COMMUNICATION METHOD USING HIERARCHICAL CELLULAR SYSTEM

PROBLEM TO BE SOLVED: To provide a hierarchical cell layer system that can effectively utilize a frequency resource. SOLUTION: In an embodiment, when a mobile unit is connected to a cell of a first cell layer, a timer is started, and when the mobile unit is disconnected from the cell, the timer is stopped. An interlayer handoff system decides whether the mobile unit is to be served by other cell layer, depending on the time when the mobile unit stays in the cell of the first layer or on its function. For example, a network compares the value of the timer or its function with a threshold, so that number of handoff times is at a level or lower at each cell layer.