LoRa modulation and demodulation method and system based on four-dimensional constellation diagram

Abstract

The invention relates to the technical field of wireless communication, and provides a LoRa modulation and demodulation method and system based on a four-dimensional constellation diagram, and the method comprises the steps: segmenting the bit of to-be-transmitted information into four modulation bit sequences and a constellation mapping bit sequence at a transmitting end, determining the coordinates of four-dimensional constellation points, carrying out the LoRa modulation of each modulation bit sequence, and carrying out the LoRa modulation of each modulation bit sequence; a corresponding LoRa modulation signal is generated; wherein the at least one LoRa modulation signal is modulated based on an up chirp linear frequency modulation signal, and the at least one LoRa modulation signal is modulated based on a down chirp linear frequency modulation signal; superposing the multiple paths of signals to generate a transmitting signal; and performing demodulation processing on the received signal at a receiving end based on the up chirp linear frequency modulation signal and the down chirp linear frequency modulation signal. Compared with the prior art, the signal transmission speed under the LoRa technology is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a LoRa modulation and demodulation method and system based on a four-dimensional constellation diagram. Background Technology

[0002] In recent years, with the rapid development of IoT technology, low-power wide-area communication (LPWAN) has played an increasingly important role in large-scale deployment scenarios such as smart agriculture, environmental monitoring, and smart buildings. To meet the demands for long-distance, low-power communication, LPWAN technology has gradually become a key infrastructure in the IoT system. Among various LPWAN technology paths, LoRa (Long Range) has been widely used in various IoT terminal devices due to its mature industry chain and flexible networking capabilities, forming a relatively complete ecosystem. Although LoRa technology has the advantage of adjustable transmission distance, its communication performance is still limited by the configuration of the spreading factor.

[0003] Currently, while increasing the spreading factor can extend communication distance, it significantly reduces data transmission rate, weakens the real-time performance of data exchange, increases communication latency, and raises the probability of data loss in weak signal or interference environments. On the other hand, rate limitation reduces channel utilization efficiency, restricts the number of concurrent devices the system can support within a given time period, and thus constrains the overall capacity and scalability of the IoT system. Furthermore, given the increasing prevalence of high-speed communication demands, low-rate transmission modes struggle to support high-frequency data acquisition and real-time control applications, impacting end-user experience and system market competitiveness. Summary of the Invention

[0004] To overcome the shortcomings of low transmission efficiency described in the prior art, this invention provides a LoRa modulation and demodulation method and system based on a four-dimensional constellation diagram.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: A LoRa modulation and demodulation method based on a four-dimensional constellation diagram includes the following steps: At the transmitting end, the bits of information to be transmitted are divided into four modulation bit sequences and one constellation mapping bit sequence; the four-dimensional constellation point coordinates are determined according to the constellation mapping bit sequence, wherein the modulation bit sequences correspond one-to-one with the different dimensions of the four-dimensional constellation point coordinates; LoRa modulation is performed on each modulation bit sequence to generate a corresponding LoRa modulation signal; wherein at least one LoRa modulation signal is modulated based on an up chirp linear frequency modulation signal, and at least one LoRa modulation signal is modulated based on a down chirp linear frequency modulation signal; each LoRa modulation signal is multiplied by the corresponding dimension of the four-dimensional constellation point coordinates to generate multiple signals, and the multiple signals are superimposed to generate the transmitted signal; At the receiving end, the received signal is demodulated based on the up chirp linear frequency modulation (LFM) signal and the down chirp LFM signal.

[0006] As a preferred embodiment, the real and imaginary parts of the four-dimensional constellation point coordinates are determined according to a preset mapping relationship, and a preset energy constraint condition is satisfied. The expression of the preset energy constraint condition is as follows:

[0007] in, These are the coordinates of the four-dimensional constellation points in the four dimensions.

[0008] As a preferred embodiment, the four modulation bit sequences are, in order, a first modulation bit sequence, a second modulation bit sequence, a third modulation bit sequence, and a fourth modulation bit sequence; wherein, the first and second modulation bit sequences are modulated based on an up chirp linear frequency modulation signal, and the third and fourth modulation bit sequences are modulated based on a down chirp linear frequency modulation signal.

