HARQ NDI Toggling During C-DRX Measurement Gaps
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Solution Overview
Problem
In wireless communication networks, the challenge of handling HARQ transmissions during C-DRX mode is exacerbated by measurement gaps, which can cause the C-DRX inactivity timer to expire, leading to undesirable power consumption and latency issues.
Innovation Solution
The proposed method involves toggling the NDI to restart the C-DRX inactivity timer during HARQ retransmissions, ensuring that the UE remains active during measurement gaps, thereby reducing latency and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the C-DRX inactivity timer is used to manage UE power consumption, then power efficiency is improved, but latency increases when measurement gaps cause timer expiration
Solution Approach 1:
The base station performs preliminary actions by transmitting HARQ retransmissions before the C-DRX inactivity timer expires, even during measurement gaps. By proactively sending retransmissions and using techniques like early data transmission and buffer management, the system prevents timer expiration and avoids the high-latency inactive state, thus balancing power efficiency with low latency
Solution Approach 2:
The system dynamically adjusts the C-DRX inactivity timer behavior based on ongoing HARQ processes and measurement gap configurations. The timer is restarted or extended when HARQ retransmissions are detected, creating a dynamic adaptation mechanism that responds to real-time communication conditions, thereby preventing unnecessary UE inactivity while managing power consumption
2Reliability
If HARQ retransmissions are performed during measurement gaps, then data reliability is improved, but the C-DRX inactivity timer expires causing increased power consumption
Solution Approach 1:
The system uses feedback mechanisms where the base station monitors HARQ acknowledgments and measurement gap status to determine whether to restart the C-DRX inactivity timer. This feedback-driven approach ensures that the UE remains active only when necessary for reliable data transmission, avoiding unnecessary power consumption while maintaining data reliability through targeted timer restarts
Solution Approach 2:
The system changes the state of the C-DRX inactivity timer parameter based on HARQ retransmission detection. When a HARQ retransmission is identified during a measurement gap, the timer is restarted or extended, changing the UE's operational state from inactive to active, thereby ensuring reliable delivery without premature power-saving transitions
3Use of energy by moving object
If the UE enters C-DRX inactive state to save power, then power consumption is reduced, but data transmission latency increases
Solution Approach 1:
The base station performs preliminary actions by detecting HARQ retransmissions before the C-DRX inactivity timer expires and proactively restarting the timer or scheduling retransmissions during active periods. This prevents the UE from entering the inactive state when data transmission is still ongoing, thereby avoiding the high latency associated with state transitions while maintaining power-efficient operation during genuine idle periods
Data Source
AI summary
A method for handling DL and UL HARQ transmissions for a UE. The method includes performing a first HARQ transmission including information related to a single HARQ process to the UE with an associated new data indicator, NDI. Toggling of the NDI indicates at least a change of information of the single HARQ process over a previous HARQ transmission and the first HARQ transmission moreover starting a C-DRX inactivity timer, and determining that a HARQ NACK has been received for the transmitted information from the UE. The method includes detecting a measurement gap has started and awaiting an end of the measurement gap. If the C-DRX inactivity timer has not expired at a time where the measurement gap has ended, then performing a second HARQ transmission of the information, with associated NDI to the UE for the single HARQ process. The value of the NDI is toggled in relation to a value of the NDI of the first HARQ transmission.