Mobile Handover via Direct X2 Interface for Latency Reduction
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Solution Overview
Problem
Current handover processes between access nodes associated with different mobile management entities (MMEs) in mobile communications networks are inefficient, leading to increased latency and load on the core network, especially during national roaming agreements, as there is no direct signaling interface between MMEs, resulting in longer handover times and potential session interruptions.
Innovation Solution
The implementation of a handover process where access nodes can initiate a path switch request with a flag to determine if the target node is capable of direct data transfer, allowing for either direct X2-based handover or fallback to S1-based handover through the core network, enabling efficient handover management even between nodes from different MMEs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If handover messages are passed via access control systems (MMEs) for nodes associated with different MMEs, then handover can be accomplished between different operators, but handover latency and core network load increase
Solution Approach 1:
The patent introduces a direct X2 interface between source and target access nodes as an intermediary communication path, bypassing the core network MMEs for handover signaling. This allows handover messages to be exchanged directly between nodes while maintaining the ability to handle inter-operator scenarios, thus reducing latency without sacrificing adaptability.
Solution Approach 2:
The patent segments the handover process into two distinct paths: a direct X2-based path for fast handover between compatible nodes, and an S1-based path through MMEs for inter-operator handovers. This segmentation allows the system to choose the optimal path based on the specific scenario, minimizing latency when possible while maintaining versatility.
2Adaptability or versatility
If handover messages are passed via access control systems (MMEs), then handover can be accomplished between different operators, but load on the core network increases
Solution Approach 1:
The direct X2 interface acts as a local intermediary that handles handover signaling between access nodes without involving core network MMEs. This reduces the quantity of signaling messages traversing the core network while preserving the ability to handle inter-operator handovers through the S1 path when necessary.
Solution Approach 2:
The patent extracts the handover signaling function from the core network MMEs and places it directly at the access nodes via the X2 interface. This extraction removes unnecessary core network involvement from the handover process, reducing core network load while maintaining inter-operator capability through the S1 fallback path.
3Speed
If X2-based handover is used between nodes managed by the same MME, then handover speed increases, but compatibility with nodes from different MMEs decreases
Solution Approach 1:
The patent makes the handover path dynamic by allowing access nodes to select between X2-based and S1-based handover mechanisms based on the specific scenario. Nodes can dynamically choose the direct X2 path for fast handover when both nodes are managed by the same MME, and automatically fall back to the S1 path through MMEs when dealing with nodes from different MMEs, thus maintaining both speed and compatibility.
Solution Approach 2:
The access nodes are designed with multi-functionality to support both X2-based and S1-based handover mechanisms. This universality allows the same node to efficiently handle intra-MME handovers using the fast X2 path while also being capable of inter-MME handovers through the S1 path, thus achieving both high speed and broad compatibility.
4Loss of time
If direct signaling interface between MMEs is established, then handover latency reduces, but system complexity increases
Solution Approach 1:
Instead of establishing complex direct signaling interfaces between MMEs, the patent uses the existing X2 interface between access nodes as an intermediary. This approach achieves fast handover by keeping signaling local to the access network, avoiding the need for complex inter-MME signaling while still reducing latency compared to S1-based handover.
Data Source
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AI summary
A handover process for enabling a user terminal (10) to transfer a connect to a network (6) from a route by way of a source access node (1) to a route by way of a target access node (11), where the nodes (1, 11) are controlled by different respective control systems (2, 12) is initiated by establishing a link (28) between the terminal (10) and the target node (11) and a data forwarding tunnel (43) between the access nodes (1, 11) to allow data transmitted over a link 25 from the network (6) to the source node (1) to continue to be transmitted to the terminal. The backhaul connection (25) is then re-routed by co-ordination between the access control systems (2, 12). The source node (1) transmits a flag (90) to the target node (11) which identifies its respective access control system (2). This flag is forwarded by the target node (11) to its respective access control system (12) to allow it to set up a data link (5) over which relocation instructions (45, 38) can be co-ordinated to set up a data link (27) between the network (6) and the target node (11), and to close the data link (25) between the network (6) and the source node (1).