Guard Interval Length Detection in OFDM Signals
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Solution Overview
Problem
Existing guard interval length detection methods for OFDM signals are susceptible to noise and channel effects, making it difficult to accurately determine the guard interval length, especially in environments with multipath interference.
Innovation Solution
A guard interval length detector is introduced, comprising a delay conjugate multiplier, phase detector, and period detector, which multiplies input signals with their delayed complex conjugates to determine phase values and detect periods, thereby determining the guard interval length robustly against noise and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If correlation methods are used to detect guard interval length by performing correlation to the magnitudes of the received signals, then the detection can be performed using existing signal processing techniques, but the detection becomes susceptible to noise, channel effects and sampling frequency offset
Solution Approach 1:
The patent introduces an intermediary processing stage that computes the correlation between the received signal and a delayed version of itself, then extracts phase information from this correlation result. This intermediary correlation step acts as a mediator that enhances the signal characteristics, making the subsequent phase detection more robust against noise and channel effects while maintaining implementation feasibility.
Solution Approach 2:
The patent replaces direct magnitude correlation methods with a phase-based detection mechanism. Instead of relying on the magnitude of correlated signals which is sensitive to noise, the system uses phase information extracted from the correlation result, substituting a more robust phase detection mechanism for the vulnerable magnitude-based approach.
2Measurement precision
If normalization is applied to the correlation results to handle noise and channel effects, then the detection accuracy improves, but the detection process becomes more complex and requires additional processing steps
Solution Approach 1:
The patent extracts phase information directly from the correlation result without requiring normalization of the correlation magnitude. By taking out only the phase component rather than the full correlated signal, the system achieves detection accuracy while avoiding the complexity of normalization processing, thus resolving the contradiction between precision and complexity.
3Ease of operation
If threshold definition is attempted for correlation of magnitudes, then the detection can be simplified, but it becomes difficult to define the threshold accurately due to noise and channel effects
Solution Approach 1:
The patent substitutes magnitude-based threshold detection with phase-based detection. Instead of trying to define thresholds for correlated magnitudes which is difficult due to noise, the system uses phase information that can be detected more reliably, thereby achieving both simplicity and accuracy without the threshold definition problem.
4Difficulty of detecting and measuring
If correlation methods are used to detect the beginning of packets, then the detection can be performed, but the transmission mode cannot be detected
Solution Approach 1:
The patent creates a universal detection mechanism that serves multiple functions: it detects both the presence of packets and determines the transmission mode (2K or 8K) simultaneously. The phase detection method is versatile enough to handle different transmission modes, making the system adaptable to various OFDM configurations while maintaining packet detection capability.
Data Source
AI summary
A guard interval length detector is introduced. The guard interval length detector includes a delay conjugate multiplier capable of delaying a plurality of input signals to provide delayed input signals and multiplying each of the plurality of input signals with a complex conjugate of a corresponding one of the delayed input signals to provide multiplied signals, a phase detector capable of determining phase values corresponding to the multiplied signals, and a period detector capable of detecting a period according to the phase values, and determining a guard interval length of the input signals according to the period.