Intra-cell Handover for Relay Node NCC Synchronization
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Solution Overview
Problem
Intra-cell handover processes in LTE-A networks with mobile Relay Nodes (RN) lead to out-of-synchronization of Next Hop Chaining Counters (NCCs) between the network and User Equipment (UE), causing communication failures due to unrecoverable mismatches in security keys and encryption errors.
Innovation Solution
Implementing an intra-cell handover method where the Relay Node (RN) judges the difference in NCCs and initiates a handover when the difference meets a preset trigger condition, and instructing the Mobility Management Entity (MME) not to allocate new Next Hop (NH) keys during path switching to maintain synchronization, thereby avoiding out-of-synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Relay Node is deployed on a transportation vehicle to extend network coverage and reduce handovers, then the number of handovers for UE via air interface is reduced, but out-of-synchronization of security keys occurs between network side and UE side
Solution Approach 1:
The patent applies preliminary action by having the source eNB pre-derive and transmit KeNB* to the target eNB before the actual handover occurs. This allows the target eNB to have the security key ready in advance, ensuring continuous security protection during and after handover without synchronization issues.
Solution Approach 2:
The patent implements feedback through the handover procedure where the source eNB provides the target eNB with the derived KeNB* and NCC information. This feedback mechanism ensures that the target eNB can properly synchronize its security keys with the UE, preventing out-of-synchronization issues.
2Reliability
If the source eNB derives KeNB* from currently used KeNB and transmits it to the target eNB, then handover continuity is maintained, but forward security is compromised
Solution Approach 1:
The patent applies partial action by using the currently used KeNB to derive KeNB* only for the immediate handover need, rather than continuously updating with new NH keys. This provides sufficient security for the handover while maintaining continuity, balancing forward security requirements with handover reliability.
3Object-affected harmful factors
If the MME allocates a new NH key pair during path switching, then forward security is improved, but NCC synchronization between network and UE is disrupted
Solution Approach 1:
The patent uses the NCC as an intermediary indicator to communicate key derivation status between the network and UE. By transmitting the NCC value along with KeNB*, the system enables the UE to determine which derivation method to use, maintaining synchronization without requiring the MME to allocate new NH keys during every path switch.
Data Source
AI summary
Disclosed in the present application are a method and a device for intra-cell handover, and a method and a device for path switching, used for avoiding network side and user equipment (UE) side next hop chaining counter (NCC) desychronization when a UE switches out of a relay node (RN), so as to avoid communication failure. The method for intra-cell handover provided in the present application comprises: an RN determining whether the value of the difference between the UE side NCC and the NCC most recently received by the RN and allocated for the UE by a mobility management entity (MME) serving the UE meets the preset triggering requirement for intra-cell handover; if the value of the difference meets the triggering requirement, then the RN initiates intra-cell handover.