Hierarchical HARQ Decoupling Multi-Level Coded Modulation
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Solution Overview
Problem
Wireless communication systems face inefficiencies in hybrid automatic repeat request (HARQ) procedures due to decoding level dependencies, leading to error propagation and increased overhead in multi-level coding scenarios, where the failure of a lower decoding level can cause failures in higher levels, resulting in unnecessary retransmissions.
Innovation Solution
A hierarchical HARQ procedure is implemented, where the receiving device identifies the lowest failing decoding level and transmits feedback to the base station, allowing for selective and gradual retransmission of codewords, decoupling higher decoding levels from lower ones, and enabling retransmission of only the necessary code blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-level coding with multi-level sequential demodulation and decoding is used, then spectral efficiency is improved, but HARQ retransmission overhead increases due to error propagation from lower decoding levels
Solution Approach 1:
The patent segments the decoding process into multiple independent levels, where each decoding level processes its own codewords separately. This segmentation prevents error propagation between levels, as failures at one level do not cause failures at other levels. The receiver can successfully decode higher-level codewords even when lower-level decoding fails, thereby reducing unnecessary retransmissions and overhead while maintaining spectral efficiency.
2Reliability
If lower decoding level codewords fail CRC, then higher decoding level codewords will also fail, but this leads to increased retransmission overhead
Solution Approach 1:
The patent divides the coupled decoding system into independent decoding levels. Each level operates autonomously with its own CRC checking and HARQ process. When lower-level codewords fail CRC, it does not automatically cause higher-level codeword failures because they are decoded independently. This segmentation maintains decoding reliability at each level while preventing cascading failures that would waste retransmission time.
3Loss of substance
If hierarchical HARQ with selective retransmission is implemented, then retransmission overhead is reduced, but feedback message complexity increases
Solution Approach 1:
The patent segments the feedback mechanism to provide granular control over retransmissions. Instead of treating all codewords uniformly, the system generates separate feedback information for each decoding level and codeword based on their individual CRC results. This segmented feedback approach enables selective retransmission of only failed codewords at specific levels, reducing overall retransmission overhead while the added feedback structure provides the necessary control information.
Solution Approach 2:
The patent implements a detailed feedback mechanism where the receiver reports CRC results for each codeword at each decoding level separately. This feedback information includes identification of which specific codewords failed and at which decoding levels, enabling the transmitter to perform targeted retransmissions. The feedback principle reduces retransmission overhead by avoiding retransmission of successfully decoded codewords while the structured feedback message format organizes the complexity in a manageable way.
Data Source
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AI summary
Methods, systems, and devices for wireless communications are described. One method may include a user equipment (UE) receiving, in a first transmission time interval, a code block group including a set of code blocks associated with a set of codewords, each codeword being associated with one of a set of decoding levels introduced in communication scheme that uses multi-level coded modulation and multi-level sequential decoding. The UE may determine that a decoding procedure is unsuccessful, and transmit a feedback message including a first indicator that the decoding procedure was unsuccessful and a second indicator of a lowest decoding level for which the decoding procedure was unsuccessful. The UE may then receive, from the base station in a second transmission time interval, a retransmission of code blocks of the lowest failed decoding level coupled to a new data transmission for code blocks associated with all other decoding levels.