Start-up's SOA framework links wireless sensor networks, IP backbone

A startup in wireless sensor nets has unveiled products with a service-oriented architecture that makes a sensor net an extension of the enterprise IP backbone.

There are two key benefits from SOA. "One, it simplifies development, and two, it allows for "pieces" of the underlying wireless sensor net to be directly interacted with by outside applications, without a lot of customized programming," Lucero says.

There are a host of vendors focusing on wireless sensor nets and machine-to-machine (dubbed M2M) communications. They're offering an almost bewildering range of processors, network protocols, radio frequencies, operating systems and applications that wirelessly link scores or hundreds of sensors measuring temperature, humidity, pressure, vibration, fluid flow and corrosion.

TinyOS is one example of the operating system software for the sensor nodes themselves, and the ZigBee Alliance protocol stack is often, but not always, used for the mesh network layer. The IEEE 802.15.4 wireless mesh standard is widely used for the physical layer, but others, such as 802.11, are used.

SOA is an emerging technique for simplifying application development for these systems, but not the only one, says ABI's Sam Lucero. Some vendors, including Tendril, MeshNetics, Atalum, and Crossbow with MoteWorks let enterprise IT applications be built with little or no embedded-programming experience needed by the application developer. Systems vendors, such as Dust Networks, attempt a similar simplification with their APIs and tools, though Lucero says these sometimes need a "bit more 'out-of-the-box' work."

That kind of simplification is a big reason why Bikash Sabata, CTO for Aginova in Freehold, N.J., has been evaluating Arch Rock. Aginova sells wireless sensor nets for what's called condition-based maintenance of a range of industrial gear in the manufacturing and oil/gas industries. The sensors record oil pipe corrosion, for example, and issue an alert so a pipe section can be replaced before it fails.

The company built its first-generation products on the TinyOS-based sensor infrastructure from Crossbow, adding its own application, analysis, and management software above that foundation. Sabata wants to replace that foundation and Arch Rock is one candidate.

"We need something that's much more like 'plug-and-play,'" he says. "At one level, we can have this [Arch Rock] software layer be completely opaque and we'll just call the API's to do what we want."

He's been especially impressed with the effectiveness of the Arch Rock gateway's high-level SOA APIs, which form the interface with applications and databases on the enterprise network. "We used their Web services to build an application on our portal," he says. "The gateway can store data locally, until our portal is ready and calls for it. And we can do all the gateway maintenance and configuration via another set of APIs."

"We started building our application about 18 months ago, [including] building our APIs and the translations between the TinyOS network and the Internet," Sabata says. "If we'd had SOA back then, our product would have been ready 12 months ago."

Arch Rock's architecture is intended to make that possible. The sensor nodes themselves, which combine some kind of sensor with an onboard computer and 802.15.4 radio, use Arch Rock's own version of TinyOS version 2.0 (the company says it’s the first to implement this latest release). Arch Rock's enhancements focused on minimizing power use, and making the radio links highly reliable, Culler says.

Each node, often called a mote, can do local sensing, run one or more local applications to process the data it collects, and route packets for and through its neighbors. Expansion ports can link the node to devices such as analog switches.

All wireless traffic links to the Arch Rock Bridge Node, which attaches to the Arch Rock Gateway Server, typically located in the general area of the sensors. The Gateway can support wired Ethernet or 802.11 wireless LAN connections to the enterprise net. It's software handles supports the Web services interfaces, the configuration and management of the gateway itself, of the nodes, and the 802.15.4 radio environment.

The Arch Rock SOA implementation extends from the Gateway to the nodes themselves. The Gateway presents its applications and data to the wider enterprise via Web services interfaces. But each node also uses the same kind of interfaces, to present its data or alarms or alerts, as well as network information, such as the identity of neighboring nodes used in routing decisions.

Rivals make limited use of Web services, by contrast, says Roland Acra, Arch Rock co-founder and CEO. "Most of them pull the [sensor] data out of the sensor network into a database, then point query tools and schema representations at this [via Web services]," he says.

One area that's lacking, says Aginova's Sabata, is access to lower-level Web services interfaces. Sabata wants to be able to program the sensor motes to behave and measure based on certain conditions, such as threshold reading. "You want to be able to program these 'scenarios' easily into the motes," he says. "They don't have any APIs at that level. We've requested one for this."

The Arch Rock Primer Pack, available now, includes the Gateway appliance; the wireless bridge node; and six sensor nodes with on-board temperature, light, and humidity sensors along with all the software, expansion ports and preinstalled sensor drivers. List price for the bundle is $4,995, with additional sensor nodes priced at $275.

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