Multi-user signal processing method for low-orbit satellite communication

Abstract

The invention belongs to the related technical field of wireless communication, and particularly relates to a low-orbit satellite communication multi-user signal processing method, which comprises the following steps of: acquiring a pre-compensated digital domain mixed signal y; according to a preset user sequence, the standard symbol sets of the N users corresponding to y are combined and arranged into a combined symbol set of N user combined signals s; traversing and calculating the likelihood probability of all kinds of combined symbols corresponding to each element in y; according to all the likelihood probabilities and the prior probability of each user subjected to iterative feedback updating, calculating the posterior probabilities that all the emission bits of the emission signal xn of the user n in the mixed signal y are 0 in the current iteration; carrying out de-interleaving and channel decoding on the posterior probability vector corresponding to each user obtained by current iteration; if iteration is terminated, judging and outputting the probability after channel decoding; otherwise, the probability after channel decoding is used as the new prior probability of the user for repeated iteration. According to the invention, the demodulation bit error rate performance is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field related to wireless communications, and more specifically, relates to a multi-user signal processing method for low-orbit satellite communications. Background Art

[0002] Low-orbit satellites are developing rapidly due to their advantages such as low orbital altitude, low construction cost, low power consumption, and short propagation delay. According to the ITU satellite system rules and my country's satellite-ground integrated network planning, it is an inevitable trend to accelerate the construction of large-scale low-orbit satellite networks. With the increase in the number of low-orbit satellites and the number of users, multi-satellite beams will lead to overlapping beam coverage, aggravate inter-beam interference, and greatly reduce communication quality. Moreover, compared with ground mobile communications and high-orbit satellite communications, low-orbit satellite communications have inherent defects such as limited onboard resources, high channel dynamics, and severe Doppler effects. It is difficult to estimate channel state information, which further increases the difficulty of multi-user signal processing.

[0003] In traditional interference cancellation signal detection, successive interference cancellation (SIC) is often used to eliminate interference between signals. However, the premise of using the SIC algorithm is that there is a power difference between the signal and the interference signal. In satellite communication systems, since the channel environment differences between ground users are not obvious, the power of the interference signal can be equivalent to or even exceed the power of the useful signal. Based on this, traditional interference cancellation schemes are not suitable for satellite communication systems. In addition, although frequency reuse and precoding technology can alleviate interference between satellites to a certain extent, it cannot completely suppress interference, and the receiving end still faces interference caused by many uncertain factors. In addition, iterative interference cancellation based on forward error correction coding can also alleviate interference to a certain extent, but it still faces the problems of low demodulation accuracy and high computational complexity. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a method for processing multi-user signals in low-orbit satellite communications, which aims to ensure the demodulation bit error rate performance when processing mixed signals with equivalent power received by a receiving end.

[0005] To achieve the above object, according to one aspect of the present invention, a method for processing multi-user signals in low-orbit satellite communication is provided, comprising:

[0006] S1. Obtain a pre-compensated time domain mixed signal, which is a signal formed by mixing multiple pre-compensated user signals at the receiving end; sample the time domain mixed signal to obtain a mixed signal y in the digital domain; and arrange the standard symbol sets of N users corresponding to the mixed signal y into a combined symbol set of N user combined signals s according to a preset user order;

[0007] S2, based on the mixed signal y and the low-orbit satellite channel information H corresponding to each usern , traversing and calculating the likelihood probabilities of all kinds of combination symbols corresponding to each element in the mixed signal y, wherein the all kinds of combination symbols are all kinds of combination symbols in the combination symbol set;

[0008] S3, based on the likelihood probabilities of all kinds of combination symbols corresponding to each element in the mixed signal y and the prior probability of each user n updated by iterative feedback, calculate the transmission signal x of user n in the mixed signal y in the current iteration n The posterior probability of all transmitted bits being 0 constitutes the posterior probability vector corresponding to user n;

[0009] S4. Deinterleave the a posteriori probability vector corresponding to each user n obtained in the current iteration; perform channel decoding on the deinterleaved a posteriori probability vector; if the iteration termination condition is met, make a decision output on the probability after channel decoding to realize the extraction and separation of the transmission signal of the user n in the mixed signal y; if not met, use the probability after channel decoding as the new prior probability of the user n, and repeat S3 to enter the next iteration.

