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Helpful I.T. Terms:
2Wire Home Portal: 2Wire's comprehensive router, which acts as a
portal to your home network.
2Wire PC Port: PC Port Phone line USB Adapter, used in conjunction
with 2Wire Home Portal to provide home networking.
4 miniDIN Female: Used as the keyboard and mouse port on Macintosh
computers.
- A -
AC adapter: Electrical Power adapter that converts AC Power and into
DC power. This type of power adapter is frequently used on a laptop
computer when it is not running off its internal battery.
Application: A software program or program package that makes calls
to the operating system and manipulates data and/or files, thus allowing a
user to perform a specific job (such as accounting or word processing).
ASCII: American Standard Code for Information Interchange is a data
transmission method in which each character is represented by a distinct
eight-bit code (example: A=65, B=66, C=67, etc.). Some ASCII characters are
not "printable" characters and are used to control communications
between devices and/or computers.
- B -
Bandwidth: Carrying capacity of a circuit, usually measured in bits
per second for digital circuits, hertz (cycles) for analog circuits.
Binary: Numbering system using only zeros and ones that all digital
computers are based on.
BIOS (Basic Input/Output System): Contains the basic instructions
for the PC to handle devices.
Bit: A unit of data representing either a one or a zero. Combined,
eight bits make up a byte, which is the common unit of measure for storage
in a computer.
Broadband: Characteristic of any network that multiplexes multiple,
independent network carriers on a single cable. Traffic from one network
does not interfere with traffic from another network because they
communicate on different frequencies (similar to TV channels and radio
stations).
Buffer: A temporary holding place for data while it is being
transferred between two or more devices and/or computers.
Byte: Eight bits of data. The byte is the most common unit of
measure for storage in a computer system. Each character (see ASCII) takes
up one byte of storage. Mass storage is usually measured by powers of two
in KB (KiloBytes, 1KB = 1,024 bytes), MB (MegaBytes, 1MB = 1,048,576
bytes), GB (GigaBytes, 1GB = 1,073,741,824 bytes), TB (TeraBytes, 1TB =
1,099,511,627,776 bytes). These mass storage amounts are typically rounded
to thousands.
- C -
Cache: High-speed memory that holds blocks of data being worked on,
designed to minimize the amount of time that is used to access data from a
slower device. CPUs use cache to minimize the time spent accessing the much
slower RAM. Hard disks use cache memory to minimize the time that it takes
to access frequently used (and much slower) hard-disk data.
CD-R: CD-R stands for Compact Disk Recordable. CD-Rs allow you to
record onto compact disks (CD-R type).
CD-ROM: Optical storage medium used to hold up to 800MB of data.
CD-RW: CD-RW stands for Compact Disk ReWritable. CD-RWs allow you to
record onto and overwrite compact disks (CD-RW type).
Character: Group of eight bits operated on as a unit. Also called a
byte or octet.
Circuit: Any path that can carry an electrical current.
CMOS (Complementary Metal Oxide Semiconductor): Commonly refers to
the chip that is the official record of components installed. CMOS is a
type of low-power usage memory that retains data when the power is turned
off, as long as the battery supplying electricity is connected and charged.
Compression: Method of compacting data into a smaller number of bits
for more efficient transmission or storage.
CPU (Central Processing Unit): The chip at the heart of every PC.
This is where all calculations are performed.
CRT: Cathode Ray Tube is the standard technology for computer
monitors. A CRT fires three scanning beams of electrons (red, green and
blue) at the front of the glass screen, which is covered with a phosphorus
compound, causing it to light text and images.
- D -
Decryption: Unscrambling encrypted data. Requires a "key"
or "code" to unlock the data and present it in a readable form.
Dial-up: Dial-up connections are used by traditional modems to
connect your computer to other computers or the download speeds up to
56Kbps (56,000 bits per second), and upload speeds up to 33Kbps.
Download: Downloading is the process where files are transferred to
your computer from a host computer (typically over the Internet).
Driver (Device Driver): A block of code tailored to control a
specific hardware peripheral (i.e. video card, sound card).
