Symbol stream processing, communication transmission metric determination method, apparatus, and storage medium

Abstract

The present specification relates to a symbol stream processing method, a communication transmission index determination method, a device and a storage medium, wherein the processing method comprises: performing photon counting on a received optical signal to obtain a first counting vector of an MPPM symbol; an element in the first counting vector represents the number of photons included in each time slot; determining a pulse time slot in the MPPM symbol from a plurality of time slots included in the MPPM symbol based on the number of photons represented by the element in the first counting vector, to obtain a second time slot vector for representing the MPPM symbol; an element in the second time slot vector is used to represent whether the corresponding time slot in the MPPM symbol is a pulse time slot; and performing mapping processing on the second time slot vector by using a preset mapping rule to obtain bit stream data corresponding to the MPPM symbol. The processing method of the present specification embodiment can demodulate the optical signal received by the photon counting receiver end to obtain the MPPM symbol, so as to obtain the original bit stream data sent by the sending end based on the demodulated MPPM symbol.

Description

Technical Field

[0001] This specification relates to the field of optical communication technology, and in particular to a symbol stream processing, communication transmission index determination method, apparatus and storage medium. Background Technology

[0002] Optical communication offers greater transmission bandwidth and capacity compared to radio frequency communication. Photon-counting-based optical communication systems are typically used in low-light environments, employing highly sensitive photon-counting detectors to receive optical signals.

[0003] Because optical signals are very weak, they typically require pulse modulation schemes for signal conversion. MPPM (Multipulse Pulse-Position Modulation) modulation technology ensures spectral efficiency in data transmission and has low requirements for the receiver, thus it is increasingly used in optical communication systems. Currently, there is a pressing need for an MPPM symbol processing method to support the application of MPPM modulation technology in optical communication systems. Summary of the Invention

[0004] This specification aims to at least partially address one of the technical problems in the related art. To this end, one objective of this specification is to propose a symbol stream processing method capable of demodulating an optical signal received by a photon counting receiver to obtain MPPM symbols, thereby obtaining the original bit stream data transmitted by the transmitter based on the demodulated MPPM symbols.

[0005] The second objective of this specification is to propose a method for determining communication transmission indicators.

[0006] The third objective of this specification is to propose a symbol stream processing device.

[0007] The fourth objective of this specification is to provide a device for determining communication transmission indicators.

[0008] The fifth objective of this specification is to provide a computer-readable storage medium.

[0009] The sixth objective of this specification is to provide an electronic device.

[0010] To achieve the above object, an embodiment of the first aspect of this specification proposes a symbol stream processing method. The processing method includes: performing photon counting on the received optical signal to obtain a first counting vector of MPPM symbols with multi-pulse position modulation; wherein, the optical signal is generated by driving a light source to emit light using a first time slot vector for representing MPPM symbols; the MPPM symbol includes multiple time slots; the elements in the first counting vector represent the number of photons included in each time slot; based on the number of photons represented by the elements in the first counting vector, determining the pulse time slots in the MPPM symbol among the multiple time slots included in the MPPM symbol to obtain a second time slot vector for representing the MPPM symbol; wherein, the elements in the second time slot vector are used to represent whether the corresponding time slot in the MPPM symbol is a pulse time slot; performing mapping processing on the second time slot vector using a preset mapping rule to obtain the bit stream data corresponding to the MPPM symbol.

[0011] According to the symbol stream processing method of the embodiment of this specification, after receiving the optical signal, photon counting is performed on each time slot in the MPPM symbol, and the first counting vector is used to record the number of photons in each time slot of the MPPM symbol. Then, based on the number of photons represented by the elements in the first counting vector, the pulse time slots in the MPPM symbol are determined. The demodulated MPPM symbol is represented by the second time slot vector, and then using the preset mapping rule, the second time slot vector is inversely mapped to obtain the bit stream data corresponding to the MPPM symbol, completing the data transmission from the sending end to the receiving end. It realizes the application of the MPPM multi-pulse position modulation technology in the optical communication system of the photon counting receiving end.

[0012] In some embodiments of this specification, the MPPM symbol includes M time slots, and there are N pulse time slots in the M time slots; wherein, N < M, and both M and N are positive integers; the first counting vector includes M elements, and the M elements correspond to the M time slots one by one; based on the number of photons represented by the elements in the first counting vector, determining the pulse time slots in the MPPM symbol among the multiple time slots included in the MPPM symbol includes: determining N target elements among the M elements according to the number of photons in each element of the first counting vector; taking the time slots corresponding to the target elements among the multiple time slots included in the MPPM symbol as the pulse time slots in the MPPM symbol.

[0013] In some embodiments of this specification, determining N target elements among the M elements according to the number of photons in each element of the first counting vector includes: determining the N elements whose number of photons satisfies the preset number condition among the M elements as the N target elements.

[0014] In some embodiments of this specification, determining N target elements from M elements based on the photon count of each element in the first counting vector includes: determining the element with the highest photon count from the M elements based on the photon count of each element in the first counting vector; wherein the number of elements to be determined is greater than N, and the elements to be determined include a first elements with the same photon count, and b second elements with a photon count greater than the photon count of the first elements; if the sum of a and b is greater than N, determining c first elements and b second elements randomly selected from the a first elements as target elements; wherein c is equal to the difference between N and b.

[0015] To achieve the above objectives, a second aspect of this specification provides a method for determining communication transmission indicators. This method includes: determining the number of erroneous time slots in the second time slot vector based on a first time slot vector representing the MPPM symbol when transmitting a multi-pulse position modulated (MPPM) symbol and a second time slot vector representing the MPPM symbol obtained by demodulation after receiving an optical signal; wherein the MPPM symbol includes multiple time slots. The optical signal is generated by driving a light source to emit light using the first time slot vector; the MPPM symbol corresponds to a first counting vector; the second time slot vector is obtained by determining the pulse time slots in the MPPM symbol from among the multiple time slots included in the MPPM symbol based on the number of photons represented by the elements in the first counting vector; the elements in the second time slot vector are used to indicate whether the corresponding time slot in the MPPM symbol is a pulse time slot; the number of erroneous time slots is the number of misjudged pulse time slots or the number of misjudged empty time slots in the second time slot vector; based on the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol, the achievable rate of the MPPM symbol in communication transmission is determined.

[0016] The transmission index determination method according to the embodiments of this specification can calculate the achievable rate in the MPPM symbol transmission process based on the theoretical foundation of the symbol stream processing method of this specification, and obtain the amount of bit data that an MPPM symbol can carry at the receiving end based on photon counting. With the achievable rate as data support, it is possible to clearly determine whether the MPPM multipulse position modulation technology is suitable for current optical communication systems.

[0017] In some embodiments of this specification, determining the achievable rate of an MPPM symbol in communication transmission based on the number of erroneous time slots, the number of time slots in an MPPM symbol, and the number of pulse time slots in an MPPM symbol includes: determining the probability of misjudgment corresponding to the number of erroneous time slots; determining the number of possible scenarios for bit errors in an MPPM symbol based on the number of erroneous time slots, the number of time slots in an MPPM symbol, and the number of pulse time slots in an MPPM symbol; and determining the achievable rate based on the probability of misjudgment and the number of possible scenarios.

[0018] In some embodiments of this specification, the achievable rate is determined using the following formula based on the probability of misjudgment and the number of possible scenarios:

[0019]

[0020] Among them, the Indicates the achievable rate; the Indicates the number of possible cases; p w (w) represents the probability of misjudgment; w represents the number of erroneous time slots; N represents the number of pulse time slots in an MPPM symbol; M represents the number of time slots in an MPPM symbol;

[0021] In some embodiments of this specification, the determination method further includes: determining the symbol error rate based on the probability of misjudgment and the number of possible scenarios; wherein the symbol error rate is the total probability of symbol errors occurring during the process of the receiver receiving the optical signal.

[0022] In some embodiments of this specification, the symbol error rate is determined using the following formula based on the probability of misjudgment and the number of possible scenarios:

[0023]

[0024] Among them, P SER Indicates the symbol error rate; p represents the number of possible outcomes. w (w) represents the probability of misjudgment; w represents the number of incorrect time slots; N represents the number of pulse time slots in the MPPM symbol; M represents the number of time slots in the MPPM symbol.

[0025] In some embodiments of this specification, determining the probability of misjudgment corresponding to the number of erroneous time slots includes: determining a pulse time slot counting vector and a space time slot counting vector in a first counting vector; determining a first target element with the smallest number of photons in the pulse time slot counting vector; determining a first element number in the space time slot counting vector that has the same number of photons as the first target element; determining a second element number in the pulse time slot counting vector that has the same number of photons as the first target element; and determining the probability of misjudgment based on the number of photons of the first target element, the number of first elements, the number of second elements, the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol.

