Bit-Rate Discrimination Using Preamble Signal Correlation
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Solution Overview
Problem
Conventional bit-rate discrimination circuits are unable to rapidly discriminate bit-rates in signals where the bit-rate changes quickly, due to their reliance on edge detection methods that require lengthy integration times and lowpass filters, making them unsuitable for modern point-to-multipoint networks handling diverse transmission speeds.
Innovation Solution
A bit-rate discrimination method utilizing the periodicity of a preamble signal, where the repetition of a pattern is converted into a consecutive identical signal, allowing for faster discrimination by integrating this signal within a shorter time frame, and using exclusive-NOR or exclusive-OR circuits with delayed inputs to differentiate between bit-rates, even when they do not have an integral multiple or fraction relationship.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If edge detection method is used to discriminate bit-rate by integrating edge portions, then discrimination accuracy is improved, but discrimination speed deteriorates due to lengthy integration time required
Solution Approach 1:
The invention extracts the preamble signal portion from the entire data signal and uses only this extracted portion for bit-rate discrimination. By focusing on the periodic preamble signal rather than the entire random data stream, the system achieves accurate bit-rate detection without requiring lengthy integration times, thus resolving the contradiction between accuracy and speed.
Solution Approach 2:
The preamble signal is prepared in advance with a known periodic pattern before data transmission begins. This preliminary structured signal allows the discrimination circuit to immediately identify bit-rate through correlation detection without requiring long integration periods, enabling both high accuracy and fast discrimination.
2Measurement precision
If lowpass filter with low frequency band is used to detect low-frequency component, then bit-rate discrimination is achieved, but response time increases due to large time constant required
Solution Approach 1:
The invention extracts and utilizes the periodic low-frequency component of the preamble signal specifically for bit-rate discrimination. By isolating this known periodic component rather than filtering the entire signal, the system achieves accurate detection with a smaller time constant, reducing response time while maintaining detection accuracy.
Solution Approach 2:
The preamble signal contains a deliberate periodic pattern that matches the bit-rate. By detecting this periodic action directly through correlation or frequency analysis, the system can accurately determine bit-rate without requiring a large time constant lowpass filter, thus achieving fast response time.
3Adaptability or versatility
If conventional bit-rate discrimination circuit is used, then existing bit-rates can be handled, but high-speed following of constantly-changing bit-rate cannot be achieved
Solution Approach 1:
A preamble signal with known periodic characteristics is inserted before the actual data transmission. This preliminary signal allows the receiver to quickly acquire and lock onto the current bit-rate before data reception begins, enabling the system to follow constant bit-rate changes at high speed while maintaining compatibility with existing bit-rate standards.
Solution Approach 2:
The invention replaces conventional edge-detection-based mechanical integration methods with a correlation-based detection method that utilizes the periodic preamble signal. This substitution enables much faster response to bit-rate changes while maintaining adaptability to various existing bit-rate standards through the flexible correlation approach.
Data Source
AI summary
In the present invention, unlike a conventional circuit, discrimination is not made by integrating a logical code that includes “0” and “1” to some extent and produced from a random code, but repetition of an identical pattern of a well-known preamble signal added to a head portion of a signal is discriminated when a bit-rate of the signal is changed. More specifically, the repetition of the identical pattern is converted into a consecutive identical signal to generate the consecutive identical signal (having a length of tens bits to thousands bits). Although the consecutive identical signal is longer than a same-code continuation length included in the signal, and is shorter than a time constant necessary to the conventional circuit by about one to three digits. Therefore, an integration time can be shortened to the same degree as the generated consecutive identical signal length, and the bit-rate can be discriminated at high speed within a preamble signal receiving time.