LDPC Bit Interleaver Permutation for 256-Symbol Burst Error Distribution
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Solution Overview
Problem
Bit-Interleaved Coded Modulation (BICM) systems face rapid performance degradation due to burst errors in digital broadcast channels, necessitating an optimized bit interleaver design for modulation order and error correction code parameters.
Innovation Solution
A bit interleaver optimized for an LDPC coder with a length of 16200 and code rate of 4/15, using 256-symbol mapping, is designed to effectively distribute burst errors by interleaving LDPC codewords on a bit group basis with a specific permutation order, suitable for next-generation broadcasting systems like ATSC 3.0.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bit interleaver is used in BICM systems, then the system structure remains simple, but burst errors in the channel cause rapid performance degradation
Solution Approach 1:
The patent segments the LDPC codeword into multiple bit groups (e.g., 45 bit groups of 360 bits each) and applies permutation to each bit group independently. This segmentation allows the interleaver to distribute burst errors effectively across different bit groups while maintaining a manageable design complexity through structured permutation patterns.
Solution Approach 2:
The patent optimizes the permutation order parameters specifically for 256-symbol mapping and LDPC codes with length 16200 and code rate 4/15. By tailoring the permutation parameters to match the specific modulation order and code parameters, the interleaver achieves optimal error distribution performance without requiring overly complex adaptive mechanisms.
2Reliability
If the bit interleaver is optimized for specific modulation order and code parameters, then error distribution performance improves, but adaptability to different configurations decreases
Solution Approach 1:
The patent employs parameterized permutation patterns where the permutation order is defined as a function of the bit group index and configurable parameters. This allows the same interleaver structure to be adapted to different modulation orders and code parameters by simply changing the parameter values, rather than redesigning the entire interleaver for each configuration.
Solution Approach 2:
The interleaver design uses a universal permutation framework that can handle different LDPC code lengths, code rates, and modulation orders through parameter adjustment. The core interleaving mechanism remains the same, but the permutation parameters can be configured to match various broadcasting standards and system requirements, providing multi-functional capability.
3Reliability
If burst errors are distributed through bit group-based interleaving, then error correction performance improves, but the processing complexity increases
Solution Approach 1:
By dividing the codeword into fixed-size bit groups and applying deterministic permutation patterns to each group, the patent achieves effective error distribution while keeping the processing complexity manageable. The segmentation allows parallel processing of bit groups and uses simple index-based permutation calculations rather than complex lookup tables or iterative algorithms.
Solution Approach 2:
The patent replaces complex mechanical or iterative error distribution mechanisms with a mathematical permutation-based system. The interleaving operation is performed through direct index calculation and array reordering based on permutation formulas, which can be efficiently implemented in hardware or software without requiring iterative optimization or complex control logic.
Data Source
AI summary
A bit interleaver, a bit-interleaved coded modulation (BICM) device and a bit interleaving method are disclosed herein. The bit interleaver includes a first memory, a processor, and a second memory. The first memory stores a low-density parity check (LDPC) codeword having a length of 16200 and a code rate of 4/15. The processor generates an interleaved codeword by interleaving the LDPC codeword on a bit group basis. The size of the bit group corresponds to a parallel factor of the LDPC codeword. The second memory provides the interleaved codeword to a modulator for 256-symbol mapping.