Testing Low Power Connectivity for the Internet of Things

Remotely monitoring for forest fires with solar-powered sensors, tracking modules installed on fleets of delivery trucks, and connecting smart meters to a local power plant are all potential applications for low power cellular LTE-M and NB-IoT networks.

These technologies are based on the LTE standard but consume vastly lower power and transmit smaller amounts of information. They were designed to connect sensors and other devices that need to send data over long distances, last for several years on a single battery charge, and work in factories, on city streets, or even underground.

These electronic devices present challenges for testing. Test equipment companies like Keysight Technologies and Anritsu are jostling to help engineers meet the strict power and coverage requirements of NB-IoT and LTE-M – also called CAT-M1 or eMTC – on ever-tightening product budgets and deadlines.

“There are always challenges in testing new technology or new formats in the wireless industry,” said Hanglu Bai, product marketing lead for Keysight, in an email. But with LTE-M and NB-IoT technology, “the cost per test and speed of test is more important as a massive number of devices need to be deployed.”

Bai added that “the massive deployment of low cost devices means the device will not be tested as rigorously as testing a cellphone in a manufacturing environment.” The wireless industry is targeting LTE-M and NB-IoT modules that cost less than five dollars each and run on a single battery charge for a decade.

The LTE-M standard has taken the lead in the United States. Last year, AT&T completed a series of software updates that expanded its LTE-M network with peak downloads of one megabit per second to all the places covered by its 4G infrastructure, including Mexico. Verizon also launched its LTE-M network nationwide last year.

LTE-M technology can send more data per second than NB-IoT, which uses less power with peak downloads of about 200 kilobits per second.  Most companies in Europe and Asia are targeting NB-IoT at smart meters, industrial sensors, and other nonmoving devices. Unlike LTE-M, NB-IoT cannot transmit and receive simultaneously.

China Unicom, one of the country’s largest wireless carriers, expects to subscribe more than 100 million devices on its NB-IoT network within two years. Deutsche Telekom, the largest telecom company in Europe, has expanded its network into about 600 towns and cities in Germany, while providing service in eight other countries in Europe.

In response, test equipment companies have been rolling out software upgrades so that customers can use existing tools to measure LTE-M and NB-IoT devices against these low power standards. Anritsu, Rohde & Schwarz, and Keysight are competing to deliver equipment that can probe power consumption, coverage, interoperability and reliability.

Richardson, Texas-based Anritsu released a series of software updates last year for testing NB-IoT and LTE-M devices for power consumption and wireless coverage. Last year, Rohde & Schwarz updated its CMW500 wideband communications radio tester to check that these devices meet 3GPP standards from prototyping all the way to production.

Keysight’s UXM system has been upgraded to “emulate a real network scenario, device under test scenarios, and custom test cases” for NB-IoT and LTE-M. “The biggest benefit is the device is validated in early prototyping and later in system integration to ensure the product that rolls out to market is both compliant and reliable in the field,” said Bai.

The company has also collaborated with Bluetest on over-the-air test equipment used to evaluate how antenna placement – inside a street lamp or behind a refrigerator door – affects wireless coverage. That is critical for NB-IoT devices, which could be installed in the same warehouse shelf or underground on a farm for over a decade.

Other companies are focused on finished products. TÜV Rheinland, one of the world’s largest safety and quality inspection firms, opened a laboratory in Silicon Valley last year to provide certification for LTE-M, NB-IoT and other low power wide area wireless standards like LoRa and SigFox, which both use unlicensed spectrum.

The hardware is already available. Sequans Communications recently announced a cellular modem for NB-IoT networks to compete with rival chipsets from the startup Riot Micro, Altair Semiconductor, Mediatek, Qualcomm and Huawei’s HiSilicon unit. These chips are typically packaged into modules that can be dropped into products.

The number of NB-IoT and LTE-M devices will grow from around 25 million in 2018, up to around 300 million – overtaking rival unlicensed standards like LoRa and SigFox – in 2021, according to a report from Mobile Experts. The revenue from connectivity modules will grow from about $1 billion in 2016 to $33 billion in 2021, the report said.

And the price of these modules is falling as the technology improves and more companies use it. AT&T charges around $1.50 for every LTE-M device per month. The wireless carrier also sells modules for $7.50 each, half the cost of the LTE-M modules it released in 2016.

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