The representative of the symmetric power spectrum is the U-shaped spectrum and the Gaussian spectrum, and the basic assumption of this channel is that the scattering around the transmitter and receiver is uniform. When the above conditions are not met, for example, in the COST207 channel model, there are Gaussian I and Gaussian II asymmetric Doppler power spectrum models.

[0004] In the actual development scene of communication equipment, it is often impossible to complete equipment testing in the actual channel environment. Therefore, channel simulation and its simulation algorithm plays a very important role. Among them, the sine wave superposition method is often used as an algorithm for generating and simulating channels in large channel simulators because of its good computational parallelism and stability.

[0005] However, the general sense of the sine wave superposition method is suitable for generating symmetric spectrum, and it is difficult to generate asymmetric spectrum, so the simulation of asymmetric Gaussian Doppler power spectrum is difficult, and there are few existing channel simulation methods based on the sine wave superposition method for asymmetric Gaussian Doppler power spectrum. SUMMARY

[0006] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a wireless fading channel simulation system and method for asymmetric Doppler power spectrum, which is based on the traditional sine wave superposition method and expands its application range to any asymmetric Doppler power spectrum.

[0007] To achieve the above object, the present application adopts the following technical solutions to achieve the above object:

[0008] The wireless fading channel simulation method of the asymmetric Doppler power spectrum comprises the following steps:

[0009] The asymmetric Doppler power spectrum is established;

[0010] The asymmetric Doppler power spectrum is divided into a first part power spectrum and a second part power spectrum; the harmonic amplitude and the harmonic phase of the two power spectrums are obtained through the harmonic superposition method, and the harmonic frequency of the two power spectrums is obtained through spectrum shift;

[0011] The harmonic parameters of the first part power spectrum and the harmonic parameters of the second part power spectrum are combined through a Hilbert filter to obtain the fading coefficient of the asymmetric Doppler power spectrum;

[0012] The original signal is processed through the fading coefficient to obtain and output the processed signal.

[0013] Further improvement of the present application is that:

[0014] Preferably, the asymmetric Doppler power spectrum is:

[0015]

[0016] Wherein, f max is the frequency parameter of the Gaussian power spectrum, A G is the amplitude parameter of the Gaussian power spectrum.

[0017] Preferably, the process of obtaining the harmonic amplitude and the harmonic phase of the power spectrum through the harmonic superposition method comprises the following steps:

[0018] (1) establishing an approximate expression form of the basic waveform of the power spectrum, and the approximate expression form is expressed through the harmonic superposition method;

[0019] (2) dividing the power spectrum density into N parts according to the area, establishing a multinomial expression of the power spectrum density, and solving the multinomial expression through the Newton iteration method or the dichotomy method;

[0020] (3) obtaining the harmonic amplitude and the harmonic phase based on the solved multinomial expression.

[0021] Preferably, in step (1), the approximate expression form of the basic waveform of the power spectrum is:

[0022]

[0023] Wherein, c i is the amplitude of the harmonic, f i_b is the frequency of the harmonic of the basic waveform, and θ iis the phase of the harmonic, t is time.

[0024] Preferably, in step (2), the polynomial expression of the power spectral density is:

[0025]

[0026] where a0, a1, a2, a3, a4, and a5 are fitting parameters, f i_b is the frequency of the fundamental waveform.

[0027] Preferably, in step (3), the harmonic amplitude is:

[0028] The harmonic amplitude of the first part of the power spectrum is:

[0029]

[0030] The harmonic phase θ i1 is a random number uniformly distributed over the interval [0, 2π);

[0031] The harmonic amplitude of the second part of the power spectrum is:

[0032]

[0033] The harmonic phase θ i2 is a random number uniformly distributed over the interval [0, 2π).

