CN113949475B - Multimode waveguide modeling method for describing near field characteristics of wireless channel - Google Patents
Multimode waveguide modeling method for describing near field characteristics of wireless channel Download PDFInfo
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- CN113949475B CN113949475B CN202111233071.2A CN202111233071A CN113949475B CN 113949475 B CN113949475 B CN 113949475B CN 202111233071 A CN202111233071 A CN 202111233071A CN 113949475 B CN113949475 B CN 113949475B
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- 238000009826 distribution Methods 0.000 claims description 13
- 230000007306 turnover Effects 0.000 claims description 6
- 230000008859 change Effects 0.000 claims description 5
- 230000005284 excitation Effects 0.000 claims description 4
- 230000010363 phase shift Effects 0.000 claims description 3
- 238000004364 calculation method Methods 0.000 description 5
- 230000003287 optical effect Effects 0.000 description 3
- 238000012512 characterization method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005094 computer simulation Methods 0.000 description 1
- 230000005672 electromagnetic field Effects 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
- H04B17/391—Modelling the propagation channel
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
- H04B17/309—Measuring or estimating channel quality parameters
- H04B17/318—Received signal strength
- H04B17/327—Received signal code power [RSCP]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
- H04B17/391—Modelling the propagation channel
- H04B17/3912—Simulation models, e.g. distribution of spectral power density or received signal strength indicator [RSSI] for a given geographic region
Abstract
The invention discloses a multimode waveguide modeling method for describing near field characteristics of a wireless channel. The invention establishes a novel multimode waveguide model, combines geometric optics and the waveguide model, and considers the rough loss of the wall in the tunnel. The multimode waveguide model corrects the limitation that the single-mode waveguide model cannot represent multimode channels in the near field, and takes the rough loss of the wall into consideration, so that the model has universality. The multimode waveguide model can be used for analyzing the influence of factors such as working frequency, roadway sectional area and the like on the power of a received signal under the multimode condition, and can be used for an air-to-air roadway with rough wall in an underground mine.
Description
Technical Field
The invention belongs to the field of channel modeling, and particularly relates to a multimode waveguide modeling method for describing near-field characteristics of a wireless channel.
Background
For underground mine channels, there are mainly three solutions: geometric optics models, waveguide models, and full wave models. In the geometric optical model, electromagnetic waves are approximately modeled as optical rays. The electromagnetic field is obtained by summing the rays reflected on the side walls. Geometric optics models rely on computer modeling to obtain a numerical solution of path loss and signal delay at arbitrary locations, but as the signal path lengthens, the computational effort increases dramatically. The waveguide model does not require detailed information to describe the tunnel, it is the only one that can provide an analytical solution, but is not suitable for describing and analyzing near field signal propagation and cannot be used for high density networks. The full-wave model can solve maxwell's equations under any boundary condition by using numerical methods such as FDTD, and solve partial differential equations on discrete time and discrete points (finite grids), but the size of the required space finite grid is less than one tenth of the wavelength of free space, the time integration step length must be less than the grid size divided by the speed of light, and the calculation burden is far more than expected in consideration of the large size and high working frequency in the underground mine environment. In some existing multimode waveguide models, the functions of reasonable calculation complexity, characterization of channel characteristics in a near-field scene and the like are realized. However, they do not account for some of the unique features in underground mines, such as the wall complexity of mine roadways.
Disclosure of Invention
The invention aims to provide a multimode waveguide modeling method for describing near field characteristics of a wireless channel, which aims to solve the problem that the calculated amount of a geometric optical model is increased sharply, and a waveguide model is not suitable for describing and analyzing signal propagation of near field and cannot be used for a high-density network.
In order to solve the technical problems, the specific technical scheme of the invention is as follows:
a multimode waveguide modeling method for describing near field characteristics of a wireless channel, comprising the steps of:
step 1, a multimode waveguide model is established; the field intensity of each point in the roadway is equal to the sum of the field intensity of all reflected images of the point and the field intensity of a source on an excitation surface; the method comprises the steps of solving a Maxwell equation set, expressing field distribution of each point in a roadway by using a turnover method, obtaining received signal power of each point in the roadway under the condition of a smooth wall by using the relation between received signal power and field distribution, and subtracting rough loss of the wall in the roadway by using the received signal power to obtain the received signal power of each point in the roadway under the condition of a rough wall;
and 2, after the multimode waveguide model is established, simulating and analyzing the influence of factors of working frequency, roadway sectional area, antenna position and dielectric constant on the received signal power under the multimode condition, and correcting the limitation of the single-mode waveguide model in the near field by analyzing the received signal power of each point.
