Auxiliary Handover Command for LTE Reliability
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Solution Overview
Problem
In wireless communication systems, particularly in LTE, handover processes in urban canyon scenarios face reliability issues due to interference and low signal-to-noise ratios, leading to service interruptions and increased control signaling, especially under high network loads or high UE mobility.
Innovation Solution
A method involving the storage of a context identifier between a mobile communication device and a source network controlling device, with the device listening for an original handover command on one channel and receiving an auxiliary handover command on another channel, which includes the context identifier for authentication and secure handover to a target network controlling device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If handover command is transmitted on a single channel in urban canyon scenarios, then the signaling process is simple, but the reliability of handover signaling deteriorates due to interference and low signal-to-noise ratios
Solution Approach 1:
The patent introduces an auxiliary handover command transmitted on a second channel (BCCH) as an intermediary backup mechanism. When the original handover command on the first channel (PDSCH) fails due to poor signal conditions in urban canyon scenarios, the auxiliary command serves as a mediator to deliver the handover information, thereby improving reliability without fundamentally changing the overall handover process complexity
Solution Approach 2:
The auxiliary handover command is prepared and transmitted in advance on the second channel before the actual handover execution. This preliminary action ensures that if the primary handover command fails, the UE already has the necessary handover information available, reducing service interruption time and improving handover reliability in challenging radio environments
2Reliability
If auxiliary handover command with context identifier is implemented, then security against replay attacks is improved, but the signaling overhead increases
Solution Approach 1:
The patent extracts only the essential context identifier from the full handover command and transmits it in the auxiliary handover command. This selective extraction provides sufficient authentication information to prevent replay attacks while minimizing the additional signaling overhead, as the UE can verify the auxiliary command's authenticity without transmitting the entire handover message
Solution Approach 2:
The patent changes the parameter of the auxiliary handover command to include only the context identifier rather than the complete handover command parameters. This parameter optimization maintains security functionality while significantly reducing the information loss and signaling overhead associated with transmitting redundant handover data
3Loss of time
If single channel handover command is used, then the control signaling is minimal, but service interruption time increases due to command transmission failures
Solution Approach 1:
The patent ensures continuity of useful action by maintaining the auxiliary handover command on the second channel as a persistent backup. This continuous availability of handover information prevents service interruption caused by failed primary command transmission, as the UE can immediately execute handover using the auxiliary command without waiting for retransmission
Solution Approach 2:
The patent implements a feedback mechanism where the UE monitors both channels and provides implicit feedback by attempting to execute the auxiliary handover command when the primary command fails. This feedback loop reduces service interruption time by enabling rapid fallback to the auxiliary command without requiring explicit error reporting and retransmission protocols
Data Source
Figure 1A~1B
Figure 2
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AI summary
An auxiliary handover message is sent from a target eNB to a UE being handed over from a source eNB. The auxiliary handover message includes a context identifier that is established between the source eNB and the UE, which the source eNB provides to the target eNB during context data exchange when preparing for the handover. The UE uses the context identifier to verify that the auxiliary handover message is valid. Various approaches are detailed for minimizing signaling overhead and minimizing the time the UE must monitor the separate channel for the auxiliary handover message in the event the UE does not properly receive the original handover message from the source eNB. The context identifier may be a random number, a C-RNTI, an eNB-ID, or a token. The auxiliary handover command sent from the target eNB may be the context identifier with or without a copy of the handover command.