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HART (Highway Addressable Remote Transducer) is a communication Protocol that provides communication among filed instruments and Host Systems . HART is a global standard for smart process instrumentation and there are more than 20 million HART enabled devices. The HART protocol makes use of the Bell 202 Frequency Shift Keying (FSK) standard to superimpose digital communication signals at a low level on top of the 4-20mA.
HART 7 is a wireless HART protocol that is the first open wireless mesh network communication standard designed especially for simple, reliable, secure, and low power wireless communication for applications such as measurement, control and asset management.
The three main elements of wireless HART architecture are wireless field devices, gateways and a network manager . The network uses IEEE 802.15.4 compatible radios operating in the 2.4GHz Industrial, Scientific, and Medical radio band. Bluetronix swarm routing protocol is also mesh routing protocol used for IEEE 802.15.4 compatible radios operating in the 2.4GHz.
According to HART, each device in the mesh network can serve as a router for messages from other devices. In other words, a device doesn't have to communicate directly to a gateway, but just forward its message to the next closest device. This extends the range of the network and provides redundant communication routes to increase reliability. The interference and other factors has to be taken into consideration before forwarding the packet on the run so as to make sure that the path chosen will always be the best path. Swarm finds the better alternative paths on the move using the approach of “learning while routing”. Swarm algorithm guarantees the reliable relay of message. Malfunctioning nodes can be isolated in swarm routing i.e. swarm has inherent security mechanism. HART using source routing must have much more overhead than the Swarm algorithm as in source routing packets carries lots of overhead. Moreover, HART’s radio, if programmed by Swarm algorithm, provides easy setup; intelligent decision making to forward the message via known-good paths; quick and self reconfiguration capability with addition and removal of nodes from the network. This suites most of the HART’s routing solutions. A new variation of swarm algorithm (Location Based Swarm algorithm) can be used for wireless applications that require location information such as locating the assets. Swarm routing can be very promising in WirelessHart’s most of the applications – in peer-to-peer communication; in simple monitoring and closed loop control systems with its sensor data acquisition and relay capability; in process automation by providing the best alternative paths achieving system redundancy.
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