User guide

Appendix I - Glossary I-3
DRAM Dynamic Random Access Memory
DSCP Differentiated Services Code Point – The 6-bit field in an IP packet header that
is used for packet classification purposes and is the portion of ToS that is
detected by Vipersat modems.
DSP Digital Signal Processor – A microprocessor chip optimized for signal process-
ing applications.
DVB Digital Video Broadcast
DVP Digital Voice Processor – Used in packet voice applications.
E
E
b
/N
o
E
b
/N
o
is the ratio of E
b
(energy per bit) and N
o
(noise power density per Hz).
The bit error rate (BER) for digital data is a decreasing function of this ratio. E
b
is the energy of an information bit measured in Joules or, equivalently, in Watts
per Hertz.
F
FAST Code Fully Accessible System Topology Code – Designation for feature code used
by Comtech EF Data for their satellite modems. The FAST method makes it
easy to quickly upgrade the feature options of a modem while it is running live
in the network, either on site or remotely.
FDMA Frequency Division Multiple Access – A technique where multiple users can
access a common resource (e.g., satellite) by each being allocated a distinct
frequency for operation. See also TDMA.
FEC Forward Error Correction – A process whereby data being transmitted over a
communications link can have error correction bits added which may be used at
the receiving end to determine/correct any transmission errors which may occur.
FIFO First In First Out – A simple buffer or queue technique whereby data queued
the longest is transmitted first.
FTP File Transfer Protocol – An application for transferring computer files over the
Internet. See also TFTP.