Wireless Local Area Network, WLAN for short, denotes a wireless, local network that is based on the IEEE 802.11 standard and is compatible with wired Ethernet.
It is therefore often referred to as Wireless Ethernet. In Ethernet-based automation networks such as PROFINET RT, EtherNet/IP™ or Modbus/TCP, Wireless LAN enables automation devices to be integrated wirelessly.
The different technologies are specified in a group of standards: IEEE 802.11. The most important standards from IEEE 802.11 are:
The main difference in the standards is the data rate that can be achieved, whereby the effective achievable net data rate is only around 50% (see graphic).
Wireless LAN is characterized by the fact that, as is the case with Ethernet, large networks can be constructed with several devices. In contrast to wired Ethernet, however, this wireless medium is a so-called shared medium, which must be shared by all devices in the network or frequency band.
This results in longer latencies, increased jitter, and, generally speaking, a reduced bandwidth the more devices there are in the network in comparison to a wired connection. These factors must be taken into account when planning the automation application. The industrial WLAN products from Phoenix Contact are optimized for short latencies with low jitter.
One particular strength of Wireless LAN is the mobility of the devices in the network. The devices in a large WLAN network can move freely and therefore switch their wireless connection automatically to the access point with the best wireless signal. This process is known as roaming.
The wireless field of a WLAN network can be infinitely extended through the use of additional access points. The speed and reliability with which the devices - so-called WLAN clients - can switch cells is decisive in automation applications. Fast and reliable roaming is a quality feature of industrial WLAN products from Phoenix Contact.
The latest Wireless LAN systems according to the IEEE 802.11n standard offer a considerably higher data rate of several 100 Mbps in comparison to older WLAN standards together with a longer range and increased reliability.
The most important technical feature of IEEE 802.11n is the MIMO (Multiple Input, Multiple Output) antenna technology. It sends and receives several parallel streams of data at the same time via up to three active antennas. As such, reflections in the room are used in a targeted way to increase the data rate and improve the reliability and stability of the wireless connection, particularly in industrial environments.
Wireless LAN's areas of application in industrial environments are diverse and on the increase. The increasing need to communicate process and operating data together with the increasing mobility and remote nature of numerous applications rely on the use of wireless network communication.