MIMO (Multiple Input Multiple Output)-based improved ultraviolet light communication method and system

Abstract

The invention belongs to the technical field of photoelectric information communication methods, and relates to an improved ultraviolet light communication method based on an MIMO system, and the method specifically comprises the following steps: S1, constructing the MIMO system; s2, selecting an equal-gain diversity combining technology and coding; s3, selecting a Bussgang type blind equalization algorithm, and carrying out the optimization of the Bussgang type blind equalization algorithm; and S4, combining the MIMO system with a signal equalizer, verifying that the system can obviously suppress intersymbol interference, and ensuring the reliability of information transmission. In order to solve the problem of serious inter-symbol crosstalk in wireless ultraviolet light communication, the MIMO technology is adopted to preliminarily reduce the influence of the inter-symbol crosstalk; and subsequently, a signal equalizer is added at a receiving end to further suppress the intersymbol interference, and the result shows that the reliability of the ultraviolet light communication system is ensured to be improved by adopting the mode.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic information communication methods, and is an ultraviolet light communication method and system based on an improved MIMO system. Background Art

[0002] The wavelength range of ultraviolet light is 10nm-400nm. Since the atmosphere has strong absorption characteristics for ultraviolet light in the 200nm-280nm band, the radiation in this band of sunlight reaching the earth's surface is very small, so this band is called "solar-blind" ultraviolet light. Using "solar-blind" ultraviolet light for communication has the excellent characteristics of low background noise and all-weather operation; wireless ultraviolet light also has strong scattering characteristics, and non-line-of-sight (NLOS) communication can be achieved by using the scattering effect of atmospheric molecules, aerosol particles and other particles on wireless ultraviolet light; NLOS wireless ultraviolet light communication can make up for the deficiency of laser communication requiring precise alignment, and can be applied to complex terrain environments.

[0003] Based on the above advantages, it can not only meet the needs of military secret communications, but also be suitable for certain special occasions where safety accidents are prone to occur; but due to large path loss and serious inter-code interference, the system is affected by obstacles, noise, atmospheric absorption, reflection and refraction, which limits the transmission distance and rate of ultraviolet light communication. Therefore, there are problems of slow communication rate and short communication distance, which limits the application of wireless ultraviolet light communication technology; in order to improve the performance of wireless ultraviolet light communication, it is necessary to study signal processing technology suitable for wireless ultraviolet light channels and suppress the deterioration of communication performance caused by inter-code interference; therefore, the combined use of MIMO system and channel equalization technology is expected to further suppress inter-code crosstalk and reduce bit error rate, which has important research prospects and significance.

[0004] The Chinese patent publication number is "CN202011127448.1", and the name is "Noise Reduction Processing Method for Wireless Ultraviolet Communication". The invention establishes a diversity reception model for ultraviolet direct-line and non-direct-line communication; then, according to the established diversity reception model, the signal at the transmitting end is subjected to diversity reception noise reduction processing; the data signal after diversity reception and fusion is first subjected to hardware filtering, and then subjected to wavelet transform noise reduction processing; finally, the noise reduction processing for ultraviolet direct-line and non-direct-line communication is completed. Wavelet transform has a good inhibitory effect on the dark current noise generated by the photomultiplier tube and the thermal noise generated by the circuit components, and can further suppress the Gaussian noise and background noise caused by multipath transmission, retain the useful signal to the maximum extent, and improve the signal-to-noise ratio of the received signal at the receiving end; but only the noise reduction processing at the receiving end is considered, and it can be improved at the transmitting end on this basis to further reduce the bit error rate. Therefore, it is an important problem that the present invention needs to solve to design a method to gradually reduce inter-symbol interference, further reduce the bit error rate, and improve the reliability of the channel. Summary of the invention

[0005] 1. Technical issues to be solved

[0006] In view of the deficiencies of the prior art, the present invention provides a new ultraviolet light communication method and system with faster encoding, which solves the problem that the existing ultraviolet light communication can only reduce the bit error rate but cannot increase the transmission rate.

[0007] (II) Technical solution

[0008] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0009] An improved ultraviolet light communication method based on a MIMO system, the method specifically comprising the following steps:

[0010] S1: construct the MIMO system;

[0011] S2: Select equal gain diversity combining technique and coding;

[0012] S3: Select the Bussgang type blind equalization algorithm and optimize it;

[0013] S4: Combine the MIMO system with the signal equalizer to verify that the system can significantly suppress inter-symbol interference and ensure the reliability of information transmission.

