Hitachi, Ltd.

Hitachi-Kokusai Electric Inc.

Hitachi Cable, Inc.

Hitachi Communication Technologies, Ltd.

Tsuyoshi Tamaki

Takashi Yano

Tomoaki Ishifuji

Takaki Uta

Nobukazu Doi

Takashi Ishikawa

Satoshi Tamaki

Kenzaburo Fujishima

Rintaro Katayama

Masaaki Shida

Atsushi Ogino

Ryota Yamasaki

Yunjian Jia

Shinji Murai

Hitoshi Ishida

Kazuko Hamaguchi

Toshiyuki Saito

Shigenori Hayase

Tomonori Yamamoto

Ryouichi Tanaka

Kingo Miyoshi

Naoto Matsuzawa

Katsumi Sakai

Koichi Hashimoto

Taichi Murakawa

When a frequency channel is shared between adjacent cells in a wireless communication system of time-division duplex operation utilizing a white space, more efficient communications can be achieved. In a wireless communication system of time-division duplex operation utilizing a white space, which is a temporally and spatially unused frequency, to perform wireless communications and having frames in which downstream and upstream subframes are alternately arranged on the time axis, a network controller calculates a common split position, which is to be used in synchronization between base stations sharing a frequency, from collected information in response to a frequency sharing trigger and synchronizes the determined split position between the base stations, thereby allowing the frequency channel to be shared.

Wireless communication system, frequency channel sharing method, and network controller device

The objective of the invention is to improve the communication performance of a secondary system within such a range that does not affect a primary system. A wireless communication system comprises: a primary system that can use a given frequency on a priority basis; secondary wireless communication systems each of which is operated with the same frequency; and a network control apparatus that controls the secondary wireless communication systems. The network control apparatus comprises: a primary system information acquiring unit that acquires information of the primary system; a secondary system information acquiring unit that acquires communication quality information of the secondary wireless communication systems; and an optimum computing unit that calculates, on the basis of the primary and secondary system information acquiring units, the transmission powers of a plurality of base stations of the secondary wireless communication systems.

Wireless communication system, transmission power control method, and network control apparatus

A macro base station includes a communication prohibited period setting unit of setting an uplink communication prohibited period to a user equipment belonging to the base station, and prohibits an uplink communication from the user equipment to a wireless communication base station per se during the uplink communication prohibited period. The user equipments belonging to the wireless communication base station per se and the second base station are divided into plural groups, and the uplink communication prohibited period is set to different time periods for the respective groups. Thereby, a communication characteristic is prohibited from being deteriorated at the second base station by an interference affected with the second base station separately from the first base station by the user equipment communicating with the first base station in the uplink communication.

Base station, system, and method of macro and pico base station interference coordination using uplink prohibition period

An optimum communication mode and an optimum antenna are selected according to traffic and a radio propagation status of a terminal. With the use of traffic information between a base station and the terminal, an SISO communication or an SIMO communication is conducted if the traffic is small. It is determined whether the MIMO communication should be conducted, or not, if the traffic is large. An antenna that can exert the effect as the MIMO communication is selected by using the radio propagation channel state information between the distributed antennas of the base station and the antenna of the terminal. Also, because the selection of the antenna is changed by conducting the MIMO communication, an antenna optimum for the terminal that conducts the SISO communication or the SIMO communication is re-selected taking the interference influence on the terminal that conducts the SISO communication or the SIMO communication into account.

Distributed antenna system, base station device, and antenna selection control method

A frame time having a certain period of time is divided into: a time period (for inter-base-station time division multiplex communication) in which one of the base stations has a transmission right in the simultaneous transmission and carries out inter-base-station time division multiplex communication so as to avoid interference between the base stations; and a time period (for inter-base-station simultaneous communication) for communication which is simultaneously carried out between the plurality of base stations. Furthermore, the time periods are switched for the communication.

Wireless communication system, integrated base station, and terminal

To reduce an uplink interference in a network with a first base station of a large output and a second base station of a small output. Detecting the interference, the second base station urges the first base station to hand over a terminal causing it to the second base station. Multiple base stations and one or more terminals exist in this system, each terminal connects with one base station, and a serving base station is changed according to a communication state of each terminal. If the different second base station other than the first base station to which the terminal connects detects a large interference, the second base station will multicast transmit information for urging handover to the base stations except itself. The base station having received the information specifies a terminal giving the interference to the second base station, and makes it to be handed over thereto.

Wireless communication system and base station

To secure a constant level or more of radio communication quality for each user equipment performing radio communication with a base station apparatus, and to increase the number of user equipment which the base station apparatus can accommodate under a condition of assuring the radio communication quality. In a radio communication system where there exist a base station apparatus having multiple antennas and user equipment for performing radio communication with a first antenna group including one or more of the antennas, the first antenna group is made configurable for each user equipment individually, and addition/deletion of the antenna to/from the first antenna group is performed based on the communication quality of each user equipment so that the number of antennas within the first antenna group may be minimized within a range satisfying a required value of the communication quality between the base station apparatus ad the user equipment.

