Ultraviolet light communication power self-adaptive transmission method

Abstract

The invention discloses an ultraviolet light communication power self-adaptive transmission method, which comprises the following steps of: performing frame error rate simulation on a system modulation coding scheme to obtain signal intensity required by successful decoding under different background noise intensities; the transmitting end transmits a plurality of data frames to the receiving end, and records the transmitting power of the current link; the receiving end obtains signal intensity and noise intensity data of the current link through a channel estimation method, quantifies the signal intensity and noise intensity data and feeds back the quantified data to the transmitting end; the transmitting end judges the noise intensity, if the noise intensity is within the set noise intensity interval, the background noise at the moment is judged to be within the ith quantization interval, and the signal intensity required by successful decoding is obtained; and according to the current sending power and the signal strength required by successful decoding, obtaining the feedback transmitting power, and selecting the corresponding ultraviolet LED power to send the signal, thereby realizing adjustable transmission power. According to the method, different transmission powers can be selected under different transmission distances, and reliable data transmission under low power consumption is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless ultraviolet light communication, and in particular to a method for adaptive transmission of ultraviolet light communication power. Background Art

[0002] Wireless optical communication is a communication technology that uses light waves in free space to transmit information. Depending on the light waves used, it can be divided into visible light communication, infrared light communication and ultraviolet light communication. Ultraviolet light communication generally uses ultraviolet light with a wavelength of 200-280nm for communication. The ultraviolet light radiation in this band of sunlight will be absorbed by the ozone layer and is difficult to reach the ground. Therefore, the ultraviolet light in this band is also called "solar blind zone" ultraviolet light. Ultraviolet light communication has the characteristics of non-line-of-sight communication, high confidentiality and low background noise.

[0003] As one of the bottom-line communication methods, ultraviolet light communication can achieve a certain transmission rate in a strong electromagnetic interference environment, and has good safety characteristics due to its strong attenuation. Under different transmission powers and distances, the received signal and noise show different intensities and have different achievable transmission rates. The current common ultraviolet light communication system only uses a fixed transmission power to send data, which causes serious power loss when the transmission distance is short. Therefore, it is necessary to design an ultraviolet light communication power adaptive transmission scheme that can achieve different transmission powers at different transmission distances and meet the low power consumption requirements of ultraviolet light communication. Summary of the invention

[0004] The purpose of the present invention is to provide a method for adaptive transmission of ultraviolet light communication power, which can select different transmission powers at different transmission distances, achieve reliable data transmission with low power consumption, and solve the problem of excessive power consumption in existing fixed transmission power systems.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A method for adaptive transmission of ultraviolet light communication power, the method comprising:

[0007] Step 1: By performing frame error rate simulation on the system modulation and coding scheme, a system frame error rate curve under different background noise intensities is obtained, and the signal strength required for successful decoding under different background noise intensities is obtained;

[0008] Step 2: The transmitter sends several data frames to the receiver and records the transmission power P of the current link. t ′;

[0009] Step 3: The receiving end obtains the signal strength of the current link through the channel estimation method and noise intensity data, and obtain the signal strength of the current link and noise intensity After quantization, it is fed back to the transmitter;

[0010] Step 4: The transmitter receives the signal strength feedback and noise intensity After the noise intensity interval parameter is obtained, the signal strength required for successful decoding is obtained.

[0011] Step 5: The transmitter sends the current link power P recorded in step 2. t ′ and the signal strength required for successful decoding obtained in step 4, and the transmission power after feedback is calculated It is expressed as:

[0012] Step 6: Transmitter's transmission power after receiving feedback Finally, the corresponding UV LED power is selected to send the signal, realizing adjustable transmission power.

[0013] It can be seen from the technical solution provided by the present invention that the above method can select different transmission powers at different transmission distances, achieve reliable data transmission with low power consumption, and solve the problem of excessive power consumption in existing fixed transmission power systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0015] Figure 1 A schematic flow chart of a method for adaptive transmission of ultraviolet light communication power provided by an embodiment of the present invention;

[0016] Figure 2 This is a schematic diagram of the results of frame error rate simulation under different signal strengths and noise strengths of the example of the present invention;

[0017] Figure 3 A schematic diagram of the simulation results of the frame error rate of the example system of the present invention;

[0018] Figure 4 It is a schematic diagram of the average output power of the example system of the present invention at different transmission distances. DETAILED DESCRIPTION

[0019] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings 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, which does not constitute a limitation of the present invention. 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.

