LDPC Bit Interleaver Permutation for 4096-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 64800 and code rate of 2/15, using 4096-symbol mapping, which interleaves the LDPC codeword on a bit group basis with a parallel factor of 360, effectively distributing burst errors through a specific permutation order.
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 (180 groups of 360 bits each) and applies independent permutation operations to each group. This segmentation allows the interleaver to effectively distribute burst errors across different groups while maintaining a manageable design complexity through modular processing
Solution Approach 2:
The patent optimizes the permutation parameters specifically for 4096-QAM modulation and LDPC(64800, 2/15) code rate. By tailoring the permutation sequence to these specific parameters, the interleaver achieves optimal performance for the given modulation and coding scheme without requiring overly complex adaptive mechanisms
2Reliability
If the bit interleaver is optimized for specific LDPC parameters and modulation order, then performance is improved, but the adaptability to different configurations decreases
Solution Approach 1:
The patent employs parameter-specific optimization by designing the permutation sequence based on the parallel factor (360) and total codeword length (64800). This allows the same interleaver structure to be adapted to different configurations by changing the permutation parameters rather than redesigning the entire system
Solution Approach 2:
The interleaver design provides a universal framework that can handle different LDPC code rates and modulation schemes by adjusting the permutation sequence. The same basic interleaver structure serves multiple functions across different BICM configurations, achieving both optimization and adaptability
3Reliability
If burst errors are not distributed, then the system structure remains simple, but error correction performance degrades rapidly
Solution Approach 1:
By dividing the codeword into 180 bit groups and applying permutation to each group independently, the system effectively distributes burst errors across multiple groups. This segmentation approach achieves excellent error distribution with a relatively simple modular structure
Solution Approach 2:
The bit-group-based permutation acts as an intermediary mechanism between the LDPC decoder and the modulation scheme. It provides the necessary error distribution function without requiring direct complex interaction between the decoder and modulator, simplifying the overall system design
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 64800 and a code rate of 2/15. 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 4096-symbol mapping.