Ntt Docomo, Inc.

Tatsuki Okuyama

Satoshi Suyama

Yukihiko Okumura

Tatsunori Obara

Jun Mashino

Shohei Yoshioka

Nobuhide Nonaka

Jiyun Shen

Yuuta Takahashi

A control apparatus includes a control section that determines, for each terminal, a method for a coordinated operation performed between a plurality of radio apparatuses for signal transmission to the terminal, and a transmission section that outputs control information on the method determined.

Control apparatus, radio communication system, and control method

Deterioration in communication characteristics is prevented by performing scheduling in which movement/stillness of user terminals is taken into consideration. Received-power measurement sectionmeasures the power of a reference signal from each of the user terminals. Movement/stillness determination sectiondetermines whether each of the user terminals is a moving terminal or an unmoving terminal based on over-time variations in received power at transmission points for each of the user terminals. Group selection sectiongroups the user terminals into a moving terminal group and an unmoving terminal group, and selects one of the groups as a signal-transmission target. Transmission control sectionperforms open-loop signal processing without precoding when the moving terminal group is selected, or performs closed-loop signal processing with precoding when the unmoving terminal group is selected.

Base station and transmission method

This base station comprises: a control unit that allocates, on the basis of a doppler shift estimated using an uplink reference signal, a downlink reference signal common to a plurality of beams; and a transmission unit that transmits the common downlink reference signal via the plurality of beams. According to this base station communication method, the base station allocates, on the basis of a doppler shift estimated using an uplink reference signal, a downlink reference signal common to a plurality of beams, and transmits the common downlink reference signal via the plurality of beams.

Base station and base station communication method

A radio terminal that performs radio communication with a radio base station including a plurality of transmission points each including at least one antenna element and a signal processing unit connected to the plurality of transmission points includes a plurality of antenna elements, an estimating section that estimates path-loss between each of the plurality of antenna elements and the plurality of transmission points, and a calculating section that calculates a power control weight for controlling transmission power of the plurality of antenna elements based on the path-loss for the antenna element that has been estimated by the estimating section.

Wireless terminal, transmission power control method, and wireless base station

Radio base stationin a radio communication system that performs MIMO transmission between a plurality of radio base stations and at least one user terminalincludes: precoding sectionthat applies precoding to data signals based on channel information indicating channels between radio base stationsand the user terminal; and communication sectionthat transmits the precoded data signals, in which the precoding in a first radio base station of the plurality of radio base stations is applied based on the channel information including at least a channel between the first radio base station and a first user terminal connected to a second radio base station other than the first radio base station.

Wireless base station and wireless communication method

A radio base station includes: an obtaining section that obtains a first communication quality of each of first communication terminals and obtains a second communication quality of each of second communication terminals having a lower communication speed than the first communication terminals; and a scheduler that schedules the first communication terminals based on the first communication qualities and schedules the second communication terminals based on the second communication qualities, and when the scheduler schedules the first communication terminals and the second communication terminals, the scheduler subjects the first communication terminals to space-division multiplexing and subjects the second communication terminals to frequency-division multiplexing or time-division multiplexing.

Wireless base station and scheduling method

In a radio base station including: a plurality of transmission points each including at least one antenna element; and a signal processing unit connected to the plurality of transmission points, the signal processing unit includes: an estimating section that estimates, in each of the antenna elements, a path-loss with a radio terminal; and a calculating section that calculates a power control weight for controlling transmission power of each of the antenna elements based on the path-loss of the antenna element, which is estimated by the estimating section.

Wireless base station and transmission power control method

In a radio communication system that performs beamforming in MIMO transmission between a radio base station and at least one user terminal, radio base station () includes: weight control section () that determines a beamforming weight used for the beamforming, for each of subbands formed by dividing a transmission band; and communication section () that transmits a signal to which the beamforming is applied using the beamforming weight.

In user terminal, communication sectionreceives a data signal to which precoding based on first channel information indicating a channel between radio base stationand user terminalestimated in first channel estimation and beamforming are applied. The first channel information is an equivalent channel matrix including a beamforming weight. Stage-2 channel estimation sectionperforms second channel estimation for estimating second channel information indicating a channel between radio base stationand user terminal. The second channel information is an equivalent channel matrix including the beamforming weight and a precoding matrix. Postcoding sectionperforms postcoding on the data signal based on the second channel information.

