24.pdf

Chapter 24

Web, Wi-Fi, Wireless

and PC Technology

With the Internet and the Personal Com-

puter (PC) more commonplace in homes and

ham shacks around the world, some fear it

may actually destroy Amateur Radio! Their

reasoning is that increasingly powerful PCs,

coupled with access to the Internet or world-

wide web (www), will primarily divert

youth from the lure, mystique and magic of

radio. Could an advancement in technology

with the corresponding economies-of-scale

actually deprive Amateur Radio of an influx

of fresh, young operators and enthusiasts?

The PC and its Internet link to the world

around us have surely changed many

lifestyles — young and old and those in

between. But far from destroying Ama-

teur Radio as we know it, these technolo-

gies have greatly enhanced and improved

the ham radio experience of countless

operators! Many hams with an interest or

passion in homebrewing, DXing, contest-

ing, and the wide variety of other related

areas of interest now take for granted

nearly instantaneous access to informa-

tion and interest-related Web sites. Com-

puters and modems are sometimes used

for the operation of various modes, and

can also be a primary part of the actual

ham radio equipment (e.g., a transceiver

or receiver ).

In this chapter, in addition to covering

many of these exciting areas described

above, we will also review the personal/

commercial wireless world around us that

is extraneous to ham frequencies, equip-

ment or operation. This chapter was writ-

ten by Donald R. Greenbaum, N1DG, and

Dana G. Reed, W1LC. It also includes

contributions from John J. Champa,

K8OCL, Reed E. Fisher, W2CQH,

Howard S. Huntington, K9KM, and

Ronnie P. Milione, KB2UAN.

The World Wide Web (www) — The Internet

SEARCH ENGINES

The Internet encompasses millions and

millions of pages of information. There is

simply too much information on the subject

of ham radio to find without properly using

search engines. There are many related ham

sites, but the most popular are listed in the

sidebar A Ham’s Guide to Useful Internet

Sites . In any event, the most popular search

engines are Google , Yahoo , Ask Jeeves ,

Alta Vista , Dogpile , Look Smart , Overture ,

Teoma and Find What .

The secret to a successful search is to be

specific by limiting the results or hits .

Simply typing "ham radio" as the topic of

interest to you is not sufficient. A query on

ham yielded links to Web sites mention-

ing ham radio, ham (the food) and other

hits totaling over 7 million pages! A more

specific search of ham radio reduced the

page count to 1.7 million pages, still too

numerous to be helpful. Narrowing and

refining your search is as simple as adding

Search Engines — Electronic Parts and

Cross Referencing

A QRP list member was trying to search, or cross reference, a semicon-

ductor in Google, but without success. He had probably only entered the

exact part number. The part was described as possibly of one family of

semiconductor, but apparently in Google he used the part number

“IRF331A” which indeed comes up blank.

However, a knowledge of manufacturing prefixes or numbering systems

used for semiconductors or other components can be very valuable.

Originally, IRF was the prefix for International Semiconductor Parts.

Entering that in Google.com, I came up with a Web page: www.irf.com .

From there, I came to a search engine on the page that eventually led to

their cross reference guide — and the fact that the IRF331A can possibly

be replaced (depending on the application) by the IRF330. However, an

upgraded part is the IRF440, or the 2N6760.

Knowing a general supplier of replacement semiconductors, my next stop

— had this not worked out — would have been www.NTE.com . The main

point here is to study distributors catalogs, for knowledge of part-number-

ing conventions for whatever electronics you might need. Get to know

company logos that are applied to parts as these will shorten your

searches if the company still exists, using that logo. For the totally unfamil-

iar part, a logo can be very helpful to focus your search.—Stuart Rohre,

K5KVH

Web, Wi-Fi, Wireless and PC Technology

24.1

VOICE OVER INTERNET

PROTOCOL — VoIP

Like our airwaves, the Internet can carry

our transmissions over great distances. Un-

like ham radio, the Internet is only digital. If

we are use voice or video over that medium

those modes must be converted into that

digital format before sending and converted

back to analog upon receipt. Two software

packages have emerged to allow hams to

converse over the Internet in what is known

as Voice over Internet Protocol, or VoIP.

ARRL offers a new publication titled VoIP:

Internet Linking for Radio Amateurs . The

book discusses in great detail the brief out-

line of the topic that follows. 1

A HAM’S GUIDE TO USEFUL INTERNET SITES

Since website URLs change so often, any attempt to present a comprehen-

sive list here would be out of date by the time of publication. Accordingly, we

have instead listed general ham-related sites that contain current links to

many of the specific radio sites on the Web:

ARRL: www.arrl.org Where else would you go for ham radio news?

