Lamb wave pulse code frequency division multiple access synchronous communication method and system

Abstract

The application belongs to the technical field of information transmission, and specifically discloses a Lamb wave pulse code frequency division multiple access synchronous communication method and system, which comprises the following steps: S1, a central base station inputs to-be-sent information into a PCF-DMA multiple access coding layer, and superimposes a plurality of FPPM code word streams corresponding to different users into a single PCF-DMA code word stream; S2, the obtained single PCF-DMA code word stream is used to excite a transmitting piezoelectric transducer, the piezoelectric transducer generates Lamb waves in the structure, the Lamb waves propagate along the structure to a plurality of receiving piezoelectric transducers and are converted into different electric signals; and S3, a PCF-DMA decoding layer decodes the received signals by using a shift-invariant sparse deconvolution method, and obtains original information. By using the technical scheme, the central base station can synchronously and independently send information to a plurality of users through a multiple access coding layer, a physical transmission layer and a multiple access decoding layer, and the technical scheme has the characteristics of strong anti-interference ability and high communication rate.

Description

Technical Field

[0001] This invention belongs to the field of information transmission technology and relates to a Lamb wave pulse code frequency division multiple access synchronous communication method and system. Background Technology

[0002] In aerospace and underwater equipment, there is an urgent need for wireless control of external actuators or sensors. For example, in space solar power plants, commands need to be issued by a central controller to adjust the attitude and angle of solar panels in real time to improve power generation efficiency. In long-service submarines, commands need to be sent to shut down externally battery-powered monitoring sensors upon completion of their missions to extend their lifespan. Furthermore, various actuators can replace manual operation in hazardous environments. Traditional wired transmissions compromise structural strength and airtightness, which would be catastrophic for both space and underwater applications. Wireless transmissions based on electromagnetic waves are susceptible to interference from space radiation and metallic structures.

[0003] Overall, these application scenarios present the following challenges to data transmission systems:

[0004] (1) Wireless cross-space transmission unaffected by electromagnetic radiation;

[0005] (2) Transmit information to multiple users synchronously and independently;

[0006] (3) It has strong reliability in harsh working environments.

[0007] Lamb waves are a special type of elastic wave guided by the upper and lower surfaces of a plate-like structure. By attaching piezoelectric sensors to the structure, Lamb waves can be excited and received based on the inverse piezoelectric effect and the direct piezoelectric effect, respectively. Lamb waves possess advantages such as long transmission distance, low attenuation, immunity to electromagnetic radiation, and the ability to propagate on curved surfaces. Due to these advantages, Lamb wave-based solid-state structure communication has attracted researchers' attention in recent years and is considered a strong candidate for solving the aforementioned challenges.

[0008] However, in scenarios where a central base station simultaneously controls multiple users, interference between different channels (inter-address interference) can severely degrade the reliability of the transmission system. Common multiple access strategies include frequency division multiple access (FDMA), code division multiple access (CDMA), and time division multiple access (TDMA). FDMA requires high-performance filters and mixers, as well as large frequency spacing to suppress inter-address interference, which is difficult for a large number of users and situations with limited bandwidth. In CDMA, different spreading codes are used to distinguish users, which requires complex signal processing and decoding techniques, resulting in high complexity of the communication system. In TDMA, time is divided into multiple time slots, and each user transmits data within its own time slot. As the number of users increases, the time slot corresponding to each user becomes shorter, leading to slower transmission.

[0009] Furthermore, since different users use different time slots, precise synchronous transmission is impossible, which is unacceptable for scenarios with high synchronization requirements. Finally, and most importantly, due to structural boundaries, Lamb wave propagation suffers from severe multipath fading, exacerbating inter-access interference in multi-user transmission systems, reducing the reliability of traditional multiple access technologies, and limiting the application of Lamb wave communication technology in multi-user scenarios. Summary of the Invention

[0010] The purpose of this invention is to provide a Lamb wave pulse code frequency division multiple access synchronous communication method and system, which enables the central base station to transmit information synchronously and independently to multiple users, with strong anti-interference ability and high communication rate.

