A communication device is disclosed, having a transceiving circuit, a timer circuit, and a control circuit. The transceiving circuit is used to transceive frequency hopping signals according to at least part of good channels in a channel map. The timer circuit is used to calculate a timespan of one or more communication intervals in which the transceiving circuit transceives the frequency hopping signals. The control circuit is used to compare the timespan with a time threshold to determine whether signal transmission tests with one or more bad channels in the channel map should be performed to update the channel map.