AC6V: www.ac6v.com/ Rod has links to over 6,000 other radio related

sites covering all topics imaginable.

AA1V: www.goldtel.net/aa1v/ Don has the usual DX links plus some pretty

good NASA links not found on other sites.

DX Zone: www.dxzone.com/ A good commercially-run site that is well laid

out providing 4500 links to other commercial and private ham run sites.

425 DX News: www.425dxn.org/ Good Italian non-commercial site for DX

News and links to DX-related sites.

Echolink

Recognizing the growing use of the

Internet by hams, K1RFD wrote a soft-

ware program called Echolink. Now even

antenna-restricted hams can enjoy the fun

with a computer, a microphone and an

Internet connection. You can connect via

Echolink to other licensed hams on comput-

ers, mobiles transmitting through repeaters

linked to the Internet via connected VHF

repeaters and even nodes connected via HF.

There are more than 120,000 registered us-

ers in 147 countries worldwide. There are

also conference nodes, some specific to

other hobbies such as aviation. It is the ulti-

mate party line encompassing computers,

radio and the Internet. Like radio, it is non-

duplex; both stations cannot talk at once. The

software is free (you must be licensed) and

is downloadable from www.echolink.org .

The software is very user friendly, and all

control features are click-of-a-mouse en-

abled. The only requirement of your PC is a

sound card and microphone.

K4UTE: www.nfdxa.com/K4UTE/K4UTE.HTML One of the best sources

of QSL routes and links to other DX-related activities.

NG3K: www.ng3k.com/Misc/adxo.html Want to know who’s going where

and the link to their Web site? Since 1996, Bill has been keeping track of

these things on this Web site and has everything archived for searching.

QSL.NET: www.qsl.net/master.htm Al, K3TKJ, provides free hosting to

thousands of hams for radio-related Web pages.

K1BV Awards Directory: www.dxawards.com/ Are you into wallpaper?

Ted has one of the best sites for award information and links to those

offering them.

MODS: www.mods.dk/ Modifying your radio? Find hundreds of links

compiled over the last eight years by Erik, OZ2AEP.

Linux Ham Radio Software Directory: radio.linux.org.au/ Do you prefer

Linux to Windows? This site lists Perl scripts ranging from modeling antennas

to European Microwave Beacon propagation forecasting.

Satellite Tracking Software: www.david-taylor.pwp.blueyonder.co.uk/

software/wxtrack.htm

QSL Museum: www.hamgallery.com/ In addition to one of the most

complete online QSL collections, Tom (K8PX) has one of the more complete

ham radio link sites on the web.

IRLP

Unlike Echolink, which allows two

hams to communicate without having a

radio, IRLP takes a different approach to

VoIP. David Cameron, VE7LTD, de-

signed the Internet Radio Linking Project

(IRLP). As he says on his Web site, he

designed the software to provide a simple

and easy system to link radio systems to-

gether using the Internet as the communi-

cations backbone.

IRLP users do not need to own com-

puters. They simply access the network

nodes using VHF or UHF FM trans-

ceivers.

The IRLP network is Linux based and

requires a Linux -based Pentium PC at each

node running Speak Freely software, an in-

terface card (purchased inexpensively from

VE7LTD), your radio and a sound card. The

sound card takes the analog audio from the

radio, converts it to compressed digital

packets and sends short streams over the

more words. This is called using key-

words, and choosing them wisely will re-

duce the page count to manageable levels.

Ham radio software reduces our search to

427,000 pages while ham radio dsp soft-

ware reduces it to 18,600 pages; you can

keep refining your search by adding key-

words, and there is no need to include the

word and between the words.

Another way to reduce hits on your

search is to exclude categories. For in-

stance, if you want to search for ham you

can exclude the food ham by ham –food .

If you want to search for an item but only

want to search for it on a specific Web

site, you can do that too. For instance, to

look on the ARRLWeb you can do license

renewal site: www.arrl.org.

Searching for specific part numbers for

your do-it-yourself projects is similarly

easy. In the PC Technology section of this

chapter we discuss isolation transformers.

A search for 273-1374 brings you right

into the RadioShack catalog, as well as

pages on how to build other projects with

it. There is a fine line for being too spe-

cific in searches. Sometimes the part num-

ber can be too exact, and adding either a

manufacturer or looking up the descrip-

tion of isolation transformers are a

broader alternative that will help if the

specific part search comes up negative.

