UE Channel Access Procedure for Unlicensed Spectrum Coexistence
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Solution Overview
Problem
In the New Radio (NR) system, there is a lack of methods to determine the appropriate Listen Before Talk (LBT) type for User Equipment (UE) during initial access procedures in unlicensed spectrum, particularly for Physical Random Access Channel (PRACH) and Physical Uplink Shared Channel (PUSCH) transmissions, which can lead to unfair coexistence with other communication systems in the same band.
Innovation Solution
The proposed solution involves a method for a UE to determine channel access procedures for PRACH and PUSCH transmissions based on the relationship between RACH occasion resources and PUSCH occasion resources, including the use of Type 1, Type 2, Type 2A, Type 2B, and Type 2C channel access procedures, depending on the timing gaps and channel occupancy times, to ensure fair coexistence with other systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UE performs channel access procedure to initiate COT for PRACH transmission, then UE can access channel independently, but channel access probability decreases and access time increases
Solution Approach 1:
The base station performs preliminary channel sensing and initiates COT before UE needs to access the channel. The COT is pre-established with a duration that covers the expected PRACH transmission window, so when UE needs to transmit, the channel is already reserved and ready, eliminating the need for UE to perform its own lengthy channel access procedure.
Solution Approach 2:
The base station acts as an intermediary that performs channel access on behalf of the UE. Instead of UE directly competing for channel access, the base station secures the channel through LBT and shares the COT with UE, allowing UE to transmit PRACH within the granted COT without performing independent channel sensing.
2Adaptability or versatility
If multiple UEs perform independent channel access procedures simultaneously, then each UE can access channel independently, but channel collision probability increases and coexistence fairness deteriorates
Solution Approach 1:
Multiple UEs merge their channel access requirements into a single base station-initiated COT. Instead of each UE performing separate LBT procedures that could collide, the base station performs one LBT and creates a shared COT that multiple UEs can utilize for their PRACH transmissions, coordinating their access through the common COT framework.
3Ease of operation
If UE uses LBT mode with lower priority to access channel independently, then UE maintains access autonomy, but channel acquisition probability decreases
Solution Approach 1:
The system dynamically adjusts the LBT priority mode based on whether COT sharing is configured. When COT sharing is enabled, UE switches to utilizing the higher-priority base station-initiated COT. When COT sharing is not configured, UE falls back to independent lower-priority LBT access. This dynamic adaptation allows UE to optimize between autonomy and acquisition probability based on network configuration.
Data Source
AI summary
Embodiments of the present disclosure provide an access control method and device. The method comprises: obtaining a RO resource for PRACH transmission and a PO resource for Msg A PUSCH transmission on the channel (Step S1001); determining a first channel access procedure for PRACH transmission and a second channel access procedure for Msg A PUSCH transmission (Step S1002), wherein the first channel access procedure comprises: a channel access procedure to initiate a first COT; or, a channel access procedure to share a second COT initiated by a network device, if the RO resource is within the second COT.