Clock error compensation method, orthogonal frequency division multiplexing system and storage medium

Abstract

The invention provides a clock error compensation method and an orthogonal frequency division multiplexing system using the clock error compensation method, and the compensation method comprises the steps: determining a second synchronous pilot symbol at a corresponding position in a received signal through a first synchronous pilot symbol of an orthogonal frequency division multiplexing symbol selected according to a system pilot signal; the method comprises the following steps: receiving a received signal, further determining a first synchronous pilot signal and a second synchronous pilot signal, after synchronizing the first synchronous pilot signal and the second synchronous pilot signal, determining the position of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronous pilot symbol, and demodulating the received signal based on the position. According to the method, the phase deviation value of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronous pilot symbol in the frequency domain is determined, and finally, frequency domain phase compensation is performed on each orthogonal frequency division multiplexing symbol in the received signal according to the calculated phase deviation value, so that clock error compensation of the received signal is realized, and the precision of phase compensation is improved.

Description

Technical Field

[0001] The present application relates to the field of communication technology, and in particular to a clock error compensation method, an orthogonal frequency division multiplexing system and a storage medium. Background Art

[0002] Orthogonal Frequency Division Multiplexing (OFDM) is a modern high-speed data transmission technology, which is a type of multi-carrier modulation. It is widely used due to its many advantages such as high bandwidth utilization, high transmission rate, and ability to effectively combat multipath delay and narrowband interference.

[0003] The receiving end of the OFDM system is mainly responsible for receiving the signal transmitted from the transmitting end, and recovering the original data information through a series of processing steps. These processing steps include synchronization, removing the guard interval, parallel-to-serial conversion, FFT (Fast Fourier Transform), etc. In synchronous digital communication, ideally, the transmitting end sends a symbol every cycle driven by the transmitting end sampling clock, and correspondingly, the receiving end samples once every cycle driven by the receiving end sampling clock to obtain the symbol. Obviously, the symbol value is optimal only when the transmitting end sampling clock and the receiving end sampling clock are synchronized.

[0004] However, in practical applications, since the crystal oscillator at the transmitting end and the crystal oscillator at the receiving end are two independent crystal oscillators, without external signal control, the two crystal oscillators cannot have exactly the same sampling frequency and phase, which will cause the OFDM signal received by the receiving end to have frequency and phase deviations, thereby causing the subcarriers in the OFDM signal to shift in phase, and no longer maintain orthogonality, thereby generating interference between carriers, causing signal-to-noise ratio loss, and when the frequency deviation is relatively large, it will cause symbol timing offset, making it impossible for the receiving end to accurately determine the starting position of valid data in the OFDM signal. Therefore, it is very necessary to compensate the sampling clock of the receiving end in the OFDM system to keep it synchronized with the sampling clock of the transmitting end.

[0005] An existing technology is to set counters at the transmitting end and the receiving end respectively, compare and obtain the sampling clock errors of the transmitting end and the receiving end, and perform frequency deviation calibration on the clock error by extraction or interpolation. However, the correction accuracy depends on the accuracy of the counter. In order to achieve better correction accuracy, a high-precision counter is required, which undoubtedly increases the computing resources; and the clock frequency of the receiving end counter must be much larger than the clock frequency of the transmitting end counter. For high-bandwidth, high-sampling rate OFDM systems, the sampling frequency of the receiving end counter may even be as high as several GHz. At the same time, hardware support such as extraction filters is also required. It can be seen that the existing technology is difficult to control the accuracy of the sampling clock compensation of the OFDM system receiving end, and the computing efficiency is not high. Summary of the invention

[0006] The present application provides a clock error compensation method, an orthogonal frequency division multiplexing system and a storage medium, which can solve the technical problems of the prior art in compensating the sampling clock of the OFDM system receiving end so that it keeps synchronization with the sampling clock of the system transmitting end, such as difficulty in precision control, low calculation efficiency and high complexity.

[0007] In a first aspect, an embodiment of the present application provides a clock error compensation method, which is applied to a receiving end of an orthogonal frequency division multiplexing system, and is characterized by comprising: Acquire a pilot signal of the system according to configuration parameters and mapping rules preset by the system; Determine a reference pilot signal according to the pilot signal, select any orthogonal frequency division multiplexing symbol as a first synchronization pilot symbol, and determine a first synchronization pilot signal based on the first synchronization pilot symbol; Determine a second synchronization pilot symbol according to the first synchronization pilot signal, and determine a second synchronization pilot signal based on the second synchronization pilot symbol; wherein the second synchronization pilot symbol is an orthogonal frequency division multiplexing symbol at a position corresponding to a preset condition of correlation with the first synchronization pilot signal in the received signal; Synchronize the first synchronization pilot signal and the second synchronization pilot signal to determine the position of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol; Starting from the position where the second synchronization pilot symbol is located, performing orthogonal frequency division multiplexing demodulation on each orthogonal frequency division multiplexing symbol in the received signal to obtain a demodulated signal, and determining a received pilot signal according to the demodulated signal; Performing clock error calculation on the reference pilot signal and the received pilot signal to determine a phase deviation value of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain; According to the phase deviation value, frequency domain phase compensation is performed on each orthogonal frequency division multiplexing symbol in the received signal to achieve clock error compensation of the received signal.

[0008] In some embodiments, determining a reference pilot signal according to the pilot signal, and selecting any orthogonal frequency division multiplexing symbol as the first synchronization pilot symbol includes: Generating a pilot distribution resource grid of the system according to the pilot signal of the system; Selecting pilot signals corresponding to all orthogonal frequency division multiplexing symbols in the orthogonal frequency division multiplexing symbol set in the pilot distribution resource grid of the system as reference pilot signals; Generate an orthogonal frequency division multiplexing symbol set according to the pilot distribution resource grid of the system; the orthogonal frequency division multiplexing symbol set is a set of all orthogonal frequency division multiplexing symbols including at least N subcarrier data in the pilot distribution resource grid of the system; wherein N is a positive integer; Selecting any orthogonal frequency division multiplexing symbol in the orthogonal frequency division multiplexing symbol set as a first synchronization pilot symbol; The determining a first synchronization pilot signal based on the first synchronization pilot symbol comprises: All subcarrier data corresponding to the first synchronization pilot symbol in the pilot distribution resource grid of the system are selected as the first synchronization pilot signal.

[0009] In some embodiments, the first synchronization pilot symbol is the first symbol in the orthogonal frequency division multiplexing symbol set.

[0010] In some embodiments, determining a second synchronization pilot symbol according to the first synchronization pilot signal, and determining a second synchronization pilot signal based on the second synchronization pilot symbol includes: Performing an inverse Fourier transform on the first synchronization pilot signal to obtain a synchronization seed signal; Perform sliding correlation processing on the synchronization seed signal and the received signal, and use an orthogonal frequency division multiplexing symbol at a corresponding position in the received signal that satisfies a preset condition of correlation with the first synchronization pilot signal as a second synchronization pilot symbol; Taking the position of the second synchronization pilot symbol as a starting point, pilot data of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal are selected as the second synchronization pilot signal.

[0011] In some embodiments, taking the position of the second synchronization pilot symbol as a starting point, selecting pilot signals of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal as the second synchronization pilot signal includes: Taking the position of the second synchronization pilot symbol as a starting point, performing Fourier transform on data of one symbol length in the received signal; According to the transformation result, pilot signals of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal are selected as second synchronization pilot signals.

[0012] In some embodiments, the position corresponding to the preset correlation condition is the position corresponding to the correlation peak in the sliding correlation processing result of the received signal and the synchronization seed signal.

