Patent Grant
11218169
The present technology relates to a transmission method and a reception device, and more particularly to, for example, a transmission method and a reception device for securing favorable communication quality in data transmission using an LDPC code.
Low density parity check (LDPC) codes have high error correction capability and are in recent years widely adopted in transmission systems for digital broadcasting and the like, such as the digital video broadcasting (DVB)-S.2 in Europe and the like, DVB-T.2, DVB-C.2, and the advanced television systems committee (ATSC) 3.0 in the United States, and the like, for example (see, for example, Non-Patent Document 1).
With recent researches, it has been found that the LDPC codes are able to obtain performance close to the Shannon limit as the code length is increased, similarly to turbo codes and the like. Furthermore, the LDPC codes have a property that the minimum distance is proportional to the code length and thus have a good block error probability characteristic, as characteristics. Moreover, a so-called error floor phenomenon observed in decoding characteristics of turbo codes and the like hardly occur, which is also an advantage.
In data transmission using an LDPC code, for example, the LDPC code is symbols (symbolized) of quadrature modulation (digital modulation) such as quadrature phase shift keying (QPSK), and the symbols are mapped at signal points of the quadrature modulation and are sent.
The data transmission using an LDPC code is spreading worldwide and is required to secure favorable communication (transmission) quality.
The present technology has been made in view of such a situation, and aims to secure favorable communication quality in data transmission using an LDPC code.
A first transmission method of the present technology is a transmission method including a coding step of performing LDPC coding on the basis of a parity check matrix of an LDPC code with a code length N of 17280 bits and a coding rate r of 2/16, a group-wise interleaving step of performing group-wise interleaving in which the LDPC code is interleaved in units of bit groups of 360 bits, and a mapping step of mapping the LDPC code to one of 64 signal points of uniform constellation (UC) of 64QAM on a 6-bit basis, in which in the group-wise interleaving, an (i+1)th bit group from a head of the LDPC code is set as a bit group i, and a sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into a sequence of bit groups
In the first transmission method of the present technology, LDPC coding is performed on the basis of the parity check matrix of the LDPC code with the code length N of 17280 bits and the coding rate r of 2/16, and group-wise interleaving to interleave the LDPC code in units of bit groups of 360 bits is performed. Then, the LDPC code is mapped to any one of 64 signal points of uniform constellation (UC) in 64QAM on a 6-bit basis. In the group-wise interleaving, the (i+1)th bit group from a head of the LDPC code is set as the bit group i, and the sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into the sequence of bit groups
The parity check matrix includes the A matrix of M1 rows and K columns expressed by a predetermined value M1 and an information length K=N×r of the LDPC code, the A matrix being an upper left matrix of the parity check matrix, the B matrix of M1 rows and M1 columns, the B matrix having a step structure adjacent to right of the A matrix, the Z matrix of M1 rows and N−K−M1 columns, the Z matrix being a zero matrix adjacent to right of the B matrix, the C matrix of N−K−M1 rows and K+M1 columns, the C matrix being adjacent to below the A matrix and the B matrix, and the D matrix of N−K−M1 rows and N−K−M1 columns, the D matrix being an identity matrix adjacent to right of the C matrix, the predetermined value M1 is 1800, the A matrix and the C matrix are represented by a parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the A matrix and the C matrix for every 360 columns, and is
A first reception device of the present technology is a reception device including a decoding unit configured to decode an LDPC code with a code length N of 17280 bits and a coding rate r of 2/16 obtained from data transmitted by a transmission method including a coding step of performing LDPC coding on the basis of a parity check matrix of the LDPC code, a group-wise interleaving step of performing group-wise interleaving in which the LDPC code is interleaved in units of bit groups of 360 bits, and a mapping step of mapping the LDPC code to one of 64 signal points of uniform constellation (UC) of 64QAM on a 6-bit basis, in which in the group-wise interleaving, an (i+1)th bit group from a head of the LDPC code is set as a bit group i, and a sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into a sequence of bit groups
the parity check matrix includes an A matrix of M1 rows and K columns represented by a predetermined value M1 and an information length K=N×r of the LDPC code, the A matrix being an upper left matrix of the parity check matrix, a B matrix of M1 rows and M1 columns, having a step structure adjacent to right of the A matrix,
a Z matrix of M1 rows and N−K−M1 columns, the Z matrix being a zero matrix adjacent to right of the B matrix, a C matrix of N−K−M1 rows and K+M1 columns, adjacent to below the A matrix and the B matrix, and a D matrix of N−K−M1 rows and N−K−M1 columns, the D matrix being an identity matrix adjacent to right of the C matrix, the predetermined value M1 is 1800, the A matrix and the C matrix are represented by a parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the A matrix and the C matrix for every 360 columns, and is
In the first reception device of the present technology, the LDPC code obtained from the data transmitted by the first transmission method is decoded.
A second transmission method of the present technology is a transmission method including a coding step of performing LDPC coding on the basis of a parity check matrix of an LDPC code with a code length N of 17280 bits and a coding rate r of 4/16, a group-wise interleaving step of performing group-wise interleaving in which the LDPC code is interleaved in units of bit groups of 360 bits, and a mapping step of mapping the LDPC code to one of 64 signal points of uniform constellation (UC) of 64QAM on a 6-bit basis, in which in the group-wise interleaving, an (i+1)th bit group from a head of the LDPC code is set as a bit group i, and a sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into a sequence of bit groups
the parity check matrix includes an A matrix of M1 rows and K columns represented by a predetermined value M1 and an information length K=N×r of the LDPC code, the A matrix being an upper left matrix of the parity check matrix, a B matrix of M1 rows and M1 columns, having a step structure adjacent to right of the A matrix, a Z matrix of M1 rows and N−K−M1 columns, the Z matrix being a zero matrix adjacent to right of the B matrix, a C matrix of N−K−M1 rows and K+M1 columns, adjacent to below the A matrix and the B matrix, and a D matrix of N−K−M1 rows and N−K−M1 columns, the D matrix being an identity matrix adjacent to right of the C matrix, the predetermined value M1 is 1080, the A matrix and the C matrix are represented by a parity check matrix initial value table, and
the parity check matrix initial value table is a table representing positions of elements of 1 of the A matrix and the C matrix for every 360 columns, and is
In the second transmission method of the present technology, LDPC coding is performed on the basis of the parity check matrix of the LDPC code with the code length N of 17280 bits and the coding rate r of 4/16, and group-wise interleaving to interleave the LDPC code in units of bit groups of 360 bits is performed. Then, the LDPC code is mapped to any one of 64 signal points of uniform constellation (UC) in 64QAM on a 6-bit basis. In the group-wise interleaving, the (i+1)th bit group from a head of the LDPC code is set as the bit group i, and the sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into the sequence of bit groups
The parity check matrix includes the A matrix of M1 rows and K columns expressed by a predetermined value M1 and an information length K=N×r of the LDPC code, the A matrix being an upper left matrix of the parity check matrix, the B matrix of M1 rows and M1 columns, the B matrix having a step structure adjacent to right of the A matrix, the Z matrix of M1 rows and N−K−M1 columns, the Z matrix being a zero matrix adjacent to right of the B matrix, the C matrix of N−K−M1 rows and K+M1 columns, the C matrix being adjacent to below the A matrix and the B matrix, and the D matrix of N−K−M1 rows and N−K−M1 columns, the D matrix being an identity matrix adjacent to right of the C matrix, the predetermined value M1 is 1080, the A matrix and the C matrix are represented by a parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the A matrix and the C matrix for every 360 columns, and is
A second reception device of the present technology is a reception device including a decoding unit configured to decode an LDPC code with a code length N of 17280 bits and a coding rate r of 4/16 obtained from data transmitted by a transmission method including a coding step of performing LDPC coding on the basis of a parity check matrix of the LDPC code, a group-wise interleaving step of performing group-wise interleaving in which the LDPC code is interleaved in units of hit groups of 360 bits, and a mapping step of mapping the LDPC code to one of 64 signal points of uniform constellation (UC) of 64QAM on a 6-bit basis, in which in the group-wise interleaving, an (i+1)th bit group from a head of the LDPC code is set as a bit group i, and a sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into a sequence of bit groups
the parity check matrix includes an A matrix of M1 rows and K columns represented by a predetermined value M1 and an information length K=N×r of the LDPC code, the A matrix being an upper left matrix of the parity check matrix, a B matrix of M1 rows and M1 columns, having a step structure adjacent to right of the A matrix,
a Z matrix of M1 rows and N−K−M1 columns, the Z matrix being a zero matrix adjacent to right of the B matrix, a C matrix of N−K−M1 rows and K+M1 columns, adjacent to below the A matrix and the B matrix, and a D matrix of N−K−M1 rows and N−K−M1 columns, the D matrix being an identity matrix adjacent to right of the C matrix, the predetermined value M1 is 1080, the A matrix and the C matrix are represented by a parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the A matrix and the C matrix for every 360 columns, and is
In the second reception device of the present technology, the LDPC code obtained from the data transmitted by the second transmission method is decoded.
A third transmission method of the present technology is a transmission method including a coding step of performing LDPC coding on the basis of a parity check matrix of an LDPC code with a code length N of 17280 bits and a coding rate r of 6/16, a group-wise interleaving step of performing group-wise interleaving in which the LDPC code is interleaved in units of bit groups of 360 bits, and a mapping step of mapping the LDPC code to one of 64 signal points of uniform constellation (UC) of 64QAM on a 6-bit basis, in which in the group-wise interleaving, an (i+1)th bit group from a head of the LDPC code is set as a bit group i, and a sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into a sequence of bit groups
the parity check matrix includes an A matrix of M1 rows and K columns represented by a predetermined value M1 and an information length K=N×r of the LDPC code, the A matrix being an upper left matrix of the parity check matrix, a B matrix of M1 rows and M1 columns, having a step structure adjacent to right of the A matrix, a Z matrix of M1 rows and N−K−M1 columns, the Z matrix being a zero matrix adjacent to right of the B matrix, a C matrix of N−K−M1 rows and K+M1 columns, adjacent to below the A matrix and the B matrix, and a D matrix of N−K−M1 rows and N−K−M1 columns, the D matrix being an identity matrix adjacent to right of the C matrix, the predetermined value M1 is 720, the A matrix and the C matrix are represented by a parity check matrix initial value table, and
the parity check matrix initial value table is a table representing positions of elements of 1 of the A matrix and the C matrix for every 360 columns, and is
In the third transmission method of the present technology, LDPC coding is performed on the basis of the parity check matrix of the LDPC code with the code length N of 17280 bits and the coding rate r of 6/16, and group-wise interleaving to interleave the LDPC code in units of bit groups of 360 bits is performed. Then, the LDPC code is mapped to any one of 64 signal points of uniform constellation (UC) in 64QAM on a 6-bit basis. In the group-wise interleaving, the (i+1)th bit group from a head of the LDPC code is set as the bit group i, and the sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into the sequence of bit groups
30 14 40 26 21 5 12 3 18 17 11 38 4 46 7 31 0 1 27 36 8 10 2 22 13 9 37 42 41 32 15 39 23 25 34 24 35 28 20 16 19 33 6 43 29 45 47 44.
The parity check matrix includes the A matrix of M1 rows and K columns expressed by a predetermined value M1 and an information length K=N×r of the LDPC code, the A matrix being an upper left matrix of the parity check matrix, the B matrix of M1 rows and M1 columns, the B matrix having a step structure adjacent to right of the A matrix, the Z matrix of M1 rows and N−K−M1 columns, the Z matrix being a zero matrix adjacent to right of the B matrix, the C matrix of N−K−M1 rows and K+M1 columns, the C matrix being adjacent to below the A matrix and the B matrix, and the D matrix of N−K−M1 rows and N−K−M1 columns, the D matrix being an identity matrix adjacent to right of the C matrix, the predetermined value M1 is 720, the A matrix and the C matrix are represented by a parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the A matrix and the C matrix for every 360 columns, and is
A third reception device of the present technology is a reception device including a decoding unit configured to decode an LDPC code with a code length N of 17280 bits and a coding rate r of 6/16 obtained from data transmitted by a transmission method including a coding step of performing LDPC coding on the basis of a parity check matrix of the LDPC code, a group-wise interleaving step of performing group-wise interleaving in which the LDPC code is interleaved in units of bit groups of 360 bits, and a mapping step of mapping the LDPC code to one of 64 signal points of uniform constellation (UC) of 64QAM on a 6-bit basis, in which in the group-wise interleaving, an (i+1)th bit group from a head of the LDPC code is set as a bit group i, and a sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into a sequence of bit groups
the parity check matrix includes an A matrix of M1 rows and K columns represented by a predetermined value M1 and an information length K=N×r of the LDPC code, the A matrix being an upper left matrix of the parity check matrix, a B matrix of M1 rows and M1 columns, having a step structure adjacent to right of the A matrix,
a Z matrix of M1 rows and N−K−M1 columns, the Z matrix being a zero matrix adjacent to right of the B matrix, a C matrix of N−K−M1 rows and K+M1 columns, adjacent to below the A matrix and the B matrix, and a D matrix of N−K−M1 rows and N−K−M1 columns, the D matrix being an identity matrix adjacent to right of the C matrix, the predetermined value M1 is 720, the A matrix and the C matrix are represented by a parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the A matrix and the C matrix for every 360 columns, and is
In the third reception device of the present technology, the LDPC code obtained from the data transmitted by the third transmission method is decoded.
