LDPC (Low Density Parity Check)-assisted non-orthogonal multiple access interference elimination method, receiving method, sending method and device

Abstract

The invention provides an LDPC-assisted non-orthogonal multiple access interference elimination method, receiving method, sending method and device, and relates to the technical field of transmission, and the interference elimination method comprises the steps: carrying out the continuous interference elimination of a non-orthogonal multiple access signal recovered from an optical signal, so as to obtain a large signal and a small signal, performing LDPC decoding on the large signal to obtain a decoded bit sequence; and reconstructing the large signal based on the decoding bit sequence to obtain a target large signal, and obtaining a target small signal based on the target large signal and the non-orthogonal multiple access signal. According to the invention, the noise generated by the judgment error of the large signal on the small signal can be effectively reduced in the non-orthogonal multiple access interference elimination process, the error rate of the small signal can be effectively reduced, the application performance of the small signal can be improved, and the power margin can be more reasonably utilized; and the reasonability of distributing the signals to the users can be improved to improve the user experience.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of transmission technology, in particular to an LDPC-aided non-orthogonal multiple access interference cancellation method, a receiving method, a sending method and a device. BACKGROUND

[0002] In the passive optical network downlink transmission, due to the different lengths of optical fibers from the optical line terminal to each optical network unit and the different numbers of optical splitters passed, the attenuation degrees of each link are different. However, in order to increase the number of access users, a non-orthogonal multiple access (NOMA) scheme is used, in which a small signal is superimposed on a large signal. Compared with the scheme without superimposing the small signal, a performance cost is inevitably generated, because the mutual crosstalk between the large signal and the small signal affects the performance, which leads to the fact that, compared with the power budget when the small signal is not superimposed, the power budget of the optical network unit allocated to the large signal in the NOMA or the optical network unit allocated to the small signal in the NOMA is reduced. Therefore, allocating the large signal to the far-end user with a more nervous power margin and the small signal to the near-end user with a more sufficient power margin can more reasonably utilize the power margin. However, due to the crosstalk of the large signal on the small signal, the small signal still faces the dilemma of insufficient power margin. In the traditional successive interference cancellation, the decision of the small signal is affected by the decision error of the large signal, and the performance of the small signal still has room for improvement.

[0003] Therefore, in addition to adjusting the performance of the large signal and the small signal by adjusting the power ratio between the large signal and the small signal, further improving the performance of the small signal has important practicality and practical significance. SUMMARY

[0004] In view of this, the embodiments of the present application provide an LDPC-aided non-orthogonal multiple access interference cancellation method, a receiving method, a sending method and a device to eliminate or improve one or more defects in the prior art.

[0005] A first aspect of the present application provides an LDPC-aided non-orthogonal multiple access interference cancellation method, comprising: performing successive interference cancellation on a non-orthogonal multiple access signal recovered from a self optical signal to obtain a large signal and a small signal, wherein the transmission rate of the small signal is lower than that of the large signal; performing low-density parity-check (LDPC) decoding on the large signal to obtain a decoding bit sequence corresponding to the large signal; reconstructing the large signal based on the decoding bit sequence to obtain a target large signal, and obtaining a target small signal based on the target large signal and the non-orthogonal multiple access signal.

[0006] In the embodiments of the present application, the low-density parity-check (LDPC) decoding of the large signal to obtain a decoded bit sequence corresponding to the large signal comprises: performing soft decision on the large signal to obtain a log-likelihood ratio (LLR) value of a bit sequence corresponding to the large signal; inputting the LLR value of the bit sequence into a preset LDPC decoder to enable the LDPC decoder to perform LDPC decoding on the large signal based on a number of iterations and a check equation restriction and output a decoded bit sequence corresponding to the large signal.

[0007] In the embodiments of the present application, the LDPC-aided non-orthogonal multiple access interference cancellation method further comprises: performing symbol-to-bit mapping processing on the target large signal to obtain an original large signal encoding bit sequence corresponding to the target large signal; and performing symbol-to-bit mapping processing on the target small signal to obtain an original small signal encoding bit sequence corresponding to the target small signal.

[0008] In the embodiments of the present application, before the symbol-to-bit mapping processing on the target small signal to obtain an original small signal encoding bit sequence corresponding to the target small signal, further comprising: if the signal type of the target small signal is a pulse amplitude modulation signal, performing time domain descrambling processing on the target small signal based on a random ±1 sequence; wherein the transmitting end of the optical signal performs time domain interference processing on the original small signal after sample repetition encoding based on the random ±1 sequence in advance; performing mean value decimation processing on the target small signal after the time domain descrambling processing for a preset number of times; wherein the preset number of times is the same as the number of times of sample repetition encoding of the original small signal performed by the transmitting end of the optical signal.

[0009] In the embodiments of the present application, before the symbol-to-bit mapping processing on the target small signal to obtain an original small signal encoding bit sequence corresponding to the target small signal, further comprising: if the signal type of the target small signal is a discrete multi-tone signal, performing fast Fourier transform on the target small signal; performing discrete multi-tone demodulation processing on the target small signal after the fast Fourier transform; performing frequency domain descrambling processing on the target small signal after the discrete multi-tone demodulation processing based on a random sequence; wherein the transmitting end of the optical signal performs frequency domain interference processing on the original small signal after sample repetition encoding based on the random sequence in advance. performing mean value decimation processing on the target small signal after the frequency domain descrambling processing by a preset number of times, wherein the preset number of times is the same as a number of sample repetition encoding performed on the original small signal by a transmission end of the optical signal.

[0010] A second aspect of the present application provides a signal receiving method, comprising: receiving an optical signal transmitted via an optical fiber; performing photoelectric detection, analog-to-digital conversion and resampling on the optical signal to obtain a corresponding digital signal; performing matched filtering and channel equalization processing on the digital signal to recover a non-orthogonal multiple access signal from the optical signal; obtaining the target large signal and the target small signal corresponding to the non-orthogonal multiple access signal based on the LDPC-aided non-orthogonal multiple access interference cancellation method, to obtain an original large signal encoding bit sequence corresponding to the target large signal and an original small signal encoding bit sequence corresponding to the target small signal; performing LDPC decoding processing on the original large signal encoding bit sequence and the original small signal encoding bit sequence respectively, to obtain a large signal bit sequence corresponding to the original large signal encoding bit sequence and a small signal bit sequence corresponding to the original small signal encoding bit sequence.

[0011] A third aspect of the present application provides a signal transmitting method, comprising: performing LDPC encoding processing on a large signal bit sequence and a small signal bit sequence to obtain an original large signal encoding bit sequence corresponding to the large signal bit sequence and an original small signal encoding bit sequence corresponding to the small signal bit sequence, wherein a transmission rate of the small signal bit sequence is lower than a transmission rate of the large signal bit sequence; performing bit-to-symbol mapping processing on the original large signal encoding bit sequence to obtain a target large signal corresponding to the original large signal encoding bit sequence, and performing bit-to-symbol mapping processing on the original small signal encoding bit sequence to obtain a target small signal corresponding to the original large signal encoding bit sequence; superimposing the target large signal and the target small signal to obtain a non-orthogonal multiple access signal.