[0011] To achieve the above objectives, the basic solution of this invention is: a Lamb wave pulse code frequency division multiple access synchronous communication method, comprising the following steps:

[0012] S1, the central base station inputs the information to be transmitted into the PCF-DMA multiple access coding layer, and superimposes multiple fast pulse position modulation (FPPM) codeword streams corresponding to different users into a single PCF-DMA codeword stream;

[0013] S2, using the obtained single PCF-DMA codeword stream to excite the transmitting piezoelectric transducer, the piezoelectric transducer generates a Lamb wave in the structure, the Lamb wave propagates along the structure to multiple receiving piezoelectric transducers and is converted into different electrical signals;

[0014] S3, the PCF-DMA decoding layer uses a shift-invariant sparse deconvolution method to decode the received signal and obtain the original information.

[0015] The working principle and beneficial effects of this basic scheme are as follows: This technical scheme proposes a fast pulse position modulation (FPPM) method by introducing a new dimension "frame". Compared with the traditional pulse position modulation method, this method can further improve the data communication rate.

[0016] Starting from the characteristics of Lamb wave excitation pulses, pulse code frequency division multiple access (FDMA) coding is performed, utilizing pulse position modulation information and distinguishing users based on pulse cycle number and center frequency. The normalized cross-correlation coefficient is used as a reliability design index for multi-user communication, which helps suppress inter-address crosstalk in multi-user communication systems. Based on the Lamb wave propagation channel itself, a time-invariant sparse deconvolution method is proposed for information decoding. This invention is used for synchronous independent wireless multi-user communication, facilitating the application of Lamb communication methods in the field of wireless multi-user communication. It features high communication speed, strong anti-interference capability, adaptability to various environments, and ease of implementation.

[0017] Furthermore, the method for obtaining the FPPM codeword streams for different users is as follows:

[0018] The raw information to be sent to different users is converted into a bit stream;

[0019] Based on the Fast Pulse Position Modulation (FPPM) codebook, the bit streams corresponding to different users are mapped to FPPM codeword streams;

[0020] The width of each codeword is T. c It is divided into N f Each width is T f The frames are further subdivided into N. ts Each width is T ts In the time slot, the pulse width is set to be equal to the frame width, and the FPPM codeword stream x FPPM (t) is represented as:

[0021]

[0022] Where * denotes convolution operation, δ denotes unit impulse function, t denotes time; k denotes the k-th codeword in the FPPM codeword stream, l∈{0,1,2,…,N} ts} indicates that the pulse start position and the frame start position differ by l time slots, and data information is mapped here; the pulse function g(t) uses a Lamb wave to excite a Hanning window modulation signal commonly used in this process, and is expressed as:

[0023]

[0024] Among them, f c A is the center frequency, A is the pulse amplitude, and n is the number of cycles.

[0025] Based on traditional pulse position modulation, a new dimension, "frame," is introduced between codewords and time slots to obtain the Fast Pulse Position Modulation (FPPM) method.

[0026] Furthermore, multiple FPPM codeword streams corresponding to different users are superimposed into a single PCF-DMA codeword stream, and different users are distinguished by changing the number of cycles and center frequency of the Lamb wave pulse g(t);

[0027] Using the normalized cross-correlation coefficient between different layers of Lamb pulses as a reliability design metric for multiple access communication:

[0028]

[0029] Among them, NCC ij Represents the normalized cross-correlation coefficient between any two layers. This represents the cross-correlation function between the i-th layer and the j-th layer; τ and g represent the maximum values ​​of the autocorrelation functions of their respective layers; τ represents the independent variable in the autocorrelation function; g i (t) represents the lambda pulse function at time t of the i-th layer; i and j represent any two layers for the normalized cross-correlation operation;

