An interleaved iterative non-orthogonal multiple access communication system based on quantum coherent states

Abstract

The present application belongs to the technical field of quantum communication, and specifically relates to an interleaving iterative non-orthogonal multiple access communication system based on quantum coherent states. The system comprises a transmitting end, an atmospheric channel model and a receiving end. The transmitting end comprises a channel encoder, an interleaver, a modulator, a random switcher and a transmitting laser. The switcher is used to switch the signals modulated to coherent states on the basis of interleaving multiple access, so as to realize the sparseness of multiple user signals. The receiving end comprises a Kennedy quantum receiver and a multi-user detection module. The quantum receiver is used to displace the received coherent state signals, and then photon counting is performed. An iterative soft interference cancellation algorithm module is introduced into the multi-user detection module, so as to effectively resist turbulence interference and multiple access interference, and reduce the bit error rate of the system. The system can obtain greater coding gain than a code division multiple access system, and improve the utilization rate of frequency band resources. Meanwhile, the system can realize the sparseness of multiple user signals, and improve the quality of the communication system.

Description

Technical Field

[0001] This invention belongs to the field of quantum communication technology, specifically an interleaved iterative nonorthogonal multiple access communication system. Background Technology

[0002] Human civilization has developed to the point where various information technologies are widely used. Regarding communication systems, classical laser communication systems typically use electromagnetic waves as the physical carrier of information, and their physical behavior can be described by Maxwell's equations. With the continuous development of science and technology, these information technologies based on classical theory are gradually approaching their performance limits due to factors such as shot noise. Within the framework of classical theory, the classical limit of communication system channel capacity is the Shannon limit; channel capacity cannot exceed the Shannon limit and can only be approached through coding methods. Similarly, the performance of classical receivers in communication systems cannot exceed the standard quantum limit. With the advent of quantum mechanics and other quantum physics theories, researchers have begun using coherent states or corresponding density operators as the physical carriers of information in communication systems. Their physical behavior is described by quantized electromagnetic field theory, and the communication performance limit obtained based on quantum mechanical properties can break through the standard quantum limit. Therefore, how to realize quantum communication using coherent state signals has become a hot research topic in recent years.

[0003] In 1973, R.S. Kennedy in the United States proposed the first physically realizable quantum receiver—the Kennedy quantum receiver—through theoretical derivation. The Kennedy quantum receiver is a near-optimal quantum receiver for binary modulated signal sets. The Kennedy receiver performs a shift operation on the coherent state signal modulated by BPSK. The output signal after the shift operation is detected by photon counting using an ON-OFF single-photon detector, and the decision is made by whether the photon count result is greater than zero. When the average photon count is large, the Kennedy receiver can break the standard quantum limit.

[0004] Multi-user transmissions typically suffer from multiple access interference and shot noise. In traditional non-orthogonal multiple access schemes—interleaved multiple access—joint detection can be performed using the spreading sequences of each user. This allows channel coding to not only provide an additional performance gain but also offer exchangeable mutual information between the multi-user detectors and channel decoders, thereby improving the overall performance of each user. To further improve system transmission quality and communication rate, we propose adding switched multiple access (SDMA) to a traditional IDMA multi-user system to achieve sparsity of multi-user signals. This invention proposes a multi-user IDMA-ODMA communication system under Poisson noise, utilizing quantum coherent state signals as information carriers, with the receiver designed as a Kennedy quantum receiver. Specifically, switched multiple access and an iterative soft interference cancellation algorithm are designed to effectively resist turbulence interference and multi-user interference, improving the communication system quality. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide an interleaved iterative nonorthogonal multiple access communication method and apparatus based on quantum coherent states, so as to effectively resist turbulence interference and multi-user interference and reduce the bit error rate of the system.