[0026] In some embodiments of this specification, determining the probability of misjudgment based on the number of photons of the first target element, the number of first elements, the number of second elements, the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol includes: determining a first total probability of bit error combinations corresponding to the pulse time slot counting vector based on the number of photons of the first target element, the number of second elements, the number of erroneous time slots, and the number of pulse time slots in the MPPM symbol; determining a second total probability of bit error combinations corresponding to the empty time slot counting vector based on the number of photons of the first target element, the number of first elements, the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol; determining the total number of combinations based on the number of first elements and the number of second elements; wherein the total number of combinations is the total number of combinations in which all pulse time slots of the number of second elements exist in the pulse time slot counting vector, or the total number of combinations in which all empty time slots of the number of first elements exist in the empty time slot counting vector; and determining the probability of misjudgment based on the first total probability, the second total probability, and the total number of combinations.

[0027] In some embodiments of this specification, the first total probability of the pulse slot counting vector bit error combination is determined using the following formula based on the number of photons of the first target element, the number of the second element, the number of erroneous time slots, and the number of pulse time slots in the MPPM symbol:

[0028]

[0029] in, Indicates the first total probability;

[0030] α represents the number of photons of the first target element;

[0031] v represents the number of the second element;

[0032] w represents the number of erroneous time slots;

[0033] N represents the number of pulse slots in the MPPM symbol;

[0034] k1 represents the number of elements in the pulse slot counting vector that have a bit error and whose photon count is equal to α.

[0035] This represents the average number of arriving photons in the pulse slot within the MPPM symbol;

[0036] This represents the average number of arriving photons in the empty time slot of the MPPM symbol;

[0037] as well as Both are probability density functions of Poisson distribution;

[0038] as well as Both are cumulative distribution functions of the Poisson distribution.

[0039] In some embodiments of this specification, the second total probability of the empty slot count vector bit error combination is determined using the following formula based on the number of photons of the first target element, the number of the first element, the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol:

[0040]

[0041] in, Indicates the second total probability;

[0042] α represents the number of photons of the first target element;

[0043] u represents the number of the first element;

[0044] w represents the number of erroneous time slots;

[0045] N represents the number of pulse slots in the MPPM symbol;

[0046] M represents the number of time slots in the MPPM symbol;

[0047] k2 represents the number of elements in the space-time slot counting vector that have bit errors, where the number of photons is equal to α.

[0048] This represents the average number of arriving photons in the pulse slot within the MPPM symbol;

[0049] This represents the average number of arriving photons in the empty time slot of the MPPM symbol;

[0050] as well as Both are probability density functions of Poisson distribution;

[0051] as well as Both are cumulative distribution functions of the Poisson distribution.

[0052] In some embodiments of this specification, the total number of combinations is determined using the following formula based on the number of the first element and the number of the second element:

[0053]

[0054] in, This represents the total number of possible combinations;

[0055] v represents the number of the second element;

[0056] u represents the number of the first element.

[0057] In some embodiments of this specification, the probability of misjudgment is determined using the following formula based on the first total probability, the second total probability, and the total number of combinations:

[0058]

[0059] Where, p w (w) represents the probability of a misjudgment;

[0060] α represents the number of photons of the first target element;

[0061] u represents the number of the first element;

[0062] v represents the number of the second element;

[0063] w represents the number of erroneous time slots;

[0064] N represents the number of pulse slots in the MPPM symbol;

[0065] M represents the number of time slots in the MPPM symbol.

[0066] To achieve the above objectives, a symbol stream processing apparatus is proposed in a third aspect of this specification. The processing apparatus includes: a receiving module, configured to count photons in a received optical signal to obtain a first counting vector for an MPPM symbol; wherein the optical signal is generated by driving a light source to emit light using a first time slot vector representing the MPPM symbol; the MPPM symbol includes multiple time slots; and the elements in the first counting vector represent the number of photons included in each time slot. A demodulation module, configured to determine the pulse time slots in the MPPM symbol from among the multiple time slots included in the MPPM symbol based on the number of photons represented by the elements in the first counting vector, to obtain a second time slot vector representing the MPPM symbol; wherein the elements in the second time slot vector indicate whether the corresponding time slot in the MPPM symbol is a pulse time slot. A mapping module, configured to perform mapping processing on the second time slot vector using a preset mapping rule to obtain bit stream data corresponding to the MPPM symbol.

[0067] According to the symbol stream processing apparatus of the embodiments of this specification, after receiving an optical signal, photon counting is performed on each time slot of the MPPM symbol, and a first counting vector is used to record the number of photons in each time slot of the MPPM symbol. Then, based on the number of photons represented by the elements in the first counting vector, the pulse time slots in the MPPM symbol are determined. The demodulated MPPM symbol is represented by a second time slot vector, and then the second time slot vector is inversely mapped using a preset mapping rule to obtain the bit stream data corresponding to the MPPM symbol, completing the data transmission from the transmitter to the receiver. This realizes the application of MPPM multi-pulse position modulation technology to an optical communication system with a photon counting receiver.

[0068] To achieve the above objectives, a communication transmission index determination apparatus is proposed in the fourth aspect of this specification. The apparatus includes: an error determination module, configured to determine the number of erroneous time slots in the second time slot vector based on a first time slot vector representing the MPPM symbol during transmission and a second time slot vector representing the MPPM symbol obtained by demodulation after receiving an optical signal; wherein the MPPM symbol includes multiple time slots. The optical signal is generated by driving a light source to emit light using the first time slot vector; the MPPM symbol corresponds to a first counting vector; the second time slot vector is obtained by determining the pulse time slots in the MPPM symbol from among the multiple time slots included in the MPPM symbol based on the number of photons represented by the elements in the first counting vector; the elements in the second time slot vector are used to indicate whether the corresponding time slot in the MPPM symbol is a pulse time slot; the number of erroneous time slots is the number of misjudged pulse time slots or the number of misjudged empty time slots in the second time slot vector; and a rate determination module, configured to determine the achievable rate of the MPPM symbol in communication transmission based on the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol.

[0069] The communication transmission index determination apparatus according to the embodiments of this specification can calculate the achievable rate of MPPM symbols based on the theoretical basis of the symbol stream processing method of this specification, and obtain the amount of bit data that an MPPM symbol can carry at a photon-count-based receiver. Using this achievable rate as data support, it is possible to clearly and definitively determine whether MPPM multipulse position modulation technology is suitable for current optical communication systems.

[0070] To achieve the above objectives, a fifth aspect of this specification provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements a symbol stream processing method as described in any embodiment of the first aspect or a communication transmission index determination method as described in any embodiment of the second aspect.

[0071] According to embodiments of this specification, a computer-readable storage medium, when a computer program is executed by a processor, enables the application of MPPM (Multipulse Position Modulation) technology to an optical communication system at a photon counting receiver.

[0072] To achieve the above objectives, a sixth aspect of this specification provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements a symbol stream processing method as described in any embodiment of the first aspect or a communication transmission index determination method as described in any embodiment of the second aspect.

[0073] The electronic device according to the embodiments of this specification, when the processor executes a computer program, can realize the application of MPPM multipulse position modulation technology to an optical communication system at a photon counting receiver.

[0074] Additional aspects and advantages of this specification will be set forth in part in the description which follows, and in part will be obvious from the description or may be learned by practice of this specification. Attached Figure Description

[0075] Figure 1a This is a schematic diagram of a scenario from an embodiment of this specification.

[0076] Figure 1b This is a flowchart of the signal processing at the transmitting end in an embodiment of this specification.

[0077] Figure 1c This is a schematic diagram of the MPPM symbol according to one embodiment of this specification.

[0078] Figure 1d This is a flowchart of the signal processing at the receiving end in an embodiment of this specification.

[0079] Figure 2 This is a flowchart of a symbol stream processing method according to an embodiment of this specification.

[0080] Figure 3 This is a flowchart of the communication transmission index determination method according to an embodiment of this specification.

[0081] Figure 4 This is a schematic diagram of the spectral efficiency of one embodiment of this specification.

[0082] Figure 5 This is a structural block diagram of the symbol stream processing apparatus according to an embodiment of this specification.

[0083] Figure 6 This is a structural block diagram of the communication transmission index determination device according to an embodiment of this specification.

[0084] Figure 7 This is a structural block diagram of an electronic device according to an embodiment of this specification. Detailed Implementation

[0085] The embodiments of this specification are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this specification, and should not be construed as limiting this specification.

[0086] Compared to radio frequency (RF) communication, optical communication offers greater transmission bandwidth and capacity. Optical communication systems based on photonics technology are typically used in low-light environments, employing highly sensitive photon counting detectors to receive optical signals. Because optical signals are extremely weak, pulse modulation schemes are usually required for signal conversion.

[0087] In related technologies, common pulse modulation schemes include on-off keying (OOK) and pulse position modulation (PPM). OOK keying transmits information by the presence or absence of an optical signal. For example, a time slot with an optical signal represents a "1" bit, while a time slot without an optical signal represents a "0" bit. In PPM, a single PPM symbol can encompass multiple time slots, only one of which contains a pulse. Different symbols are represented by the different positions of the pulses.

