The third-largest US mobile operator is learning lessons in the gambling capital that should help it to expand both its NB-IoT infrastructure and the ecosystem of devices that will help to populate the network with devices and applications, according to Daniel Herb, T-Mobile's director of IoT.

The Internet of Things is expected to require LPWANs to link billions of small devices such as sensors and meters around the world. In the US, mobile behemoths AT&T Inc. (NYSE: T) and Verizon Wireless have rolled out national networks using LTE-M, one of two major LPWANs based on existing LTE networks. T-Mobile US Inc. -- as usual -- just had to be different. It's using NB-IoT, the LTE-based system adopted more widely in Europe and Asia. (See US Carriers Claim Progress on Different LPWA Paths and AT&T Pushes Cat M LTE for Cellular IoT in the Americas.)

T-Mobile kicked off NB-IoT service earlier this year in Las Vegas. The "Un-Carrier" will offer the service across its national LTE footprint by the middle of next year. It will also roll out LTE-M as a "fast follow" to NB-IoT, Herb said in an interview at the LPWA Americas conference this week, without specifying a date for that rollout.

NB-IoT uses just one-sixth as much radio spectrum as LTE-M, so T-Mobile can run the network without using any of the spectrum devoted to regular LTE services, Herb said. This means it won't crowd out smartphones when IoT deployments ramp up, which will raise the cost of services, he said. (In fact, a Verizon executive told the conference on Tuesday that its current pricing with no data limits may change when IoT use grows.)

But T-Mobile's Las Vegas rollout helped the carrier find and head-off one issue that might have affected cellular users in the future, he said. It learned that NB-IoT can affect the performance of 4x4 MIMO, the multiple-antenna system that helps T-Mobile deliver high bandwidth for activities like streaming video on smartphones.

This hasn't affected consumer subscribers, partly because NB-IoT use is still light and is mostly concentrated in industrial areas rather than crowded spots like the Las Vegas Strip, Herb said. T-Mobile started addressing the issue immediately and has developed and tested a firmware fix that should be rolled out by the end of this month, Herb said. It won't compromise the performance of either network.

Another real-world lesson is that some developers hope to use very low-cost hardware modules in NB-IoT devices but also expect capabilities found in smartphones, such as high-accuracy, fast-fix GPS for location tracking.

"You can get narrowband that is actually at the promised price targets if you strip everything else out," Herb said. So developers need to learn how to set their expectations.

Even though the cost of the hardware module is typically less than 10% of the cost of a total solution, it plays into the choices developers make, Herb said. Achieving the right mix of cost, power consumption and capability requires trade-offs that application and device developers are beginning to learn about.

On the other hand, T-Mobile is seeing more interest in NB-IoT for devices that don't need the 10-to-15-year battery life that's been promised with the new networks, Herb said. Instead, it's gear that may be plugged in or only need two years of battery life.

"Nobody actually cares what was promised, as opposed to what they want to get done," Herb said.

Some applications that are getting customers interested in NB-IoT include asset tracking, fleet management, smart buildings, smart lighting, metering, and construction equipment, he said.

— Stephen Lawson, special to Light Reading