LTE Random Access ZC Sequence Generation for Doppler Shift Interference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing LTE system faces mutual interference issues between multiple UE random access sequences due to Doppler frequency shifts greater than one PRACH subcarrier spacing and less than two times the PRACH subcarrier spacing, which affects decoding accuracy.
Innovation Solution
A method where the base station notifies UE to use a second restricted set for generating a random access ZC sequence when the Doppler frequency shift is greater than or equal to a first predetermined value, greater than one PRACH subcarrier spacing, to avoid interference and improve decoding accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the existing LTE system uses standard random access sequences for high-speed moving terminals, then the system can maintain compatibility with existing protocols, but mutual interference occurs between multiple UE random access sequences when Doppler frequency shift exceeds one PRACH subcarrier spacing
Solution Approach 1:
The patent segments the random access sequence set into different subsets based on Doppler frequency shift ranges. When Doppler shift exceeds one PRACH subcarrier spacing, the system selectively uses a specific subset of sequences designed for high-mobility scenarios, separating them from standard sequences to avoid interference while maintaining protocol compatibility.
Solution Approach 2:
The patent changes key parameters of the random access sequences including cyclic shift values, root indices, and sequence lengths to create sequences that are robust against Doppler frequency shifts greater than one PRACH subcarrier spacing. These parameter modifications ensure orthogonality is maintained even under high-mobility conditions.
2Object-affected harmful factors
If the system increases the PRACH subcarrier spacing to accommodate higher Doppler shifts, then mutual interference is reduced, but the system loses adaptability for terminals with lower moving speeds that require finer frequency resolution
Solution Approach 1:
The patent implements a dynamic sequence selection mechanism where the base station determines the appropriate random access sequence subset based on the terminal's mobility state. The system can switch between standard sequences for low-mobility terminals and Doppler-resistant sequences for high-mobility terminals, optimizing performance for each scenario without compromising the other.
Solution Approach 2:
The patent introduces an additional dimension of sequence selection beyond the traditional single sequence set. By creating multiple sequence subsets with different properties (standard vs. Doppler-resistant), the system adds a selection dimension that allows adaptation to different mobility scenarios without changing the underlying PRACH subcarrier spacing.
3Measurement precision
If the system uses Doppler frequency shift compensation techniques, then decoding accuracy is maintained, but the system complexity increases due to additional processing requirements
Solution Approach 1:
The patent applies preliminary action by pre-designing specific random access sequences with inherent resistance to Doppler frequency shifts. Instead of performing complex real-time compensation processing, the system uses sequences that are already optimized for high-mobility scenarios, reducing the need for additional processing while maintaining decoding accuracy.
Solution Approach 2:
The patent converts the harmful effect of Doppler frequency shifts into a beneficial feature by designing sequences whose properties (cyclic shifts, root indices) are specifically chosen to exploit the Doppler effect in a controlled manner. This allows the system to maintain orthogonality and decoding accuracy even when Doppler shifts exceed one PRACH subcarrier spacing.
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
This approach effectively reduces mutual interference and enhances the accuracy of random access sequence decoding by specifically managing Doppler frequency shifts within the LTE system.
Implementation Method 1
signal frequencies of a receive end of the UE and a receive end of the base station may change, which is referred to as a Doppler frequency shift fD
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
Embodiments of the present invention provide a method for generating a random access channel ZC sequence, and an apparatus. A method for generating a random access channel ZC sequence includes: generating, by a base station, notification signaling, where the notification signaling is used to instruct user equipment UE to generate a random access ZC sequence by using a second restricted set in a random access set; and sending, by the base station, the notification signaling to the UE, so that the UE generates the random access ZC sequence by using the second restricted set, where the random access set includes an unrestricted set, a first restricted set, and the second restricted set; and the second restricted set is a random access set that the UE needs to use when a Doppler frequency shift of the UE is greater than or equal to a first predetermined value, and the first predetermined value is greater than one time a physical random access channel PRACH subcarrier spacing.