See also the sidebar Search Engines —

Electronic Parts and Cross Referencing .

24.2

Chapter 24

and stop the streams. CTCSS is also used by

the transmitting user to pass commands to

the nodes for the information as to which

node a user wants to connect to, start and

stop the connection and a host of other

settable parameters to control the process.

Streams can be sent to one or many nodes.

The software, interface cards and all

manuals are available from the IRLP

website at www.irlp.net

tool as a ham could want. As shown in

Fig 24.2 , a real-time graphic can be found

at the Solar Terrestrial Dispatch Web site:

www.spacew.com/www/realtime.html .

VIRUS PROTECTION AND

FIREWALLS

Lastly, no Internet user should be con-

necting to the Web without up-to-date virus

protection. Norton Antivirus and McAfee

are the two most popular commercial prod-

ucts. There are also some shareware prod-

ucts available. However, virus protection

alone does not offer full protection from

intruders. Hams increase the risk of being

infected by opening ports to allow IRLP,

Telnet, Instant Messenger, VoIP, or FTP

applications. The solution is installing one

of two types of firewalls. The first is an in-

expensive software-based firewall from

Norton or McAfee for under $50. They de-

tect both internal and external attempts to

compromise your personal computer (PC).

The more expensive but more capable solu-

tion is a hardware-based device commonly

known as a Firewall Appliance. In addition

to the simple intruder detection found in

firewall software, they contain an intruder

prevention system, the ability to connect

multiple PCs (as a router or switch), monitor

ability on all traffic in and out of the net-

work, open secure ports (VPN) and auto-

matically obtain updates to firmware.

PROPAGATION FORCASTING

One of the most valuable pieces of in-

formation available on the Web is the vari-

ous real time propagation statistics and

tools. Current gray-line paths are vital to

the LF operator. MUF values are helpful

to HF operators. Current observed sunspot

activity, solar storm indexes, etc. are all

posted on various ham and government

Web sites giving the Internet-connected

ham useful tools to know where the best

paths to the DX are. Current solar flux

numbers are published by the Canadian

Space Agency as monitored at its

Penticton Observatory: www.drao-ofr.

hia-iha.nrc-cnrc.gc.ca/icarus/www/

current_flux.shtml

Since Auroral activity is harmful to HF

transmissions over the globe, NOAA pro-

vides both North and South Pole real time

auroral maps: sec.noaa.gov/pmap/gif/

pmapN.gif . A recent North Pole image is

shown in Fig 24.1 .

Knowing which frequencies are usable

in real time is also as handy a propagation

Fig 24.1 — NOAA North Pole map image

of recent, real-time auroral activity.

Fig 24.2 — Solar Terrestrial Dispatch

graphic depicting frequency usability in

real time.

Internet to the connected nodes via the inter-

face card. The control software controls the

packets along with continuous tone coded

sub audible squelch signals (CTCSS) to start

Notes

1 See ARRLWeb at www.arrl.org/shop ;

Order no. 9264.

Wi-Fi Glossary

Access Point (AP) — A wireless bridg-

ing device that connects 802.11 stations to

shared resources and a wired network such

as the Internet.

Ad Hoc — In wireless LAN (WLAN)

networks this is a direct wireless connec-

tion between two laptop computers with-

out the use of an AP.

AP — Access point.

Carrier Sense Multiple Access / Colli-

sion Avoidance (CSMA/CA) — The wire-

less method that tries to avoid simultaneous

access or collisions by not transmitting, if

another signal is detected on the same fre-

quency channel.

Direct-Sequence Spread Spectrum

(DSSS) — The type of modulation used in

802.11b that is capable of maximum half-

duplex data speeds of 11 Mbps.

Frequency Hopping Spread Spectrum

(FHSP) — A type of modulation used in

early 802.11 devices that uses a time-var-

ied narrow signal to spread the signal over

a wide band. Maximum half-duplex data

rate is 2 Mbps.

Institute of Electrical and Electronics

Engineers (IEEE) — The professional

standards setting organization for data net-

working devices.

Orthogonal Frequency Division Mul-

tiplexing (OFDM) — A type of modula-

tion that splits a wide frequency band into

many narrow frequency bands. Both

802.11a and 802.11g use OFDM.

Service Set Identity (SSID) — The

identification for an AP. It is transmitted

continuously in the form of a beacon.