[0034] Preferably, the frequency of the first part of the power spectrum obtained by spectral shifting is:

[0035] f i1_1 = 0.8f max - f i1_b (16)

[0036] f i1_2 = 0.8f max + f i1_b (17)

[0037] The frequency of the second part of the power spectrum is

[0038] f i2_1 = 0.4f max - f i2_b (16)

[0039] f i2_2 = 0.4f max + f i2_b (17);

[0040] where f max is a frequency parameter defining the Gaussian power spectrum.

[0041] Preferably, the harmonic parameters are combined to obtain the fading coefficient h k The formula of (t) is:

[0042]

[0043] Wherein, n is the sampling time, N is the number of the area of Doppler power spectrum density, f max is the frequency parameter of the defined Gaussian power spectrum.

[0044] Preferably, the faded signal is obtained by calculating the fading coefficient,

[0045]

[0046] Wherein, s(t) is the signal of the input channel simulator of the sending end, τ k is the time delay, n is the sampling time

[0047] The asymmetric Doppler power spectrum wireless fading channel simulation system comprises:

[0048] A power spectrum unit is configured to establish an asymmetric Doppler power spectrum.

[0049] A parameter unit is configured to divide the asymmetric Doppler power spectrum into a first partial power spectrum and a second partial power spectrum; harmonic amplitudes and harmonic phases of the two power spectrums are obtained by a harmonic superposition method, and harmonic frequencies of the two power spectrums are obtained by spectrum shifting.

[0050] A combination unit is configured to combine the harmonic parameters of the first partial power spectrum and the harmonic parameters of the second partial power spectrum by a Hilbert filter to obtain a fading coefficient of the asymmetric Doppler power spectrum.

[0051] An output unit is configured to process an original signal by the fading coefficient to obtain and output a processed signal. Compared with the prior art, the present application has the following beneficial effects:

[0052] The application discloses a wireless fading channel simulation method of asymmetric Doppler power spectrum, and the whole process takes asymmetric Doppler power spectrum Gaussian I type as an example, is based on the harmonic superposition method, and is expanded to be applicable to forming asymmetric Doppler power spectrum and corresponding channel fading coefficients, and is a kind of soft and hardware joint simulation calculation method.The steps include, according to actual needs, configuring the shape and related parameters of the corresponding Doppler power spectrum;Software end calculates the amplitude, phase and frequency parameters of the harmonic by splitting asymmetric spectrum type, spectrum shift and other operations;Hardware FPGA end receives the harmonic parameters transmitted by host computer through interface, merges the corresponding harmonic of asymmetric Doppler power spectrum by using Hilbert filter principle, and calculates the channel fading coefficient in real time;According to the channel parameter calculation result, the original signal of input end is processed, the fading simulation of signal is completed, and the signal is output by radio frequency end.The present application is based on the harmonic superposition method, and simple parallel structure is designed in FPGA while ensuring accuracy, and has high adaptability of parallel calculation.

[0053] The application discloses a wireless fading channel simulation system of asymmetric Doppler power spectrum, which is based on the traditional harmonic superposition method, perfects the calculation steps for any Doppler power spectrum, and can be expanded to asymmetric Doppler power spectrum.The amplitude, frequency and phase of the harmonic calculated by the method are used as parameters to complete parallel superposition operation in FPGA to generate channel fading coefficients.The method can solve asymmetric Doppler spectrum, and general sine wave superposition method can only solve symmetric Doppler spectrum.Meanwhile, the basic algorithm, i.e., the harmonic superposition method, is more suitable for implementation on parallel FPGA than the shaping filter method, the calculation structure is more simple, can be unified with the calculation structure of symmetric Doppler, and resource consumption is less.Meanwhile, the method can flexibly control spectrum type by configuring different coefficients, and practicability and flexibility of the method are very excellent. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 It is a flow chart of the system;

[0055] Figure 2 It is a Doppler power spectrum generation schematic diagram;

[0056] Figure 3 It is a Gaussian I type power spectrum generation calculation step diagram;

[0057] Figure 4 It is a Gaussian I type Doppler power spectrum algorithm simulation result (logarithmic coordinate);

[0058] Figure 5 It is a Gaussian I type Doppler power spectrum algorithm simulation result (absolute value coordinate); DETAILED DESCRIPTION

