CN115580378A - Method for identifying scrambling code parameters of physical layer of satellite digital broadcast television signal - Google Patents

Abstract

The invention discloses a method for identifying scrambling code parameters of a physical layer of satellite digital broadcast television signals. The invention firstly presets a data storage space RAM and a scrambling code storage space ROM in a receiver chip, stores a check matrix into the ROM, obtains an orthogonal IQ signal after satellite signal demodulation, calculates soft information of the orthogonal IQ signal and stores the soft information into the RAM. And reading the position information of the check node and the data node in the ROM, reading the soft information of the corresponding position, and putting the soft information into the data node position of the iterative computation unit. And performing data hard decision after updating the check nodes and the data nodes to obtain a one-dimensional matrix, calculating to obtain a check equation, wherein if the check equation is 0 in the iteration process, the corresponding one-dimensional matrix is the output scrambling code parameter, and otherwise, the one-dimensional matrix corresponding to the last iteration is used as the output scrambling code parameter. The method of the invention does not need to strictly specify that the frame signal must have pilot frequency or empty frame, and has wider application range.

Description

Method for identifying scrambling code parameters of physical layer of satellite digital broadcast television signal

Technical Field

The invention belongs to the technical field of communication, particularly relates to the technical field of digital satellite television broadcasting, and particularly relates to a method for identifying scrambling code parameters of a physical layer of a satellite digital broadcasting television signal, which is used for identifying a scrambling code initial value of a target satellite signal source.

Background

In the application of digital satellite television broadcasting, it is inevitable that two or more satellites simultaneously use the same frequency band to transmit different signals, which may lead to Co-Channel interference (CCI); or the mutual interference of signals of different polarization directions of the same satellite on the same frequency band due to the pseudo-orthogonality of the receiving antenna is also one of the co-channel interference. The co-channel interference problem is widely present in existing digital communication systems. The second generation satellite digital television transmission standard DVB-S2/S2X in Europe adopts intra-frame scrambling to reduce the burst influence of same frequency interference, the scrambling technology can solve the burst same frequency interference and continuous narrow-band same frequency interference, and the principle is to whiten the same frequency interference signal while matching with the target signal. This is a common measure to improve system robustness.

For the method for resisting the same frequency interference of DVB-S2/S2X, the DVB-S2/S2X uses a scrambling code generator with a fixed structure and a given scrambling code initial value n, wherein n has a fixed numerical value range of 0-262141. Different random number sequences can be obtained by using different initial values of the scrambling codes, and a certain n corresponds to a certain known random sequence. As shown in particular in figure 1. And scrambling the target data by using the scrambling code random number sequence and then sending the scrambled target data to the air interface, wherein the air interface has an interference signal, so that the signal received by the receiver end is the sum of the scrambled target data and the interference signal. The received signal is descrambled at the receiver end, and the effects of recovering the target signal and whitening the interference signal can be realized. However, when the initial value of the scrambling code of the target signal is unknown, the random sequence of the scrambling code cannot be accurately obtained, and thus the target data cannot be descrambled correctly, and the target data at the transmitting end cannot be recovered.

Under the condition of unknown initial value of the scrambling code, the initial value of the random sequence of the scrambling code recovered according to the received interfered signal is called as an initial value identification method of the scrambling code. In the scrambling code initial identification method, because a generator polynomial is known, the simplest method is violence traversal correlation, and peak judgment is carried out. However, such a method requires calculation 2 in DVB-S2/S2X ¹⁸ 1 calculation, which is obviously difficult to achieve. Patent CN106330800B proposes a fast physical layer scrambling code parameter searching method based on pilot symbols, but this method is only suitable for the case with pilot symbols, and cannot be used without pilot symbols. Patent CN106330396B proposes a fast physical layer scrambling code parameter search method based on padding frame, and the defect of the method is the same as that of patent CN106330800B in application defect: i.e. without padding frames, also fails. The patent CN103560863B proposes a method for identifying a pseudorandom scrambling code, which identifies the initial state of the scrambling code based on convolution correlation, and although the problem of identifying the initial value of the scrambling code without known data is solved, the storage complexity of the algorithm is greatly increased due to the conversion into the convolution code, so that the problems of high complexity of chip implementation, high chip cost and the like exist, and finally, the method is difficult to be widely applied to civil broadcast television receivers.