[0013] In some embodiments, synchronizing the first synchronization pilot signal and the second synchronization pilot signal to determine the position of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol includes: Conjugate multiplying the first synchronization pilot signal and the second synchronization pilot signal to obtain synchronization data; Dividing the synchronization data into a first data segment and a second data segment in the order of pilot subcarriers from small to large, and performing conjugate multiplication on the first data segment and the second data segment; Calculate, according to the result of conjugate multiplication of the first data segment and the second data segment, an average value of the phase difference at corresponding positions of the first data segment and the second data segment as a phase offset value of the second synchronization pilot symbol in the received signal; The position of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol is determined according to the phase offset value of the second synchronization pilot symbol in the received signal.

[0014] In some embodiments, starting from the position where the second synchronization pilot symbol is located, performing orthogonal frequency division multiplexing demodulation on each orthogonal frequency division multiplexing symbol in the received signal to obtain a demodulated signal, and determining the received pilot signal according to the demodulated signal includes: Starting from the position where the second synchronization pilot symbol is located, remove the data of the cyclic prefix length of each orthogonal frequency division multiplexing symbol, and perform Fourier transform processing on the data corresponding to each orthogonal frequency division multiplexing symbol in the received signal; Generate a demodulated signal according to a mapping relationship between the Fourier transformed received signal and each orthogonal frequency division multiplexing symbol; Generating, according to the demodulated signal, a pilot distribution resource grid of a received signal corresponding to the demodulated signal; A pilot signal corresponding to all orthogonal frequency division multiplexing symbols in the orthogonal frequency division multiplexing symbol set in the pilot distribution resource grid of the received signal is selected as a received pilot signal.

[0015] In some embodiments, the step of calculating the clock error of the reference pilot signal and the received pilot signal to determine the phase deviation value of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain includes: Conjugate multiplying the reference pilot signal and the received pilot signal to obtain phase deviation calculation data; Dividing the phase deviation calculation data into a third data segment and a fourth data segment according to the order of pilot subcarriers from small to large, and performing conjugate multiplication on the third data segment and the fourth data segment; Calculate, according to the result of conjugate multiplication of the third data segment and the fourth data segment, an average value of the phase difference at a corresponding position of each orthogonal frequency division multiplexing symbol in the third data segment and the fourth data segment as a phase deviation value of the orthogonal frequency division multiplexing symbol; Calculating the distance of each of the orthogonal frequency division multiplexing symbols relative to the second synchronization pilot symbol; According to each OFDM symbol value and its distance relative to the second synchronization pilot symbol, a phase offset value of each OFDM symbol relative to the second synchronization pilot symbol in the frequency domain is calculated and obtained.

[0016] In some embodiments, performing frequency domain phase compensation on each orthogonal frequency division multiplexing symbol in the received signal according to the phase offset value includes: Based on the position of the second synchronization pilot symbol in the pilot distribution resource grid of the received signal, frequency domain phase compensation is performed on each orthogonal frequency division multiplexing symbol in the pilot distribution resource grid of the received signal.

[0017] In some embodiments, performing frequency domain phase compensation on each orthogonal frequency division multiplexing symbol in the pilot distribution resource grid of the received signal includes: Obtaining the order of each orthogonal frequency division multiplexing symbol in the pilot distribution resource grid of the received signal; For an orthogonal frequency division multiplexing symbol before the second synchronization pilot symbol, a phase compensation value is a product of the phase offset value and a distance from the orthogonal frequency division multiplexing symbol to the second synchronization pilot symbol; For an OFDM symbol following the second synchronization pilot symbol, a phase compensation value is a product of a negative value of the phase offset value and a distance from the OFDM symbol to the second synchronization pilot symbol.

[0018] In a second aspect, an embodiment of the present application provides an orthogonal frequency division multiplexing system, including a transmitting end and a receiving end, wherein the receiving end includes: A communication unit, used for acquiring a received signal; A first processing unit is configured to obtain a pilot signal of the system according to a configuration parameter and a mapping rule preset by the system; determine a reference pilot signal according to the pilot signal, select any orthogonal frequency division multiplexing symbol as a first synchronization pilot symbol, and determine a first synchronization pilot signal based on the first synchronization pilot symbol; A second processing unit is used to determine a second synchronization pilot symbol according to the first synchronization pilot signal, and determine a second synchronization pilot signal based on the second synchronization pilot symbol; wherein the second synchronization pilot symbol is an orthogonal frequency division multiplexing symbol at a position corresponding to a preset condition of correlation with the first synchronization pilot signal in the received signal; a synchronization unit, configured to synchronize the first synchronization pilot signal with the second synchronization pilot signal, and determine a position of each orthogonal frequency division multiplexing symbol in a received signal relative to the second synchronization pilot symbol; A demodulation unit, configured to perform orthogonal frequency division multiplexing demodulation on each orthogonal frequency division multiplexing symbol in the received signal starting from the position where the second synchronization pilot symbol is located, to obtain a demodulated signal, and to determine a received pilot signal according to the demodulated signal; A clock error calculation unit, configured to perform clock error calculation on the reference pilot signal and the received pilot signal, and determine a phase deviation value of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain; The compensation unit is used to perform frequency domain phase compensation on each orthogonal frequency division multiplexing symbol in the received signal according to the phase deviation value, so as to achieve clock error compensation of the received signal.

[0019] In a fourth aspect, an embodiment of the present application provides a readable storage medium, on which a program or instruction is stored. When the program or instruction is executed by a processor, the steps of the clock error compensation method described in the first aspect are implemented.

[0020] In a fifth aspect, an embodiment of the present application provides a computer program product, which is stored in a storage medium and is executed by at least one processor to implement the steps of the clock error compensation method as described in the first aspect.

[0021] In the sixth aspect, an embodiment of the present application provides a chip, which includes at least one processor and a communication interface, and the communication interface and the processor are coupled; the at least one processor is used to execute a computer program or instruction to implement the steps of the clock error compensation method as described in the first aspect.

[0022] The clock error compensation method provided by the embodiment of the present application and the orthogonal frequency division multiplexing system using the method for clock error compensation method, the compensation method determines the second synchronization pilot symbol at the corresponding position in the received signal by selecting the first synchronization pilot symbol of the orthogonal frequency division multiplexing symbol according to the system pilot signal, and then determines the first synchronization pilot signal and the second synchronization pilot signal. After synchronizing the first synchronization pilot signal and the second synchronization pilot signal, the position of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol is determined, and the received signal is demodulated based on this, and the phase deviation value of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain is determined. Finally, according to the calculated phase deviation value, frequency domain phase compensation is performed on each orthogonal frequency division multiplexing symbol in the received signal to achieve clock error compensation of the received signal.

[0023] The present application determines the OFDM symbol as a reference, calculates the phase deviation of each OFDM symbol in the received signal, and performs phase compensation on each OFDM symbol in the received signal in the frequency domain, thereby realizing time error compensation based on OFDM symbols. Compared with the prior art, the accuracy of phase compensation is improved according to the calculation results of the phase deviation of multiple OFDM symbols; at the same time, the compensation process is performed in the frequency domain, and phase compensation is performed directly in the frequency domain, which also reduces the overhead of system data processing.

[0024] In addition, the present application also provides a computer-readable storage medium, a computer program product, and a chip, which have the same beneficial effects as the above-mentioned clock error compensation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0026] Figure 1 A flowchart of a clock error compensation method provided by an embodiment of the present application; Figure 2 A flowchart for determining a reference pilot signal, a first synchronization pilot symbol and a first synchronization pilot signal provided by an embodiment of the present application; Figure 3 A schematic diagram of a pilot distribution resource grid provided in one embodiment of the present application; Figure 4 A flowchart of determining a second synchronization pilot symbol and a second synchronization pilot signal provided by an embodiment of the present application; Figure 5 A flowchart for determining a second synchronization pilot signal provided by an embodiment of the present application; Figure 6A flowchart for determining the position of each orthogonal frequency division multiplexing symbol in a received signal provided by an embodiment of the present application; Figure 7 A flowchart of determining a demodulation signal and receiving a pilot signal provided by an embodiment of the present application; Figure 8 A flowchart for determining a phase offset value of each orthogonal frequency division multiplexing symbol in a received signal provided by an embodiment of the present application; Fig. 9 A flowchart of frequency domain phase compensation provided by an embodiment of the present application; Fig.10 A schematic diagram of the structure of a clock error compensation module provided in one embodiment of the present application.

