Communication waveform design method based on multimode index modulation

Abstract

The invention discloses a communication waveform design method based on multimode index modulation, and belongs to the field of signal modulation. Aiming at the problems of low spectrum efficiency and low resource utilization rate caused by selective activation of subcarriers and idle waste of part of subcarriers in the existing AFDM-IM technology, the method comprises the following steps of: grouping AFDM subcarriers, splitting an information bit stream transmitted by the AFDM subcarriers into index bits and data bits, selecting a constellation mode through the index bits, and allocating the constellation mode to the subcarriers, the method comprises the following steps: selecting a constellation mode, modulating data bits by using the selected constellation mode, generating AFDM sub-blocks, performing AFDM modulation, adding a cyclic prefix, transmitting, removing the cyclic prefix by a receiving end, performing DAFT demodulation, and recovering a bit stream. According to the invention, all subcarriers are fully utilized, the spectrum efficiency and the energy efficiency are improved, more reliable data transmission is realized in a high-mobility scene, and an efficient waveform scheme is provided for 6G high-mobility communication.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of signal modulation technology, in particular to a communication waveform design method based on multi-mode index modulation. BACKGROUND

[0002] With the development of 6G wireless networks, communication networks are expanding from traditional ground to space-air-ground integration. High-speed rail, satellite, and Internet of Vehicles are becoming the core application fields of 6G, which puts forward strict requirements on communication systems: first, high-speed mobile support: to meet the terminal moving speed ≥1000km / h, far exceeding the 500km / h upper limit of 5G; second, high spectral efficiency: the spectrum resources of terahertz frequency band need to be used efficiently to support peak rates of more than 100Gbps; third, strong anti-interference ability: to resist double-selective fading and ensure communication reliability.

[0003] The core modulation technology of current 4G / 5G is usually OFDM, which achieves high spectral efficiency through the orthogonality of subcarriers. However, in high mobility scenarios, the Doppler shift will destroy the orthogonality between subcarriers, leading to inter-carrier interference and unable to guarantee reliable transmission.

[0004] AFDM (affine frequency division multiplexing) technology maps signals to the discrete affine Fourier domain through discrete affine Fourier transform, which can effectively separate time / frequency selective fading in channel paths, achieve full diversity gain, and has low pilot overhead, becoming a key alternative to OFDM in 6G high mobility scenarios.

[0005] To improve the spectral efficiency of AFDM, some researchers have proposed AFDM-IM technology by combining AFDM with index modulation: by activating part of the subcarriers to transmit PSK / QAM symbols, the index information is carried by the position of the activated subcarriers, which improves the spectral efficiency without increasing energy consumption. However, this technology has defects: only a limited number of subcarriers are activated, and the unactivated subcarriers are completely idle, resulting in low resource utilization and failing to fully exploit the potential of AFDM.

[0006] To address the resource waste problem of AFDM-IM, existing research has proposed various improvement schemes, including AFDM-QIM (quadrature index modulation AFDM) and AFDM-PIM (pre-chirp index modulation AFDM), etc. However, AFDM-QIM still has unactivated subcarriers, and the resource utilization rate has not been fundamentally solved. AFDM-PIM pre-chirp parameter adjustment increases the system complexity, which is not conducive to hardware implementation. Therefore, a new communication waveform design method is needed to achieve full subcarrier utilization, improve spectral efficiency and resource utilization, while maintaining low complexity, to support reliable transmission in 6G high mobility scenarios. SUMMARY

[0007] To address the shortcomings in the aforementioned background technology, this invention proposes a communication waveform design method based on multi-mode indexed modulation, called MM-AFDM-IM, to solve the resource waste problem caused by the underutilization of inactive subcarriers in traditional AFDM-IM, improve spectral efficiency and energy efficiency, and thus improve data transmission efficiency and reduce communication energy consumption.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A communication waveform design method based on multi-mode index modulation includes the following steps: Step S1: Group all subcarriers of an AFDM frame in the DAF domain into groups, with each group including several subcarriers; Specifically, an AFDM frame in the DAF domain is composed of Composed of AFDM subcarriers, the transmission consists of... These information bits will The average number of subcarriers is divided into There are 1 group, each containing 1 group. Subcarriers.

