A frequency offset estimation method, a terminal device and a storage medium

Abstract

This application discloses a frequency offset estimation method, terminal device, and storage medium, relating to the field of wireless communication technology. The method includes: acquiring first time slot data from M consecutive subframe signals, and performing modulation information cancellation on the first time slot data to obtain corresponding spectrum data; grouping the corresponding spectrum data into pairs according to the receiving time order, adding a preset sequence to each group of spectrum data to obtain N groups of sequences; processing the N groups of sequences to obtain corresponding frequency offset estimates; calculating frequency offset estimates for the M subframe signals based on the frequency offset estimates of the N groups of sequences; and performing frequency offset compensation based on the frequency offset estimates of the M subframe signals. This application improves the accuracy of frequency offset estimation to a certain extent by jointly calculating the frequency offset estimates of the subframe signals using first time slot data from multiple consecutive subframe signals, thereby effectively achieving frequency offset compensation and avoiding inaccurate frequency offset estimation due to large frequency offset change rates.

Description

Technical Field

[0001] This application relates to the field of wireless communication technology, and in particular to a frequency offset estimation method, terminal device, and storage medium. Background Technology

[0002] With the rapid development of communication technology, satellite communication is becoming increasingly widespread. Satellite communication systems use satellites as relay stations to forward radio waves, thereby enabling wireless communication between terminal devices. Satellite communication systems can achieve various forms of communication, such as voice, data, and video, globally, and are characterized by large communication capacity, wide coverage, seamless global connectivity, and strong anti-interference capabilities.

[0003] Synchronization is a crucial factor affecting wireless communication performance. Correct coherent demodulation can only be achieved when the frequency and phase of the local carrier are synchronized with the received signal. Frequency synchronization is an indispensable part of the synchronization process. In satellite communication systems with large frequency shifts and low signal-to-noise ratios, how terminal equipment estimates frequency offset after receiving signals from the satellite transmitter to achieve carrier synchronization is a problem worthy of further research.

[0004] In current technologies, the commonly used frequency offset estimation method for satellite communication is generally a data-assisted method. The terminal device uses known data to estimate the frequency offset. For example, the terminal device estimates the frequency offset based on locally known synchronization sequences, which are generally sequences with good autocorrelation characteristics.

[0005] However, the frequency offset estimation methods commonly used in current technology have low accuracy and therefore cannot effectively achieve frequency offset compensation, which in turn makes it impossible to correctly achieve coherent demodulation of the signal. Summary of the Invention

[0006] This application provides a frequency offset estimation method, terminal device, and storage medium, which improves the accuracy of frequency offset estimation to a certain extent, thereby effectively realizing frequency offset compensation, so as to enable subsequent coherent demodulation of the signal.

[0007] To achieve the above objectives, this application adopts the following technical solution:

[0008] This application provides a frequency offset estimation method, comprising: acquiring first time slot data from M consecutive subframe signals, and performing modulation information cancellation on the first time slot data of the M subframe signals to obtain spectrum data corresponding to the first time slot data of the M subframe signals; grouping the spectrum data corresponding to the first time slot data of the M subframe signals into pairs according to the reception time order of the M subframe signals, and adding a preset sequence to each group of spectrum data to obtain N sets of sequences corresponding to the M subframe signals; processing the N sets of sequences to obtain frequency offset estimates corresponding to the N sets of sequences; calculating the frequency offset estimates of the M subframe signals based on the frequency offset estimates of the N sets of sequences; and performing frequency offset compensation on the M subframe signals based on the frequency offset estimates of the M subframe signals. Specifically, frequency offset compensation can be performed on all M subframe signals, or it can be performed on a portion of the M subframe signals. The frequency offset estimates of the subframe signals are jointly calculated using the first time slot data of multiple subframe signals. This application calculates the frequency offset estimate of a subframe signal based on the first time slot data of the subframe signal itself. Compared with the current technology that only obtains the frequency offset estimate based on the known synchronization sequence, the accuracy of the frequency offset estimation is higher. Furthermore, since the frequency offset estimation is based on the first time slot data of multiple subframe signals, it relies on more prior information, which improves the accuracy of the frequency offset estimation to a certain extent. This enables effective frequency offset compensation, facilitating the subsequent correct coherent demodulation of the signal. Moreover, by jointly calculating the frequency offset estimate of the subframe signal using multiple subframe signals, the large frequency offset variation rate in satellite communication is also considered, which to some extent avoids inaccurate frequency offset estimation caused by a large frequency offset variation rate.

[0009] In one possible implementation, the length of the preset sequence added to each set of spectral data is the difference between the length of a subframe signal and the length of the first time slot. The absolute value of this difference is used to combine the two subframe signals more effectively and to avoid the influence of other time slot data on frequency offset estimation.

[0010] In one possible implementation, when initially acquiring the first time slot data from M consecutive subframe signals, it is necessary to continuously receive M subframe signals and extract the first time slot data from these M subframe signals to achieve the acquisition of the first time slot data from the M consecutive subframe signals. Furthermore, the first time slot data from these M subframe signals can be stored. This allows for direct retrieval of the first time slot data from storage during subsequent frequency offset estimation, simplifying the process of acquiring the first time slot data.

[0011] In one possible implementation, when acquiring the first time slot data from M consecutive subframe signals (not the first time), only the first subframe signal (the Mth subframe signal out of the M subframe signals) is received, and the first time slot data of the first subframe signal is extracted. The first time slot data from the first subframe signal to the Nth subframe signal out of the M subframe signals are then acquired to achieve the acquisition of the first time slot data from the M consecutive subframe signals. Furthermore, the received first time slot data of the first subframe signal can be stored so that the first time slot data of the first subframe signal can be directly retrieved from storage when performing subsequent frequency offset estimation.

[0012] In one possible implementation, when the first time slot data of M subframe signals is acquired for the first time, the frequency offset estimate of the first subframe signal among the M subframe signals is a pre-set constant, i.e., a standard frequency offset estimate. The frequency offset estimate of the second subframe signal among the M subframe signals is obtained based on the average of the frequency offset estimates of the first and second sets of sequences. Subsequently, the frequency offset estimate of the y-th subframe signal is calculated based on the frequency offset estimate of the x-th sequence and the frequency offset estimate of the x-th subframe signal. This differential iterative calculation method can effectively improve the accuracy of the frequency offset estimation.

[0013] In one possible implementation, the frequency offset estimates of the M subframe signals are used to perform frequency offset estimation on the M subframe signals one-to-one. For example, the frequency offset estimate of the first subframe signal is used to compensate for the frequency offset of the first subframe signal; the frequency offset estimate of the second subframe signal is used to compensate for the frequency offset of the second subframe signal; and so on, the frequency offset estimate of the Mth subframe signal is used to compensate for the frequency offset of the Mth subframe signal.

[0014] In one possible implementation, frequency offset compensation is performed on the first subframe signal based on the frequency offset estimate (constant) of the first subframe signal; frequency offset compensation is performed on the remaining subframe signals based on the frequency offset estimate of the Mth subframe signal, which simplifies the complexity of the frequency offset compensation steps while effectively achieving frequency offset compensation.

[0015] In one possible implementation, the frequency offset estimate of the Mth subframe signal is calculated based on the frequency offset estimate of the Nth sequence in the N sets of sequences and the frequency offset estimate of the Nth subframe signal in the M subframe signals. When the frequency offset estimates of the M subframe signals are not obtained for the first time, only the frequency offset estimate of the Mth subframe signal needs to be calculated.

[0016] In one possible implementation, when the frequency offset estimates of the M subframe signals are not obtained for the first time, the frequency offset estimate of the Mth subframe signal is used to perform frequency offset compensation on the Mth subframe signal, since the frequency offset compensation of the other subframe signals has already been completed.

[0017] In one possible implementation, the frequency offset compensation value of the phase-locked loop (PLL) is calculated by summing the known frequency offset estimates of all subframe signals. Based on the PLL's frequency offset compensation value, the frequency of the PLL oscillator is adjusted to achieve PLL frequency offset compensation. Since the accuracy of the subframe signal frequency offset estimation is improved, the accuracy of the PLL frequency offset compensation value calculated from the subframe signal frequency offset estimates is also improved, thus enabling more effective PLL frequency offset compensation.