DSL: Digital Subscriber Lines are used for high-speed (up to 1.2Mbit
per second) Internet connections. DSL lines are typically two to over 20
times faster than conventional dial-up connections.
DVD: DVDs are similar to compact discs, with the exception that they
are double-sided, unlike traditional CDs. They also store data at a much
higher density.
- E -
Encryption: Scrambling data into a format that is undecipherable to
anyone who does not possess the decryption key.
- F -
Floppy: Typically a 3.5" micro diskette with 1.44MB storage
capacity.
FTP: File Transfer Protocol is typically used to move files between
computers over the Internet.
- H -
Hard disk: Nonvolatile storage for programs and data.
Home network: A group or network of computers within your home that
share devices (printers) or documents (disk drives). These may be connected
by a physical wire (phone line) or by a wireless network.
Home portal: 2Wire's comprehensive router, which acts as a portal to
your home network.
HPNA: Home Portal Network Adaptor, also known as a 2Wire PC Port.
The HPNA, in combination with 2Wires family of HomePortal residential
gateways, represents a complete solution for high-speed Internet sharing.
Using the PC Port with a 2Wire HomePortal allows you to share Internet
access throughout your home via your phone line.
HTTP: HyperText Transfer Protocol is the most common way information
is transferred and displayed over the Internet.
- I -
Install: Installing is a means of adding something to your computer.
Installation is the process you must take to move a program from its host
(usually a CD or floppy disk) to your computer.
Internet: Often referred to as the "World Wide Web," the
internet connects millions of computers together, allowing you to chat with
fellow users, download software, do research, read news and entertainment
and more.
ISP: Internet Service Providers allow you the link to access the
Internet through dial-up, DSL, cable or satellite connections.
- J -
Joystick: Joysticks are typically used as interfaces that allow you
to interact with games more effectively than with a keyboard (flying,
moving, aiming, etc.).
- K -
Kernel: The core of an operating system that is responsible for
managing system resources.
Keyboard: A keyboard is what you use to type information. It is
similar to the typewriter. Shortkeys on your keyboard help to speed you
through programs and your operating system with tremendous ease. Standard
keyboards have 104 keys. Some keyboards come with added features and
buttons, and many are designed ergonomically for comfort.
- L -
LAN: A local-area network is a system that links computers together
to form a network, usually with a wire-based cabling scheme. LANs connect
personal computers and electronic office equipment, enabling users to
communicate, share resources such as data storage and printers, and access
remote hosts or other networks.
Laptop computer: A portable personal computer also referred to as a
notebook computer. Usually is easily able to be used on your lap and does
not require an electrical connection.
LCD: Liquid Crystal Display uses a high-density matrix of small
squares in a very thin layer to display information. It is usually the
monitor for a laptop.
- M -
MBps, or Megabits (Million Bits) per second: A measurement of data
transfer rate measuring how fast the data can move in one second. For
example, 12 Mbps would be a transfer rate of 12 million bits in each
second.
Modem: The sole purpose of a modem (Modulator/demodulator) is to
connect your computer to the outside world. A modem is hooked up through
your phone line and is capable of dialing another computer, connecting to
the Internet or making phone calls. A modem is a bridge between digital
(computer type) and analog (phone type) signals. More advanced modems are
used for DSL, cable and satellite connections. Modems may be internal
(inside the computer) or external.
Monitor: Monitors look like small TV screens, although monitors
typically are of much higher resolution, and provide a viewing space. Some
monitors (such as in laptops) are based on LCD displays instead of using a
CRT.
Motherboard: Main system board. Typically contains slots for
peripheral devices, CPU, RAM, video.
- N -
Nonvolatile: Storage (hard disk, CD-ROM, tape, floppy, etc.) that
does not change when the power is turned off, unlike volatile storage,
which is erased when the power is off.
Notebook computer: See "laptop computer."
- O -
Operating system: Your operating system is the overall program that
your machine uses to function, catalog information and connect you to
programs, fonts, and system resources.
- P -
PCI: Peripheral Component Interconnects give you high-speed
connections between your CPU and its devices. PCI slots can be 32 or 64
bits wide and can transfer data up to 133MB per second.
