Clock Error Compensation Method, Orthogonal Frequency Division Multiplexing System, and Storage Medium

Abstract

The present application provides a clock error compensation method and an orthogonal frequency division multiplexing (OFDM) system using this method for clock error compensation. The compensation method determines a second synchronization pilot symbol at a corresponding position in the received signal by using a first synchronization pilot symbol of an OFDM symbol selected according to the system pilot signal, and further 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, it determines the position of each OFDM symbol in the received signal relative to the second synchronization pilot symbol, demodulates the received signal based on this, determines the phase offset value of each OFDM symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain, and finally performs frequency domain phase compensation on each OFDM symbol in the received signal according to the calculated phase offset value to achieve clock error compensation of the received signal and improve the accuracy of phase compensation.

Description

Technical Field

[0001] This application relates to the field of communication technologies, and particularly 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 belongs to a type of multi-carrier modulation. It has been widely used due to its many advantages such as high frequency band utilization rate, high transmission rate, and effective resistance to multi-path delay and narrowband interference.

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

[0004] However, in practical applications, since the crystal oscillators at the sending end and the receiving end are two independent crystal oscillators, without external signal control, these two crystal oscillators cannot have exactly the same sampling frequency and phase, which will cause frequency and phase deviations in the OFDM signals received at the receiving end, resulting in phase deflection of the sub-carriers in the OFDM signals and no longer maintaining orthogonality, thus generating interference between carriers, causing signal-to-noise ratio loss. Moreover, 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 the valid data in the OFDM signal. Therefore, it is very necessary to compensate the sampling clock at the receiving end of the OFDM system to keep it synchronized with the sampling clock at the sending end.

[0005] One existing technique is to set counters at the sending end and the receiving end respectively, compare to obtain the error of the sampling clocks at the sending end and the receiving end, and perform frequency offset calibration on the clock error by decimation or interpolation. However, its calibration accuracy depends on the accuracy of the counters. To achieve better calibration accuracy, high-precision counters are required, which undoubtedly increases the computing resources. Moreover, the clock frequency of the counter at the receiving end has to be much higher than that of the counter at the sending end. For OFDM systems with high bandwidth and high sampling rate, the sampling frequency of the counter at the receiving end even needs to be as high as several GHz. At the same time, hardware support such as decimation filters is also required. It can be seen that it is difficult to control the accuracy of the sampling clock compensation at the receiving end of the existing technique for OFDM systems, and the computing efficiency is not high. Summary of the Invention

[0006] This 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 existing technique in compensating the sampling clock at the receiving end of an OFDM system to keep it synchronized with the sampling clock at the sending end of the system, with difficult accuracy control, low computing efficiency, and high complexity.

[0007] In a first aspect, an embodiment of this application provides a clock error compensation method, which is applied to the receiving end of an orthogonal frequency division multiplexing system, and is characterized by including:

[0008] Obtain the pilot signal of the system according to the configuration parameters and mapping rules preset by the system;

[0009] Determine a reference pilot signal according to the pilot signal, select any orthogonal frequency division multiplexing symbol as the first synchronization pilot symbol, and determine a first synchronization pilot signal based on the first synchronization pilot symbol;

[0010] 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 the orthogonal frequency division multiplexing symbol at the corresponding position in the received signal that satisfies the preset condition of the correlation degree with the first synchronization pilot signal;

[0011] 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;

[0012] 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 a received pilot signal according to the demodulated signal;

[0013] Calculate the clock error between the reference pilot signal and the received pilot signal, and determine the phase offset value of each orthogonal frequency division multiplexing (OFDM) symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain;

[0014] 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.

[0015] In some embodiments, determining the reference pilot signal according to the pilot signal and selecting any OFDM symbol as the first synchronization pilot symbol includes:

[0016] Generate the pilot distribution resource grid of the system according to the pilot signal of the system;

[0017] Select the pilot signals corresponding to all OFDM symbols within the OFDM symbol set in the pilot distribution resource grid of the system as the reference pilot signal;

[0018] Generate an OFDM symbol set according to the pilot distribution resource grid of the system; the OFDM symbol set is the set of all OFDM symbols including at least N subcarrier data in the pilot distribution resource grid of the system; where N is a positive integer;

[0019] Select any OFDM symbol in the OFDM symbol set as the first synchronization pilot symbol;

[0020] Determining the first synchronization pilot signal based on the first synchronization pilot symbol includes:

[0021] 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.

[0022] In some embodiments, the first synchronization pilot symbol is the first symbol in the OFDM symbol set.

[0023] In some embodiments, determining the second synchronization pilot symbol according to the first synchronization pilot signal and determining the second synchronization pilot signal based on the second synchronization pilot symbol includes:

[0024] Perform inverse Fourier transform on the first synchronization pilot signal to obtain the synchronization seed signal;

[0025] Perform sliding correlation processing on the synchronization seed signal and the received signal, and use the OFDM symbol at the corresponding position in the received signal whose correlation with the first synchronization pilot signal meets the preset condition as the second synchronization pilot symbol;

[0026] Starting from the position of the second synchronization pilot symbol, select the pilot data of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal as the second synchronization pilot signal.

[0027] In some embodiments, the step of starting from the position of the second synchronization pilot symbol and 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 includes:

[0028] Starting from the position of the second synchronization pilot symbol, perform Fourier transform on the data of one symbol length in the received signal;

[0029] According to the transformation result, select the pilot signals of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal as the second synchronization pilot signal.

[0030] In some embodiments, the position corresponding to the preset correlation condition is the position corresponding to the peak of the correlation degree in the sliding correlation processing result of the received signal and the synchronization seed signal.

