UE Reject Cause Indicator for PLMN Signaling Optimization
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Solution Overview
Problem
Current Non-Access Stratum (NAS) protocols lack flexibility in handling service re-requests from user equipment (UE) when switching between Public Land Mobile Networks (PLMNs), leading to unnecessary signaling and delayed service deployment due to inflexible UE behavior and lack of differentiation between equivalent and non-equivalent PLMNs.
Innovation Solution
Enhancing signaling between the network and UE to explicitly indicate whether re-requests for services or features are allowed, using scope indicators to differentiate between equivalent and non-equivalent PLMNs, and providing a list of equivalent PLMNs during registration processes to optimize service re-attempts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the UE is configured to send the same request only after registering with another PLMN not in the list of equivalent PLMNs, then unnecessary signaling is reduced when the service is not supported in equivalent PLMNs, but the UE may not be able to reattempt the request to an equivalent PLMN that would be able to support the feature or service
Solution Approach 1:
The patent introduces a reject cause indicator that provides differentiated information about whether the rejection applies to equivalent PLMNs or not. This allows the UE to adapt its re-request behavior locally based on the specific reject cause, rather than applying a uniform restriction across all PLMN scenarios. The network can specify whether the UE should avoid re-requests in equivalent PLMNs or can re-attempt, enabling fine-grained control over signaling behavior.
Solution Approach 2:
The patent makes the UE's re-request behavior dynamic by introducing conditional logic based on the reject cause indicator. Instead of a static rule that prevents all re-requests to equivalent PLMNs, the UE now dynamically adjusts its behavior based on the network's indication. When the indicator shows the service might be available in equivalent PLMNs, the UE can re-attempt; when it shows the service is not available, the UE avoids unnecessary re-requests.
2Adaptability or versatility
If the UE is configured to send the same request after registration with any other PLMN regardless of equivalence, then service re-attempts are enabled more frequently, but unnecessary additional signaling occurs when the feature or service is not supported in equivalent PLMNs
Solution Approach 1:
The reject cause indicator provides localized information about service availability in equivalent PLMNs, allowing the UE to make informed decisions about re-requests. Rather than universally allowing or blocking re-requests, the network can specify the local condition (whether equivalent PLMNs support the service), enabling the UE to optimize signaling based on actual service availability in each PLMN context.
Solution Approach 2:
The network provides feedback to the UE through the reject cause indicator, informing the UE about the likelihood of success if it re-requests the service in an equivalent PLMN. This feedback mechanism allows the UE to adjust its re-request behavior accordingly, avoiding unnecessary signaling when the service is not supported in equivalent PLMNs while enabling re-requests when the service is available.
3Device complexity
If a single UE behavior rule is specified for all network configurations, then implementation is simplified, but network operators must coordinate deployment across all equivalent PLMNs which delays service rollout
Solution Approach 1:
The network performs preliminary action by providing the reject cause indicator in advance, before the UE attempts re-requests. This allows the UE to be pre-informed about service availability in equivalent PLMNs, enabling it to make intelligent decisions about re-requests without complex coordination between network operators. The service can be deployed independently in each PLMN based on local capabilities.
Solution Approach 2:
The patent segments the reject cause information into different categories (whether the service is available in equivalent PLMNs or not). This segmentation allows the network to provide targeted guidance to the UE, enabling differentiated re-request behavior for different service scenarios. Each PLMN can independently manage its service deployment without requiring coordination with other equivalent PLMNs.
Data Source
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AI summary
Briefly, in accordance with one or more embodiments, a user equipment, UE, (110) and a network node of a first Public Land Mobile Network, PLMN, (112) are described. The UE (110) decodes a list of equivalent PLMNs (112, 114) encoded by the network node. The UE (110) sends a PDN CONNECTIVITY REQUEST to the first PLMN (112), which is received by the network node. The UE (110) receives a PDN CONNECTIVITY REJECT from the first PLMN (112), sent from the network node. The PDN CONNECTIVITY REJECT comprises information which indicates whether the UE (110) is allowed to re-attempt the PDN CONNECTIVITY REQUEST with an equivalent PLMN (112, 114) that is included in the list of equivalent PLMNs (112, 114).