Technical background

The mathematical principle behind Geolocation is Time Difference of Arrival (TDoA). An uplink message of an end device is received by a gateway and the exact arrival time (timestamp) at this gateway (nanoseconds) is attached to the uplink. The different timestamps between the gateways are used by the “Locsolver” to calculate the exact position of the device. In order for multilateriation of arrival times to work properly, it is required to use a minimum of three gateways. The formula and visualization of this principle are shown in the figure below.

Formula and visualization of the TDoA principle

Algorithm

The locsolver algorithm uses different clusters, cluster sizes, time windows and historical data to calculate new locations of a device. Several operational examples are found below; they are summarized in the table below.

The algorithm uses the information it receives within a time window of 30,000 seconds. This is combined with the data in the cluster of the last 8 calculated locations. If the motion indicator Static is used, the algorithm also tries to detect if the device has moved in the last hour and it adopts the cluster size used in the calculation of the location.

Motion indicator

Time (seconds)

Cluster

History (seconds)

Static

30,000

8

3,600

This table is subject to change with the optimization of the locsolver algorithm.