DRX and SPS Uplink Transmission Handling
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Solution Overview
Problem
In LTE systems, user equipment (UE) may miss control commands transmitted during the off duration of discontinuous reception (DRX) cycles, leading to inefficient uplink transmission handling due to asynchronous HARQ processes and lack of explicit UL grants for retransmissions.
Innovation Solution
A network and method that configures a discontinuous reception (DRX) operation and semi-persistent scheduling (SPS) UL grants for communication devices, initiating a HARQ process with a timer for successful transmissions and dynamically scheduling retransmissions when the timer expires, ensuring timely retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If semi-persistent scheduling (SPS) UL grants are configured for uplink transmissions, then uplink resource allocation efficiency is improved, but control commands may be missed during DRX off duration
Solution Approach 1:
The patent applies dynamics by making the HARQ RTT timer configurable and adaptable to DRX cycle configurations. The timer duration can be dynamically adjusted based on the DRX off duration, allowing the system to optimize between maintaining SPS for efficiency while ensuring the UE wakes up in time to receive retransmission grants, thus resolving the contradiction between uplink efficiency and control command reliability.
Solution Approach 2:
The patent implements preliminary action by configuring the HARQ RTT timer in advance based on expected DRX cycle parameters. This pre-configured timing ensures that the UE will wake up at the appropriate time to receive control commands before the DRX off duration begins, preventing missed commands while maintaining SPS operation.
2Use of energy by moving object
If DRX off duration is extended to save power, then energy consumption is reduced, but control commands are more likely to be missed
Solution Approach 1:
The patent applies preliminary action by pre-configuring the HARQ RTT timer duration to account for the DRX off duration. This ensures that the UE wakes up early enough to receive control commands before entering the extended DRX off duration, maintaining reliability while allowing longer sleep periods for energy savings.
Solution Approach 2:
The patent changes parameters by making the HARQ RTT timer duration configurable based on DRX cycle characteristics. This parameter adjustment allows the system to optimize the balance between extended DRX for power saving and timely command reception, resolving the contradiction between energy efficiency and control reliability.
3Device complexity
If asynchronous HARQ processes are used without explicit UL grants, then device complexity is reduced, but retransmission scheduling becomes inefficient
Solution Approach 1:
The patent applies self-service by enabling the UE to autonomously determine when to expect retransmission grants through the pre-configured HARQ RTT timer. The UE self-manages the timing without requiring complex network coordination, maintaining low device complexity while improving retransmission scheduling efficiency through predictable, timer-driven wake-up behavior.
Data Source
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AI summary
A communication device comprises a storage device for storing instructions of receiving a semi-persistent scheduling (SPS) uplink (UL) grant in a transmission time interval (TTI) from a base station (BS), wherein the SPS UL grant indicates a UL frequency resource periodically allocated to the communication device; storing the SPS UL grant as a configured UL grant; initializing the configured UL grant to start in an earliest TTI after the first TTI and applying the configured UL grant to a plurality of TTIs after the earliest TTI; transmitting at least one first repetition of a UL transmission by using a hybrid automatic repeat request (HARQ) process according to the configured UL grant; starting a UL HARQ round trip time (RTT) timer for the HARQ process in response to the UL transmission; and starting a drx-ULRetransmissionTimer for the HARQ process, when the UL HARQ RTT timer expires.