Uplink Scheduling via Base Station COT Acquisition
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Solution Overview
Problem
The 3GPP specification for 5G NR-U devices does not adequately address scenarios where a UE may not successfully complete the 'listen-before-talk' procedure due to energy detection on unlicensed carriers, especially in connected or idle states, leading to unauthorized uplink transmissions and interference with other networks.
Innovation Solution
A base station configures a UE to perform specific channel access procedures, such as Category 4 or Category 2 LBT, based on the availability of a transmission time period indicated by the base station, allowing the UE to selectively choose between procedures to ensure successful channel access and minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE performs LBT procedure before transmitting uplink data, then the UE can avoid interference with other networks, but the UE may not successfully complete LBT when energy is detected on the unlicensed carrier
Solution Approach 1:
The base station performs LBT procedure in advance to acquire channel access rights and establish a COT before the UE needs to transmit. This preliminary action ensures the channel is ready for the UE's upcoming transmission, eliminating the need for the UE to perform LBT again and ensuring transmission success without interference.
Solution Approach 2:
The base station acts as an intermediary that performs LBT procedure on behalf of the UE. By acquiring channel access rights first and then providing the UE with transmission opportunities within the established COT, the base station mediates between the UE's transmission needs and the channel access requirements, eliminating direct LBT conflicts for the UE.
2Ease of operation
If the base station provides COT indication to the UE, then the UE can be authorized to transmit within the COT, but the UE cannot transmit if it detects energy during LBT procedure
Solution Approach 1:
The base station performs LBT and acquires COT before providing transmission opportunities to the UE. This preliminary channel acquisition ensures that when the UE receives COT indication and is authorized to transmit, the channel is already clear and ready, eliminating the conflict where UE would detect energy during its own LBT procedure.
Solution Approach 2:
The base station serves as an intermediary that handles channel access procedures and provides transmission authorization to the UE. By managing LBT and COT establishment centrally, the base station ensures that UE transmissions are authorized only when the channel is actually available, resolving the contradiction between authorization validity and energy detection conflicts.
3Reliability
If the UE continues to perform LBT procedure after COT, then the UE can ensure channel access, but the UE is not authorized to transmit when COT has ended
Solution Approach 1:
The base station performs LBT and establishes COT in advance, then provides the UE with specific transmission opportunities within that pre-acquired time window. This eliminates the need for the UE to perform LBT after COT, as the channel access is already secured for the designated transmission occasions within the COT period.
Solution Approach 2:
The system dynamically adjusts the transmission timing based on the COT duration. The base station configures the UE with transmission occasions that fall within the dynamically established COT, allowing flexible transmission timing while ensuring channel access is already secured by the time of transmission.
4Adaptability or versatility
If the UE performs Category 4 LBT procedure, then the UE can ensure fair coexistence with other devices, but the UE cannot complete LBT when energy is detected on the carrier
Solution Approach 1:
The base station performs Category 4 LBT procedure in advance to acquire channel access rights and establish COT before the UE needs to transmit. This preliminary action ensures the channel is ready for the UE's upcoming transmission, eliminating the need for the UE to perform LBT again and ensuring transmission success without interference from energy detection.
Solution Approach 2:
The base station acts as an intermediary that performs the complex Category 4 LBT procedure on behalf of the UE. By acquiring channel access rights first and then providing the UE with transmission opportunities within the established COT, the base station mediates between the UE's transmission needs and the fair coexistence requirements, eliminating direct LBT conflicts for the UE.
Data Source
AI summary
A user device (UE) for scheduling an uplink transmission assignment with a base station that communicates with the user device via a shared carrier, receives, from the base station, a configuration that indicates (i) a first channel access procedure for the user device to perform prior to transmitting an uplink transmission and (ii) at least one occasion at which the user device is to transmit the uplink transmission (1602); receives, from the base station via the shared carrier, a signal indicating at least a portion of a transmission time period during which the shared carrier is available to the base station (1604); and performs the first channel access procedure or a second channel access procedure before transmitting the uplink transmission based at least in part on whether the occasion is within the transmission time period (1606).