Self-interference signal offset method based on CMP power amplifier model

Abstract

The invention provides a self-interference signal counteracting method based on a CMP power amplifier model, and relates to the technical field of simulation domain self-interference counteracting, and the method comprises the steps: training a CMP model, enabling a local modulation signal to pass through the CMP model, and obtaining a reference signal of a first adaptive filter; the reference signal and the hydrophone receiving signal pass through a first adaptive filter together to complete digital domain self-interference reconstruction to obtain a self-interference reconstruction signal, and the self-interference reconstruction signal and the receiving signal are offset in an analog domain to obtain a signal subjected to analog domain self-interference offset; and enabling the obtained signal and the reference signal to pass through a second adaptive filter together to finish residual digital domain self-interference offset, and further demodulating the error of the second adaptive filter to obtain far-end expected signal information. According to the method, the self-interference cancellation performance of the in-band full-duplex underwater acoustic communication system can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of analog domain self-interference cancellation, and in particular to a self-interference signal cancellation method based on a CMP power amplifier model. Background Art

[0002] In the process of analog domain self-interference cancellation, it is important to consider how to cancel the nonlinear components to improve the performance of analog domain self-interference cancellation. Digitally assisted analog domain self-interference cancellation technology is the mainstream method of analog domain self-interference cancellation technology. This technology models or extracts the nonlinear part in the power amplifier through an auxiliary link so that the reference signal contains nonlinear components. Therefore, this analog domain self-interference cancellation technology can effectively eliminate some nonlinear interference.

[0003] In response to the above problems, Wu Wei from Nanjing University of Posts and Telecommunications published a paper titled "A Wireless Full-Duplex Multipath Self-Interference Signal Cancellation Method Based on Segmented Inverse Transformation" in the Journal of Signal Processing, which records an analog domain self-interference cancellation method suitable for full-duplex equipment in a wireless multipath environment. This method is based on the Rayleigh distribution model and uses a wireless full-duplex multipath self-interference signal cancellation method based on segmented inverse transformation to directly generate digital domain cancellation parameters, and converts the cancellation signal to the analog domain through an additional transmission link for self-interference elimination. Compared with other analog domain cancellation schemes assisted by the digital domain, this scheme does not need to establish a complex channel model in the digital domain, estimate channel parameters, or couple the transmitter signal, and the structure is simplified. Zhou Jiaqiong from Harbin Engineering University proposed a digital-assisted analog self-interference cancellation scheme in his master's thesis "Research on Digital and Analog Self-Interference Cancellation Technology for Full-Duplex Underwater Acoustic Communication", and studied the nonlinear effects of the power amplifier involved in the analog self-interference cancellation, using a memory polynomial model to describe the nonlinear effects of the power amplifier. There are two simulated self-interference cancellation schemes. The first is to use the power amplifier output and the estimated underwater acoustic channel to reconstruct the self-interference signal to achieve simulated cancellation; the second is to use the modulated signal through the memory polynomial model and the estimated underwater acoustic channel to reconstruct the self-interference signal to achieve simulated cancellation. Zhao Yujie from Northeast Electric Power University proposed a time-varying minimum mean square adaptive filtering algorithm with gradually attenuated convergence parameters in his master's degree "Research on Self-Interference Elimination Technology of Simultaneous and Co-Frequency Full-Duplex System". The improved inverse tangent function is used to coordinate the control step size with the help of the relationship between the time parameter and the correlation value of the error signal, so as to maintain ideal convergence, channel tracking ability and interference cancellation ratio at a low computational complexity, so that the self-interference signal in the RF stage of the simultaneous and co-frequency full-duplex system can be effectively suppressed. Professor Liu Ying's team from the University of Electronic Science and Technology of China published a patent titled "A digitally assisted analog domain interference cancellation method and device". The method includes four steps: signal transmission, signal feedback, signal reconstruction, and signal reception. In the signal feedback step, a nonlinear extraction unit is used to estimate the nonlinear parameter vector, and in the signal reconstruction step, a nonlinear reconstruction unit is used to calculate and reconstruct the digital transmission signal. The method can effectively suppress the nonlinear interference introduced by the transmission RF channel, and can conveniently perform nonlinear estimation and parameter adjustment in the digital domain. It can conveniently estimate the multipath channel between the transmission RF channel and the receiving RF channel in the digital domain, and adjust the parameters, which is more conducive to expansion to other application scenarios and more robust. Huawei's Wireless Communication Technology Laboratory proposed the use of multi-stage self-interference cancellation technology at the IEEE Global Communication Conference, and realized single-antenna CCFD wireless communication on the laboratory's homemade equipment. In this system, in addition to line-of-sight (LOS) communication, the multipath effect of signal propagation is also considered, and the multipath interference components are correspondingly offset in the analog domain.