[0018] In one possible implementation, the first time slot data is the valid time slot data. Although non-data-aided frequency offset estimation methods have higher accuracy than data-aided frequency offset estimation methods, the low signal-to-noise ratio in current non-data-aided frequency offset estimation methods may introduce significant noise into the first time slot data, thus affecting the accuracy of frequency offset estimation. This application extracts only the valid time slot data, thereby avoiding the impact of noisy data on the accuracy of frequency offset estimation and further improving the accuracy of frequency offset estimation.

[0019] Secondly, this application provides a terminal device, which includes a processor and a memory; the memory stores computer-executable instructions; the processor executes the computer-executable instructions stored in the memory, causing the processor to perform the method described in the first aspect.

[0020] Thirdly, this application provides a computer-readable storage medium storing a computer program or instructions that, when executed, implement the method described in the first aspect.

[0021] Fourthly, this application provides a computer program product, including a computer program or instructions that, when executed by a processor, implement the method described in the first aspect. Attached Figure Description

[0022] Figure 1 A schematic flowchart illustrating an overall signal processing method on the receiver side provided in an embodiment of this application;

[0023] Figure 2 A flowchart illustrating a frequency offset estimation method provided in an embodiment of this application;

[0024] Figure 3 A schematic diagram illustrating the length of a set of fourth-power data with zeros in the middle, provided in an embodiment of this application;

[0025] Figure 4 A schematic diagram of a subframe signal for a frequency offset estimation method provided in an embodiment of this application;

[0026] Figure 5A flowchart illustrating another frequency offset estimation method provided in this application embodiment;

[0027] Figure 6 This is a component example diagram of an electronic device provided in an embodiment of this application. Detailed Implementation

[0028] The terms "first," "second," and "third," etc., used in this application specification, claims, and drawings are used to distinguish different objects, not to limit a specific order.

[0029] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0030] To ensure clarity and conciseness in the description of the following embodiments, a brief introduction to the related technologies is given first:

[0031] Frequency offset, in wireless communication systems, refers to the difference between the carrier frequency of the received signal and the carrier frequency of the transmitted signal. Due to factors such as multipath fading and the Doppler effect during signal propagation, the frequency of the received signal deviates from the frequency of the transmitted signal. Frequency offset leads to demodulation errors in the received signal, thus affecting the performance of the communication system.

[0032] The purpose of frequency offset estimation is to estimate the deviation between the carrier frequency of the received signal and the carrier frequency of the transmitted signal, and to perform frequency compensation based on the estimation results to ensure correct demodulation of the received signal.

[0033] Frequency offset compensation is a compensation measure taken to eliminate or reduce signal distortion or interference caused by frequency offset. It can be simply understood as frequency offset compensation based on frequency offset estimation, in order to eliminate or reduce the deviation between the frequency of the received signal and the frequency of the transmitted signal.

[0034] As described above, to reduce the impact of frequency offset on communication system performance, frequency offset estimation and compensation are necessary at the receiver side to achieve frequency synchronization. This avoids problems such as signal distortion, high bit error rate, and reduced transmission rate caused by frequency offset. In communication systems, frequency offset estimation is an indispensable step in achieving frequency synchronization. The accuracy of frequency offset estimation directly affects the accuracy of subsequent frequency offset compensation, frequency offset synchronization, and even subsequent channel decoding, thus impacting the overall performance of the communication system.

[0035] Before introducing the various embodiments of this application, firstly, in conjunction with Figure 1 Here is a brief introduction to the overall signal processing flow on the receiver side.

[0036] After receiving a signal, the receiver (e.g., a terminal device) first separates and extracts the useful signal from the received signal through a digital front-end. The digital front-end (DFE) is part of the RRU (Remote Radio Unit) system. The RRU system consists of two parts: a remote radio unit and a baseband processing unit. The RRU is defined as all transceiver circuits and various processing units between the antenna and the baseband processing. Specifically, the transceiver circuits and processing units between the ADC / CDA and the baseband processing are defined as the digital front-end.

[0037] Then, the signal output from the digital front end is synchronized, including time synchronization and frequency synchronization. Synchronization is a crucial factor affecting wireless communication performance; only when the frequency and phase of the local carrier are synchronized with the received signal can correct coherent demodulation of the signal be achieved.

[0038] After synchronizing the signal output from the digital front end, the synchronized signal undergoes channel equalization, soft demodulation, channel decoding, and CRC check to obtain the valid signal from the received signal, completing the overall signal processing flow. Channel equalization aims to counteract the effects of multipath interference and frequency-selective fading encountered during signal propagation, thereby improving the quality of the received signal. Soft demodulation aims to recover the original bit sequence from the received signal. Channel decoding aims to restore the original data as accurately as possible. CRC check (cyclic redundancy check) is a commonly used data transmission error detection method that checks whether the data carried by the signal has been erroneous or corrupted during transmission.

[0039] In such Figure 1The present application provides a frequency offset estimation method that is applied to the frequency synchronization process in the overall signal processing flow. Specifically, the frequency offset of the received signal is estimated, and the frequency offset of the received signal is compensated based on the frequency offset estimation, thereby achieving frequency synchronization.

[0040] The advantages of the frequency offset estimation method provided in this application will be explained below in conjunction with the frequency offset estimation methods in the current technology.

[0041] During satellite communication, due to the characteristics of satellite communication, the signals received by terminal equipment often exhibit significant frequency deviation, low signal-to-noise ratio, and short duration and burstiness. The specific reasons include at least three aspects: First, because the satellite moves at a very high speed relative to the terminal equipment, there is a considerable Doppler shift (signal deviation) between the frequency of the signal received by the terminal equipment and the carrier frequency of the satellite transmitter, along with a large rate of change of this frequency deviation. Second, due to the large distance between the satellite and the terminal equipment, the signal-to-noise ratio of the signal received by the terminal equipment is very low. Third, because satellite communication involves small data volumes and low symbol rates, the signals received by the terminal equipment are bursty and transient. Doppler shift refers to the phenomenon where the observed frequency of a wave deviates from the frequency emitted by the wave source when there is relative motion between the wave source and the observer. In short-duration, bursty communication systems like satellite communication systems, when the received signal has a large frequency offset and a low signal-to-noise ratio, the accuracy of current frequency offset estimation techniques is low, the error is large, and the low signal-to-noise ratio renders the frequency offset estimation ineffective, thus preventing subsequent signal synchronization and proper coherent demodulation. The specific reasons are explained below in conjunction with commonly used frequency offset estimation methods in current technology:

[0042] The first type of frequency offset estimation method is the data-assisted method. The terminal device performs frequency offset estimation based on known data. For example, the terminal device estimates the frequency offset of the received signal based on a locally known synchronization sequence, so as to perform frequency offset compensation and complete frequency synchronization. Generally, the known synchronization sequence is usually a sequence with good autocorrelation characteristics. After convolving the synchronization sequence with the received signal itself, a peak value is obtained. The position of this peak value can represent the offset between the synchronization sequence and the signal. Frequency offset estimation can be achieved based on this offset value. The relationship between the known synchronization sequence length and the signal length is: signal length = known synchronization sequence length * m, where m is a positive integer, meaning the signal length is an integer multiple of the known synchronization sequence length. In satellite communication, the signals received by terminal devices are bursty and transient. This burstiness and transient nature means that the received signals have a finite existence in time, are short in length, and are not continuous. Since the received signal length is short, according to the formula signal length = known synchronization sequence length * m (m is a positive integer), the corresponding known synchronization sequence length is also short. Therefore, there is less prior information for frequency offset estimation, leading to a larger frequency offset estimation error and lower accuracy.

[0043] The second type of frequency offset estimation method is the non-data-assisted method. In this method, the terminal device does not rely on any known data but estimates the frequency offset based solely on the received data. It's important to note that the non-data-assisted frequency offset estimation method does not restrict the type of subframe signal. For example, after receiving a signal from a satellite, the terminal device estimates the frequency offset for each subframe signal. For a single subframe signal, the terminal device estimates the frequency offset based on the target time slot data within that subframe signal, facilitating frequency offset compensation and frequency synchronization. To address the low accuracy of data-assisted frequency offset estimation, the non-data-assisted method truncates the target time slot to a larger length, thus increasing prior information. However, due to the low signal-to-noise ratio of the signal received by the terminal device in satellite communication, the target time slot data in that subframe signal carries significant noise (i.e., less effective data in the target time slot data), resulting in a larger error and lower accuracy in frequency offset estimation based on the target time slot data of the subframe signal. Furthermore, when the signal-to-noise ratio of the signal received by the terminal device is too low, it may even cause the frequency offset estimation to fail, making it impossible to perform frequency synchronization of the signal (i.e., the frequency synchronization function fails as a whole) and thus impossible to achieve coherent demodulation of the signal.

