A base station, central station and method of non-linear signal processing

Abstract

The application discloses a base station, a central station and a nonlinear signal processing method. The base station comprises a plurality of radio frequency links, an optical module and a feature calculation module. The optical module is used for performing electro-optical conversion on signals of the plurality of radio frequency links, transmitting obtained optical signals to the central station, performing photoelectric conversion on the optical signals to obtain electrical signals. In the plurality of radio frequency links, there are a first radio frequency link and at least one second radio frequency link. The optical module comprises a nonlinear component. After the signals of the at least one second radio frequency link pass through the nonlinear component, nonlinear distortion signals having an overlap with a corresponding frequency band of the first radio frequency link are generated. The nonlinear distortion signals are contained in the optical signals. The feature calculation module is used for extracting target signals of the corresponding frequency band of the first radio frequency link from the electrical signals, and calculating nonlinear distortion prediction signals according to the target signals and the signals of the at least one second radio frequency link. The first radio frequency link is used for performing predistortion processing on the signals of the corresponding frequency band according to the nonlinear distortion prediction signals.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to a base station, a central station, and a nonlinear signal processing method. Background Technology

[0002] Wireless communication links in wireless communication systems contain many nonlinear components, such as low-noise amplifiers, power amplifiers (PA), optical-electro (O / E) components, and electro-optical (E / O) components. These nonlinear components may cause nonlinear distortion in the signals on the communication link. Specifically, the output signal of the nonlinear component will contain new frequency components that are not present in the input signal, i.e., nonlinear distortion signals. Nonlinear distortion signals can interfere with the subsequent processing of some normal signals and affect the performance of the wireless communication system.

[0003] Currently, to address the nonlinear distortion problem in communication links of wireless communication systems, simulated predistortion can be used to correct the nonlinear characteristics of nonlinear components in the system, thereby reducing the impact of nonlinear distortion caused by these components. Simulated predistortion involves processing the signal input to the nonlinear component in advance, so that the signal change caused by this processing cancels out the nonlinear distortion generated after the signal is input to the nonlinear component, thus correcting the nonlinear distortion caused by the nonlinear component. However, in this method, the link used to correct the nonlinear parameters of the nonlinear component is generally fixed. The ability to fit nonlinear distortion during simulated predistortion is limited, and it can only specifically improve the characteristics of a certain type of nonlinear component to a certain extent. Therefore, this method has a relatively low ability to correct nonlinear distortion. Summary of the Invention

[0004] This application provides a base station, a central station, and a nonlinear signal processing method to improve the accuracy of calculating nonlinear distortion signals caused by nonlinear components, thereby further improving the performance of correcting or compensating for nonlinear distortion caused by nonlinear components.

[0005] In a first aspect, this application provides a base station, comprising: multiple radio frequency links, an optical module, and a feature calculation module; wherein the number of the multiple radio frequency links is greater than or equal to 2; each radio frequency link is used to receive a signal of a corresponding frequency band through an antenna, and after performing radio frequency processing on the signal, transmit the signal to the optical module; the optical module is used to perform electro-optic conversion processing on the multiple signals from the multiple radio frequency links to obtain an optical signal containing the processed multiple signals; wherein the optical module includes a nonlinear component, the multiple radio frequency links include a first radio frequency link and at least one second radio frequency link, the signal of the at least one second radio frequency link generates a nonlinear distortion signal after passing through the nonlinear component, the frequency band of the nonlinear distortion signal overlaps with the frequency band corresponding to the first radio frequency link, and the optical signal also contains the nonlinear distortion signal; the optical signal is transmitted to a central station, and the optical signal is subjected to optical processing. An electrical signal is obtained through electrical conversion processing and sent to the feature calculation module. Each second RF link is further configured to perform RF processing on one signal of the corresponding frequency band received and send the resulting signal to the feature calculation module. The feature calculation module is configured to extract a target signal from the electrical signal from the optical module. The target signal includes a signal of the frequency band corresponding to the first RF link contained in the electrical signal. A nonlinear distortion prediction signal is calculated based on the target signal and at least one signal from the at least one second RF link, and the nonlinear distortion prediction signal is sent to the first RF link. The nonlinear distortion prediction signal is a first prediction signal of the nonlinear distortion signal. The first RF link is further configured to perform pre-distortion processing and RF processing on the signal of the corresponding frequency band of the first RF link based on the nonlinear distortion prediction signal, and send the processed signal to the optical module.

[0006] In this scheme, the base station can predict and calculate the nonlinear distortion signal generated when subsequent signals pass through the nonlinear components based on the signals that have previously passed through the nonlinear components and the nonlinear distortion signal caused by the nonlinear components. This can improve the accuracy of the determined nonlinear distortion prediction signal. Furthermore, the base station can perform pre-distortion processing on the signals transmitted on the transmission link based on the determined nonlinear distortion prediction signal, thereby correcting the nonlinear distortion problem generated when signals pass through the nonlinear components on the transmission link and improving the accuracy of nonlinear distortion correction.

[0007] In one possible design, the start frequency of the nonlinear distortion signal is greater than or equal to a first frequency, and the cutoff frequency of the nonlinear distortion signal is less than or equal to a second frequency, wherein: when there is one second RF link among the plurality of RF links, the first frequency is twice the start frequency of the frequency band corresponding to the one second RF link, and the second frequency is twice the cutoff frequency of the frequency band corresponding to the one second RF link; or, when there are two second RF links among the plurality of RF links, the first frequency is the sum of the start frequencies of the frequency bands corresponding to the two second RF links, and the second frequency is the sum of the cutoff frequencies of the frequency bands corresponding to the two second RF links; or, the first frequency is the difference between the start frequencies of the frequency bands corresponding to the two second RF links, and the second frequency is the difference between the cutoff frequencies of the frequency bands corresponding to the two second RF links.

[0008] In one possible design, the feature calculation module includes an iterative calculation module, which is used to: calculate target parameters based on the target signal, wherein the target parameters are used to characterize the nonlinear distortion characteristics of the nonlinear component; calculate a target prediction signal based on at least one signal of the at least one second RF link, wherein the target prediction signal is a second prediction signal of the nonlinear distortion signal; and correct the target prediction signal based on the target parameters to obtain the nonlinear distortion prediction signal.

[0009] In this scheme, the base station calculates the nonlinear distortion characteristic parameters of the nonlinear element based on the actual signal passing through the nonlinear element and the actual nonlinear distortion signal generated after the signal passes through the nonlinear element. This can improve the accuracy of determining the nonlinear distortion characteristics of the nonlinear element, and thus improve the accuracy of correcting the target prediction signal based on the nonlinear distortion characteristic parameters of the nonlinear element.

[0010] In one possible design, when the iterative calculation module calculates the target parameters based on the target signal, it is specifically used to: calculate the target parameters based on a set first calculation model and the target signal, wherein the first calculation model is used to represent the correspondence between one signal among the multiple signals input to the nonlinear component, the nonlinear distortion signal output by the nonlinear component in the same frequency band as the one signal, and the nonlinear distortion characteristic parameter of the nonlinear component; when the iterative calculation module calculates the target prediction signal based on at least one signal of the at least one second RF link, it is specifically used to: calculate the target prediction signal based on a set second calculation model and at least one signal of the at least one second RF link, wherein the second calculation model is used to represent the correspondence between at least one signal passing through the nonlinear component and the nonlinear distortion signal generated after the at least one signal passes through the nonlinear component.

[0011] In this scheme, the base station uses the useful signal and the distorted signal to perform modeling calculations, and predicts the nonlinear distorted signal generated after the useful signal passes through nonlinear components. The target prediction signal that needs to be calculated can be obtained simply, quickly and accurately through the calculation model.

[0012] In one possible design, when the iterative calculation module corrects the target prediction signal according to the target parameters to obtain the nonlinear distortion prediction signal, it is specifically used to: multiply the target parameters by the target prediction signal to obtain the nonlinear distortion prediction signal.

[0013] In this scheme, the base station can further improve the accuracy of the determined nonlinear distortion prediction signal by correcting the predicted nonlinear distortion signal based on the nonlinear distortion characteristic parameters of the nonlinear components.

[0014] In one possible design, the optical module includes: an electro-optic conversion module, a photoelectric conversion module, a first port, a second port, and a third port; the electro-optic conversion module is used to perform electro-optic conversion processing on the multiple signals, and the electro-optic conversion module includes the nonlinear component; the photoelectric conversion module is used to perform photoelectric conversion processing on the optical signal; the first port is used to receive the multiple signals; the second port is used to send the optical signal to the central station; and the third port is used to send the electrical signal to the feature calculation module.

[0015] In this scheme, by improving the structure of the optical module in the base station and adding a signal transmission port and photoelectric conversion module, it is possible to obtain the electrical signal corresponding to the optical signal sent by the base station to the central station. Thus, the nonlinear distortion signal generated after the useful signal passes through the nonlinear components of the optical module can be obtained from the electrical signal and fed back to the base station digital link, which facilitates the modeling and pre-distortion correction of the nonlinear components.

[0016] In one possible design, the feature calculation module further includes a filtering module; the filtering module is used to filter the electrical signal to obtain the target signal.

[0017] In this scheme, the base station filters the signal through a filtering module, which can retain only the required signal and avoid interference from some useless signals in the subsequent processing, thereby improving the accuracy of signal processing.

[0018] In one possible design, the feature calculation module further includes a feedback module, which is used to: perform time delay correction processing on the target signal and at least one signal of the at least one second radio frequency link to obtain the target signal and at least one signal of the at least one second radio frequency link with consistent time delay.

[0019] In this scheme, the base station can ensure that the nonlinear distortion prediction signal determined based on the target signal corresponds in time with the signal of at least one second radio frequency link by performing time delay correction processing on the target signal and the signal of at least one second radio frequency link, thereby avoiding errors caused by time delay during signal processing.

[0020] In one possible design, the feedback module includes: a latching module, a correlator, a threshold decision module, a delay calculation module, and a delay alignment module; the latching module is used to latch signals from the at least one second RF link for a set time slot length, and send the latched signals to the correlator; the correlator is used to perform correlation processing on the target signal and the signal from the latching module to obtain a correlation signal, and send the correlation signal to the threshold decision module, wherein the correlation signal is a non-linear signal; the threshold decision module is used to determine whether the correlation value of the received correlation signal is greater than or equal to a set value, and if so, send the correlation signal to the delay calculation module. Otherwise, the relevant signals are not processed; the delay calculation module is used to calculate the delay between the signal of the first RF link and the signal of the at least one second RF link with a set time slot length based on the relevant signal when it receives the relevant signal from the threshold decision module, and send the delay to the delay alignment module; the delay alignment module is used to remove the signal in the target signal that has the delay with the signal of the at least one second RF link with a set time slot length based on the delay after receiving the delay from the delay calculation module, and to remove the signal in the signal of the set time slot length of each second RF link that has the delay with the target signal.

[0021] In this scheme, the base station can determine the time delay between the target signal and the signal of at least one second radio frequency link through time delay calculation, and then perform time delay correction on the target signal and the signal of the at least one second radio frequency link based on the time delay. At the same time, the time delay calculation process is controlled by a lock number control method to reduce the signal processing load to a certain extent.

[0022] In one possible design, the threshold decision module is further configured to: when determining that the correlation value of the related signal is greater than or equal to the set value, instruct the latching module to latch signals from the at least one second RF link for a set time slot length respectively, and replace the previously latched signal with the currently latched signal; when determining that the correlation value of the related signal is less than the set value, instruct the latching module to stop latching signals from the at least one second RF link for a set time slot length.

[0023] In this scheme, the threshold decision module of the base station controls the triggering of the lock count module based on the correlation value of the nonlinear distortion signal and the related signal corresponding to at least one second radio frequency link. This enables the control of the lock count update based on the actual signal conditions in the actual scenario, thereby improving the accuracy and scenario adaptability of the relevant control.

[0024] In one possible design, when the first RF link performs pre-distortion processing on the signal in the corresponding frequency band of the first RF link based on the nonlinear distortion prediction signal, it is specifically used to: subtract the nonlinear distortion prediction signal from the signal in the corresponding frequency band of the first RF link to obtain the signal after pre-distortion processing of the signal in the corresponding frequency band of the first RF link.

[0025] Secondly, this application provides a base station, comprising: multiple radio frequency links, an optical module, and a feature calculation module; wherein the number of the multiple radio frequency links is greater than or equal to 2; each radio frequency link is used to receive a signal of a corresponding frequency band through an antenna, and after performing radio frequency processing on the signal, transmit the signal to the optical module; the optical module is used to perform electro-optic conversion processing on the multiple signals from the multiple radio frequency links to obtain an optical signal containing the processed multiple signals; wherein the optical module includes nonlinear components, the multiple radio frequency links include a first radio frequency link and at least one second radio frequency link, the signal of the at least one second radio frequency link generates a nonlinear distortion signal after passing through the nonlinear components, the frequency band of the nonlinear distortion signal overlaps with the frequency band corresponding to the first radio frequency link, and the optical signal also contains the nonlinear distortion signal; the optical signal is transmitted to the central station, and received from the central station... The target signal is subjected to photoelectric conversion processing, and the processed target signal is sent to the feature calculation module. The target signal includes a signal in the frequency band corresponding to the first RF link. Each second RF link is further configured to perform RF processing on one signal in the corresponding frequency band and send the resulting signal to the feature calculation module. The feature calculation module is configured to receive the target signal from the optical module; calculate a nonlinear distortion prediction signal based on the target signal and at least one signal from the at least one second RF link, and send the nonlinear distortion prediction signal to the first RF link. The nonlinear distortion prediction signal is a first prediction signal of the nonlinear distortion signal. The first RF link is further configured to perform pre-distortion processing and RF processing on the signal in the frequency band corresponding to the first RF link based on the nonlinear distortion prediction signal, and send the processed signal to the optical module.

[0026] In this scheme, the base station sends the signal after passing through the nonlinear component to the central station, and then receives the signal looped back from the central station, which contains the useful signal and the nonlinear distortion signal caused by the nonlinear component. Based on the signal that previously passed through the nonlinear component and the nonlinear distortion signal caused by the nonlinear component, the base station can predict and calculate the nonlinear distortion signal generated when the subsequent signal passes through the nonlinear component. This can improve the accuracy of the determined nonlinear distortion prediction signal. Furthermore, the base station can perform pre-distortion processing on the signal transmitted on the transmission link based on the determined nonlinear distortion prediction signal, thereby correcting the nonlinear distortion problem generated when the signal passes through the nonlinear component on the transmission link and improving the accuracy of nonlinear distortion correction.

[0027] In one possible design, the start frequency of the nonlinear distortion signal is greater than or equal to a first frequency, and the cutoff frequency of the nonlinear distortion signal is less than or equal to a second frequency, wherein: when there is one second RF link among the plurality of RF links, the first frequency is twice the start frequency of the frequency band corresponding to the one second RF link, and the second frequency is twice the cutoff frequency of the frequency band corresponding to the one second RF link; or, when there are two second RF links among the plurality of RF links, the first frequency is the sum of the start frequencies of the frequency bands corresponding to the two second RF links, and the second frequency is the sum of the cutoff frequencies of the frequency bands corresponding to the two second RF links; or, the first frequency is the difference between the start frequencies of the frequency bands corresponding to the two second RF links, and the second frequency is the difference between the cutoff frequencies of the frequency bands corresponding to the two second RF links.

[0028] In one possible design, the feature calculation module includes an iterative calculation module, which is used to: calculate target parameters based on the target signal, wherein the target parameters are used to characterize the nonlinear distortion characteristics of the nonlinear component; calculate a target prediction signal based on at least one signal of the at least one second RF link, wherein the target prediction signal is a second prediction signal of the nonlinear distortion signal; and correct the target prediction signal based on the target parameters to obtain the nonlinear distortion prediction signal.

[0029] In one possible design, when the iterative calculation module calculates the target parameters based on the target signal, it is specifically used to: calculate the target parameters based on a set first calculation model and the target signal, wherein the first calculation model is used to represent the correspondence between one signal among the multiple signals input to the nonlinear component, the nonlinear distortion signal output by the nonlinear component in the same frequency band as the one signal, and the nonlinear distortion characteristic parameter of the nonlinear component; when the iterative calculation module calculates the target prediction signal based on at least one signal of the at least one second RF link, it is specifically used to: calculate the target prediction signal based on a set second calculation model and at least one signal of the at least one second RF link, wherein the second calculation model is used to represent the correspondence between at least one signal passing through the nonlinear component and the nonlinear distortion signal generated after the at least one signal passes through the nonlinear component.

