Self-interference elimination method, system and device in full-duplex communication

Abstract

The invention relates to the technical field of wireless communication, in particular to a self-interference elimination method, system and device in full-duplex communication, and the method comprises the steps: configuring two antennas for each user, and periodically switching the receiving and transmitting functions of the antennas to generate a pseudo-Doppler effect; in the second half section of each period, phase shift processing is carried out on the received signals of all the users, and equivalent channel responses for receiving self-interference signals and receiving expected signals are obtained; calculating a self-interference channel frequency domain transfer function (a first transfer function) and an expected channel frequency domain transfer function (a second transfer function); and determining a frequency range capable of eliminating self-interference by using the two functions, filtering a received signal of the mixed self-interference signal, and extracting a desired signal. According to the invention, good self-interference elimination capability can be maintained under the conditions of different transmitting powers, different communication distances and different channels, the self-interference problem in full-duplex communication is effectively solved, and the performance and reliability of a wireless communication system are improved.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a method, system and device for eliminating self-interference in full-duplex communication. Background Art

[0002] Wireless communication systems currently mainly use half-duplex mode, such as Figure 1 As shown, link 1 and link 2 do not communicate at the same time and frequency to avoid self-interference. If they communicate at the same time, frequency division multiplexing is used; if they communicate at the same frequency, time division multiplexing is used. Figure 2 As shown in the figure, the full-duplex communication system allows link 1 and link 2 to communicate at the same time and at the same frequency. The transmitting antenna and receiving antenna of the same user are very close, and the transmission power needs to be very strong to ensure the communication quality of the desired user at a long distance. This will cause strong self-interference to its own received signal, making the received self-interference signal much higher than the desired signal, which becomes the main difficulty in achieving full-duplex with unified time and frequency. The current existing methods for eliminating self-interference in full-duplex communication systems can be divided into five categories, namely, physical isolation of antennas, spatial beamforming, self-interference channel modeling, analog circuit compensation, and digital filtering compensation. There are still the following disadvantages: First, antenna physical isolation and spatial beamforming limitations: The residual self-interference of these two methods is still high, which is difficult to meet the signal detection requirements of the receiver.

[0003] Second, the limitations of reconstructing and extracting self-interference signals: Self-interference channel modeling, analog circuit compensation, digital filter compensation and other methods are essentially to reconstruct and extract self-interference signals. However, due to the limitations of algorithms and hardware conditions, there is a difference between the reconstructed signal and the actual received self-interference signal, which makes it impossible to completely eliminate self-interference. Summary of the invention

[0004] To solve the above technical problems, the present invention provides a method, system and device for eliminating self-interference in full-duplex communication. The method is applicable to user A and user B performing full-duplex communication at the same time and at the same frequency, and comprises the following steps: S1: Two antennas are configured for user A and user B, namely antenna 1 and antenna 2, and the transceiver functions of antenna 1 and antenna 2 are switched through the set antenna switching cycle to generate a pseudo-Doppler effect; in the second half of each cycle, the received signal of each user is phase-shifted to obtain the equivalent channel response of the received self-interference signal and the equivalent channel response of the received desired signal; S2: Based on the equivalent channel response of the received self-interference signal, a transfer function of the equivalent self-interference channel in the frequency domain is obtained, which is recorded as a first transfer function. At the same time, based on the equivalent channel response of user A or user B receiving the desired signal, a transfer function of the channel receiving the desired signal in the frequency domain is calculated, which is recorded as a second transfer function. S3: obtaining a frequency range within which the self-interference signal can be eliminated according to the first transfer function and the second transfer function, and filtering the received signal including the self-interference signal within the frequency range within which the self-interference signal can be eliminated to extract a desired signal.

[0005] In one embodiment of the present invention, in S1, the method for generating a pseudo-Doppler effect by switching the transceiver functions of antenna 1 and antenna 2 according to a set antenna switching cycle includes: dividing the antenna switching cycle into a front and a rear sub-cycle of equal length: in the front sub-cycle, antenna 1 of each user performs a transmitting task, and antenna 2 performs a receiving task; and in the rear sub-cycle, antenna 2 of each user switches to a transmitting state, and antenna 1 switches to a receiving state.

[0006] In one embodiment of the present invention, the antenna switching frequency corresponding to the antenna switching period is set to be greater than or equal to the larger value of the baseband bandwidth of the self-interference signal and the baseband bandwidth of the desired signal plus the bandwidth of the desired signal.

[0007] In one embodiment of the present invention, in S1, the method for obtaining the equivalent channel response of the received self-interference signal is: the received signal of each user is phase-shifted by π in the second half sub-period of any antenna switching period, and the equivalent channel response of the received self-interference signal is obtained. : , in, Indicates user A or user B, represents the self-interference channel fading parameter of user A or user B, t represents time, represents the antenna switching period, Any integer.

[0008] In one embodiment of the present invention, in S2, the method for obtaining the transfer function of the equivalent self-interference channel in the frequency domain is as follows: Calculate the equivalent channel response of the received self-interference signal The Fourier series of : , in, represents an exponential function with base e, while the periodic function The Fourier coefficients of ; Based on the equivalent channel response The Fourier series of the equivalent self-interference channel in the frequency domain is obtained, which is recorded as the first transfer function : , in, f represents frequency, j represents imaginary unit, l Indicates the harmonic order, represents the impulse function, It is the unit pseudo-Doppler frequency shift introduced by the switching of the transmitting and receiving antennas, i.e. its fundamental frequency; Since the periodic function The Fourier coefficients of , the center frequency amplitude of the transfer function of the equivalent self-interference channel in the frequency domain, that is, the main frequency component is zero.

