Setting Up a Wireless Network, Radio, Range

DSL-2740B 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- 2740B, 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- 2740B 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-2740B).

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-2740B 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-2740B including WPA, WPA2, and mixed WPA/WPA2 (including PSK). Authentication may use an open system or a shared key. Read below for more information on configuring security for the wireless interface.