Multi-antenna receiving method for cooperative interference suppression

Abstract

The invention discloses a cooperative interference suppression-oriented multi-antenna receiving method, which comprises the following steps of: at an information source node, converting a digital useful signal into a radio frequency signal after digital-to-analog conversion and up-conversion, and transmitting the radio frequency signal by a useful signal antenna; at the cooperative node, the digital cooperative interference signal is converted into a radio frequency signal after digital-to-analog conversion and up-conversion, and the radio frequency signal is transmitted by a cooperative signal antenna; performing down-conversion and analog-to-digital conversion on the received signal at the authorized node; cooperative interference reconstruction and offset are carried out on the signal of each receiving antenna; analyzing a covariance matrix of residual cooperative interference; analyzing a useful signal covariance matrix containing a frequency offset error; deriving a weight vector which enables the signal to interference plus noise ratio of the combined output signal to be maximized; and combining the branch signals according to the weight vector to obtain a combined output signal. According to the invention, the negative influence of the residual interference and the frequency offset error on the performance of the single-input multi-output system can be minimized.

Description

Technical Field

[0001] This invention belongs to the field of physical layer security in wireless communication and relates to a multi-antenna receiving method for cooperative interference suppression. Background Technology

[0002] In recent years, the integrated air-space-ground information network and IoT applications such as smart cities have developed rapidly, and the deployment scale of IoT devices in 6G networks has reached an unprecedented level. However, with the gradual realization of the vision of the Internet of Everything, the number of nodes in wireless networks has increased dramatically, and the inherent broadcast characteristics of wireless channels make it easy for any node to intercept transmission signals. At the same time, the large-scale and distributed nature of IoT networks makes the deployment and management of traditional key-based encryption mechanisms difficult and complex. In addition, IoT devices are often exposed to open or uncontrollable environments, making them highly vulnerable to security threats such as eavesdropping, resulting in the leakage of sensitive data during communication and even endangering the security of the entire network system. Against this backdrop, the development of efficient and reliable secure communication technologies has become urgent.

[0003] Cooperative jamming technology reduces the signal-to-interference-plus-noise ratio (SNR) of eavesdroppers by utilizing independent nodes to transmit jamming signals. Simultaneously, authorized receivers use prior information about the jamming to reconstruct and suppress it, thus achieving secure communication. Furthermore, single-transmitter-multiple-receiver systems (SMRs) bring significant benefits to a massive number of terminal devices—enhanced coverage, reduced power consumption, and improved reliability—with only a small increase in network-side cost.

[0004] Because cooperative interference is affected by non-ideal factors during transmission, it cannot be completely canceled out at the authorized receiving end. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a multi-antenna receiving method for cooperative interference suppression. By analyzing the impact of frequency offset error on cooperative interference suppression and useful signal, an optimal merging scheme is proposed to minimize the negative impact of residual interference and frequency offset error on the performance of single-transmit multiple-receive system.

[0006] The objective of this invention is achieved through the following technical solution: a multi-antenna receiving method for cooperative interference suppression, comprising the following steps:

[0007] Step S1. At the source node, the digital useful signal is converted into a radio frequency signal after digital-to-analog conversion and up-conversion, and then transmitted by the useful signal antenna;

[0008] Step S2. At the cooperative node, the digital cooperative interference signal is converted into a radio frequency signal after digital-to-analog conversion and up-conversion and then transmitted by the cooperative signal antenna;

[0009] Step S3. At the authorized node, the received signal is down-converted and analog-to-digital converted. The authorized node is equipped with... A multi-antenna receiver with one antenna;

[0010] Step S4. Perform cooperative interference reconstruction and cancellation on the signal of each receiving antenna;

[0011] Step S5. Analyze the covariance matrix of residual cooperative disturbances;

[0012] Step S6. Analyze the covariance matrix of the useful signal containing frequency offset error;

[0013] Step S7. Based on the covariance matrix of the residual cooperative interference and the useful signal, derive the weight vector that maximizes the signal-to-interference-plus-noise ratio of the combined output signal;

[0014] Step S8. Combine the signals of each branch according to the derived weight vector to obtain the combined output signal.

[0015] The beneficial effects of this invention are: by analyzing the impact of frequency offset error on cooperative interference suppression and useful signals, this invention proposes an optimal merging scheme to minimize the negative impact of residual interference and frequency offset error on the performance of single-transmitter multiple-receiver systems. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the principle architecture of a multi-antenna receiving method for cooperative interference suppression.

