CN113890577A - Rapid diversity method based on signal similarity - Google Patents

Rapid diversity method based on signal similarity Download PDF

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CN113890577A
CN113890577A CN202111148562.7A CN202111148562A CN113890577A CN 113890577 A CN113890577 A CN 113890577A CN 202111148562 A CN202111148562 A CN 202111148562A CN 113890577 A CN113890577 A CN 113890577A
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frame header
frame
channel
error energy
minimum
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CN113890577B (en
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李廷军
陈子健
杨海宁
程钰间
樊勇
方凯
王海明
高原
蒋俊
邓江明
王倩
姜宏伟
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University of Electronic Science and Technology of China
CRRC Zhuzhou Locomotive Co Ltd
Hunan CRRC Times Signal and Communication Co Ltd
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University of Electronic Science and Technology of China
CRRC Zhuzhou Locomotive Co Ltd
Hunan CRRC Times Signal and Communication Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
    • H04B1/3822—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving specially adapted for use in vehicles
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Abstract

The invention discloses a rapid diversity method based on signal similarity, which comprises the following steps: s1, receiving input signals of a plurality of channels and demodulating the input signals to obtain frame signals; s2, a plurality of channels calculate error energy in parallel, the rising edge of the effective door signal of the effective frame header detected firstly is used as the starting time, and the preset time is delayed backwards to be used as the frame header receiving time window; s3, calculating frame header error energy in a frame header receiving time window; judging whether the frame header error energy has a minimum value and the minimum value is smaller than a preset threshold value, if so, storing the minimum frame header error energy; s4, comparing all the minimum frame header error energies, and selecting a channel corresponding to the minimum value if only one minimum value exists; and if a plurality of minimum values exist, selecting the channel with the top rank from the channels corresponding to the minimum values. The invention provides a similarity calculation and judgment method of spatial multi-group data information frames on the basis of spatial diversity, which can quickly select an optimal channel.