[0009] As a preferred embodiment, the step of modulation based on the up-chirp linear frequency modulated signal includes: Map the modulated bit sequence to decimal sign values; The up chirp linear frequency modulation signal is modulated using the decimal sign value to generate a frequency modulation signal carrying information. The LoRa modulation signal is obtained by multiplying the frequency-modulated signal by the real or imaginary part of the complex coordinates corresponding to the four-dimensional constellation diagram; the LoRa modulation signal corresponding to the first modulation bit sequence. The generatrices are as follows:

[0010]

[0011] in, This represents a discrete-time up-chirp linear frequency modulated signal. Represents the energy of the transmitted symbol. , where n represents the time-domain index. This represents the decimal information carried by the modulated bit sequence. SF Spreading factor; first modulation bit sequence ; The LoRa modulation signal corresponding to the second modulation bit sequence The generatrices are as follows:

[0012]

[0013] in, j It is the symbol for imaginary numbers. This represents the decimal information carried by the second LoRa signal; the second modulation bit sequence. .

[0014] As a preferred embodiment, the step of modulation based on the down chirp linear frequency modulated signal includes: Map the modulated bit sequence to decimal sign values; The down chirp linear frequency modulation signal is modulated using the decimal sign value to generate a frequency modulation signal carrying information. The LoRa modulation signal is obtained by multiplying the frequency-modulated signal by the real or imaginary part of the complex coordinates corresponding to the four-dimensional constellation diagram; the LoRa modulation signal corresponding to the third modulation bit sequence. The generatrices are as follows:

[0015]

[0016] in, It is a LoRa modulated signal. This represents a discrete-time up-chirp linear frequency modulated signal. Represents the energy of the transmitted symbol. , where n represents the time-domain index. This represents the decimal information carried by the first LoRa signal. SF Spreading factor; third modulation bit sequence ; LoRa modulated signal corresponding to the fourth modulation bit sequence The generatrices are as follows:

[0017]

[0018] in, j It is the symbol for imaginary numbers. This represents the decimal information carried by the second LoRa signal, and the fourth modulation bit sequence. .

[0019] As a preferred embodiment, the step of demodulating the received signal based on the up-chirp linear frequency modulation signal and the down-chirp linear frequency modulation signal at the receiving end includes: splitting the received signal into two signals, multiplying them respectively with the initial up-chirp linear frequency modulation signal and the initial down-chirp linear frequency modulation signal, performing a discrete Fourier transform, and extracting the maximum value index and the maximum value based on the real part and the imaginary part of the transformed signal to recover the modulation bit sequence and the constellation mapping bit sequence.

[0020] As a preferred embodiment, the received signal also includes the effects of channel fading and additive white Gaussian noise, the expression of which is as follows:

[0021] in, It is the amplitude of the fading channel coefficient. With a mean of zero and a variance of , Additive white Gaussian noise.

[0022] The present invention also proposes a LoRa modulation and demodulation system based on a four-dimensional constellation diagram, the system comprising a transmitter and a receiver; The transmitter includes: The bitstream processing module is used to divide the total bitstream into multiple modulation bit sequences and a constellation-mapped bit sequence; The modulation mapping module is used to generate four-dimensional constellation point coordinates based on the constellation mapping bit sequence, and after performing LoRa modulation on each of the modulation bit sequences, to perform mapping and multiplication processing on the generated modulation signal and the corresponding dimension of the four-dimensional constellation point coordinates. The signal synthesis and generation module is used to superimpose the multiple signals processed by the modulation and mapping module to generate a transmission signal and send it to the receiving end; The receiving end includes: The signal receiving and processing module is used to perform coherent processing and transformation based on up chirp and down chirp on the received signal, and to recover the modulation bit sequence and the constellation mapping bit sequence.

[0023] The present invention also proposes an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement a LoRa modulation and demodulation method based on a four-dimensional constellation diagram as described in the present invention.

[0024] The present invention also proposes a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements a LoRa modulation and demodulation method based on a four-dimensional constellation diagram as described in the present invention.

