A method for identifying physical layer scrambling code parameters of satellite digital broadcast television signals

Abstract

The present invention discloses a method for identifying physical layer scrambling code parameters of satellite digital broadcasting and television signals. The present invention first pre-sets data storage space RAM and scrambling code storage space ROM in a receiver chip, stores a check matrix in the ROM, and obtains an orthogonal IQ signal after demodulating the satellite signal. The soft information of the orthogonal IQ signal is calculated and stored in the RAM. The position information of the check node and the data node in the ROM is read, and the soft information of the corresponding position is read and placed in the data node position of the iterative calculation unit. After the check node and the data node are updated, a hard decision of the data is performed to obtain a one-dimensional matrix, and a check equation is calculated. If the check equation is 0 during the iteration process, the corresponding one-dimensional matrix is ​​the output scrambling code parameter, otherwise the one-dimensional matrix corresponding to the last iteration is used as the output scrambling code parameter. The method of the present invention does not need to strictly specify that there must be a pilot or an empty frame in the frame signal, and has a wider range of applications.

Description

Technical Field

[0001] The invention belongs to the field of communication technology, in particular to the field of digital satellite television broadcasting technology, and specifically relates to a method for identifying physical layer scrambling code parameters of satellite digital broadcasting television signals, and identifies the initial value of the scrambling code of a target satellite signal source. Background Art

[0002] In digital satellite television broadcasting applications, it is inevitable that two or more satellites will simultaneously transmit different signals using the same frequency band, which will inevitably lead to co-channel interference (CCI). Alternatively, signals from the same satellite with different polarization directions on the same frequency band, due to the pseudo-orthogonality of the receiving antenna, can interfere with each other, which is also a form of CCI. Co-channel interference is a common problem in existing digital communication systems. DVB-S2 / S2X, Europe's second-generation satellite digital television transmission standard, uses intra-frame scrambling to mitigate the sudden effects of CCI. This scrambling technology can generally resolve both sudden CCI and continuous narrowband CCI by matching the target signal while whitening the interfering signal. This is a common measure used to improve system robustness.

[0003] For DVB-S2 / S2X's anti-co-channel interference method, DVB-S2 / S2X uses a fixed-structure scrambling code generator and a given scrambling code initial value n, which has a fixed value range of 0≤n≤262141. Using different scrambling code initial values ​​can produce different random number sequences. A certain n corresponds to a certain known random sequence. Figure 1 As shown in the figure, the target data is scrambled using a scrambling code random number sequence and then sent to the air interface. Due to the presence of interference signals in the air interface, the signal received by the receiver is the sum of the scrambled target data and the interference signal. Descrambling the received signal at the receiver can restore the target signal and whiten the interference signal. However, if the initial scrambling code value of the target signal is unknown, the scrambling code random sequence cannot be accurately obtained, making it impossible to correctly descramble the target data and recover the target data at the sender.

[0004] In the case of unknown scrambling code initial value, the initial value of the scrambling code random sequence is recovered based on the received interfered signal, which is called the scrambling code initial value identification method. In the scrambling code initial identification method, since the generator polynomial is known, the simplest method is to brute force the correlation and make peak judgment. However, this method needs to calculate 2 in DVB-S2 / S2X. 18-1 calculation, which is obviously difficult to achieve. Patent CN106330800B proposes a fast physical layer scrambling code parameter search method based on pilot symbols, but this method is only applicable to the case where there are pilot symbols and cannot be used when there are no pilots. Patent CN106330396B proposes a fast physical layer scrambling code parameter search method based on padded frames. Its defect is the same as that of patent CN106330800B: that is, it is also ineffective when there are no padded frames. Patent CN103560863B proposes a pseudo-random scrambling code identification method. This method identifies the initial state of the scrambling code based on convolution correlation. Although it solves the problem of identifying the initial value of the scrambling code in the absence of known data, the storage complexity of the algorithm is greatly increased due to the conversion to a convolutional code. Therefore, there are problems such as high chip implementation complexity and high chip cost. Ultimately, it is difficult to be widely used in civilian radio and television receivers. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for identifying physical layer scrambling code parameters of satellite digital broadcast television signals, so as to solve the problem of identifying the initial value of the scrambling code of the target satellite signal source without the assistance of pilot signals or empty frames.

