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CN-121984816-A - Sparse code multiple access SCMA message transmission detection system and method suitable for 2FSK modulation

CN121984816ACN 121984816 ACN121984816 ACN 121984816ACN-121984816-A

Abstract

The invention provides a sparse code multiple access SCMA message transmission detection system and method suitable for 2FSK modulation, wherein the method comprises the following steps that a channel coding module codes original binary data information of a user; the system comprises a 2FSK modulation module for modulating channel coding bit sequences, an SCMA mapping module for performing SCMA sparse mapping on modulation symbol sequences of all users, a 2FSK coherent demodulation module for performing 2FSK coherent demodulation on received signals, and a message transmission detection module for performing multi-user detection on demodulated output signals. According to the invention, the 2FSK coherent demodulation module performs SCMA sparse mapping on the modulation symbol sequences output by the 2FSK modulation modules, performs 2FSK coherent demodulation on the mapped multiple received signals, and the message transfer detection module detects the output signals in two frequency states obtained by demodulation through the factor graph model, so that the detection precision is higher.

Inventors

  • HAN KUNPENG
  • SONG GUANGHUI
  • LI YING

Assignees

  • 西安电子科技大学

Dates

Publication Date
20260505
Application Date
20260130

Claims (10)

  1. 1. A sparse code multiple access SCMA message transmission detection system suitable for binary frequency shift keying 2FSK modulation comprises The system comprises a plurality of channel coding modules, SCMA mapping modules and 2FSK coherent demodulation modules, wherein the SCMA mapping modules and the 2FSK coherent demodulation modules are cascaded with each other, and the system is characterized in that the output end of each channel coding module is cascaded with a 2FSK modulation module, and the output end of each 2FSK coherent demodulation module is cascaded with a message transmission detection module.
  2. 2. A method of detecting a system according to claim 1, comprising the steps of: (1) The channel coding module codes the original binary data information of the user: First, the Original binary data information of corresponding users by each channel coding module Coding to obtain the first Channel coded bit sequence for individual users ; (2) The 2FSK modulation module modulates the channel coding bit sequence: 2FSK modulation module codes bit sequence for channel Modulating to obtain the first 2FSK modulation symbol sequences for individual users ; (3) The SCMA mapping module performs SCMA sparse mapping on the modulation symbol sequences of all users: the SCMA mapping module uses the SCMA codebook matrix Will be Mapping modulation symbol sequences of individual users to On each resource block, get the content Each received signal Is a collection of (3); (4) The 2FSK coherent demodulation module carries out 2FSK coherent demodulation on the received signal: the 2FSK coherent demodulation module outputs the received signal to the SCMA mapping module Respectively carrying out correlation operation with local reference signals of two frequency states corresponding to binary frequency shift keying (2 FSK) modulation to obtain signals used for characterization Demodulation of output signals in two frequency states And ; (5) The message passing detection module performs multi-user detection on the demodulated output signal: The message passing detection module is based on SCMA codebook matrix Constructing a factor graph model, adopting a Log-MAX approximate message transfer algorithm, and demodulating an output signal through the factor graph model And Detecting to obtain the first Individual user modulation symbol sequences Log-likelihood ratio of (2) 。
  3. 3. The method of claim 2, wherein the channel coding module in step (1) is configured to code the original binary data information of the user And coding is realized by adopting a Polar coding mode.
  4. 4. The method of claim 2, wherein said encoding the channel-coded bit sequence in step (2) Modulating, wherein the implementation steps are as follows: (2a) 2FSK modulation module codes bit sequence for channel The "0" bit and the "1" bit in the code sequence respectively select the corresponding baseband frequency as Discrete baseband signals of (a) And baseband frequency is Discrete baseband signals of (a) : ; ; Wherein, the For each symbol period Number of internal sampling points Is used for the indexing of (a), ; (2B) Encoding a channel bit sequence in time order The discrete baseband signals corresponding to all bits in the code sequence are spliced to obtain the first code sequence 2FSK modulation symbol sequences for individual users 。
  5. 5. The method of claim 4, wherein the received signal in step (3) The expression is: ; ; ; ; Wherein, the Representing dimensions as Is a matrix of SCMA codebooks of (c) and (d), Representation of A matrix of modulation symbol sequences for individual users, Indicating the operation of the transpose, Represent the first The first of individual users The number of modulation symbols is one, , Representing the number of modulation symbols per user, Is an additive white gaussian noise vector.
  6. 6. The method of claim 5, wherein the demodulation of the output signal in step (4) And The calculation formulas are respectively as follows: ; ; ; Wherein the method comprises the steps of Is a normalization factor.
  7. 7. The method according to claim 6, wherein the factor graph model in step (5) is constructed by: message passing detection module construction The resource blocks are sum nodes to A factor graph model with variable nodes as individual users, wherein the connecting edges between the variable nodes and the nodes in the factor graph model pass through an SCMA codebook matrix The value of non-zero element in the data is determined when Middle (f) Line 1 When the column element is a non-zero element, the first element is represented Individual variable nodes And the first Personal sum node The weight is as follows The value of the corresponding position in the table Is connected with the connecting edge of (1) 。
  8. 8. The method of claim 7, wherein said pair of demodulation output signals in step (5) And The detection is carried out, and the implementation steps are as follows: (5a) The number of initialization iterations is The maximum iteration number is Each sum node The number of variable nodes connected is And node The index set of the variable nodes connected is From the slave Delete in The obtained set is First, the Second iteration (a) Personal sum node To the first Individual variable nodes The transferred message is First, the Individual variable nodes To the first Personal sum node The transferred message is And order , Wherein Representing the combination of all the connecting edges in the factor graph; (5b) Message passing algorithm using Log-MAX approximation and pass through Second iteration factor graph model Individual variable nodes To the first joint side Personal sum node Transmitted logarithmic domain information Calculation of the first of the factor graph models Personal sum node To the first joint side Individual variable nodes Transmitting log domain information Then pass through Computing variable nodes Is a modulation symbol sequence of (2) Log likelihood information of (a) ; (5C) Judging Whether or not it is true, if so, output the first Iteration variable node Is a modulation symbol sequence of (2) Log likelihood information of (a) Otherwise let And calculate the first of the factor graph models Individual variable nodes To the first joint side Personal sum node Transmitted logarithmic domain information And (5 b) executing the step.
  9. 9. The method of claim 8, wherein the logarithmic domain information of step (5 b) Log likelihood information The calculation formulas are respectively as follows: ; ; Wherein the method comprises the steps of 、 Represent the first Personal sum node The corresponding two paths of received signals are used for receiving the signal, Representing noise Is used for the power spectral density of (a), Represent the first Individual variable nodes Is a value of (a).
  10. 10. The method of claim 8, wherein the factor graph model of step (5 c) is the th Individual variable nodes To the first joint side Personal sum node Transmitted logarithmic domain information The calculation formula is as follows: 。

