The transmission of data between devices in the network takes place by the simple process of modulation with radio frequencies acting as carriers of the information being transmitted. The RF is modulated according to the information signal and carried to the receiving end. At the receiving end the exact information is extracted from the modulated signal by the process of demodulation. A number of signals can be transmitted through air at the same time provided that their frequencies have a considerable gap between them. In other words the frequency of operation should be different and they will not interfere. There are one or more devices known as 'access points' through which the wireless devices communicate. An access point (AP) is a simple transmitter/receiver or 'Transceiver'.
A wireless network interface card (NIC) is required to access a wireless network which is available in various forms. Nowadays devices are available with built in NIC's. But they can also be installed separately latter. These NIC's also require necessary software drivers to be installed for their functioning.
Narrowband WLAN's keep the bandwidth of the radio frequency signal as narrower as possible, in order to just pass the information. Although the distance between the devices is reasonable but the speeds achieved are not as good as required by the corporate users. A general problem that could arise in WLAN's is the interference, which can be overcome by allotting different frequencies to different individuals. In this case since the bandwidth is narrow, interference can very well be avoided.
Spread spectrum wireless LAN's
These WLAN's use wideband RF. The use of wideband signal helps in attaining greater speeds. The most popular WLAN being used is 802.11b attaining a speed of about 11 Mbps. With the advancement of technology the speeds have been boosted even up to 50 Mbps and more. A disadvantage with spread spectrum WLAN's is the reduction of reliability, integrity and security. Since wideband signal is used, therefore it is obviously easier to detect it by an unauthorised person, making it less secure.
Infrared wireless LAN's
Infrared WLAN's have not been used much commercially as the speeds achieved in this case are very less and also shorter ranges are available. The speeds in this case are in the range of 115 Kbps to 4Mbps. Very fast infrared (VFIR) wireless WLAN's are coming up in the near future which will increase the speeds considerably. IR frequencies are very high frequencies and have a disadvantage, like light, of not being able to penetrate opaque objects. Devices using infrared technology should be in line of sight which makes their use limited. However there are some IR WLAN's which do not require line of sight, but still their range is limited.
Advantages and disadvantages
Wireless LAN's have many advantages over wired LAN's as stated below.
One can access the network from anywhere within the range of access point allowing the users to remain connected even when they are moving inside the range.
It is relatively easy to