阅读说明：本技术 一种用于真空管道磁悬浮车地无线通信的分集接收方法及系统 (Diversity receiving method and system for ground wireless communication of vacuum pipeline magnetic levitation vehicle ) 是由 虞凯 韦道准 谢联莲 杨捷 李廷军 庞雪春 杨岗 陈昳 王学林 王业立 王富斌 于 2021-08-17 设计创作，主要内容包括：本发明公开了一种用于真空管道磁悬浮车地无线通信的分集接收方法及系统。本发明使用多路天线接收实现空间分集,通过低噪放处理以及二次变频对信号进行调理,得到中频信号基于电平幅值对其采样,以电平幅值的采样值作为选择依据,对中频信号进行选择性合并,实现了改善接收信号的多径效应现象,提高接受信号质量,同时系统装置结构简单,制作成本低,易于制造与投入应用。(The invention discloses a diversity receiving method and a system for ground wireless communication of a vacuum pipeline magnetic levitation vehicle. The invention uses multi-path antenna receiving to realize space diversity, conditions the signal through low noise amplification processing and secondary frequency conversion, obtains the intermediate frequency signal and samples the intermediate frequency signal based on the level amplitude value, and selectively combines the intermediate frequency signal by taking the sampling value of the level amplitude value as the selection basis, thereby realizing the multipath effect phenomenon of the received signal and improving the quality of the received signal.)

1. A diversity reception method for vacuum pipeline magnetic levitation train ground wireless communication is characterized by comprising the following steps:

step 101, independently receiving the same signal sent by a base station through N antennas to obtain N paths of independent signals, wherein N is an integer greater than or equal to 2;

102, performing signal conditioning on the N paths of independent signals to obtain N paths of intermediate frequency signals;

103, performing AD sampling and time delay processing on the N paths of intermediate frequency signals to obtain a signal data frame of each path of intermediate frequency signal and a level amplitude sampling value of each frame;

104, selecting a signal data frame with the largest level amplitude sampling value, taking an intermediate frequency signal corresponding to the signal data frame as a target intermediate frequency signal, and outputting the target intermediate frequency signal;

and 105, repeating the steps 101-104, and continuously outputting the target intermediate frequency signal.

2. The diversity reception method for vacuum pipeline magnetic levitation vehicle-ground wireless communication as claimed in claim 1, wherein in step 102, the signal conditioning employs a low noise amplifier to amplify the received N independent signals.

3. The diversity reception method for vacuum pipeline magnetic levitation train ground wireless communication as claimed in claim 2, wherein the intermediate frequency signal is obtained by using double frequency conversion based on the signal amplified by the low noise amplifier.

4. The diversity receiving method for vacuum pipeline magnetic levitation vehicle-ground wireless communication as claimed in claim 1, wherein in step 103, the AD sampling is to sample the level amplitude when detecting the high level frame of the signal data frame of each intermediate frequency signal.

5. The diversity reception method for vacuum pipe maglev vehicle-to-ground wireless communication as claimed in claim 1, wherein in step 103, the level amplitude sampling value is delayed by a delay amount τ, wherein τ is a data frame length.

6. The diversity reception method for vacuum pipeline maglev vehicle-to-ground wireless communication as claimed in claim 5, wherein there is a delay relationship between the level amplitude sample value input to the selective combining module and the intermediate frequency signal, and the level amplitude sample value of the previous frame is used to select the intermediate frequency signal of the next frame.

7. A diversity reception system for vacuum tube magnetic levitation vehicle-to-ground wireless communication, the system comprising:

the diversity receiving module comprises N antennas which are respectively erected on the train body and used for independently receiving the same signal sent by the base station to obtain N paths of independent signals, wherein N is an integer greater than or equal to 2;

the signal conditioning module is used for conditioning the N paths of independent signals to obtain N paths of intermediate frequency signals;

the AD sampling and time delay module is used for carrying out AD sampling and time delay processing on the N paths of intermediate frequency signals to obtain a signal data frame of each path of intermediate frequency signal and a level amplitude value sampling value of each frame;

and the selective combination module comprises a digital signal processing unit and is used for selecting the signal data frame with the maximum level amplitude value sampling value, taking the intermediate frequency signal corresponding to the signal data frame as a target intermediate frequency signal and outputting the target intermediate frequency signal.

