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

Abstract

The invention discloses a power line carrier signal blind identification method and system based on OFDM signal characteristics, and the method comprises the steps: 1, receiving a power line carrier signal, and modulating the power line carrier signal through OFDM; step 2, blind estimation is carried out on the subcarrier number, the signal center frequency point and the subcarrier interval of the power line carrier signal, and prior information of the power line carrier signal is obtained; and step 3, decoding the received power carrier signal according to the prior information of the power carrier signal. According to the method and the system, the subcarrier number, the signal center frequency point and the subcarrier interval of the power line carrier are estimated according to the characteristic value of the OFDM modulation signal under the condition of not knowing protocol information, so that the protocol and modulation parameters of the power line carrier are determined, convenience is provided for establishing a link between an RX end and a TX end, and the link efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power line carrier communication, and in particular to a method and system for blindly identifying power line carrier signals based on OFDM signal characteristics. Background Art

[0002] With the continuous improvement of power automation and intelligence, power carrier communication technology has developed rapidly. In this process, the power carrier protocol has always been used as a technical standard and has undergone multiple stages of development and evolution. In the process of evolution, many standards and protocols have been generated, including domestic and foreign, high-speed, medium-speed and low-speed. Before the power carrier establishes communication between the receiving end RX and the transmitting end TX, the receiver and the sender do not know what power carrier protocol the other party is using. Therefore, it is necessary to poll and try various power carrier protocol modes to match according to various protocols, and try to decode to establish a link. Due to the wide variety of power carrier protocols, this not only wastes time to establish a connection, but is also prone to errors. When encountering unrecognizable signals, it will be more confused, which brings difficulties to station survey 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 method and system for blind recognition of power carrier signals based on OFDM signal characteristics in view of the deficiencies in the prior art.

[0004] In order to solve the above technical problems, in the first aspect, a method for blindly identifying a power carrier signal based on OFDM signal characteristics is disclosed, comprising:

[0005] Step 1, receiving a power carrier signal, wherein the power carrier signal is modulated by OFDM;

[0006] Step 2, blindly estimating the number of subcarriers, the signal center frequency and the subcarrier spacing of the power carrier signal to obtain prior information of the power carrier signal;

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

[0008] Further, in step 2, blindly estimating the number of subcarriers of the power carrier signal includes:

[0009] Step 2-1, calculate the autocorrelation matrix R of the power carrier signal xx ;

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

[0011] Step 2-3, take the numbers with large values ​​in the eigenvalue diagonal array b to form an array C, and the number of data in array C is the blind estimate of the number of subcarriers of the received power carrier signal.

[0012] Further, step 2-1 includes: recording the received power carrier signal Y(i)=S T (i)+u(i), i∈{1,2,…,L*m}, L*m represents the data sampling length; S T (i) represents the transmitted signal, u(i) represents the noise. According to the characteristics of the power carrier and the amount of calculation, Y(i) is divided into m groups of length L, where L is greater than the maximum number of subcarriers of all power 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} is the signal vector group, X u ={x u1 ,x u2 ,x u3 ,…,x um} is a noise vector group;

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

[0014]

[0015] Since the signal and noise are uncorrelated, we get

[0016]

[0017] Thus we get

[0018] Further, step 2-2 includes: recording the signal matrix According to 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] It is the characteristic value of the power carrier signal when there is no noise;

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

[0024] R xx W=bW

[0025]

[0026] is the characteristic value of the noise.

[0027] Further, step 2-3 includes: the characteristic value of the power carrier signal when there is no noise Eigenvalue of noise The value of is large, the autocorrelation matrix R xx Normalize the eigenvalue diagonal matrix b and take the numbers with large values ​​to form an array The number of data in array C is a blind estimate of the number of subcarriers of the received power carrier signal. The number of subcarriers in all power carrier protocols is adapted according to the blind estimated number of subcarriers, and the one closest to the blind estimated number of subcarriers is determined as the number of subcarriers of the power carrier signal.