[0030] The PCF-DMA codeword stream x obtained after superposition PCF-DMA (t) is represented as:

[0031]

[0032] in, This represents the PCF-DMA codeword stream at time t in layer m, where M indicates there are M layers in total, i.e., M users, and m corresponds to layer m. (m) This represents the k-th codeword in the m-th layer FPPM codeword stream. l represents the width of each codeword in the m-th layer FPPM codeword stream. (m) This represents the number of time slots between the pulse start position and the frame start position in the m-th layer FPPM codeword stream. G represents the slot width for further subdivision of the frame of each codeword in the m-th layer FPPM codeword stream. (m) (t) represents the lambda pulse function at time t in the m-th layer, A (m) Let be the pulse amplitude of the pulse function of the m-th layer lambda wave. Let n be the center frequency of the lambda pulse function of the m-th layer. (m) Let be the number of periods of the lambda pulse function in the m-th layer;

[0033] Set the time slot width T for different layers ts Frame width T f and codeword width T c Equal, ensuring that the transmission rate is equal for different users.

[0034] Obtain a single PCF-DMA codeword stream for later use.

[0035] Furthermore, the PCF-DMA codeword stream is used to excite the physical transport layer of the PCF-DMA, generating a Lamb wave in the structure and transmitting it to the user's PCF-DMA decoding layer. The specific method is as follows:

[0036] The PCF-DMA physical transmission layer is excited by the PCF-DMA codeword stream. The PCF-DMA physical transmission layer includes multiple piezoelectric transducers attached to the structure. Lamb waves are generated in the structure using the inverse piezoelectric effect and transmitted along the structure to the user's PCF-DMA decoding layer. The positive piezoelectric effect is used to convert them into electrical signals.

[0037] The original signal y received by the i-th user(i) (t) is:

[0038]

[0039] Among them, h (i) (t) is the impulse response of the physical channel between the central transmitter and the i-th user; M represents the total number of layers, i.e., M users, and m corresponds to the m-th layer; x PCF-DMA g(t) represents the PCF-DAM codeword stream; g(t) represents the impulse function; * represents the convolution operation; δ represents the unit impulse function; t represents time; k represents the k-th codeword in the FPPM codeword stream; l∈{0,1,2,…,N} ts} indicates that the pulse start position and the frame start position differ by l time slots, and data information is mapped here; n(t) represents the channel noise.

[0040] Lamb waves propagate along the structure to multiple receiving piezoelectric transducers, where they are converted into electrical signals using the positive piezoelectric effect, facilitating signal transmission.

[0041] Furthermore, the PCF-DMA decoding layer employs a shift-invariant sparse deconvolution method to decode the received signal, and the method for obtaining the original information is as follows:

[0042] For the i-th user, only the information from the i-th layer is useful and needs to be decoded; information from other layers is considered inter-address interference. Therefore, the signal received by the i-th user simplifies to:

[0043]

[0044] Where, n (i) (t) represents inter-address interference and channel noise from other layers;

[0045] Define atom a (i) (t)=h (i) (t)*g (i) (t), which indicates that the transmitter sends only one single pulse g corresponding to the i-th layer. (i) (t) represents the response of the i-th user; define a sparse position vector. The signal received by the i-th user can be further simplified to:

[0046] y (i) (t)=a (i) (t)*s (i) (t)+n (i) (t)

[0047] For a pre-designed PCF-DMA codebook, each user's atom a (i) (t) is fixed, i.e., shift invariant; sparse position vector s (i)Only a small number of elements in (t) are non-zero, representing atoms in y (i) At different positions in (t), the sparse position vector s is obtained by using time-invariant sparse deconvolution. (i) (t), the optimal sparse position vector is obtained by using the quasi-Newton method during the deconvolution process;

[0048] The optimal sparse position vector is mapped to the bit stream based on the FPPM encoding, and then the recovered bit stream is converted back into the original information.