[0030] In one possible design, when the iterative calculation module corrects the target prediction signal according to the target parameters to obtain the nonlinear distortion prediction signal, it is specifically used to: multiply the target parameters by the target prediction signal to obtain the nonlinear distortion prediction signal.

[0031] In one possible design, the feature calculation module further includes a filtering module; the filtering module is used to filter the electrical signal to obtain the target signal.

[0032] In one possible design, when the optical module receives a target signal from the central station, performs photoelectric conversion processing on the target signal, and sends the processed target signal to the feature calculation module, it is specifically used to: receive a downlink signal from the central station, perform photoelectric conversion processing on the downlink signal, and send the processed downlink signal to the feature calculation module, wherein the downlink signal contains the target signal and other signals to be sent to the base station; when the feature calculation module receives the target signal from the optical module, it is specifically used to: receive the downlink signal from the optical module, and perform filtering processing on the downlink signal to obtain the target signal.

[0033] In this scheme, the base station can extract the target signal from the signal from the central station, facilitating subsequent processing of the target signal and avoiding interference from other signals in the target signal processing, thereby improving the accuracy of signal processing. Simultaneously, since the target signal is looped back through the central station, it can also correct for some nonlinear distortion issues in related nonlinear components within the central station.

[0034] In one possible design, the feature calculation module further includes a feedback module, which is used to: perform time delay correction processing on the target signal and at least one signal of the at least one second radio frequency link to obtain the target signal and at least one signal of the at least one second radio frequency link with consistent time delay.

[0035] In one possible design, the feedback module includes: a latching module, a correlator, a threshold decision module, a delay calculation module, and a delay alignment module; the latching module is used to latch signals from the at least one second RF link for a set time slot length, and send the latched signals to the correlator; the correlator is used to perform correlation processing on the target signal and the signal from the latching module to obtain a correlation signal, and send the correlation signal to the threshold decision module, wherein the correlation signal is a non-linear signal; the threshold decision module is used to determine whether the correlation value of the received correlation signal is greater than or equal to a set value, and if so, send the correlation signal to the delay calculation module. Otherwise, the relevant signals are not processed; the delay calculation module is used to calculate the delay between the signal of the first RF link and the signal of the at least one second RF link with a set time slot length based on the relevant signal when it receives the relevant signal from the threshold decision module, and send the delay to the delay alignment module; the delay alignment module is used to remove the signal in the target signal that has the delay with the signal of the at least one second RF link with a set time slot length based on the delay after receiving the delay from the delay calculation module, and to remove the signal in the signal of the set time slot length of each second RF link that has the delay with the target signal.

[0036] In one possible design, the threshold decision module is further configured to: when determining that the correlation value of the related signal is greater than or equal to the set value, instruct the latching module to latch signals from the at least one second RF link for a set time slot length respectively, and replace the previously latched signal with the currently latched signal; when determining that the correlation value of the related signal is less than the set value, instruct the latching module to stop latching signals from the at least one second RF link for a set time slot length.

[0037] In one possible design, when the first RF link performs pre-distortion processing on the signal in the corresponding frequency band of the first RF link based on the nonlinear distortion prediction signal, it is specifically used to: subtract the nonlinear distortion prediction signal from the signal in the corresponding frequency band of the first RF link to obtain the signal after pre-distortion processing of the signal in the corresponding frequency band of the first RF link.

[0038] Thirdly, this application provides a central station, comprising: an optical module and a signal processing module; the optical module is used to receive an optical signal from a base station, perform photoelectric conversion processing on the optical signal to obtain an electrical signal, and send the electrical signal to the signal processing module; wherein, the electrical signal includes a nonlinear distortion signal and multiple signals received by multiple radio frequency links of the base station through antennas, the number of multiple radio frequency links is greater than or equal to 2, the multiple radio frequency links include a first radio frequency link and at least one second radio frequency link, the base station includes a nonlinear component, the signal of the at least one second radio frequency link generates the nonlinear distortion signal after passing through the nonlinear component, and the frequency band of the nonlinear distortion signal overlaps with the frequency band corresponding to the first radio frequency link; the signal processing module is used to receive the electrical signal from the optical module, extract a target signal of the frequency band corresponding to the first radio frequency link from the electrical signal, and send the target signal to the optical module; the optical module is further used to perform electro-optical conversion processing on the target signal and send the processed target signal to the base station.

[0039] In this scheme, the central station and the base station can form a loopback link. The central station loops the signal from the base station back to the base station, allowing the base station to predict and calculate the nonlinear distortion signal generated when the subsequent signal passes through nonlinear components based on the actual signal. The base station can also perform pre-distortion processing on the signal transmitted on the transmission link based on the predicted nonlinear distortion signal, thereby improving the accuracy of nonlinear distortion correction of the communication link between the base station and the central station. At the same time, it can correct nonlinear distortion problems in the base station and also correct some nonlinear distortion problems in the central station, thus improving the accuracy of communication between the central station and the base station.

[0040] In one possible design, the start frequency of the nonlinear distortion signal is greater than or equal to a first frequency, and the cutoff frequency of the nonlinear distortion signal is less than or equal to a second frequency, wherein: when there is one second RF link among the plurality of RF links, the first frequency is twice the start frequency of the frequency band corresponding to the one second RF link, and the second frequency is twice the cutoff frequency of the frequency band corresponding to the one second RF link; or, when there are two second RF links among the plurality of RF links, the first frequency is the sum of the start frequencies of the frequency bands corresponding to the two second RF links, and the second frequency is the sum of the cutoff frequencies of the frequency bands corresponding to the two second RF links; or, the first frequency is the difference between the start frequencies of the frequency bands corresponding to the two second RF links, and the second frequency is the difference between the cutoff frequencies of the frequency bands corresponding to the two second RF links.

[0041] In one possible design, the signal processing module includes a filtering module, which receives the electrical signal from the optical module, filters the electrical signal to obtain the target signal, and when the optical module performs electro-optical conversion on the target signal and sends the processed target signal to the base station, it specifically performs electro-optical conversion on the target signal and other signals to be sent to the base station to obtain a downlink signal containing the target signal and other signals to be sent to the base station, and sends the downlink signal to the base station.

[0042] In this scheme, the central station filters the signal using a filtering module, retaining only the necessary signals and avoiding interference from unwanted signals in subsequent processing, thereby improving the accuracy of signal processing. The central station transmits the target signal along with other signals to the base station, making full use of existing transmission links and avoiding the overhead of additional transmission links, thus improving resource utilization.

[0043] Fourthly, this application provides a central station, comprising: an optical module, a signal processing module, and a feature calculation module; the optical module is used to receive optical signals from at least one base station, and perform photoelectric conversion processing on the optical signals of each of the at least one base station to obtain an electrical signal for each base station; wherein, the electrical signal of any base station includes a nonlinear distortion signal and multiple signals received by multiple radio frequency links of the base station through antennas, the number of the multiple radio frequency links is greater than or equal to 2, the multiple radio frequency links include a first radio frequency link and at least one second radio frequency link, the base station includes a nonlinear component, the signal of the at least one second radio frequency link generates the nonlinear distortion signal after passing through the nonlinear component, and the frequency band of the nonlinear distortion signal overlaps with the frequency band corresponding to the first radio frequency link; the electrical signals of each base station are respectively sent to the signal processing module and the feature calculation module; the feature calculation module is used to receive the electrical signals of each base station from the optical module respectively; and perform feature calculation on the electrical signals of each base station respectively. The system performs calculations to obtain a nonlinear distortion prediction signal corresponding to each base station, and sends the nonlinear distortion prediction signal corresponding to each base station to the signal processing module. The feature calculation processing for the electrical signal of any base station includes the following steps: extracting the target signal of the frequency band corresponding to the first radio frequency link from the electrical signal, and extracting at least one signal from the at least one second radio frequency link from the electrical signal; calculating the nonlinear distortion prediction signal based on the target signal and the at least one signal from the at least one second radio frequency link, wherein the nonlinear distortion prediction signal is a first prediction signal of the nonlinear distortion signal; the signal processing module is used to receive electrical signals from each base station of the optical module; perform combining processing on the electrical signals of the at least one base station to obtain a target combined signal; receive the nonlinear distortion prediction signal corresponding to each base station from the feature calculation module; and sequentially perform distortion correction processing on the target combined signal based on the nonlinear distortion prediction signal corresponding to each base station.

[0044] In this scheme, when the central station processes signals from at least one base station, it can predict and calculate the nonlinear distortion signal generated when subsequent signals pass through the nonlinear components, based on the signals previously passed through the nonlinear components in the base stations and the nonlinear distortion signal caused by those components. This improves the accuracy of the determined nonlinear distortion prediction signal. Furthermore, based on the determined nonlinear distortion prediction signal, more accurate distortion correction processing can be performed on signals transmitted from at least one base station. Simultaneously, in this scheme, the central station can perform distortion correction processing on signals from different base stations, and can effectively correct the nonlinear distortion problems of both the base stations and the central station.

[0045] In one possible design, the start frequency of the nonlinear distortion signal is greater than or equal to a first frequency, and the cutoff frequency of the nonlinear distortion signal is less than or equal to a second frequency, wherein: when there is one second RF link among the plurality of RF links, the first frequency is twice the start frequency of the frequency band corresponding to the one second RF link, and the second frequency is twice the cutoff frequency of the frequency band corresponding to the one second RF link; or, when there are two second RF links among the plurality of RF links, the first frequency is the sum of the start frequencies of the frequency bands corresponding to the two second RF links, and the second frequency is the sum of the cutoff frequencies of the frequency bands corresponding to the two second RF links; or, the first frequency is the difference between the start frequencies of the frequency bands corresponding to the two second RF links, and the second frequency is the difference between the cutoff frequencies of the frequency bands corresponding to the two second RF links.

[0046] In one possible design, the feature calculation module includes an iterative calculation module, which is used to: calculate target parameters based on the target signal, wherein the target parameters are used to characterize the nonlinear distortion characteristics of the nonlinear component; calculate a target prediction signal based on at least one signal from the at least one second RF link, wherein the target prediction signal is a second prediction signal of the nonlinear distortion signal; and correct the target prediction signal based on the target parameters to obtain the nonlinear distortion prediction signal.

[0047] In this scheme, the central station calculates the nonlinear distortion characteristic parameters of the nonlinear components based on the actual signal passing through the nonlinear components and the actual nonlinear distortion signal generated after the signal passes through the nonlinear components. This can improve the accuracy of determining the nonlinear distortion characteristics of the nonlinear components, and thus improve the accuracy of correcting the target prediction signal based on the nonlinear distortion characteristic parameters of the nonlinear components.

[0048] In one possible design, when the iterative calculation module calculates the target parameters based on the target signal, it is specifically used to: calculate the target parameters based on a set first calculation model and the target signal, wherein the first calculation model is used to represent the correspondence between one signal among the multiple signals input to the nonlinear component, the nonlinear distortion signal output by the nonlinear component in the same frequency band as the one signal, and the nonlinear distortion characteristic parameter of the nonlinear component; when the iterative calculation module calculates the target prediction signal based on at least one signal of the at least one second RF link, it is specifically used to: calculate the target prediction signal based on a set second calculation model and at least one signal of the at least one second RF link, wherein the second calculation model is used to represent the correspondence between at least one signal passing through the nonlinear component and the nonlinear distortion signal generated after the at least one signal passes through the nonlinear component.

[0049] In this scheme, the central station uses the useful signal and the distorted signal to perform modeling and calculation, and predicts the nonlinear distorted signal generated after the useful signal passes through nonlinear components. The target prediction signal that needs to be calculated can be obtained simply, quickly and accurately through the calculation model.

[0050] In one possible design, when the iterative calculation module corrects the target prediction signal according to the target parameters to obtain the nonlinear distortion prediction signal, it is specifically used to: multiply the target parameters by the target prediction signal to obtain the nonlinear distortion prediction signal.

[0051] In this scheme, the central station can further improve the accuracy of the determined nonlinear distortion prediction signal by correcting the predicted nonlinear distortion signal based on the nonlinear distortion characteristic parameters of the nonlinear components.

[0052] In one possible design, the feature calculation module further includes a filtering module; the filtering module is used to filter the combined electrical signal to obtain the target signal.

[0053] In this scheme, the central station filters the signal through a filtering module, which can retain only the required signal and avoid interference from some useless signals in the subsequent processing, thereby improving the accuracy of signal processing.

[0054] In one possible design, the feature calculation module further includes a feedback module, which is used to: perform time delay correction processing on the target signal and at least one signal of the at least one second radio frequency link to obtain the target signal and at least one signal of the at least one second radio frequency link with consistent time delay.

[0055] In this scheme, the central station can ensure that the nonlinear distortion prediction signal determined based on the target signal corresponds in time with the signal of at least one second radio frequency link by performing time delay correction processing on the target signal and the signal of at least one second radio frequency link, thereby avoiding errors caused by time delay during signal processing.

[0056] In one possible design, the feedback module includes: a latching module, a correlator, a threshold decision module, a delay calculation module, and a delay alignment module; the latching module is used to latch signals from the at least one second RF link for a set time slot length, and send the latched signals to the correlator; the correlator is used to perform correlation processing on the target signal and the signal from the latching module to obtain a correlation signal, and send the correlation signal to the threshold decision module, wherein the correlation signal is a non-linear signal; the threshold decision module is used to determine whether the correlation value of the received correlation signal is greater than or equal to a set value, and if so, send the correlation signal to the delay calculation module. Otherwise, the relevant signals are not processed; the delay calculation module is used to calculate the delay between the signal of the first RF link and the signal of the at least one second RF link with a set time slot length based on the relevant signal when it receives the relevant signal from the threshold decision module, and send the delay to the delay alignment module; the delay alignment module is used to remove the signal in the target signal that has the delay with the signal of the at least one second RF link with a set time slot length based on the delay after receiving the delay from the delay calculation module, and to remove the signal in the signal of the set time slot length of each second RF link that has the delay with the target signal.

[0057] In this scheme, the central station can determine the time delay between the target signal and the signal of at least one second radio frequency link through time delay calculation, and then perform time delay correction on the target signal and the signal of the at least one second radio frequency link based on the time delay. At the same time, the time delay calculation process is controlled by the lock number control method to reduce the signal processing load to a certain extent.

[0058] In one possible design, the threshold decision module is further configured to: when determining that the correlation value of the related signal is greater than or equal to the set value, instruct the latching module to latch signals from the at least one second RF link for a set time slot length respectively, and replace the previously latched signal with the currently latched signal; when determining that the correlation value of the related signal is less than the set value, instruct the latching module to stop latching signals from the at least one second RF link for a set time slot length.

[0059] In this scheme, the threshold decision module of the central station controls the triggering of the lock count module based on the correlation value of the nonlinear distortion signal and the corresponding signal of at least one second radio frequency link. This enables the lock count update to be controlled based on the actual signal conditions in the actual scenario, thereby improving the accuracy and scenario adaptability of the relevant control.

[0060] In one possible design, the at least one base station includes a first base station and a second base station. The signal processing module, when sequentially performing distortion correction processing on the target combined signal based on the nonlinear distortion prediction signal corresponding to each base station, specifically performs the following: performs distortion correction processing on the target combined signal based on the nonlinear distortion prediction signal corresponding to the first base station to obtain a first target combined signal; and performs distortion correction processing on the first target combined signal based on the nonlinear distortion prediction signal corresponding to the second base station to obtain a second target combined signal.

[0061] In one possible design, when the signal processing module performs distortion correction processing on the target combined signal based on the nonlinear distortion prediction signal corresponding to the first base station to obtain the first target combined signal, it is specifically used to: subtract the nonlinear distortion prediction signal corresponding to the first base station from the target combined signal to obtain the first target combined signal.

[0062] Fifthly, this application provides a nonlinear signal processing method applied to a base station or central station. The method includes: calculating target parameters based on a target signal, wherein the target signal includes: a first signal passing through a nonlinear component, and a nonlinear distortion signal generated after at least one second signal passes through the nonlinear component, wherein the frequency band of the nonlinear distortion signal overlaps with the frequency band of the first signal, and the target parameters are used to characterize the nonlinear distortion characteristics of the nonlinear component; calculating a target prediction signal based on the at least one second signal, wherein the target prediction signal is a prediction signal of the nonlinear distortion signal; and correcting the target prediction signal based on the target parameters to obtain a nonlinear distortion prediction signal, wherein the nonlinear distortion prediction signal is a corrected prediction signal of the nonlinear distortion signal.