[0059] The application will be described in further detail below with reference to the drawings:

[0060] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application; the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise explicitly specified and limited, the terms "mounting", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, or it can be a detachable connection; it can be directly connected, or indirectly connected through an intermediate medium; it can be the communication between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0061] One of the embodiments of the present application is to disclose a wireless fading channel simulation system method of asymmetric Doppler power spectrum, see Figure 1 The specific steps of the method are as follows:

[0062] Step 1, according to the actual needs, configure the shape and related parameters of the corresponding Doppler power spectrum.

[0063] First, initialize the parameters. The common asymmetric Doppler spectrum S asy (f) can be represented by the following general formula (1):

[0064] S asy (f) = A[D1(f-f1) + D2(f+f2)] (1)

[0065] Where A represents the amplitude, specifically the amplitude of the Doppler power spectrum, D1 and D2 represent the specific Doppler power spectrum function respectively, and f1 and f2 represent the offset frequency of D1 and D2 respectively, and f represents the frequency.

[0066] For the convenience of description, in the following steps, a typical asymmetric Doppler power spectrum, Gaussian I-type power spectrum, is used to complete the description of the whole method. It should be particularly noted that the present method is generally applicable to asymmetric Doppler power spectrum.

[0067] Gaussian I-type power spectrum S G (f) combines the definition of Gaussian I-type power spectrum and formula (1), and is specifically represented by the following formula (2):

[0068]

[0069] The definition of parameters and formula (1) corresponding, where f max is the frequency parameter defining the Gaussian power spectrum, A G is the amplitude parameter defining the Gaussian power spectrum.

[0070] Step 2, the software end through the split asymmetric spectrum, spectrum shift operation, calculate the amplitude, phase and frequency parameters for generating the harmonic of Doppler power spectrum and channel fading coefficient.

[0071] Step 2.1 by splitting the target asymmetric Doppler power spectrum waveform, determine the basic waveform of the asymmetric waveform, for asymmetric Doppler power spectrum, the basic waveform corresponds to D1 and D2 in formula (1) respectively.

[0072] Take Gaussian I type power spectrum as an example, Gaussian I type power spectrum (2) formula, corresponding formula (1), split into two parts with different waveforms, respectively, the first part power spectrum waveform S G1 (f) and the second part power spectrum waveform S G2 (f),

[0073]

[0074]

[0075] In the context of Gaussian I type power spectrum, the basic waveform D1 and D2 are derived from the same waveform, and are the common Gaussian type Doppler power spectrum S gaussian , that is:

[0076]

[0077] Where, σ 2 is the defined variance of Gaussian power spectrum, which is also the shape parameter of the corresponding basic waveform, and D1 and D2 are different.

[0078] Combined with formula (5), the basic waveform of the first part power spectrum S G1_b (f) and the basic waveform of the second part power spectrum S G2_b (f), respectively, as shown in (6) and (7) formula:

[0079]

[0080]

[0081] Step 2.2 calculate the harmonic parameters of the first part power spectrum;

[0082] For Gaussian type I, the first part of the power spectrum waveform to be calculated is the formula (3).

[0083] In order to generate the first part of the power spectrum waveform S G1 (f), it is necessary to first generate the basic waveform S G1_b (f) of the first part of the power spectrum.

[0084] The way of harmonic superposition is adopted, and the way of superposition of N harmonics is adopted to approximately generate It can be expressed by the following formula:

[0085]

[0086] Where Spectrum represents the method of solving the power spectrum by sampling in the time domain. Such methods have mature technology applications and are not discussed in this method. Corresponding to the basic waveform of the first part of the power spectrum, c i1 is the amplitude of the harmonic, f i1_b is the frequency of the harmonic of the basic waveform, θ i1 is the phase of the harmonic, and t is the time. N is the number of harmonics. It can be proved that when N is large enough, can approximate S G1_b .