[0010] Furthermore, the time domain mixed signal is pre-compensated in the following manner:

[0011] According to the low-orbit satellite system parameters and the position and elevation angle of each user, the time delay and frequency deviation of the user relative to the satellite are calculated, and the signal to be transmitted by the user is pre-compensated based on the time delay and frequency deviation, so that the signal to be transmitted by the user is quasi-synchronous at the satellite receiving end.

[0012] Further, the likelihood probability in S2 is specifically the likelihood symbol probability;

[0013] Among them, the likelihood symbol probability p(y) of the p-th combination symbol among all users corresponding to the i-th element in the mixed signal y i |s i,p )for:

[0014]

[0015] In the formula, y i represents the i-th element in the mixed signal y; s i,p Indicates the pth combination symbol corresponding to the i-th element in the combination signal s; Indicates i,p The constituent elements in 2 represents the Gaussian white noise power; Denotes the channel matrix H of the nth user n The i-th column of .

[0016] Further, in S4, according to the Bayesian criterion, the signal x transmitted by user n in the mixed signal y is calculated. nThe a posteriori bit probability that all transmitted bits are 0 is calculated, specifically, the a posteriori bit probability that the qth bit corresponding to the element of the transmitted signal of each user in each element of the mixed signal y is 0;

[0017] Among them, from the i-th element y of the mixed signal y i Separate The a posteriori bit probability Specifically:

[0018]

[0019] In the formula, Indicates that user n transmits signal x n The i-th element The qth bit; P(y i |s i ) represents a combined symbol set In The combination symbols s corresponding to the qth bit being 0 i The likelihood probability, Represents the known prior probability information What you seek The prior symbol probability of Represents the known prior probability information What you seek The prior symbol probability of ; Indicates that All the combination symbols s i The other user m contained in the transmission signal x m The i-th element in .

[0020] Further, the S4 is specifically:

[0021] The posterior bit probability vector corresponding to each user n obtained in the current iteration is Deinterleave to obtain the deinterleaved a posteriori bit probability vector of user n Where superscript t represents the number of iterations, subscript b represents the bit, and subscript c represents the code. The posterior bit probability vector is calculated in the form of bit probability. Perform bit probability channel decoding; if the iteration termination condition is met, the bit probability after channel decoding is judged and output, so as to realize the extraction and separation of the transmission signal of user n in the mixed signal y; if the iteration termination condition is not met, the bit probability after channel decoding is used as the new prior probability of user n, and S3 is repeated to enter the next iteration.

[0022] According to another aspect of the present invention, a low-orbit satellite receiving end is provided, which extracts and separates the mixed signals of each user on the same resource block from the received mixed signals by executing a low-orbit satellite communication multi-user signal processing method as described above.

[0023] According to another aspect of the present invention, an electronic device is provided, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0024] According to another aspect of the present invention, a computer-readable storage medium is provided, wherein the computer-readable storage medium includes a stored computer program, wherein when the computer program is executed by a processor, the device where the storage medium is located is controlled to execute the steps of the method described above.

[0025] In general, compared with the prior art, the technical solution conceived by the present invention has the following beneficial effects:

[0026] 1. A multi-user signal processing method for low-orbit satellites of the present invention obtains a pre-compensated time domain mixed signal, which is a signal formed by mixing multiple pre-compensated user signals at the receiving end. The number of mixed users is determined according to the energy intensity of the time domain mixed signal, and then a combination symbol set of the mixed signal is constructed according to the number of mixed users in a preset order. The likelihood symbol probability corresponding to each element in the symbol set is solved using the channel information output by the received signal and the channel estimation module. After obtaining the likelihood probability, the posterior probability of each user signal is solved one by one in combination with the prior probability of each user. The solved posterior probability is bit-channel decoded, and after the decoding is completed, it is determined whether the termination iteration condition is met. If it is met, the iteration is exited, and the bit probability of each user signal after decoding is judged as a bit and output to obtain the final output signal. If the termination condition is not met, the decoded signal is re-interleaved as the prior probability of the user signal to enter the next iteration. The present invention solves the likelihood probability of the mixed signal in the form of combined symbols, and then uses the likelihood probability of the mixed signal and the prior probability to solve the posterior probability of the multi-user signal in parallel, and then corrects the erroneous bits that may occur in the demodulation process through soft-input and soft-output iterative detection, which can greatly reduce the mutual influence between signals and improve the detection efficiency of the mixed signal.

[0027] 2. When decoding mixed signals, the present invention uses a very complicated log-likelihood ratio (LLR) calculation process to simultaneously process multi-user signals when solving the posterior probability. The bit probability is used instead of the LLR. This step reduces a large number of logarithmic operations when simultaneously calculating the bit probabilities of multiple signals, thereby reducing the complexity of multi-user signal detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flowchart of a method for processing multi-user signals in low-orbit satellite communications provided by an embodiment of the present invention;

[0029] Figure 2 is a model diagram of a low-orbit satellite communication system provided by an embodiment of the present invention;

[0030] Figure 3 is a bit error rate performance comparison simulation diagram provided by an embodiment of the present invention;

[0031] Figure 4 It is a module diagram of multi-user signal processing at a low-orbit satellite receiving end provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] Embodiment 1

[0034] A multi-user signal processing method for low-orbit satellite communication, such as Figure 1 As shown, including:

[0035] S1. Obtain a pre-compensated time domain mixed signal, which is a signal formed by mixing multiple pre-compensated user signals at the receiving end; sample the time domain mixed signal to obtain a mixed signal y in the digital domain; and arrange the standard symbol sets of N users corresponding to the mixed signal y into a combined symbol set of N user combined signals s according to a preset user order;

[0036] S2, based on the mixed signal y and its corresponding low-orbit satellite channel information H of each user n , traversing and calculating the likelihood probabilities of all kinds of combination symbols between all user signals corresponding to each element in the mixed signal y, wherein the all kinds of combination symbols are all kinds of combination symbols in the combination symbol set;

[0037] S3, based on the likelihood probabilities of all combinations of symbols between all user signals corresponding to each element in the mixed signal y and the prior probability of each user n updated by iterative feedback, calculate in the current iteration to separate the transmission signal x of user n from the mixed signal y n The posterior probability that the qth bit of all elements of is 0 constitutes the posterior probability vector corresponding to the user n;

[0038] S4. Deinterleave the a posteriori probability vector corresponding to each user n obtained in the current iteration; perform channel decoding on the deinterleaved a posteriori probability vector; if the iteration termination condition is met, make a decision output on the probability after channel decoding to realize the extraction and separation of the transmission signal of the user n in the mixed signal y; if not met, use the probability after channel decoding as the new prior probability of the user n, and repeat S3 to enter the next iteration.

[0039] In S1, the N user combined signals s can be expressed as s = {x1 … x N}, each vector x represents any transmission signal of the corresponding user. In addition, the number N of mixed users can be determined according to the energy intensity of the received signal after pre-compensation, such as Figure 2 A model of a low-orbit satellite communication system is shown.

[0040] Mixed Signal Among them, H n represents the channel state information matrix corresponding to user n, n represents additive Gaussian white noise, N represents the total number of users corresponding to the mixed signal, x n represents the transmitted signal of the nth user. n Standard symbol set The combination symbol set of the combined signal s is obtained by combining in a certain order Among them, the combined symbol set The construction method is

[0041] This embodiment retains the likelihood probabilities corresponding to all combination symbols when calculating the likelihood probability of the mixed signal, and then fully utilizes the likelihood probabilities of all combination symbols when solving the posterior probability of each user, that is, the complete information of the signal is retained during the calculation process, reducing the information loss caused by the judgment and improving the detection accuracy. In addition, for the above-mentioned iterative process of S3 and S4, each user performs it synchronously.

