Connected-State GNSS Position Fix Scheduling for IoT NTN UEs
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Solution Overview
Problem
In IoT NTN systems, UEs face challenges in efficiently re-acquiring a valid GNSS position fix in the RRC_CONNECTED state without transitioning to IDLE mode, which leads to increased power consumption, signaling overhead, and delay due to frequent re-access to the network, especially for long connection times and high mobility scenarios.
Innovation Solution
The UE reports GNSS assistance information to the network, determining if the GNSS position fix duration is shorter than a network-scheduled duration, and performs the fix in RRC_CONNECTED state if yes, or transitions to RRC_IDLE if no, using configured measurement gaps or timers to manage GNSS validity and synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE transitions to RRC_IDLE state to re-acquire GNSS position fix, then the GNSS position fix can be obtained, but the signaling overhead and delay increase due to frequent re-access to the network
Solution Approach 1:
The network configures the UE with measurement gaps or timers in advance during RRC_CONNECTED state, enabling the UE to perform GNSS measurements without transitioning to IDLE. This preliminary configuration allows the UE to proactively acquire fresh GNSS position fixes while maintaining connection, thereby avoiding the time loss and signaling overhead associated with frequent re-access procedures.
2Reliability
If the UE transitions to RRC_IDLE state to re-acquire GNSS position fix, then the GNSS position fix can be obtained, but the power consumption increases
Solution Approach 1:
The network configures measurement gaps or timers in advance, allowing the UE to perform GNSS measurements while remaining in RRC_CONNECTED state. This prevents the UE from transitioning to IDLE state frequently, thereby reducing the power consumption associated with connection establishment and maintenance procedures.
3Reliability
If the network configures measurement gaps for GNSS acquisition, then the UE can maintain connection during measurement, but the available time for data transmission decreases
Solution Approach 1:
The measurement gap duration and frequency are dynamically configured by the network based on UE mobility conditions and data transmission requirements. When UE mobility is low or data transmission is urgent, the network can extend the measurement gap interval or reduce gap duration. When mobility is high, the network increases measurement frequency. This dynamic adjustment optimizes the balance between connection reliability and data transmission efficiency.
4Reliability
If the UE performs frequent GNSS measurements in RRC_CONNECTED state, then the position fix validity is maintained, but the device complexity increases
Solution Approach 1:
The network monitors UE mobility conditions and GNSS measurement results, and provides feedback to adjust measurement gap configuration. Based on this feedback mechanism, the network can optimize the measurement frequency and gap duration, preventing unnecessary frequent measurements that would increase device complexity. The system adapts measurement management to actual conditions, maintaining position fix validity while minimizing complexity.
Data Source
AI summary
Apparatus and methods are provided for GNSS position fix in connected state. In one novel aspect, the UE reports GNSS assistance information to the network entity in the NTN system, wherein the GNSS assistance information includes a GNSS position fix time duration for measurement. When the UE detects the GNSS position out-of-date condition in the RRC_CONNECTED stated, the UE determines whether the GNSS position fix time duration for measurement is smaller than the network scheduled duration for GNSS measurement and performs the GNSS position acquisition procedure in the RRC_CONNECTED state if determined yes. In another embodiment, the network scheduled duration for GNSS measurement is configured for the UE to re-acquire GNSS position fix in the RRC_CONNECTED state and may further include duration to re-acquire downlink (DL) synchronization with or without NTN system information block (SIB). In one embodiment, the network scheduled duration for GNSS measurement is a new scheduling gap or a GNSS timer.