Radio frequency signal demodulation method and device

Abstract

The invention discloses a radio frequency signal demodulation method and device. The method comprises the following steps: receiving an OFDM (Orthogonal Frequency Division Multiplexing)-based radio frequency signal comprising a plurality of subcarriers, each subcarrier time slot comprising a column of pilot signals; performing conversion processing on the radio frequency signal to obtain a frequency domain signal corresponding to each subcarrier, the frequency domain signal comprising a plurality of OFDM symbols; for each frequency domain signal, primary frequency offset compensation is carried out on each OFDM symbol in the frequency domain signal based on the pilot signal, and for a far-end OFDM symbol whose distance from the position of the pilot signal exceeds a preset distance, secondary frequency offset compensation is carried out on the far-end OFDM symbol based on the distribution state of each constellation point mapped to the constellation diagram; and recovering each frequency domain signal subjected to frequency offset compensation into original bit data. According to the method and the device, the technical problem that the error vector amplitude of a remote symbol demodulation result is relatively large when only a single-column pilot signal is configured in a subcarrier time slot in a traditional demodulation scheme is solved.

Description

Technical Field

[0001] This application relates to the field of wireless communication technology, and more specifically, to a method and apparatus for demodulating radio frequency signals. Background Technology

[0002] In the field of wireless communication, especially in 5G mobile communication, OFDM (Orthogonal Frequency Division Multiplexing) technology has become a key technology for physical layer signal transmission due to its high spectral efficiency and robust resistance to multipath interference. However, frequency offset is one of the main factors affecting the performance of OFDM systems. It can lead to the destruction of orthogonality between subcarriers, resulting in inter-symbol interference and phase rotation, which seriously affects demodulation performance and bit error rate.

[0003] In related technologies, OFDM systems typically utilize pilot signals distributed across time slots for channel estimation and frequency offset compensation, a process crucial for ensuring correct signal demodulation. When multiple pilots are deployed within each time slot, frequency offset compensation can be performed relatively accurately because the pilot signals provide sufficient channel information to precisely estimate and compensate for the frequency offset.

[0004] However, in resource-constrained or specific application scenarios, it becomes common to configure only a single column of pilots per time slot. In this case, although the frequency offset compensation at the pilot is accurate, the frequency offset compensation for signals far from the pilot (far-end symbols) becomes inaccurate due to the lack of sufficient local reference signals. This leads to a decrease in the demodulation performance of far-end symbols, manifested as an increase in the error vector amplitude and a higher bit error rate during decoding, thus affecting the overall communication quality.

[0005] There is currently no effective solution to the above problems. Summary of the Invention

[0006] This application provides a method and apparatus for demodulating radio frequency signals, which at least solves the technical problem that the error vector amplitude of the far-end symbol demodulation result is large when only a single pilot signal is configured in the subcarrier time slot in traditional demodulation schemes.

[0007] According to one aspect of the embodiments of this application, a demodulation method for radio frequency (RF) signals is provided, comprising: receiving an OFDM-based RF signal, wherein the RF signal includes multiple subcarriers, and each subcarrier includes a pilot signal in its time slot; performing conversion processing on the RF signal to obtain a frequency domain signal corresponding to each subcarrier, wherein the frequency domain signal includes multiple OFDM symbols; for each frequency domain signal, performing initial frequency offset compensation on each OFDM symbol in the frequency domain signal based on the target pilot signal in the time slot of the subcarrier corresponding to the frequency domain signal; for a far-end OFDM symbol whose position is more than a preset distance from the pilot signal, performing a second frequency offset compensation on the far-end OFDM symbol based on the distribution state of each constellation point mapped to the constellation diagram; and restoring each frequency domain signal after frequency offset compensation to its original bit data.

[0008] Optionally, the radio frequency signal is converted to obtain a frequency domain signal corresponding to each subcarrier, including: performing down-conversion processing on the radio frequency signal to obtain a first signal, wherein the center frequency of the first signal is the baseband frequency; performing frame synchronization processing on the first signal to divide the first signal into multiple subcarriers; for each subcarrier, removing the cyclic prefix of the subcarrier, and using fast Fourier transform to convert the subcarrier from a time domain signal to a frequency domain signal.

[0009] Optionally, the initial frequency offset compensation is performed on each OFDM symbol in the frequency domain signal based on the target pilot signal in the subcarrier time slot corresponding to the frequency domain signal, including: determining the signal-to-noise ratio (SNR) corresponding to the radio frequency signal; if the SNR is greater than a preset SNR threshold, performing the initial frequency offset compensation on each OFDM symbol in the frequency domain signal based on the target pilot signal using a zero-forcing algorithm; if the SNR is not greater than the preset SNR threshold, performing the initial frequency offset compensation on each OFDM symbol in the frequency domain signal based on the target pilot signal using a minimum mean square error algorithm.

[0010] Optionally, the zero-forcing algorithm is used to perform initial frequency offset compensation for each OFDM symbol in the frequency domain signal based on the target pilot signal, including: performing channel estimation based on the following formula to determine the channel response matrix: In the formula, s represents the target pilot signal transmitted from the transmitter, y represents the received target pilot signal, and h represents the channel response matrix; signal estimation is performed for each OFDM symbol in the frequency domain signal based on the following formula: In the formula, Denotes the conjugate transpose of h. Represents OFDM symbols within the frequency domain signal. Represents the estimated original OFDM symbols; based on each original OFDM symbol, the corresponding OFDM symbol in the frequency domain signal is subjected to initial frequency offset compensation.

