User Terminal Retransmission Control via Codeblock Group Segmentation
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Solution Overview
Problem
In future radio communication systems like 5G, the increased segmentation of transport blocks into codeblock groups leads to inefficient retransmissions, as error-free codeblocks are also retransmitted, causing a decline in performance and throughput due to control being managed at the transport block level.
Innovation Solution
A user terminal is designed to receive and transmit retransmission control information at the codeblock group level, determining the number of bits based on the total number of codeblock groups for proper retransmission control, allowing for more precise management of retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If retransmission control is performed in TB units as in existing LTE systems, then the system maintains simplicity in control management, but efficiency deteriorates because error-free codeblocks are also retransmitted when TBS is segmented into many CBs
Solution Approach 1:
The transport block is divided into multiple codeblock groups (CBGs), and retransmission control is performed independently for each CBG rather than for the entire TB. This segmentation allows the system to retransmit only the specific CBGs that contain errors, avoiding the retransmission of error-free CBGs and thereby improving throughput while reducing unnecessary retransmission overhead.
2Quantity of substance
If TBS is increased to support higher speed and larger capacity communication, then communication capacity is improved, but the number of CBs per TB increases leading to more segmentation and worse retransmission efficiency
Solution Approach 1:
By segmenting the TB into multiple CBGs and enabling independent retransmission control for each CBG, the system can handle large TBS values more efficiently. When errors occur, only the affected CBGs need to be retransmitted rather than the entire large TB, thus maintaining retransmission efficiency even as data capacity increases through higher TBS values.
3Productivity
If retransmission control is performed per CBG instead of per TB, then retransmission efficiency is improved by avoiding retransmission of error-free codeblocks, but control complexity increases
Solution Approach 1:
The TB is segmented into multiple CBGs, each with its own retransmission control. This segmentation enables finer-grained control where only erroneous CBGs are retransmitted, improving efficiency. The complexity increase is managed by organizing control information at the CBG level, which is a systematic approach that balances the trade-off between control granularity and system complexity.
Data Source
AI summary
The present invention is designed to control retransmission properly in smaller units than TBs (for example, in units of CBs or in units of CBGs). According to one example of the present invention, a user terminal has a receiving section that receives a transport block (TB) including one or more codeblock groups (CBG), a transmission section that transmits retransmission control information that indicates an ACK or a NACK in response to each CBG, and a control section that, when at least one CBG in the TB is subject to retransmission, determines the number of bits of the retransmission control information based on the total number of CBGs in the TB or the number of CBGs that are retransmitted.