Portal: An entry point. With a home network this is the connecting
point for all related hardware. On the World Wide Web (WWW) this often
refers to search programs.
Printer: Printers are used to transfer information (text, graphics,
etc.) from within your computer to paper, transparencies, slides, etc.
Processor: See "CPU."
Protocol: The set of rules that allow computers to connect with one
another, specifying the format, timing, sequencing and error checking for
data transmission.
- Q -
Query: The process of extracting data from a database and presenting
it for use.
Queue: A line or list formed by items waiting for service, such as
documents waiting to be printed, tasks waiting to be performed, stations
waiting for connection or messages waiting for transmission.
- R -
RAM (Random Access Memory): The temporary scratchpad area used by
the CPU to perform calculations.
Router: A device that forwards/routes data flow between and within a
network.
- S -
Scanner: A device used to take a "picture" of a document
or photo and convert it to a graphic image file inside your computer.
SCSI: Small Computer Systems Interface is a means to connect
components to your computer. Often called "scuzzy", these are
ports that allow you to add internal devices (hard disks, CD-ROMs, etc.)
and external devices (scanners, printers, etc.).
Serial port: Serial ports are used for nondemanding communications
between your computer and other external devices (example: modems,
printers, digital cameras, etc.). Serial ports operate at speeds up to
115Kbps (115,000 bits per second).
Software: Software is a portable medium that you can install on your
machine. Software is transported by floppy disk, compact disk and is
downloadable from the Internet. Once installed, the program will typically
run independently of the disk or CD.
Sound card: Sound cards allow you to hear sounds associated with
programs and play music (CDs, MP3s, MIDI files). Typically, sound cards
also allow you to record music and plug in game devices (example:
joysticks).
Storage: Storage is where computers keep your files and data.
Storage is usually classified as volatile (example: memory or RAM) or more
typically nonvolatile (example: hard disk).
Surge protection: The process to reduce voltage surges that may
occur as a result of lighting or a power supply surge which can produce
more than twice the voltage normally expected from the power source.
Surge protector: A device between your computer and the power source
which controls power surges.
- T -
Tape: Sequential mass storage device.
Trojan horse: A computer program that carries within itself a means
to allow the programs creator access to the system using it. A Trojan
normally will not do any damage by itself.
- U -
Upload: Uploading is the process where files are transferred from
your computer to a host computer (typically over the Internet.
URL: Universal Resource Locators are the addresses you use to find
sites on the Internet. A URL typically is made up of the protocol (example:
http, ftp, etc.), a prefix (example: www, support, etc.), and a domain name
(example: yahoo.com). Some URLs also contain page names and other
parameters after the domain name (example: index.htm).
USB: Universal Serial Bus ports are similar to standard serial ports,
except that they are faster and take up less memory to operate. It is a
standard bus type for all kinds of devices including mice, scanners,
digital cameras, printers, and others. It supports 12 Mbps transfer rate.
It is also a "Hot swappable" device, which can be connected and
disconnected while computer is on.
- V -
Video: Source of video signal for the monitor, may be an add-on
board, or built right into the motherboard.
Virus: A program that, when loaded, infects, alters or destroys
other programs and/or data. Some virus programs cause major problems, while
others are nothing more than an annoyance.
Volatile: Storage (cache, RAM, etc.) that is erased when the power
is turned off.
- W -
WAP: Wireless Access Point is a device that allows the connection of
laptop and other computers on a network over radio waves.
Wireless networking: A computer network connected by radio instead
of a physical connection.
Worm: A computer program that replicates itself and is
self-propagating. Worms, as opposed to viruses, are meant to spawn in
network environments. Worms are usually designed to slow down a network, or
even crash it.
- Y -
Y-adapter: Connecting plug to connect two network or telephone wires
to one wire.
- Z -
Zip drive: A Zip® drive (by Iomega) is a removable media that stores
data (similar to a floppy disk). As of this printing, Zip drives come in
100MB and 250MB capacities.
Zip file: A Zip file contains one or more files in a highly
compressed format. An "unzip" program (example: WINZIP®) is
required to use the file(s) that the zip file contains.