[0011] Optionally, the minimum mean square error algorithm is used to perform initial frequency offset compensation for each OFDM symbol in the frequency domain signal based on the target pilot signal, including: performing channel estimation based on the following formula to determine the channel response matrix and noise: In the formula, s represents the target pilot signal transmitted from the transmitter, y represents the received target pilot signal, h represents the channel response matrix, and n represents noise; signal estimation is performed for each OFDM symbol in the frequency domain signal based on the following formula: In the formula, Denotes the conjugate transpose of h. Represents OFDM symbols within the frequency domain signal. Represents the estimated original OFDM symbols; based on each original OFDM symbol, the corresponding OFDM symbol in the frequency domain signal is subjected to initial frequency offset compensation.

[0012] Optionally, a second frequency offset compensation is performed on the far-end OFDM symbol based on the distribution of each constellation point in the constellation diagram. This includes: for each far-end OFDM symbol that has completed the initial frequency offset compensation, mapping the far-end OFDM symbol to the constellation diagram based on a preset quadrature amplitude modulation order to obtain multiple constellation points; determining the frequency offset estimate corresponding to each quadrant based on the distribution of the multiple constellation points in the four quadrants, and determining the average value of the frequency offset estimates corresponding to the four quadrants as the target frequency offset estimate; and performing a second frequency offset compensation on the far-end OFDM symbol based on the target frequency offset estimate.

[0013] Optionally, the frequency offset estimate for each quadrant is determined based on the distribution of multiple constellation points in the four quadrants, including: determining the frequency offset estimate for each quadrant according to the following formulas: , , , In the formula, , , , These represent the frequency offset estimates for the first, second, third, and fourth quadrants, respectively. , , , These represent the number of constellation points in the first, second, third, and fourth quadrants, respectively. , , , These represent the expected number of constellation points that should be located in the first, second, third, and fourth quadrants, respectively.

[0014] Optionally, the frequency domain signals that have undergone frequency offset compensation are restored to their original bit data, including: for each frequency domain signal that has undergone frequency offset compensation, the frequency domain signals are sequentially demodulated, descrambled, and decoded to restore the frequency domain signals to their original bit data.

[0015] According to another aspect of the embodiments of this application, a demodulation apparatus for radio frequency signals is also provided, comprising: a receiving module for receiving an OFDM-based radio frequency signal, wherein the radio frequency signal includes multiple subcarriers, and each subcarrier includes a pilot signal in its time slot; a conversion module for converting the radio frequency signal to obtain a frequency domain signal corresponding to each subcarrier, wherein the frequency domain signal includes multiple OFDM symbols; a compensation module for performing initial frequency offset compensation on each OFDM symbol in the frequency domain signal based on the pilot signal in the time slot of the subcarrier corresponding to the frequency domain signal for each frequency domain signal, and performing a second frequency offset compensation on the far-end OFDM symbol whose position is more than a preset distance from the pilot signal based on the distribution state of each constellation point mapped to the constellation diagram of the far-end OFDM symbol; and a recovery module for restoring each frequency domain signal after frequency offset compensation to its original bit data.

[0016] According to another aspect of the embodiments of this application, a computer program product is also provided, the computer program product comprising: a computer program, wherein the computer program, when executed by a processor, implements the above-described method for demodulating radio frequency signals.

[0017] According to another aspect of the embodiments of this application, an electronic device is also provided, the electronic device including: a memory and a processor, wherein the memory stores a computer program, and the processor is configured to execute the above-described demodulation method of radio frequency signals through the computer program.

[0018] In this embodiment, considering that when only a single pilot signal is configured in the subcarrier time slot, the frequency offset compensation of the far-end OFDM symbols, which are far from the pilot signal, becomes inaccurate due to the lack of sufficient local reference signals, the following approach is adopted: Based on the frequency offset compensation of each received OFDM symbol according to the pilot signal, a second frequency offset compensation is performed on the far-end OFDM symbols based on the distribution of constellation points mapped to the constellation diagram. This improves the accuracy of the frequency offset compensation and reduces the error vector amplitude and bit error rate of the overall signal demodulation result. This scheme effectively solves the technical problem of large error vector amplitude in the demodulation result of far-end symbols when only a single pilot signal is configured in the subcarrier time slot, a problem inherent in traditional demodulation schemes. 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 flowchart illustrating an optional radio frequency signal demodulation method according to an embodiment of this application;

[0021] Figure 2 This is a schematic diagram of an optional radio frequency signal according to an embodiment of this application;

[0022] Figure 3a This is a schematic diagram showing the result of mapping a subcarrier to a constellation diagram according to a conventional scheme;

[0023] Figure 3b This is a schematic diagram showing the result of subcarrier mapping to a constellation diagram according to an embodiment of this application;

[0024] Figure 4 This is a schematic diagram of an optional radio frequency signal demodulation device according to an embodiment of this application;

[0025] Figure 5 This is a schematic diagram of the structure of an optional electronic device according to an embodiment of this application. Detailed Implementation

[0026] 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.

[0027] It should be noted that the terms "first," "second," etc., used in the specification, claims, and 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.

[0028] To better understand the embodiments of this application, the following is a translation and explanation of some nouns or terms that appear in the description of the embodiments of this application:

[0029] OFDM (Optical Frequency Direction Modulation) is a multi-carrier modulation technique widely used in wireless communication. It divides a high-speed serial data stream into multiple low-speed parallel data streams, which are then modulated and transmitted on different carriers. Each carrier is called a subcarrier, and they are orthogonal in frequency, effectively utilizing spectrum resources and resisting inter-symbol interference caused by multipath propagation. OFDM technology improves bandwidth utilization and robustness of data transmission through its high speed and high frequency efficiency.

