the wireless range seems to be quite straight forward for the solutions using plain Ethernet and maybe TCP/UDP encapsulation of fieldbus application layers (see also Fig. 4), such as Ethernet/IP with the CIP or MODBUS.
In these cases, Ethernet could be replaced by a wireless technology providing an IP channel. The availability of an IP layer is not a matter, of course, in the various wireless technologies currently considered for automation networks.
It exists for WLAN but not natively for WPAN.
The current work on 6loWPAN (IPv6 over WPAN, in particular IEEE 802.15.4) will mitigate this problem