A Beam Scanning Anti-Deep Fading Method for a High-Speed Maglev Train-Ground Communication System

Abstract

The present invention discloses a method for beam scanning anti-fading in a high-speed maglev vehicle-ground communication system, comprising the following steps: Step 1, load a transceiver beam adjustment table into the vehicle-mounted base station and the ground base station; Step 2, periodically transmit and receive data, and the received signal power is P r (d n ); Step 3, set thresholds P r1 (d n ) and P r2 (d n ). If P r (d n ) ≥ P r1 (d n ), then do not change the beam direction, otherwise make a change; Step 4, determine the base station that makes the adjustment first, and mark the one that adjusts first as end 1 and the one that adjusts later as end 2; Step 5, adjust the azimuth beam pointing of end 1; Step 6, adjust the elevation beam pointing of end 1; Step 7, perform beam adjustment at end 2; Step 8, repeat Steps 3 to 7 until the entire journey is completed. The method for beam scanning anti-fading in the high-speed maglev vehicle-ground communication system proposed by the present invention reduces the problem of occupying hardware resources to a certain extent, reduces the algorithm complexity, and improves the system robustness.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-speed maglev trains, and relates to a method for improving the anti-deep fade performance of a high-speed maglev vehicle-ground communication system by adjusting the azimuth and elevation beam pointing of the transceiver base stations of the high-speed maglev vehicle-ground communication system to destroy the formation conditions of deep fade of the received signal. Background Art

[0002] The operating environment of high-speed maglev trains is complex and diverse, and radio signals between vehicle and ground base stations are prone to multipath effects when passing through the channel, causing signal fading. The multipath effect refers to the fact that the signal is affected by obstacles such as mountains, buildings, and tunnels during transmission, and after reflection, refraction, and scattering, multiple path signals reach the receiving end. Due to different propagation paths, the arrival times of the transmitted waves are different, resulting in multipath delay spread of the signal, and causing unstable signal strength, data damage, and other results. Therefore, in order to ensure the stable operation of the high-speed maglev train communication system, it is necessary to solve the problem of deep signal fade caused by multipath effects.

[0003] Currently, there are mainly the following methods for solving the deep fade problem in high-speed maglev wireless communication systems:

[0004] Method 1: Utilize a tapped delay line (TDL) model. This model consists of a group of taps with different fading coefficients and different time delays. The fading coefficient of the TDL model is obtained by multiplying the output of the fading channel generator by the tap power. The channel impulse response is obtained by using the tap gain, multipath signals, and the impulse response with time delay, and finally the TDL channel model is implemented by an FIR filter. This method is often used for multipath channel modeling, and the implementation method is simple. However, when the multipath delay of the channel is larger, the number of taps of the channel is more, and at this time, it is easy to consume more hardware and software resources.

[0005] Method 2: Orthogonal time-frequency-space (OTFS) modulation. In this technology, a symplectic finite Fourier transform is mainly utilized, which can convert the signal in the time-frequency domain and the delay-Doppler domain to achieve time-frequency selection, thereby reducing the influence of signal fading. The performance of this method has been verified to be superior to OFDM. However, it is found in the actual operation process that the OTFS modulation requires the signal gain to be greater than 5 dB to achieve the target effect. In addition, this method has high requirements for the sparsity of the channel extension function.

[0006] Method 3: Utilize an intelligent reflecting surface (IRS). This technology integrates a large number of passive reflecting elements on a plane, and by reconfiguring the wireless propagation environment, the signal is intelligently enhanced or nulled in a directional manner during signal propagation, thereby solving the deep fade problem caused by multipath effects. However, this method will increase the consumption and occupation of hardware and software resources, and at the same time, how to optimize the device configuration on the operating line will consume a lot of energy of the early designers. Summary of the Invention

[0007] An object of the present invention is to overcome the deficiency of the deep fade problem of the received composite signal caused by the channel multipath effect in the vehicle-ground communication system of a high-speed maglev train, and to provide a beam scanning anti-deep fade method for the vehicle-ground communication system of a high-speed maglev train, which can change the phase difference between the received multipath signals by adjusting the azimuth and elevation beam pointing of the phased array transceiver base station, so that the signals do not cancel each other out, thereby being able to destroy the formation conditions of the deep fade of the received signal and improving the anti-deep fade performance of the vehicle-ground communication system of the high-speed maglev train.