[0006] The present invention specifically is:

[0007] Step (1) Preset the data storage space RAM and the scrambling code storage space ROM in the receiver chip, the two spaces are equal and less than or equal to 1Mbit;

[0008] Step (2) stores the check matrix H into the scrambling code storage space ROM, Among them, the unit array m=18,integer T≥5,F x Represents the matrixed scrambling code equation; the check matrix H is a sparse matrix of either 0 or 1, and the positions where the check matrix H is 1 are stored in the scrambling code storage space ROM. The nodes with 1 in the columns of the check matrix H are data nodes, and the nodes with 1 in the rows are check nodes;

[0009] Step (3) The receiver uses an analog-to-digital converter to collect satellite signals sent via the antenna;

[0010] Step (4) demodulates the received satellite signal, completes the timing recovery operation and the frame synchronization operation, obtains the orthogonal IQ signal, and uniformly regards it as a QPSK signal;

[0011] Step (5) Calculate the soft information of the orthogonal IQ signal where u n The nth data of the signal sent by the satellite, y n is the nth data in the current frame of the received satellite signal, P(u n =0|yn ) is received y n Under the condition u n =0 probability, P(u n =1|y n ) is received y n Under the condition u n =1 probability;

[0012] Step (6) converts the soft information L(u n )=(LLR(I n ),LLR(Q n )) are stored in the data storage space RAM in sequence;

[0013] Step (7) The iterative calculation unit first reads the position information of the check node and the data node in the scrambling code storage space ROM, and then reads the soft information of the corresponding position in the data storage space RAM according to the position information, and puts it into the data node position of the iterative calculation unit;

[0014] Step (8) Check node update: The iterative calculation unit calculates the data information to be placed in the check node based on the soft information of all data node positions. p represents the pth data node, q and q′ represent the qth and q′th check nodes, Q is the check node set, Q(p) is the check node set connected to the pth data node, p→q means that the pth data node sends its own information to the qth check node; function x is a variable, tanh(·) represents the hyperbolic tangent; p→q (u q ) is placed in the qth check node position in the iterative calculation unit to replace the original information at that position;

[0015] Step (9) Data node update: The iterative calculation unit calculates the data information to be put into the data node based on the data information of the check node position. p′ represents the p′th data node, P is the set of data nodes, P(q) is the set of data nodes connected to the qth check node, and q→p means that the qth check node sends its own information to the pth data node;

[0016] Step (10) Data hard decision: P n represents the set of check nodes connected to the nth data node, m represents the mth check node; if λ n (u n )≥0, then determine u n is 1, otherwise it is judged that u n is 0, and we get a one-dimensional matrix U=[u1,u2,…,u 36 ], n=1,2,…,36;

[0017] Step (11) convert the one-dimensional matrix U = [u1,u2,…,u N ] is multiplied by the check matrix H to obtain the check equation HU Τ , Τ represents transpose;

[0018] Step (12) Repeat steps (8) to (11). If HU Τ = 0, then exit the iteration, the corresponding one-dimensional matrix U = [u1,u2,…,u 36 ] is the physical layer scrambling code parameter of the identified satellite digital broadcasting television signal; if the maximum number of iterations is reached and no HU Τ = 0, then the one-dimensional matrix corresponding to the last iteration is U = [u1,u2,…,u 36 ] as the physical layer scrambling code parameters of the identified satellite digital broadcasting television signal.

[0019] The method of the present invention does not require the use of pilot signals and empty frames to assist in hypothetical trials, but rather regards the scrambling process as a process of passing through a binary symmetric channel (BSC) after a known linear shift feedback register code (LSFRC). The method of the present invention proposes to use a bit soft information demapping method to extract the soft information of each bit, and then use the LFSR generator structure to construct a set of codewords of a specified length, and finally use the confidence propagation method to iteratively solve the initial scrambling code value. After obtaining the initial scrambling code value, the scrambling code sequence is re-manufactured using a known scrambling code generator to complete the normal descrambling operation. The method of the present invention has a wider range of applications and does not require strict specification that there must be a pilot signal or an empty frame in the frame signal; even if there is no pilot signal in an entire frame and it is all payload data, the method of the present invention can also be used to identify the physical layer scrambling code parameters of the satellite digital broadcasting and television signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the scrambling code generation method for DVB-S2 / S2X;

[0021] Figure 2 is a flow chart of the method of the present invention;

[0022] Figure 3 Schematic diagram of the soft information extraction method. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described below with reference to the accompanying drawings.

[0024] Figure 1This article explains the DVB-S2 / S2X scrambling code generation method. A shift register (LFSR) cyclically generates a pseudo-random sequence, which is then multiplied with a random TV signal after conversion. The sequence then passes through a digital-to-analog converter (DAC) and a radio frequency converter, and is transmitted via an antenna into the sky. After being forwarded by a satellite, it is distributed to user receivers. The receiver requires the correct initial scrambling code value to decipher the random signal source. The following steps are performed in the receiver to identify the physical layer scrambling code.

