RRC State Transition Using CFRA for Low-Latency 5G Access
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current 3GPP specifications for 5G NR do not allow the use of Contention Free Random Access (CFRA) during RRC_INACTIVE to RRC_CONNECTED state transitions, leading to delays and latency issues, particularly for high-priority UEs such as those providing emergency services or Ultra Reliable Low Latency Communications (URLLC).
Innovation Solution
Enabling UEs to use CFRA by providing configuration information for dedicated preambles during state transitions, allowing UEs to access the network without competing for resources, thereby reducing latency and improving transition speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Contention Based Random Access (CBRA) is used during RRC_INACTIVE to RRC_CONNECTED state transitions, then all UEs can access the network, but latency increases and transition speed decreases
Solution Approach 1:
The patent segments the random access procedure into two types: CBRA for general access and CFRA for priority UEs. By dividing the access mechanism based on UE priority levels, the system allows high-priority UEs (emergency services, URLLC) to use CFRA with dedicated preambles for immediate access, while other UEs continue using CBRA. This segmentation resolves the contradiction by providing different access paths for different UE categories.
Solution Approach 2:
The patent applies preliminary action by pre-configuring dedicated CFRA preambles for high-priority UEs before they need to transition states. The network provides CFRA configuration information to eligible UEs in advance, so when these UEs need to transition from RRC_INACTIVE to RRC_CONNECTED, they can immediately use their pre-assigned preambles without waiting for contention-based allocation, thereby reducing latency.
2Loss of time
If CFRA is enabled for all UEs, then latency is reduced, but network signalling load increases
Solution Approach 1:
The patent applies local quality by providing CFRA capability selectively to specific UEs based on their priority level and service requirements, rather than enabling it universally. The network determines which UEs receive CFRA configuration information (e.g., emergency services, URLLC) and provides them with dedicated preambles, while other UEs continue with standard CBRA procedures. This localized application of CFRA reduces overall signalling load while still achieving latency reduction for critical UEs.
3Speed
If CFRA configuration information is provided during state transition, then transition speed improves, but device complexity increases
Solution Approach 1:
The patent applies partial action by providing CFRA configuration information only when and where it is needed, rather than always. The network includes CFRA configuration in RRCRelease messages only for UEs that require priority access, and the UE is designed to process this configuration only when received. This approach enables fast transition for eligible UEs without requiring all UEs to have complex CFRA processing capabilities, thus balancing speed improvement with manageable device complexity.
Data Source
AI summary
Examples of the present disclosure relates to a user equipment (UE), centralized unit (gNB-CU) of an access node (gNB), a distributed unit (gNB-DU), and an access node for managing the UE's state transition. In an example of the present disclosure there is provided a UE comprising means receiving, from an access node, at least one first message for transitioning the UE from an RRC connected state to an RRC inactive state, wherein the at least one message comprises configuration information that enables the UE to use Contention Free Random Access (CFRA). The UE further comprises means for sending, using CFRA based at least in part on the configuration information, at least one second message for transitioning the UE from a Radio Resource Control (RRC) inactive state to an RRC connected state.