beautypg.com

Chapter - appendix – Asus WL-320gE User Manual

Page 54

background image

.

Appendix

ASUS 802.11g Access Point

Chapter - Appendix

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.

Encryption

This provides wireless data transmissions with a level of security.

Extended Service Set (ESS)
A set of one or more interconnected basic service set (BSSs) and integrated

local area networks (LANs) can be configured as an Extended Service

Set.

ESSID (Extended Service Set Identifier)

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

its wireless clients. The ESSID is a unique identifier for your wireless

network.

Ethernet

The most widely used LAN access method, which is defined by the IEEE

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