SNR MER Measurement via Known Training Sequence
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Solution Overview
Problem
Current methods for assessing data link quality in video and audio transmission systems, such as the DVB standard, are limited in their ability to measure bit error rate (BER) outside a narrow range around the Quasi-Error Free (QEF) point, requiring alternative metrics like Signal to Noise Ratio (SNR) or Modulation Error Ratio (MER), which are challenging to calculate due to separating signal and noise energy, especially at higher modulation modes and when the demodulator is unlocked.
Innovation Solution
A method that inserts a sequence of 8 known phase change symbols into the data stream, allowing for SNR/MER measurement regardless of modulation mode or symbol rate, using a pseudo-random generator and measurement packet insertion synchronized with sync inversions, enabling accurate link quality assessment across a wide range without impacting data throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If BER measurement is used around QEF point, then link quality assessment is accurate, but measurement range is limited to narrow range around QEF
Solution Approach 1:
The patent introduces a known training sequence (intermediary signal) as a mediator between the transmitted signal and the measurement process. This training sequence contains known symbols that allow the receiver to calculate expected values and compare them with received values, enabling SNR/MER measurements across a wide range without being limited to the narrow QEF range where BER measurements are valid.
2Adaptability or versatility
If SNR or MER is calculated from demodulated signals, then measurement range is extended, but separating signal energy from noise energy is challenging
Solution Approach 1:
The patent applies preliminary action by pre-processing the received signal through synchronization and correlation with the known training sequence before SNR/MER calculation. This preliminary step isolates the signal component from noise, making the subsequent energy separation and measurement straightforward without requiring complex computational methods.
3Measurement precision
If long time average method is used to separate signal from noise, then SNR/MER can be calculated, but computational demand increases with higher modulation modes
Solution Approach 1:
The patent extracts the signal component from the received signal by correlating with the known training sequence before calculating SNR/MER. This extraction approach separates the signal energy from noise energy efficiently, avoiding the need for computationally intensive long-time averaging methods while maintaining measurement accuracy across all modulation modes.
4Reliability
If measurement sequence is inserted into data stream, then continuous link quality monitoring is enabled, but data throughput is impacted
Solution Approach 1:
The patent implements periodic action by inserting measurement sequences at regular intervals (e.g., once per second or at defined packet boundaries) rather than continuously. This periodic insertion enables continuous link quality monitoring capability while minimizing the impact on data throughput, as the measurement overhead is limited to specific time slots rather than affecting the entire data stream.
Data Source
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AI summary
The invention relates to a method and system for use in assessing the quality and integrity of a data transmission path or link between a data transmitting location and at least one receiving location at which a broadcast data receiver is located with means to allow an error rate calculation to be made with respect to a known data signal sequence which is inserted into the transmitted signal. On the basis of the calculations made and sent to the transmitting location a particular data modulation scheme is adopted to provide the most efficient data transmission method for each receiving location. The invention is of particular use in cable data transmission networks of the type which for example allow television channels and other services to be provided to a plurality of receiving locations.