DSL-G604T 54Mbps Wireless ADSL2/2+ Modem/Router Manual
Radio Transmission
Wireless LAN or WLAN devices use electromagnetic waves within a broad, unlicensed range of the
radio spectrum to transmit and receive radio signals. When a wireless access point is present, it
becomes a base station for the WLAN nodes in its broadcast range. WLAN nodes transmit digital data
using FM (frequency modulation) radio signals. WLAN devices generate a carrier wave and modulate
this signal using various techniques. Digital data is superimposed onto the carrier signal. This radio
signal carries data to WLAN devices within range of the transmitting device. The antennae of WLAN
devices listen for and receive the signal. The signal is demodulated and the transmitted data extracted.
The transmission method used by the access point is called Direct Sequence Spread Spectrum (DSSS)
and operates in a range of the radio spectrum between 2.4GHz and 2.5GHz for transmission. See the
technical specifications for more details on wireless operation.
Range
Range should not be a problem in most homes or small offices. If you experience low or no signal
strength in some areas, consider positioning the Router in a location between the WLAN devices that
maintains a roughly equal straight-line distance to all devices that need to access the Router through
the wireless interface. Adding more 802.11g access points to rooms where the signal is weak can
improve signal strength. Read the section about placement of the Router titled Location in the next
chapter, Hardware Installation, for more information.
SSID
Wireless networks use an SSID (Service Set Identifier) to allow wireless devices to roam within the
range of the network. Wireless devices that wish to communicate with each other must use the same
SSID.
Several access points can be set up using the same SSID so that wireless stations can move
from one location to another without losing connection to the wireless network.
The DSL-G604T operates in
Infrastructure
mode. It controls network access on the wireless interface
in its broadcast area. It will allow access to the wireless network to devices using the correct SSID
after a negotiation process takes place. By default the DSL-G604T broadcasts its SSID so that any
wireless station in range can learn the SSID and ask permission to associate with it. Many wireless
adapters are able to survey or scan the wireless environment for access points. An access point in
Infrastructure mode allows wireless devices to survey that network and select an access point with
which to associate. You may disable SSID broadcasting in the web manager’s wireless menu.
Wireless Security
Various security options are available on the DSL-G604T including open or WEP, WPA, and WPA-
PSK. Authentication may use an open system or a shared key. For details on these methods and how to
use them, please read the wireless LAN configuration information in chapters 3 (Basic Router
Configuration) and 4 (Advanced Router Configuration) below.
About 802.11g Wireless
Today's 11-megabits-per-second 802.11b wireless networks are fine for broadband Internet access
(which typically tops out at about 1 Mbps) but rather slow for large internal file transfers or streaming
video. However, 54-Mbps, corporate-oriented 802.11a is expensive--and because its radio uses the 5-
GHz band and 802.11b uses the 2.4-GHz band, upgrading to an 802.11a network means either
scrapping 802.11b gear or buying even-pricier hardware that can support both standards.
But 802.11g promises the same speed as 802.11a and the ability to coexist with 802.11b equipment on
one network, since it too uses the 2.4-GHz band.
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