[0009] In one embodiment of the present invention, in S1, the method for acquiring the equivalent channel response of user A or user B receiving the desired signal is: In the second half of any antenna switching cycle, the received signal of each user is phase-shifted by π, and the equivalent channel responses of user A and user B receiving the desired signal are obtained as follows: in, represents the equivalent channel response of user A receiving the desired signal, represents the equivalent channel response of user B receiving the desired signal; represents the channel fading parameter between antenna 1 of user A and antenna 2 of user B, represents the channel fading parameter between antenna 2 of user A and antenna 1 of user B; t represents time, represents the antenna switching period, Any integer.

[0010] In one embodiment of the present invention, in S2, based on the equivalent channel response of user A or user B receiving the desired signal, the method for calculating the transfer function of the channel receiving the desired signal in the frequency domain is as follows: Calculate the equivalent channel response for user A or user B to receive the desired signal The Fourier series of : , in, Indicates user A or user B, is a periodic function The Fourier coefficients of When , the channel center frequency, i.e., the main frequency coefficient, of the desired signal received by user A is: , The channel center frequency, i.e., the main frequency coefficient, of the desired signal received by user B is: , when When , the channel harmonic frequency coefficient of user A or user B receiving the desired signal is: ; Based on the equivalent channel response The Fourier series of the channel receiving the desired signal is obtained in the frequency domain, which is recorded as the second transfer function : , in, f represents frequency, j represents imaginary unit, l Indicates the harmonic order, represents the impulse function, It is the unit pseudo-Doppler frequency shift introduced by the switching of the transmitting and receiving antennas, that is, its fundamental frequency.

[0011] In one embodiment of the present invention, in S3, the method for obtaining the frequency range that can eliminate the self-interference signal is: selecting a frequency range that satisfies the value of the first transfer function is zero and the value of the second transfer function is not zero.

[0012] In one embodiment of the present invention, in S3, the method for extracting the desired signal is: within the frequency range that can eliminate the self-interference signal, the cutoff frequency of the low-pass filter is set, and the received signal is filtered at the center frequency of each user's received signal, i.e., the main frequency, by using the low-pass filter.

[0013] In one embodiment of the present invention, the minimum value of the cutoff frequency is the desired signal baseband bandwidth, and the maximum value of the cutoff frequency is the antenna switching frequency corresponding to the antenna switching period minus the larger value of the self-interference signal baseband bandwidth and the desired signal baseband bandwidth.

[0014] Based on the same inventive concept, the present invention also provides a system for eliminating self-interference in full-duplex communication, which is used to implement the steps of the method for eliminating self-interference in full-duplex communication, and the system includes the following modules: The pseudo-Doppler effect building module is used to configure antenna 1 and antenna 2 for user A and user B respectively, and switch the transceiver functions of antenna 1 and antenna 2 through the set antenna switching cycle to generate the pseudo-Doppler effect; in the second half of each cycle, the received signal of each user is phase-shifted to obtain the equivalent channel response of the received self-interference signal and the equivalent channel response of the received desired signal; A channel transfer function calculation module is used to obtain a transfer function of an equivalent self-interference channel in the frequency domain based on the equivalent channel response of the received self-interference signal, which is recorded as a first transfer function, and to calculate a transfer function of a channel for receiving the desired signal in the frequency domain based on the equivalent channel response of the user A or the user B receiving the desired signal, which is recorded as a second transfer function; The desired signal extraction module is used to obtain a frequency range in which the self-interference signal can be eliminated according to the first transfer function and the second transfer function, and to filter the received signal containing the self-interference signal within the frequency range in which the self-interference signal can be eliminated to extract the desired signal.

[0015] In one embodiment of the present invention, the pseudo-Doppler effect building module includes a received signal phase shift unit, which performs an inversion or phase shift operation on the received signal in the second half of each antenna switching cycle, and uses the inversion or phase shift operation to obtain an equivalent channel response of the received self-interference signal and an equivalent channel response of the received desired signal.

[0016] In one embodiment of the present invention, the desired signal extraction module includes a received signal filtering unit, which sets a cutoff frequency of a low-pass filter within the frequency range in which the self-interference signal can be eliminated, and uses the low-pass filter to filter the received signal of user A or user B at the center frequency, i.e., the main frequency, of the signal.

[0017] The present invention also provides a self-interference elimination device in full-duplex communication, the device comprising the self-interference elimination system, a first user terminal, a second user terminal and a control module; the first user terminal and the second user terminal both comprise a radio frequency or baseband transceiver module, a radio frequency or baseband switch matrix, a phase shift unit, an antenna 1 and an antenna 2, the self-interference elimination system is synchronized by the control module, the radio frequency or baseband transceiver module connects the antenna 1 and the antenna 2 via the radio frequency or baseband switch matrix, the control module controls the connection between the radio frequency or baseband switch matrix and the phase shift unit, and the radio frequency or baseband switch matrix connects the phase shift unit; Among them, the control module controls the switching period of the RF or baseband switch matrix and the phase shift processing of the phase shift unit based on the system, completes the switching of the transceiver functions of the antenna 1 and the antenna 2, generates a pseudo-Doppler effect, and coordinates the RF or baseband transceiver modules of the first user end and the second user end to transmit and receive signals; the phase shift unit is an inverter or a phase shifter.

