Base Station Coordination for UE-Initiated NR-U Low-Latency Uplink
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Solution Overview
Problem
The requirement for a user equipment (UE) to detect a downlink transmission prior to performing uplink transmissions in NR-U increases latency, particularly for latency-sensitive services like ultra-reliable low latency communications (URLLC), as only gNB-initiated listen before talk (LBT) is currently supported, leading to inefficiencies in channel access.
Innovation Solution
Configuring the UE with both a base station (gNB)-initiated fixed frame period (gNB-FFP) and a UE-initiated FFP (UE-FFP), allowing the UE to schedule and perform uplink transmissions during its own FFP when certain conditions are met, such as no detected downlink transmissions and high-priority data availability, thereby enabling UE-initiated channel access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a UE is required to detect a downlink transmission prior to performing uplink transmissions in NR-U, then channel access fairness with other incumbent technologies is maintained, but uplink latency increases
Solution Approach 1:
The patent inverts the traditional channel access procedure by allowing the UE to initiate uplink transmissions without first detecting a downlink transmission from the gNB. This reversal enables the UE to perform LBT and transmit uplink data autonomously, thereby reducing uplink latency while maintaining fairness through regulated LBT procedures and gNB coordination.
2Device complexity
If only gNB-initiated listen before talk (LBT) is supported, then downlink channel access control is simplified, but uplink transmission opportunities are reduced for latency-sensitive services
Solution Approach 1:
The patent enables the UE to perform self-service channel access by implementing its own LBT procedure and autonomously initiating uplink transmissions during UE-initiated FFPs. The UE independently senses the channel, determines availability, and transmits uplink data without waiting for gNB downlink signals, thereby increasing transmission opportunities for latency-sensitive services while the gNB maintains overall coordination.
3Stability of the object's composition
If the UE waits for downlink signal detection before uplink transmission, then channel coordination between gNB and UE is maintained, but transmission timing is delayed
Solution Approach 1:
The patent implements preliminary action by allowing the UE to perform LBT and prepare for uplink transmission in advance during UE-initiated FFPs, independent of gNB downlink signals. The gNB configures the UE with FFP parameters and uplink resources beforehand, enabling the UE to autonomously access the channel and transmit data without waiting for real-time downlink coordination, thus reducing transmission timing delays.
Data Source
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AI summary
A base station (BS) configures a user equipment (UE) with parameters for channel access operations on a shared channel. The BS transmits to the UE a first configuration for a BS-initiated fixed frame period (FFP) (BS-FFP) and a second configuration for a UE-initiated FFP (UE-FFP), wherein the BS-FFP overlaps the UE-FFP, schedules an uplink (UL) transmission during the UE-FFP and when there is no downlink (DL) transmission in the BS-FFP, receiving the UL transmission from the UE during the BS-FFP.