Efento SP. J.
Ul.Krupnicza 14/5
31-123 Kraków
from the server. The only possible way to transfer data from the server to the logger is to send them in
response to the data packet received from the logger.
The NB-IoT standard provides for the retry of data transmission, if it is impossible to send it correctly.
The method of repeating the transmission is not configurable by the user, it is done automatically by the
logger. The number of retries is determined by the ECL (Coverage Enhancement Level) parameter,
which specifies the number of retries of failed transmission attempts defined as 2
i
(i = 1… 7). The
parameter is set from 0 (normal operation) to 2 (bad signal quality / high noise, large number of
retransmissions required). The higher the ECL value, the higher the energy cost of sending data, and
therefore the shorter the battery life. When installing the NB-IoT logger, it is worth checking the ECL
level in the place where it is to work (the issue is described in "Device status" section).
NB-IoT devices should not move between base stations, as this results in the need to re-register to the
network each time the base station changes. The registration process takes a relatively long time,
therefore frequent relocation of the logger between base stations adversely affects the battery life.
Data usage
The amount of data sent and received by the logger depends mainly on the measurement interval and
the transmission interval. For example, a logger that measures only the temperature, performs a
measurement every 3 minutes, sends data every 3 hours, and four times a month sends data because
of exceeding the thresholds, consumes 60.5 kB per month. The same settings for a temperature and
humidity logger will require 89.3 KB of data per month. It is safe to assume that the monthly data usage
of a single device with three slots is 150 kB. This includes firmware updates and configuration changes.
Battery life
The battery life of a device depends on many factors and it is not easy to build a model that will precisely
determine this time. Efento NB-IoT loggers battery life time is up to 10 years or 130,000 transmissions
(standard battery pack: 2 x AA batteries, 4200 mAh).
The main factors affecting battery life are:
● Signal quality - the worse the signal quality, the greater the number of retransmissions is
necessary to send data to the server. The number of retransmissions is represented by the ECL
parameter and battery life is significantly reduced at higher ECL values (1 or 2)
● Transmission period - the more frequent the transmissions, the shorter the battery life of the
device. With brand new battery pack, the device should send data about 130,000 times (2
batteries in a battery pack) or 195 000 times (3 batteries in a battery pack) (assumptions: room
temperature, ECL = 0, 20 measurements / transmission, transmission period small enough to
make 130,000 transmissions within 10 years)
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