Ntt Docomo, Inc.

Nippon Telegraph and Telephone Corporation

Toshiaki Takao

Narumi Umeda

Hijin Sato

Kobaruto Shimada

Lan Chen

Tadashi Shirato

Yoshifumi Suzuki

A mobile communication system includes a base station connected to a backbone network, and a mobile station configured to communicate with the base station using a radio frequency. The system has a first communication mode, in which a first radio frequency is used for an uplink and a second radio frequency is used for a downlink; a second communication mode, in which the first radio frequency is used for the uplink, and the second radio frequency is shared by the uplink and the downlink; a third communication mode, in which the second radio frequency is used for the downlink, and the first radio frequency is shared by the uplink and the downlink; and a mode switcher configured to switch the first through third communication modes in accordance with data transfer volumes on the uplink and the downlink.

Mobile communication systems

In a wireless base station, when a newly provided control unit receives an IP packet from one mobile station (), it refers to a destination address in control information added to the IP packet (), and determines whether the IP packet is one to be broadcast or multicast (). If the value of destination address is at a value indicative of broadcasting or the like defined by IP, the IP packet is copied according to the subnet, and is sent back to a wireless link layer processor with its contents intact (). Further, the wireless link layer processor is commanded to broadcast the sent-back IP packet in a wireless area and so forth (), whereby the IP packet can be broadcast into a cell and so forth.

Mobile communication system, mobile communication method, wireless base station, mobile station, and program

The present invention is configured such that, in a multicast service providing system in which multicast information distribution service is made from an information distributing apparatus to radio terminals present within a service area via a radio section, the radio terminal has service continuation request signal transmitting a service continuation request signal for requesting continuation of the multicast information distribution service to the information distributing apparatus, the information distributing apparatus has service continuation management means managing as to whether or not request for the service continuation has been made by the radio terminal for the multicast information distribution service, and the information distributing apparatus transmits information indicating as to whether or not continuation request has been made for the multicast information distribution service managed by the service continuation management means.

Multicast service providing system, multicast service providing method, information distributor, radio terminal, and radio base station

One preferred embodiment of the invention provides a wireless base station which provides a multicasting service to simultaneously transmit identical data to a plurality of wireless terminals. A wireless base station is connected to a plurality of wireless terminals and provides a multicasting service for a plurality of wireless terminals. The wireless base station determines autonomously whether it provides the multicasting service for the plurality of wireless terminals. Another preferred embodiment of the invention provides a method of selecting a wireless base station for a wireless terminal, the wireless base station providing a multicasting service for the wireless terminal. When the wireless terminal can receive the same multicasting information from a plurality of wireless base stations, the wireless terminal selects one of the plurality of wireless base stations so as to make the number of the wireless base stations that send the same multicasting information as small as possible.

Wireless base station, method of selecting wireless base station, method of multicasting, and wireless terminal

In handover control methods and systems which switch a radio base station serving as a communicating counterpart of a mobile station, the present invention provides a handover control method and a system thereof wherein a detection is made when a communication while a predetermined minimum bandwidth secured is not possible at any mobile station communicating with the radio base station and upon the detection the communicating counterpart of the mobile station that communicates with the radio base station mentioned above is switched from the radio base station to other radio base stations.

Handover control method and system

A clock timing recovery circuit for recovering the clock timing from a baseband signal obtained by detection of a received signal. The clock timing is rapidly established using a clock signal which has been phase-shifted from the desired clock timing to sample the baseband signal, and by obtaining the optimum phase from the sampled signal obtained as a result. A clock-timing recovery circuit according to this invention does not require oversampling and provides easy optimization of circuit constants.

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Yokohama, Japan

Toshiaki Takao