Wireless Glossary
Mobile Glossary
1xEV D0
CDMA 1x Evolution (Data Only)
An evolution of CDMA2000, this "data optimized" version is also
an approved 3G standard. 1xEV-DO provides peak data rates of up 2.4 Mbps
(700kbps average) in a standard 1.25 MHz CDMA channel for fixed, portable
and mobile applications.
1xEV DV
CDMA 1x Evolution (Data and Voice)
2.4Mbs of data and improved voice service performance.
While 1xEV DO is approved by ITU (International Telecommunications Union),
this standard is still pending approval.
1xRTT
Single carrier Radio Transmission Technology 144K
Phase 1 of CDMA 2000, otherwise known as CDMA 2000, IS-2000, MC-1X or
IMT-CDMA Multicarrier. Purely a 2.5G technology but sometimes marketed as
3G and currently being deployed by a few U.S. Carriers.
1xRTT supports data rates of 144Kbps, although most people will see
50-60Kbps.
3xRTT
3 carrier Radio Transmission Technology 2Mbps
Phase 2 of CDMA 2000, otherwise known as MC-3X or IMT-CDMA Multicarrier 3X.
Data rates might hit 2Mbps and is a true 3G standard.
AMPS
Advanced Mobile Phone System
Frequencies in the range of 800 and 900 Mhz, where half of the frequency
range is allocated to sending of voice information and the other half for
receiving. The frequency spectrum is then subdivided into
"channels" by using FDMA - Frequency Division Multiple Access.
Each channel is assigned to only one cellular phone at a time.
CDMA
Code Division Multiple Access. CDMA takes analog information, converts it
to a digital pattern and then somewhat like TDMA communicates across the
whole available spectrum range at once. Unlike TDMA is also has the ability
to communicate across multiple carriers or, put simply, can talk to
multiple cellular base stations. Because of the ability to communicate
across bases, there is increased security and fewer call dropoffs when a
user moves from one area to another.
CDPD
Cellular Digital Packet Data
EDGE
Enhanced Data rates for Global Evolution
An upgrade to GSM's data standard GPRS, EDGE offers data rates up to 384
Kbps and an "Always On" connection. Built on the GSM standard, it
shares many qualities with TDMA.
GPRS
General Packet Radio Service. GPRS is a packet-based wireless data
communication system that allows for data rates up to 114 Kbps and an
"always-on" connection.
GSM
Global System for Mobile communications. GSM converts voice communication
into a digital signal, compresses it and sent with two other streams of
user data. Having most of its popularity in Europe, it has recently been
adopted in the United States by companies such as VoiceStream, AT&T and
Cingular Wireless. While the U.S. was resistant to this standard for some
time, these companies have finally realized the benefits of such a system:
economy of scale, global roaming, better inter-US roaming & fewer
"dead-spots". Not to mention that GSM is paired with the 2.5 G
standard GPRS, which IS a packet based data network with a
clear upgrade path.
HDR
High Data Rate
iDEN
Integrated Digital Enhanced Network
IS-136B/HS
GPRS Architecture for IS-136(TDMA)
Mobitex
Mobitex is everything from the over-the-air protocol to the base station
that Ericsson built. In the United States, it is primarily used by Cingular
and received much praise in the wake of the 9/11 attacks for being the only
communication network that worked near the site (all cell companies were
overloaded).
TDMA
Time Division Multiple Access (IS-136)
TDMA takes information that would normally be allocated to one 'channel' as
seen in AMPS and divides it across an entire frequency range (multiple
channels) for all users across the spectrum range at once.
Wireless Matrix
Using the MSAT-2 satellite at an attitude of 22K miles Wireless Matrix provides
100% coverage of the United States at a data rate of about 6Kbps.
PDA Glossary
Access profile
A set of parameters for an employee or group of employees that determines
the allowable access to data on the enterprise.
Authenticated access
Access to data that is allowed only after the user has been identified by a
password or other security measure.
"Back-door" PDAs
Handheld devices purchased and supported by employees for personal use but
are also used to access corporate enterprise data.