[0088] While the OOK on / off keying is simple to implement, it requires the receiver to estimate channel state information in real time to determine the optimal decision threshold, thus increasing the receiver's design complexity. In contrast, the PPM (Pulse Position Modulation) method divides a PPM symbol into multiple time slots and transmits pulses within different time slots to complete information transmission. The receiver for PPM demodulation only needs to select the largest sample value from the various time slots within the width of the PPM symbol as the pulse time slot to demodulate the PPM signal, without requiring channel state information. However, PPM demodulation incurs a loss in spectral efficiency. To address this issue, MPPM (Multipulse Pulse-Position Modulation) can be applied for information transmission. An MPPM symbol can transmit pulses in multiple time slots, transmitting more information than a PPM symbol, thus improving spectral efficiency. Furthermore, MPPM has the same receiver requirements as PPM, eliminating the need for real-time channel state estimation. Therefore, there is an urgent need for a symbol stream processing method to apply MPPM (Multipulse Position Modulation) technology to optical communication systems.

[0089] Figure 1a This is a schematic diagram illustrating a scenario from an embodiment of this specification. For example... Figure 1aAs shown, the optical communication system in this specification must include at least a transmitter 110 and a receiver 120. The transmitter 110 needs to transmit the original bitstream data to the receiver 120 to complete the information transmission. However, since the receiver 120 uses a photon counting detector, it can only receive optical signals. Therefore, the transmitter 110 cannot directly transmit bitstream data; it needs to convert the bitstream data into optical signals before transmission.

[0090] refer to Figure 1b The embodiments described in this specification employ MPPM (Multi-Pulse Position Modulation) technology. Therefore, when transmitting bitstream data, the transmitter 110 needs to perform two conversions: bitstream data to MPPM symbols, and MPPM symbols to optical signals. For example, the transmitter 110 can use a preset mapping rule to perform bit symbol mapping processing on the bitstream data to obtain the corresponding MPPM symbol stream. Then, the MPPM symbol stream is used to drive the light source, causing it to emit light and transmitting the MPPM symbols as optical signals.

[0091] It should be noted that MPPM symbols are usually written as (M,N)MPPM. Here, M represents the total number of time slots in an MPPM symbol, N represents the number of time slots containing pulses in an MPPM symbol, and MN represents the number of empty time slots in an MPPM symbol. A (M,N)MPPM symbol has a total of [number missing] time slots depending on the different positions of the N pulses. There are a maximum of 10 possible permutations and combinations. Therefore, one MPPM symbol can represent at most 100 different permutations and combinations. Each bit of data. For example, such as... Figure 1c The MPPM symbol shown is a combination of five time slots. The first and third time slots are pulse time slots, while the remaining three are empty time slots. Therefore, the MPPM symbol can be written as (5,2)MPPM.

[0092] refer to Figure 1d The photon counting detector at receiver 120 can receive the optical signal transmitted by transmitter 110. After receiver 120 and transmitter 110 maintain symbol synchronization, the photon counting detector can count the number of photons in each time slot within an MPPM symbol transmitted by transmitter 110, obtaining a counting vector y = [y1, y2, ..., y...] corresponding to that MPPM symbol. MEach element in the counting vector y corresponds sequentially to each time slot of the MPPM symbol, representing the number of photons in the time slot. For example, element y1 in the counting vector y indicates that the first time slot of the MPPM symbol contains y1 photons. After obtaining the counting vector corresponding to the MPPM symbol, MPPM demodulation is performed based on the counting vector y to reconstruct the MPPM symbol. Then, using a preset mapping rule, the reconstructed MPPM symbol undergoes symbol bit mapping processing to obtain the bitstream data corresponding to the MPPM symbol. Ideally, if the receiver 120 does not encounter any errors during the reception of the optical signal and MPPM demodulation process, the bitstream data obtained after symbol bit mapping processing is completely identical to the bitstream data of the transmitter 110.

[0093] It should be noted that the preset mapping rule used by the transmitting end 110 for bit symbol mapping processing is the same as the preset mapping rule used by the receiving end 120 for symbol bit mapping processing.

[0094] In the embodiments of this specification, vectors may be used to represent MPPM symbols. For example, a time slot vector x = [x1, x2, ..., x...] may be used. M The symbol ] represents an MPPM symbol, and each element in the time slot vector x corresponds sequentially to each time slot of the MPPM symbol. Elements in the time slot vector x have only two values: 1 and 0. If an element is 1, it indicates that the corresponding time slot is a pulse time slot; if an element is 0, it indicates that the corresponding time slot is an empty time slot.

[0095] The process of MPPM demodulation performed by receiver 120 is illustrated by way of example, that is, the processing of MPPM symbols by receiver 120. Receiver 120 performs photon counting on the received optical signal to obtain the first counting vector of the MPPM symbol. The optical signal is generated by transmitter 110 using the first time slot vector representing the MPPM symbol to drive the light source to emit light. For example, after bit symbol mapping processing, transmitter 110 obtains an MPPM symbol comprising five time slots, three of which are pulse time slots and two are empty time slots. The first time slot vector of this MPPM symbol can be x = [0,1,1,0,1]. This indicates that the 2nd, 3rd, and 5th time slots in the MPPM symbol are pulse time slots. The transmitter uses the first time slot vector of the MPPM symbol to drive the light source to emit light, sending the MPPM symbol to receiver 120 in the form of an optical signal. After receiving the optical signal, receiver 120 performs photon counting to obtain the first counting vector y of the MPPM symbol. Assume y = [2,9,8,1,8]. The elements in the first counting vector y represent the number of photons included in each time slot of the MPPM symbol. For example, the third element 8 in the first counting vector y indicates that the third time slot of the MPPM symbol contains 8 photons.

[0096] Based on the photon counts represented by the elements in the first counting vector, pulse time slots within the multiple time slots included in the MPPM symbol are determined to obtain a second time slot vector representing the MPPM symbol. The elements in the second time slot vector indicate whether a corresponding time slot in the MPPM symbol is a pulse time slot. For example, in the first counting vector y = [2, 9, 8, 1, 8], three pulse time slots are determined based on the photon counts represented by the elements. Specifically, three target elements with preset photon count conditions can be determined from the first counting vector y, and the time slots corresponding to these three target elements are recorded as pulse time slots of the MPPM symbol. Satisfying the preset count condition can be exceeding a preset threshold, or sorting the elements in the counting vector y according to the photon count and selecting the top three target elements, or other count conditions that can determine the pulse time slots. Assuming that the second, third, and fifth elements are determined as target elements based on the first counting vector y, then the second, third, and fifth time slots in the MPPM symbol are pulse time slots. Therefore, the second time slot vector z = [0,1,1,0,1] can be obtained to represent the MPPM symbol.

[0097] By using the preset mapping rules used when mapping bit symbols with the transmitter 110, the second time slot vector z is mapped to obtain the bit stream data corresponding to the MPPM symbol.

[0098] The following is combined with Figure 2 This specification provides a detailed description of the symbol stream processing method described in the embodiments. Figure 2 This is a flowchart of a symbol stream processing method according to an embodiment of this specification. For example... Figure 2 As shown, the processing method includes:

[0099] S210, perform photon counting on the received optical signal to obtain the first counting vector of the MPPM symbol with multi-pulse position modulation.

[0100] The optical signal is generated by driving the light source to emit light using a first time slot vector used to represent an MPPM symbol; the MPPM symbol includes multiple time slots; and the elements in the first counting vector represent the number of photons included in each time slot.

[0101] Specifically, the optical signal is generated by the transmitter using a first time slot vector, which represents an MPPM symbol, to drive the light source to emit light. The first time slot vector is obtained by the transmitter through bit symbol mapping of the bit stream data using a preset mapping rule. Each element in the first time slot vector corresponds sequentially to each time slot of the MPPM symbol, and its elements are used to indicate whether the time slot in the MPPM symbol is a pulse time slot.

[0102] The receiver uses a photon counting detector to receive the optical signal transmitted by the transmitter and counts the photons in the received optical signal to obtain the number of photons included in each time slot of the MPPM symbol, thus obtaining the first counting vector of the MPPM symbol. Each element in the first counting vector corresponds to each time slot of the MPPM symbol, and its element represents the number of photons included in each time slot.

[0103] For example, suppose an MPPM symbol includes five time slots, three of which are pulse time slots and two are empty time slots. The first time slot vector used to represent this MPPM symbol is x = [0,1,1,0,1]. From the first time slot vector, it can be seen that the second, third, and fifth time slots in this MPPM symbol are pulse time slots, while the first and fourth time slots are empty time slots. The first time slot vector is used to drive the light source to emit light, transmitting the MPPM symbol as an optical signal.

[0104] After receiving the optical signal, the receiver counts the photons in each time slot of the MPPM symbol to obtain the first counting vector of that MPPM symbol. Since the pulse time slot carries data, it contains a large number of photons. However, the empty time slot contains only a small number of photons due to noise or light source fluctuations. Therefore, typically, the number of photons represented by the element corresponding to the pulse time slot in the first counting vector should be greater than the number of photons represented by the element corresponding to the empty time slot. For example, for the MPPM symbol represented by the first time slot vector, the first counting vector of this MPPM symbol can be y = [1, 8, 9, 3, 5]. In the first counting vector, the number of photons represented by the second, third, and fifth elements is greater than the number of photons represented by the first and fourth elements.

