NV-600WI Managed Industrial Grade Wireless VDSL2 Router USER’S MANUAL Ver. A2
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5. Question:
What is SNR (Signal-to-Noise)? (Only reference)
Answer:
Signal-to-noise ratio (often abbreviated SNR or S/N) is a measure used in science and engineering
that compares the level of a desired signal to the level of background noise. It is defined as the ratio
of signal power to the noise power. A ratio higher than 1:1 indicates more signal than noise. While
SNR is commonly quoted for electrical signals, it can be applied to any form of signal (such as
isotope levels in an ice core or biochemical signaling between cells). The ratio is usually measured
in decibels(dB)
The signal-to-noise ratio, the bandwidth, and the channel capacity of a communication channel are
connected by the Shannon–Hartley theorem.
In digital communications, the SNR will probably cause a reduction in data speed because of
frequent errors that require the source (transmitting) computer or terminal to resend some packets of
data. SNR measures the quality of a transmission channel over a network channel. The greater the
ratio, the easier it is to identify and subsequently isolate and eliminate the source of noise.
6. Symptom:
Connected the CO Router with CPE Router within 300 meters RJ-11 phone cable got only less than
10 Mbit/s.
Cause:
Some testing programs which are based on TCP/IP protocols such as FTP, Iperf, NetIQ, the testing
bandwidth outcome will be limited by TCP window size.
Solution:
We recommend testing VDSL2 bandwidth using Smartbits® equipment or IPERF program. The
TCP window size must be set to max. 64k, the parameter as iperf –c server IP address –i 1 –t 50 –w
65535 for client side.
