DRX Timer Management for HARQ Retransmission in 5G UEs
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Solution Overview
Problem
In wireless communication systems, particularly in 5G networks, managing discontinuous reception (DRX) related timers by user equipment (UE) is challenging due to the need for efficient resource utilization and low latency, especially in applications requiring high reliability and low latency like ultra-reliable and low-latency communications (URLLC) and massive machine-type communications (mMTC).
Innovation Solution
A method for processing downlink signals by a user equipment (UE) involves configuring not to transmit Hybrid Automatic Repeat and Request (HARQ) feedback for the DL HARQ process, starting a timer upon detecting a Physical Downlink Control Channel (PDCCH) for retransmission, and monitoring subsequent PDCCHs related to retransmissions while the timer runs, regardless of successful decoding, to optimize DRX retransmission timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE continuously monitors PDCCH for HARQ retransmission, then retransmission reliability is improved, but power consumption increases
Solution Approach 1:
The patent implements discontinuous reception (DRX) where the UE alternates between active monitoring periods and sleep periods. During active periods, the UE monitors PDCCH for HARQ retransmissions; during sleep periods, the UE stops monitoring to save power. This periodic action resolves the contradiction by providing reliability during active periods while reducing power consumption during sleep periods.
Solution Approach 2:
The patent dynamically adjusts the DRX cycle parameters including onDurationTimer, drx-HARQ-RTT-TimerDL, and drx-RetransmissionTimerDL based on traffic conditions and retransmission needs. The UE transitions between different operational states (monitoring vs. sleeping) based on real-time conditions, dynamically balancing reliability and power consumption.
2Loss of time
If the UE monitors PDCCH immediately after receiving DL data, then retransmission latency is reduced, but unnecessary monitoring increases power consumption
Solution Approach 1:
The patent pre-configures DRX parameters including the drx-HARQ-RTT-TimerDL that determines when the UE should wake up to monitor for retransmissions. This preliminary configuration allows the UE to sleep during guaranteed no-retransmission periods and only wake up when retransmissions are possible, reducing unnecessary monitoring while maintaining low latency.
Solution Approach 2:
The patent changes the monitoring behavior by introducing time-based parameters (DRX cycles, timers) that control when monitoring occurs. Instead of continuous monitoring, the UE uses parameter-driven periodic monitoring at specific intervals, reducing power consumption while maintaining responsiveness to retransmissions.
3Reliability
If the UE transmits HARQ feedback for every DL transmission, then communication reliability is improved, but uplink resource utilization increases
Solution Approach 1:
The patent extracts the HARQ feedback transmission from being mandatory for every DL transmission. Instead, HARQ feedback is selectively transmitted only when necessary (e.g., when the UE is in active DRX state and actually needs to acknowledge or request retransmission). This reduces uplink resource utilization while maintaining communication reliability through selective feedback.
Data Source
AI summary
A method for processing downlink (DL) signals by a user equipment (UE) in a wireless communication system is disclosed. Especially, the UE is configured not to transmit a Hybrid Automatic Repeat and request (HARQ) feedback for the DL HARQ process. The method comprises steps of upon a first Physical downlink Control Channel (PDCCH) for the DL HARQ process is detected, starting a timer for monitoring subsequent PDCCHs related to retransmission of the DL HARQ process, without transmitting the HARQ feedback; and monitoring subsequent PDCCHs related to retransmission of the DL HARQ process while the timer is running.