| 摘要 |
PROBLEM TO BE SOLVED: To provide a communication device and a method that can easily check whether or not the device is currently situated in a wider region or a region corresponding to many positions.SOLUTION: A communication device determines a first position at a certain time point and a second position at a later time point about the device, defines an assumed mobile area of the device, which is a rectangular geographic region, including the first position, stores its upper limit and lower limit longitudes and its upper limit and lower limit latitudes, stores a transition area set in a frame shape in the assumed mobile area by the upper limit and lower limit longitudes and the upper limit and lower limit latitudes indicating its inner boundary, transmits information indicating the assumed mobile area to a database and obtains a list indicating effective channels from the database, selects a channel to be used from the list and controls a communication function unit to use the channel, compares the second position with the upper limit and lower limit longitudes and the upper limit and lower limit latitudes indicating the inner boundary of the transition area, and thereby checks whether the second position reaches the transition area or not. |