[0018] In one embodiment of the present invention, the RF or baseband switch matrix is ​​controlled by the control module, and in the first half sub-period of any antenna switching cycle, the source transmission signal of the RF or baseband transceiver module of each user terminal is guided to the antenna 1 of the user terminal for transmission, and the signal received by the antenna 2 of each user terminal is introduced into the destination port of the RF or baseband transceiver module of the user terminal; in the second half sub-period, the source transmission signal of the RF or baseband transceiver module of each user terminal is switched to the antenna 2 of the user terminal for transmission, and the signal received by the antenna 1 of each user terminal is connected to the destination port of the RF or baseband transceiver module through the phase shift unit.

[0019] In one embodiment of the present invention, the first user terminal and the second user terminal both include a low-pass filter, and the sink port of the RF or baseband transceiver module is connected to the low-pass filter, and the low-pass filter filters the received signal introduced into the sink port at the center frequency of the signal, i.e., the main frequency.

[0020] The above technical solution of the present invention has the following advantages compared with the prior art: First, the present invention generates a pseudo-Doppler effect by switching the antenna receiving and transmitting functions of each user, and can effectively separate the channel transfer function of the received self-interference signal and the channel transfer function of the received desired signal in the frequency domain, thereby effectively separating the received self-interference signal and the received desired signal in the frequency domain, ensuring that the baseband signal extracted after low-pass filtering achieves the ideal state of zero residual self-interference, thereby significantly improving the quality of full-duplex communication.

[0021] Second, the self-interference solution proposed in the present invention has extremely low implementation complexity. It can completely eliminate self-interference only through antenna switching, phase shift processing and low-pass filtering. It does not require complex hardware design and algorithm implementation, and does not rely on any interference elimination technology of traditional full-duplex communication systems. It can achieve results that are superior to all traditional self-interference elimination solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein: Figure 1 It is a schematic diagram of the structure of a half-duplex communication system; Figure 2 It is a schematic diagram of the structure of a time-frequency unified full-duplex communication system; Figure 3 is a flow chart of a method for eliminating self-interference in full-duplex communication provided in an embodiment of the present invention; Figure 4 yes Figure 3 Schematic diagram of signal reception and transmission at each user end in the first half of the sub-period of self-interference elimination based on pseudo-Doppler effect; Figure 5 yes Figure 3 Schematic diagram of signal reception and transmission at each user end in the second half of the sub-period of self-interference elimination based on pseudo-Doppler effect; Figure 6 (a) represents the equivalent channel amplitude spectrum of the received self-interference signal, and (b) represents the equivalent channel amplitude spectrum of the received desired signal; Figure 7 (a) represents the power spectrum of the self-interference signal of user A, that is, the power spectrum of the signal transmitted by user A; (b) represents the power spectrum of the desired signal of user A, that is, the power spectrum of the signal transmitted by user B; (c) represents the power spectrum of the self-interference signal and the desired signal received by user A; Figure 8 It is a schematic diagram of the experimental results of the self-interference elimination capability of the present invention; Fig. 9 The self-interference elimination method of the present invention is compared with the experimental results of the traditional self-interference elimination method in terms of self-interference elimination capability; Fig.10 It is a schematic diagram of the structure of a self-interference elimination system in full-duplex communication provided in an embodiment of the present invention; Fig.11 1 is a schematic diagram of the connection of a self-interference elimination device in full-duplex communication in the first half sub-period provided in an embodiment of the present invention; Fig.12 1 is a schematic diagram of the connection of a self-interference elimination device in full-duplex communication in the second half sub-period provided in an embodiment of the present invention; Explanation of the reference numerals in the specification: 10, pseudo-Doppler effect building module; 101, receiving signal phase shift unit; 20, channel transfer function calculation module; 30, desired signal extraction module; 301, receiving signal filtering unit. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention. Embodiment 1

[0024] like Figures 3-5 As shown, the present invention provides a method for eliminating self-interference in full-duplex communication, which is applicable to user A and user B performing full-duplex communication at the same time and at the same frequency, and includes the following steps: S1: Two antennas are configured for user A and user B, namely antenna 1 and antenna 2, and the transceiver functions of antenna 1 and antenna 2 are switched through the set antenna switching cycle to generate a pseudo-Doppler effect; in the second half of each cycle, the received signal of each user is phase-shifted to obtain the equivalent channel response of the received self-interference signal and the equivalent channel response of the received desired signal; S2: Based on the equivalent channel response of the received self-interference signal, a transfer function of the equivalent self-interference channel in the frequency domain is obtained, which is recorded as a first transfer function. At the same time, based on the equivalent channel response of user A or user B receiving the desired signal, a transfer function of the channel receiving the desired signal in the frequency domain is calculated, which is recorded as a second transfer function. S3: obtaining a frequency range within which the self-interference signal can be eliminated according to the first transfer function and the second transfer function, and performing low-pass filtering on the received signal including the self-interference signal within the frequency range within which the self-interference signal can be eliminated to extract a desired signal.

