A shortwave DRM reliable reception method and system based on time-frequency retransmission

Abstract

The present application relates to the field of shortwave communication technology. To address the issues of low combining gain and limited anti-fading performance resulting from direct hard combining in traditional DRM reception combining methods, which fail to consider the impact of channel quality and signal-to-noise ratio, a reliable shortwave DRM reception method, system, computer-readable storage medium, and electronic device based on time-frequency retransmission are disclosed. The method comprises obtaining the QAM modulation order of each signal copy based on quick access channel information; obtaining the signal-to-noise ratio of each signal copy using a channel estimation algorithm; if the QAM modulation order of each signal copy is the same, weighted combining of each signal copy based on the signal-to-noise ratio on a QAM constellation diagram; and if the QAM modulation order of each signal copy is different, weighted combining of each signal copy based on the signal-to-noise ratio on a bit stream to obtain an enhanced DRM information bit stream. This method can increase combining gain and improve the anti-fading performance of the receiving end.

Description

Technical Field

[0001] The present application relates to the field of shortwave communication technology, and more specifically, to a shortwave DRM reliable reception method, system, computer-readable storage medium, and electronic device based on time-frequency retransmission. Background Art

[0002] Traditional analog AM broadcasting uses transmission frequencies below 30 MHz, encompassing three bands: long, medium, and short. However, due to its limited program coverage and poor sound quality, it faces significant challenges compared to other digital media. Therefore, the full digitization of AM broadcasting is urgent. For this reason, the worldwide digital radio community has developed the Digital Radio Mondiale (DRM) standard. This standard not only retains the advantages of analog AM broadcasting, including its wide coverage and suitability for mobile reception, but also overcomes its shortcomings, including poor transmission quality, limited services, and high transmission power. It also offers additional data services, demonstrating its enormous potential for development. A co-frequency network established using multiple transmitters not only expands coverage but also leverages the inherent multipath mitigation of OFDM systems to achieve multipath gain and increase channel capacity.

[0003] DRM uses shortwave communication. Compared to other communication methods, shortwave communication boasts a longer range, is compact, flexible, and easy to use, and can maintain effective communication even under extremely harsh conditions. Its unique advantages make it irreplaceable by other communication methods, and its importance in long-distance communication is undeniable. However, due to the harsh shortwave channel environment and the severe time- and frequency-selective fading of the signal, DRM signal detection presents significant challenges. Because the received signal structure is fixed, communication quality cannot be improved by adjusting the signal structure. Diversity reception combining is typically used to mitigate the effects of fading. The transmitter reduces the probability of simultaneous fading of signal components by sending two or more copies of a multi-tone modulated signal containing the same information. Diversity combining at the receiver effectively compensates for channel fading, significantly reducing the impact of fading channels and improving the capacity and reliability of shortwave communication. Therefore, research on shortwave multi-carrier modulation diversity reception technology is of vital importance for high-quality and reliable communication in shortwave fading channels. Current diversity reception combining of DRM signals suffers from the following main shortcomings:

[0004] 1. Merging fails to consider the impact of channel quality and signal-to-noise ratio: Currently, multiple signal replicas are combined using only maximum ratio combining. This also includes some signal replicas with poor channel quality or low signal-to-noise ratio, increasing the combining complexity without improving performance.

[0005] 2. The combining method is relatively simple: The current combining method uses hard combining, that is, combining directly on the demodulated bit stream, and does not use soft combining on the QAM constellation diagram. The combining gain is low and the anti-fading performance is poor. Summary of the Invention

[0006] In order to solve the problems that traditional DRM reception combining methods do not consider the influence of channel quality and signal-to-noise ratio, and the combining method is relatively single, resulting in low combining gain and poor anti-fading performance, the present invention provides a shortwave DRM reliable reception method, system, computer-readable storage medium and electronic device based on time-frequency retransmission. By selecting the combining method according to whether the modulation method is consistent and performing weighted processing according to the signal-to-noise ratio, the combining gain can be increased and the anti-fading performance of the receiving end can be improved, providing strong support for the time-frequency retransmission combining method of shortwave communication.