[0004] Although the methods commonly used by existing technologies can achieve good results, digital domain technology alone cannot solve the problem of failure to obtain the desired signal at the far end caused by saturation of the above-mentioned acquisition signal. In underwater acoustic channels, traditional radio field methods (such as antenna polarization, antenna orthogonality, etc.) are no longer applicable, the performance of spatial domain self-interference cancellation is limited, and is limited by the influence of the current environment (such as the number of array elements, sea surface fluctuations, sea breeze, etc.). Analog domain self-interference cancellation technology is mostly circuit simulation, software simulation, etc., lacking physical-based solutions and hardware system joint debugging design. How to combine the analog domain and the digital domain to perform low-complexity self-interference cancellation, and design related hardware equipment connection solutions and field experimental verification that can be performed in real time are issues that need to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to provide a self-interference signal cancellation method based on a CMP power amplifier model. Aiming at the problems in the analog domain self-interference cancellation process, the concept of digitally assisted analog self-interference cancellation is introduced, so that the analog domain self-interference cancellation can eliminate the nonlinear components in the self-interference signal and further improve the self-interference cancellation performance.

[0006] To achieve the above object, the present invention provides a self-interference signal cancellation method based on a CMP power amplifier model, the method comprising the following steps: S101, generate a known broadband initial signal , the amplifier output signal is delayed and attenuated to obtain the signal ,Will Joint Broadband Initial Signal , after the CMP model training process, the CMP nonlinear distortion model parameters of the power amplifier are calculated, n are discrete sampling points; S102: The local signal source is modulated and the transducer sends out a transmission signal x [ n ], x [ n ]Through the self-interference channel , received by the hydrophone, recorded as the hydrophone received signal y [ n ], the hydrophone receives the signal y [ n ] After passing through a low noise amplifier, the data is collected locally; S103: After the transmitted signal is processed by the CMP model, a reference signal of the first adaptive filter is obtained. ; S104: reference signal Receiving signals with hydrophone y [ n] pass through the first adaptive filter together to complete the digital domain self-interference reconstruction and obtain the estimated self-interference channel , and the self-interference reconstruction signal , ; S105, canceling the self-interference reconstruction signal and the received signal in the analog domain to obtain a signal after self-interference cancellation in the analog domain ; S106, It is collected locally by the system ADC and passes through the two ends of the second adaptive filter together with the reference signal to complete the residual digital domain self-interference cancellation and obtain the estimated residual self-interference channel , and the residual reconstructed signal , the error of the second adaptive filter e [ n ] is the remote communication signal to be demodulated. At this time, the relationship between the error and the residual reconstructed signal is: ; S107, error of the second adaptive filter Demodulate and obtain the desired signal information at the far end.

[0007] Furthermore, the hydrophone receives the signal y [ n The expression of ] is:

[0008] in, is the local self-interference signal received by the local receiving hydrophone, , is the remote communication signal received by the local receiving hydrophone, is the environmental noise received by the local receiving end.

[0009] Furthermore, the CMP model training process specifically includes the following steps: S201, initialization, confirmation and , set the model parameter , and , represents the order of the interaction between the signal and the polynomial memory, represents the number of delayed samples, represents the order of the interaction term between the signal and the lagged envelope, Indicates the memory depth of the signal, represents the number of sampling points of the hysteresis envelope, represents the order of the interaction term between the signal and the leading envelope, Indicates the memory depth of the signal, Indicates the number of sampling points of the leading envelope; S202, determine a CMP model expression, the CMP model expression is as follows:

[0010]

[0011]

[0012] By fitting the model, we can estimate the model parameters 、 and , k represents the nonlinear order, l Indicates delay, m Delayed samples representing positive and negative intertemporal time offsets; S203, define a loss function; S204. Construct design matrix and define design matrix X and parameter vector β , then:

[0013] represents the real output, the design matrix X Each column corresponds to a CMP model term, and each row corresponds to a time sample n. 、 and Expand to obtain the parameter vector β , the dimension of the parameter vector corresponds to the number of columns of the design matrix; S205. Estimate the parameter vector using the least squares method. The expression is:

[0014] get Then, decompose it into 、 and , as the final result of the CMP model; S206, will 、 and Substitute into the CMP model and calculate the reference signal , according to the loss function , and Adjustments are made to obtain the final output CMP model.