A fourth transmission method of the present technology is a transmission method including a coding step of performing LDPC coding on the basis of a parity check matrix of an LDPC code with a code length N of 17280 bits and a coding rate r of 8/16, a group-wise interleaving step of performing group-wise interleaving in which the LDPC code is interleaved in units of bit groups of 360 bits, and a mapping step of mapping the LDPC code to one of 64 signal points of uniform constellation (UC) of 64QAM on a 6-bit basis, in which in the group-wise interleaving, an (i+1)th bit group from a head of the LDPC code is set as a bit group i, and a sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into a sequence of bit groups
the LDPC code includes information bits and parity bits, the parity check matrix includes an information matrix portion corresponding to the information bits and a parity matrix portion corresponding to the parity bits, the information matrix portion is represented by a parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the information matrix portion for every 360 columns, and is
In the fourth transmission method of the present technology, LDPC coding is performed on the basis of the parity check matrix of the LDPC code with the code length N of 17280 bits and the coding rate r of 8/16, and group-wise interleaving to interleave the LDPC code in units of bit groups of 360 bits is performed. Then, the LDPC code is mapped to any one of 64 signal points of uniform constellation (UC) in 64QAM on a 6-bit basis. In the group-wise interleaving, the (i+1)th bit group from a head of the LDPC code is set as the bit group i, and the sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into the sequence of bit groups
The LDPC code includes the information bits and parity bits, the parity check matrix includes the information matrix portion corresponding to the information bits and the parity matrix portion corresponding to the parity bits, the information matrix portion is represented by the parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the information matrix portion for every 360 columns, and is
A fourth reception device of the present technology is a reception device including a decoding unit configured to decode an LDPC code with a code length N of 17280 bits and a coding rate r of 8/16 obtained from data transmitted by a transmission method including a coding step of performing LDPC coding on the basis of a parity check matrix of the LDPC code, a group-wise interleaving step of performing group-wise interleaving in which the LDPC code is interleaved in units of bit groups of 360 bits, and a mapping step of mapping the LDPC code to one of 64 signal points of uniform constellation (UC) of 64QAM on a 6-bit basis, in which in the group-wise interleaving, an (i+1)th bit group from a head of the LDPC code is set as a bit group i, and a sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into a sequence of bit groups
the LDPC code includes information bits and parity bits, the parity check matrix includes an information matrix portion corresponding to the information bits and a parity matrix portion corresponding to the parity bits, the information matrix portion is represented by a parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the information matrix portion for every 360 columns, and is
In the fourth reception device of the present technology, the LDPC code obtained from the data transmitted by the fourth transmission method is decoded.
A fifth transmission method of the present technology is a transmission method including a coding step of performing LDPC coding on the basis of a parity check matrix of an LDPC code with a code length N of 17280 bits and a coding rate r of 10/16, a group-wise interleaving step of performing group-wise interleaving in which the LDPC code is interleaved in units of bit groups of 360 bits, and a mapping step of mapping the LDPC code to one of 64 signal points of uniform constellation (UC) of 64QAM on a 6-bit basis, in which in the group-wise interleaving, an (i+1)th bit group from a head of the LDPC code is set as a bit group i, and a sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into a sequence of bit groups
the LDPC code includes information bits and parity bits, the parity check matrix includes an information matrix portion corresponding to the information bits and a parity matrix portion corresponding to the parity bits, the information matrix portion is represented by a parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the information matrix portion for every 360 columns, and is
In the fifth transmission method of the present technology, LDPC coding is performed on the basis of the parity check matrix of the LDPC code with the code length N of 17280 bits and the coding rate r of 10/16, and group-wise interleaving to interleave the LDPC code in units of bit groups of 360 bits is performed. Then, the LDPC code is mapped to any one of 64 signal points of uniform constellation (UC) in 64QAM on a 6-bit basis. In the group-wise interleaving, the (i+1)th bit group from a head of the LDPC code is set as the bit group i, and the sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into the sequence of bit groups
The LDPC code includes the information bits and parity bits, the parity check matrix includes the information matrix portion corresponding to the information bits and the parity matrix portion corresponding to the parity bits, the information matrix portion is represented by the parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the information matrix portion for every 360 columns, and is
A fifth reception device of the present technology is a reception device including a decoding unit configured to decode an LDPC code with a code length N of 17280 bits and a coding rate r of 10/16 obtained from data transmitted by a transmission method including a coding step of performing LDPC coding on the basis of a parity check matrix of the LDPC code, a group-wise interleaving step of performing group-wise interleaving in which the LDPC code is interleaved in units of bit groups of 360 bits, and a mapping step of mapping the LDPC code to one of 64 signal points of uniform constellation (UC) of 64QAM on a 6-bit basis, in which in the group-wise interleaving, an (i+1)th bit group from a head of the LDPC code is set as a bit group i, and a sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into a sequence of bit groups
the LDPC code includes information bits and parity bits, the parity check matrix includes an information matrix portion corresponding to the information bits and a parity matrix portion corresponding to the parity bits, the information matrix portion is represented by a parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the information matrix portion for every 360 columns, and is
In the fifth reception device of the present technology, the LDPC code obtained from the data transmitted by the fifth transmission method is decoded.
A sixth transmission method of the present technology is a transmission method including a coding step of performing LDPC coding on the basis of a parity check matrix of an LDPC code with a code length N of 17280 bits and a coding rate r of 12/16, a group-wise interleaving step of performing group-wise interleaving in which the LDPC code is interleaved in units of bit groups of 360 bits, and a mapping step of mapping the LDPC code to one of 64 signal points of uniform constellation (UC) of 64QAM on a 6-bit basis, in which in the group-wise interleaving, an (i+1)th bit group from a head of the LDPC code is set as a bit group i, and a sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into a sequence of bit groups
the LDPC code includes information bits and parity bits, the parity check matrix includes an information matrix portion corresponding to the information bits and a parity matrix portion corresponding to the parity bits, the information matrix portion is represented by a parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the information matrix portion for every 360 columns, and is
In the sixth transmission method of the present technology, LDPC coding is performed on the basis of the parity check matrix of the LDPC code with the code length N of 17280 bits and the coding rate r of 12/16, and group-wise interleaving to interleave the LDPC code in units of bit groups of 360 bits is performed. Then, the LDPC code is mapped to any one of 64 signal points of uniform constellation (UC) in 64QAM on a 6-bit basis. In the group-wise interleaving, the (i+1)th bit group from a head of the LDPC code is set as the bit group i, and the sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into the sequence of bit groups
The LDPC code includes the information bits and parity bits, the parity check matrix includes the information matrix portion corresponding to the information bits and the parity matrix portion corresponding to the parity bits, the information matrix portion is represented by the parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the information matrix portion for every 360 columns, and is
A sixth reception device of the present technology is a reception device including a decoding unit configured to decode an LDPC code with a code length N of 17280 bits and a coding rate r of 12/16 obtained from data transmitted by a transmission method including a coding step of performing LDPC coding on the basis of a parity check matrix of the LDPC code, a group-wise interleaving step of performing group-wise interleaving in which the LDPC code is interleaved in units of bit groups of 360 bits, and a mapping step of mapping the LDPC code to one of 64 signal points of uniform constellation (UC) of 64QAM on a 6-bit basis, in which in the group-wise interleaving, an (i+1)th bit group from a head of the LDPC code is set as a bit group i, and a sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into a sequence of bit groups
the LDPC code includes information bits and parity bits, the parity check matrix includes an information matrix portion corresponding to the information bits and a parity matrix portion corresponding to the parity bits, the information matrix portion is represented by a parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the information matrix portion for every 360 columns, and is
In the sixth reception device of the present technology, the LDPC code obtained from the data transmitted by the sixth transmission method is decoded.
A seventh transmission method of the present technology is a transmission method including a coding step of performing LDPC coding on the basis of a parity check matrix of an LDPC code with a code length N of 17280 bits and a coding rate r of 14/16, a group-wise interleaving step of performing group-wise interleaving in which the LDPC code is interleaved in units of bit groups of 360 bits, and a mapping step of mapping the LDPC code to one of 64 signal points of uniform constellation (UC) of 64QAM on a 6-bit basis, in which in the group-wise interleaving, an (i+1)th bit group from a head of the LDPC code is set as a bit group i, and a sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into a sequence of bit groups
the LDPC code includes information bits and parity bits, the parity check matrix includes an information matrix portion corresponding to the information bits and a parity matrix portion corresponding to the parity bits, the information matrix portion is represented by a parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the information matrix portion for every 360 columns, and is
In the seventh transmission method of the present technology, LDPC coding is performed on the basis of the parity check matrix of the LDPC code with the code length N of 17280 bits and the coding rate r of 14/16, and group-wise interleaving to interleave the LDPC code in units of bit groups of 360 bits is performed. Then, the LDPC code is mapped to any one of 64 signal points of uniform constellation (UC) in 64QAM on a 6-bit basis. In the group-wise interleaving, the (i+1)th bit group from a head of the LDPC code is set as the bit group i, and the sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into the sequence of bit groups
The LDPC code includes the information bits and parity bits, the parity check matrix includes the information matrix portion corresponding to the information bits and the parity matrix portion corresponding to the parity bits, the information matrix portion is represented by the parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the information matrix portion for every 360 columns, and is
A seventh reception device of the present technology is a reception device including a decoding unit configured to decode an LDPC code with a code length N of 17280 bits and a coding rate r of 14/16 obtained from data transmitted by a transmission method including a coding step of performing LDPC coding on the basis of a parity check matrix of the LDPC code, a group-wise interleaving step of performing group-wise interleaving in which the LDPC code is interleaved in units of bit groups of 360 bits, and a mapping step of mapping the LDPC code to one of 64 signal points of uniform constellation (UC) of 64QAM on a 6-bit basis, in which in the group-wise interleaving, an (i+1)th bit group from a head of the LDPC code is set as a bit group i, and a sequence of bit groups 0 to 47 of the 17280-bit LDPC code is interleaved into a sequence of bit groups
the LDPC code includes information bits and parity bits, the parity check matrix includes an information matrix portion corresponding to the information bits and a parity matrix portion corresponding to the parity bits, the information matrix portion is represented by a parity check matrix initial value table, and the parity check matrix initial value table is a table representing positions of elements of 1 of the information matrix portion for every 360 columns, and is
In the seventh reception device of the present technology, the LDPC code obtained from the data transmitted by the seventh transmission method is decoded.
Note that the transmission device and the reception device that implement the transmission method may be independent devices or may be internal blocks configuring one device.
According to the present technology, good communication quality can be secured in data transmission using an LDPC code.
Note that effects described here are not necessarily limited, and any of effects described in the present disclosure may be exhibited.
Hereinafter, an embodiment of the present technology will be described. Before the description of the embodiment, an LDPC code will be described.
<Ldpc Code>
Note that the LDPC code is a linear code and is not necessarily binary. However, description will be given on the assumption that the LDPC code is binary.
An LDPC code is most characterized in that a parity check matrix defining the LDPC code is sparse. Here, a sparse matrix is a matrix in which the number of “1”s of matrix elements is very small (a matrix in which most elements are 0).
In the parity check matrix H in
In coding with an LDPC code (LDPC coding), for example, a codeword (LDPC code) is generated by generating a generator matrix G on the basis of the parity check matrix H and multiplying binary information bits by the generator matrix G.
Specifically, a coding device for performing the LDPC coding first calculates the generator matrix G that holds an expression GHT=0 with a transposed matrix HT of the parity check matrix H. Here, in a case where the generator matrix G is a K×N matrix, the coding device multiplies the generator matrix G by a bit string (vector u) of information bits including K bits and generates a codeword c (=uG) including N bits. The codeword (LDPC code) generated by the coding device is received at a reception side via a predetermined communication path.
Decoding of the LDPC code can be performed by an algorithm called probabilistic decoding proposed by Gallager, which is a message passing algorithm according to belief propagation on a so-called Tanner graph including a variable node (also called message node) and a check node. Here, as appropriate, the variable node and the check node are hereinafter also simply referred to as nodes.
Note that, hereinafter, a real value (received LLR) expressing “0” likeliness of a value of an i-th code bit of the LDPC code (1 codeword) received on the reception side, using a log likelihood ratio, is also referred to as a received value u0i as appropriate. Furthermore, a message output from the check node is uj and a message output from the variable node is vi.
First, in decoding the LDPC code, as illustrated in
Here, dv and dc in the expressions (1) and (2) are arbitrarily selectable parameters respectively indicating the numbers of “1”s in a vertical direction (column) and a cross direction (row) of the parity check matrix H. For example, in the case of the LDPC code ((3, 6) LDPC code) for the parity check matrix H with the column weight of 3 and the row weight of 6 as illustrated in
Note that, in each of the variable node operation in the expression (1) and the check node operation in the expression (2), a message input from an edge (a line connecting the variable node and the check node) that is about to output a message is not an object for the operation. Therefore, an operation range is 1 to dv−1 or 1 to dc−1. Furthermore, the check node operation in the expression (2) is performed by, in practice, creating a table of a function R (v1, v2) illustrated in the expression (3) defined by one output for two inputs v1 and v2, in advance, and continuously (recursively) using the table as illustrated in the expression (4).
[Math. 3]
x=2 tan h−1{tan h(v1/2)tan h(v2/2)}=R(v1,v2) (3)
[Math. 4]
uj=R(v1R(v2,R(v3, . . . R(vd
In step S12, the variable k is further incremented by “1”, and the processing proceeds to step S13. In step S13, whether or not the variable k is larger than a predetermined number of repetitive decoding times C is determined. In a case where the variable k is determined not to be larger than C in step S13, the processing returns to step S12 and hereinafter similar processing is repeated.
Furthermore, in a case where the variable k is determined to be larger than C in step S13, the processing proceeds to step S14, the operation illustrated in the expression (5) is performed to obtain the message vi as a decoding result to be finally output and the message vi is output, and the decoding processing for the LDPC code is terminated.
Here, the operation in the expression (5) is performed using messages uj from all the edges connected to the variable node, different from the variable node operation in the expression (1).
In the parity check matrix H in
Here, in
In other words, in a case where an element of the j-th row and the i-th column of the parity check matrix is 1, the i-th variable node from the top (“=” node) and the j-th check node from the top (“+” node) are connected by an edge in
In a sum product algorithm that is a decoding method of an LDPC code, the variable node operation and the check node operation are repeatedly performed.
In the variable node, the message vi corresponding to the edge to be calculated is obtained by the variable node operation in the expression (1) using messages u1 and u2 from the remaining edges connected to the variable node and the received value u0i. Messages corresponding to other edges are similarly obtained.
Here, the check node operation in the expression (2) can be rewritten to the expression (6), using a relationship of an expression a×b=exp {ln(|a|)+ln(|b|)}×sign (a)×sign (b). Note that sign (x) is 1 when x≥0 and −1 when x<0.
When the function φ(x) is defined as an expression φ(x)=ln(tan h(x/2)) when x≥0, an expression φ−1(x)=2 tan h−1(e−x) holds and thus the expression (6) can be deformed into the expression (7).
In the check node, the check node operation in the expression (2) is performed according to the expression (7).
In other words, in the check node, the message u corresponding to the edge to be calculated is obtained by the check node operation in the expression (7) using messages v1, v2, v3, v4, and v5 from the remaining edges connected to the check node, as illustrated in
Note that the function φ(x) in the expression (7) can be expressed by the expression φ(x)=in((ex+1)/(ex−1)), and φ(x)=φ−1(x) holds when x>0. When the functions φ(x) and φ−1(x) are implemented in hardware, the functions may be implemented using look up tables (LUTs), and the LUTs are the same.