[0027] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below by specific embodiments in conjunction with the accompanying drawings. Wherein similar elements in different embodiments adopt associated similar element numbers. In the following embodiments, many detailed descriptions are for making the present application better understood. However, those skilled in the art can easily recognize that some features can be omitted in different situations, or can be replaced by other elements, materials, methods. In some cases, some operations related to the present application are not shown or described in the specification, this is to avoid the core part of the present application being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0029] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementations. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a required sequence, unless otherwise specified that a certain sequence must be followed.

[0030] The terms "first", "second", etc. in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable when appropriate, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are usually a class, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated before and after are in an "or" relationship. The "connection" and "connection" mentioned in this application, unless otherwise specified, include direct and indirect connections (connections).

[0031] Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation technology that is widely used in wireless communications and broadband networks for efficient data transmission. The basic principle of OFDM is to divide the channel into several orthogonal sub-channels, convert the high-speed data signal into parallel low-speed sub-data streams, and then modulate them onto these orthogonal sub-carriers for transmission. These sub-carriers are orthogonal in the frequency domain, which means that the spectrum between them can overlap without interfering with each other.

[0032] The OFDM system mainly consists of two parts: the transmitter and the receiver. The transmitter includes at least a data source, a serial-to-parallel converter, a modulator, an IFFT processor, a cyclic prefix adder, and an RF transmitter. Among them, the data source provides the data signal to be transmitted, the serial-to-parallel converter first converts the high-speed serial data into low-speed parallel data, and then the modulator modulates the data on each subcarrier. The IFFT processor further performs an inverse fast Fourier transform (IFFT) on the modulated parallel data, converting it from the frequency domain to the time domain to form an OFDM symbol. The cyclic prefix adder adds a cyclic prefix to each OFDM symbol to combat multipath interference. Finally, the time domain signal is converted into an analog signal through the RF transmitter and transmitted to the receiver through the RF link. The receiver includes at least an RF receiver, a cyclic prefix remover, an FFT processor, a demodulator, and a serial-to-parallel converter. The RF receiver is used to receive the RF signal transmitted by the transmitter and convert it into a digital signal. The cyclic prefix remover removes the cyclic prefix of the OFDM symbol in the received signal. The FFT processor performs a fast Fourier transform (FFT) on the received time domain signal to convert it from the time domain to the frequency domain. The demodulator further demodulates the data on each subcarrier, extracts the data on each subcarrier, and restores the original data. Finally, the parallel-to-serial converter converts the low-speed parallel data into high-speed serial data to form the final data output. That is, the working process of the OFDM system can be divided into the following steps: data segmentation and modulation, IFFT transformation and time domain signal generation, cyclic prefix addition and signal transmission, signal reception and FFT transformation, demodulation and data recovery, parallel-to-serial conversion and data output. The OFDM system achieves the dual improvement of high-speed data transmission and anti-interference ability through clever signal segmentation, modulation, IFFT transformation, cyclic prefix addition and FFT transformation.

[0033] The OFDM system has the advantages of high spectrum efficiency, strong anti-multipath interference capability, simple channel equalization and high flexibility, but it also has the limitations of increased system complexity and high requirements for frequency and time synchronization. The symbol value is optimal only when the sampling clock of the transmitter and the sampling clock of the receiver are synchronized. In the OFDM system, it is very necessary to compensate the sampling clock of the receiver to keep it synchronized with the sampling clock of the transmitter.

[0034] The clock error compensation method proposed in the present application can compensate the sampling clock of the receiving end of the OFDM system so that it can be synchronized with the sampling clock of the transmitting end of the system and has high control accuracy.

[0035] The technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0036] Figure 1 This is a flow chart of a clock error compensation method provided by an embodiment of the present application. Figure 1 As shown, the clock error compensation method provided in this embodiment is applied to the receiving end of an orthogonal frequency division multiplexing system, and specifically includes the following steps: Step S101: Acquire the system pilot signal according to the system preset configuration parameters and mapping rules.

[0037] In this embodiment, the preset configuration parameters of the orthogonal frequency division multiplexing system (hereinafter referred to as: OFDM system) include carrier frequency, bandwidth, modulation mode, coding mode, etc., which can determine the insertion position and method of the pilot signal. The mapping rules preset by the OFDM system are mainly used to determine how the orthogonal frequency division multiplexing symbols (hereinafter referred to as: OFDM symbols) are mapped to subcarriers. In an OFDM system, this usually involves modulating the constellation symbols onto each subcarrier. Therefore, for a certain OFDM system, according to its configuration parameters and mapping rules, it is possible to determine the mapping of data to each subcarrier and generate a pilot signal, that is, for a certain OFDM system, the pilot signal is usually a known data sequence that can be used for channel estimation and synchronization.

[0038] Step S102: determine a reference pilot signal according to the pilot signal, select any orthogonal frequency division multiplexing symbol as a first synchronization pilot symbol, and determine a first synchronization pilot signal based on the first synchronization pilot symbol.

[0039] In this embodiment, the pilot signal is mainly used as a phase reference in the OFDM system for channel estimation. Since all subcarriers will have a certain phase offset, by inserting a known pilot signal into the signal, the receiver can estimate the channel response based on the assumption that the pilot and data are similarly distorted. The OFDM symbol is the basic unit for transmitting information on a subcarrier, and is composed of a group of orthogonal subcarriers, each of which carries independent information. Since the subcarriers are orthogonal, the OFDM symbol can transmit information simultaneously on the same frequency band, thereby achieving efficient spectrum utilization.

[0040] The pilot distribution resource grid of the OFDM system can be generated according to the system preset configuration parameters and mapping rules. The pilot distribution resource grid refers to the part of the spectrum resources of the communication system that is specifically used to transmit the pilot signal. In the OFDM system, the pilot signal is inserted into a specific subcarrier, and these subcarriers form a certain distribution pattern on the spectrum, namely the pilot distribution resource grid.

[0041] In this embodiment, the reference pilot signal is the pilot data corresponding to the OFDM symbol in the pilot distribution resource grid of the system. From the pilot distribution resource grid, any orthogonal frequency division multiplexing symbol is selected as the first synchronization pilot symbol. The first synchronization pilot signal is all subcarrier data corresponding to the first synchronization pilot symbol in the pilot distribution resource grid of the OFDM system.

[0042] Step S103: Determine a second synchronization pilot symbol according to the first synchronization pilot signal, and determine a second synchronization pilot signal based on the second synchronization pilot symbol, wherein the second synchronization pilot symbol is an orthogonal frequency division multiplexing symbol at a position corresponding to a preset correlation condition with the first synchronization pilot signal in the received signal.

[0043] In some embodiments, the first synchronization pilot signal determined in step S102 is subjected to sliding correlation processing with the received signal, and the correlation degree between the received signal and the first synchronization pilot signal can be obtained from the correlation processing result. The OFDM symbol at the position corresponding to the position where the correlation between the two meets certain preset conditions is the second synchronization pilot symbol.

[0044] In some embodiments, the position corresponding to the preset correlation condition may be the position corresponding to the correlation peak in the sliding correlation processing result of the received signal and the synchronization seed signal.

[0045] In some embodiments, the second synchronization pilot signal is pilot data of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal.

[0046] Step S104: synchronize the first synchronization pilot signal and the second synchronization pilot signal to determine the precise position of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol.