[0044] Furthermore, both types of frequency offset estimation methods suffer from significant errors and decreased accuracy due to the large frequency offset variation rate of the signals received by the terminal in satellite communication. Taking data-aided frequency offset estimation as an example, which estimates the frequency of the received signal based on a locally known synchronization sequence, if the frequency offset variation rate is large, the signal's frequency offset has already changed significantly during the estimation period. This results in a significant error between the obtained frequency offset estimate and the current signal's frequency offset, leading to inaccurate frequency offset estimation. Therefore, current technology struggles to achieve rapid frequency offset synchronization in satellite communication with its high dynamic frequency offset variation rate.

[0045] In summary, in satellite communication systems, the frequency offset estimation methods currently used have low accuracy, large errors, and even instances of frequency offset estimation failure.

[0046] This application provides a frequency offset estimation method, which involves acquiring first time slot data from multiple consecutive subframe signals, and performing modulation information cancellation (e.g., fourth-order processing, quadratic processing, etc.) on the first time slot data to obtain the spectrum data corresponding to the first time slot data in the multiple subframe signals; grouping the spectrum corresponding to the first time slot data in the multiple subframe signals into pairs according to the reception time order of the multiple subframe signals, and adding a preset sequence to each group of spectrum data to obtain multiple corresponding sequences; processing the multiple groups of sequences to obtain frequency offset estimation values ​​corresponding to the multiple groups of sequences; calculating the frequency offset estimation values ​​of the multiple subframe signals based on the frequency offset estimation values ​​of the multiple groups of sequences; and performing frequency offset compensation on the multiple subframe signals based on the frequency offset estimation values ​​of the multiple subframe signals. This application calculates the frequency offset estimate of a subframe signal by jointly using the first time slot data of multiple consecutive subframe signals. Compared with the current technology that only uses the known synchronization sequence to obtain the frequency offset estimate, the frequency offset estimate is more accurate. Furthermore, the frequency offset estimate based on the first time slot data of multiple subframe signals relies on more prior information, which improves the accuracy of the frequency offset estimate to a certain extent and can effectively achieve frequency offset compensation, so as to correctly achieve coherent demodulation of the signal in the future.

[0047] Furthermore, by jointly calculating the frequency offset estimate of the subframe signal through multiple subframe signals, the large frequency offset variation rate in satellite communication is also taken into account, which to some extent avoids the situation where the frequency offset estimate is inaccurate due to the large frequency offset variation rate.

[0048] Furthermore, the first time slot can be selected as the effective time slot, that is, the frequency offset estimate of the current subframe signal is jointly calculated based on the effective time slot data of multiple consecutive subframe signals. Although the non-data-aided frequency offset estimation method in the current technology can improve the accuracy of frequency offset estimation compared with the data-aided frequency offset estimation method, the low signal-to-noise ratio in the current non-data-aided frequency offset estimation method may introduce noisy data into the target time slot data, affecting the accuracy of frequency offset estimation. This application extracts the effective time slot data, avoids the impact of noisy data on the accuracy of frequency offset estimation, further improves the accuracy of frequency offset estimation, and avoids the situation of frequency offset estimation failure.

[0049] Example 1:

[0050] The following is combined Figures 2-4 This paper will provide a detailed description of a frequency offset estimation method provided in the embodiments of this application.

[0051] Before detailing the frequency offset estimation method provided in the embodiments of this application, let's first introduce the frame, subframe, time slot, and effective time slot.

[0052] A frame is the largest organizational unit in a wireless communication system, containing a set of related data and control information. A frame typically consists of multiple subframes or time slots, and its length depends on the specific wireless communication standard or protocol.

[0053] A subframe is a portion of a frame and is typically shorter than the frame. In some wireless communication systems, a frame is divided into several subframes, each with its own specific function. The use of subframes increases the flexibility of data transmission.

[0054] A time slot is a short time interval within a frame or subframe, typically used for finer-grained resource allocation and data transmission. A frame or subframe can contain multiple time slots, each containing a certain number of symbols or sampling points. For example, a subframe typically lasts 1 ms, and each time slot lasts 0.5 ms; therefore, a complete subframe is transmitted within two consecutive time slots. Furthermore, an effective time slot generally refers to the remaining time slots within a frame or subframe, excluding those used for synchronization, control signals, or other non-data information transmission, that can be used to transmit actual data (e.g., voice, video). In other words, an effective time slot is one that can be used to transmit valid data. In practical applications, not all time slots can be used for data transmission; time slots not used for data transmission are not effective time slots.

[0055] As can be seen from the above concepts, the relationship between frames, subframes, and time slots can be simply understood as a hierarchical structure from the whole to the part, that is, a frame contains multiple subframes, and a subframe contains one or more time slots. The effective time slot is the time slot used to transmit effective data.

[0056] like Figure 1 As shown in the overall signal processing flow, frequency synchronization includes frequency offset estimation and frequency offset compensation. Therefore, the frequency offset estimation process is performed after the signal's time synchronization. Thus, the frequency offset estimation method provided in this application embodiment is applied to the time-synchronized signal. For ease of description, the signals described in Embodiment 1 are all signals after time synchronization. See below. Figure 2 The frequency offset estimation method provided in this application includes the following steps:

[0057] S201. Set initialization parameters for the terminal device.

[0058] Terminal device initialization parameters n=0, F n =F0=F initial .

[0059] Here, n is the time index. The time index represents the temporal order of the subframe signals and uniquely identifies each subframe signal. For example, if the time index of a subframe signal is n = 0, then the subframe signal with time index 0 is the first subframe signal received by the terminal device. Furthermore, since the time index uniquely identifies each subframe signal, it serves as a unique identifier for the subframe signal.

[0060] It should be noted that n can also be the subframe ID of the subframe signal. The subframe ID is also one of the unique identifiers of the subframe signal. The applicable unique identifier can be selected according to the actual situation. In this embodiment, only the unique identifier of the subframe signal as the time index is used as an example for illustration. However, this application does not specifically limit the type of unique identifier of the subframe signal.

[0061] Among them, F n To estimate the frequency offset of the subframe signal corresponding to time index n, the initialization parameter F is set. n =F0=F initial That is, the frequency offset estimate corresponding to the first subframe signal received by the terminal device is F0, where F0 = F initial The F initial This is a standard frequency offset value set based on the frequency difference between the transmitting and receiving ends of the signal.

[0062] Specifically, the terminal device first sets the time index of the first subframe signal received to n=0, and the corresponding F0 is the frequency offset estimate of the first subframe signal received.

[0063] S202. When the terminal device receives three consecutive subframe signals for the first time, it extracts and stores the effective time slot data from the three subframe signals.

[0064] Among them, the effective time slot data is the data carried by the signal in the effective time slot of the subframe signal.

[0065] Specifically, the terminal device first receives three consecutive subframe signals, with corresponding time indices n, n+1, and n+2, where n=0. That is, the time indices of the first three consecutive subframe signals are 0, 1, and 2. The effective time slot data of the first three consecutive subframe signals are extracted to obtain the effective time slot data corresponding to the three subframe signals. The effective time slot data corresponding to the three subframe signals are represented by FID0, FID1, and FID2, respectively.

[0066] The effective time slot data of three consecutive subframe signals are extracted, and the noise part of the subframe signal is removed, so that only the effective time slot data of the subframe signal is obtained, thereby avoiding the impact of subsequent noise part data on the accuracy of frequency offset estimation.

[0067] Furthermore, the effective time slot data FID0, FID1, and FID2 of the three consecutive subframe signals received for the first time are stored.

[0068] S203. The terminal device performs a fourth power operation on the effective time slot data in the three subframe signals respectively to obtain the fourth power data corresponding to the three subframe signals.

