Data recovery or integrity mechanisms

Explanation on how Sensolus guarantees data integrity.

Sending messages over communication networks is not 100% reliable, data loss is always possible. This can be due to bad communication network coverage, limitation of message sizes when communicating over the network to send all data at once or difficulties to send data when moving (especially over the Sigfox network). Sensolus guarantees a 99,9% data delivery. Therefore we use a dedicated and patented data recovery mechanism.

Data recovery mechanism

The Sensolus patented selective resend strategy ensures that only lost messages are send again. Therefore, the cloud keeps track of the received messages and uses daily bidirectional communication to inform the tracker about them. The tracker stores all messages until it receives confirmation they are received. The ones that were not acknowledged will be sent out again.

The advantage of this strategy is that no energy is wasted on resending messages that already were received.

The second advantage is that there is no time limit to recover messages. Even if the tracker is out of coverage for weeks, the tracker will still be able to recover non-acknowledged messages.

How much data can be recovered?

When no network is available, or messages cannot be send from the tracker to the network, data is kept in the memory of the tracker. As this memory is limited this can result in some data being thrown away. As not all data is as important, Sensolus created a prioritization of data to be kept in the memory that can be resend (in priority) once the tracker is again in covered area or in the possibility to send data over the network.

Note: The internal memory of the TRACK 1130 is smaller then one on the Sensolus trackers (TRACK 1000, 1100,…). For both trackers data are recovered, but from the TRACK 1130 less data will be kept on the device.

Prioritization of data types when resending data

The prioritization of data recovery depends on the timing of a message and the priority level of a message. We created a rather complicated resending mechanism of which the basics are explained here.

In general, this is the order of prioritization of resending data:

  1. Newest and high priority messages.
  2. Older and high priority messages.
  3. Newest and normal priority messages.
  4. Older and normal priority messages.
  5. Newest and low priority messages.
  6. Older and low priority messages.
The priority level of different message types are the following:
Table 1. Priority level of message types
Priority level
High priority
Sensor alert messages (= trigger-based sending)
STOP messages (STOP locations generated via GNSS, Wi-Fi, geobeacon or BLE anchor)
Orientation change messages
Boot messages
Normal priority
START messages
Sensor data (= periodic sending)
All other location messages (periodic, scheduled … messages) except OTM messages
Keep alive messages
Low priority
Debug messages
OTM (= On The Move) messages

When is data recovered for trackers communicating over the Sigfox and NB-IoT communication networks?

The timing of the recovery check and action (recovery trigger) is different for trackers communicating over the Sigfox or the NB-IOT communication network. The reason for this is that Sensolus always keeps in mind the impact on battery lifetime of a tracker and the specifications of the communication networks. As shown in the table below trackers communicating over the NB-IoT network check and recover more often then trackers communicating over the Sigfox network. This implies that for trackers using the Sigfox network recovered messages will arrive on the platform later then for trackers communicating over the NB-IoT network.

Table 2. Data recovery check & actions
Recovery trigger Sigfox NB-IoT
Keep alive message x x
STOP message x

Data communication service

General information on the data integrity strategy applied on your tracker and on the data communication service are shown here:

Admin → Asset trackers → Select tracker → Tracker configuration → data communication service.