Joint frequency offset compensation method and apparatus, and electronic device

Abstract

The application discloses a joint frequency offset compensation method and device and electronic equipment. The method comprises the following steps: in the case that a target time slot is configured with only single-column pilot symbols, determining frequency offset estimation values corresponding to a plurality of orthogonal frequency division multiplexing symbols in the target time slot, wherein the frequency offset estimation value is a phase difference estimation value caused by the frequency offset corresponding to the orthogonal frequency division multiplexing symbol; performing first frequency offset compensation on the plurality of orthogonal frequency division multiplexing symbols according to the frequency offset estimation values corresponding to the plurality of orthogonal frequency division multiplexing symbols, to obtain a plurality of target orthogonal frequency division multiplexing symbols; determining a far-end symbol from the plurality of target orthogonal frequency division multiplexing symbols, wherein the far-end symbol is a target orthogonal frequency division multiplexing symbol with a distance greater than a preset threshold to the pilot symbol of the target time slot; determining an average frequency offset compensation value corresponding to the far-end symbol, and performing second frequency offset compensation on the far-end symbol according to the average frequency offset compensation value, to obtain the far-end symbol after the second frequency offset compensation.

Description

Technical Field

[0001] This application relates to the field of wireless communication, and more specifically, to a joint frequency offset compensation method, apparatus, and electronic device. Background Technology

[0002] The New Radio (NR) interface of fifth-generation mobile communication technology (5G) uses Orthogonal Frequency Division Multiplexing (OFDM) technology as the basis for its physical layer signal transmission. OFDM technology has advantages such as high spectrum utilization, flexible resource allocation, and effective resistance to multipath effects, and is widely used in wireless communication systems. However, OFDM systems are very sensitive to carrier frequency offset. Frequency offset affects each subcarrier, destroying the orthogonality of subcarriers, leading to performance degradation of the OFDM system, increased error vector magnitude (EVM) during demodulation, and higher block error rate (BLER) during decoding.

[0003] The performance of a communication system at the receiver depends on channel estimation and equalization algorithms. This is achieved by calculating the frequency offset using pilots within each time slot, compensating for the offset, and then using frequency domain equalization to compensate for the negative effects on each subcarrier, restoring the signal to its normal state and improving the system's demodulation performance. In related technologies, to improve the performance of channel estimation and equalization algorithms, communication systems configure two or more pilot columns within each time slot. Frequency offset is calculated based on the information from these two or more pilot columns to compensate for each subcarrier. When multiple pilot columns are present in a time slot, the frequency offset compensation in the frequency domain is more accurate. However, when only a single pilot column is configured per time slot, the receiver can only use the pilot symbol at that single time domain location to estimate the frequency offset. While the frequency offset compensation at the pilot position within the time slot is accurate, errors occur in the compensation for symbols farther from the pilot. This leads to a more divergent constellation diagram and a larger EVM for far-end symbols within the time slot.

[0004] There is currently no effective solution to the above problems. Summary of the Invention

[0005] This application provides a joint frequency offset compensation method, apparatus, and electronic device to at least solve the technical problem in 5G NR systems where, when only a single column of pilots is configured in a time slot, the demodulation performance (EVM) of symbols far from the pilot position is reduced due to frequency offset estimation errors.

[0006] According to one aspect of the embodiments of this application, a joint frequency offset compensation method is provided, comprising: when only a single column of pilot symbols is configured in the target time slot, determining frequency offset estimates corresponding to multiple orthogonal frequency division multiplexing (OFDM) symbols in the target time slot, wherein the frequency offset estimates are phase difference estimates caused by the frequency offset of the OFDM symbols; performing a first frequency offset compensation on the multiple OFDM symbols based on the frequency offset estimates corresponding to the multiple OFDM symbols to obtain multiple target OFDM symbols; determining a far-end symbol from the multiple target OFDM symbols, wherein the far-end symbol is a target OFDM symbol whose distance from the pilot symbols of the target time slot is greater than a preset threshold; determining the average frequency offset compensation value corresponding to the far-end symbol, and performing a second frequency offset compensation on the far-end symbol based on the average frequency offset compensation value to obtain the far-end symbol after the second frequency offset compensation, wherein the average frequency offset compensation value is determined based on the frequency offset compensation values ​​of the target constellation points mapped to the far-end symbols in multiple quadrants.

[0007] Optionally, determining the frequency offset estimates corresponding to multiple orthogonal frequency division multiplexing symbols within the target time slot includes: obtaining the cyclic prefix and tail data corresponding to the multiple orthogonal frequency division multiplexing symbols; for each orthogonal frequency division multiplexing symbol, performing cross-correlation operations on the cyclic prefix and tail data corresponding to the orthogonal frequency division multiplexing symbol to obtain the frequency offset estimate corresponding to each orthogonal frequency division multiplexing symbol.

[0008] Optionally, based on the frequency offset estimates corresponding to the multiple orthogonal frequency division multiplexing (OFDM) symbols, a first frequency offset compensation is performed on the multiple OFDM symbols to obtain multiple target OFDM symbols. This includes: obtaining the cyclic prefix length and time-domain sampling index value corresponding to the multiple OFDM symbols; determining the phase rotation factor corresponding to the multiple OFDM symbols based on the frequency offset estimates, cyclic prefix length, and time-domain sampling index value; and compensating the phase rotation factor corresponding to the multiple OFDM symbols to the corresponding OFDM symbols to obtain multiple target OFDM symbols.

[0009] Optionally, determining the far-end symbol from multiple target orthogonal frequency division multiplexing (OFDM) symbols includes: obtaining the position index value of the pilot symbol in the target time slot; obtaining the position index values ​​corresponding to the multiple target OFDM symbols in the target time slot respectively; for each target OFDM symbol among the multiple target OFDM symbols, determining the target distance in the following manner, and determining the target OFDM symbol whose target distance is greater than a preset threshold as the far-end symbol: determining the absolute value of the difference between the target position index value and the position index value of the pilot symbol as the target distance of the first target OFDM symbol, wherein the first target OFDM symbol is any one of the multiple target OFDM symbols, and the target position index value is the position index value of the first target OFDM symbol.

[0010] Optionally, determining the average frequency offset compensation value corresponding to the far-end symbol includes: determining multiple reference constellation points corresponding to the far-end symbol; determining multiple target constellation points from the multiple reference constellation points, wherein the multiple target constellation points correspond one-to-one with multiple quadrants; determining the frequency offset compensation value corresponding to each of the multiple target constellation points, wherein the frequency offset compensation value is used to compensate for the phase rotation caused by the frequency offset of the target constellation points; and determining the average value of the frequency offset compensation values ​​corresponding to the multiple target constellation points as the average frequency offset compensation value corresponding to the far-end symbol.

[0011] Optionally, multiple target constellation points are determined from multiple reference constellation points, including: determining a constellation diagram corresponding to the modulation scheme used by the far-end symbol, wherein the constellation diagram contains the positions of all reference constellation points mapped to multiple quadrants, the multiple quadrants including the first quadrant to the fourth quadrant; in each quadrant of the multiple quadrants of the constellation diagram, selecting the reference constellation point farthest from the origin of the constellation diagram to determine the target constellation point, thereby obtaining multiple target constellation points.

[0012] Optionally, determining the frequency offset compensation values ​​corresponding to multiple target constellation points includes: determining multiple expected values ​​corresponding to multiple target constellation points, wherein one target constellation point corresponds to one expected value; obtaining the number of constellation points mapped from multiple reference constellation points to each quadrant in multiple quadrants; obtaining the theoretical reference phase corresponding to each of the multiple target constellation points; and determining the frequency offset compensation values ​​corresponding to each of the multiple target constellation points based on the number of constellation points corresponding to each of the multiple quadrants, the expected values ​​corresponding to the target constellation points corresponding to each of the multiple quadrants, and the theoretical reference phase.

