Asus WL-160G User Manual download pdf (Page 55)

5. Appendix

ASUS 802.11g Access Point 55

Chapter 5 - Appendix

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 specifically 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 reflection recovery, thanks to its encoding scheme

and error correction.

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 specifies 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.

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 Configuration 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.

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Asus WL-160G User Manual Page 55