What is the minimum Mer in dB at which a 256-QAM signal should operate at the headend?
When measuring MER, ensure that the CNR at the point of measurement meets or exceeds the SCTE-40 and/or DOCSIS stated minimum values. In the downstream, the SCTE-40 minimum CNR is 27 dB for 64- QAM and 33 dB for 256-QAM. The DOCSIS assumed downstream minimum CNR is 35 dB for both constellations.
What is Mer in cable signal?
From Wikipedia, the free encyclopedia. The modulation error ratio or MER is a measure used to quantify the performance of a digital radio (or digital TV) transmitter or receiver in a communications system using digital modulation (such as QAM).
What is MER measurement?
The MER Measurement block outputs the modulation error ratio (MER). MER is a measure of the signal-to-noise ratio (SNR) in digital modulation applications. The block measures all outputs in dB. The MER Measurement block accepts a received signal at input port Rcv .
Can cable signal be too strong for modem?
Many modems are even rated to +/- 15 dBmV. Too low means your signal is weak, and too high means the signal is strong – possibly too strong (and will need to be corrected with an attenuator or splitter). Upstream power levels should be between 40 – 50 dBmV.
What is a good MER level?
Good engineering practice suggests that operational MER be 3 to 6 decibels (dB) or more above the MER failure threshold for the modulation type in use. These values are all a few dB above the respective failure thresholds, but the higher the better.
What causes low Mer?
Some problems like transmitter and receiver phase noise, incorrect modulation profiles and even data collisions can certainly contribute to low reported MER, but the most common causes typically are the things that should be done correctly in the first place.
What causes bad Mer in cable?
Micro-reflections, which come from impedance mismatches, and the resulting amplitude and group delay ripple, mess up digital signals by causing inter-symbol interference and degraded MER. Amplitude tilt is often related to active device misalignment, and also can cause inter-symbol interference and degraded MER.
How is Mer expressed?
The MER is expressed as a percentage of the average dollar amount of a fund investment. For example if an investor holds assets of $10,000 and the fund incurs annual costs of $78, the MER is 0.78%.
What is QAM signal?
Key Takeaway: QAM (quadrature amplitude modulation) is a modulation scheme used by network operators when transmitting data. QAM relates to a way of changing the amplitude, or power level, of two signals. QAM enables an analog signal to efficiently transmit digital information and increases the useable bandwidth.
How do you know your modem is bad?
5 Warning Signs Your Cable Modem is Dying
- Connection indicator lights have turned off even if you can still surf the web.
- Data transfers/downloads are slow.
- The connection speeds are slow.
- The modem is making a lot of loud or weird noises.
- The modem turns off or stops functioning.
What is the difference between 16 QAM and 256 QAM?
In 256-QAM, each symbol is represented by 8 bits. As the level increases, QAM technique becomes more bandwidth efficient but it requires very robust algorithms in order to decode complex symbols to bits at receiver. For example 256-QAM is complex than 16-QAM.
What is 256 QAM modulation used for?
In the US, 64 QAM and 256 QAM are the mandated modulation schemes for digital cable as standardised by the SCTE in the standard ANSI/SCTE 07 2000. In addition to this, variants of QAM are also used for many wireless and cellular technology applications.
What are the 64 QAM bits per symbol?
The 64 qam bits per symbol are 6 (six). In 64-QAM, each symbol is represented by 6 bits as shown in the 64-QAM constellation diagram above. In 256-QAM, each symbol is represented by 8 bits. As the level increases, QAM technique becomes more bandwidth efficient but it requires very robust algorithms in order…
What are the different QAM formats?
QAM Formats: 8-QAM, 16-QAM, 32-QAM, 64-QAM, 128-QAM, 256-QAM Quadrature amplitude modulation can be used with a variety of different formats: 8QAM, 16QAM, 64QAM, 128QAM, 256QAM, but there are performance differences and trade-offs Quadrature Amplitude Modulation, QAM Tutorial Includes:
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