Blind Bandwidth Detection via Autocorrelation Phase Variance
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Solution Overview
Problem
Traditional OFDM receiver methods for bandwidth detection in complex valued sample streams are computationally challenging due to the need to process numerous possible patterns, making them ineffective in environments with large pattern variations.
Innovation Solution
A method involving correlating and transforming preamble symbols to generate frequency diverse autocorrelated portions, determining phase variances across different bandwidth regions, and comparing these variances to determine the bandwidth of the complex valued sample stream, without requiring prior knowledge of patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If supervised bandwidth detection techniques are used that require knowledge of complex valued sample stream patterns, then detection accuracy can be maintained, but computational complexity increases significantly when processing large numbers of possible patterns
Solution Approach 1:
The patent extracts only the essential autocorrelation properties of the preamble symbol that are necessary for bandwidth detection, rather than processing the complete complex valued sample stream patterns. By taking out and processing only the autocorrelation function values at specific time lags, the system achieves bandwidth detection without the computational burden of analyzing all possible patterns.
Solution Approach 2:
The patent introduces the autocorrelation function as an intermediary between the raw complex valued sample stream and the bandwidth detection process. The autocorrelation function serves as a mediator that transforms the complex pattern recognition problem into a simpler measurement of correlation magnitude, enabling efficient bandwidth detection without direct pattern analysis.
2Device complexity
If blind bandwidth detection methods are implemented that do not require prior pattern knowledge, then computational complexity is reduced, but detection reliability may be compromised without sufficient signal characteristics
Solution Approach 1:
The patent performs preliminary action by utilizing the preamble symbol structure that is inherently present in the OFDM signal before bandwidth detection begins. The cyclic prefix structure of the preamble symbol provides built-in autocorrelation properties that can be exploited directly, eliminating the need for prior pattern knowledge while maintaining detection reliability through the signal's own structural characteristics.
Solution Approach 2:
The patent enables the signal itself to serve the detection function by exploiting the self-autocorrelation properties of the preamble symbol. The cyclic prefix structure causes the signal to correlate with itself at specific time lags, allowing the system to detect bandwidth through self-service mechanisms without requiring external pattern information or complex processing.
Data Source
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AI summary
A method for determining a bandwidth of a complex valued sample stream may include correlating a first portion of a preamble symbol of the complex valued sample stream with a second portion of the preamble symbol to generate a time autocorrelated portion (40). The method may further include transforming the time autocorrelated portion to generate a frequency diverse autocorrelated portion (42). The method may further include determining a first phase variance over a first region of the frequency diverse autocorrelated portion, wherein the first region has a first bandwidth (44). The method may further include determining a second phase variance over a second region of the frequency diverse autocorrelated portion, wherein the second region has a second bandwidth greater than the first bandwidth (46). The method may further include determining the bandwidth of the complex valued sample stream by comparing the first phase variance with the second phase variance (48).