[0069] Among them, the fourth power data is the result of the calculation obtained by performing a fourth power operation on the effective time slot data.

[0070] The purpose of performing a fourth power operation on the effective time slot data is to eliminate modulation information and extract phase information from the effective time slot data, so as to facilitate subsequent frequency offset estimation.

[0071] It should be noted that, generally, the signal modulation and demodulation method in satellite communication is Quadrature Phase Shift Keying (QPSK), which is a quaternary phase modulation and demodulation method. Therefore, in order to eliminate modulation, the effective time slot data is subjected to a fourth power operation. In addition, the signal modulation and demodulation method in satellite communication can also be Binary Phase Shift Keying (BPSK), which is a binary phase modulation and demodulation method. Therefore, in order to eliminate modulation, the effective time slot data is subjected to a quadratic operation. In this embodiment of the application, QPSK is used as an example for description, and this application does not make specific limitations.

[0072] Specifically, when the terminal device first receives three consecutive subframe signals, it performs a fourth power operation on FID0, FID1, and FID2 to obtain the corresponding fourth power data.

[0073] S204. The terminal device groups the fourth power data corresponding to the three subframe signals into pairs, adds 0 to each group of fourth power data, and obtains two sets of sequences corresponding to the three subframe signals.

[0074] The length of the added zeros is the interval slot length, which equals the subframe signal length minus the effective slot length. Specifically, the zeros added to each group of fourth-power data form an all-zero sequence, which is a sequence consisting entirely of zeros, and its length is the difference between the subframe signal length and the effective slot length.

[0075] Specifically, when the terminal device first receives three consecutive subframe signals, it will... Grouped in pairs according to the time index, we get and Two sets of data. and Adding 0s to the two sets of fourth-power data, we get two sequences as follows: and in This represents a sequence of all zeros formed by adding zeros to each group of fourth-power data.

[0076] To better understand the length of the zeros added between each group of fourth-power data, the following is a combination of... Figure 3 Let's illustrate with examples.

[0077] Assume that subframe signal A with time index 1 and subframe signal B with time index 2 comprise 5 time slots, and the effective time slot is the first time slot in the subframe signal. Then, the fourth power data corresponding to subframe signal A and subframe signal B is... Depend on Figure 3 It is known that the subframe signal length of subframe signal A and subframe signal B is 5 time slots, and the effective time slot length of subframe signal A and subframe signal B is 1 effective time slot. Therefore, the interval time slot length = subframe signal length (5 time slots) - effective time slot length (1 time slot) = 4 time slots. Thus, the length of adding 0 is 4 time slots. Adding four zeros representing the length of the time slot, we get the corresponding sequence.

[0078] S205. The terminal device performs Fast Fourier Transform on the two sets of sequences corresponding to the three subframe signals respectively to obtain the frequency offset estimates corresponding to the two sets of sequences respectively.

[0079] The Fast Fourier Transform (FFT) is an efficient algorithm for computing the Discrete Fourier Transform (DFT). The FFT solves the complex computational problem by breaking down the DFT into smaller subproblems, thus achieving a faster speed than directly computing the DFT.

[0080] Specifically, when the terminal device first receives three consecutive subframe signals, it sets two sequences corresponding to these three subframe signals. and FFT operations are performed separately to obtain the spectral peak values ​​corresponding to the two sets of sequences. Frequency offset estimation is then performed based on these peak values ​​to obtain frequency offset estimates f1 and f2 for each set of sequences. The index of the frequency offset estimate f can be used to indicate which sequence in the two sets the frequency offset estimate corresponds to; that is, according to the subframe signal reception order (time order), the sequence... For the first sequence, the corresponding frequency offset estimate can be represented by f1. If the sequence is the second group, then the corresponding frequency offset estimate can be represented by f2.

[0081] Because the frequency offset rate in satellite communication is relatively large (approximately 300 Hz / s), the effective time slots in the three subframe signals will have different frequency offsets due to the time interval, sometimes even differing significantly. Therefore, the two frequency offset estimates f1 and f2 obtained from the spectral peaks of the two sets of sequences can only characterize the frequency offset value at the midpoint between the two sets of sequences. The specific reasons are as follows:

[0082] In wireless communication (especially satellite communication), terminal devices have the same sampling frequency, i.e., the same sampling period. Furthermore, each subframe signal includes the same number of time slots, each time slot lasts for the same duration, and the time interval between effective time slots in adjacent subframe signals is the same; that is, the number of time slots between effective time slots in adjacent subframe signals is the same. Because the time interval between each effective time slot is the same, the spectral distribution obtained by performing a Fast Fourier Transform on each sequence is periodic, and the spectral peak is generally located in the middle position.

[0083] To facilitate understanding, the following section will explain in detail the calculation process for obtaining the spectral peaks corresponding to the sequence, using formulas (1) and (2). We will take the example of performing a Fast Fourier Transform on a set of sequences to obtain the corresponding spectral peaks.

[0084] The FFT operation on the input sequence z(m) yields Z(k), whose calculation expression is shown in formula (1). Here, z(m) is a sequence of total length M, i.e., z(m) is an M-point sequence. For example: when When, then the sequence It is an M-point sequence.

[0085]

[0086] Where m = 0, 1, ..., M-1, z(m) is the (m+1)th data in the sequence, which may be the fourth power of the effective time slot signal, or it may be 0. For example: when And when m=0, k represents the nth spectral point after the Fast Fourier Transform. For an M-point sequence z(m), k = 0, 1, ..., M-1.

[0087] The FFT operation on sequence z(m) yields Z(k), a complex sequence of length M. The real and imaginary parts of Z(k) represent the amplitudes of the sine and cosine components of z(m) at the k-th spectral point, respectively, thus representing the spectrum at that k-th point. After obtaining the FFT result Z(k) for sequence z(m), the frequency offset estimate f for that sequence z(m) is obtained based on Z(k). d Its calculation expression is shown in formula (2).

[0088]

[0089] Among them, f d To obtain the frequency offset estimate of the sequence z(m) through the peak value of the FFT spectrum, d is used to indicate that the sequence is the d-th sequence in two sets of sequences. For example, if the time indices of three consecutive subframe signals are 0, 1, and 2, then the sequence... Let d be the first sequence of the two sets of sequences, i.e., d = 1, and the sequence... Defined as the second sequence in a two-sequence set, i.e., d = 2. M is the total number of symbols in sequence z(m), which can also be understood as the number of time slots contained in sequence z(m). T s The duration of a symbol can also be understood as the duration of a time slot. Since the effective time slot signal is subjected to a fourth-order nonlinear operation in S203, the phase information of the signal is amplified by a factor of 4. Therefore, the frequency offset estimate corresponding to z(m) needs to be scaled to obtain the correct multiple of the frequency offset estimate.

[0090] S206. The terminal device calculates the frequency offset estimate of the three subframe signals based on the frequency offset estimate values ​​corresponding to the two sets of sequences.

[0091] When the terminal device receives three consecutive subframe signals for the first time, it calculates the frequency offset estimates of the three subframe signals based on the frequency offset estimates of the two sets of sequences corresponding to the three subframe signals, and represents them as F0, F1, and F2 respectively.

[0092] Specifically, the two sets of sequences corresponding to these three subframe signals are: and The frequency offset estimates for the two sets of sequences are f1 and f2, respectively. Since each subframe signal contains the same number of time slots, each time slot lasts for the same duration, and the effective time slots are located in the same position within the subframe signal (i.e., the time interval between effective time slots in adjacent subframe signals is the same), F1 = (f1 + f2) / 2 and f2 = (F1 + F2) / 2. Solving these two equations, we can obtain F2 = 1.5f2 - 0.5f1.

[0093] In one possible implementation, for the subframe signal with time index 0 (i.e., the first subframe signal received by the terminal device), the subframe signal with time index 0 is set during initialization, i.e., F0 = F initial For the subframe signal with time index 1, F2 = (f1 + f2) / 2. For the subframe signal with time index 2, F2 = 1.5f2 - 0.5f1.

[0094] In another possible implementation, for the subframe signal with time index 0 (i.e., the first subframe signal received by the terminal device), the subframe signal with time index 0 is set during initialization, i.e., F0 = F initial For the subframe signal with time index 1 and the subframe signal with time index 2, F1 = F2 = 1.5f2 - 0.5f1.