Description

Sparse code multiple access SCMA message transmission detection system and method suitable for 2FSK modulation Technical Field The invention belongs to the technical field of wireless communication and multiple access, and relates to a sparse code multiple access SCMA message transmission system and method suitable for binary Frequency Shift Keying (FSK) modulation, which can be used in the fields of Internet of things, wireless communication and the like. Background Sparse code multiple access, SCMA, is a non-orthogonal multiple access technique that enables multiplexed transmission of multiple users over a limited time-frequency resource unit by allocating multi-dimensional codewords with sparse structures to different users. The Sparse Code Multiple Access (SCMA) message transmission detection is carried out, and modulation symbols of a plurality of users are mapped to a shared resource unit through the corresponding sparse codebook for superposition transmission. Because the SCMA code words have a sparse structure in the resource dimension, a receiving end can construct a factor graph model according to the non-zero distribution relation of the codebook, wherein variable nodes correspond to different users, the nodes correspond to each resource unit, and the connection relation between the variable nodes and the nodes is determined by the positions of non-zero elements in the codebook. And carrying out message transfer detection on the output signals, and based on the factor graph model, the SCMA message transfer detection method realizes joint detection on multi-user superposition signals by iteratively exchanging logarithmic domain messages between variable nodes and sum nodes. In the detection process, the sum node calculates and updates the corresponding log domain information according to the received signals and the information transmitted by the variable nodes connected in the factor graph, and the variable nodes update the posterior probability of the user symbol sequence by combining the information from a plurality of sum nodes connected in the factor graph. For example, patent document filed as CN108075857a discloses a system and method for sparse code multiple access, which can realize coding gain by directly coding binary data into multidimensional code words, thus avoiding QAM symbol mapping adopted by traditional CDMA coding technology. Furthermore, multiple access can be achieved by assigning different codebooks to different multiplexing layers. In addition, sparse codewords may be used to reduce the baseband processing complexity at the receiver side of the network, since sparse codewords may be detected within a multiplexed codeword according to the message passing algorithm MPA. But the invention mainly detects the modulation signal based on amplitude and phase information, so that when the invention is applied to non-phase modulation such as binary frequency shift keying (2 FSK), the matching between the input of a message transmission detection module and the statistic of 2FSK coherent demodulation output is poor, the adaptability to non-phase modulation scenes is reduced, and the detection precision is further improved. The binary frequency shift keying 2FSK is used as a classical low-order digital modulation technology, so that information is carried in a frequency state form, dependence on carrier phase information is avoided, and the binary frequency shift keying 2FSK has good anti-interference capability, thereby reducing the requirement of a system on phase synchronization precision, providing a more stable judgment basis for subsequent detection, and being beneficial to improving signal detection precision. Disclosure of Invention The invention aims to overcome the defects in the prior art, and provides a sparse code multiple access SCMA message transmission detection system and method suitable for 2FSK modulation, which solve the technical problem of lower detection precision in the prior art. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: a sparse code multiple access SCMA message transmission detection system suitable for binary frequency shift keying 2FSK modulation comprises The system comprises a plurality of channel coding modules, SCMA mapping modules and 2FSK coherent demodulation modules, wherein the SCMA mapping modules and the 2FSK coherent demodulation modules are cascaded with each other, the output end of each channel coding module is cascaded with a 2FSK modulation module, and the output end of each 2FSK coherent demodulation module is cascaded with a message transmission detection module. A sparse code multiple access SCMA message passing detection method suitable for binary frequency shift keying 2FSK modulation comprises the following steps: (1) The channel coding module codes the original binary data information of the user: First, the Original binary data information of corresponding users by each chann