[0008] The object of the present invention is achieved by the following technical solutions: A beam scanning anti-deep fade method for a vehicle-ground communication system of a high-speed maglev train, comprising the following steps:

[0009] Step 1: Before the train starts running, load the respective transceiver beam adjustment tables into the on-vehicle base station and the ground base station; the transceiver beam adjustment table records the azimuth and elevation angles of the transceiver beams required locally in different train operating environments and train positions, as well as the received signal power of the previous time.

[0010] Step 2: After the train starts running and the on-vehicle base station and the ground base station establish a communication connection, use any one of the base stations as the transmitting base station and the other base station as the receiving base station; look up the azimuth and elevation angles of the transceiver beams at the position of the vehicle in the transceiver beam adjustment table, and the transmitting base station sends and receives data periodically at this angle, and the receiving base station records the received signal power P r (d n ), where d n is the current driving position of the train;

[0011] Step 3: Set the signal power thresholds for starting and stopping beam adjustment at each position respectively, and denote the signal power thresholds for starting and stopping beam adjustment at position d n as P r1 (d n ) and P r2 (d n ), where P r1 (d n ) < P r2 (d n ); the receiving base station sends the received power information back to the transmitting base station, and at the transmitting end, compare P r (d n ) with P r1 (d n ), if P r (d n ) ≥ P r1 (d n), there is no need to change the beam direction in the transceiver beam adjustment table, and the transceiver beam continues to adjust the beam pointing according to the current vehicle position and the transceiver beam adjustment table; if P r (d n ) < P r1 (d n ), then it is necessary to change the beam direction in the transceiver beam adjustment table and enter the next step;

[0012] Step 4. Determine the base station to be adjusted first according to the maximum adjustable angles of the transmitting base station and the receiving base station: The maximum adjustable beam pointing angles of the transmitting base station and the receiving base station are respectively denoted as θ maxT 、θ maxR ; if θ maxT ≥θ maxR , then adjust the transmitting end beam pointing first, and set the transmitting end as end 1 and the receiving end as end 2; if θ maxT <θ maxR , then adjust the receiving end beam pointing first, and set the receiving end as end 1 and the transmitting end as end 2; preferentially adjust the beam pointing of end 1; after determining the base station to be adjusted, first adjust the azimuth beam pointing, and if the received power still cannot meet the requirements, then adjust the elevation beam pointing;

[0013] Step 5. The adjustment method of the azimuth beam pointing is as follows: First, calculate the change rate k n of the received power, and then obtain the number of single - end one - way adjustment times M to be reserved through , Δd = d n - d n-1 , P min is the minimum demodulable signal power; determine the adjustment step size during adjustment according to the maximum adjustable beam pointing angle θ max and the number of adjustments Initialize the current number of adjusted times m = 0;

[0014] Determine the adjustment direction: Set the beam pointing of the base station to be adjusted at the next position as θ n+1 = θ n + Δθ, θ n is the beam pointing at the current position; if P r (d n+1 )≥P r (d n ) + k n Δd, that is, it is considered that the beam pointing adjustment in this direction is effective, then continue to adjust in this direction with Δθ as the step size, that is, θ n+m+1 = θ n+m + Δθ; if P r (d n+1 )<P r (d n ) + kn If Δd, it is determined that the adjustment in this direction is ineffective, and the position θ before this adjustment is returned. n , that is, θ n+1 = θ n , and then continue to adjust in this direction with Δθ as the step size, that is, θ n+m+1 = θ n+m -Δθ; where m = 0,..., M, and m is incremented by 1 after each adjustment;