[0095] S207. The terminal device performs frequency offset compensation on the three subframe signals based on the frequency offset estimate of the three subframe signals.

[0096] Based on the frequency offset estimate of the current subframe signal, frequency offset compensation is performed on the current subframe signal to eliminate the frequency offset between the received and transmitted signals caused by Doppler effect, clock deviation, etc., thereby achieving clock synchronization. In one possible implementation, when the terminal device first receives three consecutive subframe signals, i.e., the subframe signals corresponding to time indices 0, 1, and 2 respectively, then the initialization parameter F0 = F... initial Frequency offset compensation is performed on the subframe signal with time index 0, and frequency offset compensation is performed on the subframe signals with time indices 1 and 2 respectively by F1 = F2 = 1.5f2 - 0.5f1, so that the entire frequency offset compensation process is implemented through a single logical process.

[0097] In another possible implementation, the terminal device first receives three consecutive subframe signals, specifically the subframe signals corresponding to time indices 0, 1, and 2. At this time, the initialization parameter F0 = F... initialFrequency offset compensation is performed on the subframe signal with time index 0, frequency offset compensation is performed on the subframe signal with time index 1 using F1 = (f1 + f2) / 2, and frequency offset compensation is performed on the subframe signal with time index 2 using F2.

[0098] S208. The terminal device performs frequency offset compensation of the phase-locked loop based on the frequency offset estimates of the three subframe signals.

[0099] Specifically, while performing frequency offset compensation for subframe signals, the terminal device calculates the frequency offset compensation value of the phase-locked loop (PPL) based on the frequency offset estimates of the three subframe signals. Based on the frequency offset compensation value of the PPL, the frequency of the terminal device's oscillator is adjusted to achieve frequency offset compensation of the PPL, thereby eliminating or reducing frequency offset as much as possible.

[0100] The phase-locked loop (PPL) is a feedback control system that includes a phase detector, a low-pass filter, and a voltage-controlled oscillator (VCO). After frequency offset compensation is performed on the subframe signal, the frequency of the PPL's ​​oscillator should also be compensated accordingly to minimize the frequency offset between the PPL's ​​input and output signals, thereby achieving more accurate tracking of the input signal's frequency changes.

[0101] Specifically, the phase-locked loop frequency offset compensation value is obtained through formula (3):

[0102]

[0103] Among them, F pll F is the frequency offset compensation value for the phase-locked loop. i This is the frequency offset estimate for the subframe signal with time index i. For example, when three consecutive subframe signals are received for the first time, n = 0, then F... pll =F0+F1+F2.

[0104] S209. The terminal device iterates n = n + 1 and receives the subframe signal with time index n + 2.

[0105] Specifically, after the terminal device completes frequency offset compensation for the subframe signal and the phase-locked loop (PLL), it needs to continue with frequency offset estimation and compensation for the next subframe signal. At this point, the terminal device iterates n = n + 1, and then continues to receive the subframe signal with time index n = 2. For example, after the terminal device completes frequency offset compensation for the first three consecutive received subframe signals and the corresponding PLL frequency offset compensation, iterates n = 0 + 1 = 1, and then receives the subframe signal with time index 3, meaning the terminal device receives the fourth subframe signal.

[0106] S210. The terminal device extracts the valid time slot data of the subframe signal with time index n+2, and obtains the valid time slot data of the subframe signals with time indices n and n+1, thus obtaining the valid time slot data of three consecutive subframe signals.

[0107] Specifically, the terminal device extracts the valid time slot data of the subframe signal with time index n+2 and stores this valid time slot data. Furthermore, it retrieves the valid time slot data of the subframe signals with time indices n and n+2 from the terminal device's storage, obtaining the valid time slot data of three consecutive subframe signals. The valid time slot data of these three consecutive subframe signals are then processed through FID. n FID n+1 FID n+2 To express.

[0108] It should be noted that the three consecutive subframe signals corresponding to the subframe signal with time index n+2 are the subframe signals with time indices n, n+1, and n+2.

[0109] For example, the terminal device iterates n = 0 + 1 = 1. After receiving the subframe signal with time index 3, the terminal device extracts the valid time slot data of the subframe signal with time index 3 and stores it. Furthermore, it retrieves the valid time slot data of the subframe signals with time indices 1 and 2 from the terminal device's storage, obtaining the valid time slot data of three consecutive subframe signals. It should be noted that the valid time slot data of the subframe signals with time indices 1 and 2 is extracted and stored after the first reception of three consecutive subframe signals (subframe signals with time indices 0, 1, and 2). Therefore, the valid time slot data of the subframe signals with time indices 1 and 2 has already been stored in the terminal device.

[0110] S211. The terminal device performs a fourth power operation on the effective time slot data of the three consecutive subframe signals to obtain the fourth power data corresponding to the three consecutive subframe signals.

[0111] Specifically, the terminal devices respectively support FID n FID n+1 FID n+2 Perform the fourth power operation to obtain the corresponding fourth power data.

[0112] S212. The terminal device groups the fourth power data corresponding to the three consecutive subframe signals into pairs, adds 0 to each group of fourth power data, and obtains two sets of sequences corresponding to the three consecutive subframe signals.

[0113] Specifically, the terminal device will Grouped in pairs according to the time index, we obtain... and Two sets of sequences. Add zeros to the middle of each set of fourth-power data to obtain two sets of sequences corresponding to three consecutive subframe signals. and To express.

[0114] S213. The terminal device performs Fast Fourier Transform on the two sets of sequences corresponding to the three consecutive subframe signals to obtain the frequency offset estimates corresponding to the two sets of sequences.

[0115] Specifically, the two sets of sequences corresponding to the three subframe signals are... and Perform FFT operations separately to obtain the spectral peaks corresponding to the two sets of sequences. Based on the spectral peaks of the two sets of data, perform frequency offset estimation to obtain frequency offset estimates f1 and f2 for the two sets of sequences, respectively. The subscript of the frequency offset estimate f can be used to indicate which set of sequences the frequency offset estimate corresponds to. For example, the two sets of sequences corresponding to three consecutive subframe signals are... and According to the order of subframe signal reception (time order), this sequence... If the sequence is the second group, then the corresponding frequency offset estimate can be obtained through f2.

[0116] S214. The terminal device calculates the frequency offset estimate of the subframe signal with time index n+2 based on the frequency offset estimates corresponding to the two sets of sequences.

[0117] When the terminal device receives three consecutive subframe signals (not the first time), these three consecutive subframe signals are subframe signals with time indices n, n+1, and n+2. Among them, the subframe signals with time indices n and n+1 have already undergone frequency offset compensation. For example, if n=1, the three consecutive subframe signals are subframe signals with time indices 1, 2, and 3. The subframe signals with time indices 1 and 2 have already undergone frequency offset compensation in S201-S208, so there is no need to perform frequency offset compensation again for the subframe signals with time indices 1 and 2. Therefore, it is not necessary to calculate the frequency offset estimate for the subframe signals with time indices 1 and 2.

[0118] Specifically, two sets of sequences and The corresponding frequency offset estimates f1 and f2 are respectively, and the frequency offset estimate of the effective time slot signal corresponding to the subframe signal with time index n+1 is expressed as F. n+1 The frequency offset estimate corresponding to the subframe signal with time index n+2 is represented as F. n+2This is represented as follows. Since each subframe signal includes the same number of time slots, each time slot lasts for the same duration, and the time interval between effective time slots in adjacent subframe signals is the same, F... n+1 = (f1+f2) / 2, and f2=(F n+1 +F n+2 ) / 2, by solving the above two equations, we can obtain F n+2 =1.5f2-0.5f1.