[0063] In one possible design, calculating target parameters based on a target signal includes: calculating the target parameters based on a set first calculation model and the target signal, wherein the first calculation model is used to represent the correspondence between one signal among multiple signals input to the nonlinear component, the nonlinear distortion signal output by the nonlinear component in the same frequency band as the one signal, and the nonlinear distortion characteristic parameters of the nonlinear component.

[0064] In one possible design, calculating the target prediction signal based on the at least one second signal includes: calculating the target prediction signal based on a set second calculation model and the at least one second signal, wherein the second calculation model is used to represent the correspondence between at least one signal passing through the nonlinear component and the nonlinear distortion signal generated after the at least one signal passes through the nonlinear component.

[0065] In one possible design, the target prediction signal is modified according to the target parameters to obtain the nonlinear distortion prediction signal, which includes: multiplying the target parameters by the target prediction signal to obtain the nonlinear distortion prediction signal.

[0066] In a sixth aspect, this application provides an apparatus comprising a memory and a processor; the memory is used to store a computer program; the processor is used to execute the computer program stored in the memory to implement the method described in the fifth aspect or any possible design of the fifth aspect.

[0067] In a seventh aspect, this application provides a communication system comprising: a base station as described in the first aspect or any possible design of the first aspect, or a base station as described in the second aspect or any possible design of the second aspect, and a central station as described in the third aspect or any possible design of the third aspect, or a central station as described in the fourth aspect or any possible design of the fourth aspect.

[0068] For the beneficial effects of the second aspect mentioned above, please refer to the description of the relevant beneficial effects of the first aspect mentioned above. For the beneficial effects of the fifth to seventh aspects mentioned above, please refer to the description of the beneficial effects of the first to fourth aspects mentioned above. They will not be repeated here. Attached Figure Description

[0069] Figure 1 This is a schematic diagram of the architecture of a ROF system;

[0070] Figure 2 This is a schematic diagram of radio frequency signal transmission in a ROF system;

[0071] Figure 3 Example diagrams for three scenarios that generate IMD2 in the ROF system;

[0072] Figure 4a This is a schematic diagram of a simulated predistortion nonlinear correction link.

[0073] Figure 4b This is a schematic diagram of a nonlinear distortion correction link based on a push-pull structure and joint adaptive post-compensation.

[0074] Figure 5 This application provides a schematic diagram of the architecture of an ROF system.

[0075] Figure 6 A schematic diagram of a base station provided in an embodiment of this application;

[0076] Figure 7 A schematic diagram of a feedback module in a base station provided in an embodiment of this application;

[0077] Figure 8 A schematic diagram of a ROF system provided in an embodiment of this application;

[0078] Figure 9 A schematic diagram of a ROF system provided in an embodiment of this application;

[0079] Figure 10 This is a comparative schematic diagram of an optical module structure provided in an embodiment of this application;

[0080] Figure 11 This is a simplified structural diagram of a base station structure provided in an embodiment of this application;

[0081] Figure 12 A schematic diagram of a base station and a central station provided for an embodiment of this application;

[0082] Figure 13 A schematic diagram of a ROF system provided in an embodiment of this application;

[0083] Figure 14 A schematic diagram of a central station provided for an embodiment of this application;

[0084] Figure 15 A schematic diagram of a ROF system provided in an embodiment of this application;

[0085] Figure 16 This is a schematic diagram of a nonlinear signal processing method provided in an embodiment of this application. Detailed Implementation

[0086] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the embodiments of this application will be further described in detail below with reference to the accompanying drawings. In the description of the embodiments of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0087] For ease of understanding, exemplary descriptions of concepts related to this application are provided for reference.

[0088] 1) Nonlinear distortion refers to the fact that the output signal of a component (or electronic component) is not linearly related to the input signal, which is caused by the nonlinear characteristics of the component. Nonlinear distortion manifests as multiple signals of the same or different frequencies generating new harmonic components or new frequency components as interference signals after passing through a nonlinear component (such as a laser diode, photodiode, amplifier, etc.).

[0089] Nonlinear distortion includes harmonic distortion (HD), intermodulation distortion (IMD), and cross-modulation distortion. Intermodulation distortion, in particular, is a distortion introduced by nonlinear components that affects the sum or difference of the frequency components of an input signal. When a signal enters a nonlinear component, its nonlinear characteristics cause mutual modulation between signals, generating additional signals not present in the original signal. These additional signals may interfere with parts of the original signal.

[0090] In the embodiments of this application, nonlinear components include, but are not limited to, electronic-optical converters (OE), electro-optic converters, and amplifiers. For example, the electronic-optical converter may be a photodiode (PD); the electro-optic converter may be a laser diode (LD); and the amplifier may be a low-noise amplifier (LNA).

[0091] 2) Predistortion refers to a preprocessing procedure performed on the signal before it passes through the nonlinear component. This preprocessing process has characteristics opposite to those of the nonlinear distortion caused by the nonlinear component, so that the signal can compensate for the nonlinear distortion generated when it passes through the nonlinear component, thereby reducing or avoiding the nonlinear distortion caused by the nonlinear component.

[0092] It should be understood that in the embodiments of this application, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, a and b, a and c, b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0093] Currently, with the promotion of 5G technology and the research and development of 6G technology, mobile networks urgently need technologies to support ultra-large-scale wireless access and ultra-high-speed data transmission. ROF (radioover fiber) technology was developed to meet the demand for high-speed, high-capacity wireless communication.

[0094] ROF (Remote Optical Frame) is a wireless access technology that combines fiber optic and wireless communication. An ROF system typically includes a center station (CS) and base stations (BS), which communicate with each other via optical fiber. The center station / base station modulates radio frequency electrical signals into optical signals for transmission to the other end. It can also achieve simultaneous ultra-wideband transmission of multiple frequency bands of wireless carrier signals through carrier multiplexing, helping to reduce the cost, power consumption, and complexity of communication systems. ROF is widely used in mobile wireless communication systems, cable television (CATV) systems, and satellite communication systems.

[0095] Figure 1 A schematic diagram of the architecture of a ROF system is shown. Figure 1 As shown, the ROF system may include a central station, base stations, and user equipment.

[0096] In this embodiment of the application, the base station may also be referred to as the headend, analog headend, or remote radio unit (RRU). The central station may also be referred to as the mother station, analog mother station, or baseband unit (BBU).

[0097] Reference Figure 1 In a ROF system, taking the downlink communication process as an example, the central station can modulate a radio frequency electrical signal (also known as an electromagnetic wave / microwave) onto a laser. The modulated light wave is then transmitted to the base station via an optical fiber link. Upon receiving the light wave signal from the central station, the base station demodulates the signal using photoelectric conversion to obtain an electrical signal, which is then transmitted to the user equipment via an antenna. The downlink communication process is the reverse of the uplink communication process described above, and will not be elaborated upon here.

[0098] In a ROF system, optical fiber or hybrid optical-electrical cable links serve as the transmission links between the central station and base stations. These links directly utilize optical carriers to transmit radio frequency signals, thereby reducing signal transmission loss. The optical carrier links only handle signal transmission; signal switching, control, and regeneration are all centralized at the central station. Base stations can perform optoelectronic format conversion of signals. This allows complex, high-cost equipment to be centralized at the central station, enabling multiple base stations to share its resources and reducing power consumption and cost.

[0099] The advantages of ROF systems in wireless communication mainly include the following: ROF systems use optical transmission technology for signal transmission, which has lower transmission loss compared to electrical transmission technology (typically, fiber optic attenuation is less than 0.4dB / km); ROF systems support ultra-wideband signal transmission capabilities (transmission frequencies can reach 0-40GHz); ROF systems are easy to install and maintain (the weight of optical fiber is about one-tenth that of coaxial cable, and the cost of optical fiber is lower); and ROF systems offer strong security (the transmitted signal is carried by optical fiber, which can resist electromagnetic interference, enhancing security and confidentiality).

[0100] While possessing significant advantages, ROF systems also have some drawbacks. For example, ROF systems are analog transmission systems, making them susceptible to signal impairments (such as noise and distortion); nonlinear effects such as dispersion may occur in the optical link; ROF systems require electrical-optical (EO) and optical-electrical (OE) conversions, increasing processing complexity and deployment costs; and some nonlinear components in ROF systems can cause nonlinear distortion of the signal, reducing the performance of the ROF system.

[0101] Figure 2 This is a schematic diagram of radio frequency (RF) signal transmission in a ROF system. Figure 2 As shown, in the RF signal transmission of the ROF system, some nonlinear components such as laser diodes, photodiodes, and RF amplifiers can be used to achieve functions such as signal processing and transmission. However, these nonlinear components may cause nonlinear distortion of the signal during signal processing and transmission, affecting the accurate processing of the signal. Especially in multi-user scenarios, this can severely degrade the performance of the ROF system.

[0102] Common nonlinear distortion problems in ROF systems include harmonic distortion, intermodulation distortion, and cross-modulation distortion. The following explanation uses second-order intermodulation distortion (IMD2) as an example. IMD2 can be generated by passing two signals of different frequency bands through nonlinear components, or it can be generated by passing signals of the same frequency band through nonlinear components. Figure 3 Example diagrams for three scenarios that generate IMD2 in the ROF system.

[0103] For example, in the first possible scenario, such as Figure 3 In scenario 1 shown, IMD2 represents the distortion of the sum of the frequency components of two frequency bands of a signal passing through a nonlinear component. For example, signal S... F1 The center frequency is F1, and the signal S F1 The signal frequency range is frequency band F11~F12, signal S F2 The center frequency is F2, and the signal S F2 The signal frequency range is frequency band F21~F22, signal S F1 With signal S F2 Simultaneously, after passing through nonlinear components, an IMD2 signal may be generated. The frequency range of this IMD2 signal is between (F11+F21) and (F12+F22). Then, a signal S whose frequency range overlaps with the frequency range of this IMD2 signal... F3 With signal S F1 Signal S F2 Simultaneously, when passing through the nonlinear component, the signal S F1 With signal S F2 The IMD2 signal generated after passing through the nonlinear components will strike signal S. F3 For signal S F3 This causes interference and affects subsequent signal S. F3 Normal processing.

[0104] In the second possible scenario, such as Figure 3 In scenario 2 shown, IMD2 represents the distortion due to the difference in frequency components between two frequency bands of the signal after passing through a nonlinear component. For example, the aforementioned signal S... F1 With signal S F2 Meanwhile, the frequency range of the IMD2 signal generated after passing through the nonlinear components is between (F11-F21) and (F12-F22). The frequency band of this IMD2 signal is similar to that of the aforementioned signal S. F3 When the frequency bands overlap, they will also hit the signal S. F3 For signal S F3 This causes interference and affects subsequent signal S. F3 Normal processing.

[0105] In the third possible scenario, such as Figure 3In scenario 3 shown, IMD2 is the distortion of the sum of the frequency components of a signal passing through a nonlinear component. For example, in the aforementioned signal S... F1 With signal S F2 The same, for example, only signal S F1 At that time, signal S F1 The frequency range of the IMD2 signal generated after passing through the nonlinear components is the frequency band 2F11 to 2F12. The frequency band of this IMD2 signal is the same as that of the aforementioned signal S. F3 When the frequency bands overlap, they will also hit the signal S. F3 For signal S F3 This causes interference and affects subsequent signal S. F3 Normal processing.

[0106] The second-order intermodulation distortion signals in the above three scenarios will affect the normal processing of useful signals, thereby affecting the performance of the ROF system.

[0107] Currently, in order to solve the problem of nonlinear distortion caused by nonlinear components in ROF systems, one approach is to correct the nonlinear distortion in ROF systems by simulating pre-distortion, and another approach is to correct the nonlinear distortion in ROF systems based on a push-pull structure combined with adaptive post-compensation.

[0108] Figure 4a This is a schematic diagram of a simulated predistortion nonlinear correction link. Figure 4a As shown, in the scheme for correcting nonlinear distortion in a ROF system using simulated predistortion, multiple functional units from the nonlinear distortion signal generation unit to the second phase adjustment unit constitute a simulated predistortion correction link. This simulated predistortion correction link can be built using simulated components with pre-designed fixed parameters and component characteristics to achieve simulated predistortion functionality, which can improve some nonlinear distortion problems to a certain extent. However, in this scheme, since the predistortion correction link is generally relatively fixed, it can only specifically correct nonlinear distortion caused by a certain type of nonlinear component, and cannot achieve adaptive iterative correction processing for nonlinear distortion caused by different nonlinear components, thus limiting its application scope. At the same time, the fixed simulated predistortion correction link also has relatively limited fitting ability for nonlinear distortion signals, resulting in limited correction performance. In addition, the simulated predistortion correction link cannot adaptively fit the nonlinear effects caused by temperature changes.

[0109] Figure 4b This is a schematic diagram of a nonlinear distortion correction link based on a push-pull structure and joint adaptive post-compensation. Figure 4bAs shown, in the scheme for correcting nonlinear distortion in a ROF system based on a push-pull structure and adaptive post-compensation, the push-pull structure maintains the phase difference between the uplink and downlink in the system at around 180 degrees. The receiver uses balanced detection to suppress all even-order nonlinear distortions, and then an adaptive compensation algorithm is used to suppress the main odd-order nonlinear distortions. This scheme can simultaneously and adaptively suppress even-order distortions (such as second-order intermodulation distortion IMD2 and second-order harmonic distortion HD2) and odd-order distortions (such as third-order intermodulation distortion IMD3 and third-order cross-modulation distortion XMD3) caused by the nonlinearity of nonlinear components in the system. However, this scheme requires the deployment of two sets of LD and PD in the correction link, resulting in high system deployment costs and large component deployment area.

[0110] The aforementioned nonlinear distortion correction schemes suffer from low performance and high cost. Therefore, this application provides a base station, a central station, and a nonlinear signal processing method to deploy a nonlinear distortion correction system at a lower cost, while improving the accuracy of calculating the nonlinear distortion signal, thereby further enhancing the performance of correcting or compensating for nonlinear distortion based on the determined nonlinear distortion signal.

[0111] The following embodiments of this application take the solution of the second-order intermodulation distortion problem of the ROF system as an example to provide a detailed description of the base station, central station and nonlinear signal processing method provided in the embodiments of this application.

[0112] It should be understood that the base station, central station, and nonlinear signal processing method provided in this application are not limited to ROF systems, but can also be applied to ROF-based analog optical wireless communication network architectures, communication network architectures similar to central stations and distributed base station unit networking, and communication network architectures where multiple analog headends are connected to a small number of central stations through optical transmission media (e.g., fiber optic or optoelectronic hybrid cables) (e.g., a network architecture where multiple analog headends are connected to one central station). Furthermore, the base station, central station, and nonlinear signal processing method provided in this application can also be applied to various other wireless communication systems to solve the nonlinear distortion problem caused by nonlinear components in wireless communication systems. Such wireless communication systems may include, for example, Long Term Evolution (LTE) systems, 2G, 3G, 4G, 5G communication systems, or next-generation communication systems (e.g., 6G systems). It should also be understood that the base station, central station, and nonlinear signal processing method provided in this application are not limited to solving second-order intermodulation distortion problems, but can also solve various nonlinear distortion problems such as harmonic distortion (e.g., HD2) and intermodulation distortion (e.g., IMD3).

[0113] Figure 5 This is a schematic diagram of the architecture of a ROF system provided in an embodiment of this application. Figure 5 As shown in the embodiments of this application, the ROF system adopts a hybrid digital-analog architecture. In the ROF system, the base station mainly consists of optical modules, digital links, analog links, etc. These components constitute the downlink transmit (TX) link and uplink receive (RX) link in the base station. The base station can send signals from the user equipment to the central station through the uplink receive link, and it can also send signals from the central station to the user equipment through the downlink transmit link.

[0114] The optical module is primarily used to convert radio frequency electrical signals into optical signals and send them to the central station, or to receive optical signals from the central station and convert them back into radio frequency electrical signals. The digital link section can be implemented using field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), or digital signal processors (DSPs). The digital link section can perform functions such as digital filtering, channel selection, and digital processing. The analog link section includes at least amplifiers (such as power amplifiers (PAs), LNAs, etc.) and other components or modules. The analog link can be used to perform preliminary processing of the signals received by the base station and transmit the signals to the digital link for further processing. It should be noted that... Figure 5 The example used is a digital link implemented as a DSP and an analog link containing a PA or LNA, but the structure or implementation of the digital or analog link is not limited to this. Figure 5 The method is illustrated in the image.

