Method for evaluating communication efficiency of short-wave access network

Abstract

The invention discloses a communication efficiency evaluation method for a short-wave access network. The method comprises the following steps: step 1, selecting a short-wave communication transmitting station; 2, initializing a background ionized layer; step 3, calculating short-wave communication power based on a ray tracing theory of a complex refractive index; step 4, determining the passable range of the polar region short-wave access network; and step 5, evaluating the efficiency of the polar region short-wave networking. According to the method disclosed by the invention, the short-wave communication power is calculated by using a ray tracing theory based on a complex refractive index, a transmitting station is selected according to actual needs, and the coverage range and efficiency evaluation of polar region short-wave networking communication is given.

Description

Technical Field

[0001] The present invention belongs to the technical field of short-wave networking communication, and particularly relates to a method for evaluating the communication efficiency of a polar region short-wave access network based on the ray tracing theory of complex refractive index in this field. Background Art

[0002] The value of the Arctic shipping route has become increasingly prominent due to global warming, which will change the international trade network structure with the Malacca Strait, the Suez Canal, etc. as the main lines, and affect the entire world economy and geopolitical pattern. In recent years, with the increasing annual traffic volume of the Arctic shipping route, the demand for polar region communication guarantee technology has become more urgent. On the one hand, geostationary satellites and high-orbit navigation satellites do not cover the polar region; on the other hand, ground navigation radar networks and ground-based ship networking are also blank in the vast Arctic Ocean. Reliable over-the-horizon short-wave communication across the polar region has become the backup communication means, and reliable communication guarantee in the Arctic region has become a new hot spot and technical difficulty.

[0003] The polar ionosphere can be simply considered as a region containing the middle-latitude trough, the auroral oval, and the polar cap. After the solar wind energetic particles enter the Earth's magnetosphere, they can sink along the magnetic field lines to the polar ionosphere and the middle and upper atmosphere, generating a series of important geophysical phenomena, such as auroras, magnetic storms, magnetospheric substorms, ionospheric storms, polar cap absorption, westward surges, etc. These space weather processes occur first and most strongly in the polar region and gradually spread to the mid-latitudes and low-latitudes. Due to the special configuration of the Earth's magnetic field in the polar region, the polar ionosphere is tightly coupled with the magnetosphere through large-scale processes such as particle precipitation and plays an important role in the solar wind-magnetosphere-ionosphere and thermosphere coupling. The geomagnetic field structure makes the polar region a window for the Earth's space to open to space, and the solar wind, magnetospheric energetic charged particles, and currents directly enter the ionosphere, severely affecting the radio wave propagation characteristics of the ionosphere and directly affecting the reliability of short-wave communication in the polar region. Therefore, evaluating the communication efficiency of the polar region short-wave access network is of great significance for studying the polar adaptability of the polar region communication system. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for evaluating the communication efficiency of a short-wave access network, which can improve the low communication availability and communication limitation of short-wave communication in the complex polar environment, ensure the navigation, aviation communication needs and personnel safety of the Arctic shipping route, and has important application value and prospects.

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

[0006] A method for evaluating the communication efficiency of a short-wave access network, the improvement lies in that it includes the following steps:

[0007] Step 1, Selection of Shortwave Communication Transmitting Station:

[0008] Set the shortwave signal transmitting station according to the actual shortwave communication coverage requirements in the polar region;

[0009] Step 2, Initialization of the Background Ionosphere;

[0010] Step 3, Calculate the Shortwave Communication Power Based on the Ray Tracing Theory of Complex Refractive Index:

[0011] Assume Δs i is the step length at the i-th point, then the propagation path R i is:

[0012]

[0013] If S is the total number of steps, then the total propagation path R is:

[0014]

[0015] Let the attenuation L i at the i-th point be:

[0016]

[0017] In the above formula, f is the incident wave frequency, n is the phase refractive coefficient, and c is the speed of light;

[0018] Then the cumulative attenuation is expressed as:

[0019]

[0020] The total attenuation L M is:

[0021]

[0022] In the above formula, M represents the total number of paths;

[0023] The signal intensity I i at the i-th point is:

[0024]

[0025] In the above formula, P t is the transmitting power, and G t is the transmitting gain;

[0026] The received power P r at the receiving point is:

[0027]

[0028] In the above formula, G r is the receiving gain;

[0029] Step 4, determine the accessible range of the shortwave access network in the polar region:

[0030] Obtain shortwave communication link information, including shortwave ray propagation trajectories, coverage ranges, and field strengths;

[0031] Step 5, evaluate the effectiveness of shortwave networking in the polar region:

[0032] Examine the ray tracing results of networking communication under different azimuth angles, obtain the shortwave networking power coverage distribution map, and conduct an evaluation of the effectiveness of shortwave networking.

