A Time-Frequency Synchronization Method and Device Applicable to DRM

Abstract

The present invention provides a time-frequency synchronization method and apparatus applicable to DRM, belonging to the field of communication technologies. The method includes: determining the robust mode and the symbol coarse timing starting point of the received DRM signal; estimating and compensating the fractional frequency offset at the symbol coarse timing starting point; determining the transmission frame coarse starting point according to the time pilot signal; estimating and compensating the integer frequency offset at the transmission frame coarse starting point by using the time pilot; estimating the precise transmission frame starting point by using the gain pilot; and estimating and compensating the precise fractional frequency offset at the precise transmission frame starting point by using the gain pilot. The present invention is applicable to various robust modes and spectrum occupancy situations of DRM. Its synchronization performance is not affected by the initial frequency offset. By continuously tracking the symbol timing offset and carrier frequency offset to reduce ISI and ICI, it has the advantages of high precision, good robustness, simple process, and being suitable for transplantation to a hardware system.

Description

Technical Field

[0001] The present invention relates to the field of communication technologies, and in particular, to a time-frequency synchronization method and apparatus applicable to DRM. Background Art

[0002] The Digital Radio Mondiale (DRM) standard is proposed by the World Digital Radio Organization. It occupies the transmission frequency below 30 MHz of traditional analog amplitude modulation (AM) broadcasting. It not only retains the advantages of wide coverage and suitability for mobile reception of analog AM broadcasting, but also overcomes the disadvantages of poor transmission quality, single service, and large transmission power of analog AM broadcasting, and can provide additional data services, and has achieved great development globally.

[0003] DRM uses Orthogonal Frequency Division Multiplexing (OFDM) technology to carry audio and data services, and uses a Cyclic Prefix (CP) as a guard interval. Due to the clock asynchronization between the DRM receiver and the radio station, there are disorders such as carrier frequency offset, sampling rate deviation, and symbol timing deviation in the radio signal received by the DRM receiver. These disorders will bring Inter Symbol Interference (ISI) and Inter-Channel Interference (ICI), resulting in the amplitude attenuation and phase rotation of the cell, and in severe cases, even making it difficult for the DRM receiver to decode service information.

[0004] Traditional time-frequency synchronization methods often use the maximum likelihood method based on CP to estimate symbol timing deviation and carrier frequency offset. Such methods have large estimation errors and can obtain rough timing starting points and frequency deviations, which is not conducive to the DRM receiver decoding service information. Summary of the Invention

[0005] The present invention provides a time-frequency synchronization method and apparatus applicable to DRM to solve the defect of large estimation errors in the prior art.

[0006] In a first aspect, the present invention provides a time-frequency synchronization method applicable to DRM, including: Step 1: Determine the robust mode and symbol rough timing starting point of the received DRM signal;

[0007] Step 2: Estimate and compensate the fractional frequency offset at the symbol rough timing starting point;

[0008] Step 3: Determine the rough starting point of the transmission frame according to the time pilot signal;

[0009] Step 4: Estimate and compensate for the integer multiple frequency offset at the rough starting point of the transmission frame using the time pilot;

[0010] Step 5: Estimate the exact starting point of the transmission frame using the gain pilot;

[0011] Step 6: At the exact starting point of the transmission frame, estimate and compensate for the exact fractional frequency offset using the gain pilot.

[0012] According to the time-frequency synchronization method applicable to DRM provided by the present invention, the said Step 3 includes: performing cross-correlation on the time pilot signal and the DRM signal to generate a cross-correlation result; taking the sample number corresponding to the maximum peak of the cross-correlation result as the rough starting point of the transmission frame.

[0013] According to a time-frequency synchronization method applicable to DRM provided by the present invention, after Step 6, it further includes: periodically executing Step 5 and 6 based on the received DRM signal.

