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ArcLight Hub User’s Guide
Rev. 001 1081006 xxiii
PN Pseudorandom number A number generated by a process that
appears random, but is not.
Pseudorandom sequences typically exhibit
statistical randomness while being
generated by an entirely deterministic
causal process.
Policy Router A Cisco 3600 computer An ArcLight system router that runs Cisco
IOS software.
PWM Pulse width modulation Pulse-width modulation of a signal or
power source involves the modulation of
its duty cycle, to either convey information
over a communications channel or control
the amount of power sent to a load.
QPSK Quadrature phase shift keying A digital modulation scheme that conveys
data by changing, or modulating, the
phase of a reference signal (the carrier
wave).
RF Radio frequency That portion of the electromagnetic
spectrum in which electromagnetic waves
can be generated by alternating current
fed to an antenna.
RtNMS
Real-time network management The Real-time server communicates
System with the NRTS to receive data about the
VMTs in the network, and with the VMTs
(using the FLM and Forward Link) to
adjust their transmit power and
frequency, based on information it
receives from the MCD.
SCPS
Space communications protocol A set of extension to existing protocols
Standard and new protocols developed by the
Consultative Committee for Space Data
Systems (CCSDS) to improve performance
of Internet protocols in space
environments.
SGW
Satellite gateway A ViaSat Mobile Broadband Router in a
VMT.
SNMP
Simple network management An Application Layer protocol that is used
Protocol by network management systems for
monitoring network-attached devices for
conditions that warrant administrative
attention.
SNR
Signal-to-noise ratio The ratio of a given transmitted signal to
the background noise of the transmission
medium.