Power carrier signal blind identification method and system based on OFDM signal characteristics

Abstract

The application discloses a power carrier signal blind identification method and system based on OFDM signal characteristics, and the method comprises the following steps: step 1, receiving a power carrier signal, wherein the power carrier signal is modulated by OFDM; step 2, blind estimating the subcarrier number, signal center frequency point and subcarrier interval of the power carrier signal to obtain prior information of the power carrier signal; and step 3, decoding the received power carrier signal according to the prior information of the power carrier signal. According to the characteristic value of the OFDM modulated signal, the subcarrier number, signal center frequency point and subcarrier interval of the power carrier are estimated without knowing the protocol information, so that the protocol and modulation parameters of the power carrier are determined, the link between the RX end and the TX end is facilitated, and the link efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of power line carrier communication technology, and particularly relates to a blind identification method and system for power line carrier signals based on OFDM signal characteristics. Background Technology

[0002] Power line carrier communication technology has developed rapidly with the continuous improvement of power automation and intelligence. Throughout this process, power line carrier protocols have served as the technical standard, undergoing multiple stages of development and evolution. This evolution has resulted in numerous standards and protocols, including domestic and international ones, and high-speed, medium-speed, and low-speed protocols. Before communication is established between the receiver (RX) and transmitter (TX), neither party knows which power line carrier protocol the other is using. Therefore, they need to poll and try various power line carrier protocol modes to match and attempt decoding to establish a connection. Due to the large number of power line carrier protocols, this process wastes connection establishment time and is prone to errors. Encountering unrecognized signals can be confusing, complicating site surveying and maintenance. Summary of the Invention

[0003] Purpose of the invention: The technical problem to be solved by the present invention is to provide a blind identification method and system for power line carrier signals based on OFDM signal characteristics, which addresses the shortcomings of the existing technology.

[0004] To address the aforementioned technical problems, in a first aspect, a blind identification method for power line carrier signals based on OFDM signal characteristics is disclosed, comprising:

[0005] Step 1: Receive a power line carrier signal, which is modulated by OFDM;

[0006] Step 2: Blindly estimate the number of subcarriers, the center frequency of the signal, and the subcarrier spacing of the power line carrier signal to obtain prior information about the power line carrier signal;

[0007] Step 3: Decode the received power carrier signal based on the prior information of the power carrier signal.

[0008] Furthermore, the blind estimation of the number of subcarriers of the power line carrier signal in step 2 includes:

[0009] Step 2-1: Calculate the autocorrelation matrix R of the power line carrier signal. xx ;

[0010] Step 2-2, for the autocorrelation matrix R xx Perform eigenvalue decomposition to obtain the eigenvalue diagonal matrix b and the eigenvector W;

[0011] Steps 2-3: Take the largest values ​​from the eigenvalue diagonal matrix b to form array C. The number of data in array C is the blind estimate of the number of subcarriers of the received power line carrier signal.

[0012] Further, step 2-1 includes: recording the received power line carrier signal Y(i) = S T (i)+u(i), i∈{1,2,…,L*m}, L*m represents the data sampling length; S T Y(i) represents the transmitted signal, u(i) represents the noise. Based on the characteristics of power line carrier and considering the computational complexity, Y(i) is divided into m groups of length L, where L is greater than the maximum number of subcarriers for all power line carrier protocols, forming a vector array X, X = {x1, x2, x3, ..., x...} m}={x s1 ,x s2 ,x s3 ,…,x sm}+{x u1 ,x u2 ,x u3 ,…,x um}, where X s ={x s1 ,x s2 ,x s3 ,…,x sm Let} be the signal vector group, X u ={x u1 ,x u2 ,x u3 ,…,x um} represents the noise vector set;

[0013] The autocorrelation matrix R of the received power line carrier signal xx for

[0014]

[0015] Because the signal and noise are uncorrelated, the obtained

[0016]

[0017] Thus obtain

[0018] Further, step 2-2 includes: recording the signal matrix. Based on the characteristics of OFDM signals, the rank p of the signal matrix S is the number of subcarriers;

[0019] Perform eigenvalue decomposition on the signal matrix S to obtain the eigenvalue diagonal matrix a and eigenvector Q of the signal matrix S:

[0020] SQ = aQ

[0021]

[0022] These are the characteristic values ​​of a power line carrier signal when there is no noise.

