Adaptive Modulation Channel Estimation for Fast SNR Tracking
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Solution Overview
Problem
Existing adaptive modulation systems require a long time period to obtain a reliable estimator of Signal to Noise Ratio (SNR) and are slow to react to fast variations in radio channels due to the use of receiver information after error correction, which affects their ability to adapt to changing channel conditions.
Innovation Solution
A method and device for adaptive modulation systems that measure and utilize both pre-FEC decoding and post-FEC decoding error information, including Mean Squared Error (MSE) and temporal averages of errors, to quickly adjust transmission modes based on channel conditions, using a weighted combination of these error metrics for faster channel condition detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If post-FEC decoding error information (BER) is used for channel estimation, then the reliability of the estimator is improved, but the response time to channel variations becomes too slow
Solution Approach 1:
The patent segments the error information measurement into two distinct parts: pre-FEC decoding error information (first error information) and post-FEC decoding error information (second error information). By measuring both segments and combining them, the system achieves both fast response (from pre-FEC measurements) and reliable estimation (from post-FEC measurements), resolving the contradiction between speed and reliability.
2Measurement precision
If a long time period is used to obtain a reliable SNR estimator, then the measurement precision is improved, but the adaptability to fast channel variations deteriorates
Solution Approach 1:
The patent performs preliminary measurement of pre-FEC decoding error information before the complete FEC decoding process finishes. This preliminary action provides an early indication of channel conditions, enabling the system to respond quickly to channel variations while still obtaining the final reliable post-FEC error information for precise estimation.
3Measurement precision
If only post-error correction BER measurements are used, then the accuracy of channel condition detection is improved, but the system complexity increases due to additional shift margins
Solution Approach 1:
The patent uses pre-FEC decoding error information to provide early channel condition detection, which reduces the need for additional shift margins that would otherwise be required to prevent bit errors during modulation shifts. The pre-FEC error information serves the system by providing timely channel quality indication, reducing the complexity of modulation control.
Data Source
AI summary
A device (20) for an adaptive modulation communication system is provided. The device (20) comprises an input device (21) adapted to receive, from a communication channel, data encoded through a FEC code. A FEC decoder (23) connected downstream of the input device (21) is also provided for FEC decoding the received encoded data and providing error information determined by the FEC decoding. The device according to the invention further comprises means for measuring first error information of the encoded data before FEC decoding the received encoded data, and means for measuring second error information determined by the FEC decoder (23). Means (25) for estimating a condition of the communication channel based on both the first error information and the second error information are also provided.