[0025] like Figure 2 As shown, a method for identifying physical layer scrambling code parameters of satellite digital broadcast television signals has the following specific process:

[0026] Step (1) A data storage space RAM and a scrambling code storage space ROM are preset in the receiver chip, and the two spaces are equal and less than or equal to 1 Mbit.

[0027] Step (2) stores the check matrix H into the scrambling code storage space ROM, Among them, the unit array m=18,integer T≥5,F x The matrix scrambling equation is represented by 1+x. 7 +x 18 , the scrambling equation of the Q channel signal is 1+x 5 +x 7 +x 10 +x 18 , x is a variable; the check matrix H is a sparse matrix of either 0 or 1, and the positions where the check matrix H is 1 are stored in the scrambling code storage space ROM.

[0028] The first column of the check matrix H is the scrambling code matrix, and the remaining columns constitute the coefficient check matrix. Nodes with a 1 in the columns of the check matrix H are data nodes, and nodes with a 1 in the rows are check nodes. That is, nodes with a 1 are both data nodes and check nodes. Storing the check matrix H in the scrambling code storage space ROM stores the positions of the check nodes and data nodes in the check matrix H in the scrambling code storage space ROM.

[0029] Step (3) The receiver uses an analog-to-digital converter to collect satellite signals sent via the antenna.

[0030] Step (4) using automatic gain control (AGC) technology to control the amplitude of the received satellite signal so that it stabilizes at a fixed signal power level;

[0031] Step (5) uses timing recovery technology to correct the timing deviation of the received satellite signal to obtain a satellite frame signal;

[0032] Step (6) completing the frame synchronization operation according to the frame structure characteristics of the satellite frame signal to obtain an orthogonal IQ signal. The orthogonal IQ signal may be one of QPSK, 8PSK, 16APSK, 32APSK, 64APSK, 128APSK, and 256APSK constellations, and is uniformly regarded as a QPSK signal;

[0033] Steps (3) to (6) are existing technologies used in traditional satellite receivers.

[0034] Step (7) is as follows Figure 3 , calculate the soft information of the orthogonal IQ signal where u n The nth data of the signal sent by the satellite, y n is the nth data in the current frame of the received satellite signal, P(u n =0|y n ) is received y n Under the condition u n =0 probability, P(u n =1|y n ) is received y n Under the condition u n =1 probability; soft information L(u n )=(LLR(I n ),LLR(Q n ))Including I-channel signal soft information and Q-channel signal soft information I and Q represent the current signal values ​​of I and Q channels respectively, σ 2 Indicates the noise variance of the current channel.

[0035] Step (8) converts the soft information L(u n )=(LLR(I n ),LLR(Q n )) are stored in the data storage space RAM in sequence.

[0036] In step (9), the iterative calculation unit first reads the position information of the check node and the data node in the scrambling code storage space ROM, and then reads the soft information of the corresponding position in the data storage space RAM according to the position information, and puts it into the data node position of the iterative calculation unit.

[0037] Step (10) Check node update: The iterative calculation unit calculates the data information to be placed in the check node based on the soft information of all data node positions. p represents the pth data node, q and q′ represent the qth and q′th check nodes, Q is the check node set, Q(p) is the check node set connected to the pth data node, p→q means that the pth data node sends its own information to the qth check node; function x is a variable, tanh(·) represents the hyperbolic tangent; p→q (u q ) is placed in the qth check node position in the iterative calculation unit to replace the original information at that position.

[0038] Step (11) Data node update: The iterative calculation unit calculates the data information to be put into the data node based on the data information of the check node position. p′ represents the p′th data node, P is the set of data nodes, P(q) is the set of data nodes connected to the qth check node, and q→p means that the qth check node sends its own information to the pth data node.

[0039] Step (12) Data hard decision: P n represents the set of check nodes connected to the nth data node, m represents the mth check node; if λ n (u n )≥0, then determine u n is 1, otherwise it is judged that u n is 0, and we get a one-dimensional matrix U=[u1,u2,…,u 36 ], n=1,2,…,36.

[0040] Step (13) convert the one-dimensional matrix U = [u1,u2,…,u N ] is multiplied by the check matrix H to obtain the check equation HU Τ , Τ represents transpose;

[0041] Step (14) Repeat steps (10) to (13). If HU Τ = 0, then exit the iteration, the corresponding one-dimensional matrix U = [u1,u2,…,u 36 ] is the physical layer scrambling code parameter of the identified satellite digital broadcasting television signal; if the maximum number of iterations is reached and no HU Τ = 0, then the one-dimensional matrix corresponding to the last iteration is U = [u1,u2,…,u 36 ] as the physical layer scrambling code parameters of the identified satellite digital broadcasting television signal.