[0023] For the autocorrelation matrix R xx Perform eigenvalue decomposition to obtain the autocorrelation matrix R. xx eigenvalue diagonal matrix b and eigenvector W:

[0024] R xx W = bW

[0025]

[0026] It is a characteristic value of noise.

[0027] Furthermore, steps 2-3 include: the characteristic values ​​of the power line carrier signal when there is no noise. Eigenvalues ​​of noise A large value indicates a large autocorrelation matrix R. xx Normalize the eigenvalue diagonal matrix b, and select the largest values ​​from it to form an array. The number of data in array C is the blind estimate of the number of subcarriers of the received power line carrier signal. The number of subcarriers in all power line carrier protocols is adapted based on the blindly estimated number of subcarriers, and the one that is closest to the blindly estimated number of subcarriers is determined as the number of subcarriers of the power line carrier signal.

[0028] Furthermore, the blind estimation of the signal center frequency of the power line carrier signal in step 2 includes:

[0029] Taken from the correlation matrix R xx The vectors corresponding to the feature values ​​in array C from the feature vector W form the effective subcarrier space vector array W. c =[r1,r2,r3,…,r p ];

[0030] Will Divide into L equal parts, corresponding to Divide the L frequency points into an array F_list = [F1, F2, F3, ..., F p ,F p+1 ,…,F L ];in The corresponding frequency point is Where FS is the signal sampling frequency, v represents the frequency index, and 1≤v≤L.

[0031] Based on the array F_list, obtain the angular frequency vector array S0 = e for all subcarriers. 2*F_list*i*(0～L-1) , where i represents an imaginary number.

[0032] The effective subcarrier space vector array W c Multiplying the array S0 with the angular frequency vector array corresponding to all subcarriers yields the array S1 = W. c *S0, this array has a size of p rows and L columns;

[0033] Add the numbers in each column of array S1 to obtain the effective subcarrier space vector and the correlation value array S2 of all subcarriers. The size of array S2 is 1 row and L columns.

[0034] Sort the array S2 by absolute value from largest to smallest. Sort the array F_list according to the same rule. Take the first p numbers from F_list and obtain the F values ​​in F_list corresponding to the largest p numbers in array S2, forming the array FX_list = [FX1, FX2, FX3, ..., FX]. p ];

[0035] Calculate the average value of the array FX_list to obtain the blind estimate of the center frequency FX. center =mean(FX_list), which adapts the center frequency of all power line carrier protocols to the center frequency of the blindly estimated center frequency, and determines the center frequency of the power line carrier signal that is closest to the blindly estimated center frequency.

[0036] Interference is generally severe on power lines, resulting in less than ideal signal-to-noise ratios. The autocorrelation of the received signal Y(i) is calculated to obtain the signal subspace W of the effective subcarriers. c W c The vectors corresponding to the effective subcarriers in S0 have good correlation, W c The vector correlation with the invalid subcarriers in S0 is relatively poor, thus the position of the valid subcarriers in Y(i) can be estimated. Even when the signal-to-noise ratio of the received Y(i) signal is less than 0 dB, increasing the sampling length of Y(i), i.e., making the value of m relatively large, can still effectively distinguish the position of the valid subcarriers in the received Y(i) signal. Therefore, the center frequency can be estimated based on the position of the valid subcarriers. This effective subcarrier position information provides the necessary conditions for the next step of estimating the subcarrier spacing, making the estimation more accurate.

[0037] Further, the blind estimation of the subcarrier spacing of the power line carrier signal in step 2 includes:

[0038] For the array FX_list = [FX1, FX2, FX3, ..., FX p Sort the results in ascending order to obtain FXX_list = [FXX1, FXX2, FXX3, ..., FXX]. p ]; This obtains the ascending order of the effective subcarrier positions.

