Patent ID: 8364190

Claim:
A mobile station which (i) monitors, in a monitor cycle, a paging channel slot which stores a message therein and is transmitted by a radio base station in a transmission cycle, and (ii) performs a process according to the message, comprising: a PTT setting reception unit operable to receive a PTT setting operation from a user for setting a PTT (Push to Talk) mode, in which a voice packet communication is available; a monitor cycle switching unit operable to switch, when the PTT setting reception unit receives the PTT setting operation, the monitor cycle to a predetermined short cycle which is for the PTT mode and shorter than cycles for other modes; a PTT communication processing unit operable to perform, when the PTT setting reception unit receives the PTT setting operation, PTT communication processing that is processing for transmission and reception of a voice packet and includes voice reproduction processing through which the PTT communication processing unit receives a voice packet which is transmitted from the radio base station after a PTT CALL is detected in the message, and reproduces a voice based on the voice packet, the PTT CALL being a request for the voice packet communication; and a control unit operable, when a predetermined period has elapsed without transmission nor reception of a voice packet from a start of the PTT communication processing, to have the PTT communication processing unit finish the PTT communication processing and to have the monitor cycle switching unit change the predetermined short cycle back to the monitor cycle which has been used until the PTT setting reception unit receives the PTT setting operation.