[0105] S220, based on the number of photons represented by the elements in the first counting vector, determine the pulse time slot in the MPPM symbol among the multiple time slots included in the MPPM symbol, so as to obtain a second time slot vector for representing the MPPM symbol.

[0106] The elements in the second time slot vector are used to indicate whether the corresponding time slot in the MPPM symbol is a pulse time slot.

[0107] Since the elements in the first counting vector correspond sequentially to each time slot of the MPPM symbol, their values ​​represent the number of photons included in the corresponding time slot. Based on the characteristics of the light source emitting the optical signal, the number of photons arriving at the receiver within a pulse time slot follows a certain pattern, while the number of photons arriving at the receiver within an empty time slot follows another pattern. Therefore, based on the number of photons represented by the elements in the first counting vector, it is possible to determine which elements correspond to pulse time slots, thus obtaining the second time slot vector of the MPPM symbol. Ideally, if no errors occur at the receiver during the process of receiving the optical signal and determining the time slot pulse based on the first counting vector, the second time slot vector will be identical to the first time slot vector.

[0108] S230: The second time slot vector is mapped using a preset mapping rule to obtain the bit stream data corresponding to the MPPM symbol.

[0109] In the embodiments of this specification, the preset mapping rule used by the receiving end to map the second time slot vector is the same as the preset mapping rule used by the transmitting end to map the bitstream data. At the transmitting end, the preset mapping rule is used to map the bitstream data into a first time slot vector representing an MPPM symbol. At the receiving end, the preset mapping rule is used to inversely map the second time slot vector to obtain the bitstream data corresponding to the MPPM symbol.

[0110] If no errors occur during the process of receiving the optical signal and determining the time slot pulse based on the first counting vector, that is, if no bit errors occur during the processing of the MPPM symbol, then the bit stream data obtained by the reverse mapping at the receiving end is the same as the bit stream data before the mapping at the transmitting end.

[0111] According to the embodiments of this specification, after receiving the optical signal, photon counting is performed on each time slot of the MPPM symbol, and the number of photons in each time slot of the MPPM symbol is recorded using a first counting vector. Then, based on the number of photons represented by the elements in the first counting vector, the pulse time slots in the MPPM symbol are determined. The demodulated MPPM symbol is represented by a second time slot vector, and then the second time slot vector is inversely mapped using a preset mapping rule to obtain the bit stream data corresponding to the MPPM symbol, completing the data transmission from the transmitter to the receiver. This realizes the application of MPPM multi-pulse position modulation technology to an optical communication system with a photon counting receiver.

[0112] In some embodiments of this specification, an MPPM symbol includes M time slots, and there are N pulse time slots among the M time slots; where N < M, and both M and N are positive integers; the first counting vector includes M elements, and the M elements correspond one-to-one to the M time slots; determining the pulse time slots in the MPPM symbol among the multiple time slots included in the MPPM symbol based on the number of photons represented by the elements in the first counting vector includes: determining N target elements among the M elements according to the number of photons of each element in the first counting vector; taking the time slots corresponding to the target elements among the multiple time slots included in the MPPM symbol as the pulse time slots in the MPPM symbol.

[0113] Reference Figure 1c , the MPPM symbol may include M time slots, and the M time slots include N pulse time slots and M - N empty time slots. The MPPM symbol can be written as (M,N)MPPM. The elements in the first counting vector are used to represent the number of photons in the time slots of the MPPM symbol. Therefore, the first counting vector also includes M elements, and the M elements correspond one-to-one to the M time slots of the MPPM symbol.

[0114] Specifically, in the first counting vector, there are N elements corresponding to the pulse time slots. Therefore, N target elements can be determined according to the number of photons of each element in the first counting vector, and the time slots corresponding to the N target elements in the MPPM symbol are used as the pulse time slots of the MPPM symbol.

[0115] In some embodiments of this specification, determining N target elements among the M elements according to the number of photons of each element in the first counting vector includes: determining N elements whose photon numbers meet the preset number condition among the M elements as the N target elements.

[0116] Since the number of photons included in the pulse time slots is generally greater than the number of photons included in the empty time slots. Therefore, meeting the preset number condition can be exceeding the preset number threshold, or sorting the M elements in the first counting vector according to the magnitude of the photon numbers, and selecting the N elements with the top photon numbers as the target elements, or other number conditions that can determine the number of pulse time slots.

[0117] Exemplarily, if M is equal to 5 and N is equal to 3. The first counting vector of the MPPM symbol is y = [1, 8, 9, 3, 5]. Then, 3 target elements that meet the preset number condition need to be determined in the first counting vector. Sort the 5 elements in the first counting vector according to the magnitude, and get y' = [9, 8, 5, 3, 1], and determine the elements with the top 3 photon numbers as the target elements, that is, element 9, element 8, and element 5 are the target elements.

[0118] In some embodiments of this specification, determining N target elements from M elements based on the photon count of each element in the first counting vector includes: determining the element with the highest photon count from the M elements based on the photon count of each element in the first counting vector; wherein the number of elements to be determined is greater than N, and the elements to be determined include a first elements with the same photon count, and b second elements with a photon count greater than the photon count of the first elements; if the sum of a and b is greater than N, determining c first elements and b second elements randomly selected from the a first elements as target elements; wherein c is equal to the difference between N and b.

[0119] In some cases, when the receiver receives an optical signal and performs photon counting, the photons in the time slots include not only those generated by the transmitter using the first time slot vector to drive the light source, but also noise photons or photons emitted due to a driving error of the light source. This can lead to situations where the number of photons included in pulse time slots and empty time slots is the same.

[0120] In the embodiments of this specification, the M elements in the first counting vector can be sorted in descending order of photon count, and the element with the highest photon count among the M elements can be determined. At this time, the number of elements to be determined is greater than N. The elements to be determined include a first elements with the same photon count and b second elements with a photon count greater than the first element. For example, if M is 8 and N is 4, the first counting vector for the (8,4) MPPM symbol is y = [1,6,6,9,3,8,7,2]. Then, after sorting the 8 elements in the first counting vector y according to photon count, the results are 9, 8, 7, 6, 6, 3, 2, 1. Since there are 4 pulse slots in the (8,4) MPPM symbol, it is necessary to determine 4 target elements in the first counting vector. When determining the 4 elements with the highest photon count in the first counting vector, there are two elements with a photon count of 6. At this time, it is impossible to determine which of these two elements with the same photon count corresponds to a pulse slot. Therefore, the five elements with photon counts of 9, 8, 7, 6, and 6 can be temporarily considered as elements to be determined. Among these five elements, there are a = two first elements with the same number of photons, and b = three second elements with a photon count greater than 6.

[0121] If the sum of a and b is greater than N, then c first elements can be randomly selected from a first elements as target elements. Simultaneously, b second elements are also selected as target elements. Here, c = Nb. For example, still using M = 8 and N = 4, the first counting vector of the (8, 4)MPPM symbol is y = [1, 6, 6, 9, 3, 8, 7, 2]. In this case, a = 2 and b = 3. The sum of a and b is 5, which is greater than N. Therefore, c = 1 first element can be randomly determined from the two first elements as target elements. c is obtained by subtracting b from N.

[0122] In some implementations, if M is 8 and N is 4, and the first counting vector of the (8,4)MPPM symbol is y = [1,7,6,9,3,8,7,2] or y = [1,9,6,9,3,8,7,2], the time slots corresponding to the four elements with the highest photon count can be directly determined as pulse time slots.

[0123] The above are embodiments of the symbol stream processing method described in this specification. In related technologies, there are various other pulse demodulation techniques for optical communication systems, such as the OOK on / off keying and PPM pulse position modulation methods mentioned above. Therefore, based on the theoretical foundation of the symbol stream processing method in this specification, indicators in the MPPM symbol transmission process based on photon counting can be calculated, such as the achievable rate based on MPPM multi-pulse modulation technology or the symbol error rate at the receiving end during transmission. Based on the achievable rates of various pulse modulation techniques, the most suitable pulse modulation technique for the current optical communication system can be selected.

[0124] Figure 3 This is a flowchart of a communication transmission index determination method according to an embodiment of this specification. The determination method includes:

[0125] S310, based on the first time slot vector used to represent the MPPM symbol when transmitting the multi-pulse position modulated MPPM symbol and the second time slot vector used to represent the MPPM symbol after demodulation of the received optical signal, determine the number of erroneous time slots in the second time slot vector.

[0126] The MPPM symbol includes multiple time slots; the optical signal is generated by driving the light source to emit light using the first time slot vector; the MPPM symbol corresponds to a first counting vector; the second time slot vector is obtained by determining the pulse time slot in the MPPM symbol from the multiple time slots included in the MPPM symbol based on the number of photons represented by the elements in the first counting vector; the elements in the second time slot vector are used to indicate whether the corresponding time slot in the MPPM symbol is a pulse time slot; the number of erroneous time slots is the number of erroneously judged pulse time slots or the number of erroneously judged empty time slots in the second time slot vector.