[0009] Step S2: Divide the total information bits into several parallel bit streams, each bit stream corresponding to a subcarrier group, and each bit stream is further divided into index bits and data bits; Specifically, combining the grouping in step S1, the total information bits Also classified as 4 parallel bit streams, each bit stream corresponding to a subcarrier group, each bit stream containing 12 parallel bit streams. Each bit, from the corresponding subcarrier group Transmit each subcarrier, and then in each bit stream Each bit is further divided into index bits and One data bit, .

[0010] Step S3: Determine the constellation mode corresponding to each subcarrier in each subcarrier group according to the preset mapping table and index bits; Specifically, step S3 includes: S31. According to the mapping rules, the first... The index bits of the bit stream corresponding to each subcarrier group Mapped to a unique combination of MAP and CAP, where, MAP is the constellation mode activation scheme for the target subcarrier group, specifically representing the activation scheme from the preset... Choose one of the constellation modes The activation scheme for each constellation mode, CAP is the subcarrier allocation scheme for the target subcarrier group, specifically indicating the selected subcarriers. Each constellation pattern is assigned to The allocation scheme for each subcarrier; S32. Determine the constellation mode corresponding to each subcarrier in the target subcarrier group based on MAP and CAP; Specifically, the mapping rules in step S31 include: S311, Move the index bits Convert to decimal ; S312. Find unique index pairs of MAP and CAP that satisfy the following conditions. : ; in, and These represent the indices in the feasible sets of MAP and CAP, respectively. , and These represent the number of elements in the feasible sets of MAP and CAP, respectively; S313. Based on the preset mapping table and index pair Determine MAP and CAP; where the mapping table represents the index pairs. The mapping relationship between MAP and CAP is defined in the mapping table, which includes all feasible sets of MAP and CAP.

[0011] Step S4: Based on the constellation pattern corresponding to each subcarrier in each subcarrier group determined in Step S3, extract the data bits from the bitstream corresponding to each subcarrier group. Modulated into data symbols, which are then transmitted by corresponding subcarriers; and then... Each subcarrier group corresponds to the generation of The AFDM sub-block, carrying the data symbols of the _____th ... Each AFDM sub-block is represented as: ; The generated Each AFDM sub-block is assembled into an information symbol vector in the DAF domain, represented as: ; Step S5: AFDM modulation is performed on the information symbol vector, a cyclic prefix is ​​added, and then serialization is performed before sending it to the time-frequency dual-selection channel; Specifically, step S5 includes: S51. Use the N-point inverse discrete affine Fourier transform to map the information symbol vector obtained in step 4 to the time domain, i.e., perform AFDM modulation. The signal after AFDM modulation is represented as: ; The matrix form is: ; S52. To combat the effects of multipath propagation, a chirp-periodic prefix (CPP) is added to the modulated signal: ; Then, a parallel-to-serial conversion is performed; S53. Send the serial signal to the time-frequency dual-selection channel for transmission.

[0012] Step S6: Receive the signal transmitted in the time-frequency dual-selection channel, remove the cyclic prefix from the received signal and perform a discrete affine Fourier transform to convert the signal from the time domain to the frequency domain and restore the bit stream of the information. Specifically, step S6 includes: S61. The receiving end receives the signal transmitted through the time-frequency dual-select channel, removes the linear frequency modulation period prefix, and performs serial-to-parallel conversion. The signal received after passing through the time-frequency dual-selection channel is: ; in It is additive Gaussian noise. It is time and delay The impulse response, , and Indicates the first Complex gain, Doppler shift, and integer delay of each path; After removing CPP, the matrix form can be represented as: ; in , It is a forward cyclic shift matrix: ; at the same time , yes Diagonal matrix: ; Then the signal is converted from serial to parallel; S62. Application of the converted signal Demodulation is performed using a point-based discrete affine Fourier transform (DAF), at which point the signal returns from the time domain to the DAF domain, yielding the received signal in the frequency domain. ; The matrix form is: ; in This represents the effective channel matrix in the DAF domain.

[0013] S63. Using a joint maximum likelihood detector on the demodulated frequency domain received signal, the data symbols and their corresponding constellation modes are reconstructed by searching all possible implementations of MAP, CAP, and data symbols: ; in Represents the complete index of all subcarrier group constellation mode selection schemes, each element Corresponding to the MAP index of each subcarrier group Represents the complete index of all subcarrier group subcarrier allocation schemes, each element Corresponding to the CAP index for each subcarrier group.

