Handover Cause Value Encoding for Wireless Network Interoperability
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Solution Overview
Problem
In wireless communications networks, particularly in LTE systems, handover cause values encoded using X2 and S1 interfaces are not interoperable, leading to ambiguity when a target network node receives history information from previous handovers, as it cannot correctly interpret cause values associated with different interfaces used in prior handovers.
Innovation Solution
Implementing interface-independent encoding for handover cause values, where a first field uses interface-dependent encoding and a second field uses interface-independent encoding, allowing network nodes to exchange unambiguous cause values and map cause values between different interfaces, thereby enabling consistent reporting in a wireless device's history information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If interface-dependent encoding is used for handover cause values, then the encoding can be optimized for specific interface requirements, but the target network node cannot correctly interpret cause values from previous handovers using different interfaces
Solution Approach 1:
The handover cause value information is segmented into two separate fields: a first field containing the interface-dependent encoded cause value and a second field containing the interface-independent encoded cause value. This segmentation allows the system to maintain both interface-specific optimization and universal interpretability, resolving the contradiction by preserving both encoding types rather than replacing one with the other.
Solution Approach 2:
The interface-independent encoding acts as an intermediary layer that translates interface-dependent cause values into a universal format. This intermediary encoding ensures that target network nodes can correctly interpret cause values regardless of which interface (X2 or S1) was used for previous handovers, while still allowing optimization for specific interfaces when needed.
2Adaptability or versatility
If different enumerated HO Cause Values are associated with different handover causes on different interfaces, then each interface can use its own encoding scheme, but ambiguity arises when target nodes receive history information from previous handovers
Solution Approach 1:
The information is segmented into distinct fields where the first field preserves interface-dependent encoding for flexibility and optimization, while the second field provides interface-independent encoding for unambiguous interpretation. This segmentation prevents information loss by maintaining both the original interface-specific encoding and a standardized interpretation layer.
Solution Approach 2:
The encoding parameter changes from interface-dependent to interface-independent in the second field. This parameter transformation allows the same cause value to be consistently interpreted across different interfaces while preserving the ability to optimize for specific interfaces through the first field's interface-dependent encoding.
3Device complexity
If only a single cause value field is used, then the data structure is simple, but the target node cannot accurately interpret cause values from handovers using different interfaces
Solution Approach 1:
The single cause value field is segmented into two fields: one for interface-dependent encoding and one for interface-independent encoding. This segmentation increases structural complexity slightly but dramatically improves measurement precision by ensuring unambiguous cause value interpretation across different interfaces, allowing target nodes to accurately identify handover reasons regardless of the original interface used.
Data Source
AI summary
According to an embodiment there is provided a first network node (122) for use in a wireless network (100), the first network node (122) being adapted to forward information on movements of a wireless device to a second network node (124) over an interface (106; 108); wherein the information on movements is represented by a cause value in a first field that uses an interface-dependent encoding and a cause value in a second field that uses an interface-independent encoding. A corresponding second network node and methods of operating the network nodes are also provided.