[0014] In a second aspect, the present invention also provides a time-frequency synchronization device applicable to DRM, including:

[0015] A robust mode indication and symbol timing rough estimation module, used to determine the robust mode and the rough symbol timing starting point of the received DRM signal;

[0016] A fractional frequency offset rough estimation and compensation module, used to estimate and compensate for the fractional frequency offset at the rough symbol timing starting point;

[0017] A transmission frame starting point rough estimation module, used to determine the rough starting point of the transmission frame according to the time pilot signal;

[0018] An integer multiple frequency offset estimation and compensation module, used to estimate and compensate for the integer multiple frequency offset at the rough starting point of the transmission frame using the time pilot;

[0019] A symbol timing fine estimation module, used to estimate the exact starting point of the transmission frame using the gain pilot;

[0020] A fractional frequency offset fine estimation and compensation module, used to estimate and compensate for the exact fractional frequency offset at the exact starting point of the transmission frame using the gain pilot.

[0021] According to a time-frequency synchronization device applicable to DRM provided by the present invention, it further includes: a periodic execution control module; the periodic execution control module controls the symbol timing fine estimation module and the fractional frequency offset fine estimation and compensation module to work periodically based on the received DRM signal.

[0022] In a third aspect, the present invention provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the steps of any one of the above-mentioned time-frequency synchronization methods applicable to DRM are implemented.

[0023] In a fourth aspect, the present invention further provides a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of any one of the above-mentioned time-frequency synchronization methods applicable to DRM are implemented.

[0024] In view of the defect of relatively large time-frequency synchronization error in the existing DRM receiver, the present invention provides a technical solution for time-frequency synchronization applicable to DRM. This solution is applicable to various robust modes and spectrum occupancy situations of DRM. Its synchronization performance is not affected by the initial frequency offset. By continuously tracking the symbol timing offset and carrier frequency offset to reduce ISI and ICI, it has the advantages of high accuracy, good robustness, simple process, and is suitable for transplantation to a hardware system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1 is a flowchart of the time-frequency synchronization method applicable to DRM provided by the present invention;

[0027] Figure 2 is a framework diagram of the time-frequency synchronization device applicable to DRM provided by the present invention;

[0028] Figure 3 is a result diagram of the robust mode indication and symbol timing coarse estimation module provided by the present invention;

[0029] Figure 4 is a diagram of the timing result of the transmission frame start point coarse estimation module provided by the present invention;

[0030] Figure 5 is a result diagram of the integer multiple frequency offset estimation and compensation module provided by the present invention;

[0031] Figure 6 is a result diagram of the symbol timing fine estimation module provided by the present invention;

[0032] Figure 7 is a structural diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] To make the objectives, technical solutions and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the present invention in conjunction with the accompanying drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts fall within the scope of protection of the present invention.

[0034] It should be noted that in the description of the embodiments of the present invention, the terms "comprising", "including" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. Without further limitations, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0035] The following will describe Figures 1-7 the time-frequency synchronization method and device applicable to DRM provided by the embodiments of the present invention.

[0036] Figure 1 is a schematic flowchart of the time-frequency synchronization method applicable to DRM provided by the present invention. As Figure 1 shown, it includes but is not limited to the following steps:

[0037] Step 1: Determine the robust mode of the received DRM signal and the symbol coarse timing starting point.

[0038] Specifically, by means of the configuration information of the CP duration and the OFDM valid part duration in various robust modes, perform sliding correlation between the DRM discrete samples and the discrete samples separated by one OFDM valid part duration. Compare the sliding correlation peaks under various robust mode configurations, and the largest peak indicates the robust mode adopted by the radio station. Consider the sample number corresponding to the largest peak as the symbol coarse timing starting point.

[0039] Step 2: Estimate and compensate the fractional frequency offset at the symbol coarse timing starting point.

[0040] Step 3: Determine the transmission frame coarse starting point according to the time pilot signal.

[0041] Step 4: Estimate and compensate the integer multiple frequency offset at the transmission frame coarse starting point using the time pilot.

[0042] Optionally, Step 4 specifically includes the following steps:

[0043] Step 401: Take an OFDM signal from the rough start point of the transmission frame, transform the OFDM signal to the frequency domain, and extract the modulation symbols at the positions of the time pilots, denoted as the received time pilot cells.

