Filter
Top Products
PCE-N10 WLAN Card User Manual
24
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 predened 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 specications. 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.