Viterbi Decoder State Constraint for Known Padding Bits
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Solution Overview
Problem
Conventional forward error correction schemes in communications networks are inefficient when dealing with known padding bits, as they perform redundant encoding and decoding operations, increasing the probability of errors during data decoding due to unawareness of padding bits.
Innovation Solution
The method involves constraining the start and/or end state of the Viterbi decoder using known padding bits to skip over decoding of padding bits, thereby improving decoding accuracy by only processing actual data bits and pruning erroneous paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional FEC schemes encode and decode the entire data block including padding bits, then the decoding process is simple and uniform, but the decode success rate decreases due to redundant operations on known padding bits
Solution Approach 1:
The data block is segmented into two parts: known padding bits and unknown data bits. The Viterbi decoder is modified to process only the unknown data bits after skipping the known padding bits. This segmentation allows the decoder to avoid redundant operations on padding bits while maintaining a relatively simple implementation by using the known padding bits to constrain the initial state of the decoder.
Solution Approach 2:
The known padding bits are used in advance to determine and set the initial state of the Viterbi decoder before processing the unknown data bits. This preliminary action eliminates the need to decode the padding bits and provides a known starting point for the decoding process, improving the decode success rate without significantly increasing complexity.
2Productivity
If the Viterbi decoder processes all bits in the data block, then the implementation is straightforward, but the number of operations increases and error probability increases
Solution Approach 1:
The known padding bits are extracted and removed from the decoding process. The Viterbi decoder is configured to skip over these known bits and process only the unknown data bits. This extraction eliminates redundant operations on padding bits, improving both decoding efficiency and reliability by reducing the total number of operations and the probability of errors.
Solution Approach 2:
The parameters of the Viterbi decoder are changed to reflect the presence of known padding bits. Specifically, the initial state of the decoder is set based on the known padding bits, and the number of bits to be processed is adjusted to exclude the padding bits. This parameter change improves decoding efficiency by reducing the processing load and enhances reliability by avoiding errors in decoding known information.
3Ease of manufacture
If padding bits are included in the convolutional encoding process, then the encoding is uniform and simple, but the probability of errored data decoding increases
Solution Approach 1:
The known padding bits serve as an intermediary between the data source and the Viterbi decoder. Instead of having the decoder process the padding bits directly, the known values are used to constrain the initial state of the decoder, effectively mediating the transition from known to unknown data. This approach maintains encoding simplicity while improving decode success rate by preventing error propagation from redundant padding bit decoding.
Data Source
AI summary
A method and system of decoding a convolutionally encoded data block having known padding bits. A Viterbi decoder is constrained to a state corresponding to k−1 padding bits immediately adjacent to data bits of the data block, where k is a constraint length of a convolution encoder used to encode the data block. Symbols of the encoded data block that have influence only from the padding bits are discarded.