[0025] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows: This invention achieves synchronous transmission of multi-bit information within one LoRa symbol period through a collaborative architecture of parallel transmission of four orthogonal signals and mapping of a four-dimensional constellation diagram. It maps and superimposes four modulation signals with different dimensions of a four-dimensional constellation point. This is equivalent to compressing four traditional LoRa symbols and additional constellation diagram encoding information into the same symbol period for transmission, thereby multiplying the transmission rate per unit time and significantly accelerating the transmission speed. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the LoRa modulation and demodulation method based on a four-dimensional constellation diagram in Example 1; Figure 2 This is a schematic diagram of the transmitter frame of Example 1.

[0027] Figure 3 This is a schematic diagram of the receiving end of Example 1.

[0028] Figure 4 This is a diagram of the LoRa modulation and demodulation system architecture based on a four-dimensional constellation diagram, as shown in Example 2.

[0029] Figure 5 This is a comparison of the number of bits carried by each symbol in the method of this application and the traditional LoRa modulation scheme under different spreading factors when Np=4 in Example 3.

[0030] Figure 6 This is a comparison of the number of bits carried by each symbol in the method of this application and the traditional LoRa modulation scheme under different spreading factors when Np=8 in Example 3. Detailed Implementation

[0031] In the embodiments of this application, certain software, components, models and other existing solutions in the industry may be mentioned. These should be regarded as exemplary and are only intended to illustrate the feasibility of implementing the technical solution of this application. However, they do not mean that the applicant has used or necessarily used the solution.

[0032] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent. To better illustrate this embodiment, some parts in the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions; It will be understood by those skilled in the art that certain well-known structures and their descriptions may be omitted in the accompanying drawings.

[0033] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] Example 1 This embodiment proposes a LoRa modulation and demodulation method based on a four-dimensional constellation diagram, such as... Figure 1 The diagram shown is a schematic flowchart of a LoRa modulation and demodulation method based on a four-dimensional constellation diagram in this embodiment.

[0035] A LoRa modulation and demodulation method based on a four-dimensional constellation diagram, the method comprising: At the transmitting end, the bits of information to be transmitted are divided into four modulation bit sequences and one constellation mapping bit sequence; the four-dimensional constellation point coordinates are determined according to the constellation mapping bit sequence, wherein the modulation bit sequences correspond one-to-one with the different dimensions of the four-dimensional constellation point coordinates; LoRa modulation is performed on each modulation bit sequence to generate a corresponding LoRa modulation signal; wherein at least one LoRa modulation signal is modulated based on an up chirp linear frequency modulation signal, and at least one LoRa modulation signal is modulated based on a down chirp linear frequency modulation signal; each LoRa modulation signal is multiplied by the corresponding dimension of the four-dimensional constellation point coordinates to generate multiple signals, and the multiple signals are superimposed to generate the transmitted signal; At the receiving end, the received signal is demodulated based on the up chirp linear frequency modulation (LFM) signal and the down chirp LFM signal.

[0036] In this embodiment, a high-dimensional signal space is constructed by segmenting the bitstream into multiple modulation sequences and mapping them to four-dimensional constellation points, combined with hybrid modulation of upchirp and downchirp linear frequency modulation signals. This embodiment expands the modulation dimension of traditional LoRa through the four-dimensional constellation diagram, significantly increasing the number of bits carried per symbol, thereby improving the transmission rate. The multi-dimensional modulation mechanism enhances the parallel processing capability of the signal, reduces data transmission time, and meets the stringent real-time response requirements of IoT applications. Simultaneously, the hybrid use of upchirp and downchirp signals increases signal diversity, reduces the risk of channel interference, and improves overall communication efficiency.

[0037] In an optional embodiment, the real and imaginary parts of the four-dimensional constellation point coordinates are determined according to a preset mapping relationship, and a preset energy constraint condition is satisfied. The expression of the preset energy constraint condition is as follows:

[0038] in, These are the coordinates of the four-dimensional constellation points in the four dimensions.

[0039] In this embodiment, by introducing energy constraints, the energy of the four-dimensional constellation point coordinates is ensured to be evenly distributed, avoiding the peak power problem caused by concentrated signal energy, enhancing the robustness of the method under fading channels, and further improving transmission reliability.