[0049] The optimal sparse position vector is mapped to the bit stream based on the FPPM encoding, and then the recovered bit stream is converted back into the original information.

[0050] The present invention also provides a Lamb wave pulse code frequency division multiple access synchronous communication system based on the method described in the present invention, comprising a multiple access coding layer, a physical transport layer and a multiple access decoding layer connected in sequence;

[0051] The multiple access coding layer is used to superimpose multiple FPPM codeword streams corresponding to different users into a single PCF-DMA codeword stream;

[0052] The physical transport layer is used to generate Lamb waves in the structure;

[0053] The multiple access decoding layer is used to decode the received signal and obtain the original information.

[0054] This system enables wireless multi-user synchronous independent communication, featuring high communication speed, strong anti-interference capability, adaptability to various environments, and ease of implementation.

[0055] Furthermore, the physical transmission layer includes multiple piezoelectric transducers mounted on the structure.

[0056] The physical transport layer has a simple structure and uses the inverse piezoelectric effect to generate Lamb waves within the structure.

[0057] Furthermore, the multiple access decoding layer includes a decoding atom module, an optimal sparse position vector module, and a recovered bitstream module connected in sequence. The information received by the multiple access decoding layer is input into the decoding atom module, and the self-recovery bitstream module outputs the recovered information.

[0058] The multiple access decoding layer uses a shift-invariant sparse deconvolution method to perform multiple access decoding and restore the original information. Attached Figure Description

[0059] Figure 1 This is a flowchart illustrating the Lamb wave pulse code frequency division multiple access synchronous communication method of the present invention;

[0060] Figure 2This is a schematic diagram of the PCF-DMA multiple access coding process of the Lamb wave pulse code frequency division multiple access synchronous communication method of the present invention;

[0061] Figure 3 This is a flowchart illustrating the fast pulse position modulation process of the Lamb wave pulse code frequency division multiple access synchronous communication method of the present invention. Detailed Implementation

[0062] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0063] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0064] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0065] This invention discloses a Lamb wave pulse code frequency division multiple access synchronous communication method for wireless multi-user synchronous independent communication. It enables a central base station to synchronously and independently transmit information to multiple users, and features high communication speed, strong anti-interference capability, adaptability to various environments, and ease of implementation. Figure 1 As shown, the method includes the following steps:

[0066] S1, the central base station inputs the information to be transmitted (i.e. the original information) into the PCF-DMA (Lamb Wave Pulse Code Frequency Division Multiple Access) multiple access coding layer, and superimposes multiple fast pulse position modulation (FPPM) codeword streams corresponding to different users into a single PCF-DMA codeword stream;

[0067] S2, using the obtained single PCF-DMA codeword stream to excite the transmitting piezoelectric transducer, the piezoelectric transducer generates a Lamb wave in the structure (e.g., a thin plate structure, such as a 2 mm thick, 1 square meter square aluminum plate used in the experiment), the Lamb wave propagates along the structure to multiple receiving piezoelectric transducers and is converted into different electrical signals.

[0068] S3, the PCF-DMA decoding layer uses a shift-invariant sparse deconvolution method to decode the received signal and obtain the original information.

[0069] In a preferred embodiment of the present invention, such as Figure 3 As shown, the method for obtaining the FPPM codeword stream for different users is as follows:

[0070] The raw information to be sent to different users (such as control commands to be sent to different actuators, such as "forward 5 cm" or "turn left 90 degrees") is converted into bit streams (such as "14535125..." or "13425235...").

