Dialing in a Clear Signal on Low-Power Networks

By Mary Catherine O'Connor

Are low-power networks key to ramping up the Internet of Things?

Objects can be connected with each other and to the Internet via a long and growing list of wireless technologies and networking protocols. For applications in which communicating with objects does not require high bandwidth, or by which an end user wants to install a backup communication network to ensure connectivity if the primary cellular and Wi-Fi network fails, ultra-narrowband (UNB) technology could be a good fit.

UNB technology relies on very narrow slices of the unlicensed ISM frequency band to connect devices over long distances with low battery consumption. It has long been used for niche applications, such as the automatic reading of utility meters. But now, a number of companies, including French firm Sigfox and Neul (founded in the United Kingdom but recently purchased by Chinese telecommunications company Huawei), are working hard to advance UNB as an alternative to cellular-based connectivity for a range of IoT deployments.

Thomas Nicholls, Sigfox's head of communication

M2M Spectrum Networks, based in Phoenix, Ariz., also offers a low-power machine-to-machine communication network. It does not use UNB, but rather allocates unused spectrum transmitted over what CEO Barclay Knapp calls "cognitive radios" that send and receive data via 800 MHz, 900 MHz or 200 MHz signals (see M2M Spectrum Launches Nationwide Wireless Machine-to-Machine Network). The company is building out its network in a handful of U.S. states, including Georgia and Florida. It is already offering its service in remote parts of North Dakota, where a trucking company is using it to track its fleet and drivers in the Bakken oil fields.

Sigfox has rolled out its network via UNB antennas and gateways, operating at 868 MHz, installed across a number of European cities. In the United States, where it will use the unlicensed 902 MHz band, it is currently building out infrastructure in order to debut its technology in the region, extending from San Francisco to the cities of Silicon Valley, located 40 miles south.

Thomas Nicholls, Sigfox's head of communication, told IOT Journal that his company believes its low-power, ultra-narrowband technology is the key to scaling the Internet of Things. Realizing Cisco's projection that there will be 50 billion things linked to the IoT by 2020, he says, "won't happen with existing connectivity solutions." Linking devices over cellular networks present two main problems that UNB addresses, he adds: high connectivity costs and short battery life.

"The majority of linked objects would never need access to high-bandwidth connectivity," Nicholls states. In addition, the batteries used to power them generally cannot be easily recharged or replaced. Using the Sigfox networks, he explains, allows for both "long battery life and connectivity at low cost," thanks to operating on the unlicensed ISM band.

Avoiding the cost of GSM cellular connections could lower the bar of entry for end users that do not require high-bandwidth links to the connected devices they deploy. One example is Whistle Labs, which offers a dog tag with an embedded accelerometer used to track the animal's activity—in essence, FitBit for dogs—and sends reports to the owner via Wi-Fi or Bluetooth. The company plans to use the Sigfox network to link its tags to the Internet over the network Sigfox is rolling out in San Francisco. (Only customers within the Sigfox network range will be able to use the service.) Whistle already offers a Whistle GPS version that lets users find missing pets over a cellular network. This service costs customers $5 per month, but that fee can be reduced for those using Sigfox.

Sigfox has several big customers, including Securitas Direct, a major provider of commercial and residential building-security systems. Partnering with Abertis Telecom, Sigfox will send an upgrade to the 868 MHz radios already inside millions of Securitas Direct alarms installed in Spain, which means the transition to running Sigfox does not require any new infrastructure. The alarms already utilize a telephone network to send alerts when a security breach is detected, but it will use the Sigfox network as a backup system should telephone service become unavailable.

A network visualization, courtesy Simon Cockell/Flickr

On Sept. 30, the European Telecommunications Standards Institute (ETSI) released three specifications developed by its Low Throughput Network (LTN) standardization group. ETSI describes an LTN as "a wide area bidirectional wireless network [that]… enables long-range data transmission (distances around 40 km in open field) and/or communication with buried underground equipment and operates with minimal power consumption allowing several years of operation even with standard batteries." The three specifications describe protocols, interfaces, functional architecture and use cases for low-throughput networks. The Sigfox protocol complies with the specification, Nicholls says, but also includes some proprietary elements.

Sigfox initiated and chairs ETSI's LTN standards group, which also includes Semtech, a manufacturer of analog and mixed-signal semiconductors. "Semtech is a vendor of the sub-GHz RF transceiver needed to operate on our network," Nicholls says, though he adds that Sigfox's software protocol is compatible with a range of hardware using sub-GHz radios operating on the ISM band—including such common devices as garage door openers. "Some customers already have these types of transceivers in their devices," he notes, "but most do not."

Clearly, many IoT applications have bandwidth and geographic requirements that exceed the capabilities of UNB networks like Sigfox's. That's not to mention the fact that the infrastructure to support UNB networks as an alternative to G3 or LTE cellular network are still in their infancy.

Agriculture is one sector that could benefit from UNB networks, in regions in which cellular connectivity is poor and getting out to the field to replace batteries is especially burdensome. Outside and with no obstructions, UNB antennas can transmit across a span of 500 kilometers (311 miles), whereas in those same ideal circumstances, a GSM cellular antenna's range is 35 kilometers (22 miles). In an urban environment, however, interference from various sources can reduce those ranges considerably.

One could also imagine city governments might see UNB as a fitting solution for linking every streetlight and fire hydrant into an intelligent network. Neul and Sigfox are each running smart city pilot projects in the United Kingdom, in fact.

But Macario Namie, VP of marketing with Jasper Technologies, which runs a cloud-based software platform enabling companies to manage networks of connected sensors, says cities want to outsource IoT applications to vendors that, most likely, deploy similar networks in other cities and thus likely already deploy equipment on cellular connectivity.

While Namie sees some utility in building low-power networks that can function in parallel with cellular or Wi-Fi networks, he worries that end users could find themselves limited in terms of where they deploy their devices, and that marrying themselves to non-standard networks could come back to hurt them. Neul has developed its own specification, known as Weightless, but it has not become an international standard, and Sigfox's standards-based technology includes some proprietary elements.

"Coverage is king," Namie says. The benefit of cellular networks, despite their relatively higher connectivity costs, is that they are standardized worldwide. "If Sigfox [or Neul] goes out of business, none of those devices running its protocol will connect."