Preconfigured Uplink Resources for NTN Cell Reselection
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Solution Overview
Problem
Non-Terrestrial Networks (NTNs) face challenges in efficiently managing Pre-configured Uplink Resources (PURs) for satellite-based communication systems, particularly in Low Earth Orbit (LEO) systems where satellite movement leads to frequent cell reselection, resulting in power consumption overhead and reduced power savings due to the need for Radio Resource Control (RRC) connections.
Innovation Solution
The network configures multiple PURs for each satellite beam or cell, allowing User Equipment (UE) to transmit data without an RRC connection, pre-compensating for uplink channel propagation delays based on position and satellite orbit information, and using time domain periodicity and frequency domain resources for transmissions, enabling efficient data transfer without continuous network grant requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If PUR is used for periodic sensor data transmission, then power consumption is reduced, but uplink timing synchronization becomes inaccurate due to satellite movement and cell reselection
Solution Approach 1:
The network pre-configures multiple PURs with different timing parameters before the UE needs to transmit. When the UE experiences cell reselection or timing drift, it can switch to a pre-configured PUR with updated timing parameters without needing to re-establish RRC connection, thus maintaining power savings while correcting timing synchronization
Solution Approach 2:
The patent introduces dynamic PUR configuration where the network can update PUR parameters (including timing offsets) while the UE remains in RRC inactive state. This allows the timing synchronization to adapt to satellite movement without requiring continuous RRC connections, resolving the contradiction between power saving and timing accuracy
2Measurement precision
If RRC connection is maintained for accurate timing synchronization, then uplink timing accuracy is improved, but power consumption increases
Solution Approach 1:
Instead of maintaining continuous RRC connection, the network periodically updates PUR configurations at predetermined intervals. This allows timing synchronization to be refreshed periodically without continuous connection overhead, reducing power consumption while maintaining adequate timing accuracy for periodic sensor data transmission
3Adaptability or versatility
If multiple PURs are configured for different beams, then adaptability to cell reselection is improved, but device complexity increases
Solution Approach 1:
The patent segments the PUR configuration into multiple independent PUR entries, each associated with a specific beam or cell. When cell reselection occurs, the UE simply switches to the PUR corresponding to the new cell without needing to reconfigure anything. This segmentation approach improves adaptability while keeping the UE implementation relatively simple through straightforward configuration switching
Data Source
AI summary
In an aspect, a satellite-based non-terrestrial network configures multiple preconfigured uplink resources (PURs) for a user equipment (UE). The PURs may be configured one PUR per beam, one PUR per cell, or one PUR for multiple cells. A serving cell of the UE and one or more cells adjacent to the serving cell may each have an associated PUR. The UE selects one of the multiple PURs and sends a transmission using the selected PUR without the UE have a connection to the network. The network sends an ACK in response to the transmission. Either the UE or the network can specify that the UE is to transmit using a first PUR and receive the ACK on a second PUR. The UE can specify when and which PUR to use in the transmission and the network can specify when and which PUR to use in the ACK.