In addition to difficulties in realising general reliability
and timeliness requirements, the characteristics of wireless
transmission can negatively affect specific fieldbus methodologies.
Fieldbusses often utilise unacknowledged transmission,
since the probability of data not being received at all is
relatively low. Such a strategy is unsuitable for wireless where
the possibility of nonreception of a broadcast is significantly
higher. This is especially troublesome in the case of tokenpassing
networks, where the loss of the token may result in
the bus needing to reinitialise to re-establish which device is
the current master. Since interference is generally not uniform,
some equipment may receive a broadcast while others do
not. This can result in data inconsistency across a network
in which the producer-consumer model is utilised. The halfduplex
operation of wireless also means that carrier sensing
with collision avoidance is not possible and a protocol such
as CAN cannot be implemented.