[0020] like Figure 1 The figure is a schematic flow chart of a method for adaptive transmission of ultraviolet light communication power provided by an embodiment of the present invention, the method comprising:

[0021] Step 1: By performing frame error rate simulation on the system modulation and coding scheme, a system frame error rate curve under different background noise intensities is obtained, and the signal strength required for successful decoding under different background noise intensities is obtained;

[0022] In this step, in the ultraviolet light communication using on-off keying, when the transmitter sends bits "0" and "1" respectively, the number of photons received by the receiver conforms to the Poisson distribution model shown below:

[0023]

[0024] Where N i =n|s i =1 means that when the transmitter sends a bit "1", the number of photons received by the receiver is n, N i =n|s i =0 means that when the transmitter sends a bit "0", the number of photons received by the receiver is n; s represents the average signal strength, that is, the average number of photons received by the receiver when sending a bit "1"; b Represents the background noise intensity, that is, the average number of photons received by the receiver when the bit "0" is sent;

[0025] It can be obtained that the signal received by the receiving end is related to two parameters, namely, noise strength and signal strength. When performing channel decoding, a belief propagation decoding algorithm based on log-likelihood ratio is used to decode LDPC. The input information of the decoding algorithm is expressed as follows:

[0026]

[0027] Among them, z i =N means that the number of photons in one code element received by the receiving end is N; and They respectively represent the signal strength and noise strength values ​​obtained after the receiving end performs channel estimation;

[0028] Therefore, the same set of channel coding will have different performances under different noise strengths and signal strengths. In order to explore the required receiving end signal strength for successful decoding of channel coding under different noise strengths, By simulating the frame error rate of the modulation and coding scheme of the system, the signal strength required for successful decoding under different background noise intensities is obtained, that is, the signal strength required when the channel coding can achieve a certain frame error rate under different noise intensities. Since the background noise in the atmosphere is a continuous value, in order to implement the system, the background noise is first quantized, and the quantization level of the noise intensity is defined as {λ b1 ,λ b2 ,...,λ bm}, each noise intensity quantization level λ bi The signal strength required for successful decoding corresponding to (1≤i≤m) is expressed as Th i .

[0029] Step 2: The transmitter sends several data frames to the receiver and records the transmission power P of the current link. t ′;

[0030] Step 3: The receiving end obtains the signal strength of the current link through the channel estimation method and noise intensity data, and obtain the signal strength of the current link and noise intensity After quantization, it is fed back to the transmitter;

[0031] In this step, the receiving end estimates the channel parameters by adding a set of pilot sequences before sending the data frame. It is assumed that the pilot sequence is represented by a pseudo-random sequence s = {s1, s2, ..., s L}, and the pseudo-random sequence s is known at the receiving end, define the set Z1 = {z i |s i =1} and Z0 = {z i |s i =0} are the number of photons received by the receiving end when 1 and 0 are sent in the pilot sequence, respectively. Then the receiving end obtains the signal strength of the current link through the channel estimation algorithm. and noise intensity Data, expressed as:

[0032]

[0033] After completing the channel estimation, the receiving end will obtain the signal strength of the current link and noise intensity After quantization, it is fed back to the transmitter. Specifically:

[0034] First, the noise intensity is divided into m levels. If the channel estimation is obtained In the interval (λ bi-1 ,λ bi ], it is considered that the current channel background noise intensity is within the i-th order of magnitude; the background noise is divided into 10 orders of magnitude, and the receiving end uses 4 bits of information to feedback the noise intensity interval; the system transmission rate is 1Mbps, and the receiving end sampling rate is 100MHz, so the maximum estimated value of the signal strength is 100, and 7 bits of information are used to feedback the signal strength;

[0035] The 11 bits of the feedback link are filled with 19 bits from 0 to 30 bits, and then the (150,30) LDPC code is encoded, the encoded information is spread four times, and then the spread data is repeatedly encoded, that is, when transmitting the information sequence, a rate several times lower than that of the forward link is used for transmission. The specific process is as follows:

[0036] For a set of (n, k) block codes C = [c1, c2, c3, ..., c k ,c k+1 ,…,c n ], the channel coding rate is defined as That is, the ratio of the information bit length to the codeword length in the code group. In the encoding process, k information bits are passed through the encoder to obtain (nk) supervision bits, which are added after the information bits to form the encoded codeword. The encoding process is expressed as:

[0037]

[0038] u=[u1,u2,u3,…,u k ]

[0039] C=u*G=[c1,c2,c3,…,c k ,c k+1 ,…,c n ]

[0040] Among them, G represents the generator matrix, which is obtained by the check matrix. The element g in the matrix G is ij ,1≤i≤k,1≤j≤

[0041] n, which is 0 or 1. The specific value is determined by the parameters and construction method of the check matrix; u represents the information bit before encoding. The element u in the matrix u is k represents the information to be encoded; C represents the encoded sequence, and the element c in the matrix C k , 1≤k≤n represents the encoded information, which takes 1 or 0;

[0042] From the above, we can see that the coded codeword is obtained by multiplying the information bit with the matrix G. Assuming that the sequence of a codeword after spreading by the spreading code is expressed as Take 0 or 1. Specifically, a bit 1 encoded by the transmitter is spread spectrum processed into a code block of length four. The encoded bit 0 is processed by spreading spectrum to form a code block According to the joint probability distribution, the sequence after spread spectrum conforms to the Poisson distribution model shown below:

[0043]

[0044] i=0,1,

[0045] j=1,2,3,4, where N j Indicates that the sender sends The number of photons received by the receiving end at s t represents the bit after channel coding; Indicates that the sender sends The channel-related parameters obtained after the receiving end performs channel estimation; i and j are just serial numbers here, and different To distinguish, i = 0 means that the code block sent is the code block after 0 spread; i = 1 means that the code block sent is the code block after 1 spread. Each code block after spread consists of four code elements, which are distinguished by j.

[0046] Get the log-likelihood ratio information L(P t ) is expressed as:

[0047]

[0048] Among them, the receiving end transmits power at the maximum state when feeding back information, that is, P t =P max , where P t and P max They respectively represent the current transmit power of the system and the maximum power that the system can transmit.

[0049] Step 4: The transmitter receives the signal strength feedback and noise intensity After the noise intensity interval parameter is obtained, the signal strength required for successful decoding is obtained.

[0050] Step 5: The transmitter sends the current link power P recorded in step 2. t ′ and the signal strength required for successful decoding obtained in step 4, and the transmission power after feedback is calculated It is expressed as:

[0051] Step 6: Transmitter's transmission power after receiving feedback Finally, the corresponding UV LED power is selected to send the signal, realizing adjustable transmission power.

[0052] In this step, if Then P t =P max ;

[0053] like Then P t =P min ;

[0054] In other cases,

[0055] Where P t Indicates the current transmission power of the system; P max Indicates the maximum power that the system can transmit; P min Indicates the minimum power that the system can transmit.

[0056] In a specific implementation, the transmitting end and the receiving end are both composed of ultraviolet LEDs and photomultiplier tubes, forming an integrated transmitting and receiving device.

[0057] The method described in the embodiment of the present invention is described in detail with a specific example. In this example, due to the good encoding and decoding performance of the 5G-NR-LDPC code, the 5G-NR-LDPC code with a code rate of (2176, 1280) is used. In order to decode the LDPC code, the minimum sum decoding algorithm based on LLR information is used at the decoding end, and the number of decoding iterations is 20. Considering the system transmission rate is R s =1Mbps, the noise intensity is:

[0058] λ b =[0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0]

[0059] First, the frame error rate of the LDPC code with a code rate of (2176,1280) is simulated under different signal strengths and noise strengths, such as Figure 2 The figure shows the result of the frame error rate simulation under different signal strengths and noise strengths in the example of the present invention. Figure 2 The data in the code is used to obtain the signal strength Th required for successful decoding under different noise intensities. i , as shown in Table 1 below:

[0060] Table 1

[0061] <![CDATA[λ b ]]> 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Th 4 4 4 5 5 5 5 5 6 6

[0062] After obtaining the signal strength threshold required for successful decoding under different noise intensities, the transmission power is adjusted according to the method described in the embodiment of the present invention, and the system is simulated and tested. Here we set the maximum power of the transmitter to 100mW, and the adjustable transmission power set is [10, 20, 30, 40, 50, 60, 70, 80, 90, 100]mW. Since the signal strength at different transmission powers and transmission distances in the direct line of sight link scenario can be calculated by the following formula:

[0063]

[0064] Where λ s represents the signal strength; η represents the quantum efficiency of the optical receiving antenna; g t represents the path loss between the transmitting and receiving ends; P out represents the transmitting power of the transmitter; h represents the Planck constant; v represents the frequency of the transmitted signal; R s Indicates the transmitted symbol rate.