[0031] In some embodiments, the step of synchronizing the first synchronization pilot signal and the second synchronization pilot signal to determine the position of each orthogonal frequency division multiplexing (OFDM) symbol in the received signal relative to the second synchronization pilot symbol includes:

[0032] Perform conjugate multiplication on the first synchronization pilot signal and the second synchronization pilot signal to obtain synchronization data;

[0033] Arrange the synchronization data into a first data segment and a second data segment in ascending order of pilot subcarriers, and perform conjugate multiplication on the first data segment and the second data segment;

[0034] According to the result of conjugate multiplication of the first data segment and the second data segment, calculate the average value of the phase differences at the corresponding positions 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;

[0035] According to the phase deviation value of the second synchronization pilot symbol in the received signal, determine the position of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol.

[0036] In some embodiments, the step of starting from the position of the second synchronization pilot symbol, 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:

[0037] Starting from the position where the second synchronization pilot symbol is located, remove the data with the cyclic prefix length of each orthogonal frequency division multiplexing (OFDM) symbol, and perform Fourier transform processing on the data corresponding to each OFDM symbol in the received signal;

[0038] Generate a demodulated signal according to the mapping relationship between the received signal after Fourier transform and each OFDM symbol;

[0039] Generate a pilot distribution resource grid of the received signal corresponding to the demodulated signal according to the demodulated signal;

[0040] Select the pilot signals corresponding to all OFDM symbols within the OFDM symbol set in the pilot distribution resource grid of the received signal as the received pilot signals.

[0041] In some embodiments, the calculating the clock error between the reference pilot signal and the received pilot signal to determine the phase offset value of each OFDM symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain includes:

[0042] Perform conjugate multiplication on the reference pilot signal and the received pilot signal to obtain phase offset calculation data;

[0043] Divide the phase offset calculation data into a third data segment and a fourth data segment in ascending order of pilot subcarriers, and perform conjugate multiplication on the third data segment and the fourth data segment;

[0044] According to the result of conjugate multiplication of the third data segment and the fourth data segment, calculate the average value of the phase differences at the corresponding positions of each OFDM symbol in the third data segment and the fourth data segment as the phase offset value of the OFDM symbol;

[0045] Calculate the distance of each OFDM symbol relative to the second synchronization pilot symbol;

[0046] Calculate the phase offset value of each OFDM symbol relative to the second synchronization pilot symbol in the frequency domain according to the value of each OFDM symbol and its distance relative to the second synchronization pilot symbol.

[0047] In some embodiments, the performing frequency domain phase compensation on each OFDM symbol in the received signal according to the phase offset value includes:

[0048] Taking the position of the second synchronization pilot symbol in the pilot distribution resource grid of the received signal as a reference, perform frequency domain phase compensation on each OFDM symbol in the pilot distribution resource grid of the received signal.

[0049] In some embodiments, the frequency-domain phase compensation for each orthogonal frequency-division multiplexing (OFDM) symbol in the pilot distribution resource grid of the received signal includes:

[0050] Obtaining the order of each OFDM symbol in the pilot distribution resource grid of the received signal;

[0051] For an OFDM symbol before the second synchronization pilot symbol, the phase compensation value is the product of the phase deviation value and the distance from this OFDM symbol to the second synchronization pilot symbol;

[0052] For an OFDM symbol after the second synchronization pilot symbol, the phase compensation value is the product of the negative value of the phase deviation value and the distance from this OFDM symbol to the second synchronization pilot symbol.

[0053] In a second aspect, an embodiment of the present application provides an orthogonal frequency-division multiplexing (OFDM) system, including a transmitting end and a receiving end, characterized in that the receiving end includes:

[0054] A communication unit, configured to obtain a received signal;

[0055] A first processing unit, configured to obtain a pilot signal of the system according to configuration parameters and mapping rules preset in the system; determine a reference pilot signal according to the pilot signal, select any OFDM symbol as a first synchronization pilot symbol, and determine a first synchronization pilot signal based on the first synchronization pilot symbol;

[0056] A second processing unit, configured 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 OFDM symbol at a corresponding position in the received signal that satisfies a preset condition of correlation with the first synchronization pilot signal;

[0057] A synchronization unit, configured to synchronize the first synchronization pilot signal and the second synchronization pilot signal, and determine the position of each OFDM symbol in the received signal relative to the second synchronization pilot symbol;

[0058] A demodulation unit, configured to start from the position where the second synchronization pilot symbol is located, perform orthogonal frequency-division multiplexing demodulation on each OFDM symbol in the received signal to obtain a demodulated signal, and determine a received pilot signal according to the demodulated signal;

[0059] A clock error calculation unit, configured to calculate a clock error between the reference pilot signal and the received pilot signal, and determine the phase deviation value of each OFDM symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain;

[0060] A compensation unit is configured to perform frequency-domain phase compensation on each orthogonal frequency-division multiplexing (OFDM) symbol in the received signal according to the phase offset value, so as to achieve clock error compensation for the received signal.

[0061] 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.

[0062] 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 described in the first aspect.

[0063] In a 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 is coupled to the processor; the at least one processor is configured to execute a computer program or instruction to implement the steps of the clock error compensation method described in the first aspect.

[0064] The clock error compensation method provided by the embodiments of the present application and the orthogonal frequency-division multiplexing system using this method for clock error compensation. In this compensation method, the first synchronization pilot symbol of the orthogonal frequency-division multiplexing symbol selected according to the system pilot signal is used to determine the second synchronization pilot symbol at the corresponding position in the received signal, and then the first synchronization pilot signal and the second synchronization pilot signal are determined. 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. Based on this, the received signal is demodulated 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. Finally, according to the calculated 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 for the received signal.

[0065] The present application takes the orthogonal frequency-division multiplexing symbol as a reference to calculate the phase offset of each orthogonal frequency-division multiplexing symbol in the received signal relative to this reference, and performs phase compensation on each orthogonal frequency-division multiplexing symbol in the received signal in the frequency domain, thereby achieving time error compensation based on the orthogonal frequency-division multiplexing symbol. Compared with the prior art, the accuracy of phase compensation is improved according to the phase offset calculation results of multiple orthogonal frequency-division multiplexing symbols; at the same time, the compensation process is all carried out in the frequency domain, and phase compensation is directly performed in the frequency domain, which also reduces the system data processing overhead.