[0007] To achieve the above object, according to a first aspect of the present invention, a shortwave DRM reliable reception method based on time-frequency retransmission is provided, comprising:

[0008] Obtain the QAM modulation order of each signal copy according to the fast access channel information;

[0009] Obtain the signal-to-noise ratio of each signal copy through a channel estimation algorithm;

[0010] If the QAM modulation order of each signal copy is the same, then the signal copies are weighted and combined according to the signal-to-noise ratio on the QAM constellation diagram to obtain enhanced QAM symbols;

[0011] If the QAM modulation order of each signal copy is different, the signal copies are weighted and combined according to the signal-to-noise ratio on the bit stream to obtain an enhanced DRM information bit stream.

[0012] Furthermore, the QAM modulation order of each signal copy is obtained according to the quick access channel information, including obtaining the quick access channel information based on low-order modulation in each signal copy; and obtaining the QAM modulation order of each signal copy according to the quick access channel information.

[0013] Furthermore, the signal-to-noise ratio of each signal copy is obtained by a channel estimation algorithm, including obtaining the signal-to-noise ratio of each signal copy by a channel estimation algorithm; and filtering signal copies with a signal-to-noise ratio lower than a set threshold.

[0014] Furthermore, if the QAM modulation order of each signal copy is the same, weighted merging of each signal copy is performed on the QAM constellation diagram according to the signal-to-noise ratio to obtain an enhanced QAM symbol, including setting a first signal-to-noise ratio threshold; screening out signal copies whose signal-to-noise ratio is not lower than the first signal-to-noise ratio threshold; weighting at least one screened signal copy according to the signal-to-noise ratio, and merging them on the QAM constellation diagram to obtain an enhanced QAM symbol.

[0015] Furthermore, the above-mentioned shortwave DRM reliable reception method based on time-frequency retransmission also includes QAM demapping and decoding the enhanced QAM symbols to obtain an enhanced DRM information bit stream.

[0016] Furthermore, if the QAM modulation order of each signal copy is different, weighted merging of each signal copy is performed on the bit stream according to the signal-to-noise ratio to obtain an enhanced DRM information bit stream, including setting a second signal-to-noise ratio threshold; screening out signal copies whose signal-to-noise ratio is not lower than the second signal-to-noise ratio threshold; and weighted merging of at least one screened signal copy on the bit stream according to the signal-to-noise ratio to obtain an enhanced DRM information bit stream.

[0017] Furthermore, the at least one signal copy selected is weightedly combined on the bit stream according to the signal-to-noise ratio to obtain an enhanced DRM information bit stream, including QAM demapping and decoding the at least one signal copy selected; and each demapped and decoded data is weightedly combined on the bit stream according to the signal-to-noise ratio to obtain an enhanced DRM information bit stream.

[0018] According to the second aspect of the present invention, a shortwave DRM reliable receiving system based on time-frequency retransmission is also provided, comprising: a QAM modulation order acquisition unit, configured to acquire the QAM modulation order of each signal copy according to quick access channel information; a channel estimation unit, configured to acquire the signal-to-noise ratio of each signal copy through a channel estimation algorithm; a soft merging unit, configured to, when the QAM modulation order of each signal copy is the same, perform weighted merging of each signal copy on a QAM constellation diagram according to the signal-to-noise ratio to obtain an enhanced QAM symbol; a hard merging unit, configured to, when the QAM modulation order of each signal copy is different, perform weighted merging of each signal copy on a bit stream according to the signal-to-noise ratio to obtain an enhanced DRM information bit stream; and an output unit, configured to perform QAM demapping and decoding on the enhanced QAM symbols to output the enhanced DRM information bit stream.

[0019] According to a third aspect of the present invention, a computer-readable storage medium is provided, in which a computer program is stored, wherein the computer program is configured to execute the above-mentioned shortwave DRM reliable reception method based on time-frequency retransmission when running.

[0020] According to a fourth aspect of the present invention, an electronic device is also provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the shortwave DRM reliable reception method based on time-frequency retransmission through the computer program.

[0021] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0022] (1) The present invention provides a shortwave DRM reliable reception method based on time-frequency retransmission. The receiving end receives multiple signal copies obtained by the time and frequency diversity methods, and selects a merging method according to whether the QAM modulation order of each signal copy is consistent. That is, when the modulation orders are the same, the soft merging method is selected, that is, the signal copies of each channel are weighted and merged according to the signal-to-noise ratio on the QAM constellation diagram to obtain enhanced QAM symbols; when the modulation orders are different, the hard merging method is selected, that is, the signal copies of each channel are weighted and merged according to the signal-to-noise ratio on the bit stream, and finally the enhanced DRM information bit stream is output. Compared with the traditional single diversity merging method, this method can increase the merging gain, improve the anti-fading performance of the receiving end, and provide a guarantee for the reliable reception of DRM signals.