<Configuration Example of Transmission System to which Present Technology is Applied>
The transmission system in
The transmission device 11 performs transmission (broadcasting) of, for example, a television broadcast program or the like. In other words, the transmission device 11 encodes target data to be transmitted, such as image data and audio data as a program, into an LDPC code, and transmits the LDPC code via a communication path 13 such as a satellite line, a ground wave, or a cable (wired line), for example.
The reception device 12 receives the LDPC code transmitted from the transmission device 11 via the communication path 13, decodes the LDPC code to the target data, and outputs the target data.
Here, it is known that the LDPC code used in the transmission system in
Meanwhile, in the communication path 13, burst errors and erasures may occur. For example, in particular, in a case where the communication path 13 is a ground wave, power of a certain symbol becomes zero (erasure) in some cases according to a delay of an echo (a path other than a main path) in a multipath environment where a desired to undesired ratio (D/U) is 0 dB (power of undesired=echo is equal to power of desired=main path) in an orthogonal frequency division multiplexing (OFDM) system.
Furthermore, power of the entire symbols of OFDM at a specific time may become zero (erasure) due to a Doppler frequency in the case where D/U is 0 dB even in a flutter (a communication path in which a delay is 0 and to which an echo with Doppler frequency is added).
Moreover, a burst error may occur due to a wiring condition from a receiving unit (not illustrated) on the reception device 12 side such as an antenna that receives a signal from the transmission device 11 to the reception device 12, or power supply instability of the reception device 12.
Meanwhile, in decoding the LDPC code, the variable node operation in the expression (1) with addition of (the received value u0i of) the code bit of the LDPC code is performed, as illustrated in
Then, in decoding the LDPC code, the check node operation in the expression (7) is performed in the check node using the messages obtained at the variable nodes connected to the check node. Therefore, if the number of check nodes in which (the code bits of the LDPC codes corresponding to) a plurality of connected variable nodes becomes error (including erasure) at the same time is large, the performance of the decoding deteriorates.
In other words, for example, if two or more of the variable nodes connected to the check node become erasures at the same time, for example, the check node returns a message informing that a probability of a value being 0 and a probability of a value being 1 are equal to all the variable nodes. In this case, the check node returning the equal probability message will not contribute to one decoding processing (a set of the variable node operation and the check node operation). As a result, a large number of repetitions of the decoding processing is required, resulting in deterioration of the performance of the decoding and an increase in the power consumption of the reception device 12 for decoding the LDPC code.
Therefore, in the transmission system in
<Configuration Example of Transmission Device 11>
In the transmission device 11, one or more input streams as the target data are supplied to a mode adaptation/multiplexer 111.
The mode adaptation/multiplexer 111 performs processing such as mode selection and multiplexing of the one or more input streams supplied thereto as necessary, and supplies resulting data to a padder 112.
The padder 112 performs necessary zero padding (insertion of null) to the data from the mode adaptation/multiplexer 111, and supplies resulting data to a base band (BB) scrambler 113.
The BB scrambler 113 applies BB scramble to the data from the padder 112, and supplies resulting data to a BCH encoder 114.
The BCH encoder 114 performs BCH coding for the data from the BB scrambler 113, and supplies resultant data to an LDPC encoder 115 as LDPC target data to be LDPC-encoded.
The LDPC encoder 115 (encoding unit) performs, for the LDPC target data from the BCH encoder 114, LDPC coding according to a parity check matrix and the like in which a parity matrix that is a portion corresponding to a parity bit of the LDPC code has a step (dual diagonal) structure, and outputs an LDPC code having the LDPC target data as information bits, for example.
In other words, the LDPC encoder 115 performs LDPC coding for coding the LDPC target data to an LDPC code (corresponding to the parity check matrix) defined in a predetermined standard such as DVB-S.2, DVB-T.2, DVB-C.2, or ATSC 3.0 or to another LDPC code, and outputs a resulting LDPC code.
Here, the LDPC code defined in the standard of DVB-S.2 or ATSC 3.0 is an irregular repeat accumulate (IRA) code, and (a part or all of) the parity matrix in the parity check matrix of the LDPC code has a step structure. The parity matrix and the step structure will be described below. Furthermore, the IRA code is described in, for example, “Irregular Repeat-Accumulate Codes,” H. Jin, A. Khandekar, and R. J. McEliece, in Proceedings of 2nd International Symposium on Turbo codes and Related Topics, pp. 1-8, September 2000.
The LDPC code output by the LDPC encoder 115 is supplied to a bit interleaver 116.
The bit interleaver 116 performs bit interleaving described below for the LDPC code from the LDPC encoder 115, and supplies the LDPC code after the bit interleaving to a mapper (Mapper) 117.
The mapper 117 maps the LDPC code from the bit interleaver 116 to a signal point representing one symbol of quadrature modulation in units of code bits of one bit or more (in units of symbols) of the LDPC code and performs quadrature modulation (multiple value modulation).
In other words, the mapper 117 maps the LDPC code from the bit interleaver 116 into signal points determined by a modulation method for performing the quadrature modulation of an LDPC code, on a constellation that is an IQ plane defined with an I axis representing an I component in phase with a carrier and a Q axis representing a Q component orthogonal to the carrier, and performs the quadrature modulation.
In a case where the number of constellation signal points used in the modulation method of the quadrature modulation performed by the mapper 117 is 2m, the mapper 117 maps the LDPC code from the bit interleaver 116 into signal points representing symbols, of 2m signal points, in units of symbols, where m-bit code bits of the LDPC code are a symbol (one symbol).
Here, examples of the modulation method of the quadrature modulation performed by the mapper 117 include the modulation method defined in the standard such as DVB-S.2 or ATSC 3.0, and other modulation methods, in other words, for example, binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), phase-shift keying (8PSK), amplitude phase-shift keying (16APSK), 32APSK, quadrature amplitude modulation (16QAM), 16QAM, 64QAM, 256QAM, 1024QAM, 4096QAM, and pulse amplitude modulation (4PAM). Which modulation method of the quadrature modulation is used in the mapper 117 is set in advance according to an operation of an operator of the transmission device 11, for example.
Data obtained by the processing in the mapper 117 (the mapping result of mapped symbols at the signal points) is supplied to a time interleaver 118.
The time interleaver 118 performs time interleaving (interleaving in a time direction) in units of symbols, for the data from the mapper 117, and supplies resulting data to a single input single output/multiple input single output (SISO/MISO) encoder 119.
The SISO/MISO encoder 119 applies space-time coding to the data from the time interleaver 118, and supplies the data to a frequency interleaver 120.
The frequency interleaver 120 performs frequency interleaving (interleaving in a frequency direction) in units of symbols, for the data from the SISO/MISO encoder 119, and supplies the data to a frame builder/resource allocation unit 131.
Meanwhile, control data (signalling) for transmission control such as base band (BB) signaling (BB header) is supplied to a BCH encoder 121, for example.
The BCH encoder 121 performs BCH coding for the control data supplied thereto, similarly to the BCH encoder 114, and supplies resulting data to an LDPC encoder 122.
The LDPC encoder 122 performs LDPC coding for the data from the BCH encoder 121 as LDPC target data, similarly to the LDPC encoder 115, and supplies a resulting LDPC code to a mapper 123.
The mapper 123 maps the LDPC code from the LDPC encoder 122 to a signal point representing one symbol of quadrature modulation in units of code bits of one bit or more (in units of symbols) of the LDPC code and performs quadrature modulation, similarly to the mapper 117, and supplies resulting data to a frequency interleaver 124.
The frequency interleaver 124 performs frequency interleaving in in units of symbols, for the data from the mapper 123, similarly to the frequency interleaver 120, and supplies resulting data to a frame builder/resource allocation unit 131.
The frame builder/resource allocation unit 131 inserts pilot symbols into necessary positions of the data (symbols) from the frequency interleavers 120 and 124, and configures a frame by a predetermined number of symbols (for example, a physical layer (PL) frame, a T2 frame, a C2 frame, or the like) from resulting data (symbols), and supplies the frame to an OFDM generation unit 132.
The OFDM generation unit 132 generates an OFDM signal corresponding to the frame from the frame builder/resource allocation unit 131, and transmits the OFDM signal via the communication path 13 (
Note that the transmission device 11 can be configured without including part of the blocks illustrated in
<Configuration Example of Bit Interleaver 116>
The bit interleaver 116 has a function to interleave data, and is configured by a parity interleaver 23, a group-wise interleaver 24, and a block interleaver 25.
The parity interleaver 23 performs parity interleaving to interleave the position of another parity bit with the parity bit of the LDPC code from the LDPC encoder 115, and supplies the LDPC code after the parity interleaving to the group-wise interleaver 24.
The group-wise interleaver 24 performs group-wise interleaving for the LDPC code from the parity interleaver 23, and supplies the LDPC code after the group-wise interleaving to the block interleaver 25.
Here, in the group-wise interleaving, the LDPC code from the parity interleaver 23 is interleaved in units of bit groups, where 360 bits of one section is set as a bit group, the one section being obtained by dividing the LDPC code of one code from the head of the LDPC code into sections in units of 360 bits, the unit being equal to a parallel factor P to be described below, and taking one of the divided sections as the one section.
In a case of performing the group-wise interleaving, an error rate can be improved as compared with a case of not performing the group-wise interleaving. As a result, favorable communication quality can be secured in data transmission.
The block interleaver 25 performs block interleaving for demultipiexing the LDPC code from the group-wise interleaver 24 to symbolize the LDPC code of one code into an m-bit symbol that is a unit of mapping, and supplies the symbol to the mapper 117 (
Here, in the block interleaving, for example, the LDPC code from the group-wise interleaver 24 is written in a column (vertical) direction and is read in a row (cross) direction with respect to a storage region in which columns as storage regions each storing a predetermined bit length in the column direction are arranged in the row direction by the number of bit length m of the symbol, whereby the LDPC code is symbolized into the m-bit symbol.
<Parity Check Matrix of LDPC Code>
The parity check matrix H has a low-density generation matrix (LDGM) structure and can be expressed as an expression H=[HA|HT] (elements of the information matrix HA are on the left side and elements of the parity check matrix HT are on the right side) using an information matrix HA of a portion corresponding to the information bits and a parity matrix HT corresponding to the parity bits, of the code bits of the LDPC code.
Here, the bit length of the information bits and the bit length of the parity bits, of the code bits of the LDPC code of one code (one codeword), are respectively referred to as an information length K and a parity length M, and the bit length of the code bits of one (one codeword) LDPC code is referred to as code length N(=K+M).
The information length K and the parity length M of the LDPC code of a given code length N are determined by a coding rate. Furthermore, the parity check matrix H is a matrix of M×N in rows×columns (M-row N-column matrix). Then, the information matrix HA is an M×K matrix, and the parity matrix Hr is an M×M matrix.
As the parity matrix HT of the parity check matrix H used for LDPC coding in the LDPC encoder 115, a parity matrix HT similar to the parity check matrix H of the LDPC code defined in the standard such as DVB-T.2 can be adopted, for example.
The parity matrix HT of the parity check matrix H of the LDPC code defined in the standard such as DVB-T.2 is a matrix having a step structure (lower bidiagonal matrix) in which elements of 1 are arranged in a step-like manner, as illustrated in
As described above, the LDPC code of the parity check matrix H in which the parity matrix HT has the step structure can be easily generated using the parity check matrix H.
In other words, the LDPC code (one codeword) is expressed with a row vector c, and a column vector obtained by transposing the row vector thereof is represented as cT. Furthermore, a portion of the information bits, of the row vector c that is the LDPC code, is expressed with a row vector A, and a portion of the parity bits, of the row vector c, is expressed with a row vector T.
In this case, the row vector c can be expressed as an expression c=[A|T] (elements of the row vector A are on the left side and elements of the row vector T are on the right side) using the row vector A as the information bits and the row vector T as the parity bits.
The parity check matrix H and the row vector c=[A|T] as the LDPC code need to satisfy an expression HcT=0, and the row vector T as the parity bits constituting the row vector c=[A|T] satisfying the expression HcT=0 can be sequentially obtained (in order) by sequentially setting the element of each row to 0 from the element in the 1st row of the column vector HcT in the expression HcT=0 in a case where the parity matrix HT of the parity check matrix H=[HA|HT] has the step structure illustrated in
In the parity check matrix H of the LDPC code defined in the standard such as DVB-T.2, the column weight is X in KX columns from the 1st column, 3 in following K3 columns, 2 in following M−1 columns, and 1 in the last one column.
Here, KX+K3+M−1+1 is equal to the code length N.
In the standard such as DVB-T.2, LDPC codes having code lengths N of 64800 bits and 16200 bits are defined.
Then, eleven coding rates (nominal rates) of 1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6, 8/9, and 9/10 are defined for the LDPC code with the code length N of 64800 bits. Ten coding rates of 1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6, and 8/9 are defined for the LDPC code with the code length N of 16200 bits.
Here, the code length N of 64800 bits is also referred to as 64 k bits and the code length N of 16200 bits is also referred to as 16 k bits.
In regard to the LDPC code, code bits corresponding to a column having a larger column weight of the parity check matrix H tend to have a lower error rate.
In the parity check matrix H defined in the standard such as DVB-T.2 illustrated in
<Parity Interleaving>
The parity interleaving by the parity interleaver 23 in
As illustrated in
By the way, the LDPC code output from the LDPC encoder 115 in
A in
In the parity matrix Hr having a step structure, elements of 1 are adjacent (except the 1st row) in rows. Therefore, in the Tanner graph of the parity matrix HT, two adjacent variable nodes corresponding to columns of the two adjacent elements where values of the parity matrix HT are 1 are connected to the same check node.
Therefore, when the parity bits corresponding to the above two adjacent variable nodes become errors at the same time due to burst errors, erasures, or the like, the check node connected to the two variable nodes corresponding to the two error parity bits (variable nodes seeking a message using the parity bits) returns the message informing that a probability of a value being 0 and a probability of a value being 1 are equal to the variable nodes connected to the check node. Therefore, the performance of the decoding deteriorates. Then, when a burst length (the bit length of the parity bits which become errors in succession) becomes large, the number of check nodes returning the message of equal probability increases, and the performance of the decoding further deteriorates.
Therefore, the parity interleaver 23 (
Here, the information matrix HA of the parity check matrix H corresponding to the LDPC code output by the LDPC encoder 115 has a cyclic structure, similarly to the information matrix of the parity check matrix H corresponding to the LDPC code defined in the standard such as DVB-T.2.