[0127] In the embodiments of this specification, the first time slot vector is obtained by the transmitting end through bit symbol mapping of the bit stream data using a preset mapping rule. The elements in the first time slot vector indicate whether a time slot in the MPPM symbol is a pulse time slot. The transmitting end then uses the first time slot vector to drive the light source to emit light, sending the MPPM symbol to the receiving end in the form of an optical signal. After receiving the optical signal, the receiving end counts the photons in each time slot of the MPPM symbol, obtaining a first counting vector corresponding to the MPPM symbol. The elements in the first counting vector correspond one-to-one with the time slots of the MPPM symbol, and each element represents the number of photons in each time slot of the MPPM symbol. The receiving end demodulates the MPPM symbol based on the number of photons represented by the elements in the first counting vector, obtaining a second time slot vector representing the MPPM symbol. Ideally, under normal circumstances where the receiving end makes no errors, the second time slot vector is identical to the first time slot vector. However, various errors and problems often arise during the transmission of the optical signal and the demodulation process based on the first counting vector. Therefore, the second time slot vector may contain elements that are different from the first time slot vector, that is, the pulse time slot of the MPPM symbol is misjudged or the empty time slot of the MPPM symbol is misjudged.

[0128] For example, taking the (5,2) MPPM symbol as an example, assume the first time slot vector x = [0,1,1,0,0]. The first counting vector corresponding to the (5,2) MPPM symbol is y = [y1,y2,y3,y4,y5]. The receiver demodulates the (5,2) MPPM symbol based on the first counting vector y to obtain the second time slot vector z = [0,1,0,1,0]. From the first time slot vector x and the second time slot vector z, it can be seen that the third and fourth time slots of the (5,2) MPPM symbol are misjudged in the second time slot vector. Since the number of pulse time slots of the (5,2) MPPM symbol is known, if w pulse time slots are misjudged as empty time slots in the second time slot vector, then w empty time slots are misjudged as pulse time slots. Therefore, the range of the number of misjudged time slots w is [0, min(N,MN)]. The number of erroneous time slots w in the second time slot vector is 1, that is, in the second time slot vector, one pulse time slot is misjudged as an empty time slot, and one empty time slot is misjudged as a pulse time slot.

[0129] S320 determines the achievable rate of MPPM symbols in communication transmission based on the number of erroneous time slots, the number of time slots in MPPM symbols, and the number of pulse time slots in MPPM symbols.

[0130] In the embodiments of this specification, the achievable rate can be understood as the maximum number of bits that one MPPM symbol can transmit. Under the current transmission conditions of optical communication systems, information transmission at or below the achievable rate can achieve error-free transmission. If data is transmitted beyond the achievable rate, bit errors may occur. Bit errors refer to misidentifying a pulse time slot as an empty time slot, or vice versa.

[0131] As described above, the achievable rate can be expressed as the number of bits transmitted per time slot. Based on the number of erroneous time slots, the number of time slots in an MPPM symbol, and the number of pulse time slots in an MPPM symbol, the amount of bit data carried by the receiver in the MPPM symbol can be determined. Using the ratio of the bit data amount to the number of time slots in the MPPM symbol, the achievable rate of the receiver in receiving the MPPM symbol can be obtained.

[0132] Since a (M,N)MPPM symbol has a total of [number] different positions of N pulses, [number] such symbols are used to represent different MPPM symbols. There are a maximum of 10 possible permutations and combinations. Therefore, one MPPM symbol can represent at most 100 different permutations and combinations. Each MPPM symbol carries a number of bits of data. Since errors can occur during information transmission, the actual number of bits of data carried by a single MPPM symbol during transmission can be determined based on the number of erroneous time slots and the theoretical basis of log₂Ω.

[0133] For example, the achievable rate can be determined based on the ratio of the bit data determined by the number of erroneous time slots and log2Ω to the number of time slots in the MPPM symbol. Alternatively, the error situation of the MPPM symbol received by the receiver can be determined based on the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol. When determining the bit data, the error situation is taken into account, thereby determining the actual amount of bit data carried by the MPPM symbol in the event of misjudgment; the achievable rate is then determined based on the ratio of the actual amount of bit data to the number of time slots in the MPPM symbol.

[0134] In some embodiments of this specification, determining the achievable rate of an MPPM symbol in communication transmission based on the number of erroneous time slots, the number of time slots in an MPPM symbol, and the number of pulse time slots in an MPPM symbol includes: determining the probability of misjudgment corresponding to the number of erroneous time slots; determining the number of possible scenarios for bit errors in an MPPM symbol based on the number of erroneous time slots, the number of time slots in an MPPM symbol, and the number of pulse time slots in an MPPM symbol; and determining the achievable rate based on the probability of misjudgment and the number of possible scenarios.

[0135] In the embodiments of this specification, the probability of misjudgment represents the probability that the number of erroneous time slots w will occur after the receiver receives an MPPM symbol.

[0136] If the number of erroneous time slots in an MPPM symbol is w, it means that w pulse time slots were misclassified as empty time slots, and correspondingly, w empty time slots were misclassified as pulse time slots. In an (M,N) MPPM symbol, there are N pulse time slots and MN empty time slots. Therefore, the total number of cases where there are w errors in N pulse time slots for an (M,N) MPPM symbol is: The total number of cases where w errors occur in MN space slots is Therefore, based on the number of erroneous time slots, the number of time slots in an MPPM symbol, the number of pulse time slots in an MPPM symbol, and the number of possible scenarios for bit errors in an MPPM symbol, the following can be determined:

[0137] Determining the achievable rate based on the probability of misjudgment and the number of possible scenarios can be achieved by: using the product of the probability of misjudgment and the number of possible scenarios to determine the achievable rate, or by using the probability of misjudgment and the number of possible scenarios to represent the error scenarios encountered by the receiver in receiving MPPM symbols. When determining the bit data, error scenarios are taken into account to determine the actual amount of bit data carried by the MPPM symbol in the event of a misjudgment; the achievable rate is then determined based on the ratio of the actual amount of bit data to the number of time slots in the MPPM symbol.

[0138] Since MPPM symbols are used to carry bit data for transmission, after determining the probability of misjudgment, a maximum of [number] symbols can be represented by one MPPM symbol. Based on the data of Ω, the product of Ω and the probability of misjudgment is processed by symbol bit conversion to obtain the amount of data that an MPPM symbol can carry when w erroneous time slots occur. Since the receiving end receives an MPPM symbol stream, which includes multiple MPPM symbols, after adding the error cases of the receiving end receiving MPPM symbols, the error cases of the receiving end receiving MPPM symbols can be represented by the probability of misjudgment and the number of possible cases.

[0139] Specifically, the achievable rate can be determined using the following formula based on the symbol error rate and the amount of data in bits.

[0140]

[0141] in, Indicates the achievable rate; p represents the number of possible outcomes. w (w) represents the probability of misjudgment; w represents the number of erroneous time slots; N represents the number of pulse time slots in the MPPM symbol; M represents the number of time slots in the MPPM symbol;

[0142] In some embodiments of this specification, the determination method further includes: determining the symbol error rate based on the probability of misjudgment and the number of possible scenarios; wherein the symbol error rate is the total probability of symbol errors occurring during the process of the receiver receiving the optical signal. In the embodiments of this specification, the symbol error rate is the total probability of symbol errors occurring during the process of the receiver receiving the optical signal, which is the same as the aforementioned achievable rate property, and can also be used as an evaluation index for MPPM symbol communication transmission based on photon counting in the embodiments of this specification.

[0143] The symbol error rate (BER) can be determined by multiplying the probability of misjudgment by the number of possible scenarios. Since the number of erroneous time slots (w) of the demodulated MPPM symbols obtained at the receiver during optical signal reception ranges from [0, min(N, MN)], the BER can also be determined based on the sum of [0, min(N, MN)] erroneous scenarios. Here, the BER can be used to represent the error scenarios encountered by the receiver in receiving MPPM symbols.

[0144] In some embodiments of this specification, the symbol error rate can be determined using the following formula based on the probability of misjudgment and the number of possible scenarios:

[0145]

[0146] Among them, P SER Indicates the symbol error rate; p represents the number of possible outcomes. w (w) represents the probability of misjudgment; w represents the number of incorrect time slots; N represents the number of pulse time slots in the MPPM symbol; M represents the number of time slots in the MPPM symbol.

[0147] In some embodiments of this specification, determining the probability of misjudgment corresponding to the number of erroneous time slots includes: determining a pulse time slot counting vector and a space time slot counting vector in a first counting vector; determining a first target element with the smallest number of photons in the pulse time slot counting vector; determining the number of first elements in the space time slot counting vector that have the same number of photons as the first target element; determining the number of second elements in the pulse time slot counting vector that have the same number of photons as the first target element; and determining the probability of misjudgment based on the number of photons in the first target element, the number of first elements, the number of second elements, the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol.

