Alternative PDU Session Control for Fault-Tolerant Wireless Links
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Solution Overview
Problem
Existing wireless systems face challenges in ensuring end-to-end reliability and fault tolerance, particularly in ultra-reliable low latency communications (URLLC), due to the lack of efficient mechanisms for managing redundant protocol data unit (PDU) sessions and packet replication in 5G networks.
Innovation Solution
A wireless transmit/receive unit (WTRU) is equipped with the ability to determine PDU session states based on indication information, allowing it to transmit or receive data accordingly, thereby optimizing redundant transmission through N3/N9 tunnels and enhancing reliability and latency performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant PDU sessions are established to improve reliability, then the reliability parameter is improved, but the device complexity increases due to multiple session management requirements
Solution Approach 1:
The patent implements dynamic state management for alternative PDU sessions, where sessions can transition between active and dropped states based on network conditions. The WTRU dynamically determines whether to use the alternative PDU session by monitoring the state of the primary session, thereby adapting the system behavior to current conditions without maintaining both sessions in a static active state simultaneously.
Solution Approach 2:
The patent applies different quality characteristics to different PDU sessions by marking the alternative session with specific indication information. This allows the system to treat the alternative session differently from the primary session - maintaining it in a ready state but not actively using it, thus reducing complexity while preserving reliability capability.
2Reliability
If packet replication is implemented through redundant N3/N9 tunnels to improve reliability, then the reliability is improved, but the loss of time increases due to packet duplication and elimination processing
Solution Approach 1:
The patent establishes redundant PDU sessions and N3/N9 tunnels in advance before actual data transmission occurs. The alternative session is pre-configured with all necessary network elements (SMF, UPF, NG-RAN nodes) so that when a failure is detected, the switch to the alternative session can occur immediately without requiring time for session establishment. This preliminary setup eliminates the latency that would otherwise be incurred during failure recovery.
3Reliability
If alternative PDU sessions are maintained in ready state to improve fault tolerance, then the reliability is improved, but the use of energy increases due to continuous monitoring and readiness maintenance
Solution Approach 1:
The patent implements a partial readiness approach where the alternative PDU session is maintained in a limited readiness state rather than a fully active state. The session includes necessary network elements and configuration information but does not maintain full data path activation. This partial action approach provides fault tolerance capability while significantly reducing the energy consumption that would be required for maintaining a fully active redundant path.
Data Source
AI summary
A wireless transmit/receive unit (WTRU) may transmit a request message to establish or modify a protocol data unit (PDU) session with a network. In an example, the request message may indicate that the PDU session is an alternative PDU session. Also, the WTRU may receive, from the network, indication information indicating that the PDU session is the alternative PDU session. Further, the WTRU may determine, based on the received indication information, whether the PDU session is in a drop state. Moreover, the WTRU may transmit, based on a determination that the PDU session is no longer in the drop state, uplink data associated with the PDU session. In a further example, the determination that the PDU session is no longer in the drop state may be based on indication information in an attention (AT) command. In addition, the indication information in the AT command may be received from an application.