Motorola SURFBOARD SVG2500 - Manual (Page 169)

17 GLOSSARY
154
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.