[0013] Optionally, frequency offset compensation values ​​for multiple target constellation points are determined based on the number of constellation points corresponding to each of the multiple quadrants, the expected mathematical values ​​of the target constellation points corresponding to each of the multiple quadrants, and the theoretical reference phase. This includes: determining the frequency offset compensation value of the first target constellation point based on the number of constellation points corresponding to the first quadrant, the expected mathematical value of the first target constellation point, and the theoretical reference phase, wherein the first target constellation point is a target constellation point mapped to the first quadrant; determining the frequency offset compensation value of the second target constellation point based on the number of constellation points corresponding to the second quadrant, the expected mathematical value of the second target constellation point, and the theoretical reference phase, wherein the second target constellation point is a target constellation point mapped to the second quadrant; determining the frequency offset compensation value of the third target constellation point based on the number of constellation points corresponding to the third quadrant, the expected mathematical value of the third target constellation point, and the theoretical reference phase, wherein the third target constellation point is a target constellation point mapped to the third quadrant; and determining the frequency offset compensation value of the fourth target constellation point based on the number of constellation points corresponding to the fourth quadrant, the expected mathematical value of the fourth target constellation point, and the theoretical reference phase, wherein the fourth target constellation point is a target constellation point mapped to the fourth quadrant.

[0014] According to another aspect of the embodiments of this application, a joint frequency offset compensation device is also provided, comprising: a first determining module, configured to determine frequency offset estimates corresponding to multiple orthogonal frequency division multiplexing (OFDM) symbols in a target time slot when only a single column of pilot symbols is configured in the target time slot, wherein the frequency offset estimates are phase difference estimates caused by the frequency offset corresponding to the OFDM symbols; a first frequency offset compensation module, configured to perform a first frequency offset compensation on the multiple OFDM symbols based on the frequency offset estimates corresponding to the multiple OFDM symbols, to obtain multiple target OFDM symbols; a second determining module, configured to determine a far-end symbol from the multiple target OFDM symbols, wherein the far-end symbol is a target OFDM symbol whose distance from the pilot symbols of the target time slot is greater than a preset threshold; and a second frequency offset compensation module, configured to determine the average frequency offset compensation value corresponding to the far-end symbol, and perform a second frequency offset compensation on the far-end symbol based on the average frequency offset compensation value, to obtain the far-end symbol after the second frequency offset compensation, wherein the average frequency offset compensation value is determined based on the frequency offset compensation values ​​of the target constellation points mapped to the far-end symbols in multiple quadrants.

[0015] According to another aspect of the embodiments of this application, a non-volatile storage medium is also provided, wherein a program is stored in the non-volatile storage medium, wherein the program controls the device where the non-volatile storage medium is located to execute the above-mentioned joint frequency offset compensation method when it runs.

[0016] According to another aspect of the embodiments of this application, an electronic device is also provided, including: a memory and a processor, wherein the processor is configured to run a program stored in the memory, wherein the program executes the above-described joint frequency offset compensation method during runtime.

[0017] According to another aspect of the embodiments of this application, a computer program product is also provided, including computer instructions that, when executed by a processor, implement the above-described joint frequency offset compensation method.

[0018] In this embodiment, when only a single pilot symbol is configured in the target time slot, frequency offset estimates are determined for each of the multiple orthogonal frequency division multiplexing (OFDM) symbols within the target time slot. These frequency offset estimates are phase difference estimates caused by the frequency offset of the OFDM symbols. Based on these frequency offset estimates, a first frequency offset compensation is performed on the multiple OFDM symbols to obtain multiple target OFDM symbols. The far-end symbol is then determined from among the multiple target OFDM symbols, where the far-end symbol is the symbol relative to the target time slot. The target orthogonal frequency division multiplexing symbol is located at a distance greater than a preset threshold. The average frequency offset compensation value corresponding to the far-end symbol is determined, and the far-end symbol is subjected to a second frequency offset compensation based on the average frequency offset compensation value to obtain the far-end symbol after the second frequency offset compensation. The average frequency offset compensation value is determined by mapping the far-end symbol to the frequency offset compensation value of the target constellation point in multiple quadrants. When only a single column of pilots is configured in the time slot, the frequency offset compensation is performed twice in succession to correct the frequency offset error and improve the demodulation performance (EVM). This solves the technical problem in 5G NR system where the demodulation performance (EVM) of symbols far from the pilot position is reduced due to frequency offset estimation error when only a single column of pilots is configured in the time slot. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0020] Figure 1 This is a hardware structure block diagram of a computer terminal for implementing a joint frequency offset compensation method according to an embodiment of this application;

[0021] Figure 2 This is a flowchart of a joint frequency offset compensation method provided according to an embodiment of this application;

[0022] Figure 3 This is a schematic diagram of a single-column pilot signal according to an embodiment of this application;

[0023] Figure 4 This is a signal processing flowchart provided according to an embodiment of this application;

[0024] Figure 5 This is a schematic diagram of a first type of EVM provided according to an embodiment of this application;

[0025] Figure 6 This is a schematic diagram of a second type of EVM provided according to an embodiment of this application;

[0026] Figure 7 This is a schematic diagram of a combined frequency offset compensation device provided according to an embodiment of this application. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0028] The information collected in this application embodiment is information and data authorized by the user or fully authorized by all parties. The collection, storage, use, processing, transmission, provision, disclosure and application of the relevant data all comply with the relevant laws, regulations and standards of the relevant regions, and necessary confidentiality measures have been taken. It does not violate public order and good morals, and provides corresponding operation entry points for users to choose to authorize or reject the automated decision results. If the user chooses to reject, the process will proceed to the expert decision-making process.

[0029] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0030] To better understand the embodiments of this application, the technical terms involved in the embodiments of this application are explained below:

[0031] Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation technique. It divides a high-speed data stream into multiple low-speed sub-data streams and transmits them in parallel on multiple mutually orthogonal narrowband subcarriers. Its advantages include high spectral efficiency and effective resistance to frequency-selective fading and multipath effects.

[0032] Error Vector Magnitude (EVM): Block error rate is an important indicator of the quality of digitally modulated signals. It represents the root mean square value of the vector distance between the points of the modulated signal constellation and the points of the ideal reference constellation. The smaller the EVM, the less signal distortion and the better the demodulation performance.

[0033] Block Error Rate (BLER): The proportion of protocol data units (such as MAC PDUs or RLC PDUs) that are decoded incorrectly at the receiving end during data transmission. It is a key indicator for evaluating channel quality and selecting modulation and coding strategies.

[0034] Minimum Mean Square Error (MMSE): A signal estimation algorithm. In channel estimation, the MMSE algorithm optimizes the estimation result by minimizing the mean square error between the estimated channel response and the actual channel response. Compared to zero-forcing algorithms, MMSE considers the influence of noise, thus performing better in low signal-to-noise ratio environments.

[0035] In related technologies, the performance of a communication system at the receiver depends on channel estimation and equalization algorithms. The approach is to calculate the frequency offset by performing channel estimation using pilots in each time slot, compensate for the frequency offset, and compensate for the negative effects of each subcarrier using frequency domain equalization techniques, so that the signal is restored to a normal state, thereby improving the demodulation performance of the system.

[0036] At the physical layer frequency domain receiver, the frequency domain data at the pilot location can be represented by the following formula:

[0037] (1), where y represents the received pilot signal, h is the channel estimation response, s is the locally generated pilot signal, and n is noise.

[0038] The zero-forcing algorithm is used to estimate h in the above, without considering noise, that is, the noise n is zero, so that the value of formula (2) is minimized: (2).

[0039] The theoretical pilot frequency domain data is represented by the following formula (3):

[0040] (3), among which, This represents the theoretical pilot frequency domain data (the theoretical estimated value after equalization corresponding to s; at the pilot position, it corresponds to the estimated value of the pilot; at the data position, it corresponds to the estimated value of the data symbol). The weighting factor is used for each column of frequency domain data in the current time slot (target time slot). In frequency domain equalization, each column of data within the time slot is multiplied by the weighting factor to obtain the equalized data. .

