Asus P5W DH Deluxe: Glossary

Glossary

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Access Point (AP)

A networking device that seamlessly connects wired and wireless networks. Access

Points combined with a distributed system support the creation of multiple radio

cells that enable roaming throughout a facility.

Ad Hoc

A wireless network composed solely of stations within mutual communication range

of each other (no Access Point).

Basic Rate Set

This option allows you to specify the data transmission rate.

Basic Service Area (BSS)

A set of stations controlled by a single coordination function.

Broadband

A type of data transmission in which a single medium (such as cable) carries

several channels of data at once.

Channel

An instance of medium use for the purpose of passing protocol data units that

may be used simultaneously, in the same volume of space, with other instances

of medium use (on other channels) by other instances of the same physical layer,

with an acceptably low frame error ratio due to mutual interference.

Client

A client is the desktop or mobile PC that is connected to your network.

COFDM (for 802.11a or 802.11g)

Signal power alone is not enough to maintain 802.11b-like distances in an

802.11a/g environment. To compensate, a new physical-layer encoding technology

was designed that departs from the traditional direct-sequence technology being

deployed today. This technology is called COFDM (coded OFDM). COFDM was

developed specically for indoor wireless use and offers performance much

superior to that of spread-spectrum solutions. COFDM works by breaking one

high-speed data carrier into several lower-speed subcarriers, which are then

transmitted in parallel. Each high-speed carrier is 20 MHz wide and is broken

up into 52 subchannels, each approximately 300 KHz wide. COFDM uses 48 of

these subchannels for data, while the remaining four are used for error correction.

COFDM delivers higher data rates and a high degree of multipath reection

recovery, thanks to its encoding scheme and error correction.

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Each subchannel in the COFDM implementation is about 300 KHz wide. At the low

end of the speed gradient, BPSK (binary phase shift keying) is used to encode 125

Kbps of data per channel, resulting in a 6,000-Kbps, or 6 Mbps, data rate. Using

quadrature phase shift keying, you can double the amount of data encoded to 250

Kbps per channel, yielding a 12-Mbps data rate. And by using 16-level quadrature

amplitude modulation encoding 4 bits per hertz, you can achieve a data rate of

24 Mbps. The 802.11a/g standard species that all 802.11a/g-compliant products

must support these basic data rates. The standard also lets the vendor extend the

modulation scheme beyond 24 Mbps. Remember, the more bits per cycle (hertz)

that are encoded, the more susceptible the signal will be to interference and fading,

and ultimately, the shorter the range, unless power output is increased.

Default Key

This option allows you to select the default WEP key. This option allows you to

use WEP keys without having to remember or write them down. The WEP keys

generated using the Pass Phrase is compatible with other WLAN products. The

Pass Phrase option is not as secure as manual assignment.

Device Name

Also known as DHCP client ID or network name. Sometimes provided by an ISP

when using DHCP to assign addresses.

DHCP (Dynamic Host Conguration Protocol)

This protocol allows a computer (or many computers on your network) to be

automatically assigned a single IP address from a DHCP server.

DNS Server Address (Domain Name System)

DNS allows Internet host computers to have a domain name and one or more IP

addresses. A DNS server keeps a database of host computers and their respective

domain names and IP addresses, so that when a user enters a domain name into

the Internet browser, the user is sent to the proper IP address. The DNS server

address used by the computers on your home network is the location of the DNS

server your ISP has assigned.

DSL Modem (Digital Subscriber Line)

A DSL modem uses your existing phone lines to transmit data at high speeds.

Direct-Sequence Spread Spectrum (for 802.11b)

Spread spectrum (broadband) uses a narrowband signal to spread the transmission

over a segment of the radio frequency band or spectrum. Direct-sequence is a

spread spectrum technique where the transmitted signal is spread over a particular

frequency range.

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Direct-sequence systems communicate by continuously transmitting a redundant

pattern of bits called a chipping sequence. Each bit of transmitted data is mapped

into chips and rearranged into a pseudorandom spreading code to form the

chipping sequence. The chipping sequence is combined with a transmitted data

stream to produce the output signal.