Disclosure of Invention

The invention aims to provide a method for identifying scrambling code parameters of a physical layer of satellite digital broadcast television signals, which solves the problem of identifying the initial value of a scrambling code of a target satellite signal source under the condition of no pilot frequency and no empty frame assistance.

The invention specifically comprises the following steps:

the method comprises the following steps that (1) a data storage space RAM and a scrambling code storage space ROM are preset in a receiver chip, wherein the two spaces are equal and less than or equal to 1Mbit;

step (2) storing the check matrix H into a scrambling code storage space ROM,

wherein, the unit array

m =18, integer T ≧ 5,F _x Representing a matrixed scrambling code equation; the check matrix H is a sparse matrix which is not 0 and is 1, the position where the check matrix H is 1 is stored in a scrambling code storage space ROM, nodes with 1 in the columns of the check matrix H are data nodes, and nodes with 1 in the rows are check nodes;

step (3) the receiver uses the analog-to-digital converter to collect the satellite signal sent by the antenna;

demodulating the received satellite signals, completing timing recovery operation and frame synchronization operation, obtaining orthogonal IQ signals, and uniformly regarding the orthogonal IQ signals as QPSK signals;

step (5) calculating soft information of orthogonal IQ signal

Wherein u is _n Transmitting the nth data of the signal, y, for the satellite _n For the nth data in the current frame of the received satellite signal, P (u) _n ＝0|y _n ) To receive y _n Under the condition of u _n Probability of =0, P (u) _n ＝1|y _n ) To receive y _n Under the condition of u _n Probability of = 1;

step (6) is to use the soft information L (u) of the orthogonal IQ signal _n )＝(LLR(I _n ),LLR(Q _n ) In sequence into a data storage space RAM;

step (7) the iterative computation unit firstly reads the position information of the check node and the data node in the scrambling code storage space ROM, then reads the soft information of the corresponding position in the data storage space RAM according to the position information, and puts the soft information into the data node position of the iterative computation unit;

and (8) updating the check node: the iterative computation unit computes the data information of the check node to be placed according to the soft information of all the data node positions

p represents a p-th data node, Q and Q 'represent a Q-th check node and a Q' -th check node, Q is a check node set, Q (p) is a check node set connected with the p-th data node, and p → Q represents that the p-th data node sends self information to the Q-th check node; function(s)

x is a variable, tanh (·) denotes hyperbolic tangent; will be Λ _p→q (u _q ) Putting the q-th check node position in the iterative computation unit to replace the original information of the position;

and (9) updating the data node: the iterative calculation unit calculates the data information of the data nodes to be placed according to the data information of the positions of the check nodes

P 'represents the P' th data node, P is a data node set, P (q) is a data node set connected with the q check node, and q → P represents the information sent by the q check node to the P data node;

step (10), hard data judgment:

P _n representing that the nth data node is connected with a set of check nodes, and m represents the mth check node; if λ _n (u _n ) If u is more than or equal to 0, then u is judged _n Is 1, otherwise u is determined _n To 0, a one-dimensional matrix U = [ U ] is obtained ₁ ,u ₂ ,…,u ₃₆ ]，n＝1,2,…,36；

Step (11) one-dimensional matrix U = [ U = [ U ] ₁ ,u ₂ ,…,u _N ]Multiplying with check matrix H to obtain check equation HU ^Τ γ represents transpose;

step (12) repeating steps (8) - (11) if HU appears in the iterative process ^Τ If not, the iteration is stopped, and the corresponding one-dimensional matrix U is not opened (U) ₁ ,u ₂ ,…,u ₃₆ ]The identified scrambling code parameter of the physical layer of the satellite digital broadcast television signal is obtained; if the set maximum iteration number is reached, HU still does not appear ^Τ If not, the one-dimensional matrix U corresponding to the last iteration is not opened (U) =0 ₁ ,u ₂ ,…,u ₃₆ ]As the identified physical layer scrambling code parameter of the satellite digital broadcast television signal.

