An improved broadband shortwave channel simulation calculation method, system and storage medium based on ITS

Abstract

The present invention discloses an improved broadband shortwave channel simulation calculation method based on ITS, comprising the following steps: step 1, random modulation function simulation: step 2, phase determination function simulation: step 3, improved delay power distribution function simulation: step 4, defining the time-varying pulse response as a function of time and delay variables. The method disclosed by the present invention improves the delay power distribution function in the ITS channel model, making its calculation process simpler, thereby realizing the simulation calculation of broadband shortwave channels more quickly and conveniently, and the obtained shortwave channel model takes into account the shortwave signal delay and Doppler expansion effect caused by the ionosphere, and can simulate and calculate the shortwave link channel in any region of the world.

Description

Technical Field

[0001] The invention belongs to the field of shortwave channel model simulation calculation, and particularly relates to an improved broadband shortwave channel simulation calculation method, system and storage medium based on ITS in the field. Background Art

[0002] Shortwave and satellite are two important means of communication. Compared with satellite communication, shortwave communication has many advantages, such as low construction and maintenance costs, simple equipment, flexibility and strong anti-destruction ability. Shortwave communication mainly uses sky waves to propagate through the ionosphere, and can achieve long-distance communication without the use of relay stations. Due to the openness and indestructibility of the ionosphere, shortwave communication has great advantages in long-distance communication compared with cables, optical cables, satellites and other communication means. At the same time, the networking of shortwave communication is very convenient and fast, with strong mobility, strong ability to resist natural disasters and war destruction, and the equipment is small in size, the frequency change is very convenient, it can effectively avoid human interference, and has strong recovery ability.

[0003] Based on the experimental summary and the improvement of the shortwave channel model, the ITS organization in the United States derived a channel model suitable for broadband and narrowband shortwave communications. This is the ITS model that is still widely recognized and widely used. The ITS model comprehensively characterizes the statistical characteristics of the three modules of the shortwave channel: Doppler spread, Doppler frequency shift, and channel propagation delay power spectrum. This model is the best broadband shortwave channel model so far. However, the time delay power distribution function of the ITS model is complex and the parameters are difficult to obtain. The parameters require complex iterative calculations (usually using the Newton method), and appropriate iterative initial values ​​need to be selected. Summary of the invention

[0004] The technical problem to be solved by the present invention is to modify the time delay power distribution function and provide an improved broadband shortwave channel simulation calculation method, system and storage medium based on ITS.

[0005] The present invention adopts the following technical solution:

[0006] An improved broadband shortwave channel simulation calculation method based on ITS, the improvement of which is that it includes the following steps:

[0007] Step 1, random modulation function simulation:

[0008] The K mutually unrelated random modulation functions of the broadband shortwave channel simulation implementation model are expressed as:

[0009]

[0010] In the above formula, and are mutually independent zero-mean real Gaussian random processes, which can be expressed as follows according to the central limit theorem:

[0011]

[0012] In the above formula, n=1,2,…,N i , N i is the number of sinusoidal oscillators used in a real Gaussian random process, c i,n is the Doppler fading coefficient, f i,n is the discrete Doppler frequency, θ i,n is the Doppler phase;

[0013] Step 2, determine the phase function simulation:

[0014] The phase function is defined as:

[0015]

[0016]

[0017] According to Euler's formula:

[0018] D(t,τ)=cos2π[f s +b(τ-τ c )]t+jsin2π[f s +b(τ-τ c )]t

[0019] Written in discrete form:

[0020]

[0021] In the above formula, t is the time variable, τ is the delay variable; τ c is the delay corresponding to the power peak; τ L is the lower limit of delay when the power is the receiving threshold, b is the rate of change of Doppler frequency shift relative to τ; f s is τ=τ c The Doppler frequency shift at time, f sL Indicates that τ = τ L The Doppler value at time, f Ts Indicates the sampling frequency of the channel;

[0022] Step 3: Improved delay power distribution function simulation:

[0023] The mathematical statistical model of the channel delay power profile function is:

[0024]

[0025]

[0026] In the above formula, A is the peak power of the receiving channel, α represents the parameter of the delayed power profile curve shape; Γ(·) is the gamma distribution function; τ is the delay variable; τ c is the delay corresponding to the power peak; Δ controls the width of the delay spread;

[0027] Delay power distribution function S(τ):

[0028]

[0029] The total power of the delay power distribution S(τ) is 1, B rms is the RMS delay spread of the corresponding propagation path, that is, the RMS delay spread of P(τ);

[0030] P(τ) in σ c ≈σ τ / 2, the function curve is about τ c Symmetrical, the curve is equivalent to a Gaussian distribution, the root mean square delay spread of the symmetrical shape P(τ) As follows:

