Asset tracker combines WiFi and NB-IoT cellular

September 11, 2020 // By Nick Flaherty
Asset tracker combines WiFi and NB-IoT cellular connections
Crosby Technologies' ShipSafe uses Wi-Fi for 10m positional accuracy with Nordic Semiconductor’s nRF9160 system-in-package for LTE-M NB-IoT connectivity

A System-in-Package (SiP) with an integrated LTE-M/NB-IoT modem and GPS from Nordic Semiconductor is being used in a new asset tracker design alongside WiFi positioning.

New York-based Crosby Technologies is using Nordic's nRF9160 SIP in its 'ShipSafe' asset tracker along with a 3200mAh battery for a two year battery life.

ShipSafe enables users to remotely monitor the location and condition of valuable shipments using widespread cellular infrastructure. Critical equipment being monitored during the Covid-19 pandemic include ventilators, biomedical equipment and human organs for transplant as well as high-end industrial equipment.

ShipSafe takes advantage of the nRF9160 SiP's support of eDRX and eDRX in NB-IoT at very low currents to extend battery life to over two years between charges with unlimited location requests. eDRX dramatically extends the time that a cellular IoT device can spend in a very low power sleep mode from just a few seconds to up to 40 minutes before waking up still synchronized with LTE-M's "paging windows" - the period when data can be transmitted and/or received from the network. The nRF9160 SiP also supports Power Saving Mode (PSM), a second energy-saving function..

When the device wakes up, it uses Wi-Fi tracking to determine its position within 10m and reports that location using the nRF9160 SiP's LTE-M connectivity. This method of tracking extends the ShipSafe's battery life to approximately two years on a single charge. 

The SiP's 64MHz Arm Cortex-M33 processor runs the LTE-M cellular connectivity and all the  other product functionality in 1 MB Flash and 256 KB RAM.

ShipSafe uses Wi-Fi signal triangulation as a primary means of tracking, leveraging the location of over five billion Wi-Fi routers. If the device senses limited Wi-Fi signal strength and is unable to report a location with satisfactory accuracy, Shipsafe determines its location using traditional GPS functionality. ShipSafe's software and platform is provided by M2MD Technologies, an Atlanta-based software firm, that develops IoT cellular systems with improved power and latency.

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