[0047] In this embodiment, the first synchronization pilot signal and the second synchronization pilot signal are synchronized, including time synchronization and frequency synchronization, and the synchronization of the signals can identify the starting position and timing information of the first synchronization pilot signal and the second synchronization pilot signal. On the premise of determining the position of the second synchronization pilot symbol, the precise position of each OFDM symbol in the received signal relative to the second synchronization pilot symbol can be determined according to the synchronization result.

[0048] Step S105: Starting from the position where the second synchronization pilot symbol is located, perform orthogonal frequency division multiplexing demodulation on each orthogonal frequency division multiplexing symbol in the received signal to obtain a demodulated signal, and determine the received pilot signal according to the demodulated signal.

[0049] In this embodiment, orthogonal frequency division multiplexing demodulation converts high-speed serial data into multiple low-speed parallel data, and modulates them onto multiple orthogonal subcarriers for transmission, thereby improving spectrum efficiency and anti-interference capability. The OFDM system needs to perform orthogonal frequency division multiplexing demodulation on each OFDM symbol to restore the original data. Before the receiving end of the OFDM system demodulates the received signal, it is necessary to pre-process the received signal, including filtering, amplification, and synchronization. By performing a fast Fourier transform (FFT) on the OFDM symbol, the time domain signal is converted back to the frequency domain signal, and then the signal on each subcarrier is demodulated.

[0050] In some embodiments, the received pilot signal is pilot data corresponding to an OFDM symbol in a received signal pilot distribution resource grid.

[0051] Step S106: Calculate the clock error of the reference pilot signal and the received pilot signal to determine the phase offset value of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain.

[0052] In this embodiment, the same processing method as step S105 is used to calculate the clock error of the reference pilot signal and the received pilot signal, identify the starting position and timing information of the reference pilot signal and the received pilot signal, and determine the position of the second synchronization pilot symbol. Based on the synchronization result, the phase deviation value of each OFDM symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain can be determined.

[0053] Step S107: Perform frequency domain phase compensation on each OFDM symbol in the received signal according to the phase offset value to achieve clock error compensation of the received signal.

[0054] In this embodiment, in the OFDM system, each OFDM symbol in the received signal is subjected to frequency domain phase compensation, mainly to correct the phase deviation between subcarriers caused by channel transmission characteristics (such as phase distortion, multipath effect, etc.), which helps to ensure accurate data recovery. After determining the phase deviation value of each OFDM symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain, frequency domain phase compensation is performed on each OFDM symbol in the received signal, that is, the signal on each subcarrier is individually adjusted accordingly, and the phase offset in the frequency domain signal is corrected, so that the receiving end can decode and recover the received signal and perform subsequent processing such as.

[0055] To summarize, the clock error compensation method provided in this embodiment determines the second synchronization pilot symbol at the corresponding position in the received signal by selecting the first synchronization pilot symbol of the orthogonal frequency division multiplexing symbol according to the system pilot signal, and then determines the first synchronization pilot signal and the second synchronization pilot signal. After synchronizing the first synchronization pilot signal and the second synchronization pilot signal, the position of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol is determined, and the received signal is demodulated based on this to determine the phase deviation value of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain. Finally, according to the calculated phase deviation value, frequency domain phase compensation is performed on each orthogonal frequency division multiplexing symbol in the received signal to achieve clock error compensation of the received signal.

[0056] This embodiment determines the OFDM symbol as a reference, calculates the phase deviation of each OFDM symbol in the received signal, and performs phase compensation on each OFDM symbol in the received signal in the frequency domain, thereby realizing time error compensation based on the OFDM symbol. Compared with the prior art, the accuracy of phase compensation is improved according to the calculation results of the phase deviation of multiple OFDM symbols; at the same time, the compensation process is performed in the frequency domain, and phase compensation is performed directly in the frequency domain, which also reduces the system data processing overhead.

[0057] Figure 2 A flowchart of determining a reference pilot signal, a first synchronization pilot symbol, and a first synchronization pilot signal is provided in an embodiment of the present application. Figure 2 As shown, for the above embodiment, step S102, according to the pilot signal, determines the reference pilot signal, selects any orthogonal frequency division multiplexing symbol as the first synchronization pilot symbol, and determines the first synchronization pilot signal based on the first synchronization pilot symbol, specifically including the following steps: Step S201: Generate a pilot distribution resource grid of the system according to the pilot signal of the system.

[0058] It can be understood that the pilot distribution resource grid refers to the part of the spectrum resources of the communication system that is specifically used to transmit the pilot signal. In the OFDM system, the pilot signal can be determined according to the preset configuration parameters. The pilot signal is inserted into a specific subcarrier. The OFDM symbol can be mapped to the position on the subcarrier through the preset mapping rules. These subcarriers form a certain distribution pattern on the spectrum, namely the pilot distribution resource grid.

[0059] Figure 3 A schematic diagram of a pilot distribution resource grid provided in one embodiment of the present application. Figure 3As shown in the figure, all pilot data are transmitted on the pilot distribution resource grid. The horizontal axis is the OFDM symbol, the OFDM symbol number (m=1,2,…,M), M is the number of OFDM symbols in a frame of data, and M=280 in some OFDM systems; the vertical axis is the subcarrier, the subcarrier number (k=0,1,2,…,N-1), N is the total number of subcarriers under a certain channel bandwidth, and N=3276 in some OFDM systems. The pilot signal is determined according to the preset configuration parameters, and then the pilot data is mapped to the subcarrier according to the mapping rules, and the pilot distribution resource grid of the system is obtained. Figure 3 The grey grids in the figure represent pilot data.

[0060] In general, in order to obtain better channel estimation performance, pilot signals can be evenly or unevenly distributed in the frequency domain. This ensures that more accurate channel estimation results can be obtained throughout the frequency band. The insertion density of pilot signals can be adjusted according to the time-varying nature of the channel and the spectrum efficiency requirements of the system. In the case of fast channel changes, the insertion density of pilot signals needs to be increased to obtain more accurate channel estimation results; in the case of slow channel changes, the insertion density of pilot signals can be appropriately reduced to improve the spectrum efficiency of the system.

[0061] Step S202: Select pilot signals corresponding to all OFDM symbols in an OFDM symbol set in a pilot distribution resource grid of the system as reference pilot signals.

[0062] Step S203, generating an OFDM symbol set according to the pilot distribution resource grid of the system; the OFDM symbol set is a set of all OFDM symbols including at least N subcarrier data in the pilot distribution resource grid of the system; wherein N is a positive integer.

[0063] In this embodiment, all OFDM symbols whose number of pilot subcarriers (the total number of gray grids on the vertical axis) exceeds N subcarriers are selected from the pilot distribution resource grid of the system, and their numbers M are recorded to form a set L. N is an actual empirical value, and in some embodiments, N= 6. For example, an OFDM system adopts 5G new air interface technology and is configured as a wireless channel with a bandwidth of 100MHz (NR 100M). The elements in its OFDM symbol set L can be: [2, 16, 30, 44, 58, 72, 86, 100, 114, 128, 142, 156, 170, 184, 198, 212, 226, 240, 254, 268], and the numbers of the OFDM symbols in the set are arranged in sequence.

[0064] Step S204: Select any orthogonal frequency division multiplexing symbol in the orthogonal frequency division multiplexing symbol set as a first synchronization pilot symbol.

[0065] In this embodiment, the first synchronization pilot symbol is used as a basis for determining the second synchronization pilot symbol in the received signal. After the second synchronization pilot symbol is determined, the precise position of all OFDM symbols in the received signal relative to the second synchronization pilot symbol can be obtained through a series of data processing. The first synchronization pilot symbol is one of the OFDM symbol set determined based on the pilot distribution resource grid of the system, and can be regarded as a reference of the pilot signal, so it can be any one of the OFDM symbol set.

[0066] In some embodiments, the first synchronization pilot symbol is the first symbol in an orthogonal frequency division multiplexing symbol set.

[0067] Step S205: Select all subcarrier data corresponding to the first synchronization pilot symbol in the pilot distribution resource grid of the system as the first synchronization pilot signal.