[0012] performing resampling, digital-to-analog conversion and electro-optical modulation on the non-orthogonal multiple access signal to obtain an optical signal; transmitting the optical signal to a receiving end via an optical fiber, so that the receiving end performs the signal receiving method.

[0013] In some embodiments of the present application, before the bit-to-symbol mapping of the original small-signal coded bit sequence to obtain the target small-signal corresponding to the original large-signal coded bit sequence, the method further comprises: if the signal type of the original small-signal is pulse amplitude modulation signal, the original small-signal is subjected to preset number of sample repetition coding; the original small-signal subjected to the sample repetition coding is subjected to time-domain interference processing based on a random ±1 sequence.

[0014] In some embodiments of the present application, before the bit-to-symbol mapping of the original small-signal coded bit sequence to obtain the target small-signal corresponding to the original large-signal coded bit sequence, the method further comprises: if the signal type of the original small-signal is discrete multi-tone signal, the original small-signal is subjected to preset number of sample repetition coding; the original small-signal subjected to the sample repetition coding is subjected to frequency-domain interference processing based on a random sequence; the original small-signal subjected to the frequency-domain interference processing is subjected to fast Fourier transform.

[0015] A fourth aspect of the present application provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the LDPC-aided non-orthogonal multiple access interference cancellation method of the first aspect, the signal receiving method of the second aspect, or the signal sending method of the third aspect.

[0016] A fifth aspect of the present application provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program is executable by a processor to implement the LDPC-aided non-orthogonal multiple access interference cancellation method of the first aspect, the signal receiving method of the second aspect, or the signal sending method of the third aspect.

[0017] A sixth aspect of the present application provides a computer program product comprising a computer program, wherein the computer program is executable by a processor to implement the LDPC-aided non-orthogonal multiple access interference cancellation method of the first aspect, the signal receiving method of the second aspect, or the signal sending method of the third aspect.

[0018] The application provides an LDPC-assisted non-orthogonal multiple access interference cancellation method, which comprises the following steps: performing successive interference cancellation on a non-orthogonal multiple access signal recovered from a self optical signal to obtain a large signal and a small signal, wherein the transmission rate of the small signal is lower than that of the large signal; performing LDPC decoding on the large signal to obtain a decoding bit sequence corresponding to the large signal; and reconstructing the large signal based on the decoding bit sequence to obtain a target large signal, and obtaining a target small signal based on the target large signal and the non-orthogonal multiple access signal. The method can effectively reduce the noise generated by the large signal decision error on the small signal in the non-orthogonal multiple access interference cancellation process, effectively reduce the small signal error rate and improve the application performance of the small signal, can more reasonably utilize the power margin, and further can improve the rationality of signal distribution to users to improve the user experience.

[0019] Additional advantages, objects, and features of the application will be set forth in part by the description that follows, and will become apparent to those skilled in the art upon examination of the following detailed description and drawings. The objects and other advantages of the application can be realized and attained by means of the instrumentalities particularly pointed out in the description and drawings.

[0020] Those skilled in the art will appreciate that the objects and advantages of the application can be realized and attained by means of the instrumentalities and combinations particularly pointed out in the following detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description, serve to explain the principles of the application. The components in the drawings are not drawn to scale, but are merely intended to illustrate the principles of the application. For ease of illustration and description of some parts of the application, the corresponding parts in the drawings can be enlarged, i.e., can become larger than other components in the exemplary device actually manufactured according to the application. In the drawings: Figure 1 The first flowchart of the LDPC-assisted non-orthogonal multiple access interference cancellation method in an embodiment of the application.

[0022] Figure 2 The second flowchart of the LDPC-assisted non-orthogonal multiple access interference cancellation method in an embodiment of the application.

[0023] Figure 3 The execution logic diagram of step 200 in an embodiment of the application.

[0024] Figure 4 The architecture diagram of the slice LDPC decoder in an embodiment of the application.

[0025] Figure 5 The second flowchart of the LDPC-aided non-orthogonal multiple access interference cancellation method in an embodiment of the present application.

[0026] Figure 6 The flowchart of the signal receiving method in an embodiment of the present application.

[0027] Figure 7 The first flowchart of the signal sending method in an embodiment of the present application.

[0028] Figure 8 The second flowchart of the signal sending method in an embodiment of the present application.

[0029] Figure 9 The third flowchart of the signal sending method in an embodiment of the present application.

[0030] Figure 10 The flowchart of the signal transmission method in an application example of the present application.

[0031] Figure 11 The architecture diagram of the signal transmission system in an application example of the present application.

[0032] Figure 12 The architecture diagram of the downlink passive optical network non-orthogonal multiple access interference cancellation in an application example of the present application.

[0033] Figure 13 The power ratio-received optical power difference diagram of the large signal and the small signal obtained by using the successive interference cancellation, the LDPC-aided small signal obtained by using the LDPC-aided successive interference cancellation, and the power ratio-received optical power difference diagram of the large signal without superimposing the small signal when the small signal superimposed in the application example of the present application is the PAM signal and the repetition number n=8.

[0034] Figure 14 The power ratio-received optical power difference diagram of the large signal and the small signal obtained by using the successive interference cancellation, the LDPC-aided small signal obtained by using the LDPC-aided successive interference cancellation, and the power ratio-received optical power difference diagram of the large signal without superimposing the small signal when the small signal superimposed in the application example of the present application is the DMT signal and the repetition number n=8. DETAILED DESCRIPTION

[0035] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be described in further detail below with reference to the embodiments and drawings. Herein, the illustrative embodiments of the present application and their descriptions are used to explain the present application but not to limit the present application.

[0036] It should also be noted that, in order not to obscure the present application with unnecessary details, only the structures and / or processing steps closely related to the solutions according to the present application are shown in the drawings, and other details not closely related to the present application are omitted.

[0037] It should be emphasized that the terms "comprise / comprising" when used herein are to be interpreted as specifying the presence of the stated features, elements, steps or components but do not preclude the presence or addition of one or more other features, elements, steps or components.

[0038] It should also be noted that, if not specifically stated, the term "connected" herein can not only mean direct connection but also mean indirect connection in the presence of an intermediate.

[0039] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same or similar components, or the same or similar steps.

[0040] In order to solve the problem that in the existing non-orthogonal multiple access, the noise generated by the decision error of the large signal superimposed on the small signal recovered in the successive interference cancellation method is high, and the power margin required is insufficient, the embodiments of the present application respectively provide an LDPC-aided non-orthogonal multiple access interference cancellation method, a signal receiving method, a signal sending method, an entity device, a computer readable storage medium and a computer program product, the large signal and the small signal are obtained by performing successive interference cancellation on the recovered NOMA signal, and on this basis, the large signal LDPC iterative decoding is further performed to obtain a large signal coded bit sequence with lower error rate, and the more accurate large signal symbol is reconstructed from the sequence bit-symbol mapping. Since the noise generated by the decision error of the large signal in the successive interference cancellation method is superimposed on the small signal. Therefore, the LDPC-aided non-orthogonal multiple access interference cancellation method and system can reduce the noise generated by the decision error of the large signal on the small signal after the large signal LDPC iterative decoding, and the present application can achieve the effect of improving the performance of the small signal.