8. The diversity receiving system for the ground wireless communication of the vacuum pipeline magnetic levitation train as claimed in claim 7, wherein the N antennas are respectively arranged at the head and the tail of the train.

9. The diversity receiving system for the ground wireless communication of the vacuum pipeline magnetic levitation train as claimed in claim 8, wherein the number of the N antennas is 4, and the number of the head and the number of the tail of the train are two.

10. The diversity receiving system for vacuum pipe maglev vehicle-to-ground wireless communication of claim 9, wherein the distance between the head and tail antennas is d1, d1 is an odd multiple of λ/4, where λ is the signal wavelength.

Technical Field

The invention relates to the technical field of wireless communication, in particular to a diversity receiving method and a system for vacuum pipeline magnetic levitation train ground wireless communication.

Background

Because the train runs in the closed pipeline, the radio signal can generate frequent reflection and refraction phenomena, so that the received signal is combined by signals from different paths, the delay of each path is different, the amplitude of the combined signal is fluctuated, random fading is easy to generate, and the multipath effect is caused. In addition, compared with a magnetic suspension train in an open environment, the low-vacuum pipeline high-speed magnetic suspension train has higher running speed, the time-varying Doppler frequency shift can be caused by the high-speed movement of the train, further random frequency modulation is introduced on different paths, the periodic fading of received signals is caused, and the multipath effect is further aggravated.

At present, diversity combining technology is mostly adopted at home and abroad to improve the condition of received signal fading in a train-ground wireless communication system, the diversity mode comprises space diversity, polarization diversity, angle diversity, frequency diversity and the like, and the combining mode comprises selective combining, maximum ratio combining and equal gain combining.

In the diversity technology, space diversity uses antenna groups which are mutually independent in space to simultaneously receive transmitted signals, a plurality of independently fading channels are obtained, and diversity gain is obtained through information complementation among multiple channels. For space diversity, the larger the diversity branch number M, the better the diversity effect. But when M is larger, the complexity of the diversity increases, and the gain of the diversity increases slowly as M increases. The polarization diversity is characterized in that signals transmitted by two antennas with mutually orthogonal polarization directions at the same place present uncorrelated fading characteristics, and by utilizing the characteristic, vertical polarization antennas and horizontal polarization antennas are respectively arranged at the same place of a transmitting end, and vertical polarization antennas and horizontal polarization antennas are respectively arranged at the same position of a receiving end, so that two paths of uncorrelated signals with fading characteristics can be obtained. Polarization diversity can be seen as a special case of spatial diversity. This method has the advantages of compactness and space saving, and the disadvantage of 3dB loss of signal power due to the distribution of the transmission power to the two antennas. In the angle diversity, at the receiving end, directional antennas are used to point to different signal arrival directions, and the multipath signals received by each directional antenna are uncorrelated. The frequency diversity is to transmit the information to be transmitted at different carrier frequencies, and as long as the interval between the carrier frequencies is larger than the coherence bandwidth, the signal with uncorrelated fading characteristics can be obtained at the receiving end. The method can reduce the number of antennas, but occupies more frequency resources.

In the combining technology, the maximum ratio combining mode has the best performance, can fully utilize the redundant information of the multipath signals, can adapt to various channel environments, and particularly can combine each branch signal with seriously deteriorated signal-to-noise ratio into a useful signal with acceptable signal-to-noise ratio. However, the maximal ratio combining requires real-time analysis of the snr of each channel of signals, the equipment is relatively complex, and the reliability requirement for the channel estimator is also high, and a severe transmission performance degradation will be caused by an erroneous estimation. The performance of the equal gain combining mode is inferior to that of the maximum combining mode, the equipment is relatively simpler, but the performance is achieved when the signal-to-noise ratio of each branch is smaller. When one path of signal is seriously faded or shielded under the extreme condition, the noise of the weak path of signal is fully amplified to participate in combination, and the signal-to-noise ratio after equal gain combination is worse than that of a single branch, so the application range is very limited. The performance of the selective combining mode is poorer than that of the former two combining modes, and the redundant information of each channel cannot be fully utilized. But the algorithm is reliable, the equipment is simple, and the application is mature.

