Time correlation photon cumulative counting communication method

Abstract

The invention relates to a communication method, in particular to a time correlation photon accumulative counting communication method. According to the invention, a time correlation accumulation photon counting strategy is adopted, and the signal-to-noise ratio of the photon counting receiver can be improved through a time correlation photon accumulation method under certain background noise, so that the background noise resistance of the receiver is improved, and the communication sensitivity of the system is improved. Besides, a signal synchronization strategy of high-frequency sampling and sliding correlation is adopted, so that the problems that the initial position of the signal is not easy to position and the signal period is not easy to extract due to the randomness of signal output of the photon counting detector are effectively solved with relatively low system complexity; the synchronization and demodulation of photon counting detection output signals can be realized under the condition that the number of photons is small.

Description

Technical Field

[0001] The present invention relates to a communication method, and particularly to a time-related photon cumulative counting communication method. Background Art

[0002] Optical communication has become an important communication technology in the field of wireless communication due to its advantages such as high communication rate, low latency, good confidentiality, and low system power consumption.

[0003] In an optical communication channel, due to the influence of optical effects such as absorption, scattering, and turbulence, the distance of optical communication is limited. Therefore, the research on extending the distance of wireless optical communication faces great challenges. The photon counting reception technology based on single-photon detectors can be used to extend the distance of wireless optical communication.

[0004] However, on the one hand, since the output electrical pulses of the photon counting detector exhibit discrete Poisson distribution characteristics in time, this directly leads to the inability to directly apply the time slot synchronization technology based on digital phase-locked loops and interpolation algorithms to photon detectors. On the other hand, since the optical carrier of the optical communication system is in the visible light band, and the photon counting receiver has a high optical reception sensitivity, both will result in a decrease in the signal-to-noise ratio of the photon receiver and an increase in the bit error rate. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems that it is difficult to extract the clock and synchronize the time slots for the discrete output signals of the existing photon counting communication system, and the communication performance deterioration caused by background light fluctuations, and to provide a time-related photon cumulative counting communication method.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A time-related photon cumulative counting communication method, characterized in that it includes the following steps:

[0008] S1. Design the transmitted data frame sequence;

[0009] S2. Design the structure of the data frame, including the frame header sequence and the data sequence;

[0010] S3. Perform high-frequency sampling on the sequence output by the photon counting detector to obtain a sampling sequence;

[0011] S4. Perform sampling processing on the known frame header sequence to obtain a received frame header sequence;

[0012] S5. Perform binarization processing on the sampling sequence obtained in step S3 to obtain a binarized sampling sequence;

[0013] S6. Perform a correlation operation on the received frame header sequence and the binarized sampling sequence obtained in steps S4 and S5 to obtain the periodic clock of the received frame header sequence, and locate the initial position of the first data frame in the data frame sequence to obtain the first-frame sampling sequence of the data frame sequence;

[0014] S7. Perform a correlation operation on the first-frame sampling sequence obtained in step S6 and the data frames after the first frame in the binarized sampling sequence to locate the initial position of the second data frame in the data frame sequence and obtain the second-frame sampling sequence of the data frame sequence;

[0015] S8. Perform an accumulation operation on the sampling sequences obtained in steps S6 and S7 to obtain the data frame sampling sequence with one accumulation;

[0016] S9. Perform a correlation operation on the data frame sampling sequence obtained in step S8 and the data frames after the second frame in the binarized sampling sequence to locate the initial position of the third data frame in the data frame sequence and obtain the third-frame sampling sequence of the data frame sequence;

[0017] S10. Perform an accumulation operation on the sampling sequences obtained in steps S8 and S9 to obtain the data frame sampling sequence with two accumulations;

[0018] S11. By analogy, obtain the data frame sampling sequence with N - 1 accumulations in the same manner as steps S9 and S10; N is the preset number of accumulations;

[0019] S12. Statistically calculate the average value of the accumulated count values of the sampling points in the 1-bit time slot and 0-bit time slot of the frame header sequence in the data frame sampling sequence obtained in step S11, obtain the decision threshold based on this average value, and successively compare the accumulated count value of the sampling points in a single bit time slot within a single symbol in the data sequence with the decision threshold. If the count value is less than the decision threshold, it is determined as the 1-bit time slot; otherwise, it is determined as the 0-bit time slot, thereby restoring the data frame sequence and completing the communication.