[0044] Step 402: Append a normalized integer multiple frequency offset ε I ∈Ω IFO to the received time pilot cells, and then perform cross-correlation with the generated time pilot cells to obtain η Time (∈); specifically:

[0045]

[0046] where * represents taking the conjugate, k refers to the subcarrier number, and Φ TP refers to the set of subcarrier numbers occupied by the time pilots.

[0047] Step 403: Determine the integer multiple carrier frequency offset Time (ε I ) according to the maximum value of the modulus of η Specifically:

[0048]

[0049] where Ω IFO refers to the range of integer multiple frequency offset values.

[0050] Step 404: Compensate for the integer multiple carrier frequency offset .

[0051] Step 5: Use the gain pilots to estimate the exact start point of the transmission frame.

[0052] Optionally, Step 5 specifically includes the following steps:

[0053] Step 501: Generate a gain pilot signal Divide the gain pilot signal into M segments equally in the time domain; where N refers to the number of FFT points;

[0054] Step 502: Select a set of sample numbers Γ Time around the rough start point of the transmission frame, and extract DRM signals r Time of the same length as the gain pilot signal from each sample number value l ∈ Γ n+l , n = 0, 1, …, N - 1, and divide the DRM signals into M segments equally;

[0055] Step 503: Perform sliding correlation between the segmented gain pilot signals and the DRM signals, and multiply the squared modulus values of each segment of the correlation, to obtain the final correlation result Π(l); specifically:

[0056]

[0057] Step 504: Consider the sample number corresponding to the first Π(l) that exceeds λ·Π max as the exact starting point of the transmission frame; where Π max is the maximum peak of the relevant result Π(l), and λ refers to the weighting coefficient.

[0058] Step 6: At the exact starting point of the transmission frame, use the gain pilot to estimate the exact fractional frequency offset and compensate for it.

[0059] Optionally, Step 6 specifically includes the following steps:

[0060] Step 601: At the exact starting point of the transmission frame, take the 0th and 3Lth OFDM symbols, transform them to the frequency domain, and then extract the cell set of the gain pilot in the 0th and 3Lth OFDM symbols;

[0061] where the cell set of the gain pilot is denoted as L is a positive integer, and Φ GP is the set of subcarrier numbers occupied by the gain pilot on the 0th and 3Lth OFDM symbols;

[0062] Step 602: Generate the cell set of the gain pilot in the 0th and 3Lth OFDM symbols, denoted as

[0063] Step 603: Calculate the differential correlation value η Gain ; specifically:

[0064]

[0065] Step 604: Calculate the normalized fractional frequency offset Gain according to the differential correlation value η ; specifically:

[0066]

[0067] where N 3L refers to the interval length between the 0th and 3rd OFDM symbols, and Phase() refers to taking the argument;

[0068] Step 605: Compensate for the fractional frequency offset

[0069] Based on the content of the above embodiments, the time-frequency synchronization method provided by the present invention applicable to DRM, after Step 6, further includes:

[0070] Step 7: Every time several DRM transmission frames are received, repeat Steps 5 and 6.

[0071] ​In view of the large time-frequency synchronization error of the existing DRM receiver, the present invention provides a technical solution for time-frequency synchronization applicable to DRM. This solution is applicable to various robust modes and spectrum occupancy situations of DRM. Its synchronization performance is not affected by the initial frequency offset. By continuously tracking the symbol timing offset and carrier frequency offset to reduce ISI and ICI, it has the advantages of high precision, good robustness, simple process, and being suitable for transplantation into a hardware system.

