Error correction circuit and error correction method
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsHiroyuki Senda, Akira Kisoda, Takehiro Kamada
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Abstract
The present invention provides an error correction circuit for receiving and decoding a trellis-encoded signal of a series of data Zq, Zq−1, . . . ,Z1 which comprises convolutional-encoded bits and unencoded bits, the convolutional-encoded bits being obtained by convolutional-encoding lower t bits Xt, Xt−1, . . . ,X1 of an input p-bit series of data Xp, Xp−1, . . . , X1 (where p≧2, q≧p, and p>t≧1), and the unencoded bits being obtained by not convolutional-encoding upper (p-t) bits thereof. The circuit includes: a maximum likelihood decoder for preselecting one of m parallel paths of transition from state x at time k to state y at time k+1.
Claims12
An error correction method for receiving q-bit data having convolutional-encoded bits and unencoded bits as a trellis-encoded signal and for decoding the trellis-encoded signal according to a predetermined algorithm represented by a state transition diagram, the convolutional-encoded bits being obtained by convolutional-encoding lower t bits of an input p-bit data (where p>=2, q>p, and p>t>=1) by a convolutional-encoder having c internal states and the unencoded bits being upper (p-t) bits of the input p-bit data,
- wherein the state transition diagram has branches for respective transitions from c internal states at time i to c internal states at time (i+1), and each of c internal states at time i has a transition to two different internal states at time i+1, each branch including n parallel paths,
- the error correction method comprising the steps of:
- calculating a branch metric for each of the n parallel paths included in each branch, based on a level of the received trellis-encoded signal;
- selecting one of the n parallel paths for each branch, based on the branch metrics calculated for the n parallel paths of each branch;
- determining the branch metric calculated for the selected parallel path for each branch, as a branch metric for each branch;
- storing, into each branch, a candidate of a decoded value of the upper (p-t) bits corresponding to the selected parallel path for each branch;
- calculating a path metric for each of a plurality of paths, based on the determined branch metric for each branch, each of the plurality of paths representing state transitions from time (j-k) to time j;
- selecting one of the plurality of paths based on path metrics calculated for the plurality of paths;
- specifying a branch at each time from time (j-k) to time j in the selected path;
- and
- outputting the stored candidate of the decoded value of the upper (p-t) bits for the specified branch as a decoded value of the upper (p-t) bits together with a decoded value of the lower t bits based on the specified branch.
An error correction method for receiving q-bit data having convolutional-encoded bits and unencoded bits as a trellis-encoded signal and for decoding the trellis-encoded signal according to a predetermined algorithm represented by a state transition diagram, the convolutional-encoded bits being obtained by convolutional-encoding lower t bits of an input p-bit data (where p>=2, q>p, and p>t>=1) by a convolutional-encoder having c internal states and the unencoded bits being upper (p-t) bits of the input p-bit data,
- wherein the state transition diagram has branches for respective transitions from c internal states at time i to c internal states at time (i+1), and each of c internal states at time has a transition to two different internal states at time i+1,
- each branch including n parallel paths when the trellis-encoded signal is received as a signal decoded by a decoder having c internal states, and has m parallel paths (m>n) when the trellis-encoded signal is received as a signal decoded by a decoder having d internal states (d>c),
- the error correction method comprising the steps of:
- calculating a branch metric for each of the parallel paths included in each branch, based on a level of the received trellis-encoded signal;
- selecting one of the parallel paths for each branch, based on the branch metrics calculated for the parallel paths of each branch;
- determining the branch metric calculated for the selected parallel path for each branch, as a branch metric for each branch;
- calculating a path metric for each of a plurality of paths, based on the determined branch metric for each branch, each of the plurality of paths representing state transitions from time (j-k) to time j;
- selecting one of the plurality of paths based on path metrics calculated for the plurality of paths;
- and
- decoding the trellis-encoded signal based on the selected path.
An error correction circuit for receiving q-bit data having convolutional-encoded bits and unencoded bits as a trellis-encoded signal and for decoding the trellis-encoded signal according to a predetermined algorithm represented by a state transition diagram, the convolutional-encoded bits being obtained by convolutional-encoding lower t bits of an input p-bit data (where p>=2, q>p, and p>t>=1) by a convolutional-encoder having c states and the unencoded bits being upper (p-t) of the input p-bit data,
- wherein the state transition diagram has branches for respective transitions from c internal states at time i to c internal states at time (i+1), and each of c internal states at time has a transition to two different internal states at time i+1, each branch including n parallel paths,
- the error correction circuit comprising:
- means for calculating a branch metric for each of the n parallel paths included in each branch, based on a level of the received trellis-encoded signal;
- means for selecting one of the n parallel paths for each branch, based on the branch metrics calculated for the n parallel paths of each branch;
- means for determining the branch metric calculated for the selected parallel path for each branch, as a branch metric for each branch;
- means for storing, into each branch, a candidate of a decoded value of the upper (p-t) bits corresponding to the selected parallel path for each branch;
- means for calculating a path metric for each of a plurality of paths, based on the determined branch metric for each branch, each of the plurality of paths representing state transitions from time (j-k) to time j;
- means for selecting one of the plurality of paths based on path metrics calculated for the plurality of paths;
- means for specifying a branch at each time from time (j-k) to time j in the selected path;
- and
- means for outputting the stored candidate of the decoded value of the upper (p-t) bits for the specified branch as a decoded value of the upper (p-t) bits together with a decoded value of the lower t bits based on the specified branch.
An error correction circuit for receiving q-bit data having convolutional-encoded bits and unencoded bits as a trellis-encoded signal and for decoding the trellis-encoded signal according to a predetermined algorithm represented by a state transition diagram, the convolutional-encoded bits being obtained by convolutional-encoding lower t bits of an input p-bit data (where p>=2, q>p, and p>t>=1) by a convolutional-encoder having c internal states and the unencoded bits being upper (p-t) bits of the input p-bit data,
- wherein the state transition diagram has branches for respective transitions from c internal states at time i to c internal states at time (i+1), and each of the c internal states at time i has a transition to two different internal states at time i+1,
- each branch includes n parallel paths when the trellis-encoded signal is received a signal decoded by a decoder having c internal states, and has m parallel paths (m>n) when the trellis-encoded signal is received as a signal decoded by a decoder having d internal states (d>c), the error correction circuit comprising:
- means for calculating a branch metric for each of the parallel paths included in each branch, based on a level of the received trellis-encoded signal;
- means for selecting one of the parallel paths for each branch, based on the branch metrics calculated for the parallel paths of each branch;
- means for determining the branch metric calculated for the selected parallel path for each branch, as a branch metric for each branch;
- means for calculating a path metric for each of a plurality of paths, based on the determined branch metric for each branch, each of the plurality of paths representing state transitions from time (j-k) to time j;
- means for selecting one of the plurality of paths based on path metrics calculated for the plurality of paths;
- and
- means for decoding the trellis-encoded signal based on the selected path.
Dependencies are inferred from the claim text.