[0042] As a preferred implementation, the above-mentioned time domain mixed signal is pre-compensated by the following method:

[0043] According to the low-orbit satellite system parameters and the position and elevation angle of each user, the time delay and frequency deviation of the user relative to the satellite are calculated, and the signal to be transmitted by the user is pre-compensated based on the time delay and frequency deviation, so that the signal to be transmitted by the user is quasi-synchronous at the satellite receiving end.

[0044] The low-orbit satellite system parameters include the satellite orbit height h hight , satellite operating speed v, the number of antennas M configured on the satellite, etc.

[0045] The position of user n is w n =(w n,x ,wn,y ,0), the propagation delay and Doppler calculation method of user n is:

[0046]

[0047] Where c is the speed of light, f n is the center frequency of user n, and v is the satellite movement speed.

[0048] As a preferred implementation, the likelihood probability in S2 is specifically the likelihood symbol probability;

[0049] Among them, the likelihood symbol probability p(y) of the p-th combination symbol among all users corresponding to the i-th element in the mixed signal y i |s i,p )for:

[0050]

[0051] In the formula, y i represents the i-th element in the mixed signal y; s i,p Indicates the pth combination symbol corresponding to the i-th element in the combination signal s; Indicates i,p The constituent elements in 2 represents the Gaussian white noise power; Denotes the channel matrix H of the nth user n The i-th column of .

[0052] All kinds of combination symbols of each element in the mixed signal y are traversed to calculate the likelihood coincidence probability of all kinds of combination symbols of each element in the mixed signal y and keep them in an array.

[0053] This embodiment does not adopt the method of taking the maximum likelihood probability when calculating the likelihood symbol probability, but retains the likelihood symbol probabilities corresponding to all combination symbols for calculating the posterior bit probability, which is beneficial to reducing the loss of information in the decision process, making full use of all received information, reducing the information loss caused by the decision, and improving the detection accuracy. Especially when the power of multiple signals is comparable, the signals are very likely to interfere with each other and cause erroneous decisions.

[0054] As a preferred implementation, in S4, according to the Bayesian criterion, the signal x transmitted by user n is separated from the mixed signal y. n The a posteriori bit probability that the qth bit of all elements of is 0 is specifically calculated by separating the a posteriori bit probability that the qth bit of the element corresponding to each user's transmitted signal from each element of the mixed signal y is 0;

[0055] Among them, from the i-th element y of the mixed signal y i Separate The a posteriori bit probability Specifically:

[0056]

[0057] In the formula, Indicates that user n transmits signal x n The i-th element The qth bit; P(y i |s i ) represents a combined symbol set In The combination symbols s corresponding to the qth bit being 0 i The likelihood probability, Represents the known prior probability information What you seek The prior symbol probability of Represents the known prior probability information What you seek The prior symbol probability of ; Indicates that All the combination symbols s i The other user m contained in the transmission signal x m The i-th element in .

[0058] In order to avoid repeated calculations and save computational costs, the posterior bit probabilities of N users are The calculations can be performed synchronously.

[0059] In the mixed signal processing process, this embodiment adopts a multi-user signal parallel processing method, and simultaneously considers the mutual influence between multi-user signals (i.e., the likelihood probability of all combined symbols) when solving the posterior probability, which can avoid the error propagation problem caused by excessive signal power between multiple users and greatly reduce the bit error rate of mixed signal demodulation.

[0060] Defining the bit probability includes: defining the bit probability as the probability p (b0=0) that the bit b0 is 0, and correspondingly, the probability 1-p (b0=0) that the bit b0 is 1. Similarly, the bit probability may also be defined as the probability p (b0=1) that the bit b0 is 1, and correspondingly, the probability 1-p (b0=1) that the bit b0 is 0.