[0014] S64. Demap the data symbols according to the corresponding constellation pattern to restore the complete information bit stream.

[0015] In summary, the beneficial technical effects of the present invention are as follows: By assigning different modulation constellation modes to each subcarrier, the ADFM waveform is optimized, avoiding the resource waste caused by the underutilization of inactive subcarriers in traditional AFDM-IM, improving spectral efficiency and energy efficiency, and thus improving data transmission efficiency and reducing communication energy consumption. Attached Figure Description

[0016] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a system block diagram of the present invention; Figure 3 This is a performance comparison chart of the method of the present invention with classic OFDM and AFDM schemes. Detailed Implementation

[0017] To make the technical means, creative features, objectives and effects of this invention clearer and easier to understand, the invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0018] Example like Figure 1 , Figure 2 As shown, the communication waveform design method based on multi-mode index modulation provided by the present invention includes the following steps: Step S1: Group all subcarriers of an AFDM frame in the DAF domain into groups, with each group including several subcarriers; An AFDM frame in the DAF domain is Composed of AFDM subcarriers, the transmission consists of... These information bits will The average number of subcarriers is divided into There are 1 group, each containing 1 group. Subcarriers.

[0019] Step S2: Divide the total information bits into several parallel bit streams, each bit stream corresponding to a subcarrier group, and each bit stream is further divided into index bits and data bits; Combining the grouping in step S1, the total information bits B Also classified as 4 parallel bit streams, each bit stream corresponding to a subcarrier group, each bit stream containing 12 parallel bit streams. Each bit, from the corresponding subcarrier group Transmit each subcarrier, and then in each bit stream Each bit is further divided into index bits and One data bit, .

[0020] The MS-AFDM-IM system proposed in this invention uses indivual constellation mode Each subcarrier group will be from this Select from the constellation modes Each constellation mode is activated and assigned to Subcarriers, index bits The constellation mode activation pattern (MAP) and chirp allocation pattern (CAP) for each subcarrier group are determined, where MAP indicates which subcarrier group is activated. A constellation pattern, CAP indicates that this... Each constellation pattern is assigned to The scheme of one subcarrier, assuming yes Integer multiples, each constellation pattern is evenly distributed Given subcarriers, the possible implementations of MAP and CAP are respectively: ; and Therefore, the index bits It can be represented as: ; Data bits Will be A defined constellation pattern is mapped to data symbols, which are then transmitted by the corresponding subcarriers. It can be represented as: ; Step S3: Based on the preset mapping table and index bits Determine the constellation pattern corresponding to each subcarrier in each subcarrier group, specifically including: S31. According to the mapping rules, the first... The index bits of the bit stream corresponding to each subcarrier group Mapped to a unique combination of MAP and CAP, where, ; S32. Determine the constellation mode corresponding to each subcarrier in the target subcarrier group based on MAP and CAP; The mapping rules in S31 are as follows: S311, Move the index bits Convert to decimal ; S312. Find unique index pairs of MAP and CAP that satisfy the following conditions. : ; in, and These represent the indices in the feasible sets of MAP and CAP, respectively. , and These represent the number of elements in the feasible sets of MAP and CAP, respectively; S313. Based on the preset mapping table and index pair Determine MAP and CAP.

[0021] Among them, the mapping relationship table represents the index pairs. The mapping relationships between MAP and CAP are defined in the table, which includes the feasible sets of all MAPs and CAPs. The table below shows the mapping relationships when... Example of a time-mapping relationship table, where express The selected constellation pattern was assigned to the first Subcarriers, The following is a sample table of time mapping relationships: Step S4: Based on the constellation pattern corresponding to each subcarrier in each subcarrier group determined in Step S3, extract the data bits from the bitstream corresponding to each subcarrier group. Modulated into data symbols, which are then transmitted by corresponding subcarriers; and then... Each subcarrier group corresponds to the generation of The AFDM sub-block, carrying the data symbols of the _____th ... Each AFDM sub-block is represented as: ; The generated Each AFDM sub-block is assembled into an information symbol vector in the DAF domain, represented as: ; Step S5: AFDM modulation is performed on the information symbol vector, a cyclic prefix is ​​added, and then serialization is performed before sending it to the time-frequency dual-selection channel; Specifically, it includes: S51, Use The point-inverse discrete affine Fourier transform maps the information symbol vector obtained in step 4 to the time domain, i.e., performs AFDM modulation. The signal after AFDM modulation is represented as: ; The matrix form is: ; S52. To combat the effects of multipath propagation, a chirp-periodic prefix (CPP) is added to the modulated signal: ; Then the signal is converted from parallel to serial; S53. Send the serial signal to the time-frequency dual-selection channel for transmission.