[0025] It can be seen from the above technical scheme that the present invention generates a pseudo-Doppler effect by switching the antenna receiving and transmitting functions of each user, and can effectively separate the channel transfer function of the received self-interference signal and the channel transfer function of the received expected signal in the frequency domain, thereby effectively separating the received self-interference signal and the received expected signal in the frequency domain, ensuring that the baseband signal extracted after low-pass filtering can achieve complete elimination of self-interference, achieving an ideal state of zero residual self-interference, and improving communication quality; by calculating the frequency domain transfer function of the self-interference signal and the expected signal, the frequency range in which the self-interference signal can be eliminated can be dynamically determined, with high flexibility and applicable to different communication environments and requirements. The received signal is processed using low-pass filtering within a determined frequency range, and the expected signal that does not contain any self-interference components can be effectively extracted, while simplifying the complexity of signal processing and reducing system power consumption.

[0026] See also Figure 4 and Figure 5 In S1, the method of switching the transceiver functions of antenna 1 and antenna 2 by setting the antenna switching cycle includes: setting the antenna switching cycle Divide into two equal-length sub-periods: In the front sub-period, that is, In the period, antenna 1 of each user performs the transmission task, and antenna 2 performs the reception task; in the later sub-period, i.e. Within, the antenna 2 of each user switches to the transmitting state, and the antenna 1 switches to the receiving state, wherein Any integer.

[0027] Specifically, in order to ensure that the generated pseudo-Doppler frequency shift signal does not have aliasing in the frequency domain, the switching frequency corresponding to the antenna switching period is set to be greater than or equal to the larger value of the self-interference signal bandwidth and the desired signal bandwidth plus the bandwidth of the desired signal.

[0028] Furthermore, in S1, the method for obtaining the equivalent channel response of the received self-interference signal is: the received signal of each user is phase-shifted by π in the second half sub-period of any antenna switching period, and the equivalent channel response of the received self-interference signal is obtained. : , in, Indicates user A or user B, represents the self-interference channel fading parameter of user A or user B, t represents time, represents the antenna switching period, Any integer.

[0029] Further, based on the equivalent channel response of the received self-interference signal , the method of obtaining the transfer function of the equivalent self-interference channel in the frequency domain, that is, the first transfer function, is as follows: Calculate the equivalent channel response of the received self-interference signal The Fourier series of : , in, represents an exponential function with base e, while the periodic function The Fourier coefficients of ; Based on the equivalent channel response The Fourier series of the equivalent self-interference channel in the frequency domain is obtained, which is recorded as the first transfer function : , in, f represents frequency, j represents imaginary unit, l Indicates the harmonic order, represents the impulse function, It is the unit pseudo-Doppler frequency shift introduced by the switching of the transmitting and receiving antennas, i.e. its fundamental frequency; Since the periodic function The Fourier coefficients of , the center frequency amplitude of the transfer function of the equivalent self-interference channel in the frequency domain, that is, the main frequency component is zero.

[0030] Furthermore, in S1, the method for obtaining the equivalent channel response of user A or user B receiving the desired signal is: In the second half of any antenna switching cycle, the received signal of each user is phase-shifted by π, and the equivalent channel responses of user A and user B receiving the desired signal are obtained as follows: in, represents the equivalent channel response of user A receiving the desired signal, represents the equivalent channel response of user B receiving the desired signal; represents the channel fading parameter between antenna 1 of user A and antenna 2 of user B, represents the channel fading parameter between antenna 2 of user A and antenna 1 of user B; t represents time, represents the antenna switching period, Any integer.

[0031] Furthermore, based on the equivalent channel response of user A or user B receiving the desired signal, a method of calculating the transfer function of the channel receiving the desired signal in the frequency domain, that is, the second transfer function, is as follows: Calculate the equivalent channel response for user A or user B to receive the desired signal The Fourier series of : , in, Indicates user A or user B, is a periodic function The Fourier coefficients of When , the channel center frequency, i.e., the main frequency coefficient, of the desired signal received by user A is: , The channel center frequency, i.e., the main frequency coefficient, of the desired signal received by user B is: , when When , the channel harmonic frequency coefficient of user A or user B receiving the desired signal is: ; Based on the equivalent channel response The Fourier series of the channel receiving the desired signal is obtained in the frequency domain, which is recorded as the second transfer function : , in, f represents frequency, j represents imaginary unit, l Indicates the harmonic order, represents the impulse function, It is the unit pseudo-Doppler frequency shift introduced by the switching of the transmitting and receiving antennas, that is, its fundamental frequency.

[0032] In summary, the frequency domain received signals of user A and user B are: , , In the formula, represents the convolution operation, and They represent the frequency domain received signals of user A and user B respectively, and They represent the frequency domain transmission signals of user A and user B respectively, and They represent the transfer functions of the equivalent channels in the frequency domain for user A and user B to receive the desired signal, and They represent the transfer functions of the equivalent channels in the frequency domain for user A and user B to receive the self-interference signal, and are the frequency domain representations of the additive white Gaussian noise received by user A and user B respectively.

[0033] Further, in S3, the method for obtaining the frequency range that can eliminate the self-interference signal is: select a value that satisfies the first transfer function to be zero and the value of the second transfer function to be non-zero, that is, and frequency range.

[0034] Furthermore, in S3, the method for extracting the desired signal is: within the frequency range that can eliminate the self-interference signal, the cutoff frequency of the low-pass filter is set, and the low-pass filter filters the received signal at the center frequency of each user's received signal, that is, the main frequency.