[0041] The embodiments will be described in detail as follows.

[0042] Based on this, the embodiments of the present application provide an LDPC-aided non-orthogonal multiple access interference cancellation method which can be implemented by an LDPC-aided non-orthogonal multiple access interference cancellation device, as shown in Figure 1 , the LDPC-aided non-orthogonal multiple access interference cancellation method specifically comprises the following contents: Step 100: performing successive interference cancellation on the recovered non-orthogonal multiple access signal in the optical signal to obtain a large signal and a small signal, wherein the transmission rate of the small signal is lower than that of the large signal.

[0043] The LDPC-assisted non-orthogonal multiple access interference cancellation device can be provided as a functional module in an electronic device currently serving as a receiving end (i.e., a signal receiving end), and can be provided according to actual application requirements.

[0044] In one or more embodiments of the present application, LDPC refers to low density parity check, which is a linear block code based on a sparse check matrix, and can also be referred to as LDPC code.

[0045] In step 100, the optical signal can be received by the electronic device currently serving as a receiving end via an optical fiber.

[0046] Step 200: performing low density parity check (LDPC) decoding on the large signal to obtain a decoding bit sequence corresponding to the large signal.

[0047] In step 200, the LDPC decoding of the NOMA signal obtains a large signal decoding bit sequence, and the received NOMA signal is separated into a large signal and a small signal. The small signal needs to be LDPC decoded as noise first, and the decoded bit sequence is reconstructed into a large signal symbol, which is subtracted from the NOMA signal to obtain the small signal.

[0048] Step 300: reconstructing the large signal based on the decoding bit sequence to obtain a corresponding target large signal, and obtaining a target small signal based on the target large signal and the non-orthogonal multiple access signal.

[0049] The specific way of reconstructing the large signal based on the decoding bit sequence to obtain a corresponding target large signal can be: performing bit-to-symbol mapping processing (which can be written as: bit-symbol mapping) on the decoding bit sequence corresponding to the large signal to obtain a corresponding target large signal.

[0050] The specific way of obtaining a target small signal based on the target large signal and the non-orthogonal multiple access signal can be: subtracting the reconstructed target large signal from the non-orthogonal multiple access signal (which can be written as: NOMA signal) to obtain an LDPC-assisted small signal, i.e., a target small signal.

[0051] As can be seen from the above description, the LDPC-aided non-orthogonal multiple access interference cancellation method provided by the embodiments of the present application can effectively reduce the noise generated by the large signal decision error on the small signal in the non-orthogonal multiple access interference cancellation process, effectively reduce the small signal error rate and improve the application performance of the small signal, can more reasonably utilize the power margin, and further can improve the rationality of signal distribution to users to improve the user experience.

[0052] In order to further improve the effectiveness and reliability of reducing the noise generated by the large signal decision error on the small signal in the LDPC-aided non-orthogonal multiple access interference cancellation, in the LDPC-aided non-orthogonal multiple access interference cancellation method provided by the embodiments of the present application, referring to Figure 2 , the step 200 in the LDPC-aided non-orthogonal multiple access interference cancellation method specifically contains the following contents: Step 210: performing soft decision on the large signal to obtain the log-likelihood ratio value of the bit sequence corresponding to the large signal; Step 220: inputting the log-likelihood ratio value of the bit sequence into a preset LDPC decoder, so that the LDPC decoder performs LDPC decoding on the large signal based on the iteration number and the check equation restriction and outputs the decoding bit sequence corresponding to the large signal.

[0053] In a preferred implementation manner of the step 220, the LDPC decoder can adopt a sliced LDPC decoder; as shown in Figure 3 , the recovered NOMA signal is sent into a sliced LDPC decoder with l times of iterative decoding after the log-likelihood ratio (LLR) is calculated through log maximum a posteriori probability (Log-MAP) estimation, and the structure of the sliced LDPC decoder is as shown in Figure 4 In the sliced LDPC decoder, the received log-likelihood ratio (LLR) value is subjected to k (k < l) times of iterative decoding and decision to obtain the error-corrected codeword, and these codewords can be directly sent to a bit-symbol mapper to regenerate the large signal without going through the LDPC encoding process. Then, the recovered NOMA signal is subtracted from the regenerated large signal to obtain the estimated small signal. Finally, the estimated small signal is subtracted from the recovered NOMA signal, thereby obtaining a more accurate large signal. After the log-likelihood ratio (LLR) value of the more accurate large signal symbol is calculated, the more accurate large signal symbol is sent into the sliced LDPC decoder again to obtain the original large signal bit sequence.

[0054] The designer of the present application finds that the calculation complexity of the successive interference cancellation algorithm is increased due to the high calculation complexity of the iteration process of the LDPC decoder. Based on this, in order to reduce the calculation complexity, in the embodiments of the present application, the iteration number k is determined. The condition for the termination of the iteration decoding process of the LDPC decoder is that the iteration number k is reached, or whether all the decoded codewords satisfy the check equation , wherein c is the decoded codeword, H is the LDPC check matrix, is a transpose operation of the matrix.

[0055] In the early stage of the iteration process, with the increase of the iteration number k, more error bits are corrected, so that more decoded codewords satisfy the check equation, and the performance of the system is improved; in the later stage of the iteration process, the number of correctable bits gradually decreases, and even if more error bits are corrected through continuous iteration, the system gain brought by the iteration correction is far less than the cost of the system complexity brought by the increase of the iteration number. That is, when about 99.8% of the decoded codewords satisfy the check equation, the iteration decoding process can be terminated in advance. At this time, although the error rate after the LDPC correction is not 0, its influence on the system performance is very small in this case. The improved method reduces the number of iteration decoding of the LDPC in the successive interference cancellation process, so that the small signal performance is improved while the complexity of the non-orthogonal multiple access interference cancellation assisted by the LDPC is reduced.

[0056] In order to further improve the effectiveness and applicability of the non-orthogonal multiple access interference cancellation assisted by the LDPC, in an LDPC-assisted non-orthogonal multiple access interference cancellation method provided in an embodiment of the present application, referring to Figure 2 , the LDPC-assisted non-orthogonal multiple access interference cancellation method further comprises the following steps after step 300: Step 400: performing symbol-to-bit mapping processing on the target large signal to obtain the original large signal coding bit sequence corresponding to the target large signal.

[0057] Step 500: performing symbol-to-bit mapping processing on the target small signal to obtain the original small signal coding bit sequence corresponding to the target small signal.

