Scattered Pilot Location Detector for Frame Synchronism
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Solution Overview
Problem
Current ISDB-T demodulation methods require detection of synchronous symbols to establish frame synchronism, which necessitates receiving 16 or more symbols, and are prone to degradation due to DBPSK modulation, making it challenging to detect SP symbol patterns efficiently.
Innovation Solution
An SP location detector that multiplies received OFDM signals with a pseudo-random number bit sequence and uses arithmetic circuits to extract pilot symbols, calculate phase differences, and detect the maximum sum, allowing for SP symbol pattern detection without relying on the TMCC signal, thereby reducing the number of symbols needed for detection to one period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If synchronous symbol detection is performed to establish frame synchronism, then frame synchronism is established, but the number of symbols required for detection increases to 16 or more
Solution Approach 1:
The invention extracts and utilizes SP symbols directly from the received OFDM signal for synchronism establishment, separating this function from the traditional TMCC signal-based synchronous symbol detection. By taking out the SP symbol detection function and making it independent, the system can establish frame synchronism using only one symbol period without requiring 16 or more symbols.
Solution Approach 2:
Instead of using synchronous symbols from the TMCC signal to detect SP symbol patterns, the invention inverts the approach by using SP symbol patterns themselves to detect and establish frame synchronism. This reversal eliminates the dependency on DBPSK-modulated TMCC signals and their associated differential demodulation requirements.
2Reliability
If TMCC signal is used for synchronous symbol detection, then frame synchronism is established, but synchronous characteristic degrades due to DBPSK modulation and differential demodulation requirements
Solution Approach 1:
The invention extracts SP symbol pattern information directly from the OFDM signal without relying on the TMCC signal path. By taking out the synchronism establishment function from the DBPSK-modulated TMCC signal and placing it in the QPSK-modulated OFDM signal, the system eliminates the need for differential demodulation and associated complexity while maintaining reliable synchronous characteristics.
Solution Approach 2:
The invention uses SP symbols as an intermediary element that bridges the relationship between frame synchronism establishment and equalization reference. These SP symbols, being QPSK-modulated and dispersed in a known pattern, serve as a reliable mediator that provides both synchronism information and equalization reference without the complications of DBPSK differential demodulation.
3Measurement precision
If SP symbol patterns are detected using traditional methods, then equalization reference is obtained, but the detection process is slow and inefficient
Solution Approach 1:
The invention performs preliminary detection of SP symbol patterns by correlating the received signal with expected SP symbol patterns at specific positions in the OFDM frame. This preliminary action allows the system to quickly identify the correct frame synchronism and SP symbol locations within one symbol period, significantly improving detection speed while maintaining accuracy through the known dispersive pattern of SP symbols.
Data Source
AI summary
A detector of patterns corresponding to pilot symbols is capable of detecting patterns of SP symbols promptly without using a TMCC signal. The SP location detector includes a multiplier which multiplies received signals generated by demodulating OFDM modulation signals in which pilot symbols are dispersively disposed in accordance with four types of patterns and which are transmitted periodically by a pseudo-random number bit sequence, four arithmetic circuits which are respectively provided corresponding to the four types of patterns and which respectively extract pilot symbols corresponding to respective patterns from results of multiplication by the multiplier and calculate sums of phase differences between the extracted pilot symbols, followed by outputting absolute values thereof, and a pattern detection circuit which detects the corresponding arithmetic circuit maximum in the calculated absolute value from within the four arithmetic circuits.