[0119] The frequency offset estimate of the current subframe signal is calculated by using the frequency offset estimates corresponding to two sets of sequences. That is, the frequency offset estimate of the current subframe signal is calculated jointly using three consecutive subframe signals. Compared to current technologies that rely solely on limited local synchronization sequences or data from a single subframe signal, this embodiment uses more prior information for frequency offset estimation, which improves the accuracy of frequency offset estimation to some extent. Furthermore, after obtaining the frequency offset estimate of the middle position (the middle position in the time domain) of the sequence based on the peak value of the Fast Fourier Transform of the sequence, the frequency offset estimate of the current subframe signal is obtained through a differential algorithm based on the frequency offset estimates of the two sequences corresponding to the three consecutive subframe signals. This fully considers the rate of change of frequency offset during signal transmission, thereby avoiding errors in frequency offset estimation caused by the rate of change of frequency offset to some extent and improving the accuracy of frequency offset estimation of the subframe signal. Moreover, obtaining the frequency offset estimate of the current subframe signal through a differential algorithm can reduce errors generated during the calculation of the frequency offset estimate.

[0120] S215. The terminal device performs frequency offset compensation on the subframe signal with time index n+2 based on the frequency offset estimate of the subframe signal with time index n+2.

[0121] For example, when the terminal device receives three consecutive subframe signals (not the first time) and n=2, the terminal device performs frequency offset compensation on the subframe signal with time index 4 based on the frequency offset estimate F4 of the subframe signal with time index 4. The three consecutive subframe signals corresponding to the subframe signal with time index 4 are the subframe signals with time indices 2, 3, and 4. Since the subframe signals with time indices 2 and 3 have already undergone frequency offset compensation, it is not necessary to perform frequency offset compensation on the signals with time indices 2 and 3 again in this step. It should be noted that the frequency offset compensation for the subframe signal with time index 2 is based on the joint implementation of the three subframe signals with time indices 0, 1, and 2, that is, based on the corresponding two sets of sequences. and The frequency offset estimates f1 and f2 are used to obtain the frequency offset estimate F2 of the subframe signal with time index 2, and frequency offset compensation is performed on the subframe signal with time index 2. Similarly, the frequency offset compensation of the subframe signal with time index 3 is achieved by jointly implementing the frequency offset compensation based on the three subframe signals with time indices 1, 2, and 3, that is, based on the corresponding two sets of sequences. and The frequency offset estimates f1 and f2 are used to obtain the frequency offset estimate F3 of the subframe signal with time index 3, and frequency offset compensation is performed on the subframe signal with time index 3.

[0122] S216. The terminal device performs frequency offset compensation of the phase-locked loop based on the frequency offset estimate of all received subframe signals.

[0123] Specifically, while performing frequency offset compensation for the subframe signal with time index n+2, the terminal device calculates the frequency offset compensation value of the phase-locked loop (PLL) based on the frequency offset estimates of all received subframe signals, and adjusts the frequency of the terminal device's oscillator based on the PLL's frequency offset compensation value to achieve PLL frequency offset compensation.

[0124] After S216 is completed, the terminal device iterates n=n=1, that is, it loops through S209-S216 until the terminal device stops receiving subframe signals and stops looping.

[0125] The above combination Figure 2 and Figure 3 This application provides a detailed description of a frequency offset estimation method based on its embodiments. For ease of understanding, the following section combines... Figure 4 This application provides an example of a frequency offset estimation method. Starting with the terminal device receiving three consecutive subframe signals for the first time, the method is described iteratively, with initialization parameters set (n=0 and F0=F0). initial Each subframe signal consists of 5 time slots, and the first time slot of each subframe signal is the valid time slot.

[0126] like Figure 4 As shown in (a), the terminal device initially receives three consecutive subframe signals, with time indices of 0, 1, and 2. For ease of description, these three consecutive subframe signals are represented by S0, S1, and S2. The valid time slot data from S0, S1, and S2 are extracted to obtain FID0, FID1, and FID2. The valid time slot data FID0, FID1, and FID2 are then subjected to a fourth power operation to obtain the fourth power data corresponding to the three subframe signals. The fourth power data corresponding to the three subframe signals are grouped in pairs to obtain two sets of data. and Based on the time slot length between the effective time slot of S0 and the effective time slot of S1, Add 0s in the middle to get the corresponding first sequence. Based on the effective time slot length between S1 and S2, Add 0s in the middle to get the corresponding second sequence. right and Perform Fast Fourier Transform (FFT) operations on the two sets of sequences to obtain the first set of sequences. The corresponding frequency offset estimate f1 and the second set of sequences The corresponding frequency offset estimate f2; based on the frequency offset estimates f1 and f2 corresponding to the two sets of sequences, calculate the frequency offset estimate F1 = (f1 + f2) / 2 for S1 and the frequency offset estimate F2 = 1.5f2 - 0.5f1 for S2; perform frequency offset compensation for S1 based on the frequency offset estimate F1 corresponding to S1, and perform frequency offset compensation for S2 based on the frequency offset estimate F2 corresponding to S2. Complete as follows Figure 4 The frequency offset compensation in (a) is performed, and the step is n = n + 1, i.e., n = 1. Then the effective time slot data of the subframe signal with time index n + 2 is obtained, as shown in the following figure. Figure 4 As shown in (b) of the diagram.

[0127] like Figure 4 As shown in (b), the three consecutive subframe signals for this joint calculation of the frequency offset estimate are: subframe signals with time indices 1, 2, and 3, represented by S1, S2, and S3, because as... Figure 4 In the process shown in (a), the effective time slot data corresponding to S1 and S2 has been extracted, which are FID1 and FID2. Then, the effective time slot data FID3 corresponding to S3 is obtained. The effective time slot data FID1, FID2, and FID3 are subjected to a fourth power operation to obtain the fourth power data corresponding to the three subframe signals. The fourth power data corresponding to the three subframe signals are grouped in pairs to obtain two sets of data. and Based on the time slot length between the effective time slots of S1 and S2, Add 0s in the middle to get the corresponding first sequence. Based on the effective time slot length between S2 and S3, Add 0s in the middle to get the corresponding second sequence. right and Perform Fast Fourier Transform (FFT) operations on the two sets of sequences to obtain the first set of sequences. The corresponding frequency offset estimate f1 and the second set of sequences The corresponding frequency offset estimate is f2; based on the frequency offset estimates f1 and f2 corresponding to the two sets of sequences, the frequency offset estimate F3 corresponding to S3 is calculated as F3 = 1.5f2 - 0.5f1; frequency offset compensation is performed on S3 based on the frequency offset estimate F3 corresponding to S3. It should be noted that since three consecutive subframe signals are received for the first time, frequency offset compensation needs to be performed on all three subframe signals; for cases where three consecutive subframe signals are not received for the first time, the first two subframe signals have already undergone frequency offset compensation, so frequency offset compensation can be performed on the current subframe signal based on the frequency offset estimate of the current subframe signal (the third subframe signal among the three subframe signals) obtained by combining the three subframe signals. Figure 4 The frequency offset compensation of the subframe signal (current subframe signal) shown in (b) is performed, and the step is n = n + 1, i.e., n = 2. Then the effective time slot data of the subframe signal with time index n + 2 is obtained, as shown in the figure. Figure 4 As shown in (c) in the figure.

[0128] like Figure 4 As shown in (c), the three consecutive subframe signals for this joint calculation of frequency offset estimation are: subframe signals with time indices 2, 3, and 4, represented by S2, S3, and S4, and the effective time slot data FID4 corresponding to S4 is obtained; the effective time slot data FID2, FID3, and FID4 are subjected to a fourth power operation to obtain the fourth power data corresponding to the three subframe signals respectively. The fourth power data corresponding to the three subframe signals are grouped in pairs to obtain two sets of data. and Based on the time slot length between the effective time slots of S2 and S3, Add 0s in the middle to get the corresponding first sequence. Based on the effective time slot length between S3 and S4, Add 0 to the middle to get the corresponding second sequence. right and Perform Fast Fourier Transform (FFT) operations on the two sets of sequences to obtain the first set of sequences. The corresponding frequency offset estimate f1 and the second set of sequences The corresponding frequency offset estimate is f2; based on the frequency offset estimates f1 and f2 corresponding to the two sets of sequences, the frequency offset estimate F4 corresponding to S4 is calculated as 1.5f2 - 0.5f1; frequency offset compensation is performed on S4 based on the frequency offset estimate F4 corresponding to S4. This completes the process as follows: Figure 4Frequency offset compensation for the subframe signal (current subframe signal) shown in (c) is performed, and the process is accelerated by n = n + 1, i.e., n = 3. Then, the effective time slot data of the next subframe signal is obtained, and frequency offset estimation continues. Figure 4 This will not be shown further. Furthermore, during frequency offset compensation of the received subframe signal, frequency offset compensation is also performed on the oscillator of the phase-locked loop.