Wireless mobile clients receiving a direct-sequence transmission use the spreading

code to map the chips within the chipping sequence back into bits to recreate the

original data transmitted by the wireless device. Intercepting and decoding a direct-

sequence transmission requires a predened algorithm to associate the spreading

code used by the transmitting wireless device to the receiving wireless mobile

client.

This algorithm is established by IEEE 802.11b specications. The bit redundancy

within the chipping sequence enables the receiving wireless mobile client to

recreate the original data pattern, even if bits in the chipping sequence are

corrupted by interference. The ratio of chips per bit is called the spreading ratio.

A high spreading ratio increases the resistance of the signal to interference. A

low spreading ratio increases the bandwidth available to the user. The wireless

device uses a constant chip rate of 11Mchips/s for all data rates, but uses different

modulation schemes to encode more bits per chip at the higher data rates. The

wireless device is capable of an 11 Mbps data transmission rate, but the coverage

area is less than a 1 or 2 Mbps wireless device since coverage area decreases as

bandwidth increases.

Encryption

This provides wireless data transmissions with a level of security. This option

allows you to specify a 64-bit or a 128-bit WEP key. A 64-bit encryption contains

10 hexadecimal digits or 5 ASCII characters. A 128-bit encryption contains 26

hexadecimal digits or 13 ASCII characters.

64-bit and 40-bit WEP keys use the same encryption method and can interoperate

on wireless networks. This lower level of WEP encryption uses a 40-bit (10

hexadecimal digits assigned by the user) secret key and a 24-bit Initialization

Vector assigned by the device. 104-bit and 128-bit WEP keys use the same

encryption method.

All wireless clients in a network must have identical WEP keys with the access

point to establish connection. Keep a record of the WEP encryption keys.

Extended Service Set (ESS)

A set of one or more interconnected basic service set (BSSs) and integrated local

area networks (LANs) can be congured as an Extended Service Set.

ESSID (Extended Service Set Identier)

You must have the same ESSID entered into the gateway and each of its wireless

clients. The ESSID is a unique identier for your wireless network.

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Ethernet

The most widely used LAN access method, which is dened by the IEEE 802.3

standard. Ethernet is normally a shared media LAN meaning all devices on the

network segment share total bandwidth. Ethernet networks operate at 10Mbps

using CSMA/CD to run over 10-BaseT cables.

Firewall

A rewall determines which information passes in and out of a network. NAT can

create a natural rewall by hiding a local network’s IP addresses from the Internet.

A Firewall prevents anyone outside of your network from accessing your computer

and possibly damaging or viewing your les.

Gateway

A network point that manages all the data trafc of your network, as well as to the

Internet and connects one network to another.

IEEE

The Institute of Electrical and Electronics Engineers. The IEEE sets standards

for networking, including Ethernet LANs. IEEE standards ensure interoperability

between systems of the same type.

IEEE 802.11

IEEE 802.xx is a set of specications for LANs from the Institute of Electrical

and Electronic Engineers (IEEE). Most wired networks conform to 802.3, the

specication for CSMA/CD based Ethernet networks or 802.5, the specication for

token ring networks. 802.11 denes the standard for wireless LANs encompassing

three incompatible (non-interoperable) technologies: Frequency Hopping Spread

Spectrum (FHSS), Direct Sequence Spread Spectrum (DSSS), and Infrared.

802.11 species a carrier sense media access control and physical layer

specications for 1 and 2 Mbps wireless LANs.

IEEE 802.11a

Compared with 802.11b:

The 802.11b standard was designed to operate in

the 2.4-GHz ISM (Industrial, Scientic and Medical) band using direct-sequence

spread-spectrum technology. The 802.11a standard, on the other hand, was

designed to operate in the more recently allocated 5-GHz UNII (Unlicensed

National Information Infrastructure) band. And unlike 802.11b, the 802.11a standard

departs from the traditional spread-spectrum technology, instead using a frequency

division multiplexing scheme that's intended to be friendlier to ofce environments.

The 802.11a standard, which supports data rates of up to 54 Mbps, is the Fast

Ethernet analog to 802.11b, which supports data rates of up to 11 Mbps. Like

Ethernet and Fast Ethernet, 802.11b and 802.11a use an identical MAC (Media

Access Control). However, while Fast Ethernet uses the same physical-layer

encoding scheme as Ethernet (only faster), 802.11a uses an entirely different

encoding scheme, called OFDM (orthogonal frequency division multiplexing).