[0040] In one optional embodiment, the four modulation bit sequences are, in sequence, a first modulation bit sequence, a second modulation bit sequence, a third modulation bit sequence, and a fourth modulation bit sequence; wherein the first and second modulation bit sequences are modulated based on an up chirp linear frequency modulation signal, and the third and fourth modulation bit sequences are modulated based on a down chirp linear frequency modulation signal.

[0041] In this embodiment, the orthogonality and diversity of the signal are achieved by distributing the modulation bit sequence as a mixture of up chirp and down chirp signals.

[0042] In an optional embodiment, the step of modulating based on the up-chirp linear frequency modulated signal includes: Map the modulated bit sequence to decimal sign values; The up chirp linear frequency modulation signal is modulated using the decimal sign value to generate a frequency modulation signal carrying information. The LoRa modulation signal is obtained by multiplying the frequency-modulated signal by the real or imaginary part of the complex coordinates corresponding to the four-dimensional constellation diagram; the LoRa modulation signal corresponding to the first modulation bit sequence. The generatrices are as follows:

[0043]

[0044] in, This represents a discrete-time up-chirp linear frequency modulated signal. Represents the energy of the transmitted symbol. , where n represents the time-domain index. This represents the decimal information carried by the modulated bit sequence. SF Spreading factor; first modulation bit sequence ; The LoRa modulation signal corresponding to the second modulation bit sequence The generatrices are as follows:

[0045]

[0046] in, j It is the symbol for imaginary numbers. This represents the decimal information carried by the second LoRa signal; the second modulation bit sequence. .

[0047] Further optionally, the step of modulating based on the down chirp linear frequency modulated signal includes: Map the modulated bit sequence to decimal sign values; The down chirp linear frequency modulation signal is modulated using the decimal sign value to generate a frequency modulation signal carrying information. The LoRa modulation signal is obtained by multiplying the frequency-modulated signal by the real or imaginary part of the complex coordinates corresponding to the four-dimensional constellation diagram; the LoRa modulation signal corresponding to the third modulation bit sequence. The generatrices are as follows:

[0048]

[0049] in, It is a LoRa modulated signal. This represents a discrete-time up-chirp linear frequency modulated signal. Represents the energy of the transmitted symbol. , where n represents the time-domain index. This represents the decimal information carried by the first LoRa signal. SF Spreading factor; third modulation bit sequence ; LoRa modulated signal corresponding to the fourth modulation bit sequence The generatrices are as follows:

[0050]

[0051] in, j It is the symbol for imaginary numbers. This represents the decimal information carried by the second LoRa signal, and the fourth modulation bit sequence. .

[0052] The four signals are then superimposed to generate the final output signal, the expression of which is as follows:

[0053] in, This is the final output signal.

[0054] like Figure 2 The diagram shown is a frame diagram of the transmitter.

[0055] In an optional embodiment, the step of demodulating the received signal based on the up chirp linear frequency modulation signal and the down chirp linear frequency modulation signal at the receiving end includes: splitting the received signal into two signals, multiplying them by the initial up chirp linear frequency modulation signal and the initial down chirp linear frequency modulation signal respectively, performing a discrete Fourier transform, and extracting the maximum value index and the maximum value based on the real part and the imaginary part of the transformed signal to recover the modulation bit sequence and the constellation mapping bit sequence.

[0056] More specifically, the received signal also includes the effects of channel fading and additive white Gaussian noise, expressed as follows:

[0057] in, It is the amplitude of the fading channel coefficient. With a mean of zero and a variance of , Additive white Gaussian noise.

[0058] Among them, the first signal The demodulation process is as follows: First, the received signal is multiplied by the initial up-chirp linear frequency modulated signal. Then perform a discrete Fourier transform, that is:

[0059] Then, extract respectively The real and imaginary parts are obtained respectively. and ,Right now:

[0060] Then extract them separately. and The index of the maximum value in the table is the estimated value of the decimal information carried by the first and second signals:

[0061]

[0062] according to and This allows us to obtain an estimate of the bit sequences transmitted by the first and second channels: and .