[0023] (2) The shortwave DRM reliable reception method based on time-frequency retransmission provided by the present invention directly discards some signal copies with poor channel quality or low signal-to-noise ratio according to the signal-to-noise ratio output by channel estimation and the set threshold, thereby reducing the merging complexity. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 A flowchart of a shortwave DRM reliable reception method based on time-frequency retransmission provided by an embodiment of the present application;

[0026] Figure 2 A schematic diagram of a two-way frequency diversity transmission process provided in an embodiment of the present application;

[0027] Figure 3 A flowchart of a shortwave DRM reliable reception method based on time-frequency retransmission provided by another embodiment of the present application;

[0028] Figure 4A flowchart of the soft merging method provided in an embodiment of the present application;

[0029] Figure 5 A flowchart of the weighted merging step in the soft merging method provided in an embodiment of the present application;

[0030] Figure 6 A schematic diagram of the structure of a shortwave DRM reliable reception system based on time-frequency retransmission provided in an embodiment of the present application;

[0031] Figure 7 A schematic structural diagram of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0033] The terms "first," "second," "third," and the like in the specification and claims of this application and the accompanying drawings are used to distinguish between different objects, not to describe a particular order. Furthermore, the terms "including," "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or elements is not limited to the listed steps or elements, but may optionally include steps or elements not listed, or may optionally include other steps or elements inherent to the process, method, product, or apparatus.

[0034] Figure 1 This is a flow chart of a shortwave DRM reliable reception method based on time-frequency retransmission provided by an embodiment of the present application. The method is based on time-frequency diversity (also called time-frequency retransmission) technology and is executed by the receiving end. In view of the serious fading problem of the shortwave channel during the detection and reception process, among the various methods for improving the detection and reception quality, the diversity reception technology has the most significant effect and is the most widely used. The diversity reception technology is that the receiving end receives multiple statistically independent fading signals carrying the same information, and merges the multiple fading signals to reduce the impact of fading. Figure 1 As shown, the method includes the following steps:

[0035] Step 101: Obtain the QAM modulation order of each signal copy according to the quick access channel information.

[0036] The signal replica is a statistically independent signal component carrying the same information obtained by applying time diversity or frequency diversity to the original DRM signal.

[0037] Take the two signal copies obtained by frequency diversity transmission as an example, Figure 2 As shown in the figure, x(t) is the OFDM signal, c(t) is the carrier signal of different frequencies, h(t) is the response of the channel model, which reflects complex channel fading such as multipath and Doppler spread and can be regarded as multiplicative noise, n(t) is the additive noise, and s(t) is the receiving channel. The transmission model of any channel can be expressed as:

[0038]

[0039] In the above formula, c(t) is the carrier signal, which can be expressed as Then an OFDM signal x(t) after up-conversion modulation through the carrier can be expressed as e(t):

[0040]

[0041] The modulation process using formula (2) is to shift the spectrum, and the lowest subcarrier position is f c +f kmin .

[0042] Step 102: Obtain the signal-to-noise ratio of each signal replica using a channel estimation algorithm.

[0043] Step 103: If the QAM modulation order of each signal copy is the same, weighted combination of each signal copy is performed on the QAM constellation diagram according to the signal-to-noise ratio to obtain an enhanced QAM symbol.

[0044] Step 104: If the QAM modulation order of each signal copy is different, weighted combination of each signal copy is performed on the bit stream according to the signal-to-noise ratio to obtain an enhanced DRM information bit stream.

[0045] In this embodiment, a receiving end receives multiple signal copies obtained by time and frequency diversity methods, and selects a combining method based on whether the QAM modulation order of each signal copy is consistent. That is, when the modulation orders are the same, a soft combining method is selected, that is, weighted combining of each signal copy is performed on the QAM constellation diagram according to the signal-to-noise ratio to obtain an enhanced QAM symbol; when the modulation orders are different, a hard combining method is selected, that is, weighted combining of each signal copy is performed on the bit stream according to the signal-to-noise ratio to obtain an enhanced DRM information bit stream. Compared with the traditional single diversity combining method, this method can increase the combining gain, improve the anti-fading performance of the receiving end, and provide a guarantee for the reliable reception of DRM signals.

