Configured Grant Small Data Transmission With Timer-Based Retransmission
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently utilizing limited radio resources for uplink/downlink data and control information transmission, particularly in overcoming latency and delay, which is critical for applications like self-driving vehicles and remote healthcare.
Innovation Solution
A method and apparatus for performing configured grant based small data transmission (CG-SDT) by a user equipment (UE) in a wireless communication system, involving initial and retransmission processes with timers, and triggering a failure handling procedure when physical downlink control channel (PDCCH) is not received, including transitioning to a RRC IDLE state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If configured grant based small data transmission is performed in RRC INACTIVE state, then latency is reduced and resource utilization is improved, but reliability of data transmission deteriorates due to limited retransmission opportunities
Solution Approach 1:
The patent implements dynamic state transition mechanisms where the UE can transition between RRC INACTIVE and RRC CONNECTED states based on transmission success or failure. This dynamic adaptation allows the system to maintain low latency for successful transmissions while ensuring reliability through state changes that enable retransmission opportunities when failures occur.
Solution Approach 2:
The patent employs feedback mechanisms through PDCCH monitoring for HARQ acknowledgments. When the UE does not receive expected PDCCH within the configured timer period, it triggers a failure handling procedure that provides feedback about transmission status, enabling the network to respond appropriately and maintain both latency efficiency and transmission reliability.
2Reliability
If retransmission is performed upon PDCCH non-reception, then reliability of data transmission is improved, but loss of time increases due to additional transmission cycles
Solution Approach 1:
The patent configures predetermined parameters including cg-SDT-RetransmissionTimer and cg-SDT-FailureHandlingProcedure before transmission begins. These preliminary configurations establish clear thresholds and procedures for when retransmission should occur, preventing unnecessary retransmissions that would waste time while ensuring retransmission when truly needed for reliability.
Solution Approach 2:
The patent dynamically adjusts transmission parameters based on channel conditions and transmission history. By modifying parameters such as the retransmission timer duration and failure handling procedures based on observed channel quality, the system optimizes the balance between achieving reliable delivery and minimizing time loss from retransmission cycles.
3Reliability
If PDCCH monitoring is continuously performed, then reliability of acknowledging transmissions is improved, but use of energy increases due to continuous reception activity
Solution Approach 1:
The patent implements periodic PDCCH monitoring instead of continuous monitoring by configuring specific monitoring occasions and timer-based wake-up schedules. The UE monitors PDCCH at predetermined intervals defined by the cg-SDT-RetransmissionTimer and transitions to sleep mode between monitoring occasions, significantly reducing energy consumption while maintaining sufficient reliability for transmission acknowledgments.
Solution Approach 2:
The UE autonomously manages its own monitoring schedule based on locally stored configuration parameters and timer states. By self-determining when to wake up and monitor PDCCH based on its own transmission history and configured parameters, the UE eliminates the need for continuous network-scheduled monitoring, reducing overall system energy consumption while maintaining acknowledgment reliability.
Data Source
AI summary
A method for performing a configured grant based small data transmission (CG-SDT) in a Radio Resource Control (RRC) INACTIVE state by a user equipment (UE) in a wireless communication system is disclosed. The method comprises steps of performing an initial transmission for the CG-SDT on a configured grant (CG), wherein a configured grant timer (CGT) and a CG-SDT-retransmission timer (CG-SDT-RT) are started by performing the initial transmission; and based on a physical downlink control channel (PDCCH) related to the initial transmission not being received until the CG-SDT-RT expiring during the CGT is running, performing a retransmission of the initial transmission, wherein the CG-SDT-RT is re-started upon performing the retransmission of the initial transmission, wherein, based on the PDCCH related to the initial transmission not being received until the CGT expiring, a SDT failure handling procedure is triggered.