The method does not need to adopt pilot frequency and null frame auxiliary hypothesis test, but considers the scrambling process as a process passing through a Binary Symmetric Channel (BSC) after the known Linear Shift Feedback Register Coding (LSFRC). The method of the invention provides a method for extracting soft information of each bit by using a bit (bit) soft information demapping method, then a group of code words with specified length is constructed by using an LFSR generator structure, and finally a scrambling code initial value is iteratively solved by using a confidence coefficient propagation method. After the initial value of the scrambling code is obtained, the scrambling code sequence is manufactured again by utilizing the known scrambling code generator, and then the normal descrambling operation can be completed. The method has wider application range, does not need to strictly specify that pilot frequency or null frame must be arranged in the frame signal; even if the pilot frequency is not in the whole frame and all the pilot frequency is load data, the scrambling code parameter of the physical layer of the satellite digital broadcast television signal can be identified by using the method of the invention.

Drawings

FIG. 1 is a schematic diagram of a scrambling code generation method of DVB-S2/S2X;

FIG. 2 is a flow chart of the method of the present invention;

fig. 3 is a schematic diagram of a soft information extraction method.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described with reference to the accompanying drawings.

Fig. 1 illustrates a scrambling code generation method of DVB-S2/S2X, which is to generate a pseudo-random sequence cyclically by a shift register LFSR, multiply the pseudo-random sequence with a random television source signal after conversion, transmit the result to the sky through an antenna by a digital-to-analog converter and a radio frequency converter, and transmit the result to a user receiver after satellite transmission. A random source that requires the correct initial value of the scrambling code to be resolved at the receiver. In the receiver, the following steps are completed to complete the identification of the physical layer scrambling code.

As shown in fig. 2, a method for identifying scrambling code parameters of a physical layer of a satellite digital broadcast television signal includes the following specific steps:

and (1) presetting a data storage space RAM and a scrambling code storage space ROM in a receiver chip, wherein the two spaces are equal and less than or equal to 1Mbit.

Step (2) storing the check matrix H into a scrambling code storage space ROM,

wherein, the unit array

m =18, integer T ≧ 5,F _x Representing the scrambling code equation of matrixing, the scrambling code equation of the I-path signal is 1+x ⁷ +x ¹⁸ The scrambling equation of the Q path signal is 1+x ⁵ +x ⁷ +x ¹⁰ +x ¹⁸ X is a variable; the check matrix H is a sparse matrix which is not 0 or 1, and the position of the check matrix H which is 1 is stored in a scrambling code storage space ROM.

The first column in the check matrix H is a scrambling code matrix, the other columns form a coefficient check matrix, the nodes having 1 in the columns of the check matrix H are data nodes, the nodes having 1 in the rows are check nodes, that is, the nodes having 1 are both data nodes and check nodes. And storing the check matrix H into a scrambling code storage space ROM, namely storing the positions of the check nodes and the data nodes in the check matrix H into the scrambling code storage space ROM.

And (3) the receiver acquires the satellite signals transmitted by the antenna by using an analog-to-digital converter.

Step (4) using Automatic Gain Control (AGC) technology to Control the amplitude of the received satellite signal so as to stabilize the satellite signal at a fixed signal power level;

step 5, correcting the timing deviation of the received satellite signal by using a timing recovery technology to obtain a satellite frame signal;

step (6) according to the frame structure characteristics of the satellite frame signals, completing frame synchronization operation to obtain orthogonal IQ signals which may be one of QPSK, 8PSK, 16APSK, 32APSK, 64APSK, 128APSK and 256APSK constellations and are uniformly regarded as QPSK signals;

steps (3) to (6) are prior art techniques employed in conventional satellite receivers.

Step (7) As shown in FIG. 3, calculating soft information of the orthogonal IQ signal

Wherein u is _n Transmitting the nth data of the signal, y, for the satellite _n For the nth data in the current frame of the received satellite signal, P (u) _n ＝0|y _n ) To receive y _n Under the condition of u _n Probability of =0, P (u) _n ＝1|y _n ) To receive y _n Under the condition of u _n Probability of = 1; soft information L (u) _n )＝(LLR(I _n ),LLR(Q _n ) Includes soft information of the I-way signal

And Q-path signal soft information

I and Q represent the current signal values, σ, of the I and Q paths, respectively ² Representing the noise variance of the current channel.

