Channel Interleaver Constellation-Based Permutation for Burst Error Reduction
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Solution Overview
Problem
The IEEE 802.16e channel interleaving scheme suffers from intra-block and inter-block continuity issues, where adjacent encoded bits within subblocks and multiple bits across different subblocks are mapped onto the same bit reliability, leading to burst errors and poor decoder performance, especially in high-order modulation schemes like 16QAM and 64QAM.
Innovation Solution
A channel interleaver with a constellation-based permutation module that rearranges interleaved bits to prevent consecutive encoded bits within a set and adjacent bits within subblocks from being mapped onto the same bit reliability, achieving constellation diversity through block-wise or unit-wise scrambling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If subblock interleaving is used to distribute encoded bits into subblocks, then channel error averaging is achieved, but intra-block continuity causes adjacent bits to be mapped onto the same bit reliability level
Solution Approach 1:
The encoded bits are divided into multiple subblocks, and each subblock is further segmented into units of multiple bits. This hierarchical segmentation allows independent permutation operations on each unit, preventing adjacent bits from being mapped to the same reliability level while maintaining the error averaging benefit of subblock interleaving.
Solution Approach 2:
Different permutation operations are applied to different units within subblocks based on their local characteristics. The constellation-based permutation module performs unit-wise permutation where each unit can be independently scrambled, creating local diversity in bit reliability mapping that prevents intra-block continuity while preserving overall system reliability.
2Ease of manufacture
If the same interleaving equation is used for all subblocks, then implementation simplicity is maintained, but inter-block continuity causes multiple bits to be mapped onto the same bit level
Solution Approach 1:
The system transitions from static interleaving (same equation for all subblocks) to dynamic interleaving where each subblock's units undergo random permutation. The constellation-based permutation module introduces dynamic scrambling operations that vary across subblocks and units, eliminating inter-block continuity while maintaining implementation feasibility through standardized permutation procedures.
Solution Approach 2:
The invention adds a new dimension of permutation operations at the unit level within subblocks. Instead of only subblock-level interleaving, the system now operates at two dimensions: subblock interleaving and unit-wise constellation permutation. This additional dimensional operation prevents inter-block continuity without significantly complicating the overall system.
3Productivity
If high-order modulation schemes are used to increase data rate, then spectral efficiency is improved, but burst errors are exacerbated due to multiple bit reliability levels
Solution Approach 1:
The system changes the parameter of bit mapping by introducing constellation-based permutation that randomly assigns bits to different reliability levels within modulation symbols. This parameter change ensures that consecutive encoded bits are not systematically mapped to the same reliability level, reducing burst error susceptibility while maintaining high-order modulation's spectral efficiency.
Data Source
AI summary
A channel interleaver comprises a novel constellation-based permutation module. The channel interleaver first receives a plurality of sets of encoded bits generated from an FEC encoder. The encoded bits are distributed into multiple subblocks and each subblock comprises a plurality of adjacent bits. A subblock interleaver interleaves each subblock and outputs a plurality of interleaved bits. The constellation-based permutation module rearranges the interleaved bits and outputs a plurality of rearranged bits. The rearranged bits are supplied to a symbol mapper such that a plurality of consecutively encoded bits in the same set of the encoded bits generated from the FEC encoder is prevented to be mapped onto the same level of bit reliability of a modulation symbol. In addition, the plurality of adjacent bits of each subblock is also prevented to be mapped onto the same level of bit reliability to achieve constellation diversity and to improve decoding performance.