Patent attributes
When there is a connection request to a base station supporting adaptive modulation from a terminal supporting adaptive modulation, the base station measures a D wave level that indicates communication environment of the transmission path. When the measured D wave level is not lower than a threshold value of D wave level at which communication is possible by a modulation method (16QAM) having larger multi-value number, the base station permits allocation of a wireless channel to the terminal. Therefore, even when the modulation method is switched from one having smaller multi-value number (π/4 shift QPSK) to one having larger multi-value number (16QAM) during communication after channel allocation to the terminal, degradation of communication quality due to the communication environment of the transmission path can be prevented.
