Motorola SVG2500 manual Term Definition QAM, Qpsk, Term Definition RAS, Rfc

17 GLOSSARY

Q

TERM	DEFINITION
QAM	Quadrature Amplitude Modulation uses amplitude and phase
	modulation to encode multiple bits of data in one signaling
	element. QAM achieves faster data transfer than amplitude or
	phase modulation alone, but the signal is more prone to errors
	caused by noise. QAM requires a transmission circuit with a
	higher CNR than alternate modulation formats such as QPSK. Two
	types of QAM are:
	• 16 QAM, which encodes four bits per symbol as one of 16
	possible amplitude and phase combinations.
	• 64 QAM, which encodes six bits per symbol as one of 64
	possible amplitude and phase combinations.
QPSK	Quadrature Phase Shift Keying is a phase modulation algorithm.
	Phase modulation is a version of frequency modulation where the
	phase of the carrier wave is modulated to encode bits of digital
	information in each phase change.
QoS	Quality of service describes the priority, delay, throughput, and
	bandwidth of a connection.

R

TERM	DEFINITION
RAS	Remote Access Server
registration	How a cable modem makes itself known to the CMTS. The
	cable modem configuration file and authorization are verified and
	the CoS is negotiated.
return loss	A measurement of the quality of the match of the device to the
	cable system. Return loss is the ratio of the amount of power
	reflected by the device. A return loss of 20 dB or greater is
	preferred.
RF	Radio Frequency — signals used by the CMTS transmitter and
	receiver to send data over HFC. The carrier is modulated to
	encode the digital data stream for transmission across the cable
	network.
RFC	Request for Comments published on the IETF or other
	websites. Many RFCs become international standards.
RJ-11	The most common type of connector for household or office
	phones.
RJ-45	An 8-pin modular connector; the most common connector type
	for 10Base-T or 100Base-T Ethernet networks.
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