For reliable operation, what should be the minimum modulation error ratio (MER) higher than the loss of reception threshold for QAM channels?

The minimum modulation error ratio (MER) required for reliable operation in QAM (Quadrature Amplitude Modulation) channels is a critical metric that relates to the quality and stability of the signal being transmitted. A MER that is higher than the loss of reception threshold ensures that the signal can be accurately demodulated, reducing the likelihood of errors in data transmission.

Choosing a MER of 4 decibels above the loss of reception threshold strikes a balance between ensuring a robust signal and avoiding unnecessary overhead in bandwidth or power. With this level of MER, the system typically has enough margin to handle variations in signal quality due to noise or other interference without compromising the integrity of the received data.

An MER of 4 dB is widely recognized in the industry as a threshold that allows for consistent performance, ensuring that any fluctuations in the transmission environment can be accommodated. This standard is often based on empirical testing and practical experience, demonstrating that this level provides adequate protection against common signal degradation factors.

Higher values, while providing increased robustness, may not be necessary for reliable reception in most practical applications, thus making 4 dB the optimum choice for general operations.