LDPC decoding apparatus and method based on node memory
An apparatus is provided for decoding a Low-Density Parity Check (LDPC) code in a communication system. In the LDPC decoding apparatus, an edge memory stores a message delivered through an edge between a variable node and a check node. A node memory stores a node value. A node processor performs a node processing operation using information stored in at least one of the node memory and the edge memory, stores a check node value generated by performing the node processing operation in the node memory, and stores a message generated by performing the node processing operation in the edge memory. A switch switches outputs of the node memory and the node processor through a permutation operation. A parity check verifier parity-checks an output from the node memory. A controller provides a control signal for controlling the node processor.
1. An apparatus for decoding a Low-Density Parity Check (LDPC) code in a communication system, the apparatus comprising:
an edge memory for storing a message delivered through an edge between a variable node and a check node;
a node memory for storing a check node value;
a node processor performing a node processing operation using information stored in at least one of the node memory and the edge memory, storing a check node value generated by performing the node processing operation in the node memory, and storing a message generated by performing the node processing operation in the edge memory;
a switch for switching outputs of the node memory and the node processor through a permutation operation;
a parity check verifier for parity-checking an output from the node memory; and
a controller for providing a control signal for controlling the node processor.
2. The apparatus of claim 1 , wherein the check node value includes at least one of amplitude and sign of a node memory value.
3. The apparatus of claim 2 , wherein the amplitude p c and the sign q c of the node memory value are expressed as
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(
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(
m
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where v and c denote a variable node and a check node, respectively, V(c) denotes an index set of variable nodes adjacent to a c th check node, C(v) denotes an index set of check nodes adjacent to a v th variable node, sgn(x)=−1 for x<0, sgn(x)=+1 for x≧0, and m v,c VC denotes a message delivered from a v th variable node to a c th check node.
4. The apparatus of claim 1 , wherein the switch comprises:
a first switch for switching an output from the node processor to the node memory; and
a second switch for switching an output from the node memory to the node processor.
5. The apparatus of claim 1 , wherein the switch is located between the node memory and the node processor.
6. The apparatus of claim 1 , wherein the node processor generates a C2V message through an operation of the node processor for an edge connected to one predetermined variable node, generates a V2C message connected to the edge of the variable node using the generated C2V message; and sequentially repeats the generation of the V2C message for each individual variable node.
7. The apparatus of claim 1 , wherein the LDPC decoding apparatus determines an update scheme of messages stored in the node memory and the edge memory depending on a node-based serial scheduling scheme.
8. The apparatus of claim 1 , wherein the LDPC decoding apparatus terminates a decoding operation if the node memory value is +1.
9. The apparatus of claim 1 , wherein the node memory is different in bit precision from a variable node outgoing message and an input Log-Likelihood Ratio (LLR) value.
10. The apparatus of claim 1 , wherein the parity check verifier verifies an output of the node memory by checking a sign value of the node memory value.
11. The apparatus of claim 1 , wherein at least one of the node memory and the edge memory is formed of a memory bank.
12. The apparatus of claim 11 , wherein a number of the memory banks is a maximum variable node degree.
13. The apparatus of claim 1 , wherein at least one of the node memory and the edge memory is connected in a pipeline structure and updates one set every cycle.
14. The apparatus of claim 1 , wherein the control signal comprises at least one of a designation signal for designating order of the node and a termination signal of the decoding.
15. The apparatus of claim 14 , wherein the designation signal comprises at least one of a signal for determining update order according to node degree, and a signal for determining update order of the nodes according to connected configuration of the edges.
16. The apparatus of claim 1 , wherein a message updated at the node and the edge comprises previously updated edge and node messages.
17. An apparatus for decoding a Low-Density Parity Check (LDPC) code in a communication system, the apparatus comprising:
a node memory for storing a check node value;
a node processor for performing a node processing operation, and generating a check node value stored in the node memory according to the node processing operation;
a switch located between the node memory and the node processor, for switching outputs of the node memory and the node processor through a permutation operation; and
an edge memory for storing a message delivered through an edge between a variable node and a check node,
wherein the node processor performs a node processing operation using information stored in at least one of the node memory and the edge memory, stores a check node value generated by performing the node processing operation in the node memory, and stores a message generated by performing the node processing operation in the edge memory.
18. The apparatus of claim 17 , further comprises:
a switch for switching outputs of the node memory and the node processor through a permutation operation;
a parity check verifier for parity-checking an output from the node memory; and
a controller for providing a control signal for controlling the vector node processor.
19. The apparatus of claim 17 , wherein the check node value includes at least one of amplitude and sign of a node memory value.
20. The apparatus of claim 19 , wherein the amplitude p c and the sign q c of the node memory value are expressed as
m
v
,
c
VC
←
y
v
,
for
all
v
and
c
∈
C
(
v
)
,
q
c
←
∑
v
∈
V
(
c
)
F
(
m
v
,
c
VC
)
,
for
all
c
p
c
←
∏
v
∈
V
(
c
)
sgn
(
m
v
,
c
VC
)
,
for
all
c
where v and c denote a variable node and a check node, respectively, V(c) denotes an index set of variable nodes adjacent to a c th check node, C(v) denotes an index set of check nodes adjacent to a v th variable node, sgn(x)=−1 for x<0, sgn(x)=+1 for x≧0, and m v,c VC denotes a message delivered from a v th variable node to a c th check node.
21. The apparatus of claim 17 , wherein the switch comprises:
a first switch for switching an output from the node processor to the node memory; and
a second switch for switching an output from the node memory to the node processor.
22. The apparatus of claim 17 , wherein the node processor generates a C2V message through an operation of the node processor for an edge connected to one predetermined variable node, and generates a V2C message connected to the edge of the variable node using the generated C2V message; and
the node processor sequentially repeats the generation of the V2C message for each individual variable node.
23. A method for decoding a Low-Density Parity Check (LDPC) code in a communication system, the method comprising:
initializing a variable node, a check node and an edge;
updating at least one message among messages of the nodes and the edge, with previously updated edge and node message values; and
storing the updated edge message or the updated node message,
wherein the initialization comprises:
acquiring a message value of edges connected to a variable node;
generating a check node outgoing message with the acquired message value; and
generating a variable node outgoing message using the check node outgoing message.
24. The method of claim 23 , wherein the updating comprises determining an update scheme of messages stored in a node and an edge memory depending on a node-based serial scheduling scheme.
25. The method of claim 23 , wherein the node message is different in bit precision from the outgoing message and an input Log-Likelihood Ratio (LLR) value.
26. The method of claim 25 , wherein at least one of the memory storing the node message and the memory storing the edge message is formed of a memory bank.
27. The method of claim 26 , wherein a number of the memory banks is a maximum variable node degree.
28. The method of claim 23 , wherein at least one of the memory storing the node message and the memory storing the edge message is connected in a pipeline structure and updates one set every cycle.
29. The method of claim 23 , further comprising terminating a decoding operation if the memory value is +1, wherein the memory stores the node message.
30. The method of claim 23 , further comprising:
verifying a sign value of the node message; and
generating a control signal for controlling update order of the node and the edge according to the sign value.
31. The method of claim 23 , wherein the control signal comprises at least one of a designation signal for designating order of the node and a termination signal of the decoding.
32. The method of claim 31 , wherein the designation signal comprises at least one of a signal for determining update order according to node degree, and a signal for determining update order of the nodes according to connected configuration of the edges.
33. The method of claim 23 , wherein a message updated at the node and the edge comprises previously updated edge and node messages.