[0015] Furthermore, step S105 specifically includes the following steps: S301, outputting the self-interference reconstruction signal through the NI-DAQ device, adjusting the amplitude during output so that the amplitude of the self-interference reconstruction signal and the amplitude of the received signal are in the same range, and performing analog output so that the self-interference reconstruction signal and the received signal are offset in the analog domain; S302, by adjusting the delay, the amplitude of the output signal waveform of the subtractor is minimized to obtain the best delay, and obtain the signal after the analog domain self-interference is cancelled. .

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a self-interference signal cancellation method based on a CMP power amplifier model. The local modulated signal is passed through a trained CMP model to obtain a reconstructed power amplifier output signal, which is used as a reference signal to sequentially perform digital domain self-interference reconstruction, analog domain self-interference cancellation, and residual digital domain self-interference cancellation to complete digital-assisted analog domain self-interference cancellation. The method can significantly improve the self-interference cancellation performance of an in-band full-duplex underwater acoustic communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only preferred embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 It is a schematic diagram of the overall flow of a self-interference signal cancellation method based on a CMP power amplifier model provided by an embodiment of the present invention.

[0019] Figure 2 It is a schematic diagram of a sea trial experiment scenario provided by an embodiment of the present invention.

[0020] Figure 3 It is a constellation diagram of a power amplifier output signal reconstructed by a CMP model provided in an embodiment of the present invention.

[0021] Figure 4 It is a schematic diagram of the relationship between the reconstructed signal NMSE, the nonlinear order and the memory depth for a Class T homemade power amplifier provided by an embodiment of the present invention.

[0022] Figure 5 It is a schematic diagram of the relationship between the reconstructed signal NMSE, the nonlinear order and the memory depth for the BK2713 model power amplifier provided by an embodiment of the present invention.

[0023] Figure 6 It is a schematic diagram of frequency domain comparison between a power amplifier output signal and a reconstructed signal provided in an embodiment of the present invention.

[0024] Figure 7 It is a schematic diagram of NMSE curves of analog domain self-interference cancellation of different reference signals in the presence of a far-end communication signal provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The enumerated embodiments are only used to explain the present invention and are not used to limit the scope of the present invention.

[0026] Reference Figure 1 This embodiment provides a self-interference signal cancellation method based on a CMP power amplifier model, the method comprising the following steps: S101, generate a known broadband initial signal , the amplifier output signal is delayed and attenuated to obtain the signal ,Will Joint Broadband Initial Signal , after the CMP model training process, the CMP nonlinear distortion model parameters of the power amplifier are calculated, n are discrete sampling points.

[0027] Exemplarily, the broadband initial signal may be an LFM signal, or an HFM signal, or other broadband signals.

[0028] S102: The local signal source is modulated and the transducer sends out a transmission signal x [ n ], x [ n ]Through the self-interference channel , received by the hydrophone, recorded as the hydrophone received signal y [ n ], the hydrophone receives the signal y [ n ]The signal is collected locally after passing through a low noise amplifier.

[0029] In this embodiment, the received signal y [ n ] can be expressed as:

[0030] in, is the local self-interference signal received by the local receiving hydrophone, , is the remote communication signal received by the local receiving hydrophone, It is the environmental noise received by the local receiving end. When the remote communication signal (also called the remote desired signal) is not transmitted, the received signal Not included item.

[0031] S103: After the transmitted signal is processed by the CMP model, a reference signal of the first adaptive filter is obtained. .

[0032] S104: reference signal Receiving signals with hydrophone y [ n ] pass through the first adaptive filter together to complete the digital domain self-interference reconstruction and obtain the estimated self-interference channel , and the self-interference reconstruction signal , .

[0033] S105, canceling the self-interference reconstruction signal and the received signal in the analog domain to obtain a signal after self-interference cancellation in the analog domain .

