A method that has cellphones report to the cellular network signal strength and location information when the signal strength falls below a chosen threshold. Each cellphone maintains a log file of entries, each of which specifies a location and a signal strength (that is below the chosen threshold) and on a regular basis sends the information in the log file to the cellular network's provider. The provider uses the information sent by the cellphones to identify geographic regions where signal conditions are poor, and that enables the provider to upgrade its network.