LDPC Redundancy Version Positioning for Faster 5G HARQ Decoding
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently managing redundancy versions (RVs) for low-density parity check (LDPC) codes in 5G systems, particularly in high data rate scenarios, leading to issues with decoding complexity and latency, especially when using incremental redundancy HARQ (IR-HARQ) due to fixed RV positions that can cause mismatches between user equipment (UE) and base stations.
Innovation Solution
A method and apparatus for determining fixed starting positions of RVs in LDPC codes by ensuring specific separation and placement criteria, such as RV2 > RV3 > RV2 > RV1 > RV0, with RVs primarily located in parity bits regions, to mimic sequential transmission benefits while maintaining compatibility across different code rates and channel conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundancy versions are transmitted for LDPC codes in 5G systems, then transmission reliability is improved, but decoding complexity increases
Solution Approach 1:
The coded bits are segmented into multiple redundancy versions (RV0, RV1, RV2, RV3) with different starting positions in the circular buffer. Each RV contains a different subset of parity bits, allowing the receiver to accumulate information across multiple transmissions and progressively improve decoding success while managing complexity through structured segmentation.
2Reliability
If more redundancy versions are transmitted, then transmission success rate is improved, but transmission time increases
Solution Approach 1:
The starting positions of all redundancy versions are predetermined and configured in advance through higher-layer signaling. This preliminary configuration allows the receiver to immediately begin decoding with the first received RV and progressively combine information from subsequent RVs without requiring real-time negotiation or complex scheduling decisions, thereby reducing latency while achieving high transmission success rates.
3Ease of manufacture
If fixed starting positions for RVs are used, then implementation complexity is reduced, but adaptability to different code rates decreases
Solution Approach 1:
The starting positions of redundancy versions are defined as parameters that can be configured according to different code rates and transport block sizes. The patent provides specific starting position configurations for different code rates (e.g., 1/3, 2/3, 3/4, 5/6), allowing the system to maintain low implementation complexity through fixed positions while adapting to various code rates by selecting appropriate pre-configured parameter sets.
4Productivity
If redundancy versions are spaced to prioritize high-priority parity bits, then decoding efficiency is improved, but RV position configuration complexity increases
Solution Approach 1:
Different starting positions are assigned to different redundancy versions to prioritize access to high-priority parity bits in early transmissions. RV0 starts at position 0 with systematic bits and initial parity, while subsequent RVs start at different positions (e.g., 18.5z, 35z, 51.5z) to provide complementary parity information. This local differentiation in starting positions optimizes decoding efficiency by ensuring high-priority information is available early, while the overall configuration remains manageable through standardized patterns.
Data Source
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AI summary
A method comprises receiving information on a selected redundancy version at a user device. The redundancy version is associated with block coding. The block coding may be LDPC. The method may comprise using the information when communicating with a base station. The position of the redundancy version may satisfy one or more criteria.