[0063] Then extract separately and The maximum value in the range is the estimated value of the first and second dimension coordinates of the constellation point:

[0064]

[0065] The demodulation process of the second signal is as follows: First, the received signal is multiplied by the initial down-linear frequency modulated signal. Then perform a Discrete Fourier Transform (DFT), that is:

[0066] Then, extract respectively The real and imaginary parts are obtained respectively. and ,Right now:

[0067] Then extract them separately. and The index of the maximum value in the data is the estimated value of the decimal information carried by the third and fourth signals:

[0068]

[0069] according to and This allows us to obtain estimates of the bit sequences transmitted via the third and fourth paths: and .

[0070] Then extract separately and The maximum value in the range is the estimated value of the third and fourth dimension coordinates of the constellation point:

[0071]

[0072] Finally, based on the estimated coordinates of the constellation points... The mapping relationship can be used to obtain an estimate of the constellation mapping bit sequence.

[0073] like Figure 3 The diagram shown is a frame diagram of the receiving end.

[0074] In this embodiment, efficient signal demodulation is achieved through de-pathing and discrete Fourier transform. The orthogonality of upchirp and downchirp signals is utilized to improve the accuracy of signal separation, thereby quickly recovering the original information. Furthermore, by considering the effects of channel fading and additive white Gaussian noise, the robustness of the method is enhanced, enabling it to adapt to multipath fading and noise interference, and improving transmission stability.

[0075] Example 2 This embodiment proposes a LoRa modulation and demodulation system based on a four-dimensional constellation diagram, applying a LoRa modulation and demodulation method based on a four-dimensional constellation diagram proposed in Embodiment 1. For example... Figure 4 The diagram shown is an architecture diagram of a LoRa modulation and demodulation system based on a four-dimensional constellation diagram in this embodiment.

[0076] This embodiment proposes a LoRa modulation and demodulation system based on a four-dimensional constellation diagram, including a transmitter and a receiver; The transmitter includes: The bitstream processing module is used to divide the total bitstream into multiple modulation bit sequences and a constellation-mapped bit sequence; The modulation mapping module is used to generate four-dimensional constellation point coordinates based on the constellation mapping bit sequence, and after performing LoRa modulation on each of the modulation bit sequences, to perform mapping and multiplication processing on the generated modulation signal and the corresponding dimension of the four-dimensional constellation point coordinates. The signal synthesis and generation module is used to superimpose the multiple signals processed by the modulation and mapping module to generate a transmission signal and send it to the receiving end; The receiving end includes: The signal receiving and processing module is used to perform coherent processing and transformation based on up chirp and down chirp on the received signal, and to recover the modulation bit sequence and the constellation mapping bit sequence.

[0077] It is understood that the system in this embodiment corresponds to the method in Embodiment 1 above, and the options in Embodiment 1 above are also applicable to this embodiment, so they will not be described again here.

[0078] Example 3 This embodiment provides a specific implementation of the LoRa modulation and demodulation method based on a four-dimensional constellation diagram proposed in Embodiment 1.

[0079] like Figure 5 As shown, this is a comparison of the number of bits carried by each symbol in the proposed method and the traditional LoRa modulation scheme under different spreading factors when Np=4.

[0080] like Figure 6 As shown, this is a comparison of the number of bits carried by each symbol in the proposed method and the traditional LoRa modulation scheme under different spreading factors when Np=8.

[0081] Specifically, when Np=4 and SF=7, the modulation scheme proposed in this application improves the transmission rate by 357.1% compared to the LoRa modulation scheme; when Np=4 and SF=9, the proposed modulation scheme improves the transmission rate by 344.4% compared to the LoRa modulation scheme; when Np=4 and SF=12, the proposed modulation scheme improves the transmission rate by 333.3% compared to the LoRa modulation scheme; when Np=8 and SF=7, the proposed modulation scheme improves the transmission rate by 414.3% compared to the LoRa modulation scheme; when Np=8 and SF=9, the proposed modulation scheme improves the transmission rate by 388.9% compared to the LoRa modulation scheme; and when Np=8 and SF=12, the proposed modulation scheme improves the transmission rate by 366.7% compared to the LoRa modulation scheme.