[0072] Figure 2 It is a schematic framework diagram of the time-frequency synchronization device applicable to DRM provided by the present invention. As Figure 2 shown, the device includes:

[0073] A robust mode indication and symbol timing rough estimation module, used to determine the robust mode of the received DRM signal and the rough starting point of symbol timing;

[0074] A fractional frequency offset rough estimation and compensation module, used to estimate and compensate the fractional frequency offset at the rough starting point of symbol timing;

[0075] A transmission frame starting point rough estimation module, used to determine the rough starting point of the transmission frame according to the time pilot signal;

[0076] An integer multiple frequency offset estimation and compensation module, used to estimate and compensate the integer multiple frequency offset at the rough starting point of the transmission frame by using the time pilot;

[0077] A symbol timing fine estimation module, used to estimate the accurate transmission frame starting point by using the gain pilot;

[0078] A fractional frequency offset fine estimation and compensation module, used to estimate and compensate the accurate fractional frequency offset at the accurate transmission frame starting point by using the gain pilot;

[0079] And a periodic execution control module, used to control the symbol timing fine estimation module and the fractional frequency offset fine estimation and compensation module to work periodically based on the received DRM signal.

[0080] It should be noted that the time-frequency synchronization device applicable to DRM provided in the embodiments of the present invention, when specifically operating, can execute the time-frequency synchronization method applicable to DRM described in any of the above embodiments. Therefore, the specific implementation manners of each module will not be elaborated in this embodiment.

[0081] In order to more fully illustrate the implementation process and beneficial effects of the technical solution of the present invention below, a specific embodiment (simulation analysis process) will be used to elaborate below.

[0082] The simulated DRM signal uses robust mode B, with a spectrum occupancy of 3, a bandwidth of 10 kHz, and a sampling rate of 48 kHz. The simulation channel selects the 3rd channel model (Channel no 3: US Consortium), SNR = 30 dB, and the initial normalized frequency offset is 0.41.

[0083] In this embodiment, the robust mode indication and symbol timing coarse estimation module, as well as the fractional frequency offset coarse estimation and compensation module, can adopt the maximum likelihood estimation method based on CP; the transmission frame start point coarse estimation module can adopt the maximum likelihood estimation method based on the time pilot signal.

[0084] In this embodiment, the DRM signal is input into the robust mode indication and symbol timing coarse estimation module, and the selected input signal length is equal to the length of 2 OFDM symbols. Figure 3 It is a schematic diagram of the result of the robust mode indication and symbol timing coarse estimation module provided by the present invention. As Figure 3 shown, it shows the timing results of the maximum likelihood function under 5 robust mode configurations. By comparing the maximum values of the 5 timing results, it can be known that the robust mode of the received DRM signal is B. Figure 3 The maximum value in (b) corresponds to the approximate start point of the CP. The normalized fractional frequency offset estimated by the maximum likelihood estimation method at this sample number (sample sequence number) is 0.4052.

[0085] Optionally, the received signal after compensating the rough estimate of the fractional frequency offset is input into the transmission frame start point coarse estimation module, and the selected input signal duration is equal to 500 ms. Figure 4 It is a schematic diagram of the timing result of the transmission frame start point coarse estimation module provided by the present invention. As Figure 4 shown, the arrow indicates the position of the maximum peak, corresponding to the sample number 1, that is, the rough sequence number start point of the transmission frame is 1.

[0086] Optionally, the value range Ω IFO in the integer frequency offset estimation and compensation module is [-128, 128]. Figure 5 It is a schematic diagram of the result of the integer frequency offset estimation and compensation module provided by the present invention. As Figure 5 shown, the maximum value is obtained when the integer frequency offset is 0. Therefore, the integer frequency offset of the received DRM signal is 0.

[0087] Furthermore, the number of segments M in the symbol timing fine estimation module is 4, the weighting coefficient λ is 0.99, and the gain pilot signal (excluding CP) on the 0th OFDM symbol is locally generated for symbol timing fine estimation. Figure 6 It is a schematic diagram of the result of the symbol timing fine estimation module provided by the present invention. As Figure 6 shown, the received first path signal appears at the sample number (sample sequence number) of 257.

[0088] Optionally, in the fractional frequency offset fine estimation and compensation module, L = 1, that is, the gain pilots of the 0th and 3rd OFDM symbols are used to accurately estimate the fractional frequency offset. The normalized fractional frequency offset estimated at the first path position is 0.0024, and this estimated value is then compensated to the received signal for subsequent signal processing.