[0058] In order to further improve the effectiveness and reliability of the symbol-to-bit mapping processing on the target small signal, in an LDPC-assisted non-orthogonal multiple access interference cancellation method provided in an embodiment of the present application, referring to Figure 5 , the LDPC-assisted non-orthogonal multiple access interference cancellation method further comprises the following steps after step 300 and before step 500: Step 010: if the signal type of the target small signal is a pulse amplitude modulation signal, performing time domain descrambling processing on the target small signal based on a random ±1 sequence; wherein the sending end of the optical signal performs time domain interference processing on the original small signal after sample repetition coding based on the random ±1 sequence in advance.

[0059] Step 020: performing mean down-sampling processing on the target small signal after the time domain descrambling processing for a preset number of times; wherein the preset number of times is the same as the number of times of sample repetition coding of the original small signal by the sending end of the optical signal.

[0060] Wherein, the random ±1 sequence refers to a ±1 sequence in which the number and position of +1 and -1 are random.

[0061] Specifically, at the sending end, the original small signal is repeatedly sample repetition coded n times to the same data length as the original large signal. Assuming that n = 3, the data length of the original large signal is 12, and the original small signal is [+1, -1, -1, +1], then the small signal after n times of sample repetition coding is [+1, +1, +1, -1, -1, -1, -1, -1, -1, +1, +1, +1], and the data length is 12, which is the same as the data length of the original large signal. Wherein, n is the multiple of the original large signal rate and the original small signal rate , that is . The small signal after n times of sample repetition coding is multiplied by a random ±1 sequence with the same data length as the small signal to perform time domain interference processing. Therefore, the target small signal at the receiving end is multiplied by the same random ±1 sequence as the sending end to perform time domain descrambling processing, and then the target small signal after time domain descrambling is subjected to n times of mean down-sampling processing. Assuming that the target small signal after time domain descrambling is , the mean down-sampling processing is performed on every n = 3 small signals to obtain , that is , , , .

[0062] In one or more embodiments of the present application, sample repetition coding refers to n times of repetition coding of the original small signal to achieve n times of improvement of the sampling rate, n is an integer, for example, n = 3. For example: the original small signal [+1, -1, -1, +1] is repeatedly coded 3 times to become [+1, +1, +1, -1, -1, -1, -1, -1, -1, +1, +1, +1].

[0063] In one or more embodiments of the present application, the mean down-sampling is the inverse process of the sample repetition encoding, and in decoding, the mean value is calculated by every n consecutive samples to recover the original data (i.e. small signal), which can also be referred to as moving average decoding or average down-sampling per symbol mentioned later. In an example, the sample repetition encoded data can be divided into groups of 3 in sequence, and then the arithmetic mean value is taken for each group to obtain the original small signal.

[0064] Furthermore, in order to further improve the effectiveness and reliability of the symbol-to-bit mapping processing of the target small signal, in an embodiment of the present application, an LDPC assisted non-orthogonal multiple access interference cancellation method is provided, which is described below with reference to Figure 5 The LDPC assisted non-orthogonal multiple access interference cancellation method further comprises the following steps after step 300 and before step 500: Step 030: If the signal type of the target small signal is a discrete multi-tone signal, performing fast Fourier transform on the target small signal; Step 040: performing discrete multi-tone demodulation processing on the target small signal after the fast Fourier transform; Step 050: performing frequency domain descrambling processing on the target small signal after the discrete multi-tone demodulation processing based on a random sequence; wherein the transmitting end of the optical signal performs frequency domain interference processing on the original small signal after sample repetition encoding based on the random sequence in advance; Step 060: performing mean down-sampling processing on the target small signal after the frequency domain descrambling processing for a preset number of times; wherein the preset number of times is the same as the number of times of sample repetition encoding of the original small signal by the transmitting end of the optical signal.

[0065] The random sequence refers to a sequence whose number and position are random. , , ,

[0066] Specifically, at the transmitting end, the original small signal is repeatedly sample repetition encoded n times to the same data length as the original large signal. Assuming n = 3 and the data length of the original large signal is 12, the original small signal is [+1, -1, -1, +1], then the small signal after n times of sample repetition encoding is [+1, +1, +1, -1, -1, -1, -1, -1, -1, +1, +1, +1], and the data length is 12, which is the same as the data length of the original large signal. The n is a multiple of the rate of the original large signal and the rate of the original small signal , that is​ The small signal, after being repeatedly encoded from n samples, is multiplied by a random number of the same length as the small signal data. The sequence undergoes frequency domain interference processing. Therefore, at the receiving end, the target small signal is multiplied by the same random number as at the transmitting end. The sequence is descrambled in the frequency domain, and then the target small signal after frequency descrambling is downsampled n times by mean. Assume the target small signal after time descrambling is... After performing mean downsampling on every n=3 small signals, we obtain ,Right now , , , .

[0067] Based on the LDPC-assisted nonorthogonal multiple access interference cancellation method provided in the above embodiments, this application also provides a signal receiving method that can be executed by an electronic device currently acting as a receiving end. See [link to relevant documentation]. Figure 6 The signal receiving method specifically includes the following: Step 11: Receive the optical signal transmitted through the optical fiber; Step 12: Perform photoelectric detection, analog-to-digital conversion, and resampling on the optical signal to obtain the corresponding digital signal; Step 13: Perform matched filtering and channel equalization on the digital signal to recover the non-orthogonal multiple access signal from the optical signal; Step 14: Based on the LDPC-assisted non-orthogonal multiple access interference cancellation method, obtain the target large signal and the target small signal corresponding to the non-orthogonal multiple access signal, so as to obtain the original large signal coded bit sequence corresponding to the target large signal and the original small signal coded bit sequence corresponding to the target small signal; Step 15: Perform LDPC decoding on the original large-signal encoded bit sequence and the original small-signal encoded bit sequence respectively to obtain the large-signal bit sequence corresponding to the original large-signal encoded bit sequence and the small-signal bit sequence corresponding to the original small-signal encoded bit sequence.

[0068] The LDPC-assisted non-orthogonal multiple access interference cancellation method described in step 14 of the signal receiving method provided in this application can be specifically implemented based on the processing flow of the LDPC-assisted non-orthogonal multiple access interference cancellation method in the above embodiments. The flow will not be repeated here, but can be referred to the detailed description of the above embodiments of the LDPC-assisted non-orthogonal multiple access interference cancellation method.

[0069] As can be seen from the above description, the signal receiving method provided by the embodiment of the present application can effectively reduce the noise generated by the large signal decision error on the small signal in the non-orthogonal multiple access interference cancellation process, effectively reduce the small signal error rate and improve the application performance of the small signal, can more reasonably utilize the power margin, and further can improve the rationality of signal distribution to users to improve the user experience.

[0070] Based on the LDPC-aided non-orthogonal multiple access interference cancellation method and / or the signal receiving method provided by the above embodiment, the present application further provides a signal sending method which can be executed by the electronic device currently as a sending end (i.e. a signal sending end), referring to Figure 7 , the signal sending method specifically contains the following contents: Step 01: LDPC encoding processing is performed on the large signal bit sequence and the small signal bit sequence to obtain an original large signal encoding bit sequence corresponding to the large signal bit sequence and an original small signal encoding bit sequence corresponding to the small signal bit sequence, wherein the transmission rate of the small signal bit sequence is lower than that of the large signal bit sequence.

