Neighbor Cell System Information Provisioning for RLF Recovery
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Solution Overview
Problem
In LTE systems, radio link failures (RLFs) lead to significant service outages due to the time-consuming process of system information acquisition during RRC connection re-establishment, as existing methods rely on the UE to read and verify system information from neighbor cells, which can be inefficient, especially when the original system information is valid most of the time.
Innovation Solution
An eNB proactively provides system information of neighbor cells to the UE through broadcast or dedicated RRC signaling, using a new System Information Block (SIB) or extending existing RRC messages, including a systemInfoValueTag and BCCH modification period information, to reduce the need for UE to re-acquire system information during RLF situations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE reads and verifies system information from neighbor cells during RLF, then the system information acquisition is performed, but the time required for RRC connection re-establishment increases significantly
Solution Approach 1:
The serving eNB proactively provides system information of neighbor cells to the UE before RLF occurs, through broadcast or dedicated RRC signaling. This preliminary provision of system information allows the UE to have the information ready in advance, eliminating the need to read and verify it from neighbor cells after RLF, thus resolving the contradiction between verification reliability and re-establishment time
Solution Approach 2:
The serving eNB creates a copy of the neighbor cell's system information (which the neighbor cell broadcasts) and provides it to the UE. This copied information is then used by the UE during RLF recovery, avoiding the time-consuming process of reading and verifying the original system information from the neighbor cell, thereby reducing re-establishment time while maintaining accuracy
2Reliability
If the UE acquires system information from neighbor cells during RLF, then the system information is obtained, but the service outage time increases
Solution Approach 1:
The system information is provided to the UE in advance by the serving eNB before RLF occurs. This preliminary action ensures that when RLF happens, the UE already possesses the necessary system information, eliminating the acquisition process during outage and thereby reducing service outage duration while ensuring information availability
Solution Approach 2:
The serving eNB obtains a copy of the neighbor cell's system information and provides it to the UE. This copied information is made available before RLF, so the UE does not need to perform time-consuming acquisition procedures during the outage period, thus reducing service outage time while maintaining information reliability
3Reliability
If the UE performs system information verification during RLF, then the information validity is confirmed, but the RRC connection re-establishment process becomes more complex
Solution Approach 1:
The serving eNB provides a copy of the neighbor cell's system information to the UE, along with associated validity indicators (systemInfoValueTag and BCCH modification period information). The UE simply compares these indicators with stored values to determine validity, avoiding complex verification procedures while ensuring information accuracy, thus reducing process complexity while maintaining reliability
4Loss of time
If the eNB provides system information proactively, then the RRC connection re-establishment time is reduced, but the signaling overhead increases
Solution Approach 1:
The serving eNB provides system information proactively, but only when necessary (e.g., when the UE is in a specific state or when the information is likely to be needed). This partial provision approach reduces signaling overhead compared to providing all possible information all the time, while still achieving the benefit of reduced re-establishment time in critical scenarios
Solution Approach 2:
The system information provision mechanism serves multiple functions: it provides system information for RLF recovery, includes validity indicators for verification, and can be delivered through both broadcast and dedicated signaling channels. This multi-functionality allows a single mechanism to handle various scenarios, reducing the need for separate signaling procedures and thereby controlling overhead while maintaining time efficiency
Data Source
AI summary
Embodiments of the present disclosure describe systems, devices and methods for system information acquisition in radio resource connection (RRC) connection reestablishment when Radio Link Failure (RLF) happens. Various embodiments may include a serving cell that provides system information of a neighbor cell to a user equipment (UE). When the UE detects an RLF event, the UE may determine whether the previously received system information is valid and proceed with RRC connection reestablishment based on the determination. Other embodiments may be described or claimed.