[0028] Further, in step 2, blindly estimating the signal center frequency of the power carrier signal includes:

[0029] Take the autocorrelation matrix R xx The vectors corresponding to the eigenvalues ​​in array C in the eigenvector W of compose the effective subcarrier space vector array W c =[r1,r2,r3,…,r p ];

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

[0031] According to the array F_list, the angular frequency vector array S0=e corresponding to all subcarriers is obtained. 2*F_list*i*(0～L-1) , where i represents an imaginary number.

[0032] The effective subcarrier space vector array W c Multiply the angular frequency vector array S0 corresponding to all subcarriers to obtain array S1 = W c *S0, the size of this array is p rows and L columns;

[0033] Add the numbers of 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 absolute values ​​of array S2 from large to small, and array F_list is also sorted according to this rule. Take the first p numbers of F_list, and obtain the F value in array F_list corresponding to the largest p numbers in array S2, forming array FX_list = [FX1, FX2, FX3, ..., FX p ];

[0035] Calculate the average value of the array FX_list to obtain the center frequency blind estimation FX center =mean(FX_list), adapt the center frequencies of all power carrier protocols according to the blind estimated center frequency, and determine the center frequency closest to the blind estimated center frequency as the center frequency of the power carrier signal.

[0036] Generally, the interference on power lines is quite serious, and the signal-to-noise ratio is not very ideal. The autocorrelation calculation of the received signal Y(i) is performed to obtain the signal subspace W of the effective subcarrier c , W c There is a good correlation with the vector of the corresponding effective subcarrier in S0, W c The vector correlation with the corresponding invalid subcarrier in S0 is relatively poor, so the position of the valid subcarrier in Y(i) can be estimated. When the signal-to-noise ratio of the received Y(i) signal is less than 0db, in this case, when the Y(i) sampling length is increased and the m value is relatively large, the effective subcarrier position of the Y(i) received signal can be distinguished more ideally. Therefore, the center frequency point is estimated based on the effective subcarrier position. The effective information of the effective subcarrier position provides the necessary conditions for the next step of estimating the subcarrier spacing, making the estimation more accurate.

[0037] Further, in step 2, blindly estimating the subcarrier spacing of the power carrier signal includes:

[0038] For array FX_list = [FX1, FX2, FX3, ..., FX p ] to sort from small to large, and obtain FXX_list = [FXX1, FXX2, FXX3, ..., FXX p ]; get the effective subcarrier positions sorted from small to large.

[0039] Calculate the array FSUB_list = [FXX2, FXX3, ..., FXX p ]-[FXX1,FXX2,FXX3,…,FXX p-1 ], average the array FSUB_list to obtain the blind estimate of the subcarrier spacing.

[0040] With the blind estimation values ​​of the number of subcarriers, center frequency and carrier spacing, it is possible to traverse the carrier communication protocols, find the best matching protocol and configuration, and obtain the parameters of the signal received on the power line.

[0041] In the second aspect, a power carrier signal blind recognition system 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-end signal receiving module is used to receive a power carrier signal, and the power carrier signal is modulated by OFDM;

[0043] 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 carrier signal to obtain prior information of the power carrier signal;

[0044] The RX-OFDM baseband signal decoding module is used to decode the received power carrier signal according to 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 according to the autocorrelation matrix R of the power carrier signal. xx Calculate and obtain the number of subcarriers;

[0047] The signal center frequency blind estimation unit is used to estimate the center frequency of the signal according to the autocorrelation matrix R xx The effective subcarrier space vector array W c The correlation between the subcarrier frequency and the vector in F_list is used to calculate the center frequency of the signal;

[0048] The subcarrier spacing blind estimation unit is used to calculate and obtain the subcarrier spacing according to 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 according to the autocorrelation matrix R of the power carrier signal. xx Calculating the number of subcarriers includes:

[0050] Calculate the autocorrelation matrix R of the power carrier signalxx ;

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

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

[0053] Beneficial effect: The blind identification method of power carrier signal based on OFDM signal characteristics provided by the present application can obtain some information of the communication protocol by blindly estimating the number of carriers, center frequency and subcarrier spacing of OFDM signals received by the power carrier based on the characteristic value of the OFDM modulated signal without knowing the protocol information. Based on this information, the RX end selectively tries to establish a link with the TX to improve the link efficiency. When encountering unclear signals on the power carrier line, corresponding information can also be given, which brings convenience to the station survey and maintenance of the communication system and improves the efficiency of station survey and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0055] Figure 1 The normalized eigenvalues ​​of the OFDM modulated power carrier signal with an SNR of 5 db are sorted from large to small.