Further, the simulation in the step 2 specifically includes the following steps:
step 2.1, calculating eigenfunctions
In (x) 0 ，y 0 0) is the transmitting antenna coordinates, (x, y, z) the receiving antenna coordinates, m represents the waveThe number of half cycles of the change in the x-direction in the waveguide, n representing the number of half cycles of the change in the y-direction in the waveguide,represents the phase in the x-direction, +.>Representing the phase in the y-direction; a is the width of a rectangular roadway, and b is the height of the rectangular roadway; when m is even, ">When m is an odd number, the number of m,when n is odd, the element is->When n is even, ">
Step 2.2, calculating attenuation coefficient alpha of each mode component in the waveguide mn Phase shift coefficient beta mn Intensity C of each mode component mn ：
Wherein E is 0 Is the field strength at the transmitter; k (k) v Is complex electrical parameter k of the side wall of the roadway h The complex electric parameters of the tunnel ceiling and the floor are adopted, and k is wave number;
step 2.3, calculating the field distribution E of any position in the roadway R (x，y，z)：
Wherein j is an imaginary unit;
step 2.4, calculating the received signal power P of any position in the roadway under the condition of smooth wall r0 ：
Wherein P is t To transmit signal power, G t For transmitting antenna gain, G r Gain for the receiving antenna;
step 2.5, calculating the rough loss of the wall:
wherein c is the light velocity, f c R is a roughness coefficient for the working frequency;
step 2.6, calculating the received signal power P of any position in the roadway under the condition of rough wall r (x，y，z)：
P r (x，y，z)＝P r0 -L roughness (8)；
Step 2.7, received Signal Power P in case of outputting a rough wall r (x，y，z)。
Further, in step 1, the distance between the reflected image and the receiving antenna is obtained by using a turnover method:
where p represents the reflection of the reflected ray through the |p| sidewall and q represents the reflection of the reflected ray through the |q| ceiling or floor.
The multimode waveguide modeling method for describing the near field characteristics of the wireless channel has the following advantages:
1. the multimode waveguide model of the present invention has a suitable complexity compared to the geometrical-optics model.
2. The method reflects attenuation and fluctuation of the signal in the near field, and corrects the limitation that the single-mode waveguide model cannot represent the multimode channel in the near field. In an underground mine, the working frequency is far higher than the cutoff frequency of a roadway, a higher-order mode in the waveguide model is obvious, the phenomenon of rapid attenuation and fluctuation of the received signal power occurs in a near field, the influence of the higher-order mode cannot be ignored, and the single-mode waveguide model is not applicable any more. The multimode waveguide model disclosed by the invention considers the influence of a high-order mode in a near field and reflects the attenuation and fluctuation phenomena of the power of a received signal in the near field.
3. The invention considers the rough loss of the wall and is more in line with the actual situation. In some existing multimode waveguide models, the functions of reasonable calculation complexity, characterization of channel characteristics in a near-field scene and the like are realized. However, they do not account for some of the unique features in underground mines, such as the wall complexity of mine roadways. The multi-mode waveguide model disclosed by the invention considers the rough loss of the wall in the roadway, is more in line with the actual situation, and has universality.
Drawings
FIG. 1 is a schematic diagram of a multimode waveguide model of the present invention;
fig. 2 is a schematic diagram of the folding method of the present invention.
Detailed Description
For a better understanding of the objects, structures and functions of the present invention, a method for modeling a multimode waveguide describing near-field characteristics of a wireless channel is described in further detail with reference to the accompanying drawings.