[0071] Based on the Fast Pulse Position Modulation (FPPM) codebook, the bit streams corresponding to different users are mapped to FPPM codeword streams;

[0072] In traditional Pulse Position Modulation (PPM), each codeword is divided into multiple time slots, with the pulse width equal to the time slot width. As the number of time slots increases, the transmission rate of PPM decreases, significantly limiting its application. This technical solution, based on traditional PPM, introduces a new dimension, the "frame," between the codeword and time slot, resulting in Fast Pulse Position Modulation (FPPM). The width of each codeword is T. c It is divided into N f Each width is T f The frames are further subdivided into N. ts Each width is T ts The time slot, the number of frames N f ≥2, number of time slots N ts ≥1. The pulse width is set to equal the frame width, FPPM codeword stream x FPPM (t) = is expressed as:

[0073]

[0074] Where * denotes convolution operation, δ denotes unit impulse function, t denotes time; k denotes the k-th codeword in the FPPM codeword stream, l∈{0,1,2,…,N} ts} indicates that the pulse start position and the frame start position differ by l time slots, and data information is mapped here; the pulse function g(t) uses a Lamb wave to excite a Hanning window modulation signal commonly used in this process, and is expressed as:

[0075]

[0076] Among them, f c A is the center frequency, A is the pulse amplitude, and n is the number of cycles.

[0077] The transmission rate of the FPPM method is:

[0078]

[0079] This indicates that as the number of time slots N increases ts The increase in FPPM improves the transmission rate and overcomes the drawback of the limited rate of traditional PPM.

[0080] In a preferred embodiment of the present invention, such as Figure 2 As shown, the PCF-DMA codebook contains multiple layers, each corresponding to one user. Within each layer, bit information is mapped to FPPM codewords based on the FPPM codebook. Considering interference between different channels during multi-user communication, different layers are distinguished by changing the number of periods and center frequency of the Lamb wave pulse g(t).

[0081] The PCF-DMA codebook contains multiple layers, each corresponding to one user. Within each layer, bit information is mapped to FPPM codewords based on the FPPM codebook. Considering interference between different channels during multi-user communication, different layers are distinguished by changing the number of periods and center frequency of the Lamb wave pulse g(t).

[0082] Multiple FPPM codeword streams corresponding to different users are superimposed into a single PCF-DMA codeword stream. Different users are distinguished by changing the number of cycles and center frequency of the Lamb wave pulse g(t).

[0083] The normalized cross-correlation coefficient between Lamb pulses at different layers (each layer corresponds to a different user; for example, the first layer corresponds to the first user, and the second layer corresponds to the second user) is used as a reliability design metric for multiple access communication.

[0084]

[0085] Among them, NCC ij Represents the normalized cross-correlation coefficient between any two layers. This represents the cross-correlation function between the i-th layer and the j-th layer; τ and g represent the maximum values ​​of the autocorrelation functions of their respective layers; τ represents the independent variable in the autocorrelation function; g i (t) represents the lambda pulse function of the i-th layer at time t; i and j represent any two layers (users) for which the normalized cross-correlation coefficient operation is performed;

[0086] In this embodiment, when establishing the PCF-DMA encoding, it is necessary to ensure that the normalized cross-correlation coefficient between any two layers of pulses is less than 0.2, that is, weakly correlated or completely uncorrelated, in order to suppress inter-address interference.

[0087] The PCF-DMA codeword stream x obtained after superposition PCF-DMA (t) is represented as:

[0088]

[0089] in, This represents the PCF-DMA codeword stream at time t in layer m, where M indicates there are M layers in total, i.e., M users, and m corresponds to layer m. (m) This represents the k-th codeword in the m-th layer FPPM codeword stream. l represents the width of each codeword in the m-th layer FPPM codeword stream. (m) This represents the number of time slots between the pulse start position and the frame start position in the m-th layer FPPM codeword stream. G represents the slot width for further subdivision of the frame of each codeword in the m-th layer FPPM codeword stream. (m) (t) represents the lambda pulse function at time t in the m-th layer, A (m) Let be the pulse amplitude of the pulse function of the m-th layer lambda wave. Let n be the center frequency of the lambda pulse function of the m-th layer. (m) Let be the number of periods of the lambda pulse function in the m-th layer;

[0090] Set the time slot width T for different layers ts Frame width T f and codeword width T c Equal, ensuring that the transmission rate is equal for different users.