[0129] This application provides a frequency offset estimation method that jointly calculates the frequency offset estimate of the subframe signal received by the terminal device using effective time slot data from three consecutive subframe signals. This frequency offset estimation method is a non-data-assisted method, which improves the accuracy of frequency offset estimation compared to data-assisted methods. Furthermore, by extracting effective time slot data from the subframe signal, the influence of noise in the subframe signal on the accuracy of frequency offset estimation is avoided, unlike current non-data-assisted frequency offset estimation methods. However, since this embodiment only extracts effective time slot data, the prior information is reduced compared to current non-data-assisted frequency offset estimation methods. Therefore, by combining the effective time slot data from three subframe signals, the prior information for frequency offset estimation is increased. This means that more effective prior information is relied upon compared to current methods, which improves the accuracy of frequency offset estimation, reduces the error, and avoids frequency offset estimation failure, thus ensuring effective frequency offset compensation for subsequent coherent demodulation of the signal.

[0130] Furthermore, by jointly calculating the frequency offset estimate of the current subframe signal using three consecutive subframe signals, the large frequency offset variation rate of the satellite communication system is also taken into account, which to some extent avoids the situation where the frequency offset estimation accuracy is poor due to the large frequency offset variation rate.

[0131] Example 2:

[0132] The following is combined Figure 5 This paper will provide a detailed description of a frequency offset estimation method provided in the embodiments of this application. For example... Figure 5 As shown, the method includes the following steps:

[0133] S501. Obtain the first time slot data from M consecutive subframe signals, and perform modulation information cancellation on the first time slot data from the M subframe signals to obtain the spectrum data corresponding to the first time slot data from the M subframe signals.

[0134] Where M is an integer not less than 3. For example, M can be 3, 4, 5, etc., and this application does not make any specific limitation.

[0135] Among them, the subframe signal is the signal received by the terminal device that has completed time synchronization.

[0136] In one possible implementation, the method for canceling modulation information in the first time slot data of the M subframe signals is determined based on the modulation scheme of the subframe signals. For example, when the modulation scheme of the subframe signals is QPSK, the first time slot data of the M subframe signals are subjected to a fourth power operation to achieve modulation information cancellation.

[0137] In one possible implementation, the first time slot can be an effective time slot. Because current non-data-aided frequency offset estimation methods often have low signal-to-noise ratios, the first time slot data may introduce significant noise, affecting the accuracy of frequency offset estimation. This embodiment of the application can extract effective time slot data, thereby avoiding the impact of noisy data on the accuracy of frequency offset estimation and further improving the accuracy of frequency offset estimation.

[0138] There are two cases for acquiring the first time slot data of M consecutive subframe signals, which are described below:

[0139] When first acquiring the first time slot data from M consecutive subframe signals, specifically by continuously receiving M subframe signals and extracting the first time slot data from the continuously received M subframe signals, the first time slot data from the M consecutive subframe signals is obtained. Further, the first time slot data from the continuously received M subframe signals is stored.

[0140] When acquiring the first time slot data from M consecutive subframe signals (specifically, receiving the first subframe signal, which is the Mth subframe signal among the M subframe signals), the first time slot data from the first subframe signal to the Nth subframe signal within these M subframe signals is acquired, thus obtaining the first time slot data from the M consecutive subframe signals. Further, the first time slot data from the first subframe signal is stored. Where N = M-1.

[0141] S502. According to the receiving time order of the M subframe signals, group the spectrum data corresponding to the first time slot data in the M subframe signals into pairs, and add a preset sequence to each group of spectrum data to obtain N groups of sequences corresponding to the M subframe signals.

[0142] Where N = M-1, that is, N is an integer not less than 2.

[0143] The length of the preset sequence is the difference between the length of a subframe signal and the length of the first time slot. In one possible implementation, the preset sequence can be an all-zero sequence.

[0144] S503. Process N sets of sequences to obtain the frequency offset estimates corresponding to the N sets of sequences.

[0145] Specifically, perform Fast Fourier Transform (FFT) operations on each of the N sets of sequences to obtain the frequency offset estimates for each of the N sets of sequences.

[0146] S504. Based on the frequency offset estimates corresponding to N sets of sequences, calculate the frequency offset estimates of M subframe signals.

[0147] When M consecutive subframe signals are received for the first time, a constant (i.e., the standard frequency offset value) is used as the frequency offset estimate of the first subframe signal among the M subframe signals. The average of the frequency offset estimates of the first and second sets of N sequences is calculated to obtain the frequency offset estimate of the second subframe signal among the M subframe signals. Based on the frequency offset estimate of the x-th sequence in the N sets and the frequency offset estimate of the x-th subframe signal among the M subframe signals, the frequency offset estimate of the y-th subframe signal among the M subframe signals is calculated to obtain the frequency offset estimates of the third to M subframe signals among the M subframe signals. y is an integer not less than 3 and not greater than M, and x = y - 1.

[0148] For example, let M=3 and N=2, and let the frequency offset estimates of the three subframe signals be F respectively. a F b F c The frequency offset estimates for the two sets of sequences are represented as f1 and f2. a =Constant (standard frequency offset); F b = (f1+f2) / 2; by (F b +F c From f / 2 = f2, we know that F c =2f²-F b That is, x=2, y=3. Based on the frequency offset estimate f2 of the second sequence and the frequency offset estimate of the second subframe signal, calculate the frequency offset estimate of the third subframe signal.

[0149] When M consecutive subframe signals are received for the first time, the frequency offset estimate of the Mth subframe signal is calculated based on the frequency offset estimate of the Nth sequence in the Nth sequence and the frequency offset estimate of the Nth subframe signal in the M subframe signals.

[0150] S505. Based on the frequency offset estimates of the M subframe signals, perform frequency offset compensation on the M subframe signals.

[0151] When acquiring the first time slot data of M consecutive subframe signals for the first time, in one possible implementation, frequency offset compensation is performed on the M subframe signals using a one-to-one correspondence method based on the frequency offset estimates of the M subframe signals. For example, frequency offset compensation is performed on the first subframe signal using the frequency offset estimate of the first subframe signal; frequency offset compensation is performed on the second subframe signal using the frequency offset estimate of the second subframe signal; and so on, with frequency offset compensation performed on the Mth subframe signal using the frequency offset estimate of the Mth subframe signal.

[0152] When acquiring the first time slot data of M consecutive subframe signals for the first time, in another possible implementation, the frequency offset estimate of the first subframe signal is used to compensate for the frequency offset of the first subframe signal among the M subframe signals; the frequency offset estimate of the Mth subframe signal is used to compensate for the frequency offset of the second to the Mth subframe signals among the M subframe signals. That is, frequency offset compensation is performed on the first subframe signal based on a (constant) value; frequency offset compensation is performed on the remaining subframe signals based on the frequency offset estimate of the Mth subframe signal, effectively achieving frequency offset compensation while simplifying the complexity of the frequency offset compensation steps.

[0153] When acquiring the first time slot data of M consecutive subframe signals (not the first time), the frequency offset estimate of the Mth subframe signal is used to compensate for the frequency offset of the Mth subframe signal. This is because the frequency offset compensation for the remaining subframe signals has already been completed.

[0154] Furthermore, in one possible implementation, after performing S504, the method further includes: summing and calculating the frequency offset compensation value of the phase-locked loop (PLL) based on the known frequency offset estimates of all subframe signals; and adjusting the frequency of the PLL oscillator based on the PLL's frequency offset compensation value to achieve PLL frequency offset compensation. Since the accuracy of the subframe signal frequency offset estimation is improved, the accuracy of the PLL frequency offset compensation value calculated based on the subframe signal frequency offset estimates is also improved, thereby enabling more effective PLL frequency offset compensation.