[0014] Furthermore, MIMO in S1 refers to using multiple transmitting antennas and receiving antennas at the transmitting end and the receiving end respectively, so that the signal is transmitted and received through the multiple antennas at the transmitting end and the receiving end, thereby improving the communication quality; it can make full use of spatial resources, realize multiple transmission and multiple reception through multiple antennas, and can multiply the system channel capacity without increasing the spectrum resources and antenna transmission power, showing obvious advantages; the essence of MIMO is to provide the system with spatial diversity gain and spatial multiplexing gain; in the MIMO system, it is assumed that there are Nt transmitting antennas, Nr receiving antennas, and x i is the i-th transmission signal, r j represents the jth received signal, h ij is the channel fading coefficient between the i-th receiver and the j-th transmitter, and the channel fading matrix H is defined as follows:

[0015]

[0016] Furthermore, in S1, diversity technology is also required, and diversity technology includes three categories in total:

[0017] (1) Time diversity is to send the same information sequence in consecutive time slots. The bits in different time slots are almost independent, so the received signals are also independent fading signals.

[0018] (2) Frequency diversity is achieved by using different carrier frequencies. It is necessary to ensure that the transmission frequency interval is not less than the coherence bandwidth of the channel.

[0019] (3) Spatial diversity technology, also known as antenna diversity, is achieved by installing multiple antennas at the transmitter or receiver. The physical spacing ensures that different received signals are independent of each other. Usually, spatial diversity is divided into transmit diversity and receive diversity. Receive diversity refers to obtaining multiple independent signals at the receiver and merging the signals to improve system performance. Transmit diversity refers to transmitting the signal through multiple transmit antennas at the transmitter. The disadvantage of antenna diversity is that it requires multiple transceiver devices and has high hardware costs. The advantage is that when time and spectrum resources are limited, there is no need to use these resources to introduce redundant copies of the transmitted signal, and the information capacity of the system is not compressed, and the bandwidth utilization rate is not lost. Among them, spatial diversity technology is chosen.

[0020] Furthermore, in S2, the diversity merging is divided into the following two categories:

[0021] (1) Best choice merger;

[0022] (2) equal gain merging;

[0023] (3) Maximum ratio combining;

[0024] Among them, maximum ratio combining is the best in any case. Its output signal-to-noise ratio is equivalent to the sum of the output signal-to-noise ratios of each branch. There is no absolute advantage or disadvantage between equal gain combining and best choice combining. In general, the ratio of the mean value of each branch signal to the noise power is similar, and equal gain combining is better than best choice combining.

[0025] Furthermore, in S2, the following codes are applicable to the MIMO system:

[0026] (1) Alamouti coding is a diversity-based STC coding scheme that maps data symbols at two consecutive times to two transmitting antennas through transposition and replication operations. The receiving end combines the signals to recover the transmitted data.

[0027] (2) STBC coding is a coding scheme that maps data symbols to multiple antennas through matrix operations. STBC can provide the benefits of diversity and spatial multiplexing, and improve system capacity and performance by exploiting orthogonality and time relationships.

[0028] (3) STTC coding is a coding scheme that uses the relationship between time domain and space domain to improve the reliability and capacity of data transmission in the system. STTC maps data symbols to the time domain sequence on the transmitting antenna and uses the grid structure to realize the time domain and space domain correlation. Among them, the advantages of STBC are that it is simple and easy to implement, and can provide the advantages of diversity and spatial multiplexing. However, the performance of STBC may be relatively low, especially in channels with multipath interference. The advantage of STTC is that it can provide higher capacity and reliability. However, the implementation of STTC is more complicated, and usually requires maintaining a larger state space at the decoding end to realize the detection and decoding of time and space correlation. Alamouti coding is easier to implement than the above two, and the number of antennas required is also the least, which is more convenient for implementing MIMO systems.

[0029] Furthermore, in S3, a Bussgang-type blind equalization algorithm is selected. Currently, there are mainly three channel equalization calculation methods:

[0030] Bussgang-type blind equalization algorithm, high-order statistics algorithm and neural network method; among them, the main channel calculation method used is Bussgang-type blind equalization algorithm;

[0031] The blind equalization algorithm can equalize the channel characteristics by relying only on the information carried by the received sequence itself, and can make the output sequence of the equalizer as close as possible to the transmitted sequence, without relying on the equalization method of the external training sequence.