[0071] Step 02: Bit-to-symbol mapping processing is performed on the original large signal encoding bit sequence to obtain a target large signal corresponding to the original large signal encoding bit sequence.

[0072] And, Step 03: Bit-to-symbol mapping processing is performed on the original small signal encoding bit sequence to obtain a target small signal corresponding to the original large signal encoding bit sequence.

[0073] Step 04: Superposition is performed on the target large signal and the target small signal to obtain a non-orthogonal multiple access signal.

[0074] Specifically, the implementation process of Step 04 can be: multiplying the target small signal symbol by the amplitude to obtain a small signal symbol satisfying the large signal power to small signal power ratio PR, the amplitude is calculated by the formula , the large signal and the small signal adjusted to the target power ratio are superposed to obtain the non-orthogonal multiple access signal.

[0075] Step 05: Resampling, digital-to-analog conversion and electro-optical modulation are performed on the non-orthogonal multiple access signal to obtain an optical signal.

[0076] Step 06: The optical signal is transmitted to a receiving end via an optical fiber, so that the receiving end executes the signal receiving method.

[0077] In order to further improve the effectiveness and reliability of the subsequent receiving end in the LDPC-assisted non-orthogonal multiple access interference cancellation, in the signal sending method, referring to Figure 8 , the signal sending method further comprises the following steps after step 01 and before step 03: Step 031: If the signal type of the original small signal is a pulse amplitude modulation signal, the original small signal is subjected to preset times of sample repetition coding.

[0078] Step 032: Based on a random ±1 sequence, the original small signal subjected to the sample repetition coding is subjected to time domain interference processing.

[0079] In order to further improve the effectiveness and reliability of the subsequent receiving end in the LDPC-assisted non-orthogonal multiple access interference cancellation, in the signal sending method, referring to Figure 9 , the signal sending method further comprises the following steps after step 01 and before step 03: Step 033: If the signal type of the original small signal is a discrete multi-tone signal, the original small signal is subjected to preset times of sample repetition coding. Step 034: Based on a random sequence, the original small signal subjected to the sample repetition coding is subjected to frequency domain interference processing. Step 035: The original small signal subjected to the frequency domain interference processing is subjected to fast Fourier transform.

[0080] In order to further illustrate the above-mentioned embodiments of the LDPC-assisted non-orthogonal multiple access interference cancellation method, the signal receiving method and the signal sending method, the application further provides a specific application example of a signal transmission method, referring to Figure 10 , the signal transmission method comprises the following steps: S1: LDPC encoding is performed on a large signal bit sequence and a small signal bit sequence to obtain an original large signal coding bit sequence and an original small signal coding bit sequence.

[0081] S2: Bit-symbol mapping is performed on the large signal coding bit sequence and the small signal coding bit sequence to obtain a large signal symbol (i.e. a target large signal) and a small signal symbol (i.e. a target small signal). In order to enable the target small signal of different rates to be superimposed with the target large signal in the time domain, the target small signal needs to be subjected to n times of repetition coding. In S2, when the small signal is a pulse amplitude modulation (PAM) signal, a group of random ±1 sequences is multiplied with the PAM signal to perform time domain scrambling on the PAM signal.

[0082] In S2, when the small signal is a Discrete multi-tone (DMT) signal, a set of random sequences are multiplied with a Quadrature amplitude modulation (QAM) signal to perform frequency domain scrambling on the QAM signal. The QAM signal subjected to the frequency domain scrambling is subjected to DMT modulation to obtain a DMT signal, and a fast inverse Fourier transform is performed to obtain a time domain small signal.

[0083] S3, superimposed coding of the large signal symbol and the small signal symbol to obtain a NOMA signal, including the following steps S3-1 and S3-2: S3-1, multiplying the small signal symbol output by S2 by an amplitude to obtain a small signal symbol satisfying a large signal power to small signal power ratio PR, and the amplitude is calculated by the formula . S3-2, superimposing the large signal symbol output by S2 and the small signal symbol output by step S3-1 and performing shaping filtering to obtain a digital NOMA signal to be transmitted; S4, resampling, digital-to-analog conversion and electro-optical modulation are performed on the digital signal output by S3-2 to obtain an optical signal, and finally optical fiber transmission is performed, and the optical signal is used for receiving and recovering the original large signal bit sequence and the original small signal bit sequence at the receiving end; S5, optoelectronic detection, analog-to-digital conversion and resampling are performed on the received optical signal subjected to optical fiber transmission to obtain a digital signal; S6, channel equalization is performed on the S5 digital signal after matched filtering to obtain a recovered NOMA signal; S7, the large signal and the small signal are obtained from the S6 recovered NOMA signal through successive interference cancellation, that is, the large signal is obtained by performing hard decision on the NOMA signal, and the small signal is further obtained by subtracting the large signal from the NOMA signal; S8, the LDPC-aided small signal is obtained from the S6 recovered NOMA signal and the step S7 large signal through LDPC-aided successive interference cancellation, including the following steps S8-1 to S8-3: S8-1, soft decision is performed on the S7 large signal to obtain a log-likelihood ratio value corresponding to the bit sequence, which is input into an LDPC decoder for a small number of times of iterative LDPC decoding to obtain a large signal decoding bit sequence; S8-2, bit-to-symbol mapping is performed on the S8-1 large signal decoding bit sequence to reconstruct the large signal with the aid of LDPC; S8-3, the LDPC-aided reconstructed large signal obtained by step S8-2 is subtracted from the step S6 recovered NOMA signal to obtain an LDPC-aided small signal. S9, symbol-bit mapping is performed on the LDPC-assisted small signal obtained in step S8-3 and the large signal in step S7 to obtain an original large signal coded bit sequence and an original small signal coded bit sequence; In S9, when the LDPC-assisted small signal is a PAM signal, before symbol-bit mapping, the n times repeated coded small signal is divided into groups of n in sequence, and then the average of each group is taken for mean down-sampling to 1 sample per symbol, and then multiplied by the same random ±1 sequence as the sending end to perform time domain descrambling on the PAM signal. It is assumed that the target small signal after time domain descrambling is After mean down-sampling processing of every n=3 small signals, the following is obtained That is , , , .

[0084] In S9, when the LDPC-assisted small signal is a DMT signal, before symbol-bit mapping, the small signal is subjected to fast Fourier transform to obtain a frequency domain signal, and then DMT demodulation is performed on the DMT signal to obtain a QAM signal repeated n times, and then n times average is taken to reduce to 1 sample per symbol, and then multiplied by the same random ±1 sequence as the sending end to perform frequency domain descrambling on the QAM signal.