[0030] Pilot: In wireless communication systems, especially OFDM systems, a pilot is a known, predefined signal that is periodically inserted into the transmitted data stream. The main function of the pilot signal is to provide a reference point at the receiver for channel estimation and frequency synchronization.

[0031] Error Vector Magnitude (EVM) is a metric for measuring the quality of a modulated signal, commonly used to evaluate the performance of modulators and demodulators in communication systems. Ideally, the modulated signal should fall precisely at its predetermined position on the constellation diagram. However, real-world signals deviate from these positions due to various factors such as noise, phase noise, frequency shift, and linearity issues. EVM quantifies the degree of this deviation. A lower EVM value indicates better signal quality, a lower bit error rate, and higher reliability and efficiency of the communication system.

[0032] Block Error Rate (BLER) is a metric that measures the percentage of data blocks transmitted incorrectly in a wireless communication system. It represents the proportion of an entire data block that is erroneous during transmission. Data blocks are typically encoded into a series of codewords before transmission. At the receiving end, if any bit in a data block is incorrect during decoding, the entire data block is considered erroneous. BLER is an important indicator for evaluating the performance of communication systems, especially for systems employing forward error correction coding, as it reflects the system's error detection and correction capabilities under different conditions.

[0033] Quadrature Amplitude Modulation (QAM) is a modulation technique that encodes information onto the amplitude and phase of a carrier signal. In QAM, data is mapped onto a constellation diagram in the complex plane, with each constellation point representing a specific combination of amplitude and phase. QAM modulation includes various orders of modulation schemes, such as 4QAM (using 4 constellation points, each symbol carrying 2 bits of information), 16QAM (using 16 constellation points, each symbol carrying 4 bits of information), 64QAM (using 64 constellation points, each symbol carrying 6 bits of information), and 256QAM (using 256 constellation points, each symbol carrying 8 bits of information), etc. The more constellation points used, the greater the amount of information carried per symbol, but the higher the requirements for signal quality, i.e., higher EVM and SNR (Signal-to-Noise Ratio) are needed.

[0034] Example 1

[0035] According to an embodiment of this application, a method for demodulating radio frequency signals 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.

[0036] Figure 1 This is a flowchart illustrating a radio frequency signal demodulation method according to an embodiment of this application, as shown below. Figure 1 As shown, the method includes the following steps S102-S108:

[0037] Step S102: Receive an OFDM-based radio frequency signal, wherein the radio frequency signal includes multiple subcarriers, and each subcarrier includes a pilot signal in its time slot;

[0038] Step S104: The radio frequency signal is converted to obtain the frequency domain signal corresponding to each subcarrier, wherein the frequency domain signal includes multiple OFDM symbols;

[0039] Step S106: For each frequency domain signal, perform initial frequency offset compensation on each OFDM symbol in the frequency domain signal based on the target pilot signal in the subcarrier time slot corresponding to the frequency domain signal. For far-end OFDM symbols whose position is more than a preset distance from the pilot signal, perform a second frequency offset compensation on the far-end OFDM symbols based on the distribution status of each constellation point mapped to the constellation diagram.

[0040] Step S108: Restore each frequency domain signal that has undergone frequency offset compensation to its original bit data.

[0041] The following section explains each step of the radio frequency signal demodulation method in conjunction with a specific implementation process.

[0042] In a communication system, the signal receiver first receives the radio frequency signal modulated by the signal transmitter based on OFDM technology. This radio frequency signal includes multiple subcarriers. Typically, each subcarrier's time slot may include multiple pilot signals. However, the embodiments of this application mainly provide a signal demodulation scheme for situations where only a single pilot signal is configured in each subcarrier's time slot due to resource constraints or specific application scenarios.

[0043] Figure 2 This is a schematic diagram of an optional radio frequency (RF) signal. The RF signal occupies a total of 274 PRBs (Physical Resource Blocks), namely PRB0, PRB1, PRB2, ..., PRB273. Each PRB includes 12 consecutive SCs (Subcarriers) in the frequency domain, namely SC0~SC11, SC12~SC23, SC24~SC35, ..., SC3264~SC3275 in the diagram. Each PRB includes two subframes (time slots) in the time domain, with subframe numbers Subframe0 and Subframe1, and time slot numbers Slot0 and Slot1, respectively. Each subcarrier includes 14 OFDM symbols (0~13) in each time slot, where the second OFDM symbol is a pilot signal, and the remaining OFDM symbols correspond to the data to be transmitted.

[0044] As an optional implementation, the signal receiver can perform the following steps S1-S3 to convert the radio frequency signal and obtain the frequency domain signal corresponding to each subcarrier:

[0045] Step S1: Perform down-conversion processing on the radio frequency signal to obtain a first signal, wherein the center frequency of the first signal is the baseband frequency.

[0046] Radio frequency (RF) signals typically have high frequencies, ranging from hundreds of MHz to several GHz. These high-frequency signals need to be downconverted to their baseband frequency for subsequent digital signal processing. The downconversion process usually involves a mixer and a local oscillator. By multiplying the signal with a reference signal generated by the local oscillator and then filtering out unwanted high-frequency components through a low-pass filter, a first signal with a center frequency equal to the baseband frequency is obtained.

[0047] Step S2: Perform frame synchronization processing on the first signal and divide the first signal into multiple subcarriers.