[0015] After determining the adjustment direction, each time an adjustment is made, the actual received power P r (d n+m+1 ) is compared with the stop adjustment threshold P r2 (d n+m+1 ) at this position; if P r (d n+m+1 ) ≥ P r2 (d n+m+1 ), the beam adjustment process is terminated, and the beam direction at this time is updated to the corresponding transceiver beam adjustment table; otherwise, continue to repeat the above adjustment process. If M adjustments have been made in the determined adjustment direction and the received power is still less than the stop adjustment threshold P r2 (d n+M ) at this position, the pitch beam direction adjustment for the next step is entered;

[0016] Step 6: When entering the pitch beam direction adjustment, first keep the current azimuth beam direction unchanged, and then use the same steps and determination methods as for adjusting the azimuth beam direction to adjust the pitch beam direction; if the actual received signal power P r (d n+m+1 ) ≥ P r2 (d n+m+1 ), stop the adjustment, and update the azimuth and pitch beam directions at this time to the transceiver beam adjustment table; if after M adjustments, the received power is still less than the stop adjustment threshold P r2 (d n+M ) at this position, enter the next adjustment for the beam at end 2;

[0017] Step 7: When performing beam adjustment at end 2, keep the azimuth and pitch beam directions at end 1 unchanged, and then use the same steps and determination methods as at end 1 to perform azimuth and pitch beam direction adjustments at end 2; when the actual received signal power meets the stop adjustment threshold condition, stop the adjustment and record the beam direction information at this time in the transceiver beam adjustment table; if the threshold condition is not met, continue to adjust within the allowable range until the number of adjustments is reached;

[0018] Step 8: Repeat Steps 3 to 7 until the entire journey is completed. After the journey ends, upload the transceiver beam adjustment tables of the on-vehicle base station and the ground base station to the zoning control system.

[0019] The beneficial effects of the present invention are as follows: By adjusting the azimuth and elevation beam directions of the phased array transceiver base station, the phase difference between received multipath signals is changed, so that the signals do not cancel each other out, thereby being able to destroy the formation conditions of deep fading of the received signals and improving the anti-deep fading performance of the high-speed maglev vehicle-ground communication system, thus effectively solving the deep fading problem caused by multipath effects. This method does not require adjustment of the original hardware, only the internal algorithm of the system needs to be modified, which is simple to operate, cost-saving, and also improves the robustness of the communication system and can be transplanted to many scenarios where signal deep fading may occur. Description of the Drawings

[0020] Figure 1 It is a schematic diagram of signal propagation in vehicle-ground communication;

[0021] Figure 2 It is a flowchart of the method for adjusting the beam direction of the transceiver base station;

[0022] Figure 3 It is a schematic diagram of the received power for adjusting the beam direction of the transceiver base station. Detailed Embodiment

[0023] The present invention aims at the signal deep fading problem caused by multipath effects in the high-speed maglev vehicle-ground communication system. The deep fading problem is caused by the amplitude cancellation of signals due to inconsistent phases of received multipath signals. The present invention adjusts the azimuth and elevation beam directions of the phased array transceiver base station to change the phase difference between received multipath signals, so that the signals do not cancel each other out, thereby being able to destroy the formation conditions of deep fading of the received signals and improving the anti-deep fading performance of the high-speed maglev vehicle-ground communication system, thus effectively solving the deep fading problem caused by multipath effects. To a certain extent, the present invention solves the deep fading problem in the current high-speed maglev vehicle-ground communication system and improves problems such as complex algorithms and excessive occupation of hardware and software resources. Through this method, the overhead of software and hardware resources can be reduced, the complexity of the high-speed maglev vehicle-ground communication system can be lowered, and the robustness and portability of the system can be improved. The technical solution of the present invention will be further described below in conjunction with the drawings and specific embodiments.

[0024] In this embodiment, the train travels in the Figure 1 shown manner and conducts data communication with the ground base station. Next, the on-vehicle base station among them is used as the transmitting end, and the ground base station as the receiving end for specific analysis. Assume that the maximum azimuth and elevation adjustable beam directions of the train on-vehicle base station are 30° and 10° respectively, and the maximum azimuth and elevation adjustable beam directions of the ground base station are 20° and 5° respectively.