[0082] In summary, this application significantly improves the transmission rate of LoRa modulation technology. The higher rate can significantly shorten data transmission time, thereby meeting the stringent real-time response requirements of scenarios such as smart cities and remote monitoring, and greatly improving communication efficiency between devices. At the same time, the increased transmission rate helps alleviate channel congestion, reduce network latency, and effectively improve the overall system throughput, providing reliable support for high-density device access.

[0083] Example 4 This embodiment proposes a computer device, including a memory and a processor. The memory stores computer-readable instructions, wherein when the computer-readable instructions are executed by the processor, the processor performs the steps of the LoRa modulation and demodulation method based on a four-dimensional constellation diagram proposed in Embodiment 1.

[0084] By way of example, the processor may be a central processing unit (CPU), a microprocessor unit (MPU), a digital signal processor (DSP), or a field programmable gate array (FPGA), etc.

[0085] Example 5 This embodiment proposes a storage medium storing computer-readable instructions, wherein when the computer-readable instructions are executed by a processor, they implement the steps of the LoRa modulation and demodulation method based on a four-dimensional constellation diagram proposed in Embodiment 1.

[0086] By way of example, the storage medium includes, but is not limited to, USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks or optical disks, and other media capable of storing program code.

[0087] By way of example, the instructions, programs, code sets, or instruction sets may be implemented using conventional programming languages.

[0088] By way of example, the processor includes, but is not limited to, smartphones, personal computers, servers, network devices, etc., for performing all or part of the steps of the LoRa modulation and demodulation method based on a four-dimensional constellation diagram as described in Example 1.

[0089] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0090] In different specific implementations, the methods or systems described in this application can be implemented in software, hardware, or a combination thereof. Furthermore, the order of the method steps can be changed, and various elements can be added, reordered, combined, omitted, or modified.

[0091] Obviously, the above embodiments of this application are merely examples for clearly illustrating this application, and are not intended to limit the implementation of this application, nor are they intended to limit this application. For those skilled in the art, other variations or modifications can be made based on the above description. The separate structural / functional modules or units can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part. The structure and function of the separate components can be implemented as a combined structure or component. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of the claims of this application.

Claims

1. A LoRa modulation and demodulation method based on a four-dimensional constellation diagram, characterized in that, The method includes: At the transmitting end, the bits of information to be transmitted are divided into four modulation bit sequences and one constellation mapping bit sequence; the four-dimensional constellation point coordinates are determined according to the constellation mapping bit sequence, wherein the modulation bit sequences correspond one-to-one with the different dimensions of the four-dimensional constellation point coordinates; LoRa modulation is performed on each modulation bit sequence to generate a corresponding LoRa modulation signal; wherein at least one LoRa modulation signal is modulated based on an up chirp linear frequency modulation signal, and at least one LoRa modulation signal is modulated based on a down chirp linear frequency modulation signal; each LoRa modulation signal is multiplied by the corresponding dimension of the four-dimensional constellation point coordinates to generate multiple signals, and the multiple signals are superimposed to generate the transmitted signal; At the receiving end, the received signal is demodulated based on the up chirp linear frequency modulation (LFM) signal and the down chirp LFM signal.

2. The LoRa modulation and demodulation method based on a four-dimensional constellation diagram as described in claim 1, characterized in that, The four-dimensional constellation point coordinates are determined according to a preset mapping relationship, which determines the real and imaginary parts of the constellation point coordinates, and satisfies a preset energy constraint condition. The expression of the preset energy constraint condition is as follows: in, These are the coordinates of the four-dimensional constellation points in the four dimensions.

3. The LoRa modulation and demodulation method based on a four-dimensional constellation diagram as described in claim 2, characterized in that, The four modulation bit sequences are, in order, a first modulation bit sequence, a second modulation bit sequence, a third modulation bit sequence, and a fourth modulation bit sequence; wherein, the first and second modulation bit sequences are modulated based on an up chirp linear frequency modulated signal, and the third and fourth modulation bit sequences are modulated based on a down chirp linear frequency modulated signal.