[0068] In this embodiment, after the first synchronization pilot symbol is determined, all subcarrier data corresponding to the first synchronization pilot signal are selected from the pilot distribution resource grid of the system, and all the selected subcarrier data are the first synchronization pilot signal.

[0069] Figure 4 A flowchart of determining a second synchronization pilot symbol and a second synchronization pilot signal is provided in an embodiment of the present application. Figure 4 As shown, for any of the above embodiments, step S103, determining a second synchronization pilot symbol according to the first synchronization pilot signal, and determining a second synchronization pilot signal based on the second synchronization pilot symbol, specifically includes the following steps: Step S401: Perform an inverse Fourier transform on the first synchronization pilot signal to obtain a synchronization seed signal.

[0070] Step S402: Perform sliding correlation processing on the synchronization seed signal and the received signal, and use the orthogonal frequency division multiplexing symbol at the corresponding position in the received signal that meets the preset correlation condition with the first synchronization pilot signal as the second synchronization pilot symbol.

[0071] It can be understood that signal sliding correlation processing refers to comparing one signal (or template, sequence) with another signal point by point to find the similarity or correlation between the two. This processing method is widely used in signal detection, synchronization, recognition and other fields. Its basic principle is to use the correlation characteristics of the signal, that is, when two signals are aligned in time and have the same phase, their correlation results are maximized. Specifically, a fixed-size window (or convolution kernel) is defined, the window slides on the signal, and the signal data in the window is weighted averaged or other operations are performed to obtain the filtered value or correlation result. The size and shape of the window usually depend on the characteristics of the processed signal and the application requirements. On the basis of the sliding window, the signal in the window is multiplied and summed point by point with the template signal to obtain the correlation value. The size of the correlation value reflects the similarity between the signal in the window and the template signal.

[0072] In this embodiment, the subcarrier data after the first synchronization pilot signal is subjected to an inverse Fourier transform (IFFT) is used as the synchronization seed signal, that is, the template signal, and the synchronization seed signal and the received signal are slid to obtain the correlation value of the synchronization seed signal and the received signal. According to the similarity between the two and the preset correlation condition, the corresponding position in the received signal where the correlation with the first synchronization pilot signal meets the preset condition is determined, and the OFDM symbol at this position is used as the second synchronization pilot symbol.

[0073] In some embodiments, the position corresponding to the preset correlation condition is the position corresponding to the correlation peak in the sliding correlation processing result of the received signal and the synchronization seed signal. In other words, the position of the second synchronization pilot symbol in the received signal is the position corresponding to the peak in the sliding correlation result. That is, the second synchronization pilot symbol is located at the position where the correlation value between the synchronization seed signal and the received signal is the largest.

[0074] Step S403: Taking the position of the second synchronization pilot symbol as a starting point, select pilot data of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal as a second synchronization pilot signal.

[0075] In this embodiment, after the position of the second synchronization pilot symbol is determined, the pilot data of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal are selected with the position as the starting point, and the selected pilot data of all pilot subcarriers are the second synchronization pilot signal.

[0076] Figure 5 A flowchart for determining a second synchronization pilot signal is provided in an embodiment of the present application. Figure 5As shown, for any of the above embodiments, step S403, taking the position of the second synchronization pilot symbol as the starting point, selecting the pilot signals of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal as the second synchronization pilot signal, specifically includes the following steps: Step S501: Taking the position of the second synchronization pilot symbol as the starting point, perform Fourier transform on data of one symbol length in the received signal.

[0077] Step S502: According to the transformation result, the pilot signals of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal are selected as the second synchronization pilot signal.

[0078] In this embodiment, starting from the position of the second synchronization pilot symbol in the received data, data of one symbol length in the received signal is taken for Fourier transform (FFT), and then according to the mapping relationship between the system pilot distribution resource grid and the OFDM symbol, the pilot signals of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal are selected as the second synchronization pilot signal.

[0079] It should be noted that since the synchronization seed signal is the subcarrier data after the first synchronization pilot signal is subjected to inverse Fourier transform (IFFT), the synchronization seed signal and the received data are both in the frequency domain. After performing sliding correlation processing on them, the position of the second synchronization pilot symbol can be determined by judging the position of the correlation peak.

[0080] Figure 6 A flowchart for determining the position of each orthogonal frequency division multiplexing symbol in a received signal provided by an embodiment of the present application. Figure 6 As shown, for any of the above embodiments, step S104, synchronizing the first synchronization pilot signal and the second synchronization pilot signal to determine the precise position of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol, specifically includes the following steps: Step S601: Conjugate multiply the first synchronization pilot signal and the second synchronization pilot signal to obtain synchronization data.

[0081] Step S602: Divide the synchronization data into a first data segment and a second data segment in the order of the pilot subcarriers from small to large, and perform conjugate multiplication on the first data segment and the second data segment.

[0082] Step S603: Calculate the average value of the phase difference between the first data segment and the second data segment at corresponding positions according to the result of conjugate multiplication of the first data segment and the second data segment as the phase deviation value of the second synchronization pilot symbol in the received signal.

[0083] Step S604: Determine the precise position of each OFDM symbol in the received signal relative to the second synchronization pilot symbol according to the phase offset value of the second synchronization pilot symbol in the received signal.

[0084] Specifically, the first synchronization pilot signal and the second synchronization pilot signal are conjugate multiplied to obtain synchronization data, and the synchronization data is divided into two segments with the same number from the middle according to the order of the pilot subcarrier numbers from small to large, and are respectively recorded as the first data segment K1 and the second data segment K2, and then the first data segment K1 and the second data segment K2 are conjugate multiplied again to calculate the average value of the phase difference at the corresponding positions of the first data segment K1 and the second data segment K2.

[0085] Assume that both the first data segment K1 and the second data segment K2 have data corresponding to X (X=1, 2, 3, ..., x) pilot subcarriers, where the number of the pilot subcarriers in the first data segment K1 is recorded as a x , the number of the pilot subcarrier in the second data segment K2 is recorded as b x , then according to the result of conjugate multiplication, the phase difference between the first data segment K1 and the second data segment K2 at the corresponding position can be calculated and recorded as , and then further calculate the average value of the phase difference between the first data segment K1 and the second data segment K2 at the corresponding position .

[0086] ; The average value of the phase difference between the first data segment K1 and the second data segment K2 at the corresponding position , as the phase deviation value of the second synchronization pilot symbol in the received signal. Since the second synchronization pilot signal is selected from the pilot signal of all pilot subcarriers corresponding to the second synchronization pilot symbol after Fourier transform of data of one symbol length in the received signal starting from the position of the second synchronization pilot symbol in the received signal, that is, the second synchronization pilot signal is the pilot signal of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal, the calculated value is the phase deviation value of the second synchronization pilot symbol in the received signal.

[0087] Then, according to the phase offset value of the second synchronization pilot symbol in the received signal, the delay D of each OFDM symbol in the received signal relative to the second synchronization pilot symbol is determined.

[0088] ; in, SCS is the subcarrier spacing.

[0089] Finally, based on the determined position of the second synchronization pilot symbol and according to the delay D of each OFDM symbol relative to the second synchronization pilot symbol, the precise position of each OFDM symbol in the received signal relative to the second synchronization pilot symbol can be known.

[0090] Figure 7 A flowchart of determining a demodulation signal and receiving a pilot signal is provided in one embodiment of the present application. Figure 7 As shown, for any of the above embodiments, step S105, starting from the position where the second synchronization pilot symbol is located, performing orthogonal frequency division multiplexing demodulation on each orthogonal frequency division multiplexing symbol in the received signal to obtain a demodulated signal, and determining the received pilot signal according to the demodulated signal, specifically includes the following steps: Step S701: starting from the position where the second synchronization pilot symbol is located, remove the data of the cyclic prefix length of each orthogonal frequency division multiplexing symbol, and perform fast Fourier transform processing on the data corresponding to each orthogonal frequency division multiplexing symbol in the received signal.