[0032] Furthermore, in S3, in order to improve the practical feasibility of the balancing algorithm, parallel processing is used to increase the calculation speed of the Bussgang algorithm, thereby reducing delay and improving real-time performance.

[0033] Furthermore, in S4, the MIMO technology and the signal equalization technology are combined, and the signal received through the MIMO system is compensated by the signal equalization technology, so as to verify the reliability of communication.

[0034] An improved ultraviolet light communication system based on a MIMO system comprises: an initial signal is sent from a signal source, the signal is encoded and OOK modulated by an encoder, and then the electrical signal is converted into an optical signal through an electro-optical converter and emitted through two ultraviolet LED light sources, and after passing through an atmospheric channel, the optical signal is converted through two photomultiplier tubes at the receiving end, and after signal equalization, the signal is restored by OOK demodulation and decoding in turn, and finally the signal emitted by the transmitting end is obtained; the improved ultraviolet light communication method based on a MIMO system is applied to any one of claims 1-8.

[0035] (III) Beneficial effects

[0036] Compared with the prior art, the present invention provides an improved ultraviolet light communication method and system based on the MIMO system, which has the following beneficial effects:

[0037] The present invention aims at solving the problems of high bit error rate and poor communication performance in wireless ultraviolet light communication, and adopts a MIMO system to reduce inter-code interference between communications so as to improve the reliability of information transmission.

[0038] The present invention aims at the serious problem of inter-code crosstalk in wireless ultraviolet light communication, adopts signal equalization technology to reduce the influence of inter-code crosstalk, thereby improving communication reliability; and optimizes the signal equalization algorithm to improve the rate. Finally, the optimized signal equalization technology is used in conjunction with the MIMO system. The results show that this method can ensure the reliability of the ultraviolet light communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a flow chart of the present invention;

[0040] Figure 2 It is a basic block diagram of the MIMO system of the present invention;

[0041] Figure 3 It is a schematic diagram of the channel capacity curve of the MIMO system of the present invention;

[0042] Figure 4 A schematic diagram of a bit error rate curve for different numbers of antennas in the MIMO system of the present invention;

[0043] Figure 5 This is a block diagram of the Alamouti space-time coding principle of the present invention;

[0044] Figure 6 It is the structural block diagram of the CMA algorithm of the present invention;

[0045] Figure 7 This is a block diagram of the wireless ultraviolet light communication system of the present invention;

[0046] Figure 8 This is a schematic diagram of a bit error rate curve of the present invention without adding a signal equalizer;

[0047] Fig. 9 A schematic diagram of a bit error rate curve after the MIMO system and the signal equalization technology of the present invention are combined;

[0048] Fig.10 It is a structural diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] Example

[0051] like Figure 1 As shown, an improved ultraviolet light communication method based on a MIMO system comprises the following steps:

[0052] S1, construct a MIMO system, such as Figure 2 As shown in the figure, MIMO technology refers to the use of multiple transmitting antennas and receiving antennas at the transmitting end and the receiving end respectively, so that the signal is transmitted and received through multiple antennas at the transmitting end and the receiving end, thereby improving the communication quality. It can make full use of spatial resources and achieve multiple transmission and multiple reception through multiple antennas. Without increasing the spectrum resources and antenna transmission power, it can multiply the system channel capacity, showing obvious advantages. The essence of MIMO technology is to provide spatial diversity gain and spatial multiplexing gain for the system; in the MIMO system, it is assumed that there are Nt transmitting antennas and Nr receiving antennas. i is the i-th transmission signal, r j represents the jth received signal, h ij is the channel fading coefficient between the i-th receiver and the j-th transmitter. The channel fading matrix H is defined as follows:

[0053]

[0054] Assume that after coding, the information sequence to be sent on Nt transmitting antennas is represented. Without adding noise, the received signal of the MIMO system is expressed as:

[0055]

[0056] Assuming that the noise is white noise that obeys Gaussian distribution, we have:

[0057]

[0058] Therefore, the signal actually received by the MIMO system is expressed as:

[0059]

[0060] The simplified matrix is:

[0061]

[0062] in represents the received signal, H represents the channel fading matrix, For the signal sent, is the noise of the channel.