The invention comprises the following steps:
step 1, as shown in fig. 1, the present invention establishes a multimode waveguide model. The field intensity of each point in the roadway is equal to the sum of the field intensity of all reflected images of the point and the field intensity of the source on the excitation surface. By solving maxwell's equations, as shown in fig. 2, the field distribution of each point in the roadway is expressed by using a turnover method, so as to obtain the received signal power of each point in the roadway under the condition of smooth walls. Subtracting the rough loss of the wall in the roadway from the signal power to obtain the received signal power of each point in the roadway under the condition of rough wall.
The folding method is shown in fig. 2. Due to the geometric characteristics of the rectangular cross-sectional shape, the reflected image and the reflected light rays have the following characteristics:
1) From reflected image I p，q The reflected light rays of (a) undergo |p| times of side wall reflection and |q| times of ceiling or floor reflection to reach the receiving antenna.
2) Let α be the angle of incidence of the ceiling or floor and β be the angle of incidence of the side wall, these angles are equal for a particular ray.
From the above two characteristics, the distance between the reflected image and the receiving antenna can be obtained And further obtaining the field distribution of each point in the roadway.
In the multimode waveguide model, the origin of the rectangular coordinate system is set at the center of the cross section, the x-axis is parallel to the width of the cross section, the y-axis is parallel to the height of the cross section, and the transmitting antenna coordinates are (x 0 ，y 0 0), the receiving antenna coordinates are (x, y, z), the transmitting antenna power P t Transmitting antenna gain G t Receiving antenna gain G r . The cross section of the rectangular roadway is wide as a and high as b. Record k v Is complex electrical parameter k of the side wall of the roadway h Is the complex electric parameter k of the tunnel ceiling and floor a The complex electric parameters of the tunnel air are shown in the specification, and k is the wave number. Then:
wherein c is the speed of light, ε 0 For vacuum dielectric constant, ε v Is the relative dielectric constant epsilon of the side wall of the roadway h Is the relative dielectric constant epsilon of the ceiling and the floor of the roadway a For air relative permittivity, σ v ，σ h ，σ a Is of corresponding conductivity; f (f) c Is the operating frequency. Definition of relative electrical parametersThe calculation formula is as follows:
electromagnetic waves are propagated in a tunnel in a horizontally polarized mode. The propagation of electromagnetic waves in a tunnel can be seen as a superposition of modes of different field distributions and attenuation coefficients. By solving maxwell's equations, the field distribution of each mode can be derived in the form of eigenfunctions. The eigenfunctions can be calculated as:
where m represents the number of half cycles of change in the x-direction in the waveguide and n represents the y-direction in the waveguideThe number of half-cycles that varies,represents the phase in the x-direction, +.>Representing the phase in the y-direction. When m is even, ">When m is an odd number, the number of m,when n is odd, the element is->When n is even, ">
Summing the fields of all effective modes at any position in the roadway to obtain the field distribution in the roadway, namely
Wherein e is a natural index. Alpha mn Attenuation coefficient, beta, for each mode component mn The phase shift coefficients for each mode component are calculated by the following formulas:
C mn for the intensity of each mode component on the excitation surface, solving by adopting a turnover method to obtain:
substituting equations (7), (9), (10) and (11) into equation (8) gives the field distribution in the roadway. According to the relation between the received signal power and the field distribution, the received signal power under the condition of smooth wall is obtained:
wherein P is r0 To receive signal power, P t To transmit signal power, G t For transmitting antenna gain, G r For receiving antenna gain, E 0 J is an imaginary unit for the field strength at the transmitter.
The wall roughness loss calculation formula is:
subtracting equation (13) from equation (12) yields the received signal power in the case of a rough wall:
P r (x，y，z)＝P r0 (x，y，z)-L roughness (14)
and 2, after the multimode waveguide model is built, the influence of factors such as working frequency, roadway cross section area and the like on the received signal power under the multimode condition is simulated and analyzed, and the limitation of the single-mode waveguide model in the near field is corrected by analyzing the received signal power of each position in the roadway. In addition, the multimode waveguide model is more versatile in that it takes account of the rough loss of the walls.
