PURPOSE: To construct a system with high availability of frequency by dividing one radio channel into plural time slot systems in point of time, and performing communication by selecting one or plural time slot systems.

CONSTITUTION: One radio channel is divided into the plural time slot systems in point of time since a radio base station 30 and a large number of mobile radio equipment 100-1 to 100-n in the service area of the base station exist and an arbitrary number of radio equipment can communicate with the base station 30. The communication is performed by selecting one or plural time slot systems and using them. When transmission is performed from another radio equipment to the base station 30 while one radio equipment is communicating with the base station 30, one of nonuse time slot systems in radio channels in use is supplied to the radio equipment from which the communication is requested newly, which enables the communication with the base station 30 to be performed. Therefore, it is possible to obtain the system with high availability of frequency.