[0041] The MMSE algorithm is used to derive formula (1), and the theoretical pilot frequency domain data is obtained. As shown in formula (4):

[0042] (4), of which, This represents the estimation error term; Represents the identity matrix; Indicates the noise variance; This represents the MMSE equilibrium weighting factor.

[0043] Compared with formula (3), the MMSE algorithm takes into account the impact of noise on the communication system. In environments with a relatively high signal-to-noise ratio, the performance of MMSE is close to that of the zero-forcing algorithm, while in environments with a relatively low signal-to-noise ratio, the performance of the zero-forcing algorithm is worse than that of MMSE.

[0044] To improve the performance of channel estimation and equalization algorithms, communication systems configure two or more pilot columns in each time slot. Frequency offset is calculated based on the two or more pilot columns to compensate for each subcarrier. When multiple pilot columns are present in a time slot, the frequency offset compensation in the frequency domain is more accurate. However, when only a single pilot column is configured in each time slot, the receiver can only use the pilot symbol at that single time domain location to estimate the frequency offset. While the frequency offset compensation at the pilot position within the time slot is accurate, errors occur for symbols farther from the pilot, leading to a more divergent constellation diagram and a larger EVM for far-end symbols within the time slot. Therefore, in 5G NR systems, when only a single pilot column is configured in a time slot, the demodulation performance (EVM) of symbols far from the pilot position degrades due to frequency offset estimation errors. To address this issue, this application provides relevant solutions, which are detailed below.

[0045] According to an embodiment of this application, an embodiment of a joint frequency offset compensation method is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0046] The methods and embodiments provided in this application can be executed on a computer terminal or similar computing device.

[0047] Figure 1A hardware block diagram of a computer terminal for implementing a joint frequency offset compensation method is shown. Figure 1 As shown, the computer terminal 10 may include a processor 102, a memory 104 for storing data, and a transmission module 106 for communication functions. The processor 102 may include one or more processors. For ease of explanation, Figure 1 The diagram illustrates multiple processors, including a first processor 102a, a second processor 102b, ..., an nth processor 102n. The processor 102 may be a processing device including, but not limited to, a microcontroller unit (MCU) or a field-programmable gate array (FPGA).

[0048] In addition, a computer terminal may also include: a display, an input / output interface (I / O interface), a Universal Serial Bus (USB) port (which may be included as one of the ports of a BUS bus), a network interface, a power supply, and / or a camera. Those skilled in the art will understand that... Figure 1 The structure shown is for illustrative purposes only and does not limit the structure of the aforementioned electronic device. For example, computer terminal 10 may also include... Figure 1 The more or fewer components shown, or having the same Figure 1 The different configurations shown.

[0049] It should be noted that the aforementioned one or more processors 102 and / or other data processing circuits may be referred to herein as "data processing circuits". These data processing circuits may be embodied, in whole or in part, as software, hardware, firmware, or any other combination thereof. Furthermore, the data processing circuits may be a single, independent processing module, or may be integrated, in whole or in part, into any other element within the computer terminal 10. As described in the embodiments of this application, the data processing circuits serve as a form of processor control (e.g., selection of a variable resistor termination path connected to an interface).

[0050] The memory 104 can be used to store software programs and modules of application software, such as the program instructions / data storage device corresponding to the joint frequency offset compensation method in this embodiment. The processor 102 executes various functional applications and data processing by running the software programs and modules stored in the memory 104, thereby realizing the aforementioned joint frequency offset compensation method. The memory 104 may include high-speed random access memory, and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 104 may further include memory remotely located relative to the processor 102, and these remote memories can be connected to the computer terminal 10 via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0051] The transmission module 106 is used to receive or send data via a network. Specific examples of the network described above may include a wireless network provided by the communication provider of the computer terminal 10. In one example, the transmission module 106 includes a network interface controller (NIC), which can connect to other network devices via a base station to communicate with the Internet. In another example, the transmission module 106 may be a radio frequency (RF) module, used for data interaction with external networks or devices via wired and / or wireless network connections.

[0052] The display can be, for example, a touchscreen liquid crystal display (LCD), which allows the user to interact with the user interface of the computer terminal 10. In addition, the computer terminal 10 can also connect to a cursor control device and a keyboard via an input / output interface. The cursor control device (e.g., a mouse, trackball, or touchpad) is mainly used to transmit directional information and command selections to the terminal and control the movement of the cursor on the display; the keyboard is mainly used to receive letters, numbers, and other control commands input by the user, thereby enabling interaction between the user and the computer terminal 10.

[0053] It should be noted here that, in some optional embodiments, the above... Figure 1 The computer terminal shown may include hardware elements (including circuitry), software elements (including computer code stored on a computer-readable medium), or a combination of both hardware and software elements. It should be noted that... Figure 1 This is only one instance of a specific particular instance, and is intended to illustrate the types of components that may exist in the aforementioned computer terminal.

[0054] Under the above operating environment, the embodiments of this application provide a joint frequency offset compensation method, such as... Figure 2 The diagram shown is a flowchart of a joint frequency offset compensation method according to an embodiment of this application, including:

[0055] Step S202: When only a single column of pilot symbols is configured in the target time slot, determine the frequency offset estimates corresponding to the multiple orthogonal frequency division multiplexing symbols in the target time slot. The frequency offset estimates are the phase difference estimates caused by the frequency offset of the orthogonal frequency division multiplexing symbols.

[0056] In some embodiments of this application, according to 3GPP protocol TS 38.211, the number of Demodulation Reference Signals (DMRS) and the location of time-frequency domain resources in each time slot of the NR Physical Downlink Shared Channel (PDSCH) are determined by the following five parameters: DMRS_Configuration (DMRS configuration type), DMRS_Duration (DMRS duration), DMRS_add_pos (DMRS additional location configuration), PDSCH_Mapping (PDSCH time-domain mapping type), and DMRS_typeA_pos (DMRS start position offset). Wherein:

[0057] The parameter DMRS_Configuration defines the arrangement structure of DMRS in the frequency domain: it can be set to type1 and type2. Type1 means that DMRS are arranged in groups of 1 column, with a spacing of 1 subcarrier in the frequency domain (i.e., DMRS ports are arranged every 1 subcarrier in the frequency domain); type2 means that DMRS are arranged in groups of 2 columns, with a spacing of 4 subcarriers in the frequency domain (DMRS ports are arranged every 4 subcarriers in the frequency domain).

[0058] The parameter DMRS_Duration specifies the number of symbols occupied by DMRS at a given time domain location. It can be configured as Single Symbol or Double Symbol. Single Symbol is defined as a single column of pilots, while Double Symbol occupies two columns of pilots at a given time domain location.

[0059] The parameter DMRS_add_pos indicates whether to configure additional DMRS symbols. Its value ranges from 0 to 3. When the value is 0, it means that no additional DMRS symbols are configured, and only the initially configured DMRS are retained.

[0060] The parameter PDSCH_Mapping defines the time-domain mapping method of PDSCH: Type A: Fixed start symbol (symbol 0 or symbol 1) within the time slot, DMRS position is fixed relative to the start position of the time slot; Type B: Flexible start symbol of PDSCH (symbol 0~12), DMRS position is fixed relative to the start position of PDSCH.

[0061] The parameter DMRS_typeA_pos is only applicable when PDSCH_Mapping is Type A. It specifies the starting position of the first DMRS symbol, and its defined parameters are 2 and 3.

[0062] The special case of configuring only a single column of pilot symbols in the target time slot is satisfied when the following parameter combination is met:

[0063] DMRS_ Configuration ='Typel', DMRS_ Duration ='Single Symbol';

[0064] DMRS_add_pos=0, PDSCH_ Mapping='TypeA', DMRS_ typeA_pos=2.