[0056] Figure 2 The size arrangement of the normalized S2 array values ​​when L is 1024 and SNR is 5db.

[0057] Figure 3 A schematic diagram of the structure of a power carrier signal blind recognition system based on OFDM signal characteristics provided in an embodiment of the present application.

[0058] Figure 4 A schematic diagram of the structure of an OFDM blind estimation module in a power carrier signal blind recognition system based on OFDM signal characteristics provided in an embodiment of the present application. DETAILED DESCRIPTION

[0059] The embodiments of the present invention will be described below in conjunction with the accompanying drawings.

[0060] Blind recognition of OFDM communication signals on the power carrier line enables the RX end to have some protocol information on the TX end before the communication link is established, which facilitates the establishment of a link between the RX end and the TX end and improves the success rate. Blind recognition of OFDM signals on the power carrier line can also provide station survey and maintenance information when the RX and TX cannot establish a link, thereby improving the efficiency of station survey and maintenance.

[0061] The purpose of the present invention is to estimate the number of subcarriers, signal center frequency and subcarrier spacing of the power carrier according to the characteristic value of the OFDM modulated signal without knowing the protocol information, so as to determine the protocol and modulation parameters of the power carrier. There is no need to poll and try various possible communication protocols. The TX end and the RX end of the communication directly establish a link. When encountering unclear signals on the power carrier line, signal information can also be given, which brings convenience to the station survey and maintenance of the power carrier communication system. It can be applied to application scenarios such as smart grid, remote meter reading system, smart home, industrial control, on-site operation and maintenance test of power carrier communication system and station survey of power carrier communication environment.

[0062] The first embodiment of the present application discloses a method for blindly identifying a power carrier signal based on OFDM signal characteristics, comprising: step 1, receiving a power carrier signal, wherein the power carrier signal is modulated by OFDM;

[0063] Step 2, blindly estimating the number of subcarriers, the signal center frequency and the subcarrier spacing of the power carrier signal to obtain prior information of the power carrier signal;

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

[0065] Step 2-1, calculate the autocorrelation matrix R of the power carrier signal xx ;

[0066] The power carrier TX end transmits the signal, and the RX end receives the signal. The received signal can be expressed as:

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

[0068] i∈{1,2,…,L*m}, L*m represents the data sampling length. S T (i) represents the transmitted signal, u(i) represents the noise, and Y(i) represents the received signal. According to the characteristics of the power carrier and the amount of calculation, Y(i) is divided into m groups of length L, where L is greater than the maximum number of subcarriers of all power 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} is the signal vector group, X u ={x u1 ,x u2 ,x u3 ,…,x um} is a noise vector group. Considering the amount of calculation, L cannot be too large. In this embodiment, L can be 1024, 2048 or 4096, and m is in the range of 8 to 2048.

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

[0070]

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

[0072]

[0073] Thus we get

[0074]

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

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

[0077] SQ=aQ

[0078]

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

[0080] Autocorrelation matrix For the autocorrelation matrix R xx By performing eigenvalue decomposition, we can obtain the autocorrelation matrix R xx The eigenvalue diagonal matrix b and eigenvector W

[0081] R xxW=bW

[0082]

[0083] is the characteristic value of the noise.

[0084] Step 2-3, take the numbers with large values ​​in the eigenvalue diagonal array b to form an array C, and the number of data in array C is the blind estimate of the number of subcarriers of the received power carrier signal.

[0085] Eigenvalues ​​of power carrier signal without noise The value is greater than the characteristic value of the noise The value of is large. For the autocorrelation matrix R xx Normalize the eigenvalue diagonal matrix b, and take the numbers with large values ​​(0.7 can be used as the value threshold) in the normalized eigenvalue diagonal matrix to form an array The number of data in array C is a blind estimate of the number of subcarriers of the received power carrier signal. The number of subcarriers in all power carrier protocols is adapted according to the blind estimated number of subcarriers, and the one closest to the blind estimated number of subcarriers is determined as the number of subcarriers of the power carrier signal.