[0006] The interleaved iterative nonorthogonal multiple access communication system based on quantum coherent states provided by this invention, denoted as IDMA-ODMA communication system, includes a transmitter, an atmospheric channel, and a receiver. Its structural framework is described below. Figure 1 As shown, the specific details are explained below:

[0007] (a) Transmitter

[0008] A multi-user ODMA system based on quantum coherent states is a low-complexity, sparsified quantum coherent state NOMA system that can achieve sparsification of multi-user signals. Consider the following... A multi-user quantum coherent state IDMA-ODMA communication system consisting of [number] users; each user channel includes, in sequence, a channel encoder, an interleaver, a BPSK modulator, a random switch, and a laser source (emitting laser); wherein:

[0009] Each user is equipped with a single emitting laser, for the first... For an individual user, the transmitted information bit sequence is as follows: ,in Indicates the first One information bit, This is the length of the information bit sequence; then, a simple encoder is used to encode the information bit sequence with forward error correction information. The bit sequence after the encoding operation is: ,in Indicates the first One encoded bit, The length of the encoded bit sequence; each user has their own independent and specific interleaver. , No. The interleaving for a single user is represented as Through the interleaver The post-coded sequence becomes an interleaved sequence ,in Indicates the first Each chip is interleaved with bits. The interleaved sequence, after being modulated by a BPSK modulator, is loaded into a quantum coherent state, represented as:

[0010] , (1)

[0011] in, for:

[0012] , (2)

[0013] in, Let be a complex number, representing the first... The amplitude of the coherent state of each user, and the square of the amplitude. This represents the corresponding average number of photons. This is called the photon number state. This indicates the number of photons contained in that state. This represents the complex amplitude. The sequence is then keyed using an ODMA switch. At this point, there are three possible signal states transmitted in the channel: [symbol "...]"] ",symbol" "" and "idle" where no symbols are transmitted.

[0014] A random switch with the same depth as the interleaver ensures that at least one chip of each bit of information remains in the "on" state. Otherwise, the bit will not be transmitted, leading to a significant increase in the bit error rate. Furthermore, the sparsity must not be less than the repetition rate; otherwise, some bits of information will inevitably fail to be transmitted.

[0015] (II) Atmospheric Channel Model

[0016] To characterize the atmospheric turbulence fading channel, Indicates the first Turbulent fading gain between the user laser and the receiving unit. The probability density function (PDF) can be defined as:

[0017] (3)

[0018] in, It is the gamma function. It is a second type of correction. The order Bessel function. and To represent the blinking parameters, and , This invention assumes They are independent of each other if the distance between the receivers is large enough and greater than the relevant width.

[0019] (III) Receiving end

[0020] Including Kennedy quantum receiver, multi-user detection module

[0021] (1) Kennedy quantum receiver

[0022] At the receiving end, a Kennedy quantum receiver is used to receive the quantum state, and the received quantum state is:

[0023] (4)

[0024] in, For the channel matrix, This represents a sequence of quantum states sent by multiple users.

[0025] The types of signals received by the Kennedy receiver include: , Or "idle", after quantum shift operation Afterwards, the signal types are respectively , or This invention introduces variables. Indicates the first The on / off state of each user's switch. Representing the interleaved sequence encoding information, in a multi-user ODMA system based on quantum coherence states, the received quantum state can be represented as:

[0026] (5)

[0027] Among them, use express , Possible values:

[0028] (6)

[0029] That is, for the received coherent state To be honest The transmitting end is in an "idle" state; for the received coherent state To be honest The status at the transmitting end is " "; for the received coherent state To be honest The status at the transmitting end is " The signal then enters the photon counting unit. This invention uses a single-photon detector with quantum-limited sensitivity to perform photon counting on the coherent state signal after the shift operation. Considering the influence of background light at the receiver, the single-photon detector... One chip detected The conditional probability of a photon is:

[0030] (7)

[0031] in, For detection efficiency, The average number of photons under different conditions. The background photon count (including the dark count).

[0032] (2) Multi-user detection module

[0033] In this invention, both the input prior information and output extrinsic information of the multi-user signal detector are soft values, i.e., the logarithmic likelihood ratio (LLR). The multi-user detection module includes a primary signal estimation module (MUD), an interleaving / deinterleaving unit, and a decoder (DEC). Initialization is first performed within the MUD device, setting the input prior information LLRs of all users to 0. ,in Indicates the MUD module number The user The input prior LLRs of each chip are calculated by... Equivalent noise estimate for each user The corresponding external information LLRs sequences of K users are obtained. ,in Indicates the first The user The extrinsic information LLRs of each chip are then processed by a specific deinterleaver to obtain the input prior information LLRs sequence of the DEC module. ,in Indicates the first The user The external information LLRs of each chip are input to... Each DEC module performs standard posterior probability (APP) decoding; when the iteration termination condition is met, the iteration process ends, and a hard decision is made on the bit-level LLRs output by the DEC to obtain an estimate of the information bit sequence. ,in Indicates the first Estimates for each user.

