MFBI Handover Key Generation via Target Base Station Selection
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Solution Overview
Problem
In LTE networks with the Multiple Frequency Band Indicator (MFBI) function, handover source radio base stations face challenges in determining the correct Downlink E-UTRAN Absolute Radio Frequency Channel Number (DL EARFCN) for connection reestablishment when the handover target cell supports multiple bands, leading to potential security key mismatches during handovers.
Innovation Solution
The system selects the band with the highest priority for the mobile station, either an existing or new band, based on the mobile station's capabilities and broadcasts this information using System Information Block 1 (SIB 1), enabling the handover source radio base station to create and send a handover preparation signal with a radio base station key derived from the selected band's DL EARFCN to the handover target radio base station.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the handover source radio base station uses the MFBI function to notify multiple bands, then the mobile station can select from more frequency bands, but the handover source radio base station cannot determine which DL EARFCN to use for creating the security key
Solution Approach 1:
The patent applies preliminary action by having the handover target radio base station pre-determine the DL EARFCN to be used for security key generation and include this information in the handover preparation signal. This allows the handover source radio base station to create the correct security key without needing to independently determine which DL EARFCN to use among multiple bands.
Solution Approach 2:
The patent uses the handover target radio base station as an intermediary to resolve the DL EARFCN determination problem. The target base station receives band information from the mobile station, determines the appropriate DL EARFCN, and communicates this to the source base station through the handover preparation signal, thereby mediating the information flow between source and mobile station.
2Adaptability or versatility
If the handover source radio base station creates security key using DL EARFCN from multiple bands, then more band options are available, but security key mismatch occurs during handover
Solution Approach 1:
The patent implements feedback by having the handover target radio base station determine the DL EARFCN based on the mobile station's band capability information and feed this determination back to the handover source radio base station through the handover preparation signal. This feedback mechanism ensures the source base station uses the correct DL EARFCN for security key generation, preventing key mismatches.
Solution Approach 2:
The handover target radio base station performs preliminary determination of the DL EARFCN before the handover execution, incorporating this information into the handover preparation signal. This preliminary action ensures that when the handover source radio base station creates the security key, it uses the correct frequency parameter, thereby ensuring key matching reliability.
3Adaptability or versatility
If the system supports multiple overlapping bands, then frequency band flexibility increases, but the complexity of handover management increases
Solution Approach 1:
The patent extracts the DL EARFCN determination function from the handover source radio base station and assigns it to the handover target radio base station. By taking out this complex determination task from the source station, the system simplifies the handover management process while maintaining support for multiple overlapping bands.
Solution Approach 2:
The handover target radio base station acts as an intermediary that centralizes the DL EARFCN determination logic. It receives band capability information from the mobile station, determines the appropriate DL EARFCN, and communicates this to the source base station, thereby simplifying the overall handover management architecture despite supporting multiple bands.
Data Source
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AI summary
An objective of this invention is to appropriately perform a connection reestablishment procedure in a network adapted to an MFBI function. In a mobile communication system of the invention, a radio base station (eNB#A) is configured, when the radio base station (eNB#A) determines that a mobile station (UE) is adapted to the MFBI function, to select a band out of bands which are supported by a cell under a radio base station (eNB#B), the band having the highest priority to be selected by the mobile station (UE) in an "RRC_IDLE state", and to send the radio base station (eNB#B) "HO Preparation" including KeNB* created by using "DL EARFCN" of the selected band.