Inter-site Carrier Aggregation Layer 2 Abnormality Handling
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Solution Overview
Problem
In LTE's Inter-site CA operation, detecting abnormalities in layer 2 of downlink or uplink signals leads to communication disruptions and throughput deterioration due to the inability to perform intra-cell handovers and reestablish connections between radio base stations and mobile stations when C-plane and U-plane signals are transmitted across different cells.
Innovation Solution
A mobile communication system where the mobile station and radio base stations are configured to detect layer 2 abnormalities and provide predetermined notifications to facilitate appropriate actions, such as resetting or deleting U-plane bearers, across different cells, enabling seamless communication even when C-plane signals are transmitted via one radio base station and U-plane signals via another.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Intra-cell HO is performed to reset layer 2 in downlink, then layer 2 abnormality is handled, but all Scells enter deactive state causing communication disruption
Solution Approach 1:
The patent segments the cell into Pcell and Scell with independent layer 2 reset capabilities. The Pcell can trigger layer 2 reset for specific Scells without affecting other Scells, allowing selective recovery while maintaining communication through active Scells.
Solution Approach 2:
The Pcell acts as an intermediary that coordinates layer 2 reset operations. When layer 2 abnormality occurs in a specific Scell, the Pcell receives notification and triggers targeted reset, mediating between the abnormal Scell and the network to maintain overall communication.
2Reliability
If reconnection procedure is performed to reset layer 2 in uplink, then layer 2 abnormality is handled, but all Scells are released causing throughput deterioration
Solution Approach 1:
The patent enables segmented layer 2 reset where only the affected Scell undergoes reconnection procedure while other Scells remain active. This segmentation prevents complete bearer release and maintains throughput through remaining active Scells.
Solution Approach 2:
The layer 2 reset operation is applied locally to only the Scell with abnormality rather than globally to all Scells. The Pcell identifies the specific Scell needing reset and applies the reconnection procedure selectively, preserving local communication quality in unaffected Scells.
3Adaptability or versatility
If C-plane signal is transmitted via SRB in macro cell and U-plane signal via DRB in small cell, then flexible network architecture is achieved, but layer 2 abnormality notification fails across different radio base stations
Solution Approach 1:
The Pcell serves as an intermediary that receives layer 2 abnormality notifications from Scells managed by different eNBs. The notification mechanism through Pcell bridges the information gap between distributed eNBs, ensuring abnormality information is not lost despite architectural distribution.
Solution Approach 2:
The patent establishes feedback loops where Scells notify Pcell of layer 2 abnormalities, and Pcell coordinates the appropriate reset actions. This feedback mechanism ensures abnormality information flows correctly across the distributed architecture, preventing information loss.
4Reliability
If all Scells are reset when layer 2 abnormality occurs in specific DRB, then reliable connection is restored, but unnecessary reestablishment occurs in normal DRBs
Solution Approach 1:
The patent segments the reset operation to affect only the specific Scell and DRB with abnormality rather than all Scells. This selective segmentation avoids unnecessary reestablishment in normal DRBs, saving time while maintaining reliability in affected areas.
Solution Approach 2:
The layer 2 reset is applied with local quality control, targeting only the specific Scell where abnormality was detected. Normal Scells maintain their active state without unnecessary reset, reducing overall reestablishment time while ensuring reliability in the affected local area.
Data Source
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AI summary
An appropriate action is taken when an abnormality in a layer 2 is detected, even in an "Inter-site CA" operation in which communication for a C-plane signal is performed in a cell #1 under a radio base station eNB#1 via a SRB, and communication for a U-plane signal is performed in a cell #11/#12 under a radio base station eNB#11/#12 via a DRB. In a mobile communication system according to the present invention, the radio base station eNB#11/#12 is configured to provide the radio base station eNB#1 with predetermined notification, when an abnormality is detected in a layer 2 of a downlink to a mobile station UE.