User Guide: Technical Reference APPENDIX B GLOSSARY OF TERMS
PRELIMINARY
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B-3
Channel Service Unit/Data
Service Unit (CSU/DSU)
Manages digital transmission and monitors signals for problems. Performs many
functions similar to a modem with the exception of converting digital signals to/from
analog since the end device and transmission facility are both digital.
Common Management
Information Protocol
(CMIP)
A network management protocol that is consistent with an Open Systems
Interconnection (OSI) network communication model.
Coaxial cable
A type of transmission line consisting of a center conductor wire surrounded by
insulation which is in turn surrounded by a conductive shield made of metal foil or
wire braid. Often used to connect the RF unit and modem unit of a wireless
system.
Code Division Multiple
Access (CDMA)
A system in which all users occupy the same bandwidth. Uncorrelated codes are
used to allow for higher bandwidth occupancy. Also known as spread spectrum
systems.
Customer Premise
Equipment (CPE)
Any equipment which is located at the customer site. Usually in reference to those
that are connected to a network.
D
dBm
dB relative to 1 milliwatt.
dBw
dB relative to 1 watt.
Decibel (dB)
The standard unit of measurement for expressing relative signal power. It is
dimensionless and is instead referenced to a certain level.
Diffraction
The distortion of a wave as it is partially obstructed by an object in its path.
Digital Transmission
The transmission of data over a communications medium using a dual-state
(binary) mechanism to represent information.
Direct Sequence (DS)
A type of spreading technique that multiplies a higher rate PN code to the signal in
order to spread the energy of the narrow band signal over a much wider bandwidth
for transmission.
Direct Sequence Speed
Spectrum (DSSS)
DSSS may be seen as the result of two processes:
•
Data is multiplied with a higher rate digital sequence (spreading code). The
sequence has many “chips” for every data bit.
•
The resultant signal modulates the RF carrier.
DQPSK
Differential Quadrature Phase Shift Keying.
DS-0
The base unit of digital capacity equivalent to a single 64 Kbps voice-grade
communication channel.
DS-1
The equivalent of 24 multiplexed DS-0 channels. T1 or 1.544 Mbps.