[0115] The central station mainly includes optical modules and signal processing modules. The optical modules are primarily used to convert radio frequency (RF) electrical signals into optical signals for transmission to the base station, or to receive optical signals from the base station and convert them back into RF electrical signals. The signal processing modules are mainly used to perform conversion processing between baseband (BB) signals, intermediate frequency (IF) signals, and radio frequency (RF) signals.

[0116] The base station and the central station can be connected via an optical transmission medium, which can be an optical fiber, a hybrid optical-electrical cable, etc.

[0117] In the aforementioned ROF system, the base station is a hybrid analog-digital headend architecture. Compared to a conventional purely analog headend architecture, it offers greater flexibility in functional design and unique performance advantages, particularly in addressing system nonlinearity correction issues. The following detailed description will be provided in conjunction with specific embodiments.

[0118] Example 1

[0119] Figure 6 This is a schematic diagram of a base station provided in an embodiment of this application. Figure 6 As shown in this embodiment, the base station may include multiple radio frequency links (e.g., Figure 6 The radio frequency link 1, radio frequency link 2, radio frequency link 3, optical module, and feature calculation module are shown in the figure; wherein the number of the plurality of radio frequency links is greater than or equal to 2.

[0120] It should be noted that, for ease of explanation, Figure 6 The example only shows the case where the base station includes 3 radio frequency links. In actual base stations, there may be more or fewer radio frequency links, which will not be elaborated here.

[0121] In this base station, each radio frequency link is used to receive one signal in the corresponding frequency band through an antenna, perform radio frequency processing on the signal, and then transmit the signal to the optical module. Any one or more signals can originate from a single user equipment, and different signals can originate from different user equipments.

[0122] The optical module is used to perform electro-optical conversion processing on multiple signals from the plurality of radio frequency links to obtain an optical signal containing the processed multiple signals, and to send the optical signal to the central station; and to perform photoelectric conversion processing on the optical signal to obtain an electrical signal and to send the electrical signal to the feature calculation module; wherein, among the plurality of radio frequency links, there is a first radio frequency link and at least one second radio frequency link, the optical module includes a nonlinear component, and the signal of the at least one second radio frequency link generates a nonlinear distortion signal after passing through the nonlinear component, the frequency band of the nonlinear distortion signal overlaps with the frequency band corresponding to the first radio frequency link; the optical signal includes the nonlinear distortion signal and the multiple signals.

[0123] Optionally, the base station also includes a combining module. Figure 6 (Not shown in the image), the combining module is used to receive multiple signals from the plurality of radio frequency links, perform combining processing on the multiple signals to obtain a combined signal, and send the combined signal to the optical module. The optical module is then used to receive the combined signal from the combining module and perform electro-optical conversion processing on the combined signal to obtain the optical signal. For example, the combining module can be a combiner.

[0124] Each second RF link is also used to perform RF processing on one signal of the corresponding frequency band received, and then send the resulting signal to the feature calculation module.

[0125] The feature calculation module is configured to extract a target signal from the electrical signal from the optical module, wherein the target signal is a signal in the frequency band corresponding to the first radio frequency link contained in the electrical signal; calculate a nonlinear distortion prediction signal based on the target signal and at least one signal from the at least one second radio frequency link, and send the nonlinear distortion prediction signal to the first radio frequency link, wherein the nonlinear distortion prediction signal is a first prediction signal of the nonlinear distortion signal.

[0126] The first radio frequency link is further configured to perform pre-distortion processing and radio frequency processing on the signal in the corresponding frequency band of the first radio frequency link according to the nonlinear distortion prediction signal, and send the processed signal to the optical module.

[0127] In some embodiments of this application, the radio frequency processing performed on the radio frequency link may include one or more of the following processes: filtering, power or energy amplification, frequency conversion, analog-to-digital conversion, transmission rate adjustment, power adjustment, digital-to-analog conversion, etc.

[0128] In some embodiments of this application, the frequency band corresponding to the first RF link overlaps with the frequency band of the nonlinear distortion signal. The start frequency of the nonlinear distortion signal is greater than or equal to a first frequency, and the cutoff frequency of the nonlinear distortion signal is less than or equal to a second frequency. In one possible scenario, a second RF link exists among the plurality of RF links. In this case, the first frequency is twice the start frequency of the frequency band corresponding to the second RF link, and the second frequency is twice the cutoff frequency of the frequency band corresponding to the second RF link. For example... Figure 3 The scenario shown is Scenario 3. In another possible scenario, there are two second radio frequency links among the plurality of radio frequency links. In this case, the first frequency is the sum of the start frequencies of the corresponding frequency bands of the two second radio frequency links, and the second frequency is the sum of the cutoff frequencies of the corresponding frequency bands of the two second radio frequency links, for example... Figure 3 The scenario shown in Scenario 1; or, the first frequency is the difference between the start frequencies of the corresponding frequency bands of the two second RF links, and the second frequency is the difference between the cutoff frequencies of the corresponding frequency bands of the two second RF links, for example... Figure 3 The situation in scenario 2 shown.

[0129] For example, when a second radio frequency link exists among the plurality of radio frequency links, the first radio frequency link can be... Figure 6The radio frequency link 3 shown in the figure, the second radio frequency link can be Figure 6 The RF link 1 or RF link 2 shown in the diagram generates a nonlinear distortion signal after the signal passes through the nonlinear component, and the frequency band of this nonlinear distortion signal overlaps with the frequency band of the signal on RF link 3. When there are two second RF links among the plurality of RF links, the first RF link can be... Figure 6 The radio frequency chain 3 shown in the figure, the two second radio frequency links can be respectively Figure 6 The radio frequency links 1 and 2 shown in the figure generate nonlinear distortion signals after passing through the nonlinear components, and the frequency band of the nonlinear distortion signals overlaps with the frequency band of the signals on the radio frequency link 3.

[0130] In this embodiment, the optical module may include an electro-optical conversion module, a photoelectric conversion module, a first port, a second port, and a third port.

[0131] In the optical module, the first port is used to receive the multiple signals from the plurality of radio frequency links and transmit them to the electro-optical conversion module.

[0132] The electro-optic conversion module, connected to the first port, is used to perform electro-optic conversion processing on the multiple signals to obtain optical signals. The electro-optic conversion module includes the nonlinear component, which can be used to perform electro-optic conversion processing on the signals. For example, the nonlinear component is an electro-optic converter, such as an LD (Light Detector).

[0133] Optionally, when the base station includes the combining module, and the first port is connected to the combining module, the first port is used to receive the combined signal from the combining module and transmit it to the electro-optical conversion module. The electro-optical conversion module then performs electro-optical conversion processing on the combined signal to obtain the optical signal.

[0134] The second port is connected to the electro-optical conversion module and is used to send out the optical signal obtained by the electro-optical conversion module, for example, by sending the optical signal to the central station through an optical transmission medium.

[0135] The photoelectric conversion module is used to receive the optical signal from the electro-optical conversion module and perform photoelectric conversion processing on the optical signal to obtain the electrical signal. For example, the photoelectric conversion module is a photoelectric converter, such as a PD.

[0136] In some embodiments of this application, the optical signal received by the photoelectric conversion module from the electro-optical conversion module may be sampled from the optical signal obtained by electro-optical conversion processing of the electro-optical conversion module.

[0137] The third port is connected to the photoelectric conversion module and is used to send the electrical signal obtained by the photoelectric conversion module to the feature calculation module.

[0138] In this embodiment, the feature calculation module includes a filtering module and an iterative calculation module.

[0139] In the feature calculation module, the filtering module is used to receive the electrical signal sent by the photoelectric conversion module through the third port, and to filter the electrical signal to obtain the target signal. For example, the filtering module is a filter.

[0140] In some embodiments of this application, when the filtering module performs filtering processing on the electrical signal, it can use the signal frequency band of the first radio frequency link as a reference for filtering to filter out signals in the electrical signal that are in frequency bands different from the signal frequency band of the first radio frequency link.

[0141] Optionally, the feature calculation module may further include a power amplification module connected after the filter for amplifying the power or energy of the target signal obtained by the filter. For example, the power amplification module may be an LNA (Light Array Amplifier).

[0142] The iterative calculation module can be used to: receive the target signal from the filter and at least one signal from the at least one second RF link; calculate target parameters based on the target signal; calculate a target prediction signal based on the at least one signal from the at least one second RF link; and then correct the target prediction signal based on the target parameters to obtain the nonlinear distortion prediction signal. The target parameters characterize the nonlinear distortion characteristics of the nonlinear component, and the target prediction signal is a second prediction signal of the nonlinear distortion signal.

[0143] Specifically, after receiving the target signal, the iterative calculation module calculates the target parameters according to the set first calculation model and the target signal, and calculates the target predicted signal according to the set second calculation model and at least one signal from the at least one second RF link. The first calculation model represents the correspondence between one signal from the multiple input signals of the nonlinear component, the nonlinear distortion signal output by the nonlinear component in the same frequency band as the input signal, and the nonlinear distortion characteristic parameters of the nonlinear component. The second calculation model represents the correspondence between at least one signal passing through the nonlinear component and the nonlinear distortion signal generated after the at least one signal passes through the nonlinear component. The set first and second calculation models can be obtained through pre-training.

[0144] After the iterative calculation module calculates the target parameters and the target predicted signal, it multiplies the target parameters and the target predicted signal to obtain the nonlinear distortion predicted signal. The target parameters are nonlinear distortion coefficients obtained based on at least one signal actually passing through the nonlinear component and the actual nonlinear distortion signal generated after that signal passes through the nonlinear component. This more accurately reflects the nonlinear distortion characteristics of the nonlinear component. The target predicted signal is obtained by estimating the nonlinear distortion signal generated after the at least one signal from the at least one second RF link passes through the nonlinear component. Based on the estimated nonlinear distortion predicted signal (i.e., the second predicted signal), the corresponding target parameters are further used to correct the estimated nonlinear distortion predicted signal, resulting in a more accurate nonlinear distortion predicted signal (i.e., the first predicted signal). This significantly improves the accuracy of pre-distortion processing of the first RF link signal based on the final obtained nonlinear distortion predicted signal.

[0145] In some embodiments of this application, the feature calculation module further includes a feedback module, which can be used to perform time delay correction on the signal received by the radio frequency link in the base station. The feedback module can be located between the iterative calculation module and the filter. The feedback module is used to receive the target signal from the filter and at least one signal from the at least one second radio frequency link, and perform time delay correction processing on the target signal and the at least one signal from the at least one second radio frequency link to obtain the target signal and the at least one signal from the at least one second radio frequency link with consistent time delay, and send the obtained signal to the iterative calculation module.

[0146] For details, please refer to Figure 7The feedback module may include a lock count module, a correlator, a threshold decision module, a delay calculation module, and a delay alignment module.

[0147] The latching module is used to latch signals from the at least one second RF link for a set time slot length, and send the latched signals to the correlator. The latching module can be implemented using a latch.

[0148] As an optional implementation, the latching module can employ a fixed time-slot latching method. For example, the latching module can, according to the wireless communication frame structure, use a synchronization signal of a set duration (e.g., 10ms) as a reference, and acquire and latch signals from the at least one second radio frequency link with a fixed delay, wherein different delays correspond to signals in different time slots. For instance, with a fixed delay of 5ms, after the latching module acquires a signal of 10ms duration between 10-20ms, the next acquisition will acquire a signal of 10ms duration between 15-25ms.

[0149] As another optional implementation, the locking module can perform signal acquisition and latching according to the control of the threshold decision module, as detailed below.

[0150] The correlator is used to perform correlation processing on the target signal and the signal from the lock number module to obtain a correlation signal, and send the correlation signal to the threshold decision module, wherein the correlation signal is a nonlinear component signal.

[0151] Specifically, when the correlator performs correlation processing on the target signal and the signal from the lock-to-number module, it first determines the target prediction signal based on the signal from the lock-to-number module, i.e., at least one signal from the at least one second RF link. Then, it performs correlation processing on the target signal and the target prediction signal to obtain the correlation signal. The correlator can determine the target prediction signal in the same way as the iterative calculation module.

[0152] The threshold decision module is used to receive the correlation signal from the correlator, determine whether the correlation value (or accumulated value or correlation accumulated value) of the received correlation signal is greater than or equal to a set value, and if so, send the correlation signal to the delay calculation module; otherwise, do not process the correlation signal.

[0153] In some embodiments of this application, the threshold decision module can also be used to perform latching control on the latching module. Specifically, when the threshold decision module determines that the correlation value of the correlated signal is greater than or equal to the set value, it instructs the latching module to start latching or perform latching update, respectively latching signals from the at least one second RF link for a set time slot length, and replacing the previously latched signal with the currently latched signal. The set time slot length can be flexibly set according to actual needs. When the threshold decision module determines that the correlation value of the correlated signal is less than the set value, it instructs the latching module to pause signal latching, that is, to stop latching signals from the at least one second RF link for a set time slot length, until the threshold decision module again determines that the correlation value of the correlated signal from the correlator is greater than the set threshold, at which point the threshold decision module instructs the latching module to continue latching and updating the latched signal.

[0154] The delay calculation module is used to calculate the delay between the signal of the first radio frequency link and the signal of the at least one second radio frequency link with a set time slot length based on the relevant signal received from the threshold decision module, and send the delay to the delay alignment module.

[0155] The delay alignment module is configured to, upon receiving the delay from the delay calculation module, remove signals in the target signal that have the delay relative to the signals of the at least one second radio frequency link with a set time slot length, and remove signals in the signals of the set time slot length of each second radio frequency link that have the delay relative to the target signal, thereby retaining signals in the target signal and the signals of the at least one second radio frequency link with the same delay.

[0156] In this way, there is essentially no time delay between the target signal received by the iterative calculation module and the signal of the at least one second radio frequency link, which can ensure the accurate calculation of the corresponding nonlinear distortion prediction signal and thus improve the accuracy of subsequent predistortion processing.

[0157] After the iterative calculation module calculates the nonlinear distortion prediction signal, it sends the nonlinear distortion prediction signal to the first RF link. Upon receiving the nonlinear distortion prediction signal, the first RF link performs pre-distortion processing on the signal in the corresponding frequency band based on the nonlinear distortion prediction signal. Specifically, the first RF link subtracts the nonlinear distortion prediction signal from the signal in the corresponding frequency band to obtain the pre-distorted signal. After performing RF processing on the pre-distorted signal, the first RF link sends it to the optical module, which can then transmit the signal to the central station.

[0158] Optionally, the first RF link includes a predistortion processing module, which is used to perform predistortion processing on the signal in the corresponding frequency band of the first RF link according to the nonlinear distortion prediction signal. For example, the predistortion processing module can be an adder, a multiplier, or a multiply-adder combination module, wherein the multiply-adder combination module has the functions of both a multiplier and an adder.

[0159] In the above embodiments, the base station can calculate the nonlinear distortion characteristic parameters of the nonlinear element based on the actual signal passing through the nonlinear element and the actual nonlinear distortion signal generated after the signal passes through the nonlinear element, which can improve the accuracy of determining the nonlinear distortion characteristics of the nonlinear element. After determining the nonlinear distortion parameters of the nonlinear element, the base station combines these parameters with the signal currently transmitted on the transmission link to predict the nonlinear distortion prediction signal generated when the signal passes through the nonlinear element, which can improve the accuracy of the determined nonlinear distortion prediction signal. Furthermore, the base station can perform pre-distortion processing on the signal currently transmitted on the transmission link based on the determined nonlinear distortion prediction signal, thereby correcting the nonlinear distortion problem generated when the signal passes through the nonlinear element on the transmission link, improving the accuracy of nonlinear distortion correction. At the same time, this method has a wide range of applications, can more accurately predict nonlinear distortion signals caused by various nonlinear elements, and is also convenient for correcting nonlinear distortion problems caused by various nonlinear elements. Therefore, this method has strong versatility and adaptability.

[0160] The base station provided in the above embodiments of this application will be described below with reference to a specific application scenario, taking the existence of two second radio frequency links among the multiple radio frequency links as an example.

[0161] Figure 8 This is a schematic diagram of a ROF system provided in an embodiment of this application. For example, refer to... Figure 8The base station provided in this application embodiment can be applied to a ROF system. The base station includes at least three radio frequency links, namely the first radio frequency link and the two second radio frequency links. The three radio frequency links can respectively receive three signals of different frequency bands through antennas, for example... Figure 8 As shown in the figure, the first signal received by the first radio frequency link is represented as f1, and the second and third signals received by the two second radio frequency links are represented as f2 and f3, respectively.