[0020] Further, in step S1, the transmitted data frame sequence includes N data frames, and this data frame sequence x i is expressed as: x i =[x 1 , x 2 , x 3 , …, x N , and x 1 =x 2 =…=x N ;

[0021] The value of N satisfies the following relationship:

[0022]

[0023] Where: Rb where \(R\) is the communication rate; \(B\) is the modulation bandwidth; and \(R_c\) is the channel coding rate.

[0024] Further, in step S3, the sequence output by the photon counting detector is sampled by an analog-to-digital converter with a set sampling frequency \(f\) sample satisfying the following condition:

[0025]

[0026] where \(T\) pluse is the width of the electrical pulse output by the photon counting detector.

[0027] Further, step S4 specifically is to perform \(\gamma\)-times sampling processing on the known frame header sequence to obtain a received frame header sequence.

[0028] Further, in step S5, the threshold of the binarization processing is set according to the amplitude of the discrete electrical pulse output by the photon counting detector.

[0029] Further, in step S5, the threshold of the binarization processing satisfies the following formula:

[0030]

[0031] where \(I\) pluse is the amplitude of the discrete electrical pulse output by the photon counting detector; mean is the operator for calculating the average value.

[0032] Further, in step S12, the average values of the accumulated counts of the sampling points in the 1-bit time slot and the 0-bit time slot of the frame header sequence are defined as \(k_1\) 1 and \(k_0\) 0 , respectively. Then, the decision threshold \(k\) th is calculated using the following formula:

[0033]

[0034] The beneficial effects of the present invention are:

[0035] 1. The present invention not only performs time slot synchronization with fewer photons, and can greatly reduce the complexity of the photon counting receiver compared with the traditional time slot synchronization method, but also can improve the robustness of the system to channel background noise.

[0036] 2. The present invention adopts a strategy of time-correlated cumulative photon counting, which can improve the signal-to-noise ratio of a photon counting receiver through the method of time-correlated photon accumulation under a certain background noise, thereby enhancing the anti-background noise ability of the receiver and improving the communication sensitivity of the system. In addition, a signal synchronization strategy of high-frequency sampling plus sliding correlation is adopted, which effectively solves the problems that it is difficult to locate the initial position of the signal and extract the signal period due to the randomness of the signal output of the photon counting detector with a relatively low system complexity, and can realize the synchronization and demodulation of the photon counting detection output signal when the number of photons is small. Description of the Drawings

[0037] Figure 1 is a schematic diagram of the data frame structure in an embodiment of the present invention;

[0038] Figure 2 is a flowchart of an embodiment of the present invention. Detailed Embodiments

[0039] To make the objectives, advantages, and features of the present invention clearer, the following further elaborates on a time-correlated photon accumulation counting communication method proposed by the present invention in conjunction with the drawings and specific embodiments. According to the following detailed embodiments, the advantages and features of the present invention will be clearer.

[0040] Refer to Figure 2 , a time-correlated photon accumulation counting communication method in this embodiment specifically includes the following steps:

[0041] Step S1: Set the communication rate R b , the sampling frequency f sample , and the accumulation times N.

[0042] Step S2: Design of the transmitted data frame sequence: The transmitted data frame sequence includes N data frames, expressed as: x i = [x 1 , x 2 , x 3 , …, x N , and the N data frames are the same, that is: x 1 = x 2 = … = x N . Among them, the larger the value of N, the more beneficial it is to increase the anti-background noise performance of the photon counting communication system; the value of N is related to the data rate R b , the modulation bandwidth B, and the channel coding rate . The specific relationship is In this embodiment, the preferred appropriate value of N is 3.

[0043] Step S3: Data frame design: Refer to Figure 1, the data frame structure mainly consists of two parts: a frame header sequence and a data sequence. Among them, the frame header sequence is specially designed, the data frame sequence is a random data sequence, and there is no correlation between the frame header sequence and the data frame sequence. The data frame structure is Among them, represents the frame header sequence, which consists of m symbols and is expressed as represents the data sequence, which consists of n - m symbols and is expressed as

[0044] Preferably, the length m of the frame header sequence is appropriately selected as 96 / M, and the binary frame header sequence is [0,0,1,1,0,1,1,0,0,1,1,1,1,0,0,0,0,0,1,1,1,0,0,1,0,0,1,0,0,1,1,1,0,1,0,0,1,1,1,0,1,1,1,0,0,1,0,0,0,0,0,1,1,0,1,1,1,0,1,1,0,0,0,1,1,1,0,1,1,0,0,0,0,1,1,0,1,1,0,0,0,0,1,0,1,1,0,1,1,0,0,1,1,1,0,0]; the appropriate value of the length n - m of the data frame column sequence is 11200 / M, where M represents the number of bits or time slots included in each data symbol.

