802.11G Wireless - D-Link DSL-G604T User Manual

DSL-G604T Generation II ADSL2+ Wireless Modem Router

802.11g Wireless

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. 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 Transmission
Wireless local network (also 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
(a notebook computer for example) in its broadcast range. Often a wireless access point such as the AP
embedded in the DSL-G604T 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 for
data transmission. The DSL-G604T can be used by IEEE 802.11g and 802.11b devices. These two standards are
compatible but use different encoding methods 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 maintaining compatibility 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. The actual effective range of the AP can
vary depending on operating conditions. Radio signals are emitted in all directions giving the access point a
spherical range. The physical environment in which the AP is operating can impact on its effectiveness and
range. If you experience low signal strength or slow throughput, consider positioning the Router in a different
location. See Installation Considerations below concerning the wireless environment and location of the AP
(DSL-G604T).
SSID
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-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.
Channel
The AP can operate on different channels (frequency bands). This is useful when multiple APs are used in order
to avoid unwanted overlap or interference between control zones of separate APs. Wireless nodes must use the
same SSID and the same channel as the AP with which it will associate. However, using the same channel on
two different APs can contribute wireless congestion under certain circumstances. 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 Router including open or WEP, WPA and WPA2.
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