Random Access Preamble Time Adjustment for Non-Terrestrial Networks
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Solution Overview
Problem
In wireless communication systems, especially in non-terrestrial networks, the varying distances between terminal devices and network devices result in significant differences in transmission delays, leading to overlapping preamble receiving time windows and reduced success rates of network access.
Innovation Solution
The terminal device determines a time adjustment value based on its position and the network device's position, allowing it to adjust the sending time of random access preambles. This ensures that preambles from different terminal devices are received by the network device within a small time range, avoiding overlapping time windows without reducing the random access capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If terminal devices send preambles using the same RACH resource without time adjustment, then the random access procedure is simple to implement, but preambles from terminal devices at different distances arrive at significantly different times, causing overlapping receiving time windows and reduced access success rates
Solution Approach 1:
The terminal device performs preliminary calculation of a time adjustment value based on its position and the network device's position before sending the random access preamble. This preliminary time adjustment ensures that preambles from terminal devices at different distances arrive at the network device within a concentrated time window, preventing overlapping receiving windows and improving access success rates without significantly increasing system complexity
Solution Approach 2:
The invention changes the time parameter of preamble transmission by introducing a time adjustment value. This parameter modification compensates for the varying propagation delays caused by different distances between terminal devices and the network device, ensuring synchronized arrival of preambles and resolving the contradiction between maintaining simple procedures and achieving reliable access
2Reliability
If the network device increases the preamble receiving time window to accommodate all terminal devices, then all preambles can be received, but the time window becomes large and overlaps with other RACH resources, reducing random access capacity
Solution Approach 1:
Terminal devices perform preliminary time adjustment based on their positions before transmitting preambles. This ensures that preambles arrive at the network device within a concentrated, predictable time window, allowing the network device to configure a small receiving time window without missing any preambles, thereby preventing overlaps with other RACH resources and maintaining high random access capacity
Solution Approach 2:
The invention modifies the time parameter of preamble transmission at the terminal side, which indirectly optimizes the receiving time window parameter at the network side. By adjusting the transmission time based on position, the effective receiving window becomes smaller and more concentrated, eliminating the need for large time windows and preserving system productivity
Data Source
AI summary
A random access method and apparatus are provided. The method includes: a terminal device obtains a position of the terminal device and a position of a network device, the terminal device determines a time adjustment value based on the position of the terminal device and the position of the network device, and the terminal device sends a random access preamble based on the time adjustment value and a random access channel (RACH) resource configured by the network device. Based on this solution, the terminal device may determine the time adjustment value based on the position of the terminal device and the position of the network device, and adjust a time for sending the random access preamble on the RACH resource. This helps avoid a problem that random access preamble receiving time windows overlap, thereby increasing a success rate of accessing the network device by the terminal device.