[0061] Specifically, during the initialization iteration, it is assumed that the probabilities of 0 bit and 1 bit are equal, that is, the prior bit probabilities are all 0.5, and the prior symbol probabilities are also equal for each symbol, which can be calculated from the prior bit probabilities. The bit probabilities and symbol probabilities can be converted into each other.

[0062] As a preferred implementation, S4 is specifically:

[0063] The posterior bit probability vector corresponding to each user n obtained in the current iteration is Deinterleave to obtain the deinterleaved a posteriori bit probability vector of user n Where superscript t represents the number of iterations, subscript b represents the bit, and subscript c represents the code. The posterior bit probability vector is calculated in the form of bit probability. Perform bit probability channel decoding; if the iteration termination condition is met, the bit probability after channel decoding is judged and output, so as to realize the extraction and separation of the transmission signal of user n in the mixed signal y; if the iteration termination condition is not met, the bit probability after channel decoding is used as the new prior probability of user n, and S3 is repeated to enter the next iteration.

[0064] When decoding mixed signals, the log-likelihood ratio (LLR) calculation process for simultaneously processing multi-user signals when solving the posterior probability is very complicated. Using bit probability instead of LLR reduces a large number of logarithmic operations when calculating the bit probabilities of multiple signals at the same time, thereby reducing the complexity of multi-user signal detection.

[0065] In this embodiment, the operation objects of deinterleaving, channel decoding and interleaving are all bit probabilities. The above-mentioned bit decision is also in the form of bit probability. If the bit probability is defined as the probability that the bit is 0, the decision method is to judge it as 0 when the bit probability is greater than 0.5, otherwise it is judged as 1. Correspondingly, if the bit probability is defined as the probability that the bit is 1, the decision method is to judge it as 1 when the bit probability is greater than 0.5, otherwise it is judged as 0.

[0066] The method of this embodiment adopts a soft-input soft-output (SISO) iterative detection method of channel coding when decoding mixed signals at S4. The SISO iterative detection can make full use of bit information and reduce the performance loss caused by hard decisions. At the same time, the error correction function of the channel coding can correct erroneous bits and improve the bit error rate performance. Then, the algorithm converges through iteration to obtain the best bit error rate performance.

[0067] Figure 3 This is a simulation diagram of the bit error rate performance when the method in the embodiment of the present invention processes multi-user signals of a low-orbit satellite, taking the mixing of two user signals as an example, where the power ratios of the two user signals are 1:1 and 2:1 respectively. Figure 3 In the figure, the horizontal axis represents the signal-to-noise ratio in dB, and the vertical axis represents the bit error rate. Figure 3 The left figure in FIG. 1 provides the relationship between the bit error rate and the signal-to-noise ratio of the detection method proposed by the present invention and the existing detection method when the signal power ratio is 1:1. Figure 3The right figure in FIG. 1 provides the relationship between the bit error rate and the signal-to-noise ratio of the method in the embodiment of the present invention and the existing detection method when the signal power ratio is 2:1. The parameters in the method in the embodiment of the present invention are respectively set to: (N r ,N t ,Mod)=(16,16,4), where N r Indicates the number of receiving antennas, N t Represents the number of transmitting antennas, Mod represents the modulation base, here QPSK modulation, and the coding method adopts polarization coding, where the code length N = 1024 and the code rate is 1 / 2. The simulation results show that the traditional MMSE-SIC algorithm completely fails when the signal power ratio is 1:1, and can demodulate strong power signals when the signal power is 2:1, but weak power signals cannot be demodulated. Compared with symbol enumeration (SE) in this scenario, the method in the embodiment of the present invention can obtain a performance gain of more than 6dB, and compared with the soft input soft output SE (Soft-SE) method, it can obtain a performance gain of about 2dB, and the weak signal can still obtain a bit error rate performance similar to that of the strong signal. It can be seen that the method in the embodiment of the present invention has good decoding performance for multi-user mixed signals with different transmission powers, and can effectively handle the problem of aliasing of multi-type user data of low-orbit satellites under high mobility and large coverage. In addition, it can be clearly stated that the method in the embodiment of the present invention has the same applicability to other communication scenarios that generate stacked data, which will not be repeated here.