The cyclic structure is a structure in which a certain column matches a cyclically shifted another column, and includes, for example, a structure in which, for each P columns, positions of 1 of rows of the P columns become positions cyclically shifted in the column direction by a predetermined value such as a value proportional to a value q obtained by dividing the first column of the P columns by the parity length M. Hereinafter, the P columns in the cyclic structure are referred to as a parallel factor, as appropriate.
As the LDPC code defined in the standard such as DVB-T.2, there are two types of LDPC codes with the code lengths N of 64800 bits and 16200 bits as described in
Furthermore, the parity length M is a value other than a prime number represented by an expression M=q×P=q×360, using a value q that varies depending on the coding rate. Therefore, similarly to the parallel factor P, the value q is also another one of the divisors of the parity length M except 1 and M, and is obtained by dividing the parity length M by the parallel factor P (a product of P and q, which are the divisors of the parity length M, becomes the parity length M).
As described above, the parity interleaver 23 interleaves the position of (K+Py+x+1)th code bit with (K+qx+y+1)th code bit of code bits of an N-bit LDPC code, as the parity interleaving, where the information length is K, an integer from 0 to P, exclusive of P, is x, and an integer from 0 to q, exclusive of q, is y.
Since both the (K+qx+y+1)th code bit and the (K+Py+x+1)th code bit are subsequent code bits of (K+1)th code bit and thus are parity bits, the positions of the parity bits of the LDPC code are moved according to the parity interleaving.
According to such parity interleaving, (the parity bits corresponding to) the variable nodes connected to the same check node are separated by the parallel factor P, in other words, 360 bits. Therefore, in a case where the burst length is less than 360 bits, a situation where a plurality of variable nodes connected to the same check node becomes error at the same time can be avoided, and as a result, the resistance to the burst errors can be improved.
Note that the LDPC code after the parity interleaving to interleave the position of the (K+Py+x+1)th code bit with the (K+qx+y+1)th code bit matches the LDPC code of the parity check matrix (hereinafter also referred to as a transformed parity check matrix) that is obtained by performing column permutation to permutate the (K+qx+y+1)th column of the original parity check matrix H with the (K+Py+x+1)th column.
Furthermore, a pseudo cyclic structure having P columns (360 columns in
Here, the pseudo cyclic structure means a structure having a cyclic structure excluding a part.
A transformed parity check matrix obtained by applying column permutation corresponding to the parity interleaving to the parity check matrix of the LDPC code defined in the standard such as DVB-T.2 lacks one element of 1 (has an element of 0) in a portion (a shift matrix to be described below) of 360 rows×360 columns in an upper right corner portion of the transformed parity check matrix, and thus has a so-called pseudo cyclic structure, rather than a (complete) cyclic structure on that regard.
A transformed parity check matrix for the parity check matrix of the LDPC code output by the LDPC encoder 115 has a pseudo cyclic structure, similarly to the transformed parity check matrix for the parity check matrix of the LDPC code defined in the standard such as DVB-T.2, for example.
Note that the transformed parity check matrix in
The LDPC encoder 115 waits for supply of the LDPC target data from the BCH encoder 114. In step S101, the LDPC encoder 115 encodes the LDPC target data into the LDPC code on the basis of the parity check matrix and supplies the LDPC code to the bit interleaver 116. The processing proceeds to step S102.
In step S102, the bit interleaver 116 performs the bit interleaving for the LDPC code from the LDPC encoder 115, and supplies the symbol obtained by the bit interleaving to the mapper 117. The processing proceeds to step S103.
In other words, in step S102, in the bit interleaver 116 (
The group-wise interleaver 24 performs the group-wise interleaving for the LDPC code from the parity interleaver 23, and supplies the LDPC code to the block interleaver 25.
The block interleaver 25 performs the block interleaving for the LDPC code after the group-wise interleaving by the group-wise interleaver 24, and supplies a resulting m-bit symbol to the mapper 117.
In step S103, the mapper 117 maps the symbol from the block interleaver 25 to any of 2m signal points determined by the modulation method of the quadrature modulation performed by the mapper 117 and performs the quadrature modulation, and supplies resulting data to the time interleaver 118.
As described above, by performing the parity interleaving and the group-wise interleaving, the error rate of the case where a plurality of code bits of the LDPC code is transmitted as one symbol can be improved.
Here, in
In other words, both the parity interleaving and the group-wise interleaving can be performed by writing and reading code bits with respect to a memory, and can be expressed by a matrix for converting an address for writing code bits (write address) into an address for reading code bits (read address).
Therefore, by obtaining a matrix obtained by multiplying a matrix expressing the parity interleaving and a matrix expressing the group-wise interleaving, the parity interleaving is performed by converting code bits by these matrices, and further the group-wise interleaving is performed for the LDPC code after the parity interleaving, whereby a result can be obtained.
Furthermore, the block interleaver 25 can also be integrally configured in addition to the parity interleaver 23 and the group-wise interleaver 24
In other words, the block interleaving performed by the block interleaver 25 can also be expressed by the matrix converting the write address of the memory for storing the LDPC code into the read address.
Therefore, by obtaining a matrix obtained by multiplying the matrix expressing the parity interleaving, the matrix expressing the group-wise interleaving, and the matrix expressing the block interleaving, the parity interleaving, the group-wise interleaving, and the block interleaving can be collectively performed by the matrices.
Note that one or the amount of the parity interleaving and the group-wise interleaving may not be performed.
<Configuration Example of LDPC Encoder 115>
Note that the LDPC encoder 122 in
As described in
Then, the eleven coding rates of 1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6, 8/9, and 9/10 are defined for the LDPC code with the code length N of 64800 bits. The ten coding rates of 1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6, and 8/9 are defined for the LDPC code with the code length N of 16200 bits (
The LDPC encoder 115 can perform, for example, such coding (error correction coding) of the LDPC codes with the code lengths N of 64800 bits and 16200 bits and the coding rates on the basis of the parity check matrix H prepared for each code length N and each coding rate.
Furthermore, the LDPC encoder 115 can perform LDPC coding on the basis of the parity check matrix H of an LDPC code with a code length N of 17280 bits or another arbitrary code length N and a coding rate of 2/16, 3/16, 4/16, 5/16, 6/16, 7/16, 8/16, 9/16, 10/16, 11/16, 12/16, 13/16, or 14/16 or another arbitrary coding rate r.
The LDPC encoder 115 is configured by a coding processing unit 601 and a storage unit 602.
The coding processing unit 601 is configured by a coding rate setting unit 611, an initial value table reading unit 612, a parity check matrix generation unit 613, an information bit reading unit 614, a coding parity operation unit 615, and a control unit 616. The coding processing unit 601 performs the LDPC coding for the LDPC target data supplied to the LDPC encoder 115, and supplies a resulting LDPC code to the bit interleaver 116 (
In other words, the coding rate setting unit 611 sets the code length N and the coding rate r of the LDPC code, and in addition, specific information specifying the LDPC code, according to the operation of the operator, for example.
The initial value table reading unit 612 reads, from the storage unit 602, a parity check matrix initial value table to be described below, expressing the parity check matrix of the LDPC code specified with the specific information set by the coding rate setting unit 611.
The parity check matrix generation unit 613 generates the parity check matrix H on the basis of the parity check matrix initial value table read by the initial value table reading unit 612, and stores the parity check matrix H in the storage unit 602. For example, the parity check matrix generation unit 613 arranges the elements of 1 of the information matrix HA corresponding to the information length K (=the code length N−the parity length M) according to the code length N and the coding rate r set by the coding rate setting unit 611 with a period of every 360 columns (parallel factor P) in the column direction to generate the parity check matrix H, and stores the parity check matrix H in the storage unit 602.
The information bit reading unit 614 reads (extracts) the information bits of the information length K from the LDPC target data supplied to the LDPC encoder 115.
The coding parity operation unit 615 reads the parity check matrix H generated by the parity check matrix generation unit 613 from the storage unit 602, and calculates the parity bits for the information bits read by the information bit reading unit 614 on the basis of a predetermined expression using the parity check matrix H, thereby generating the codeword (LDPC code).
The control unit 616 controls the blocks constituting the coding processing unit 601.
The storage unit 602 stores, for example, a plurality of parity check matrix initial value tables respectively corresponding to the plurality of coding rates and the like illustrated in
In step S201, the coding rate setting unit 611 sets the code length N and the coding rate r for performing the LDPC coding, and in addition, the specific information specifying the LDPC code.
In step S202, the initial value table reading unit 612 reads, from the storage unit 602, the predetermined parity check matrix initial value table specified with the code length N, the coding rate r, and the like as the specific information set by the coding rate setting unit 611.
In step S203, the parity check matrix generation unit 613 obtains (generates) the parity check matrix H of the LDPC code with the code length N and the coding rate r set by the coding rate setting unit 611, using the parity check matrix initial value table read from the storage unit 602 by the initial value table reading unit 612, and supplies and stores the parity check matrix H in the storage unit 602.
In step S204, the information bit reading unit 614 reads the information bits of the information length K (=N×r) corresponding to the code length N and the coding rate r set by the coding rate setting unit 611 from the LDPC target data supplied to the LDPC encoder 115, and reads the parity check matrix H obtained by the parity check matrix generation unit 613 from the storage unit 602, and supplies the information bits and the parity check matrix H to the coding parity operation unit 615.
In step S205, the coding parity operation unit 615 sequentially operates the parity bit of the codeword c that satisfies the expression (8), using the information bits and the parity check matrix H from the information bit reading unit 614.
HcT=0 (8)
In the expression (8), c represents the row vector as the codeword (LDPC code), and cT represents transposition of the row vector c.
Here, as described above, in the case of expressing the portion of the information bits, of the row vector c as the LDPC code (one codeword), with the row vector A, and the portion of the parity bits, of the row vector c, with the row vector T, the row vector c can be expressed as the expression c=[A|T] using the row vector A as the information bits and the row vector T as the parity bits.
The parity check matrix H and the row vector c=[A|T] as the LDPC code need to satisfy the expression HcT=0, and the row vector T as the parity bits constituting the row vector c=[A|T] satisfying the expression HcT=0 can be sequentially obtained by sequentially setting the element of each row to 0 from the element in the 1st row of the column vector HcT in the expression HcT=0 in the case where the parity matrix HT of the parity check matrix H=[HA|HT] has the step structure illustrated in
The coding parity operation unit 615 obtains the parity bits T for the information bits A from the information bit reading unit 614, and outputs the codeword c=[A|T] expressed with the information bits A and the parity bits T as an LDPC coding result of the information bits A.
Thereafter, in step S206, the control unit 616 determines whether or not to terminate the LDPC coding. In a case where it is determined in step S206 that the LDPC coding is not terminated, in other words, for example, in a case where there is still LDPC target data to be LDPC-encoded, the processing returns to step S201 (or step S204), and hereinafter the processing from step S201 (or step S204) to step S206 is repeated.
Furthermore, in step S206, in a case where it is determined that the LDPC coding is terminated, in other words, for example, in a case where there is no LDPC target data to be LDPC-encoded, the LDPC encoder 115 terminates the processing.
In regard to the LDPC encoder 115, the parity check matrix initial value table (expressing the parity check matrix) of the LDPC codes of various code lengths N and coding rates r can be prepared in advance. The LDPC encoder 115 can perform the LDPC coding for the LDPC codes of various code lengths N and coding rates r, using the parity check matrix H generated from the parity check matrix initial value table prepared in advance.
<Example of Parity Check Matrix Initial Value Table>
The parity check matrix initial value table is a table representing the positions of the elements of 1 of the information matrix HΛ (
In other words, the parity check matrix initial value table represents at least the positions of the elements of 1 of the information matrix HA in every 360 columns (parallel factor P).
Furthermore, as the parity check matrix H, there are a parity check matrix in which the entire parity matrix HT has a step structure, and a parity check matrix in which a part of the parity matrix HT has a step structure and the remaining part is a diagonal matrix (identity matrix).
Hereinafter, an expression method for the parity check matrix initial value table representing the parity check matrix in which a part of the parity matrix HT has a step structure and the remaining part is a diagonal matrix is also referred to as type A method. Furthermore, an expression method for the parity check matrix initial value table indicating the parity check matrix in which the entire parity matrix HT has a step structure is also referred to as type B method.
Furthermore, the LDPC code for the parity check matrix represented by the parity check matrix initial value table by the type A method is also referred to as type A code, and the LDPC code for the parity check matrix represented by the parity check matrix initial value table by the type B method is also referred to as type B code.
The designations “type A” and “type B” are designations in accordance with the standard of ATSC 3.0. For example, in ATSC 3.0, both the type A code and type B code are adopted.
Note that, in DVB-T.2 and the like, the type B code is adopted.
In other words,
The parity check matrix generation unit 613 (
In other words,
The parity check matrix initial value table by the type B method is a table representing the positions of the elements of 1 of the entire information matrix HA corresponding to the information length K according to the code length N and the coding rate r of the LDPC code in every 360 columns (parallel factor P). In the i-th row, row numbers of the elements of 1 of the (1+360×(i−1))th column of the parity check matrix H (row numbers of when the row number of the 1st row of the parity check matrix H is counted as 0) are arranged by the number of the column weights of the (1+360×(i−1))th column.
Here, since the parity matrix HT (
The number of rows k+1 of the parity check matrix initial value table by the type B method differs depending on the information length K.
The relationship of the expression (9) holds between the information length K and the number of rows k+1 of the parity check matrix initial value table.
K=(k+1)×360 (9)
Here, 360 in the expression (9) is the parallel factor P described in
In the parity check matrix initial value table in
Therefore, the column weight of the parity check matrix H obtained from the parity check matrix initial value table in
The 1st row of the parity check matrix initial value table in
Furthermore, the 2nd row of the parity check matrix initial value table in
As described above, the parity check matrix initial value table represents the positions of the elements of 1 of the information matrix HA of the parity check matrix H in every 360 columns.
The columns other than the (1+360×(i−1))th column of the parity check matrix H, in other words, the (2+360×(i−1)th to (360×i)th columns are obtained by cyclically shifting and arranging the elements of 1 of the (1+360×(i−1))th column determined by the parity check matrix initial value table downward (downward of the columns) according to the parity length M.
In other words, for example, the (2+360×(i−1))th column is obtained by cyclically shifting the (1+360×(i−1))th column downward by M/360 (=q). The next (3+360×(i−1))th column is obtained by cyclically shifting the (1+360×(i−1))th column downward by 2×M/360 (=2×q) (by cyclically shifting the (2+360×(i−1))th column downward by M/360 (=q)).
