Wireless Preamble Signal Generation via Orthogonal Sequence Cyclic Shift
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Solution Overview
Problem
In wireless communication systems, the traditional method of using a limited set of ranging preamble codes (RPCs) for timing synchronization can lead to collisions and inaccuracies in estimating signal round-trip delays, especially in large cells and with mobile user terminals, due to inter-carrier interference (ICI) and Doppler effects, which degrades system performance.
Innovation Solution
The method involves generating a preamble signal by combining orthogonal sequences and their antipodal versions through cyclic shift or cross concatenation, and providing distinct subsets of RPCs based on estimated signal round-trip delays and Doppler effects to reduce collisions and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a limited set of ranging preamble codes is used for timing synchronization, then device complexity is reduced, but measurement precision and reliability deteriorate due to collisions and inaccuracies in estimating signal round-trip delays
Solution Approach 1:
The patent divides the limited set of ranging preamble codes into multiple subsets, where each subset is assigned to specific user terminals based on their estimated round-trip delays. This segmentation prevents collisions by ensuring that different subsets are used by different terminal groups, thereby maintaining measurement precision without requiring a single large comprehensive code set.
Solution Approach 2:
The patent dynamically assigns different preamble code subsets to user terminals based on their estimated round-trip delays and channel conditions. The base station determines which subset each terminal should use in real-time, allowing the system to adapt to varying network conditions and prevent collisions dynamically rather than using a static limited code set for all terminals.
2Ease of operation
If a limited set of ranging preamble codes is used, then ease of operation is improved, but reliability deteriorates due to collisions and inter-carrier interference in large cells
Solution Approach 1:
The patent segments the preamble code set into multiple subsets that are distributed across different user terminals based on their round-trip delay characteristics. This segmentation maintains ease of operation by keeping individual terminal code selections simple while improving reliability by preventing collisions through systematic code distribution across the network.
Solution Approach 2:
The base station estimates round-trip delays for user terminals and uses this feedback information to determine which preamble code subset each terminal should use. This feedback mechanism ensures reliable timing synchronization by adapting code assignment to actual channel conditions, preventing collisions while maintaining operational simplicity at the terminal level.
3Device complexity
If traditional ranging methods are used in large cells, then device complexity is reduced, but measurement precision deteriorates due to inter-carrier interference and Doppler effects
Solution Approach 1:
The patent segments the synchronization process into multiple stages by dividing preamble codes into subsets assigned to different terminal groups based on round-trip delays. This segmentation reduces the impact of inter-carrier interference and Doppler effects on measurement precision by ensuring that terminals with similar propagation characteristics use the same code subset, thereby maintaining accuracy without increasing overall system complexity.
Solution Approach 2:
The patent changes the parameter of preamble code assignment based on estimated round-trip delays and channel conditions. By dynamically adjusting which code subset each terminal uses according to its specific propagation characteristics, the system maintains measurement precision in large cells while keeping device complexity manageable through standardized assignment criteria.
Data Source
AI summary
A method for a user terminal to generate a preamble signal in a wireless communication system, the method including: generating an orthogonal sequence as a first sequence; performing cyclic shift on an antipodal version of the orthogonal sequence to generate a second sequence; and combining the first sequence and the second sequence to generate the preamble signal.