[0045] Step S4, sample the received signal: By using an analog-to-digital converter (ADC) with a sampling frequency of f sample to perform high-frequency sampling on the output of the photon counting detector , the obtained sampling sequence is

[0046] is the l-th sampling point in the k-th bit time slot of the j-th symbol in the i-th frame sequence, and the number of sampling points in the signal bit time slot, that is, the maximum value of l is

[0047] The sampling frequency of the ADC is related to the time width T pluse of the electrical pulse output by the photon counting detector, and the appropriate value of f sample is

[0048] Step S5, generate the local received frame header sequence at the receiving end: Perform γ-fold sampling processing on the known frame header sequence to obtain the local received frame header sequence at the receiving end as where M represents the number of bits or time slots included in each data symbol, represents the y-th sampling value in the M-th bit (time slot) of the m-th symbol.

[0049] Among them

[0050] Step S6: Perform binarization processing on the frame header sequence obtained in step S4 to obtain a binarized sampling sequence as

[0051] The setting of the binarized data processing threshold should be specifically set according to the mean value of the discrete electrical pulse amplitude I pluse output by the photon counting detector.

[0052] Preferably, the binarized data processing threshold

[0053] where mean is the operator for calculating the average value.

[0054] Step S7: Receiver signal synchronization algorithm: Use the local received frame header reception sequence obtained in steps S5 and S6 and the binarized sampling sequence to perform a correlation operation to obtain the periodic clock of the received sequence and locate the initial position of the signal frame sequence. The initial position of the sampled signal frame sequence is In the formula to obtain the first-frame sampling sequence of the data frame sequence as

[0055] S represents N (data frame length) × m (symbol length of a single frame) × k (bit time slot length) × l (sampling point length);

[0056] S · represents m (symbol length of a single frame) × k (bit time slot length) × l (sampling point length);

[0057] represents the current position of the calculated correlation value of the data frame sampling sequence;

[0058] ζ represents the position of the calculated data frame sampling sequence.

[0059] Step S8: Perform a correlation operation on the first-frame sampling sequence obtained in step S7 and the subsequent detected frame sequence to locate the initial position of the second data frame in the data frame sequence as, to obtain the second-frame sampling sequence of the data frame sequence as

[0060] Step S9: Perform an accumulation operation on the data frames obtained in steps S7 and S8 to obtain a data frame sampling sequence with 1 accumulation as

[0061] Step S10: The sampling frame sequence obtained in step S9 Perform a correlation operation with the subsequent detected frame sequence to locate the initial position of the 3rd data frame in the data frame sequence to obtain the 3rd frame sampling sequence of the data frame sequence

[0062] In operations arg{x} in S8 and S10, it means to find the position of the x value in the matrix, and max() means to find the maximum value of the matrix.

[0063] Step S11: Perform an accumulation operation on the sampling sequences obtained in steps S9 and S10 to obtain a data frame sampling sequence with 2 accumulations as

[0064] In other embodiments of the present invention, if the value of N is other numbers greater than 3, then according to the formula calculate to obtain a data frame sampling sequence with N - 1 accumulations.

[0065] Step S12: Accumulate and count the sampling points within the bit time slots in the data frame sampling sequence to obtain Statistically calculate the average values of the accumulated counts of the sampling points within the bit time slots of "1" bits and "0" bits in the first m known frame header symbols of the data frame sequence, which are k 1 and k 0 , respectively, to obtain the decision threshold for the accumulated count value of the sampling points within the data bit time slots Successively compare the accumulated count value of the sampling points within a single bit time slot within a single symbol in the data frame sequence with the threshold k th If the count value is less than k th , then it is determined as a 1 bit, otherwise, it is determined as a 0 bit, thereby restoring the data frame sequence and completing the communication.