[0033] Furthermore, in Step 2, use the International Reference Ionosphere Model IRI2016 and the Ionospheric Neutral Atmosphere Model NRLMSISE-00 to initialize the background ionosphere, and set the background ionospheric electron density, electron and ion temperatures, and neutral atmosphere density at the corresponding emission time and the longitude and latitude of the emission station.

[0034] Furthermore, in Step 4, by adjusting the elevation angle of the signal transmitted by the shortwave communication transmitting station, setting the transmission parameters and actual requirements, conduct ray tracing simulations, give the radio wave propagation path, and adjust the accessible range of the shortwave communication station network.

[0035] Furthermore, in Step 4, the ray tracing equation is solved using the Runge-Kutta method. By setting the group path step size, obtain the wave vector and coordinate vector at each point on the ray trajectory; based on the geographical location parameters of the shore station, antenna pattern parameters, background ionosphere model, and neutral atmosphere parameters, solve the ray equation.

[0036] Furthermore, in Step 4, based on the constructed background ionosphere model, obtain the electron density distribution data, input the emission point coordinates, emission elevation angle, and operating frequency; calculate the coordinates when the shortwave ray enters the ionosphere, and at the same time calculate the partial derivatives of the ionospheric electron density in all directions of the spherical coordinates; conduct ray equation solving and power calculation.

[0037] Furthermore, in Step 5, based on the link loss estimation results, background noise conditions, received power conditions, and actual requirements, determine the communication effect of shortwave networking in the polar region.

[0038] The beneficial effects of the present invention are:

[0039] The method disclosed by the present invention calculates the short-wave communication power using the ray-tracing theory based on the complex refractive index, selects the transmitting station according to actual needs, and gives the coverage range and effectiveness evaluation of the short-wave networking communication in the polar region. The traditional short-wave ray-tracing algorithm is mostly used for the calculation of propagation modes, generally only considering the influence of the real part of the refractive index. The complex refractive index ray-tracing algorithm based on the deterministic model proposed by the present invention not only considers the influence of the real part of the refractive index, the free-space spherical wave propagation loss, and the ionospheric absorption loss, but also considers the influence of the imaginary part of the refractive index. It is a beneficial expansion of the traditional ray-tracing algorithm, greatly improving the accuracy of calculating the received power and having potential advantages;

[0040] The method disclosed by the present invention realizes the predictability of the short-wave communication link, reduces the cost and uncertainty of long-distance navigation in the polar region, has the option of avoiding communication risks, and can develop short-wave communication systems such as land-based, shore-based or shipborne.

[0041] The existing single-station communication has a small coverage range, and there are problems such as poor and unstable communication quality. The short-wave access network communication method proposed by the present invention has a greatly improved communication range compared with the single-station mode, effectively solves the problem of fewer existing coastal radio facilities, improves the quality and reliability of short-wave communication, and enables it to meet the actual communication needs. The most widely used satellite communication in the polar region is the International Maritime Satellite (Inmarsat). However, the intersection point of the geostationary orbit satellite and the earth's tangent plane is 76.3°, and the higher-latitude Arctic region is a communication blind area. The polar region short-wave communication method proposed by the present invention can cover 80°N, realizing ultra-long-distance communication of more than 6000 km, enabling our country to have the communication ability of the Arctic shipping lane that is independently controllable. Brief Description of the Drawings

[0042] Figure 1 It is a schematic flow chart of the method of the present invention;

[0043] Figure 2 It is a schematic diagram of the distribution of transmitting stations and the communication coverage range;

[0044] Figure 3 It is an initialization diagram of the background ionosphere;

[0045] Figure 4 It is a ray-tracing diagram in a certain vertical plane transmitted by Manzhouli Station;

[0046] Figure 5 It is a ray-tracing diagram in a certain vertical plane transmitted by Tianjin Station;

[0047] Figure 6 It is a ray-tracing diagram in a certain vertical plane transmitted by Yili Station;

[0048] Figure 7 It is a spatial distribution diagram of the short-wave networking communication power in the polar region. Detailed Implementation Modes

[0049] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to 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 used to limit the present invention.