[0025] AsFigure 2 As shown in the figure, a method for beam scanning anti-deep fading in a high-speed maglev vehicle-ground communication system of the present invention includes the following steps:

[0026] Step 1: Before the train starts running, load the respective transceiver beam adjustment tables into the on-vehicle base station and the ground base station; the transceiver beam adjustment tables record the azimuth and elevation angles of the local required transceiver beams and the received signal power of the previous time at different train running environments and train positions; if the train runs a certain section of the journey for the first time, then the azimuth and elevation angles of the transceiver beams recorded in the table are both the array normals.

[0027] Step 2: After the train starts running and the on-vehicle base station and the ground base station establish a communication connection, use any one of the base stations as the transmitting base station and the other base station as the receiving base station; look up the azimuth and elevation angles of the transceiver beams at the vehicle position in the transceiver beam adjustment table, and the transmitting base station sends and receives data periodically at this angle, and the receiving base station records the received signal power P r (d n ), where d n is the current driving position of the train;

[0028] Step 3: Set the signal power thresholds for starting and stopping beam adjustment at each position respectively, and denote the signal power thresholds for starting and stopping beam adjustment at the d n position as P r1 (d n ) and P r2 (d n ), where P r1 (d n ) < P r2 (d n ); the receiving base station sends the received power information back to the transmitting base station, and at the transmitting end, compare P r (d n ) with P r1 (d n ), if P r (d n ) ≥ P r1 (d n ), there is no need to change the beam direction in the transceiver beam adjustment table, and the transceiver beam continues to adjust the beam direction according to the current vehicle position and the transceiver beam adjustment table; if P r (d n ) < P r1 (d n ), then it is necessary to change the beam direction in the transceiver beam adjustment table and enter the next step; as Figure 3 shown, when the train runs to the d7 position, the received signal power at the receiving end is P r (d7), and at this time P r(d7) < P r1 (d7), so it is considered that the beam pointing needs to be adjusted at d7.

[0029] Step 4: Determine the base station to be adjusted first according to the maximum adjustable angles of the transmitting base station and the receiving base station: The maximum adjustable beam pointing angles of the transmitting base station and the receiving base station are respectively denoted as θ maxT , θ maxR ; if θ maxT ≥θ maxR , then adjust the beam pointing of the transmitting end first, and set the transmitting end as end 1 and the receiving end as end 2; if θ maxT <θ maxR , then adjust the beam pointing of the receiving end first, and set the receiving end as end 1 and the transmitting end as end 2; preferentially adjust the beam pointing of end 1; in this embodiment, θ maxT (30°) > θ maxR (20°), so first adjust the beam pointing of the vehicle-mounted base station, and denote the vehicle-mounted base station as end 1 and the ground base station as end 2. After determining the base station to be adjusted, first adjust the azimuth beam pointing. If the received power still cannot meet the requirements, then adjust the elevation beam pointing.

[0030] Step 5: The method for adjusting the azimuth beam pointing is as follows: First calculate the change rate k7 of the received power, and then obtain the number of single-end one-way adjustment times M to be reserved through , where M = 5 in this embodiment, and P min is the minimum demodulable signal power level; determine the adjustment step size during adjustment according to the maximum adjustable beam pointing angle θ max (θ maxT in this embodiment) and the number of adjustment times; Initialize the currently adjusted number of times m = 0;

[0031] Determine the adjustment direction: Set the beam pointing of the base station to be adjusted at the next position as θ8 = θ7 + Δθ; if

[0032] P r (d8) ≥ P r (d7) + k7Δd, it is considered that the beam pointing adjustment in this direction is effective, then continue to adjust in this direction with Δθ as the step size, that is, θ 7+m+1 = θ 7+m + Δθ; if P r (d8) < P r (d7) + k7Δd, it is determined that the adjustment in this direction is ineffective, return to the position before this adjustment θ7, that is, θ8 = θ7, and then continue to adjust in this direction with Δθ as the step size, that is, θ 7+m+1 = θ 7+m - Δθ; where m = 0,..., M, and m is incremented by 1 after each adjustment;