[0039] Calculate the array FSUB_list = [FXX2, FXX3, ..., FXX p ]-[FXX1,FXX2,FXX3,…,FXX p-1 The subcarrier spacing blind estimate is obtained by averaging the array FSUB_list.

[0040] With blind estimates of the number of subcarriers, center frequency, and carrier spacing, we can traverse carrier communication protocols, find the best-matching protocol and configuration, and obtain the parameters of the signal received on the power line.

[0041] Secondly, a blind identification system for power line carrier signals based on OFDM signal characteristics is disclosed, including an RX-end signal receiving module, an OFDM blind estimation module, and an RX-OFDM baseband signal decoding module.

[0042] The RX terminal signal receiving module is used to receive power line carrier signals, which are modulated by OFDM.

[0043] The OFDM blind estimation module is used to blindly estimate the number of subcarriers, the center frequency of the signal, and the subcarrier spacing of the power line carrier signal, so as to obtain the prior information of the power line carrier signal.

[0044] The RX-OFDM baseband signal decoding module is used to decode the received power carrier signal based on the prior information of the power carrier signal.

[0045] Furthermore, the OFDM blind estimation module includes a subcarrier number blind estimation unit, a signal center frequency blind estimation unit, and a subcarrier spacing blind estimation unit.

[0046] The subcarrier number blind estimation unit is used to estimate the number of subcarriers based on the autocorrelation matrix R of the power line carrier signal. xx The number of subcarriers is calculated.

[0047] The signal center frequency blind estimation unit is used to estimate the signal based on the autocorrelation matrix R. xx Effective subcarrier space vector array W c The center frequency of the signal is obtained by calculating the correlation between the vectors in F_list corresponding to the subcarrier frequency points;

[0048] The subcarrier spacing blind estimation unit is used to calculate the subcarrier spacing based on the vector position in F_list corresponding to the subcarrier frequency point.

[0049] Furthermore, the subcarrier number blind estimation unit estimates the number of subcarriers based on the autocorrelation matrix R of the power line carrier signal. xx The calculation of the number of subcarriers includes:

[0050] Calculate the autocorrelation matrix R of the power line carrier signal.xx ;

[0051] For the autocorrelation matrix R xx Perform eigenvalue decomposition to obtain the eigenvalue diagonal matrix b and the eigenvector W;

[0052] Take the largest values ​​from the eigenvalue diagonal matrix b to form an array C. The number of data in array C is a blind estimate of the number of subcarriers of the received power line carrier signal.

[0053] Beneficial Effects: The blind identification method for power line carrier signals based on OFDM signal characteristics provided in this application can obtain some information about the communication protocol by blindly estimating the number of carriers, center frequency, and subcarrier spacing of the received OFDM signal on the power line carrier, without knowing the protocol information. The RX end can then selectively attempt to establish a link with the TX end based on this information, improving link efficiency. It can also provide relevant information when encountering ambiguous signals on the power line carrier, facilitating and improving the efficiency of communication system site surveying and maintenance. Attached Figure Description

[0054] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0055] Figure 1 The normalized eigenvalues ​​of an OFDM modulated power line carrier signal with an SNR of 5 dB are sorted from largest to smallest.

[0056] Figure 2 The normalized S2 array values ​​are sorted by size when L is 1024 and SNR is 5dB.

[0057] Figure 3 This is a schematic diagram of a blind identification system for power line carrier signals based on OFDM signal characteristics, provided in an embodiment of this application.

[0058] Figure 4 This is a schematic diagram of the OFDM blind estimation module in a power line carrier signal blind identification system based on OFDM signal characteristics, provided in an embodiment of this application. Detailed Implementation

[0059] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0060] Blind identification of OFDM communication signals on power line carriers allows the RX end to possess partial protocol information from the TX end before a link is established, facilitating link establishment between the RX and TX ends and improving the success rate. Blind identification of OFDM signals on power line carriers can also provide site survey and maintenance information in cases where the RX and TX cannot establish a link, thereby improving the efficiency of site survey and maintenance.