[0034] Based on the multi-user transmission scheme based on switch multiple access, a corresponding soft interference cancellation detection algorithm module is introduced into the multi-user detection module at the receiving end to realize multi-user detection. The specific content of the soft interference cancellation detection algorithm module is as follows: Indicates the first The user The on / off state of each chip.

[0035] ①: When hour:

[0036] At this time, the user In the The switch information for each chip is "off," indicating that the user... The first after the switch control The chip status is "idle". Therefore, the first chip... The count value of each received chip This does not include users. Useful information .Right now, and Since they are mutually independent, we have:

[0037] (8)

[0038] Therefore, the posterior information LLRs:

[0039] (9)

[0040] Based on the relationship between posterior information, extrinsic information, and prior information:

[0041] (10)

[0042] We can obtain:

[0043] , (11).

[0044] ②: When hour:

[0045] At this time, the user In the The switch information for each chip is "closed". Indicates user The first after the switch control Each chip status indicates External information can be represented as:

[0046] (12)

[0047] At the receiving end, substituting the Poisson probability yields:

[0048]

[0049] (13)

[0050] in, Indicates except the first Other users besides this user Indicates except the first Other users besides [user name] information, Indicates except the first Other users besides [user name] information, Indicates except the first Other users besides the first user in the [number]th ... The switching state of each chip. Based on the concept of SOIC, and utilizing... Since it is known, it can be used Conditional expectation under certain conditions is used to estimate the inclusion of other users in the above formula. The terms, namely:

[0051] (14)

[0052] because As a constant, we have:

[0053] , (15).

[0054] According to the definition of mathematical expectation, The symbol can take the following values: , , Three scenarios,

[0055] (16)

[0056] in, Indicates except the first Other users besides the first user in the [number]th ... The symbol state of each chip,

[0057] (17a)

[0058] (17b)

[0059] (17c)

[0060] (17d)

[0061] (17e)

[0062] so:

[0063] , (18).

[0064] Based on the definition of prior information, and using... Indicates that the MUD module is except for the first Other users besides the first user in the [number]th ... The prior soft values ​​LLRs of each chip can be obtained as follows:

[0065] (19a)

[0066] (19b)

[0067] so:

[0068] (20)

[0069] so:

[0070] , (twenty one)

[0071] so:

[0072] ,(twenty two) .

[0073] Combining the conclusions of ① and ②, the update formula for the SoIC algorithm of MUD can be obtained as follows:

[0074] ,(twenty three).

[0075] The steps of the SoIC algorithm in the Poisson channel IDMA-ODMA system are as follows:

[0076] Step 1: Initialize operations and record the number of iterations. The prior input information LLRs for all users in the MUD is set to 0, i.e. ;

[0077] Step 2:

[0078] (2.1) Calculate the equivalent noise estimates for all K users according to equation (14-21). ;

[0079] (2.2) Calculate the external information LLRs of the MUD output of K users according to formula (23). ;

[0080] (2.3) After deinterleaving, the DEC module is obtained. The input is fed into K DEC modules for standard APP decoding;

[0081] (2.4) The external information output by DEC becomes the prior information for the next iteration after interleaving. ;

[0082] (2.5) Once a complete iterative detection / decoding operation is completed, return to step (2.1).

[0083] Step 3: The iteration termination condition is met, the iteration process ends, and a hard decision is made on the DEC output bit-level LLRs to obtain... .

[0084] (3) External information transfer diagram

[0085] The Extrinsic Information Transfer (EXIT) diagram, originally proposed by S. tenBrink as a novel analytical tool for selecting channel coding and modulation constellation schemes, was later extended by Brink to analyze the convergence of Turbo code iterative decoding. It visualizes the external information output from the two component decoders and the feedback process in iterative decoding, demonstrating through simulation that this method can accurately estimate the system bit error rate after any number of iterations within the steep drop region of the Turbo code signal-to-noise ratio. EXIT diagrams based on mutual information metrics are the most powerful tool for describing iterative processes and analyzing convergence. First, let's review the concept of mutual information. Mutual information refers to the correlation between the transmitted and received signals, corresponding to the amount of information that each transmitted symbol can transmit. The calculation formula is the information entropy of the received signal minus the conditional entropy of the received signal under the conditions of the transmitted signal, assuming the presence of random variables. and For any and Mutual information is represented as :

[0086]

[0087] ,(twenty four)

[0088] If the input is a binary input with equal probability distribution, the mutual information expression can be simplified using the law of total probability:

[0089] (25)

[0090] The prior information at the input end and the extrinsic information at the output end in the multi-user detection module are represented as follows: and Its corresponding bit The distribution relationship between them is and Prior information and The mutual information metric is characterized as The operation expression is:

[0091] (26)

[0092] Similarly, external information and The mutual information metric is characterized as ,have:

[0093] , (27).