[0066] 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

[0067] The accompanying drawings herein are incorporated into the specification and form a part of this specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0068] Figure 1 It is a flowchart of a clock error compensation method provided for an embodiment of the present application;

[0069] Figure 2 It is a flowchart of determining a reference pilot signal, a first synchronization pilot symbol, and a first synchronization pilot signal provided for an embodiment of the present application;

[0070] Figure 3 It is a schematic diagram of a pilot distribution resource grid provided for an embodiment of the present application;

[0071] Figure 4 It is a flowchart of determining a second synchronization pilot symbol and a second synchronization pilot signal provided for an embodiment of the present application;

[0072] Figure 5 It is a flowchart of determining a second synchronization pilot signal provided for an embodiment of the present application;

[0073] Figure 6 It is a flowchart of determining the position of each orthogonal frequency division multiplexing symbol in a received signal provided for an embodiment of the present application;

[0074] Figure 7 It is a flowchart of determining a demodulated signal and a received pilot signal provided for an embodiment of the present application;

[0075] Figure 8 It is a flowchart of determining the phase offset value of each orthogonal frequency division multiplexing symbol in a received signal provided for an embodiment of the present application;

[0076] Figure 9 It is a flowchart of frequency domain phase compensation provided for an embodiment of the present application;

[0077] Figure 10 It is a schematic diagram of the structure of a clock error compensation module provided for an embodiment of the present application.

[0078] Through the above-mentioned accompanying drawings, specific embodiments of the present application have been shown, and there will be more detailed descriptions hereinafter. These accompanying drawings and written descriptions are not intended to limit the scope of the concept 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 Embodiments

[0079] The present invention will be further described in detail below in conjunction with the specific embodiments and the accompanying drawings. Similar elements in different embodiments are denoted by related similar element numbers. In the following embodiments, many detailed descriptions are provided to enable a better understanding of the present application. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, or methods. In some cases, some operations related to the present application are not shown or described in the specification, which is to avoid overwhelming the core part of the present application with excessive descriptions. 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 based on the descriptions in the specification and the general technical knowledge in the art.

[0080] In addition, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can also be reordered or adjusted in a manner obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for clearly describing a certain embodiment and do not mean a necessary sequence, unless it is stated otherwise that a certain sequence must be followed.

[0081] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type and do not limit the number of objects. For example, the first object can be one or multiple. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / " generally indicates an "or" relationship between the associated objects before and after. And the "connection" and "coupling" mentioned in the present application, unless otherwise specified, both include direct and indirect connection (coupling).

[0082] Orthogonal Frequency Division Multiplexing (OFDM) is a multi - carrier modulation technology that is widely used in wireless communication 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 their spectra can overlap without interfering with each other.

[0083] The OFDM system mainly consists of two major parts: the transmitter and the receiver. The transmitter at least includes a data source, a serial-to-parallel converter, a modulator, an IFFT processor, a cyclic prefix adder, and a radio frequency transmitter. Among them, the data source provides the data signal to be transmitted. The serial-to-parallel converter first converts high-speed serial data into low-speed parallel data. Secondly, the modulator modulates the data on each subcarrier. Further, the IFFT processor 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 for combating multipath interference before each OFDM symbol. Finally, the radio frequency transmitter converts the time-domain signal into an analog signal and transmits it to the receiver through a radio frequency link. The receiver at least includes a radio frequency receiver, a cyclic prefix remover, an FFT processor, a demodulator, and a parallel-to-serial converter. The radio frequency receiver is used to receive the radio frequency 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, converting it from the time domain to the frequency domain. Further, the demodulator 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. Through ingenious steps such as signal segmentation, modulation, IFFT transformation, cyclic prefix addition, and FFT transformation, the OFDM system realizes the dual improvement of high-speed data transmission and anti-interference ability.

[0084] The OFDM system has the advantages of high spectral efficiency, strong anti-multipath interference ability, simple channel equalization, and high flexibility. However, it also has limitations such as increased system complexity and high requirements for frequency and time synchronization. Only when the sampling clocks of the transmitter and the receiver are synchronized can the best symbol values be obtained. It is very necessary to compensate the sampling clock of the receiver in the OFDM system to keep it synchronized with the sampling clock of the transmitter.

[0085] The clock error compensation method proposed in this application can compensate the sampling clock of the receiver in the OFDM system to keep it synchronized with the sampling clock of the system transmitter and has high control accuracy.

[0086] The following uses specific embodiments to elaborate in detail on the technical solution of the present application and how the technical solution of the present application solves the above technical problems. The following several 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.

[0087] Figure 1 It is a flowchart of a clock error compensation method provided by an embodiment of the present application. As Figure 1 shown, the clock error compensation method provided by this embodiment is applied to the receiving end of an orthogonal frequency division multiplexing system, and specifically includes the following steps:

[0088] Step S101: Obtain the pilot signal of the system according to the configuration parameters and mapping rules preset by the system.

[0089] In this embodiment, the configuration parameters preset by the orthogonal frequency division multiplexing system (hereinafter referred to as: OFDM system) include carrier frequency, bandwidth, modulation method, coding method, etc., which can determine the insertion position and method of the pilot signal. The mapping rule preset by the OFDM system is mainly used to determine how the orthogonal frequency division multiplexing symbol (hereinafter referred to as: OFDM symbol) is mapped to the subcarriers. In the OFDM system, this usually involves modulating the constellation symbols onto each subcarrier. Therefore, for a determined OFDM system, according to its configuration parameters and mapping rules, the situation of data mapped to each subcarrier can be determined, and the pilot signal can be generated. That is, for a determined OFDM system, the pilot signal is usually a known data sequence and can be used for channel estimation and synchronization.

