1. A radio terminal which intermittently receives beacons transmitted from a radio base station at regular intervals and beacons each having a delivery traffic indication map transmitted from the radio base station at intervals of certain beacon intervals, in which, having recognized that its packets are buffered in the radio base station by extracting information elements included in a received beacon, the radio terminal sends the radio base station a control packet to request delivery of the packets, thereby receiving the packets buffered in the radio base station, including: a timer value changing section for dynamically changing one or more timer values according to the operation mode of each of a plurality of communication applications running on the radio terminal, the operation mode of each of the plurality of communication applications corresponding to at least one of the power-saving rate of the communication application, the priority of the communication application, and a remaining amount of charge in a battery that supplies power necessary for the operation of the radio terminal, the priority of the communication application being established relative to the priorities of the remainder of the plurality of the communication applications, one of the timer values being a random back off time range, defining a range of random wait time that must pass after the channel goes into the idle state until transmission of the packets buffered in the radio base station, the random back off time range being determined based on the priority of the communication application.