By Dick Caro, CMC Associates
The February ISA SP100 (Wireless Industrial Network Standards) meeting generated some strong end-user backlash—a sharp contrast to the previous meeting where cooperation seemed to be the mantra. The backlash reflects dissatisfaction with the process being used by SP100 as it moves toward the first draft of its standard.
The issue arose at a subcommittee meeting where Honeywell and the WNSIA group (Wireless Networks for Secure Industrial Applications) proposed adoption of a new physical layer using a narrow-band, frequency-hopping spread spectrum operating at 2.4 GHz as an alternative to the previously adopted physical layer based on the use of IEEE 802.15.4 chips using direct-sequence spread spectrum with channel-hopping.
The User Working Group was meeting separately when it received news that a vote on the alternative physical layer proposal was being taken. Most of the users left their meeting room to attend the physical layer meeting so that they could participate in the voting and express their opinions on the alternative proposal.
When the vote was taken in the PHY/MAC (physical and media access layer) task group, sufficient numbers of end users were present and voted against the motion to cause its narrow defeat. Subsequent questioning of those opposed to the proposition revealed the end users’ deep dissatisfaction with the process.
A few of the users who had heard the presentation of the alternative physical layer said their needs were not being heard. They had expected that an alternative physical layer based on one of the currently available physical layers operating at 900 MHz and using frequency-hopping spread spectrum would be among the first alternatives to be considered. This alternative would have met their requirements for an inexpensive, quickly available wireless network for data acquisition that could operate over distances typically found in refineries without a repeater.
After the meeting, the co-chair of the User Working Group resigned from the position, citing alleged harassment by one of the vendor companies, thus forcing SP100 management to consider changes in the process.
THE WIRELESS "CLOUD"
Many components make up the “wireless cloud” over process plants. (Courtesy, Honeywell Process Solutions)
What Actually Happened?
Development of a highly technical standard, such as SP100, requires the cooperation of the major industry suppliers and many other specialty firms to make complex, detailed and highly technical proposals. It also requires that end users make known their actual needs in terms familiar to them and communicate them clearly to the technical committees. In this case, the users did not circulate their draft of the User Requirements document, but held it as a working paper of the User Working Group. This document also was not widely circulated outside that working group to seek input from other users not able to attend committee meetings.
Until this hiccup, the development of the architecture for SP100 was proceeding on-plan. In previous meetings, the SP100.14 and SP100.11 subcommittees developing separate proposals for wireless networks for simple data acquisition and for control systems were combined because, except for the physical layers, the proposals were very similar. The combination was approved by SP100 so the committee could concentrate on a single standard with variation only in the physical and portions of the media access layers, SP100.11a. The “default” physical layer using IEEE 802.15.4 chips previously proposed by the Collaboration Group in its proposal for a data acquisition network had already been approved.
In this meeting, as planned, the WNSIA Group headed by Honeywell, was making its more detailed proposal based on the not-so-very-well-kept secret, second-generation wireless network code-named “Raptor.” As the meeting was going on, Honeywell was demonstrating Raptor to end users in another room. It also offered ts alternative physical layer to SP100 for use in control-oriented networks. WNSIA/Honeywell also offered its media access, network, transport and application layer proposals at the same meeting. The Collaboration Group also presented detailed proposals for the media access and network layers.
Development of a standard is a difficult process, mostly because the committee is made up of technically savvy contributors from many companies who are motivated to have their previous work written into the document. End users are involved to act as a sounding-board to make sure what is proposed meets their needs. Their presence is required in ISA standards committees to balance the suppliers. The most difficult obstacle to writing standards is that every one of the committee members has a full-time job that does not include the extensive time required to actually write the standard.
The alternative is to create a standard the way the IEC does. In that system, all proposed standards recognized by some recognized standards body can be accepted as “Publicly Available Specifications.” The result of this is a multi-part standard, such as IEC 61158 Fieldbus, which began with eight parts and soon will have more than 15, none of which interoperate.
The SP100 process, operating under ISA rules, seeks to develop a single standard designed to allow interoperability of wireless field devices for process control, a requirement users have strongly requested.