Systems and methods for determining an optimal range of frequencies of electromagnetic waves are described. In some embodiments, mobile voice communications devices measure average power received from certain ranges of such frequencies, each range associated with a communications service provider. A cost may be associated with each range. An optimal range of frequencies may be determined based on these factors. Each device may also receive a set of data identifying the location of the device. Each device may transmit one or more communications signals to a CIP with such measurements and location information, and some of this information may be stored in a database.