[0048] Frame synchronization is the process of determining the boundaries of received signal frames, which is crucial for correct signal decoding. In the first signal after downconversion, the start position of a frame can be identified by analyzing the signal (e.g., by detecting a specific frame synchronization sequence). Once the frame boundaries are found, the signal can be further divided, typically into multiple subframes (time slots), and then the subcarriers corresponding to each subframe can be determined.

[0049] Step S3: For each subcarrier, remove the cyclic prefix of the subcarrier and use Fast Fourier Transform to convert the subcarrier from a time-domain signal to a frequency-domain signal.

[0050] In OFDM systems, to avoid inter-symbol interference caused by multipath effects, a cyclic prefix is ​​added to the data of each subcarrier before transmission to ensure orthogonality between subcarriers. Before performing FFT (Fast Fourier Transform) processing on the subcarriers, the cyclic prefix needs to be removed first. Then, FFT processing is performed on the subcarriers to transform them from the time domain to the frequency domain, thus facilitating subsequent analysis and processing.

[0051] After obtaining the frequency domain signal, in order to avoid inter-symbol interference and phase rotation caused by the disruption of orthogonality between subcarriers due to frequency offset, frequency offset compensation is required to achieve signal equalization.

[0052] As an optional implementation, the embodiments of this application first perform frequency offset compensation on the frequency domain signal based on the pilot signal, mainly based on two algorithms: the zero-forcing algorithm and the minimum mean square error algorithm.

[0053] Zero-forcing is a linear channel equalization algorithm that aims to completely eliminate interference in the equalized output signal at each sampling point by selecting an equalizer coefficient matrix, i.e., making all unwanted signal components zero at the sampling point. Mathematically, a zero-forcing equalizer can be viewed as the inverse of the channel response matrix. This method is relatively simple to calculate and can theoretically completely eliminate multipath interference. However, because it does not consider the influence of noise, its performance may degrade due to noise amplification at low signal-to-noise ratios.

[0054] In contrast, the minimum mean square error (MME) algorithm considers the impact of noise, aiming to minimize the MME of the output signal, i.e., eliminating multipath interference while suppressing noise as much as possible. The coefficient matrix of the MME equalizer is obtained by solving an optimization problem whose objective function is the MME of the signal. The MME equalizer provides good performance in both high and low signal-to-noise ratio (SNR) environments because it considers the impact of noise while eliminating interference, avoiding the problem of amplifying noise. However, its solution process is relatively more complex and time-consuming.

[0055] To address the characteristics of the two algorithms, this application proposes the following frequency offset compensation scheme: Determine the signal-to-noise ratio (SNR) corresponding to the radio frequency signal; when the SNR is greater than a preset SNR threshold, use a zero-forcing algorithm to perform initial frequency offset compensation for each OFDM symbol in the frequency domain signal based on the target pilot signal; when the SNR is not greater than the preset SNR threshold, use a minimum mean square error algorithm to perform initial frequency offset compensation for each OFDM symbol in the frequency domain signal based on the target pilot signal. The preset SNR threshold can be set empirically and is not specifically limited here.

[0056] Alternatively, when using the zero-forcing algorithm to perform initial frequency offset compensation for each OFDM symbol in the frequency domain signal, it can be achieved in the following way:

[0057] First, channel estimation is performed based on the following formula to determine the channel response matrix:

[0058]

[0059] In the formula, s represents the target pilot signal transmitted from the transmitter, y represents the received target pilot signal, and h represents the channel response matrix;

[0060] Then, signal estimation is performed for each OFDM symbol in the frequency domain signal based on the following formula:

[0061]

[0062] In the formula, Denotes the conjugate transpose of h. Represents OFDM symbols within the frequency domain signal. Represents the original OFDM symbol for estimation;

[0063] Finally, initial frequency offset compensation is performed on the corresponding OFDM symbols within the frequency domain signal based on each original OFDM symbol. This is essentially based on the compensation factor in the above formula. Initial frequency offset compensation is performed on OFDM symbols.

[0064] Alternatively, when performing initial frequency offset compensation for each OFDM symbol in the frequency domain signal using the least mean square error algorithm, it can be achieved in the following way:

[0065] First, channel estimation is performed based on the following formula to determine the channel response matrix and noise:

[0066]

[0067] In the formula, s represents the target pilot signal at the transmitting end, y represents the received target pilot signal, h represents the channel response matrix, and n represents noise;

[0068] Then, signal estimation is performed for each OFDM symbol in the frequency domain signal based on the following formula:

[0069]

[0070] In the formula, Denotes the conjugate transpose of h. Represents OFDM symbols within the frequency domain signal. Represents the original OFDM symbol for estimation;

[0071] Finally, initial frequency offset compensation is performed on the corresponding OFDM symbols within the frequency domain signal based on each original OFDM symbol. This is essentially based on the compensation factor in the above formula. Initial frequency offset compensation is performed on OFDM symbols.

[0072] Considering that during the initial frequency offset compensation process, the frequency offset compensation of the far-end OFDM symbols that are far from the pilot signal may not be very accurate due to the lack of sufficient local reference signals, this application proposes a scheme to perform a second frequency offset compensation for the far-end OFDM symbols based on the distribution status of each constellation point mapped to the constellation diagram.

[0073] As an optional implementation, the second frequency offset compensation can be achieved through the following steps S1-S3:

[0074] Step S1: For each far-end OFDM symbol that has completed the initial frequency offset compensation, the far-end OFDM symbol is mapped to the constellation diagram based on the preset quadrature amplitude modulation order to obtain multiple constellation points.