[0065] The path loss at the transmitting and receiving ends can be calculated using the following formula:

[0066]

[0067] In the formula, k e =k s +k a represents the scattering coefficient k s and the absorption coefficient k a The sum of; r represents the distance between the transmitter and the receiver; r Rx represents the radius of the optical receiving antenna; φ t Indicates the divergence angle of the light beam at the transmitting end;

[0068] The parameter settings of the simulation test are shown in Table 2 below:

[0069] Table 2

[0070]

[0071] like Figure 3 FIG. 1 is a schematic diagram of the simulation results of the frame error rate of the example system of the present invention. Figure 4 The figure shows a schematic diagram of the average output power of the example system of the present invention at different transmission distances. The simulation results show that: according to the method described in the embodiment of the present invention, the system can automatically adjust the transmission power at different transmission distances, so that the system can reduce the transmission power of the system while meeting the communication requirements, thereby realizing the demand for low-power communication.

[0072] It is worth noting that the contents not described in detail in the embodiments of the present invention belong to the prior art known to professional and technical personnel in the field.

[0073] In summary, compared with the traditional ultraviolet light communication physical layer transmission technology, the method described in the embodiment of the present invention can effectively reduce the power consumption of the system and effectively improve the communication reliability of the system in different application scenarios.

[0074] In addition, a person skilled in the art can understand that all or part of the steps in the above-mentioned embodiment method can be implemented by instructing related hardware through a program, and the corresponding program can be stored in a computer-readable storage medium. The above-mentioned storage medium can be a read-only memory, a disk or an optical disk, etc.

[0075] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. A method for adaptive transmission of ultraviolet light communication power, characterized in that: The method comprises: Step 1: By performing frame error rate simulation on the system modulation and coding scheme, a system frame error rate curve under different background noise intensities is obtained, and the signal strength required for successful decoding under different background noise intensities is obtained; Step 2: The transmitter sends several data frames to the receiver and records the transmission power P of the current link. t ′; Step 3: The receiving end obtains the signal strength of the current link through the channel estimation method and noise intensity data, and obtain the signal strength of the current link and noise intensity After quantization, it is fed back to the transmitter; Step 4: The transmitter receives the signal strength feedback and noise intensity After the noise intensity interval parameter is obtained, the signal strength required for successful decoding is obtained. Step 5: The transmitter sends the current link power P recorded in step 2. t ′ and the signal strength required for successful decoding obtained in step 4, and the transmission power after feedback is calculated It is expressed as: Step 6: Transmitter's transmission power after receiving feedback Finally, the corresponding UV LED power is selected to send the signal, realizing adjustable transmission power.

2. The method for adaptive transmission of ultraviolet light communication power according to claim 1, characterized in that: In step 1, in ultraviolet light communication using on-off keying, when the transmitter sends bits "0" and "1" respectively, the number of photons received by the receiver conforms to the Poisson distribution model shown below: Where N i =n|s i =1 means that when the transmitter sends a bit "1", the number of photons received by the receiver is n; N i =n|s i =0 means that when the transmitter sends a bit "0", the number of photons received by the receiver is n; s represents the average signal strength, that is, the average number of photons received by the receiver when sending a bit "1"; b Represents the background noise intensity, that is, the average number of photons received by the receiver when sending a bit "0"; When performing channel decoding, a belief propagation decoding algorithm based on log-likelihood ratio is used to decode LDPC. The input information of the decoding algorithm is expressed as follows: Among them, z i =N means that the number of photons in one code element received by the receiving end is N; and They respectively represent the signal strength and noise strength values ​​obtained after the receiving end performs channel estimation; By simulating the frame error rate of the modulation and coding scheme of the system, the signal strength required for successful decoding under different background noise intensities is obtained, that is, the signal strength required when the channel coding can achieve a certain frame error rate under different noise intensities; first, the background noise is quantized, and the quantization level of the noise intensity is defined as {λ b1 ,λ b2 ,…,λ bm }, each noise intensity quantization level λ bi The signal strength required for successful decoding corresponding to (1≤i≤m) is expressed as Th i .