[0061] The purpose of this invention is to estimate the number of subcarriers, the signal center frequency, and the subcarrier spacing of a power line carrier based on the characteristic values ​​of the OFDM modulated signal, without knowing the protocol information, thereby determining the protocol and modulation parameters of the power line carrier. It eliminates the need to poll and try various possible communication protocols; the TX and RX ends of the communication are directly linked. Even when encountering ambiguous signals on the power line carrier, it can still provide signal information, bringing convenience to the site survey and maintenance of power line carrier communication systems. It can be applied to smart grids, remote meter reading systems, smart homes, industrial control, on-site operation and maintenance testing of power line carrier communication systems, and site surveys of power line carrier communication environments.

[0062] The first embodiment of this application discloses a blind identification method for power line carrier signals based on OFDM signal characteristics, including: step 1, receiving a power line carrier signal, wherein the power line carrier signal is modulated by OFDM;

[0063] Step 2: Blindly estimate the number of subcarriers, the center frequency of the signal, and the subcarrier spacing of the power line carrier signal to obtain prior information about the power line carrier signal;

[0064] Blindly estimating the number of subcarriers of the power line carrier signal includes:

[0065] Step 2-1: Calculate the autocorrelation matrix R of the power line carrier signal. xx ;

[0066] A power line carrier transmitter (TX) transmits a signal, and the receiver (RX) receives the signal. The received signal can be represented as:

[0067] Y(i)=S T (i)+u(i) (1)

[0068] i∈{1,2,…,L*m}, where L*m represents the data sampling length. S T Let (i) represent the transmitted signal, u(i) represent the noise, and Y(i) represent the received signal. Based on the characteristics of power line carrier and considering computational complexity, Y(i) is divided into m groups of length L, where L is greater than the maximum number of subcarriers for all power line carrier protocols, forming a vector array X, X = {x1, x2, x3, ..., x...}. m}={x s1 ,x s2 ,x s3 ,…,x sm}+{xu1 ,x u2 ,x u3 ,…,x um}, where X s ={x s1 ,x s2 ,x s3 ,…,x sm Let} be the signal vector group, X u ={x u1 ,x u2 ,x u3 ,…,x um} represents the noise vector group. Considering the computational load, L cannot be too large. In this embodiment, L can be 1024, 2048, or 4096, and m can be between 8 and 2048.

[0069] The autocorrelation matrix R of the received power line carrier signal xx for

[0070]

[0071] Since the signal and noise are uncorrelated, we can obtain

[0072]

[0073] Thus obtain

[0074]

[0075] Step 2-2, for the autocorrelation matrix R xx Perform eigenvalue decomposition to obtain the eigenvalue diagonal matrix b and the eigenvector W;

[0076] Due to X s It is an OFDM signal. Based on the characteristics of OFDM signals, the signal matrix... The rank p is the number of subcarriers. By performing eigenvalue decomposition on the signal matrix S, we can obtain the eigenvalue diagonal matrix a and the eigenvector Q of the signal matrix S.

[0077] SQ = aQ

[0078]

[0079] It is the characteristic value of a power line carrier signal when there is no noise.

[0080] Autocorrelation matrix For the autocorrelation matrix R xx By performing eigenvalue decomposition, the autocorrelation matrix R can be obtained. xx eigenvalue diagonal matrix b and eigenvector W

[0081] R xxW = bW

[0082]

[0083] It is a characteristic value of noise.

[0084] Steps 2-3: Take the largest values ​​from the eigenvalue diagonal matrix b to form array C. The number of data in array C is the blind estimate of the number of subcarriers of the received power line carrier signal.

[0085] Characteristic values ​​of power line carrier signals without noise The value is greater than the eigenvalue of the noise. The value is large. For the autocorrelation matrix R... xx Normalize the eigenvalue diagonal matrix b, and then select the largest values ​​(with a threshold of 0.7) from the normalized eigenvalue diagonal matrix to form an array. The number of data in array C is the blind estimate of the number of subcarriers of the received power line carrier signal. The number of subcarriers in all power line carrier protocols is adapted based on the blindly estimated number of subcarriers, and the one that is closest to the blindly estimated number of subcarriers is determined as the number of subcarriers of the power line carrier signal.