[0017] Figure 2 This is a flowchart of the method of the present invention;

[0018] Figure 3 The figure shows the performance of a multi-antenna receiving method for cooperative interference suppression. Detailed Implementation

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0020] like Figure 1 As shown, a multi-antenna receiving method for cooperative interference suppression includes the following steps:

[0021] Step S1. At the source node, the digital useful signal is converted into a radio frequency signal after digital-to-analog conversion and up-conversion, and then transmitted by the useful signal antenna;

[0022] At the source node, the digital useful signal is transformed into an analog useful signal after digital-to-analog conversion. After up-conversion, it is converted into a radio frequency signal. :

[0023]

[0024] in It is the carrier frequency of the useful signal.

[0025] Step S2. At the cooperative node, the digital cooperative interference signal is converted into a radio frequency signal after digital-to-analog conversion and up-conversion and then transmitted by the cooperative signal antenna;

[0026] At the cooperating node, the digital cooperative interference signal is converted into an analog useful signal after digital-to-analog conversion. After up-conversion, it is converted into a radio frequency signal. :

[0027]

[0028] in It is the carrier frequency of the cooperative interference signal.

[0029] Step S3. At the authorized node, the received signal is down-converted and analog-to-digital converted. The authorized node is equipped with... A multi-antenna receiver with one antenna;

[0030] Authorized nodes are equipped with A multi-antenna receiver with [number] antennas receives signals from each antenna, each containing a useful signal, cooperative interference signals, and Gaussian white noise. The received signals are down-converted to obtain the baseband signal. Then, the [number]th antenna... The baseband signal at the root antenna is:

[0031]

[0032] in, and From the source node and the cooperating node to the... The channel coefficient of the root receiving antenna; For the first The carrier frequency generated by the local oscillator on the root receiving antenna; It is Gaussian white noise.

[0033] Will After performing analog-to-digital conversion, the first The digital received signal for each path is:

[0034]

[0035] in, and These are the normalized propagation frequency offsets of the useful signal and the cooperative interference signal, respectively. Let be the Gaussian white noise of the i-th antenna.

[0036] Step S4. Perform cooperative interference reconstruction and cancellation on the signal of each receiving antenna;

[0037] Cooperative interference for each receiving antenna is reconstructed and canceled. Due to frequency offset, the reconstruction of cooperative interference on each receiving path is not perfect, therefore, cooperative interference cannot be completely canceled. Considering that frequency offset manifests as delay in the frequency domain, the reconstructed interference is analyzed in the frequency domain. It is assumed that each... The interference is estimated and reconstructed once for each point, and the interference is modeled using DFT (Discrete Fourier Transform). Then, the interference... The frequency domain representation of interference along a path is as follows:

[0038]

[0039] in, The inter-frequency crosstalk introduced by the frequency offset can be reconstructed in the frequency domain as follows: By using IDFT (Inverse Discrete Fourier Transform) to transform it back to the time domain, the time-domain reconstructed interference can be obtained as follows: .

[0040] The residual interference is statistically uncorrelated with the reconstructed cooperative interference and therefore cannot be eliminated by linear processing. Thus, the residual cooperative interference after interference cancellation is:

[0041]

[0042] Step S5. Analyze the statistical characteristics of residual cooperative interference (statistical characteristics are expressed using the covariance matrix).

[0043] The residual cooperative interference of each receiving branch is correlated, which will affect the merging weight analysis and the output signal-to-interference-plus-noise ratio after merging. Therefore, it is necessary to perform correlation analysis on the residual interference between each antenna.

[0044] Step S5 includes:

[0045] Correlation analysis was performed on the residual interference between antennas to determine the residual cooperative interference vector. Represented as:

[0046] ;

[0047] in, This represents the residual cooperative interference from the 1st antenna to the Lth antenna;

[0048] The covariance matrix of the residual cooperative disturbance is denoted as ; The element in the i-th row and j-th column is represented as:

[0049]

[0050] in, and This represents the residual cooperative interference between the i-th antenna and the j-th antenna, where i = 1, 2, ..., L; j = 1, 2, ..., L. Transmit power for cooperative interference.

[0051] Step S6. Analyze the statistical characteristics of the useful signal containing frequency offset error (statistical characteristics are expressed using the covariance matrix).

[0052] In a single-transmitter multiple-receiver system, the core of diversity gain merging is the in-phase superposition of useful signals from multiple branches. Gain can be achieved by compensating for channel phase and weighting the superposition amplitude. However, frequency offset causes the phases of the signals from each branch to deviate from synchronization over time, resulting in ineffective superposition of useful signal energy. Consequently, diversity gain decreases linearly with increasing frequency offset. Therefore, it is necessary to analyze the impact of useful signal correlation under unequal frequency offsets in each branch to obtain the optimal merging coefficient.