[0031]

[0032] In the above formula, σ c is the opening time, σ τ A is the delayed extension. T is the receiving signal threshold;

[0033] With σ τ / σ c There is a certain function mapping relationship between them. Let the mapping function be F(·), then there exists

[0034]

[0035] The least squares method is used to perform polynomial fitting on F(·) to obtain F(x), which is expressed as:

[0036]

[0037] In the above formula, S v =A T / A;

[0038] Step 4: define the time-varying impulse response as a function of time t and delay variable τ, expressed as:

[0039]

[0040] In the above formula, n = 1, 2, ... N represents the multipath mode, h n(t,τ) represents the impulse response of the nth shortwave propagation path, which consists of three parts: the random modulation function ψ n (t,τ), determine the phase function D n (t,τ) and the time-delay power distribution function S(τ).

[0041] An improved broadband shortwave channel simulation computing system based on ITS, the improvement of which lies in: comprising: a processor; a memory in which executable instructions of the processor are stored; the processor is configured to execute the steps of the above method by executing the executable instructions.

[0042] A computer-readable storage medium is used to store a program, wherein the improvement lies in that the steps of the above method are implemented when the program is executed.

[0043] The beneficial effects of the present invention are:

[0044] The method disclosed in the present invention improves the time delay power distribution function in the ITS channel model, making its calculation process simpler, thereby realizing the simulation calculation of broadband shortwave channels more quickly and conveniently. The obtained shortwave channel model takes into account the shortwave signal delay and Doppler spread effect caused by the ionosphere, and can simulate and calculate the shortwave link channel in any region of the world. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic flow diagram of the method of the present invention;

[0046] Figure 2 is a schematic diagram of the channel impulse response function in single path mode;

[0047] Figure 3 is a schematic diagram of the scattering function (Gaussian spectrum) in single-path mode;

[0048] Figure 4 is a schematic diagram of the channel impulse response function under two path modes;

[0049] Figure 5 It is a schematic diagram of the scattering function (Gaussian spectrum) under two path modes. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0051] Embodiment 1, this embodiment discloses an improved broadband shortwave channel simulation calculation method based on ITS, such as Figure 1 As shown, the following steps are included:

[0052] Step 1, random modulation function simulation:

[0053] The construction of random modulation function is crucial to obtain a simulated channel that conforms to the characteristics of an actual broadband shortwave channel. The essence of the random modulation function is a Rayleigh random process that obeys a Gaussian distribution or a Lorentzian Doppler spread distribution. The Rayleigh fading process can be simulated by the filter method or the sine wave superposition method (SoS).

[0054] The K mutually unrelated random modulation functions of the broadband shortwave channel simulation implementation model are expressed as:

[0055]

[0056] In the above formula, and are mutually independent zero-mean real Gaussian random processes, which can be expressed as follows according to the central limit theorem:

[0057]

[0058] In the above formula, n=1,2,…,N i , N i is the number of sinusoidal oscillators used in a real Gaussian random process, c i,n is the Doppler fading coefficient, f i,n is the discrete Doppler frequency, θ i,n is the Doppler phase;

[0059] Step 2, determine the phase function simulation:

[0060] The Doppler shift of the propagation path is achieved by multiplying the path impulse response by a deterministic phase function D(t,τ). The deterministic phase function is defined as:

[0061]

[0062]

[0063] According to Euler's formula:

[0064] D(t,τ)=cos2π[f s +b(τ-τ c )]t+jsin2π[f s +b(τ-τ c )]t

[0065] Written in discrete form:

[0066]

[0067] In the above formula, t is the time variable, τ is the delay variable; τ c is the delay corresponding to the power peak; τ L is the lower limit of delay when the power is the receiving threshold, b is the rate of change of Doppler frequency shift relative to τ; f s is τ=τ c The Doppler frequency shift at time, f sL It means that Doppler is at τ = τ L The Doppler value at time, f Ts Indicates the sampling frequency of the channel;

[0068] Step 3: Improved delay power distribution function simulation:

[0069] The ITS channel model uses the Gamma distribution form for the channel delay power profile function, and its mathematical statistical model is:

[0070]

[0071] In the above formula, A is the peak power of the receiving channel (considered to be a constant under a given propagation mode and can take a random value between 0 and 1), α represents the parameter of the shape of the delay power profile curve, and its value determines the symmetry of the delay power profile function curve; Γ(·) is the gamma distribution function; τ is the delay variable; τ c is the delay corresponding to the power peak; Δ controls the width of the delay spread;

[0072] Delay power distribution function S(τ):

[0073]