[0087] And S G1 (f) is essentially the waveform of S G1_b (f) after shifting. Therefore, the generated by multiple harmonics can also approximate S G1 In the following, how to define and calculate will be carefully explained.

[0088] How to calculate the three types of harmonic parameters, i.e. the frequency, amplitude and phase parameters of the harmonic, is the core and key of this step.

[0089] (1) The calculation of the frequency f i of the harmonic of the basic waveform of the first part of the power spectrum

[0090] To calculate , the Doppler power spectrum density is divided into N equal parts, i.e.

[0091]

[0092] Where f i is the endpoint of each interval,

[0093] By recursive derivation from (9), formula (10) containing only unknown f i is obtained: ​

[0094]

[0095] When i is constant, the right side of the equation is constant.

[0096] For the Doppler power spectrum of Gaussian class, the variable limit integral on the left side of formula (10) can have an inverse closed-form solution. Through a provable derivation, the i-th frequency point f i1_b As follows:

[0097]

[0098] In addition, for some cases Cannot show the expression to find f n , the polynomial fitting method can be taken. Specifically, the computer can be used to calculate the discrete points Then use polynomial fitting approximation to get the polynomial A x (f n ), where x is the highest polynomial order, for example Where a i , i = 1, 2...5, are computer fitting parameters.

[0099] Therefore, formula (10) can be expressed as

[0100]

[0101] Therefore, the above formula can be solved by Newton iteration method or bisection method, that is, f i . Formula (12) is a relatively general solution for solving harmonic parameters.

[0102] (2) The amplitude c i1 and θ i of the harmonic of the first part of the power spectrum waveform

[0103] According to the simultaneous solution of formulas (3), (6) and (8) and related principles, the amplitude C i1 and phase θ i1 of the harmonic superposition method can be obtained.

[0104] Wherein, the calculation formula of the amplitude C i1 is:

[0105]

[0106] θ i1 is a random number uniformly distributed in the interval [0, 2π).

[0107] (3) The frequency of the harmonic of the first part of the power spectrum waveform

[0108] Since the Gaussian I-type spectrum has a certain shift, in the simplest way, the target signal is multiplied by cos2πf0t, which shifts the frequency, where f0 is the target frequency. For the Gaussian I-type, then:

[0109]

[0110] By transforming the formula according to the trigonometric function product-sum and difference formula, the form of multiplying the above formula is expanded into a sine superposition, and for the Gaussian I-type, then:

[0111]

[0112] At this time,

[0113] f i1_1 = 0.8f max -f i1_b (16)

[0114] And

[0115] f i1_2 = 0.8f max +f i1_b (17)

[0116] f i1_1 and f i1_2 are the frequency parameters of the transmission.

[0117] And When N takes a larger value, it can be approximated as S G1 (f), thus completing the calculation of all parameters of the generated harmonic of the first part of the power spectrum waveform in this step.

[0118] Step 2.3, calculate the harmonic parameters of the generated second part of the power spectrum, for the Gaussian I-type, the second part of the power spectrum waveform that needs to be calculated is formula (4), replace the target generated in step 2.2 and the corresponding waveform, repeat the steps of formula (19)-formula (17).

[0119] Similarly, the frequency parameters f i2_1 , f i2_2 of the second part of the power spectrum waveform can be calculated, the amplitude parameter C i2 , and the phase parameter θ i2

[0120] f i2_1 = 0.4f max -f i2_b (18)

[0121] f i2_2 = 0.4f max +f i2_b(19)

[0122]

[0123] where:

[0124]

[0125] The above four frequency parameters f i1_1 , f i1_2 , f i2_1 , f i2_2 , Doppler coefficient C i1 , C i2 , and uniformly distributed random vectors θ i1 , θ i2 need to be passed through the interface into the FPGA.

[0126] Step 3, FPGA receives data from the host computer through the interface, and performs real-time sine wave superposition and channel parameter calculation process to obtain the channel fading coefficient.

[0127] This step needs to complete the superposition calculation of N harmonics in FPGA to generate the channel fading coefficient h k .