[0053] The useful signal vector is represented as Useful signal of the i-th branch Expressed as the sum of the effective portion and inter-frequency crosstalk:

[0054]

[0055] in, The time-domain form of inter-frequency crosstalk introduced by frequency offset is: the effective time-domain part of the useful signal is ;

[0056] The covariance matrix of the useful signal is , The element in the i-th row and j-th column is represented as:

[0057]

[0058] in, This represents the transmission power of the useful signal.

[0059] Step S7. Based on the covariance matrix of the residual cooperative interference and the useful signal, derive the weight vector that maximizes the signal-to-interference-plus-noise ratio of the combined output signal;

[0060] To obtain the maximum diversity gain, we use a weight vector. To each branch

[0061] The signals from each branch are combined. Since frequency offset can cause phase coupling between residual interference and the useful signal, if the weighting direction deviates from the phase of the actual useful signal, the "weighting gain" will become a "weighting loss," or even indirectly amplify the interference, further worsening the signal-to-interference-plus-noise ratio (SNR) of the combined signal. Therefore, based on the derivation in steps S5-S7, we comprehensively consider the impact of frequency offset on residual interference and the useful signal, deriving the optimal weight vector to combine the signals from each branch to maximize the output SNR.

[0062] The signal vector after interference cancellation is ,

[0063] in For the first The mixed signal after interference suppression by each receiving antenna. Based on the minimum mean square error criterion, the optimal weight vector is:

[0064]

[0065] Based on steps S4-S7, we can obtain:

[0066]

[0067]

[0068] Let Variance be the variance of Gaussian white noise. It is an identity matrix.

[0069] Step S8. Combine the signals of each branch according to the derived weight vector to obtain the combined output signal;

[0070] Using the weight vector obtained in step S7 The interference-suppressed branch signals are then combined to obtain the final output signal. It is the first The weighting coefficients for each antenna branch. The signal of each branch is multiplied by a complex coefficient. If we sum all the signals, the output sum signal can be expressed as:

[0071]

[0072] Under this merging scheme, the output merged signal with the maximum signal-to-interference-plus-noise ratio (SINR) was obtained, and the SINR of this signal is:

[0073] .

[0074] The proposed multi-antenna reception method for cooperative interference suppression is then analyzed and evaluated through simulation. Specific parameter settings are shown in the table below.

[0075] Table 1. Simulation parameter settings for multi-antenna reception methods aimed at cooperative interference suppression

[0076]

[0077] Figure 3 The combined performance of the multi-antenna receiving scheme proposed in this patent was compared with that of the maximum ratio combining scheme and the equal-gain combining scheme without considering frequency offset error. Simulation settings included 4 receiving antennas, a frequency offset error of 0 for the useful signal, and a frequency offset error of 10 for cooperative interference. -5 and 10 -4 The specific simulation parameters are shown in Table 1. As can be seen from the simulation results, when the residual cooperative interference is uncorrelated, the proposed multi-antenna receiving scheme consistently outperforms other schemes, especially when the frequency offset error is large. Since maximum ratio combining carries the risk of amplifying interference, its performance may even be worse than equal-gain combining. In scenarios with fully correlated residual interference, the performance of the proposed multi-antenna receiving scheme is the same as that of the maximum ratio combining scheme, as neither can mitigate the losses caused by residual interference. However, the proposed multi-antenna receiving scheme is still superior to the equal-gain combining scheme, especially in low received signal-to-noise ratio scenarios.

Claims

1. A multi-antenna receiving method for cooperative interference suppression, characterized in that: Includes the following steps: Step S1. At the source node, the digital useful signal is converted into a radio frequency signal after digital-to-analog conversion and up-conversion, and then transmitted by the useful signal antenna; Step S2. At the cooperative node, the digital cooperative interference signal is converted into a radio frequency signal after digital-to-analog conversion and up-conversion and then transmitted by the cooperative signal antenna; Step S3. At the authorized node, the received signal is down-converted and analog-to-digital converted. The authorized node is equipped with... A multi-antenna receiver with one antenna; Step S4. Perform cooperative interference reconstruction and cancellation on the signal of each receiving antenna; Step S5. Analyze the covariance matrix of residual cooperative disturbances; Step S6. Analyze the covariance matrix of the useful signal containing frequency offset error; Step S7. Based on the covariance matrix of the residual cooperative interference and the useful signal, derive the weight vector that maximizes the signal-to-interference-plus-noise ratio of the combined output signal; Step S8. Combine the signals of each branch according to the derived weight vector to obtain the combined output signal.