[0063] For the scenario where the transmitting and receiving antennas are the same, Nt = Nr = n, and under independent Rayleigh fading, the channel capacity is:

[0064]

[0065] As n increases, the above formula can be approximated as:

[0066]

[0067] From the above formula, we can see that when the transmission power is constant, the MIMO channel capacity is linearly related to the number of transmitting antennas and receiving antennas; Figure 3 shown.

[0068] S1, such as Figure 4 As shown, in the MIMO system, the bit error rate differences between dual-transmit and dual-receive, triple-transmit and three-receive, and quad-transmit and four-receive, considering the resources occupied by the number of antennas, the present invention selects a more convenient dual-transmit and dual-receive system.

[0069] S2, Diversity Combining Technology Commonly used combining technologies are best choice combining, equal gain combining, and maximum ratio combining; (1) Best choice combining: compare the signal-to-noise ratio of each branch and select the one with the largest signal. That is:

[0070]

[0071] The optimal combined signal-to-noise ratio can be obtained as:

[0072]

[0073] (2) Equal gain combining: The received signal is obtained by adding the signals from each channel in phase, that is:

[0074] α j =1j=1,2,3,…,N (10)

[0075] The signal-to-noise ratio of equal gain combining can be obtained as:

[0076]

[0077] (3) Maximum ratio combining: When the noise of each branch is not equal, the ratio of the signal mean value of each branch to the noise power is selected as the weighting coefficient, and the signals of each branch are added together as the received signal:

[0078]

[0079] The signal-to-noise ratio of the maximum ratio combining can be obtained as:

[0080]

[0081] Among the three diversity combining technologies, by comparing the signal-to-noise ratio, it can be seen that maximum ratio combining is the best under any circumstances, and there is no absolute advantage or disadvantage between equal gain combining and best choice combining. Generally, the ratio of the mean signal of each branch to the noise power is similar, and equal gain combining is better than best choice combining.

[0082] S2, space-time coding can be better applied to MIMO systems. If the channel information CSI can be known at the receiving end, by reasonably designing the precoding at the transmitting end, the maximum likelihood decoding method can be used when decoding at the receiving end to achieve linear decoding complexity, then this design of precoding will simplify the construction of the entire MIMO communication system; and orthogonal space-time coding is an effective way. Alamouti space-time coding is a precoding orthogonal design method with 2 transmitting antennas, such as Figure 5 Shown is a functional block diagram of the Alamouti system of the present invention.

[0083] If M-ary modulation is adopted, the Alamouti coding process is to first modulate each group of m information bits, where M = log2M; then, when performing the coding process, two consecutively transmitted symbols are transformed into a matrix according to the following formula and mapped to the transmitting antenna:

[0084]

[0085] After the encoding is completed, it is transmitted through two transmitting antennas, and each modulated two symbols are transmitted in two consecutive time slots. In time slot 1, signals X1 and X2 are transmitted from antennas 1 and 2 respectively. In time slot 2, signal -X2 * and X1 * Then transmit from antenna 1 and antenna 2 respectively. This coding method also adds spatial and temporal coding. X1 and X2 are used to represent the transmission sequences on antenna 1 and 2:

[0086] x 1 =[x1,-x2 * ]x 2 =[x2,x1 * ] (15)

[0087] The transmitted sequences of Alamouti coding are orthogonal to each other, that is, the inner product of two sequences is 0. Therefore, the coding matrix has the following characteristics:

[0088]

[0089] In the traditional Alamouti code, there are negative and complex signals, but the complex conjugate and negative numbers cannot be represented by ON and OFF. In the optical communication system, real signals are processed, so we use an improved Alamouti code suitable for ultraviolet light communication.

[0090]

[0091] In the formula Represented as the complement of the symbol x2, the complement is defined as A represents the amplitude of the pulse, which is a constant related to the intensity of the emitted light. The complement code means that the ON and OFF states of the emitted light signal are reversed. For OOK modulation, it is assumed that the signal can be expressed in the following form:

[0092] s1=0,0≤t≤T s2=A,0≤t≤T (18)

[0093] For dual-transmit and dual-receive space-time block codes, the receiving end signal is expressed as;

[0094]

[0095] h ij (i,j=1,2) represents the channel fading coefficient from the transmitting light source j to the receiving detector i, is the signal received by the receiving end detector i in the jth signal time slot, and the final signal is reconstructed as:

[0096]