[0148] Specifically, the first counting vector can be decomposed according to the number of photons represented by its elements, resulting in a pulse slot counting vector and a space slot counting vector. The elements in the pulse slot counting vector are several elements of the first counting vector corresponding to the pulse slots. The space slot counting vector is several elements of the first counting vector corresponding to the space slots.

[0149] For example, taking the (5,2) MPPM symbol as an example, assume the first time slot vector x = [0,1,1,0,0]. The first counting vector corresponding to the (5,2) MPPM symbol is y = [y1,y2,y3,y4,y5]. The receiver demodulates the (5,2) MPPM symbol based on the first counting vector y to obtain the second time slot vector z = [0,1,0,1,0]. Based on the second time slot vector z, the first counting vector y is split into y1, y2, y3, y4, y5. p and y u Therefore, y can be written as in This represents the concatenation operation between two vectors. p Including several elements in the first counting vector y that correspond to the pulse time slots in the second time slot vector z, then y p = [y2, y4]. y u Including several elements in the first counting vector corresponding to the empty time slot in the second time slot vector z, then y u =[y1,y3,y5].

[0150] Determine the pulse slot counting vector y p The first target element with the smallest number of photons. Let the first target element be α, then α = min{y} p}. In the space-time slot counting vector y u The number of the first element, which has the same number of photons as the first target element α, is determined from all elements in the array. This number can be denoted as u. The pulse time slot counting vector y... p The number of second elements among all elements that have the same number of photons as the first target element α can be denoted as v.

[0151] Based on the number of photons of the first target element, the number of the first element, the number of the second element, the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol, various probabilities of bit errors can be determined. The probability of misjudgment can be determined based on the combination of these probabilities.

[0152] In some embodiments of this specification, determining the probability of misjudgment based on the number of photons of the first target element, the number of first elements, the number of second elements, the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol includes: determining a first total probability of bit error combinations corresponding to the pulse time slot counting vector based on the number of photons of the first target element, the number of second elements, the number of erroneous time slots, and the number of pulse time slots in the MPPM symbol; determining a second total probability of bit error combinations corresponding to the empty time slot counting vector based on the number of photons of the first target element, the number of first elements, the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol; determining the total number of combinations based on the number of first elements and the number of second elements; wherein the total number of combinations is the total number of combinations in which the time slots of the number of second elements exist in the pulse time slot counting vector, or the total number of combinations in which the time slots of the number of first elements exist in the empty time slot counting vector; and determining the probability of misjudgment based on the first total probability, the second total probability, and the total number of combinations.

[0153] Since the number of photons arriving in each time slot of an MPPM symbol when a photon counting detector receives an optical signal is a random variable y, but this random variable follows a Poisson distribution, the probability density function of the number of photons in a time slot for the receiver when receiving the optical signal can be obtained by referring to... in, This represents the average number of arriving photons in the MPPM symbol time slot. If the time slot is a pulse time slot, then... If the time slot is an empty time slot, then This is the average number of arriving photons across all pulse slots in an MPPM symbol determined by the photon counting detector at the receiving end when receiving an optical signal. This represents the average number of arriving photons across all time slots within a single MPPM symbol, determined by the photon counting detector at the receiving end when receiving the optical signal. Furthermore, the cumulative distribution function of the photon number across time slots can be expressed as follows:

[0154] In the embodiments of this specification, a first total probability of the bit error combination corresponding to the pulse slot count vector is determined based on the number of photons of the first target element, the number of second elements, the number of erroneous time slots, and the number of pulse slots in the MPPM symbol. This may include: using the number of second elements, the number of erroneous time slots, and the number of pulse slots in the MPPM symbol as data, and using the number of photons of the first target element as a random variable y. or As the average number of arriving photons Substituting these values ​​into the probability density function and cumulative distribution function, we determine the first total probability. This first total probability can be understood as the total probability of all possible combinations of bit errors corresponding to the pulse slot counting vector.

[0155] Specifically, the first total probability of the error combination of the pulse slot counting vector can be determined using the following formula based on the number of photons of the first target element, the number of the second element, the number of erroneous time slots, and the number of pulse time slots in the MPPM symbol:

[0156]

[0157] in, Indicates the first total probability;

[0158] α represents the number of photons of the first target element;

[0159] v represents the number of the second element;

[0160] w represents the number of erroneous time slots;

[0161] N represents the number of pulse slots in the MPPM symbol;

[0162] k1 represents the number of elements in the pulse slot counting vector that have a bit error and whose photon count is equal to α.

[0163] This represents the average number of arriving photons in the pulse slot within the MPPM symbol;

[0164] This represents the average number of arriving photons in the empty time slot of the MPPM symbol;

[0165] as well as Both are probability density functions of Poisson distribution;

[0166] as well as Both are cumulative distribution functions of the Poisson distribution.

[0167] In the embodiments of this specification, the first counting vector y is split into y based on the second time slot vector z. p and y u Furthermore, the pulse slot counting vector can be further decomposed into y p|p and y p|u .but Among them, y p|p Included in the pulse slot counting vector y p In the first counting vector x, the element corresponds to the pulse time slot. p|u Included in the pulse slot counting vector y p In the first counting vector x, the element corresponds to the spatial time slot.

[0168] Split the space slot counting vector into y uu and y up.but Among them, y uu Included in the empty time slot counting vector y u In the first counting vector x, the element corresponding to the spatial time slot is y. up Included in the empty time slot counting vector y u In the first counting vector x, the element corresponds to the pulse time slot.

[0169] As can be seen from the above, y pp y pu y uu y up The number of elements in the middle are Nw, w, MNw, w.

[0170] For example, still taking the (5,2) MPPM symbol as an example, assume the first time slot vector x = [0,1,1,0,0]. The first counting vector corresponding to the (5,2) MPPM symbol is y = [y1,y2,y3,y4,y5]. The receiver demodulates the (5,2) MPPM symbol based on the first counting vector y to obtain the second time slot vector z = [0,1,0,1,0]. The number of erroneous time slots w is then calculated to be 1. Where y... p =[y2,y4], y u =[y1,y3,y5], y pp =[y2], y pu =[y4], y uu =[y1,y5], y up =[y3]. Therefore, if the first target element is α, then α = min{y3} p The number of the first element u is the counting vector y in the space-time slot. u The number of elements in the array whose number of photons is equal to that of the first target element α. The number of the second element v is the number of photons in the pulse time slot counting vector y. p The number of elements in each element whose photon count is equal to that of the first target element α. In the above formula, k1 represents the number of elements in the pulse slot counting vector that have a bit error and whose photon count is equal to α, that is, in vector y pu =[y4] is the number of elements in the vector y that have the same number of photons as the first target element α. This can also be expressed in the vector y. up The number of elements in [y3] that have the same number of photons as the first target element α is determined and denoted as k2.

[0171] In embodiments of this specification, a second total probability of the bit error combination corresponding to the empty slot count vector is determined based on the photon count of the first target element, the number of first elements, the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol. This may include: using the number of first elements, the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol as data, and using the photon count of the first target element as a random variable y. or As the average number of arriving photons Substituting these values ​​into the probability density function and cumulative distribution function, the second total probability is determined. This second total probability can be understood as the total probability of various error combinations corresponding to the space-time slot counting vector.

[0172] Specifically, the second total probability of the empty slot counting vector bit error combination can be determined using the following formula based on the number of photons of the first target element, the number of the first element, the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol:

[0173]

[0174] in, Indicates the second total probability;

[0175] α represents the number of photons of the first target element;

[0176] u represents the number of the first element;

[0177] w represents the number of erroneous time slots;

[0178] N represents the number of pulse slots in the MPPM symbol;

[0179] M represents the number of time slots in the MPPM symbol;

[0180] k2 represents the number of elements in the space-time slot counting vector that have bit errors, where the number of photons is equal to α.

[0181] This represents the average number of arriving photons in the pulse slot within the MPPM symbol;

[0182] This represents the average number of arriving photons in the empty time slot of the MPPM symbol;

[0183] as well as Both are probability density functions of Poisson distribution;

[0184] as well as Both are cumulative distribution functions of the Poisson distribution.

[0185] It should be noted that k2 here refers to the vector y up =[y3] determines the number of elements that have the same number of photons as the first target element α.

[0186] In the embodiments of this specification, the total number of combinations is determined based on the number of the first element and the number of the second element; wherein the total number of combinations is the total number of combinations in which the pulse slots of the second element number exist in the pulse slot counting vector, or the total number of combinations in which the empty slots of the first element number exist in the empty slot counting vector.

[0187] When the receiver receives an optical signal and performs photon counting, it may receive pulse time slots and empty time slots containing the same number of photons. In the embodiments of this specification, when encountering this situation during demodulation, c first elements are randomly selected from a first elements as target elements. Therefore, the elements in the pulse time slot counting vector whose number of second elements equals the number of α photons are randomly determined from multiple elements in the first counting vector with the same number of photons. Due to the random determination factor, there are multiple possible combinations. That is, the number of combinations where v pulse time slots are determined from u+v elements with the same number of photons in the first counting vector is equivalent to the number of combinations where u empty time slots are determined from u+v elements with the same number of photons in the first counting vector. Therefore, the total number of combinations is either the total number of combinations where the number of pulse time slots of the second element exists in the pulse time slot counting vector, or the total number of combinations where the number of empty time slots of the first element exists in the empty time slot counting vector.

