Comtech EF Data Vipersat CDM-570 User Manual page 187

PSTN
Public Switched Telephone Network – The world's public circuit-switched
telephone network, digital and analog, and includes mobile as well as land-line
voice and data communications.
PUM
Periodic Update Message – A packet message that is sent by newer Vipersat
modems (e.g., CDM-840) to the VMS every sixty seconds, providing either
registration request or status update and operating parameter information
(SUM).
Q
QAM
Quadrature Amplitude Modulation – A digital modulation technique in which
the amplitude of two carrier waves is changed to represent the data signal. These
two waves are 90 degrees out of phase with each other.
QoS
Quality of Service
QPSK Quadrature Phase Shift Keying – Sometimes referred to as 4-PSK, or 4-QAM.
A modulation technique in which the carrier is phase shifted +/-90 or +/-180
degrees. With four phases, this modulation can encode two bits per
symbol—twice the rate of BPSK. However, it also uses twice the power. See
also OQPSK and BPSK.
R
Remote Satellite earth site that links to a central network site (Hub).
Return Path
Transmission path from a Remote site to the Hub site.
RF Radio Frequency – A generic term for signals at frequencies above those used
for baseband or IF.
RFC Request For Comment – The official publication channel for Internet standards
(such as communication protocols) issued by the Internet Engineering Task
Force (IETF).
RIP Routing Information Protocol
ROSS Roaming Oceanic Satellite Server – A satellite mobility controller that is a key
component in the CEFD SOTM technology solution for marine vessels.
Provides for transition of link communications between roaming remote termi-
nal and satellite or Hub with minimal service interruption.
A p p e n d i x E - G l o s s a r y E-9