Soft Bit Generation in Sequence Estimation via Reduced Candidate Sets
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Solution Overview
Problem
Sequence estimators face high computational complexity and reduced reliability in generating soft information due to the elimination of paths during symbol sequence estimation, which compromises error correcting performance.
Innovation Solution
A demodulator is configured to generate soft bit values by constraining the state space for each symbol to a reduced set of candidate values, ensuring every bit value has a complementary value, thereby reducing computational complexity while maintaining sufficient state space for soft information generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If paths are eliminated during sequence estimation to reduce computational complexity, then device complexity is reduced, but reliability of soft information generation deteriorates
Solution Approach 1:
The state space for each symbol is segmented into a reduced set of candidate values that are strategically selected to include complementary bit values. This segmentation allows the system to focus computational resources on a manageable subset of states while preserving the necessary diversity for reliable soft information generation.
Solution Approach 2:
The invention applies local quality by ensuring that within the reduced state space, each bit value position has complementary values present. This local property of having complementary pairs enables soft information calculation without requiring the full state space, thus resolving the contradiction between reduced complexity and maintained reliability.
2Productivity
If the state space is reduced to fewer candidate values, then productivity increases, but measurement precision of bit values deteriorates
Solution Approach 1:
The invention changes the parameter of state space size from the full constellation to a reduced set, while simultaneously changing the composition parameter to ensure complementary bit values are included. This dual parameter adjustment maintains measurement precision for soft information while achieving productivity gains through reduced processing.
3Reliability
If complementary bit values are included in the reduced state space, then reliability of error correcting performance is improved, but device complexity increases
Solution Approach 1:
The invention modifies the state space parameters by selecting a reduced number of candidate values that specifically include complementary pairs for each bit position. This parameter change enables error correcting performance while keeping the state space manageable and avoiding excessive device complexity.
Data Source
AI summary
Teachings presented herein offer reduced computational complexity for symbol sequence estimation, and also provide for the generation of soft bit values representing the reliability of that estimation. A demodulator is configured to generate these soft bit values by identifying a candidate value for each symbol in the sequence which is more likely than at least one other in a defined set of candidate values. Based on the candidate value identified for each symbol, the demodulator forms a reduced set of candidate values for the symbol by selecting as many additional candidate values from the defined set as are needed to have complementary bit values for each bit value in that identified candidate value. The demodulator calculates soft bit values for the symbol sequence based on a sequence estimation process whose state space for each symbol is constrained to the corresponding reduced set.