Back-office
Internal corporate functions, such as accounting/billing, purchasing, etc.
Cradle
A stand that holds a handheld device in an upright position to allow work
on a desktop and initiate synchronization with a PC.
Custom applications
Software installed on a device that was not part of its original package
(or suite) of applications and that has been developed for a specific job
or industry (e.g., hospital data).
Data sharing
Transferring and updating data among devices and/or the network.
Device-agnostic
Open to any brand of device or operating system.
Encryption
A security measure that "scrambles" data so it is unreadable
until an approved user is authorized to access it.
Enterprise
The combination of employees, communication devices, and data available
within an organization.
Handhelds
Communication devices that fit in one's hand or palm.
Infrared
A method for transferring data between devices using infrared
(line-of-sight) technology instead of cables or other wired connections.
Infrastructure
The matrix of operating systems, software, support, security measures and
devices used by the enterprise.
Licensing fees
An upfront and either one-time or annual cost to install software developed
by a third party onto your network.
Mission-critical data
Information critical to a particular task.
Mobile
A device that is designed for use outside the office or in the field.
Off-the-shelf applications
Prepackaged software developed to accommodate common needs and thus not
typically customizable.
PDA
The acronym for Personal Digital Assistant (see below).
Personal Digital Assistant (PDA)
A mobile handheld computing/communication device.
Personal Information Management (PIM)
A suite or combination of software applications for mobile handheld devices
that typically includes an address book (or contacts), to-do lists, e-mail
functionality and a calendar/date book.
PIM
The acronym for Personal Information Management (see above).
Platform vendors
Sellers of off-the-shelf software packages specific to an operating system
or device data platform.
Pilot
Implementing a product or solution to a limited, representative group to
gain insight and evaluate feasibility for the entire organization.
Return on Investment (ROI)
The time it takes to pay back (or recoup) the amount of money invested in a
technology or strategy.
ROI
The acronym for Return On Investment (see above).
Rollout
Implementing a product or solution to an entire department, division or
organization upon completion of a successful pilot (see "pilot,"
above).
Royalties
Fees paid to the owner of a technology (e.g., a software developer) based
on sales of that technology by a reseller or vendor.
Seats
Number of handheld users or potential users.
Server-based synchronization
Data transfer through a central server, typically via the Internet.
Sales force automation (SFA)
A generic term for software applications designed specifically for sales
tasks.
SFA
The acronym for Sales Force Automation (see above).
Small form
A term used to describe handheld or palm-sized devices.
Smart handheld devices
Handheld devices with more than one function, such as a PDA with cell phone
functionality.
Synchronization
Automated data transfer.
TCO
The acronym for Total Cost of Ownership (see below).
Total Cost of Ownership (TCO)
A calculation that considers all costs associated with investment in a
technology.
Verticals
Industry-specific (e.g., healthcare or retail sales) markets.
Wireless
A connectivity option requiring no cables or wires to receive and transfer
data between devices and/or the network (e.g., Bluetooth, Infrared,
Cellular).
802.11 Glossary
802.3
The official IEEE standard employing CSMA/CD access technology. 802.3
(10M), 802.3u (100M), 802.3z (1000M).
802.11
A family of specifications developed by the IEEE for WLAN technology.
802.11 specifies an over-the-air interface between a wireless client and a
base station or between two wireless clients. 802.11 per se provides 1 or 2
Mbps transmission in the 2.4 GHz ISM band using either FHSS or DSSS.
802.11b
A revision of 802.11 standard allowing data rates up to 11Mbps in the
2.4GHz ISM band. Also known as 802.11 High-Rate and Wi-Fi. 802.11b only
uses DSSS, the maximum speed of 11Mbps has fallbacks to 5.5, 2 and 1Mbps.
802.11a
A revision of 802.11 that operates in the unlicensed 5 GHz band and allows
transmission rates of 54Mbps. 802.11a uses orthogonal frequency division
multiplexing as opposed to FHSS or DSSS. Higher data rates possible by
combining channels. Due to higher frequency, range is less than lower
frequency systems (i.e., 802.11b and 802.11g) and can increase the cost of
the overall solution because a greater number of access points may be
required. 802.11a is not directly compatible with 802.11b or 802.11g
networks. In other words, a user equipped with an 802.11b or 802.11g radio
card will not be able to interface directly to an 802.11a access point.
