VC-400RT
+
Managed VDSL2 CPE Router MANUAL Ver. A5
108
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 program which is base on TCP/IP protocol such as FTP, Iperf, NetIQ, the
bandwidth of testing outcome will be limited by TCP window size.
Solution:
We recommend to test VDSL2 bandwidth best by Smartbit equipment, if you don't have
Smartbit, we recommend test that by IPERF program, and TCP window size must be
settled max. 64k, the parameter as iperf –c server IP address –i 1 –t 50 –w 65535 for
client side.
7. Question:
I just bought a RubyTech VC-400RT+ to replace my Quest DSL modem for my home. I
was told any VDSL2 modem would replace and give me higher communication speeds. It
doesn’t get me internet when hooked up. All lights come on but no Link light. Is this the
complete wrong application for this unit?
Answer:
Re: Please note VC-400RT+ is a remote side(CPE side), it must be connected to the
CO side to work. Tone mode, Band profile and band plan setting must be compatible to
each other if not access error will show when applied. Please deactivate and activate
once the setting has been changed.