Wired Equivalent Privacy (WEP) — A

standard for providing minimal privacy of

wireless LAN communication by encrypt-

ing individual data frames.

Wireless Fidelity (Wi-Fi) — The Wire-

less Ethernet Compatibility Alliance certi-

fication program to ensure that equipment

claiming to be in compliance with 802.11

standards is truly interoperable. The term

Wi-Fi5 is sometimes applied to 802.11a

equipment that operates on the 5-GHz band.

Wireless Fidelity (Wi-Fi)

COMPUTER CONNECTIONS BY

RADIO

Wireless local area networks (WLAN)

using spread spectrum transmit in the

902-MHz range (802.11 ), in the 2.4-GHz

frequency range (802.11b and 802.11g),

and in the 5-GHz frequency range

(802.11a). Combining spread spectrum

transmission’s characteristics with a low

power output (30 to 100-mW range) means

it is highly unlikely that one spread spec-

trum network user will interfere with an-

other. Spread spectrum transmissions

distribute or “spread” a radio signal over

a broad frequency range. There are vari-

Web, Wi-Fi, Wireless and PC Technology

24.3

ous techniques for doing this spreading.

The older WLAN systems operate in the

902-MHz range based on the IEEE 802.11

standard and use frequency hopping

spread spectrum modulation, or FHSS.

This modulation technique uses what is

called a predetermined pseudo-random

sequence to transmit data. This pseudo-

random sequence is actually a predeter-

mined digital signal pattern that places

data on a combination of frequencies

across the entire spread spectrum channel.

The receiving station must know the

specific signal pattern used by the trans-

mitting station to decode the data. These

early 802.11 systems generally operated

with slightly higher power (250 mW) but

at much slower data rates of typically

2 Mbps.

are based the same type of modulation,

Orthogonal Frequency Division Multi-

plexing (OFDM) but operate on different

frequency bands. OFDM provides its

spreading function by transmitting the

data simultaneously on multiple carriers.

802.11g operating in the 2.4-GHz range

and 802.11a operating in the 5-GHz range

both specify 20-MHz wide channels with

52 carriers spaced every 312.5 kHz.

OFDM radios can be used to transmit

data rates of 6, 9, 12, 18, 24, 36, 48 and

54 Mbps.

wire each individual office and conference

room, only the various AP nodes need to

be wired together. This can produce a huge

savings in time and expense.

WLAN Security

Although the majority of WLAN oper-

ate in the open mode allowing anyone in

the area convenient access the network,

often a minimum level of information se-

curity is desirable. This can be provided

by using a WLAN encryption protocol

built into the equipment called Wired

Equivalent Privacy, or WEP. For those

situations requiring a higher level of secu-

rity, most commercial firms simply re-

employ their virtual private network

(VPN) or tunneling strategy commonly

used to allow secure network remote ac-

cess for mobile workers and teleworkers.

However, in the case of WLAN use, extra

steps need to be taken to ensure that the

VPN user ID and password are not being

wirelessly transmitted in the clear without

some form of encryption. A new WLAN

security standard called IEEE 802.1x at-

tempts to address this need but is currently

plagued with interoperability issues.

Wi-Fi systems being used in Amateur

Radio applications are typically referred

to as High Speed Multimedia (HSMM),

and these techniques are discussed in de-

tail in the HSMM section of the Modes

and Modulation Sources chapter of this

Handbook .

The WLAN Advantage

The main advantage of WLAN systems

is that the laptop PC users are not tied to an

RJ-45 type of wall outlet. At home they

can roam between the home office and the

patio. At work, they can move with ease

between an office and a conference room,

for example. There is a significant eco-

nomic advantage for businesses re-locat-

ing office areas. With the use of WLAN

technology, it is not necessary to spend

the time and money to rewire an entire

floor or building. These small radio de-

vices with their small antennas and low

power can readily transmit through sev-

eral layers of drywall. If more than one

access point, or AP, is required to cover

the business area, several AP devices can

all be linked together by putting them in

the same virtual LAN in the wired net-

work. Consequently, rather than having to

New-generation WLAN

The first of the new generation of

WLAN systems is based on the IEEE

802.11b standard and use a modulation

technique known as direct-sequence

spread spectrum, or DSSS. This modula-

tion technique achieves higher data rates

by using a different pseudo-random code

known as a Complimentary Sequence. The

8-bit Complimentary Sequence can en-

code 2 bits of data for the 5.5 Mbps data

rate or 6 bits of data for the 11 Mbps data

rate. This is known as Complimentary

Code Keying (CCK).