[0091] In a preferred embodiment of the present invention, the PCF-DMA physical transport layer is excited by the PCF-DMA codeword stream, generating a Lamb wave in the structure and transmitting it to the user's PCF-DMA decoding layer. The specific method is as follows:

[0092] The PCF-DMA physical transmission layer is excited by the PCF-DMA codeword stream. The PCF-DMA physical transmission layer includes multiple piezoelectric transducers attached to the structure. Lamb waves are generated in the structure using the inverse piezoelectric effect and transmitted along the structure to the user's PCF-DMA decoding layer. The Lamb waves propagate along the structure to multiple receiving piezoelectric transducers and are converted into electrical signals using the direct piezoelectric effect.

[0093] The original signal y received by the i-th user (i) (t) is:

[0094]

[0095] Among them, h (i) (t) is the impulse response of the physical channel between the central transmitter and the i-th user; M represents the total number of layers, i.e., M users, and m corresponds to the m-th layer; x PCF-DMA g(t) represents the PCF-DAM codeword stream; g(t) represents the impulse function; * represents the convolution operation; δ represents the unit impulse function; t represents time; k represents the k-th codeword in the FPPM codeword stream; l∈{0,1,2,…,N} ts} indicates that the pulse start position and the frame start position differ by l time slots, and data information is mapped here; n(t) represents the channel noise.

[0096] In a preferred embodiment of the present invention, the PCF-DMA decoding layer employs a shift-invariant sparse deconvolution method to decode the received signal and obtain the original information as follows:

[0097] For the i-th user, only the information from the i-th layer is useful and needs to be decoded; information from other layers is considered inter-address interference. Therefore, the signal received by the i-th user simplifies to:

[0098]

[0099] Where, n (i) (t) represents inter-address interference and channel noise from other layers;

[0100] Define atom a (i) (t)=h (i) (t)*g (i) (t), which indicates that the transmitter sends only one single pulse g corresponding to the i-th layer. (i) (t) represents the response of the i-th user; define a sparse position vector. The signal received by the i-th user can be further simplified to:

[0101] y (i) (t)=a (i) (t)*s (i) (t)+n (i) (t)

[0102] For a pre-designed PCF-DMA codebook, each user's atom a (i) (t) is fixed, i.e., shift invariant; sparse position vector s (i) Only a small number of elements in (t) are non-zero, representing atoms in y (i) At different positions in (t), the sparse position vector s is obtained by using time-invariant sparse deconvolution. (i)(t), the optimal sparse position vector is obtained by quasi-Newton method during the deconvolution process; in this embodiment, atom a (i) (t) is pre-collected, and y is obtained for each message sent. (i) (t), the sparse position vector s is solved by time-invariant sparse deconvolution. (i) (t). The optimal sparse position vector is obtained by using a quasi-Newton method during the deconvolution process;

[0103] The optimal sparse position vector is mapped to the bit stream based on the FPPM encoding, and then the recovered bit stream is converted back into the original information.

[0104] The present invention also provides a Lamb wave pulse code frequency division multiple access synchronous communication system based on the method described in the present invention, comprising a multiple access coding layer, a physical transport layer and a multiple access decoding layer connected in sequence;

[0105] The multiple access coding layer is used to superimpose multiple FPPM codeword streams corresponding to different users into a single PCF-DMA codeword stream;

[0106] The physical transport layer is used to generate Lamb waves in the structure;

[0107] The multiple access decoding layer is used to decode the received signal and obtain the original information.

[0108] This system enables wireless multi-user synchronous independent communication, featuring high communication speed, strong anti-interference capability, adaptability to various environments, and ease of implementation.