Radio communication system, base station apparatus, and radio communication method

A femto base station registers IDs of neighboring macro base stations and the ID of a terminal into a management device. When the femto base station detects that the communication state of a terminal in communication with the femto base station transited from active to idle, the femto base station hands off the communication session to one of the neighboring macro stations and enters the dormant state. When the macro base station detects that the communication state of the terminal transited from idle to active, the macro base station transmits an inquiry to the management device, identifies a femto base station to be started based on the terminal ID and the macro base station ID and starts the femto base station. When the femto base station is started, it is handed off from the macro base station to the femto base station to maintain the communication session of the terminal.

Radio base station system and base station

There is provided a wireless communication system in which a feedback volume is reduced as exceeding a communication speed demanded by a mobile station. The wireless communication system includes: a plurality of base stationsandhaving a plurality of antennas; a plurality of mobile stationstohaving a plurality of antennas; and a base station controllercollectively controlling a plurality of the base stations. During a certain period of time (time slot), there are provided an (MIMO+TDMA) communication mode by which only one of the base stations and one of the mobile stations are communicated with each other, an (SDMA+TDMA) communication mode by which one of the base stations and the plurality of the mobile stations are simultaneously communicated with each other, and a (multipoint SDMA) communication mode by which the plurality of the base stations and the plurality of the mobile stations are simultaneously communicated with each other by coordinating the plurality of the base stations with each other by the base station controller. And, it is judged by the base station or the base station controller whether or not the communication speed requested from the mobile station can be exceeded, so that an appropriate communication mode is automatically decided by switching the communication modes.

Wireless communication system and wireless communication method

The selection range of antenna candidates effective for MIMO communication is widened in a base station to increase the throughput of MIMO communication. A terminal sends a sounding signal at given time intervals with the maximum transmission power or with an antenna selection transmission power threshold or larger. With this transmission, since the number of antenna candidates that receive the signal is increased at a base station in the distributed antenna system, the radio propagation channel state between the terminal and the base station apparatus is checked to select the combination of antennas having good orthogonality. Before the terminal sends the sounding signal, the terminal reserves beforehand the transmission timing of the sounding signal or performs carrier sensing to determine whether a surrounding terminal is sending a signal to avoid the collision/interference of packets of sounding signals between terminals.

Distributed antenna system, communication control method and base station apparatus

In a distributed antenna system in which plural antennas are dispersed spatially, a base station apparatuscollects the terminal throughput of the uplink and downlink communication, the number of simultaneous communication terminals, and the information on a radio propagation channel from a distributed antenna to a terminal antenna, and estimates the throughput in each communication mode from the number of simultaneous communication terminals and the radio propagation channel information, selects a communication mode by comparing the estimated throughput with a request value, connects the distributed antenna and the base station apparatusin an antenna connection pattern in the selected communication mode, and switches the communication mode between the base station device and the terminal to continue the communication, when the terminal throughput is below the request value, or above the request value plus a certain threshold value.

Distributed antenna system, distributed antenna switching method, base station apparatus and antenna switching device

A bandwidth control system is provided, enabling the prevention of a resource shortage in the base station, caused by preliminary authentication which reserves resources in advance. The bandwidth control system limits a bandwidth of a communication path used for the preliminary authentication, in the case where a count of successful authentication of the wireless terminal belonging to the first wireless system and a count of successful preliminary authentication transmitted from the wireless terminal belonging to the second wireless system establish a predetermined relationship.

Bandwidth control system

A wireless communication system includes first and second transmitting stations cooperating with each other to transmit data signals in parallel to the same receiving station. The first transmitting station transmits data at a slot reference timing of each TDMA slot within a data transmission period. The second transmitting station calculates the adjustment amount of data transmission timing for the receiving station within a propagation delay time measurement period, and transmits data at a transmission timing determined by a slot reference timing and the adjustment amount in each TDMA slot within the data transmission period.

Wireless communication system, base station and transmission timing control method

An error correction decoder possessing a decoding method with high error correction performance and capable of operating at a low operating frequency and on a reduced circuit scale. A decoding method based on the SOVA method for improving error correction performance and boosting reliability of the soft decision output by allowing branching of paths other than the survival path at trace-back is achieved by preparing a trace-back circuit for each state, and selecting an output from that output and survival state (survival state+difference of likelihood).

Error correction decoder

A wireless communication system that detects a position of a node using an appropriate position detection method. The invention is based upon a wireless communication system provided with a plurality of nodes that mutually communicate and a server that detects a position of the node using communication between the nodes and is characterized in that the node has a battery for supplying power, measures the status of the battery, notifies the server of the measured status of the battery, the server determines a position detection method of the node based upon the status notified by the node of the battery and calculates a position of the node by the determined position detection method.

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Machida, Japan

Tsuyoshi Tamaki