802.11G Wireless - D-Link DSL-2640T User Manual

DSL-2640T ADSL 2+ Router User Guide

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-2640Twill 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-2640Tcan 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-2640T).
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-2640Tbroadcasts 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 and WPA.
7