[0188] Specifically, the total number of combinations can be determined using the following formula based on the number of the first element and the number of the second element: in, represents the total number of combinations; v represents the number of second elements; u represents the number of first elements.

[0189] Alternatively, the total number of combinations can be determined using the following formula based on the number of the first element and the number of the second element: in, represents the total number of combinations; v represents the number of second elements; u represents the number of first elements.

[0190] In the embodiments of this specification, the probability of misjudgment is determined based on a first total probability, a second total probability, and the total number of combinations. This may include determining the probability of misjudgment by multiplying the first total probability and the second total probability, or by determining the probability of misjudgment based on the ratio of the product of the first total probability and the second total probability to the total number of combinations.

[0191] Specifically, the probability of misjudgment can be determined using the following formula based on the first total probability, the second total probability, and the total number of combinations:

[0192]

[0193] Where, p w (w) represents the probability of misjudgment; α represents the number of photons of the first target element; u represents the number of the first element; v represents the number of the second element; w represents the number of erroneous time slots; N represents the number of pulse time slots in the MPPM symbol; M represents the number of time slots in the MPPM symbol.

[0194] The transmission index determination method according to the embodiments of this specification can calculate the achievable rate of MPPM symbols based on photon counting and the symbol error rate of the receiver after receiving MPPM symbols, based on the theoretical foundation of the symbol stream processing method of this specification. This yields the amount of bit data that an MPPM symbol can carry and the total probability of symbol errors occurring during the receiver's optical signal reception process, all within the context of a photon-count-based receiver. With the achievable rate and symbol error rate as data support, it is possible to clearly determine whether MPPM multipulse position modulation technology is suitable for current optical communication systems.

[0195] In related technologies, spectral efficiency is typically used to evaluate pulse modulation techniques. In the embodiments of this specification, spectral efficiency can be understood as the maximum achievable transmission rate using MPPM symbols under ideal optical communication conditions.

[0196] like Figure 4 The figure shows the spectral efficiency of the three modulation techniques under the same communication conditions. As can be seen, the spectral efficiency of OOK on / off keying remains consistently 1 BPS, always at the highest level. However, as the number of time slots M increases, the spectral efficiency of MPPM multi-pulse position modulation gradually approaches that of OOK on / off keying, and the spectral efficiency of MPPM multi-pulse position modulation is consistently higher than that of PPM pulse position demodulation. When designing optical communication systems, this can be used as a basis for comparison. Figure 4 The graph shown clearly illustrates the pulse modulation technique suitable for the design conditions.

[0197] Corresponding to the above embodiments, this specification also proposes a symbol stream processing apparatus. For example... Figure 5 As shown, the processing apparatus includes:

[0198] The receiving module 510 is used to count photons in the received optical signal to obtain a first counting vector of the MPPM symbol. The optical signal is generated by driving a light source to emit light using a first time slot vector representing the MPPM symbol; the MPPM symbol includes multiple time slots; and the elements in the first counting vector represent the number of photons included in each time slot.

[0199] The demodulation module 520 is used to determine the pulse time slot in the MPPM symbol from among the multiple time slots included in the MPPM symbol based on the number of photons represented by the elements in the first counting vector, so as to obtain a second time slot vector for representing the MPPM symbol. The elements in the second time slot vector are used to indicate whether the corresponding time slot in the MPPM symbol is a pulse time slot.

[0200] The mapping module 530 is used to map the second time slot vector using a preset mapping rule to obtain the bit stream data corresponding to the MPPM symbol.

[0201] According to the symbol stream processing apparatus of the embodiments of this specification, after receiving an optical signal, photon counting is performed on each time slot of the MPPM symbol, and a first counting vector is used to record the number of photons in each time slot of the MPPM symbol. Then, based on the number of photons represented by the elements in the first counting vector, the pulse time slots in the MPPM symbol are determined. The demodulated MPPM symbol is represented by a second time slot vector, and then the second time slot vector is inversely mapped using a preset mapping rule to obtain the bit stream data corresponding to the MPPM symbol, completing the data transmission from the transmitter to the receiver. This realizes the application of MPPM multi-pulse position modulation technology to an optical communication system with a photon counting receiver.

[0202] It should be noted that for details not disclosed in the symbol stream processing apparatus of this embodiment, please refer to the details disclosed in the embodiments of the symbol stream processing method in this specification, which will not be repeated here.

[0203] Corresponding to the above embodiments, this specification also proposes a communication transmission index determination device. For example... Figure 6 As shown, the determining device includes:

[0204] Error detection module 610 is used to determine the number of erroneous time slots in the second time slot vector based on the first time slot vector used to represent the MPPM symbol when transmitting the MPPM symbol and the second time slot vector used to represent the MPPM symbol after demodulation of the received optical signal. The MPPM symbol includes multiple time slots. The optical signal is generated by driving a light source to emit light using the first time slot vector; each MPPM symbol corresponds to a first counting vector; the second time slot vector is obtained by determining the pulse time slots in the MPPM symbol from among the multiple time slots included in the MPPM symbol based on the number of photons represented by the elements in the first counting vector; the elements in the second time slot vector indicate whether the corresponding time slot in the MPPM symbol is a pulse time slot; the number of erroneous time slots is the number of misjudged pulse time slots or the number of misjudged empty time slots in the second time slot vector.

[0205] The rate determination module 620 is used to determine the achievable rate of an MPPM symbol in communication transmission based on the number of erroneous time slots, the number of time slots in an MPPM symbol, and the number of pulse time slots in an MPPM symbol.

[0206] The communication transmission index determination apparatus according to the embodiments of this specification can calculate the achievable rate of MPPM symbols based on the theoretical basis of the symbol stream processing method of this specification, and obtain the amount of bit data that an MPPM symbol can carry at the receiving end based on photon counting. With the achievable rate as data support, it is possible to clearly and definitively determine whether MPPM multipulse position modulation technology is suitable for current optical communication systems.

[0207] It should be noted that for details not disclosed in the communication transmission index determination device of this embodiment, please refer to the details disclosed in the embodiments of the communication transmission index determination method in this specification, which will not be repeated here.

[0208] Corresponding to the above embodiments, this specification also proposes a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the symbol stream processing method as described in any of the above embodiments or the communication transmission index determination method as described in any of the above embodiments.

[0209] According to embodiments of this specification, a computer-readable storage medium, when a computer program is executed by a processor, enables the application of MPPM (Multipulse Position Modulation) technology to an optical communication system at a photon counting receiver.

[0210] Corresponding to the above embodiments, this specification also provides an electronic device.

[0211] Figure 7 This is a structural block diagram of an electronic device according to one embodiment of this specification, such as... Figure 7 As shown, the electronic device 700 includes a memory 704, a processor 702, and a computer program 706 stored in the memory 704 and executable on the processor 702. When the processor 702 executes the computer program, it implements the symbol stream processing method as described in any of the above embodiments or the communication transmission index determination method as described in any of the above embodiments.

[0212] According to the embodiments of this specification, when the processor 702 executes a computer program, the electronic device can realize the application of MPPM multipulse position modulation technology to the optical communication system of the photon counting receiver.

[0213] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0214] It should be understood that various parts of this specification can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0215] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this specification. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0216] Furthermore, the terms "first," "second," etc., used in the embodiments of this specification are for descriptive purposes only and should not be construed as indicating or implying relative importance, or implicitly specifying the number of technical features indicated in this embodiment. Therefore, features defined with terms such as "first" and "second" in the embodiments of this specification can explicitly or implicitly indicate that the embodiment includes at least one of those features. In the description of this specification, the word "multiple" means at least two or more, such as two, three, four, etc., unless otherwise explicitly specified in the embodiments.

[0217] Although embodiments of this specification have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting this specification. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this specification.

Claims

1. A symbol stream processing method, characterized in that, The method includes: Performing photon counting on the received optical signal to obtain a first counting vector of MPPM symbols of multi-pulse position modulation; wherein, the optical signal is generated by driving a light source to emit light using a first time slot vector for representing the MPPM symbol; the MPPM symbol includes multiple time slots; the elements in the first counting vector represent the number of photons included in each of the time slots; Based on the number of photons represented by the elements in the first counting vector, determining pulse time slots in the multiple time slots included in the MPPM symbol to obtain a second time slot vector for representing the MPPM symbol; wherein, the elements in the second time slot vector are used to represent whether the corresponding time slot in the MPPM symbol is a pulse time slot; Performing mapping processing on the second time slot vector using a preset mapping rule to obtain bit stream data corresponding to the MPPM symbol; The MPPM symbol includes M time slots, and there are N pulse time slots in the M time slots; where N < M, and both M and N are positive integers; the first counting vector includes M elements, and the M elements correspond to the M time slots one by one; the determining pulse time slots in the multiple time slots included in the MPPM symbol based on the number of photons represented by the elements in the first counting vector includes: determining N target elements from the M elements according to the number of photons of each element in the first counting vector; taking the time slots corresponding to the target elements in the multiple time slots included in the MPPM symbol as the pulse time slots in the MPPM symbol; The determining N target elements from the M elements according to the number of photons of each element in the first counting vector includes: determining N elements whose photon numbers meet a preset number condition as the N target elements among the M elements; determining to-be-determined elements with the front photon numbers from the M elements according to the number of photons of each element in the first counting vector; where the number of the to-be-determined elements is greater than N, the to-be-determined elements include a first elements with the same photon number, and b second elements with photon numbers greater than the photon number of the first elements; if the sum of a and b is greater than N, determining c first elements randomly selected from the a first elements and the b second elements as the target elements; where c is equal to the difference between N and b.

