Terminal Device HARQ RTT Timer Power Management
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Solution Overview
Problem
In wireless communication systems, particularly in 5G NR and LTE, terminal devices face challenges in power management due to the need to continuously monitor the physical downlink control channel (PDCCH) for HARQ processes, which consumes power and resources.
Innovation Solution
A method where a terminal device starts the uplink HARQ RTT timer after detecting an uplink grant on the PDCCH during a discontinuous reception (DRX) period, allowing it to stop monitoring the PDCCH while the timer is active, and optionally uses repetition termination messages to determine the optimal timing for starting the timer, thereby reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal device continuously monitors the PDCCH for HARQ processes, then the reliability of data transmission is improved, but the power consumption increases
Solution Approach 1:
The terminal device employs discontinuous reception (DRX) cycles with periodic PDCCH monitoring instead of continuous monitoring. The device monitors PDCCH at specific intervals defined by DRX parameters, allowing it to enter low-power states between monitoring periods while maintaining reliable HARQ operation through timer-based mechanisms.
Solution Approach 2:
The terminal device starts the uplink HARQ RTT timer in advance after detecting an uplink grant on PDCCH during a DRX period. This preliminary action allows the device to proactively stop monitoring PDCCH for the asynchronous HARQ process before the round trip time expires, ensuring reliability is maintained while reducing power consumption during the timer duration.
2Use of energy by moving object
If the terminal device stops monitoring PDCCH during HARQ RTT timer, then the power consumption is reduced, but the response time to new scheduling opportunities increases
Solution Approach 1:
The terminal device dynamically adjusts its PDCCH monitoring behavior based on the state of the uplink HARQ RTT timer. The device stops monitoring PDCCH only for asynchronous HARQ processes when the timer is running, while maintaining monitoring capability for other processes. This dynamic adaptation allows the device to optimize power consumption without permanently losing response capability, as monitoring resumes when the timer expires or is stopped.
3Use of energy by moving object
If the terminal device uses repetition termination messages to determine timer start timing, then the power saving is optimized, but the device complexity increases
Solution Approach 1:
The terminal device utilizes feedback messages (repetition termination messages, ACK/NACK frames) from the network to determine the optimal timing for starting the uplink HARQ RTT timer. This feedback mechanism allows the device to accurately synchronize with network expectations while optimizing power saving, as the timer start is triggered by actual network responses rather than fixed timing rules.
Data Source
AI summary
A wireless communication method and a terminal device are provided. The terminal device can flexibly start a hybrid automatic repeat request (HARQ) round trip time (RTT) timer, thereby saving power. The method includes monitoring, by a terminal device, a physical downlink control channel (PDCCH) in a discontinuous reception (DRX) period, where the uplink grant indicates an asynchronous HARQ process used for transmitting a physical uplink shared channel (PUSCH). The method further includes starting, by the terminal device, an uplink HARQ RTT timer for the asynchronous HARQ process at a first moment after detecting the PDCCH.