[0162] exist Figure 6 When the base station shown is used in the ROF system, the base station may also include the above-mentioned components. Figure 5 The following are examples of some components or modules in the ROF system shown, as well as other components or modules used for signal processing.

[0163] Each radio frequency link in a base station includes a digital link and an analog link, wherein the digital link can be implemented, for example, as follows: Figure 8 The analog link of the DSP shown can be implemented, for example, as follows: Figure 8 The LNA shown is an example of an amplifier circuit. An LNA can function as a high-frequency or intermediate-frequency preamplifier or amplifier circuit, capable of amplifying the power or energy of a signal, and offering advantages such as low noise and high gain.

[0164] Optionally, each radio frequency link in the base station may also include filters, adders, data processing modules, etc. Filters can be used to filter signals, retaining or filtering signals in specific frequency bands (or frequencies). Adders can be used to subtract the nonlinear distortion prediction signal from the signal in the corresponding frequency band of the first radio frequency link, achieving pre-distortion processing of the signal in the corresponding frequency band of the first radio frequency link. Data processing modules can be used to adjust the transmission rate, gain, and other characteristics of the signal on the radio frequency link. Of course, other components or modules can also be included in the radio frequency link. The specific components or modules included in the radio frequency link can be flexibly adjusted according to actual needs, and will not be detailed here.

[0165] The combining module in the base station is a combiner. The combiner is used to combine the signals of the three radio frequency links to obtain a combined signal. Alternatively, the combiner is used to combine the signals of multiple radio frequency links, including the three radio frequency links, in the base station to obtain a combined signal. Optionally, the function of the combiner can be implemented by an adder, that is, the combiner can be an adder.

[0166] The optical module in the base station may include an electro-optical conversion element such as an LD (Light Detector), which can transmit the converted signal to the central station. Optionally, the optical module in the base station may also include an opto-electric conversion element such as a PD (Photoelectric Detector), which converts the signal from the central station into an electrical signal.

[0167] The feature calculation module in a base station may include a photoelectric converter, a filtering module, a power amplification module, an analog feedback module, a digital feedback module, and an iterative calculation module. The analog feedback module is mainly used for analog-to-digital conversion of the signal, which can be implemented using an analog-to-digital converter. The digital feedback module, which is the aforementioned feedback module, is used for time delay correction processing of the signal. The functions of other components or modules are described in the above embodiments and will not be repeated here.

[0168] For example, such as Figure 8As shown, signal f1 from the first RF link and signals f2 and f3 received from the two second RF links are sent to a combiner after a series of RF processing steps. The combiner combines signals f1, f2, and f3 to obtain a combined electrical signal. During this process, since the feature calculation module has not yet sampled the signal for calculation, it has no output, and signal f1 remains unchanged after passing through the adder. The combined electrical signal of signals f1, f2, and f3 is transmitted to the electro-optical converter of the optical module. The electro-optical converter converts the electrical signal into an optical signal and transmits it to the central station via the optical transmission medium. Simultaneously, the feature calculation module can sample the optical signal obtained by the electro-optical converter and convert the sampled optical signal back into an electrical signal via a photoelectric converter. The electro-optic converter is a nonlinear component. Due to its nonlinear characteristics, during the electro-optic conversion of the combined electrical signals f1, f2, and f3, signals f2 and f3 will intermodulate, generating a second-order intermodulation nonlinear distortion signal, denoted as imd2 (the frequency band of signal imd2 overlaps with that of signal f1). Therefore, the signal output by the photoelectric converter contains signals f1, f2, f3, and imd2. Similarly, the signal output after photoelectric conversion of the optical signal also contains signals f1, f2, f3, and imd2. After filtering this signal, only signals with the same frequency band as signal f1 can be obtained, i.e., the target signal. This target signal contains part or all of the signals in signal f1 and signal imd2 that share the same frequency band as signal f1 (for ease of description, it is still referred to as signal imd2 in this embodiment). This target signal is processed by the power amplification module and the analog feedback module before reaching the digital feedback module. After performing time delay correction processing on the target signal, signal f2, and signal f3, the digital feedback module sends the corrected target signal, signal f2, and signal f3 to the iterative calculation module. The iterative calculation module calculates the first nonlinear distortion prediction signal based on the corrected target signal, signal f2, and signal f3, and sends the calculated first nonlinear distortion prediction signal to the pre-distortion processing module (such as an adder) on the first RF link. Subsequently, the signal f1 received on the first RF link is processed by the adder, and after the first nonlinear distortion prediction signal (the predicted imd2 signal) is subtracted, it is transmitted to the electro-optical converter of the optical module through relevant components. During the electro-optical conversion process of the signal, the generated imd2 signal compensates for the previously subtracted first nonlinear distortion signal, effectively removing the imd2 signal from the optical signal obtained by the electro-optical converter, thereby minimizing the interference of the imd2 signal on signal f1.

[0169] It should be noted that the first RF link and the two second RF links receive signals synchronously, that is, the three RF links receive the corresponding three signals simultaneously.

[0170] See below. Figure 9 ,right Figure 8 The processing procedure of the digital feedback module shown is briefly explained. For example... Figure 9 As shown, the digital feedback module samples and latches signals from the two second RF links respectively through the latching module, and sends the latched signals to the correlator. The latched signals from the two second RF links are represented as signals f2_latch and f3_latch, respectively. The correlator performs prediction calculations on the nonlinear distortion signals generated after signals f2_latch and f3_latch pass through the electro-optic converter to obtain the corresponding nonlinear distortion prediction signals. It then performs correlation processing on these nonlinear distortion signals and the target signal fb to obtain the correlation signal of the nonlinear component. The threshold decision module determines that when the correlation value of this correlation signal is greater than or equal to a set threshold, it sends the correlation signal to the time delay calculation module. The time delay calculation module calculates the time delay between the target signal fb and signals f2 and f3 based on the correlation signal and sends it to the time delay alignment module. The time delay alignment module can extract signals with consistent time delays from the target signal fb, signal f2, and signal f3 based on the predicted time delays and send them to the iterative calculation module. Among them, the signal extracted by the delay alignment module from the target signal is signal fb_align, the signal extracted from the signal f2_latch is signal f2_latch_align, and the signal extracted from the signal f3_latch is signal f3_latch_align. There is no delay between signals fb_align, f2_latch_align and f3_latch_align.

[0171] It should be noted that the above Figure 8 or Figure 9 The system architecture shown is merely an example illustrating the system architecture applicable to the embodiments of this application. The system architecture applicable to the embodiments of this application is different from that of the system architecture used in this application. Figure 8 or Figure 9 The system architecture shown can also be modified to add other entities or remove some entities. Figure 8 or Figure 9 The terminal structure shown can also have other structures added or some structures (or components) removed. (The above...) Figure 8 or Figure 9 The various components shown are merely examples of components capable of performing the corresponding functions, and each component can be replaced with other components capable of performing the corresponding functions.

[0172] In the above embodiments, the base station is a hybrid analog-digital architecture, thus offering greater flexibility in functional design compared to conventional purely analog base station architectures, while also possessing unique performance advantages. Specifically, in the ROF system's receiving link, a feedback channel is designed within the optical module, incorporating a photoelectric conversion module and a feature calculation module. This feedback coupling within the optical module enables the coupled sampling of nonlinear component signals, which is then looped back to the headend digital link (e.g., the aforementioned first radio frequency link). This achieves modeling and calculation of the nonlinear distortion signal and pre-distortion correction of the radio frequency link signal at the base station side. Therefore, the above... Figure 8 or Figure 9 The nonlinear distortion correction scheme shown can also be called the small loop correction scheme. This scheme can solve the nonlinear distortion caused by nonlinear components in the base station, reducing the impact of headend nonlinearity on the entire ROF system.

[0173] It should be noted that the above embodiments use the application of the nonlinear signal processing structure and method provided in this application in the receiving link of a ROF system as an example for illustration. In practical applications, the nonlinear signal processing structure and method provided in the above embodiments can also be applied to the transmitting link of a ROF system. In addition, the nonlinear signal processing structure and method provided in the above embodiments can be applied not only to the base station side but also to the central station side. For specific applications, please refer to the relevant descriptions in the above embodiments, which will not be repeated here.

[0174] In the solution provided in this application embodiment, the optical module in the base station, compared to the optical module in the existing base station structure, adds a coupling port, namely the third port mentioned in the above embodiment. In this application embodiment, signal transmission on the feedback link is achieved through this port. For example, Figure 10 This is a comparative schematic diagram of an optical module structure provided in an embodiment of this application. For example... Figure 10As shown in diagram (a), the single-transmit, single-receive (1T1R, i.e., one antenna is responsible for both signal transmission and reception) analog optical module in the current base station structure is a three-port module, including one input port for receiving electrical signals in the uplink, one output port for transmitting signals in the downlink, and one transmission port for transmitting optical signals, which are ports 1, 2, and 3 shown in diagram (a), respectively. In the scheme of this application embodiment, the optical module in the base station is a four-port module, including one input port for receiving electrical signals in the uplink, one output port for transmitting signals in the downlink, one transmission port for transmitting optical signals, and one electrical signal coupling port for transmitting sampling signals, which are ports 1, 2, 3, and 4 shown in diagram (b), respectively. Ports 2, 3, and 4 are the first port, second port, and third port described in the above embodiments, respectively. Their specific application methods can be referred to the description in the above embodiments, and will not be repeated here.

[0175] It should be noted that the above Figure 8 , Figure 9 or Figure 10 The optical module structure shown in the embodiment of this application is that of a 1T1R optical module. In fact, for multiple transmit-multiple receive (multiple T-multiple R, i.e., multiple antennas are responsible for transmitting and receiving signals respectively) optical modules, multiple feedback channels, including feature calculation modules, provided in the above embodiments of this application can be added to achieve the same function as described above. Among them, for multi-T-multiple R optical modules, each 1T1R can correspond to one feedback channel (including feature calculation module and front-end and back-end links), or multiple 1T1Rs can share one feedback channel.

[0176] Figure 11 This is a simplified structural diagram of a base station structure provided in an embodiment of this application. In some embodiments of this application, such as... Figure 11 As shown, the above Figure 8 or Figure 9In the small loopback correction scheme shown, the structure of each RF link can be divided into an analog link and a forward link. The analog link is mainly used for analog signal processing functions such as signal transmission and analog-to-digital conversion. The forward link is used for digital signal processing functions related to nonlinear distortion signal prediction and pre-distortion correction. For example, the forward link portion of the two second RF links can be used to send signals to the feature calculation module, and the forward link portion of the first RF link can be used for pre-distortion correction processing. The optical module mainly includes an electro-optical conversion module and a photoelectric conversion module. Refer to the description in the above embodiments. The feedback link can be combined with existing system links to construct a feedback channel and achieve time delay alignment between the useful signal and the nonlinear distortion signal. It mainly includes the aforementioned feedback module. The solution link can use the useful signal processed by the feedback link and the nonlinear distortion signal to perform solution modeling, calculate the nonlinear distortion prediction signal, and then feed it back to the forward link of the first RF link. This allows the forward link of the first RF link to perform pre-distortion processing on the signal on the first RF link based on the nonlinear distortion prediction signal to compensate for the nonlinear distortion in the link.

[0177] It should be noted that the above division of the base station structure is illustrative and is only a logical functional division. In actual implementation, there may be other division methods. In addition, each functional module in the various embodiments of this application may exist physically separately, or two or more modules may be integrated into one module.

[0178] Example 2

[0179] Figure 12 A schematic diagram of a base station and a central station provided in an embodiment of this application is shown below. Figure 12 As shown in this embodiment, the base station may include multiple radio frequency links (e.g., Figure 12 The diagram shows radio frequency link 1, radio frequency link 2, optical module, and feature calculation module; wherein the number of the plurality of radio frequency links is greater than or equal to 2.

[0180] It should be noted that, for ease of explanation, Figure 12 The example only shows the case where the base station includes two radio frequency links. In reality, there may be more or fewer radio frequency links in a base station, which will not be elaborated here.

[0181] In the base station, each radio frequency link is used to receive a signal of the corresponding frequency band through an antenna, perform radio frequency processing on the signal, and then send the signal to the optical module.

[0182] The optical module is used to perform electro-optical conversion processing on multiple signals from the plurality of radio frequency links to obtain an optical signal containing the processed multiple signals, and to send the optical signal to the central station. It also receives a target signal from the central station, performs photoelectric conversion processing on the target signal, and sends the processed target signal to the feature calculation module. Among the plurality of radio frequency links, there is a first radio frequency link and at least one second radio frequency link. The optical module includes nonlinear components. The signal from the at least one second radio frequency link generates a nonlinear distortion signal after passing through the nonlinear components. The frequency band of the nonlinear distortion signal overlaps with the frequency band corresponding to the first radio frequency link. The optical signal also contains the nonlinear distortion signal. The target signal contains a signal from the frequency band corresponding to the first radio frequency link.

[0183] Optionally, the base station also includes a combining module. Figure 12 (Not shown in the image), the combining module is used to receive multiple signals from the plurality of radio frequency links, perform combining processing on the multiple signals to obtain a combined signal, and send the combined signal to the optical module. The optical module is then used to receive the combined signal from the combining module and perform electro-optical conversion processing on the combined signal to obtain the optical signal. For example, the combining module can be a combiner.

[0184] Each second RF link is also used to perform RF processing on one signal of the corresponding frequency band received, and then send the resulting signal to the feature calculation module.

[0185] The feature calculation module is configured to receive the target signal from the optical module; calculate a nonlinear distortion prediction signal based on the target signal and at least one signal from the at least one second radio frequency link; and send the nonlinear distortion prediction signal to the first radio frequency link, wherein the nonlinear distortion prediction signal is a first prediction signal of the nonlinear distortion signal.

[0186] The first radio frequency link is further configured to perform pre-distortion processing and radio frequency processing on the signal in the corresponding frequency band of the first radio frequency link according to the nonlinear distortion prediction signal, and send the processed signal to the optical module.

[0187] In this embodiment, the optical module includes an electro-optical conversion module, which performs electro-optical conversion processing on the multiple signals to obtain an optical signal. The electro-optical conversion module includes the nonlinear component, which can be used to perform electro-optical conversion processing on the signal. For example, the electro-optical conversion module can be an LD (Light Detector).

[0188] After the optical module sends the converted optical signal to the central station, it can receive the target signal from the central station, perform photoelectric conversion processing on the target signal, and send the processed target signal to the feature calculation module. As an optional implementation, the optical module can directly receive the target signal from the central station and send it to the feature calculation module. As another optional implementation, the optical module can receive downlink signals from the central station, perform photoelectric conversion processing on the downlink signals, and send the processed downlink signals to the feature calculation module. In this downlink signal, the target signal and other signals to be sent to the base station can be included. In this method, the feature calculation module can obtain the target signal by receiving the downlink signal from the optical module and filtering it.

[0189] In this embodiment, the feature calculation module includes a filtering module and an iterative calculation module.

[0190] In the feature calculation module, the filtering module receives the downlink signal from the optical module and filters the downlink signal to obtain the target signal. For example, the filtering module is a filter. The function of the iterative calculation module can be found in the description of the iterative calculation module in Embodiment 1 above, and will not be repeated here.

[0191] Optionally, the feature calculation module may further include a frequency division module, which is connected to the optical module and the filtering module. The frequency division module can receive downlink signals from the optical module, perform frequency division processing on the downlink signals to obtain signals in the frequency band corresponding to the first radio frequency link, and send the signals in the frequency band corresponding to the first radio frequency link to the filter. The filter can then be used to filter the signals in the frequency band corresponding to the first radio frequency link to obtain the target signal.

[0192] In some embodiments of this application, the feature calculation module further includes a feedback module. The structure and function of the feedback module can be referred to the description of the feedback module in Embodiment 1 above, and will not be repeated here.

[0193] Furthermore, it should be noted that, unless otherwise specified, the structure, function, and characteristics of each module in the base station in this embodiment can be referred to the relevant descriptions in Embodiment 1 above, and will not be repeated in this embodiment.

[0194] In this embodiment, the central station may include an optical module and a signal processing module.