[0042] It should be understood that the above examples are merely illustrative of the present invention, rather than limiting the present invention. Any inventions that do not exceed the essential spirit of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for identifying physical layer scrambling code parameters of satellite digital broadcast television signals, characterized by: Step (1) Preset the data storage space RAM and the scrambling code storage space ROM in the receiver chip, the two spaces are equal and less than or equal to 1Mbit; Step (2) stores the check matrix H into the scrambling code storage space ROM, Among them, the unit array m=18,integer T≥5,F x Represents the matrixed scrambling code equation; the check matrix H is a sparse matrix of either 0 or 1, and the positions where the check matrix H is 1 are stored in the scrambling code storage space ROM. The nodes with 1 in the columns of the check matrix H are data nodes, and the nodes with 1 in the rows are check nodes; Step (3) The receiver uses an analog-to-digital converter to collect satellite signals sent via the antenna; Step (4) demodulates the received satellite signal, completes the timing recovery operation and the frame synchronization operation, obtains the orthogonal IQ signal, and uniformly regards it as a QPSK signal; Step (5) Calculate the soft information of the orthogonal IQ signal where u n The nth data of the signal sent by the satellite, y n is the nth data in the current frame of the received satellite signal, P(u n =0|y n ) is received y n Under the condition u n =0 probability, P(u n =1|y n ) is received y n Under the condition u n =1 probability; Step (6) converts the soft information L(u n )=(LLR(I n ),LLR(Q n )) are stored in the data storage space RAM in sequence; Step (7) The iterative calculation unit first reads the position information of the check node and the data node in the scrambling code storage space ROM, and then reads the soft information of the corresponding position in the data storage space RAM according to the position information, and puts it into the data node position of the iterative calculation unit; Step (8) Check node update: The iterative calculation unit calculates the data information to be placed in the check node based on the soft information of all data node positions. p represents the pth data node, q and q′ represent the qth and q′th check nodes, Q is the check node set, Q(p) is the check node set connected to the pth data node, p→q means that the pth data node sends its own information to the qth check node; function x is a variable, tanh(·) represents the hyperbolic tangent; p→q (u q ) is placed in the qth check node position in the iterative calculation unit to replace the original information at that position; Step (9) Data node update: The iterative calculation unit calculates the data information to be put into the data node based on the data information of the check node position. p′ represents the p′th data node, P is the set of data nodes, P(q) is the set of data nodes connected to the qth check node, and q→p means that the qth check node sends its own information to the pth data node; Step (10) Data hard decision: P n represents the set of check nodes connected to the nth data node, m represents the mth check node; if λ n (u n )≥0, then determine u n is 1, otherwise it is judged that u n is 0, and we get a one-dimensional matrix U=[u1,u2,…,u 36 ], n=1,2,…,36; Step (11) convert the one-dimensional matrix U = [u1,u2,…,u N ] is multiplied by the check matrix H to obtain the check equation HU Τ , Τ represents transpose; Step (12) Repeat steps (8) to (11). If HU Τ = 0, then exit the iteration, the corresponding one-dimensional matrix U = [u1,u2,…,u 36 ] is the physical layer scrambling code parameter of the identified satellite digital broadcasting television signal; if the maximum number of iterations is reached and no HU Τ = 0, then the one-dimensional matrix corresponding to the last iteration is U = [u1,u2,…,u 36 ] as the physical layer scrambling code parameters of the identified satellite digital broadcasting television signal.

2. The method for identifying physical layer scrambling code parameters of a satellite digital broadcast television signal according to claim 1, wherein: The scrambling equation F x In the example, the scrambling equation of the I-channel signal is 1+x 7 +x 18 , the scrambling equation of the Q channel signal is 1+x 5 +x 7 +x 10 +x 18 , x is a variable.

3. The method for identifying physical layer scrambling code parameters of a satellite digital broadcast television signal according to claim 1, wherein: The orthogonal IQ signal described in step (4) is one of the constellations of QPSK, 8PSK, 16APSK, 32APSK, 64APSK, 128APSK, and 256APSK.

4. The method for identifying physical layer scrambling code parameters of a satellite digital broadcast television signal according to claim 1, wherein: The soft information L(u n )=(LLR(I n ),LLR(Q n ))Including I-channel signal soft information and Q-channel signal soft information I and Q represent the current signal values ​​of I and Q channels respectively, σ 2 Indicates the noise variance of the current channel.

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