GNSS Measurement Gap Updates for NTN Position Fix Validity
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Solution Overview
Problem
Frequent switching between connected and idle states due to GNSS position fix failures leads to significant power consumption and inefficient resource usage in UE devices connected to non-terrestrial networks, particularly in NB-IoT devices, as they cannot perform simultaneous radio communication and GNSS position fixes.
Innovation Solution
The network provides triggering conditions for the UE to signal an updated GNSS validity duration, allowing the UE to transmit this information, which in turn enables the network to update the measurement gap configuration, ensuring timely and efficient GNSS position fixes without unnecessary state transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the UE performs GNSS position fix procedures frequently to maintain position validity, then position accuracy is improved, but power consumption increases significantly
Solution Approach 1:
The measurement gap configuration is made dynamic and adaptable. The network entity configures measurement gaps based on real-time conditions including UE mobility state (detected through timing advance changes), GNSS signal availability, and current position validity. This dynamic configuration allows the system to perform GNSS position fixes frequently when needed for accuracy while reducing frequency when conditions allow, thereby resolving the contradiction between position accuracy and power consumption.
Solution Approach 2:
The network entity performs preliminary assessment of UE conditions (mobility state, timing advance stability, signal quality) before configuring measurement gaps. By evaluating these parameters in advance and pre-configuring appropriate measurement gap patterns, the system prepares optimal GNSS measurement opportunities without requiring frequent reactive state transitions, thus improving position accuracy while managing power consumption efficiently.
2Reliability
If the network reconfigures measurement gaps frequently to maintain up-to-date GNSS validity, then position fix reliability is improved, but communication overhead increases
Solution Approach 1:
The system implements feedback mechanisms where the UE reports timing advance information and GNSS measurement results to the network entity. The network entity uses this feedback to assess whether current measurement gap configurations remain appropriate or need adjustment. This feedback-driven approach ensures position fix reliability is maintained through informed reconfiguration decisions while minimizing unnecessary reconfiguration signaling, thus reducing communication overhead.
Solution Approach 2:
The network entity monitors changes in key parameters (timing advance values, UE mobility state, signal quality metrics) and only reconfigures measurement gaps when parameter changes indicate a genuine need. By tying reconfiguration decisions to specific parameter thresholds and changes rather than frequent periodic updates, the system maintains position fix reliability while significantly reducing communication overhead associated with unnecessary reconfiguration messages.
3Use of energy by moving object
If the UE switches to idle state when GNSS position validity expires, then power consumption is reduced, but communication latency increases
Solution Approach 1:
The measurement gap configuration is dynamically adjusted based on UE mobility state and position validity requirements. For moving UEs where position accuracy is critical, the network maintains connected state with optimized measurement gaps rather than allowing idle transitions. For stationary or low-mobility UEs, the system can permit idle state transitions when position validity expires. This dynamic state management resolves the contradiction by adapting the connected/idle behavior to specific operational contexts.
Solution Approach 2:
The network entity performs preliminary evaluation of UE conditions before allowing state transitions. By assessing timing advance stability, mobility state, and GNSS signal availability in advance, the network can determine whether a UE is suitable for idle state transitions or requires maintained connected state. This preliminary assessment prevents premature idle transitions that would cause latency while still enabling power-saving idle states when appropriate, thus resolving the energy-latency tradeoff.
Data Source
AI summary
Devices in a wireless communication system perform methods related to a GNSS position fix procedure. A user equipment connected to a network entity via a non-terrestrial network receives a measurement gap configuration and an indication of a remaining-validity-duration-update triggering condition. The UE conducts a GNSS position fix procedure for estimating a UE position during a measurement gap according to the measurement gap configuration. When the GNSS position fix procedure is successfully completed, the UE transmits a remaining GNSS validity duration. When the remaining-validity-duration-update triggering condition is met, the UE transmits an updated remaining GNSS validity duration.