[0128] If the above frequencies are directly substituted into the calculation, the resulting frequency spectrum is still symmetric. Therefore, according to the relevant principles of Hilbert filter, it is processed. Since the signal itself is a special form of superposition of sine waves, the result after the filter still retains the form of harmonic superposition.

[0129] That is, cos(2πft) is converted to cos(2πft)±jsin(2πft), and for Gaussian I type, the fading coefficient h k is:

[0130]

[0131] After calculating formula (22), the Rayleigh fading of Gaussian I type can be obtained. Generally, FPGA has IP core to generate sine wave, which is usually cosx function. Therefore, in order to simplify the calculation, the following formula can be directly calculated:

[0132]

[0133] From the above formula (17), the essence of the process completed in FPGA is the superposition of multiple harmonics, which has very obvious parallelism. Real-time completion of the superposition process can obtain the fading coefficient h k .

[0134] Step 4, according to the channel parameter calculation results to the original signal input processing, and then in the radio frequency end signal output.

[0135] The above calculation is carried out on the FPGA, and after the multipath delay, complex multiplication and other processes, the result after fading can be obtained. As the formula:

[0136]

[0137] Where s(n) is the signal of the input channel simulator of the sending end, τ k is the time delay, and n is the sampling time.

[0138] This step includes the digital-to-analog conversion, analog-to-digital conversion and other parts of the FPGA, and finally the faded signal is transmitted to the receiver through the radio frequency band.

[0139] The above steps 1 to 2 are completed on the host computer end, and steps 3 and 4 are completed on the FPGA and radio frequency hardware, which can realize the function of asymmetric Doppler channel simulation.

[0140] The above and other objects, features and advantages of the present application will be better understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0141] Referring to Figure 1 , the flowchart of the system, after the user sets the spectral shape, the host PC end generates the Doppler coefficient, frequency and random phase, the FPGA end calculates the channel coefficient, on the other hand, after the signal is input, after the system sampling and analog-to-digital conversion, after the generated channel coefficient processing, finally through digital-to-analog conversion, the signal is sent in the radio frequency end.

[0142] Referring to Figure 2 , a schematic diagram of the method for generating a Doppler power spectrum, according to the steps, the Doppler power spectrum to be generated is first divided into two parts and moved to the baseband. According to the basic principle of harmonic superposition method, N corresponding harmonics are generated, and through the operation of spectrum shift, the Doppler spectrum is shifted to the specified position, and the Hilbert filter related principle is used to complete the filtering process of the signal spectrum, and finally the merging of the two is realized, which is called the complete Doppler power spectrum.

[0143] Without loss of generality, for a typical asymmetric Doppler power spectrum Gaussian I type, the number of harmonics is set to N = 48, the shift frequency f max = 10000 Hz, A G = 1.

[0144] Figure 3For the specific steps of generating the fading coefficient process of the harmonic superposition of Gaussian I type, according to the filtering principle, the filtering of the half spectrum of the signal is completed, and due to the fact that the signal itself is in the form of superposition of special sine waves, the result after the filter still retains the form of harmonic superposition.

[0145] Figure 4 The result of the harmonic superposition is the generated spectrum image after simulation. The image is the result of Gaussian I type in the logarithmic coordinate system, the blue line is the simulation image, and the red line is the envelope, which conforms to the fading characteristics of the Gaussian I type power spectrum.

[0146] Figure 5 The result of the simulation image of the harmonic superposition in the absolute value coordinate system can more obviously find the spectral characteristics.