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

[0087] Take the autocorrelation matrix R xx The vectors corresponding to the eigenvalues ​​in array C in the eigenvector W of compose the effective subcarrier space vector array W c =[r1,r2,r3,…,r p ];

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

[0089] According to the array F_list, the angular frequency vector array S0=e corresponding to all subcarriers is obtained. 2*F_list*i*(0～L-1) , where i represents an imaginary number.

[0090] The effective subcarrier space vector array W c Multiply the angular frequency vector array S0 corresponding to all subcarriers to obtain array S1 = W c *S0, the size of this array is p rows and L columns;

[0091] Add the numbers of 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 absolute values ​​of array S2 from large to small, and array F_list is also sorted according to this rule. Take the first p numbers of F_list, and obtain the F value in array F_list corresponding to the largest p numbers in array S2, forming array FX_list = [FX1, FX2, FX3, ..., FX p ];

[0093] Calculate the average value of the array FX_list to obtain the center frequency blind estimation FX center =mean(FX_list), adapt the center frequencies of all power carrier protocols according to the blind estimated center frequency, and determine the center frequency closest to the blind estimated center frequency as the center frequency of the power carrier signal.

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

[0095] For array FX_list = [FX1, FX2, FX3, ..., FX p ] are sorted from small to large, and FXX_list = [FXX1, FXX2, FXX3, ..., FXX p ]. Get the order of effective subcarrier positions from small to large. Then calculate the array FSUB_list = [FXX2, FXX3, ..., FXX p ]-[FXX1,FXX2,FXX3,…,FXX p-1 ], and average the array FSUB_list to get the blind estimate of the subcarrier spacing.

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

[0097] Figure 1 The figure shows the normalized eigenvalues ​​of the OFDM modulated power carrier signal Y(i) with an SNR of 5db, sorted from large to small. It can be seen that the first 191 eigenvalues ​​are significantly larger than the latter ones. From the figure, the number of subcarriers of the OFDM signal is blindly estimated to be 191. Figure 2 It is the normalized S2 array value size arrangement when L is 1024 and SNR is 5db. The center frequency and subcarrier spacing can be calculated.

[0098] The second embodiment of the present application discloses a power carrier signal blind recognition system 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-end signal receiving module is used to receive a power carrier signal, and the power carrier signal is 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 carrier signal to obtain the prior information of the power carrier signal, specifically, 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 according to the autocorrelation matrix R of the power carrier signal. xx Calculate the number of subcarriers, specifically, including: calculate the autocorrelation matrix R of the power carrier signal xx ; For the autocorrelation matrix R xx Perform eigenvalue decomposition to obtain the eigenvalue diagonal matrix b and the eigenvector W; take the numbers with larger values ​​in the eigenvalue diagonal matrix b to form an array C, and the number of data in the array C is a blind estimate of the number of subcarriers of the received power carrier signal.

[0102] The signal center frequency blind estimation unit is used to estimate the center frequency of the signal according to the autocorrelation matrix R xx The effective subcarrier space vector array W c The correlation between the subcarrier frequency and the vector in F_list is used to calculate the center frequency of the signal;

[0103] The subcarrier spacing blind estimation unit is used to calculate and obtain the subcarrier spacing according to 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 according to the prior information of the power carrier signal.

[0105] Figure 3 It is a block diagram of the entire power 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 an OFDM baseband signal, and the TX end signal transmission module is used to send the OFDM baseband signal to the RX end through the power line.

[0106] 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 based on the OFDM estimation information obtained by the blind estimation module. There is no need to poll all possible protocol modes of the power carrier protocol to find a matching protocol mode.

[0107] By blindly identifying the OFDM carrier signal of the power carrier line, the number of subcarriers, center frequency and subcarrier spacing of the OFDM signal can be obtained. Based on this information, the prior information of the OFDM signal can be obtained. When TX and RX are not linked and the RX side does not have any information from the TX side, RX can infer the protocol of the TX side based on these blind identification information and various protocols of power carrier communication. Therefore, RX can directly establish a link with the TX side based on the inferred protocol. RX does not need various protocol polling matching to establish a link with the TX side.

