NTN RACH Procedures with Timing Advance and Doppler Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenges of large round trip delays and Doppler shifts in non-terrestrial networks (NTN) affect the reliability of random access procedures, particularly in satellite communications, where existing methods struggle to support the extended delays and frequency offsets.
Innovation Solution
A method for random access procedures in NTN that involves UEs calculating and pre-compensating timing advance using GNSS data, applying intentional random delays and cyclic shifts to differentiate user equipment, and optimizing PRACH preamble designs to enhance orthogonality and reduce interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If random access procedures are designed for terrestrial networks with small round trip delays, then the procedures are simple and efficient for terrestrial use, but they become unreliable when applied to non-terrestrial networks with large round trip delays
Solution Approach 1:
The patent applies preliminary action by having UEs pre-calculate and apply timing advance values based on predicted propagation delays to non-terrestrial network nodes before actual communication begins. This pre-compensation mechanism addresses the large round trip delays in NTN by proactively adjusting transmission timing, thereby maintaining reliability of random access procedures despite the time loss inherent in satellite communications.
2Productivity
If multiple UEs transmit random access messages simultaneously to handle high user demand, then access efficiency improves, but contention and interference between UEs increase
Solution Approach 1:
The patent applies local quality by introducing UE-specific parameters including cyclic shift values and orthogonal cover codes that differentiate each UE's random access preamble. This allows multiple UEs to transmit simultaneously with reduced interference by giving each UE a locally unique signature, thereby maintaining high access efficiency while minimizing contention and interference between simultaneous transmissions.
3Measurement precision
If timing advance values are calculated without considering Doppler shifts, then calculation complexity is reduced, but timing synchronization accuracy deteriorates in non-terrestrial networks
Solution Approach 1:
The patent applies parameter changes by incorporating Doppler shift compensation into the timing advance calculation formula. The UE calculates timing advance based on predicted propagation delay and applies corrections for Doppler effects caused by relative motion between satellite and ground terminals. This enhances timing synchronization accuracy in NTN environments while managing calculation complexity through efficient mathematical models.
4Adaptability or versatility
If PRACH preambles are designed for terrestrial delay ranges, then the design is simple and compatible with existing infrastructure, but they fail to support the extended delays characteristic of non-terrestrial networks
Solution Approach 1:
The patent applies dynamics by making the PRACH preamble design adaptable to different propagation delay ranges through configurable parameters. The system can dynamically select appropriate preamble formats, cyclic prefix lengths, and timing structures based on whether the network is terrestrial or non-terrestrial. This provides versatility to support extended delays in NTN while maintaining compatibility with existing terrestrial infrastructure when appropriate.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances the reliability and efficiency of random access procedures in NTN by reducing contention and interference, allowing for accurate timing synchronization and differentiated UE identification, even in scenarios with significant propagation delays and frequency offsets.
Implementation Method 1
UEs calculating and pre-compensating timing advance using GNSS data
Implementation Method 2
challenges of large round trip delays and Doppler shifts in non-terrestrial networks
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A system and method for random access procedures in a non-terrestrial network. In some embodiments, the method includes calculating (605), by a user equipment, UE, a timing advance based on location information of the UE and on an ephemeris of a non-terrestrial network node. The method may further include randomly selecting (610) a random value from a plurality of values, and sending (615), at a transmission time, by the UE, to the non-terrestrial network node, a random access, RA, message, which may include a signature. The transmission time may differ from a nominal transmission time by an amount based on the random value, the nominal transmission time being based on the timing advance, or the signature may differ from a nominal signature by a cyclic shift based on the random value.