[0050] Embodiment 1 discloses a method for evaluating the communication efficiency of a short-wave access network, as Figure 1 shown, which includes the following steps:

[0051] Step 1, selection of short-wave communication transmitting stations:

[0052] According to the actual requirements of the short-wave communication coverage in the polar region, short-wave signal transmitting stations are set;

[0053] In this embodiment, Manzhouli Station, Tianjin Station and Yili Station are selected. The specific addresses of the transmitting stations are:

[0054] Manzhouli: 49.58°N, 117.48°E; Tianjin: 39.13°N, 117.2°E; Yili: 47.84°N, 88.14°E. The distribution of each transmitting station and the communication coverage are as Figure 2 shown.

[0055] Step 2, initialization of the background ionosphere:

[0056] Using the International Reference Ionosphere Model IRI2016 and the Ionospheric Neutral Atmosphere Model NRLMSISE-00, the background ionosphere is initialized, and the background ionospheric electron density, electrons, ion temperature (T e / i ), and neutral atmosphere density and other parameters such as the corresponding emission time and the longitude and latitude of the transmitting station are set to provide reliable inputs for the short-wave communication access network efficiency evaluation model.

[0057] In the simulation calculation, the IRI-2016 and NRLMSISE-00 models are selected as the inputs of the background ionosphere to construct a background ionosphere model, which can provide the ionospheric electrons, ions (O + , H + , O2 + , NO + ), neutral atmosphere (O2, N2, O, etc.) density, electrons, ion and neutral atmosphere temperature within the corresponding time, longitude and latitude and altitude required by this embodiment, and generate the spatial distribution of the background electrons and neutral atmosphere density as Figure 3 shown;

[0058] Step 3, calculating the short-wave communication power based on the ray tracing theory of the complex refractive index:

[0059] Including numerical analysis of ray tracing equations, calculation of complex refractive index, calculation of free space propagation loss and collision attenuation on the ray path, calculation of received power, ray tracing theory of complex refractive index, ionospheric absorption attenuation effect, shortwave communication power calculation, etc.

[0060] According to the characteristics of ionospheric radio wave propagation, the ray tracing theory of complex refractive index is adopted to determine the background ionospheric model, then the ionospheric absorption attenuation effect is calculated, and finally the shortwave communication power is calculated. Based on the ray tracing theory of complex refractive index, considering the influence of the imaginary part of the refractive index and the collision effect, it has the advantages of stable algorithm and high accuracy.

[0061] For three-dimensional ray tracing, Haselgrove gave the three-dimensional Hamilton operator in spherical coordinates, which is related to the vector The relationship with the refractive index n is:

[0062]

[0063] In the above formula, k r 、k θ and are the normalized wave normal directions of the propagation vector, and in free space, they satisfy:

[0064]

[0065] In the above formula, ω = 2πf is the angular frequency of the wave; c is the propagation speed variable of electromagnetic waves in free space; r, θ, and are the coordinates of a point on the ray path in spherical coordinates;

[0066] The corresponding relationship between longitude and latitude and θ and is as follows:

[0067] lat = θ (3)

[0068]

[0069] The three components of the wave vector in the local coordinate system are:

[0070] k r = ksinβ (5)

[0071] k θ = kcosβcosα (6)

[0072]

[0073] In the above formula, β is the ray elevation angle; α is the ray azimuth angle.

[0074] In the spherical coordinate system, the ray equation with the group path of radio wave propagation as a parameter can be described as:

[0075]

[0076]

[0077] In the above formula, P' is the propagation group path; k r , k θ , are the three components of the wave vector in the spherical coordinate system; c is the speed of light; H is the Hamiltonian operator.

