Using electromagnetic waves, WLAN devices transmit and receive data through the air; eliminating the need for network cables and making them fail in a wireless LAN. Thus, if a company has a LAN, to move to another seat is not required cabling and drilling in the walls and ceilings they require, but simply move their computers and networks can work immediately. True, they generally WLAN networks are used together with conventional LANs, especially for network printing part for connection to the server.
LAN sites using electromagnetic waves of radio and infrared field. The first type is the most common, since radio waves pass through walls and other solid objects, while infrared radiation, as light cannot pierce the opaque objects and has a much smaller range. However, this latter type is considered by some solutions for connecting to equipment not running while data is transferred.
As I said, in most cases is a link between the WLAN and LAN. This is done by so-called access points (access points, AP). An access point, which is a transmitter or a wireless receiver, connects to a LAN cable. It receives stores and transmits data from / to devices in the WLAN and the LAN and has a range that goes from 30 to 300 meters. For example Air Connect from 3COM equipment has a range of 60 meters in standard office buildings. Such equipment used outdoors, although they are not designed only for use in rooms, reaches up to 300-400 meters.
Users access the WLAN through special adapters, which is in the form of PCI and ISA cards for desktop PCs, or to external equipment for notebooks. They work as a classical network cards and installed operating systems treat them as network adapters. Basically, that there is a wireless connection instead of cable is transparent to the operating system.
In phase configurations as with LAN, WLAN and the there are several topologies. The simplest WLAN site is independent. Each time when two PCs are in reach of their wireless LAN adapters, can establish a connection. This configuration requires no special configuration or administration. An access point added to this configuration almost doubles the range, operating as a receiver.
Extending the analogy with LAN networks, the access point acts as a hub, doubling the maximum distance between PCs.
The second topology is called infrastructure, where several WLAN access points connecting to your wired LAN, allowing users to efficiently use network resources. APs are not just about LAN, but also manage the WLAN traffic in their range of action. Several APs can cover even a very large building.
Wireless communication distance is limited Dew which covers a WLAN equipment, the latter being a feature of the power transmitter / receiver. WLAN using cell sites, which here are called micro-cells to expand the coverage area of WLAN’s. A microcell is coverage of an access point. The principle is similar to cellular telephony. At any time a user has a mobile PC equipped with WLAN adapter is associated to a single microcells. Since the passage microcells overlap from one user to another does not interrupt microcell communication between him and the network. There is one case where it is continuous: if your protocol uses TCP / IP. Data transfer over TCP / IP and the transition from a microcell to another point of attachment to network change (AP changed since), but IP address does not change. This can lead to packet loss. But even this case, there are solutions to restore the connection without losing data. 3COM IP phones to work as follows: the transition from AP to another WLAN adapter lets first address the second AP so that all packets are routed first to the second access point and to notify the user that has not changed AP site.