[0090] Step S102: Determine a reference pilot signal according to the pilot signal, 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.

[0091] In this embodiment, the pilot signal mainly serves as a phase reference in the OFDM system for channel estimation. Since a certain phase offset will occur in all subcarriers, by inserting a known pilot signal in 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 the subcarriers, consisting of a group of orthogonal subcarriers, and each subcarrier carries independent information. Due to the orthogonality between subcarriers, OFDM symbols can transmit information simultaneously in the same frequency band, thus achieving efficient spectrum utilization.

[0092] The pilot distribution resource grid of the OFDM system can be generated according to the configuration parameters and mapping rules preset by the system. The pilot distribution resource grid refers to the part of the spectrum resources in the communication system that is specifically used to transmit pilot signals. In the OFDM system, the pilot signals are inserted into specific subcarriers, and these subcarriers form a certain distribution pattern in the spectrum, that is, the pilot distribution resource grid.

[0093] 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 the subcarrier data corresponding to the first synchronization pilot symbol in the pilot distribution resource grid of the OFDM system.

[0094] Step S103: Determine the 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 the orthogonal frequency division multiplexing symbol at the corresponding position in the received signal that satisfies the preset condition of the correlation degree with the first synchronization pilot signal.

[0095] In some embodiments, according to the first synchronization pilot signal determined in step S102, perform a sliding correlation process on it and the received signal. From the correlation processing result, the correlation degree between the received signal and the first synchronization pilot signal can be obtained. The OFDM symbol at the position corresponding to the two correlation degrees satisfying a certain preset condition is the second synchronization pilot symbol.

[0096] In some embodiments, the position corresponding to the preset condition of the correlation degree can be the position corresponding to the peak value of the correlation degree in the sliding correlation processing result of the received signal and the synchronization seed signal.

[0097] In some embodiments, the second synchronization pilot signal is the pilot data of all the pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal.

[0098] Step S104: Synchronize the first synchronization pilot signal and the second synchronization pilot signal to determine the exact position of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol.

[0099] In this embodiment, synchronizing the first synchronization pilot signal and the second synchronization pilot signal includes time synchronization and frequency synchronization. The synchronization of the signals can identify the starting positions 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, according to the synchronization result, the exact position of each OFDM symbol in the received signal relative to the second synchronization pilot symbol can be determined.

[0100] Step S105: Starting from the position where the second synchronization pilot symbol is located, perform orthogonal frequency division multiplexing (OFDM) demodulation on each OFDM symbol in the received signal to obtain a demodulated signal, and determine the received pilot signal based on the demodulated signal.

[0101] In this embodiment, OFDM demodulation converts high-speed serial data into multiple low-speed parallel data streams, which are then modulated onto multiple orthogonal subcarriers for transmission, thereby improving spectral efficiency and anti-interference ability. An OFDM system needs to perform OFDM demodulation on each OFDM symbol to recover the original data. Before the receiving end of the OFDM system demodulates the received signal, it is necessary to preprocess the received signal, including operations such as 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 signals on each subcarrier are demodulated.

[0102] In some embodiments, the received pilot signal is the pilot data corresponding to the OFDM symbol in the pilot distribution resource grid of the received signal.

[0103] Step S106: Calculate the clock error between the reference pilot signal and the received pilot signal to determine the phase deviation value of each OFDM symbol in the received signal relative to the second synchronization pilot symbol in the frequency domain.

[0104] In this embodiment, using the same processing method as in step S105, calculate the clock error between the reference pilot signal and the received pilot signal, identify the starting positions and timing information of the reference pilot signal and the received pilot signal. On the premise of determining the position of the second synchronization pilot symbol, according to 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.

[0105] Step S107: Perform frequency-domain phase compensation on each OFDM symbol in the received signal according to the phase deviation value to achieve clock error compensation of the received signal.

[0106] In this embodiment, in an OFDM system, when performing frequency-domain phase compensation on each OFDM symbol in the received signal, it is mainly to correct the phase deviation between subcarriers caused by channel transmission characteristics (such as phase distortion, multipath effects, etc.). This helps to ensure the accurate recovery of data. 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, perform frequency-domain phase compensation on each OFDM symbol in the received signal, that is, perform corresponding phase adjustments on the signals on each subcarrier separately. The phase offset in the frequency-domain signal is corrected, so as to facilitate subsequent processing such as decoding and recovery of the received signal at the receiving end.

[0107] In summary, for the clock error compensation method provided in this embodiment, the first synchronization pilot symbol of the orthogonal frequency division multiplexing (OFDM) symbol selected according to the system pilot signal is used to determine the second synchronization pilot symbol at the corresponding position in the received signal, and then the first synchronization pilot signal and the second synchronization pilot signal are determined. After synchronizing the first synchronization pilot signal and the second synchronization pilot signal, the position of each OFDM symbol in the received signal relative to the second synchronization pilot symbol is determined. Based on this, the received signal is demodulated to determine the phase deviation value of each OFDM 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 OFDM symbol in the received signal to achieve clock error compensation of the received signal.

[0108] In this embodiment, by determining the OFDM symbol as the reference, calculating the phase deviation of each OFDM symbol in the received signal with respect to this reference, and performing phase compensation on each OFDM symbol in the received signal in the frequency domain, time error compensation based on the OFDM symbol is achieved. Compared with the prior art, the accuracy of phase compensation is improved according to the phase deviation calculation results of multiple OFDM symbols; at the same time, the compensation process is all carried out in the frequency domain, directly performing phase compensation in the frequency domain, which also reduces the system data processing overhead.