[0108] The power carrier signal blind identification system based on OFDM signal characteristics also includes a station survey information display module, which is used to receive the number of subcarriers, signal center frequency and subcarrier spacing information of the power carrier signal sent by the OFDM blind estimation module. When encountering unclear signals on the power carrier line, the system can also provide corresponding information, which brings convenience to the station survey and maintenance of the communication system and improves the efficiency of station survey and maintenance.

[0109] In a specific implementation, the present application provides a computer storage medium and a corresponding data processing unit, wherein the computer storage medium can store a computer program, and when the computer program is executed by the data processing unit, the invention content of a method for blindly identifying a power carrier signal based on OFDM signal characteristics provided by the present invention and some or all of the steps in each embodiment can be run. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0110] Those skilled in the art can clearly understand that the technical solutions in the embodiments of the present invention can be implemented by means of computer programs and their corresponding general hardware platforms. Based on this understanding, the technical solutions in the embodiments of the present invention are essentially or partly contributed to the prior art can be embodied in the form of a computer program, i.e., a software product, which can be stored in a storage medium and includes several instructions for enabling a device including a data processing unit (which can be a personal computer, a server, a single-chip microcomputer, a MUU or a network device, etc.) to execute the methods described in various embodiments of the present invention or certain parts of the embodiments.

[0111] The present invention provides a method and system for blind identification of power carrier signals based on OFDM signal characteristics. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented using existing technologies.

Claims

1. A blind recognition method for power carrier signals based on OFDM signal characteristics, characterized in that: include: Step 1, receiving a power carrier signal, wherein the power carrier signal is modulated by OFDM; Step 2, blindly estimating the number of subcarriers, the signal center frequency and the subcarrier spacing of the power carrier signal to obtain prior information of the power carrier signal; Step 3: Decode the received power carrier signal according to the prior information of the power carrier signal.

2. A method for blindly identifying power carrier signals based on OFDM signal characteristics according to claim 1, characterized in that: In step 2, blindly estimating the number of subcarriers of the power carrier signal includes: Step 2-1, calculate the autocorrelation matrix R of the power carrier signal xx ; Step 2-2, the autocorrelation matrix R xx Perform eigenvalue decomposition to obtain the eigenvalue diagonal matrix b and eigenvector W; Step 2-3, take the numbers with large values ​​in the eigenvalue diagonal array b to form an array C, and the number of data in array C is the blind estimate of the number of subcarriers of the received power carrier signal.

3. A method for blindly identifying power carrier signals based on OFDM signal characteristics according to claim 2, characterized in that: Step 2-1 includes: record the received power carrier signal Y(i)=S T (i)+u(i), i∈{1,2,…,L*m}, L*m represents the data sampling length; S T (i) represents the transmitted signal, u(i) represents the noise. According to the characteristics of the power carrier and the amount of calculation, Y(i) is divided into m groups of length L, where L is greater than the maximum number of subcarriers of all power 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 } is the signal vector group, X u ={x u1 ,x u2 ,x u3 ,…,x um } is a noise vector group; The autocorrelation matrix R of the received power carrier signal xx for Since the signal and noise are uncorrelated, we get Thus we get 4. A method for blindly identifying power carrier signals based on OFDM signal characteristics according to claim 3, characterized in that: Step 2-2 includes: recording the signal matrix According to the characteristics of OFDM signals, the rank p of the signal matrix S 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: SQ=aQ It is the characteristic value of the power carrier signal when there is no noise; For the autocorrelation matrix R xx Perform eigenvalue decomposition to obtain the autocorrelation matrix R xx The eigenvalue diagonal matrix b and eigenvector W of : R xx W=bW is the characteristic value of the noise.

5. A method for blindly identifying power carrier signals based on OFDM signal characteristics according to claim 4, characterized in that: Step 2-3 includes: characteristic value of the power carrier signal when there is no noise Eigenvalue of noise The value of is large, the autocorrelation matrix R xx Normalize the eigenvalue diagonal matrix b and take the numbers with large values ​​to form an array The number of data in array C is a blind estimate of the number of subcarriers of the received power carrier signal. The number of subcarriers in all power carrier protocols is adapted according to the blind estimated number of subcarriers, and the one closest to the blind estimated number of subcarriers is determined as the number of subcarriers of the power carrier signal.