[0075] The quadrature amplitude modulation order mentioned above can be 4QAM, 16QAM, 64QAM, 256QAM, etc., and can be selected according to the application environment. No specific limitation is made here.

[0076] Step S2: Determine the frequency offset estimate for each quadrant based on the distribution of multiple constellation points in the four quadrants, and determine the average of the frequency offset estimates for the four quadrants as the target frequency offset estimate.

[0077] When the far-end OFDM symbol undergoes frequency offset, the distribution of constellation points deviates from its ideal position, typically manifesting as constellation diagram rotation and divergence. This deviation is particularly pronounced for higher-order modulation schemes such as 16QAM and 64QAM. The embodiments of this application statistically map the constellation points to reference points in each quadrant (e.g., the first quadrant). The second quadrant The third quadrant and the fourth quadrant By calculating the number of constellation points and their average position, the expected value at each reference point can be determined. Then, based on the difference between the expected value and the ideal position of each reference constellation point, the residual frequency offset for the far-end OFDM symbol can be calculated. This calculation takes into account the actual distribution of the constellation points, thus more accurately reflecting the frequency offset experienced by the far-end symbol. By performing a second frequency offset compensation on the far-end OFDM symbol based on the calculated residual frequency offset value, the constellation points can be remapped to their ideal positions, thereby reducing the error vector amplitude, improving demodulation performance, and reducing the bit error rate.

[0078] Alternatively, the frequency offset estimate for each quadrant can be determined using the following formula:

[0079]

[0080]

[0081]

[0082]

[0083] In the formula, , , , These represent the frequency offset estimates for the first, second, third, and fourth quadrants, respectively. , , , These represent the number of constellation points in the first, second, third, and fourth quadrants, respectively. , , , These represent the expected number of constellation points that should be located in the first, second, third, and fourth quadrants, respectively.

[0084] Step S3: Perform a second frequency offset compensation on the far-end OFDM symbol based on the target frequency offset estimate.

[0085] Finally, for each frequency domain signal that has completed frequency offset compensation, the frequency domain signal can be demodulated, descrambled, and decoded in sequence to restore the frequency domain signal to the original bit data.

[0086] Demodulation is the process of converting a frequency-domain signal back to a time-domain signal. It typically involves removing the received signal from its carrier frequency to recover the original baseband signal. Different communication systems use different modulation techniques, so the specific methods of demodulation will also differ. For example, for QAM, it is necessary to recover both the amplitude and phase information of the signal simultaneously.

[0087] In some communication systems, signals are spread before transmission, which involves multiplying the signal with a high-bandwidth pseudo-random sequence (i.e., a spreading code) to reduce peak power and improve interference immunity. Descrambling involves multiplying the signal with the same spreading code to recover the original signal. This process can be viewed as signal compression; by matching with the spreading code, unnecessary noise and interference can be filtered out, improving the signal-to-noise ratio.

[0088] Decoding is the process of converting the recovered signal back into the original bit data. It typically requires a reverse operation based on specific encoding rules (such as convolutional codes, Turbo codes, LDPC codes, etc.). The encoding process at the transmitting end improves the robustness and fault tolerance of the signal by adding redundant information to the original data. Therefore, the decoding process is the process of removing this redundant information and recovering the original data.

[0089] To verify the effectiveness of the above solution, the following simulation operation was also performed in this application embodiment:

[0090] Based on the actual environment, the channel parameters were set as follows: signal-to-noise ratio (SNR) was set to 30dB, Doppler frequency shift was added at 100Hz, path loss was set to 0dB, -10dB, and -20dB respectively, subcarrier spacing was set to 15kHz, system bandwidth was 100MHz, OFDM symbol count per time slot was 14, cyclic prefix type was set to conventional, modulation scheme was selected as 16QAM, and pilot signal type 1 was used. Based on the above configuration, signal demodulation operations were performed according to both the conventional signal demodulation scheme and the signal demodulation scheme of this application (far-end OFDM symbols were defined as symbols 12 and 13). The simulation results are as follows. Figure 3a and Figure 3b As shown in Table 1, the magnitude of the corresponding error vector is statistically analyzed.

[0091] Table 1

[0092]

[0093] In the conventional signal demodulation scheme, the error vector amplitude of the far-end OFDM symbol 12 is 6.7846% and the error vector amplitude of the far-end OFDM symbol 13 is 7.799%. However, according to the signal demodulation scheme of this application, the error vector amplitude of the far-end OFDM symbol 12 is 6.1643% and the error vector amplitude of the far-end OFDM symbol 13 is 7.151%. That is, compared with the conventional signal demodulation scheme, the error vector amplitude of the far-end OFDM symbol 12 is reduced by 9.14% and the error vector amplitude of the far-end OFDM symbol 13 is reduced by 8.30%. Therefore, the scheme of this application can effectively improve the signal demodulation performance.

[0094] In this embodiment, considering that when only a single pilot signal is configured in the subcarrier time slot, the frequency offset compensation of the far-end OFDM symbols, which are far from the pilot signal, becomes inaccurate due to the lack of sufficient local reference signals, the following approach is adopted: Based on the frequency offset compensation of each received OFDM symbol according to the pilot signal, a second frequency offset compensation is performed on the far-end OFDM symbols based on the distribution of constellation points mapped to the constellation diagram. This improves the accuracy of the frequency offset compensation and reduces the error vector amplitude and bit error rate of the overall signal demodulation result. This scheme effectively solves the technical problem of large error vector amplitude in the demodulation result of far-end symbols when only a single pilot signal is configured in the subcarrier time slot, a problem inherent in traditional demodulation schemes.

