ISAs SP100 Industrial Wireless standardization committee continues its heavy schedule of teleconferences, email debates and frequent face-to-face meetings. The process control suppliers, meanwhile, continue to introduce wireless transmitters and system products at a rapid pace without any claims of standardization. End-user demand for wireless products is rapidly increasing, but end-user participation in the work of SP100 remains sparse.
In September 2006, at the invitation of SP100, suppliers and other interested parties submitted presentations and supporting whitepapers proposing their complete or partial wireless solutions At the time, there was a separation between simple data acquisition applications (SP100.14) and more complex system-wide use of wireless for control networks (SP100.11). Some 25 presentations were submitted along with 15 whitepapers. When the issues settled, members of the SP100 committee realized that there were few technical differences between the submitted proposals! In the general meeting following ISA Expo in Houston, the committee unanimously agreed to end the division between the two types of applications, and merge the effort into a single wireless solution for the industrial plant and shop floor.
The standard being developed is now labeled SP100.11a, which will define the OSI layer specifications (e.g. PHY, DLL, etc), security specifications, and management (including network and device configuration) specifications for wireless devices serving application classes 1 (closed loop control) through 5 (data acquisition) and optionally class 0 (safety) for fixed, portable and moving devices. The standard is to focus on performance needs for periodic monitoring and process control where latencies, on the order of 100 ms, can be tolerated with optional behavior for shorter latency.
The standard is to provide consideration for the following:
- Low energy consumption devices,
- Scalability to address both small and large installations,
- Wireless infrastructure,
- Interfaces to and interoperability with legacy infrastructure and applications,
- Security and network management requirements in a functionally scalable manner,
- Robustness in the presence of interference found in harsh industrial environments,
- Coexistence with other wireless devices anticipated in the industrial work space, such as IEEE 802.11x (Wi-Fi), 802.16x (WiMedia), ZigBee, cell phones, Bluetooth and other relevant standards,
- Interoperability of SP100 devices.
Suppliers working on the standard have now coalesced into two groups, each advocating a similar field network, but differing approaches to control system integration. The WNSIA (Wireless Networks for Secure Industrial Applications) group includes Honeywell, Adaptive Instruments, 3eTechnologies International, Endress+Hauser, Flowserve, Omnex and Yokogawa. WNSIA proposes a field network centered around a set of field access points to reduce the number of hops necessary to get data from sensors to controllers. Their rationale is to minimize latency for feedback control connections. Additionally, WNSIA proposes a fully integrated protocol linking the field network to legacy control systems through a gateway device.
The Collaborative Initiative (CI) group is centered around a very complete network architecture proposed by Dust Networks with backing from Emerson, Invensys (Foxboro), Apprion, Certicom, Sensicast, Advanced Industrial Networks, Siemens, General Electric, Software Technology Group, NewTrax, Machine Talker, Oak Ridge National Laboratory and Texas Instruments/Chipcon. The CI/Dust proposal calls for a self-healing wireless mesh field network using channel-hopping. The mesh network provides greater distances at low-power consumption and alternate routing in case of obstructions and interference sources.
Politics, Collaboration and Hidden Agendas
SP100 committee members are from many types of suppliers and a few end users. At present, it appears that no supplier is attempting to pre-empt committee work to foster its own agenda. The level of cooperation and collaboration is high. End-user members currently represent process manufacturing with little representation from discrete parts manufacturing. As a result, the current objectives of the main working group, SP100.11a, is to define a wireless network architecture and protocol for typical continuous and batch process control applications. Each of the two groups have different and generally complementary technology to offer. The challenge will be to develop a single standard serving the end user with an inexpensive, highly reliable, secure, easy-to-use wireless network.
In addition, wireless HART is progressing at a rapid pace with its own agenda to supplement the wired 4-20 ma HART specification with an appropriate wireless technology similar to that of SP100s two groups.
All groups use IEEE 802.15.4 radios in a similar way. No cooperation or interoperability discussions are currently underway or even planned between wireless HART and SP100. However, many of the same suppliers and committee experts are on both committees, and offer some opportunity for cooperation.
Conclusions and Concerns
The SP100 committee appears to be on schedule to produce a standard by 2008. Some process control vendor products are already very close to the proposed physical layer, while others are not. However, all suppliers seem willing to modify current products to use whatever becomes the SP100 standard. Vendor infighting seems not to be impeding progress in the committee. In fact, in Amsterdam recently, a working group vote was taken tentatively deciding on a major protocol, with the possibility for a second one if circumstances warrant.
A major concern is that end users havent provided very much insight to the committee on potential use of wireless networks in their operations, beyond the obvious replacement of wires, once they become available at reasonable prices. Introduction of a disruptive technology such as wireless has changed every other industry when it has achieved a reasonable pricing level, for example, home networks and telephony.
SP100 should enable wireless applications for process automation well beyond simple data acquisition and control, not inhibit it.
[Editor's Note: For the complete wireless report from Dick Caro, read "ISA SP100 keeps on its wireless path."]