By Jim Taylor, VDC, and Joe Feeley, Editor in Chief
THE ANALYSTS at Venture Development conducted a comprehensive survey of industrial machine builders, system integrators, and end users regarding their understanding and use of both wireless and wired Ethernet. The study was concluded last year and readers of Industrial Networking were among those participating in the survey.
In the Spring 2005 issue of Industrial Networking magazine, we had a quick look at the overall market, identified where current activity and future growth are centered, and began to identify user preferences that emerged from the data [Network Distinctions—Part I]. Here, in Part II, we’ll explore current and emerging protocols, connectivity issues, and a host of selection, installation and operational criteria.
Data transfer over wired [wireline] or wireless Ethernet networks today is possible between the general enterprise and many classes of systems and products found in industrial facilities, including supervisory control and data acquisition systems (SCADA); HMI (operator interfaces); controllers such as PLCs, motion, temperature, etc.; distributed/remote I/O; and device-level components such as actuators, sensors, etc. Data transfer over wired or wireless Ethernet networks, of course, also is possible between these systems and products within industrial facilities.
Among the users of wired Ethernet, the largest use was noted in communication between the enterprise and the HMI and controllers (both were noted by 60% of respondents), between the HMI and controllers (61%), and, not surprisingly, between controllers (64%). In general, the smallest share of the surveyed participants use wired Ethernet to provide communications with distributed/remote I/O and device-level components, although the largest gains in use are expected for these types of data communication.
Among the wireless Ethernet users, the largest segments use these networks in data transfer between the enterprise and HMI and controllers (both registered 41% of respondents), and between controllers and distributed/remote I/O (also 41%). The lowest stated shares were for data transfer with device-level components.
More of the users expect to be using wired and wireless Ethernet as a communication network between all the classes of devices above in 2006.
Performance and Requirements
Rapid Response in Eye of Beholder — Users were queried about the minimum response times they require for their applications. For wired Ethernet, response times varied widely, with 10 msec being the most noted (by 17%) of respondents), followed by 500 msec, noted by 16%. The median required response was 85 msec.
Required response time in a wireless configuration showed similar levels of variety. The two most noted response times were 100 msec and 1,000 msec, both garnering 16%. The median response time for wireless configurations was 100 msec. Figure 1 details the variety in both wireless and wired response times. (Click the Download Now button below to view a .pdf version of all charts and tables referred to in this article.)
Transmission Distances/Topologies — For wired Ethernet users, maximum transmission differences also showed wide variation. While the median distance was 300 ft (noted by 29% of participants), 23% of the respondents reported distances in excess of 1,500 ft, and 17% indicated their maximum distances to be 100 ft or less. Over these transmission paths, the participants indicated a median message length of 512 bytes; the smallest noted was 32 bytes, the largest 5 Mbytes. The respondents also showed a clear preference for star/hub topology use (87%), as opposed to rings/daisy chains (40%).
The wireless users also summarized their topologies, showing a preference for more than one: 73% have multipoint configurations, 58% indicated point-to-point, and 42% identified peer-to-peer.
Network Load — Given the stated requirements of distance and message size, users of both wired and wireless networks also were asked about the number of devices they connect to their networks. Again, given the mix of users and machine builders, the study found large variation. While a maximum of 50 devices was the wired network median response (with the high in the several thousands, and nine being the low), the respondents said the median typical number of devices on their network was 20.
The wireless users, as would be expected, reported smaller numbers, with 10 being the median maximum, across a range that varied from 2 to 1,000 devices.
Support Our Network Troops
The survey participants were asked to describe the types of outside support services they’ve used in the implementation of their networks. Five services were proposed to consider: integration, testing, custom engineering, configuration development, and configuration management. Of these five, assistance in integration of the system was the top service needed by both camps. Forty-three percent of wireless network users and 37% of wired network users identified this need. Testing, at 28%, came second for the wired network users, while custom engineering (37%) was the second most-noted need of the wireless camp. Figure 2 details the findings here. (Click the Download Now button below to view a .pdf version of all charts and tables referred to in this article.)