[0068] Embodiment 2

[0069] A low-orbit satellite receiving end realizes extracting and separating mixed signals of various users on the same resource block from received mixed signals by executing a low-orbit satellite communication multi-user signal processing method as described above.

[0070] like Figure 4 As shown, the low-orbit satellite receiving end may include a combined symbol set construction module, a combined symbol likelihood probability solution module, a mixed signal decomposition module, a bit deinterleaving module, a bit channel decoding module, a bit interleaving module, a circulation module and a bit decision and output module.

[0071] Among them, the combination symbol set construction module is used to construct the combination symbol set of received data, judge the number of mixed users according to the energy intensity of the received signal, combine all user standard symbol sets in a certain order, and all combinations constitute the combination symbol set. The combination symbol likelihood probability solution module is used to solve the likelihood bit probability of the combination symbol, calculate the likelihood symbol probability corresponding to all combination symbols in the combination symbol set according to the received mixed signal and the corresponding channel information, and retain the data in the array. The mixed signal decomposition module updates the user prior bit probability according to iterative feedback, decomposes the mixed signal one by one according to the combination order of the mixed signal, and updates the posterior bit probability of each user signal. The deinterleaving module is used to deinterleave the posterior bit probability of the user signal, and the input and output of the deinterleaver are both in the form of bit probability. The channel decoding module is used to decode the bit probability channel of the deinterleaved signal, using a soft input soft output (SISO) decoder. The input and output of the bit channel decoding module are both in the form of bit probability. In the decoding process, the calculation part of the likelihood information (LLR) needs to be changed to bit probability calculation accordingly. The interleaving module is used to interleave the decoded bit probabilities, and the input and output of the interleaver are both in the form of bit probabilities. The loop module is used to loop and control the iterative execution of the a posteriori bit probability update module, the deinterleaving module, the decoding module and the interleaving module until the set number of iterations is reached. The bit decision and output module is used to decide the output bit probability as a bit, and decide the output bit according to the definition of the bit probability. If the bit probability is defined as the probability that the bit is 0, the decision method is to decide as 0 when the bit probability is greater than 0.5, otherwise it is decided as 1. Correspondingly, if the bit probability is defined as the probability that the bit is 1, the decision method is to decide as 1 when the bit probability is greater than 0.5, otherwise it is decided as 0.

[0072] The relevant technical solutions are the same as above and will not be described in detail here.

[0073] Embodiment 3

[0074] An electronic device includes a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0075] The electronic device may be a computing device such as a desktop computer, a notebook, a PDA, a cloud server, etc. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. The memory may be used to store computer programs and / or modules, and the processor may perform various functions of the electronic device by running or executing computer programs and / or modules stored in the memory, and calling data stored in the memory.

[0076] The relevant technical solutions are the same as above and will not be described again here.

[0077] Embodiment 4

[0078] A computer-readable storage medium stores a computer program, which implements the steps of the above method when executed by a processor.

[0079] Specifically, the memory may include a high-speed random access memory, and may also include a non-volatile memory, such as a hard disk, an internal memory, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0080] The relevant technical solutions are the same as above and will not be described again here.

