ISA100 Wireless Tutorial: An In-Depth Overview

This tutorial provides a comprehensive guide to ISA100 Wireless, covering its features, frequency bands, architecture, protocol stack, benefits, and applications.

Introduction

The ISA100.11a standard, developed and managed by the ISA (International Society of Automation), addresses various aspects of wireless technologies used in plant automation. Based on the IEEE 802.15.4 protocol, it can coexist with other wireless networks like Bluetooth, Wi-Fi, and WirelessHART. Utilizing IPv6, it gains many advantages over IPv4 in IP networks.

ISA100 Wireless Features

Here are the key features of ISA100 Wireless technology:

• Compliant with the Internet of Things (IoT) protocol stack.
• Employs 128-bit AES encryption, providing robust security at both the transport and data link layers.
• Ensures secure communication between instruments using the ISA100.11a protocol.
• Allows seamless integration with cable networks through the gateway’s Ethernet port.
• Uses very low power for communication, ensuring the safety of personnel in the plant.
• Similar to WirelessHART, but with some differences.
• An open standard that supports interoperability between devices from multiple vendors.
• Network and transport layers are based on 6LoWPAN, IPv6, and UDP.
• Utilizes TDMA/CSMA for resource sharing and collision avoidance.
• Employs mesh/star topology for communication.

ISA100 Wireless Frequency Bands

Fig-1: ISA100 Wireless Frequency Bands

The ISA100 wireless network uses the 2.4 GHz frequency band, similar to Wi-Fi and Bluetooth. It supports a total of 16 channels as shown in Figure 1. To avoid interference, it uses frequency hopping techniques. Furthermore, it automatically blacklists channels used by other protocols, improving performance and immunity against interference.

ISA100.11a Architecture

Fig-2: ISA100.11a Architecture

Figure 2 illustrates the ISA100.11a architecture, which consists of field devices and backbone devices. Field devices include non-routing I/O devices, handheld devices, and routing devices, and can be fixed, portable, or mobile. Backbone devices include a backbone router, Gateway, System Manager, and Security Manager.

The ISA100 architecture uses mesh, star-mesh, and star topologies. All nodes connected using these topologies are known as the DL subnet (Down Link subnet). The ISA100 network connects with the plant network via a gateway. Packet flow between these entities is described in the following protocol stack. Address translation is performed as needed for routing to the final destination.

ISA100 Protocol Stack

Fig-3: ISA100 protocol stack

Figure 3 shows the ISA100.11a protocol stack, which consists of five layers: physical, data link, network, transport, and application. In ISA100 wireless, a central system manager is responsible for scheduling communication for network routing. The figure depicts protocol layers at various ISA100 network entities, such as I/O devices, routing devices, backbone routers, WISN (Wireless Industrial Sensor Network) gateways, and control systems.

I/O devices are sensors and actuators that provide and/or consume data. This is the fundamental functionality needed to participate in the ISA100 network.

Here’s a breakdown of the functions of each layer:

• Physical Layer: Based on the IEEE 802.15.4-2006 2.4GHz DSSS layer.
• Data Link Layer: Provides creation, maintenance, and packet forwarding functionalities for wireless sensors in the ISA100 network. It handles data packet structure, frame formation, error detection, and bus arbitration. This layer also covers all functionalities supported by a generic MAC layer, including adaptive channel hopping, detection and recovery of message loss, clock sync, message addressing, local link addressing, message forwarding, and time and integrity checking. The DLC layer creates and uses graph-based routing.
• Network Layer: Uses 6LoWPAN and IPv6 addressing for end-to-end routing. In the ISA100 network, server/client pairs typically generate IPv6 packets, which are forwarded through 6LoWPAN routers to 6LoWPAN compliant ISA devices. The router handles protocol conversion from IPv6 to 6LoWPAN format (and vice versa) as required. Routing information present in the DLL header is used in the ISA100.11a network for delivering IP packets to the destination.
• Transport Layer: Supports connectionless protocol service based on UDP (User Datagram Protocol). Message integrity check and end-to-end security are enhanced.
• Application Layer: No specific process and control application layer is defined in ISA100 to work with its communication protocol stack. It specifies only a set of services for user applications, focusing on system management rather than process automation.

ISA100.11a Benefits

Besides the features mentioned earlier, ISA100 benefits from adopting the IPv6 protocol:

• Increased IP address size.
• Enhanced security due to IPsec.
• Robust QoS due to the elimination of NAT (Network Address Translation).
• More efficient packet processing due to simplified headers and the removal of checksums at the IP level (as in IPv4).
• More efficient routing due to a reduction in routing table size.
• Superior multicasting, saving network bandwidth.
• Automatic address configuration exists in IPv6.

ISA100 wireless benefits companies, users, and suppliers by improving performance, reducing downtime, lowering asset life cycle costs, and providing a platform for continuous improvement and innovation.

ISA100 Wireless Applications

ISA100 wireless technology is used in a wide variety of applications:

• Health monitoring of machines
• Environment monitoring
• Process control
• Gas Detection
• Monitoring of well heads
• Monitoring of tank levels
• Process monitoring from remote locations
• Fuel tank gauging
• Steam trap monitoring
• Monitoring of leaks
• Diagnosis of field devices
• Stranded data capture
• Open Loop Control
• Condition checking of equipment

The table below shows the usage classes of the ISA100.11a wireless technology standard:

It’s used for categories such as safety, control, and monitoring for class types 0 to 5 across various applications.