PRACH Transmission in Unlicensed Spectrum via CCA
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Solution Overview
Problem
Current 3GPP communication systems face challenges in efficiently performing Physical Random Access Channel (PRACH) transmissions over unlicensed channels, particularly in ensuring clear channel assessment and adapting to varying channel occupancy times.
Innovation Solution
The proposed solution involves a user equipment (UE) that configures symbols of an unlicensed channel's occupancy time for uplink communication based on received channel access configurations. The UE performs a clear channel assessment (CCA) before PRACH transmissions, ensuring the channel is clear, and adapts its scheduling to accommodate transmission gaps within the channel occupancy time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the UE performs PRACH transmission immediately at the indicated timing of channel resources, then the transmission speed is improved, but the reliability deteriorates due to potential channel collision or interference
Solution Approach 1:
The UE performs Clear Channel Assessment (CCA) before the PRACH transmission at the indicated timing. This preliminary action checks whether the channel is clear before transmitting, preventing channel collision and interference while maintaining efficient transmission scheduling.
2Reliability
If the UE performs CCA for a gap duration before PRACH transmission, then the reliability is improved by avoiding channel collision, but the transmission time is increased due to the additional assessment period
Solution Approach 1:
The gap duration for CCA is configured dynamically based on the channel occupancy time and PRACH timing indications. The network can adjust the gap duration adaptively to balance between reliable channel assessment and minimizing transmission delays, optimizing the trade-off between reliability and time loss.
3Adaptability or versatility
If the UE configures symbols of occupancy time for uplink communication, then the adaptability is improved for unlicensed channel access, but the device complexity increases due to additional configuration management
Solution Approach 1:
The configured symbols of occupancy time are used for multiple purposes: they define the uplink communication window, indicate PRACH transmission opportunities, and establish CCA assessment periods. This multi-functionality reduces the need for separate configuration mechanisms, thereby limiting the increase in device complexity while maintaining high adaptability.
4Productivity
If the network provides timing indication for channel resources, then the productivity is improved by enabling efficient PRACH transmission scheduling, but the loss of information increases due to potential timing misalignment with channel occupancy
Solution Approach 1:
The network provides timing indications for channel resources used for PRACH transmission, and the UE provides feedback through the random access procedure. This feedback mechanism allows the network to verify timing alignment and adjust future timing indications, ensuring accurate synchronization while maintaining efficient scheduling productivity.
Data Source
AI summary
The present disclosure relates to a user equipment (UE) and base station (BS) involved in an improved physical random access channel, PRACH, transmission. The UE configures, based on a received unlicensed channel access configuration, symbols of an occupancy time of the respective unlicensed channel for uplink communication; receives an indication of a timing of channel resources which are to be used for a PRACH transmission; determines whether or not the indicated timing of channel resources is included within the symbols configured for uplink communication; if successful, performs a clear channel assessment, CCA, for a gap duration before the start of the indicated timing of channel resources which are to be used for the PRACH transmission; and if successful, transmits a random access, RA, preamble within the symbols configured for uplink communication at the indicated timing of channel resources which are to be used for the PRACH transmission.