[0022] Step S6: Receive the signal transmitted in the time-frequency dual-selection channel, remove the cyclic prefix from the received signal and perform a discrete affine Fourier transform to convert the signal from the time domain to the frequency domain and restore the bit stream of the information. Step S6 specifically includes: S61. The receiving end receives the signal transmitted through the time-frequency dual-select channel, removes the linear frequency modulation period prefix, and performs serial-to-parallel conversion. The signal received after passing through the time-frequency dual-selection channel is: ; in It is additive Gaussian noise. It is time and delay The impulse response, , and Indicates the first Complex gain, Doppler shift, and integer delay of each path; ; in , It is a forward cyclic shift matrix: ; at the same time , yes Diagonal matrix: ; Then the signal is converted from serial to parallel; S62. Application of the converted signal Demodulation is performed using a point-based discrete affine Fourier transform (DAF), at which point the signal returns from the time domain to the DAF domain, yielding the received signal in the frequency domain. ; The matrix form is: ; in This represents the effective channel matrix in the DAF domain.

[0023] S63. Using a joint maximum likelihood detector on the demodulated frequency domain received signal, the data symbols and their corresponding constellation modes are reconstructed by searching all possible implementations of MAP, CAP, and data symbols: ; in Represents the complete index of all subcarrier group constellation mode selection schemes, each element Corresponding to the MAP index of each subcarrier group Represents the complete index of all subcarrier group subcarrier allocation schemes, each element Corresponding to the CAP index for each subcarrier group.

[0024] S64. Demap the data symbols according to the corresponding constellation pattern to restore the complete information bit stream.

[0025] Figure 3 Shown in Under time-frequency dual-selection channels, the performance of the MM-AFDM-IM proposed in this invention is compared with AFDM-IM, distributed AFDM-IM, and SuM-OFDM-IM. All systems are configured at the same spectral efficiency to ensure fairness. The parameter set of the MM-AFDM-IM scheme of this invention is as follows: The eight subcarriers are divided into two groups of four, with four constellation modes, each with a modulation order of 2. Two modes from each group are selected and allocated to the subcarriers. The AFDM-IM and distributed AFDM-IM schemes use 8-QAM modulation, activating four of the eight subcarriers in each group. The SuM-OFDM-IM scheme uses 4-mode 16-QAM modulation. Figure 3 As shown, compared with other solutions, the MM-AFDM-IM of the present invention has the advantages of... The signal-to-noise ratio gain of more than 1.5dB is demonstrated at a low bit error rate level, proving the superiority of the MM-AFDM-IM scheme proposed in this invention.

[0026] Therefore, this invention provides a communication waveform design method based on multi-mode index modulation. Through the core process of mapping index bits to constellation patterns and allocating them to all subcarriers, generating AFDM sub-blocks and information symbol vectors through full-subcarrier data modulation, and combining IDAFT modulation with the linear frequency modulation periodic prefix (CPP), it achieves an efficient end-to-end communication link of "index information embedding - full subcarrier utilization - AFDM waveform transmission" in high-mobility scenarios. This solves the pain point of wasted spectrum resources due to inactive subcarriers in existing AFDM-IM technologies, improves spectrum efficiency and resource utilization in high-mobility scenarios, enhances the ability to combat Doppler shift and multipath fading, achieves more reliable data transmission, and maintains low complexity. It provides an efficient waveform solution for 6G high-mobility communication, ensuring the reliability and effectiveness of communication in high-mobility scenarios.

