CN-122027422-A - Demodulation method and device for radio frequency signals

CN122027422ACN 122027422 ACN122027422 ACN 122027422ACN-122027422-A

Abstract

The application discloses a demodulation method and device of a radio frequency signal. The method comprises the steps of receiving radio frequency signals comprising a plurality of subcarriers based on OFDM, wherein each subcarrier time slot comprises a column of pilot signals, converting the radio frequency signals to obtain frequency domain signals corresponding to each subcarrier, wherein each frequency domain signal comprises a plurality of OFDM symbols, performing primary frequency offset compensation on each OFDM symbol in each frequency domain signal based on the pilot signals, performing secondary frequency offset compensation on far-end OFDM symbols with positions exceeding a preset distance from the pilot signals based on distribution states of constellation points mapped to a constellation diagram, and recovering each frequency domain signal subjected to frequency offset compensation into original bit data. The application solves the technical problem that the error vector amplitude of the remote symbol demodulation result is larger when the traditional demodulation scheme only configures a single-column pilot signal in the subcarrier time slot.

Inventors

ZHOU LONG
ZHANG HAORAN
WANG DEQIAN

Assignees

中国电信股份有限公司卫星通信分公司

Dates

Publication Date: 20260512
Application Date: 20260116

Claims (11)

1. A method for demodulating a radio frequency signal, comprising: Receiving a radio frequency signal based on Orthogonal Frequency Division Multiplexing (OFDM), wherein the radio frequency signal comprises a plurality of subcarriers, and a column of pilot signals are included in a time slot of each subcarrier; performing conversion processing on the radio frequency signals to obtain frequency domain signals corresponding to each subcarrier, wherein the frequency domain signals comprise a plurality of OFDM symbols; for each frequency domain signal, performing primary frequency offset compensation on each OFDM symbol in the frequency domain signal based on a target pilot signal in a subcarrier time slot corresponding to the frequency domain signal, and for a far-end OFDM symbol with a position exceeding a preset distance from the pilot signal, performing secondary frequency offset compensation on the far-end OFDM symbol based on the distribution state of the far-end OFDM symbol mapped to each constellation point in a constellation diagram; Each frequency domain signal for which frequency offset compensation is completed is restored to original bit data.
2. The method of claim 1, wherein converting the radio frequency signal to obtain a frequency domain signal corresponding to each subcarrier comprises: Performing down-conversion processing on the radio frequency signal to obtain a first signal, wherein the center frequency of the first signal is a baseband frequency; Performing frame synchronization processing on the first signal, and dividing a plurality of subcarriers in the first signal; 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 by using a fast fourier transform.
3. The method of claim 1, wherein performing primary frequency offset compensation for each OFDM symbol in the frequency domain signal based on a target pilot signal in a subcarrier slot corresponding to the frequency domain signal comprises: determining a signal-to-noise ratio corresponding to the radio frequency signal; under the condition that the signal-to-noise ratio is larger than a preset signal-to-noise ratio threshold value, performing primary frequency offset compensation on each OFDM symbol in the frequency domain signal based on the target pilot signal by using a zero forcing algorithm; And under the condition that the signal-to-noise ratio is not greater than a preset signal-to-noise ratio threshold value, performing primary frequency offset compensation on each OFDM symbol in the frequency domain signal based on the target pilot signal by utilizing a minimum mean square error algorithm.
4. The method of claim 3, wherein performing initial frequency offset compensation for each OFDM symbol within the frequency domain signal based on the target pilot signal using a zero forcing algorithm comprises: channel estimation is performed based on the following formula, and a channel response matrix is determined: wherein s represents a target pilot signal of a transmitting end, y represents a received target pilot signal, and h represents a channel response matrix; signal estimation is performed for each OFDM symbol within the frequency domain signal based on the following formula: In the formula, The conjugate transpose of h is represented, Representing OFDM symbols within the frequency domain signal, Representing the estimated original OFDM symbol; And performing primary frequency offset compensation on the corresponding OFDM symbols in the frequency domain signal based on each original OFDM symbol.
5. The method of claim 3, wherein performing primary frequency offset compensation for each OFDM symbol within the frequency domain signal based on the target pilot signal using a minimum mean square error algorithm comprises: channel estimation is performed based on the following formula, and a channel response matrix and noise are determined: wherein s represents a target pilot signal of a transmitting end, y represents a received target pilot signal, h represents a 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, The conjugate transpose of h is represented, Representing OFDM symbols within the frequency domain signal, Representing the estimated original OFDM symbol; And performing primary frequency offset compensation on the corresponding OFDM symbols in the frequency domain signal based on each original OFDM symbol.
6. The method of claim 1, wherein performing a second frequency offset compensation for the far-end OFDM symbol based on the distribution state of the far-end OFDM symbol mapped to each constellation point in a constellation diagram comprises: For each far-end OFDM symbol with primary frequency offset compensation, mapping the far-end OFDM symbol into a constellation diagram based on a preset quadrature amplitude modulation order to obtain a plurality of constellation points; Determining a frequency offset estimation value corresponding to each quadrant based on the distribution state of the constellation points in the four quadrants, and determining the average value of the frequency offset estimation values corresponding to the four quadrants as a target frequency offset estimation value; and performing second frequency offset compensation on the far-end OFDM symbol based on the target frequency offset estimation value.
7. The method of claim 6, wherein determining a frequency offset estimate for each quadrant based on the distribution of the plurality of constellation points in four quadrants, comprises: and determining a frequency offset estimation value corresponding to each quadrant according to the following formula: In the formula, 、、、 Respectively representing frequency offset estimated values corresponding to the first quadrant, the second quadrant, the third quadrant and the fourth quadrant, 、、、 Respectively representing the number of constellation points in the first quadrant, the second quadrant, the third quadrant and the fourth quadrant, 、、、 The expected values of the number of constellation points that should be located in the first quadrant, the second quadrant, the third quadrant, and the fourth quadrant are represented, respectively.
8. The method of claim 1, wherein recovering each frequency domain signal for which frequency offset compensation is completed to original bit data, comprises: And for each frequency domain signal with frequency offset compensation, sequentially demodulating, descrambling and decoding the frequency domain signal, and recovering the frequency domain signal into original bit data.
9. A demodulation apparatus for a radio frequency signal, comprising: A receiving module, configured to receive an OFDM-based radio frequency signal, where the radio frequency signal includes a plurality of subcarriers, and a column of pilot signals is included in a time slot of each subcarrier; the conversion module is used for carrying out conversion processing on the radio frequency signals to obtain frequency domain signals corresponding to each subcarrier, wherein the frequency domain signals comprise a plurality of OFDM symbols; The compensation module is used for carrying out primary frequency offset compensation on each OFDM symbol in the frequency domain signal based on a pilot signal in a subcarrier time slot corresponding to the frequency domain signal, and carrying out secondary frequency offset compensation on a far-end OFDM symbol which is more than a preset distance away from the position of the pilot signal based on the distribution state of the far-end OFDM symbol mapped to each constellation point in a constellation diagram; And the recovery module is used for recovering each frequency domain signal subjected to frequency offset compensation into original bit data.
10. A computer program product comprising a computer program, wherein the computer program when executed by a processor implements the method of demodulating a radio frequency signal according to any one of claims 1 to 8.
11. An electronic device comprising a memory and a processor, wherein the memory has a computer program stored therein, the processor being configured to perform the method of demodulating a radio frequency signal according to any one of claims 1 to 8 by means of the computer program.

