Control Sequence Rearrangement for Low-Delay Tail-Biting Decoding
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Solution Overview
Problem
Conventional Viterbi decoding methods for tail-biting convolutional codes result in increased processing delay and error rates due to repetitive processing and truncation errors, particularly at the ends of the decoded sequence.
Innovation Solution
The solution involves rearranging control information sequences to limit the number of possible states in the encoder, allowing for low-delay processing and reducing decoding errors by forming a coding target sequence with predictable bit sequences, which are then encoded using the tail-biting convolutional coding scheme, mimicking the termination coding scheme's decoding characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tail-biting method is used for convolutional coding, then the initial state and end state of the encoder are the same (cyclic trellis), but the decoder cannot predict the initial state, leading to increased processing delay and error rates
Solution Approach 1:
The invention performs preliminary actions by conducting multiple ACS calculations iteratively to converge on the correct initial state before final decoding. The decoder performs preliminary traceback operations to identify valid state transitions that satisfy the tail-biting constraint, thereby preparing the decoding path in advance and reducing overall processing delay.
Solution Approach 2:
The invention applies periodic action through iterative ACS calculations and multiple passes of traceback operations. The decoder periodically checks whether the decoded sequence satisfies the tail-biting constraint (initial state equals end state) and repeats the decoding process with adjusted parameters until convergence, thereby resolving the state prediction problem systematically.
2Measurement precision
If repetitive processing is performed to decode tail-biting codes, then decoding accuracy may improve, but processing delay increases significantly
Solution Approach 1:
The invention applies partial action by performing a limited number of iterative ACS calculations and traceback operations rather than exhaustive repeated processing. The decoder performs just enough iterations to converge on the correct initial state and satisfy the tail-biting constraint, avoiding excessive repetitive processing that would unnecessarily increase delay while still achieving adequate decoding accuracy.
3Ease of operation
If the termination method is used with known initial signals, then the decoder can identify initial and end states, but the coding block structure is more complex and requires attaching known signals
Solution Approach 1:
The invention applies inversion by reversing the conventional approach: instead of attaching known signals to identify states (termination method), the tail-biting method assumes the initial and end states are the same and uses this constraint to identify valid decoding paths. The decoder works backwards from the end state to verify it matches the initial state, inverting the traditional state identification approach and simplifying the coding block structure.
Data Source
AI summary
The coding apparatus, coding processing target sequence forming method and Viterbi decoding apparatus of the present invention can realize low delay processing with a minimum number of repetitive processing and suppress the degradation of the accuracy of decoding at the ends of a decoded sequence due to truncation error. In the coding apparatus mounted on the transmitting apparatus (100), a control information rearranging section (130) receives as input a control information sequence, in which a plurality of control information blocks are arranged in a predetermined order, and forms a coding processing target sequence by rearranging the order of the plurality of control information blocks to form an assembled sequence grouping control information blocks comprised of predictable bit sequences in the plurality of control information blocks, and to allocate the assembled sequence to a predetermined position in the control information sequence. Further, an encoding section (140) encodes the coding target sequence using the tail-biting convolutional coding scheme.