[0091] It is understandable that an OFDM symbol usually includes a cyclic prefix, which is formed by copying a portion of the data at the end of the OFDM symbol to its beginning. The main function of the cyclic prefix is ​​to reduce inter-symbol interference (ISI). At the receiving end, the correlation between the cyclic prefix and the main body of the OFDM symbol can be used to determine the boundary of the symbol. By calculating the correlation between the cyclic prefix and the data sequence at different positions, the position with the highest correlation can be found, that is, the starting position of the OFDM symbol. Before determining the second synchronization pilot signal based on the first synchronization pilot signal and the second synchronization pilot symbol, it is necessary to first filter out the data of the cyclic prefix length in the first synchronization pilot signal, that is, only retain the OFDM symbol data.

[0092] Step S702: Generate a demodulated signal according to the mapping relationship between the received signal after the fast Fourier transform and each orthogonal frequency division multiplexing symbol.

[0093] In this embodiment, after filtering out the data of the cyclic prefix length in the second synchronization pilot signal, before demodulating the received signal as described above, the received signal needs to be preprocessed, including filtering, amplification, synchronization and other operations, to restore the original OFDM symbol. Then, for the received signal after filtering, the OFDM symbol is subjected to a fast Fourier transform (FFT), the time domain signal is converted back to a frequency domain signal, and then the signal on each subcarrier is demodulated, and further according to the mapping relationship corresponding to each OFDM symbol in the pilot distribution resource grid, the demodulated signal can be obtained.

[0094] Step S703: Generate a pilot distribution resource grid of a received signal corresponding to the demodulated signal according to the demodulated signal.

[0095] Step S704: Select the pilot signals corresponding to all the orthogonal frequency division multiplexing symbols in the orthogonal frequency division multiplexing symbol set in the pilot distribution resource grid of the received signal as the received pilot signal.

[0096] In this embodiment, as described above, for a certain OFDM system, according to its configuration parameters and mapping rules, the data mapping to each subcarrier can be determined, and a pilot signal can be generated, that is, the pilot distribution resource grid of the OFDM system is obtained. The pilot signals corresponding to all OFDM symbols in the OFDM symbol set in the pilot distribution resource grid of the system are selected as reference pilot signals.

[0097] Based on the mapping relationship between the system pilot distribution resource grid and the OFDM symbol, the pilot distribution resource grid of the received signal corresponding to the demodulated signal can be obtained according to the demodulated signal. It should be noted that the system pilot distribution resource grid is obtained according to the preset configuration parameters, such as Figure 3 As shown, only the gray pilot data in the system pilot distribution resource grid is valid (reference pilot), and since the pilot data is calculated based on the preset configuration parameters, it can be regarded as an ideal value, and the white part is empty and can be regarded as useless data. As for the pilot distribution resource grid of the received signal, its size is the same as the system pilot distribution resource grid. The gray part is the pilot data, which is calculated by the pre-configured parameters at the transmitting end, and then modulated by OFDM together with the user data in the white part, and then sent through the channel. After being received at the receiving end, it is demodulated by OFDM, and the gray part is the received pilot data and the white part is the user data.

[0098] After the pilot distribution resource grid of the received signal is determined, the pilot signals corresponding to all OFDM symbols in the OFDM symbol set in the pilot distribution resource grid of the received signal may be selected as the received pilot signals.

[0099] Figure 8 A flowchart for determining the phase offset value of each orthogonal frequency division multiplexing symbol in a received signal provided by an embodiment of the present application. Figure 8 As shown, for any of the above embodiments, step S106, synchronizing the reference pilot signal and the received pilot signal, and determining the phase offset value of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain, specifically includes the following steps: Step S801: Conjugate multiply the reference pilot signal and the received pilot signal to obtain phase deviation calculation data.

[0100] Step S802: divide the phase deviation calculation data into a third data segment and a fourth data segment in the order of the pilot subcarriers from small to large, and perform conjugate multiplication on the third data segment and the fourth data segment.

[0101] Step S803: Calculate the average value of the phase difference at the corresponding position of each OFDM symbol in the third data segment and the fourth data segment according to the result of conjugate multiplication of the third data segment and the fourth data segment as the phase deviation value of the OFDM symbol.

[0102] Step S804: Calculate the distance between each OFDM symbol and the second synchronization pilot symbol.

[0103] Step S805: Calculate and obtain the phase offset value of each OFDM symbol relative to the second synchronization pilot symbol in the frequency domain according to each OFDM symbol value and its distance relative to the second synchronization pilot symbol.

[0104] Specifically, the reference pilot signal and the received pilot signal are conjugate multiplied to obtain phase deviation calculation data, which can remove the influence of the original signal phase and only leave the phase difference caused by the channel, vibration wave frequency deviation and clock error. Similarly, according to the order of the pilot subcarrier numbers from small to large, the phase deviation calculation data is divided into two segments with the same number from the middle, which are respectively recorded as the third data segment K3 and the fourth data segment K4, and then the third data segment K3 and the fourth data segment K4 are conjugate multiplied again to calculate the average phase difference at the corresponding position of each orthogonal frequency division multiplexing symbol in the third data segment K3 and the fourth data segment K4.

[0105] Assume that the third data segment K3 and the fourth data segment K4 both have data corresponding to Y (Y=1, 2, 3, ..., y) pilot subcarriers, where the number of the pilot subcarriers in the third data segment K3 is recorded as c y , the number of the pilot subcarrier in the fourth data segment K4 is recorded as d y , then according to the result of conjugate multiplication, the phase difference at the corresponding position of each OFDM symbol in the third data segment K3 and the fourth data segment K4 can be calculated and recorded as , and then further calculate the average value of the phase difference at the corresponding position of the third data segment K3 and the fourth data segment K4 .

[0106] ; The average value of the phase difference between the third data segment K3 and the fourth data segment K4 at the corresponding position , as the phase offset value of the OFDM symbol.

[0107] For a certain OFDM system, the length of each OFDM symbol is ,in is the cyclic prefix length of the OFDM symbol, When performing fast Fourier transform on OFDM symbols, the length of the array or data sequence to be transformed is the number of points into which the data is divided for calculation.

[0108] As in the above-mentioned system pilot distribution resource grid, the number of OFDM symbols is M, and the OFDM symbols are numbered (m=1, 2, ..., M). For all M OFDM symbols, the distance of each OFDM symbol relative to the second synchronization pilot symbol is recorded as L m ,but: ; Finally, according to the phase deviation of each OFDM symbol and its distance relative to the second synchronization pilot symbol L m , calculate the phase offset value of each OFDM symbol relative to the second synchronization pilot symbol in the frequency domain .

[0109] .

[0110] Fig. 9 A flowchart of frequency domain phase compensation provided by an embodiment of the present application. Fig.10 As shown, for any of the above embodiments, step S107, performing frequency domain phase compensation on each orthogonal frequency division multiplexing symbol in the received signal according to the phase offset value, includes: Based on the position of the second synchronization pilot symbol in the pilot distribution resource grid of the received signal, frequency domain phase compensation is performed on each orthogonal frequency division multiplexing symbol in the pilot distribution resource grid of the received signal.

[0111] More specifically, frequency domain phase compensation is performed on each orthogonal frequency division multiplexing symbol in a pilot distribution resource grid of a received signal, including: Step S901: Obtain the order of each orthogonal frequency division multiplexing symbol in the pilot distribution resource grid of the received signal.

[0112] Step S902: For an OFDM symbol before a second synchronization pilot symbol, a phase compensation value is a product of a phase offset value and a distance from the OFDM symbol to the second synchronization pilot symbol.

[0113] For an OFDM symbol following the second synchronization pilot symbol, the phase compensation value is the product of the negative value of the phase offset value and the distance from the OFDM symbol to the second synchronization pilot symbol.

