Uplink Timing Advance for Satellite NB-IoT Propagation Delay
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Solution Overview
Problem
The existing Narrow Band Internet of Things (NB-IoT)/Enhanced Machine Type Communication (eMTC) uplink synchronization mechanism fails to track and compensate for rapid changes in propagation delay caused by the movement of satellites, leading to uplink interference among multiple users and carriers.
Innovation Solution
A method that divides the transmission time of the uplink signal into multiple time segments, calculates open-loop and closed-loop uplink timing advances for each segment, and adjusts the transmission time based on these advances to account for the changing propagation delay, using both terminal device and network device processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the existing NB-IoT/eMTC uplink synchronization mechanism is used, then the system complexity is low, but the propagation delay cannot be tracked and compensated for rapid changes caused by satellite movement
Solution Approach 1:
The patent segments the timing advance adjustment into two independent parts: open-loop timing advance (calculated by terminal based on satellite ephemeris) and closed-loop timing advance (adjusted by network based on uplink signal detection). This segmentation allows each mechanism to operate independently, improving synchronization accuracy without requiring complete redesign of the entire synchronization system.
Solution Approach 2:
The patent implements preliminary action by having the terminal calculate the open-loop timing advance in advance using satellite ephemeris information before actual uplink transmission. This preliminary timing adjustment compensates for the majority of propagation delay, reducing the burden on closed-loop adjustments and improving overall synchronization response to satellite movement.
2Area of stationary object
If satellite communication is used to extend coverage area, then the communication range is large and reliability is high, but the propagation delay changes rapidly due to satellite movement
Solution Approach 1:
The patent implements a dual feedback mechanism: open-loop feedback where terminal calculates timing advance based on satellite ephemeris and position information, and closed-loop feedback where network device detects uplink signal arrival time and sends timing advance corrections to terminal. This dual feedback system maintains uplink synchronization stability despite rapid propagation delay changes caused by satellite movement, enabling reliable communication over large coverage areas.
Data Source
AI summary
A method for transmitting an uplink signal is performed by a terminal device, and includes: dividing a transmission time of the uplink signal into a plurality of time segments according to a duration; obtaining an open-loop uplink timing advance and a closed-loop uplink timing advance for each time segment, and generating a timing advance for each time segment according to the open-loop uplink timing advance and the closed-loop uplink timing advance for each time segment; and adjusting a transmission time of one of the plurality of time segments of the uplink signal according to a corresponding timing advance for the one of the plurality of time segments.