Step (8) is to use the soft information L (u) of the orthogonal IQ signal _n )＝(LLR(I _n ),LLR(Q _n ) In turn into the data storage space RAM.

And (9) the iterative computation unit firstly reads the position information of the check nodes and the data nodes in the scrambling code storage space ROM, then reads the soft information of the corresponding position in the data storage space RAM according to the position information, and puts the soft information into the data node position of the iterative computation unit.

Step (10), updating check nodes: the iterative computation unit computes the data information of the check node to be placed according to the soft information of all the data node positions

p represents a p-th data node, Q and Q 'represent a Q-th check node and a Q' -th check node, Q is a check node set, Q (p) is a check node set connected with the p-th data node, and p → Q represents that the p-th data node sends self information to the Q-th check node; function(s)

x is a variable, tanh (·) denotes hyperbolic tangent; will be Λ _p→q (u _q ) And putting the q-th check node position in the iterative computation unit to replace the original information of the position.

And (11) updating the data node: the iterative calculation unit calculates the data information of the data nodes to be placed according to the data information of the positions of the check nodes

P 'represents the P' th data node, P is a data node set, P (q) is a data node set connecting the q-th check node, and q → P represents the transmission of the information of the q-th check node to the P-th data node.

Step (12) data hard decision:

P _n representing that the nth data node is connected with a set of check nodes, and m represents the mth check node; if λ _n (u _n ) If u is more than or equal to 0, then u is judged _n Is 1, otherwise u is determined _n To 0, a one-dimensional matrix U = [ U ] is obtained ₁ ,u ₂ ,…,u ₃₆ ]，n＝1,2,…,36。

Step (13) of converting the one-dimensional matrix U = [ U ] ₁ ,u ₂ ,…,u _N ]Multiplying by a check matrix H to obtainCheck equation HU ^Τ γ represents transpose;

step (14) repeating steps (10) - (13), if HU appears in the iteration process ^Τ If not, the iteration is stopped, and the corresponding one-dimensional matrix U is not opened (U) ₁ ,u ₂ ,…,u ₃₆ ]The identified scrambling code parameter of the physical layer of the satellite digital broadcast television signal is obtained; if the set maximum iteration number is reached, HU still does not appear ^Τ If not, the one-dimensional matrix U corresponding to the last iteration is not opened (U) =0 ₁ ,u ₂ ,…,u ₃₆ ]As the identified physical layer scrambling code parameter of the satellite digital broadcast television signal.

It is to be understood that the above examples are illustrative of the present invention and are not to be construed as limiting the invention, and any invention which does not depart from the spirit and scope of the invention is deemed to be within the scope and spirit of the invention.

Claims (5)

1. A method for identifying scrambling code parameters of a physical layer of satellite digital broadcast television signals is characterized by comprising the following steps:

the method comprises the following steps that (1) a data storage space RAM and a scrambling code storage space ROM are preset in a receiver chip, wherein the two spaces are equal and less than or equal to 1Mbit;

step (2) storing the check matrix H into a scrambling code storage space ROM,

wherein, the unit array

m =18, integer T ≧ 5,F _x Representing a matrixed scrambling code equation; the check matrix H is a sparse matrix which is not 0 and is 1, the position where the check matrix H is 1 is stored in a scrambling code storage space ROM, nodes with 1 in the columns of the check matrix H are data nodes, and nodes with 1 in the rows are check nodes;

step (3) the receiver uses the analog-to-digital converter to collect the satellite signal sent by the antenna;

demodulating the received satellite signals, completing timing recovery operation and frame synchronization operation, obtaining orthogonal IQ signals, and uniformly regarding the orthogonal IQ signals as QPSK signals;

step (5) calculating soft information of orthogonal IQ signal

Wherein u is _n Transmitting the nth data of the signal, y, for the satellite _n For the nth data in the current frame of the received satellite signal, P (u) _n ＝0|y _n ) To receive y _n Under the condition of u _n Probability of =0, P (u) _n ＝1|y _n ) To receive y _n Under the condition of u _n Probability of = 1; l (u) _n )

