CN-121984607-A - Cross polarization interference cancellation method and system based on independent component analysis

CN121984607ACN 121984607 ACN121984607 ACN 121984607ACN-121984607-A

Abstract

The invention discloses a cross polarization interference cancellation method and a system based on independent component analysis, which mainly solve the problems that the prior art cannot converge, the output arrangement is fuzzy and the frequency spectrum utilization rate is low under the condition of path delay difference. The implementation scheme comprises the steps of calculating a cross-correlation function of a received main signal and an interference signal, searching a peak value of the cross-correlation function as an optimal synchronization position, adjusting the interference signal according to the optimal synchronization position to obtain a synchronized interference signal, constructing a new input vector by using the interference signal and the main signal, whitening the new input vector to obtain a whitened vector, iteratively updating the weight vector, calculating two paths of separated signals by using the updated weight vector and the whitened vector, calculating the modulus value of the main signal to be cross-correlated with the modulus values of the two paths of separated signals respectively, and selecting one path with a larger cross-correlation result as an output signal after interference cancellation. The invention improves the accuracy, reliability and spectrum utilization rate of channel identification after blind source separation, has extremely strong time delay interference resistance, and can be used for signal receiving processing in a satellite communication polarization multiplexing system.

Inventors

ZHANG YAN
HUA ZHUO
MENG MING
GAO LIHUA
LI PING
NING SHEN
WANG YUXUAN
SONG TAO
Zhao Shuaihu

Assignees

西安电子科技大学

Dates

Publication Date: 20260505
Application Date: 20260130

Claims (10)

1. A cross-polarization interference cancellation method based on independent component analysis, comprising: (1) Let the processing data length be N, and the two received signals be respectively And Is provided with As a main signal, the signal is a main signal, Is an interference signal; (2) Calculating the cross-correlation function of the main signal and the interference signal Searching the maximum peak value of the modulus value as the optimal synchronous position ; (3) According to the best synchronous position To interference signals Delay or advance adjustment is carried out to obtain synchronized interference signals By using it and the main signal Construction of new input vectors ; (4) For input vector Performing whitening treatment to obtain whitened vector And iteratively updating weight vectors Using updated weight vectors And whitened vector Calculating to obtain two paths of separated signals ; (5) Calculating a primary signal The modulus of (a) is respectively separated from two paths of signals Is related to the modulus of And selecting one path with a larger cross-correlation result as an output signal after interference cancellation.
2. The method of claim 1, wherein the main signal is calculated in (2) Interference signal Cross-correlation function of (2) The formula is as follows: ; Wherein E represents the desire, Representing a delay variable.
3. The method of claim 1, wherein the synchronized interfering signal is obtained in (3) New constructed input vector The formulas are as follows: , 。
4. the method of claim 1, wherein the pair of input vectors in (4) Performing whitening treatment to obtain whitened vector The implementation includes: (4a) For input vector Performing decentralization treatment to obtain data with zero mean value : ; Wherein E [ And represents the mean value; (4b) According to the data Calculating to obtain a covariance matrix R: , Wherein E [ And is representative of the mathematical expectation, Representing a matrix transpose; (4c) Performing eigenvalue decomposition on the covariance matrix R to obtain an eigenvalue diagonal matrix D and an eigenvector matrix F: ; (4d) Calculating a whitening matrix Q according to the eigenvalue diagonal matrix D and the eigenvector matrix F: ; (4e) Based on the whitening matrix Q and data Obtaining whitened vector : 。
5. The method of claim 1, wherein the weight vector is iteratively updated in (4) The implementation includes: (4f) Initializing a weight vector W; (4g) Obtaining an updated weight vector according to an iterative updating formula : , Wherein, the As a nonlinear function Is used for the purpose of determining the derivative of (c), Is that Is a derivative of (2); (4h) Normalizing the updated weight vector Obtaining : , Wherein, the Representing the 2 norms of the matrix; (4i) Judging the normalized weight vector Whether or not the convergence condition is satisfied : If not, returning to the step (4 g); If so, the iteration is ended, As a means of , Wherein, the For the weight vector of the last iteration, Is a small constant of statistical significance, Representing the matrix transpose.
6. The method of claim 1, wherein the updated weight vector is utilized in (4) And whitened vector Calculating to obtain two paths of separated signals The formula is as follows: , Wherein, the In order to contain a vector of two separate signals, Representing the matrix transpose.
7. The method of claim 1, wherein the main signal is calculated in (5) The modulus of (a) is respectively separated from two paths of signals Is related to the modulus of The formula is as follows: , Wherein E represents the desire, Representing a delay variable.
8. The cross polarization interference cancellation system based on independent component analysis is characterized in that a dual-channel parallel processing architecture is adopted, two independent signal recovery branches are respectively established for a first polarized signal and a second polarized signal, and each signal recovery branch comprises the following modules connected in cascade: the synchronous position searching module is used for calculating the correlation characteristics of the main signal and the interference signal and searching the best matching point so as to determine the best synchronous position; The time delay alignment module is used for performing time delay adjustment on the interference signals according to the optimal synchronous position output by the synchronous position search module and constructing the main signals and the adjusted interference signals into time aligned vectors; The independent component analysis module is used for carrying out blind source separation processing on the vector output by the time delay alignment module, and outputting two paths of separation signals by iteratively updating the weight vector; and the output sequencing module is used for calculating the envelope characteristics of the two paths of separated signals output by the independent component analysis module and identifying the separated main signals through the envelope correlation operation between the two paths of separated signals and the main signals.
9. The system of claim 8, wherein the delay alignment module comprises: The control buffer sub-module is used for controlling the buffer vector to delay or read the interference signal in advance according to the delay quantity indicated by the optimal matching point so as to compensate the transmission delay introduced by the physical channel and obtain the interference signal after time domain alignment; and the vector construction submodule is used for combining the main signal with the aligned interference signal to obtain an input vector meeting the instantaneous mixing model.
10. The system of claim 8, wherein the independent component analysis module comprises: The preprocessing sub-module is used for carrying out decentralization processing on the input vector to remove the mean value, carrying out whitening processing to remove the correlation among the components and normalize the variance, and obtaining a whitened vector; the iterative updating sub-module is used for initializing the weight vector and repeatedly updating the weight vector by using an iterative algorithm until the weight vector converges; And the separation output sub-module is used for carrying out matrix operation on the converged weight vector and the whitened vector to obtain two paths of separation signals.