[0034] S106, It is collected locally by the system ADC and passes through the two ends of the second adaptive filter together with the reference signal to complete the residual digital domain self-interference cancellation and obtain the estimated residual self-interference channel , and the residual reconstructed signal , , the error of the second adaptive filter e [ n ] is the remote communication signal to be demodulated. At this time, the error e [ n ] and the residual reconstruction signal is:

[0035] S107, error of the second adaptive filter Demodulate and obtain the desired signal information at the far end.

[0036] As a possible implementation method, the CMP model training process specifically includes the following steps: S201, initialization, confirmation and , set the model parameter , and . represents the order of the interaction between the signal and the polynomial memory, represents the number of delayed samples, represents the order of the interaction term between the signal and the lagged envelope, Indicates the memory depth of the signal, represents the number of sampling points of the hysteresis envelope, represents the order of the interaction term between the signal and the leading envelope, Indicates the memory depth of the signal, Indicates the number of samples leading the envelope.

[0037] S202, determine a CMP model expression, the CMP model expression is as follows:

[0038]

[0039]

[0040] By fitting the model, we can estimate the model parameters 、 and , k represents the nonlinear order, l Indicates delay, m Delayed samples representing positive and negative intertemporal time offsets. Represents the current sample, represents the previous delayed sample, Represents backward delayed samples.

[0041] S203, define the loss function. In order to estimate 、 and , we need to minimize the predicted output And the real output of error.

[0042] In this embodiment, the least square error is used As a loss function:

[0043] N is the number of data samples.

[0044] S204. Construct design matrix and define design matrix X and parameter vector β , then:

[0045] represents the real output, the design matrix X Each column corresponds to a CMP model term, for example, each row corresponds to a time sample n, and all coefficients 、 and Expand to obtain the parameter vector β , the dimension of the parameter vector corresponds to the number of columns of the design matrix.

[0046] S205. Estimate the parameter vector using the least squares method. The expression is:

[0047] get Then, decompose it into 、 and , as the final result of the CMP model; S206, will 、 and Substitute into the CMP model and calculate the reference signal , according to the loss function , and Adjustments are made to obtain the final output CMP model.

[0048] As another possible implementation, step S105 specifically includes the following steps: S301, outputting the self-interference reconstruction signal through the NI-DAQ device, adjusting the amplitude during output so that the amplitude of the self-interference reconstruction signal and the amplitude of the received signal are in the same range, and performing analog output so that the self-interference reconstruction signal and the received signal are offset in the analog domain.

[0049] S302, by adjusting the delay, the amplitude of the output signal waveform of the subtractor is minimized to obtain the best delay, and obtain the signal after the analog domain self-interference is cancelled. .

[0050] The CMP model-based power amplifier output reconstruction simulation self-interference cancellation method provided in this embodiment can significantly improve the self-interference cancellation performance of the in-band full-duplex underwater acoustic communication system. The present invention makes a detailed analysis of the impact of the CMP model reconstruction power amplifier output signal on the self-interference cancellation performance, and completes the self-interference cancellation performance based on the CMP model. Figure 2 Sea trial of the scheme shown.

[0051] Figure 3 The constellation diagram of the power amplifier output signal reconstructed by the CMP model is shown. Figure 3 It can be seen that after the reconstruction of the CMP model, the constellation diagram of the output signal is basically fitted, and the output signal of the power amplifier after fitting the CMP model has nonlinear characteristics.

[0052] Figure 4 , Figure 5 It shows that for the homemade Class T amplifier, when the minimum NMSE is reached in the amplifier output reconstruction based on the CMP model, the nonlinear order of the model is 1, the memory depth is 11, and the minimum NMSE is -21.89dB. For the BK2713 amplifier, when the minimum NMSE is reached in the amplifier output reconstruction based on the CMP model, the nonlinear order of the model is 1, the memory depth is 11, and the minimum NMSE is -24.84dB. It can be seen that the amplifier output reconstruction based on the CMP model does not require a very high nonlinear order, and the NMSE is relatively stable with the change of memory depth. However, the homemade Class T amplifier has a higher nonlinear influence on the self-interference signal.

[0053] Figure 6 The comparison of the frequency spectrum of the output signal of the BK2713 model / self-made T-class power amplifier reconstructed by the CMP model is shown. From the figure, it can be seen that the output of the power amplifier after fitting the CMP model also has a good fitting effect in the part within the system frequency band.