[0066] According to the above specific solution, the present invention is based on a time-related cumulative photon counting communication method. Compared with the traditional photon counting time slot synchronization method, this method locates the initial position of each data through the method of frame header sliding correlation, reducing the complexity of signal time slot synchronization; by designing a data frame structure composed of N identical frame sequences at the transmitting end and improving the signal-to-noise ratio of the photon receiver through the method of correlation accumulation at the receiving end, the anti-background noise performance of the photon counting receiver is improved, and the receiver sensitivity is enhanced. The present invention is particularly suitable for photon communication in an extremely weak light environment and has reliability against background light noise.

Claims

1. A time-correlated photon cumulative counting communication method, characterized in that: The following steps are involved: S1. Design the transmitted data frame sequence; S2. Design the structure of the data frame, including the frame header sequence and the data sequence; S3, performing high frequency sampling on the sequence output by the photon counting detector to obtain a sampling sequence; S4, sampling the known frame header sequence to obtain a received frame header sequence; S5, binarizing the sampling sequence obtained in step S3 to obtain a binarized sampling sequence; S6, performing correlation operation on the received frame header sequence and the binary sampling sequence obtained in step S4 and step S5 to obtain a periodic clock of the received frame header sequence, and locating the initial position of the first data frame in the data frame sequence to obtain the first frame sampling sequence of the data frame sequence; S7, performing a correlation operation on the first frame sampling sequence obtained in step S6 and the data frame after the first frame in the binary sampling sequence, locating the initial position of the second data frame in the data frame sequence, and obtaining the second frame sampling sequence of the data frame sequence; S8, performing a cumulative operation on the sampling sequences obtained in step S6 and step S7 to obtain a data frame sampling sequence accumulated once; S9, performing a correlation operation on the data frame sampling sequence obtained in step S8 and the data frames after the first frame in the binarized sampling sequence, locating the initial position of the third data frame in the data frame sequence, and obtaining the third frame sampling sequence of the data frame sequence; S10, performing a cumulative operation on the sampling sequences obtained in step S8 and step S9 to obtain a data frame sampling sequence accumulated twice; S11, and so on, in the same manner as step S9 and step S10, a data frame sampling sequence accumulated N-1 times is obtained; N is a preset number of accumulation times; S12, calculating the average value of the accumulated count values ​​of the sampling points in the 1-bit time slot and the 0-bit time slot of the frame header sequence in the data frame sampling sequence obtained in step S11, obtaining a decision threshold based on the average value, and comparing the accumulated count values ​​of the sampling points in a single bit time slot in a single symbol in the data sequence with the decision threshold in turn, if the count value is less than the decision threshold, it is judged as a 1-bit time slot, otherwise, it is judged as a 0-bit time slot, thereby restoring the data frame sequence and completing the communication.

2. A time-correlated photon cumulative counting communication method according to claim 1, characterized in that: In step S1, the transmitted data frame sequence includes N data frames. i Expressed as: x i =[x1, x2, x3, …, x N ], and x1=x2=…=x N ; The value of N satisfies the following relationship: Where: R b is the communication rate; B is the modulation bandwidth; is the channel coding rate.

3. A time-correlated photon cumulative counting communication method according to claim 2, characterized in that: In step S3, the sequence output by the photon counting detector is sampled by an analog-to-digital converter with a set sampling frequency, wherein the set sampling frequency f sample The following conditions must be met: Where: T pluse The width of the electrical pulse output by the photon counting detector.

4. A time-correlated photon cumulative counting communication method according to claim 3, characterized in that: Step S4 specifically includes performing γ-fold sampling processing on the known frame header sequence to obtain a received frame header sequence.

5. A time-correlated photon cumulative counting communication method according to any one of claims 1 to 4, characterized in that: In step S5, the threshold of the binarization process is set according to the amplitude of the discrete electrical pulse output by the photon counting detector.

6. A time-correlated photon cumulative counting communication method according to claim 5, characterized in that: In step S5, the threshold value of the binarization process is Satisfies the following formula: Where: I pluse is the discrete electrical pulse amplitude output by the photon counting detector; mean is the operator for calculating the average value.

7. A time-correlated photon cumulative counting communication method according to claim 6, characterized in that: In step S12, the average values ​​of the accumulated count values ​​of the sampling points in the 1-bit time slot and the 0-bit time slot of the frame header sequence are defined as k1 and k0 respectively, and the decision threshold k is calculated using the following formula: th :

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