[0065] Figure 3 This is a single-column pilot diagram provided in an embodiment of this application. With a subframe spacing of 15 kHz, one subframe equals one time slot, with a duration of 1 ms. One time slot contains 14 OFDM symbols (…). Figure 3 The symbols 0-13 in the time domain contain one DMRS, whose time domain position is on the third symbol of each time slot. Figure 3 (Identified as 2). For example Figure 3 As shown, the time slot structure with subframe numbers Subframe0 and Subframe1 and time slot numbers Slot0 and Slot1 is illustrated. The green squares in the figure represent pilot signals, and the white squares represent data. Figure 3 The PRB on the left represents a resource block. Figure 3 Resource blocks 0-273 (PRB0-PRB273) are presented as an example. SC represents the subcarrier index. PRB0, 11SC0 refers to PRB 0 corresponding to the lowest frequency subcarriers 0-11, PRB 1 corresponding to subcarriers 12-23, and so on up to PRB273.

[0066] When only a single column of pilot symbols is configured in the target time slot, for the NR receiver, configuring one column of DMRS symbols per slot can be considered as the channel being in a slowly changing state. Based on this, a joint algorithm for steps S202-S208 is proposed. First, through steps S202-S24, cross-correlation and frequency offset self-compensation using the cyclic prefix (CP) are used to complete frequency offset estimation and compensation. The principle of calculating carrier frequency offset (frequency offset) using CP cross-correlation is as follows: In OFDM systems, frequency offset will destroy the orthogonality between subcarriers, leading to a deterioration in demodulation performance. Since the single column of pilots is sparsely distributed in the time domain, relying solely on pilots for frequency offset estimation cannot effectively cover symbols far from the pilot positions, resulting in a large residual frequency offset for far-end symbols. However, ideally, the CP portion of each OFDM symbol should have the same sampling point at the tail of the corresponding symbol. But if there is a carrier frequency offset, the received signal will undergo a phase rotation that varies linearly with time, resulting in a phase difference between the CP portion and the symbol tail. The magnitude of the frequency offset can be calculated by cross-correlation of the CP. Utilizing this characteristic, the frequency offset can be independently estimated for each OFDM symbol without additional pilots, thereby determining the frequency offset estimates for multiple OFDM symbols within the target time slot. This achieves coarse frequency offset compensation across the entire time slot, laying the foundation for subsequent fine compensation based on constellation points.

[0067] In the technical solution provided in step S202, there are multiple ways to determine the frequency offset estimates corresponding to multiple orthogonal frequency division multiplexing symbols in the target time slot. For example, the cyclic prefix and tail data corresponding to multiple orthogonal frequency division multiplexing symbols are obtained. For each orthogonal frequency division multiplexing symbol, cross-correlation operation is performed on the cyclic prefix and tail data corresponding to the orthogonal frequency division multiplexing symbol to obtain the frequency offset estimate corresponding to each orthogonal frequency division multiplexing symbol.

[0068] Specifically, after completing frame synchronization and carrier synchronization, the receiver first extracts the time-domain sampling data of each OFDM symbol before removing the cyclic prefix from the received multiple OFDM symbols. Assuming the target time slot contains multiple OFDM symbols (14 in a 15kHz subcarrier spacing), for the nth OFDM symbol (n is the symbol index, ranging from 0 to the total number of OFDM symbols),... Let m represent the nth orthogonal frequency division multiplexing (OFDM) symbol, where m is the time-domain sampling index within the current symbol. According to the OFDM modulation principle, each OFDM symbol consists of a guard interval (i.e., cyclic prefix, CP) and a data portion (i.e., symbol tail data). The cyclic prefix and tail data corresponding to multiple OFDM symbols are obtained. Then, for each OFDM symbol, cross-correlation is performed using the obtained cyclic prefix and tail data to obtain the frequency offset estimate for each OFDM symbol. The following discussion uses the nth OFDM symbol as an example. To further illustrate the process of obtaining the corresponding frequency offset estimate, let's take an example:

[0069] Obtain the cyclic prefix and tail data of the nth orthogonal frequency division multiplexing (OFDM) symbol, where the tail data includes the tail portion of the valid data of the OFDM symbol. Each sampling point further determines the cyclic prefix length as follows: For the nth orthogonal frequency division multiplexing symbol, its cyclic prefix CP part corresponds to the time-domain sampling index k, and its value is denoted as k. k represents the k-th sampling point within the n-th orthogonal frequency division multiplexing (CP) symbol, and the value of k ranges from 0 to... Simultaneously, a reference sampling point is obtained for cross-correlation calculation with the k-th sampling point of the cyclic prefix portion, and its value is denoted as... ,in, This indicates the length of the Fast Fourier Transform (FFT). The mapping relationship for the tail data index is explained below: In a time-domain sampled sequence based on the FFT length, the valid data portion occupies the index. arrive Therefore, the index corresponding to the starting sampling point (k=0) of the tail data is... Then the index of the k-th sampling point in the time-domain sequence is The value is . This refers to the value of the tail data sampling point in the nth OFDM symbol, which corresponds to the kth sampling point of the cyclic prefix.

[0070] For 0 to Perform cross-correlation operation on the sampling points respectively to convert the cyclic prefix sampling points conjugate complex value With reference sampling point Multiplying these values ​​yields the frequency offset estimate for the nth orthogonal frequency division multiplexing symbol. The formula for cross-correlation is as follows: (5)

[0071] (5), among which, This represents the frequency offset estimate of the nth orthogonal frequency division multiplexing symbol. This represents the conjugate complex value of the k-th sampling point in the CP part of the nth orthogonal frequency division multiplexing symbol. Indicates the length of the cyclic prefix. Indicates the first The value of the tail data sampling point corresponding to each sampling point, where k represents the sampling point within the current nth orthogonal frequency division multiplexing symbol CP. Indicates the length of the FFT. This is used to extract the phase angle of the summation result within the parentheses of a complex number. Since frequency offset is mainly manifested as the phase rotation of the time-domain signal, the magnitude of the frequency offset can be obtained by taking the phase.

[0072] Through the above steps, the receiver can independently calculate the coarse frequency offset estimate for each OFDM symbol within the target time slot. This process utilizes the signal's inherent cyclic prefix characteristic, eliminating the need for additional pilot resources and thus achieving high spectral efficiency. Furthermore, this method maintains good robustness in multipath channel environments because CP cross-correlation is insensitive to amplitude fading caused by multipath interference; it primarily extracts phase information. This is achieved by obtaining the phase information of each symbol. The receiver can initially eliminate the linear phase rotation caused by carrier frequency offset, significantly improve the concentration of the constellation diagram, and provide an accurate initial estimate for subsequent fine compensation of residual frequency offset for far-end symbols, thereby reducing the error vector magnitude (EVM) of the entire time slot and improving demodulation performance.

[0073] It should be noted that the target time slot is any one of the multiple receiving time slots. In some embodiments of this application, steps S202-S208 can be performed on multiple time slots in parallel.

[0074] Step S204: Based on the frequency offset estimates corresponding to the multiple orthogonal frequency division multiplexing symbols, perform the first frequency offset compensation on the multiple orthogonal frequency division multiplexing symbols to obtain multiple target orthogonal frequency division multiplexing symbols.

[0075] In the technical solution provided in step S204, there are multiple ways to perform the first frequency offset compensation on the multiple orthogonal frequency division multiplexing symbols based on the frequency offset estimates corresponding to the multiple orthogonal frequency division multiplexing symbols to obtain multiple target orthogonal frequency division multiplexing symbols. For example, the methods include: obtaining the cyclic prefix length and time-domain sampling index value corresponding to the multiple orthogonal frequency division multiplexing symbols; determining the phase rotation factor corresponding to the multiple orthogonal frequency division multiplexing symbols based on the frequency offset estimates, cyclic prefix length, and time-domain sampling index value; and compensating the phase rotation factor corresponding to the multiple orthogonal frequency division multiplexing symbols to the corresponding orthogonal frequency division multiplexing symbols to obtain multiple target orthogonal frequency division multiplexing symbols.