[0089] The present invention has conducted in-depth research on the key technologies related to time-frequency synchronization at the DRM receiver end, analyzed and solved the problem of low estimation accuracy of traditional time-frequency synchronization, created a detailed time-frequency synchronization scheme for the DRM receiver end, and has the advantages of high accuracy, good robustness, simple structure, and being suitable for transplantation to a hardware platform.

[0090] It should be understood that the parts not elaborated in detail in this specification all belong to the prior art.

[0091] Figure 7 is a schematic structural diagram of the electronic device provided by the present invention. As Figure 7 shown, the electronic device may include: a processor 710, a communications interface 720, a memory 730, and a communication bus 740. Among them, the processor 710, the communications interface 720, and the memory 730 complete mutual communication through the communication bus 740. The processor 710 can call the logical instructions in the memory 730 to execute a time-frequency synchronization method applicable to DRM, and the method includes: Step 1: Determine the robust mode and the symbol coarse timing starting point of the received DRM signal; Step 2: Estimate and compensate the fractional frequency offset at the symbol coarse timing starting point; Step 3: Determine the transmission frame coarse starting point according to the time pilot signal; Step 4: Estimate and compensate the integer frequency offset at the transmission frame coarse starting point by using the time pilot; Step 5: Estimate the accurate transmission frame starting point by using the gain pilot; Step 6: At the accurate transmission frame starting point, estimate and compensate the accurate fractional frequency offset by using the gain pilot.

[0092] In addition, when the logical instructions in the above-mentioned memory 730 can be implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs.

[0093] On the other hand, the present invention also provides a computer program product. The computer program product includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions. When the program instructions are executed by a computer, the computer can execute the time-frequency synchronization method applicable to DRM provided in the above-mentioned various embodiments. The method includes: Step 1: Determine the robust mode and the symbol coarse timing starting point of the received DRM signal; Step 2: Estimate and compensate the fractional frequency offset at the symbol coarse timing starting point; Step 3: Determine the transmission frame coarse starting point according to the time pilot signal; Step 4: Estimate and compensate the integer frequency offset at the transmission frame coarse starting point by using the time pilot; Step 5: Estimate the precise transmission frame starting point by using the gain pilot; Step 6: At the precise transmission frame starting point, estimate and compensate the precise fractional frequency offset by using the gain pilot.

[0094] In yet another aspect, the present invention also provides a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it is configured to execute the time-frequency synchronization method applicable to DRM provided in the above-mentioned various embodiments. The method includes: Step 1: Determine the robust mode and the symbol coarse timing starting point of the received DRM signal; Step 2: Estimate and compensate the fractional frequency offset at the symbol coarse timing starting point; Step 3: Determine the transmission frame coarse starting point according to the time pilot signal; Step 4: Estimate and compensate the integer frequency offset at the transmission frame coarse starting point by using the time pilot; Step 5: Estimate the precise transmission frame starting point by using the gain pilot; Step 6: At the precise transmission frame starting point, estimate and compensate the precise fractional frequency offset by using the gain pilot.