Now, in a case where the numerical value of the j-th column (j-th from the left) in the i-th row (i-th from the top) of the parity check matrix initial value table is represented as hi,j and the row number of the element of j-th 1 of the w-th column of the parity check matrix H is represented as Hw-j, the row number Hw-j of the element of 1 of the w-th column that is a column other than the (1+360×(i−1))th column of the parity check matrix H can be obtained by the expression (10).
Hw-j=mod(hi,j+mod((w−1),P)×q,M) (10)
Here, mod (x, y) means the remainder of dividing x by y.
Furthermore, P is the above-described parallel factor, and in the present embodiment, P is 360 as in DVB-T.2 or the like and the standard of ATSC 3.0, for example. Moreover, q is a value M/360 obtained by dividing the parity length M by the parallel factor P (=360).
The parity check matrix generation unit 613 (
Moreover, the parity check matrix generation unit 613 (
The parity check matrix by the type A method is configured by an A matrix, a B matrix, a C matrix, a D matrix, and a Z matrix.
The A matrix is an upper left matrix in the parity check matrix H, of M1 rows and K columns expressed by a predetermined value M1 and the information length K=the code length N×the coding rate r of the LDPC code.
The B matrix is a matrix of M1 rows and M1 columns having a step structure adjacent to the right of the A matrix.
The C matrix is a matrix of N−K−M1 rows and K+M1 columns adjacent to below the A matrix and the B matrix.
The D matrix is an identity matrix of N−K−M1 rows and N−K−M1 columns adjacent to the right of the C matrix.
The Z matrix is a zero matrix (0 matrix) of M1 rows and N−K−M1 columns adjacent to the right of the B matrix.
In the parity check matrix H by the type A method configured by the above A matrix to D matrix and Z matrix, the A matrix and a part of the C matrix constitute the information matrix, and the B matrix, the rest of the C matrix, the D matrix, and the Z matrix constitute the parity matrix.
Note that, since the B matrix is a matrix with a step structure and the D matrix is an identity matrix, a part (the part of the B matrix) of the parity matrix of the parity check matrix H by the type A method has the step structure and the remaining part (the part of the D matrix) is a diagonal matrix (identity matrix).
The A matrix and the C matrix have a cyclic structure of every parallel factor P columns (for example, 360 columns), similarly to the information matrix of the parity check matrix H by type B method, and the parity check matrix initial value table by the type A method represents the positions of the elements of 1 of the A matrix and the C matrix in every 360 columns.
Here, as described above, since the A matrix and a part of the C matrix constitute the information matrix, the parity check matrix initial value table by the type A method representing the positions of the elements of 1 of the A matrix and the C matrix in every 360 columns can be said to represent at least the positions of the elements of 1 of the information matrix in every 360 columns.
Note that, since the parity check matrix initial value table by the type A method represents the positions of the elements of 1 of the A matrix and the C matrix in every 360 columns, the parity check matrix initial value table can also be said to represent the positions of the elements of 1 of a part (the remaining part of the C matrix) of the parity check matrix in every 360 columns.
In other words,
The parity check matrix initial value table by the type A method is a table representing the positions of the elements of 1 of the A matrix and the C matrix in every parallel factor P. In the i-th row, row numbers of the elements of 1 of the (1+P×(i−1))th column of the parity check matrix H (the row numbers of when the row number of the 1st row of the parity check matrix H is counted as 0) are arranged by the number of the column weight of the (1+P×(i−1))th column.
Note that, here, to simplify the description, the parallel factor P is 5, for example.
The parity check matrix H by the type A method has M1, M2, Q1, and Q2 as parameters.
M1 (
M2 (
Here, since the information length K is N×r=35×2/7=10 and the parity length M is N−K=35−10=25, M2 is M−M1=25−15=10.
Q1 is obtained according to an expression Q1=M1/P, and represents the number of shifts (the number of rows) of cyclic shift in the A matrix.
In other words, the columns other than the (1+P×(i−1))th column of the A matrix of the parity check matrix H by the type A method, in other words, the (2+P×(i−1))th to (P×i)th columns are obtained by cyclically shifting and arranging the elements of 1 of the (1+P×(i−1))th column determined by the parity check matrix initial value table downward (downward of the columns), and Q1 represents the number of shifts of the cyclic shift in the A matrix.
Q2 is obtained according to an expression Q2=M2/P, and represents the number of shifts (the number of rows) of cyclic shift in the C matrix.
In other words, the columns other than the (1+P×(i−1))th column of the C matrix of the parity check matrix H by the type A method, in other words, the (2+P×(i−1))th to (P×i)th columns are obtained by cyclically shifting and arranging the elements of 1 of the (1+P×(i−1))th column determined by the parity check matrix initial value table downward (downward of the columns), and Q2 represents the number of shifts of the cyclic shift in the C matrix.
Here, Q1 is M1/P=15/5=3, and Q2 is M2/P=10/5=2.
In the parity check matrix initial value table in
In other words, the 1st row of the parity check matrix initial value table in
Here, in this case, since the A matrix (
Therefore, rows #2 and #6 of the rows with the row numbers 2, 6, and 18 (hereinafter described as rows #2, #6, and #18) are rows of the A matrix, and the row #18 is a row of the C matrix.
The 2nd row of the parity check matrix initial value table in
Here, in the 6th (=(1+5×(2−1))th) column of the parity check matrix H, the rows #2 and #10 of the rows #2, #10, and #19 are rows of the A matrix, and the row #19 is a row of the C matrix.
The 3rd row of the parity check matrix initial value table in
Here, the row #22 is a row of the C matrix in the 11th (=(1+5×(3−1))th) column of the parity check matrix H.
Similarly, 19 in the 4th row of the parity check matrix initial value table in
As described above, the parity check matrix initial value table represents the positions of the elements of 1 of the A matrix and the C matrix of the parity check matrix H in every parallel factor P=5 columns.
The columns other than the (1+5×(i−1))th column of the A matrix and the C matrix of the parity check matrix H, in other words, the (2+5×(i−1))th to (5×i)th columns are obtained by cyclically shifting and arranging the elements of 1 of the (1+5×(i−1))th column determined by the parity check matrix initial value table downward (downward of the columns) according to the parameters Q1 and Q2.
In other words, for example, the (2+5×(i−1))th column of the A matrix is obtained by cyclically shifting the (1+5×(i−1))th column downward by Q1 (=3). The next (3+5×(i−1))th column is obtained by cyclically shifting the (1+5×(i−1))th column downward by 2×Q1 (=2×3) (by cyclically shifting the (2+5×(i−1))th column downward by Q1).
Furthermore, for example, the (2+5×(i−1))th column of the C matrix is obtained by cyclically shifting the (1+5×(i−1))th column downward by Q2 (=2). The next (3+5×(i−1))th column is obtained by cyclically shifting the (1+5×(i−1))th column downward by 2×Q2 (=2×2) (by cyclically shifting the (2+5×(i−1))th column downward by Q2).
In the A matrix in
Then, the columns from the 2nd (=(2+5×(1−1))th) to 5th (=(5+5×(1−1))th) columns are obtained by cyclically shifting the previous columns downward by Q1=3.
Moreover, in the A matrix in
Then, the columns from the 7th (=(2+5×(2−1))th) to 10th (=(5+5×(2−1))th) columns are obtained by cyclically shifting the previous columns downward by Q1=3.
The parity check matrix generation unit 613 (
In the C matrix in
Then, the columns from the 2nd (=(2+5×(1−1))th) to 5th (=(5+5×(1−1))th) columns of the C matrix are obtained by cyclically shifting the previous columns downward by Q2=2.
Moreover, in the C matrix in
Then, columns from the 7th (=(2+5×(2−1))th) to the 10th (=(5+5×(2−1))th) columns, columns from the 12th (=(2+5×(3−1))th) to 15th (=(5+5×(3−1))th) columns, columns from the 17th (=(2+5×(4−1))th) to 20th (=(5+5×(4−1))th) columns, and columns from the 22nd (=(2+5×(5−1))th) to the 25th (=(5+5×(5−1))th) columns are obtained by cyclically shifting the previous columns downward by Q2=2.
The parity check matrix generation unit 613 (FIG. 18) generates the C matrix using the parity check matrix initial value table and arranges the C matrix below the A matrix and the B matrix (after parity interleaving).
Moreover, the parity check matrix generation unit 613 arranges the Z matrix adjacent to the right of the B matrix and arranges the D matrix adjacent to the right of the C matrix to generate the parity check matrix H illustrated in
The parity check matrix generation unit 613 treats the D matrix after generating the parity check matrix H in
(The coding parity operation unit 615 (
Here, the LDPC code generated using the parity check matrix H in
The LDPC encoder 115 can perform LDPC coding (generates an LDPC code) using the parity check matrix H in
In a case of performing the LDPC coding using the parity check matrix H in
The transformed parity check matrix is, as described below, a matrix represented by a combination of a P×P identity matrix, a quasi identity matrix in which one or more of is in the identity matrix are 0, a shift matrix obtained by cyclically shifting the identity matrix or the quasi identity matrix, a sum matrix that is a sum of two or more of the identity matrix, the quasi identity matrix, and the shift matrix, and a P×P zero matrix.
By using the transformed parity check matrix for decoding the LDPC code, architecture of performing P check node operations and variable node operations at the same time can be adopted in decoding the LDPC code, as described below.
<New LDPC Code>
One of methods of securing favorable communication quality in data transmission using an LDPC code, there is a method using an LDPC code with high performance.
Hereinafter, a new LDPC code with high performance (hereinafter also referred to as a new LDPC code) will be described.
As the new LDPC code, for example, the type A code or the type B code corresponding to the parity check matrix H having a cyclic structure with the parallel factor P of 360 similar to that of DVB-T.2, ATSC 3.0, or the like, can be adopted.
The LDPC encoder 115 (
Furthermore, the LDPC encoder 115 can perform LDPC coding to obtain a new LDPC code on the basis of (a parity check matrix H obtained from) a parity check matrix initial value table of the new LDPC code with the code length N of 17280 bits (17 k bits), for example, which is shorter than 64 k bits, and the coding rate r of any of 2/16, 3/16, 4/16, 5/16, 6/16, 7/16, 8/16, 9/16, 10/16, 11/16, 12/16, 13/16, or 14/16, for example.
In the case of performing the LDPC coding to the new LDPC code with the code length N of 17280 bits, a parity check matrix initial value table of the new LDPC code is stored in the storage unit 602 of the LDPC encoder 115 (
The new LDPC code is an LDPC code with high performance.
Here, the LDPC code with high performance is an LDPC code obtained from an appropriate parity check matrix H.
The appropriate parity check matrix H is, for example, a parity check matrix that satisfies a predetermined condition that makes a bit error rate (BER) (and a frame error rate (FER)) smaller when the LDPC code obtained from the parity check matrix H is transmitted at low Es/N0 or Eb/No (signal power to noise power ratio per bit).
The appropriate parity check matrix H can be obtained by, for example, performing a simulation to measure BERs of when LDPC codes obtained from various parity check matrices satisfying the predetermined condition are transmitted at low Es/No.
Examples of the predetermined condition to be satisfied by the appropriate parity check matrix H include a good analysis result obtained by an analysis method of performance of code called density evolution, absence of a loop of the elements of 1, called cycle 4, and the like.
Here, it is known that the decoding performance of the LDPC code is degraded if the elements of 1 are densely packed in the information matrix HA as in the cycle 4, and therefore, absence of the cycle 4 is desirable in the parity check matrix H.
In the parity check matrix H, a minimum value of the length of a loop (loop length) configured by the elements of 1 is called girth. The absence of the cycle 4 means that the girth is greater than 4.
Note that the predetermined condition to be satisfied by the appropriate parity check matrix H can be appropriately determined from the viewpoints of improvement of the decoding performance of the LDPC code, facilitation (simplification) of the decoding processing for the LDPC code, and the like.
The density evolution is a code analysis method of calculating an expected value of an error probability for the entire LDPC code (ensemble) with the code length N of ∞ characterized by a degree sequence to be described below.
For example, when increasing a variance of noise from 0 on an AWGN channel, the expected value of the error probability of an ensemble is initially 0, but the expected value becomes not 0 when the variance of noise becomes a certain threshold or greater.
According to the density evolution, good or bad of the performance of the ensemble (appropriateness of the parity check matrix) can be determined by comparing the threshold of the variance of noise (hereinafter also referred to as performance threshold) at which the expected value of the error probability becomes not 0.
Note that, for a specific LDPC code, an ensemble to which the LDPC code belongs is determined, and the density evolution is performed for the ensemble, whereby rough performance of the LDPC code can be predicted.
Therefore, if an ensemble with high performance is found, the LDPC code with high performance can be found from LDPC codes belonging to the ensemble.
Here, the above-described degree sequence indicates what ratio the variable nodes and check nodes having weights of respective values exist to the code length N of the LDPC code.
For example, a regular (3, 6) LDPC code with the coding rate of 1/2 belongs to an ensemble characterized by a degree sequence indicating that the weights (column weights) of all the variable nodes are 3 and the weights (row weights) of all the check nodes are 6.
In a Tanner bluff in
Three edges with an equal column weight are connected to each variable node. Therefore, there are a total of 3N edges connected to the N variable nodes.
Furthermore, six edges with an equal row weight are connected to each check node. Therefore, there are a total of 3N edges connected to the N/2 check nodes.
Moreover, in the Tanner graph in
The interleaver randomly rearranges the 3N edges connected to the N variable nodes and connects each edge after the rearrangement to any of the 3N edges connected to the N/2 check nodes.
The number of patterns for rearranging the 3N edges connected to the N variable nodes in the interleaver is (3N) ! (=(3N)×(3N−1)× . . . ×1). Therefore, the ensemble characterized by the degree sequence indicating that the weights of all the variable nodes are 3 and the weights of all the check nodes are 6 is a set of (3N)!LDPC codes.
In the simulation for finding the LDPC code with high performance (appropriate parity check matrix), a multi-edge type ensemble has been used in the density evolution.
In the multi-edge type ensemble, the interleaver which the edges connected to the variable nodes and the edges connected to the check nodes go through is divided into multi edges, whereby characterization of the ensemble is more strictly performed.
In the Tanner graph in
Furthermore, in the Tanner graph in
Moreover, in the Tanner graph in
Here, the density evolution and its implementation are described in, for example, “On the Design of Low-Density Parity-Check Codes within 0.0045 dB of the Shannon Limit”, S. Y. Chung, G. D. Forney, T. J. Richardson, R. Urbanke, IEEE Communications Leggers, VOL. 5, NO. 2, February 2001.