[0035] Specifically, due to the periodic function Fourier coefficients , the center frequency amplitude of the transfer function of the equivalent channel receiving the interference signal in the frequency domain, that is, the main frequency component is zero, such as Figure 6 As shown in (a), the self-interference signal received by each user is 0 at the center frequency, as shown in Figure 7 As shown in (c); while the periodic function The Fourier coefficients of , the center frequency amplitude of the transfer function of the equivalent channel receiving the desired signal in the frequency domain, that is, the main frequency component is not zero, such as Figure 6 As shown in (b), the expected signal received by each user is not zero at the center frequency, as shown in Figure 7 Based on this, by using a low-pass filter to filter the received signal containing the self-interference signal at the center frequency (i.e., the main frequency) of each user's received signal, the desired signal can be effectively extracted, and the self-interference signal has been completely eliminated.

[0036] In addition, for setting the cutoff frequency of the low-pass filter, its minimum value is the baseband bandwidth of the desired signal to ensure that all frequency components in the desired signal can pass through the filter smoothly. At the same time, the maximum value of the cutoff frequency is the antenna switching frequency corresponding to the antenna switching period minus the larger value of the baseband bandwidth of the self-interference signal and the baseband bandwidth of the desired signal. In this way, self-interference can be effectively and completely eliminated, and the requirements for the design accuracy of the low-pass filter can be reduced.

[0037] Taking user A as an example, the power spectrum of the self-interference signal and the desired signal received by the user is as follows: Figure 7 As shown in (a) to (c), the power spectrum of the received signal of user B is similar to this. It can be seen that the present invention can completely eliminate the self-interference from the center frequency (ie, the main frequency) of the received signal of each user.

[0038] In order to verify the self-interference elimination capability of the present invention, a targeted performance test experiment was conducted. The experimental conditions were common scenarios in 5G systems: the carrier frequency was 3 GHz, the path loss constant was -42 dB, the path fading index was 3, the power spectral density of additive Gaussian white noise was -174 dBm / Hz, the system bandwidth was 4 MHz, and the distance between user A and user B was 100 meters. Three different antenna spacings were tested, that is, the distances between antenna 1 and antenna 2 of each user were 0.05 meters, 0.1 meters, and 0.15 meters, respectively. Under the conditions of different antenna spacings, the relationship between the transmission power of the user signal and the self-interference elimination capability was explored. In this experiment, the self-interference elimination capability was evaluated by the difference in output signal-to-noise ratio (unit: dB) with and without self-interference elimination.

[0039] The experimental results are as follows Figure 8 As shown, it can be observed that when the distance between antenna 1 and antenna 2 is 0.05 meters, as the transmission power increases, its self-interference elimination capability performs best. This is because the smaller the antenna distance, the stronger the received self-interference, and the more self-interference eliminated by the present invention. Since the present invention can completely eliminate the self-interference on the center frequency of each user's received signal, its self-interference elimination capability is enhanced as the transmission power increases. This means that under higher transmission power conditions, the system can achieve a higher output signal-to-noise ratio, thereby improving the signal transmission quality and reliability.

[0040] In contrast, traditional self-interference cancellation methods encounter challenges when dealing with high transmit power. This is because their output signal-to-noise ratio is limited by residual self-interference. As the transmit power increases, the residual self-interference also increases, causing the output signal-to-noise ratio to tend to a constant. This shows that traditional self-interference cancellation methods have bottlenecks when dealing with high transmit power signals and cannot meet the growing demand for high-performance communications.

[0041] In order to further highlight the advantages of the present invention, it is compared with the currently available optimal self-interference elimination method. The experimental conditions are common scenarios in 5G systems: carrier frequency is 3 GHz, path loss constant is -42 dB, path fading index is 3, power spectrum density of additive Gaussian white noise is -174 dBm / Hz, system bandwidth is 4 MHz, and the distance between user A and user B is 100 meters. The comparison of self-interference elimination capabilities is based on two different antenna spacings, that is, the spacing between the two antennas of each user is 0.05 meters and 0.1 meters respectively. The experimental results are as follows: Fig. 9 shown.

[0042] It can be seen from the figure that when the antenna spacing is 0.05 meters and the transmission power is 1 dBm, the self-interference elimination capability of the present invention is about 90 dB, while the self-interference elimination capability of the traditional optimal method that can suppress interference up to 103 dB is about 70 dB. As the transmission power gradually increases to 33dBm, the self-interference elimination capability of the present invention steadily increases to about 120 dB, while the self-interference elimination capability of the traditional optimal method that can suppress interference up to 103 dB is about 77 dB, which is significantly lower than the method described in the present invention.

[0043] When the antenna spacing is 0.1 meters and the transmission power is 1 dBm, the self-interference elimination capability of the present invention is about 80 dB, while the self-interference elimination capability of the traditional optimal method that can suppress interference up to 103 dB is about 63 dB. As the transmission power increases to 33dBm, the self-interference elimination capability of the present invention increases to about 110 dB, while the self-interference elimination capability of the traditional optimal method that can suppress interference up to 103 dB is about 76 dB.

[0044] This shows that, whether it is a small antenna spacing or a relatively large antenna spacing, as the transmission power increases, the present invention is significantly better than the traditional optimal self-interference suppression method in terms of self-interference elimination capability. This means that the present invention can more effectively eliminate self-interference under different antenna spacing conditions, thereby improving the output signal-to-noise ratio of the system, and providing a strong guarantee for achieving high-quality and high-reliability signal transmission.