[0095] Example 2

[0096] According to an embodiment of this application, a radio frequency signal demodulation apparatus for implementing the radio frequency signal demodulation method in Embodiment 1 is also provided, such as... Figure 4 As shown, the demodulation device for the radio frequency signal includes at least: a receiving module 41, a conversion module 42, a compensation module 43, and a recovery module 44, wherein:

[0097] The receiving module 41 is used to receive OFDM-based radio frequency signals, wherein the radio frequency signals include multiple subcarriers, and each subcarrier includes a pilot signal in its time slot;

[0098] The conversion module 42 is used to convert the radio frequency signal to obtain the frequency domain signal corresponding to each subcarrier, wherein the frequency domain signal includes multiple OFDM symbols;

[0099] The compensation module 43 is used to perform initial frequency offset compensation on each OFDM symbol in the frequency domain signal based on the pilot signal in the subcarrier time slot corresponding to the frequency domain signal for each frequency domain signal, and to perform a second frequency offset compensation on the far OFDM symbol for the far OFDM symbol whose position is more than a preset distance from the pilot signal based on the distribution state of each constellation point mapped to the constellation diagram of the far OFDM symbol.

[0100] The recovery module 44 is used to restore the frequency domain signals that have completed frequency offset compensation to their original bit data.

[0101] The following section describes the functions of each module in the RF signal demodulation device, using a specific implementation process as an example.

[0102] As an optional implementation, the conversion module can perform the conversion processing on the radio frequency signal to obtain the frequency domain signal corresponding to each subcarrier in the following manner: perform down-conversion processing on the radio frequency signal to obtain a first signal, wherein the center frequency of the first signal is the baseband frequency; perform frame synchronization processing on the first signal to divide the first signal into multiple subcarriers; for each subcarrier, remove the cyclic prefix of the subcarrier, and use fast Fourier transform to convert the subcarrier from a time domain signal to a frequency domain signal.

[0103] As an optional implementation, when the compensation module performs initial frequency offset compensation for each OFDM symbol in the frequency domain signal based on the target pilot signal in the subcarrier time slot corresponding to the frequency domain signal, it can do so in the following way: determine the signal-to-noise ratio (SNR) corresponding to the radio frequency signal; if the SNR is greater than a preset SNR threshold, use a zero-forcing algorithm to perform initial frequency offset compensation for each OFDM symbol in the frequency domain signal based on the target pilot signal; if the SNR is not greater than the preset SNR threshold, use a minimum mean square error algorithm to perform initial frequency offset compensation for each OFDM symbol in the frequency domain signal based on the target pilot signal.

[0104] Optionally, when the compensation module performs initial frequency offset compensation for each OFDM symbol in the frequency domain signal based on the target pilot signal using the zero-forcing algorithm, it can do so in the following way:

[0105] Channel estimation is performed based on the following formula to determine the channel response matrix:

[0106]

[0107] In the formula, s represents the target pilot signal transmitted from the transmitter, y represents the received target pilot signal, and h represents the channel response matrix;

[0108] Signal estimation is performed for each OFDM symbol in the frequency domain signal based on the following formula:

[0109]

[0110] In the formula, Denotes the conjugate transpose of h. Represents OFDM symbols within the frequency domain signal. Represents the original OFDM symbol for estimation;

[0111] Initial frequency offset compensation is performed on the corresponding OFDM symbols within the frequency domain signal based on each original OFDM symbol.

[0112] Optionally, when the compensation module performs initial frequency offset compensation for each OFDM symbol in the frequency domain signal based on the target pilot signal using the minimum mean square error algorithm, it can do so in the following way:

[0113] Channel estimation is performed based on the following formula to determine the channel response matrix and noise:

[0114]

[0115] In the formula, s represents the target pilot signal at the transmitting end, y represents the received target pilot signal, h represents the channel response matrix, and n represents noise;

[0116] Signal estimation is performed for each OFDM symbol in the frequency domain signal based on the following formula:

[0117]

[0118] In the formula, Denotes the conjugate transpose of h. Represents OFDM symbols within the frequency domain signal. Represents the original OFDM symbol for estimation;

[0119] Initial frequency offset compensation is performed on the corresponding OFDM symbols within the frequency domain signal based on each original OFDM symbol.

[0120] As an optional implementation, when the compensation module performs a second frequency offset compensation on the far-end OFDM symbol based on the distribution of each constellation point in the constellation diagram mapped to the far-end OFDM symbol, it can be done in the following way: For each far-end OFDM symbol that has completed the first frequency offset compensation, the far-end OFDM symbol is mapped to the constellation diagram based on a preset quadrature amplitude modulation order to obtain multiple constellation points; the frequency offset estimate corresponding to each quadrant is determined based on the distribution of multiple constellation points in the four quadrants, and the average value of the frequency offset estimates corresponding to the four quadrants is determined as the target frequency offset estimate; the far-end OFDM symbol is then compensated for a second frequency offset based on the target frequency offset estimate.

[0121] Optionally, when determining the frequency offset estimate for each quadrant based on the distribution of multiple constellation points in the four quadrants, the compensation module can do so in the following way:

[0122] The frequency offset estimate for each quadrant is determined using the following formulas:

[0123]

[0124]

[0125]

[0126]

[0127] In the formula, , , , These represent the frequency offset estimates for the first, second, third, and fourth quadrants, respectively. , , , These represent the number of constellation points in the first, second, third, and fourth quadrants, respectively. , , , These represent the expected number of constellation points that should be located in the first, second, third, and fourth quadrants, respectively.