[0195] The optical module is used to receive optical signals from the base station, perform photoelectric conversion on the optical signals to obtain electrical signals, and send the electrical signals to the signal processing module. The electrical signals include nonlinear distortion signals and multiple signals received by multiple radio frequency links of the base station through antennas. The number of multiple radio frequency links is greater than or equal to 2. Among the multiple radio frequency links, there is a first radio frequency link and at least one second radio frequency link. The base station includes nonlinear components. The signal of the at least one second radio frequency link generates the nonlinear distortion signal after passing through the nonlinear components. The frequency band of the nonlinear distortion signal overlaps with the frequency band corresponding to the first radio frequency link.

[0196] In some embodiments of this application, the optical module of the central station may include a photoelectric conversion module, which receives optical signals from the base station and converts the optical signals into electrical signals. Optionally, the photoelectric conversion module includes nonlinear components. For example, the photoelectric conversion module may be a photodiode (PD).

[0197] For example, such as Figure 12 As shown, after the optical module of the base station obtains the optical signal through the electro-optical conversion module, it sends the optical signal to the central station. The optical module of the central station converts the optical signal into an electrical signal through the photoelectric conversion module and sends it to the signal processing module.

[0198] The signal processing module is configured to receive the electrical signal from the optical module, extract the target signal of the frequency band corresponding to the first radio frequency link from the electrical signal, and send the target signal to the optical module.

[0199] Optionally, the signal processing module includes a filtering module, which receives the electrical signal from the optical module, filters the electrical signal to obtain the target signal, and sends it to the optical module.

[0200] The optical module is further configured to perform electro-optical conversion processing on the target signal and transmit the processed target signal to the base station. Specifically, after receiving the target signal from the signal processing module, as an optional implementation, the optical module can directly transmit the target signal to the base station alone. As another optional implementation, the optical module can perform electro-optical conversion processing on the target signal and other signals to be transmitted to the base station to obtain a downlink signal containing the target signal and other signals to be transmitted to the base station, and transmit the downlink signal to the base station.

[0201] In some embodiments of this application, the optical module of the central station may further include an electro-optical conversion module, which converts an electrical signal into an optical signal and then transmits the optical signal to the base station. Optionally, the electro-optical conversion module includes nonlinear components. For example, the electro-optical conversion module may be an LD (Light Detector).

[0202] In some embodiments of this application, the start frequency of the nonlinear distortion signal is greater than or equal to a first frequency, and the cutoff frequency of the nonlinear distortion signal is less than or equal to a second frequency. In one possible scenario, one of the plurality of RF links is a second RF link, where the first frequency is twice the start frequency of the corresponding frequency band of the second RF link, and the second frequency is twice the cutoff frequency of the corresponding frequency band of the second RF link. In another possible scenario, two second RF links are present among the plurality of RF links, where the first frequency is the sum of the start frequencies of the corresponding frequency bands of the two second RF links, and the second frequency is the sum of the cutoff frequencies of the corresponding frequency bands of the two second RF links; or, the first frequency is the difference between the start frequencies of the corresponding frequency bands of the two second RF links, and the second frequency is the difference between the cutoff frequencies of the corresponding frequency bands of the two second RF links.

[0203] In the above embodiments, the base station sends the signal passing through the nonlinear component and the nonlinear distortion signal generated after the signal passes through the nonlinear component to the central station. The central station obtains the target signal based on the signal and then sends the target signal back to the base station. The base station then calculates the nonlinear distortion characteristic parameters of the nonlinear component based on the target signal. On the one hand, this allows the base station to calculate the nonlinear distortion characteristic parameters based on the actual signal and the corresponding actual nonlinear distortion signal, improving the accuracy of determining the nonlinear distortion characteristics of the nonlinear component. After determining the nonlinear distortion parameters of the nonlinear component, the base station combines these parameters with the signal currently transmitted on the transmission link to predict the nonlinear distortion prediction signal generated when the signal passes through the nonlinear component. This improves the accuracy of the determined nonlinear distortion prediction signal. Furthermore, the determined nonlinear distortion prediction signal can be used to perform pre-distortion processing on the signal currently transmitted on the transmission link, thereby correcting the nonlinear distortion problem generated when the signal passes through the nonlinear component on the transmission link and improving the accuracy of nonlinear distortion correction. On the other hand, the signal on which the base station calculates the nonlinear distortion characteristic parameters has been transmitted back to the central station. Therefore, the transmission path of this signal includes some transmission links in the central station. The correction method for nonlinear distortion in the base station can correct the entire link where the nonlinear components are located. Therefore, this scheme can correct some nonlinear distortion problems in the central station while correcting the nonlinear distortion problems in the base station, thereby improving the accuracy of communication between the central station and the base station.

[0204] The base station and central station provided in the above embodiments of this application will be described below with reference to a specific application scenario, taking the existence of a second radio frequency link among the multiple radio frequency links as an example.

[0205] Figure 13 This is a schematic diagram of a ROF system provided in an embodiment of this application. For example, refer to... Figure 13 The base station and central station provided in this application embodiment can be applied to a ROF system. The base station includes at least two radio frequency links, namely a first radio frequency link and a second radio frequency link. The two radio frequency links can respectively receive two signals of different frequency bands through antennas, for example... Figure 13 As shown in the figure, the first signal received by the first radio frequency link is represented as f4, and the second signal received by the second radio frequency link is represented as f5.

[0206] exist Figure 13 When the base station shown is used in the ROF system, the base station may also include the above-mentioned components. Figure 5 The components or modules in the ROF system shown, as well as other components or modules used for signal processing, can be referred to the relevant descriptions in Embodiment 1 above, and will not be repeated here.

[0207] For example, such as Figure 13As shown, the signal f4 received by the first RF link and the signal f5 received by the second RF link are sent to the combiner after a series of RF processing steps. The combiner performs the combining to obtain an electrical signal of signals f4 and f5. This electrical signal is transmitted to the electro-optical converter of the optical module. The electro-optical converter converts the electrical signal into an optical signal and sends it to the central station through the optical transmission medium. The electro-optical converter is a nonlinear component. Due to its nonlinear characteristics, during the electro-optical conversion of the combined electrical signal of signals f4 and f5, the frequency components of signal f5 will undergo intermodulation, generating a second-order intermodulation nonlinear distortion signal, denoted as imd2 (the frequency band of signal imd2 overlaps with the frequency band of signal f4). Therefore, the signal sent from the base station's electro-optical converter to the central station includes signals f4, f5, and imd2. After receiving the optical signal, the optoelectronic conversion module of the central station converts the optical signal into an electrical signal and sends the electrical signal to the signal processing module. The signal processing module of the central station filters the electrical signal to obtain a signal containing only the same frequency band as signal f4, i.e., the target signal. This target signal includes part or all of the signals in signal f4 and signal imd2 that share the same frequency band as signal f4 (for ease of description, it is still referred to as signal imd2 in this embodiment). This target signal, along with other signals to be sent to the base station, is transmitted to the base station after passing through the electro-optical converter of the central station. After receiving the signal from the central station, the photoelectric converter of the base station performs photoelectric conversion processing on the signal to obtain the corresponding electrical signal, and sends it to the feature calculation module. The feature calculation module of the base station performs frequency division processing on the electrical signal through the frequency division module to obtain the signal corresponding to the frequency band of the first radio frequency link, and filters the signal through a filter to obtain the target signal. This target signal is then processed by the power amplification module and the analog feedback module before reaching the digital feedback module. After performing time delay correction processing on the target signal and signal f5, the digital feedback module sends the obtained signal to the iterative calculation module. The iterative calculation module calculates a first nonlinear distortion prediction signal based on the target signal and signal f5, and sends the calculated first nonlinear distortion prediction signal to an adder on the first RF link. The adder processes the signal f4 on the first RF link by subtracting the first nonlinear distortion prediction signal (the predicted IMD2 signal), and then transmits the result to the electro-optical converter of the optical module through relevant components. During the electro-optical conversion process, the generated IMD2 signal compensates for the previously subtracted first nonlinear distortion signal, effectively removing the IMD2 signal from the optical signal obtained by the electro-optical converter, thus minimizing interference from the IMD2 signal on signal f4.

[0208] It should be noted that, Figure 13In the central station shown, the photoelectric converter and the electro-optic converter are also nonlinear components. If the signal from the base station also generates a nonlinear distortion signal that overlaps with the frequency band of signal f4 when passing through the photoelectric converter or the electro-optic converter, then part or all of the nonlinear distortion signal that overlaps with the frequency band of signal f4 will also be carried in the target signal and transmitted back to the base station. When the base station calculates the nonlinear distortion prediction signal based on the target signal, it can take into account the nonlinear distortion problem of the signal during the process of passing through the central station, and can correct some nonlinear distortions in the central station during the pre-distortion processing, thereby further improving the nonlinear distortion correction performance of the ROF system.

[0209] In the above embodiments, the signal starts from the air interface antenna receiver of the base station, undergoes nonlinearity generation via the radio frequency link and the electro-optical converter of the optical module within the base station, is transmitted through optical fiber, is received by the optoelectronic converter at the central station, undergoes signal processing at the central station, is transmitted via the electro-optical converter on the transmitting side, loops back through optical fiber to the optoelectronic converter at the base station, is frequency-divided, and coupled to the feedback link through the feedback channel for nonlinear distortion signal prediction and other processing. This allows for large-loop sampling of the nonlinear distortion signal using the existing optical modules at the base station and central station, sending it to the base station's feature calculation module for nonlinear distortion signal prediction. Thus, at the base station side, modeling and calculation of nonlinear distortion signals on the base station and central station links and pre-distortion correction of the radio frequency link signal are achieved. Therefore, the above... Figure 13 The nonlinear distortion correction scheme shown can also be called the large loop closure correction scheme. This scheme can solve the nonlinear distortion caused by nonlinear components in the base station and central station, reducing the impact of nonlinearity in the base station and central station on the entire ROF system.

[0210] Example 3

[0211] Figure 14 A schematic diagram of a central station provided in an embodiment of this application is shown below. Figure 14 As shown in the figure, in this embodiment, the central station may include an optical module, a signal processing module, and a feature calculation module.

[0212] The optical module is used to receive optical signals from at least one base station, perform photoelectric conversion processing on the optical signals of each of the at least one base station to obtain the electrical signals of each base station, and send the electrical signals of each base station to the signal processing module and the feature calculation module respectively. The electrical signals of any base station include nonlinear distortion signals and multiple signals received by multiple radio frequency links of the base station through antennas. The number of multiple radio frequency links is greater than or equal to two, and there is a first radio frequency link and at least one second radio frequency link among the multiple radio frequency links. The base station includes nonlinear components, and the signal of the at least one second radio frequency link generates the nonlinear distortion signal after passing through the nonlinear components. The frequency band of the nonlinear distortion signal overlaps with the frequency band corresponding to the first radio frequency link.

[0213] The optical module transmits the electrical signals from each base station to the signal processing module via different links. The optical module also transmits the electrical signals from each base station to the feature calculation module via different links.

[0214] The feature calculation module is configured to receive electrical signals from each base station of the optical module; perform feature calculation processing on the electrical signals of each base station to obtain a nonlinear distortion prediction signal corresponding to each base station, and send the nonlinear distortion prediction signal corresponding to each base station to the signal processing module; wherein, the feature calculation processing on the electrical signals of any base station includes the following steps: extracting the target signal of the frequency band corresponding to the first radio frequency link from the electrical signals, and extracting at least one signal from the at least one second radio frequency link from the electrical signals; calculating the nonlinear distortion prediction signal based on the target signal and the at least one signal from the at least one second radio frequency link, wherein the nonlinear distortion prediction signal is a first prediction signal of the nonlinear distortion signal.

[0215] The signal processing module is configured to receive electrical signals from each base station of the optical module; perform radio frequency processing on the electrical signals of the at least one base station to obtain a target combined signal; wherein the target combined signal includes signals of the frequency band corresponding to the first radio frequency link; the radio frequency processing may include combining processing and frequency division processing; receive nonlinear distortion prediction signals corresponding to each base station from the feature calculation module; and sequentially perform distortion correction processing on the target combined signal according to the nonlinear distortion prediction signals corresponding to each base station.

[0216] In some embodiments of this application, the start frequency of the nonlinear distortion signal is greater than or equal to a first frequency, and the cutoff frequency of the nonlinear distortion signal is less than or equal to a second frequency. In one possible scenario, one of the plurality of RF links is a second RF link, where the first frequency is twice the start frequency of the corresponding frequency band of the second RF link, and the second frequency is twice the cutoff frequency of the corresponding frequency band of the second RF link. In another possible scenario, two second RF links are present among the plurality of RF links, where the first frequency is the sum of the start frequencies of the corresponding frequency bands of the two second RF links, and the second frequency is the sum of the cutoff frequencies of the corresponding frequency bands of the two second RF links; or, the first frequency is the difference between the start frequencies of the corresponding frequency bands of the two second RF links, and the second frequency is the difference between the cutoff frequencies of the corresponding frequency bands of the two second RF links.

[0217] In this embodiment, the optical module includes a photoelectric conversion module, which is used to perform photoelectric conversion processing on the optical signals from the at least one base station to obtain electrical signals. Optionally, the photoelectric conversion module includes nonlinear components, which can be used to perform photoelectric conversion processing on the signals. For example, the photoelectric conversion module can be a photoelectric generator (PD).

[0218] In this embodiment, the structure and function of the feature calculation module can be referred to the description of the feature calculation module in Embodiment 1 above, and will not be repeated here.

[0219] In some embodiments of this application, the signal processing module includes a radio frequency (RF) processing module and a digital processing and compensation module. The RF processing module is used to perform RF processing on the signals received by the optical module corresponding to each base station. For example, it may include: combining the electrical signals of the at least one base station to obtain a combined signal, and performing frequency division processing on the combined signal to obtain the signal of the frequency band corresponding to each RF link. The signal of each RF link corresponding to the frequency band includes the signal of the frequency band corresponding to the at least one base station, and nonlinear distortion signals overlapping with that frequency band. For example... Figure 14 The diagram shows the signals corresponding to the first and second radio frequency links. The signal corresponding to the first radio frequency link is the target combined signal. The digital processing and compensation module is used to sequentially perform distortion correction processing on the target combined signal based on the nonlinear distortion prediction signal corresponding to each base station. Specifically, the digital processing and compensation module subtracts the nonlinear distortion prediction signal corresponding to each base station from the target combined signal sequentially to obtain the target combined signal with the nonlinear distortion signal removed.

[0220] For example, when the at least one base station includes a first base station and a second base station, and each base station receives two signals through two radio frequency links, the signal sent from the first base station to the central station includes the signal on the first radio frequency link of the first base station, the signal on the second radio frequency link of the first base station, and the nonlinear distortion signal generated after the signal on the second radio frequency link passes through nonlinear components. The signal sent from the second base station to the central station includes the signal on the first radio frequency link of the second base station, the signal on the second radio frequency link of the first base station, and the nonlinear distortion signal generated after the signal on the second radio frequency link passes through nonlinear components. Therefore, the combined signal obtained by the radio frequency processing module performing combined processing on the electrical signals of the at least one base station includes at least the above six signals. After the radio frequency processing module performs frequency division processing on the combined signal to obtain the target combined signal (including the signal from the first radio frequency link of the first base station, the nonlinear distortion signal from the first base station, and the signal from the first radio frequency link of the second base station, and the nonlinear distortion signal from the second base station), the target combined signal can then be subjected to distortion correction processing according to the nonlinear distortion prediction signal corresponding to each base station. Specifically, the signal processing module can first perform distortion correction processing on the target combined signal based on the nonlinear distortion prediction signal corresponding to the first base station to obtain a first target combined signal, and then perform distortion correction processing on the first target combined signal based on the nonlinear distortion prediction signal corresponding to the second base station to obtain a second target combined signal. Specifically, the signal processing module obtains the first target combined signal by subtracting the nonlinear distortion prediction signal corresponding to the first base station from the target combined signal, and obtains the second target combined signal by subtracting the nonlinear distortion prediction signal corresponding to the second base station from the first target combined signal.

[0221] In some embodiments of this application, when the radio frequency processing module performs radio frequency processing on the signal corresponding to each base station received by the optical module, it may also perform multiplexing processing on the electrical signals of the at least one base station to obtain a multiplexed signal. This multiplexed signal is then sent as the target multiplexed signal to the digital processing and compensation module. The digital processing and compensation module is used to sequentially subtract the nonlinear distortion prediction signal corresponding to each base station from the target multiplexed signal to obtain the multiplexed signal of the at least one base station after removing the nonlinear distortion signal. The central station can perform frequency division processing on the signal during subsequent processing of the multiplexed signal of the at least one base station to obtain the signal of the frequency band corresponding to each radio frequency link.

