Industrial wireless meshes with productivity applications

Do you remember the feeling of freedom that came when you first got your driver’s license? The newfound self-sufficiency and the expanded range of possibilities reshaped where you went and what you did. Although it’s probably not as personally fulfilling, those same characteristics of autonomy and extended range are inherent in wireless mesh networks, which are generating excitement among plant operators and engineers as the basis for the next generation of industrial automation solutions.

You don’t have to look far to see that automation product vendors and standards bodies are increasingly integrating wireless technologies into their products and standards to support the next generation of plant automation. Going wireless is seen as a way to cost effectively add additional monitoring and points of measurement. However, for wireless to work in these often challenging and dynamic environments, the technology must deliver robust performance, ease of use and cost effectiveness.

The move to use wireless technology to reduce costs and improve efficiency has been underway for some time in other parts of the manufacturing organization: in the warehouse for asset tracking and supply chain management; and at entry points for security and access control, for example. Part of the challenge to broader use of wireless for the plant floor and production facility is making these networks reliable and scalable enough to deal with these dense, harsh environments. To achieve these goals, vendors have turned to advanced networking techniques such as mesh networking.

In mesh networks, individual nodes are aware of their neighbors and can self organize, linking to each other to create a reliable message relay of network hops over short distances. This allows networks to be extended far beyond the reach of an individual link to a gateway, while at the same time providing redundant available paths to the gateway.

Although wireless is often heralded as the next big thing in automation, it certainly isn’t new. Industrial facilities have been using wireless as part of SCADA systems, telemetry and microwave communications for decades, in places ranging from waste water treatment facilities to offshore oil platforms. Two-way radios are found in virtually every plant and refinery.

The reason for increasing interest in wireless has to do in part with the emergence of mesh network architectures – many born in the enterprise IT arena – that are being adapted to meet the special needs of industrial settings. Standards-based technologies such as 802.11 are being hardened to allow mobile workers to take ruggedized tablet PCs and PDAs into the plant, while newer radios such as 802.15.4, optimized to support wireless sensor networks, are being embedded into industrial instrumentation. In addition, wireless standards are emerging from standards organizations, such as IETF and ISA, as well as industry organizations, such as the HART Foundation, which utilize mesh networking as the underlying network topology.

What does one radio talking to another to make a mesh network have to do with me getting my job done? The features that make mesh networks effective in challenging industrial environments also work well to support the people who move around those same environments.

In the early 1990s, the enterprise saw a huge increase in adoption of workforce mobility solutions that used wireless technologies such as cellular and WiFi to enable mobile workers to access information and do their jobs in the field. This transformed the way service organizations and sales forces worked, and resulted in a significant rise in workforce productivity. The mobile worker now had remote access to trouble tickets, equipment manuals, customer records and most of the information resources that used to tie them to the office.

In the world of automation, manual processes still abound for everything from measurement taking to the management of remote sites. By extending the range and lowering the costs of plant and process network communications, mesh networks offer a tremendous opportunity for improvement in the effectiveness and overall efficiency of plant workers and applications.

New wireless monitoring sensors can leverage the existing network to drive more points into the control system, while operators in the field are now able to see the control system HMIs as they make field adjustments or bring up the processes. In the past, these benefits may have simply been too costly to achieve, while in some cases they simply couldn’t be done at all without wireless, and couldn’t be done effectively without mesh technology.

Since there are no 'free lunches,’ what’s the catch? Mesh networks, like most things in life, have tradeoffs. Depending on the type of applications and configuration, mesh networks may not meet latency or bandwidth requirements. In some instances, the mesh network operation is optimized to run on battery power, which can result in a predictable and noticeable amount of latency. This may be several seconds to several minutes depending on how often the nodes 'wake up’ to listen and relay messages before going back into a sleep cycle to preserve power.

Another factor to consider in mesh network design is the possibility of diminished bandwidth. Creating multiple hops in WiFi networks decreases the amount of bandwidth available by 50% for every 'hop’ between the gateway and the client device. This makes it difficult to support a large number of broadband or Quality of Service (QoS)-dependent applications such as voice and video over wireless.

In the end, the industrial wireless revolution will encompass many technologies and topologies. Vendors and users should avail themselves of all of the wireless network tools at their disposal.

Mesh networks will be an indispensable tool for years to come and will surely coexist with point-to-point as well as star network topologies. For end users this means greater efficiency in doing their jobs, and just maybe a distant recollection of youthful excitement over the freedom to roam.