[0094] Mutual information Seen as The external information transfer characteristic function is defined as a function of the signal-to-noise ratio (SNR):

[0095] (28)

[0096] For a given SNR, it simplifies to:

[0097] , (29).

[0098] The probability density function of prior and extrinsic information is obtained by histogram statistics through Monte Carlo simulation. Then, numerical algorithms are used to approximate the integral, and the result is obtained. This operation requires no prior assumptions about the probability density function and is satisfied for any distribution.

[0099] The main features and advantages of this invention are:

[0100] The multi-user IDMA-ODMA communication system based on quantum coherent states under Poisson noise proposed in this invention has significant advantages over traditional IDMA multi-user wireless communication systems, reducing the bit error rate.

[0101] (1) The present invention adopts a transmitter based on quantum coherent state, and uses coherent state as the physical carrier of information carried by the communication system. Its physical behavior is described by quantized electromagnetic field theory. The communication performance limit obtained based on quantum mechanical properties can break through the standard quantum limit.

[0102] (2) The present invention adopts ODMA-IDMA technology, which completes the unique feature marking of users at the receiving end according to different interleaving schemes between users, obtains a larger coding gain than code division multiple access, and improves the utilization rate of frequency band resources; at the same time, ODMA technology is a low-complexity sparsity NOMA method, which can realize the sparsity of multi-user signals and improve the quality of communication system.

[0103] (3) The present invention designs a multi-user soft value detection algorithm that combines Kennedy quantum receiver with iterative soft interference cancellation algorithm, which can effectively resist turbulence interference and multi-user interference. Attached Figure Description

[0104] Figure 1 Block diagram of a multi-user IDMA-ODMA communication system based on quantum coherent states under Poisson noise designed for this invention.

[0105] Figure 2 This is a block diagram illustrating the displacement and photon counting principle of the Kennedy quantum receiver.

[0106] Figure 3 This is a module for the iterative soft interference elimination SoIC detection algorithm.

[0107] Figure 4 This is a graph showing the relationship between the bit error rate of the system and the average information bit energy of the user in this invention.

[0108] Figure 5 This is a graph showing the change in the bit error rate of the system of the present invention as a function of the number of iterations.

[0109] Figure 6 This is an external information transfer diagram of the system of the present invention. Detailed Implementation

[0110] The present invention will now be described in detail with reference to the accompanying drawings and specific examples.

[0111] This invention proposes a multi-user IDMA-ODMA communication system based on quantum coherent states under Poisson noise, providing a novel quantum coherent state scheme for future wireless network communication. The specific steps are as follows:

[0112] like Figure 1 As shown, the transmitter of a multi-user quantum coherent state IDMA-ODMA communication system has For a single user, a free-space laser communication transmitting and receiving system model is adopted. The signal, after passing through a forward encoder and a specific interleaver at the transmitter, is modulated onto a coherent state signal using BPSK, then transmitted by the laser transmitter. After channel fading, the signal is received at the receiver. Figure 2 The Kennedy quantum receiver shown performs shift operations and photon counting, and then utilizes... Figure 3 The soft interference cancellation SoIC detection algorithm shown implements multi-user detection, reduces multi-user interference, performs soft demodulation of the signal, and finally outputs the result after hard decision. This invention simulates and analyzes the bit error rate performance of a multi-user IDMA-ODMA communication system based on quantum coherent states under atmospheric turbulent fading. In the simulation, the parameters are set as follows: scintillation coefficient of strong Gamma-Gamma turbulent fading. and The wavelength of the light is 0.4 μm, and the aperture diameter of the receiver is 2 cm. The distance between the receivers is also greater than 12 cm. Since the distance between the receivers is sufficiently large and exceeds the coherence distance, fading between channels can be considered negligible. They are independent of each other. The background noise, i.e., the dark current intensity, is set to 30 photons / bit.