[0081] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for processing multi-user signals in low-orbit satellite communications, characterized in that: include: S1, obtaining a pre-compensated time domain mixed signal, which is a signal formed by mixing multiple pre-compensated user signals at a receiving end; Sampling the mixed signal in the time domain to obtain a mixed signal y in the digital domain; According to a preset user order, the standard symbol sets of N users corresponding to the mixed signal y are combined and arranged into a combined symbol set of N user combined signals s; S2, based on the mixed signal y and the low-orbit satellite channel information H corresponding to each user n , traversing and calculating the likelihood probabilities of all kinds of combination symbols corresponding to each element in the mixed signal y, wherein the all kinds of combination symbols are all kinds of combination symbols in the combination symbol set; S3, based on the likelihood probabilities of all kinds of combination symbols corresponding to each element in the mixed signal y and the prior probability of each user n updated by iterative feedback, calculate the transmission signal x of user n in the mixed signal y in the current iteration n The posterior probability of all transmitted bits being 0 constitutes the posterior probability vector corresponding to user n; S4. Deinterleave the a posteriori probability vector corresponding to each user n obtained in the current iteration; perform channel decoding on the deinterleaved a posteriori probability vector; if the iteration termination condition is met, make a decision output on the probability after channel decoding to realize the extraction and separation of the transmission signal of the user n in the mixed signal y; if not met, use the probability after channel decoding as the new prior probability of the user n, and repeat S3 to enter the next iteration.

2. A method for processing multi-user signals in low-orbit satellite communication according to claim 1, characterized in that: The time domain mixed signal is pre-compensated by: According to the low-orbit satellite system parameters and the position and elevation angle of each user, the time delay and frequency deviation of the user relative to the satellite are calculated, and the signal to be transmitted by the user is pre-compensated based on the time delay and frequency deviation, so that the signal to be transmitted by the user is quasi-synchronous at the satellite receiving end.

3. A method for processing multi-user signals in low-orbit satellite communication according to claim 1, characterized in that: The likelihood probability in S2 is specifically the likelihood symbol probability; Among them, the likelihood symbol probability p(y) of the p-th combination symbol among all users corresponding to the i-th element in the mixed signal y i |s i,p )for: In the formula, y i represents the i-th element in the mixed signal y; s i,p Indicates the pth combination symbol corresponding to the i-th element in the combination signal s; Indicates i,p The constituent elements in 2 represents the Gaussian white noise power; Denotes the channel matrix H of the nth user n The i-th column of .

4. A method for processing multi-user signals in low-orbit satellite communications according to any one of claims 1 to 3, characterized in that: In S4, according to the Bayesian criterion, the signal x transmitted by user n in the mixed signal y is calculated. n The a posteriori bit probability that all transmitted bits are 0 is calculated, specifically, the a posteriori bit probability that the qth bit corresponding to the element of the transmitted signal of each user in each element of the mixed signal y is 0; Among them, from the i-th element y of the mixed signal y i middle The a posteriori bit probability Specifically: In the formula, Indicates that user n transmits signal x n The i-th element The qth bit; P(y i |s i ) represents the combination symbol set x such that The combination symbols s corresponding to the qth bit being 0 i The likelihood probability, Represents the known prior probability information What you seek The prior symbol probability of Represents the known prior probability information What you seek The prior symbol probability of ; Indicates that All the combination symbols s i The other user m contained in the transmission signal x m The i-th element in .

5. A method for processing multi-user signals in low-orbit satellite communication according to claim 4, characterized in that: The S4 is specifically: The posterior bit probability vector corresponding to each user n obtained in the current iteration is Deinterleave to obtain the deinterleaved a posteriori bit probability vector of user n Where superscript t represents the number of iterations, subscript b represents the bit, and subscript c represents the code. The posterior bit probability vector is calculated in the form of bit probability. Perform bit probability channel decoding; if the iteration termination condition is met, the bit probability after channel decoding is judged and output, so as to realize the extraction and separation of the transmission signal of user n in the mixed signal y; if the iteration termination condition is not met, the bit probability after channel decoding is used as the new prior probability of user n, and S3 is repeated to enter the next iteration.

6. A low-orbit satellite receiving terminal, characterized in that: By executing a low-orbit satellite communication multi-user signal processing method as described in any one of claims 1 to 5, it is possible to extract and separate the mixed signals of each user on the same resource block from the received mixed signals.

7. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 5 are implemented.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored computer program, wherein when the computer program is executed by a processor, the device where the storage medium is located is controlled to perform the steps of any one of the methods according to claims 1 to 5.

Images