Protograph LDPC HARQ Retransmission for Flexible Coding Rates
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Solution Overview
Problem
Current communication systems face challenges in efficiently utilizing polar codes and LDPC codes, particularly in cellular networks, due to limitations in channel resource management and the need for flexible coding rates to support varying channel conditions and retransmissions.
Innovation Solution
The proposed solution involves using polar codes for successive HARQ retransmissions with adaptive information bit allocation and different polar code schemes for each retransmission, and employing rate-compatible LDPC codes based on protographs to support varying input block lengths and coding rates, allowing for efficient channel resource utilization and improved error correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If polar codes are used for HARQ retransmissions with fixed block length N (power of 2), then encoding and decoding complexity is reduced, but flexibility in adapting to varying channel conditions and coding rates is limited
Solution Approach 1:
The patent applies dynamics by enabling the polar code block length N to be dynamically adjusted based on channel conditions and retransmission requirements. Instead of being fixed at power-of-2 values, the system can adapt N to match the actual data size and channel state, allowing optimal performance across varying conditions while maintaining the structured benefits of polar codes.
Solution Approach 2:
The patent changes the parameter N (block length) from a fixed power-of-2 value to a flexible parameter that can be adjusted according to channel conditions, coding rate requirements, and retransmission needs. This parameter change enables the system to optimize between complexity and adaptability by selecting appropriate N values for different operational scenarios.
2Adaptability or versatility
If puncturing is performed on polar code output to achieve non-power-of-2 block lengths, then adaptability to varying data sizes is improved, but code construction complexity and frozen bit management become more difficult
Solution Approach 1:
The patent applies segmentation by dividing the polar code construction into manageable components: a base code of power-of-2 length and a punctured portion. This segmentation allows the system to maintain the structured benefits of polar codes for the base portion while adding flexibility through controlled puncturing, reducing overall construction complexity compared to designing entirely new codes for each data size.
Solution Approach 2:
The patent makes the puncturing pattern dynamic rather than fixed, allowing the system to adjust which bits are punctured based on channel conditions and performance requirements. This dynamic approach optimizes the balance between adaptability and complexity by selectively applying puncturing only when and where needed.
3Reliability
If different polar code schemes are used for each retransmission to optimize performance, then error correction capability is improved, but system complexity and processing overhead increase
Solution Approach 1:
The patent applies local quality by using different polar code configurations (different N values, different puncturing patterns, or different frozen bit assignments) for specific retransmission scenarios where they provide the most benefit. Instead of uniformly applying complex schemes to all retransmissions, the system selectively optimizes local aspects of the code construction based on channel conditions and performance needs.
Solution Approach 2:
The patent performs preliminary action by pre-calculating and storing multiple polar code configurations and their corresponding performance characteristics. This allows the system to quickly select appropriate codes for retransmissions without performing complex real-time optimization, reducing processing overhead while maintaining error correction capability.
4Adaptability or versatility
If rate-compatible LDPC codes based on protographs are used to support varying input block lengths, then flexibility in coding rate adaptation is improved, but code construction and parity check matrix generation become more complex
Solution Approach 1:
The patent applies universality by designing a base protograph that can serve multiple functions: generating LDPC codes for different block lengths, supporting various coding rates, and enabling rate-compatible retransmissions. This single universal protograph structure replaces the need for separate code constructions for each scenario, reducing overall complexity while maintaining flexibility.
Solution Approach 2:
The patent implements the nested doll principle by creating a hierarchical code structure where a base LDPC code is nested within extended versions that support larger block lengths and different rates. The protograph serves as the innermost layer, with systematic expansion rules that generate outer layers for different operational requirements, allowing compact storage and efficient generation of multiple code variants.
Data Source
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AI summary
A method and apparatus for transmitting data using low density parity check (LDPC) encoding is disclosed. The method may comprise transmitting a first signal derived from a first subset of a set of low density parity check (LDPC) coded bits; receiving retransmission information; and transmitting a second signal derived from a second subset of the set of LDPC coded bits which is different than the first subset, in response to receiving the retransmission information, wherein the second subset is selected from the set of LDPC coded bits based on a lifting size of an LDPC base graph.