Setting the scope for ISA100 standard

Creating uniformity and building standardization into industrial wireless communications is a necessary objective for peaceful coexistence. Without standardization, uncoordinated transmissions over the same frequency – at the same time and in the same area – leads to congestion and interference, creating a losing proposition for everyone.

The ISA100 standard will support multiple protocols, including its own native protocol and others such as HART, Profibus, CIP and Foundation Fieldbus, on a single, integrated wireless network. The current release of the standard, ISA100.11a – the component of ISA100 that is involved with wireless transport of field transmitter measurements – is focused on process automation, but will not exclude factory automation or monitoring applications.

The scope for Release 1 of ISA100.11a is to create a simple and easy-to-deploy solution that will address the needs of end users ranging from the unsophisticated to networking experts. The primary focus is to serve process industry applications, assure multi-vendor device interoperability and standardize the necessary interfaces, while leaving other aspects for vendor customization. Using only 2.4 GHz 802.15.4-2006 radios to facilitate vendor interoperability, ISA100.11a addresses Class 1 (non-critical) to Class 5 applications such as monitoring. The standard’s single wireless network will accommodate current and future application or system protocol needs, while preserving existing protocol investments.

Release 1 architecture will support both process industrial wireless applications using radio bands and security features that are deployable world wide. This release will feature field device meshing for increased robustness, enhanced reliability and greater tolerance to interference. The star mesh configuration provides for quicker response times than are often necessary in some types of critical applications.

The coexistence strategy of Release 1 includes autonomous operation, planned configuration and cooperative operation. To define these further, autonomous operation negates the need for special setup; planned configuration allows operators to coordinate the wireless network parameters such as frequency use, transmit powers and directional antennas themselves; and cooperative operation permits the wireless networks to share their intended use of wireless media and operate in a manner that minimizes mutual interference. The use of channel-hopping to support coexistence and increase reliability is a proven technique to minimize the impact of interference in a congested band.

Providing a simple, flexible and scaleable security to address major industrial threats leveraging 802.15.4-2006 security, is a major design facet of ISA100.11a. This will allow for reduced costs, quicker implementations and a broad consensus among security experts. Careful consideration of security requirements has been given throughout the whole system – not just at the Phy layer or MAC sub-layer.

Critical and extremely time-sensitive applications will be served in later releases and will provide for reliable and secure operation for non-critical monitoring, alerting, supervisory control, open loop control and closed loop control applications. A definition of the specifications for low data rate wireless connectivity with fixed, portable and moving devices supporting very limited power consumption requirements will be provided.

The application is focused on needs for monitoring and process control where latencies on the order of 100 ms can be tolerated with optional behavior for shorter latency.

This will provide robustness in the presence of interference found in harsh industrial environments and with legacy systems.

WirelessHART is a wireless mesh network communications protocol for process automation applications. The Hart Communications Foundation has issued its specification, under HART 7.0, for a wireless physical layer alternative to its original 4-20 mA wired infrastructure. It adds wireless capabilities to the HART Protocol while maintaining compatibility with existing HART devices, commands and tools. The network uses IEEE 802.15.4-compatible radios operating in the 2.4 GHz Industrial, Scientific and Medical (ISM) radio band and while WirelessHART mesh and ISA100.11a mesh will operate independently, a single gateway device could service both networks.

HCF and ISA100 established a joint task force in October 2007 to evaluate interoperability and co-existence options for WirelessHART and ISA100.11a. To ensure compatibility, continuity and uniformity, the two groups are cooperating and relying heavily on end user and vendor input.

ISA100.11a’s Release 1 will attempt to accommodate the HART7 wireless protocol through a dual-gateway architecture, followed by a potentially more integrated approach in Release 2.

The development schedule, which includes all steps in the standards development process per ISA’s procedures as accredited by the American National Standards Institute, calls for the standard to be available in draft form for committee review by the end of March.

After circulating the draft, editing based on comments from the committee and recirculation of any further drafts, the committee will release the standard for official committee ballot, ISA review and ANSI review in early September. The ANSI review process, depending on comments received, could be complete by late October, with a final draft sent to the ISA Standards and Practices Board in the beginning of November.

Once the final draft of ISA100.11a has been approved by the Board, the standard will officially be published. The committee has agreed that the final steps will be complete by mid-November.

The ultimate goal for ISA100 is an open, easy-to-use, quality standard that will stand the test of time by adapting to changes within the industrial environment. Completion of the WirelessHART and ISA100 standards is critical in enabling a variety of industries to finally – and enthusiastically – embrace wireless technology to improve productivity.

The combined WirelessHART and ISA100 standards will end niche application implementation and usher in the widespread plant adoption rates that have been anticipated in the marketplace for years.