[0109] Figure 2 It is a flowchart for determining the reference pilot signal, the first synchronization pilot symbol, and the first synchronization pilot signal provided in an embodiment of this application. As Figure 2 shown, for the above embodiment, in step S102, according to the pilot signal, the reference pilot signal is determined, any OFDM symbol is selected as the first synchronization pilot symbol, and the first synchronization pilot signal is determined based on the first synchronization pilot symbol. Specifically, it includes the following steps:

[0110] Step S201: Generate the pilot distribution resource grid of the system according to the pilot signal of the system.

[0111] It can be understood that the pilot distribution resource grid refers to the part of the spectrum resources in the communication system that is specifically used to transmit pilot signals. In the OFDM system, according to the preset configuration parameters, the pilot signal can be determined. The pilot signal is inserted into specific subcarriers, and the positions of the OFDM symbols mapped to the subcarriers can be determined through the preset mapping rules. These subcarriers form a certain distribution pattern in the spectrum, that is, the pilot distribution resource grid.

[0112] Figure 3 It is a schematic diagram of the pilot distribution resource grid provided in an embodiment of this application. As Figure 3As shown, all pilot data is transmitted on the pilot distribution resource grid. The abscissa is the OFDM symbol, and the number of the OFDM symbol is (m = 1, 2, …, M), where M is the number of OFDM symbols in one frame of data. In some OFDM systems, M = 280; the ordinate is the subcarrier, and the number of the subcarrier is (k = 0, 1, 2, …, N - 1), where N is the total number of subcarriers under a certain channel bandwidth. In some OFDM systems, N = 3276. The pilot signal is determined according to the preset configuration parameters, and then the pilot data is mapped to the subcarriers according to the mapping rule, and the pilot distribution resource grid of the system is obtained. Figure 3 The pilot data is represented by gray grids in it.

[0113] Generally, in order to obtain better channel estimation performance, the pilot signal can usually be evenly distributed or unevenly distributed in the frequency domain. This can ensure that relatively accurate channel estimation results can be obtained throughout the entire frequency band. According to the time-variation of the channel and the spectral efficiency requirements of the system, the insertion density of the pilot signal can be adjusted. In the case of a faster-changing channel, the insertion density of the pilot signal needs to be increased to obtain more accurate channel estimation results; while in the case of a slower-changing channel, the insertion density of the pilot signal can be appropriately reduced to improve the spectral efficiency of the system.

[0114] Step S202: Select the pilot signals corresponding to all the orthogonal frequency division multiplexing (OFDM) symbols within the OFDM symbol set in the pilot distribution resource grid of the system as the reference pilot signals.

[0115] Step S203: Generate an OFDM symbol set according to the pilot distribution resource grid of the system; the OFDM symbol set is the set of all OFDM symbols including at least N subcarrier data in the pilot distribution resource grid of the system; where N is a positive integer.

[0116] In this embodiment, select all the OFDM symbols whose number of subcarriers (the total number of gray grids on the vertical axis) for pilots exceeds N subcarriers from the pilot distribution resource grid of the system, and record their numbers M to form a set L. N is an actual empirical value. In some embodiments, N = 6. For example, an OFDM system adopts 5G new radio technology and is configured for a wireless channel with a bandwidth of 100 MHz (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]. The numbers of the OFDM symbols in the set are arranged in order.

[0117] Step S204: Select any OFDM symbol in the OFDM symbol set as the first synchronization pilot symbol.

[0118] In this embodiment, the first synchronization pilot symbol serves as the basis for determining the second synchronization pilot symbol in the subsequent received signal. After determining the second synchronization pilot symbol, through a series of data processing, the exact positions of all OFDM symbols in the received signal relative to the second synchronization pilot symbol can be obtained. The first synchronization pilot symbol is one of the OFDM symbol sets determined based on the pilot distribution resource grid of the system and can be regarded as a reference for the pilot signal. Therefore, it can be any one of the OFDM symbol sets.

[0119] In some embodiments, the first synchronization pilot symbol is the first symbol in the orthogonal frequency division multiplexing symbol set.

[0120] 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.

[0121] In this embodiment, after determining the first synchronization pilot symbol, all subcarrier data corresponding to the first synchronization pilot signal are selected from the pilot distribution resource grid of the system, and the selected all subcarrier data are the first synchronization pilot signal.

[0122] Figure 4 This is a flowchart for determining the second synchronization pilot symbol and the second synchronization pilot signal provided by an embodiment of the present application. As Figure 4 shown, in any of the above embodiments, in step S103, according to the first synchronization pilot signal, determine the second synchronization pilot symbol, and based on the second synchronization pilot symbol, determine the second synchronization pilot signal, which specifically includes the following steps:

[0123] Step S401: Perform an inverse Fourier transform on the first synchronization pilot signal to obtain a synchronization seed signal.

[0124] Step S402: Perform a sliding correlation process 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 satisfies the preset condition of the correlation degree with the first synchronization pilot signal as the second synchronization pilot symbol.

[0125] It can be understood that the signal sliding-related processing refers to sliding a signal (or called a template, sequence) to perform point-by-point comparison with another signal, so as to find the similarity or correlation between the two. This processing method is widely used in fields such as signal detection, synchronization, and recognition. Its basic principle is to utilize the correlation characteristics of signals, that is, when two signals are aligned in time and have the same phase, their correlation result reaches the maximum. Specifically, a window with a fixed size (or called a convolution kernel) is defined, and this window slides on the signal, performs weighted averaging or other operations on the signal data within the window to obtain the filtered value or correlation result. The size and shape of the window usually depend on the signal characteristics to be processed and application requirements. Based on the sliding window, the signals within the window are multiplied point by point with the template signal and summed to obtain the correlation value. The magnitude of the correlation value reflects the similarity degree between the signal within the window and the template signal.