[0114] That is, taking the second synchronization pilot symbol as a reference point, assuming that the number of the second synchronization pilot symbol in the pilot distribution resource grid of the received signal is m j (m j is an integer from 1 to M), then, For OFDM symbols before the second synchronization pilot symbol, that is, for OFDM symbols with numbers less than m j OFDM symbol, when frequency domain phase compensation is performed on the symbol, the phase compensation value is the product of the phase offset value of the OFDM symbol relative to the second synchronization pilot symbol and the distance, that is: ; For OFDM symbols before the second synchronization pilot symbol, that is, for OFDM symbols numbered greater than m j OFDM symbol, when frequency domain phase compensation is performed on the symbol, the phase compensation value is the product of the negative value of the phase offset of the OFDM symbol relative to the second synchronization pilot symbol and the distance, that is: .

[0115] To summarize, the clock error compensation method provided in the embodiment of the present application determines the second synchronization pilot symbol at the corresponding position in the received signal by selecting the first synchronization pilot symbol of the orthogonal frequency division multiplexing symbol according to the system pilot signal, and then determines the first synchronization pilot signal and the second synchronization pilot signal. After synchronizing the first synchronization pilot signal and the second synchronization pilot signal, the position of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol is determined, and the received signal is demodulated based on this, and the phase deviation value of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain is determined. Finally, according to the calculated phase deviation value, frequency domain phase compensation is performed on each orthogonal frequency division multiplexing symbol in the received signal to achieve clock error compensation of the received signal.

[0116] The present application determines the OFDM symbol as a reference, calculates the phase deviation of each OFDM symbol in the received signal, and performs phase compensation on each OFDM symbol in the received signal in the frequency domain, thereby realizing time error compensation based on OFDM symbols. Compared with the prior art, the accuracy of phase compensation is improved according to the calculation results of the phase deviation of multiple OFDM symbols; at the same time, the compensation process is performed in the frequency domain, and phase compensation is performed directly in the frequency domain, which also reduces the overhead of system data processing.

[0117] Fig.10 This is a schematic diagram of the structure of a clock error compensation module provided by an embodiment of the present application. Fig.10 As shown, in this embodiment, the clock error compensation module is arranged at the receiving end of an orthogonal frequency division multiplexing system (OFDM system), and the clock error compensation module includes a communication unit 1001, a first processing unit 1002, a second processing unit 1003, a synchronization unit 1004, a demodulation unit 1005, a clock error calculation unit 1006 and a compensation unit 1007.

[0118] In this embodiment, the communication unit 1001 is used to obtain a received signal.

[0119] The first processing unit 1002 is used to obtain the system's pilot signal according to the system's preset configuration parameters and mapping rules; and determine the reference pilot signal based on the pilot signal, and select any orthogonal frequency division multiplexing symbol as the first synchronization pilot symbol, and determine the first synchronization pilot signal based on the first synchronization pilot symbol.

[0120] The second processing unit 1003 is used to determine a second synchronization pilot symbol according to the first synchronization pilot signal, and determine the second synchronization pilot signal based on the second synchronization pilot symbol; wherein the second synchronization pilot symbol is an orthogonal frequency division multiplexing symbol at a position corresponding to a preset condition of correlation with the first synchronization pilot signal in the received signal.

[0121] The synchronization unit 1004 is used to synchronize the first synchronization pilot signal and the second synchronization pilot signal to determine the precise position of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol.

[0122] The demodulation unit 1005 is configured to perform OFDM demodulation on each OFDM symbol in the received signal starting from the position of the second synchronization pilot symbol to obtain a demodulated signal, and determine a received pilot signal according to the demodulated signal.

[0123] Clock error calculation 1006, used to synchronize the reference pilot signal and the received pilot signal, and determine the phase offset value of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain; The compensation unit 1007 is used to perform frequency domain phase compensation on each OFDM symbol in the received signal according to the phase offset value, so as to achieve clock error compensation of the received signal.

[0124] In some embodiments, all steps for each unit in the clock error compensation module to implement functions are the same as or similar to the steps of the above-mentioned clock error compensation method, and have the technical effects of any embodiment of the above-mentioned clock error compensation method. To avoid repetition, they will not be repeated here.

[0125] The present application also provides a readable storage medium, on which a program or instruction is stored. When the program or instruction is executed by a processor, the various processes of the clock error compensation method embodiment described in any of the above embodiments are implemented, and the same technical effect can be achieved. To avoid repetition, it will not be repeated here.

[0126] The processor is the processor in the electronic device described in the above embodiment. The readable storage medium includes a computer readable storage medium, such as a computer read-only memory ROM, a random access memory RAM, a magnetic disk or an optical disk.

[0127] Those skilled in the art will appreciate that all or part of the functions of the various methods in the above-mentioned embodiments can be implemented by hardware or by computer programs. When all or part of the functions in the above-mentioned embodiments are implemented by computer programs, the program can be stored in a computer-readable storage medium, and the storage medium can include: read-only memory, random access memory, disk, optical disk, hard disk, etc., and the program is executed by a computer to implement the above-mentioned functions. For example, the program is stored in the memory of the device, and when the program in the memory is executed by the processor, all or part of the above-mentioned functions can be implemented. In addition, when all or part of the functions in the above-mentioned embodiments are implemented by computer programs, the program can also be stored in a storage medium such as a server, another computer, disk, optical disk, flash disk or mobile hard disk, and can be downloaded or copied and saved in the memory of the local device, or the system of the local device is updated, and when the program in the memory is executed by the processor, all or part of the functions in the above-mentioned embodiments can be implemented.

[0128] An embodiment of the present application also provides a computer program product, which is stored in a storage medium. The program product is executed by at least one processor to implement the various processes of the clock error compensation method embodiment as described in any of the above embodiments, and can achieve the same technical effect. To avoid repetition, it will not be repeated here.

[0129] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the inspiration of the present application, ordinary technicians in the field can make several simple deductions, deformations or substitutions based on the ideas of the present application without departing from the scope of protection of the purpose of the present application and the claims. All of these are within the protection of the present application.

Claims

1. A clock error compensation method, applied to a receiving end of an orthogonal frequency division multiplexing system, characterized in that: include: Acquire a pilot signal of the system according to configuration parameters and mapping rules preset by the system; Determine a reference pilot signal according to the pilot signal, select any orthogonal frequency division multiplexing symbol as a first synchronization pilot symbol, and determine a first synchronization pilot signal based on the first synchronization pilot symbol; Determine a second synchronization pilot symbol according to the first synchronization pilot signal, and determine a second synchronization pilot signal based on the second synchronization pilot symbol; wherein the second synchronization pilot symbol is an orthogonal frequency division multiplexing symbol at a position corresponding to a preset condition of correlation with the first synchronization pilot signal in the received signal; Synchronize the first synchronization pilot signal and the second synchronization pilot signal to determine the position of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol; Starting from the position where the second synchronization pilot symbol is located, performing orthogonal frequency division multiplexing demodulation on each orthogonal frequency division multiplexing symbol in the received signal to obtain a demodulated signal, and determining a received pilot signal according to the demodulated signal; Performing clock error calculation on the reference pilot signal and the received pilot signal to determine a phase deviation value of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain; According to the phase offset value, frequency domain phase compensation is performed on each orthogonal frequency division multiplexing symbol in the received signal to achieve clock error compensation of the received signal.