[0085] That is, the application application instance discloses a low density parity check (Low density parity check, LDPC) assisted non-orthogonal multiple access (Non-orthogonal multiple access, NOMA) interference cancellation method and system, which obtains a large signal and a small signal through bit-symbol mapping after LDPC encoding of a large signal bit sequence and a small signal bit sequence at a sending end, and obtains a NOMA signal by superimposing and encoding the large signal and the small signal after scrambling and adjusting the power ratio of the small signal. The NOMA signal recovered at the receiving end is preliminarily obtained by continuous interference cancellation to obtain a large signal and a small signal, and the large signal is further obtained by LDPC iterative decoding to obtain a large signal coded bit sequence with a lower bit error rate. The more accurate large signal symbol is reconstructed by bit-symbol mapping of the sequence. Since the noise caused by the decision error of the large signal in the continuous interference cancellation is superimposed on the small signal, the LDPC-assisted non-orthogonal multiple access interference cancellation method and system can reduce the noise caused by the decision error of the large signal on the small signal, and the application can improve the performance of the small signal.

[0086] ​This application also provides a signal transmission system to eliminate the interference of large-signal decision errors on small-signal decision-making, thereby improving the performance of small signals in NOMA; see [link to application example]. Figure 11 The transmitting end of this signal transmission system specifically includes: (1) NOMA signal generation unit, which is used to generate NOMA signals encoded by LDPC; (2) Digital-to-analog converter, used to convert signals from digital to analog; (3) Electro-optic modulator, used to electro-optically modulate the analog electrical signal output by the digital-to-analog converter to obtain the optical signal to be transmitted through the optical fiber. The optical signal is used by the receiving end to receive and recover the original coded bit sequence. The NOMA signal generation unit includes: (1.1) LDPC encoding subunit, used to perform LDPC encoding on large signal bit sequences and small signal bit sequences to obtain large signal encoded bit sequences and small signal encoded bit sequences; (1.2) Bit-symbol mapping subunit, used to perform bit-symbol mapping on large signal coded bit sequence and small signal coded bit sequence to obtain large signal symbol and small signal symbol; (1.3) Superposition coding subunit, used to multiply the amplitude of a small signal that has been repeated and scrambled n times. The power ratio between the large signal and the small signal is then adjusted. The large signal and the small signal are superimposed to obtain the NOMA signal, which is then shaped and filtered to obtain the digital signal to be transmitted.

[0087] See Figure 11 The receiving end of this signal transmission system specifically includes: (1) Photodetector, used to photodetect the optical signal from the transmitting end after it has been transmitted through optical fiber, and obtain an analog electrical signal; (2) Analog-to-digital converter, used to convert analog electrical signals into digital signals; (3) NOMA signal recovery unit, used to recover the original large-signal coded bit sequence and the original small-signal coded bit sequence from the NOMA signal: The NOMA signal recovery unit includes: (3.1) Channel equalization subunit, used to perform matched filtering on digital signals to obtain matched filtered signals, and then channel equalization on matched filtered signals to obtain recovered NOMA signals; (3.2) Continuous interference cancellation subunit, used to cancel continuous interference from the recovered NOMA signal. First, a hard decision is made on the recovered NOMA signal to obtain a large signal. Then, the large signal obtained by the hard decision is subtracted from the recovered NOMA signal to obtain a small signal. (3.3) LDPC-aided successive interference cancellation subunit, for sending the log-likelihood ratio value corresponding to the bit sequence obtained by symbol-to-bit mapping of the large signal obtained by successive interference cancellation into an LDPC decoder for LDPC decoding to obtain a large signal decoding bit sequence, bit-to-symbol mapping again to obtain an LDPC-aided reconstructed large signal, and subtracting the LDPC-aided reconstructed large signal from the recovered NOMA signal by successive interference cancellation to obtain an LDPC-aided small signal; (3.4) symbol-to-bit mapping subunit, for symbol-to-bit mapping of the large signal and the LDPC-aided small signal to obtain an original large signal encoding bit sequence and an original small signal encoding bit sequence.

[0088] The above is the basic implementation of the application example two, which can be further optimized, improved and limited on the basis of the basic implementation: When the small signal is a PAM signal, the small signal is obtained by repeating the PAM signal obtained by bit-to-symbol mapping of the small signal encoding bit sequence n times and multiplying it by a random ±1 sequence for time domain scrambling. Before corresponding small signal symbol-to-bit mapping, the corresponding random ±1 sequence is multiplied for time domain descrambling, and then each group of n repeated small signal symbols is divided in order, and then the arithmetic mean of each group is taken for mean down-sampling to 1 sample per symbol.

[0089] When the small signal is a DMT signal, the small signal is first obtained by repeating the QAM signal obtained by bit-to-symbol mapping of the small signal encoding bit sequence n times and multiplying it by a random sequence for frequency domain scrambling to obtain a DMT signal, and then performing inverse fast Fourier transform to obtain a time domain small signal. Before corresponding small signal symbol-to-bit mapping, the DMT signal is first fast Fourier transformed to the frequency domain, then demodulated by discrete multi-tone to obtain n times repeated QAM signals, multiplied by the corresponding random sequence for frequency domain descrambling, then divided into groups of n in order, and then the arithmetic mean of each group is taken for mean down-sampling to 1 sample per symbol.

[0090] The above application example one uses a certain PAM signal as a small signal for testing, and the test process and test results are also applicable to the low-density parity-check-aided non-orthogonal multiple access interference cancellation system of the application example, which will not be repeated here.

[0091] The above application example one uses a certain DMT signal as a small signal for testing, and the test process and test results are also applicable to the low-density parity-check-aided non-orthogonal multiple access interference cancellation system of the application example, which will not be repeated here.

[0092] The application example adopts the LDPC-aided successive interference cancellation technology, performs LDPC iterative decoding on the large signal recovered from the NOMA signal by the successive interference cancellation technology, reconstructs a more accurate large signal to reduce noise generated by large signal decision errors, and performs the successive interference cancellation technology again on the small signal, so that the noise generated by the superimposed large signal decision errors is smaller, the small signal error rate is lower, the performance of the small signal is improved, and the performance cost of the small signal is reduced.

[0093] The following takes a certain PAM signal as the small signal to test and illustrate the technical effect difference between the application example and the traditional non-orthogonal multiple access interference cancellation scheme. The traditional non-orthogonal multiple access interference cancellation scheme is as follows: after steps S1 to S7 are completed, step S8 is skipped, and step S9 is performed, and the large signal and the small signal obtained in step S7 are directly subjected to symbol-bit mapping to obtain the original large signal encoding bit sequence and the original small signal encoding bit sequence.

[0094] Figure 12 The figure shows a downlink passive optical network non-orthogonal multiple access interference cancellation architecture diagram, which shows that the optical line terminal obtains a transmitted NOMA signal, that is, a large signal with an amplitude of ±1 and a small signal with an amplitude of ± The transmitted NOMA signal is transmitted through an optical fiber and an optical splitter, and a near-end user recovers the small signal with an amplitude of ± from the NOMA signal, and a far-end user recovers the large signal with an amplitude of ±1 from the NOMA signal.