[0128] As an optional implementation, the recovery module can restore each frequency domain signal that has completed frequency offset compensation to its original bit data in the following way: for each frequency domain signal that has completed frequency offset compensation, the frequency domain signal is sequentially demodulated, descrambled and decoded to restore the frequency domain signal to its original bit data.

[0129] It should be noted that each module in the radio frequency signal demodulation device in this application corresponds one-to-one with each implementation step of the radio frequency signal demodulation method in Embodiment 1. Since Embodiment 1 has been described in detail, some details not shown in this embodiment can be referred to Embodiment 1, and will not be elaborated further here.

[0130] Example 3

[0131] According to an embodiment of this application, a computer program product is also provided, which includes a computer program, wherein when the computer program is executed by a processor, it implements the radio frequency signal demodulation method in Embodiment 1.

[0132] According to an embodiment of this application, a non-volatile storage medium is also provided, which includes a stored computer program, wherein the device containing the non-volatile storage medium executes the radio frequency signal demodulation method in Embodiment 1 by running the computer program.

[0133] According to an embodiment of this application, a processor is also provided for running a computer program, wherein the computer program executes the radio frequency signal demodulation method in Embodiment 1 during runtime.

[0134] According to an embodiment of this application, an electronic device is also provided, comprising: a memory and a processor, wherein the memory stores a computer program, and the processor is configured to execute the demodulation method for radio frequency signals in Embodiment 1 through the computer program.

[0135] Specifically, the computer program executes the following steps during runtime: receiving an OFDM-based radio frequency signal, wherein the radio frequency signal includes multiple subcarriers, and each subcarrier's time slot includes a series of pilot signals; performing conversion processing on the radio frequency signal to obtain a frequency domain signal corresponding to each subcarrier, wherein the frequency domain signal includes multiple OFDM symbols; for each frequency domain signal, performing initial frequency offset compensation on each OFDM symbol in the frequency domain signal based on the target pilot signal in the time slot of the corresponding subcarrier; for far-end OFDM symbols whose positions are more than a preset distance from the pilot signals, performing a second frequency offset compensation on the far-end OFDM symbols based on the distribution status of each constellation point mapped to the constellation diagram; and restoring each frequency domain signal after frequency offset compensation to its original bit data.

[0136] As an alternative implementation, the above-mentioned electronic device may exist in the form of a mobile terminal, a computer terminal, or a similar computing device. Figure 5 A hardware block diagram of an electronic device for implementing a radio frequency signal demodulation method is shown. Figure 5 As shown, the electronic device 50 may include one or more (shown as 502a, 502b, ..., 502n) processors 502 (processors 502 may include, but are not limited to, processing devices such as microprocessors or programmable logic devices), a memory 504 for storing data, and a transmission device 506 for communication functions. In addition, it may also include: a display, an input / output interface, a universal serial bus 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 5 The structure shown is for illustrative purposes only and does not limit the structure of the electronic device described above. For example, electronic device 50 may also include... Figure 5 The more or fewer components shown, or having the same Figure 5 The different configurations shown.

[0137] It should be noted that the aforementioned one or more processors 502 and / or other data processing circuits are generally referred to herein as "data processing circuits". These data processing circuits may be embodied, in whole or in part, in 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 of the electronic device 50. As involved in the embodiments of this application, the data processing circuits serve as a processor control mechanism (e.g., selection of a variable resistor termination path connected to an interface).

[0138] The memory 504 can be used to store software programs and modules of application software, such as the program instructions / data storage device corresponding to the radio frequency signal demodulation method in this embodiment. The processor 502 executes various functional applications and data processing by running the software programs and modules stored in the memory 504, thereby implementing the above-mentioned application vulnerability detection method. The memory 504 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 504 may further include memory remotely located relative to the processor 502, and these remote memories can be connected to the electronic device 50 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.

[0139] The transmission device 506 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 electronic device 50. In one example, the transmission device 506 includes a network adapter that can connect to other network devices via a base station to communicate with the Internet. In another example, the transmission device 506 may be a radio frequency module used for wireless communication with the Internet.

[0140] The display can be, for example, a touchscreen LCD display that allows the user to interact with the user interface of the electronic device 50.

[0141] The sequence numbers of the above embodiments are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0142] 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.

[0143] 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 example, 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 couplings, direct couplings, or communication connections may be through some interfaces; indirect couplings or communication connections between units or modules may be electrical or other forms.

[0144] 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.

[0145] 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.

[0146] 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 the prior art, 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 of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, read-only memory, random access memory, portable hard drive, magnetic disk, or optical disk.

[0147] The above are merely preferred embodiments of this application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for demodulating radio frequency signals, characterized in that, include: Receive radio frequency signals based on orthogonal frequency division multiplexing (OFDM), wherein the radio frequency signals include multiple subcarriers, and each subcarrier includes a pilot signal in its time slot; The radio frequency signal is converted to obtain a frequency domain signal corresponding to each subcarrier, wherein the frequency domain signal includes multiple OFDM symbols; For each frequency domain signal, the first frequency offset compensation is performed on each OFDM symbol in the frequency domain signal based on the target pilot signal in the subcarrier time slot corresponding to the frequency domain signal. For the far OFDM symbol whose position is more than a preset distance from the pilot signal, the second frequency offset compensation is performed on the far OFDM symbol based on the distribution state of each constellation point mapped to the constellation diagram. The frequency domain signals that have undergone frequency offset compensation are restored to their original bit data.

