Abstract: Application data generated by an ECU is wireless transmitted by a transmission device in a subject vehicle so as to periodically change a communications distance by changing, every transmission timing, at least one of (i) a transmission rate, which is used in transforming a transmission packet into a transmission signal in a modulation section, and (ii) a transmission power, which is configured by an amplification section to amplify the transmission signal. As a result, the data transmission from the subject vehicle can be made (i) in high repetition times with respect to a nearby vehicle having a greater risk of collision (i.e., time to collision being shorter), and (ii) in low repetition times with respect to a distant vehicle having a less risk of collision (i.e., time to collision being longer).

Abstract: A mobile communication system uses efficiently a radio band of a previously-connected base station, when a mobile terminal that executes multicast communication moves among radio base stations. The mobile communication system includes a layer-2 switch. Upon switching from one radio base station over to the other radio base station, the mobile terminal transmits a path formation request related to a multicast group via the connected radio base station. The path formation request reaches the wired port of the one radio base station through the layer-2 switch. Here, “leave” of the mobile terminal from the control of the one radio base station is detected, and the delivery of multicast is halted. The other radio base station, on the other hand, starts delivering the multicast.

Abstract: A mobile communication system uses efficiently a radio band of a previously-connected base station, when a mobile terminal that executes multicast communication moves among radio base stations. The mobile communication system includes a layer-2 switch. Upon switching from one radio base station over to the other radio base station, the mobile terminal transmits a path formation request related to a multicast group via the connected radio base station. The path formation request reaches the wired port of the one radio base station through the layer-2 switch. Here, “leave” of the mobile terminal from the control of the one radio base station is detected, and the delivery of multicast is halted. The other radio base station, on the other hand, starts delivering the multicast.

Abstract: A wireless base station and a wireless mobile station repeat, via a wireless communication section therebetween, transmission of contents data from a server to a terminal. Each of the wireless base station and the wireless mobile station periodically transmits camouflage data to each of the server and the terminal, respectively, when the wireless communication section is incommunicative. This causes each of the server and the terminal to determine that a connection for data communication between the server and the terminal is continuing. Processing for the transmission/reception in the data communication is thereby prevented from being interrupted even when a wireless communication environment deteriorates and the wireless communication section becomes incommunicative.