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The 802.11b spectrum is plagued by saturation from wireless phones, microwave

ovens and other emerging wireless technologies, such as Bluetooth. In contrast,

802.11a spectrum is relatively free of interference.

The 802.11a standard gains some of its performance from the higher frequencies

at which it operates. The laws of information theory tie frequency, radiated power

and distance together in an inverse relationship. Thus, moving up to the 5-GHz

spectrum from 2.4 GHz will lead to shorter distances, given the same radiated

power and encoding scheme.

Compared with 802.11g:

802.11a is a standard for access points and radio NICs

that is ahead of 802.11g in the market by about six months. 802.11a operates in the

5GHz frequency band with twelve separate non-overlapping channels. As a result,

you can have up to twelve access points set to different channels in the same

area without them interfering with each other. This makes access point channel

assignment much easier and signicantly increases the throughput the wireless

LAN can deliver within a given area. In addition, RF interference is much less likely

because of the less-crowded 5 GHz band.

IEEE 802.11b

In 1997, the Institute of Electrical and Electronics Engineers (IEEE) adopted the

802.11 standard for wireless devices operating in the 2.4 GHz frequency band. This

standard includes provisions for three radio technologies: direct sequence spread

spectrum, frequency hopping spread spectrum, and infrared. Devices that comply

with the 802.11 standard operate at a data rate of either 1 or 2 Mbps.

In 1999, the IEEE created the 802.11b standard. 802.11b is essentially identical

to the 802.11 standard except 802.11b provides for data rates of up to 11 Mbps

for direct sequence spread spectrum devices. Under 802.11b, direct sequence

devices can operate at 11 Mbps, 5.5 Mbps, 2 Mbps, or 1 Mbps. This provides

interoperability with existing 802.11 direct sequence devices that operate only at 2

Mbps.

Direct sequence spread spectrum devices spread a radio signal over a range of

frequencies. The IEEE 802.11b specication allocates the 2.4 GHz frequency band

into 14 overlapping operating Channels. Each Channel corresponds to a different

set of frequencies.

IEEE 802.11g

802.11g is a new extension to 802.11b (used in majority of wireless LANs today)

that broadens 802.11b's data rates to 54 Mbps within the 2.4 GHz band using

OFDM (orthogonal frequency division multiplexing) technology. 802.11g allows

backward compatibility with 802.11b devices but only at 11 Mbps or lower,

depending on the range and presence of obstructions.

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Infrastructure

A wireless network centered about an access point. In this environment, the access

point not only provides communication with the wired network but also mediates

wireless network trafc in the immediate neighborhood.

IP (Internet Protocol)

The TCP/IP standard protocol that denes the IP datagram as the unit of

information passed across an Internet and provides the basis for connectionless

packet delivery service. IP includes the ICMP control and error message protocol

as an integral part. It provides the functional equivalent of ISO OSI Network

Services.

IP Address

An IP address is a 32-bit number that identies each sender or receiver of

information that is sent across the Internet. An IP address has two parts: the

identier of a particular network on the Internet and an identier of the particular

device (which can be a server or a workstation) within that network.

ISM Bands (Industrial, Scientic, and Medicine Bands)

Radio frequency bands that the Federal Communications Commission (FCC)

authorized for wireless LANs. The ISM bands are located at 902 MHz, 2.400 GHz,

and 5.7 GHz.

ISP (Internet Service Provider)

An organization that provides access to the Internet. Small ISPs provide service

via modem and ISDN while the larger ones also offer private line hookups (T1,

fractional T1, etc.).

LAN (Local Area Network)

A communications network that serves users within a dened geographical area.

The benets include the sharing of Internet access, les and equipment like

printers and storage devices. Special network cabling (10 Base-T) is often used to

connect the PCs together.

MAC Address (Media Access Control)

A MAC address is the hardware address of a device connected to a network.

NAT (Network Address Translation)

NAT masks a local network’s group of IP addresses from the external network,

allowing a local network of computers to share a single ISP account. This process

allows all of the computers on your home network to use one IP address. This will

enable access to the Internet from any computer on your home network without

having to purchase more IP addresses from your ISP.

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