LTE Reconnection via CGI-Based Context Acquisition
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Solution Overview
Problem
In LTE systems, reconnection procedures fail when the reconnection destination radio base station does not manage the context information of a mobile station, particularly due to PCI confusion in heterogeneous networks with multiple picocells using the same Physical Cell Identity.
Innovation Solution
A mobile communication method where a mobile station initiates a reconnection procedure by transmitting the CGI of the first cell to a second radio base station, and if the second station does not manage the context information, it acquires this information from the first radio base station designated based on the CGI, enabling successful reconnection even in environments with many cells using the same PCI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If many picocells use the same PCI in a macrocell area, then network capacity is increased, but the macrocell cannot uniquely designate a picocell leading to PCI confusion
Solution Approach 1:
The patent introduces CGI (Cell Global Identity) as an intermediary identifier to resolve the ambiguity caused by PCI reuse. When a mobile station needs to identify a specific picocell, it uses the CGI reported by the mobile station rather than relying solely on PCI, thereby enabling unique cell designation despite PCI confusion in heterogeneous networks
2Loss of energy
If reconnection destination radio base station does not manage UE context, then resource usage is optimized, but reconnection procedure fails
Solution Approach 1:
The patent implements preliminary action by having the source radio base station store and forward UE context information to the target radio base station before the mobile station actually needs to reconnect. The target base station proactively acquires and stores the UE context (including security parameters) in advance, so when reconnection is needed, the procedure can succeed without requiring the target to have pre-managed the context
Solution Approach 2:
The patent uses the X2 interface between radio base stations as an intermediary mechanism to transfer UE context information. When the target radio base station needs UE context, it requests and receives it from the source base station through this intermediary interface, enabling successful reconnection without the target needing to permanently store all possible UE contexts
3Device complexity
If security parameters are not transferred in HO preparation, then signaling overhead is reduced, but security cannot be established after reconnection
Solution Approach 1:
The patent applies preliminary action by transferring security parameters (KeNB*, NCC) from the source radio base station to the target radio base station during the handover preparation phase through the X2 interface. This advance transfer ensures that when the mobile station reconnects to the target base station, the security context is already in place and security can be immediately established without additional signaling overhead during the reconnection procedure
Data Source
AI summary
A reconnection procedure is successfully performed even when a connection destination radio base station does not manage “UE Context” for a mobile station UE. A mobile communication method according to the present invention includes a step B in which the mobile station UE transmits CGI of cell #1 to a radio base station eNB#2 in the reconnection procedure, and a step C in which the radio base station eNB#2 acquires “UE Context” for the mobile station UE from a radio base station eNB#1 managing cell #1 designated based on the CGI when not managing “UE Context” for the mobile station UE in the reconnection procedure.