[0046] In one embodiment, the above step 101 includes obtaining quick access channel information based on low-order modulation in each signal copy; and obtaining the QAM modulation order of each signal copy according to the quick access channel information.

[0047] Among them, low-order modulation refers to a modulation method in which each symbol has only two states of "0" or "1", such as binary amplitude shift keying 2ASK, binary frequency shift keying 2PSK, etc.

[0048] In one embodiment, Figure 3 As shown, a shortwave DRM reliable reception method based on time-frequency retransmission is provided, comprising the following steps:

[0049] S302, obtaining the QAM modulation order of each signal copy according to the quick access channel information;

[0050] S304, channel estimation to obtain the signal-to-noise ratio of each signal replica;

[0051] S306, determining whether the QAM modulation order of each channel is consistent, and selecting a combining method based on whether the modulation order is consistent;

[0052] S308, when the QAM modulation order of each channel is consistent, setting a signal-to-noise ratio threshold (i.e., a first signal-to-noise ratio threshold) and directly discarding signal copies below the signal-to-noise ratio threshold;

[0053] S310, the remaining signal copies are weighted according to the signal-to-noise ratio and combined on the QAM constellation diagram;

[0054] S312, obtaining enhanced QAM symbols;

[0055] S314, performing QAM demapping and decoding on the enhanced QAM symbols to obtain an enhanced DRM information bit stream (also referred to as an enhanced DRM signal);

[0056] S316, when the QAM modulation order of each channel is inconsistent, a signal-to-noise ratio threshold (i.e., a second signal-to-noise ratio threshold) is set, and signal copies with a signal-to-noise ratio lower than the threshold are directly discarded;

[0057] S318, performing QAM demapping and decoding on the remaining signal copies;

[0058] S320: weightedly combine each channel of demapped and decoded data on the bit stream according to the signal-to-noise ratio to obtain an enhanced DRM information bit stream.

[0059] Figure 4This is a flow chart of the soft combining method in a reliable shortwave DRM reception method based on time-frequency retransmission provided by an embodiment of the present application. The method primarily includes modules such as the RF front-end hardware module, baseband signal acquisition, signal synchronization, FFT demodulation, channel estimation, signal replica rejection, QAM constellation weighted combining, and demapping and decoding.

[0060] Figure 5 A schematic diagram of weighted merging of the soft merging method in a shortwave DRM reliable reception method based on time-frequency retransmission provided in an embodiment of the present application, taking two channels as an example. The receiving end generates and superimposes independent white noise sequences (n1(t), n2(t), n3(t)) on the input carrier signal x(t), and obtains multiple independent signal replicas s k (t), and perform independent time-frequency synchronization, channel estimation and equalization. According to the signal-to-noise ratio results after channel estimation, the QAM data sequence C of each branch is k Perform weighted merging.

[0061] For each branch (a total of L branches), the noise (fading and noise) signal (one OFDM symbol) s k (t) After independent signal estimation and equalization, a sequence C containing N QAM signals is generated. k (i), and the corresponding average signal-to-noise ratio SNR k , after weighted combination of the QAM signals of each branch according to the average signal-to-noise ratio, the combined signal C′(i) can be expressed as:

[0062]

[0063] Perform QAM demapping and decoding on the combined QAM signal sequence C′(i).

[0064] Based on the same inventive concept, embodiments of the present application also provide a system for implementing the above-mentioned shortwave DRM reliable reception based on time-frequency retransmission. The solution provided by this system is similar to the solution described in the above-mentioned method. Therefore, the specific limitations in one or more system embodiments provided below can be found in the above-mentioned limitations on the shortwave DRM reliable reception method based on time-frequency retransmission, and will not be repeated here.

[0065] Figure 6 FIG is a structural diagram of a shortwave DRM reliable receiving system based on time-frequency retransmission according to an embodiment of the present application, such as Figure 6 As shown, the system may include:

[0066] A QAM modulation order acquisition unit 602 is configured to acquire the QAM modulation order of each signal copy according to the quick access channel information;

[0067] A channel estimation unit 604 is configured to obtain a signal-to-noise ratio of each signal replica using a channel estimation algorithm;

[0068] A soft combining unit 606 is configured to perform weighted combining of the signal copies according to the signal-to-noise ratio on the QAM constellation diagram to obtain enhanced QAM symbols when the QAM modulation order of each signal copy is the same;

[0069] A hard combining unit 608 is configured to perform weighted combining of the signal copies according to the signal-to-noise ratio on the bit stream when the QAM modulation order of each signal copy is different, thereby obtaining an enhanced DRM information bit stream;

[0070] The output unit 610 is configured to perform QAM demapping and decoding on the enhanced QAM symbols, and output an enhanced DRM information bit stream.