Description

Rapid diversity method based on signal similarity
Technical Field
The invention belongs to the technical field of wireless communication, and particularly relates to a rapid diversity method based on signal similarity.
Background
The communication system of the high-speed magnetic suspension train has strict requirements on reliability, the performance of the communication system influences the normal operation of the whole system, and the accurate and timely realization of data reception is the technical key point of the high-speed railway communication system. The wireless communication has intersymbol interference and channel fading caused by multipath effect, the carrier aggravates Doppler frequency shift when moving at high speed, and the communication quality is reduced, and the improvement measures comprise shortening transmission distance, spreading, diversity reception and the like.
The basic principle of diversity reception as a main technique for solving channel fading is as follows: the diversity receiving device is used for carrying out multi-path acquisition on signals received by a plurality of channels (time, frequency or space), because the transmission characteristics of the plurality of channels are different, the fading of a plurality of signal copies carrying the same information cannot be the same, and a receiver combines the plurality of copies according to a certain strategy to better recover the original transmitted signals. In a mobile wireless environment, particularly high-speed maglev track traffic, and a high-speed mobile wireless environment with multiple antennas and multiple base stations, since signals come from different time, frequency and space, the transmission quality and processing speed of a wireless communication channel can be improved by adopting a diversity method, and the application of the diversity technology is very important for the application scenarios.
The diversity technique makes the receiving end obtain a plurality of independent branch signals, and the merging technique solves the problem of combining a plurality of paths of signals in which way to improve the signal-to-noise ratio of the output. The traditional merging methods are mainly divided into three categories: combining (SC), Equal Gain Combining (EGC) and Maximal Ratio Combining (MRC) are selected.
MRC weights the branch signals by phase adjusting them and multiplying them by a factor related to the noise power so that the branches add in phase and the signal is emphasized to attenuate the noise. MRC combining requires continuous detection of each diversity branch to estimate the fading amplitude and phase of the channel, which makes the receiver complex.
EGC is less complex than MRC and differs from MRC in that the signal amplitudes are not weighted, and EGC can be considered as a special case of MRC. Although the estimation of the fading amplitude of the signal is reduced and the complexity is reduced, since only the phase is compensated, a problem more serious than MRC occurs when the phase estimation has an error, and at the same time, the branches with more signal attenuation participate in the combination with the same amplitude coefficient, which may result in introducing more noise.
The SC method is to select only one signal with the largest instantaneous snr to output the signal, and since channel estimation is not needed, the complexity is the lowest, but the branch snr needs to be calculated in real time, and the combining gain is sacrificed.
The application background of the technology is directed at a high-speed magnetic levitation wireless communication environment, the three traditional combining technologies are difficult to compromise between the performance gain of a diversity system and the technical implementation simplicity, and particularly in a specific occasion with extremely short processing time, the received multipath signals need to be diversity-processed quickly in a short time, so that the traditional diversity method is low in efficiency and difficult to implement.
Disclosure of Invention
The invention aims to solve the problems of slow time for processing multipath signals, poor signal recovery quality, long time for calculating the signal to noise ratio and the like in the prior art, provides a similarity calculation and judgment method for a plurality of groups of spatial data information frames on the basis of space diversity, and can quickly select a path of optimal channel based on the signal similarity.
The invention aims to provide a rapid diversity method based on signal similarity, which comprises the following steps:
s1, receiving input signals of a plurality of channels, and demodulating the input signals of each channel respectively to obtain frame signals;
s2, taking the frame header with length of N code elements in each channel as the object of rapid diversity processing, performing M times oversampling to all N code elements in the frame header to obtain the frame header sequence with length of NxM, sliding the frame header sequence obtained by oversampling into the shift register, calculating the frame header error energy S in the form of autocorrelation calculation with the frame header code element specified by the data frame protocol stored in the shift registerijSending the frame signal and the frame header error energy into FIFO for subsequent judgment;
s3, judging whether the frame header energy error meets the following two conditions:
a、Si(k-1)＞Sikand Si(k+1)＞SikIn which S isi(k-1)、Sik、Si(k+1)Respectively representing frame header energy errors of ith channel at k-1, k and k +1 moments;
b、Sik＜SRthat is, the frame header error energy of the ith path at the time k is smaller than the preset threshold value SR；
If the energy error of the channel i at the kth moment meets the two conditions, the channel i generates a channel effective gate signal with one frame length; taking the rising edge of the channel effective gate signal which firstly meets the two conditions as the starting time, delaying for a preset time later and taking the delayed time as a frame header receiving time window;
s4, for each channel, the frame head error energy value changes with the sliding process of the frame head into the shift register, in the frame head receiving time window, the M times oversampling is carried out to all N sections of code elements in the frame head, the code element sequence obtained by oversampling is slid into the shift register, and the frame head error energy S is calculated successively with the frame head code element specified by the data frame protocol stored in the shift registerij(ii) a Judging whether frame header error energy of each channel in a frame header receiving time window has a minimum value and the minimum value is smaller than a preset threshold value, if so, comparing the frame header error energy with frame header error energy stored in FIFO (first in first out) and updating in real time, storing the minimum frame header error energy, and storing the frame signal as an effective signal; otherwise, the frame signal is regarded as an invalid signal to be removed;
s5, after the frame header receiving time window is finished, comparing the minimum frame header error energy stored in all channels, if the minimum frame header error energy only has a minimum value, selecting the channel corresponding to the minimum frame header error energy as the receiving channel of the receiver; if the minimum frame header error energy has a plurality of minimum values, selecting a channel with the most front channel sequence from the channels corresponding to the minimum frame header error energy as a receiving channel of the receiver; after the transmission of the whole signal frame is finished, the effective gate signal of the channel is set to zero, FIFO is emptied, and a new round of diversity reception is started.
The invention has the beneficial effects that: the invention provides a signal similarity-based rapid diversity receiving method, which solves the problems of slow time for processing multipath signals, poor signal recovery quality, long signal-to-noise ratio calculation time and the like of the traditional diversity method, and provides a similarity calculation and judgment method of a plurality of spatial groups of data information frames on the basis of spatial diversity, so that an optimal channel can be rapidly selected.
Drawings
FIG. 1 is a diagram illustrating a usage scenario of a fast diversity method based on signal similarity according to the present invention;
FIG. 2 is a flow chart of a fast diversity method based on signal similarity according to the present invention;
FIG. 3 is a process for fast frame header error energy calculation according to the present invention;
FIG. 4 is a schematic diagram of frame header error energy determination according to the present invention;
FIG. 5 is a diagram of the multipath signal processing process of the present invention.
Detailed Description
Fig. 1 is a schematic diagram of a communication device layout according to the present invention, in which a ground base station distributes signals to a plurality of receiving antennas disposed on a train. The receiving channels corresponding to a plurality of receiving antennas on the train receive a plurality of copies bearing the same information, because the transmission characteristics of the plurality of channels are different, the fading of the plurality of copies of the signal is not the same, and the channels are mutually independent to finish the process of combining and receiving the signal.
The technical scheme of the invention is further explained by combining the attached drawings.
As shown in fig. 2, a fast diversity method based on signal similarity according to the present invention includes the following steps:
s1, receiving a plurality of channels R1～RnThe input signal of (2) demodulating the input signal of each channel respectively to obtain a frame signal;
s2, taking the frame header with length of N code elements in each channel as the object of rapid diversity processing, performing M times oversampling to all N code elements in the frame header to obtain the frame header sequence with length of NxM, sliding the frame header sequence obtained by oversampling into the shift register, calculating the frame header error energy S in the form of autocorrelation calculation with the frame header code element specified by the data frame protocol stored in the shift registerijAs shown in fig. 3;
in order to compare the correlation degree of two frame header symbols, the concept of correlation coefficient in digital signal processing is introduced. Such as a channel RiThe sequence of frame header code elements obtained at the moment j is [ y ]i(j)，yi(j+1)，...，yi(j+N*M-1)]The frame header code element sequence specified by the data frame protocol is [ x ]i(0)，xi(1)，...，xi(NxM-1)]If so, the frame header energy error S of two frame header code elements at the time jijComprises the following steps:
Figure BDA0003284041520000031
a can use the method of XOR operation to choose as 1, obtain the expression of frame header error energy:
Figure BDA0003284041520000041
sending the frame signal and the frame header error energy into FIFO for subsequent judgment;
s3, judging whether the frame header energy error meets the following two conditions:
a、Si(k-1)＞Sikand Si(k+1)＞SikIn which S isi(k-1)、Sik、Si(k+1)Respectively representing frame header energy errors of ith channel at k-1, k and k +1 moments;
b、Sik＜SRthat is, the frame header error energy of the ith path at the time k is smaller than the preset threshold value SR；
If the energy error of the channel i at the kth moment meets the two conditions, the channel i generates a channel effective gate signal with one frame length; taking the rising edge of the channel effective gate signal which firstly meets the two conditions as the starting time, delaying for a preset time later and taking the delayed time as a frame header receiving time window;
s4, for each channel, the frame header error energy value changes at any moment along with the process of sliding the frame header into the shift register, so the frame header error energy of each channel needs to be recalculated in the frame header receiving time window after the frame header receiving time window is determined; within the frame header receiving time window, the frame header is pairedPerforming M times oversampling on all N code elements, sliding the code element sequence obtained by oversampling into the shift register, and calculating frame head error energy S successively with the frame head code element specified by the data frame protocol stored in the shift registerij(ii) a Judging whether the frame header error energy of each channel in the frame header receiving time window has a minimum value and the minimum value is smaller than a preset threshold value, if so, comparing the frame header error energy with the frame header error energy stored in the FIFO and updating the frame header error energy in real time, storing the minimum frame header error energy and storing the frame signal as an effective signal, as shown in FIG. 4; otherwise, the frame signal is regarded as an invalid signal to be removed;
s5, after the frame header receiving time window is finished, comparing the minimum frame header error energy stored in all channels, if the minimum frame header error energy only has a minimum value, selecting the channel corresponding to the minimum frame header error energy as the receiving channel of the receiver; if the minimum frame header error energy has a plurality of minimum values, selecting a channel with the highest channel sequence from the channels corresponding to the minimum frame header error energy as a receiving channel of the receiver, as shown in fig. 5; after the transmission of the whole signal frame is finished, the effective gate signal of the channel is set to zero, FIFO is emptied, and a new round of diversity reception is started.
The traditional Selection Combination (SC) needs to calculate the signal-to-noise ratio of each branch signal, and the calculation processing time of each branch is the length T of the whole signal framescThe calculation processing time of the invention is actually the time window T, so the aim of quick diversity reception is achieved.
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.