Multimode NICs will solve this problem.
802.11g
An extension to 802.11b. 802.11g will broaden 802.11b's data rates to 54
Mbps within the 2.4 GHz band using OFDM (orthogonal frequency division
multiplexing) technology. An 802.11b radio card will interface directly
with an 802.11g access point (and vice versa) at 11 Mbps or lower depending
on range. Range at 54 Mbps is less than 802.11b access points operating at
11 Mbps.
Ad-hoc mode
An 802.11 framework in which devices communicate directly with each other,
without the use of an access point. Ad-hoc mode is also referred to as
peer-to-peer mode or an Independent Basic Service Set (IBSS).
AP access point
A transceiver device serving as an interface between a wired LAN and
wireless LAN clients. APs can improve aspects of wireless security and
extend the physical range of service.
Authentication
The process of identifying an individual in order for other processes to
confer appropriate access rights to system facilities. Authentication
merely ensures that the individual is who he or she claims to be.
Backbone network
A network used as a transmission path between other networks. Usually high
speed.
Bandwidth
A figure stated for a communications device (specified in Hz, kHz, MHz,
GHz) that ultimately dictates the amount of information that it can convey.
Baseband
A transmission system in which information signals are transmitted in their
core frequency spectrum without resource to modulation.
Bit
Stands for "Binary digIT." The smallest unit of information.
(True/False, Yes/No, Hot/Cold, On/Off etc).
Bluetooth
A wireless person area networking technology initially proposed by
Ericsson. It uses FHSS in the 2.4GHz ISM band at approx 1600 hops/s. Data
rates of up to 1Mbit/s over a range of 10m can be achieved (range can be
extended). Bluetooth is the "cableless" technology intended to
allow radio interfacing of peripheral devices and will be seen in many
consumer devices such as PDAs. See 802.15 standards on WPAN.
Bridge
A device used to partition a LAN into multiple access domains based upon
MAC (layer-2) information. There are two common forms of bridge Transparent
Bridges (Ethernet systems) and Source Routing Bridges (Token Ring), the
former being the most common. Partitioning a network using bridges offers
several advantages. 1. Access concurrency. 2. Reduced contention. 3. Speed
matching 4. Increased distance 5. Increased node count.
Broadband
A transmission system involving modulation techniques in which several data
streams are each modulated onto a different frequency, the frequencies are
mixed to create a composite, and the composite signal containing all component
data streams placed on the transmission medium.
Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
The media access control method used by Ethernet and 802.3 standards.
Devices first Carrier Sense (i.e. listen) and only transmit if the channel
is clear. If two devices see a clear channel and transmit at the same time,
a collision will occur. This is resolved by the Collision Detection
mechanism of the protocol, in which devices continuously read data off the
channel and compare with their own contribution; if a difference is
detected a collision is assumed and they terminate transmission. A new
attempt at transmission is made after waiting a random amount of time.
Client/Server architecture
An environment in which applications are distributed between a host server
and a remote client. Processing may be shared between client and server,
the nature of this sharing will effect the bandwidth utilizations of the
communications channel.
Code Division Multiple Access (CDMA)
A spread-spectrum digital cellular radio system in which different codes
are used to distinguish sources.
Data link layer
Layer-2 of the OSI model. Split into two sublayers called LLC and MAC. The
MAC layer is responsible for accessing a shared media and implements some form
of access technique such as CSMA/CD/CA or token passing, performs error
detection, and requires the use of physical addressing. LLC comes in
different flavors but can, if required, implement error correction and
flow-control.
Decibel
A logarithmic measure used to represent a gain or loss relative to some
reference point. The overall gain(loss) of a network may be found by adding
or subtracting the gains (losses) of each cascaded stage, this is the
benefit of logarithmic measure. dBm represents a power level relative to
1milliwatt.
