A method and system controls timing of network performance information logging of a cellular network by configuring a mobile device to automatically collect data about physical characteristics of the cellular network and log that data. The mobile device initially receives network performance information logging configuration from its registered cellular network. Based on the configuration, the mobile device configures itself to collect and log the network performance information relating to physical characteristics of the cellular network. While in idle mode, the mobile device collects and logs the information. A logging duration timer corresponds to a specified time duration over which the mobile device logs network performance information. If the mobile device starts the logging duration timer at the time of configuration, it maintains the timer even after the transition to idle mode. The mobile device may also start the logging duration timer after it transitions to idle mode.