[0155] This application provides a frequency offset estimation method, including: acquiring first time slot data from M consecutive subframe signals, and performing modulation information cancellation on the first time slot data of the M subframe signals to obtain spectrum data corresponding to the first time slot data of the M subframe signals; grouping the spectrum data corresponding to the first time slot data of the M subframe signals into pairs according to the reception time order of the M subframe signals, and adding a preset sequence to each group of spectrum data to obtain N groups of sequences corresponding to the M subframe signals; processing the N groups of sequences to obtain frequency offset estimation values ​​corresponding to the N groups of sequences; calculating the frequency offset estimation values ​​of the M subframe signals based on the frequency offset estimation values ​​corresponding to the N groups of sequences; and performing frequency offset compensation on the M subframe signals based on the frequency offset estimation values ​​of the M subframe signals. Specifically, frequency offset compensation can be performed on all M subframe signals, or it can be performed on some of the M subframe signals. The frequency offset estimation values ​​of the subframe signals are jointly calculated using the first time slot data of multiple subframe signals. This application calculates the frequency offset estimate of a subframe signal based on the first time slot data of the subframe signal itself. Compared with the current technology that only obtains the frequency offset estimate based on the known synchronization sequence, the accuracy of the frequency offset estimation is higher. Furthermore, since the frequency offset estimation is based on the first time slot data of multiple subframe signals, it relies on more prior information, which improves the accuracy of the frequency offset estimation to a certain extent. This enables effective frequency offset compensation, facilitating the subsequent correct coherent demodulation of the signal. Moreover, by jointly calculating the frequency offset estimate of the subframe signal using multiple subframe signals, the large frequency offset variation rate in satellite communication is also considered, which to some extent avoids inaccurate frequency offset estimation caused by a large frequency offset variation rate.

[0156] In addition, this application provides a terminal device. In some embodiments, the terminal device may be a mobile phone, tablet computer, desktop computer, laptop computer, notebook computer, ultra-mobile personal computer (UMPC), handheld computer, netbook, personal digital assistant (PDA), wearable terminal device, smartwatch, etc. This application does not impose any special limitations on the specific form of the above-mentioned terminal device. In this embodiment, the structure of the terminal device may be as follows: Figure 6 As shown.

[0157] like Figure 6 As shown, the terminal device may include a processor 610, an internal memory 620, an antenna 1, an antenna 2, a mobile communication module 630, a wireless communication module 640, etc.

[0158] The processor 610 may include one or more processing units, such as an application processor (AP), a modem processor, an image signal processor (ISP), a controller, a video codec, a digital signal processor (DSP), a baseband processor, and / or a neural network processing unit (NPU).

[0159] The controller can serve as the nerve center and command center of the terminal device. Based on the instruction opcode and timing signals, the controller generates operation control signals to control the fetching and execution of instructions.

[0160] The wireless communication function of the terminal device can be implemented through antenna 1, antenna 2, mobile communication module 630, wireless communication module 640, modem processor, and baseband processor.

[0161] The mobile communication module 630 can provide solutions for wireless communication applications, including 2G / 3G / 4G / 5G, on terminal devices.

[0162] The wireless communication module 640 can provide solutions for wireless communication applications on terminal devices, including wireless local area networks (WLAN) (such as wireless fidelity (Wi-Fi) networks), Bluetooth (BT), global navigation satellite system (GNSS), frequency modulation (FM), near field communication (NFC), and infrared (IR) technologies.

[0163] In some embodiments, antenna 1 of the terminal device is coupled to mobile communication module 630, and antenna 2 is coupled to wireless communication module 640, enabling the terminal device to communicate with networks and other devices via wireless communication technology.

[0164] This embodiment also provides a computer-readable storage medium including instructions that, when executed on a terminal device, cause the terminal device to perform the relevant method steps in the above embodiment to implement the method in the above embodiment.

[0165] This embodiment also provides a computer program product containing instructions. When the computer program product is run on a terminal device, it causes the user terminal to execute the relevant method steps as described in the above embodiments to implement the methods described in the above embodiments.

[0166] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A frequency offset estimation method, characterized in that, include: The system acquires the first time slot data from M consecutive subframe signals, and performs modulation information cancellation on the first time slot data from the M subframe signals to obtain the spectrum data corresponding to the first time slot data from the M subframe signals; where M is an integer not less than 3; and the subframe signal is a time-synchronized signal received by the terminal device. The first time slot data is the data transmitted by the subframe signal in the first time slot; Based on the receiving time order of the M subframe signals, the spectrum data corresponding to the first time slot data in the M subframe signals are grouped into pairs, and a preset sequence is added to each group of spectrum data to obtain N groups of sequences corresponding to the M subframe signals; where N=M-1. Process the N sets of sequences to obtain the frequency offset estimates corresponding to the N sets of sequences; Based on the frequency offset estimates corresponding to the N sets of sequences, calculate the frequency offset estimates of the M subframe signals; Based on the frequency offset estimates of the M subframe signals, frequency offset compensation is performed on the M subframe signals; The step of calculating the frequency offset estimates of the M subframe signals based on the frequency offset estimates corresponding to the N sets of sequences includes: Based on the frequency offset estimate of the Nth sequence in the Nth sequence and the frequency offset estimate of the Nth subframe signal in the M subframe signals, calculate the frequency offset estimate of the Mth subframe signal in the M subframe signals.

2. The method according to claim 1, characterized in that, The length of the preset sequence added to each set of spectrum data is the difference between the length of a subframe signal and the length of the first time slot.

3. The method according to claim 1, characterized in that, The acquisition of the first time slot data from M consecutive subframe signals includes: Receive M subframe signals continuously, and extract the first time slot data from the M subframe signals received continuously.

4. The method according to claim 1, characterized in that, The acquisition of the first time slot data from M consecutive subframe signals includes: Receive the first subframe signal and extract the first time slot data of the first subframe signal; the first subframe signal is the Mth subframe signal among the M subframe signals; Obtain the first time slot data from the first subframe signal to the Nth subframe signal among the M subframe signals.

5. The method according to claim 1, characterized in that, The step of calculating the frequency offset estimates of the M subframe signals based on the frequency offset estimates corresponding to the N sets of sequences includes: The constant is used as the frequency offset estimate of the first subframe signal among the M subframe signals; Calculate the average of the frequency offset estimates of the first and second sequences in the N sets of sequences to obtain the frequency offset estimate of the second subframe signal in the M subframe signals; Based on the frequency offset estimate of the xth sequence in the N sets of sequences and the frequency offset estimate of the xth subframe signal in the M subframe signals, the frequency offset estimate of the yth subframe signal in the M subframe signals is calculated to obtain the frequency offset estimate of the third subframe signal to the Mth subframe signal in the M subframe signals; where y is an integer not less than 3 and not greater than M; and x = y - 1.

6. The method according to claim 5, characterized in that, The frequency offset compensation of the M subframe signals based on the frequency offset estimates of the M subframe signals includes: Using the frequency offset estimates of the M subframe signals, frequency offset compensation is performed on the M subframe signals in a one-to-one correspondence manner.

7. The method according to claim 5, characterized in that, The frequency offset compensation of the M subframe signals based on the frequency offset estimates of the M subframe signals includes: Using the frequency offset estimate of the first subframe signal, frequency offset compensation is performed on the first subframe signal among the M subframe signals; using the frequency offset estimate of the Mth subframe signal, frequency offset compensation is performed on the second to the Mth subframe signals among the M subframe signals.

8. The method according to claim 1, characterized in that, The frequency offset compensation of the M subframe signals based on the frequency offset estimates of the M subframe signals includes: Frequency offset compensation is performed on the Mth subframe signal using the frequency offset estimate of the Mth subframe signal.

9. The method according to claim 1, characterized in that, After calculating the frequency offset estimates of the M subframe signals based on the frequency offset estimates corresponding to the N sets of sequences, the method further includes: Based on the known frequency offset estimates of all subframe signals, the frequency offset compensation value of the phase-locked loop is calculated by summing them. Based on the frequency offset compensation value of the phase-locked loop, the frequency of the oscillator of the phase-locked loop is adjusted to achieve frequency offset compensation of the phase-locked loop.

10. The method according to claim 1, characterized in that, The first time slot data includes: valid time slot data; the valid time slot data is the data transmitted by the subframe signal in the valid time slot.

11. A terminal device, characterized in that, Including processor and memory; The memory stores computer-executed instructions; The processor executes computer execution instructions stored in the memory, causing the processor to perform the method as described in any one of claims 1-10.

12. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program or instructions that, when executed, implement the method as described in any one of claims 1-10.

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