[0086] Blindly estimating the center frequency of the power line carrier signal includes:

[0087] Taken from the correlation matrix R xx The vectors corresponding to the feature values ​​in array C from the feature vector W form the effective subcarrier space vector array W. c =[r1,r2,r3,…,r p ];

[0088] Will Divide into L equal parts, corresponding to Divide the L frequency points into an array F_list = [F1, F2, F3, ..., F p ,F p+1 ,…,F L ];in The corresponding frequency point is Where FS is the signal sampling frequency, v represents the frequency index, and 1≤v≤L.

[0089] Based on the array F_list, obtain the angular frequency vector array S0 = e for all subcarriers. 2*F_list*i*(0～L-1) , where i represents an imaginary number.

[0090] The effective subcarrier space vector array W c Multiplying the array S0 with the angular frequency vector array corresponding to all subcarriers yields the array S1 = W. c *S0, this array has a size of p rows and L columns;

[0091] Add the numbers in each column of array S1 to obtain the effective subcarrier space vector and the correlation value array S2 of all subcarriers. The size of array S2 is 1 row and L columns.

[0092] Sort the array S2 by absolute value from largest to smallest. Sort the array F_list according to the same rule. Take the first p numbers from F_list and obtain the F values ​​in F_list corresponding to the largest p numbers in array S2, forming the array FX_list = [FX1, FX2, FX3, ..., FX]. p ];

[0093] Calculate the average value of the array FX_list to obtain the blind estimate of the center frequency FX. center =mean(FX_list), which adapts the center frequency of all power line carrier protocols to the center frequency of the blindly estimated center frequency, and determines the center frequency of the power line carrier signal that is closest to the blindly estimated center frequency.

[0094] Blindly estimating the subcarrier spacing of the power line carrier signal includes:

[0095] For the array FX_list = [FX1, FX2, FX3, ..., FX p Sort the results in FXX_list = [FXX1, FXX2, FXX3, ..., FXX] in ascending order. p The effective subcarrier positions are sorted in ascending order. Then the array FSUB_list = [FXX2, FXX3, ..., FXX] is calculated. p ]-[FXX1,FXX2,FXX3,…,FXX p-1 By averaging the array FSUB_list, we can obtain the blind estimate of the subcarrier spacing.

[0096] Step 3: Decode the received power carrier signal based on the prior information of the power carrier signal.

[0097] Figure 1 This is a graph showing the normalized eigenvalues ​​of an OFDM modulated power line carrier signal Y(i) with an SNR of 5 dB, sorted from largest to smallest. It can be seen that the first 191 eigenvalues ​​are significantly larger than the later ones. From the graph, the blind estimate of the number of subcarriers in the OFDM signal is 191. Figure 2 This is the normalized S2 array values ​​arranged in ascending order when L is 1024 and SNR is 5dB. The center frequency and subcarrier spacing can be calculated from this.

[0098] The second embodiment of this application discloses a blind identification system for power line carrier signals based on OFDM signal characteristics, including an RX-end signal receiving module, an OFDM blind estimation module, and an RX-OFDM baseband signal decoding module.

[0099] The RX terminal signal receiving module is used to receive power line carrier signals, which are modulated by OFDM.

[0100] The OFDM blind estimation module is used to blindly estimate the number of subcarriers, the signal center frequency, and the subcarrier spacing of the power line carrier signal, thereby obtaining prior information about the power line carrier signal. Specifically, for example... Figure 4 As shown, it includes a subcarrier number blind estimation unit, a signal center frequency blind estimation unit, and a subcarrier spacing blind estimation unit.

[0101] The subcarrier number blind estimation unit is used to estimate the number of subcarriers based on the autocorrelation matrix R of the power line carrier signal. xx The number of subcarriers is calculated, specifically including: calculating the autocorrelation matrix R of the power line carrier signal. xx For the autocorrelation matrix R xx Perform eigenvalue decomposition to obtain the eigenvalue diagonal matrix b and the eigenvector W; select the largest values ​​in the eigenvalue diagonal matrix b to form an array C, and the number of data in array C is a blind estimate of the number of subcarriers of the received power line carrier signal.

