Asus PCI-N10 User Manual

Page 27

PCI-N10 WLAN Card User Manual

ASUS WLAN Card

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.
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 predefined 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 specifications. 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.