Adaptive RACH Preamble Scaling for NTN Random Access Timing
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Solution Overview
Problem
Existing random access protocols in non-terrestrial networks (NTNs) are ineffective due to the large distances between user equipment (UE) and satellite stations, leading to timing uncertainty and unacceptably high signaling overhead.
Innovation Solution
Adapting the length and repetition of random access channel (RACH) preambles based on the difference between the expected minimum and maximum distances from the edges of a cell served by the base station, using prime numbers and longer repetition times to ensure effective communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing random access protocols are used in NTNs, then the protocol structure is simple, but timing uncertainty and signaling overhead become unacceptably high due to large distances
Solution Approach 1:
The patent applies dynamics by making the RACH preamble length adaptive rather than fixed. The preamble length is dynamically adjusted based on the distance between the satellite and user equipment, allowing the system to optimize timing accuracy for each specific scenario while avoiding excessive signaling overhead. This is achieved through configuring different preamble lengths according to the propagation delay characteristics of the NTN environment.
Solution Approach 2:
The patent changes the parameter of preamble length to resolve the contradiction. By varying the preamble length parameter based on distance conditions, the system achieves reliable timing synchronization for distant satellites while minimizing the time resources consumed. The base station configures appropriate preamble lengths and repetition factors according to the specific NTN scenario parameters.
2Reliability
If longer RACH preambles with more repetitions are used, then signal-to-noise ratio improves, but signaling overhead increases
Solution Approach 1:
The patent applies dynamics by making the repetition factor adaptive. Instead of using a fixed high repetition count for all scenarios, the system dynamically adjusts the number of repetitions based on the distance and channel conditions. This allows the system to achieve the necessary SINR improvement only when needed, thereby reducing unnecessary signaling overhead in scenarios with better channel conditions.
Solution Approach 2:
The patent changes the parameter of repetition factor to balance SINR improvement and overhead. By adjusting this parameter based on distance and channel quality, the system achieves reliable detection for distant users while minimizing the time resources consumed by repetitions. The base station configures appropriate repetition factors according to the specific NTN scenario.
3Area of stationary object
If RACH preamble length is increased to cover larger cell ranges, then coverage extends beyond 100km, but processing complexity increases
Solution Approach 1:
The patent applies dynamics by making the preamble length adaptive to the coverage requirements. Instead of always using the maximum preamble length, the system dynamically selects appropriate lengths based on the actual cell radius and distance conditions. This allows extended coverage when needed while reducing processing complexity in scenarios with smaller coverage requirements.
Solution Approach 2:
The patent changes the parameter of preamble length to extend coverage while managing complexity. By configuring different preamble lengths based on the specific NTN scenario parameters such as cell radius and distance, the system achieves coverage beyond 100km when required while avoiding unnecessary complexity in scenarios where shorter preambles suffice.
Data Source
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AI summary
Provided are methods and apparatuses for performing a random access of a terminal in a wireless communication system. A method, performed by a terminal, of performing a random access, according to an embodiment, includes receiving preamble configuration information from a base station, obtaining a RACH (random access channel) preamble scaled in length in proportion to a difference between an expected minimum distance and an expected maximum distance to the base station from opposed edges of a cell served by the base station, based on the preamble configuration information and transmitting the obtained RACH preamble to the base station to access a NTN (non-terrestrial network).