Highway addressable remote transducer protocol

A particular field network protocol known as HART (Highway Addressable Remote Transducer) is the most widely used field network protocol. It is estimated that as of 2004 there are more than 14 million HART-enabled devices installed globally and that 70 percent... 

The WirelessHART (EC 62591) is a reliable, secure, cost-effective, multivendor, interoperable international wireless standard based on the Highway Addressable Remote Transducer (HART) protocol [35]. This standard supports operation in the 2.4 GHz ISM band using EEE 802.15.4 standard radios with data rate up to 250 kbps and is characterized by a time-synchronized, self-organizing, and self-healing mesh architecture. In WirelessHART, TDMA is used with 10-ms duration for each time slot to ensure contention-free transmission and a channel-hopping scheme for added system data bandwidth and robustness is employed. There are up to 15 radio frequency channels (16 with ISAlOO.lla in some world areas). OQPSK is used. Although the use of the WirelessHART standard is supposed to be easy, the implementation is more complex than the wired counterpart. 

An example of a hybrid analog/digital protocol that is open (not proprietary) and in use by several vendors is the highway addressable remote transducer (LIART) protocol. Digital communications utilize the same two wires that provide the 4 to 20 mA process control signal without disrupting the actual process... 

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