[0126] In this embodiment, the subcarrier data after performing inverse Fourier transform (IFFT) on the first synchronization pilot signal is used as the synchronization seed signal, that is, the template signal. The synchronization seed signal and the received signal are slid to obtain the correlation value between the synchronization seed signal and the received signal. According to the similarity degree between the two and the preset correlation degree condition, the position corresponding to the received signal where the correlation degree 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.

[0127] In some embodiments, the position corresponding to the preset correlation degree condition is the position corresponding to the peak of the correlation degree in the sliding correlation processing result of the received signal and the synchronization seed signal. That is to say, 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.

[0128] Step S403: Starting from the position of the second synchronization pilot symbol, select the pilot data of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal as the second synchronization pilot signal.

[0129] In this embodiment, after determining the position of the second synchronization pilot symbol, starting from this position, select the pilot data of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal. The pilot data of all selected pilot subcarriers is the second synchronization pilot signal.

[0130] Figure 5 It is a flowchart for determining the second synchronization pilot signal provided by an embodiment of this application. As Figure 5As shown in the figure, in any of the above embodiments, in step S403, starting from the position of the second synchronization pilot 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, which specifically includes the following steps:

[0131] Step S501: Starting from the position of the second synchronization pilot symbol, perform a Fourier transform on the data of one symbol length in the received signal.

[0132] Step S502: According to the transformation result, select the pilot signals of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal as the second synchronization pilot signal.

[0133] In this embodiment, starting from the position of the second synchronization pilot symbol in the received data, the 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.

[0134] It should be noted that since the synchronization seed signal is the subcarrier data after performing an inverse Fourier transform (IFFT) on the first synchronization pilot signal, both the synchronization seed signal and the received data are in the frequency domain. After performing a sliding correlation process on them, the position of the second synchronization pilot symbol can be determined by judging the position of the correlation peak.

[0135] Figure 6 This is a flowchart for determining the position of each orthogonal frequency division multiplexing symbol in the received signal provided by an embodiment of the present application. As Figure 6 shown, in any of the above embodiments, in step S104, synchronize the first synchronization pilot signal and the second synchronization pilot signal to determine the exact position of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol, which specifically includes the following steps:

[0136] Step S601: Multiply the first synchronization pilot signal and the second synchronization pilot signal conjugately to obtain synchronization data.

[0137] Step S602: Divide the synchronization data into a first data segment and a second data segment in ascending order of pilot subcarriers, and multiply the first data segment and the second data segment conjugately.

[0138] Step S603: According to the result of multiplying the first data segment and the second data segment conjugately, calculate the average value of the phase differences at the corresponding positions 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.

[0139] Step S604: Determine the exact positions of each orthogonal frequency division multiplexing (OFDM) symbol in the received signal relative to the second synchronization pilot symbol according to the phase deviation value of the second synchronization pilot symbol in the received signal.

[0140] Specifically, conjugate multiply the first synchronization pilot signal and the second synchronization pilot signal to obtain synchronization data. According to the order of pilot subcarrier numbers from smallest to largest, divide the synchronization data into two segments with the same number of numbers from the middle, denoted as the first data segment K1 and the second data segment K2 respectively. Then, conjugate multiply the first data segment K1 and the second data segment K2 again, and calculate the average value of the phase differences at the corresponding positions of the first data segment K1 and the second data segment K2.

[0141] 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. Among them, the numbers of the pilot subcarriers in the first data segment K1 are denoted as a x , and the numbers of the pilot subcarriers in the second data segment K2 are denoted as b x . Then, according to the result of conjugate multiplication, the phase difference at the corresponding positions of the first data segment K1 and the second data segment K2 can be calculated and denoted as . Further, calculate the average value of the phase differences at the corresponding positions of the first data segment K1 and the second data segment K2 .

[0142] ;

[0143] Take the average value of the phase differences at the corresponding positions of the first data segment K1 and the second data segment K2 as the phase deviation value of the second synchronization pilot symbol in the received signal. Since the second synchronization pilot signal is selected as the pilot signals of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal after performing Fourier transform on the data of one symbol length in the received signal starting from the position of the second synchronization pilot symbol, that is, the second synchronization pilot signal is the pilot signals of all pilot subcarriers corresponding to the second synchronization pilot symbol in the received signal, so the calculated

[0144] is the phase deviation value of the second synchronization pilot symbol in the received signal. Then, according to the phase deviation value of the second synchronization pilot symbol in the received signal, determine the delay D of each OFDM symbol in the received signal relative to the second synchronization pilot symbol.

[0145] ;

[0146] where SCS is the subcarrier spacing.

[0147] 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 exact position of each OFDM symbol in the received signal relative to the second synchronization pilot symbol can be known.

[0148] Figure 7 The figure is a flowchart for determining a demodulated signal and a received pilot signal provided by an embodiment of the present application. As Figure 7 shown, in any of the above embodiments, step S105: Starting from the position where the second synchronization pilot symbol is located, perform orthogonal frequency division multiplexing (OFDM) demodulation on each OFDM symbol in the received signal to obtain a demodulated signal, and determine a received pilot signal according to the demodulated signal, which specifically includes the following steps:

[0149] Step S701: Starting from the position where the second synchronization pilot symbol is located, remove the data with the length of the cyclic prefix of each OFDM symbol, and perform fast Fourier transform processing on the data corresponding to each OFDM symbol in the received signal.

[0150] It can be understood that an OFDM symbol usually includes a cyclic prefix, which is formed by copying a part 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 symbol boundary. By calculating the correlation between the cyclic prefix and data sequences at different positions, the position with the highest correlation can be found, which is the starting position of the OFDM symbol. Before determining the second synchronization pilot signal according to the first synchronization pilot signal and the second synchronization pilot symbol, it is necessary to first filter out the data with the length of the cyclic prefix in the first synchronization pilot signal, that is, only retain the OFDM symbol data.

[0151] Step S702: Generate a demodulated signal according to the mapping relationship between the received signal after fast Fourier transform and each OFDM symbol.

