D-Link DSL-604+ User Manual - Wireless Overview (802.11B)
DSL-604+ ADSL Ethernet Router User’s Guide
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Wireless Overview (802.11b)
Introduction to 802.11b Wireless
The IEEE 802.11b standard is the most widely used standard for wireless LANs today. A wireless LAN
(WLAN) is a cellular computer network that transmits data using radio signals instead of cables. WLAN
technology is commonly used on home, small office and large corporate networks. WLAN devices have a high
degree of mobility and flexibility that allow network to be quickly set up or dismantled and allow them to roam
freely throughout the network.
Wireless LAN users can use the same network applications used on an Ethernet LAN. 802.11b adapter cards
used on laptop and desktop computers support the same protocols as Ethernet adapter cards. For most users,
there is no functional difference between a computer attached to a wired Ethernet LAN or a mobile 802.11b
workstation except that hardware is not physically attached to the network. For most networks however, it may
be desirable for mobile network devices to be able to link to the wired Ethernet LAN to use shared resources
such as servers, printers or an Internet connection. The DSL-604+ unites Ethernet and 802.11b wireless private
networks with an Internet connection. The DSL-604+ supports data rates of up to 22 Mbps for wireless operation
when used in conjunction with other D-Link AirPlus devices.
Wireless LAN Basics
Some basic understanding of 802.11b wireless technology and terminology when is useful when you are setting
up the Router or any wireless access point. If you are not familiar with wireless networks please take a few
minutes to learn the basics.
Radio Transmission
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. In this way, digital
data can then be 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. DSSS is preferred method used on many 802.11b devices.
Range
Range should not be a problem in most homes or s mall offices. If you experience low or no signal strength in
some areas, consider positioning the device in a location between the WLAN devices maintaining a roughly
equal straight-line distance to all devices that need to access the Router through the wireless interface. Adding
more 802.11b 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-604+ 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. The DSL-604+ 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.