Random Access Preamble Transmission in Unlicensed Bands
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Solution Overview
Problem
The random access procedure in unlicensed bands is excessively delayed due to the need for clear channel assessment (CCA) to confirm channel state, which prolongs the completion of the random access procedure in wireless communication systems.
Innovation Solution
A method where a wireless device receives configuration information and indication information from a base station to dynamically allocate transmission resources for the random access preamble, allowing the device to transmit without additional CCA operations or with reduced CCA duration, thereby preventing transmission delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If clear channel assessment (CCA) is performed to confirm channel state in unlicensed bands, then channel access reliability is improved, but random access procedure delay increases
Solution Approach 1:
The base station performs CCA assessment and channel status confirmation in advance before the wireless device needs to access the channel. The BS obtains channel occupation permission and determines transmission resources beforehand, so that when the device needs to transmit, the channel is already confirmed as available, eliminating the need for the device to perform separate CCA procedures and reducing access delay
Solution Approach 2:
The base station acts as an intermediary that performs the CCA assessment on behalf of the wireless device. Instead of each device independently performing CCA, the BS consolidates this function, uses its obtained channel access rights to grant transmission opportunities to multiple devices, thereby reducing overall system access delay while maintaining reliability
2Loss of time
If dynamic transmission resource allocation is implemented, then transmission delay is reduced, but device complexity increases
Solution Approach 1:
The base station pre-determines and configures multiple transmission resource candidates for the wireless device before actual transmission is needed. These candidates include different time slots, frequency resources, and preamble formats. When channel conditions permit, the device can immediately use the pre-configured resources without needing to perform complex real-time resource selection, reducing delay while keeping device complexity manageable
Solution Approach 2:
The system implements dynamic resource allocation where the base station can adjust and update transmission resource candidates based on changing channel conditions and traffic demands. The indication information dynamically points to different pre-configured resources, allowing the system to adapt to varying conditions without requiring the device to maintain complex real-time decision-making capabilities
Data Source
AI summary
A method for performing a random access procedure and a device using the method are provided. The device receives indication information from a base station. The indication information instructs one of a plurality of transmission resource candidates. The device transmits a random access preamble by using the instructed transmission resource candidate.