3. The method for adaptive power transmission of ultraviolet light communication according to claim 1, characterized in that: In step 3, The receiving end estimates the channel parameters by adding a set of pilot sequences before sending the data frame. Assume that the pilot sequence is represented by a pseudo-random sequence s = {s1, s2, ..., s L }, and the pseudo-random sequence s is known at the receiving end, define the set Z1 = {z i |s i =1} and Z0 = {z i |s i =0} are the number of photons received by the receiving end when 1 and 0 are sent in the pilot sequence, respectively. Then the receiving end obtains the signal strength of the current link through the channel estimation algorithm. and noise intensity The data is represented as: After completing the channel estimation, the receiving end will obtain the signal strength of the current link and noise intensity After quantization, it is fed back to the transmitter. Specifically: First, the noise intensity is divided into m levels. If the channel estimation is obtained In the interval (λ bi-1 ,λ bi ], the current channel background noise intensity is considered to be within the i-th order of magnitude; the background noise is divided into 10 orders of magnitude, and the receiving end uses 4 bits of information to feedback the noise intensity interval; The transmission rate of the system is 1Mbps, and the sampling rate of the receiving end is 100MHz, so the maximum estimated value of the signal strength is 100, and 7 bits of information are used to feedback the signal strength; The 11 bits of the feedback link are filled with 19 bits from 0 to 30 bits, and then the (150,30) LDPC code is encoded, the encoded information is spread four times, and then the spread data is repeatedly encoded, that is, when transmitting the information sequence, a rate several times lower than that of the forward link is used for transmission. The specific process is as follows: For a set of (n, k) block codes C = [c1, c2, c3, ..., c k ,c k+1 ,…,c n ], the channel coding rate is defined as That is, the ratio of the information bit length to the codeword length in the code group. In the encoding process, k information bits are passed through the encoder to obtain (nk) supervision bits, which are added after the information bits to form the encoded codeword. The encoding process is expressed as: u=[u1,u2,u3,…,u k ] C=u*G=[c1,c2,c3,…,c k ,c k+1 ,…,c n ] Among them, G represents the generator matrix, which is obtained by the check matrix. The element g in the matrix G is ij , 1≤i≤k,1≤j≤n, takes 0 or 1, and the specific value is determined by the parameters and construction method of the check matrix; u represents the information bit before encoding, and the element u in the matrix u k represents the information to be encoded; C represents the encoded sequence, and the element c in the matrix C k , 1≤k≤n represents the encoded information, which takes 1 or 0; The coded codeword is obtained by multiplying the information bit with the matrix G. Assume that the sequence of a codeword after spreading by the spreading code is expressed as Take 0 or 1. Specifically, a bit 1 encoded by the transmitter is spread spectrum processed into a code block of length four. The encoded bit 0 is processed by spreading spectrum to form a code block According to the joint probability distribution, the sequence after spread spectrum conforms to the Poisson distribution model shown below: Here N j Indicates that the sender sends The number of photons received by the receiving end at s t represents the bit after channel coding; Indicates that the sender sends The channel-related parameters obtained after the receiving end performs channel estimation; i and j represent sequence numbers, for different To distinguish, i = 0 means that the code block sent is the code block after 0 spread; i = 1 means that the code block sent is the code block after 1 spread. Each code block after spread consists of four code elements, which are distinguished by j. Get the log-likelihood ratio L(P t ) is expressed as: Among them, the receiving end transmits power at the maximum state when feeding back information, that is, P t =P max , where P t and P max They respectively represent the current transmit power of the system and the maximum power that the system can transmit.

4. The method for adaptive transmission of ultraviolet light communication power according to claim 1, characterized in that: In step 6, like Then P t =P max ; like Then P t =P min ; In other cases, Where P t Indicates the current transmission power of the system; P max Indicates the maximum power that the system can transmit; P min Indicates the minimum power that the system can transmit.

5. The method for adaptive power transmission of ultraviolet light communication according to claim 1, characterized in that: The transmitting end and the receiving end are both composed of ultraviolet LEDs and photomultiplier tubes, forming a transmitting and receiving integrated device.

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