| 3G |
 |
A short term for third-generation wireless, it refers to near-future
developments in personal and business wireless technology, especially
mobile communications.
|
| ANSI |
|
American National Standards Institute
|
| Availability |
|
Link availability is the fraction of time a link
is useable in specific weather encountered in various climates,
assuming no outages due to equipment failure or other system
problem. Availability is typically quoted in nines. For example,
99.9%, or three-nines (3-9's) availability, means, on average,
the link is expected to be not available 0.1% of the time, or
an average of 43 minutes per month. Four-nines (4-9's) availability
translates into only four minutes per month of down-time and
five-nines averages just 30 seconds of downtime per month.
|
| Backbone |
|
The part of the communications network that connects main
nodes, central offices or LANs. When speaking of the Internet,
the backbone refers to the set of paths that local or regional
networks connect to for long-distance interconnection.
|
| Backhaul |
|
In cellular/PCS systems, the transmission links between cell
sites and the system operator's switching center. In general,
transmitting data from remote locations to a point from which
it can be distributed over a network.
|
| Bandwidth |
|
In analog communications, bandwidth referred to the width
of the frequency range allocated for transmission. In
the digital world, it is more common to talk about bandwidth
in terms of the number of bits transmitted per second (bps).
|
| BER |
|
Bit Error Rate. A way to measure data transmission
integrity. The bit error rate (BER) is a ratio of bad
bits to total bits.
|
| Bit |
|
Binary Digit.
A unit of data represented as a one or a zero. Memory or
data transferred per unit of time is measured in bits. Bits
are lowercase (b) when used in abbreviations.
|
| Broadband |
|
The original meaning for broadband was incorporating more
than one channel into a communications transmission. T1
is a broadband communications protocol because it carries 24
conversations over four wires. Cable TV is also broadband because
it carries many TV channels over one coax. Currently, broadband
refers to communications technologies capable of transmitting
over 45 Mbps over any type of media. For example, a 155
Mbps Free Space Optics link would be considered broadband even
though only one channel is being transmitted in either direction.
|
| Byte |
|
Eight bits. Memory storage is measured in bytes. Bytes are
uppercase (B) when used in abbreviations.
|
| Carrier |
|
A telephone or other company that sells or rents telecommunication
transmission services. A local exchange carrier (LEC) is a local
phone company and an inter-exchange carrier (IEC or IXC) carries
long-distance calls.
|
| Cost/bit |
|
The cost to transmit one bit.
|
| Dark Fiber |
|
Dark fiber refers to unlit and therefore unused fiber-optic
cable. Often, companies lay more fiber lines than are needed
at the time, and defer the cost of the associated fiber-optic
components until increased network traffic justifies the extra
investment.
|
| DWDM |
|
Dense Wavelength Division Multiplexing
An optical technology used to increase bandwidth over existing
fiber. DWDM combines and transmits multiple signals simultaneously
at different wavelengths on the same fiber.
|
| EMI |
|
Electromagnetic Interference
Interference caused by a radio signal or other electromagnetic
field. Any device or system that generates an electromagnetic
field in the radio frequency spectrum has the potential to
disrupt the operation of electronic components, devices and
systems in its vicinity.
|
| Ethernet |
|
One of the oldest communication protocols for networking personal
computers, and the most widely-used local area network (LAN)
technology. Generally refers now to 10BASE-T systems, operating
at 10 Mbps.
|
| Fast Ethernet |
|
Fast Ethernet is a local area network (LAN) transmission standard
that provides a data rate of 100 megabits per second (referred
to as "100BASE-T").
|
| FDDI |
|
Fiber-Distributed Data Interface
A set of ANSI protocols for sending digital data over fiber
optic cable. Typically used as a LAN backbone protocol.
|
| Fixed Wireless |
|
The operation of wireless devices or systems in fixed locations
such as homes and offices.
|
| FSO |
|
Free Space Optics (FSO), also called Free Space Photonics
(FSP) or Optical Wireless, refers to the transmission of modulated
visible or infrared (IR) beams through the atmosphere to obtain
broadband communications. FSO systems can function over distances
of several kilometers. As long as there is a clear line of sight
between the source and the destination, communication is theoretically
possible, given enough power.
|
| Giga |
|
(G) Engineering notation for one billion.
|
| Gigabit |
|
One billion bits. In data communications, a gigabit
is one billion bits. Commonly used for measuring the amount
of data that is transferred in a second between two telecommunication
points.
|
| Gigabit Ethernet |
|
A transmission technology based on the Ethernet frame format
and protocol used in local area networks (LANs), provides a
data rate of 1 billion bits per second (one Gigabit). Gigabit
Ethernet is carried primarily on optical fiber (with very short
distances possible on copper media).
|
| Gigabyte |
|
One billion bytes
|
| GPS |
|
Global Positioning System.