Chinese patent CN106357308A entitled "receiving method and system based on combination of space diversity and location diversity" discloses a method for receiving millimeter wave signals of two base stations at the front and the rear of a train respectively by using multiple receiving channels, performing same-frequency receiving diversity after signal demodulation to form two paths of signals, and performing diversity reception based on two vehicle-mounted control units. The invention firstly uses diversity receiving method, after frequency conversion, collects level amplitude of signal data frame, secondly uses selective combination and uses sampling value of level amplitude as selection basis to screen and output signal. The two schemes are different in implementation method and system, and different in beneficial effect.

Disclosure of Invention

The invention aims to overcome the defect of multipath effect caused by received signal fading in the prior art, and provides a diversity receiving method and a system for vacuum pipeline magnetic levitation train ground wireless communication.

In order to achieve the above purpose, the invention provides the following technical scheme:

a diversity reception method for vacuum pipeline magnetic levitation train ground wireless communication is characterized by comprising the following steps:

step 101, independently receiving the same signal sent by a base station through N antennas to obtain N paths of independent signals, wherein N is an integer greater than or equal to 2;

102, performing signal conditioning on the N paths of independent signals to obtain N paths of intermediate frequency signals;

103, performing AD sampling and time delay processing on the N paths of intermediate frequency signals to obtain a signal data frame of each path of intermediate frequency signal and a level amplitude sampling value of each frame;

104, selecting a signal data frame with the largest level amplitude sampling value, taking an intermediate frequency signal corresponding to the signal data frame as a target intermediate frequency signal, and outputting the target intermediate frequency signal;

and 105, repeating the steps 101-104, and continuously outputting the target intermediate frequency signal.

Preferably, in the diversity reception method for vacuum pipeline magnetic levitation train ground wireless communication, the signal conditioning adopts a low noise amplifier to amplify the received N independent signals.

Preferably, in the diversity reception method for vacuum pipeline magnetic levitation train ground wireless communication, an intermediate frequency signal is obtained by utilizing secondary frequency conversion based on a signal amplified by a low noise amplifier.

Preferably, in the diversity reception method for vacuum pipeline magnetic levitation train-ground wireless communication, the AD sampling is to sample a level amplitude of a signal data frame of each intermediate frequency signal when a high level frame of the signal data frame is detected.

Preferably, in the diversity reception method for vacuum pipeline magnetic levitation train ground wireless communication, a sampled value of a level amplitude is subjected to time delay processing, wherein the time delay is τ, and τ is the length of one data frame.

Preferably, in the diversity reception method for vacuum pipeline magnetic levitation train ground wireless communication, a delay relationship exists between a level amplitude sampling value input into the selective combining module and an intermediate frequency signal, and the level amplitude sampling value of a previous frame is used for selecting the intermediate frequency signal of a next frame.

A diversity reception system for vacuum tube magnetic levitation vehicle-to-ground wireless communication, the system comprising:

the diversity receiving module comprises N antennas which are respectively erected on the train body and used for independently receiving the same signal sent by the base station to obtain N paths of independent signals, wherein N is an integer greater than or equal to 2;

the signal conditioning module is used for conditioning the N paths of independent signals to obtain N paths of intermediate frequency signals;

the AD sampling and time delay module is used for carrying out AD sampling and time delay processing on the N paths of intermediate frequency signals to obtain a signal data frame of each path of intermediate frequency signal and a level amplitude value sampling value of each frame;

and the selective combination module comprises a digital signal processing unit and is used for selecting the signal data frame with the maximum level amplitude value sampling value, taking the intermediate frequency signal corresponding to the signal data frame as a target intermediate frequency signal and outputting the target intermediate frequency signal.

Preferably, in the diversity receiving system for vacuum pipeline magnetic levitation train ground wireless communication, the N antennas are respectively erected at the head and the tail of the train.

Preferably, in the diversity receiving system for vacuum pipeline magnetic levitation train ground wireless communication, the value of N is 4 for the N antennas, and the train head and the train tail are respectively two.

Preferably, in the diversity receiving system for the ground wireless communication of the vacuum pipeline magnetic levitation train, the distance between the head antenna and the tail antenna is d1, and d1 is an odd multiple length of lambda/4, wherein lambda is the signal wavelength.

In summary, due to the adoption of the technical scheme, the invention at least has the following beneficial effects:

the invention adopts a space diversity mode, receives signals through multiple paths of antennas, selectively merges the received signals by taking a sampling value of a signal data frame level amplitude as a selection basis, fully utilizes redundant information of multiple paths of channels, inhibits the multipath effect in the high-speed magnetic suspension train ground wireless communication under the low vacuum pipeline environment on the one hand, and improves the quality of the received signals; on the other hand, the device has simple structure and low cost while ensuring the performance.

