Supplementary Uplink Carrier Selection for Random Access
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Solution Overview
Problem
In wireless communications, base stations configured with high-frequency uplink carriers often experience limited coverage, making it difficult for wireless devices to initiate a random access procedure due to high channel occupancy levels in unlicensed frequency bands.
Innovation Solution
A wireless device selects an uplink carrier for a random access procedure based on the channel occupancy levels of normal uplink (NUL) and supplementary uplink (SUL) carriers, either both in unlicensed frequency bands, or one in an unlicensed band and the other in a licensed band, to optimize access opportunities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an uplink carrier is configured in a high frequency band, then the data rate is improved, but the coverage is limited
Solution Approach 1:
The uplink carrier is segmented into two distinct carriers: a first uplink carrier in a first frequency band and a second uplink carrier in a second frequency band. This segmentation allows the system to utilize both carriers for different purposes - one for high data rate transmission and the other for extended coverage, thereby resolving the contradiction between data rate and coverage.
2Power
If a wireless device attempts to initiate a random access procedure via the cell with high-frequency uplink carrier, then the data rate is improved, but the access difficulty increases due to high channel occupancy levels
Solution Approach 1:
The second uplink carrier acts as an intermediary carrier with lower channel occupancy levels. When the first uplink carrier has high occupancy making random access difficult, the wireless device can use the second uplink carrier as an alternative pathway to initiate random access procedure, thereby reducing access difficulty while maintaining the ability to access high data rate services through the first carrier when conditions permit.
3Productivity
If the channel occupancy level of an uplink carrier is high, then the carrier utilization is improved, but the random access success rate deteriorates
Solution Approach 1:
The system changes the parameter of channel occupancy level by providing a second uplink carrier with different occupancy characteristics. When the first uplink carrier exhibits high occupancy levels that hinder random access, the system transitions to or utilizes the second uplink carrier with lower occupancy levels, thereby improving random access success rate while maintaining overall carrier utilization efficiency.
Data Source
AI summary
Wireless communications for selecting an uplink carrier for a random access procedure are described. A base station may configure a wireless device with one or more uplink carriers associated with a downlink carrier of a cell. The one or more uplink carriers may comprise at least a normal uplink (NUL) carrier and a supplemental uplink (SUL) carrier. The wireless device may measure one or more downlink reference signals and channel occupancy level(s) of an NUL and/or an SUL. The wireless device may select one of an NUL or an SUL for a random access procedure, for example, based on a signal strength of the one or more downlink reference signals and/or the channel occupancy level(s).