Interleaved LDPC Codeword Mapping for High-Order Modulation Reliability
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Solution Overview
Problem
Conventional bit-interleaved low-density parity-check (LDPC) coded modulation schemes for wireless communications face challenges in achieving reliable error rates, especially with high-order modulations, due to the non-systematic nature of NR LDPC codes and the lack of efficient reliability-based bit mapping in transmission and reception processes.
Innovation Solution
A transmitting device and receiving device configuration that jointly interleaves and deinterleaves systematic and parity-check bits, mapping them to modulation label positions with different reliabilities, and adjusts these mappings based on transmission type (initial or re-transmission) to enhance error protection and coding gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional bit-interleaved LDPC coded modulation is used with high-order modulations, then spectral efficiency is improved, but error rate performance deteriorates
Solution Approach 1:
The patent applies local quality by differentiating the treatment of systematic bits and parity-check bits through separate interleaving processes. Systematic bits are interleaved first to preserve their reliability for initial decoding attempts, while parity-check bits are interleaved separately to provide additional redundancy. This localized differentiation of bit treatment resolves the contradiction by maintaining high spectral efficiency through high-order modulation while improving error rate performance through differentiated bit protection strategies.
Solution Approach 2:
The patent segments the LDPC codeword into systematic bits and parity-check bits, applying distinct interleaving operations to each segment. This segmentation allows the system to optimize the protection level for different bit types, thereby improving overall error rate performance while maintaining the spectral efficiency benefits of high-order modulations.
2Productivity
If NR LDPC codes with adaptive modulations up to 256QAM are used, then spectral efficiency is improved, but the non-systematic nature of codes increases complexity of reliable transmission
Solution Approach 1:
The patent applies preliminary action by performing rate matching and interleaving operations on the LDPC codeword before modulation and transmission. The systematic bits are interleaved first, followed by parity-check bits, creating a pre-processed structure that facilitates more reliable decoding at the receiver. This preliminary processing reduces the complexity of achieving reliable transmission while maintaining high spectral efficiency.
Solution Approach 2:
The patent implements dynamic adaptation by adjusting the interleaving and rate matching parameters based on channel conditions and transmission requirements. The system can dynamically switch between different modulation orders (up to 256QAM) and adjust the proportion of systematic versus parity bits, thereby optimizing the balance between spectral efficiency and transmission reliability without excessive complexity.
3Reliability
If joint interleaving of systematic and parity-check bits is performed, then error protection is improved, but mapping complexity increases
Solution Approach 1:
The patent resolves the mapping complexity issue by segmenting the interleaving process into two distinct stages: first interleaving systematic bits, then interleaving parity-check bits separately. This segmentation simplifies the mapping complexity compared to joint interleaving, while still achieving improved error protection through the coordinated arrangement of both bit types in the final modulation mapping.
Data Source
AI summary
A transmitting device is described for a communication system. The transmitting device obtains an information message comprising information bits addressed for a receiving device and encodes the information message to obtain a codeword. The transmitting device rate-matches the codeword to produce a rate-matched codeword comprising systematic bits and parity-check bits. Furthermore, the transmitting device jointly interleaves the systematic bits and parity-check bits of the rate-matched codeword to obtain an interleaved codeword. The systematic bits of the interleaved codeword are mapped to modulation label positions of a modulation constellation with first reliabilities, and the parity-check bits of the interleaved codeword are mapped to modulation label positions of the modulation constellation with second reliabilities.