Description of the drawings:

FIG. 1 is a schematic view of a vehicle antenna installation;

fig. 2 is a block diagram of a diversity reception system;

FIG. 3 is a flow diagram of a signal conditioning module;

FIG. 4 is a schematic diagram of the selective combination principle;

FIG. 5 is a flow chart of a diversity reception system;

FIG. 6 is a graph showing the relationship between the distance traveled by the train and the variation in the reception level of the mobile station;

FIG. 7 is a graph showing the length of the delay τ;

the labels in the figure are: 1-diversity receiving module, 2-signal conditioning module, 3-AD sampling and delay module, 4-selective combining module

Detailed Description

The present invention will be described in further detail with reference to test examples and specific embodiments. It should be understood that the scope of the above-described subject matter is not limited to the following examples, and any techniques implemented based on the disclosure of the present invention are within the scope of the present invention.

Example 1

The invention utilizes a multi-path antenna to receive signals, conditions the received signals, selects the signals according to the level amplitude of a signal data frame through AD sampling and time delay processing, and screens out qualified signals as final output signals.

A diversity receiving system for vacuum pipeline magnetic suspension train ground wireless communication is shown in figure 2.

The diversity receiving module 1 comprises N antennas, when N is 4, the antennas are divided into two groups, as shown in fig. 1, two antennas are respectively arranged at the head and tail of the train, the distance between the antennas is d1, d1 is odd times of lambda/4, lambda is signal wavelength, and the unit is millimeter; the four antennas are used for independently receiving the same signal sent by the base station to obtain four independent signals, and the four independent signals are output to the signal conditioning module 2.

The signal conditioning module 2 comprises a Low Noise Amplifier (LNA), a frequency converter and a band-pass filter (BPF), based on the received four independent signals, the four independent signals are firstly subjected to low noise amplification through the low noise amplifier, the intermediate frequency is reserved through the frequency conversion of the first frequency converter and the filter, the intermediate frequency is reserved through the frequency conversion of the second frequency converter and the filter, and the intermediate frequency signal is output to the AD sampling and delay module and the selective combining module.

The AD sampling and delay module 3 receives the intermediate frequency signals, firstly detects and samples each path of intermediate frequency signals by using AD sampling to obtain a signal data frame of each path of intermediate frequency signals and each frame of level amplitude value sampling value, and outputs the signal data frame and each frame of level amplitude value sampling value to the selective combining module after delay processing.

The selective combining module 4 uses the level amplitude sampling value as a signal selection basis, as shown in fig. 4, selects a signal data frame with the largest level amplitude sampling value by using the digital signal processing unit, and outputs an intermediate frequency signal corresponding to the signal data frame as a target intermediate frequency signal.

A flow chart of a diversity reception method for vacuum pipeline magnetic levitation train ground wireless communication is shown in fig. 5, which comprises the following steps:

step 101, independently receiving the same signal sent by a base station through N antennas to obtain N paths of independent signals, wherein N is an integer greater than or equal to 2;

in mobile radio communication, large field intensity change may occur due to slight spatial variation, when two or more antennas are used to receive signals, they are not correlated to fading influence, and the possibility that both are affected by fading point at the same time is small, so that it can adopt space diversity scheme of multiple antenna reception, and utilize multiple antennas to independently receive the same signal, then combine and output, and the fading degree can be greatly reduced.

Specifically, two antennas are respectively erected at the head and the tail of the train, and the four antennas independently receive the same signal sent by the base station to obtain four independent signals r₁(t)、r₂(t)、r₃(t)、r₄(t), the channels where the four independent signals are located are respectively a diversity channel 1, a diversity channel 2, a diversity channel 3 and a diversity channel 4, wherein other interference signals n also exist in the process that the signals are transmitted from the base station to the antenna for receiving₁(t)、n₂(t)、n₃(t)、n₄(t) as shown in FIG. 4.