[0095] Figure 13 The figure shows the power ratio-received optical power difference value diagram of the large signal and the small signal obtained by using the successive interference cancellation, and the LDPC-aided small signal obtained by using the LDPC-aided successive interference cancellation when the small signal repetition number n is 8, as shown in Figure 13 It can be seen that: When the power ratio of the large signal and the small signal at the transmitting end is 9 dB, there is a 1.4 dB received optical power difference between the small signal obtained by using the LDPC-aided successive interference cancellation and the small signal obtained by using the successive interference cancellation, and the received optical power difference, that is, the performance cost, is the difference in received optical power required for the error rate of the NOMA signal superimposed with the small signal to reach the 20% soft decision forward error correction threshold and the error rate of the NOMA signal without superimposing the small signal under the same channel condition. It is illustrated that the application example has great advantages in reducing the performance cost of the small signal in the non-orthogonal multiple access signal. The system error rate curve illustrates that the above system is indeed feasible.

[0096] The following takes a certain DMT signal as the small signal to test and illustrate the technical effect difference between the application example and the traditional non-orthogonal multiple access interference cancellation scheme. The traditional non-orthogonal multiple access interference cancellation scheme is: after completing steps S1 to S7, skipping step S8, performing step S9, and directly performing symbol-bit mapping on the large signal and the small signal obtained in step S7 to obtain the original large signal encoding bit sequence and the original small signal encoding bit sequence.

[0097] Figure 14 The power ratio-small signal power difference value diagram when the small signal repetition number n=8 is shown, using the large signal and the small signal obtained by successive interference cancellation and the LDPC-aided small signal obtained by LDPC-aided successive interference cancellation, and without superimposing the small signal, as shown in Figure 14 It can be seen that: When the power ratio of the large signal to the small signal at the sending end is 9dB, there is a 1.9dB difference in received optical power between the small signal obtained by using LDPC-aided successive interference cancellation and the small signal obtained by using successive interference cancellation, and the difference in received optical power, i.e. the performance cost, is the difference in received optical power required for the bit error rate of the NOMA signal with the large signal superimposed on the small signal to reach the 20% soft decision forward error correction threshold under the same channel conditions without superimposing the small signal. It is explained that the application example has great advantages in reducing the performance cost of the small signal in the non-orthogonal multiple access signal. The system bit error rate curve shows that the above system is indeed feasible.

[0098] Therefore, the results shown by Figure 13 and Figure 14 can prove that the LDPC-aided non-orthogonal multiple access interference cancellation method of the application example can effectively improve the performance of the small signal in the non-orthogonal multiple access signal.

[0099] The above tests prove that the LDPC-aided non-orthogonal multiple access interference cancellation method of the application example can reduce the performance cost of the small signal in the non-orthogonal multiple access signal. Therefore, the encoding of the LDPC-based encoder and the iterative decoding of the decoder of the application example can reduce the bit error rate of the large signal in the non-orthogonal multiple access signal, thereby reducing the decision noise generated by the large signal due to the decision error of the small signal superimposed in the non-orthogonal multiple access signal, which is beneficial to reduce the bit error rate of the small signal. Therefore, the LDPC-aided non-orthogonal multiple access interference cancellation method of the application example can reduce the decision error of the large signal, and further reduce the bit error rate of the small signal.

[0100] The electronic device can include a processor, a memory, a receiver and a transmitter. The processor is configured to perform the LDPC-aided non-orthogonal multiple access interference cancellation method, the signal receiving method or the signal transmitting method mentioned in the embodiments. The processor and the memory can be connected by a bus or other means. The receiver can be connected to the processor and the memory by wired or wireless means.

[0101] The processor can be a central processing unit (CPU). The processor can also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or a combination thereof.

[0102] The memory is a non-transitory computer-readable storage medium, which can be used to store non-transitory software programs, non-transitory computer-executable programs and modules, such as program instructions / modules corresponding to the LDPC-aided non-orthogonal multiple access interference cancellation method in the embodiments. The processor executes various functions and data processing of the processor by running the non-transitory software programs, instructions and modules stored in the memory, i.e. implements the LDPC-aided non-orthogonal multiple access interference cancellation method, the signal receiving method or the signal transmitting method in the above method embodiments.

[0103] The memory can include a program storage area and a data storage area. The program storage area can store an operating system and at least one application required by a function. The data storage area can store data created by the processor and the like. In addition, the memory can include a high-speed random access memory, and can also include a non-transitory memory, such as at least one magnetic disk storage device, a flash memory device, or other non-transitory solid-state memory device. In some embodiments, the memory can optionally include a memory remotely arranged with respect to the processor, which can be connected to the processor through a network. Examples of the network include but are not limited to the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof.

[0104] The one or more modules are stored in the memory and executed by the processor to perform the LDPC-aided non-orthogonal multiple access interference cancellation method, the signal receiving method or the signal transmitting method in the embodiments.

[0105] In some embodiments of the present application, the user equipment can include a processor, a memory, and a transceiver which can include a receiver and a transmitter, the processor, the memory, the receiver and the transmitter can be connected through a bus system, the memory is used to store computer instructions, and the processor is used to execute the computer instructions stored in the memory to control the transceiver to transceive signals.

[0106] As an implementation manner, the functions of the receiver and the transmitter in the present application can be implemented by a transceiving circuit or a transceiving dedicated chip, and the processor can be implemented by a dedicated processing chip, a processing circuit or a general-purpose chip.

[0107] As another implementation manner, the server provided by the embodiments of the present application can be implemented by using a general-purpose computer. That is, the program codes for implementing the functions of the processor, the receiver and the transmitter are stored in the memory, and the general-purpose processor implements the functions of the processor, the receiver and the transmitter by executing the codes in the memory.

[0108] The embodiments of the present application further provide a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the steps of the aforementioned LDPC-aided non-orthogonal multiple access interference cancellation method, signal receiving method or signal sending method. The computer readable storage medium can be a tangible storage medium, such as a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a floppy disk, a hard disk, a removable storage disk, a CD-ROM, or any other form of storage medium known in the technical field.

[0109] The embodiments of the present application further provide a computer program product, which includes a computer program, and the computer program is executed by a processor to implement the steps of the aforementioned LDPC-aided non-orthogonal multiple access interference cancellation method, signal receiving method or signal sending method.

[0110] Those skilled in the art should understand that the exemplary components, systems and methods described in connection with the embodiments disclosed herein can be implemented in hardware, software or a combination thereof. The actual implementation depends on the specific application and design constraints imposed on the overall system. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application. When implemented in hardware, it can be, for example, an electronic circuit, an application specific integrated circuit (ASIC), appropriate firmware, a plug-in, a functional card, etc. When implemented in software, the elements of the present application are program or code segments used to perform the required tasks. The program or code segments can be stored in a machine readable medium or transmitted through a data signal carried in a carrier wave in a transmission medium or communication link.