[0076] After completing step S202, the receiver has obtained a coarse frequency offset estimate for each OFDM symbol within the time slot. However, the frequency offset estimate only represents the phase difference estimate generated by the symbol in the CP cross-correlation calculation, and its direct application to the received signal cannot eliminate the frequency offset. The carrier frequency offset (CFO) in the time domain manifests as a phase rotation of the received signal relative to the local oscillator signal that varies linearly with time. To recover the constellation point position of the original signal, a corresponding phase rotation factor must be constructed based on the estimated phase difference, and applied in the time domain to the complete OFDM symbol containing the cyclic prefix (CP) and the effective data portion (i.e.,...). Complex multiplication is performed to cancel out the phase rotation caused by frequency offset.

[0077] Specifically, based on the frequency offset estimates corresponding to multiple orthogonal frequency division multiplexing (OFDM) symbols, the first frequency offset compensation for these symbols is coarse, which makes the demodulated constellation diagram more concentrated. For each OFDM symbol, a phase rotation factor needs to be determined using the corresponding frequency offset estimate, cyclic prefix length, and time-domain sampling index value. This phase rotation factor is then compensated to the corresponding OFDM symbol to obtain the target OFDM symbol. The following discussion uses the nth OFDM symbol as an example. Taking any orthogonal frequency division multiplexing symbol as an example, the process of performing the first frequency offset compensation can be further explained. The first frequency offset compensation can be performed using the following formula (6):

[0078] (6).

[0079] in, This represents the compensated symbol (i.e., the nth orthogonal frequency division multiplexing symbol). (Corresponding target orthogonal frequency division multiplexing symbol); The nth orthogonal frequency division multiplexing symbol is uncompensated; j is the imaginary unit; The cyclic prefix length of the nth orthogonal frequency division multiplexing symbol; This is the time-domain sampling index value; Let be the phase rotation factor for the nth orthogonal frequency division multiplexing symbol; for the nth OFDM symbol, Multiplying the corresponding phase rotation factor point by point yields the compensated target orthogonal frequency division multiplexing symbol. .

[0080] By performing step S204 on multiple OFDM symbols, multiple target OFDM symbols are obtained. Phase correction is performed on all OFDM symbols in the time domain. The first frequency offset compensation effectively eliminates the linear phase rotation caused by the carrier frequency offset, making the compensated constellation diagram more concentrated than before compensation. Although due to the sparse distribution of single-column pilots, the coarse estimation based on CP cross-correlation still has some error at the far-end symbols (i.e., residual frequency offset), after this compensation step, the EVM (error vector magnitude) of the far-end symbols is significantly improved, and the divergence of constellation points is greatly reduced. This provides a more accurate initial state for subsequent steps (such as steps S206-S208) to perform fine estimation and compensation of residual frequency offset based on the equalized far-end symbol constellation points, thereby ultimately improving the demodulation performance of the entire time slot.

[0081] Since the target time slot is configured with only a single column of pilot symbols (e.g., the second symbol at the beginning of the time slot), although coarse frequency offset estimation based on CP can eliminate most of the linear phase rotation, a certain frequency offset will still remain after coarse compensation for symbols far from the pilot position (i.e., far-end symbols). This is because the carrier frequency offset may drift slightly over time or there may be other higher-order phase errors. This residual frequency offset will cause further rotation and divergence in the constellation diagram of far-end symbols, thereby degrading demodulation performance (e.g., increasing EVM). In order to perform fine compensation for these symbols that are greatly affected by the residual frequency offset, it is necessary to first identify which symbols belong to the far-end symbols. Step 206 calculates the time-domain distance between each symbol and the pilot symbol, and filters out the symbols whose distance exceeds a preset threshold as the target objects for subsequent residual frequency offset estimation based on constellation points.

[0082] Step S206: Determine the far-end symbol from multiple target orthogonal frequency division multiplexing (OFDM) symbols. The far-end symbol is the target OFDM symbol whose distance from the pilot symbol of the target time slot is greater than a preset threshold.

[0083] In the technical solution provided in step S206, determining the far-end symbol from multiple target orthogonal frequency division multiplexing (OFDM) symbols can be achieved in various ways, such as: obtaining the position index value of the pilot symbol in the target time slot; obtaining the position index values ​​corresponding to the multiple target OFDM symbols in the target time slot respectively; for each target OFDM symbol among the multiple target OFDM symbols, the target distance is determined in the following way, and the target OFDM symbol whose target distance is greater than a preset threshold is determined as the far-end symbol: the absolute value of the difference between the target position index value and the position index value of the pilot symbol is determined as the target distance of the first target OFDM symbol, wherein the first target OFDM symbol is any one of the multiple target OFDM symbols, and the target position index value is the position index value of the first target OFDM symbol.

[0084] Specifically, based on the DMRS configuration parameters (such as DMRS_Configuration, DMRS_Duration, PDSCH_Mapping, etc.) determined in step S202, the time-domain symbol position index K (i.e., the pilot symbol position index value) of the DMRS symbol in the target time slot is extracted. For example, assume that under the current single-column pilot configuration (DMRS is located in the 3rd symbol, i.e., the pilot symbol position index value is K=2).

[0085] The target time slot contains multiple OFDM symbols with an index range of 0 to N, where N is the total number of OFDM symbols (e.g., 0-13 at 15kHz). For any target orthogonal frequency division multiplexing symbol, its symbol index is denoted as n, which represents the target location index value of the symbol in the time slot.

[0086] For the nth target orthogonal frequency division multiplexing symbol (corresponding to the first target orthogonal frequency division multiplexing symbol mentioned above), calculate the distance between its position index n and the pilot symbol position index K. This distance reflects how close the symbol is to the pilot in the time domain; the greater the distance, the larger the frequency offset residual error based on the single-column pilot estimation may be. The target distance is taken as the absolute value of the difference (nK).

[0087] After obtaining the target distances corresponding to multiple target orthogonal frequency division multiplexing (OFDM) symbols, the OFDM symbols whose target distances are greater than a preset threshold are identified as far-end symbols. There can be multiple far-end symbols. For example, the preset threshold is set to 9. The position index values ​​of the multiple target OFDM symbols are 0-13, and the position index value of the pilot symbol is 2. In this case, the target OFDM symbols with position indices of 12 and 13 are far-end symbols.

[0088] In step S206, the receiver accurately identifies the far-end symbols in the time slot that are significantly affected by residual frequency offset. By setting a distance threshold to filter out far-end symbols, this application can perform targeted subsequent fine estimation of residual frequency offset based on constellation points for these key symbols. This differentiated processing avoids unnecessary complex calculations for near-end symbols (where the frequency offset is already relatively accurate), reducing the overall algorithm complexity, while ensuring that a more accurate compensation algorithm is applied to the far-end symbols where demodulation performance is most vulnerable. Thus, while ensuring controllable system overhead, it minimizes the EVM across all time slots and improves the demodulation reliability of the communication system.

[0089] Step S208: Determine the average frequency offset compensation value corresponding to the far-end symbol, and perform a second frequency offset compensation on the far-end symbol based on the average frequency offset compensation value to obtain the far-end symbol after the second frequency offset compensation. The average frequency offset compensation value is determined based on the frequency offset compensation values ​​of the target constellation points mapped to the far-end symbol in multiple quadrants.

