AT&T this week launched what the company says is the first LTE-M enabled commercial site, which will support an Internet of Things pilot involving several companies, including PepsiCo, Samsung and others. “We think LTE-M will be the workhorse for low-power wide area” connectivity, said Cameron Coursey, AT&T vice president of product development for IoT solutions, in an interview. So what is LTE-M?
What is LTE-M? The Standard
The term low-power wide area (LPWA) is a category of wireless communications optimized for IoT applications. Low power requirements are important to IoT because long battery life is critical. AT&T claims battery life of up to 10 years for some types of LTE-M devices.
Excellent range also is important because IoT devices may be installed in remote areas. According to an AT&T white paper, LTE-M offers seven times the range of traditional LTE communications.
As Coursey explained, another way of describing this is to say that LTE-M provides 15 decibels better coverage, which means that it also does a better job of penetrating walls and floors – another important capability for IoT applications, where wireless sensors or other devices may have to be located in basements or other environments that can be challenging for traditional cellular communications.
LTE-M achieves the 15 db/7x range improvement by repeatedly transmitting the same communications, Coursey explained.
He also explained that LTE-M is a marketing name for Category M1 LTE, which was developed specifically for IoT applications. LTE-M follows on a previous AT&T rollout of Category 1 LTE, which was also developed for IoT.
Devices must be designed specifically to use Category 1 or Category M1/LTE-M communications, Coursey said. Category 1 LTE was a breakthrough in cellular communications for IoT when AT&T began supporting it last year because a Category 1 module costs about $15, which according to Coursey made “the lowest cost LTE-only radio module.”
The Category M1 standard is shooting for an even lower price point by scaling back on some capabilities of Category 1 devices, including bandwidth. While Category 1 supports data rates up to 10 Mbps, Category M1/LTE-M supports date rates up to 1 Mbps when used in full-duplex mode or 384 kbps when used in half-duplex mode. IoT communications typically aren’t bandwidth-intensive; accordingly, Coursey expects half-duplex communications to be most popular.
Coursey is hopeful that after economies of scale kick in, the cost of LTE-M modules will “approach the five-dollar range.”
He doesn’t expect LTE-M to make Category 1 devices obsolete, however.
“IoT is so diverse, we continue to find new use cases,” observed Coursey. “There will be uses for Category 1 for a long time to come. We will continue to see a family of IoT technologies.”
What is LTE-M? Network Considerations
Because AT&T already has an LTE network, deploying either LTE Category 1 or LTE-M is relatively easy and can be done with a software upgrade, Coursey noted.
Coursey declined to detail how AT&T plans to price LTE-M connectivity. “We’re looking at different scenarios,” he said, adding that the pilot should provide information to help in making pricing decisions.
Samsung’s role in the pilot will be to evaluate an LTE-M-based solution that might be used in wearables or other devices. PepsiCo plans to evaluate smart vending machines. Other participants in the pilot will be looking at smart water devices and connected vehicles.