[0111] It is to be understood that the application is not limited to particular configurations and processes described herein and shown in the drawings, which can vary. For the sake of brevity and clarity, detailed descriptions of well-known methods and apparatuses will not be repeated. In the above embodiments, several specific steps are described and / or illustrated as examples. However, the method processes of the present application are not limited to the specific steps described and / or illustrated, and the order of the steps can be changed, and various changes, modifications and additions can be made thereto without departing from the spirit and scope of the application.

[0112] In this application, features described and / or illustrated with respect to one embodiment can be used in the same or similar manner in one or more other embodiments and / or combined with or substituted for features of other embodiments.

[0113] The above description is merely illustrative of the application, and is not intended to limit the scope of the application. Various modifications and changes can be made by persons of ordinary skill in the art, which should be included in the scope of the application as defined by the following claims.

Claims

1. A method for LDPC-aided non-orthogonal multiple access interference cancellation, the method comprising: include: Continuous interference cancellation is performed on the non-orthogonal multiple access signal recovered from the optical signal to obtain a large signal and a small signal, wherein the transmission rate of the small signal is lower than the transmission rate of the large signal. The large signal is subjected to low-density parity-check (LDPC) decoding to obtain the decoded bit sequence corresponding to the large signal. The large signal is reconstructed based on the decoded bit sequence to obtain the corresponding target large signal, and the target small signal is obtained based on the target large signal and the non-orthogonal multiple access signal.

2. The LDPC-assisted non-orthogonal multiple access interference cancellation method according to claim 1, characterized in that, The step of performing low-density parity-check (LDPC) decoding on the large signal to obtain the decoded bit sequence corresponding to the large signal includes: A soft decision is performed on the large signal to obtain the log-likelihood ratio of the bit sequence corresponding to the large signal; The log-likelihood ratio of the bit sequence is input into a preset LDPC decoder, so that the LDPC decoder performs LDPC decoding on the large signal based on the number of iterations and the check equation constraint, and outputs the decoded bit sequence corresponding to the large signal.

3. The LDPC-assisted non-orthogonal multiple access interference cancellation method according to claim 1, characterized in that, Also includes: The target large signal is subjected to symbol-to-bit mapping processing to obtain the original large signal encoded bit sequence corresponding to the target large signal; Furthermore, the target small signal is subjected to symbol-to-bit mapping processing to obtain the original small signal encoded bit sequence corresponding to the target small signal.

4. The LDPC-assisted non-orthogonal multiple access interference cancellation method according to claim 3, characterized in that, Before performing symbol-to-bit mapping on the target small signal to obtain the original small signal encoded bit sequence corresponding to the target small signal, the method further includes: If the target small signal is a pulse amplitude modulation signal, then the target small signal is descrambled in the time domain based on a random ±1 sequence; wherein, the transmitting end of the optical signal pre-processes the original small signal after sample repetition encoding with time domain interference based on the random ±1 sequence; The target small signal after the time-domain descrambling process is subjected to a preset number of mean downsampling processes; wherein the preset number of times is the same as the number of times the optical signal transmitter performs sample re-encoding on the original small signal.

5. The LDPC-assisted non-orthogonal multiple access interference cancellation method according to claim 3, characterized in that, Before performing symbol-to-bit mapping on the target small signal to obtain the original small signal encoded bit sequence corresponding to the target small signal, the method further includes: If the target small signal is a discrete multi-tone signal, then perform a fast Fourier transform on the target small signal; Discrete multitone demodulation processing is performed on the target small signal after the fast Fourier transform; Based on randomness The sequence will undergo frequency domain descrambling processing on the target small signal after the discrete multi-tone demodulation process; wherein, the transmitting end of the optical signal pre-based on the random... The sequence performs frequency domain interference processing on the original small signal after sample repetition encoding; The target small signal after frequency domain descrambling is subjected to a preset number of mean downsampling operations; wherein the preset number of operations is the same as the number of times the optical signal transmitter performs sample re-encoding on the original small signal.

6. A signal receiving method, characterized in that, include: Receive optical signals transmitted via optical fiber; The optical signal is subjected to photoelectric detection, analog-to-digital conversion, and resampling to obtain the corresponding digital signal; The digital signal is subjected to matched filtering and channel equalization to recover the non-orthogonal multiple access signal from the optical signal; Based on the LDPC-assisted non-orthogonal multiple access interference cancellation method as described in any one of claims 1 to 5, the target large signal and the target small signal corresponding to the non-orthogonal multiple access signal are obtained, so as to obtain the original large signal coded bit sequence corresponding to the target large signal and the original small signal coded bit sequence corresponding to the target small signal; The original large-signal encoded bit sequence and the original small-signal encoded bit sequence are subjected to LDPC decoding to obtain the large-signal bit sequence corresponding to the original large-signal encoded bit sequence and the small-signal bit sequence corresponding to the original small-signal encoded bit sequence.

7. A signal transmission method, characterized in that, include: LDPC encoding is performed on the large signal bit sequence and the small signal bit sequence to obtain the original large signal encoded bit sequence corresponding to the large signal bit sequence and the original small signal encoded bit sequence corresponding to the small signal bit sequence, wherein the transmission rate of the small signal bit sequence is lower than the transmission rate of the large signal bit sequence. The original large signal encoded bit sequence is subjected to bit-to-symbol mapping to obtain the target large signal corresponding to the original large signal encoded bit sequence; and the original small signal encoded bit sequence is subjected to bit-to-symbol mapping to obtain the target small signal corresponding to the original large signal encoded bit sequence. The target large signal and the target small signal are superimposed to obtain a non-orthogonal multiple access signal; The non-orthogonal multiple access signal is resampled, converted from digital to analog, and electro-optically modulated to obtain an optical signal; The optical signal is transmitted to the receiving end via an optical fiber, so that the receiving end performs the signal receiving method as described in claim 6.

8. The signal transmission method according to claim 7, characterized in that, Before performing bit-to-symbol mapping on the original small-signal encoded bit sequence to obtain the target small signal corresponding to the original large-signal encoded bit sequence, the method further includes: If the original small signal is a pulse amplitude modulation signal, then the original small signal is subjected to sample repetition encoding for a preset number of times; Based on a random ±1 sequence, the original small signal after repeated encoding of the sample is subjected to time-domain interference processing.

9. The signal transmission method according to claim 7, characterized in that, Before performing bit-to-symbol mapping on the original small-signal encoded bit sequence to obtain the target small signal corresponding to the original large-signal encoded bit sequence, the method further includes: If the original small signal is a discrete polyphonic signal, then the original small signal is subjected to sample repetition encoding for a preset number of times; Based on randomness The sequence is subjected to frequency domain interference processing on the original small signal after repeated encoding of the sample; A fast Fourier transform is performed on the original small signal after the frequency domain interference processing.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the LDPC-assisted nonorthogonal multiple access interference cancellation method as described in any one of claims 1 to 5, the signal receiving method as described in claim 6, or the signal transmitting method as described in any one of claims 7 to 9.

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