6. A method for blindly identifying power carrier signals based on OFDM signal characteristics according to claim 5, characterized in that: In step 2, blindly estimating the signal center frequency of the power carrier signal includes: Take the autocorrelation matrix R xx The vectors corresponding to the eigenvalues ​​in array C in the eigenvector W of compose the effective subcarrier space vector array W c =[r1,r2,r3,…,r p ]; Will Divide into L equal parts, corresponding to The average frequency points are L, and the array F_list = [F1, F2, F3, ..., F p ,F p+1 ,…,F L ];in The corresponding frequency is Where FS is the signal sampling frequency, v represents the frequency index, 1≤v≤L; According to the array F_list, the angular frequency vector array S0=e corresponding to all subcarriers is obtained. 2*F_list*i*(0～L-1) , where i represents an imaginary number; The effective subcarrier space vector array W c Multiply the angular frequency vector array S0 corresponding to all subcarriers to obtain array S1 = W c *S0, the size of this array is p rows and L columns; Add the numbers of 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 from large to small. Array F_list is also sorted according to this rule. Take the first p numbers of F_list and obtain the F value in array F_list corresponding to the largest p numbers in array S2 to form array FX_list = [FX1, FX2, FX3, ..., FX p ]; Calculate the average value of the array FX_list to obtain the center frequency blind estimation FX center =mean(FX_list), adapt the center frequencies of all power carrier protocols according to the blind estimated center frequency, and determine the center frequency closest to the blind estimated center frequency as the center frequency of the power carrier signal.

7. A method for blindly identifying power carrier signals based on OFDM signal characteristics according to claim 6, characterized in that: In step 2, blindly estimating the subcarrier spacing of the power carrier signal includes: For array FX_list = [FX1, FX2, FX3, ..., FX p ] to sort from small to large, and obtain FXX_list = [FXX1, FXX2, FXX3, ..., FXX p ]; get the order of effective subcarrier positions from small to large; Calculate the array FSUB_list = [FXX2, FXX3, ..., FXX p ]-[FXX1,FXX2,FXX3,…,FXX p-1 ], average the array FSUB_list to obtain the blind estimate of the subcarrier spacing.

8. A blind recognition system for power carrier signals based on OFDM signal characteristics, characterized in that: It includes RX signal receiving module, OFDM blind estimation module and RX-OFDM baseband signal decoding module. The RX-end signal receiving module is used to receive a power carrier signal, and the power carrier signal is modulated by OFDM; 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 carrier signal to obtain prior information of the power carrier signal; The RX-OFDM baseband signal decoding module is used to decode the received power carrier signal according to the prior information of the power carrier signal.

9. A power carrier signal blind recognition system based on OFDM signal characteristics according to claim 8, characterized in that: 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. The subcarrier number blind estimation unit is used to estimate the number of subcarriers according to the autocorrelation matrix R of the power carrier signal. xx Calculate and obtain the number of subcarriers; The signal center frequency blind estimation unit is used to estimate the center frequency of the signal according to the autocorrelation matrix R xx The effective subcarrier space vector array W c The correlation between the subcarrier frequency and the vector in F_list is used to calculate the center frequency of the signal; The subcarrier spacing blind estimation unit is used to calculate and obtain the subcarrier spacing according to the vector position in F_list corresponding to the subcarrier frequency point.

10. A power carrier signal blind recognition system based on OFDM signal characteristics according to claim 9, characterized in that: The subcarrier number blind estimation unit is based on the autocorrelation matrix R of the power carrier signal xx Calculating the number of subcarriers includes: Calculate the autocorrelation matrix R of the power carrier signal xx ; For the autocorrelation matrix R xx Perform eigenvalue decomposition to obtain the eigenvalue diagonal matrix b and eigenvector W; The numbers with the largest values ​​in the eigenvalue diagonal matrix b are taken to form an array C. The number of data in the array C is a blind estimate of the number of subcarriers of the received power carrier signal.

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