Direct Sequence Spread Spectrum (DSSS)
A type of spread spectrum that spreads its signal continuously over a wide
frequency band. DSSS is a transmission technology in which a data signal at
the sending station is mapped into a higher data rate bit sequence using a
"chipping" code. The chipping code (also known as processing
gain) introduces redundancy, which allows data recovery if certain bit
errors occur during transmission. The FCC rules the minimum processing gain
should be 10; typical systems use processing gains of 20.
Dwell Time
In a FHSS systems this is the amount of time (dwell) a device is allowed to
spend transmitting on any one of the frequencies.
Extension point
A base-station 2-radio transceiver that bridges the gap between a wireless
client and an access point or between a wireless client and another
extension point.
Frequency Division Multiple Access (FDMA)
A digital radio technology that divides the available spectrum into
separate radio channels. FMDA is normally used in conjunction with Time
Division Multiple Access (TDMA) or Code Division Multiple Access (CDMA).
Frequency Hopping Multiple Access (FHMA)
A system using frequency hopping spread spectrum to permit multiple,
simultaneous conversations or data sessions by assigning different hopping
patterns to each.
Frequency Hopping Spread Spectrum (FHSS)
A type of radio communications in which the transmitter and receiver hop in
synchronization through a prearranged pattern of frequencies. This reduces
the effect of narrow band noise. FHSS modulates information onto a
narrowband carrier signal that "hops" in a pseudorandom but
predictable sequence from frequency to frequency. This technique reduces
interference because a signal from a narrowband system will affect only
part of the spectrum. Transmission frequencies are determined by a
so-called spreading, or hopping, code. Receivers must be set to the same
hopping code and must listen to the incoming signal at the right time and
correct frequency in order to properly decode the signal. FCC regulations
require manufacturers to use 75 or more frequencies per transmission
channel with a maximum dwell time (the time spent at a particular
frequency) of 400 ms.
Frequency Shift Keying (FSK)
A modulation scheme for data communications using a limited number of
discrete frequencies to convey binary information. Used by earlier modems
V.21, V.22 etc.
Fresnel Zone
The area around the visual line-of-sight between transmitter and receiver.
Radio waves disperse as they leave the antenna. Obstructions in this zone
of dispersion (Fresnel Zone) attenuate the signal. In the 2.4GHz ISM band
this is particularly true of objects with a large moisture content such as
trees.
Gigahertz (GHz)
One billion hertz.
Hand-off
In a cellular network, refers to the process of terminating communications
with one cell and establishing communications with an adjacent cell when a
mobile user travels between cells. Hand-offs normally involve switching
from one pair of frequencies to another.
Hertz (Hz)
Cycles per second. Used to measure frequency.
HomeRF
Is a specification for wireless digital communication between PCs and
consumer electronic devices used within the home environment. Based on
frequency hopping for the transmission of voice and data. HomeRF has a
range of up to 150 feet and uses the Shared Wireless Access Protocol.
HyperLAN/HiperLAN
A wireless LAN protocol developed by ETSI (European Telecommunications
Standards Institute), akin to 802.11. There are two types of HiperLAN, both
operating in the 5GHz band. HiperLAN/1 provides data-rates up to 20 Mbps,
and HiperLAN/2 data-rates up to 54 Mbps.
IEEE (Institute of Electrical and Electronics Engineers)
A professional society serving electrical engineers through its
publications, conferences and standards development activities.
Infrastructure Mode
Refers to an 802.11 framework in which communication takes place via an
Access Point. In infrastructure mode, wireless devices use the AP to
communicate with each other and with devices on a wired network. Most
corporate WLANs operate in infrastructure mode in order to access to the
wired LAN.
Internet Protocol (IP)
A connectionless network-layer protocol from the TCP/IP suite It provides a
best-efforts (fire and forget) datagram delivery service. The reliability
of the Internet comes from TCP, which is (CO) and implements timeouts and
auto-retransmission.
Local Area Network (LAN)
A network interconnecting devices in the same office, floor or building, or
areas inside buildings with areas just outside.
Media Access Control (MAC)
Protocols used to control access to a shared network medium. Common MAC
techniques include: CSMA/CD, CSMA/CA, Token Passing, and polling.
