D-Link DWA-140 manual Adsl Technology, Range

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 the preferred method used on many 802.11b and 802.11g devices.

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 802.11b 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-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. 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.

It is important to understand the difference between the SSID and a BSSID (Basic Service Set Identifier) or Preferred BSSID. The Preferred BSSID is defined by wireless stations to designate an access point used for access to the wireless network. The Preferred BSSID is the MAC address of the access point. Therefore any wireless stations (wireless clients) that use the DSL-G604T through the wireless interface must use its MAC address for the Preferred BSSID. A wireless station that scans the network for available access points may present the user with a choice of access points identified by their BSSID.

ADSL Technology

Asymmetric Digital Subscriber Line (ADSL) is a broadband technology that utilizes ordinary copper telephone lines to enable high-speed digital data transmission and interactive multimedia applications for business and residential customers.

ADSL greatly increases the signal-carrying capacity of copper telephone lines for faster downloads and more reliable connectivity without interfering with regular telephone services. ADSL devices make it possible to enjoy benefits such as high-speed Internet access without experiencing any loss of quality or disruption of voice/fax telephone capabilities.

ADSL provides a dedicated service over a single telephone line operating at speeds of up to 8 Mbps downstream and up to 640 Kbps upstream, depending on local telephone line conditions. A secure point-to-point connection is established between the user and the central office of the service provider.

D-Link ADSL devices incorporate the recommendations of the ADSL Forum regarding framing, data format, and upper layer protocols.

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