102, performing signal conditioning on the N paths of independent signals to obtain N paths of intermediate frequency signals;

to the received four independent signals r₁(t)、r₂(t)、r₃(t)、r₄(t) performing low noise amplification and secondary frequency conversion, and as shown in fig. 3, first amplifying the signal by a Low Noise Amplifier (LNA); secondly, the signal is converted into an intermediate frequency signal by utilizing secondary frequency conversion, and simultaneously, the suppression is carried outSpecifically, the frequencies of a first local oscillator (LO1) and a second local oscillator (LO2) are f1 and f2, respectively, the frequency of a received signal is f0, low-pass filtering is performed after first frequency conversion, an intermediate frequency signal with a frequency of If being f0-f1 is retained, low-pass filtering is performed after second frequency conversion, an intermediate frequency signal with a frequency of If being f0-f1-f2 is retained, and four paths of intermediate frequency signals are input into the selective combining module on one hand and input into the AD sampling and delay module on the other hand.

The image frequency is a signal which is different from the local oscillator signal by an intermediate frequency, when the image frequency is mixed with a received signal, an "intermediate frequency signal" which can be represented as f1-If is generated in the frequency conversion, and the "intermediate frequency signal" can cause interference to the real intermediate frequency signal, which often exists in the first-stage frequency conversion, as can be known from If 0-f1, when the first-stage frequency conversion of the second-stage frequency conversion adopts a local oscillator LO1 with a low frequency, a high-frequency intermediate frequency is output, and the image frequency f1-If which is different from the local oscillator by an intermediate frequency is suppressed, so that the effect of suppressing the image frequency is achieved. Therefore, the secondary frequency conversion process can suppress the interference of the image frequency with the frequency f1-If, and the intermediate frequency signal is easier to process.

103, performing AD sampling and time delay processing on the N paths of intermediate frequency signals to obtain a signal data frame of each path of intermediate frequency signal and a level amplitude sampling value of each frame;

the AD sampling module carries out level detection on the four paths of intermediate frequency signals after receiving the four paths of intermediate frequency signals, samples a signal data frame of the current intermediate frequency signal when a higher level is detected, and outputs a signal data frame of each path of intermediate frequency signal and a level amplitude value sampling value of each frame, supposing that the level amplitude value sampling values of the four paths of signal data frames are respectively V1, V2, V3 and V4, and the magnitude relation is V1 > V2 > V3 > V4; because the four antennas cannot necessarily receive signals at the same time, the sampling value of the level amplitude of each frame of signal is guaranteed to be successfully input to the selective combining module by using time delay, specifically, the sampling result is stored by time delay τ and then is sent to the selective combining module as a signal selection basis, and τ is the length of one data frame, as shown in fig. 7.

In particular, because the sampling storage has a time-consuming problem and the transmission speed of the data frame is relatively fast, i.e. for the signal sampling storage of the current frame, when the operation is completed, the next frame data is already transmitted, but because the level change of the signal is continuous and has small fluctuation within a certain time, as shown in fig. 6, the sampling value of the current frame data and the sampling value of the next frame data are not greatly different, and the current sampling value can be used as the approximate value of the sampling value of the next frame. It can be understood that the condition of the signal input to the selective combination module in the next frame is determined by using the signal level amplitude value sampling value input to the selective combination module in the previous frame.

104, selecting a signal data frame with the largest level amplitude sampling value, taking an intermediate frequency signal corresponding to the signal data frame as a target intermediate frequency signal, and outputting the target intermediate frequency signal;

the selective combination module receives the intermediate frequency signal and the level amplitude value sampling value, the level amplitude value sampling values V1, V2, V3 and V4 are used as selection basis, the digital signal processing unit selects the intermediate frequency signal corresponding to the signal data frame as a target intermediate frequency signal according to the maximum level amplitude value sampling value, and automatically switches to one path of diversity channel where the target intermediate frequency signal is located, namely the diversity channel corresponding to the level amplitude value sampling value V1, the target intermediate frequency signal of the current diversity channel is reserved and output, the intermediate frequency signals of other diversity channels are abandoned, and the selection of the four paths of currently received independent signals is completed.

And 105, repeating the steps 101-104, and continuously outputting the target intermediate frequency signal.

Because the same signal sent by the base station all contains four independent signals independently received by four antennas, namely all contain multi-frame signal data frames, the system needs to repeat the steps when selecting each frame signal data frame and outputting the target intermediate frequency signal.

In summary, the same signal is independently received by a plurality of antennas and then combined and output, so that the signal fading degree can be reduced; meanwhile, the level amplitude can reflect the fading condition of the signal, so that the selective combination can avoid the adverse effect of the signal with too serious fading condition on the subsequent processing.

It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.