Synchronization Signal Subcarrier Spacing Detection
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Solution Overview
Problem
User Equipment (UE) in mobile communication systems needs to detect subcarrier spacing without requiring two different synchronization signal designs, as existing methods increase complexity or cell search time.
Innovation Solution
Generating and transmitting synchronization signals with specific time domain representations that indicate either a single instance or multiple instances of a basic waveform, allowing the UE to determine the subcarrier spacing based on correlation results, thereby eliminating the need for distinct signal designs for different spacings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two different synchronization signal designs are used for different subcarrier spacings, then the UE can detect the correct spacing, but the device complexity increases as the UE must implement and search for both signal designs in parallel
Solution Approach 1:
A single synchronization signal design is created that can function for both 15 kHz and 7.5 kHz subcarrier spacings. The signal structure uses a base sequence that is inherently compatible with both spacings, eliminating the need for the UE to implement separate detection algorithms for each spacing type.
Solution Approach 2:
Instead of creating different signals for different spacings and having the UE detect which one is present, the invention inverts the approach by creating one signal that encodes the spacing information within its structure. The UE detects the spacing by analyzing properties of the single signal rather than searching for multiple distinct signals.
2Measurement precision
If two different synchronization signal designs are used for different subcarrier spacings, then the UE can detect the correct spacing, but the cell search time increases as the UE must sequentially search for both signal types
Solution Approach 1:
The single synchronization signal design serves multiple functions by encoding spacing information within its structure. The UE performs one detection process that simultaneously identifies both the presence of the synchronization signal and the subcarrier spacing, eliminating sequential search delays.
Solution Approach 2:
The spacing identification information is embedded in advance within the synchronization signal structure itself. This allows the UE to determine the subcarrier spacing as part of the initial synchronization process without requiring additional detection steps or extending the cell search time.
3Duration of action of stationary object
If a smaller subcarrier spacing (7.5 kHz) is used for SFN operation, then the OFDM symbol duration increases enabling longer cyclic prefix, but the overhead increases which is not attractive
Solution Approach 1:
The system dynamically adjusts the subcarrier spacing parameter between 15 kHz and 7.5 kHz depending on the operational mode. For SFN operation requiring longer cyclic prefix, the system switches to 7.5 kHz spacing which naturally provides longer OFDM symbol duration. The overhead is managed by optimizing the resource allocation and signal structure to maintain efficiency despite the parameter change.
Data Source
AI summary
A cellular communications system that utilizes OFDM in its radio interface is capable of utilizing either a first subcarrier spacing or a second subcarrier spacing. Which of these is presently in use is indicated by generating a first type of synchronization signal in response to the first subcarrier spacing presently being in use, and generating a second type of synchronization signal in response to the second subcarrier spacing presently being in use. Whichever of the first type of synchronization signal and the second type of synchronization signal was generated is transmitted. To distinguish between the first and second types of synchronization signals, a time domain representation of the second type of synchronization signal includes a plurality of instances of the first type of synchronization signal.