In the simulation for finding (the parity check matrix of) the new LDPC code, an ensemble in which the performance threshold that is Eb/N0 (signal power to noise power ratio per bit) at which BER starts to drop (starts to become small) becomes a predetermined value or less has been found by the multi-edge type density evolution, and the LDPC code that makes BER in a case of using one or more quadrature modulations such as QPSK small has been selected from among the LDPC codes belonging to the ensemble, as the LDPC code with high performance.
(The parity check matrix initial value table representing the parity check matrix of) the new LDPC code has been obtained by the above simulation.
Therefore, according to the new LDPC code, favorable communication quality can be secured in data transmission.
In regard to the parity check matrix H of the type A code, as illustrated in
Note that K1+K2+K3 is equal to the information length K, and M1+M2 is equal to the parity length M. Therefore, K1+K2+K3+M1+M2 is equal to the code length N=17280 bits.
Furthermore, in regard to the parity check matrix H of the type A code, the column weight of M1−1 columns from the 1st column of the B matrix is 2, and the column weight of the M1-th column (last column) of the B matrix is 1. Moreover, the column weight of the D matrix is 1 and the column weight of the Z matrix is 0.
K, X1, K1, X2, K2, X3, K3, XM1, M1, and M2 as parameters of the parity check matrices H of the type A codes of r=2/16, 3/16, 4/16, 5/16, 6/16, and 7/16 are as illustrated in
The parameters X1, K1, X2, K2, X3, K3, XM1, M1 (or M2) are set to further improve the performance (for example, the error rate or the like) of the LDPC codes.
In regard to the parity check matrix H of the type B code, as illustrated in
Note that KX1+KX2+KX3+KX4+KY1 is equal to the information length K, and KX1+KX2+KX3+KX4+KY1+M is equal to the code length N=17280 bits.
Furthermore, in regard to the parity check matrix H of the type B code, the column weight of M−1 columns excluding the last one column, of the last M columns, is 2, and the column weight of the last one column is 1.
K, X1, KX1, X2, KX2, X3, KX3, X4, KX4, Y1, KY1, and M as parameters of the parity check matrices H of the type A codes of r=7/16, 8/16, 9/16, 10/16, 11/16, 12/16, 13/16, and 14/16 are as illustrated in
The parameters X1, KX1, X2, KX2, X3, KX3, X4, KX4, Y1, and KY1 are set so as to further improve the performance of the LDPC codes.
According to the new LDPC code, favorable BER/FER is realized, and a capacity (communication path capacity) close to the Shannon limit is realized.
That is,
The parameters K, X1, K1, X2, K2, X3, K3, XM1, M1, and M2 are the parameters described in
The parameters K, X1, KX1, X2, KX2, X3, KX3, X4, KX4, Y1, KY1, and M are the parameters described in
<Constellation>
In the transmission system in
One or more constellations can be set for one MODCOD.
As the constellation, there are a uniform constellation (UC) in which arrangement of signal points is uniform and a non uniform constellation (NUC) in which arrangement of signal points is not uniform.
Furthermore, as the NUC, there are a constellation called 1-dimensional (M2-QAM) non-uniform constellation (1D-NUC), a constellation called 2-dimensional (QQAM) non-uniform constellation (2D-NUC), and the like, for example.
In general, the BER is further improved in the 1D-NUC than the UC, and moreover, the BER is further improved in the 2D-NUC than the 1D-NUC.
The constellation with the modulation method of QPSK is the UC. For example, the UC or the 2D-NUC can be adopted as a constellation for the modulation method of 16QAM, 64QAM, 256QAM, or the like. For example, the UC or the 1D-NUC can be adopted as a constellation for the modulation method of 1024QAM, 4096QAM, or the like.
In the transmission system in
In other words, in the case where the modulation method is QPSK, for example, the same UC can be used for the coding rates r of the LDPC codes.
Furthermore, in the case where the modulation method is 16QAM, 64QAM, or 256QAM, for example, the same UC can be used for the coding rates r of the LDPC codes. Moreover, in the case where the modulation method is 16QAM, 64QAM, or 256QAM, for example, different 2D-NUCs can be used for the coding rates r of the LDPC codes, respectively.
Furthermore, in the case where the modulation method is 1024QAM, or 4096QAM, for example, the same UC can be used for each coding rate r of the LDPC code. Moreover, in the case where the modulation method is 1024QAM, or 4096QAM, for example, different 1D-NUCs can be used for the coding rates r of the LDPC codes, respectively.
Here, the UC of QPSK is also described as QPSK-UC, and the UC of 2mQAM is also described as 2mQAM-UC. Furthermore, the 1D-NUC and 2D-NUC of 2mQAM are also described as 2mQAM-1D-NUC and 2mQAM-2D-NUC, respectively.
Hereinafter, some of constellations defined in ATSC 3.0 will be described.
In
In
In
In
In the 2D-NUC, a signal point in the second quadrant of the constellation is arranged at a position obtained by symmetrically moving a signal point in the first quadrant with respect to a Q axis, and a signal point in the third quadrant of the constellation is arranged at a position obtained by symmetrically moving a signal point in the first quadrant with respect to the origin. Then, a signal point in the fourth quadrant of the constellation is arranged at a position obtained by symmetrically moving a signal point in the first quadrant with respect to an I axis.
Here, in the case where the modulation method is 2mQAM, m bits are regarded as one symbol, and the one symbol is mapped to a signal point corresponding to the symbol.
The m-bit symbol can be expressed by, for example, an integer value of 0 to 2m−1. Now, symbols y(0), y(1), . . . , y(2m−1) expressed by integer values of 0 to 2m−1 can be classified into four groups of symbols y(0) to y(b−1), y(b) to y(2b−1), y(2b) to y(3b−1), and y(3b) to y(4b−1), where b=2m/4.
In
Then, a coordinate of a signal point corresponding to a symbol y(k+b) in a range of symbols y(b) to y(2b−1) is represented as −conj(w #k), and a coordinate of a signal point corresponding to a symbol y(k+2b) in a range of symbols y(2b) to y(3b−1) is represented as conj(w #k). Furthermore, a coordinate of a signal point corresponding to a symbol y(k+3b) in a range of symbols y(3b) to y(4b−1) is represented by −w #k.
Here, conj(w #k) represents a complex conjugate of w #k.
For example, in a case where the modulation method is 16QAM, symbols y(0), y(1), . . . , and y(15) of m=4 bits are classified into four groups of symbols y(0) to y(3), y(4) to y(7), y(8) to y(11), and y(12) to y(15), where b=24/4=4.
Then, for example, the symbol y(12), of the symbols y(0) to y(15), is a symbol y(k+3b)=y(0+3×4) in the range of symbols y(3b) to y(4b−1)) and k=0, and therefore the coordinate of the signal point corresponding to the symbol y(12) is −w #k=−w0.
Now, w0 in a case where the modulation method is 16QAM and the coding rate r is 9/15 is 0.2386+j0.5296 according to
In
Now, it is assumed that the 10-bit symbol y of 1024QAM is expressed as, from the head bit (most significant bit), y0,s, y1,s, y2,s, y3,s, y4,s, y5,s, y6,s, y7,s, y8,s, and y9,s.
A in
B in
In a case where the 10-bit symbol y=(y0,s, y1,s, y2,s, y3,s, y4,s, y5,s, y6,s, y7,s, y8,s, y9,s) of 1024QAM is (0,0,1,0,0,1,1,1,0,0), for example, the odd-numbered 5 bits (y0,s, y2,s, y4,s, y6,s, y8,s) are (0, 1, 0, 1, 0) and the even-numbered 5 bits (y1,s, y3,s, y5,s, y7,s, y9,s) are (0, 0, 1, 1, 0).
In A in
In B in
Meanwhile, when the coding rate r of the LDPC code is 6/15, for example, u3 is 0.1295 and u11 is 0.7196 according to
Therefore, the real part Re (zs) of the signal point zs corresponding to the symbol y=(0, 0, 1, 0, 0, 1, 1, 1, 0, 0) is u11=0.7196 and the imaginary part Im(zs) is u3=0.1295. As a result, the coordinate of the signal point zs corresponding to the symbol y=(0, 0, 1, 0, 0, 1, 1, 1, 0, 0) is expressed by 0.7196+j0.1295.
Note that the signal points of the 1D-NUC are arranged in a lattice on a straight line parallel to the I axis and a straight line parallel to the Q axis in the constellation. However, the interval between signal points is not constant. Furthermore, average power of the signal points on the constellation can be normalized in transmission of (data mapped to) the signal points. Normalization can be performed by, where the root mean square of absolute values of all (the coordinates of) the signal points on the constellation is Pave, multiplying each signal point zs on the constellation by a reciprocal 1/(√Pave) of the square root √Pave of the root mean square value Pave.
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B in
Since the way of obtaining the coordinate of the signal point zs of when the 10-bit symbol y of 1024QAM is mapped to the signal point zs of 1024QAM-1D-NUC defined in
In other words,
In other words, now, it is assumed that the 12-bit symbol y of 4096QAM is expressed as, from the head bit (most significant bit), y0,s, y1,s, y2,s, y3,s, y4,s, y5,s, y6,s, y7,s, y8,s, y9,s, y10,s, and y11,s.
Since the way of obtaining the coordinate of the signal point zs of when the 12-bit symbol y of 4096QAM is mapped to the signal point zs of 4096QAM-1D-NUC defined in
Note that average power of the signal points on the constellation can be normalized in transmission of (data mapped to) the signal points of the NUCs in
<Block Interleaver 25>
The block interleaving is performed by dividing the LDPC code of one codeword into a part called part 1 and a part called part 2 from the head of the LDPC code.
Npart 1+Npart 2 is equal to the code length N, where the length (bit length) of part 1 is Npart 1 and the length of part 2 is Npart 2.
Conceptually, in the block interleaving, columns as storage regions each storing Npart1/m bits in a column (vertical) direction as one direction are arranged in a row direction orthogonal to the column direction by the number m equal to the bit length m of the symbol, and each column is divided from the top into a small unit of 360 bits that is the parallel factor P. This small unit of column is also called column unit.
In the block interleaving, as illustrated in
Then, when the writing to the first column unit of the rightmost column is completed, the writing returns to the leftmost column, and writing downward from the top of the second column unit of the column is performed in the columns from the left to right direction, as illustrated in
When the writing of part 1 of the LDPC code of one codeword is completed, part 1 of the LDPC code is read in units of m bits in the row direction from the first column of all the m columns, as illustrated in
The unit of m bits of part 1 is supplied from the block interleaver 25 to the mapper 117 (
The reading of part 1 in units of m bits is sequentially performed toward lower rows of the m columns. When the reading of part 1 is completed, part 2 is divided into units of m bits from the top and is supplied from the block interleaver 25 to the mapper 117 as the m-bit symbol.
Therefore, part 1 is symbolized while being interleaved, and part 2 is sequentially dividing into m bits and symbolized without being interleaved.
Npart1/m as the length of the column is a multiple of 360 as the parallel factor P, and the LDPC code of one codeword is divided into part 1 and part 2 so that Npart1/m becomes a multiple of 360.
In a case where the modulation scheme is QPSK, 16QAM, 64QAM, and 256QAM, part 1 has 17280 bits and part 2 has 0 bits in any case.
<Group-Wise Interleaving>
In the group-wise interleaving, as illustrated in
Here, the (i+1)th bit group from the head of when the LDPC code of one codeword is divided into bit groups is hereinafter also described as bit group i.
In a case where the parallel factor P is 360, for example, an LDPC code with the code length N of 1800 bits is divided into 5 (=1800/360) bit groups of bit groups 0, 1, 2, 3, and 4. Moreover, for example, an LDPC code with the code length N of 69120 bits is divided into 192 (=69120/360) bit groups of the bit groups 0, 1, . . . , 191. Moreover, for example, an LDPC code with the code length N of 17280 bits is divided into 48 (=17280/360) bit groups of the bit groups 0, 1, . . . , 47.
Hereinafter, the GW pattern is represented by a sequence of numbers representing a bit group. For example, regarding the LDPC code of five bit groups 0, 1, 2, 3, and 4 with the code length N of 1800 bits, GW patterns 4, 2, 0, 3, and 1 represent interleaving (rearranging) a sequence of the bit groups 0, 1, 2, 3, and 4 with a sequence of the bit groups 4, 2, 0, 3, and 1, for example. Note that the sequence of the bit groups or the GW pattern is represented by a comma-separated sequence of numbers representing the bit groups (for example, 4, 2, 0, 3, 1) or a space-separated sequence of numbers representing the bit groups (for example, 4 2 0 3 1).
For example, now, it is assumed that the (i+1)th code bit from the head of the LDPC code with the code length N of 1800 bits is represented by xi.
In this case, according to the group-wise interleaving of the GW patterns 4, 2, 0, 3, and 1, the 1800-bit LDPC code {x0, x1, . . . , x1799} is interleaved with arrangement of {x1440, x1441, . . . , x1799}, {x720, x721, . . . , x1079}, {x0, x1, . . . , x359}, {x1080, x1081, . . . , x1439}, and {x360, x361, . . . , x719}.
The GW pattern can be set for each code length N of the LDPC code, each coding rate r, each modulation method, each constellation, or each combination of two or more of the code length N, the coding rate r, the modulation method, and the constellation.
<Example of GW Pattern for LDPC Code>
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The first to forty-fifth examples of the GW pattern for the LDPC code with the code length N of 17280 bits can be applied to any combination of the LDPC code with the code length N of 17280 bits and an arbitrary coding rate r, an arbitrary modulation method, and an arbitrary constellation.
Note that, as for the group-wise interleaving, the applied GW pattern is set for each combination of the code length N of the LDPC code, the coding rate r of the LDPC code, the modulation method, and the constellation, whereby the error rate can be further improved for each combination.
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<Configuration Example of Reception Device 12>
An OFDM processing unit (OFDM operation) 151 receives an OFDM signal from the transmission device 11 (
The frame management unit 152 processes (interprets) a frame configured by the data supplied from the OFDM processing unit 151, and supplies a signal of resulting target data and a signal of control data to frequency deinterleavers 161 and 153, respectively.
The frequency deinterleaver 153 performs frequency deinterleaving for the data from the frame management unit 152 in units of symbols, and supplies the data to a demapper 154.
The demapper 154 performs demapping (signal point arrangement decoding) and quadrature demodulation for the data (data on the constellation) from the frequency deinterleaver 153 on the basis of arrangement (constellation) of the signal points determined by the quadrature modulation performed on the transmission device 11 side, and supplies resulting data ((likelihood) of the LDPC code) to an LDPC decoder 155.
