Ref.:
TM-0149
Model: All Model
Date: June 3, 2002
Basic Wireless LAN
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WHAT IS WIRELESS LAN?
Wireless Local Area Network (WLAN) systems offer a great number of advantages over traditional wired systems. WLAN is flexible and easy to setup and manage. They are also more economical than wired LAN systems. Using radio frequency (RF) technology, WLAN transmit and receive data through the air. WLAN combine data connectivity with user mobility. For example, users can roam from a conference room to their office without being disconnected from the LAN. Using WLAN, users can conveniently access shared information, and network administrators can configure and augment networks without installing or moving network cables. WLAN technology provides users with many convenient and cost saving features: - Mobility: WLAN provide LAN users with access to real time information anywhere in their organization, providing service opportunities that are impossible with wires networks. - Ease of installation: Installing is easy for novice and expert user alike, eliminating the need to install network cables in walls and ceilings. - Scalability: WLAN can be configured in a variety of topologies to adapt to specific applications and installations. Configurations are easily changed and range from peer-to-peer net works suitable for small number of users to full infrastructure networks of thousands of users roaming over a broad area.
WIRELESS LAN CONFIGURATION
Wireless can be configured in one of following ways: - Typical WLAN Configuration - Independent WLANs (Ad-Hoc Network) - Infrastructure WLANs - Microcells and Roaming
Typical WLAN Configuration In a typical WLAN configuration, a transmitter/receiver (transceiver) device, called an access point, connects to the wired network from a fixed location using standard Ethernet cable (Figure 1.). At a minimum, the access point receives, buffers, and transmits data between the WLAN and the wired network infrastructure. A single access point can support a small group of users and can function within a range of less than one hundred to several hundred feet.
Figure 1. Typical WLAN Configuration Independent WLANs (Ad-Hoc Network) The simple WLAN configuration is an independent (or peer-to-peer) WLAN that connects a set of PCs with wireless adapters. Any time two or more wireless adapter are within range of each other, they can set up an independent network (Figure 2.). These on-demand network typical require no administration or preconfiguration.
Figure 2. Independent WLAN
Access point can extend the range of independent WLANs by acting as a repeater (Figure 3.), effectively doubling the distance between wireless PCs.
Figure 3. Extended-Range independent WLAN using Access Point as Repeater
Infrastructure WLANs In infrastructure WLANs, multiple access point link the WLAN to the wired network and allow users to efficiently share network resources. The access point not only provide communication with the wired network but also mediate wireless network traffic in the immediate neighborhood. Multiple access points can provide wireless coverage for an entire building or campus (Figure 4.)
Figure 4. Infrastructure WLAN
Microcells and Roaming Wireless communication is limited by how for signals carry for give power output. WLANs use cells, call microcells, similar to cellular telephone system to extend the range of wireless connectivity. At any point in time, a mobile PC equipped with a WLAN adapter is associated with a single access point and its microcell, or area of coverage (Figure 5.). Individual microcells overlap to allow continuous communication within wired network. They handle low power signals and “hand off” users as they roam though a given geographic area.
Figure 5. Handing Off the WLAN connection between Access Points
NOETS ON WIRELESS LAN CONFIGURATION
When configuring a wireless LAN (WLAN), be sure to note the following points:
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