[0097] S3, CMA algorithm stands for Constant Modulus Algorithm, which is a classic algorithm in this field. It can converge even in the presence of phase error. CMA algorithm is the most stable and best equalization algorithm among Bussgang blind equalization algorithms. This algorithm is not only simple in calculation process but also can effectively reduce the bit error rate. Its characteristics are to construct the cost number by using the high-order statistical characteristics of implicit combination, and to find the extreme point of the cost function by adjusting the weight vector of the equalizer. Its idea is similar to that of LMS algorithm. Its structure is as follows: Figure 6 Shown:

[0098] Its structure includes:

[0099] (1) a(n) is an independent and identically distributed transmission signal with zero mean;

[0100] (2) c(n) is the channel impulse response;

[0101] (3) w(n) is additive Gaussian white noise;

[0102] (4) y(n) is the equalizer received signal;

[0103] (5)f(n) is the equalizer weight vector;

[0104] (6) z(n) is the equalizer output signal;

[0105] (7) Output signal for the subsequent decision device to decide z(n);

[0106] The CMA error function is:

[0107]

[0108] Its cost function is:

[0109] J=E[e 2 (n)]=E{[|z(n)| 2 -R 2 ] 2} (twenty two)

[0110] Therefore, the weight vector iteration formula is:

[0111] f(n+1)=f(n)-μ(|z(n)| 2 -R 2 )y * (n)z(n)=f(n)-μe 2 (n)z(n)y * (n) (23)

[0112] At the same time, in order to make the final result of the signal equalization technology more accurate, the present invention optimizes the signal equalization algorithm in parallel, and combines the CMA algorithm with the LMS (least equalization algorithm) equalization algorithm. This hybrid algorithm strategy can take advantage of the advantages of each algorithm at different communication stages, use the CMA algorithm to quickly approach the optimal solution at the initial stage of signal reception, and then switch to the LMS algorithm to improve the final equalization accuracy.

[0113] S4, combines signal equalization technology with MIMO system, Figure 7 This is a schematic diagram of a wireless ultraviolet communication system. Figure 8 This is a bit error rate curve without using signal equalization technology. It can be seen that the bit error rate reduction is not very obvious.

[0114] like Fig. 9 As shown, after the signal equalization technology is combined with the MIMO system, the bit error rate is further reduced, ensuring the reliability of the entire communication system.

[0115] Embodiments of the present invention Fig.10As shown, an improved ultraviolet light communication system based on a MIMO system is provided, including: an initial signal is sent from a signal source, the signal is encoded and OOK modulated by an encoder, and then the electrical signal is converted into an optical signal through an electro-optical converter and emitted through two ultraviolet LED light sources, and after passing through the atmospheric channel, the optical-electrical conversion is performed at the receiving end after passing through two photomultiplier tubes, and after signal equalization, the signal is restored by OOK demodulation and decoding in turn, and finally the signal sent by the transmitting end is obtained.

[0116] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An improved ultraviolet light communication method based on a MIMO system, characterized in that: The method specifically comprises the following steps: S1: construct the MIMO system; S2: Select equal gain diversity combining technique and coding; S3: Select the Bussgang type blind equalization algorithm and optimize it; S4: Combine the MIMO system with the signal equalizer to verify that the system can significantly suppress inter-symbol interference and ensure the reliability of information transmission.

2. The improved ultraviolet light communication method based on MIMO system according to claim 1, characterized in that: MIMO in S1 refers to using multiple transmitting antennas and receiving antennas at the transmitting end and the receiving end respectively, so that the signal is transmitted and received through the multiple antennas at the transmitting end and the receiving end, thereby improving the communication quality; It can make full use of spatial resources and achieve multiple transmission and multiple reception through multiple antennas. Without increasing spectrum resources and antenna transmission power, it can multiply the system channel capacity, showing obvious advantages. The essence of MIMO is to provide the system with spatial diversity gain and spatial multiplexing gain. In the MIMO system, it is assumed that there are Nt transmitting antennas, Nr receiving antennas, and x i is the i-th transmission signal, r j represents the jth received signal, h ij is the channel fading coefficient between the i-th receiver and the j-th transmitter, and the channel fading matrix H is defined as follows:

