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DSL-G684T Wireless ADSL Router User Guide
Setting Up a Wireless Network
In order to get the best performance from the wireless component of the Router, you should have some basic
understanding of how wireless networks operate. Wireless networking is a relatively new technology and there are more
factors to consider when setting up or designing a wireless network than designing a wired network. If you are setting
up a wireless network, especially if you are using multiple access points and/or covering a large area, good planning
from the outset can ensure the best possible reliability, performance, coverage and effective security.
Radio
Wireless local network (as called WI-FI) devices such as notebook computers and wireless access points use
electromagnetic waves within a broad, unlicensed range of the radio spectrum (between 2.4GHz and 2.5GHz) to
transmit and receive radio signals. A wireless access point (AP) becomes a base station for the wireless nodes (notebook
computer for example) in its broadcast range. Often a wireless access point such as the AP embedded in the
DSL-G684T, will also provide a connection to a wired network - usually Ethernet - and ultimately an Internet
connection. The IEEE 802.11 standard precisely defines the encoding techniques used to digitally used for data
transmission. The DSL-G68T can be used by IEEE 802.11g and 802.11b devices. These two standards are compatible
but use different algorithms for data transmission.
802.11g uses a method called Orthogonal Frequency Division Multiplexing (OFDM) for transmitting data at higher data
rates. OFDM is a more efficient encoding method than Direct Sequence Spread Spectrum (DSSS) transmission, the
method used by 802.11b devices. However, in order to support different data transmission rates while also be
compatible with 802.11b, 802.11g uses a combination of OFDM and DSSS when 802.11b devices are present.
Range
An access point will send and receive signals within a limited range. Also, be aware that the radio signals are emitted in
all directions giving the access point a spherical operating range. The physical environment in which the AP is
operating can have a huge impact on its effectiveness. If you experience low signal strength or slow throughput,
consider positioning the Router in a different location. See the discussion below concerning the wireless environment
and location of the AP (DSL-G684T).
SSID and Channel
Wireless networks use an SSID (Service Set Identifier) as means of identifying a group of wireless devices, similar to a
domain or subnet. This allows wireless devices to roam from one AP to another and remain connected. 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 embedded wireless access point of the Router 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-G684T 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.
In addition, the AP can use different channels (frequency bands) to avoid unwanted overlap or interfere between control
zones of separate APs. Wireless nodes must use the same SSID and the same channel as the AP with which it wishes to
associate. However, because of the nature of the CSMA/CA (carrier sense multiple access with collision avoidance)
protocol, using the same channel on two different APs can contribute significantly to wireless congestion. If you are
using multiple APs on your network and are experiencing low throughput or significant transmission delay, carefully
consider how channels are assigned to the different APs.
Wireless Security
Various security options are available on the DSL-G684T including open or WEP and WPA (including WPA-PSK).
Authentication may use an open system or a shared key. Read below for more information on configuring security for
the wireless interface.
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