[0113] Figure 4 The system bit error rate (BER) versus the average information bit energy per user (ABI) is presented as a graph. ABI is measured in dBJ, and changing ABI alters the number of photons detected in the target signal. Simulations using a 4-user system with a repetition rate of 1 / 8 show that a higher photon count results in a lower BER. Under the same ABI conditions, the IDMA-ODMA system has a lower BER than the pure IDMA system, and the 1 / 4 sparse system has a lower BER than the 1 / 2 sparse system.

[0114] Figure 5 A graph showing the change in system bit error rate (BER) with the number of iterations is presented. Simulations of a system with 4 users, a repetition rate of 1 / 8, and an average information bit energy per user of -167 dBJ show that the BER gradually decreases with increasing iteration count, stabilizing around the fifth iteration. Compared to traditional IDMA systems, the IDMA-ODMA system exhibits a lower BER.

[0115] Figure 6A comparison of the external information transfer diagrams of a 4-user, repetition code IDMA system with a repetition rate of 1 / 8 and an average information bit energy per user of -167 dBJ, and a 1 / 4 sparse IDMA-ODMA system are presented. The convergence of the system can be analyzed from the external information transfer trajectory and asymptotic curves of the transfer characteristics in the EXIT diagram. The convergence point depends on the intersection point of the two transfer characteristic curves (symptotic lines) of the component decoder in the EXIT diagram; the closer the intersection point is to 1 on the horizontal axis, the lower the bit error rate obtained by the system after iteration. The order of the external information transfer trajectory line represents the number of iterations required for convergence. Figure 6 As can be seen, the 1 / 4 sparse IDMA-ODMA system approaches convergence after 4 iterations, and the intersection point is close to the position of the vertical axis 1; and Figure 5 The simulation results are basically the same; however, the step size of the transfer trajectory of the repeating code IDMA system is smaller than that of the 1 / 4 sparse IDMA-ODMA system, and the approximate convergence position is lower than that of the 1 / 4 sparse IDMA-ODMA system, which confirms that the bit error rate obtained by the IDMA-ODMA system after iteration is lower than that of the repeating code IDMA system, and fewer iterations are required.

[0116] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A quantum coherent state-based interleaved iterative nonorthogonal multiple access communication system, denoted as IDMA-ODMA communication system, characterized in that, Includes the transmitter, atmospheric channel model, and receiver, among which: (a) Transmitter Consider by A multi-user quantum coherent state IDMA-ODMA communication system consisting of [number] users, where each user channel includes, in sequence, a channel encoder, an interleaver, a BPSK modulator, a random switch, and a transmitting laser; wherein: Each user is equipped with a single emitting laser, for the first... For an individual user, the transmitted information bit sequence is as follows: ,in Indicates the first One information bit, This is the length of the information bit sequence; then, the information bit sequence is encoded using an encoder to obtain forward error correction information. The bit sequence after encoding is: ,in Indicates the first The encoded bits of a chip The length of the encoded bit sequence; each user has their own independent interleaver. , No. The interleaving for a single user is represented as via interleaver It then becomes an interleaved sequence ,in Indicates the first The interleaved bits of each chip; the interleaved sequence is modulated by a BPSK modulator and loaded into a quantum coherent state, represented as: ， （1） in, for: ，（2） Let be a complex number, representing the first... The amplitude of the coherent state of each user, and the square of the amplitude. This represents the corresponding average number of photons; This is called the photon number state. This indicates the number of photons contained in the photon number state. This represents the complex amplitude; the sequence is keyed by an ODMA switch using a random switch; at this time, there are three signal states transmitted in the channel: symbol " ",symbol" ", and "idle" where no symbols are transmitted; (II) Atmospheric Channel Model To characterize the atmospheric turbulence fading channel, Indicates the first Turbulent fading gain between individual user lasers and receiving units; The probability density function (PDF) is defined as: ，(3) in, It is the gamma function; It is a second type of correction. Bessel function of order 1; and To represent the blinking parameters, and , ; Assumption They are independent of each other if the distance between the receivers is large enough and greater than the relevant width. (III) Receiving end Includes the Kennedy quantum receiver and a multi-user detection module; among which: (1) Kennedy quantum receiver At the receiving end, a Kennedy quantum receiver is used to receive the quantum state, and the received quantum state is: ，(4) in, For the channel matrix, This represents a sequence of quantum states sent by multiple users. The types of signals received by the Kennedy receiver include: , Or "idle", after quantum shift operation The following are respectively , or Introducing variables Indicates the first The on / off state of each user's switch. If the interleaved sequence is encoded as information, then the received quantum state is represented as: (5) Among them, use express , The value can be: ，(6) That is, for the received coherent state To be honest The transmitting end is in an "idle" state; for the received coherent state... To be honest The status at the transmitting end is " "; for the received coherent state To be honest The status at the transmitting end is " ";Then the signal enters the photon counting unit, specifically using a single-photon detector with quantum-limited sensitivity, to perform photon counting on the coherent state signal after the shift operation, taking into account the influence of background light at the receiver. The single-photon detector in the first..." One chip detected The conditional probability of a photon is: ，(7) in, For detection efficiency, The average number of photons under different conditions. Background photon number; (2) Multi-user detection module Since the input prior information and output extrinsic information of the multi-user signal detection module are both soft values, i.e., the logarithmic likelihood ratio (LLR), the multi-user detection module includes a primary signal estimation module (MUD), an interleaving / deinterleaving unit, and a decoder (DEC). Within the MUD, an initialization operation is first performed, setting the input prior information LLRs of all users to 0. ,in Indicates the MUD module number The user The input prior LLRs of each chip are calculated by... Equivalent noise estimate for each user This yields the external information sequences for the corresponding K users. ,in Indicates the first The user The external information LLRs of each chip are then obtained through a deinterleaver. ,in Indicates the first The user The external information LLRs of each chip are input to... Each DEC module performs standard posterior probability (APP) decoding; when the iteration termination condition is met, the iteration process ends, and a hard decision is made on the bit-level LLRs output by the DEC to obtain an estimate of the information bit sequence. ,in Indicates the first Estimated values ​​for each user; Indicates except the first Other users besides the one mentioned.