[0090] In the technical solution provided in step S208, determining the average frequency offset compensation value corresponding to the far-end symbol includes: determining multiple reference constellation points corresponding to the far-end symbol; determining multiple target constellation points from the multiple reference constellation points, wherein the multiple target constellation points correspond one-to-one with multiple quadrants; determining the frequency offset compensation value corresponding to each of the multiple target constellation points, wherein the frequency offset compensation value is used to compensate for the phase rotation caused by the frequency offset of the target constellation points; and determining the average value of the frequency offset compensation values ​​corresponding to the multiple target constellation points as the average frequency offset compensation value corresponding to the far-end symbol.

[0091] In the above steps, determining multiple target constellation points from multiple reference constellation points includes: determining the constellation diagram corresponding to the modulation scheme used by the far-end symbol, wherein the constellation diagram contains the positions of all reference constellation points mapped to multiple quadrants, the multiple quadrants including the first quadrant to the fourth quadrant; in each quadrant of the multiple quadrants of the constellation diagram, selecting the reference constellation point farthest from the origin of the constellation diagram to determine the target constellation point, thus obtaining multiple target constellation points.

[0092] Determining the frequency offset compensation values ​​corresponding to multiple target constellation points includes: determining multiple expected values ​​corresponding to multiple target constellation points, wherein each target constellation point corresponds to one expected value; obtaining the number of constellation points mapped from multiple reference constellation points to each quadrant in multiple quadrants; obtaining the theoretical reference phase corresponding to each of the multiple target constellation points; and determining the frequency offset compensation values ​​corresponding to each of the multiple target constellation points based on the number of constellation points corresponding to each quadrant, the expected values ​​corresponding to the target constellation points in each quadrant, and the theoretical reference phase.

[0093] To further eliminate the residual frequency offset of far-end symbols, this application proposes a fine-grained frequency offset estimation and compensation mechanism based on constellation points. This mechanism utilizes the known modulation format characteristics of far-end symbols (such as the symmetry and determinism of QAM constellation diagrams) to estimate the residual frequency offset by statistically analyzing the phase shift of specific reference constellation points. Specifically, the reference constellation point farthest from the origin in each quadrant is selected as the observation target because these points are relatively less affected by noise and amplitude distortion, and their phase information is more reliable. By calculating the difference between the actual and theoretical phases of these target constellation points and combining this with the statistical distribution characteristics of constellation points within the quadrant, the residual frequency offset can be estimated with high accuracy. Averaging the frequency offset compensation values ​​estimated from the four quadrants yields a more robust average frequency offset compensation value, which is used for a second frequency offset compensation of the far-end symbols, thereby significantly reducing the EVM of the far-end symbols and improving demodulation performance. The process of the second frequency offset compensation is further explained below using any one far-end symbol (e.g., the nth far-end symbol) as an example:

[0094] First, the receiver performs channel equalization on the signal of the nth far-end symbol after the first frequency offset compensation, to obtain the frequency-equalized data of the far-end symbol. Subsequently, the frequency-equalized data of the far-end symbol is mapped into constellation points in complex form. The real and imaginary parts of each data point are extracted to determine its demodulated position in the complex plane. These constellation points are the reference constellation points. Multiple reference constellation points corresponding to the far-end symbol are determined through the above steps. Due to residual frequency offset, these reference constellation points will rotate and diverge relative to their ideal positions. Taking 16QAM as an example, there are 16 reference constellation points. (where i takes values ​​from 1 to 16), distributed across the four quadrants.

[0095] The receiver determines the known modulation scheme (such as 16QAM, 64QAM, etc.) used by the current far-end symbol based on pre-acquired modulation configuration information (e.g., notification via physical layer control channel or higher-layer signaling). Based on this known modulation scheme, the receiver obtains the corresponding ideal reference constellation diagram (i.e., the constellation diagram corresponding to the modulation scheme). This constellation diagram contains the theoretical positions of all reference constellation points mapped to the first to fourth quadrants under ideal noise-free and frequency-offset conditions.

[0096] To reduce the impact of noise and improve the accuracy of frequency offset estimation, in each quadrant, the reference constellation point farthest from the origin of the constellation diagram is selected as the target constellation point for that quadrant. This results in four target constellation points. The process of determining the frequency offset compensation values ​​corresponding to these multiple target constellation points is explained below:

[0097] The frequency offset compensation value of the first target constellation point is determined based on the number of constellation points corresponding to the first quadrant, the mathematical expectation value of the first target constellation point, and the theoretical reference phase. The first target constellation point is the target constellation point mapped to the first quadrant. It can be expressed by the following formula (7):

[0098] (7), among which, This represents the frequency offset compensation value for the first target constellation point. Indicates being in The number of constellation points (i.e., the number of constellation points corresponding to the first quadrant); This represents the expected value of the first target constellation point. This represents the constellation point in the first quadrant that is furthest from the origin in the balanced data (i.e., the first target constellation point). For π; This represents the theoretical reference phase of the first target constellation point. This represents the arctangent function, used to extract the phase angle of a complex number.

[0099] The frequency offset compensation value of the second target constellation point is determined based on the number of constellation points corresponding to the second quadrant, the mathematical expectation value of the second target constellation point, and the theoretical reference phase. The second target constellation point is the target constellation point mapped to the second quadrant. It can be expressed by the following formula (8):

[0100] (8), among which, This represents the frequency offset compensation value for the second target constellation point. This indicates the number of constellation points located in the second quadrant. This represents the expected value of the second target constellation point. This represents the constellation point in the second quadrant that is furthest from the origin in the balanced data (i.e., the second target constellation point). For π; This represents the theoretical reference phase of the second target constellation point. This represents the arctangent function, used to extract the phase angle of a complex number.

[0101] The frequency offset compensation value of the third target constellation point is determined based on the number of constellation points corresponding to the third quadrant, the mathematical expectation value of the third target constellation point, and the theoretical reference phase. The third target constellation point is the target constellation point mapped to the third quadrant. It can be expressed by the following formula (9):

[0102] (9), among which, This represents the frequency offset compensation value for the third target constellation point. This indicates the number of constellation points located in the third quadrant. This represents the expected value of the third target constellation point. This represents the constellation point in the third quadrant that is furthest from the origin in the balanced data (i.e., the third target constellation point). For π; This represents the theoretical reference phase of the third target constellation point. This represents the arctangent function, used to extract the phase angle of a complex number.

[0103] The frequency offset compensation value of the fourth target constellation point is determined based on the number of constellation points corresponding to the fourth quadrant, the mathematical expectation value of the fourth target constellation point, and the theoretical reference phase. The fourth target constellation point is the target constellation point mapped to the fourth quadrant. It can be expressed by the following formula (10):

[0104] (10)

[0105] in, This represents the frequency offset compensation value for the fourth target constellation point. This indicates the number of constellation points located in the fourth quadrant; This represents the expected value of the fourth target constellation point. This represents the constellation point in the fourth quadrant that is furthest from the origin (i.e., the fourth target constellation point) in the balanced data. For π; This represents the theoretical reference phase of the fourth target constellation point. This represents the arctangent function, used to extract the phase angle of a complex number.

[0106] The next step is to determine the average frequency offset compensation value corresponding to multiple target constellation points as the average frequency offset compensation value corresponding to the far-end symbol. Finally, a second frequency offset compensation is performed on the nth far-end symbol based on the average frequency offset compensation value. The second frequency offset compensation process involves applying an additional phase rotation correction to the far-end symbol in the time or frequency domain to eliminate residual frequency offset, resulting in the far-end symbol after the second frequency offset compensation. For example, when the far-end symbols are 12 and 13, this calculated average frequency offset compensation value is applied to far-end symbols 12 and 13 respectively to correct the frequency offset of the far-end symbols and reduce their EVM.

[0107] In step S208, this application utilizes the constellation point distribution characteristics corresponding to the far-end symbol, specifically selecting far-end reference points in each quadrant that are relatively less affected by noise, and combining this with the statistical number of constellation points within each quadrant, to accurately estimate the residual frequency offset error after the first coarse compensation. By averaging the frequency offset estimates across the four quadrants, estimation biases caused by noise and anomalies in individual constellation points are further suppressed. A second frequency offset compensation is then performed on the far-end symbol based on this average frequency offset compensation value, which significantly corrects the phase rotation of the far-end symbol, making the constellation points more concentrated, thereby effectively reducing the EVM (Error Vector Magnitude) of the far-end symbol.

