HARQ Retransmission Using Vertical Check Blocks and RV-Indexed Interleavers
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Solution Overview
Problem
Current HARQ retransmission schemes in wireless communications, particularly in 5G's New Radio release, face inefficiencies due to high overhead in feedback mechanisms for code block group-based retransmissions, as they require feedback on successfully decoded CBGs to avoid retransmitting already recovered blocks, which increases latency and resource usage.
Innovation Solution
The implementation of a 2D HARQ retransmission scheme using vertical check blocks generated with subblock interleavers, where each subblock interleaver set is uniquely mapped to a redundancy version index, allowing only the RV index to be communicated for retransmissions, enabling the receiving node to utilize vertical check blocks for decoding without needing explicit feedback on successfully decoded CBGs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CBG-based HARQ retransmission is used to retransmit only failed code blocks, then retransmission efficiency is improved, but feedback overhead increases due to requiring detailed CBG index feedback
Solution Approach 1:
The patent extracts the essential retransmission information (which CBGs need retransmission) and separates it from the detailed feedback mechanism. Instead of requiring the receiver to send back specific CBG indices, the system only needs to transmit a compact RV index that implicitly conveys the retransmission pattern, thereby reducing feedback overhead while maintaining retransmission efficiency
Solution Approach 2:
The redundancy version index serves multiple functions: it identifies the specific retransmission pattern, indicates which CBGs require retransmission, and enables the transmitter to select appropriate check blocks. This multi-functionality eliminates the need for separate feedback messages, reducing overall overhead while preserving CBG-based retransmission benefits
2Reliability
If TB-based HARQ retransmission is used to ensure reliability, then decoding reliability is improved, but resource usage increases due to retransmitting all FEC blocks even when some are correctly received
Solution Approach 1:
The transport block is segmented into multiple code block groups (CBGs), allowing independent handling of each group. This segmentation enables selective retransmission of only the failed CBGs rather than retransmitting the entire TB, thereby reducing resource usage while maintaining the reliability needed for successful decoding
Solution Approach 2:
Instead of retransmitting the complete TB (excessive action), the system performs partial retransmission by sending only the specific CBGs that failed decoding. This partial action reduces resource consumption while still achieving the required decoding reliability for the entire TB
3Reliability
If subblock interleavers are used for check block generation, then decoding performance is improved, but system complexity increases due to multiple interleaver sets
Solution Approach 1:
Multiple subblock interleaver sets are pre-configured and stored in the system before operation. During retransmission, the appropriate pre-configured interleaver set is selected based on the RV index, avoiding the need for complex real-time computation and reducing operational complexity while maintaining decoding performance benefits
Solution Approach 2:
The system changes the parameter of the interleaver selection by using the RV index to dynamically select among pre-configured interleaver sets. This parameter-based selection mechanism provides flexibility and optimized decoding performance for different retransmission scenarios without requiring complex adaptive algorithms
Data Source
AI summary
Methods and systems for wireless communications by performing HARQ-based retransmissions using vertical check blocks are described. After performing an initial transmission, a first retransmission is performed. The first retransmission includes at least one vertical check block from a first set of vertical check blocks generated using a first subblock interleaver set associated with a first RV index of the first retransmission. A second retransmission is performed, including at least one vertical check block from a second set of vertical check blocks generated using a second subblock interleaver set associated with a second RV index of the second retransmission.