2. The interleaved iterative non-orthogonal multiple access communication system according to claim 1, characterized in that, In the multi-user detection module at the receiving end, a corresponding soft interference cancellation detection algorithm module is used to achieve multi-user detection. Indicates the first The user The on / off state of each chip; the specific contents of the soft interference cancellation detection algorithm module are as follows: ①: When hour: user In the The switch information for each chip is "off," indicating that the user... The first after the switch control The chip status is "idle"; at this time, the chip status is "idle". The count value of each received chip This does not include users. Useful information ,Right now, and Since they are mutually independent, we have: ，(8) Posterior information LLRs: ，(9) Based on the relationship between posterior information, extrinsic information, and prior information: ，(10) have to: ， (11) ②: When hour: user In the The switch information for each chip is "closed," indicating that the user... The first after the switch control The status of each chip is At this point, the external information is represented as: ， (12) At the receiving end, substituting the Poisson probability, we get: ，(13) in, Indicates except the first Other users besides this user Indicates except the first Other users besides [user name] information, Indicates except the first Other users besides [user name] information, Indicates except the first Other users besides the first user in the [number]th ... The switching state of each chip; according to SoIC, and Given that, use Conditional expectation under certain conditions is used to estimate the inclusion of other users in the above formula. The terms, namely: ， (14) because As a constant, we have: ， (15) According to the definition of mathematical expectation, The symbol can take the following values: , , Three scenarios; ，(16) in, ， (17a) ， (17b) ， (17c) ， (17d) ， (17e) so: ， (18) According to the definition of prior information: ， (19a) ， (19b) Therefore: ， (20) Therefore: ， (21) Therefore: ，（22） Combining the conclusions of ① and ②, the update formula for the SoIC algorithm of MUD is: ，(23)。 3. The interleaved iterative non-orthogonal multiple access communication system according to claim 2, characterized in that, The working steps of the SoIC detection algorithm module are as follows: Step 1: Initialize operations and record the number of iterations. The prior input information LLRs for all users in the MUD is set to 0, i.e. ; Step 2: (2.1) Calculate the equivalent noise estimates for all K users according to equation (14-21). ; (2.2) Calculate the external information LLRs of the MUD output of K users according to formula (23). ; (2.3) After unintertwining, we obtain K DEC modules perform standard APP decoding; (2.4) The external information output by DEC becomes the prior information for the next iteration after interleaving. ; (2.5) Once a complete iterative detection / decoding operation is completed, return to step (2.1). Step 3: The iteration termination condition is met, the iteration process ends, and a hard decision is made on the DEC output bit-level LLRs to obtain... .

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