2. A method for determining communication transmission indicators, characterized in that, The method includes: The number of erroneous time slots in the second time slot vector is determined based on the first time slot vector used to represent the MPPM symbol when transmitting a multi-pulse position modulated (MPPM) symbol and the second time slot vector used to represent the MPPM symbol after demodulation of the received optical signal. The MPPM symbol includes multiple time slots; the optical signal is generated by driving a light source to emit light using the first time slot vector; each MPPM symbol corresponds to a first counting vector; the second time slot vector is obtained by determining the pulse time slots in the MPPM symbol from among the multiple time slots included in the MPPM symbol based on the number of photons represented by the elements in the first counting vector; the elements in the second time slot vector indicate whether the corresponding time slot in the MPPM symbol is a pulse time slot; the number of erroneous time slots is the number of misjudged pulse time slots or the number of misjudged empty time slots in the second time slot vector. Determining the achievable rate of the MPPM symbol in communication transmission based on the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol includes: determining the probability of misjudgment corresponding to the number of erroneous time slots; determining the number of possible scenarios for bit errors in the MPPM symbol based on the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol; and determining the achievable rate based on the probability of misjudgment and the number of possible scenarios. The achievable rate is determined using the following formula based on the probability of misjudgment and the number of possible scenarios: Among them, the Indicates the achievable rate; The , indicating the number of possible scenarios; The Indicates the probability of a misjudgment; w represents the number of erroneous time slots; N represents the number of pulse slots in an MPPM symbol; M represents the number of time slots in an MPPM symbol; The .

3. The method according to claim 2, characterized in that, The method further includes: The symbol error rate is determined based on the probability of misjudgment and the number of possible scenarios; wherein, the symbol error rate is the total probability of symbol errors occurring during the process of the receiver receiving the optical signal.

4. The method according to claim 3, characterized in that, The false symbol rate is determined using the following formula based on the probability of false positives and the number of possible scenarios: Among them, the This represents the symbol error rate; The , indicating the number of possible scenarios; The Indicates the probability of a misjudgment; w represents the number of erroneous time slots; N represents the number of pulse slots in an MPPM symbol; M represents the number of time slots in the MPPM symbol.

5. The method according to claim 2, characterized in that, Determining the probability of misjudgment corresponding to the number of erroneous time slots includes: In the first counting vector, the pulse time slot counting vector and the space time slot counting vector are determined; Determine the first target element with the smallest number of photons in the pulse slot counting vector; The number of first elements in the space-time slot counting vector that is equal to the number of photons of the first target element is determined; The number of second elements, which is equal to the number of photons of the first target element, is determined in the pulse slot counting vector; The probability of misjudgment is determined based on the number of photons of the first target element, the number of the first element, the number of the second element, the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol.

6. The method according to claim 5, characterized in that, The step of determining the probability of misjudgment based on the number of photons of the first target element, the number of the first element, the number of the second element, the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol includes: Based on the number of photons of the first target element, the number of the second element, the number of erroneous time slots, and the number of pulse time slots in the MPPM symbol, determine the first total probability of the bit error combination corresponding to the pulse time slot counting vector; The second total probability of the bit error combination corresponding to the empty slot counting vector is determined based on the number of photons of the first target element, the number of the first element, the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol. The total number of combinations is determined based on the number of the first element and the number of the second element; wherein the total number of combinations is the total number of combinations in which all pulse slots of the second element number exist in the pulse slot counting vector, or the total number of combinations in which all empty slots of the first element number exist in the empty slot counting vector. The probability of misjudgment is determined based on the first total probability, the second total probability, and the total number of possible combinations.

7. The method according to claim 6, characterized in that, The first total probability of the error combination of the pulse slot count vector is determined using the following formula based on the number of photons of the first target element, the number of the second element, the number of erroneous time slots, and the number of pulse time slots in the MPPM symbol: Among them, the This represents the first total probability; The This represents the number of photons in the first target element; v represents the number of the second element; w represents the number of erroneous time slots; N represents the number of pulse slots in the MPPM symbol; The The number of photons among the elements indicating that the pulse slot counting vector has a bit error is equal to the number of elements indicating that the pulse slot counting vector has a bit error. The number of elements; The This represents the average number of arriving photons in the pulse slot of the MPPM symbol; The This represents the average number of arriving photons in the empty time slot of the MPPM symbol; The and the Both are probability density functions of Poisson distribution; The and the Both are cumulative distribution functions of the Poisson distribution.

8. The method according to claim 6, characterized in that, The second total probability of the bit error combination of the space slot counting vector is determined using the following formula based on the number of photons of the first target element, the number of the first elements, the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol: Among them, the This represents the second total probability; The This represents the number of photons in the first target element; u represents the number of the first element; w represents the number of erroneous time slots; N represents the number of pulse slots in the MPPM symbol; M represents the number of time slots in the MPPM symbol; The The number of photons among the elements of the space-time slot counting vector that have encountered errors is equal to the number of photons in the space-time slot counting vector. The number of elements; The This represents the average number of arriving photons in the pulse slot of the MPPM symbol; The This represents the average number of arriving photons in the empty time slot of the MPPM symbol; The and the Both are probability density functions of Poisson distribution; The and the Both are cumulative distribution functions of the Poisson distribution.

9. The method according to claim 6, characterized in that, The total number of combinations is determined using the following formula based on the number of the first element and the number of the second element: Among them, the This represents the total number of possible combinations. v represents the number of the second element; u represents the number of the first element.

10. The method according to claim 6, characterized in that, The probability of misjudgment is determined using the following formula based on the first total probability, the second total probability, and the total number of possible combinations: Among them, the Indicates the probability of a misjudgment; The This represents the number of photons in the first target element; u represents the number of the first element; v represents the number of the second element; w represents the number of erroneous time slots; N represents the number of pulse slots in the MPPM symbol; M represents the number of time slots in the MPPM symbol; The This represents the first total probability; The This represents the second total probability; The This represents the total number of possible combinations.

11. A symbol stream processing apparatus, characterized in that, The apparatus for implementing the symbol stream processing method as described in claim 1 includes: A receiving module is configured to count photons in a received optical signal to obtain a first counting vector of a multi-pulse position modulated (MPPM) symbol; wherein the optical signal is generated by driving a light source to emit light using a first time slot vector representing the MPPM symbol; the MPPM symbol includes multiple time slots; and the elements in the first counting vector represent the number of photons included in each time slot. The demodulation module is used to determine the pulse time slot in the MPPM symbol among the multiple time slots included in the MPPM symbol based on the number of photons represented by the elements in the first counting vector, so as to obtain a second time slot vector for representing the MPPM symbol; wherein, the elements in the second time slot vector are used to indicate whether the corresponding time slot in the MPPM symbol is a pulse time slot; The mapping module is used to map the second time slot vector using a preset mapping rule to obtain the bit stream data corresponding to the MPPM symbol.

12. A communication transmission index determination device, characterized in that, The apparatus for implementing the communication transmission index determination method as described in claims 2-10 includes: An error detection module is configured to determine the number of erroneous time slots in the second time slot vector based on a first time slot vector representing the MPPM symbol when transmitting a multi-pulse position modulated (MPPM) symbol and a second time slot vector representing the MPPM symbol obtained by demodulation after receiving the optical signal. The MPPM symbol includes multiple time slots; the optical signal is generated by driving a light source to emit light using the first time slot vector; each MPPM symbol corresponds to a first counting vector; the second time slot vector is obtained by determining the pulse time slots within the MPPM symbol from among the multiple time slots included in the MPPM symbol based on the number of photons represented by the elements in the first counting vector; the elements in the second time slot vector indicate whether the corresponding time slot in the MPPM symbol is a pulse time slot; and the number of erroneous time slots is the number of misjudged pulse time slots or the number of misjudged empty time slots in the second time slot vector. The rate determination module is used to determine the achievable rate of the MPPM symbol in communication transmission based on the number of erroneous time slots, the number of time slots in the MPPM symbol, and the number of pulse time slots in the MPPM symbol.

13. A computer-readable storage medium, characterized in that, It stores a computer program that, when executed by a processor, implements the symbol stream processing method as described in claim 1 or the communication transmission index determination method as described in any one of claims 2-10.

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