MT Convolutional Decoder (Viterbi Hard Decision, Rate)
- Updated2023-02-17
- 4 minute(s) read
MT Convolutional Decoder (Viterbi Hard Decision, Rate)
Decodes a convolutionally encoded bit stream using a specified code rate. The code rate is equal to the ratio of the data word length to the code word length.
Inputs/Outputs
input bit stream
Bit sequence representing the code word to decode.
rate
The convolutional code rate, which is a ratio of k/n, where k is the input data word length and n is the output code word length.
1/2 |
Supports constraint lengths of 3,4,5,6,7,8,9,10,11,12,13,14,15,16,17 |
1/3 |
Supports constraint lengths of 3,4,5,6,7,8,9,10,11,12,13,14 |
1/4 |
Supports constraint lengths of 3,4,5,6,7,8,9,10,11,12,13,14 |
2/3 |
Supports constraint lengths of 2,3,4,5,6 |
3/4 |
Supports constraint lengths of 2,3,4 |
Default value: 1/2
constraint length
The maximum number of encoded bits that can be affected by a single input bit. This value represents (1 + maximal memory order), where maximal memory order refers to the length of the longest shift register chain in the convolutional encoder.
Default value: 3
initial state
The initial parent state for the decode operation. When reset? is set to TRUE, the trellis structure is set to this state, thereby initializing the Viterbi decoding operation. On the first call to this node, and thereafter when reset? is set to FALSE, the survivor state from the previous iteration is used to continue performing Viterbi decoding and this parameter is ignored.
Default value: 0
error in
Error conditions that occur before this node runs.
The node responds to this input according to standard error behavior.
Default value: No error
traceback depth
The number of trellis stages used in the Viterbi decoding process.
Default value: 15
reset?
A Boolean that determines whether the internal state of the decoder is cleared.
TRUE |
Clears any buffered bits from previous iterations. Also initializes the Viterbi algorithm to start decoding from initial state. The relationship of the length of output bit stream,
Lout, to the length of input bit stream,
Lin, is described by the following equation:
Lout = k × [floor(Lin/n) - D] where k is the input data word length, n is the output data word length, and D is the decoder traceback depth in symbols. |
FALSE | Continues decoding from the previous iteration. The length of output bit stream is given by the following equation:
Lout = k × floor(Lin/n). |
- Append max(D,K-1)×k zeros to the end of the message prior to performing convolutional encoding. Here k represents the message word length.
- Append D×n zeros to the end of the encoded bit stream prior to calling MT Convolutional Decoder. Here, D is the traceback depth employed in the convolutional decoder, and n is the code word length.
Default value: TRUE
output bit stream
Bit sequence decoded by this node.
final state
The survivor state after decoding the entire input bit stream.
error out
Error information.
The node produces this output according to standard error behavior.