[0102] The signal center frequency blind estimation unit is used to estimate the signal based on the autocorrelation matrix R. xx Effective subcarrier space vector array W c The center frequency of the signal is obtained by calculating the correlation between the vectors in F_list corresponding to the subcarrier frequency points;

[0103] The subcarrier spacing blind estimation unit is used to calculate the subcarrier spacing based on the vector position in F_list corresponding to the subcarrier frequency point.

[0104] The RX-OFDM baseband signal decoding module is used to decode the received power carrier signal based on the prior information of the power carrier signal.

[0105] Figure 3 This is a block diagram of the entire power line carrier communication system. The TX end includes an OFDM baseband signal generation module and a TX end signal transmission module. The OFDM baseband signal generation module is used to generate OFDM baseband signals, and the TX end signal transmission module is used to transmit OFDM baseband signals to the RX end through power lines.

[0106] Based on the OFDM estimation information obtained by the blind estimation module, the RX-OFDM baseband signal decoding module can directly select the protocol mode corresponding to the OFDM estimation information to receive and decode the RX signal. It does not need to poll all possible power line carrier protocol modes to find a matching mode.

[0107] By blindly identifying the OFDM carrier signal on a power line, the number of subcarriers, center frequency, and subcarrier spacing of the OFDM signal can be obtained. Based on this information, prior information about the OFDM signal can be derived. Even when no link is established between the TX and RX ends, and the RX end has no information from the TX end, the RX end can deduce the protocol of the TX end based on this blind identification information and various power line communication protocols. Therefore, the RX end can directly establish a link with the TX end based on the deduced protocol. The RX end does not need to use various protocol polling and matching methods to establish a link with the TX end.

[0108] The power line carrier signal blind identification system based on OFDM signal characteristics also includes a site survey information display module. This module receives information from the OFDM blind estimation module regarding the number of subcarriers, the signal center frequency, and the subcarrier spacing of the power line carrier signal. Even when encountering ambiguous signals on the power line carrier, the system can provide corresponding information, facilitating communication system site survey and maintenance and improving its efficiency.

[0109] In its specific implementation, this application provides a computer storage medium and a corresponding data processing unit. The computer storage medium is capable of storing a computer program, which, when executed by the data processing unit, can run the invention's content regarding a blind identification method for power line carrier signals based on OFDM signal characteristics, as well as some or all of the steps in various embodiments. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0110] Those skilled in the art will clearly understand that the technical solutions in the embodiments of the present invention can be implemented using computer programs and their corresponding general-purpose hardware platforms. Based on this understanding, the technical solutions in the embodiments of the present invention, or the parts that contribute to the prior art, can be embodied in the form of computer programs, i.e., software products. These computer program software products can be stored in a storage medium and include several instructions to cause a device containing a data processing unit (which may be a personal computer, server, microcontroller, MUU, or network device, etc.) to execute the methods described in various embodiments or certain parts of the embodiments of the present invention.

