Sonim Technologies unveils ultra-rugged FirstNet devices, support for direct-mode PTT module

Plaschke said the XP8 and the XP5S are the first phones to include dual SIM cards, which could be used to let a user have one SIM dedicated to work-related activities and another SIM for personal use, Plaschke said.

Perhaps the most intriguing innovation for both the XP8 and XP5S is Sonim’s XPand Interface, which supports rugged attached peripherals that are attached to the top of the devices. Plaschke said some potential peripherals include a fingerprint reader or a driver’s-license scanner, but the most notable module that will be available immediately is one that supports direct-mode push-to-talk communications between devices when network connectivity is not available.

Push-to-talk over cellular (PoC) solutions—including AT&T’s push-to-talk service powered by technology owned by Motorola Solutions, which purchased Kodiak last year—have become increasingly popular as network-based performance has improved with the maturation of products. However, these PoC services do not support device-to-device—direct-mode—communications when a device is not connected to a network.

With this in mind, 3GPP—the global standards body that oversees the development of LTE technology—approved a mission-critical push-to-talk standard two years ago that included a direct-mode capability known as proximity services. But the proximity-services approach has many doubters, in large part because commercial LTE devices typically use 0.25 watts when transmitting signals, which is well below the 1-3 watts of power that land-mobile-radio subscribers utilize.

Sonim’s direct-mode module lets users transmit signals between devices with 1 watt of power, leveraging the LoRa (Long Range) modulation scheme. LoRa technology operates on unlicensed spectrum in the 900 MHz Industrial, Scientific and Medical (ISM) bands and was designed to support communications with sensors in Internet of Things (IoT) systems.

Plaschke said the Sonim direct-mode module will enable communications up to 3-5 miles in ideal outdoor conditions and a range as little as 1 mile in more difficult outdoor environments.

“[Sonim’s direct-mode capability is] certainly leverageable inside of buildings and inside of physical structures, consistent with a traditional direct-mode experience that you would see on an LMR device,” Plaschke said.

Switching from on-network LTE communications to LoRa-based direct-mode PTT service would be similar to changing channels on an LMR portable, Plaschke said. A user could not communicate in direct mode and with the LTE network simultaneously, he said.

Sonim’s initial direct-mode module will support only direct-mode push-to-talk communications, but a future release also will enable direct-mode text and data communications, according to Plaschke.

Although Sonim’s XP7 ultra-rugged smartphone has been a popular device in early public-safety LTE trials, the company “started from scratch” when designing the XP8, which is “30-40% thinner and more like a traditional smartphone,” Plaschke said.

Key improvements in the XP8 begin with a “massive upgrade from a chip perspective, Plaschke said.

“It uses the Qualcomm 630, which is kind of the top end of their [chipset] range and significantly increases flash memory and stored memory,” he said.