WLAN
WLAN (Wireless Local Area Network) is standardized in acc. with IEEE 802.11b/g for local wireless networks. The WLAN uses the 2.4 GHz ISM band (Industrial, Scientific and Medical) as a transmission medium. This cost- and license-free frequency band is available worldwide.
WLAN uses the frequency spread method as the transmission method (DSSS - Direct Sequence Spread Spectrum). Here, the available frequency band is divided into frequencies from 2.401 GHz to 2.483 GHz on 13 channels, each having a bandwidth of 22 MHz. But not all channels are released for use in all countries, however. In Europe, channels 1-13 are permitted, and in the USA and Canada, Channels 1-11.
Since the channels overlap each other, not all channels can be used at the same time without the devices interfering with each other. This results in the recommendation to only use channels 1 | 6 | 11. In Europe, one can also use channels 1 | 7 | 13 or 2 | 7 | 12 or even 3 | 8 | 13 in parallel without them influencing each other.
Based on WLAN, high-performance wireless networks can be realized with many devices since theoretically there is no limit to the number of devices. However, the involved devices must share the available bandwidth (shared medium). The data rate can be up to 54 Mbps, depending on the surrounding conditions. Thus, WLAN, for example, is optimally suited for Ethernet communication with mobile controls. Since data is transmitted with a transparent protocol, WLAN systems can be easily integrated in IT networks.
The maximum permissible transmission power for the 2.4 GHz ISM band is limited to 20 dBm (100 mW). Thus, a range of 200 m can be reached outdoors. Under certain conditions, such as when using panel antennas, the range can be extended even further. In any case, however, it must be considered that the range depends on the surrounding conditions.
In order to guarantee high data security, various encryption mechanisms (WEP, WPA, WPA PSK .) and authentication (EAP) are used.