[0045] In summary, unlike the limited self-interference elimination capability of the traditional method, the self-interference elimination capability of the present invention is enhanced as the transmission power increases, so it has a wider applicability in practical applications. Whether it is a low-power IoT device or a high-power base station system, the present invention can provide an effective solution. Embodiment 2

[0046] Based on the same inventive concept as that of the first embodiment, the present invention also provides a system for eliminating self-interference in full-duplex communication, which is used to implement the steps of the method for eliminating self-interference in full-duplex communication described in the first embodiment. Fig.10 As shown, the system includes the following modules: The pseudo-Doppler effect building module 10 is used for configuring antenna 1 and antenna 2 for user A and user B respectively, and switching the transceiver functions of antenna 1 and antenna 2 through the set antenna switching cycle to generate the pseudo-Doppler effect; in the second half of each cycle, the received signal of each user is phase-shifted to obtain the equivalent channel response of the received self-interference signal and the equivalent channel response of the received desired signal; The channel transfer function calculation module 20 is used to obtain the transfer function of the equivalent self-interference channel in the frequency domain based on the equivalent channel response of the received self-interference signal, which is recorded as a first transfer function, and calculate the transfer function of the channel receiving the desired signal in the frequency domain based on the equivalent channel response of the user A or the user B receiving the desired signal, which is recorded as a second transfer function; The desired signal extraction module 30 is used to obtain a frequency range in which the self-interference signal can be eliminated according to the first transfer function and the second transfer function, and to filter the received signal containing the self-interference signal within the frequency range in which the self-interference signal can be eliminated to extract the desired signal.

[0047] Furthermore, the pseudo-Doppler effect building module 10 includes a received signal phase shift unit 101, which performs an inversion or phase shift operation on the received signal in the second half of each antenna switching cycle, and uses the inversion or phase shift operation to obtain an equivalent channel response of the received self-interference signal and an equivalent channel response of the received desired signal.

[0048] Furthermore, the desired signal extraction module 30 includes a received signal filtering unit 301, which sets a cutoff frequency of a low-pass filter within the frequency range in which the self-interference signal can be eliminated, and uses the low-pass filter to filter the received signal of user A or user B at the center frequency, i.e., the main frequency, of the signal.

[0049] The present embodiment proposes a system for eliminating self-interference in full-duplex communication, which is used to implement the aforementioned method for eliminating self-interference in full-duplex communication. Therefore, the specific implementation of the system can be seen from the embodiment of the aforementioned method for eliminating self-interference in full-duplex communication. For example, the functions implemented by the pseudo-Doppler effect construction module 10, the channel transfer function calculation module 20 and the expected signal extraction module 30 are consistent with steps S1, S2 and S3 in the method in the first embodiment. Therefore, its specific implementation can refer to the description of the corresponding embodiments of each part. In order to avoid redundancy, it will not be repeated here. Embodiment 3

[0050] like Fig.11 and Fig.12As shown, the present invention also provides a self-interference elimination device in full-duplex communication, the device includes the self-interference elimination system described in the second embodiment, a first user terminal, a second user terminal and a control module; the first user terminal and the second user terminal both include a radio frequency or baseband transceiver module, a radio frequency or baseband switch matrix, a phase shift unit, an antenna 1 and an antenna 2, the self-interference elimination system is synchronized by the control module, the radio frequency or baseband transceiver module connects the antenna 1 and the antenna 2 through the radio frequency or baseband switch matrix, the control module controls the connection between the radio frequency or baseband switch matrix and the phase shift unit, and the radio frequency or baseband switch matrix connects the phase shift unit; Wherein, the control module controls the switching cycle of the RF or baseband switch matrix and the phase shift processing of the phase shift unit based on the self-interference elimination system, completes the switching of the transceiver functions of the antenna 1 and the antenna 2, generates a pseudo-Doppler effect, and coordinates the RF or baseband transceiver modules of the first user end and the second user end to transmit and receive signals; the phase shift unit is an inverter or a phase shifter. Fig.11 and Fig.12 " "express.

[0051] Furthermore, the RF or baseband switch matrix, through the control of the control module, guides the source transmission signal of the RF or baseband transceiver module of each user end to the antenna 1 of the user end for transmission in the first half sub-cycle of any antenna switching cycle, and introduces the signal received by the antenna 2 of each user end into the destination port of the RF or baseband transceiver module of the user end; in the second half sub-cycle, the source transmission signal of the RF or baseband transceiver module of each user end is switched to the antenna 2 of the user end for transmission, and the signal received by the antenna 1 of each user end is connected to the destination port of the RF or baseband transceiver module through the phase shift unit.

[0052] Furthermore, the first user end and the second user end both include a low-pass filter, and the destination ports of the RF or baseband transceiver module are connected to the low-pass filter, and the low-pass filter filters the received signal introduced into the destination port at the center frequency of the signal, i.e., the main frequency.

[0053] For the setting of the low-pass filter cutoff frequency, its minimum value should be equal to the baseband bandwidth of the desired signal to ensure that all frequency components in the desired signal can pass through the filter completely. At the same time, the maximum value of the cutoff frequency should be set to the antenna switching frequency corresponding to the antenna switching period minus the larger value of the baseband bandwidth of the self-interference signal and the baseband bandwidth of the desired signal. This setting method can not only effectively and completely eliminate self-interference, but also reduce the requirements for the design accuracy of the low-pass filter, thereby maximizing the integrity of the desired signal while eliminating interference.

