NR Network Slice Recovery via LTE Registration Feedback
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Solution Overview
Problem
User Equipment (UE) experiences difficulties in connecting to a network slice in a New Radio (NR) network even after the slice is removed from the rejected network slice list due to various reasons such as unavailability in the current Public Land Mobile Network (PLMN) or Standalone Non-Public Network (SNPN), leading to persistent connectivity issues.
Innovation Solution
The UE configures a transceiver to transmit registration requests to both a first and a second network within the PLMN, decodes messages to manage network slice lists, and utilizes Extended Protocol Configuration Options (ePCO) to enable connectivity by removing slices from rejected lists and enabling disabled modes, allowing access to previously rejected network slices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the UE removes the network slice from the rejected network slice list after receiving it on LTE network, then the network slice appears available, but the UE still cannot connect to the network slice on NR network
Solution Approach 1:
The UE performs preliminary registration on the LTE network to receive the network slice configuration before attempting to connect on the NR network. This preliminary action ensures the network slice is properly configured and available in the UE's allowed NSSAI list before the actual connection attempt, resolving the issue where removal from rejected list does not guarantee connectivity.
2Adaptability or versatility
If the UE registers on LTE network to receive rejected network slice, then the network slice can be accessed on LTE, but the UE cannot access the same network slice on NR network
Solution Approach 1:
The LTE network acts as an intermediary that provides network slice configuration information to the UE through the activate default EPS bearer context request message. This intermediary mechanism allows the UE to obtain network slice details from the LTE network and use them for subsequent NR network registration, enabling cross-network slice access.
3Reliability
If the network rejects network slice availability with cause code #62, then the network slice is added to rejected list, but the UE cannot recover connectivity without additional network actions
Solution Approach 1:
The network provides feedback through the activate default EPS bearer context request message that includes the network slice information and PLMN identifier. This feedback mechanism informs the UE which network slices are actually available and allows the UE to update its rejected NSSAI list accordingly, enabling informed recovery decisions.
Solution Approach 2:
The UE autonomously manages the rejected NSSAI list by removing network slices that are confirmed available through LTE network feedback. The UE independently performs registration on NR network using the updated allowed NSSAI list without requiring explicit network intervention, enabling self-service recovery.
Data Source
AI summary
A user equipment (UE) configured to transmit a first registration request comprising a first request for a network slice to a first network of a Public Land Mobile Network (PLMN), decode a registration reject message indicating the registration request for the network slice has been rejected by the first network, store the network slice in a rejected network slice list, register with a second network of the PLMN, decode an activate default evolved packet system (EPS) bearer context request message comprising an indication of the network slice and the PLMN indicating the UE can access the network slice on the second network, remove the network slice from the rejected network slice list, transmit a second registration request comprising a second request for the network slice to the first network of the PLMN and decode a registration accept message indicating the registration request for the network slice has been allowed.