Asus PCI-N10 User Manual download pdf (Page 26)

PCI-N10 WLAN Card User Manual

ASUS WLAN Card

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 lowerspeed subcarriers, which are then

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

up into 52 subchannels, each approximately 300KHz 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.

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

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

encode 125Kbps of data per channel, resulting in a 6,000Kbps, or 6Mbps, data

rate. Using quadrature phase shift keying, you can double the amount of data

encoded to 250Kbps per channel, yielding a 12Mbps data rate. And by using

16-level quadrature amplitude modulation encoding 4bits per hertz, you can

achieve a data rate of 24Mbps. 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 24Mbps. 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.

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Asus PCI-N10 User Manual Page 26