2. The clock error compensation method according to claim 1, characterized in that: The step of determining a reference pilot signal according to the pilot signal and selecting any orthogonal frequency division multiplexing symbol as a first synchronization pilot symbol includes: Generating a pilot distribution resource grid of the system according to the pilot signal of the system; Selecting pilot signals corresponding to all orthogonal frequency division multiplexing symbols in the orthogonal frequency division multiplexing symbol set in the pilot distribution resource grid of the system as reference pilot signals; Generate an orthogonal frequency division multiplexing symbol set according to the pilot distribution resource grid of the system; the orthogonal frequency division multiplexing symbol set is a set of all orthogonal frequency division multiplexing symbols including at least N subcarrier data in the pilot distribution resource grid of the system; wherein N is a positive integer; Selecting any orthogonal frequency division multiplexing symbol in the orthogonal frequency division multiplexing symbol set as a first synchronization pilot symbol; The determining a first synchronization pilot signal based on the first synchronization pilot symbol comprises: All subcarrier data corresponding to the first synchronization pilot symbol in the pilot distribution resource grid of the system are selected as the first synchronization pilot signal.

3. The clock error compensation method according to claim 2, characterized in that: The first synchronization pilot symbol is the first symbol in the orthogonal frequency division multiplexing symbol set.

4. The clock error compensation method according to claim 1, characterized in that: The determining a second synchronization pilot symbol according to the first synchronization pilot signal, and determining a second synchronization pilot signal based on the second synchronization pilot symbol, comprises: Performing an inverse Fourier transform on the first synchronization pilot signal to obtain a synchronization seed signal; Perform sliding correlation processing on the synchronization seed signal and the received signal, and use an orthogonal frequency division multiplexing symbol at a position corresponding to a preset condition of correlation with the first synchronization pilot signal in the received signal as a second synchronization pilot symbol; Taking the position of the second synchronization pilot symbol as a starting point, pilot data of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal are selected as the second synchronization pilot signal.

5. The clock error compensation method according to claim 4, characterized in that: The step of taking the position of the second synchronization pilot symbol as a starting point and selecting pilot signals of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal as the second synchronization pilot signal comprises: Taking the position of the second synchronization pilot symbol as a starting point, performing Fourier transform on data of one symbol length in the received signal; According to the transformation result, pilot signals of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal are selected as second synchronization pilot signals.

6. The clock error compensation method according to claim 4, characterized in that: The position corresponding to the preset correlation condition is the position corresponding to the correlation peak in the sliding correlation processing result between the received signal and the synchronization seed signal.

7. The clock error compensation method according to claim 1, characterized in that: The step of synchronizing the first synchronization pilot signal and the second synchronization pilot signal to determine a position of each orthogonal frequency division multiplexing symbol in a received signal relative to the second synchronization pilot symbol includes: Conjugate multiplying the first synchronization pilot signal and the second synchronization pilot signal to obtain synchronization data; Dividing the synchronization data into a first data segment and a second data segment in the order of pilot subcarriers from small to large, and performing conjugate multiplication on the first data segment and the second data segment; Calculate, according to the result of conjugate multiplication of the first data segment and the second data segment, an average value of the phase difference at corresponding positions of the first data segment and the second data segment as a phase offset value of the second synchronization pilot symbol in the received signal; The position of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol is determined according to the phase offset value of the second synchronization pilot symbol in the received signal.

8. The clock error compensation method according to claim 1, characterized in that: The method of performing orthogonal frequency division multiplexing demodulation on each orthogonal frequency division multiplexing symbol in the received signal starting from the position where the second synchronization pilot symbol is located to obtain a demodulated signal, and determining a received pilot signal according to the demodulated signal includes: Starting from the position where the second synchronization pilot symbol is located, remove the data of the cyclic prefix length of each orthogonal frequency division multiplexing symbol, and perform Fourier transform processing on the data corresponding to each orthogonal frequency division multiplexing symbol in the received signal; Generate a demodulated signal according to a mapping relationship between the Fourier transformed received signal and each orthogonal frequency division multiplexing symbol; Generating, according to the demodulated signal, a pilot distribution resource grid of a received signal corresponding to the demodulated signal; A pilot signal corresponding to all orthogonal frequency division multiplexing symbols in the orthogonal frequency division multiplexing symbol set in the pilot distribution resource grid of the received signal is selected as a received pilot signal.

9. The clock error compensation method according to claim 1, characterized in that: The step of calculating the clock error of the reference pilot signal and the received pilot signal to determine the phase deviation value of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain includes: Conjugate multiplying the reference pilot signal and the received pilot signal to obtain phase deviation calculation data; Dividing the phase deviation calculation data into a third data segment and a fourth data segment according to the order of pilot subcarriers from small to large, and performing conjugate multiplication on the third data segment and the fourth data segment; Calculate, according to the result of conjugate multiplication of the third data segment and the fourth data segment, an average value of the phase difference at a corresponding position of each orthogonal frequency division multiplexing symbol in the third data segment and the fourth data segment as a phase deviation value of the orthogonal frequency division multiplexing symbol; Calculating the distance of each of the orthogonal frequency division multiplexing symbols relative to the second synchronization pilot symbol; The phase offset value of each OFDM symbol relative to the second synchronization pilot symbol in the frequency domain is calculated and obtained according to the phase offset value of each OFDM symbol and its distance relative to the second synchronization pilot symbol.

10. The clock error compensation method according to claim 1, characterized in that: The method of performing frequency domain phase compensation on each orthogonal frequency division multiplexing symbol in the received signal according to the phase offset value comprises: Based on the position of the second synchronization pilot symbol in the pilot distribution resource grid of the received signal, frequency domain phase compensation is performed on each orthogonal frequency division multiplexing symbol in the pilot distribution resource grid of the received signal.

11. The clock error compensation method according to claim 10, characterized in that: The performing frequency domain phase compensation on each orthogonal frequency division multiplexing symbol in the pilot distribution resource grid of the received signal comprises: Obtaining the order of each orthogonal frequency division multiplexing symbol in the pilot distribution resource grid of the received signal; For an orthogonal frequency division multiplexing symbol before the second synchronization pilot symbol, a phase compensation value is a product of the phase offset value and a distance from the orthogonal frequency division multiplexing symbol to the second synchronization pilot symbol; For an OFDM symbol following the second synchronization pilot symbol, a phase compensation value is a product of a negative value of the phase offset value and a distance from the OFDM symbol to the second synchronization pilot symbol.

12. An orthogonal frequency division multiplexing system, comprising a transmitting end and a receiving end, characterized in that: The receiving end comprises: A communication unit, used for acquiring a received signal; A first processing unit is configured to obtain a pilot signal of the system according to a configuration parameter and a mapping rule preset by the system; determine a reference pilot signal according to the pilot signal, select any orthogonal frequency division multiplexing symbol as a first synchronization pilot symbol, and determine a first synchronization pilot signal based on the first synchronization pilot symbol; A second processing unit is used to determine a second synchronization pilot symbol according to the first synchronization pilot signal, and determine a second synchronization pilot signal based on the second synchronization pilot symbol; wherein the second synchronization pilot symbol is an orthogonal frequency division multiplexing symbol at a position corresponding to a preset condition of correlation with the first synchronization pilot signal in the received signal; a synchronization unit, configured to synchronize the first synchronization pilot signal and the second synchronization pilot signal to determine a position of each orthogonal frequency division multiplexing symbol in a received signal; A demodulation unit, configured to perform orthogonal frequency division multiplexing demodulation on each orthogonal frequency division multiplexing symbol in the received signal starting from the position where the second synchronization pilot symbol is located, to obtain a demodulated signal, and to determine a received pilot signal according to the demodulated signal; A clock error calculation unit, configured to perform clock error calculation on the reference pilot signal and the received pilot signal, and determine a phase deviation value of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain; The compensation unit is used to perform frequency domain phase compensation on each orthogonal frequency division multiplexing symbol in the received signal according to the phase deviation value, so as to achieve clock error compensation of the received signal.

13. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a processor, they are used to implement the steps of the clock error compensation method according to any one of claims 1 to 11.

14. A computer program product, characterized in that The program product is stored in a storage medium, and the program product is executed by at least one processor to implement the steps of the clock error compensation method according to any one of claims 1 to 11.

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