The LDPC decoder 155 (decoding unit) performs LDPC decoding for the LDPC code from the demapper 154, and supplies resulting LDPC target data (here, BCH code) to a BCH decoder 156.
The BCH decoder 156 performs BCH decoding for the LDPC target data from the LDPC decoder 155, and outputs resulting control data (signaling).
Meanwhile, the frequency deinterleaver 161 performs frequency deinterleaving in units of symbols for the data from the frame management unit 152, and supplies the data to an SISO/MISO decoder 162.
The SISO/MISO decoder 162 performs space-time decoding of the data from the frequency deinterleaver 161 and supplies the data to a time deinterleaver 163.
The time deinterleaver 163 deinterleaves the data from the SISO/MISO decoder 162 in units of symbols and supplies the data to a demapper 164.
The demapper 164 performs demapping (signal point arrangement decoding) and quadrature demodulation for the data (data on the constellation) from the time deinterleaver 163 on the basis of arrangement (constellation) of the signal points determined by the quadrature modulation performed on the transmission device 11 side, and supplies resulting data to a bit deinterleaver 165.
The bit deinterleaver 165 performs bit deinterleaving for the data from the demapper 164, and supplies (likelihood of) the LDPC code that is data after the bit deinterleaving to the LDPC decoder 166.
The LDPC decoder 166 performs LDPC decoding for the LDPC code from the bit deinterleaver 165, and supplies resulting LDPC target data (here, the BCH code) to a BCH decoder 167.
The BCH decoder 167 performs BCH decoding for the LDPC target data from the LDPC decoder 155, and supplies resulting data to a BB descrambler 168.
The BB descrambler 168 applies BB descrambling to the data from the BCH decoder 167, and supplies resulting data to a null deletion unit 169.
The null deletion unit 169 deletes the null inserted by the padder 112 in
The demultiplexer 170 demultiplexes each of one or more streams (target data) multiplexed into the data from the null deletion unit 169, applies necessary processing, and outputs a result as an output stream.
Note that the reception device 12 can be configured without including a part of the blocks illustrated in
<Configuration Example of Bit Deinterleaver 165>
The bit deinterleaver 165 is configured by a block deinterleaver 54 and a group-wise deinterleaver 55, and performs (bit) deinterleaving of the symbol bit of the symbol that is the data from the demapper 164 (
In other words, the block deinterleaver 54 performs, for the symbol bit of the symbol from demapper 164, block deinterleaving corresponding to the block interleaving performed by the block interleaver 25 in
The group-wise deinterleaver 55 performs, for example, for the LDPC code from the block deinterleaver 54, group-wise deinterleaving corresponding to the group-wise interleaving performed by the group-wise interleaver 24 in
Here, in a case where the parity interleaving, the group-wise interleaving, and the block interleaving have been applied to the LDPC code to be supplied from the demapper 164 to the bit deinterleaver 165, the bit deinterleaver 165 can perform all of parity deinterleaving corresponding to the parity interleaving (processing reverse to the parity interleaving, in other words, parity deinterleaving of returning the code bits of the LDPC code changed in sequence by the parity interleaving to the original sequence), the block deinterleaving corresponding to the block interleaving, and the group-wise deinterleaving corresponding to the group-wise interleaving.
Note that the bit deinterleaver 165 in
Therefore, the LDPC code for which the block deinterleaving and the group-wise deinterleaving are performed and the parity deinterleaving is not performed is supplied from (the group-wise deinterleaver 55 of) the bit deinterleaver 165 to the LDPC decoder 166.
The LDPC decoder 166 performs LDPC decoding for the LDPC code from the bit deinterleaver 165 on the basis of a transformed parity check matrix obtained by performing at least column permutation corresponding to the parity interleaving for the parity check matrix H by the type B method used for the LDPC coding by the LDPC encoder 115 in
In step S111, the demapper 164 performs demapping and quadrature demodulation for the data (the data on the constellation mapped to the signal points) from the time deinterleaver 163 and supplies the data to the bit deinterleaver 165. The processing proceeds to step S112.
In step S112, the bit deinterleaver 165 performs deinterleaving (bit deinterleaving) for the data from the demapper 164. The process proceeds to step S113.
In other words, in step S112, in the bit deinterleaver 165, the block deinterleaver 54 performs block deinterleaving for the data (symbol) from the demapper 164, and supplies code bits of the resulting LDPC code to the group-wise deinterleaver 55.
The group-wise deinterleaver 55 performs group-wise deinterleaving for the LDPC code from the block deinterleaver 54, and supplies (the likelihood) of the resulting LDPC code to the LDPC decoder 166.
In step S113, the LDPC decoder 166 performs LDPC decoding for the LDPC code from the group-wise deinterleaver 55 on the basis of the parity check matrix H used for the LDPC coding by the LDPC encoder 115 in
Note that, even in
Furthermore, in a case where the group-wise interleaving is not performed in the transmission device 11, the reception device 12 can be configured without including the group-wise deinterleaver 55 for performing the group-wise deinterleaving.
<Ldpc Decoding>
The LDPC decoding performed by the LDPC decoder 166 in
The LDPC decoder 166 in
Here, LDPC decoding for enabling suppression of a circuit scale and suppression of an operation frequency within a sufficiently feasible range by being performed using a transformed parity check matrix has been previously proposed (for example, see Japanese Patent No. 4224777).
Therefore, first, the LDPC decoding using a transformed parity check matrix, which has been previously proposed, will be described with reference to
Note that, in
In the parity check matrix H in
Row permutation:(6s+t+1)th row→(5t+s+1)th row (11)
Column permutation:(6x+y+61)th column→(5y+x+61)th column (12)
Note that, in the expressions (11) and (12), s, t, x, and y are integers in ranges of 0≤s<5, 0≤t<6, 0≤x<5, and 0≤t<6, respectively.
According to the row permutation of the expression (11), permutation is performed in such a manner that the 1, 7, 13, 19, and 25th rows where the remainder becomes 1 when being divided by 6 are respectively permutated to the 1, 2, 3, 4, and 5th rows, and the 2, 8, 14, 20, and 26th rows where the remainder becomes 2 when being divided by 6 are respectively permutated to the 6, 7, 8, 9, and 10th rows.
Furthermore, according to the column permutation of the expression (12), permutation is performed for the 61st and subsequent columns (parity matrix) in such a manner that the 61, 67, 73, 79, and 85th columns where the remainder becomes 1 when being divided by 6 are respectively permutated to the 61, 62, 63, 64, and 65th columns, and the 62, 68, 74, 80, and 86th columns where the remainder becomes 2 when being divided by 6 are respectively permutated to the 66, 67, 68, 69, and 70th columns.
A matrix obtained by performing the row and column permutation for the parity check matrix H in
Here, the row permutation of the parity check matrix H does not affect the arrangement of the code bits of the LDPC code.
Furthermore, the column permutation of the expression (12) corresponds to parity interleaving with the information length K of 60, the parallel factor P of 5, and the divisor q (=M/P) of the parity length M (30 here) of 6, of the parity interleaving of interleaving the position of the (K+Py+x+1)th code bit with the (K+qx+y+1)th code bit.
Therefore, the parity check matrix H′ in
When multiplying the transformed parity check matrix H′ in
From the above, the transformed parity check matrix H′ in
Therefore, a similar decoding result to the case of decoding the LDPC code of the original parity check matrix H using the parity check matrix H can be obtained by performing the column permutation of the expression (12) for the LDPC code c of the original parity check matrix H, decoding (LDPC decoding) the LDPC code c′ after the column permutation using the transformed parity check matrix H′ in
In
It can be said that the transformed parity check matrix H′ in
For decoding of an LDPC code of a parity check matrix represented by a P×P configuration matrix, an architecture that simultaneously performs P check node operations and variable node operations can be used.
In other words,
The decoding device in
First, a method of storing data in the edge data storage memories 300 and 304 will be described.
The edge data storage memory 300 is configured by the six FIFOs 3001 to 3006, the six corresponding to a number obtained by dividing the number of rows of 30 of the transformed parity check matrix H′ in
In the FIFO 3001, data (message vi from the variable node) corresponding to the positions of 1 of the 1st to 5th rows of the transformed parity check matrix H′ in
Data corresponding to the positions of 1 of from the 6th to 10th rows of the transformed parity check matrix H′ in
In other words, in regard to the configuration matrix with the weight of 2 or more, when the configuration matrix is expressed by a form of a sum of some matrices of a P×P identity matrix with the weight of 1, a quasi identity matrix in which one or more of the elements of 1 of the identity matrix are 0, and a shift matrix obtained by cyclically shifting the identity matrix or the quasi identity matrix, the data corresponding to the position of 1 of the identity matrix with the weight of 1, the quasi identity matrix, or the shift matrix (message corresponding to the edge which belongs to the identity matrix, the quasi identity matrix, or the shift matrix) is stored in the same address (the same FIFO of FIFOs 3001 to 3006).
Hereinafter, data is stored in association with the transformed parity check matrix H′, similarly in the storage regions of the third to ninth stages.
Data are similarly stored in the FIFOs 3003 to 3006 in association with the transformed parity check matrix H′.
The edge data storage memory 304 is configured by the eighteen FIFOs 3041 to 30410, the eighteen corresponding to a number obtained by dividing the number of columns of 90 of the transformed parity check matrix H′ by the number of columns (parallel factor P) of 5 of the configuration matrix. The FIFO 304x (x=1, 2, . . . , 18) includes storage regions of a plurality of stages, and messages corresponding to five edges, the five corresponding to the number of rows and the number of columns (parallel factor P) of the configuration matrix, can be read and written at the same time with respect to the storage regions of the respective stages.
In the FIFO 3041, data (message uj from the check node) corresponding to the positions of 1 of the 1st to 5th columns of the transformed parity check matrix H′ in
In other words, in regard to the configuration matrix with the weight of 2 or more, when the configuration matrix is expressed by a form of a sum of some matrices of a P×P identity matrix with the weight of 1, a quasi identity matrix in which one or more of the elements of 1 of the identity matrix are 0, and a shift matrix obtained by cyclically shifting the identity matrix or the quasi identity matrix, the data corresponding to the position of 1 of the identity matrix with the weight of 1, the quasi identity matrix, or the shift matrix (message corresponding to the edge which belongs to the identity matrix, the quasi identity matrix, or the shift matrix) is stored in the same address (the same FIFO of FIFOs 3041 to 30418).
Hereinafter, data is stored in association with the transformed parity check matrix H′, similarly in the storage regions of the fourth and fifth stages. The number of stages of the storage regions of the FIFO 3041 is five that is the maximum value of the number of is (Hamming weights) in the row direction in the 1st to 5th columns of the transformed parity check matrix H′.
Data is similarly stored in the FIFOs 3042 and 3043 in association with the transformed parity check matrix H′, and respective lengths (stages) are five. Data is similarly stored in the FIFOs 3044 to 30412 in association with the transformed parity check matrix H′, and respective lengths are three. Data is similarly stored in the FIFOs 30413 and 30418 in association with the transformed parity check matrix H′, and respective lengths are two.
Next, the operation of the decoding device in
The edge data storage memory 300 includes six FIFOs 3001 to 3006, and selects FIFO to store data from among the six FIFOs 3001 to 3006 according to information (matrix data) D312 indicating which row of the transformed parity check matrix H′ in
Furthermore, in reading data, the edge data storage memory 300 sequentially reads the five messages D3001 from the FIFO 3001 and supplies the read messages to the next selector 301. The edge data storage memory 300 sequentially reads the messages from the FIFOs 3002 to 3006 after completion of the reading of the message from the FIFO 3001, and supplies the messages to the selector 301.
The selector 301 selects the five messages from the FIFO currently being read out, of the FIFOs 3001 to 3006, according to a select signal D301, and supplies the messages as message D302 to the check node calculation unit 302.
The check node calculation unit 302 includes five check node calculators 3021 to 3025, and performs the check node operation according to the expression (7), using the messages D302 (D3021 to D3025) (the messages vi of the expression (7)) supplied through the selector 301, and supplies five messages D303 (D3031 to D3035) obtained as a result of the check node operation (messages uj of the expression (7)) to the cyclic shift circuit 303.
The cyclic shift circuit 303 cyclically shifts the five messages D3031 to D3035 obtained by the check node calculation unit 302, on the basis of information (matrix data) D305 indicating how many identity matrices (or quasi identify matrices), which are the basis of the transformed parity check matrix H′, have been cyclically shifted for the corresponding edge, and supplies a result as a message D304 to the edge data storage memory 304.
The edge data storage memory 304 includes eighteen FIFOs 3041 to 30418, and selects FIFO to store data from among the FIFOs 3041 to 30419 according to information D305 indicating which row of the transformed parity check matrix H′ five messages D304 supplied from the previous cyclic shift circuit 303 belong to, and collectively stores the five messages D304 to the selected FIFO in order. Furthermore, in reading data, the edge data storage memory 304 sequentially reads five messages D3061 from the FIFO 3041 and supplies the read messages to the next selector 305. The edge data storage memory 304 sequentially reads the messages from the FIFOs 3042 to 30410 after completion of the reading of the data from the FIFO 3041, and supplies the messages to the selector 305.
The selector 305 selects the five messages from the FIFO currently being read out, of the FIFOs 3041 to 30418, according to a select signal D307, and supplies the messages as message D308 to the variable node calculation unit 307 and the decoded word calculation unit 309.
Meanwhile, the received data rearranging unit 310 rearranges an LDPC code D313 corresponding to the parity check matrix H in
The variable node calculation unit 307 includes five variable node calculators 3071 to 3075, and performs the variable node operation according to the expression (1), using the messages D308 (D3081 to D3085) (messages uj of the expression (1)) supplied via the selector 305, and the five received values D309 (received values u0i of the expression (1)) supplied from the received data memory 306, and supplies messages D310 (D3101 to D3105) (messages vi of the expression (1)) obtained as a result of the operation to the cyclic shift circuit 308.
The cyclic shift circuit 308 cyclically shifts the messages D3101 to D3105 calculated by the variable node calculation unit 307 on the basis of information indicating how many identity matrices (or quasi identify matrices), which are the basis of the transformed parity check matrix H′, have been cyclically shifted for the corresponding edge, and supplies a result as a message D311 to the edge data storage memory 300.
By one round of the above operation, one decoding (variable node operation and check node operation) of the LDPC code can be performed. After decoding the LDPC code a predetermined number of times, the decoding device in
In other words, the decoded word calculation unit 309 includes five decoded word calculators 3091 to 3095, and calculates, as a final stage of the plurality of times of decoding, the decoding result (decoded word) on the basis of the expression (5), using the five messages D308 (D3081 to D3085) (messages uj of the expression (5)) output by the selector 305, and the five received values D309 (received values u0i of the expression (5)) supplied from the received data memory 306, and supplies resulting decoded data D315 to the decoded data rearranging unit 311.
