RRC-Inactive EDT Carrier Selection Using NUL and SUL PRACH
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently managing carrier selection and early data transmission (EDT) in RRC_INACTIVE state, particularly for devices like BL UEs and NB-IoT UEs, due to limited PRACH resources and inconsistent uplink carrier availability, which can lead to suboptimal data transmission performance.
Innovation Solution
The solution involves UE devices initiating EDT by selecting either a normal uplink (NUL) or supplementary uplink (SUL) carrier based on the availability of PRACH resources for EDT, optimizing the Random Access (RA) procedure to enhance data transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the UE initiates EDT in RRC_INACTIVE state with limited PRACH resources, then early data transmission can be achieved, but the transmission reliability deteriorates due to insufficient random access resources
Solution Approach 1:
The patent segments the random access resources by introducing separate PRACH resources for EDT on NUL carrier and SUL carrier. This segmentation allows the UE to select appropriate resources based on coverage conditions, thereby improving EDT transmission reliability without increasing overall resource consumption excessively.
Solution Approach 2:
The patent introduces a new dimension for resource selection by adding SUL carrier as an additional uplink option alongside NUL carrier. This dimensional expansion provides the UE with more resource choices, enabling reliable EDT transmission in challenging coverage conditions where traditional NUL resources may be insufficient.
2Productivity
If the UE selects carrier based on PRACH resource availability, then data transmission efficiency improves, but the device complexity increases due to additional carrier selection logic
Solution Approach 1:
The patent applies preliminary action by pre-configuring PRACH resources for both NUL and SUL carriers before the UE needs to perform EDT. The network provides resource availability information in advance, allowing the UE to make carrier selection decisions based on pre-known resource status rather than complex real-time analysis, thus improving efficiency while limiting complexity increase.
3Reliability
If separate PRACH resources are configured for EDT on both NUL and SUL carriers, then transmission reliability improves, but the loss of substance increases due to additional resource allocation
Solution Approach 1:
The patent applies dynamics by making the PRACH resource allocation adaptive rather than static. The network dynamically configures and indicates which carrier (NUL or SUL) has available PRACH resources for EDT based on current load conditions. This dynamic approach ensures high transmission reliability by directing traffic to available resources while optimizing overall resource utilization and avoiding waste.
Data Source
AI summary
A method and apparatus are disclosed. In an example from the perspective of a User Equipment (UE), the UE initiates a first Early Data Transmission (EDT) in RRC_INACTIVE state. Responsive to initiating the first EDT, the UE initiates a Random Access (RA) procedure in a cell configured with a normal uplink (NUL) carrier and a supplementary uplink (SUL) carrier. The UE selects the SUL carrier or the NUL carrier for performing the RA procedure based on at least one of whether there are one or more available Physical Random Access Channel (PRACH) resources for EDT on the SUL carrier or whether there are one or more available PRACH resources for EDT on the NUL carrier.