[0033] After determining the adjustment direction, each time an adjustment is made, the actual received power P r (d n+m+1 ) is compared with the stop adjustment threshold P r2 (d n+m+1 ) at this position; if P r (d n+m+1 ) ≥ P r2 (d n+m+1 ), the beam adjustment process is terminated, and the beam direction at this time is updated to the corresponding transceiver beam adjustment table; otherwise, the above adjustment process is repeated. If M adjustments have been made in the determined adjustment direction and the received power is still less than the stop adjustment threshold P r2 (d n+M ) at this position, the next step of pitch beam direction adjustment is entered;

[0034] Step 6: When entering the pitch beam direction adjustment, first keep the current azimuth beam direction unchanged, and then use the same steps and determination method as for adjusting the azimuth beam direction to adjust the pitch beam direction; that is, first confirm the adjustment step size Then adjust one step size in one direction first. If the adjustment is effective, continue to adjust in this direction with step size Δθ. If the adjustment in this direction is ineffective, adjust in the opposite direction with step size Δθ. If the actual received signal power P r (d n+m+1 ) ≥ P r2 (d n+m+1 ), stop the adjustment and update the azimuth and pitch beam directions at this time to the transceiver beam adjustment table; if after M adjustments, the received power is still less than the stop adjustment threshold P r2 (d n+M ) at this position, enter the next step of adjusting the beam at the 2nd end;

[0035] Step 7: When adjusting the beam at the 2nd end, keep the azimuth and pitch beam directions of the 1st end unchanged, and then use the same steps and determination method as for the 1st end to adjust the azimuth and pitch beam directions at the 2nd end; that is, first adjust the azimuth beam direction of the 2nd end. If the received signal power exceeds the stop adjustment threshold within the reserved number of adjustments, stop the adjustment and record the beam direction at this time; otherwise, adjust the pitch beam direction of the 2nd end. When the actual received signal power meets the stop adjustment threshold condition, stop the adjustment and record the beam direction information at this time in the beam direction table; if the threshold condition is not met, continue to adjust within the allowable range until the number of adjustments is reached;

[0036] For the case where the ground base station is the transmitter and the vehicle-mounted base station is the receiver, the adjustment method is the same as above.

[0037] Step 8: Repeat Steps 3 to 7 until the entire journey is completed. After the journey ends, upload the transceiver beam adjustment tables of the vehicle-mounted base station and the ground base station to the zoning control system. When repeating this journey later, refer to the beam pointing table and make the above adjustments according to the weather and specific environment at that time to improve the efficiency of the system.

[0038] Those of ordinary skill in the art will realize that the embodiments described herein are for helping the reader understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations that do not depart from the essence of the present invention based on the technical revelations disclosed in the present invention, and these deformations and combinations are still within the protection scope of the present invention.