Description

Demodulation method and device for radio frequency signals Technical Field The present application relates to the field of wireless communication technologies, and in particular, to a method and an apparatus for demodulating a radio frequency signal. Background In the field of wireless communication, especially in 5G mobile communication, OFDM (Orthogonal Frequency Division Multiplexing ) technology is a key technology for physical layer signal transmission due to its high spectral efficiency and robust multipath interference resistance. However, frequency offset is one of the main factors affecting the performance of the OFDM system, and it may cause the orthogonality between subcarriers to be broken, thereby causing inter-symbol interference and phase rotation, severely affecting demodulation performance and bit error rate. In the related art, an OFDM system generally performs channel estimation and frequency offset compensation using pilot signals scattered in a slot, which is essential to ensure correct demodulation of signals. When multiple columns of pilots are deployed in each slot, frequency offset compensation may be performed relatively accurately because the pilot signals provide sufficient channel information to accurately estimate and compensate for the frequency offset. However, in resource-constrained or special application scenarios, it is common to configure only a single column of pilots per slot. In this case, although the frequency offset compensation at the pilot is accurate, the frequency offset compensation becomes inaccurate due to the lack of a sufficient local reference signal for the signal (far-end symbol) that is far away from the pilot. This results in a decrease in demodulation performance of the far-end symbol, which is manifested by an increase in the magnitude of the error vector and an increase in the bit error rate upon decoding, thereby affecting the overall communication quality. In view of the above problems, no effective solution has been proposed at present. Disclosure of Invention The embodiment of the application provides a method and a device for demodulating a radio frequency signal, which at least solve the technical problem that the error vector amplitude of a remote symbol demodulation result is larger when only a single-column pilot signal is configured in a subcarrier time slot in a traditional demodulation scheme. According to one aspect of the embodiment of the application, a demodulation method of a radio frequency signal is provided, which comprises the steps of receiving the radio frequency signal based on OFDM, wherein the radio frequency signal comprises a plurality of subcarriers, each time slot of each subcarrier comprises a column 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 comprises a plurality of OFDM symbols, performing primary frequency offset compensation on each OFDM symbol in the frequency domain signal based on a target pilot signal in a time slot of the subcarrier corresponding to the frequency domain signal, performing secondary frequency offset compensation on a far-end OFDM symbol which is more than a preset distance away from the position of the pilot signal based on the distribution state of each constellation point in a constellation diagram, and recovering each frequency domain signal with frequency offset compensation to original bit data. Optionally, the conversion processing is performed on the radio frequency signal to obtain a frequency domain signal corresponding to each subcarrier, which includes performing down conversion processing on the radio frequency signal to obtain a first signal, where a center frequency of the first signal is a baseband frequency, performing frame synchronization processing on the first signal, dividing a plurality of subcarriers in the first signal, removing a cyclic prefix of the subcarrier for each subcarrier, and converting the subcarrier from a time domain signal to a frequency domain signal by using fast fourier transform. Optionally, performing primary frequency offset compensation on each OFDM symbol in the frequency domain signal based on a target pilot signal in a subcarrier time slot corresponding to the frequency domain signal comprises determining a signal-to-noise ratio corresponding to the radio frequency signal, performing primary frequency offset compensation on each OFDM symbol in the frequency domain signal based on the target pilot signal by using a zero forcing algorithm when the signal-to-noise ratio is greater than a preset signal-to-noise ratio threshold, and performing primary frequency offset compensation on each OFDM symbol in the frequency domain signal based on the target pilot signal by using a minimum mean square error algorithm when the signal-to-noise ratio is not greater than the preset signal-to-noise ratio threshold. Option