Environment temperature has an effect on energy consumption. The energy estimate value does not take environment temperature into consideration. This can be noted when optimizing energy consumption using the %CONEVAL service.
Graph Temperature's impact on energy consumption and energy estimate value shows temperature's effect on energy consumption in an LTE-M network and the energy estimate values from %CONEVAL responses. The measurements were done with a Rohde & Schwarz CMW500 LTE protocol tester and temperature chamber. SMS was used as test data. One SMS consists of two transmissions and two receptions: the short message itself (< 200 bytes) and the needed ACKs in both uplink and downlink. This means that the transmission characteristics for an SMS are the same as for any similar amount of normal data exchange.
Notes for the following graph:
- X-axis: Energy estimate value.
- Y-axis: Energy consumption where the average of energy estimate value 7 in 25°C is normalized to be 1.
- Red curve: Average of energy consumption per energy estimate value in 80°C.
- Green curve: Average of energy consumption per energy estimate value in 55°C.
- Orange curve: Average of energy consumption per energy estimate value in 25°C.
- Blue curve: Average of energy consumption per energy estimate value in –10°C.
The graph shows that energy consumption increases when the temperature increases. The amount of increase compared to the nominal temperature of 25°C can be seen on the y-axis. If energy estimate value 7 is returned in 25°C, the normalized energy consumption level is 1. In 85°C, the energy consumption level is approximately 1.18. This means that if the temperature changes from 25°C to 85°C with the energy estimate value 7, energy consumption is expected to increase in this example by 18 %.
In a modem, the lowest energy consumption is gained in low temperatures, which is shown by the –10°C curve in Temperature's impact on energy consumption and energy estimate value. An application can use the temperature information to plan for energy efficient data transmission. For example, if the daytime temperature is significantly higher than the nighttime temperature, data transmission can be centered around the nighttime. However, there can be other reasons for an application to avoid transmitting in very low temperatures, such as reduced battery capacity in lower temperatures.
If an application needs to consider temperature when checking the conditions for an energy efficient transmission, temperature notifications can be subscribed with the Nordic-proprietary %XTEMP AT command.