Unlike wired communication, radio communication links are dynamic because they are affected by environmental changes. Changes such as addition of new radios, construction, weather events and tree foliating are among the many influences that can affect radio communication performance and overall network availability. High network availability and reliability are the building blocks of Honeywell’s OneWireless network DNA. This white paper details the features that contributes to the OneWireless network’s wired-like performance and data availability; hence ensuring that no alarms or alerts are caused by potential data packet losses or link degradation.
OneWireless network overview
OneWireless is a flexible industrial wireless network that can be tailored to meet the coverage requirements of industrial automation applications, from a simple sensor mesh network providing wireless coverage for ISA100 wireless field devices to a plant-wide wireless local area network providing coverage for WiFi devices.
OneWireless’s flexibility is based on its rich portfolio of meshing components, i.e. Wireless Device Manager (WDM), Field Device Access Point (FDAP), Cisco Aironet 1552S access point and Cisco wireless local area network (WLAN) controller.
Wireless Device Manager
WDM manages all wireless field devices, including ISA100 Wireless field instruments and network infrastructure devices such as FDAPs and the Cisco Access Points. Assuming the roles of the wireless field instrument network gateway and system and security manager, WDM is used for initial wireless device configuration and storing wireless network system data that is used to configure wireless devices. It also generates, issues and manages the security keys for all field devices required to join the secured network. Keys can be provisioned to a wireless field device via infrared or over-the-air provisioning methods, as defined by the ISA100 Wireless Standard. Finally, the WDM hosts the required interfaces needed to send ISA100 wireless data to the control application: Modbus, OPC UA, OPC DA, HART, Gateway General Client Interface, Honeywell Enraf, and Honeywell Experion PKS CDA are all supported.
Field Device Access Point
The FDAP is a rugged industrial access point for ISA100 wireless field instruments. Once deployed in the field, FDAPs self-discover and self-organise into a managed, secure and redundant wireless field instrument mesh network. They are the bridge between the sensor network and the wireless or wired infrastructure (backhaul).
Cisco Aironet 1552S outdoor access point
The Cisco Aironet 1552S access point is a rugged industrial device for WiFi (IEEE 802.11 a/b/g/n) clients and ISA100 wireless field instruments. Once deployed in the field, the access point self-discovers and self-organises into a high-speed wireless LAN capable of tunnelling data between ISA100 Wireless and WiFi devices and associated host applications such as Honeywell’s Experion PKS control system.
Cisco wireless controllers
Cisco wireless controllers manage the Cisco 1552S access points by extending the network policy and security from the wired network core to the wireless edge.
OneWireless XYR 6000 field instruments and other ISA100 wireless devices
Honeywell OneWireless XYR 6000 field instruments let customers capture information from locations where running wire is cost-prohibitive or measurement is in a hazardous location. In addition to its sensing capabilities, Honeywell’s wireless field devices can act as routing devices; meaning that they can route data received from neighbouring wireless field instruments as well as their own data.
Reliability features
Meshing technology
Industrial wireless products have been used within plant facilities for decades. So what technological evolution has triggered the wider adoption and usage of wireless within the process industry? The short answer is wireless meshing. Wireless meshing permits neighbouring devices communicating using the same protocol to be interconnected and exchange data amongst themselves, hence significantly increasing the availability and reliability of the data being communicated over a non-deterministic medium.
Optimised graph routing for path diversity
Although the ISA100 Wireless Standard supports two types of routing – graph and sourcing – Honeywell has opted for graph routing for its ISA100 wireless meshing algorithm. The graph routing is managed by the system manager and is based on device-generated reports that indicate instantaneously the quality of wireless connectivity to neighbouring devices. Honeywell’s graph routing algorithm has been optimised to take into account key link health metrics including the received signal strength indicator (RSSI), received signal quality indicator (RSQI), transmit fail ratio and hop count. The algorithm also takes into account other parameters such as data throughput, data frequency, individual channel characteristics, power constraints and latency requirements. Once the system manager makes its routing decisions it configures the optimum routes for each device in the network. The routes are dynamically recomputed to deal with any upsets in the network such as radio interference, path obstructions and node failure, and provide a field device with multiple graph routes to send its data to the WDM.
Wireless Device Manager redundancy
The WDM is the heart of the ISA100 Wireless network as it manages the routes and hosts the interfaces required to send the data to host applications such as a control system or historian. A WDM failure will result in total loss of the ISA100 Wireless network and the data being sent by the field devices. To improve the network’s availability and eliminate single point of failure, Honeywell offers redundant WDMs. Two WDMs can be configured as a redundant pair, consisting of a primary and secondary. The primary will constantly synchronise configuration and process data to the secondary in real-time. The secondary will switch to the primary role if a failure occurs on the primary.
Backbone routers
OneWireless leverages ISA100’s IPv6 protocols to offer an extremely scalable network. The ISA100 Wireless Standard defines an access point as a backbone router (BBR). A backbone router connects the wireless network to a backbone such as a wired Ethernet network or a wireless Ethernet network. In other words, an FDAP connected to the WDM via an Ethernet cable is a backbone router. Similarly, a Cisco 1552S access point also contains a backbone router, as within the enclosure there is an ISA100 backbone router connected to a wireless Ethernet bridge. Each ISA100 backbone router embedded in the Cisco 1552S access point will have a dedicated IPv6 address.
It is important to note that an ISA100 field instrument is not restricted to a specific access point. It can connect to multiple access points to send its data back to the process control network. Honeywell recommends each ISA100 Wireless field instrument to communicate with at least two access points. Once the wireless infrastructure is in place, the site can install hundreds of wireless field devices within the facility without having to worry about the device association with a specific access point. The device will send its data through the network to the WDM.
Conclusion
The Honeywell OneWireless network has been designed by automation professionals for automation professionals. Features such as meshing, graph routing, support of multiple access points, system manager redundancy and dedicated VLAN enhance the network’s availability, security and reliability. More than 500 plants have extended their process control network with OneWireless and are leveraging its highly reliable network for applications that go beyond non-critical monitoring. They are using wireless field instruments for critical monitoring applications, environmental compliance applications and non-critical control applications.
For more information contact Boni Magudulela, Honeywell Southern Africa, +27 (0)11 695 8000, [email protected], www.honeywell.com
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