4. The LoRa modulation and demodulation method based on a four-dimensional constellation diagram as described in claim 3, characterized in that, The steps for modulation based on the up-chirp linear frequency modulated signal include: Map the modulated bit sequence to decimal sign values; The up chirp linear frequency modulation signal is modulated using the decimal sign value to generate a frequency modulation signal carrying information. The LoRa modulation signal is obtained by multiplying the frequency-modulated signal by the real or imaginary part of the complex coordinates corresponding to the four-dimensional constellation diagram; the LoRa modulation signal corresponding to the first modulation bit sequence. The generatrices are as follows: in, This represents a discrete-time up-chirp linear frequency modulated signal. Represents the energy of the transmitted symbol. , where n represents the time-domain index. This represents the decimal information carried by the modulated bit sequence. SF Spreading factor; first modulation bit sequence ; The LoRa modulation signal corresponding to the second modulation bit sequence The generatrices are as follows: in, j It is the symbol for imaginary numbers. This represents the decimal information carried by the second LoRa signal; the second modulation bit sequence. .

5. The LoRa modulation and demodulation method based on a four-dimensional constellation diagram as described in claim 3, characterized in that, The steps for modulation based on the down chirp linear frequency modulated signal include: Map the modulated bit sequence to decimal sign values; The down chirp linear frequency modulation signal is modulated using the decimal sign value to generate a frequency modulation signal carrying information. The LoRa modulation signal is obtained by multiplying the frequency-modulated signal by the real or imaginary part of the complex coordinates corresponding to the four-dimensional constellation diagram; the LoRa modulation signal corresponding to the third modulation bit sequence. The generatrices are as follows: in, It is a LoRa modulated signal. This represents a discrete-time up-chirp linear frequency modulated signal. Represents the energy of the transmitted symbol. , where n represents the time-domain index. This represents the decimal information carried by the first LoRa signal. SF Spreading factor; third modulation bit sequence ; LoRa modulated signal corresponding to the fourth modulation bit sequence The generatrices are as follows: in, j It is the symbol for imaginary numbers. This represents the decimal information carried by the second LoRa signal, and the fourth modulation bit sequence. .

6. The LoRa modulation and demodulation method based on a four-dimensional constellation diagram as described in any one of claims 3 to 5, characterized in that, The steps for demodulating the received signal at the receiving end based on the up-chirp linear frequency modulation (LFM) signal and the down-chirp LFM signal include: splitting the received signal into two signals, multiplying them by the initial up-chirp LFM signal and the initial down-chirp LFM signal respectively, performing a discrete Fourier transform, and extracting the maximum value index and maximum value based on the real and imaginary parts of the transformed signal to recover the modulation bit sequence and the constellation mapping bit sequence.

7. The LoRa modulation and demodulation method based on a four-dimensional constellation diagram as described in claim 6, characterized in that, The received signal also includes the effects of channel fading and additive white Gaussian noise, the expression of which is as follows: in, It is the amplitude of the fading channel coefficient. With a mean of zero and a variance of , Additive white Gaussian noise.

8. A LoRa modulation and demodulation system based on a four-dimensional constellation diagram, characterized in that, The LoRa modulation and demodulation method based on a four-dimensional constellation diagram according to any one of claims 1 to 7, wherein the system includes a transmitter and a receiver; The transmitter includes: The bitstream processing module is used to divide the total bitstream into multiple modulation bit sequences and a constellation-mapped bit sequence; The modulation mapping module is used to generate four-dimensional constellation point coordinates based on the constellation mapping bit sequence, and after performing LoRa modulation on each of the modulation bit sequences, to perform mapping and multiplication processing on the generated modulation signal and the corresponding dimension of the four-dimensional constellation point coordinates. The signal synthesis and generation module is used to superimpose the multiple signals processed by the modulation and mapping module to generate a transmission signal and send it to the receiving end; The receiving end includes: The signal receiving and processing module is used to perform coherent processing and transformation based on up chirp and down chirp on the received signal, and to recover the modulation bit sequence and the constellation mapping bit sequence.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the LoRa modulation and demodulation method based on a four-dimensional constellation diagram as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the LoRa modulation and demodulation method based on a four-dimensional constellation diagram as described in any one of claims 1 to 7.

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