Overlapped multiplexing-based modulation and demodulation method and device
An overlapped multiplexing-based modulation and demodulation method and device are disclosed. In the modulation method, a precoding structure is used, and a transmit end first performs parity check product code-based coding on an input information sequence, generates a factor graph for a coding result and according to a coding rule, then performs overlapped multiplexing-based modulation and coding, and transmits a coded signal by using an antenna. In the demodulation method, a signal is transmitted by using a channel, and after receiving the signal by using an antenna, a receive end first performs digital signal processing, including processes such as synchronization and equalization, then performs overlapped multiplexing-based demodulation and decoding, and finally performs factor graph-based belief propagation decoding on a decoding result, to finally obtain a decoded sequence. In this application, a product code-based decoding method is used, a parity check code is used as a subcode, and a belief propagation idea of the factor graph is applied to a decoder end. Therefore, a parity check product code in a simple structure is used. In addition, in the method, the factor graph is used in a decoding process, thereby reducing operation complexity.
1. An overlapped multiplexing-based modulation method, comprising:
obtaining input information;
performing parity check product code-based coding on the input information, to generate a factor graph;
performing overlapped multiplexing-based modulation and coding; and
transmitting a coded signal;
wherein the performing parity check product code-based coding on the input information comprises:
filling the input information into information bits in a coding structure;
performing row coding on the information in the information bits;
performing column coding on the information in the information bits; and
generating the factor graph for a coding result according to a coding rule;
wherein the performing parity check product code-based coding on the input information further comprises:
writing an input information sequent into corresponding information bits according to a k c ×k r two-dimensional structure, wherein a length of the input information is N=k c ×k r , wherein k r represents a quantity of rows, and k c represents a quantity of columns;
performing row coding by assuming that information in the (k r +1) th bit of each row is a modulo-2 addition result of the first k c th columns of the current row;
performing column coding by assuming that information in the (k c +1) th bit of each column is a modulo-2 addition result of the first k r th rows of the current column; and
generating the factor graph for the coding result according to the coding rule.
2. The method according to claim 1 , wherein the coding structure is a diagonal coding structure, a two-dimensional coding structure, a three-dimensional coding structure, or a four-dimensional coding structure.
3. An overlapped multiplexing-based demodulation method, comprising:
obtaining an input signal;
performing overlapped multiplexing-based demodulation and decoding on the input signal;
performing factor graph-based belief propagation decoding; and
outputting a decoding result;
wherein the performing factor graph-based belief propagation decoding comprises:
calculating an initial log-likelihood ratio;
setting a maximum quantity of iterations;
calculating a check node and updating check information;
calculating a variable node and updating an information message;
calculating a log-likelihood ratio when all check nodes related to information bits provide information;
performing decision; and
outputting the decoding result after a specific preset condition is satisfied.
4. The method according to claim 3 , comprising: calculating the check node by using a formula
δ
ij
=
2
tanh
-
1
(
∏
j
′
∈
N
(
i
)
\
j
tanh
(
λ
j
′
i
/
2
)
)
or
δ
ij
=
min
(
λ
j
′
i
)
(
∏
j
′
∈
N
(
i
)
\
j
sign
(
λ
j
′
i
)
)
,
and updating the check information, wherein δ ij , is the check information, and represents a log-likelihood ratio when other variable nodes except the j th variable node provide information; λ j′i the information message, and represents a log-likelihood ratio when other check nodes except the i th check node provide information; N(i) is a partial element information set constrained by the check node; N(i)\j represents a subset of N(i) that does not comprise the j th variable node; and Π is a continuous multiplication operation; and/or
the preset condition is that the maximum quantity of iterations is reached.
5. The method according to claim 3 , comprising:
calculating the variable node by using a formula
λ
ji
=
llr
(
x
j
)
+
∑
i
′
∈
M
(
j
)
\
i
δ
i
′
j
,
and updating the information message; and
calculating the log-likelihood ratio when all the check nodes related to the information bits provide information by using a formula
λ
j
=
llr
(
x
j
)
+
∑
i
′
∈
M
(
j
)
δ
i
′
j
,
wherein
x j is a transmit codeword in a transmit signal of a transmitter; y j is a receive codeword in the input signal received by a receiver; M(j) is a check set in which the variable node participates; M(j)\i represents a subset of the M(j) that does not comprise the i th check node; δ i′j is the check information, and represents a log-likelihood ratio when other variable nodes except the j th variable node provide information; llr(x j ) is a representation form of a log-likelihood ratio when the receiver initially receives channel information; λ ji the information message, and represents a log-likelihood ratio when other check nodes except the i th check node provide information; and λ j represents the log-likelihood ratio when all the check nodes related to the information bits provide information.
6. An overlapped multiplexing-based modulation device, which comprises a hardware processor and a memory, and the hardware processor is configure to executed programming modules stored in the memory, and the programming modules comprising:
an input information obtaining module, configured to obtain input information;
a parity check product code-based coding module, configured to perform parity check product code-based coding on the input information;
an overlapped multiplexing-based modulation and coding module, configured to perform overlapped multiplexing-based modulation and coding; and
a signal transmission module, configured to transmit a coded signal;
the parity check product code-based coding module is further configured to:
write an input information sequent into corresponding information bits according to a k c ×k r two-dimensional structure, wherein a length of the input information is N=k c ×k r , wherein k r represents a quantity of rows, and k c represents a quantity of columns;
perform row coding by assuming that information in the (k r +1) th bit of each row is a modulo-2 addition result of the first k c th columns of the current row;
perform column coding by assuming that information in the (k c +1) th bit of each column is a modulo-2 addition result of the first k r th rows of the current column; and
generate the factor graph for the coding result according to the coding rule.
7. The overlapped multiplexing-based demodulation device according to claim 6 , the programming modules further comprising:
a second input signal obtaining module, configured to obtain an input signal;
an overlapped multiplexing-based demodulation and decoding module, configured to perform overlapped multiplexing-based demodulation and decoding on the input signal;
a factor graph-based belief propagation decoding module, configured to perform factor graph-based belief propagation decoding; and
a decoding result output module, configured to output a decoding result;
wherein the factor graph-based belief propagation decoding module is further configured to:
calculate an initial log-likelihood ratio;
set a maximum quantity of iterations;
calculate a check node and updating check information;
calculate a variable node and updating an information message;
calculate a log-likelihood ratio when all check nodes related to information bits provide information;
perform decision; and
output the decoding result after a specific preset condition is satisfied.