The latest generation of WLAN devices

Wireless Technology Glossary

AMPS (Advanced Mobile Phone Ser-

vice) — First standardized cellular service

in the world, released in 1983. Uses the

800-900 MHz frequency band.

Analog — A signal that can vary con-

tinuously between a maximum and mini-

mum value. For example, the voice

voltage waveform from the output of a

microphone is analog. RF voltage wave-

forms (as those from AM, FM and SSB

transmitters) are also analog.

Cap Code — A specific address en-

coded into both a data transmission and

the intended receiving equipment so the

receiving equipment can discriminate

against unintended or unwanted messages.

CDMA (Code Division Multiple Ac-

cess) — A digital radio system that sepa-

rates users by digital codes.

Cellular — Characteristic of or pertain-

ing to a system of wireless communica-

tion made up of many individual cell units.

The term itself is derived from the typical

geographic honeycomb shape of the areas

into which a coverage region is divided.

CELP (Codebook Excited Linear

Predictive coding) — A type of low-bit-

rate voice coder that emulates a single

human voice tract. Details can be found in

Ref. 3 at the end of this chapter.

CSMA/CD (Carrier Sense Multiple

Access / Collision Detection) — A set of

rules that determine how network devices

respond when two devices attempt to use a

data channel simultaneously (called a colli-

sion ). After detecting a collision, a device

waits a random delay time and then attempts

to re-transmit the message. If the device

detects a collision again, it now waits twice

as long to try to re-transmit the message.

DHCP (Dynamic Host Configuration

Protocol) — An external assignment

mechanism that provides a “care-of ad-

dress” to a mobile client (see also Foreign

Agent ).

Digital — A signal that has only discrete

values, usually two (logic 1 and logic 0), that

changes at predetermined intervals. The

value (e.g., voltage) present in a single time

period is called a bit. The number of bits

transferred per second is called the bit rate

that has units of bits per second (bit/s), or

kilobits per second (kbit/s), etc.

E-mail — Electronic mail sent and re-

ceived via computers with modems.

Transmission media can be existing tele-

phone or other communication lines, wire-

less, or not uncommonly—both.

Encode — The process whereby a

transmission contains additional data or

code added to facilitate proper routing of

the transmission to the desired point or

points.

Encryption — Technology used to

form a secure channel between a wireless

client and the server to support user au-

thentication, data integrity, and data pri-

vacy.

ESN (Electronic Serial Number) — A

manufacturer-assigned identity contained

in a data transmission from a call placed to

verify that the hardware used belongs to a

24.4

Chapter 24

valid cellular account.

Ethernet — A local-area network

(LAN) protocol. Ethernet uses a bus or star

topology and supports data transfer rates

of 10 Mbit/s, 100 Mbit/s, 1 Gbit/s and

10 Gbit/s. Ethernet uses the CSMA/CD

access method to handle simultaneous

demands, and is one of the most widely

implemented LAN standards.

FDMA (Frequency Division Multiple

Access) — A radio system that separates

user channels by frequency. Amateur

Radio equipment presently uses FDMA.

Footprint — The coverage area of an

individual cell.

Foreign Agent — A special “node”

which is present on a foreign network and

provides mobility services to visiting

mobile nodes.

GPS (Global Positioning System) —

A Dept. of Defense-developed, world-

wide, satellite-based radio navigation

system.

Handoff — Process whereby a mobile

telephone network automatically transfers

a call from cell to cell—possibly to an-

other channel—as a mobile crosses adja-

cent cells.

Home Agent — A host on a mobile’s

home network responsible for trapping its

packets, and forwarding them to the

mobile’s present location.

LAN (Local Area Network) — A com-

puter network that spans a relatively small

area. Most LANs are confined to a single

building or group of buildings. However,

one LAN can be connected to other LANs

over any distance via telephone lines and

radio waves. A system of LANs connected

in this way is called a wide-area network

(WAN) . Most LANs connect workstations

and personal computers. Each node (indi-

vidual computer) in a LAN has its own

central processing unit (CPU) with which

it executes programs, but it is also able to

access data and devices anywhere on the

LAN. This means that many users can share

expensive devices, such as laser printers,

as well as data. Users can also use the LAN

to communicate with each other, by send-

ing e-mail or engaging in chat sessions.

Mobile Host — Also known as a “mo-

bile node,” this addressed entity in the

Mobile IP protocol roams between its

home network and foreign networks.

