Zadoff-Chu Cyclic Shift Adjustment for High-Speed Random Access
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Solution Overview
Problem
In high-speed communication scenarios, the Doppler frequency shift causes mutual interference and vagueness issues during random access in LTE systems, particularly when the Doppler frequency shift exceeds one PRACH subcarrier spacing but remains below twice the PRACH subcarrier spacing, leading to reduced success rates and increased random access times.
Innovation Solution
A method for sending and receiving random access preamble sequences using Zadoff-Chu sequences with specific cyclic shift values, where the terminal device and base station adjust the cyclic shift based on defined formulas to avoid interference, ensuring unique cyclic shift values for each terminal device, thereby improving detection accuracy and success rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the LTE system performs communication at a higher working frequency or when a terminal device has a very high movement speed, then the carrier frequency increases, but the Doppler frequency shift becomes greater than one time the PRACH subcarrier spacing and less than twice the PRACH subcarrier spacing, causing mutual interference between terminal devices and vagueness problem during base station detection
Solution Approach 1:
The patent changes the cyclic shift parameter of the Zadoff-Chu sequence based on the Doppler frequency shift conditions. When the Doppler frequency shift is greater than one but less than twice the PRACH subcarrier spacing, the patent applies a specific cyclic shift value that ensures the shifted sequences do not overlap with other terminal devices' sequences, thereby eliminating mutual interference and detection vagueness while maintaining reliable random access at high speeds
2Productivity
If the Doppler frequency shift is greater than one time the PRACH subcarrier spacing and less than twice the PRACH subcarrier spacing, then the frequency difference increases, but mutual interference between terminal devices during random access occurs
Solution Approach 1:
The patent applies different cyclic shift values to different terminal devices based on their specific Doppler frequency shift conditions. By locally adjusting the cyclic shift parameter for each terminal device experiencing high Doppler shift, the patent ensures that each device's preamble sequence is uniquely shifted and does not interfere with other devices' sequences, thereby eliminating mutual interference while maintaining high random access speed
3Speed
If the Doppler frequency shift is greater than one time the PRACH subcarrier spacing and less than twice the PRACH subcarrier spacing, then the frequency difference increases, but a vagueness problem occurs during base station detection
Solution Approach 1:
The patent adjusts the cyclic shift parameter of the Zadoff-Chu sequence specifically for terminal devices moving at high speeds where the Doppler frequency shift is between one and twice the PRACH subcarrier spacing. This parameter change ensures that the cyclically shifted preamble sequences maintain distinct peaks that are easily detectable by the base station, thereby eliminating detection vagueness while supporting high terminal device speeds
Data Source
AI summary
This application relates to the mobile communications field, and in particular, to a random access technology in a wireless communications system. This application provides a method for receiving a random access preamble sequence, an apparatus, and a system. In this solution, a device obtains a cyclic shift value that satisfies a high-speed movement scenario and receives a random access preamble sequence corresponding to the cyclic shift value.