SCADA Applications Benefit from SDR Wireless Communications Products
Most consumers would be surprised to learn that their cellular phones are based on an old technology that their grandparents used in lieu of TV for entertainment – the old-fashioned radio. Today, there are over 1 billion digital cellular phones in use that are serviced by more than a million base stations. These cellular phones and base stations are actually sophisticated transmitters/receivers (transceivers). Unlike cellular radios and analog tuners of yesteryear, today’s cellular phone devices are actually software-defined radios (SDRs) with coded radio functions executing on embedded microprocessors.
California-based ArWest Communications Corporation is putting this same class of radio technology to good use in the Supervisory Control and Data Acquisition (SCADA) market. The diverse applications of SCADA include asset-management for real-time inventory tracking; remote control/reporting within the utilities, oil/gas and water industries; crop monitoring and reporting for agriculture; Global Navigation Satellite System (GNSS) operations (which is a satellite-based radio navigation system that also uses ground-based systems to improve the accuracy of positional data); and wireless data systems for public safety and transportation to improve the flow of traffic. (Wireless data systems are typically used by dispatchers, police officers, emergency medical services and the military personnel.)
As ArWest began to develop its transceiver aimed at the SCADA market, they searched for a processor with low power consumption that could handle both microcontroller (MCU) and signal processing tasks. ArWest chose the Blackfin® ADSP-BF532 processor from Analog Devices, Inc. (ADI) because it exhibited the lowest power consumption in its class of processors. “Since our wireless communications systems are deployed in the field during rugged conditions,” said Barrie Hogarth, Vice President of Marketing at ArWest, “low power consumption and high reliability are an absolute must.”
Typical SCADA Applications
GNSS is a network of satellites that transmit signals used for positioning and navigation anywhere around the globe, on land, in the air, or at sea. The United States uses GPS, Russia uses GLONASS, and Europe will soon use GALILEO − all are examples of GNSS. The systems themselves have a positional accuracy in the order of tens of meters, which is more than adequate for most users. Users who require higher accuracy will need to use “differential techniques,” which involves a process whereby a GNSS receiver is placed at a known location (a base). Measurement errors that cause position errors are provided as “corrections” to the GPS unit (the rover) for which the position needs to be determined. Correction services that improve the accuracy to the order of a few meters are suitable for most applications, but accuracies in the sub-meter to the millimeter level are also available. The corrections are typically provided in real-time via a dedicated wireless data service.Reliable wireless data links are an integral part of precision agriculture. This is where knowing and caring about where you are in the field is vital. Wireless data networks combine accurate position and sensor output such as soil moisture level, fertilizer requirements and crop yield. This makes farming much more scientific than intuitive and helps the farmer make better decisions. It also enables a reduction in chemicals and fertilizer costs through more efficient application, more accurate farm records, increased profits, and a reduction in pollution.Battlefield management is especially important today because of the interaction of technology and national security. Battlefield commanders need access to vital information so they can make informed decisions about how and when to deploy vehicles, tanks, troops, and helicopters. They can use radios with high degrees of encryption to meet military requirements for the 50 MHz to 800 MHz range to ensure maximum signal availability.
Relying on Technology
As noted above, SCADA technology is a vital component within many industries − from distribution to exploration to production. This technology enables work crews to be dispatched quickly to any problem area without the use of expensive leased lines, and i allows a user to monitor and control the processing and delivery of a product. In keeping with SCADA technology, wireless data communication must not only be reliable, it must also be cost-effective. Care must also be taken to minimize system interruptions and the costs associated with operational downtime.
ArWest set about to develop its VHF/UHF narrow-band radio transceiver using signal-processing technology originally developed for the cellular phone market. Ultimately, the company developed systems that can be managed, monitored and modified through the Internet. Basing its products on SDR, the company was also able to incorporate many other technologies, including high-level modulation techniques − GMSK/BPSK, QPSK, 8PSK, and 16QAM − that allow the user to achieve the highest data speed (over-the-air of 38400 bps at 25 kHz and 19200 bps at 12.5 kHz) for up to 50 miles.
“To meet our stringent design requirements, we wanted a processor with 240 MHz and power consumption less than 300 mW,” said Hogarth. With performance of 240 MHz, the Blackfin ADSPBF532 processor met ArWest’s performance needs, and with the chip powered at 3.3 V, power dissipation was low enough to meet the company’s stated requirements.
Blackfin processors provide world-class power management and performance and are created in a lowpower and low-voltage design. This family of processors features on-chip dynamic power management with the ability to vary both the voltage and the frequency of operation to significantly lower overall power consumption.
“We also wanted a chip that could handle both MCU and signal processing tasks simultaneously,” said Gagik Harutyunyan, Chief Technology Officer at ArWest, “and Blackfin was ideal.” Blackfin processors combine breakthrough signal-processing performance and power efficiency in a RISC programming model. The processors allow flexible resource allocation between hard real-time signal processing tasks and non-real-time control tasks, with system control tasks often running in the shadow of signal-processing tasks. Blackfin processors also include advanced memory management that support memory-protected embedded operating systems. ArWest used Express Logic’s ThreadX® realtime operating system to host the application.
Rich Set of Peripherals
ArWest’s current line of AlphaWave (AW) radio modems are pre-configured to operate in the following frequency ranges: the AW400 operates in the 403 to 470 MHz band; the AW200 operates in the 220 to 235 MHz band; and the AW100 operates in the 150 to 170 MHz band. These products can be software configured with inter-channel spacing of 25, 12.5 or 6.25 kHz to eliminate cross talk. The AW400 can be configured to both “Transmit/Receive” or to “Receive Only.” ArWest products transmit power of 100 mW to 35 W, complying with European Telecommunications Standards Institute (ETSI) regulations and Federal Communications Commission (FCC) regulations.
These radio modems include other features such as selectable error correction, which improves the operation of the radio modems under interference, data scrambling, frequency hopping, low power consumption, sleep modes and plug-and-play installation for remote terminals. “There’s no need for periodic calibrations as with older radio modems,” said Hogarth. “Our new AlphaWave radio modems are ideal for meeting the varied conditions of SCADA users in a diversity of markets.”
| Distributed via Avnet, Inc. ArWest purchased the Blackfin processors through Avnet, Inc., one of the world’s largest B2B distributors of semiconductors, interconnect, passive and electromechanical components, enterprise network and computer equipment, and embedded subsystems from leading manufacturers. |
The Blackfin ADSP-BF532 processor contains a rich set of peripherals connected to the core via several high bandwidth busses, providing flexibility in system configuration as well as excellent overall system performance. This set of functions satisfies a wide variety of typical system support needs and is augmented by the system expansion capabilities. Thanks to Blackfin, ArWest’s AW products can be maintained without interruption and the radio parameter settings can be changed through the unit’s two dedicated maintenance RS-232 serial ports. The software of the AW radio modem resides in Flash memory, which can be re-programmed through an RS-232 interface or over the air.
For tool support and to help facilitate its architecture evaluation, ArWest took advantage of ADI’s EZKit, which includes an evaluation board and VisualDSP++.
As ArWest prepares its next generation of AW products − a dedicated base station with a direct connection to Ethernet − Hogarth stated this design would include ADI’s ADSP-BF537 Blackfin processor.
For more information about ArWest Communications, visit the company Web site at
www.arwestcom.com.