Claims (1)

1. The fast diversity method based on the signal similarity is characterized by comprising the following steps:
s1, receiving input signals of a plurality of channels, and demodulating the input signals of each channel respectively to obtain frame signals;
s2, taking the frame header with length of N code elements in each channel as the object of rapid diversity processing, performing M times oversampling to all N code elements in the frame header to obtain the frame header sequence with length of NxM, sliding the frame header sequence obtained by oversampling into the shift register, calculating the frame header error energy S in the form of autocorrelation calculation with the frame header code element specified by the data frame protocol stored in the shift registerijSending the frame signal and the frame header error energy into FIFO for subsequent judgment;
s3, judging whether the frame header energy error meets the following two conditions:
a、Si(k-1)＞Sikand Si(k+1)>SikIn which S isi(k-1)、Sik、Si(k+1)Respectively representing frame header energy errors of ith channel at k-1, k and k +1 moments;
b、Sik＜SRthat is, the frame header error energy of the ith path at the time k is smaller than the preset threshold value SR；
If the energy error of the channel i at the kth moment meets the two conditions, the channel i generates a channel effective gate signal with one frame length; taking the rising edge of the channel effective gate signal which firstly meets the two conditions as the starting time, delaying for a preset time later and taking the delayed time as a frame header receiving time window;
s4, in the frame head receiving time window, performing M times oversampling to all N sections of code elements in the frame head, sliding the code element sequence obtained by oversampling into the shift register, and calculating the frame head error energy S successively with the frame head code element specified by the data frame protocol stored in the shift registerij(ii) a Judging whether frame header error energy of each channel in a frame header receiving time window has a minimum value and the minimum value is smaller than a preset threshold value, if so, comparing the frame header error energy with frame header error energy stored in FIFO (first in first out) and updating in real time, storing the minimum frame header error energy, and storing the frame signal as an effective signal; otherwise, the frame signal is regarded as an invalid signal to be removed;
s5, after the frame header receiving time window is finished, comparing the minimum frame header error energy stored in all channels, if the minimum frame header error energy only has a minimum value, selecting the channel corresponding to the minimum frame header error energy as the receiving channel of the receiver; if the minimum frame header error energy has a plurality of minimum values, selecting a channel with the most front channel sequence from the channels corresponding to the minimum frame header error energy as a receiving channel of the receiver; after the transmission of the whole signal frame is finished, the effective gate signal of the channel is set to zero, FIFO is emptied, and a new round of diversity reception is started.
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