| 摘要 |
To perform communication at a higher speed than in the past using a new communication device without giving influence on the existing slave communication device, on a master device of a communication system such as PHS, there are provided two series of modulators and demodulators for conventional speed and for higher speed, the two different speeds being changeable by a changeover switch. A slave device to be added newly is also designed in almost the same configuration. In the link setup phase, an information to request change of modulation method is notified together with a request of communication from the slave device to the master device. From the master device, an information to specify time slots to be used in the communication phase and an information to specify modulation method are notified to the slave device. In the communication phase, communication is performed using the modulation method and the time slots as specified. The slave device can select the modulation method corresponding to the transmitting speed as required. In case the modulation method is not specified from the slave device, the same modulation method as that of the link setup phase is used in the communication phase, and the existing slave device not equipped with the means to specify the modulation method can be used without any change.
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