PROFINET supports WLAN and Bluetooth as part of its specification. PROFINET enables wireless connections without limitations*, even with safety messages (PROFIsafe). Since PROFINET is based on standard Ethernet, it does not require specialized networking hardware. Commercial off-the-shelf Wireless Access Points (WAPs) can be part of a PROFINET network. Even though specialized industrial WAPs are not a requirement, they are common in manufacturing environments.
Industrial WAPs are robust and rugged devices. They can withstand a factory setting with challenging environmental characteristics, such as extreme temperatures, excessive moisture, vibrations, and dust. Also, industrial WAPs may have unique features designed for factory environments that require high levels of availability and reliability. The following list includes some of those specialized features:
Bandwidth Reservation: It allows users to reserve a portion of a frequency band for critical I/O traffic. All other traffic transmits through a secondary frequency band.
Antenna Diversity: Two or more antennas improve communication quality and reliability in environments with reflection issues. An indoor or outdoor setting with no clear line-of-sight between the transmitter and the receiver may have reflection issues. Signals might reflect several times before reaching the receiver. Each reflection can introduce signal degradations, such as phase shifts, time delays, attenuations, and distortions. Even with reflection issues, each antenna in the WAP receives a different signal, and collectively, they provide robust communication.
Redundancy: Redundancy increases the reliability of a wireless network by adding redundant paths of communication. For example, devices with mesh capabilities establish several paths of communication and increase reliability dramatically.
Point Coordination Function (PCF): PCF is a common solution for applications requiring continuous data flows. It describes a media access control technique defined in the 802.11 standard. PCF allows one or more WAPS to act as central administrators in the network. One WAP then assigns time slots to the other nodes, the clients: Within these slots, the frequency is reserved for these clients, and they can transmit without being disturbed. PCF allows for fast roaming; the client can switch from one cell to another quickly and minimizing connection delays. Also, there are vendor-specific PCF versions for PROFINET applications, such as iPCF.
Radio Coaxial Cable: Radio coaxial cables operate as antennas for WAPs. The coaxial cable carries the signals. Then, radio waves transmit through slits in the coaxial cable shielding. The waves are directed to a precise location, minimizing interference.
Do you want to learn more? Read this Wireless White Paper:
*More on PROFINET over Wireless here: Wireless PROFINET overview