[0108] Figure 4 This is a signal processing flowchart provided according to an embodiment of this application, illustrating the processing process of received signals by an OFDM receiver in related technologies, such as... Figure 4 As shown, during demodulation, the channel receiver first performs down-conversion on the received signal, then performs frame synchronization and carrier synchronization (not shown in the figure). After synchronization, OFDM demodulation is performed on the signal: removing the cyclic prefix, converting the time domain to the frequency domain (converting the time domain signal to the frequency domain signal), de-resource mapping, channel estimation (the process of estimating the channel's gain and phase impact on each subcarrier based on the known reference signal (local pilot), channel equalization, demodulation, descrambling, and decoding to recover the original bits, and calculating the bit error rate.

[0109] In some embodiments of this application, a signal processing flow is provided, relative to Figure 4The provided technical process, in addition to removing the cyclic prefix, converting the time domain to the frequency domain (converting the time domain signal to the frequency domain signal), de-resource mapping, channel estimation (the process of estimating the channel's gain and phase impact on each subcarrier based on the known reference signal (local pilot), channel equalization, and demodulation, introduces CP frequency offset compensation (i.e., the first frequency offset compensation) during the time domain to frequency domain conversion, and performs channel equalization, then performs frequency offset compensation again (i.e., the second frequency offset compensation), and finally performs demodulation to obtain the constellation diagram (this constellation diagram is the actual constellation diagram obtained after demodulation after two frequency offset compensations).

[0110] In some embodiments of this application, for the use of Figure 4 The EVM obtained by simulating the process was compared with the EVM obtained by simulating according to the method of this application. The DMRS configuration is as follows: DMRS_Configuration ='Type1', DMRS_Duration ='Single Symbol', DMRS_add_pos=0, PDSCH_Mapping='TypeA', DMRS_typeA_pos=2; the signal-to-noise ratio is set to 30dB, the Doppler frequency shift is added to 100Hz, the path loss is set to 0dB, -10dB, and -20dB respectively, the subcarrier spacing is set to 15KHz, the system bandwidth is 100MHz, the number of OFDM symbols per time slot is 14, the CP type is conventional, the modulation method is selected as 16QAM, and the DMRS adopts type1.

[0111] Figure 5 This is a schematic diagram of a first type of EVM provided according to an embodiment of this application, illustrating the use of... Figure 4 The process is simulated to obtain the EVM. iSymb represents a symbol. iSymb:0-iSymb:13 represent 14 orthogonal frequency division multiplexing symbols with index positions 0-13. Among them, iSymb:2 corresponds to the pilot symbol. iSymb:12 and 13 are far-end symbols. Figure 5The EVM values ​​for each orthogonal frequency division multiplexing symbol are as follows: iSymb: 0 EVM: 0.078843; iSymb: 1 EVM: 0.068101; iSymb: 3 EVM: 0.04727; iSymb: 4 EVM: 0.037534; iSymb: 5 EVM: 0.029532; iSymb: 6 EVM: 0.024197; iSymb: 7 EVM: 0.023816; iSymb: 8 EVM: 0.029325; iSymb: 9 EVM: 0.036288; iSymb: 10 EVM: 0.046768; iSymb: 11 EVM: 0.056815; iSymb: 12 EVM: 0.067846; iSymb: 13 EVM: 0.07799.

[0112] Figure 6 This is a second EVM schematic diagram provided according to an embodiment of this application, showing the EVM obtained by simulation using the method of this embodiment. iSymb represents a symbol, and iSymb:0-iSymb:13 represents 14 orthogonal frequency division multiplexing symbols with index positions 0-13, where iSymb:2 corresponds to the pilot symbol. iSymb:12 and 13 are far-end symbols. Figure 5 The EVM values ​​for each orthogonal frequency division multiplexing symbol are as follows: iSymb: 0 EVM: 0.078843; iSymb: 1 EVM: 0.068101; iSymb: 3 EVM: 0.04727; iSymb: 4 EVM: 0.037534; iSymb: 5 EVM: 0.029532; iSymb: 6 EVM: 0.024197; iSymb: 7 EVM: 0.023816; iSymb: 8 EVM: 0.029325; iSymb: 9 EVM: 0.036288; iSymb: 10 EVM: 0.046768; iSymb: 11 EVM: 0.056815; iSymb: 12 EVM: 0.061584; iSymb: 13 EVM: 0.071452.

[0113] according to Figure 5 We can see that the EVM for the far-end symbol 12 is 0.067846 (6.7846%), and the EVM for symbol 13 is 0.07799 (7.799%). Figure 6 Based on the improved scheme of this application, the EVM of remote symbol 12 is 0.061584 (6.1584%), and the EVM of symbol 13 is 0.071452 (7.1452%), relative to... Figure 5The EVM for far-end symbol 12 was reduced by 9.23%, and the EVM for symbol 13 was reduced by 8.38%, improving demodulation performance.

[0114] By executing steps S202-S208, the method of this embodiment first calculates a coarse frequency offset based on the CP cross-correlation principle and compensates for this value to each symbol (first frequency offset compensation). After demodulation, the method uses the mapping position after demodulation of a certain far-end symbol and calculates the mathematical expectation of the mapping to the four outermost constellation points. It then calculates the residual frequency offset between the mathematical expectation and the mapping position and compensates for the residual frequency offset to the far-end symbol in the current time slot (second frequency offset compensation). Finally, it compares the EVM values ​​before and after compensation. The method of this embodiment optimizes the frequency offset based on CP cross-correlation, eliminating the need for additional pilot calculations. It also maintains good robustness in multipath channels and is compatible with other frequency domain estimation algorithms. The method of this embodiment calculates the residual frequency offset based on far-end symbol information, rather than pilot information. This scheme is applicable not only to NR but also to LTE, making it widely applicable and also suitable for other QAM modulation schemes.

[0115] Figure 7 This is a schematic diagram of a combined frequency offset compensation device according to an embodiment of this application, comprising:

[0116] The first determining module 702 is used to determine the frequency offset estimates corresponding to multiple orthogonal frequency division multiplexing symbols in the target time slot when only a single column of pilot symbols is configured in the target time slot. The frequency offset estimates are the phase difference estimates caused by the frequency offset of the orthogonal frequency division multiplexing symbols.

[0117] The first frequency offset compensation module 704 is used to perform the first frequency offset compensation on the multiple orthogonal frequency division multiplexing symbols based on the frequency offset estimates corresponding to the multiple orthogonal frequency division multiplexing symbols, so as to obtain multiple target orthogonal frequency division multiplexing symbols.

[0118] The second determining module 706 is used to determine the far-end symbol from multiple target orthogonal frequency division multiplexing symbols, wherein the far-end symbol is a target orthogonal frequency division multiplexing symbol whose distance from the pilot symbol of the target time slot is greater than a preset threshold.

[0119] The second frequency offset compensation module 708 is used to determine the average frequency offset compensation value corresponding to the far-end symbol, and to perform a second frequency offset compensation on the far-end symbol based on the average frequency offset compensation value to obtain the far-end symbol after the second frequency offset compensation. The average frequency offset compensation value is determined based on the frequency offset compensation value of the target constellation points mapped to the far-end symbol in multiple quadrants.

[0120] It should be noted that, Figure 7 The combined frequency offset compensation device shown is used to perform Figure 2 The combined frequency offset compensation method shown, therefore Figure 2 The relevant explanations in the joint frequency offset compensation method also apply to this joint frequency offset compensation device, and will not be repeated here.