[0071] It should be noted that each unit in the above-mentioned shortwave DRM reliable reception system based on time-frequency retransmission can be implemented in whole or in part through software, hardware, or a combination thereof. Each of the above-mentioned units can be embedded in or independent of a processor in a computer device in hardware form, or can be stored in a memory in the computer device in software form, so that the processor can call and execute the corresponding operations of each of the above-mentioned units. Through the above-mentioned shortwave DRM reliable reception system based on time-frequency retransmission, the QAM modulation order of each signal copy is obtained based on the fast access channel information; the signal-to-noise ratio of each signal copy is obtained through a channel estimation algorithm; a merging method is selected based on the modulation method; if the QAM modulation order of each channel is the same, a soft merging method is selected, that is, weighted merging is performed on the QAM constellation diagram according to the signal-to-noise ratio; if they are different, a hard merging method is selected, that is, weighted merging is performed on the bit stream according to the signal-to-noise ratio; and finally, an enhanced DRM information bit stream is obtained. It solves the problem that the traditional DRM reception combining method does not consider the influence of channel quality and signal-to-noise ratio, and directly performs hard combining processing, which leads to low combining gain and limited anti-fading performance, and provides strong support for the time-frequency retransmission combining method of shortwave communication.

[0072] It should be noted here that the examples and scenarios implemented by the above modules and corresponding steps are the same, but are not limited to the contents disclosed in the above embodiments. It should be noted that the above modules as part of the device can run in a hardware environment, can be implemented by software, and can also be implemented by hardware, where the hardware environment includes a network environment.

[0073] According to another aspect of the embodiments of the present application, a storage medium is further provided. Optionally, in this embodiment, the storage medium can be used to execute the program code of any of the above-mentioned shortwave DRM reliable reception methods based on time-frequency retransmission in the embodiments of the present application.

[0074] Among them, computer-readable storage media may include, but are not limited to, any type of disk, including floppy disks, optical disks, DVDs, CD-ROMs, microdrives and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic or optical cards, nanosystems (including molecular memory ICs), or any type of medium or device suitable for storing instructions and / or data.

[0075] According to another aspect of the embodiments of the present application, an electronic device for implementing the above-mentioned shortwave DRM reliable reception method based on time-frequency retransmission is also provided. The electronic device can be a server, a terminal, or a combination thereof.

[0076] Figure 7 is a structural diagram of an electronic device according to an embodiment of the present application, such as Figure 7 As shown, the present invention includes a processor 702, a communication interface 704, a memory 706 and a communication bus 708, wherein the processor 702, the communication interface 704 and the memory 706 communicate with each other via the communication bus 708, wherein the memory 706 is used to store computer programs; the processor 702 is used to implement the above-mentioned shortwave DRM reliable reception method based on time-frequency retransmission when executing the computer program stored in the memory 706.

[0077] Optionally, the communication bus may be a PCI (Peripheral Component Interconnect) bus or an EISA (Extended Industry Standard Architecture) bus. The communication bus may be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 7 The communication interface is used for communication between the electronic device and other devices.

[0078] The memory may include RAM, or may include non-volatile memory, such as at least one disk memory. Alternatively, the memory may also be at least one storage device located away from the aforementioned processor.

[0079] The above-mentioned processor can be a general-purpose processor, including but not limited to: CPU (Central Processing Unit), NP (Network Processor), etc.; it can also be DSP (Digital Signal Processing), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.

[0080] Optionally, the specific examples in this embodiment may refer to the examples described in the above embodiments, and this embodiment will not be described in detail here.

[0081] It should be noted that for the aforementioned method embodiments, for the sake of simplicity, they are all expressed as a series of action combinations, but those skilled in the art should be aware that this application is not limited by the order of the actions described, because according to this application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by this application.

[0082] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0083] The above is only an exemplary embodiment of the present disclosure and cannot be used to limit the scope of the present disclosure. That is, any equivalent changes and modifications made according to the teachings of the present disclosure are still within the scope of the present disclosure. After considering the specification and practicing the disclosure herein, those skilled in the art will easily think of the implementation scheme of the present disclosure. This application is intended to cover any variation, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary technical means in the art that are not recorded in the present disclosure. The description and examples are to be regarded as exemplary only, and the scope and spirit of the present disclosure are defined by the claims.

