Despite the similar operational philosophy of the protocols,
they feature different network stacks and are incompatible.
Some of the key differences are that WIA-PA and ISA100.11a
allow for some of the network management functionality to be
implemented in the routing devices, while WirelessHART only
allows for centralised management by the management device.
WIA-PA implements a two-level data aggregation system,
ISA100.11a a single level of aggregation and WirelessHART
does not specify any aggregation functionality. All three
standards specify a time synchronization function to allow for
time division multiple access to the communications medium,
with ISA100.11a having an adjustable timeslot aligned to
international atomic time. WirelessHART and WIA-PA use
fixed timeslots of 10ms aligned to coordinated universal time
[37].