Step (6) is to use the soft information L (u) of the orthogonal IQ signal _n )＝(LLR(I _n ),LLR(Q _n ) In sequence into a data storage space RAM;

step (7) the iterative computation unit firstly reads the position information of the check node and the data node in the scrambling code storage space ROM, then reads the soft information of the corresponding position in the data storage space RAM according to the position information, and puts the soft information into the data node position of the iterative computation unit;

and (8) updating the check node: the iterative computation unit computes the data information of the check node to be placed according to the soft information of all the data node positions

p represents a p-th data node, Q and Q 'represent a Q-th check node and a Q' -th check node, Q is a check node set, Q (p) is a check node set connected with the p-th data node, and p → Q represents that the p-th data node sends self information to the Q-th check node; function(s)

x is a variable, tanh (·) denotes hyperbolic tangent; will be Λ _p→q (u _q ) Putting the q-th check node position in the iterative computation unit to replace the original information of the position;

and (9) updating the data node: the iterative computation unit checks the data of the node position according toInformation, calculating data information to be put into data node

P 'represents the P' th data node, P is a data node set, P (q) is a data node set connected with the q check node, and q → P represents the information sent by the q check node to the P data node;

step (10), hard decision of data:

P _n representing that the nth data node is connected with a set of check nodes, and m represents the mth check node; if λ _n (u _n ) If u is more than or equal to 0, then u is judged _n Is 1, otherwise, u is judged _n To 0, a one-dimensional matrix U = [ U ] is obtained ₁ ,u ₂ ,…,u ₃₆ ]，n＝1,2,…,36；

Step (11) one-dimensional matrix U = [ U = [ U ] ₁ ,u ₂ ,…,u _N ]Multiplying with check matrix H to obtain check equation HU ^Τ Tau represents transpose;

step (12) repeating steps (8) - (11) if HU appears in the iterative process ^Τ If not, the iteration is stopped, and the corresponding one-dimensional matrix U is not opened (U) ₁ ,u ₂ ,…,u ₃₆ ]The identified scrambling code parameter of the physical layer of the satellite digital broadcast television signal is obtained; if the set maximum iteration number is reached, HU still does not appear ^Τ If not, the one-dimensional matrix U corresponding to the last iteration is not opened (U) =0 ₁ ,u ₂ ,…,u ₃₆ ]As the identified physical layer scrambling code parameter of the satellite digital broadcast television signal.

2. The method as claimed in claim 1, wherein the physical layer scrambling code parameter identification method comprises: said scrambling code equation F _x In the middle, the scrambling equation of the I path signal is 1+x ⁷ +x ¹⁸ The scrambling equation of the Q path signal is 1+x ⁵ +x ⁷ +x ¹⁰ +x ¹⁸ And x is a variable.

3. The method as claimed in claim 2, wherein the physical layer scrambling code parameter identification method comprises: the first column in the check matrix H is a scrambling code matrix, other columns form a coefficient check matrix, and nodes with 1 in the check matrix H are data nodes and check nodes; the check matrix H is stored in the scrambling code storage space ROM, namely, the positions of check nodes and data nodes in the check matrix H are stored in the scrambling code storage space ROM.

4. The method for identifying scrambling code parameters of physical layer of satellite digital broadcasting television signal as claimed in claim 1, characterized in that: the quadrature IQ signal in the step (4) is one of QPSK, 8PSK, 16APSK, 32APSK, 64APSK, 128APSK, 256APSK constellations.

5. The method as claimed in claim 1, wherein the physical layer scrambling code parameter identification method comprises: the soft information L (u) in the step (5) _n )＝(LLR(I _n ),LLR(Q _n ) Include I-way signal soft information

And Q-path signal soft information

I and Q represent the current signal values, σ, of the I and Q paths, respectively ² Representing the noise variance of the current channel.

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