Multi-Level HARQ Retransmission for Low-Latency Code Block Groups
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Solution Overview
Problem
Wireless communications systems with multi-level coding and multi-level sequential demodulation and decoding face increased latency due to hierarchical HARQ procedures, particularly when error propagation occurs across decoding levels, leading to inefficiencies in retransmissions and higher latency for latency-sensitive data types.
Innovation Solution
Implementing a latency minimization technique where a base station retransmits all code blocks associated with a failed code block group, regardless of the failing decoding level, to ensure simultaneous retransmission of both lower and higher decoding level code blocks over the same channel resources, allowing for immediate HARQ combining and reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If hierarchical HARQ procedures are used for multi-level coding, then spectral efficiency is improved, but latency increases due to error propagation across decoding levels
Solution Approach 1:
The code block group is segmented into multiple code blocks associated with different decoding levels. Each code block can be independently decoded and acknowledged, allowing the system to process and retransmit only the necessary segments rather than waiting for complete multi-level decoding, thus reducing latency while maintaining spectral efficiency through targeted retransmissions
Solution Approach 2:
The base station prepares and transmits all code blocks associated with different decoding levels in advance within the same TTI. This preliminary action ensures that when decoding failures occur, the retransmission can immediately utilize already-prepared code blocks without waiting for sequential decoding completion, thereby minimizing latency
2Productivity
If selective retransmission of failed code blocks is implemented, then retransmission efficiency is improved, but latency increases due to sequential processing requirements
Solution Approach 1:
The base station merges the retransmission of multiple code blocks (both failed and successfully decoded) into a single retransmission event within the same TTI. This combining approach allows the system to maintain high retransmission efficiency by sending only necessary code blocks while reducing latency by avoiding sequential processing delays across multiple TTIs
3Loss of time
If all code blocks are retransmitted together, then latency is reduced through simultaneous processing, but retransmission overhead increases
Solution Approach 1:
The base station applies local quality by differentiating the treatment of code blocks based on their decoding status. Successfully decoded code blocks are not retransmitted, while failed code blocks are retransmitted with appropriate redundancy versions. This selective approach reduces retransmission overhead by avoiding unnecessary transmissions of already-successful code blocks while still achieving low latency through simultaneous retransmission preparation
Data Source
AI summary
Methods, systems, and devices for wireless communications employing multi-level coding with set partitioning on transmitting side and multi-level sequential decoding on the receiving side for latency minimization are described. In some systems, a transmitting device may transmit a code block group (CBG) to a receiving device including a first set of code blocks associated with a first decoding level and a second set of code blocks associated with a second decoding level. The receiving device may unsuccessfully decode one or more code blocks of the first set or the second set of code blocks and transmit a feedback message to the transmitting device. The transmitting device may determine that the data to be communicated via the CBG is latency-sensitive data and, as such, determine to retransmit both the first set and the second set of code blocks to the receiving device in response to receiving the feedback message.