Terminal Apparatus Timer Management for Uplink Retransmission
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Solution Overview
Problem
In 5G communication systems, terminal apparatuses face inefficiencies in data retransmission procedures due to the lack of configured waiting timers for DCI retransmissions and increased power consumption when stopping data transmission, particularly in scenarios involving grant-free access and URLLC communications.
Innovation Solution
A terminal apparatus is configured with multiple timers to manage uplink data transmission and retransmissions, including a first timer for HARQ processes, a second timer for reinitializing after data cancellation, and a third timer for handling uplink grant changes, allowing for efficient data retransmission and power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the base station apparatus does not transmit ACK/NACK to the terminal apparatus stopping data transmission, then the control information overhead is reduced, but the terminal apparatus cannot determine whether to retransmit the stopped data
Solution Approach 1:
The patent introduces a timer as an intermediary mechanism to bridge the information gap. When the base station stops uplink data transmission without sending ACK/NACK, the terminal apparatus uses a timer to determine whether to retransmit. If the timer expires before receiving ACK/NACK, the terminal apparatus assumes the data should be retransmitted. This timer-based intermediary resolves the contradiction by providing a default retransmission rule when control information is absent, reducing overhead while maintaining reliability.
2Reliability
If the terminal apparatus waits for DCI to retransmit stopped data, then the retransmission reliability is improved, but the delay increases
Solution Approach 1:
The patent applies preliminary action by configuring the timer in advance before the actual retransmission decision is needed. The timer is set based on the expected DCI arrival time, allowing the terminal apparatus to proactively determine retransmission timing without waiting passively for DCI. This preliminary timer configuration reduces the actual waiting delay while maintaining reliability, as the terminal apparatus can immediately retransmit when the timer expires without unnecessary delays.
3Productivity
If multiple timers are configured for HARQ processes and data cancellation, then the data retransmission efficiency is improved, but the device complexity increases
Solution Approach 1:
The patent segments the timer management into distinct functional components: a first timer for HARQ process waiting, a second timer for data cancellation handling, and a third timer for uplink grant change detection. Each timer is configured with specific parameters and triggers different retransmission behaviors. This segmentation allows the system to handle different retransmission scenarios independently and efficiently, improving overall productivity while managing complexity through modular timer design with clear separation of concerns.
Data Source
AI summary
A terminal apparatus includes a control information detection unit configured to detect first and second DCI, and a transmitter configured to perform UL data transmission based on the first DCI or cancel a resource allocated in the second DCI. A UL grant using the first DCI is detected, when performing UL data transmission based on the UL grant, after the data transmission, a first timer for a corresponding HARQ process is started and a second timer is stopped, and when the first timer expires, the second timer for a HARQ process is started. When cancellation of the UL data transmission using the second DCI is detected, at a timing for the data transmission canceled, the second timer is restarted in a case that the first timer expires and the second timer is running, and the second timer is started in a case that the second timer is not running.