[0095] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on such an understanding, the essence of the above technical solution, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to enable a computer device (which can be a personal computer, server, or network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A time-frequency synchronization method applicable to DRM, characterized in that Including: Step 1: Determine the robust mode and the starting point of symbol coarse timing of the received DRM signal; Step 2: Estimate and compensate the fractional frequency offset at the starting point of symbol coarse timing; Step 3: Determine the coarse starting point of the transmission frame according to the time pilot signal; Step 4: Estimate and compensate the integer multiple frequency offset by using the time pilot at the coarse starting point of the transmission frame; Step 5: Estimate the accurate starting point of the transmission frame by using the gain pilot; Step 6: At the accurate starting point of the transmission frame, estimate and compensate the accurate fractional frequency offset by using the gain pilot; The said Step 4 includes: Step 401: Take an OFDM signal from the rough starting point of the transmission frame, transform the OFDM signal into the frequency domain, and extract the modulation symbols at the positions of the time pilots, which are denoted as received time pilot cells. Step 402: Attach a normalized integer multiple frequency offset ε to the received time pilot cell I _∈Ω IFO After that, perform cross-correlation with the generated time pilot cell to obtain η Time (ε I ); Specifically: where * denotes taking the conjugate, k refers to the subcarrier index, and Φ TP refers to the set of subcarrier indices occupied by the time pilots; Step 403: According to η Time (ε I ) to determine the integer multiple carrier frequency offset according to the maximum value of the modulus value Specifically: where, Ω IFO denotes the integer multiple frequency offset value range; Step 404: Compensate for the integer multiple carrier frequency offset ; The said Step 5 includes: Step 501: Generate a gain pilot signal Equally divide the gain pilot signal into M segments in the time domain; where N refers to the number of FFT points; Step 502: Select a set of sample sequence numbers Γ around the rough starting point of the transmission frame Time , and for each sample sequence number value l ∈ Γ Time , extract a DRM signal r of the same length as the gain pilot signal at that point n+l , n = 0, 1, …, N - 1, and equally divide the DRM signal into M segments; Step 503: Perform sliding correlation on the segmented gain pilot signal and the DRM signal, and multiply the squared modulus values of each segment of correlation, to obtain the final correlation result Π(l); specifically: Step 504: Consider the sample number corresponding to the first Π(l) that exceeds λ·Π max as the exact starting point of the transmission frame; where Π max is the maximum peak value of the correlation result Π(l), and λ refers to the weighting coefficient.

2. The time-frequency synchronization method applicable to DRM according to claim 1, wherein The said Step 6 includes: Step 601: At the accurate starting point of the transmission frame, take the 0th and 3Lth OFDM symbols, transform them to the frequency domain, and then take out the set of gain pilot cells in the 0th and 3Lth OFDM symbols; Among them, the cell set of the gain pilot is denoted as L is a positive integer, and Φ GP is the set of subcarrier serial numbers occupied by the gain pilot on the 0th and 3Lth OFDM symbols; Step 602: Generate a set of cells of the gain pilots in the 0th and 3Lth OFDM symbols, denoted as Step 603: Calculate the differential correlation value η Gain ; Specifically: Step 604: Calculate the normalized fractional frequency offset according to the differential correlation value η Gain Specifically: Calculate the normalized fractional frequency offset where N 3L denotes the interval length between the 0th and 3rd OFDM symbols, and Phase() denotes taking the argument; Step 605: Compensate for the fractional frequency offset ​ 3. The time-frequency synchronization method applicable to DRM according to claim 1, characterized in that After Step 6, it further includes: Step 7: Based on the received DRM signal, periodically execute Step 5 and Step 6.

4. A time-frequency synchronization device applicable to DRM, for implementing the method described in any one of claims 1 to 3, characterized in that, Including: A robust mode indication and symbol timing coarse estimation module, used to determine the robust mode and the starting point of symbol coarse timing of the received DRM signal; A fractional frequency offset coarse estimation and compensation module, used to estimate and compensate the fractional frequency offset at the starting point of symbol coarse timing; A transmission frame starting point coarse estimation module, used to determine the coarse starting point of the transmission frame according to the time pilot signal; An integer multiple frequency offset estimation and compensation module, used to estimate and compensate the integer multiple frequency offset by using the time pilot at the coarse starting point of the transmission frame; A symbol timing fine estimation module, used to estimate the accurate starting point of the transmission frame by using the gain pilot; A fractional frequency offset fine estimation and compensation module, used to estimate and compensate the accurate fractional frequency offset by using the gain pilot at the accurate starting point of the transmission frame.

5. The time-frequency synchronization device applicable to DRM according to claim 4 further comprises: A periodic execution control module; The said periodic execution control module, based on the received DRM signal, controls the symbol timing fine estimation module and the fractional frequency offset fine estimation and compensation module to work periodically.

6. An electronic device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the said processor executes the said computer program, it realizes the steps of the time-frequency synchronization method applicable to DRM as described in any one of Claims 1 to 3.

7. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the said computer program is executed by the processor, it realizes the steps of the time-frequency synchronization method applicable to DRM as described in any one of Claims 1 to 3.

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