CAZAC Sequence Hopping for LTE Inter-Cell Interference Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing LTE systems face challenges in efficiently assigning Constant Amplitude Zero Auto-Correlation (CAZAC) sequences to each cell to minimize inter-cell interference, particularly when cell configurations change.
Innovation Solution
A method involving a base station generating a predetermined hopping pattern and applying an offset to create unique hopping sequences for each cell, which are then transmitted to user equipment terminals for generating signal sequences for control channels, Demodulation Reference Signals, and Sounding Reference Signals, ensuring different CAZAC sequences are used across adjacent cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If different CAZAC sequences are assigned to adjacent cells to reduce inter-cell interference, then interference reduction is achieved, but re-assignment is required upon cell configuration changes
Solution Approach 1:
The patent implements dynamic sequence assignment by introducing hopping patterns that automatically adapt to cell configuration changes. Instead of static sequence assignment, the system uses time-varying hopping sequences generated from cell-specific parameters, allowing the sequence assignment to dynamically adjust when cells are added, removed, or modified without requiring manual re-assignment.
Solution Approach 2:
The patent changes the assignment approach from directly assigning specific CAZAC sequences to cells to assigning hopping pattern parameters (such as hopping seed values or initialization parameters) to cells. This parameter-based assignment simplifies the process, as changing cell configuration only requires updating these parameters rather than重新assigning entire sequence sets.
2Reliability
If manual re-assignment of CAZAC sequences is performed upon cell configuration changes, then sequence validity is maintained, but system efficiency decreases
Solution Approach 1:
The system implements self-service through automatic hopping sequence generation at the user equipment. Each UE independently generates its hopping sequence based on received hopping pattern information and cell-specific parameters, eliminating the need for manual or centralized sequence assignment management. The system automatically adapts to configuration changes through this self-generated approach.
Solution Approach 2:
The base station pre-configures hopping pattern information and transmits it to user equipment in advance. This preliminary action includes providing hopping seed values, pattern parameters, and initialization information, enabling UEs to autonomously generate valid sequences without requiring real-time assignment updates when cell configurations change.
3Quantity of substance
If the same CAZAC sequence is used across multiple cells, then resource utilization improves, but inter-cell interference increases
Solution Approach 1:
The patent employs periodic hopping where CAZAC sequences are cycled through different sequences at regular time intervals. This periodic action allows the same base sequence to be used across multiple cells while maintaining low interference, as each cell hops through the sequence set in a time-varying manner that reduces simultaneous collisions compared to static assignment.
Solution Approach 2:
By implementing time-varying hopping patterns, the system dynamically changes which CAZAC sequence is active in each cell over time. This dynamic approach allows greater sequence reuse across cells compared to static assignment, as interference patterns change over time rather than remaining constant, effectively reducing average inter-cell interference while improving sequence utilization.
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A signal sequence generating method of generating a signal sequence used by a user equipment terminal in a mobile communication system includes the steps of generating, by a base station, a predetermined hopping pattern; generating, by the base station, a hopping sequence by applying an offset to the predetermined hopping pattern; transmitting, by the base station, the hopping sequence to the user equipment terminal; and generating, by the user equipment terminal, the signal sequence according to the hopping sequence.