[0109] In a preferred embodiment of the present invention, the physical transport layer includes a plurality of piezoelectric transducers, which are mounted (e.g., glued) to the structure. The physical transport layer has a simple structure and utilizes the inverse piezoelectric effect to generate Lamb waves within the structure.

[0110] In a preferred embodiment of the present invention, the multiple access decoding layer includes a decoding atom module, an optimal sparse position vector module, and a recovered bitstream module connected in sequence. Information received by the multiple access decoding layer is input to the decoding atom module, and the recovered bitstream module outputs the recovered information. The multiple access decoding layer employs a time-invariant sparse deconvolution method to perform multiple access decoding and recover the original information.

[0111] This invention proposes a Fast Pulse Position Modulation (FPPM) method by introducing a new dimension, the "frame," which can further improve data communication rates compared to traditional pulse position modulation methods. Starting from the characteristics of Lamb wave excitation pulses, a pulse code frequency division multiple access (PDMA) coding method is proposed, utilizing pulse position modulation information and distinguishing users based on the number of pulse cycles and the center frequency. Furthermore, the normalized cross-correlation coefficient is used as a reliability design index for multiple access communication, which helps suppress inter-address crosstalk in multi-user communication systems. Finally, based on the Lamb wave propagation channel itself, a time-invariant sparse deconvolution method is proposed for information decoding. This invention contributes to the application of Lamb communication methods in the field of wireless multi-user communication.

[0112] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0113] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A Lamb wave pulse code frequency division multiple access synchronous communication method, characterized in that, Includes the following steps: S1, the central base station inputs the information to be transmitted into the PCF-DMA multiple access coding layer, and superimposes multiple fast pulse position modulation (FPPM) codeword streams corresponding to different users into a single PCF-DMA codeword stream; S2, using the obtained single PCF-DMA codeword stream to excite the transmitting piezoelectric transducer, the piezoelectric transducer generates a Lamb wave in the structure, the Lamb wave propagates along the structure to multiple receiving piezoelectric transducers and is converted into different electrical signals; S3, the PCF-DMA decoding layer uses a shift-invariant sparse deconvolution method to decode the received signal and obtain the original information; The method for obtaining the FPPM codeword streams of different users is as follows: The raw information to be sent to different users is converted into a bit stream; Based on the Fast Pulse Position Modulation (FPPM) codebook, the bit streams corresponding to different users are mapped to FPPM codeword streams; The width of each codeword is , divided into Each width is The frames, each frame is further subdivided into Each width is In the time slot, the pulse width is set to be equal to the frame width, and the FPPM codeword stream... Represented as: ， in, δ represents the convolution operation, t represents the unit impulse function, and t represents time. Indicates the first in the FPPM codeword stream Each code character This indicates the difference between the pulse start position and the frame start position. Each time slot maps data information; pulse function The Lamb wave excitation commonly used Hanning window modulation signal is represented as: ， in, It is the center frequency. It is the pulse amplitude. It is the number of cycles.

2. The Lamb wave pulse code frequency division multiple access synchronous communication method as described in claim 1, characterized in that, Multiple FPPM codeword streams corresponding to different users are superimposed into a single PCF-DMA codeword stream, and the Lamb wave pulses are changed between different users. They are distinguished by the number of cycles and the center frequency; Using the normalized cross-correlation coefficient between different layers of Lamb pulses as a reliability design metric for multiple access communication: ， in, Represents the normalized cross-correlation coefficient between any two layers. This represents the cross-correlation function between the i-th layer and the j-th layer; , These represent the maximum values ​​of the autocorrelation function for each layer; This represents the independent variable in the correlation function; The lambda pulse function of the i-th layer at time t; i and j represent any two layers for the normalized cross-correlation operation; The PCF-DMA codeword stream obtained after superposition Represented as: ， in, This represents the PCF-DMA codeword stream at time t in layer m, where M indicates that there are M layers in total, i.e., M users, and m corresponds to the m-th layer. Represents the m-th layer FPPM codeword stream. Each code character This represents the width of each codeword in the m-th layer FPPM codeword stream. This represents the number of time slots between the pulse start position and the frame start position in the m-th layer FPPM codeword stream. Denotes the slot width of the frame further subdivision for each codeword in the m-th layer FPPM codeword stream. Lamb wave impulse function at time t in the m-th layer Let be the pulse amplitude of the pulse function of the m-th layer lambda wave. Let be the center frequency of the lambda pulse function of the m-th layer. Let be the number of periods of the lambda pulse function in the m-th layer; Set the time slot width for different layers Frame width and code width Equal, ensuring that the transmission rate is equal for different users.

