ISA100 Wireless tutorial | What is ISA100 Wireless?
This ISA100 wireless tutorial covers ISA100.11a wireless features, frequency, ISA100 wireless architecture, ISA100.11a protocol stack, ISA100 wireless benefits and applications.
Introduction: The ISA100.11a standard has beeen developed and managed by ISA (International Society of Automation) to address all the aspects of wireless technologies used in plant automation. The standard is based on IEEE 802.15.4 protocol and it coexists with other wireless networks such as bluetooth, wifi and wireless HART. As it is based on IPv6, it leverages many benefits of IPv6 over IPv4 used in IP networks.
ISA100 Wireless features
Following are the features of ISA100 Wireless technology:
• It consists of protocol stack which is compliant with IoT (Internet of Things).
• It has 128 bit AES Encryption. Moreover it has security at two layers viz. transport and data link layer and hence it is more secure protocol.
• Communication between instruments can only be achieved with ISA100.11a protocol.
• It can be seamlessly integrated with cable network with the use of ethernet port available on the gateway.
• It uses very low power for communication and hence it will ensure safety of people working in the plant.
• It is similar to WirelessHART which some differences.
• It is an open standard and hence supports interoperability between multiple vendor devices.
• Network and transport layers are as per 6LoWPAN, Ipv6 and UDP.
• It uses TDMA/CSMA for resource sharing and collision avoidance.
• Uses mesh/star topology for communication
ISA100 Wireless Frequency Bands
Fig-1: ISA100 Wireless Frequency Bands
ISA100 wireless network uses same frequency band of 2.4 GHz as used by wifi, bluetooth etc. It supports total 16 channels as shown in the figure-1. But it employs frequency hopping technique which has immunity to interference from these other wireless systems. Moreover it automatically blacklists the channels used by another protocols and hence achive immunity against interference and better performance.
Fig-2: ISA100.11a Architecture
The figure-2 depicts ISA100.11a architecture. As shown it consists of field devices and backbone devices. Field devices include non routing I/O devices, handheld devices, routing devices. The field devices are fixed, portable or mobile. Backbone devices include backbone router, Gateway, System Manager and Security Manager.
The ISA100 architecture uses mesh, star-mesh and star topologies. All the nodes connected using these topologies are collectively known as DL subnet or Down Link subnet. The ISA100 network connects with plant network via gateway as shown. Packet flow between these entities have been described in the following protocol stack. Address translation is carried out as required for routing till the final destination is reached.
ISA100 Protocol Stack
Fig-3: ISA100 protocol stack
The figure-3 depicts ISA100.11a protocol stack. As shown it consists of five layers viz. physical layer, data link layer, network layer, transportlayer and application layer. In ISA100 wireless, central system manager is responsible for scheduling communication for network routing. Figure depicts protocol layers at various ISA100 network entities such as I/O device, routing device, backbone router, WISN (Wireless Industrial Sensor Network) gateway and control system. I/O devices are sensors and actuators. The I/O devices provide and/or consume data. This is the basic functionality to be implemented in order to participate in ISA100 network.
Following are the functions of ISA100.11a Protocol stack layers:
➨Physical Layer: It is based on IEEE 802.15.4-2006 2.4GHz DSSS layer.
➨Data Link Layer: It provides creation, maintenance, packet forwarding functionalities needed for wireless sensors in ISA100 network. Moreover it takes care of data packet structure, frame formation, error detection, bus arbitration etc. This layer also covers all the functionalities supported by generic MAC layer. ISA100.11a DLC layer supports unique features such as adaptive channel hopping, detection & recovery of message loss, clock sync, message addressing, local link addressing, message forwarding, time and integrity checking etc. The DLC layer creates and uses graph based routing.
➨Network Layer: It uses 6LoWPAN. It uses IPv6 addressing for end to end routing. In ISA100 network, server/client pairs usually generate IPv6 packets. These packets are forwarded through 6LoWPAN routers to 6LoWPAN compliant ISA devices. The router takes care of protocol conversion from IPv6 to 6LoWPAN format and vice versa as required. Routing information present in DLL header is being used in ISA100.11a network for delivery of IP packets to the destination.
➨Transport layer: It supports connectionless protocol service based on UDP (User Datagram Protocol). Message integrity check and end to end security has been enhanced.
➨Application Layer: No process and control application layer is specified in ISA100 to work with its communication protocol stack. It specifies only set of services for user applications. It does not specify process automation application. It specifies only system management application.
Other than the features outlined above, it has benefits due to adoption of IPv6 protocol.
These have been summarized below:
• Increase in IP address size.
• Security boost due to IPsec.
• Robust QoS due to elimination of NAT (Network Address Translation).
• More efficient packet processing due to simplified header and elimination of checksum used at IP level (as in IPv4).
• More efficient routing due to reduction in routing table size.
• It uses superior multicasting and hence saves network bandwidth.
• Auto address configuration exists in IPv6.
ISA100 wireless benefits companies, users and suppliers. It helps users due to performance improvement, reduction in downtime, low asset life cycle costs and provides platform for continuous improvement. It helps suppliers due to improvement in service performance, business profitability, provides platform for innovation. It is developed and used by hundreds of companies.
ISA100 Wireless Applications
ISA100 wireless technology is employed in wide variety of applications as mentioned below:
• Health monotoring of machines• Environment monitoring• Process control
• Gas Detection• Monitoring of well heads• Monitoring of tank levels
• Process monitoring from remote• Fuel tank guaging • Stream trap monitoring
• Monitoring of leaks• Diagnosis of field devices• Stranded data capture
• Open Loop Control• Condition checking of equipments
|Control||1||Closed Loop Regulatory Control|
|Control||2||Closed Loop Supervisory Control|
|Control||3||Open Loop Control|
|Monitoring||5||Logging and downloading/uploading|
The above table mentions usage classes of ISA100.11a wireless technology standard. It is used for categories such as safety, control and monitoring for class type 0 to class type 5 for different applications.