Much like Ethernet, the existing wireless technology was
developed for use outside of industry and no considerations for
real-time response or determinism are inherent in the media.
Wireless faces additional challenges that need to be addressed
for industrial application [32]. Wireless is highly susceptible
to interference from a variety of sources, which causes transmission
errors. Within the transmission channel itself, effects
such as multi-path fading and intersymbol interference are
present. Interference from other transmission channels is also
possible, such as might occur at the boundaries between two
wireless fieldbusses. Environmental electromagnetic emissions
may also affect wireless transmission, such as those produced
by large motors and electrical discharges. Thermal noise can
negatively affect transmission, as can the Doppler-shift induced
by rapidly moving equipment. Such interference is often
transient in nature, resulting in bursts of data and affecting the
reliability and determinability of the transmission. Wireless
transmission radii are limited by transmission strength and
negatively affected by path-fading, the degree of which is
determined by environmental factors. This makes it difficult to
design a wireless network for industrial use without first determining
the path-fading coefficient throughout the intended
usage area.