It will be understood that the invention has been described in terms of several embodiments, and that various changes and equivalents may be made to these features and embodiments by those skilled in the art without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (2)
1. A multimode waveguide modeling method for describing near field characteristics of a wireless channel, comprising the steps of:
step 1, a multimode waveguide model is established; the field intensity of each point in the roadway is equal to the sum of the field intensity of all reflected images of the point and the field intensity of a source on an excitation surface; the method comprises the steps of solving a Maxwell equation set, expressing field distribution of each point in a roadway by using a turnover method, obtaining received signal power of each point in the roadway under the condition of a smooth wall by using the relation between received signal power and field distribution, and subtracting rough loss of the wall in the roadway by using the received signal power to obtain the received signal power of each point in the roadway under the condition of a rough wall;
step 2, after a multimode waveguide model is established, simulating and analyzing the influence of factors of working frequency, roadway sectional area, antenna position and dielectric constant on received signal power under multimode conditions, and correcting the limitation of the single-mode waveguide model in a near field by analyzing the received signal power of each point;
the step 1 of establishing the multimode waveguide model specifically comprises the following steps:
step 1.1, calculating eigenfunctions
Where (x, y, z) is the receive antenna coordinates, m represents the number of half-cycles of the x-direction change in the waveguide, n represents the number of half-cycles of the y-direction change in the waveguide,represents the phase in the x-direction, +.>Representing the phase in the y-direction; a is the width of a rectangular roadway, and b is the height of the rectangular roadway; when m is even, ">When m is odd, the element is->When n is odd, the element is->When n is even, ">
Step 1.2, calculating attenuation coefficient alpha of each mode component in the waveguide mn Phase shift coefficient beta mn Intensity C of each mode component mn ：
Wherein E is 0 Is the field strength at the transmitter; k (k) v Is complex electrical parameter k of the side wall of the roadway h The complex electric parameters of the tunnel ceiling and the floor are adopted, and k is wave number; (x) 0 ,y 0 0) is the transmitting antenna coordinates;wherein k is a The electric parameters are repeated for the tunnel air;
step 1.3, calculating the field distribution E of any position in the roadway R (x,y,z)：
Wherein j is an imaginary unit;
step 1.4, calculating the received signal power P of any position in the roadway under the condition of smooth wall r0 ：
Wherein P is t To transmit signal power, G t For transmitting antenna gain, G r Gain for the receiving antenna;
step 1.5, calculating the rough loss of the wall:
wherein c is the light velocity, f c R is a roughness coefficient for the working frequency;
step 1.6, calculating the received signal power P of any position in the roadway under the condition of rough wall r (x,y,z)：
P r (x,y,z)＝P r0 (x,y,z)-L roughness (8)
Step 1.7, received Signal Power P in case of outputting a rough wall r (x,y,z)。
2. The multimode waveguide modeling method for describing near field characteristics of a wireless channel according to claim 1, wherein in step 1, a distance between a reflected image and a receiving antenna is obtained by using a turnover method:
where p represents the reflection of the reflected ray through the |p| sidewall and q represents the reflection of the reflected ray through the |q| ceiling or floor.
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| CN105429915A (en) * | 2015-11-30 | 2016-03-23 | 中国矿业大学 | Roadway echo canceling method based on channel estimation |
| CN105550436A (en) * | 2015-12-10 | 2016-05-04 | 中国矿业大学 | Wave mode and ray theory fused winding roadway radio wave propagation modelling method |
| CN107180122A (en) * | 2017-04-10 | 2017-09-19 | 西安电子科技大学 | A kind of analysis method of the rectangular waveguide transmission loss based on contact structures equivalent impedance |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105429915A (en) * | 2015-11-30 | 2016-03-23 | 中国矿业大学 | Roadway echo canceling method based on channel estimation |
| CN105550436A (en) * | 2015-12-10 | 2016-05-04 | 中国矿业大学 | Wave mode and ray theory fused winding roadway radio wave propagation modelling method |
| CN107180122A (en) * | 2017-04-10 | 2017-09-19 | 西安电子科技大学 | A kind of analysis method of the rectangular waveguide transmission loss based on contact structures equivalent impedance |
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| 煤矿巷道壁粗糙度对电磁波传播的影响;霍羽;房咪咪;刘逢雪;徐钊;;工矿自动化(03);全文 * |
| 矿井空巷道无线信道特性分析与仿真;姚述福;余伟健;;矿业工程研究(02);全文 * |
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