[0078] The relationship between H, the wave vector k, and the phase refractive index n can be further expressed as:

[0079]

[0080] Equations (9)-(14) are used to calculate the coordinates of points on the ray path and the wave vector at that point. Equation (13) calculates the frequency drift of electromagnetic waves in a time-varying medium. Since the frequency drift caused by the time-varying nature of the ionosphere is very small, it can be ignored when calculating the ray parameters. Therefore, no frequency adjustment is required at each step of ray tracing. When considering the magnetic field and collisions, the refractive index n is:

[0081]

[0082] If the influence of the magnetic field is not considered when considering wave refraction and reflection, the ionosphere can be regarded as an isotropic medium, the refractive index does not change with the direction of the wave vector, and there is no "magnetic splitting" phenomenon for the wave. Of course, this is an ideal situation and only applicable to approximately dealing with specific problems. In addition, collisions only cause energy absorption loss, and the collision effect does not need to be considered when calculating wave refraction and reflection. In this way, the refractive index n can be simplified to:

[0083]

[0084] In the above formula:

[0085]

[0086] Y = f H / f = eB / 2πm e f (19)

[0087] Z = υ e / 2πf (20)

[0088] In the above formula: Y T = Ysinθ; Y L = Ycosθ; f N is the ionospheric plasma frequency; f Hω is the electron cyclotron frequency; f is the incident wave frequency; ε0 is the permittivity of free space; B is the geomagnetic field; θ is the angle between the wave vector direction and the magnetic field direction, and here the dipole approximation is used. And H can be transformed into:

[0089]

[0090] According to the relationship between H, n, and X, and using the isotropic property of the medium and the relationship that the phase and group refractive indices are reciprocal to each other in the absence of a magnetic field, the equation can be simplified to:

[0091]

[0092] The system of equations (22)-(27) is the system of equations for the ray components in the ionosphere neglecting the magnetic field and collisions. It is not only related to the position of the point and the components of the wave vector at that point, etc., but also related to the rate of change of the plasma parameters at that point related. Solving the system of equations (22)-(27) according to the step size of the group path P', and then connecting the obtained points, a ray trajectory in spherical coordinates can be obtained, and the main parameters of the propagation path such as the group path, ground distance, azimuth deviation, etc. can be obtained. After appropriate transformation, the ray trajectory in other coordinate systems can also be obtained.

[0093] υ e = υ ei + υ en (28)

[0094]

[0095] Assume that Δs i is the step size at the i-th point, then the propagation path R i is:

[0096]

[0097] The free space propagation loss L1 is:

[0098]

[0099] The signal strength P e is:

[0100]

[0101] If S is the total number of step sizes, then the total propagation path R is:

[0102]

[0103] Let the attenuation L i at the i-th point be:

[0104]

[0105] In the above formula, f is the incident wave frequency, n is the refractive index, and c is the speed of light; then the cumulative attenuation is expressed as:

[0106]

[0107] The total attenuation L M is:

[0108]

[0109] In the above formula, M represents the total number of paths;

[0110] The signal strength I at the i-th point i is:

[0111]

[0112] In the above formula, P t is the transmission power, and G t is the transmission gain;

[0113] The received power P r is:

[0114]

[0115] In the above formula, G r is the receiving gain;

[0116] Step 4, determine the accessible range of the polar shortwave access network:

[0117] It mainly includes solving the ray tracing equation, shortwave link prediction, etc.

[0118] By adjusting the elevation angle of the signal transmitted by the shortwave communication transmitting station, setting the transmission parameters and actual needs, performing ray tracing simulation, giving the radio wave propagation path, and adjusting the accessible range of the shortwave communication station network, etc.

[0119] The ray tracing equation is solved by the Runge-Kutta method. By setting the group path step size, the wave vector and coordinate vector at each point on the ray trajectory are obtained; for problems such as determining the accessible range of the shortwave access network in the background ionosphere, based on equipment parameters such as the geographical location parameters of the shore station and the antenna pattern, the background ionosphere model and neutral atmosphere parameters, the ray equation is solved, and power calculations are carried out based on two strategies of single-station optimization and wide-area space diversity.

[0120] Based on the constructed background ionosphere model, obtain the electron density distribution data, input the transmitting point coordinates, transmission elevation angle and operating frequency; calculate the coordinates when the shortwave ray enters the ionosphere, and at the same time calculate the partial derivatives of the ionosphere electron density at this point in all directions of the spherical coordinates; solve the ray equation and perform power calculations.

[0121] Obtain shortwave communication link information, including shortwave ray propagation trajectories, coverage ranges, field strengths, etc.; the results are as Figures 4 - 6 shown.

[0122] Step 5, Polar region shortwave networking effectiveness evaluation:

[0123] It mainly includes shortwave networking communication power combination, shortwave networking effectiveness evaluation, etc.