[0084] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0085] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A shortwave DRM reliable reception method based on time-frequency retransmission, characterized in that: include: Obtain the QAM modulation order of each signal copy according to the fast access channel information; Obtain the signal-to-noise ratio of each signal copy through a channel estimation algorithm; If the QAM modulation order of each signal copy is the same, then the signal copies are weighted and combined according to the signal-to-noise ratio on the QAM constellation diagram to obtain enhanced QAM symbols; If the QAM modulation order of each signal copy is different, the signal copies are weighted and combined according to the signal-to-noise ratio on the bit stream to obtain an enhanced DRM information bit stream.

2. The shortwave DRM reliable reception method based on time-frequency retransmission according to claim 1, characterized in that: The obtaining of the QAM modulation order of each signal copy according to the quick access channel information includes: Obtaining fast access channel information based on low-order modulation in each signal copy; The QAM modulation order of each signal copy is obtained according to the quick access channel information.

3. The shortwave DRM reliable reception method based on time-frequency retransmission according to claim 1, characterized in that: The obtaining of the signal-to-noise ratio of each signal copy by a channel estimation algorithm includes: Obtain the signal-to-noise ratio of each signal copy through a channel estimation algorithm; The signal copies with a signal-to-noise ratio lower than the set threshold are filtered out.

4. The shortwave DRM reliable reception method based on time-frequency retransmission according to claim 1, characterized in that: If the QAM modulation order of each signal copy is the same, weighted combination of each signal copy is performed on the QAM constellation diagram according to the signal-to-noise ratio to obtain an enhanced QAM symbol, including: Setting a first signal-to-noise ratio threshold; Screening out signal copies whose signal-to-noise ratio is not lower than the first signal-to-noise ratio threshold; The at least one signal copy selected is weighted according to the signal-to-noise ratio, and is combined on the QAM constellation diagram to obtain an enhanced QAM symbol.

5. The shortwave DRM reliable reception method based on time-frequency retransmission according to claim 1, characterized in that: The method further comprises: The enhanced QAM symbols are subjected to QAM demapping and decoding to obtain an enhanced DRM information bit stream.

6. The shortwave DRM reliable reception method based on time-frequency retransmission according to claim 1, characterized in that: If the QAM modulation order of each signal copy is different, weighted merging of each signal copy is performed on the bit stream according to the signal-to-noise ratio to obtain an enhanced DRM information bit stream, including: Setting a second signal-to-noise ratio threshold; screening out signal copies whose signal-to-noise ratio is not lower than the second signal-to-noise ratio threshold; The at least one signal copy selected is weightedly combined on the bit stream according to the signal-to-noise ratio to obtain an enhanced DRM information bit stream.

7. The shortwave DRM reliable reception method based on time-frequency retransmission according to claim 6, characterized in that: The step of performing weighted merging of the at least one filtered signal copy on the bit stream according to the signal-to-noise ratio to obtain an enhanced DRM information bit stream comprises: Performing QAM demapping and decoding on at least one selected signal copy; Each channel of data after demapping and decoding is weighted and combined on the bit stream according to the signal-to-noise ratio to obtain an enhanced DRM information bit stream.

8. A shortwave DRM reliable receiving system based on time-frequency retransmission, characterized in that: include: A QAM modulation order acquisition unit, configured to acquire the QAM modulation order of each signal copy according to the quick access channel information; A channel estimation unit, configured to obtain a signal-to-noise ratio of each signal copy through a channel estimation algorithm; A soft combining unit is used to perform weighted combining of the signal copies according to the signal-to-noise ratio on the QAM constellation diagram when the QAM modulation order of each signal copy is the same, so as to obtain an enhanced QAM symbol; A hard combining unit is used to perform weighted combining of the signal copies according to the signal-to-noise ratio on the bit stream when the QAM modulation order of each signal copy is different, thereby obtaining an enhanced DRM information bit stream; The output unit is used to perform QAM demapping and decoding on the enhanced QAM symbols and output an enhanced DRM information bit stream.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored program, wherein the program executes the method according to any one of claims 1 to 7 when executed.

10. An electronic device comprising a memory and a processor, characterized in that: A computer program is stored in the memory, and the processor is configured to execute the method according to any one of claims 1 to 7 through the computer program.

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