Claims

1. A beam scanning anti-deep fade method for a high-speed maglev vehicle-ground communication system, characterized in that Including the following steps: Step 1: Before the train starts running, load the respective transceiver beam adjustment tables into the on-vehicle base station and the ground base station; the transceiver beam adjustment tables record the local required azimuth and elevation angles of the transceiver beams and the received signal power of the previous time at different train operating environments and train positions; Step 2: After the train starts running and the on-vehicle base station and the ground base station establish a communication connection, any one of the base stations is used as the transmitting base station, and the other base station is used as the receiving base station; the azimuth and elevation angles of the transmitting and receiving beams at the position of the train are found in the transceiver beam adjustment table, and the transmitting base station periodically transmits and receives data at this angle, and the receiving base station records the received signal power P after receiving the signal r (d n ), where d n is the current driving position of the train; Step 3: Set the signal power thresholds for starting and stopping beam adjustment at each position, denoted as d n The signal power thresholds for starting and stopping beam adjustment at the position are P r1 (d n ) and P r2 (d n ), where P r1 (d n ) < P r2 (d n ); The receiving base station sends the received power information back to the transmitting base station. At the transmitting end, compare P r (d n ) with P r1 (d n ). If P r (d n ) ≥ P r1 (d n ), there is no need to change the beam direction in the transceiver beam adjustment table, and the transceiver beam continues to adjust the beam pointing according to the current train position and the transceiver beam adjustment table; If P r (d n ) < P r1 (d n ), then it is necessary to change the beam direction in the transceiver beam adjustment table and enter the next step; Step 4. Determine the base station to be adjusted first according to the maximum adjustable angle sizes of the transmitting base station and the receiving base station: The maximum adjustable beam pointing angles of the transmitting base station and the receiving base station are respectively denoted as θ maxT , θ maxR ; if θ maxT ≥θ maxR , then adjust the beam pointing of the transmitting end first, and set the transmitting end as end 1 and the receiving end as end 2; if θ maxT <θ maxR , then adjust the beam pointing of the receiving end first, and set the receiving end as end 1 and the transmitting end as end 2; preferentially adjust the beam pointing of end 1; after determining the base station to be adjusted, first adjust the azimuth beam pointing, and if the received power still cannot meet the requirements, then adjust the elevation beam pointing; Step 5. The method for adjusting the azimuth beam pointing is as follows: First, calculate the change rate k of the received power n , and then obtain the number M of single-ended unidirectional adjustment times to be reserved through , Δd = d n -d n-1 , P min is the minimum demodulable signal power; Determine the adjustment step size during adjustment according to the maximum adjustable beam pointing angle θ max and the number of adjustment times; Initialize the current number of adjusted times m = 0; Determine the adjustment direction: Set the beam pointing of the base station to be adjusted at the next position as θ n+1 = θ n + Δθ, where θ n is the beam pointing at the current position; If P r (d n+1 ) ≥ P r (d n ) + k n Δd, it is considered that the adjustment of the beam pointing in this direction is effective. Then continue to adjust in this direction with Δθ as the step, that is, θ n+m+1 = θ n+m + Δθ; If P r (d n+1 ) < P r (d n ) + k n Δd, it is determined that the adjustment in this direction is invalid, and return to the position θ before this adjustment n , that is, θ n+1 = θ n , and then continue to adjust in this direction with Δθ as the step, that is, θ n+m+1 = θ n+m - Δθ; where m = 0, …, M, and m is incremented by 1 after each adjustment; After determining the adjustment direction, each time an adjustment is made, the actual received power P r (d n+m+1 ) is compared with the stop adjustment threshold P r2 (d n+m+1 ) at this position; if P r (d n+m+1 ) ≥ P r2 (d n+m+1 ), the beam adjustment process is terminated, and the beam direction at this time is updated to the corresponding transceiver beam adjustment table; otherwise, continue to repeat the above adjustment process. If M adjustments have been made in the determined adjustment direction and the received power is still less than the stop adjustment threshold P r2 (d n+M ), the next pitch beam direction adjustment is entered; Step 6: When entering the elevation beam pointing adjustment, first keep the current azimuth beam pointing unchanged, and then use the same steps and determination methods as those for adjusting the azimuth beam pointing to adjust the elevation beam pointing; If the actual received signal power P r (d n+m+1 ) ≥ P r2 (d n+m+1 ), stop the adjustment and update the azimuth and elevation beam pointing to the transceiver beam adjustment table at this time; if after M adjustments, the received power is still less than the stop adjustment threshold P r2 (d n+M ), proceed to the next adjustment of the 2-end beam; Step 7: When performing beam adjustment at the 2 end, keep the azimuth and elevation beam pointings at the 1 end unchanged, and then use the same steps and determination methods as those at the 1 end to perform azimuth and elevation beam pointing adjustments at the 2 end; when the actual received signal power meets the stop adjustment threshold condition, stop the adjustment and record the beam pointing information at this time into the transceiver beam adjustment table; if the threshold condition is not met, continue to adjust within the allowable range until the number of adjustments is reached; Step 8: Repeat steps 3 to 7 until the entire journey is completed. After the journey ends, upload the transceiver beam adjustment tables of the on-vehicle base station and the ground base station to the zonal control system.

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