[0222] In some embodiments of this application, the signal processing module may also include only a digital processing and compensation module. In this case, the digital processing and compensation module can perform distortion correction processing on the signal received by the optical module from each base station according to the nonlinear distortion prediction signal corresponding to each base station, thereby realizing independent processing of signals from different base stations.

[0223] In some embodiments of this application, the feature calculation module, in addition to the specific structure described in Embodiment 1 or Embodiment 2, may also include a signal control module. The signal control module is used to selectively control the electrical signals from the at least one base station received from the optical module, so that the feature calculation module receives only electrical signals from one base station at a time. For example, the signal control module can be a single-pole multi-throw (SPMWP) switch, wherein the stationary terminal of the SPMWP switch is connected to the filtering module in the feature calculation module, and the moving terminal of the SPMWP switch is connected to the links transmitting the electrical signals from the at least one base station. The SPMWP switch allows selection of which base station's electrical signal is transmitted from a specific link to the feature calculation module, facilitating the calculation of nonlinear distortion prediction signals for that base station.

[0224] In some embodiments of this application, the central station may have multiple feature calculation modules. That is, the central station sets up a corresponding feature calculation module for each connected base station. After the photoelectric conversion module of the central station receives the electrical signal from at least one base station, the central station couples the signal to the corresponding feature calculation module on the transmission link corresponding to each signal. The feature calculation module then calculates the nonlinear distortion prediction signal for the corresponding base station. After determining the nonlinear distortion prediction signal for each base station, the feature calculation module sends the determined nonlinear distortion prediction signal to the signal processing module.

[0225] As an optional implementation, the signal processing module can perform distortion correction processing on the electrical signal of each base station according to the nonlinear distortion prediction signal corresponding to each base station. This allows for nonlinear modeling and distortion correction processing of each individual signal component, thereby ensuring optimal performance.

[0226] As another optional implementation, the signal processing module can perform distortion correction processing on the frequency-divided electrical signals after performing multiplexing and frequency division processing on the electrical signals of the at least one base station, according to the nonlinear distortion prediction signal corresponding to each base station. This separation processing of the converged and combined signals can achieve the equivalent effect of multi-channel signal separation, and further, nonlinear modeling and distortion correction processing can be performed on each component signal, avoiding the need to set up additional physical channels.

[0227] It should be noted that, unless otherwise specified, the structure, function, and characteristics of some modules in this embodiment can be referred to the relevant descriptions in Embodiment 1 or Embodiment 2 above, and will not be repeated in this embodiment. For example, in the structure of the feature calculation module in the central station, the structure other than the signal control module can be referred to the relevant description of the feature calculation module in Embodiment 1 above.

[0228] In the above embodiments, the central station can calculate the nonlinear distortion characteristic parameters of the nonlinear element based on the signal actually passing through the nonlinear element (in the base station or central station) and the actual nonlinear distortion signal generated after the signal passes through the nonlinear element. This improves the accuracy of determining the nonlinear distortion characteristics of the nonlinear element. After determining the nonlinear distortion parameters of the nonlinear element, the central station combines these parameters with the signal currently transmitted on the transmission link to predict the nonlinear distortion prediction signal generated when the signal passes through the nonlinear element. This improves the accuracy of the determined nonlinear distortion prediction signal. Furthermore, the central station can perform distortion processing on the signal currently transmitted on the transmission link based on the determined nonlinear distortion prediction signal, thereby correcting the nonlinear distortion problem generated when the signal passes through the nonlinear element on the transmission link and improving the accuracy of nonlinear distortion correction. Simultaneously, the central station can perform nonlinear distortion correction processing on signals from multiple base stations, improving the performance and efficiency of nonlinear distortion correction.

[0229] The following description, using a specific application scenario and taking the example of a base station having a first radio frequency link and a second radio frequency link in each base station, illustrates the base station provided in the above embodiments of this application with specific examples.

[0230] Figure 15 This is a schematic diagram of a ROF system provided in an embodiment of this application. For example, refer to... Figure 15 The central station provided in this application embodiment can be applied to an ROF system. The central station includes an optical module, a feature calculation module, and a signal processing module, as detailed in the above embodiments. The ROF system also includes n base stations, where n is a positive integer. Each of the n base stations includes two radio frequency links, namely a first radio frequency link and a second radio frequency link. The two radio frequency links can respectively receive two signals of different frequency bands through antennas, for example... Figure 15 As shown, the first signal received by the first radio frequency link of the Nth base station is represented as f1_N, and the second signal received by the second radio frequency link is represented as f2_N, where N is less than or equal to n and is a positive integer. Among the n base stations, the frequency bands corresponding to the first radio frequency links of each base station are the same, and the frequency bands corresponding to the second radio frequency links of each base station are the same. After the signals of the second radio frequency links of each base station pass through nonlinear components, nonlinear distortion signals with overlapping frequency bands with the first radio frequency links are generated.

[0231] For example, such as Figure 15 As shown, the signal f1_N received by the first RF link and the signal f2_N received by the second RF link of the Nth base station are sent to a combiner after a series of RF processing steps. The combiner performs combining to obtain an electrical signal combining signals f1_N and f2_N. This electrical signal is transmitted to the electro-optical converter of the optical module. The electro-optical converter converts the electrical signal into an optical signal and sends it to the central station through the optical transmission medium. The electro-optical converter is a nonlinear component. Due to its nonlinear characteristics, during the electro-optical conversion of the combined electrical signal f1_N and f2_N, the frequency components of signal f2_N undergo intermodulation, generating a second-order intermodulation nonlinear distortion signal, denoted as imd2_N (the frequency band of signal imd2_N overlaps with that of signal f1_N). Therefore, the signal actually sent to the central station by the base station's electro-optical converter includes signals f1_N, f2_N, and imd2_N, denoted as f1_N + f2_N + imd2_N. After receiving the optical signal, the photoelectric conversion module of the central station converts the optical signal into an electrical signal and sends the electrical signal to the signal processing module. The signal processing module of the central station performs combining and frequency division processing on the electrical signals of the at least one base station through the radio frequency processing module to obtain signals corresponding to different radio frequency links in the frequency bands. The signals obtained after frequency division include at least the signals corresponding to the first radio frequency link and the signals corresponding to the second radio frequency link. Among them, the signals corresponding to the first radio frequency link include at least some or all of the signals f1_1 to f1_n and the nonlinear distortion signals that overlap with the frequency bands of signals f1_1 to f1_n. Figure 15 The expression is represented as F1+imd2, where F1+imd2=f1_1+imd2_1+f1_2+imd2_2+...+f1_n+imd2_n), and the signal in the corresponding frequency band of the second RF link contains at least signals f2_1~f2_n. Figure 15 The signal is represented as F2, where F2 = f2_1 + f2_2 + ... + f2_n. The feature calculation module calculates the nonlinear distortion prediction signal corresponding to each base station based on the electrical signal (f1_N + f2_N + imd2_N) of each base station, and sends it to the signal processing module. The signal processing module subtracts the nonlinear distortion prediction signal corresponding to each base station from the signal of the corresponding frequency band of the first radio frequency link in turn, thereby realizing the nonlinear distortion correction of the signal of the corresponding frequency band of the first radio frequency link.

[0232] In the solutions of Embodiments 1 and 2 above, nonlinear distortion correction is performed on a one-to-one basis, meaning one nonlinear distortion correction structure corresponds to one base station module or communication link. However, in cellular mobile communication systems, a central station typically connects to multiple base stations (e.g., one central station connects to eight base stations). These multiple base stations share the resources of a single central station, and therefore, the signals from multiple base stations eventually converge at one central station. Therefore, in Embodiment 3 above, by setting the correction link at the central station, one-to-many correction is achieved. That is, the central station can correct not only the nonlinear distortion caused by nonlinear devices in the base stations but also the nonlinear distortion caused by nonlinear devices in the central station.

[0233] The above embodiments provide a new ROF architecture based on hybrid analog and digital signals, which is conducive to the use of flexible digital links, more accurately solves the nonlinear distortion problem of analog devices in ROF networks, solves the constraints of nonlinear components caused by optical devices on ROF system frequency planning, realizes high-performance and low-cost ROF design, can improve the high-speed transmission performance of 5G and future multi-mode high-bandwidth networks, and enables low-cost site deployment.

[0234] It is understood that the above embodiments mainly use the solution to address the nonlinear distortion problem caused by nonlinear components in the optical module of a base station as an example to introduce the solution provided in this application. However, the application scenarios of the solution provided in this application are not limited to this. The solution provided in this application can effectively solve the nonlinear distortion problem caused by any nonlinear component in a base station or central station. In addition, the solution provided in this application is described in detail according to the correction of nonlinear distortion components. In fact, the solution provided in this application can also be applied to the correction of linear distortion components. The specific implementation methods of the solution in the above scenarios can be referred to the description of the above embodiments, and will not be described one by one here.

[0235] Based on the above embodiments and the same concept, this application also provides a nonlinear signal processing method, which can be applied to a base station or a central station. For example... Figure 16 As shown, when the nonlinear signal processing method provided in this application is applied to a base station, the method includes:

[0236] S1601: The base station calculates target parameters based on the target signal, wherein the target signal includes: a first signal passing through a nonlinear component, and a nonlinear distortion signal generated after at least one second signal passes through a nonlinear component, wherein the frequency band of the nonlinear distortion signal overlaps with the frequency band of the first signal, and the target parameters are used to characterize the nonlinear distortion characteristics of the nonlinear component.

[0237] Wherein, the frequency band of the first signal is the first frequency band, and the frequency bands of each of the at least one second signal may be the same or different.

[0238] For example, the first signal can be Figure 3 Signal S in Scenario 1 shown F3 The at least one second signal may include Figure 3 Signal S in Scenario 2 shown F1 and signal S F2 Alternatively, the first signal can be Figure 3 Signal S in Scenario 2 shown F3 The at least one second signal may include Figure 3 Signal S in Scenario 2 shown F1 and signal S F2 Alternatively, the first signal can be Figure 3 Signal S in Scenario 3 shown F3 The at least one second signal may include Figure 3 Signal S in Scenario 3 shown F1 .

[0239] In some embodiments of this application, the base station can calculate the target parameters based on a set first calculation model and the target signal, wherein the first calculation model is used to represent the correspondence between one of the multiple signals input to the nonlinear component, the nonlinear distortion signal output by the nonlinear component in the same frequency band as the one signal, and the nonlinear distortion characteristic parameters of the nonlinear component.

[0240] S1602: The base station calculates a target prediction signal based on the at least one second signal, wherein the target prediction signal is a prediction signal of the nonlinear distortion signal.

[0241] The base station can calculate the target prediction signal based on the set second calculation model and the at least one second signal. The second calculation model is used to represent the correspondence between at least one signal passing through the nonlinear component and the nonlinear distortion signal generated after the at least one signal passes through the nonlinear component.

[0242] S1603: The base station corrects the target prediction signal according to the target parameters to obtain a nonlinear distortion prediction signal.

[0243] Wherein, the nonlinear distortion prediction signal is the corrected prediction signal of the nonlinear distortion signal.

[0244] When the base station corrects the target prediction signal based on the target parameters, it can multiply the target parameters with the target prediction signal to obtain the nonlinear distortion prediction signal.

[0245] In the above embodiments, the base station can predict and calculate the nonlinear distortion signal generated when subsequent signals pass through the nonlinear components based on the nonlinear distortion signal caused by the nonlinear components. This can improve the accuracy of the determined nonlinear distortion prediction signal. Furthermore, the base station can perform pre-distortion processing on the useful signal based on the determined nonlinear distortion prediction signal, thereby correcting the nonlinear distortion problem caused by the nonlinear components and improving the accuracy of nonlinear distortion correction.

[0246] When the nonlinear signal processing method provided in this application is applied to a central station, the implementation method when applied to a base station can be referred to, and will not be repeated here.

[0247] Based on the above embodiments and the same concept, this application also provides an apparatus, the apparatus including a memory and a processor, the memory for storing a computer program, and the processor for executing the computer program stored in the memory to implement the above-mentioned... Figure 16 The nonlinear signal processing method shown is illustrated.

[0248] Based on the above embodiments and the same concept, this application also provides a chip, which may include the components or modules included in the base station in the first embodiment; or the chip may include the components or modules included in the base station in the second embodiment; or the chip may include the components or modules included in the central station in the second embodiment; or the chip may include the components or modules included in the central station in the third embodiment.

[0249] Based on the above embodiments and the same concept, this application also provides a communication system, which includes at least: the base station provided in the first embodiment, or the base station and central station provided in the second embodiment, or the central station provided in the third embodiment.

[0250] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A base station, characterized in that, include: Multiple radio frequency links, optical modules, and feature calculation modules; wherein the number of the multiple radio frequency links is greater than or equal to 2; Each radio frequency link is used to receive a signal in the corresponding frequency band through an antenna, perform radio frequency processing on the signal, and then send the signal to the optical module. The optical module is used to perform electro-optical conversion processing on multiple signals from the plurality of radio frequency links to obtain an optical signal containing the processed multiple signals; wherein, the optical module includes nonlinear components, and among the plurality of radio frequency links there is a first radio frequency link and at least one second radio frequency link, the signal of the at least one second radio frequency link generates a nonlinear distortion signal after passing through the nonlinear components, the frequency band of the nonlinear distortion signal overlaps with the frequency band corresponding to the first radio frequency link, and the optical signal also contains the nonlinear distortion signal; the optical signal is sent to the central station, and the optical signal is subjected to photoelectric conversion processing to obtain an electrical signal and the electrical signal is sent to the feature calculation module; Each second radio frequency link is also used to perform radio frequency processing on one signal of the corresponding frequency band received, and then send the resulting signal to the feature calculation module. The feature calculation module is used to extract a target signal from the electrical signal from the optical module; wherein the target signal includes a signal in the frequency band corresponding to the first radio frequency link contained in the electrical signal; calculate a nonlinear distortion prediction signal based on the target signal and at least one signal from the at least one second radio frequency link, and send the nonlinear distortion prediction signal to the first radio frequency link, wherein the nonlinear distortion prediction signal is a first prediction signal of the nonlinear distortion signal; The first radio frequency link is further configured to perform pre-distortion processing and radio frequency processing on the signal in the corresponding frequency band of the first radio frequency link according to the nonlinear distortion prediction signal, and send the processed signal to the optical module.

2. The base station according to claim 1, characterized in that, The starting frequency of the nonlinear distortion signal is greater than or equal to a first frequency, and the cutoff frequency of the nonlinear distortion signal is less than or equal to a second frequency, wherein: When a second radio frequency link exists among the plurality of radio frequency links, the first frequency is twice the start frequency of the frequency band corresponding to the second radio frequency link, and the second frequency is twice the cutoff frequency of the frequency band corresponding to the second radio frequency link; or When there are two second radio frequency links among the plurality of radio frequency links, the first frequency is the sum of the start frequencies of the corresponding frequency bands of the two second radio frequency links, and the second frequency is the sum of the cutoff frequencies of the corresponding frequency bands of the two second radio frequency links; or, the first frequency is the difference between the start frequencies of the corresponding frequency bands of the two second radio frequency links, and the second frequency is the difference between the cutoff frequencies of the corresponding frequency bands of the two second radio frequency links.

3. The base station according to claim 1 or 2, characterized in that, The feature calculation module includes an iterative calculation module, which is used for: Target parameters are calculated based on the target signal, wherein the target parameters are used to characterize the nonlinear distortion characteristics of the nonlinear component; The target prediction signal is calculated based on at least one signal from the at least one second radio frequency link, wherein the target prediction signal is a second prediction signal of the nonlinear distortion signal; The target prediction signal is corrected based on the target parameters to obtain the nonlinear distortion prediction signal.

4. The base station according to claim 3, characterized in that, The iterative calculation module, when calculating the target parameters based on the target signal, is specifically used for: The target parameters are calculated based on the set first calculation model and the target signal, wherein the first calculation model is used to represent the correspondence between one of the multiple signals input to the nonlinear component, the nonlinear distortion signal output by the nonlinear component with the same frequency band as the one signal, and the nonlinear distortion characteristic parameters of the nonlinear component; When the iterative calculation module calculates the target prediction signal based on at least one signal from the at least one second radio frequency link, it is specifically used for: The target prediction signal is calculated based on the established second calculation model and at least one signal from the at least one second radio frequency link, wherein the second calculation model is used to represent the correspondence between at least one signal passing through the nonlinear component and the nonlinear distortion signal generated after the at least one signal passes through the nonlinear component.