[0054] In summary, the technical solution of the present invention effectively solves the self-interference problem in full-duplex communication, improves the utilization rate of communication resources and the reliability of signal transmission, and is suitable for various wireless communication scenarios including 5G / 6G networks, the Internet of Things, the Internet of Vehicles, and air-ground fusion networks, and has broad application prospects.

[0055] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may take the form of a computer program product or software radio design implemented on one or more computer-usable storage media or software radio (including but not limited to disk storage, CD-ROM, optical storage, USRP, FPGA, etc.) containing computer-usable program codes.

[0056] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0057] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0058] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0059] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for eliminating self-interference in full-duplex communication, characterized in that: Applicable to user A and user B performing full-duplex communication at the same time and at the same frequency, the method comprises the following steps: S1: Two antennas are configured for user A and user B, namely antenna 1 and antenna 2, and the transceiver functions of antenna 1 and antenna 2 are switched through the set antenna switching cycle to generate a pseudo-Doppler effect; in the second half of each cycle, the received signal of each user is phase-shifted to obtain the equivalent channel response of the received self-interference signal and the equivalent channel response of the received desired signal; S2: Based on the equivalent channel response of the received self-interference signal, a transfer function of the equivalent self-interference channel in the frequency domain is obtained, which is recorded as a first transfer function. At the same time, based on the equivalent channel response of user A or user B receiving the desired signal, a transfer function of the channel receiving the desired signal in the frequency domain is calculated, which is recorded as a second transfer function. S3: obtaining a frequency range within which the self-interference signal can be eliminated according to the first transfer function and the second transfer function, and filtering the received signal including the self-interference signal within the frequency range within which the self-interference signal can be eliminated to extract a desired signal.

2. The method for eliminating self-interference in full-duplex communication according to claim 1, characterized in that: In S1, the method for generating a pseudo-Doppler effect by switching the transceiver functions of antenna 1 and antenna 2 according to a set antenna switching cycle includes: dividing the antenna switching cycle into a front and a rear sub-cycle of equal length: in the front sub-cycle, antenna 1 of each user performs a transmitting task, and antenna 2 performs a receiving task; and in the rear sub-cycle, antenna 2 of each user switches to a transmitting state, and antenna 1 switches to a receiving state.

3. The method for eliminating self-interference in full-duplex communication according to claim 2, characterized in that: The antenna switching frequency corresponding to the antenna switching period is set to be greater than or equal to the larger value of the baseband bandwidth of the self-interference signal and the baseband bandwidth of the desired signal plus the bandwidth of the desired signal.

4. The method for eliminating self-interference in full-duplex communication according to claim 1, characterized in that: In S1, the method for obtaining the equivalent channel response of the received self-interference signal is: the received signal of each user is phase-shifted by π in the second half sub-period of any antenna switching period, and the equivalent channel response of the received self-interference signal is obtained. : ， in, Indicates user A or user B, represents the self-interference channel fading parameter of user A or user B, t represents time, represents the antenna switching period, Any integer.

5. The method for eliminating self-interference in full-duplex communication according to claim 4, characterized in that: In S2, the method for obtaining the transfer function of the equivalent self-interference channel in the frequency domain is as follows: Calculate the equivalent channel response of the received self-interference signal The Fourier series of : ， in, represents an exponential function with base e, while the periodic function The Fourier coefficients of ; Based on the equivalent channel response The Fourier series of the equivalent self-interference channel in the frequency domain is obtained, which is recorded as the first transfer function : ， in, f represents frequency, j represents imaginary unit, l Indicates the harmonic order, represents the impulse function, It is the unit pseudo-Doppler frequency shift introduced by the switching of the transmitting and receiving antennas, i.e. its fundamental frequency; Since the periodic function The Fourier coefficients of , the center frequency amplitude of the transfer function of the equivalent self-interference channel in the frequency domain, that is, the main frequency component is zero.

6. The method for eliminating self-interference in full-duplex communication according to claim 1, characterized in that: In S1, the method for obtaining the equivalent channel response of user A or user B receiving the desired signal is: In the second half of any antenna switching cycle, the received signal of each user is phase-shifted by π, and the equivalent channel responses of user A and user B receiving the desired signal are obtained as follows: in, represents the equivalent channel response of user A receiving the desired signal, represents the equivalent channel response of user B receiving the desired signal; represents the channel fading parameter between antenna 1 of user A and antenna 2 of user B, represents the channel fading parameter between antenna 2 of user A and antenna 1 of user B; t represents time, represents the antenna switching period, Any integer.

7. The method for eliminating self-interference in full-duplex communication according to claim 6, characterized in that: In S2, based on the equivalent channel response of user A or user B receiving the desired signal, the method for calculating the transfer function of the channel receiving the desired signal in the frequency domain is as follows: Calculate the equivalent channel response for user A or user B to receive the desired signal The Fourier series of : ， in, Indicates user A or user B, is a periodic function The Fourier coefficients of When , the channel center frequency, i.e., the main frequency coefficient, of the desired signal received by user A is: ， The channel center frequency, i.e., the main frequency coefficient, of the desired signal received by user B is: ， when When , the channel harmonic frequency coefficient of the desired signal received by user A or user B is: ； Based on the equivalent channel response The Fourier series of the channel receiving the desired signal is obtained in the frequency domain, which is recorded as the second transfer function : ， in, f represents frequency, j represents imaginary unit, l Indicates the harmonic order, represents the impulse function, It is the unit pseudo-Doppler frequency shift introduced by the switching of the transmitting and receiving antennas, that is, its fundamental frequency.

