NB-IoT, LTE-M stay hitched to LTE waveform

While 3GPP is busy creating new standards for 5G that encompass a range of technologies, there’s one area that’s getting relatively little overhaul: LTE-based IoT.

Granted, 3GPP’s specs address Massive IoT, but global 3GPP standards aren’t focused on migrating NB-IoT or LTE-M to 5G New Radio (NR) waveforms any time soon. 5G in the view of 3GPP standards encompasses both the LTE and NR waveform.

Looking at the Release 15 standard, and even Release 16, “those [NB-IoT/LTE-M] applications are enhanced, but they’re enhanced on the LTE waveform, not the NR waveform,” explained AT&T VP of Mobility and Access Architecture Gordon Mansfield, and that isn’t likely to migrate or be suggested before Release 17.

“These IoT applications, even as we evolve to 5G, are still going to use the LTE waveform,” he told Fierce.

That’s not to say sticking with LTE is a negative, and Mansfield explained why it makes sense. The applications for NB-IoT and LTE-M differ, but both are low-power technologies that require little bandwidth. Efficiency enhancements from NR really come into play in high-bandwidth situations. Since those IoT devices use basic connectivity, there’s nothing new NR introduces that would provide incremental benefit.

“Narrowband IoT only takes a couple of [spectrum] resource blocks,” he said, in which case “there is absolutely zero difference” from using an NR waveform versus an LTE waveform because it doesn’t deliver improved efficiency.

“Therefore, why change the waveform, because now the devices that are out there will continue to work,” he said.

It’s also not to say that LTE-M and NB-IoT have been completely forgotten in the standards process. A white paper (PDF) by 5G Americas notes that “LTE-based technologies (LTE-MTC and NB-IoT) will provide the foundation for cellular-based massive MTC [massive machine type communication] in the future.” 

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Release 16 work items focused on enhancements to NB-IoT and LTE-M like increased spectral efficiency and reduced energy consumption for devices, as well as performance improvements for the anticipated continued coexistence with NR. 3GPP finalized Release 16 in July.

For Release 17, LTE work is understandably limited, but it will continue to evolve the IoT technologies to keep them up to date “in line with the expected long-term use of LTE based technology to serve massive -MTC applications,” the paper noted.

Just this week 3GPP delayed freezing Release 17, potentially by three to six months or more.

From a standards perspective for LTE-M and NB-IoT, AT&T doesn’t see anything in the next three to five years that would drive a change in the radio interface, according to Mansfield, pointing to the timeline when Release 17 capabilities are likely to be introduced into the network. It does change in terms of core processing and what can be done with that data, he said, as standards support connecting NB-IoT and LTE-M devices to standalone (SA) 5G core networks.

AT&T plans to start early deployments of its 5G SA core later this year, and scale it in 2021.

Long IoT life cycles

Sunsetting existing LTE-based technologies for IoT could be a nightmare both for operators and for users, Gus Vos, chief scientist at Sierra Wireless, told Fierce in an earlier interview. That’s because most of these low-power IoT devices are built for long life cycles. Vos called out examples like smart metering for water or gas, and smart city applications for infrastructure and monitoring.

“They don’t want to do truck rolls to change technology and the batteries are designed to last 20 years, so this is really supposed to be deployed and left in place,” Vos said.

One of the often talked about benefits of 5G NR is ultra-low latency. However, with low-bandwidth IoT applications, latency isn’t a major factor. For NB-IoT for example, devices usually don’t need to connect in milliseconds, which is how the battery life is extended for long periods because they don’t need to constantly check in with the network, Mansfield noted.

“Therefore, the latency sensitivity is not the same would see on an NR network,” Mansfield said. He cited high confidence that support for NB-IoT and LTE-M devices will continue for at least the next decade.

Similarly, Verizon’s head of IoT Platforms Shamik Basu recently told Fierce that the carrier would support activations of new CAT-M and NB-IoT devices until 2030 and “would work with customers to support longevity beyond that.”