3. The Lamb wave pulse code frequency division multiple access synchronous communication method as described in claim 1, characterized in that, The PCF-DMA codeword stream is used to excite the physical transport layer of the PCF-DMA, generating a Lamb wave in the structure and transmitting it to the user's PCF-DMA decoding layer. The specific method is as follows: The PCF-DMA physical transmission layer is excited by the PCF-DMA codeword stream. The PCF-DMA physical transmission layer includes multiple piezoelectric transducers attached to the structure. Lamb waves are generated in the structure using the inverse piezoelectric effect and transmitted along the structure to the user's PCF-DMA decoding layer. The positive piezoelectric effect is used to convert them into electrical signals. No. The raw signal received by each user for: ， in, It is the central transmitter and the first The impulse response of the physical channel between users; M represents that there are a total of M layers, that is, M users, and m corresponds to the m-th layer; Represents the PCF-DAM codeword stream; Represents the impulse function; This represents the convolution operation. This represents the unit impulse function, where t represents time. Indicates the first in the FPPM codeword stream Each code character; This indicates the difference between the pulse start position and the frame start position. Each time slot maps data information; This indicates channel noise.

4. The Lamb wave pulse code frequency division multiple access synchronous communication method as described in claim 3, characterized in that, The PCF-DMA decoding layer employs a shift-invariant sparse deconvolution method to decode the received signal and obtain the original information as follows: For the The user, only from the first Information from the first layer is useful and needs to be decoded; information from other layers is considered inter-address interference. The signal received by each user can be simplified as follows: ， in, These are inter-address interference and channel noise from other layers; Define an atom This indicates that the transmitter only sends one corresponding to the first... single pulse of the layer Time The response of each user; define a sparse location vector. , No. The signal received by each user can be further simplified to: ， For a pre-designed PCF-DMA codebook, each user's atom It is fixed, i.e., time-invariant; sparse position vectors Only a few elements in the matrix are non-zero, representing atoms in the matrix. At different positions in the vector, the sparse position vector is solved by time-invariant sparse deconvolution. The optimal sparse position vector is obtained by using the quasi-Newton method during the deconvolution process. The optimal sparse position vector is mapped to the bit stream based on the FPPM encoding, and then the recovered bit stream is converted back into the original information.

5. A Lamb wave pulse code frequency division multiple access synchronous communication system based on the method of any one of claims 1-4, characterized in that, It includes a multiple access coding layer, a physical transport layer, and a multiple access decoding layer connected in sequence; The multiple access coding layer is used to superimpose multiple FPPM codeword streams corresponding to different users into a single PCF-DMA codeword stream; The physical transport layer is used to generate Lamb waves in the structure; The multiple access decoding layer is used to decode the received signal and obtain the original information; The physical transport layer includes multiple piezoelectric transducers mounted on the structure.

6. The Lamb wave pulse code frequency division multiple access synchronous communication system as described in claim 5, characterized in that, The multiple access decoding layer includes a decoding atom module, an optimal sparse position vector module, and a recovered bitstream module connected in sequence. The information received by the multiple access decoding layer is input into the decoding atom module, and the self-recovery bitstream module outputs the recovered information.

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