8. The method for eliminating self-interference in full-duplex communication according to claim 1, characterized in that: In S3, the method for obtaining the frequency range that can eliminate the self-interference signal is: selecting a frequency range that satisfies the value of the first transfer function is zero and the value of the second transfer function is not zero.

9. The method for eliminating self-interference in full-duplex communication according to claim 1, characterized in that: In S3, the method for extracting the desired signal is: within the frequency range that can eliminate the self-interference signal, set the cutoff frequency of the low-pass filter, and use the low-pass filter to filter the received signal at the center frequency of each user's received signal, that is, the main frequency.

10. The method for eliminating self-interference in full-duplex communication according to claim 9, characterized in that: The minimum value of the cutoff frequency is the desired signal baseband bandwidth, and the maximum value of the cutoff frequency is the antenna switching frequency corresponding to the antenna switching period minus the larger value of the self-interference signal baseband bandwidth and the desired signal baseband bandwidth.

11. A self-interference elimination system in full-duplex communication, characterized in that: For implementing the steps of the method for eliminating self-interference in full-duplex communication according to any one of claims 1 to 10, the system comprises the following modules: The pseudo-Doppler effect building module is used to configure antenna 1 and antenna 2 for user A and user B respectively, and switch the transceiver functions of antenna 1 and antenna 2 through the set antenna switching cycle to generate the pseudo-Doppler effect; in the second half of each cycle, the received signal of each user is phase-shifted to obtain the equivalent channel response of the received self-interference signal and the equivalent channel response of the received desired signal; A channel transfer function calculation module is used to obtain a transfer function of an equivalent self-interference channel in the frequency domain based on the equivalent channel response of the received self-interference signal, which is recorded as a first transfer function, and to calculate a transfer function of a channel for receiving the desired signal in the frequency domain based on the equivalent channel response of the user A or the user B receiving the desired signal, which is recorded as a second transfer function; The desired signal extraction module is used to obtain a frequency range in which the self-interference signal can be eliminated according to the first transfer function and the second transfer function, and to filter the received signal containing the self-interference signal within the frequency range in which the self-interference signal can be eliminated to extract the desired signal.

12. The self-interference elimination system in full-duplex communication according to claim 11, characterized in that: The pseudo-Doppler effect building module includes a received signal phase shift unit, which performs an inversion or phase shift operation on the received signal in the second half of each antenna switching cycle, and uses the inversion or phase shift operation to obtain an equivalent channel response of the received self-interference signal and an equivalent channel response of the received desired signal.

13. The self-interference elimination system in full-duplex communication according to claim 11, characterized in that: The desired signal extraction module includes a received signal filtering unit, which sets a cutoff frequency of a low-pass filter within the frequency range in which the self-interference signal can be eliminated, and uses the low-pass filter to filter the received signal of user A or user B at the center frequency, i.e., the main frequency, of the signal.

14. A self-interference elimination device in full-duplex communication, characterized in that: The device comprises a self-interference elimination system as described in any one of claims 11 to 13, a first user terminal, a second user terminal and a control module; the first user terminal and the second user terminal both comprise a radio frequency or baseband transceiver module, a radio frequency or baseband switch matrix, a phase shift unit, an antenna 1 and an antenna 2, the self-interference elimination system is synchronized by the control module, the radio frequency or baseband transceiver module connects the antenna 1 and the antenna 2 via the radio frequency or baseband switch matrix, the control module controls the connection between the radio frequency or baseband switch matrix and the phase shift unit, and the radio frequency or baseband switch matrix connects the phase shift unit; Among them, the control module controls the switching period of the RF or baseband switch matrix and the phase shift processing of the phase shift unit based on the system, completes the switching of the transceiver functions of the antenna 1 and the antenna 2, generates a pseudo-Doppler effect, and coordinates the RF or baseband transceiver modules of the first user end and the second user end to transmit and receive signals; the phase shift unit is an inverter or a phase shifter.

15. The self-interference elimination device in full-duplex communication according to claim 14, characterized in that: The RF or baseband switch matrix is ​​controlled by the control module. In the first half sub-cycle of any antenna switching cycle, the source transmission signal of the RF or baseband transceiver module of each user terminal is guided to the antenna 1 of the user terminal for transmission, and the signal received by the antenna 2 of each user terminal is introduced into the destination port of the RF or baseband transceiver module of the user terminal; in the second half sub-cycle, the source transmission signal of the RF or baseband transceiver module of each user terminal is switched to the antenna 2 of the user terminal for transmission, and the signal received by the antenna 1 of each user terminal is connected to the destination port of the RF or baseband transceiver module through the phase shift unit.

16. The self-interference elimination device in full-duplex communication according to claim 14, characterized in that: The first user end and the second user end both include a low-pass filter, and the sink port of the RF or baseband transceiver module is connected to the low-pass filter. The low-pass filter filters the received signal introduced into the sink port at the center frequency of the signal, that is, the main frequency.

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