[0121] It should be noted that each module in the above-mentioned joint frequency offset compensation device can be a program module (for example, a set of program instructions to implement a certain function) or a hardware module. For the latter, it can be manifested in the following forms, but is not limited to them: each of the above modules is manifested as a processor, or the functions of each of the above modules are implemented by a processor.

[0122] This application also provides a non-volatile storage medium, which includes a stored program, wherein, when the program is running, it controls the device where the non-volatile storage medium is located to execute the joint frequency offset compensation method of any of the above embodiments.

[0123] This application also provides an electronic device, which includes a processor for running a program, wherein the combined frequency offset compensation method of any of the above embodiments is executed during program execution.

[0124] According to another aspect of the embodiments of this application, a computer program product is also provided, including a computer program that, when executed by a processor, implements the joint frequency offset compensation method of any of the above embodiments.

[0125] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0126] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection between units or modules may be electrical or other forms.

[0127] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0128] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0129] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to related technologies, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0130] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A joint frequency offset compensation method, characterized in that, include: When only a single column of pilot symbols is configured in the target time slot, the frequency offset estimates corresponding to multiple orthogonal frequency division multiplexing symbols in the target time slot are determined respectively, wherein the frequency offset estimates are the phase difference estimates caused by the frequency offset corresponding to the orthogonal frequency division multiplexing symbols; Based on the frequency offset estimates corresponding to the plurality of orthogonal frequency division multiplexing symbols, the plurality of orthogonal frequency division multiplexing symbols are subjected to the first frequency offset compensation to obtain a plurality of target orthogonal frequency division multiplexing symbols; The far-end symbol is determined from the plurality of target orthogonal frequency division multiplexing symbols, wherein the far-end symbol is a target orthogonal frequency division multiplexing symbol whose distance relative to the pilot symbol of the target time slot is greater than a preset threshold; The average frequency offset compensation value corresponding to the far-end symbol is determined, and the far-end symbol is subjected to a second frequency offset compensation based on the average frequency offset compensation value to obtain the far-end symbol after the second frequency offset compensation. The average frequency offset compensation value is determined based on the frequency offset compensation value of the target constellation points mapped to the far-end symbol in multiple quadrants.

2. The method according to claim 1, characterized in that, Determine the frequency offset estimates for each of the multiple orthogonal frequency division multiplexing symbols within the target time slot, including: Obtain the cyclic prefix and tail data corresponding to the plurality of orthogonal frequency division multiplexing symbols respectively; For each of the plurality of orthogonal frequency division multiplexing (OFDM) symbols, cross-correlation is performed on the cyclic prefix and the tail data corresponding to the OFDM symbol to obtain the frequency offset estimate corresponding to each OFDM symbol.

3. The method according to claim 1, characterized in that, Based on the frequency offset estimates corresponding to the plurality of orthogonal frequency division multiplexing (OFDM) symbols, a first frequency offset compensation is performed on the plurality of OFDM symbols to obtain a plurality of target OFDM symbols, including: Obtain the cyclic prefix length and time-domain sampling index value corresponding to the plurality of orthogonal frequency division multiplexing symbols; The phase rotation factor corresponding to each of the multiple orthogonal frequency division multiplexing symbols is determined based on the frequency offset estimate, the cyclic prefix length, and the time-domain sampling index value. The phase rotation factors corresponding to the plurality of orthogonal frequency division multiplexing symbols are compensated to the corresponding orthogonal frequency division multiplexing symbols to obtain the plurality of target orthogonal frequency division multiplexing symbols.

4. The method according to claim 1, characterized in that, Determining the far-end symbol from the plurality of target orthogonal frequency division multiplexing symbols includes: Obtain the position index value of the pilot symbol in the target time slot; Obtain the position index values ​​corresponding to the plurality of target orthogonal frequency division multiplexing symbols in the target time slot; For each target orthogonal frequency division multiplexing (OFDM) symbol among the plurality of target OFDM symbols, the target distance is determined in the following manner, and the target OFDM symbols whose target distance is greater than the preset threshold are determined as the far-end symbols: The absolute value of the difference between the target location index value and the location index value of the pilot symbol is determined as the target distance of the first target orthogonal frequency division multiplexing symbol, wherein the first target orthogonal frequency division multiplexing symbol is any one of the plurality of target orthogonal frequency division multiplexing symbols, and the target location index value is the location index value of the first target orthogonal frequency division multiplexing symbol.

5. The method according to claim 1, characterized in that, Determining the average frequency offset compensation value corresponding to the far-end symbol includes: Determine the multiple reference constellation points corresponding to the remote symbol; Multiple target constellation points are determined from multiple reference constellation points, wherein the multiple target constellation points correspond one-to-one with the multiple quadrants; Determine the frequency offset compensation value corresponding to each of the plurality of target constellation points, wherein the frequency offset compensation value is used to compensate for the phase rotation of the target constellation points caused by frequency offset; The average value of the frequency offset compensation values ​​corresponding to the multiple target constellation points is determined as the average frequency offset compensation value corresponding to the far-end symbol.

6. The method according to claim 5, characterized in that, Multiple target constellation points are determined from multiple reference constellation points, including: Determine the constellation diagram corresponding to the modulation scheme adopted by the far-end symbol, wherein the constellation diagram includes the positions of all reference constellation points mapped to the plurality of quadrants, the plurality of quadrants including the first quadrant to the fourth quadrant; In each of the multiple quadrants of the constellation diagram, the reference constellation point farthest from the origin of the constellation diagram is selected to determine the target constellation point, thus obtaining the multiple target constellation points.

7. The method according to claim 5, characterized in that, Determining the frequency offset compensation values ​​corresponding to the plurality of target constellation points includes: Determine multiple mathematical expectation values ​​corresponding to the multiple target constellation points, wherein one target constellation point corresponds to one mathematical expectation value; Obtain the number of constellation points mapped from the plurality of reference constellation points to each of the plurality of quadrants; Obtain the theoretical reference phase corresponding to each of the multiple target constellation points; Based on the number of constellation points corresponding to the multiple quadrants, the expected value of the target constellation point corresponding to the multiple quadrants, and the theoretical reference phase, the frequency offset compensation value corresponding to the multiple target constellation points is determined.

8. A combined frequency offset compensation device, characterized in that, include: The first determining module is used to determine the frequency offset estimates corresponding to multiple orthogonal frequency division multiplexing symbols in the target time slot when only a single column of pilot symbols is configured in the target time slot. The frequency offset estimates are the phase difference estimates caused by the frequency offset of the orthogonal frequency division multiplexing symbols. The first frequency offset compensation module is used to perform the first frequency offset compensation on the multiple orthogonal frequency division multiplexing symbols based on the frequency offset estimation values ​​corresponding to the multiple orthogonal frequency division multiplexing symbols respectively, so as to obtain multiple target orthogonal frequency division multiplexing symbols. The second determining module is used to determine the far-end symbol from the plurality of target orthogonal frequency division multiplexing symbols, wherein the far-end symbol is a target orthogonal frequency division multiplexing symbol whose distance relative to the pilot symbol of the target time slot is greater than a preset threshold; The second frequency offset compensation module is used to determine the average frequency offset compensation value corresponding to the far-end symbol, and to perform a second frequency offset compensation on the far-end symbol based on the average frequency offset compensation value to obtain the far-end symbol after the second frequency offset compensation. The average frequency offset compensation value is determined based on the frequency offset compensation value of the target constellation points mapped to the far-end symbol in multiple quadrants.

9. A non-volatile storage medium, characterized in that, The non-volatile storage medium stores a program, wherein when the program is executed, it controls the device containing the non-volatile storage medium to perform the joint frequency offset compensation method according to any one of claims 1 to 7.

10. An electronic device, characterized in that, include: A memory and a processor, the processor being configured to run a program stored in the memory, wherein the program, when running, executes the joint frequency offset compensation method according to any one of claims 1 to 7.

Images