[0054] from Figure 7 It can be seen that the analog interference cancellation scheme based on CMP power amplifier model output reconstruction has better cancellation effect than the conventional analog interference cancellation method, the self-interference cancellation performance is improved by 3.5dB, and the remote communication signal is well preserved.

[0055] In summary, in response to the problems in the analog domain self-interference cancellation process, this embodiment introduces the concept of digitally assisted analog self-interference cancellation and proposes a digitally assisted analog self-interference cancellation method based on CMP model power amplifier output reconstruction, so that the analog domain self-interference cancellation can eliminate the nonlinear components in the self-interference signal, thereby further improving the self-interference cancellation performance.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A self-interference signal cancellation method based on a CMP power amplifier model, characterized in that: The method comprises: S101, generate a known broadband initial signal , the amplifier output signal is delayed and attenuated to obtain the signal ,Will Joint Broadband Initial Signal , after the CMP model training process, the CMP nonlinear distortion model parameters of the power amplifier are calculated, n are discrete sampling points; S102: The local signal source is modulated and the transducer sends out a transmission signal x [ n ], x [ n ]Through the self-interference channel , received by the hydrophone, recorded as the hydrophone received signal y [ n ], the hydrophone receives the signal y [ n ] After passing through a low noise amplifier, the data is collected locally; S103: After the transmitted signal is processed by the CMP model, a reference signal of the first adaptive filter is obtained. ; S104: reference signal Receiving signals with hydrophone y [ n ] pass through the first adaptive filter together to complete the digital domain self-interference reconstruction and obtain the estimated self-interference channel , and the self-interference reconstruction signal , ; S105, canceling the self-interference reconstruction signal and the received signal in the analog domain to obtain a signal after self-interference cancellation in the analog domain ; S106, It is collected locally by the system ADC and passes through the two ends of the second adaptive filter together with the reference signal to complete the residual digital domain self-interference cancellation and obtain the estimated residual self-interference channel , and the residual reconstructed signal , the error of the second adaptive filter e [ n ] is the remote communication signal to be demodulated. At this time, the relationship between the error and the residual reconstructed signal is: ； S107, error of the second adaptive filter Demodulate and obtain the desired signal information at the far end.

2. The method for canceling self-interference signals based on a CMP power amplifier model according to claim 1, characterized in that: Hydrophone receiving signal y [ n The expression of ] is: in, is the local self-interference signal received by the local receiving hydrophone, , is the remote communication signal received by the local receiving hydrophone, is the environmental noise received by the local receiving end.

3. The method for canceling self-interference signals based on a CMP power amplifier model according to claim 1, characterized in that: The CMP model training process includes the following steps: S201, initialization, confirmation and , set the model parameter , and , represents the order of the interaction between the signal and the polynomial memory, represents the number of delayed samples, represents the order of the interaction term between the signal and the lagged envelope, Indicates the memory depth of the signal, represents the number of sampling points of the hysteresis envelope, represents the order of the interaction term between the signal and the leading envelope, Indicates the memory depth of the signal, Indicates the number of sampling points of the leading envelope; S202, determine a CMP model expression, the CMP model expression is as follows: By fitting the model, we can estimate the model parameters 、 and , k represents the nonlinear order, l Indicates delay, m Delayed samples representing positive and negative intertemporal time offsets; S203, define a loss function; S204. Construct design matrix and define design matrix X and parameter vector β , then: Represents the true output, the design matrix X Each column corresponds to a CMP model term, and each row corresponds to a time sample n. 、 and Expand to obtain the parameter vector β , the dimension of the parameter vector corresponds to the number of columns of the design matrix; S205. Estimate the parameter vector using the least squares method. The expression is: get Then, decompose it into 、 and , as the final result of the CMP model; S206, will 、 and Substitute into the CMP model and calculate the reference signal , according to the loss function , and Adjustments are made to obtain the final output CMP model.

4. The method for canceling self-interference signals based on a CMP power amplifier model according to claim 1, characterized in that: Step S105 specifically includes the following steps: S301, outputting the self-interference reconstruction signal through the NI-DAQ device, adjusting the amplitude during output so that the amplitude of the self-interference reconstruction signal and the amplitude of the received signal are in the same range, and performing analog output so that the self-interference reconstruction signal and the received signal are offset in the analog domain; S302, by adjusting the delay, the amplitude of the output signal waveform of the subtractor is minimized to obtain the corresponding delay, and obtain the signal after the analog domain self-interference is cancelled. .

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