The Nordic-proprietary %CONEVAL AT command requests the modem for information about the cell and current Long-Term Evolution (LTE) radio link quality. It also requests for an estimate of the probability of energy efficient transmission. The response is given as an energy estimate value. An application can use the energy estimate value to analyze the probability of energy efficiency in an upcoming data connection.
The connection evaluation is the most useful in cases where the application data that is going to be sent is not time-critical and the sending can be delayed, or even dropped, if the evaluation response indicates an increased or very high risk of poor energy efficiency.
Since the connection evaluation consumes a small amount of energy, it should be used only when there is a need to set up a radio connection for the device to send application data. The amount of energy that the connection evaluation consumes is insignificant compared to the amount of energy consumed when establishing a connection and transmitting data in poor radio conditions.
The use of connection evaluation can be beneficial in many different types of environments. Radio conditions can be equally poor indoors and outdoors as well as in rural and urban areas, and the conditions can vary in all environments even with fixed deployments. For example, a device can be permanently placed in a location with poor radio coverage, such as a basement. The application logic might include occasionally establishing a connection for critical data transmission. In such case, the device would likely not benefit from connection evaluation, and some energy could be saved by not using it at all.
For more information on the %CONEVAL command and other response values, see Evaluating connection parameters %CONEVAL in nRF9160 AT Commands or nRF91x1 Cellular AT Commands.