User terminal and wireless communication method

A management apparatus in a wireless communication system including multiple transmission points transmitting reference signals, the management apparatus managing the transmission points, and a mobile station, includes: a management unit for managing first and second clusters generated by grouping one or more transmission points used to communicate with the mobile station among the multiple transmission points; and a control unit for controlling allocation of the reference signals transmitted from the multiple transmission points in the first and second clusters. The management unit detects that multiple cells formed by the transmission points in the first cluster overlap some of multiple cells formed by the transmission points in the second cluster. When the management unit detects the overlap, the control unit allocates the orthogonal reference signals to the multiple cells formed by the transmission points in the first cluster and the multiple cells formed by the transmission points in the second cluster.

Management apparatus

A user equipment UE includes: a measurer that measures, for each of a plurality of candidate beams, a benchmark pertaining to communication quality; a comparer that compares the benchmark with a first threshold value and a second threshold value; and a feedback unit that transmits the benchmark to the base station as feedback information pertaining to an interference beam if the benchmark is the first threshold value or higher and lower than the second threshold value, transmits the benchmark to the base station as feedback information pertaining to a desired beam if the benchmark is the second threshold value or higher, and transmits no feedback information to the base station if the benchmark is lower than the first threshold value, based on the comparison results of the comparer.

User equipment and base station

There is provided a base station that supports multi-user MIMO and performs communication with a plurality of mobile stations of a radio communication system including the base station and the plurality of mobile stations, the base station including a determination unit that determines a number of a plurality of streams to be transmitted to each of the plurality of mobile stations and parameters to be applied to each of the plurality of streams to be transmitted to each of the plurality of mobile stations based on a channel estimation value for each of the plurality of mobile stations, and a transmitter that generates a determined number of streams according to the parameters determined by the determination unit to be transmitted to the respective plurality of mobile stations.

Base station

Provided is a base station for communicating with mobile stations of a radio communication system including the base station and mobile stations including an obtaining unit that obtains a channel matrix for each mobile stations; a selector that selects, among the mobile stations, a combination of two or more mobile stations with which communication based on multi-user MIMO is to be performed; and a communication unit that communicates, based on multi-user MIMO, with the two or more mobile stations of the selected combination, wherein the selector calculates, for each of all combinations of two mobile stations of the two or more mobile stations, a correlation value between the channel matrices for the two mobile stations, and selects the combination of the two or more mobile stations, so that, for all the combinations of the two mobile stations, the correlation values is less than or equal to a predetermined value.

Base station and method for performing beamforming in an MU-MIMO environment

A base station transmits first discovery signals in different transmission directions from the base station through beamforming; transmits, for one or more first transmission directions corresponding to one or more first discovery signals reported from the mobile station, second discovery signals in second transmission directions within a predetermined range from the first transmission direction; and, for transmitting the second discovery signal, transmits the second discovery signal by multiplying, by a correction precoding vector for adding, to the first transmission direction, a transmission angle difference between the first transmission direction within the predetermined range from the second discovery signal and a second transmission direction of the second discovery signal to be transmitted, and by performing beamforming for the second discovery signal to which the correction precoding vector is multiplied, using a first weight matrix for beamforming in the first transmission direction within the predetermined range from the second discovery signal.

A wireless communication system includes: a plurality of first wireless stations; a plurality of second wireless stations; and a management apparatus configured to manage the plurality of first wireless stations and the plurality of second wireless stations. The management apparatus includes a selection unit that selects a plurality of antennas to be used to transmit reference signals from a plurality of antennas included in the plurality of first wireless stations or a plurality of antennas included in the plurality of second wireless stations, and an instruction unit that instructs the plurality of first wireless stations or the plurality of second wireless stations to transmit reference signals using the plurality of antennas used to transmit the reference signals and selected by the selection unit.

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Tokyo, Japan

Tatsuki Okuyama