[0111] This invention provides a method and system for blind identification of power line carrier signals based on OFDM signal characteristics. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A blind identification method for power line carrier signals based on OFDM signal characteristics, characterized in that, include: Step 1: Receive a power line carrier signal, which is modulated by OFDM; Step 2: Blindly estimate the number of subcarriers, the center frequency of the signal, and the subcarrier spacing of the power line carrier signal to obtain prior information about the power line carrier signal; Step 3: Decode the received power carrier signal based on the prior information of the power carrier signal; Step 2, blindly estimating the number of subcarriers of the power line carrier signal, includes: Step 2-1: Calculate the autocorrelation matrix of the power line carrier signal. ; Step 2-2, for the autocorrelation matrix Perform eigenvalue decomposition to obtain the eigenvalue diagonal matrix b and the eigenvector W; Steps 2-3: Take the largest values ​​from the eigenvalue diagonal matrix b to form array C. The number of data in array C is the blind estimate of the number of subcarriers of the received power line carrier signal. Step 2-1 includes: recording the received power line carrier signal. , , Indicates the data sampling length; Represents the transmitted signal. To represent noise, based on the characteristics of power line carrier and considering the computational complexity, Divide the subcarriers into m groups according to a length L, where L is greater than the maximum number of subcarriers for all power line carrier protocols, forming a vector array X. For signal vector groups, This is a noise vector set; The autocorrelation matrix of the received power line carrier signal for ， Because the signal and noise are uncorrelated, the obtained ， Thus obtain ; Step 2-2 includes: recording the signal matrix. Based on the characteristics of OFDM signals, the signal matrix The rank p is the number of subcarriers; Perform eigenvalue decomposition on the signal matrix S to obtain the eigenvalue diagonal matrix a and eigenvector Q of the signal matrix S: ， These are the characteristic values ​​of a power line carrier signal when there is no noise. For autocorrelation matrix Perform eigenvalue decomposition to obtain the autocorrelation matrix. eigenvalue diagonal matrix b and eigenvector W: ， These are characteristic values ​​of noise; Steps 2-3 include: characteristic values ​​of the power line carrier signal when there is no noise. Eigenvalues ​​of noise A large value indicates a large impact on the autocorrelation matrix. Normalize the eigenvalue diagonal matrix b, and select the largest values ​​from it to form an array. The number of data in array C is the blind estimate of the number of subcarriers of the received power line carrier signal. The number of subcarriers in all power line carrier protocols is adapted based on the blindly estimated number of subcarriers, and the one that is closest to the blindly estimated number of subcarriers is determined as the number of subcarriers of the power line carrier signal.

2. The blind identification method for power line carrier signals based on OFDM signal characteristics according to claim 1, characterized in that, Step 2, blindly estimating the center frequency of the power line carrier signal, includes: Taken from the correlation matrix The vectors corresponding to the feature values ​​in array C from the feature vector W form the effective subcarrier space vector array. ; Will Divide into L equal parts, corresponding to Divide the L frequency points into equal parts and obtain an array. ;in The corresponding frequency point is Where FS is the signal sampling frequency, and v represents the frequency index. ; Obtain the angular frequency vector array corresponding to all subcarriers from the array F_list. , where i represents an imaginary number; Effective subcarrier space vector array Angular frequency vector array corresponding to all subcarriers Multiply to obtain an array This array has a size of p rows and L columns; Add the numbers in each column of array S1 to obtain the effective subcarrier space vector and the correlation value array S2 of all subcarriers. The size of array S2 is 1 row and L columns. Sort the absolute values ​​of array S2 in descending order, and then sort array F_list according to the same sorting rule. Given the first p numbers, obtain the F values ​​from the array F_list corresponding to the largest p numbers in array S2, and form an array. ; For arrays Calculate the average value to obtain the blind estimate of the center frequency point. The center frequency point of all power line carrier protocols is adapted based on the blindly estimated center frequency point, and the center frequency point that is closest to the blindly estimated center frequency point is determined as the center frequency point of the power line carrier signal.

3. The blind identification method for power line carrier signals based on OFDM signal characteristics according to claim 2, characterized in that, Step 2, which involves blindly estimating the subcarrier spacing of the power line carrier signal, includes: For arrays Sort by size from smallest to largest to obtain ; Obtain the ascending order of the effective subcarrier positions; Calculate array - For arrays The average value is used to obtain the blind estimate of the subcarrier spacing.

