Open protocols are also beginning to emerge and are nearing
readiness for commercial adoption. Three protocols for
wireless communication have recently been approved as IEC
standards, namely ISA100.11a, WirelessHART and Wireless
Networks for Industrial Automation - Process Automation
(WIA-PA), in standards 62734, 62591 and 62601 respectively.
The three standards share several common features, such as
the use of the IEC 802.15.4 physical layer [35]–[37] also used
in the ZigBee Protocol. These protocols overcome one of the
major weaknesses of ZigBee by modifying the 802.15.4 media
access control functionality to implement frequency hopping
[38]. WIA-PA retains full compatibility with the 802.15.4
physical standard, whereas ISA100.11.a and WirelessHART
do not [37].