Description

Cross polarization interference cancellation method and system based on independent component analysis Technical Field The invention belongs to the technical field of communication signal processing, and relates to a cross polarization interference cancellation method and a system, which can be applied to signal receiving processing in a satellite communication polarization multiplexing system, in particular to a scene with cross polarization interference and poor channel time delay. Background In modern communication systems, polarization multiplexing techniques are widely used in order to increase spectrum utilization, for example, using both horizontal polarization and vertical polarization in microwave or satellite communications. However, due to the atmospheric transmission effects such as rain fade, limitation of antenna cross polarization discrimination and non-ideal characteristics of channels, energy leakage often occurs between two paths of orthogonal signals, cross polarization interference XPIC is generated, signal to noise ratio of the signals is seriously reduced, and error rate performance of a system is affected. Existing cross-polarization interference cancellation techniques are mainly divided into two categories: 1. Pilot/training sequence based methods such as adaptive filters based on least mean square LMS algorithms. Such methods require the transmitting end to periodically insert a known pilot sequence to assist in channel estimation. Although stable in performance, the "supervised" mode occupies valuable spectrum resources, reducing the effective data throughput rate. 2. Blind source separation methods such as independent component analysis ICA. The method does not need pilot frequency, and directly utilizes the statistical characteristics of signals to separate interference. However, the traditional ICA algorithm has two main defects that firstly, the algorithm can not be converged due to the fact that the algorithm is built on the assumption of an instantaneous mixed model and the time delay difference caused by different path lengths in an actual physical channel can not be processed, and secondly, the signals separated by the ICA have arrangement ambiguity, namely, the output sequence is random, which path is the recovered main signal can not be automatically identified, and the subsequent demodulation data disorder is easy to be caused. Patent application number CN201710698651 discloses a source signal extraction method, system and storage medium, which are used for synchronizing input signals by calculating coefficient matrix for improving signal independence, separating the synchronized signals into target interference signals and useful signals by using the coefficient matrix, and finally selecting output channels according to energy or characteristics. The method adopts the processing sequence of firstly calculating the separation matrix and then synchronizing the signals, ignores the convolution mixing characteristic caused by physical time delay in an XPIC scene, has larger error in the calculated separation matrix under the condition of misaligned signals, can not meet the requirement of high-precision interference cancellation, and meanwhile, can not be applied to communication scenes with the same modulation mode and similar power of main signals and interference signals based on the output selection mechanism of energy level or specific mode recognition such as voice characteristics, and is difficult to solve the problem of channel arrangement ambiguity after blind separation. Therefore, there is a need for an interference cancellation method that can not only save spectrum resources, but also effectively overcome channel delay and solve the problem of permutation ambiguity. Disclosure of Invention The invention aims to overcome the defects of the prior art, and provides a cross polarization interference cancellation system and a method based on independent component analysis, so as to improve the spectrum utilization rate of the system and the accuracy and reliability of channel identification after blind source separation, and improve the separation precision of cross polarization interference cancellation under a physical channel delay environment. In order to achieve the above purpose, the technical scheme of the invention comprises the following steps: 1. a cross-polarization interference cancellation method based on independent component analysis, comprising: (1) Let the processing data length be N, and the two received signals be respectively AndIs provided withAs a main signal, the signal is a main signal,Is an interference signal; (2) Calculating the cross-correlation function of the main signal and the interference signal Searching the maximum peak value of the modulus value as the optimal synchronous position; (3) According to the best synchronous positionTo interference signalsDelay or advance adjustment is carried out to obtain synchronized interference si