The decoded data rearranging unit 311 rearranges the decoded data D315 supplied from the decoded word calculation unit 309 by performing reverse permutation to the column permutation of the expression (12), and outputs a final decoding result D316.
As described above, by applying one or both of the row permutation and the column permutation to the parity check matrix (original parity check matrix) to transform the parity check matrix into a parity check matrix (transformed parity check matrix) that can be represented by a combination of a P×P identity matrix, a quasi identity matrix in which one or more of is in the identity matrix are 0, a shift matrix obtained by cyclically shifting the identity matrix or the quasi identity, a sum matrix that is a sum of two or more of the identity matrix, the quasi identify matrix, and the shift matrix, and a P×P zero matrix, that is, by a combination of the configuration matrices, an architecture to perform P check node operations and variable node operations at the same time for decoding of the LDPC code, the P being a number smaller than the number of rows and the number of columns of the parity check matrix, can be adopted. In the case of adopting the architecture to perform P node operations (check node operations and variable node operations) at the same time, the P being the number smaller than the number of rows and the number of columns of the parity check matrix, a large number of repetitive decodings can be performed while suppressing the operation frequency to the feasible range, as compared with a case of performing the number of node operations at the same time, the number being equal to the number of rows and the number of columns of the parity check matrix.
The LDPC decoder 166 constituting the reception device 12 in
In other words, assuming that the parity check matrix of the LDPC code output by the LDPC encoder 115 constituting the transmission device 11 in
Since this parity interleaving corresponds to the column permutation of the expression (12) as described above, the LDPC decoder 166 does not need to perform the column permutation of the expression (12).
Therefore, in the reception device 12 in
In other words,
In
As described above, since the LDPC decoder 166 can be configured without including the received data rearranging unit 310, the scale can be reduced as compared with the decoding device in
Note that, in
In other words, in the transmission device 11 in
Furthermore, after the decoding of the LDPC code in the LDPC decoder 166, the parity part of the decoding result is unnecessary, and in a case of outputting only the information bits of the decoding result, the LDPC decoder 166 can be configured without the decoded data rearranging unit 311.
<Configuration Example of Block Deinterleaver 54>
In the block deinterleaving, reverse processing to the block interleaving by the block interleaver 25 described in
In other words, in the block deinterleaving, for example, as in the block interleaving, the LDPC code is written and read with respect to m columns, the m being equal to the bit length m of the symbol, whereby the sequence of the code bits of the LDPC code is returned to the original sequence.
Note that, in the block deinterleaving, writing of the LDPC code is performed in the order of reading the LDPC code in the block interleaving. Moreover, in the block deinterleaving, reading of the LDPC code is performed in the order of writing the LDPC code in the block interleaving.
In other words, in regard to part 1 of the LDPC code, part 1 of the LDPC code in units of m-bit symbol is written in the row direction from the 1st row of all the m columns, as illustrated in
Writing of part 1 in units of m bits is sequentially performed toward lower rows of the m columns, and when the writing of part 1 is completed, as illustrated in
When the reading to the rightmost column is completed, the reading returns to the leftmost column, and reading of part 1 downward from the top of the second column unit of the column is performed in the columns from the left to right direction, as illustrated in
When the reading of part 1 of the LDPC code of one codeword is completed, in regard to part 2 in units of m-bit symbols, the units of m-bit symbols are sequentially concatenated after part 1, whereby the LDPC code in units of symbols is returned to the sequence of code bits of the LDPC code (the LDCP code before block interleaving) of the original one codeword.
<Another Configuration Example of Bit Deinterleaver 165>
Note that, in
In other words, the bit deinterleaver 165 in
In
In other words, the block deinterleaver 54 performs, for the LDPC code from demapper 164, block deinterleaving corresponding to the block interleaving performed by the block interleaver 25 of the transmission device 11 (processing reverse to the block interleaving), in other words, block deinterleaving of returning the positions of the code bits rearranged by the block interleaving to the original positions, and supplies a resulting LDPC code to the group-wise deinterleaver 55.
The group-wise deinterleaver 55 performs, for the LDPC code from the block deinterleaver 54, group-wise deinterleaving corresponding to group-wise interleaving as rearrangement processing performed by the group-wise interleaver 24 of the transmission device 11.
The LDPC code obtained as a result of group-wise deinterleaving is supplied from the group-wise deinterleaver 55 to the parity deinterleaver 1011.
The parity deinterleaver 1011 performs, for the bit codes after the group-wise deinterleaving in the group-wise deinterleaver 55, parity deinterleaving corresponding to the parity interleaving performed by the parity interleaver 23 of the transmission device 11 (processing reverse to the parity interleaving), in other words, parity deinterleaving of returning the sequence of the code bits of the LDPC code changed in sequence by the parity interleaving to the original sequence.
The LDPC code obtained as a result of the parity deinterleaving is supplied from the parity deinterleaver 1011 to the LDPC decoder 166.
Therefore, in the bit deinterleaver 165 in
The LDPC decoder 166 performs LDPC decoding for the LDPC code from the bit deinterleaver 165 using the parity check matrix H used for the LDPC coding by the LDPC encoder 115 of the transmission device 11.
In other words, in the type B method, the LDPC decoder 166 performs, for the LDPC code from the bit deinterleaver 165, the LDPC decoding using the parity check matrix H itself (of the type B method) used for the LDPC coding by the LDPC encoder 115 of the transmission device 11 or using the transformed parity check matrix obtained by performing at least column permutation corresponding to the parity interleaving for the parity check matrix H. Furthermore, in the type A method, the LDPC decoder 166 performs, for the LDPC code from the bit deinterleaver 165, the LDPC decoding using the parity check matrix (
Here, in
Furthermore, in the LDPC decoder 166, in a case of performing LDPC decoding of the LDPC code using the transformed parity check matrix obtained by applying at least column permutation corresponding to the parity interleaving to the parity check matrix H by the type B method used for the LDPC coding by the LDPC encoder 115 of the transmission device 11 or using the transformed parity check matrix (
Note that, in
<Configuration Example of Reception System>
In
The acquisition unit 1101 acquires a signal including the LDPC code obtained by performing at least the LDPC coding for the LDPC target data such as image data and audio data of a program or the like, via a transmission path (communication path, not illustrated) such as, for example, terrestrial digital broadcasting, satellite digital broadcasting, a cable television (CATV) network, the Internet, or another network, and supplies the signal to the transmission path decoding processing unit 1102.
Here, in a case where the signal acquired by the acquisition unit 1101 is broadcasted from, for example, a broadcasting station via terrestrial waves, satellite waves, cable television (CATV) networks, or the like, the acquisition unit 1101 is configured by a tuner, a set top box (STB), or the like. Furthermore, in a case where the signal acquired by the acquisition unit 1101 is transmitted from a web server by multicast like an internet protocol television (IPTV), for example, the acquisition unit 1101 is configured by, for example, a network interface (I/F) such as a network interface card (NIC).
The transmission path decoding processing unit 1102 corresponds to the reception device 12. The transmission path decoding processing unit 1102 applies transmission path decoding processing including at least processing of correcting an error occurring in the transmission path to the signal acquired by the acquisition unit 1101 via the transmission path, and supplies a resulting signal to the information source decoding processing unit 1103.
In other words, the signal acquired by the acquisition unit 1101 via the transmission path is a signal obtained by performing at least error correction coding for correcting an error occurring in the transmission path, and the transmission path decoding processing unit 1102 applies the transmission path decoding processing such as the error correction processing to such a signal, for example.
Here, examples of the error correction coding include LDPC coding, BCH coding, and the like. Here, at least the LDPC coding is performed as the error correction coding.
Furthermore, the transmission path decoding processing may include demodulation of a modulated signal, and the like.
The information source decoding processing unit 1103 applies information source decoding processing including at least processing of decompressing compressed information into original information to the signal to which the transmission path decoding processing has been applied.
In other words, compression encoding for compressing information is sometimes applied to the signal acquired by the acquisition unit 1101 via the transmission path in order to reduce the amount of data such as image and sound as the information. In that case, the information source decoding processing unit 1103 applies the information source decoding processing such as processing of decompressing the compressed information into the original information (decompression processing) to the signal to which the transmission path decoding processing has been applied.
Note that, in a case where the compression encoding has not been applied to the signal acquired by the acquisition unit 1101 via the transmission path, the information source decoding processing unit 1103 does not perform the processing of decompressing the compressed information into the original information.
Here, an example of the decompression processing includes MPEG decoding and the like. Furthermore, the transmission path decoding processing may include descrambling and the like in addition to the decompression processing.
In the reception system configured as described above, the acquisition unit 1101 acquires the signal obtained by applying the compression encoding such as MPEG coding to data such as image and sound, for example, and further applying the error correction coding such as the LDPC coding to the compressed data, via the transmission path, and supplies the acquired signal to the transmission path decoding processing unit 1102.
The transmission path decoding processing unit 1102 applies, for example, processing similar to the processing performed by the reception device 12 to the signal from the acquisition unit 1101 as the transmission path decoding processing, and supplies the resulting signal to the information source decoding processing unit 1103.
The information source decoding processing unit 1103 applies the information source decoding processing such as MPEG decoding to the signal from the transmission path decoding processing unit 1102, and outputs resulting image or sound.
The reception system in
Note that the acquisition unit 1101, the transmission path decoding processing unit 1102, and the information source decoding processing unit 1103 can be each configured as an independent device (hardware (integrated circuit (IC) or the like) or software module).
Furthermore, the acquisition unit 1101, the transmission path decoding processing unit 1102, and the information source decoding processing unit 1103 can be configured as a set of the acquisition unit 1101 and the transmission path decoding processing unit 1102, a set of the transmission path decoding processing unit 1102 and the information source decoding processing unit 1103, or a set of the acquisition unit 1101, the transmission path decoding processing unit 1102, and the information source decoding processing unit 1103, as an independent device.
Note that, in
The reception system in
The output unit 1111 is, for example, a display device for displaying an image or a speaker for outputting a sound, and outputs an image, a sound, or the like as a signal output from the information source decoding processing unit 1103. In other words, the output unit 1111 displays an image or outputs a sound.
The reception system in
Note that, in a case where the compression encoding has not been applied to the signal acquired by the acquisition unit 1101, the signal output by the transmission path decoding processing unit 1102 is supplied to the output unit 1111.
Note that, in
The reception system in
However, the reception system in
The recording unit 1121 records (stores) the signal (for example, a TS packet of TS of MPEG) output by the transmission path decoding processing unit 1102 on a recording (storage) medium such as an optical disk, a hard disk (magnetic disk), or a flash memory.
The reception system in
Note that, in
<Embodiment of Computer>
Next, the above-described series of processing can be executed by hardware or software. In a case of executing the series of processing by software, a program that configures the software is installed in a general-purpose computer or the like.
Thus,
The program can be recorded in advance in a hard disk 705 or a ROM 703 as a recording medium built in the computer.
Alternatively, the program can be temporarily or permanently stored (recorded) on a removable recording medium 711 such as a flexible disk, a compact disc read only memory (CD-ROM), a magneto optical (MO) disk, a digital versatile disc (DVD), a magnetic disk, or a semiconductor memory. Such a removable recording medium 711 can be provided as so-called package software.
Note that the program can be installed from the above-described removable recording medium 711 to the computer, can be transferred by wireless means from a download site to the computer via a satellite for digital satellite broadcasting, or can be transferred by wired means to the computer via a network such as a local area network (LAM) or the Internet, and the program thus transferred can be received by a communication unit 708 and installed on the built-in hard disk 705 in the computer.
The computer incorporates a central processing unit (CPU) 702. An input/output interface 710 is connected to the CPU 702 via a bus 701. The CPU 702 executes the program stored in the read only memory (ROM) 703 according to a command when the command is input by the user by an operation of an input unit 707 including a keyboard, a mouse, a microphone, and the like via the input/output interface 710. Alternatively, the CPU 702 loads the program stored in the hard disk 705, the program transferred from the satellite or the network, received by the communication unit 708, and installed in the hard disk 705, or the program read from the removable recording medium 711 attached to a drive 709 and installed in the hard disk 705 to a random access memory (RAM) 704 and executes the program. As a result, the CPU 702 performs the processing according to the above-described flowchart or the processing performed by the configuration of the above-described block diagram. Then, the CPU 702 causes an output unit 706 including a liquid crystal display (LCD), a speaker, and the like to output the processing result, the communication unit 708 to transmit the processing result, and the hard disk 705 to record the processing result, via the input/output interface 710, as necessary, for example.
Here, processing steps describing the program for causing the computer to perform various types of processing do not necessarily need to be processed chronologically according to the order described in the flowcharts, and includes processing executed in parallel or individually (for example, processing by parallel processing or object).
Furthermore, the program may be processed by one computer or may be processed in a distributed manner by a plurality of computers. Moreover, the program may be transferred to a remote computer and executed.
Note that embodiments of the present technology are not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present technology.
For example, (the parity check matrix initial value table of) the above-described new LDPC code and GW pattern can be used for a satellite channel, a ground wave, a cable (wired channel), and another communication path 13 (
Furthermore, in the present specification, to make the description easy to understand, the LDPC encoder 115 (
Note that the effects described in the present specification are merely examples and are not limited, and other effects may be exhibited.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2018-006028 | Jan 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/000127 | 1/8/2019 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2019/142684 | 7/25/2019 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 10305632 | Jeong | May 2019 | B2 |
| 20160233892 | Kim | Aug 2016 | A1 |
| 20170041025 | Murakami et al. | Feb 2017 | A1 |
| Number | Date | Country |
|---|---|---|
| 2015-228647 | Dec 2015 | JP |
| 2019-12989 | Jan 2019 | JP |
| Entry |
|---|
| International Search Report dated Feb. 12, 2019 in PCT/JP2019/000127 filed on Jan. 8, 2019, 1 page. |
| ATSC Standard: Physical Layer Protocol, ATSC A/322:2016, pp. 1-258. |
| 1.9 Terrestrial Broadcast Transmission Technology, Annual Report 2017, NHK Science & Technology Research Laboratories, 11 total pages (with unedited computer-generated English translation). |
| ATSC Standard: Physical Layer Protocol, ATSC A/322:2017, pp. 23-25 and 147-163 (20 total pages). |
| Number | Date | Country | |
|---|---|---|---|
| 20200358457 A1 | Nov 2020 | US |
