Procedure to operate a wireless field device network comprising several field devices powered by a battery or storage battery, wherein each field device is designed to determine and/or to set a process variable and to transmit or receive the process variable wirelessly within the field device network by means of a first wireless module , wherein each field device powered by a battery or storage battery is further designed to determine an expected remaining operating time or a variable derived therefrom, particularly a standardized variable, on the basis of a current charge state of a battery or a storage battery and wirelessly transmit or receive the expected remaining operating time, or the variable derived therefrom, within the field device network by means of the first wireless module , wherein each field device further comprises a second wireless module designed to transmit the data wirelessly with a higher-level unit which does not belong to the field device network , and wherein the procedure provides for the following steps: - Wireless transmission of at least the process variable and the expected remaining operating time of each field device via the first wireless module to the other field devices within the field device network , such that at least the process variable and the expected remaining operating time of the other field devices of the field device network are retained in each field device ; - Activation of the second wireless module of the field device which has the highest expected remaining operating time and deactivation at least of the second radio modules of the other field devices in the field device network such that only the field device that has the highest expected remaining operating time is active and at least the second radio modules of the other field devices are deactivated; - Wireless transmission of the process variables of all the field devices of the field device network retained in the active field device , or at least a subset of the retained process variables, to the higher-level unit which is not part of the field device network using the second wireless module of the active field device . - Wireless transmission of at least the process variable and the expected remaining operating time of each field device via the first wireless module to the other field devices within the field device network , such that at least the process variable and the expected remaining operating time of the other field devices of the field device network are retained in each field device ; - Activation of the second wireless module of the field device which has the highest expected remaining operating time and deactivation at least of the second radio modules of the other field devices in the field device network such that only the field device that has the highest expected remaining operating time is active and at least the second radio modules of the other field devices are deactivated; - Wireless transmission of the process variables of all the field devices of the field device network retained in the active field device , or at least a subset of the retained process variables, to the higher-level unit which is not part of the field device network using the second wireless module of the active field device . <EOS>