2. The multi-antenna receiving method for cooperative interference suppression according to claim 1, characterized in that: Step S1 includes: At the source node, the digital useful signal is transformed into an analog useful signal after digital-to-analog conversion. ; Analog useful signal After up-conversion, it is converted into a radio frequency signal. : in It is the carrier frequency of the useful signal; radio frequency signals Transmitted via a useful signal antenna.

3. The multi-antenna receiving method for cooperative interference suppression according to claim 1, characterized in that: Step S2 includes: At the cooperating node, the digital cooperative interference signal is converted into an analog useful signal after digital-to-analog conversion. ; Analog useful signal After up-conversion, it is converted into a radio frequency signal. : in It is the carrier frequency of the cooperative interference signal; radio frequency signals Transmitted via a cooperative signal antenna.

4. The multi-antenna receiving method for cooperative interference suppression according to claim 1, characterized in that: Step S3 includes: Assume the authorized node is equipped with A multi-antenna receiver with one antenna, where the received signal from each antenna contains the useful signal, cooperative interference signal and Gaussian white noise; The received signal is down-converted to obtain the baseband signal. The baseband signal at the root antenna is: in, and From the source node and the cooperating node to the... The channel coefficient of the root receiving antenna; For the first The carrier frequency generated by the local oscillator on the root receiving antenna; It is Gaussian white noise; Will After performing analog-to-digital conversion, the first The digital received signal for each path is: in, and These are the normalized propagation frequency offsets of the useful signal and the cooperative interference signal, respectively. Let be the Gaussian white noise of the i-th antenna.

5. A multi-antenna receiving method for cooperative interference suppression according to claim 1, characterized in that: Step S4 includes: Assuming each The interference is estimated and reconstructed once for each point, and the interference is modeled using DFT. The frequency domain representation of interference along a path is as follows: in, For the inter-frequency crosstalk introduced by frequency offset, the frequency domain form of the reconstructed interference is as follows: Using IDFT to transform it back to the time domain, the time-domain reconstructed interference is obtained as follows: ; The residual interference is statistically uncorrelated with the reconstructed cooperative interference and cannot be eliminated by linear processing. Therefore, the residual cooperative interference after interference cancellation is: 。 6. A multi-antenna receiving method for cooperative interference suppression according to claim 5, characterized in that: Step S5 includes: Correlation analysis was performed on the residual interference between antennas to determine the residual cooperative interference vector. Represented as: ； in, This represents the residual cooperative interference from the 1st antenna to the Lth antenna; The covariance matrix of the residual cooperative disturbance is denoted as ; The element in the i-th row and j-th column is represented as: ； in, and This represents the residual cooperative interference between the i-th antenna and the j-th antenna, where i = 1, 2, ..., L; j = 1, 2, ..., L. Transmit power for cooperative interference.

7. A multi-antenna receiving method for cooperative interference suppression according to claim 6, characterized in that: Step S6 includes: To obtain the optimal combining coefficients, we analyze the impact of useful signal correlation when the frequency offsets of each branch are unequal. The useful signal vector is represented as Useful signal of the i-th branch Expressed as the sum of the effective portion and inter-frequency crosstalk: in, The time-domain form of inter-frequency crosstalk introduced by frequency offset is: the effective time-domain part of the useful signal is ; The covariance matrix of the useful signal is , The element in the i-th row and j-th column is represented as: in, This represents the transmission power of the useful signal.

8. A multi-antenna receiving method for cooperative interference suppression according to claim 7, characterized in that: Step S7 includes: To obtain the maximum diversity gain, use the weight vector. To combine the signals from each branch, considering the impact of frequency offset on residual interference and useful signals, the optimal weight vector is derived to combine the signals from each branch to maximize the output signal-to-interference-plus-noise ratio. The signal vector after interference cancellation is , in, For the first The mixed signal after interference suppression by each receiving antenna; according to the minimum mean square error criterion, the optimal weight vector is: in: Let Variance be the variance of Gaussian white noise. It is an identity matrix.

9. A multi-antenna receiving method for cooperative interference suppression according to claim 1, characterized in that: Step S8 includes: Based on the weight vector obtained in step S7 The interference-suppressed branch signals are then combined to obtain the final output signal: in, It is the first The weighting coefficients for each antenna branch are calculated by multiplying the signal of each branch by complex coefficients. If all signals are summed, the output sum signal is expressed as: 。

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