[0147] The above only describes the preferred embodiments of the present application and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for simulating wireless fading channels using asymmetric Doppler power spectra, characterized in that, Includes the following steps: Establish an asymmetric Doppler power spectrum; The asymmetric Doppler power spectrum is divided into a first power spectrum and a second power spectrum; the harmonic amplitude and harmonic phase of the two power spectra are obtained by the harmonic superposition method, and the harmonic frequencies of the two power spectra are obtained by spectrum shifting. By combining the harmonic parameters of the first part of the power spectrum and the harmonic parameters of the second part of the power spectrum using a Hilbert filter, the fading coefficient of the asymmetric Doppler power spectrum is obtained. The original signal is processed by the fading coefficient to obtain and output the processed signal; The asymmetric Doppler power spectrum is as follows: （2） in, It is the frequency parameter of the Gaussian power spectrum. It is the amplitude parameter of the Gaussian power spectrum. For frequency.

2. The wireless fading channel simulation method based on asymmetric Doppler power spectrum according to claim 1, characterized in that, The process of obtaining the harmonic amplitude and harmonic phase of the power spectrum through the harmonic superposition method includes the following steps: (1) Establish a basic waveform approximation of the power spectrum, which is expressed by harmonic superposition; (2) Divide the power spectral density into N equal parts according to the area, establish a polynomial expression for the power spectral density, and solve the polynomial expression by Newton's iteration method or bisection method; (3) Based on the solved polynomial expression, the harmonic amplitude and harmonic phase are obtained.

3. The wireless fading channel simulation method based on asymmetric Doppler power spectrum according to claim 2, characterized in that, In step (1), the basic waveform approximation of the power spectrum is: (8) in, The amplitude of the harmonic. The frequencies of the harmonics of the basic waveform, Let t be the phase of the harmonic, and t be time.

4. The wireless fading channel simulation method based on asymmetric Doppler power spectrum according to claim 2, characterized in that, In step (2), the polynomial expression for the power spectral density is: (12) in, , , , , and The parameters are for fitting. Let n be the frequency of the harmonics of the basic waveform, n be the sampling time, and N be the number of equal parts into which the Doppler power spectral density encloses the area. = ( .

5. The wireless fading channel simulation method based on asymmetric Doppler power spectrum according to claim 2, characterized in that, In step (3), the harmonic amplitude is: The harmonic amplitudes of the first part of the power spectrum are: （13） Harmonic phase Is A random number uniformly distributed over an interval; The harmonic amplitudes of the second part of the power spectrum are: （20） Among them, harmonic phase Is The random numbers are uniformly distributed over the interval, where N is the number of equal parts of the area enclosed by the Doppler power spectral density.

6. The wireless fading channel simulation method based on asymmetric Doppler power spectrum according to claim 1, characterized in that, The frequency of the first part of the power spectrum obtained by spectrum shifting is: The frequency of the second part of the power spectrum is in, To define the frequency parameters of the Gaussian power spectrum.

7. The wireless fading channel simulation method based on asymmetric Doppler power spectrum according to claim 1, characterized in that, The fading coefficient is obtained by combining the harmonic parameters. The formula is: +cos( + +cos( (23) Where n is the sampling time, and N is the number of equal parts into which the Doppler power spectral density encloses the area. To define the frequency parameters of the Gaussian power spectrum.

8. The wireless fading channel simulation method based on asymmetric Doppler power spectrum according to claim 1, characterized in that, The faded signal is obtained by calculating the fading coefficient. (24) Where s(t) is the signal input to the channel simulator at the transmitting end. denoted as time delay, and n as the sampling time.

9. A wireless fading channel simulation system with an asymmetric Doppler power spectrum for implementing the wireless fading channel simulation method of claim 1, characterized in that, include: Power spectral unit, used to establish asymmetric Doppler power spectrum; The parameter unit is used to divide the asymmetric Doppler power spectrum into a first part of the power spectrum and a second part of the power spectrum. The harmonic amplitude and harmonic phase of the two power spectra are obtained by harmonic superposition, and the harmonic frequencies of the two power spectra are obtained by spectrum shifting. The combination unit is used to combine the harmonic parameters of the first part of the power spectrum and the harmonic parameters of the second part of the power spectrum through a Hilbert filter to obtain the fading coefficient of the asymmetric Doppler power spectrum. The output unit is used to process the original signal using the fading coefficient, obtain and output the processed signal.

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