[0152] In this embodiment, after filtering out the data with the length of the cyclic prefix in the second synchronization pilot signal, before demodulating the received signal as described above, it is necessary to preprocess the received signal, including operations such as filtering, amplification, and synchronization, to restore the original OFDM symbol. Then, for the received signal after filtering processing, perform fast Fourier transform (FFT) on the OFDM symbol to convert the time-domain signal back to the frequency-domain signal, and then demodulate the signal on each subcarrier. Further, according to the mapping relationship corresponding to each OFDM symbol in the pilot distribution resource grid, the demodulated signal can be obtained.

[0153] Step S703: Generate a pilot distribution resource grid of the received signal corresponding to the demodulated signal.

[0154] Step S704: Select all the pilot signals corresponding to the orthogonal frequency division multiplexing (OFDM) symbols within the set of OFDM symbols in the pilot distribution resource grid of the received signal as the received pilot signals.

[0155] In this embodiment, for a given OFDM system, according to its configuration parameters and mapping rules, the mapping of data to each subcarrier can be determined, and pilot signals can be generated, thus obtaining the pilot distribution resource grid of the OFDM system. Select all the pilot signals corresponding to the OFDM symbols within the set of OFDM symbols in the pilot distribution resource grid of the system as the reference pilot signals.

[0156] Based on the mapping relationship between the system pilot distribution resource grid and the OFDM symbols, 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 preset configuration parameters. As Figure 3 shown, only the gray pilot data in the system pilot distribution resource grid is valid (reference pilot). Since the data in the pilot part is calculated according to preset configuration parameters, it can be regarded as an ideal value, and the white part is empty and can be regarded as useless data. For the pilot distribution resource grid of the received signal, its size is the same as that of the system pilot distribution resource grid. The gray part is the pilot data, which is calculated through pre-parameter configuration at the sending end, then modulated together with the user data in the white part through OFDM, and then sent through the channel. After being received at the receiving end and demodulated through OFDM, the received pilot data in the gray part and the user data in the white part are obtained.

[0157] After determining the pilot distribution resource grid of the received signal, all the pilot signals corresponding to the OFDM symbols within the set of OFDM symbols in the pilot distribution resource grid of the received signal can be selected as the received pilot signals.

[0158] Figure 8 This is a flowchart for determining the phase offset value of each orthogonal frequency division multiplexing symbol in the received signal provided by an embodiment of the present application. As Figure 8 shown, in any of the above embodiments, in step S106: Synchronize 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, which specifically includes the following steps:

[0159] Step S801: Multiply the reference pilot signal and the received pilot signal conjugately to obtain phase offset calculation data.

[0160] Step S802: Divide the phase offset calculation data into a third data segment and a fourth data segment in ascending order of the pilot subcarriers, and multiply the third data segment and the fourth data segment conjugately.

[0161] Step S803: Calculate the average value of the phase differences at the corresponding positions of each orthogonal frequency division multiplexing (OFDM) symbol in the third data segment and the fourth data segment as the phase offset value of the OFDM symbol according to the result of conjugate multiplication of the third data segment and the fourth data segment.

[0162] Step S804: Calculate the distance of each OFDM symbol relative to the second synchronization pilot symbol.

[0163] Step S805: Calculate the phase offset value of each OFDM symbol relative to the second synchronization pilot symbol in the frequency domain according to the value of each OFDM symbol and its distance relative to the second synchronization pilot symbol.

[0164] Specifically, conjugate multiply the reference pilot signal and the received pilot signal to obtain phase offset calculation data, which can eliminate the influence of the original signal phase and only leave the phase differences caused by the channel, oscillator frequency offset, and clock error. Similarly, according to the ascending order of the pilot subcarrier numbers, divide the phase offset calculation data into two segments with the same number of numbers from the middle, and denote them as the third data segment K3 and the fourth data segment K4 respectively. Then, conjugate multiply the third data segment K3 and the fourth data segment K4 again, and calculate the average value of the phase differences at the corresponding positions of each OFDM symbol in the third data segment K3 and the fourth data segment K4.

[0165] Assume that both the third data segment K3 and the fourth data segment K4 have data corresponding to Y (Y = 1, 2, 3,..., y) pilot subcarriers. Among them, the numbers of the pilot subcarriers in the third data segment K3 are denoted as c y , and the numbers of the pilot subcarriers in the fourth data segment K4 are denoted as d y . Then, according to the result of conjugate multiplication, the phase differences at the corresponding positions of each OFDM symbol in the third data segment K3 and the fourth data segment K4 can be calculated and denoted as . Further, calculate the average value of the phase differences at the corresponding positions of the third data segment K3 and the fourth data segment K4 .

[0166] ;

[0167] Take the average value of the phase differences at the corresponding positions of the third data segment K3 and the fourth data segment K4 as the phase offset value of the OFDM symbol.

[0168] For a specific OFDM system, the length of each OFDM symbol , where is the cyclic prefix length of the OFDM symbol, When performing a fast Fourier transform on an OFDM symbol, it is the length of the array or data sequence to be transformed, that is, how many points the data is divided into for calculation.

[0169] In the system pilot distribution resource grid as described above, the number of OFDM symbols is M, and the OFDM symbol numbers (m = 1, 2, …, M). For all M OFDM symbols, the distance of each OFDM symbol relative to the second synchronization pilot symbol is denoted as L m , then:

[0170] ;

[0171] Finally, according to the phase offset of each OFDM symbol and its distance L m relative to the second synchronization pilot symbol, calculate the phase offset value of each OFDM symbol relative to the second synchronization pilot symbol in the frequency domain .

[0172] .