Modulation
Used to impress an information source (intelligence) onto a transmitter's
carrier signal. Carriers are used to match the transmitted signal to the
bandpass characteristics of the transmission medium.
Multipath fading
A type of fading caused by signals taking different paths from the
transmitter to the receiver and, consequently, interfering with each other.
Network Interface Card (NIC)
A circuit board installed in each network station to allow communications
with other stations.
Node
Any network station.
Packet
Refers to the data-unit of the Network-Layer (layer-3). A packet usually
includes a logical address to be used by routing devices. Messages are
segmented and segments placed in packets with a logical address header.
Packetising data allows greater throughput through noisy or congested communications
environments. Sending a 1,000,000 bit message through an environment with a
1-in-10^6 error rate will result in zero throughput. Transmitting 10
packets of 100,000 bit will result in a 90% throughput.
Packet-switched
A communications network that uses shared facilities to route data packets
from and to different users. Unlike a circuit-switched network, a
packet-switched network does not set up dedicated circuits for each
session.
PAN
A personal area network, e.g. Bluetooth
Peer-to-peer network
A network design in which each computer shares and uses devices on an equal
basis.
Physical layer
Layer-1 of the OSI model that establishes protocols for voltage, data
transmission timing, speed, operation mode (FDX, HDX), transmission
formatting asych vs. synch, and connector pin-outs.
Protocol
The generic name used to describe communications structured according to a
strict set of predefined rules.
Radio frequency (RF)
A generic term for radio-based technology.
Repeater
A device used to extend cabling distances by regenerating signals. Signal
regeneration is not simply amplification but involves three Rs : Re-shape,
Re-time, Retransmit.
Roaming
Refers to the ability to move from one access point coverage area to
another without interruption in service or loss in connectivity.
Shared Wireless Access Protocol (SWAP)
Is a specification for wireless voice and data networking in the home. SWAP
integrates with the PSTN and Internet using existing cordless telephony and
WLAN. SWAP operates in the 2.4G ISM band at 50 hops per second at a data
rate of between 1 and 2 Mbps. A SWAP-based network will allow cordless
handheld devices to voice activate home electronic systems and access the
Internet.
Simple Network Management Protocol (SNMP)
A connectionless applications services protocol from the TCP/IP suite. It
may also be used directly over Ethernet. SNMP provided the mechanism to
retrieve MIB information from device agents. Three versions of SNMP are
available v1, v2 and v3.
Spread spectrum
A radio transmission technology that spreads the user information
(intelligence) over a much wider bandwidth but at reduced power. The
principal benefits are improved tolerance to interference and allowing
unlicensed operation.
Time Division Multiple Access (TDMA)
A digital radio technology that divides each frequency channel into
separate time slots for separate conversations or sessions.
Transmission Control Protocol/ Internet Protocol (TCP/IP)
A de facto, industry-standard protocol for interconnecting networks. TCP/IP
is the basis of the Internet and corporate intranets.
WEP: Wired Equivalent Privacy
A security protocol for wireless local-area networks. WEP was intended to
provide the same level of security as that of a wired LAN. However, it has
been found that WEP is not as secure as once believed. WEP is used at the
two lowest layers of the OSI, it therefore does not offer end-to-end
security.
Wide Area Network (WAN)
WAN implementation usually involves the use of a telco service such as
ISDN, F-Relay, X.25, ATM, SMDS. Data rates for WAN have traditionally been
lower than that of LAN due to noise factors and the cost of leasing
high-bandwidth links. One normally associates WAN implementations with a
greater communications throw (distance); however a WAN service can equally
be used to traverse a few hundred meters!
Wi-Fi
Wireless Fidelity; Wireless Ethernet Compatibility Alliance's (WECA) brand
identity for the IEEE 802.11b standard; WECA certification that ensures
products' compatibility.
Wi-Fi5
Refers to WLAN products based upon the 802.11a specification operating in
the 5 GHz radio frequency band. Only products that have passed WECA's
interoperability testing are allowed to display the Wi-Fi5 certification
logo.
Wireless
Describes any computing device that can access a network without a wired
connection.
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