UE Coordination Set for Joint Transmission on Unlicensed Bands
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Solution Overview
Problem
Conventional wireless communication systems face inefficiencies in data transmission over unlicensed frequency bands due to delays caused by listen-before-talk procedures, particularly when coordinating multiple devices for joint-transmission or reception, which can lead to suboptimal performance in 5G NR systems.
Innovation Solution
A user-equipment-coordination set is established, where a coordinating UE receives and distributes uplink data among multiple UEs, synchronizes their clear channel assessments, and determines a specified time for joint-transmission over an unlicensed frequency band, ensuring efficient data processing by the base station.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If listen-before-talk procedures are performed prior to transmitting on an unlicensed frequency band, then channel access is ensured and interference is avoided, but transmission delays occur and coordination efficiency deteriorates
Solution Approach 1:
The base station performs clear channel assessment and determines transmission timing in advance before the actual data transmission. The base station sends timing indication information to user equipment beforehand, allowing the UE to prepare for simultaneous transmission without performing LBT at the moment of transmission, thus reducing delay while ensuring reliable channel access.
Solution Approach 2:
The base station acts as an intermediary that centralizes the clear channel assessment function. Instead of each UE performing independent LBT procedures which cause coordination delays, the base station performs CCA once and mediates the transmission timing for multiple UEs, enabling efficient joint transmission while maintaining channel access reliability.
2Reliability
If multiple UEs perform independent clear channel assessments, then each UE ensures channel availability, but transmission timing synchronization becomes difficult and coordination overhead increases
Solution Approach 1:
Multiple UEs are merged into a coordination set where they share a single clear channel assessment result from the base station. The UEs combine their transmission resources and transmit simultaneously based on unified timing indication information, eliminating the need for independent LBT procedures and reducing coordination complexity while maintaining channel availability.
Solution Approach 2:
The base station serves as a mediator that performs the clear channel assessment on behalf of multiple UEs in the coordination set. It sends unified timing indication information to all UEs, simplifying the coordination process and enabling synchronized transmission without each UE needing to independently assess the channel.
3Speed
If UEs transmit data independently without coordination, then transmission speed is faster, but signal quality degrades and base station processing efficiency decreases
Solution Approach 1:
The base station performs preliminary coordination by determining optimal transmission timing and sending timing indication information to UEs before transmission. This allows UEs to transmit simultaneously at coordinated moments, maintaining high transmission speed while ensuring signal quality through synchronized joint transmission that improves base station processing efficiency.
Data Source
AI summary
This document describes techniques and apparatuses for joint-transmission over an unlicensed frequency band using a user equipment (UE)-coordination set. In aspects, a first UE in a UE-coordination set acts as a coordinating UE. The coordinating UE receives, using a local wireless network connection, uplink data from a second UE in the UE-coordination set. The coordinating UE distributes, using the local wireless network connection, the uplink data to at least a third UE in the UE-coordination set. The coordinating UE receives, from at least one UE in the UE-coordination set, respective results of a clear channel assessment of the unlicensed frequency band. The coordinating UE determines a specified time to begin joint-transmission of the uplink data based on the results and coordinates the joint-transmission by directing the at least one UE to initiate the joint-transmission of the uplink data based on the specified time.