Dick Caro reports, special to ControlGlobal.com on the plenary meetings held this week by ISA’s SP100 Committee in Research Triangle Park, North Carolina to discuss the Responses to the RFP the Committee released earlier this summer.
ISA SP100 Wireless Network Committee Shoot-out
By Dick Caro
In a rare face-to-face open meeting at ISA’s headquarters in Research Triangle Park, NC, the members of ISA’s SP100 committee heard 23 presentations from the automation vendors and significant consortiums. These groups presented their views on the protocol requirements and submitted their recommendations for the wireless technology they favor. To further clarify the technical content, each vendor and consortium was asked to supply a white paper to the committee, but these are mostly not yet available. Panel discussions were held to discuss the communications layers that were proposed during the presentations. Additionally, a special session was held to discuss how IEEE 802.15.4 and the work of the ZigBee Alliance could be harmonized. SP100 leaders stressed that the purpose of these presentations was not to select one of the proposed protocols as the SP100 standard, but to allow the innovation contained in each proposal to be identified together with the user problem it solved so that these innovative features can be considered for the SP100 standard.
Some of the consortiums were clearly identified, but some have been reported earlier. Here is a list of the cooperating companies:
• WNSIA (Wireless Network for Secure Industrial Applications) – a cooperation between Honeywell, 3eTI, Adaptive Instruments, Endress+Hauser, Flowserve, Omnex Controls, and Yokogawa
• STG (Software Technologies Group) and Sensicast
• WINA (Wireless Industrial Networking Alliance), Apprion, Invensys
• Emerson and Dust Networks
Most of the proposed protocols depend on the use of IEEE 802.15.4 radios also used by ZigBee. It also seems that there is broad consensus that the 2.4 GHz radio band currently used by Wi-Fi, ZigBee, Bluetooth, cordless telephones, and microwave ovens, should be used but with some type of protocol adjustment to allow peaceful coexistence with these other wireless networks. They generally call for the use of mesh network topology supported by these low power radios and the ZigBee Network layer. Several presenters suggested that the direct sequence spread spectrum (DSS) protocol of 802.15.4 be either replaced by or augmented with some frequency or channel hopping in order to eliminate the effects of interference. All presenters agreed that impenetrable security, high reliability, and very low power consumption were necessary elements of their proposals. Several specific recommendations were made on methods to achieve a high degree security, usually through existing methods of encryption and authentication.
The general consensus was that wireless industrial networks were too small a market to demand a dedicated frequency channel assignment, or to use custom hardware. This market would best be served by adapting use of high volume electronics and parts made for broad market wireless services such as those addressed by the IEEE 802.15.x standards.
Here is a very brief summary of the presentations:
Analog Devices – an original protocol using narrow-band adaptive-FHSS in the sub-GHz region (780 to 956 or 426/27 MHz) to escape the busy-ness of 2.4 GHz.
Emerson and Dust Networks – 802.15.4 time synchronized, channel hopping, self-organizing mesh network at 2.4 GHz with a variety of wired and wireless upper level (backhaul) networks.
WNSIA – Frequency hopping field network at either 2.4 GHz or 800/900 MHz connecting to a multiprotocol backbone network to pass EDDL-based messages highly compatible with HART, FOUNDATIONTM Fieldbus, or Profibus. Network quality of service is very similar to FOUNDATIONTM Fieldbus using distributed time-based publish and subscribe. Agreement among the WNSIA member companies was that SP100 be viewed as a wireless extension of the fieldbus networks, including HART.
Crossbow – ZigBee XMesh compatible network at 2.4 GHz with time synchronized slow frequency hopping for network coexistence. Uses XServe for application layer interface, security, and network management.
Siemens – Presented their analysis of application needs and recommended a backbone based on use of Wi-Fi with the PROFInet wireless draft specifications. They also suggested that SP100 use elements of IEEE 802.15.4 but with only selected bands within the 2.4 GHz domain and use both star and mesh topologies with TDMA.
General Electric – Recommendations for both 2.4 GHz and 5.0 GHz using both CSMA and TDMA protocols based on data rates and coexistence requirements. Security key management proposed for network authentication.
STG and Sensicast – Based on use of 802.15.4 radios with adaptive channel hopping using star connected edge nodes and mesh connected routing nodes. Use TDMA if adopted by ZigBee/802.15.4. Recommendations for using a “tunneling” strategy for simplification of mesh networking. Use 802.11a at 5 GHz for the backbone network.
AIN – Based on the use of 802.15.4 with adaptive frequency hopping using star connected edge nodes and mesh connected routing nodes. Splits the time into contention free periods and contention access periods to support event-driven access from edge devices. Recommends use of 802.11e specification for connection of gateways to Wi-Fi backbone network.
Nanotron – Introduces IEEE 802.15.4a, an addition currently in committee, for use in SP100. Offers use of either CSS (Chirp Spread Spectrum) or Ultra-wideband physical layers. Improves multipath performance in highly metallic environments, better propagation through solids, and increases available data rate.
Newtrax – Introduces applications in underground mines and in intermodal transport where conventional 2.4 GHz signals have difficulty in penetrating the ground or the container walls. Recommends the use of full mesh network topology and use of GPSK (Gaussian Phase Shift Keying) signal modulation.
Machine Talker – MachineTalker proposed Kerberos as the wireless security standard for ISA-SP100.
Texas Instruments – TI proposed the use of the entire ZigBee stack for SP100.
Certicom – Provided a tutorial on security for wireless networks and the improvements they have recommended for use in ZigBee.
Zhejiang University and SUPCON – Stressed that redundancy is often needed for wireless networks, but may be less costly in wireless than for wired redundancy. Recommended that TDMA be used to reserve time for non-contention access.
Shenyang Institute – Submitted a protocol for synchronized frequency hopping using 802.15.4 radios. Supports mesh networking at the Network layer similar to ZigBee but with advanced routing algorithms.
Oak Ridge National Laboratory – ORNL recommended that IEEE 1451 be used as the basis for SP100. IEEE 1451.5 is the wireless segment of this draft standard.
Individual presentations were given by Adaptive Instruments, Omnex, Yokogawa, and 3eTI, but each of these deferred to the WINSA presentation given by Honeywell.