Mobile IP — This mobile industry stan-

dard enhances the IP protocol to remedy

problems associated with using the stan-

dard TCP/IP with a mobile entity. It allows

for transparent routing of IP datagrams to

mobile hosts (nodes) on the Internet.

Modem — A hardware device, either

internally or externally connected to a com-

puter that provides a connection from the

computer and some of its programs to a

landline (phone or communications line).

Network Independence — The ability

to roam among networks (e.g., BellSouth

Wireless Data Network, CDPD, Wire-

less LAN, Ethernet), although tradition-

ally accomplished using the same access

media such as SLIP, PPP, etc.

Node — A unique host on a network

such as a printer, computer device,

handheld Personal Digital Assistant

(PDA), or a mainframe.

PCMCIA (Personal Computer

Memory Card International Assoc-

iation) — An organization consisting of

some 500 companies that has developed a

standard for small, credit card-sized de-

vices called PC Cards , originally designed

for adding memory to portable computers.

PDA (Personal Digital Assistant) —

A handheld device that functions as a per-

sonal organizer. Many PDAs began as

pen-based, i.e., using a writing stylus

rather than a keyboard for input, thus uti-

lizing handwriting recognition features.

Some PDAs feature voice recognition

technologies. At present, most PDAs of-

fer either a stylus or keyboard version.

POS (Point of Service) — A gener-

ation of narrowband digital, two-way,

low-powered wireless services in the 800-

900 MHz bands that will support con-

firmed delivery of message, full two-way

data transfer, voice messaging and con-

nectivity via the Internet.

PPP (Point-to-Point Protocol) — A

method of connecting a computer to the

Internet. PPP is more stable than the older

SLIP protocol and provides error-check-

ing features.

Remote Presence — The ability to es-

tablish remote network connections and

still appear to be connected to the home

network.

Security — The ability to create secure

channels for user authentication, data in-

tegrity, and data privacy.

SLIP (Serial Line Internet Protocol)

— An older method of connecting a com-

puter to the Internet. A more commonly

used method is PPP. SLIP is an older and

simpler protocol, but from a practical per-

spective, there’s not much difference be-

tween connecting to the Internet via SLIP

or PPP. In general, service providers only

offer one protocol, although some support

both protocols.

TCP/IP (Transmission Control Pro-

tocol/Internet Protocol) — The suite of

communications protocols used to con-

nect hosts on the Internet. TCP/IP uses

several protocols, the two main ones be-

ing TCP and IP. TCP/IP is built into the

UNIX operating system and is used by the

Internet, making it the de facto standard

for transmitting data over networks. Even

network operating systems that have their

own protocols, such as Netware , also sup-

port TCP/IP.

TDMA (Time Division Multiple

Access) — A digital radio system that

separates users by time.

Third Party Mobile IP — An Internet

technology solution that provides both

wireless and wireline IP network and me-

dia roaming/communications to both

Intranet and Internet services.

Throughput — The amount of data

processed, or transferred from one place

to another in a specified amount of time.

Data transfer rates for disk drives and net-

works are measured in terms of through-

put. Typically, throughput is measured in

kbit/s, Mbit/s, and Gbit/s.

TIA (Telecommunications Industry

Association) — Telecommunications In-

dustry Association, 2500 Wilson Blvd,

Arlington, VA 22001. On the web: www.

tiaonline.org .

T1P1 — The wireless group in Com-

mittee T1. Alliance for Telecommunica-

tions Industry Solutions, 122 G St. NW,

Suite 500, Washington, DC 20005. On the

web: www.atis.org .

Virtual Private Network — Network

created when a mobile user connects a data

terminal to a foreign network and estab-

lishes a presence equivalent to a direct

connection to the home network.

WAN (Wide Area Network) — A com-

puter network that spans a relatively large

geographical area. Typically, a WAN con-

sists of two or more local-area networks

(LANs). Computers connected to a wide-

area network are often connected through

public networks such as the telephone sys-

tem. They can also be connected through

leased lines or satellites. The largest WAN

in existence is the Internet.

Windows OS — Microsoft Windows

Operating System.

Wireless Data — Information or “in-

telligence,” sent or received by wireless

transmission/reception without the direct

aid of a landline.

WLAN (Wireless Local Area Network)

— A local-area network that uses high fre-

quency radio waves rather than wires to

communicate between nodes.

Web, Wi-Fi, Wireless and PC Technology

24.5

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