4. A blind identification system for power line carrier signals based on OFDM signal characteristics, characterized in that, It includes an RX-end signal receiving module, an OFDM blind estimation module, and an RX-OFDM baseband signal decoding module. The RX terminal signal receiving module is used to receive power line carrier signals, which are modulated by OFDM. The OFDM blind estimation module is used to blindly estimate the number of subcarriers, the center frequency of the signal, and the subcarrier spacing of the power line carrier signal, so as to obtain the prior information of the power line carrier signal. The RX-OFDM baseband signal decoding module is used to decode the received power carrier signal based on the prior information of the power carrier signal; The OFDM blind estimation module includes a subcarrier number blind estimation unit, which is used to estimate the number of subcarriers based on the autocorrelation matrix of the power line carrier signal. The number of subcarriers is calculated, including: Calculate the autocorrelation matrix of the power line carrier signal. Specifically, including: Record the received power line carrier signal , , Indicates the data sampling length; Represents the transmitted signal. To represent noise, based on the characteristics of power line carrier and considering the computational complexity, Divide the subcarriers into m groups according to a length L, where L is greater than the maximum number of subcarriers for all power line carrier protocols, forming a vector array X. For signal vector groups, This is a noise vector set; The autocorrelation matrix of the received power line carrier signal for ， Because the signal and noise are uncorrelated, the obtained ， Thus obtain ; For autocorrelation matrix Eigenvalue decomposition is performed to obtain the eigenvalue diagonal matrix b and the eigenvector W, specifically including: Let the signal matrix be... Based on the characteristics of OFDM signals, the signal matrix The rank p is the number of subcarriers; Perform eigenvalue decomposition on the signal matrix S to obtain the eigenvalue diagonal matrix a and eigenvector Q of the signal matrix S: ， These are the characteristic values ​​of a power line carrier signal when there is no noise. For autocorrelation matrix Perform eigenvalue decomposition to obtain the autocorrelation matrix. eigenvalue diagonal matrix b and eigenvector W: ， These are characteristic values ​​of noise; The largest values ​​in the eigenvalue diagonal matrix b are selected to form an array C. The number of data points in array C is a blind estimate of the number of subcarriers in the received power line carrier signal. Specifically, this includes: Steps 2-3 include: characteristic values ​​of the power line carrier signal when there is no noise. Eigenvalues ​​of noise A large value indicates a large impact on the autocorrelation matrix. Normalize the eigenvalue diagonal matrix b, and select the largest values ​​from it to form an array. The number of data in array C is the blind estimate of the number of subcarriers of the received power line carrier signal. The number of subcarriers in all power line carrier protocols is adapted based on the blindly estimated number of subcarriers, and the one that is closest to the blindly estimated number of subcarriers is determined as the number of subcarriers of the power line carrier signal.

5. A blind identification system for power line carrier signals based on OFDM signal characteristics according to claim 4, characterized in that, The OFDM blind estimation module further includes a signal center frequency blind estimation unit, which is used to estimate the signal center frequency based on the autocorrelation matrix. Effective subcarrier space vector array Corresponding to subcarrier frequency points The correlation of the vectors is used to calculate the center frequency of the signal, specifically including: Taken from the correlation matrix The vectors corresponding to the feature values ​​in array C from the feature vector W form the effective subcarrier space vector array. ; Will Divide into L equal parts, corresponding to Divide the L frequency points into equal parts and obtain an array. ;in The corresponding frequency point is Where FS is the signal sampling frequency, and v represents the frequency index. ; Obtain the angular frequency vector array corresponding to all subcarriers from the array F_list. , where i represents an imaginary number; Effective subcarrier space vector array Angular frequency vector array corresponding to all subcarriers Multiply to obtain an array This array has a size of p rows and L columns; Add the numbers in each column of array S1 to obtain the effective subcarrier space vector and the correlation value array S2 of all subcarriers. The size of array S2 is 1 row and L columns. Sort the absolute values ​​of array S2 in descending order, and then sort array F_list according to the same sorting rule. Given the first p numbers, obtain the F values ​​from the array F_list corresponding to the largest p numbers in array S2, and form an array. ; For arrays Calculate the average value to obtain the blind estimate of the center frequency point. The center frequency point of all power line carrier protocols is adapted based on the blindly estimated center frequency point, and the center frequency point that is closest to the blindly estimated center frequency point is determined as the center frequency point of the power line carrier signal.

6. A blind identification system for power line carrier signals based on OFDM signal characteristics according to claim 5, characterized in that, The OFDM blind estimation module further includes a subcarrier spacing blind estimation unit, which is used to estimate the subcarrier frequency point correspondence. The subcarrier spacing is obtained by calculating the mid-vector position, specifically including: [the following is unclear and likely incomplete: "for arrays"] Sort by size from smallest to largest to obtain ; Obtain the ascending order of the effective subcarrier positions; Calculate array - For arrays The average value is used to obtain the blind estimate of the subcarrier spacing.

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