A system of low Earth orbiting satellites used to measure location
on the ground or in the air. A GPS receiver contains a computer
that "triangulates" its own position by measuring its distance
from at least three of the 24 GPS satellites. The result is
the longitude and latitude of the receiver, accurate to within
about 10 meters for most receivers.
|
| HFC |
|
Hybrid Fiber Coax
When the cable companies wanted to start providing services
that required more bandwidth than their coaxial cable networks
could handle, they laid fiber and the resulting networks were
referred to as HFC.
|
| Mbps |
|
Megabits per second
Mbps stands for millions of bits per second or megabits per
second and is a measure of bandwidth (the total information
flow per unit time) in a telecommunications medium.
|
| OC-x |
|
Short for Optical Carrier; a prefix for SONET carrier hierarchies,
which is followed by a number. See table below for
specific speeds:
| OC |
bps |
| OC-1 |
51.84 Mbps |
| OC-3 |
155.52 Mbps |
| OC-12 |
622.08 Mbps |
| OC-24 |
1.244 Gbps |
| OC-48 |
2.488 Gbps |
|
| Optical Wireless |
|
Free Space Optics (FSO), also called Free Space Photonics
(FSP) or Optical Wireless, refers to the transmission of modulated
visible or infrared (IR) beams through the atmosphere to carry
broadband communications. FSO systems can function over distances
of several kilometers. As long as there is a clear line of sight
between the source and the destination, communication is theoretically
possible, given enough power.
|
| OSI |
|
Open Systems Interconnect
The OSI model for communications protocols is a global ISO
standard for communications that contains protocols in seven
layers. Control is passed from one layer to the next, starting
at one end, proceeding through the layers to the other and
back again. The following chart names the layers and their
functions:
| Layer 7 |
Application Layer |
Connects an application or program to a communications
protocol |
| Layer 6 |
Presentation Layer |
Encodes and decodes the data to be transmitted |
| Layer 5 |
Session Layer |
Establishes and maintains connection to the communications
processes in the lower layers |
| Layer 4 |
Transport Layer |
Responsible for error correction and direction of flow
(transmit/receive) |
| Layer 3 |
Network Layer |
Switching and routing layer |
| Layer 2 |
Data-link Layer |
Receives and transmits data over the physical layer
|
| Layer 1 |
Physical Layer |
The transmission medium itself (twisted pair, fiber
optic, free-space optics, etc.) |
|
| Protocol |
|
A set of processes and rules that communications equipment
use to transfer bits and bytes(data).
|
| Reliability |
|
Refers to the expected failure rate of the equipment.
|
| Router |
|
On the Internet, a router is a device or, in some cases, software
in a computer, that determines the next network point to which
a packet should be forwarded toward its destination.
|
| SDH |
|
Synchronous Digital Hierarchy
Standardized by the ITU, SDH is a family of digital carrier
rates. SDH is the term used by the ITU to refer to SONET OC
rates, as they are called in the United States. The basic
SDH building block is a rate of 155.52 Mbps, called STM-1.
|
| SNMP |
|
Simple Network Management Protocol
An IETF-defined standard for network management across network
management systems and network components. Another definition
is: Protocol that governs network management and monitoring
of network devices and their functions.
|
| SONET |
|
Synchronous Optical Network
Proposed by Bellcore in the ‘80s, SONET has become an ANSI
(American National Standards Institute) standard as well as
an ITU international standard named SDH that defines interface
standards at the physical layer 1 level. It allows data
streams of differing rates to be multiplexed. It is generally
implemented over fiber optic cable and is often configured
in a ring allowing it to reroute traffic with no interruption
of service, should a cable be cut.
|
| STM |
|
Synchronous Transfer Mode
|
| STS |
|
Synchronous Transport Signals; the electrical version
of OC (Optical Carrier)
|
| Telco |
|
Abbreviation for telephone company
|
| Transceiver |
|
A combination transmitter/receiver in the same device
|
| WDM |
|
Wavelength Division Multiplexing
Multiplexing technology developed for use on optical fiber.
WDM modulates each of several data streams onto a different
part of the light spectrum. |
