One of the phrases we often use to describe WirelessHART networks is “self-organizing.” This means the user doesn’t have to tell the individual transmitters how to communicate with each other—the network management software does this automatically. It works amazingly well and in most situations, as users let the system do its thing and are be pleased with the result.
Naturally, there are limitations. The self-organizing mechanisms can only work with the transmitters that are in the network, arranged as they are. As Bob Karschnia points out in his article, Meeting Wireless Network Management Challenges, a little help can improve network performance well beyond the basic default capabilities.
The most important step in managing any network, wired or wireless, is designing it correctly up front. A poorly designed network will present a host of challenges throughout its lifecycle as users try to correct errors made in initial design. On the other hand, a well-designed network will require minimal maintenance, with most issues due to changes in the network or its surroundings.
So what is a poorly designed network in this context? Since all the devices are wireless, they can all talk to each other, right? Well, yes and no. There is a limit to the communication range, and connections can be disrupted by plant equipment and structures. For best results, thought needs to be given to the design and installation process. As Bob points out, there are three key steps when designing a wireless device network:
Since the individual transmitters have to be able to send information among themselves, the signals have to travel freely from point to point, so the more other points one transmitter can reach, the better. Naturally, part of the self-organizing concept is the self-healing capability. If one communication path is blocked, the transmitters will automatically look for another. But if there are more obstructions than paths, communication can break down. Therefore, its’ important to have as many potential paths as possible.
A wireless mesh network gets its reliability from multiple communication pathways, so ensuring each device has multiple neighbors within range will result in the most dependable network. To achieve this, a minimum of five wireless devices should be within effective range of each gateway. Each wireless device in the network should have a minimum of three other devices with potential communication paths.
The problem is, we can’t see the radio signals, so there have to be tools to help visualize the communication paths. To use a common phrase, there’s an app for that.
Planning tools are available to assist with these network designs, such as Emerson’s AMS Wireless SNAP-ON application. This application allows users to upload a plot plan of the plant, and then design the wireless network for the designated area. Once the wireless network is designed, the application can monitor the network after installation to ensure correct ongoing operation. This monitoring includes troubleshooting tools driven by graphical displays and predictive network diagnostics, and reports of key network operating parameters. Using the software, network performance can be monitored and maintained by balancing wireless network usage and gateway capacity.
With this information, network managers can see if problems are happening, and then make adjustments to transmitter placement, or add supplementary transmitters or repeaters to reinforce the mesh network. Usually the need for this kind of assistance is minimal, and a few strategically-placed devices can make a big difference.
Wireless networks are becoming more widespread in industrial plants and facilities. Correct initial design of these networks is critical for reliable operation, and automation software-based tools exist to aid in these efforts.
You can find more information like this, and meet with other people looking at the same kinds of situations in the Emerson Exchange365 community. It’s a place where you can communicate and exchange information with experts and peers in all sorts of industries around the world. Look for the WirelessHART Group and other specialty areas for suggestions and answers.