2. The method according to claim 1, characterized in that, The radio frequency signal is converted to obtain the frequency domain signal corresponding to each subcarrier, including: The radio frequency signal is down-converted to obtain a first signal, wherein the center frequency of the first signal is the baseband frequency; The first signal is subjected to frame synchronization processing, and the first signal is divided into multiple subcarriers; For each subcarrier, the cyclic prefix of the subcarrier is removed, and the subcarrier is converted from a time-domain signal to a frequency-domain signal using a fast Fourier transform.

3. The method according to claim 1, characterized in that, Based on the target pilot signal within the subcarrier time slot corresponding to the frequency domain signal, initial frequency offset compensation is performed on each OFDM symbol in the frequency domain signal, including: Determine the signal-to-noise ratio corresponding to the radio frequency signal; When the signal-to-noise ratio is greater than a preset signal-to-noise ratio threshold, the zero-forcing algorithm is used to perform initial frequency offset compensation on each OFDM symbol in the frequency domain signal based on the target pilot signal. When the signal-to-noise ratio is not greater than a preset signal-to-noise ratio threshold, the minimum mean square error algorithm is used to perform initial frequency offset compensation on each OFDM symbol in the frequency domain signal based on the target pilot signal.

4. The method according to claim 3, characterized in that, The zero-forcing algorithm is used to perform initial frequency offset compensation on each OFDM symbol in the frequency domain signal based on the target pilot signal, including: Channel estimation is performed based on the following formula to determine the channel response matrix: In the formula, s represents the target pilot signal transmitted from the transmitter, y represents the received target pilot signal, and h represents the channel response matrix; Signal estimation is performed for each OFDM symbol within the frequency domain signal based on the following formula: In the formula, Denotes the conjugate transpose of h. This represents the OFDM symbol within the frequency domain signal. Represents the original OFDM symbol for estimation; Initial frequency offset compensation is performed on the corresponding OFDM symbols within the frequency domain signal based on each of the original OFDM symbols.

5. The method according to claim 3, characterized in that, The minimum mean square error algorithm is used to perform initial frequency offset compensation on each OFDM symbol in the frequency domain signal based on the target pilot signal, including: Channel estimation is performed based on the following formula to determine the channel response matrix and noise: In the formula, s represents the target pilot signal at the transmitting end, y represents the received target pilot signal, h represents the channel response matrix, and n represents noise; Signal estimation is performed for each OFDM symbol within the frequency domain signal based on the following formula: In the formula, Denotes the conjugate transpose of h. This represents the OFDM symbol within the frequency domain signal. Represents the original OFDM symbol for estimation; Initial frequency offset compensation is performed on the corresponding OFDM symbols within the frequency domain signal based on each of the original OFDM symbols.

6. The method according to claim 1, characterized in that, The second frequency offset compensation for the far-end OFDM symbol is performed based on the distribution of each constellation point in the constellation diagram mapped to the far-end OFDM symbol, including: For each far-end OFDM symbol that has completed the initial frequency offset compensation, the far-end OFDM symbol is mapped to the constellation diagram based on the preset quadrature amplitude modulation order to obtain multiple constellation points; Based on the distribution of the multiple constellation points in the four quadrants, determine the frequency offset estimate for each quadrant, and determine the average of the frequency offset estimates for the four quadrants as the target frequency offset estimate. A second frequency offset compensation is performed on the far-end OFDM symbol based on the target frequency offset estimate.

7. The method according to claim 6, characterized in that, Based on the distribution of the multiple constellation points in the four quadrants, the frequency offset estimate for each quadrant is determined, including: The frequency offset estimate for each quadrant is determined using the following formulas: In the formula, , , , These represent the frequency offset estimates for the first, second, third, and fourth quadrants, respectively. , , , These represent the number of constellation points in the first, second, third, and fourth quadrants, respectively. , , , These represent the expected number of constellation points that should be located in the first, second, third, and fourth quadrants, respectively.

8. The method according to claim 1, characterized in that, The frequency domain signals that have undergone frequency offset compensation are restored to their original bit data, including: For each frequency domain signal that has completed frequency offset compensation, the frequency domain signal is sequentially demodulated, descrambled, and decoded to restore the frequency domain signal to the original bit data.

9. A demodulation device for radio frequency signals, characterized in that, include: A receiving module is used to receive OFDM-based radio frequency signals, wherein the radio frequency signals include multiple subcarriers, and each subcarrier includes a pilot signal in its time slot; A conversion module is used to convert the radio frequency signal to obtain a frequency domain signal corresponding to each subcarrier, wherein the frequency domain signal includes multiple OFDM symbols; The compensation module is used to perform initial frequency offset compensation on each OFDM symbol in the frequency domain signal based on the pilot signal in the subcarrier time slot corresponding to the frequency domain signal for each frequency domain signal, and to perform a second frequency offset compensation on the far-end OFDM symbol based on the distribution state of each constellation point mapped to the constellation diagram for the far-end OFDM symbol that is more than a preset distance away from the pilot signal. The recovery module is used to restore the frequency domain signals that have undergone frequency offset compensation to their original bit data.

10. A computer program product, characterized in that, include: A computer program, wherein when executed by a processor, the computer program implements the demodulation method for radio frequency signals according to any one of claims 1 to 8.

11. An electronic device, characterized in that, include: A memory and a processor, wherein the memory stores a computer program, and the processor is configured to execute the demodulation method for radio frequency signals according to any one of claims 1 to 8 through the computer program.

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