[0173] Figure 9 This is the flowchart of frequency domain phase compensation provided by an embodiment of the present application. As Figure 10 shown, in any of the above embodiments, step S107, according to the phase offset value, perform frequency domain phase compensation on each orthogonal frequency division multiplexing symbol in the received signal, including:

[0174] Taking the position of the second synchronization pilot symbol in the pilot distribution resource grid of the received signal as a reference, perform frequency domain phase compensation on each orthogonal frequency division multiplexing symbol in the pilot distribution resource grid of the received signal.

[0175] More specifically, performing frequency domain phase compensation on each orthogonal frequency division multiplexing symbol in the pilot distribution resource grid of the received signal includes:

[0176] Step S901, obtain the order of each orthogonal frequency division multiplexing symbol in the pilot distribution resource grid of the received signal.

[0177] Step S902, for the orthogonal frequency division multiplexing symbols before the second synchronization pilot symbol, the phase compensation value is the product of the phase offset value and the distance from this orthogonal frequency division multiplexing symbol to the second synchronization pilot symbol.

[0178] For the OFDM symbols after 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 this OFDM symbol to the second synchronization pilot symbol.

[0179] That is, taking the second synchronization pilot symbol as a reference point, assuming that the serial 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,

[0180] For the OFDM symbol before the second synchronization pilot symbol, that is, for the OFDM symbol with a serial number less than m j when performing frequency-domain phase compensation on this symbol, the phase compensation value is the product of the phase deviation value of this OFDM symbol relative to the second synchronization pilot symbol and the distance, that is:

[0181] ;

[0182] For the OFDM symbol before the second synchronization pilot symbol, that is, for the OFDM symbol with a serial number greater than m j when performing frequency-domain phase compensation on this symbol, the phase compensation value is the product of the negative value of the phase deviation value of this OFDM symbol relative to the second synchronization pilot symbol and the distance, that is:

[0183] .

[0184] In summary, the clock error compensation method provided by the embodiments of the present application determines the second synchronization pilot symbol at the corresponding position in the received signal by determining the first synchronization pilot symbol of the orthogonal frequency division multiplexing symbol selected 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 based on this, the received signal is demodulated 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.

[0185] The present application determines the orthogonal frequency division multiplexing symbol as a reference, calculates the phase deviation of each orthogonal frequency division multiplexing symbol in the received signal with respect to this reference, and performs phase compensation on each orthogonal frequency division multiplexing symbol in the received signal in the frequency domain, realizing time error compensation based on the orthogonal frequency division multiplexing symbol. Compared with the prior art, the accuracy of phase compensation is improved according to the phase deviation calculation results of multiple orthogonal frequency division multiplexing symbols; at the same time, the compensation process is all performed in the frequency domain, directly performing phase compensation in the frequency domain, which also reduces the system data processing overhead.

[0186] Figure 10The figure is a schematic structural diagram of a clock error compensation module provided by an embodiment of the present application. As Figure 10 shown, in this embodiment, the clock error compensation module is disposed at the receiving end of an orthogonal frequency division multiplexing (OFDM) system. 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.

[0187] In this embodiment, the communication unit 1001 is configured to obtain a received signal.

[0188] The first processing unit 1002 is configured to obtain a pilot signal of the system according to configuration parameters and mapping rules preset by the system; and 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.

[0189] The second processing unit 1003 is configured 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 corresponding position in the received signal that satisfies a preset condition of correlation with the first synchronization pilot signal.

[0190] The synchronization unit 1004 is configured to synchronize the first synchronization pilot signal and the second synchronization pilot signal, and determine the exact position of each orthogonal frequency division multiplexing symbol in the received signal relative to the second synchronization pilot symbol.

[0191] The demodulation unit 1005 is 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, obtain a demodulated signal, and determine a received pilot signal according to the demodulated signal.

[0192] The clock error calculation 1006 is configured 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;

[0193] The compensation unit 1007 is configured to perform frequency domain phase compensation on each orthogonal frequency division multiplexing symbol in the received signal according to the phase offset value, so as to achieve clock error compensation of the received signal.

[0194] In some embodiments, all the steps of each unit in the clock error compensation module for implementing functions are the same as or similar to the steps of the above clock error compensation method, and have the technical effects of any embodiment of the above clock error compensation method. To avoid repetition, details are not described herein again.

[0195] 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, each process of the clock error compensation method embodiment described in any of the above embodiments is implemented, and the same technical effects can be achieved. To avoid repetition, details are not described herein again.

[0196] Wherein, the processor is the processor in the electronic device described in the above embodiments. 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 disc, etc.

[0197] Those skilled in the art can understand that all or part of the functions of the above methods can be implemented in a hardware manner or in a computer program manner. When all or part of the functions in the above embodiments are implemented in a computer program manner, the program can be stored in a computer-readable storage medium. The storage medium can include: read-only memory, random access memory, magnetic disk, optical disc, hard disk, etc. The above functions are implemented by a computer executing the program. For example, the program is stored in the memory of the device, and when the processor executes the program in the memory, all or part of the above functions can be implemented. In addition, when all or part of the functions in the above embodiments are implemented in a computer program manner, the program can also be stored in a storage medium such as a server, another computer, a magnetic disk, an optical disc, a flash drive or a mobile hard disk, downloaded or copied and saved to the memory of the local device, or the system of the local device is updated. When the processor executes the program in the memory, all or part of the functions in the above embodiments can be implemented.

[0198] The embodiment of the present application also provides a computer program product, which is stored in a storage medium and is executed by at least one processor to implement each process of the clock error compensation method embodiment described in any of the above embodiments, and the same technical effects can be achieved. To avoid repetition, details are not described herein again.

[0199] The embodiments of the present application have been described above in conjunction with the accompanying drawings. However, the present application is not limited to the above specific implementation manners. The above specific implementation manners are merely illustrative and not restrictive. Under the inspiration of the present application, those of ordinary skill in the art, without departing from the purpose of the present application and the scope protected by the claims, according to the idea of the present invention, can also make several simple deductions, deformations or substitutions, all of which fall within the protection scope 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 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.

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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