Priority-Aware RAR Differentiation in NR Random Access
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Solution Overview
Problem
Current NR Rel-15 and Rel-16 random access procedures lack the ability to differentiate between different types of UEs, such as mission critical UEs, until the third step of the 4-step RACH procedure, and the reliability of msgA PUSCH in the 2-step RACH can vary, making it difficult to prioritize RAR transmissions for high-priority UEs.
Innovation Solution
Configuring different PRACH configurations for UEs with varying priorities and using offset calculations or priority indications in DCI to generate unique RA-RNTI or MSGB-RNTI values, allowing early UE differentiation and prioritization of RAR transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If different PRACH configurations are used for different UE types, then early UE differentiation is enabled, but RA-RNTI ambiguity occurs when preambles from different priority levels map to the same RA-RNTI value
Solution Approach 1:
The patent applies preliminary action by pre-configuring distinct PRACH resources (time/frequency slots, preamble groups) for different UE priority levels before the random access procedure begins. This allows the network to identify UE type early in Step 1 based on which PRACH resources the UE selects, enabling differentiated handling of RAR transmissions before any ambiguity can occur.
Solution Approach 2:
The patent segments the PRACH resources into separate configurations for different UE priority levels (e.g., normal priority vs. high priority UEs). By dividing the random access resources and assigning them to different UE categories, the system enables early differentiation while avoiding RA-RNTI conflicts, as each segment operates with its own dedicated resources and identification scheme.
2Adaptability or versatility
If msgA PUSCH is used for UE identification in 2-step RACH, then higher layer data can be transmitted, but reliability varies due to potential collisions
Solution Approach 1:
The patent applies preliminary action by performing UE identification in Step 1 of the 2-step RACH procedure using the preamble transmission on PRACH, before the msgA PUSCH transmission occurs. This early identification based on PRACH resource selection provides reliable UE categorization independent of potential PUSCH collisions, while still allowing higher layer data to be transmitted in Step 2.
Solution Approach 2:
The patent segments the UE identification function across two stages: first using PRACH preamble resources for reliable priority-level identification, and then using msgA PUSCH for higher layer data transmission. This segmentation allows each function to operate in its most suitable domain without the reliability issues that would arise from attempting both functions simultaneously on the same channel.
Data Source
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AI summary
A method (1900) performed by a first UE for establishing a connection with an access point. The method includes the first UE transmitting (s1904) a random access, RA, preamble to an access point. The method also includes the first UE receiving (s1906) a message transmitted by the access point. The method also includes the first UE determining (s1908) a priority value included in or associated with the message. The method also includes the first UE determining (s1910), based on the priority value, whether or not the message is intended for a UE other than the first UE. The message is a downlink control message that was received within RAR window