[0027] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A communication waveform design method based on multi-mode index modulation, characterized in that, Includes the following steps: S1. Divide all subcarriers of an AFDM frame in the DAF domain into groups, with each group including several subcarriers; S2. Divide the total information bits into several parallel bit streams, each bit stream corresponding to a subcarrier group, and each bit stream is further divided into index bits and data bits; S3. Determine the constellation mode corresponding to each subcarrier in each subcarrier group according to the preset mapping table and index bits; S4. According to the constellation mode determined in step S3, the data bits in the bit stream corresponding to each subcarrier group are modulated into data symbols, and then an AFDM sub-block is generated for each subcarrier group. All AFDM sub-blocks are assembled into an information symbol vector in the DAF domain. S5. AFDM modulation is applied to the information symbol vector, a cyclic prefix is ​​added, and serialization is performed before sending it to the time-frequency dual-selection channel. S6. Receive the signal transmitted in the time-frequency dual-select channel, remove the cyclic prefix from the received signal, perform a discrete affine Fourier transform, convert the signal from the time domain to the frequency domain, and restore the bit stream of the information.

2. The communication waveform design method based on multi-mode index modulation according to claim 1, characterized in that, Step S1 specifically involves: transferring an AFDM frame... The average number of subcarriers is divided into There are 1 group, each group includes Subcarriers.

3. The communication waveform design method based on multi-mode index modulation according to claim 2, characterized in that, Step S2 specifically involves: converting the total information bits... Divided into Several parallel bit streams, each corresponding to a subcarrier group, each bit stream including Each bit stream contains bits. Each bit is composed of the corresponding subcarrier group Subcarrier transmission, further, each bit stream is divided into index bits and 1 data bits, of which .

4. The communication waveform design method based on multi-mode index modulation according to claim 3, characterized in that, Step S3 includes: S31. According to the mapping rules, the first... The index bits of the bit stream corresponding to each subcarrier group Mapped to a unique combination of MAP and CAP, where, MAP is the constellation mode activation scheme for the target subcarrier group, specifically representing the activation scheme from the preset... Choose one of the constellation modes The activation scheme for each constellation mode, CAP is the subcarrier allocation scheme for the target subcarrier group, specifically indicating the selected subcarriers. Each constellation pattern is assigned to The allocation scheme for each subcarrier; S32. Determine the constellation mode corresponding to each subcarrier in the target subcarrier group based on MAP and CAP.

5. The communication waveform design method based on multi-mode index modulation according to claim 4, characterized in that, The mapping rules in step S31 include: S311, Move the index bits Convert to decimal ; S312. Find unique index pairs of MAP and CAP that satisfy the following conditions. : ； in, and These represent the indices in the feasible sets of MAP and CAP, respectively. , and These represent the number of elements in the feasible sets of MAP and CAP, respectively; S313. Based on the preset mapping table and index pair Determine MAP and CAP.

6. The communication waveform design method based on multi-mode index modulation according to claim 5, characterized in that, In step S313, the mapping relationship table represents the index pairs. The mapping relationship between MAP and CAP is defined in the mapping table, which includes all feasible sets of MAP and CAP.

7. The communication waveform design method based on multi-mode index modulation according to claim 1, characterized in that, Step S5 includes: S51. Perform processing on the information symbol vector. The point-inverse discrete affine Fourier transform maps a frequency domain signal to a time domain transmission signal; S52. Add a linear frequency modulation periodic prefix to the time-domain transmission signal and perform parallel-to-serial conversion; S53. Send the serial signal to the time-frequency dual-select channel.

8. The communication waveform design method based on multi-mode index modulation according to claim 1, characterized in that, Step S6 includes: S61. The receiving end receives the signal transmitted through the time-frequency dual-select channel, removes the linear frequency modulation period prefix, and performs serial-to-parallel conversion. S62, Perform the conversion on the signal. The discrete affine Fourier transform converts a time-domain signal into a frequency-domain received signal. S63. Use a joint maximum likelihood detector to search for the constellation mode activation scheme (MAP), subcarrier allocation scheme (CAP), and data symbol combination corresponding to the frequency domain received signal, and restore the data symbol and its corresponding constellation mode. S64. Demap the data symbols according to the constellation pattern to restore the complete information bit stream.

9. A communication waveform design method based on multi-mode index modulation according to claim 8, characterized in that, The specific search method for step S63 is as follows: ； in, Represents the information symbol vector in the DAF field. Indicates passage The frequency domain received signal obtained by point discrete affine Fourier transform demodulation. This represents the effective channel matrix in the DAF domain. Represents the complete index of all subcarrier group constellation mode selection schemes, each element Corresponding to the MAP index of each subcarrier group Represents the complete index of all subcarrier group subcarrier allocation schemes, each element Corresponding to the CAP index for each subcarrier group.

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