[0074] The total power of the delay power distribution S(τ) is 1, B rms is the RMS delay spread of the corresponding propagation path, that is, the RMS delay spread of P(τ);

[0075] P(τ) in σ c ≈σ τ / 2, the function curve is about τ c Symmetrical, the curve is equivalent to a Gaussian distribution, the root mean square delay spread of the symmetrical shape P(τ) As follows:

[0076]

[0077] In the above formula, σ c is the opening time, σ τ A is the delayed extension. T is the receiving signal threshold;

[0078] With σ τ / σc There is a certain function mapping relationship between them. Let the mapping function be F(·), then there exists

[0079]

[0080] The least squares method is used to perform polynomial fitting on F(·) to obtain F(x), which is expressed as:

[0081]

[0082] In broadband shortwave ionospheric channel measurement, take S v =A T / A=0.5.

[0083] Step 4: define the time-varying impulse response as a function of time t and delay variable τ, expressed as:

[0084]

[0085] In the above formula, n = 1, 2, ... N represents the multipath mode, h n (t,τ) represents the impulse response of the nth shortwave propagation path, which consists of three parts: the random modulation function ψ n (t,τ), determine the phase function D n (t,τ) and the time-delay power distribution function S(τ).

[0086] In order to verify the effectiveness of the method of the present invention for the shortwave channel model, this embodiment provides the impulse response function and scattering function of the shortwave channel in the single-path and two-path propagation modes, respectively. Figures 2 to 5 shown.

[0087] This embodiment also discloses an improved broadband shortwave channel simulation computing system based on ITS, comprising: a processor; a memory storing executable instructions of the processor; the processor is configured to execute the steps of the above method by executing the executable instructions. And a computer-readable storage medium for storing a program, which implements the steps of the above method when executed.

Claims

1. An improved broadband shortwave channel simulation calculation method based on ITS, characterized in that: The steps include: Step 1, random modulation function simulation: The K mutually unrelated random modulation functions of the broadband shortwave channel simulation implementation model are expressed as: In the above formula, and are mutually independent zero-mean real Gaussian random processes, which can be expressed as follows according to the central limit theorem: In the above formula, n=1,2,…,N i , N i is the number of sinusoidal oscillators used in a real Gaussian random process, c i,n is the Doppler fading coefficient, f i,n is the discrete Doppler frequency, θ i,n is the Doppler phase; Step 2, determine the phase function simulation: The phase function is defined as: According to Euler's formula: D(t,τ)=cos2π[f s +b(τ-τ c )]t+jsin2π[f s +b(τ-τ c )]t Written in discrete form: In the above formula, t is the time variable, τ is the delay variable; τ c is the delay corresponding to the power peak; τ L is the lower limit of delay when the power is the receiving threshold, b is the rate of change of Doppler frequency shift relative to τ; f s is τ=τ c The Doppler frequency shift at time, f sL Indicates that τ = τ L The Doppler value at time, f Ts Indicates the sampling frequency of the channel; Step 3: Improved delay power distribution function simulation: The mathematical statistical model of the channel delay power profile function is: In the above formula, A is the peak power of the receiving channel, α represents the parameter of the delayed power profile curve shape; Γ(·) is the gamma distribution function; τ is the delay variable; τ c is the delay corresponding to the power peak; Δ controls the width of the delay spread; Delay power distribution function S(τ): The total power of the delay power distribution S(τ) is 1, B rms is the RMS delay spread of the corresponding propagation path, that is, the RMS delay spread of P(τ); P(τ) in σ c ≈σ τ / 2, the function curve is about τ c Symmetrical, the curve is equivalent to a Gaussian distribution, the root mean square delay spread of the symmetrical shape P(τ) As follows: In the above formula, σ c is the opening time, σ τ A is the delayed extension. T is the receiving signal threshold; With σ τ / σ c There is a certain function mapping relationship between them. Let the mapping function be F(·), then there exists The least squares method is used to perform polynomial fitting on F(·) to obtain F(x), which is expressed as: In the above formula, S v =A T / A; Step 4: define the time-varying impulse response as a function of time t and delay variable τ, expressed as: In the above formula, n = 1, 2, ... N represents the multipath mode, h n (t,τ) represents the impulse response of the nth shortwave propagation path, which consists of three parts: the random modulation function ψ n (t,τ), determine the phase function D n (t,τ) and the time-delay power distribution function S(τ).

2. An improved broadband shortwave channel simulation computing system based on ITS, characterized in that: include: processor; a memory storing executable instructions of the processor; The processor is configured to perform the steps of the method of claim 1 by executing the executable instructions.

3. A computer-readable storage medium for storing a program, characterized in that: When the program is executed, the steps of the method according to claim 1 are implemented.

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