HARQ Terminal Device PDCCH Listening Timer Mechanism
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Solution Overview
Problem
In LTE systems, terminal devices face high power consumption and increased retransmission delays due to continuous listening to the physical downlink control channel (PDCCH) during the random access process, and missing an uplink grant can lead to further delays.
Innovation Solution
Implementing a hybrid automatic repeat request (HARQ) method where the terminal device transmits uplink data based on an initial uplink grant, starts a first timer, and then listens to the PDCCH based on a second timer, allowing for power savings and reduced retransmission delays by controlling when to listen for subsequent grants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal device continuously listens to the PDCCH during the random access process, then the terminal device can detect uplink grants in time, but power consumption becomes very high
Solution Approach 1:
The terminal device listens to the PDCCH periodically based on timer configurations (harq-RTT-TimerUL and drx-ULRetransmissionTimer) rather than continuously. After transmitting uplink data, the terminal stops listening during the harq-RTT-TimerUL period, then resumes listening after the drx-ULRetransmissionTimer expires, creating a periodic listening pattern that reduces power consumption while maintaining grant detection capability
Solution Approach 2:
The base station sends uplink grants in advance through the PDCCH before the terminal device needs to retransmit uplink data. By listening periodically at predetermined intervals, the terminal device can detect these preliminary grants timely without requiring continuous monitoring, allowing the device to prepare for retransmission only when necessary
2Use of energy by moving object
If the terminal device does not listen to the PDCCH in time, then power consumption is reduced, but retransmission delay is increased
Solution Approach 1:
The terminal device dynamically adjusts its PDCCH listening behavior based on the expiration of configured timers. The listening pattern transitions from active (when timers are running) to inactive (when timers expire), creating a dynamic power management strategy that adapts to the random access process state while ensuring timely detection of uplink grants for retransmission
3Loss of time
If the terminal device listens to the PDCCH continuously, then retransmission delay is reduced, but power consumption increases
Solution Approach 1:
The terminal device uses its own transmitted uplink data as a trigger to control its subsequent listening behavior. After transmitting uplink data, the terminal automatically stops listening to the PDCCH during the harq-RTT-TimerUL period, then resumes listening after the drx-ULRetransmissionTimer expires. This self-service mechanism allows the terminal to manage its own power consumption while ensuring it listens at the right moments to detect retransmission grants
Data Source
AI summary
Embodiments of the present invention provide a hybrid automatic repeat request method and a terminal device. The method includes: obtaining a first uplink grant (UL grant) sent by a base station, where the first uplink grant is carried in a media access control MAC message; transmitting uplink data based on the first uplink grant, and starting a first timer; starting a second timer after the first timer expires; and listening to a physical downlink control channel PDCCH based on the second timer. According to the hybrid automatic repeat request method and the terminal device in the embodiments of the present invention, electricity can be saved, and a retransmission delay can be reduced.