5. The base station according to claim 3, characterized in that, The iterative calculation module, when correcting the target prediction signal according to the target parameters to obtain the nonlinear distortion prediction signal, is specifically used for: The nonlinear distortion prediction signal is obtained by multiplying the target parameter by the target prediction signal.

6. The base station according to claim 1 or 2, characterized in that, The optical module includes: an electro-optical conversion module, a photoelectric conversion module, a first port, a second port, and a third port; The electro-optic conversion module is used to perform electro-optic conversion processing on the multiple signals, and the electro-optic conversion module includes the nonlinear components; The photoelectric conversion module is used to perform photoelectric conversion processing on the optical signal; The first port is used to receive the multiple signals; The second port is used to send the optical signal to the central station; The third port is used to send the electrical signal to the feature calculation module.

7. The base station according to claim 1 or 2, characterized in that, The feature calculation module also includes a filtering module; The filtering module is used to filter the electrical signal to obtain the target signal.

8. The base station according to claim 1 or 2, characterized in that, The feature calculation module further includes a feedback module, which is used for: The target signal and at least one signal of the at least one second radio frequency link are subjected to time delay correction processing to obtain the target signal and at least one signal of the at least one second radio frequency link with consistent time delay.

9. The base station according to claim 8, characterized in that, The feedback module includes: a lock count module, a correlator, a threshold decision module, a delay calculation module, and a delay alignment module; The latching module is used to latch signals from the at least one second radio frequency link for a set time slot length, and send the latched signals to the correlator. The correlator is used to perform correlation processing on the target signal and the signal from the lock count module to obtain a correlation signal, and send the correlation signal to the threshold decision module, wherein the correlation signal is a nonlinear signal; The threshold decision module is used to determine whether the correlation value of the received correlation signal is greater than or equal to a set value. If so, the correlation signal is sent to the delay calculation module; otherwise, the correlation signal is not processed. The delay calculation module is used to calculate the delay between the signal of the first radio frequency link and the signal of the at least one second radio frequency link with a set time slot length based on the relevant signal received from the threshold decision module, and send the delay to the delay alignment module. The delay alignment module is configured to, upon receiving the delay from the delay calculation module, remove signals in the target signal that have the delay relative to signals of a set time slot length of the at least one second radio frequency link, and remove signals in the signals of a set time slot length of each second radio frequency link that have the delay relative to the target signal, based on the delay.

10. The base station according to claim 9, characterized in that, The threshold decision module is also used for: When the correlation value of the relevant signal is determined to be greater than or equal to the set value, the latching module is instructed to latch signals from the at least one second radio frequency link for a set time slot length, and replace the previously latched signal with the currently latched signal; When the correlation value of the relevant signal is determined to be less than the set value, the latching module is instructed to stop latching signals from the at least one second radio frequency link for a set time slot length.

11. A base station, characterized in that, include: Multiple radio frequency links, optical modules, and feature calculation modules; wherein the number of the multiple radio frequency links is greater than or equal to 2; Each radio frequency link is used to receive a signal in the corresponding frequency band through an antenna, perform radio frequency processing on the signal, and then send the signal to the optical module. The optical module is used to perform electro-optical conversion processing on multiple signals from the plurality of radio frequency links to obtain an optical signal containing the processed multiple signals. The optical module includes nonlinear components, and among the plurality of radio frequency links, there is a first radio frequency link and at least one second radio frequency link. The signal from the at least one second radio frequency link is processed by the nonlinear components to generate a nonlinear distortion signal. The frequency band of the nonlinear distortion signal overlaps with the frequency band corresponding to the first radio frequency link. The optical signal also contains the nonlinear distortion signal. The optical signal is sent to a central station, a target signal is received from the central station, the target signal is subjected to photoelectric conversion processing, and the processed target signal is sent to the feature calculation module. The target signal contains a signal from the frequency band corresponding to the first radio frequency link. Each second radio frequency link is also used to perform radio frequency processing on one signal of the corresponding frequency band received, and then send the resulting signal to the feature calculation module. The feature calculation module is configured to receive the target signal from the optical module; calculate a nonlinear distortion prediction signal based on the target signal and at least one signal from the at least one second radio frequency link; and send the nonlinear distortion prediction signal to the first radio frequency link, wherein the nonlinear distortion prediction signal is a first prediction signal of the nonlinear distortion signal. The first radio frequency link is further configured to perform pre-distortion processing and radio frequency processing on the signal in the corresponding frequency band of the first radio frequency link according to the nonlinear distortion prediction signal, and send the processed signal to the optical module.

12. The base station according to claim 11, characterized in that, The feature calculation module includes an iterative calculation module, which is used for: Target parameters are calculated based on the target signal, wherein the target parameters are used to characterize the nonlinear distortion characteristics of the nonlinear component; The target prediction signal is calculated based on at least one signal from the at least one second radio frequency link, wherein the target prediction signal is a second prediction signal of the nonlinear distortion signal; The target prediction signal is corrected based on the target parameters to obtain the nonlinear distortion prediction signal.

13. The base station according to claim 11 or 12, characterized in that, The optical module, when receiving the target signal from the central station, performing photoelectric conversion processing on the target signal, and sending the processed target signal to the feature calculation module, is specifically used for: The system receives downlink signals from the central station, performs photoelectric conversion processing on the downlink signals, and sends the processed downlink signals to the feature calculation module. The downlink signals include the target signal and other signals to be sent to the base station. The feature calculation module, upon receiving the target signal from the optical module, is specifically used for: The downlink signal from the optical module is received, and the downlink signal is filtered to obtain the target signal.

14. The base station according to claim 13, characterized in that, The feature calculation module also includes a filtering module; The filtering module is used to filter the downlink signal to obtain the target signal.

15. The base station according to claim 11 or 12, characterized in that, The feature calculation module further includes a feedback module, which is used for: The target signal and at least one signal of the at least one second radio frequency link are subjected to time delay correction processing to obtain the target signal and at least one signal of the at least one second radio frequency link with consistent time delay.

16. The base station according to claim 15, characterized in that, The feedback module includes: a lock count module, a correlator, a threshold decision module, a delay calculation module, and a delay alignment module; The latching module is used to latch signals from the at least one second radio frequency link for a set time slot length, and send the latched signals to the correlator. The correlator is used to perform correlation processing on the target signal and the signal from the lock count module to obtain a correlation signal, and send the correlation signal to the threshold decision module, wherein the correlation signal is a nonlinear signal; The threshold decision module is used to determine whether the correlation value of the received correlation signal is greater than or equal to a set value. If so, the correlation signal is sent to the delay calculation module; otherwise, the correlation signal is not processed. The delay calculation module is used to calculate the delay between the signal of the first radio frequency link and the signal of the at least one second radio frequency link with a set time slot length based on the relevant signal received from the threshold decision module, and send the delay to the delay alignment module. The delay alignment module is configured to, upon receiving the delay from the delay calculation module, remove signals in the target signal that have the delay relative to signals of a set time slot length of the at least one second radio frequency link, and remove signals in the signals of a set time slot length of each second radio frequency link that have the delay relative to the target signal, based on the delay.

17. The base station according to claim 16, characterized in that, The threshold decision module is also used for: When the correlation value of the relevant signal is determined to be greater than or equal to the set value, the latching module is instructed to latch signals from the at least one second radio frequency link for a set time slot length, and replace the previously latched signal with the currently latched signal; When the correlation value of the relevant signal is determined to be less than the set value, the latching module is instructed to stop latching signals from the at least one second radio frequency link for a set time slot length.

18. A central station, characterized in that, include: Optical modules, signal processing modules; The optical module is used to receive optical signals from the base station, perform photoelectric conversion on the optical signals to obtain electrical signals, and send the electrical signals to the signal processing module; wherein, the electrical signals include nonlinear distortion signals and multiple signals received by multiple radio frequency links of the base station through antennas, the number of multiple radio frequency links is greater than or equal to 2, there is a first radio frequency link and at least one second radio frequency link among the multiple radio frequency links, the base station includes nonlinear components, the signal of the at least one second radio frequency link generates the nonlinear distortion signal after passing through the nonlinear components, and the frequency band of the nonlinear distortion signal overlaps with the frequency band corresponding to the first radio frequency link; The signal processing module is configured to receive the electrical signal from the optical module, extract the target signal of the frequency band corresponding to the first radio frequency link from the electrical signal, and send the target signal to the optical module. The optical module is also used to perform electro-optical conversion processing on the target signal and send the processed target signal to the base station.

19. The central station according to claim 18, characterized in that, The starting frequency of the nonlinear distortion signal is greater than or equal to a first frequency, and the cutoff frequency of the nonlinear distortion signal is less than or equal to a second frequency, wherein: When a second radio frequency link exists among the plurality of radio frequency links, the first frequency is twice the start frequency of the frequency band corresponding to the second radio frequency link, and the second frequency is twice the cutoff frequency of the frequency band corresponding to the second radio frequency link; or When there are two second radio frequency links among the plurality of radio frequency links, the first frequency is the sum of the start frequencies of the corresponding frequency bands of the two second radio frequency links, and the second frequency is the sum of the cutoff frequencies of the corresponding frequency bands of the two second radio frequency links; or, the first frequency is the difference between the start frequencies of the corresponding frequency bands of the two second radio frequency links, and the second frequency is the difference between the cutoff frequencies of the corresponding frequency bands of the two second radio frequency links.

20. The central station according to claim 19, characterized in that, The signal processing module includes a filtering module, which is used to receive the electrical signal from the optical module, filter the electrical signal, and obtain the target signal. When the optical module performs electro-optical conversion processing on the target signal and sends the processed target signal to the base station, it is specifically used to: perform electro-optical conversion processing on the target signal and other signals to be sent to the base station to obtain a downlink signal containing the target signal and other signals to be sent to the base station, and send the downlink signal to the base station.

21. A central station, characterized in that, include: Optical module, signal processing module, feature calculation module; The optical module is used to receive optical signals from at least one base station, and to perform photoelectric conversion processing on the optical signals of each of the at least one base station to obtain an electrical signal for each base station; wherein, the electrical signal of any base station includes a nonlinear distortion signal and multiple signals received by multiple radio frequency links of the base station through an antenna, the number of multiple radio frequency links is greater than or equal to 2, there is a first radio frequency link and at least one second radio frequency link among the multiple radio frequency links, the base station includes a nonlinear component, the signal of the at least one second radio frequency link generates the nonlinear distortion signal after passing through the nonlinear component, and the frequency band of the nonlinear distortion signal overlaps with the frequency band corresponding to the first radio frequency link; the electrical signal of each base station is respectively sent to the signal processing module and the feature calculation module; The feature calculation module is configured to receive electrical signals from each base station of the optical module; perform feature calculation processing on the electrical signals of each base station to obtain a nonlinear distortion prediction signal corresponding to each base station, and send the nonlinear distortion prediction signal corresponding to each base station to the signal processing module; wherein, the feature calculation processing on the electrical signals of any base station includes the following steps: extracting the target signal of the frequency band corresponding to the first radio frequency link from the electrical signals, and extracting at least one signal from the at least one second radio frequency link from the electrical signals; calculating the nonlinear distortion prediction signal based on the target signal and the at least one signal from the at least one second radio frequency link, wherein the nonlinear distortion prediction signal is a first prediction signal of the nonlinear distortion signal; The signal processing module is configured to receive electrical signals from each base station of the optical module; perform radio frequency processing on the electrical signals of the at least one base station to obtain a target combined signal; wherein the target combined signal includes signals of the frequency band corresponding to the first radio frequency link; receive nonlinear distortion prediction signals corresponding to each base station from the feature calculation module; and sequentially perform distortion correction processing on the target combined signal according to the nonlinear distortion prediction signals corresponding to each base station.

22. The central station according to claim 21, characterized in that, The starting frequency of the nonlinear distortion signal is greater than or equal to a first frequency, and the cutoff frequency of the nonlinear distortion signal is less than or equal to a second frequency, wherein: When a second radio frequency link exists among the plurality of radio frequency links, the first frequency is twice the start frequency of the frequency band corresponding to the second radio frequency link, and the second frequency is twice the cutoff frequency of the frequency band corresponding to the second radio frequency link; or When there are two second radio frequency links among the plurality of radio frequency links, the first frequency is the sum of the start frequencies of the corresponding frequency bands of the two second radio frequency links, and the second frequency is the sum of the cutoff frequencies of the corresponding frequency bands of the two second radio frequency links; or, the first frequency is the difference between the start frequencies of the corresponding frequency bands of the two second radio frequency links, and the second frequency is the difference between the cutoff frequencies of the corresponding frequency bands of the two second radio frequency links.

23. The central station according to claim 21 or 22, characterized in that, The feature calculation module includes an iterative calculation module, which is used for: Target parameters are calculated based on the target signal, wherein the target parameters are used to characterize the nonlinear distortion characteristics of the nonlinear component; A target prediction signal is calculated based on at least one signal from the at least one second radio frequency link, wherein the target prediction signal is a second prediction signal of the nonlinear distortion signal; The target prediction signal is corrected based on the target parameters to obtain the nonlinear distortion prediction signal.

24. The central station according to claim 23, characterized in that, The iterative calculation module, when calculating the target parameters based on the target signal, is specifically used for: The target parameters are calculated based on the set first calculation model and the target signal, wherein the first calculation model is used to represent the correspondence between one of the multiple signals input to the nonlinear component, the nonlinear distortion signal output by the nonlinear component with the same frequency band as the one signal, and the nonlinear distortion characteristic parameters of the nonlinear component; When the iterative calculation module calculates the target prediction signal based on at least one signal from the at least one second radio frequency link, it is specifically used for: The target prediction signal is calculated based on the established second calculation model and at least one signal from the at least one second radio frequency link, wherein the second calculation model is used to represent the correspondence between at least one signal passing through the nonlinear component and the nonlinear distortion signal generated after the at least one signal passes through the nonlinear component.

25. The central station according to claim 23, characterized in that, The iterative calculation module, when correcting the target prediction signal according to the target parameters to obtain the nonlinear distortion prediction signal, is specifically used for: The nonlinear distortion prediction signal is obtained by multiplying the target parameter by the target prediction signal.

26. The central station according to claim 21 or 22, characterized in that, The feature calculation module also includes a filtering module; The filtering module is used to filter the electrical signal to obtain the target signal.

27. The central station according to claim 21 or 22, characterized in that, The feature calculation module further includes a feedback module, which is used for: The target signal and at least one signal of the at least one second radio frequency link are subjected to time delay correction processing to obtain the target signal and at least one signal of the at least one second radio frequency link with consistent time delay.

28. The central station according to claim 27, characterized in that, The feedback module includes: a lock count module, a correlator, a threshold decision module, a delay calculation module, and a delay alignment module; The latching module is used to latch signals from the at least one second radio frequency link for a set time slot length, and send the latched signals to the correlator. The correlator is used to perform correlation processing on the target signal and the signal from the lock count module to obtain a correlation signal, and send the correlation signal to the threshold decision module, wherein the correlation signal is a nonlinear signal; The threshold decision module is used to determine whether the correlation value of the received correlation signal is greater than or equal to a set value. If so, the correlation signal is sent to the delay calculation module; otherwise, the correlation signal is not processed. The delay calculation module is used to calculate the delay between the signal of the first radio frequency link and the signal of the at least one second radio frequency link with a set time slot length based on the relevant signal received from the threshold decision module, and send the delay to the delay alignment module. The delay alignment module is configured to, upon receiving the delay from the delay calculation module, remove signals in the target signal that have the delay relative to signals of a set time slot length of the at least one second radio frequency link, and remove signals in the signals of a set time slot length of each second radio frequency link that have the delay relative to the target signal, based on the delay.

29. The central station according to claim 28, characterized in that, The threshold decision module is also used for: When the correlation value of the relevant signal is determined to be greater than or equal to the set value, the latching module is instructed to latch signals from the at least one second radio frequency link for a set time slot length, and replace the previously latched signal with the currently latched signal; When the correlation value of the relevant signal is determined to be less than the set value, the latching module is instructed to stop latching signals from the at least one second radio frequency link for a set time slot length.

30. A communication system, characterized in that, include: The base station as described in any one of claims 1 to 10; or The base station as described in any one of claims 11 to 17, and the central station as described in any one of claims 18 to 20; or The central station as described in any one of claims 21 to 29.

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