[0124] Regarding the problem of simulating the power coverage characteristics of a shortwave access network in the background ionosphere, based on the above ionospheric model, carry out a polar region shortwave networking effectiveness evaluation technology based on wide-area space diversity power calculation, examine the ray tracing results of networking communication under different azimuth angle conditions, obtain the shortwave networking power coverage distribution map, and conduct shortwave networking effectiveness evaluation. The results are as Figure 7 shown.

[0125] Based on the link loss estimation results, background noise conditions, received power conditions, and actual needs, determine the communication effect of the polar region shortwave networking, etc.

[0126] In summary, the present invention proposes a method for evaluating the communication effectiveness of a polar region communication shortwave access network based on the complex refractive index and the deterministic model. Using the ray tracing method, it realizes the coverage area and effectiveness evaluation of the homeland - Arctic shortwave communication networking, can be used for homeland - Arctic shortwave communication link prediction, and can also be used as a communication guarantee means for the safe flight / navigation of aircraft, ships, etc. in the Arctic. By calculating the complex refractive index, the present invention corrects the ray tracing power calculation equation, and can effectively solve the problems such as inaccurate shortwave communication power calculation and difficult evaluation of shortwave communication effectiveness caused by the traditional ray tracing theory only considering the influence of the real part of the refractive index.

Claims

1. A method for evaluating the communication performance of a shortwave access network, characterized in that: The steps include: Step 1, shortwave communication transmitter station selection: According to the actual polar shortwave communication coverage requirements, shortwave signal transmission stations are set up; Step 2, background ionosphere initialization; Step 3, calculate the shortwave communication power based on the ray tracing theory of complex refractive index: Assume Δs i is the step length of the i-th point, then the propagation path R i for: If S is the total number of steps, the total propagation path R is: Assume that the attenuation L at the i-th point i for: In the above formula, f is the frequency of the incident wave, n is the phase refractive index, and c is the speed of light; The cumulative attenuation is then expressed as: Total attenuation L M for: In the above formula, M represents the total number of paths; The signal strength at point i is I i for: In the above formula, P t is the transmission power, G t is the transmission gain; Receiving point power P r for: In the above formula, G r for receiving gain; Step 4: Determine the range of the polar shortwave access network: Obtain shortwave communication link information, including shortwave ray propagation trajectory, coverage, and field strength; Step 5: Evaluation of polar shortwave network performance: The ray tracing results of network communication under different azimuth conditions were examined to obtain the shortwave network power coverage distribution map and conduct shortwave network performance evaluation.

2. The method for evaluating the communication efficiency of a shortwave access network according to claim 1, characterized in that: In step 2, the background ionosphere is initialized using the international reference ionosphere model IRI2016 and the ionospheric neutral atmosphere model NRLMSISE-00, and the background ionosphere electron density, electron and ion temperature and neutral atmosphere density of the corresponding transmission time and longitude and latitude of the transmitting station are set.

3. The method for evaluating the communication efficiency of a shortwave access network according to claim 1, characterized in that: In step 4, by adjusting the elevation angle of the shortwave communication transmitting station to transmit the signal, setting the transmission parameters and actual needs, performing ray tracing simulation, giving the radio wave propagation path, and adjusting the accessible range of the shortwave communication station network.

4. The method for evaluating the communication efficiency of a shortwave access network according to claim 1, characterized in that: In step 4, the ray tracing equation is solved by the Runge-Kutta method. By setting the group path step size, the wave vector and coordinate vector at each point on the ray trajectory are obtained. The ray equation is solved based on the geographical location parameters of the shore station, the antenna pattern parameters, the background ionosphere model and the neutral atmosphere parameters.

5. The method for evaluating the communication efficiency of a shortwave access network according to claim 1, characterized in that: In step 4, the electron density distribution data is obtained based on the constructed background ionosphere model, and the launch point coordinates, launch elevation angle and operating frequency are input; the coordinates of the shortwave ray when it enters the ionosphere are calculated, and the partial derivatives of the ionosphere electron density in all directions of the spherical coordinates are calculated; the ray equation is solved and the power is calculated.

6. The method for evaluating the communication efficiency of a shortwave access network according to claim 1, characterized in that: In step 5, the communication effect of the polar shortwave network is determined based on the link loss estimation results, background noise conditions, receiving power conditions and actual needs.

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