Target eNodeB Initiated S1 Handover for Reduced Latency
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Solution Overview
Problem
In wireless communication systems, the handover process from a source eNodeB to a target eNodeB can be delayed due to the need for a UE to gather additional information about the target cell, especially in scenarios where neighbor list data is incomplete, such as in deployments with many small-cell eNodeBs, leading to inefficiencies in handover operations.
Innovation Solution
The handover process is initiated by the target eNodeB upon receiving an RRC connection request from the UE, allowing it to establish a new RRC connection and signal the MME for handover without prior handover requests from the source or target eNodeB, effectively making the handover a 'pull' operation from the target eNodeB.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the handover process follows traditional source eNodeB-initiated procedures, then the handover can be triggered based on UE measurement reports, but the process is delayed when neighbor list data is incomplete or when additional target cell information is required
Solution Approach 1:
The patent inverts the traditional handover initiation role: instead of the source eNodeB initiating handover based on UE reports, the target eNodeB proactively initiates handover by sending a Handover Request to the MME when it detects a UE in its coverage area. This reversal eliminates delays associated with incomplete neighbor lists and information gathering, as the target cell takes the initiative to establish the handover process.
2Productivity
If the target eNodeB proactively initiates handover without prior requests, then handover latency is reduced, but the signaling load on the MME increases
Solution Approach 1:
The target eNodeB performs self-service by autonomously detecting UEs in its coverage area and initiating handover requests to the MME without waiting for source eNodeB instructions. This self-initiated approach accelerates handover execution while the MME manages the increased signaling load through its centralized coordination role, filtering and routing handover requests efficiently.
3Reliability
If the UE must gather additional target cell information before handover, then handover reliability can be improved, but the handover process time increases
Solution Approach 1:
The target eNodeB performs preliminary actions by pre-detecting UEs in its coverage area and pre-initiating handover requests before the UE completes traditional information gathering procedures. The MME coordinates the handover based on target eNodeB initialization, reducing the time UE spends gathering target cell information while maintaining reliability through MME-coordinated resource allocation and context transfer.
Data Source
AI summary
A mechanism for S1 handover triggered by a target eNodeB. When a UE is being served by a source eNodeB and detects threshold strong coverage of a target cell, the UE sends an RRC connection request to the target eNodeB and informs the target eNodeB that the UE is being served by the source eNodeB. In response, the target eNodeB engages in a process to invoke handover of the UE to the target eNodeB, without the target eNodeB having received from the MME or from the source eNodeB a handover request for the handover of the UE.