3. The improved ultraviolet light communication method based on MIMO system according to claim 2, characterized in that: In S1, diversity technology is also needed, and there are three types of diversity technology: (1) Time diversity is to send the same information sequence in consecutive time slots. The bits in different time slots are almost independent, so the received signals are also independent fading signals. (2) Frequency diversity is achieved by using different carrier frequencies. It is necessary to ensure that the transmission frequency interval is not less than the coherence bandwidth of the channel. (3) Spatial diversity technology, also known as antenna diversity, is achieved by installing multiple antennas at the transmitter or receiver. The physical spacing ensures that different received signals are independent of each other. Usually, spatial diversity is divided into transmit diversity and receive diversity. Receive diversity refers to obtaining multiple independent signals at the receiver and merging the signals to improve system performance. Transmit diversity refers to transmitting the signal through multiple transmit antennas at the transmitter. The disadvantage of antenna diversity is that it requires multiple transceiver devices and has high hardware costs. The advantage is that when time and spectrum resources are limited, there is no need to use these resources to introduce redundant copies of the transmitted signal, and the information capacity of the system is not compressed, and the bandwidth utilization rate is not lost. Among them, spatial diversity technology is chosen.

4. The improved ultraviolet light communication method based on MIMO system according to claim 1, characterized in that: In S2, diversity merging is divided into the following two categories: (1) Best choice merger; (2) equal gain merging; (3) Maximum ratio combining; Among them, maximum ratio combining is the best under any circumstances, and its output signal-to-noise ratio is equivalent to the sum of the output signal-to-noise ratios of each branch. There is no absolute advantage or disadvantage between equal-gain combining and best choice combining. Generally, the ratio of the mean signal of each branch to the noise power is similar, and equal-gain combining is better than best choice combining.

5. The improved ultraviolet light communication method based on MIMO system according to claim 4, characterized in that: In S2, the following codes are applicable to the MIMO system: (1) Alamouti coding is a diversity-based STC coding scheme that maps data symbols at two consecutive times to two transmitting antennas through transposition and replication operations. The receiving end combines the signals to recover the transmitted data. (2) STBC coding is a coding scheme that maps data symbols to multiple antennas through matrix operations. STBC can provide the benefits of diversity and spatial multiplexing, and improve system capacity and performance by exploiting orthogonality and time relationships. (3) STTC coding is a coding scheme that uses the relationship between time domain and space domain to improve the reliability and capacity of data transmission in the system. STTC maps data symbols to the time domain sequence on the transmitting antenna and uses the grid structure to realize the time domain and space domain correlation. Among them, the advantages of STBC are that it is simple and easy to implement, and can provide the advantages of diversity and spatial multiplexing. However, the performance of STBC may be relatively low, especially in channels with multipath interference. The advantage of STTC is that it can provide higher capacity and reliability. However, the implementation of STTC is more complicated, and usually requires maintaining a larger state space at the decoding end to realize the detection and decoding of time and space correlation. Alamouti coding is easier to implement than the above two, and the number of antennas required is also the least, which is more convenient for implementing MIMO systems.

6. The improved ultraviolet light communication method based on MIMO system according to claim 1, characterized in that: In S3, the Bussgang blind equalization algorithm is selected. Currently, there are mainly three channel equalization calculation methods: Bussgang-type blind equalization algorithm, high-order statistics algorithm and neural network method; among them, the main channel calculation method used is Bussgang-type blind equalization algorithm; The blind equalization algorithm can equalize the channel characteristics by relying only on the information carried by the received sequence itself, and can make the output sequence of the equalizer as close as possible to the transmitted sequence, without relying on the equalization method of the external training sequence.

7. The improved ultraviolet light communication method based on MIMO system according to claim 6, characterized in that: In S3, in order to improve the practical feasibility of the balancing algorithm, parallel processing is used to increase the calculation speed of the Bussgang algorithm, thereby reducing delay and improving real-time performance.

8. The improved ultraviolet light communication method based on MIMO system according to claim 1, characterized in that: In S4, the MIMO technology and the signal equalization technology are combined, and the signal received by the MIMO system is compensated by the signal equalization technology, so as to verify the reliability of communication.

9. An improved ultraviolet light communication system based on a MIMO system, characterized in that: include: An initial signal is sent from the signal source, which is encoded and OOK modulated by the encoder, and then converted into an optical signal by the electro-optical converter and emitted by two ultraviolet LED light sources. After passing through the atmospheric channel, it is photoelectrically converted by two photomultiplier tubes at the receiving end. After signal equalization, the signal is restored by OOK demodulation and decoding in turn, and finally the signal sent by the transmitter is obtained; An improved ultraviolet light communication method based on a MIMO system as described in any one of claims 1-8.

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