Ntt Docomo, Inc.

Tatsunori Obara

Yukihiko Okumura

Satoshi Suyama

Tatsuki Okuyama

Jiyun Shen

Riichi Kudou

Shinpei Yasukawa

In order to prevent wireless resources from becoming scarce in a Sidelink V2X communication, a UE () that carries out the Sidelink V2X communication causes: a free resource search unit () to search for free resources within a first resource range; a transmission processing unit () to transmit a first transmission packet by using the free resources within the first resource range; a transmission inhibition timer unit () to set transmission inhibition time which is time for inhibiting start of a second resource range after the transmission of the first transmission packet within the first resource range; and the free resource search unit () to search for free resources within the second resource range after the expiration of the transmission inhibition time.

Wireless communication apparatus 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 server device for determining, on the basis of a communication cost in a communication area in which at least one terminal is communicatable and the position of the at least one terminal, a first terminal to which uplink data is to be transmitted in a first communication area, in which the communication cost is less than a threshold, transmitting to the first terminal an indication for uplink data transmission in the first communication area, and receiving uplink data from the first terminal.

Server device and communication method

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.

Wireless communication system and management apparatus

There is provided an estimation device including an acquisition unit that acquires a channel estimation value for each combination of all of a plurality of combinations between a plurality of transmission antenna elements included in a base station and a plurality of reception antenna elements included in a mobile station; and an estimation unit that calculates a channel impulse response for each combination of all of the plurality of combinations between the plurality of transmission antenna elements and the plurality of reception antenna elements using the channel estimation values, and that estimates power delay profile by averaging, over all the combinations of the plurality of combinations between the plurality of transmission antenna elements and the plurality of reception antenna elements, power values for the respective combinations that are calculated from the calculated channel impulse responses for the respective combinations.

Estimation device

A number Lof receive beamforming circuits provided in a receive beamformer execute receive beamforming (N/L) times with respect to a received signal vector received by Nreception antennas A, thereby generating a receive beamforming (BF) output vector having Nreceive BF output components. A calculation processor calculates a reception power for each of the Nreceive BF output components, selects Lreceive BF output components in decreasing order of reception power, and determines a suitable receive BF weight matrix including Lreception orthogonal BF weight vectors corresponding to the selected receive BF output components.

Radio communication control method and radio communication system

To improve system performance for mobile communications (group mobility) in a plurality of terminals existing inside the same moving object, a radio base station, which forms a cell on a moving path of a moving object to communicate with a mobile station provided in the moving object using beam forming, is provided with a transmission section that transmits a plurality of acquisition signals applied with different beam forming weights respectively to at least an edge region of the cell formed on the moving path of the moving object, and a control section that controls a beam forming weight to apply to a data signal transmitted to the mobile station, based on information notified from the mobile station receiving an acquisition signal.

Radio base station, mobile station and radio communication method

A communication control method includes: for each of plurality of receivers UE, calculating excluding channel matrices that include a plurality of equivalent channel matrices acquired by multiplying a transmit BF weight matrix corresponding to that receiver UE by each of a plurality of channel matrices corresponding to receivers UE other than that receiver UE, acquiring a first eigenvector that is included in a right-singular matrix obtained from single value decomposition of the excluding channel matrices, the first eigenvector corresponding to a noise subspace of the excluding channel matrices, acquiring a second eigenvector that is included in a right-singular matrix obtained from single value decomposition of a product of an equivalent channel matrix including the transmit BF weight matrix corresponding to that receiver UE and the first eigenvector, the second eigenvector corresponding to a signal subspace of the product, and obtaining a precoding matrix corresponding to that receiver UE by multiplying the first eigenvector by the second eigenvector.

BF weight vector determination is executed for each of M number of streams. In a first stage, by repeating switching of transmission BF weight (transmission beam) candidates in a small base station, a transmission BF weight vector with the best reception quality in a user apparatus UE is selected from among tried transmission BF weight vectors. In a second stage, by repeating switching of reception BF weight (reception beam) candidates in the user apparatus, a reception BF weight vector with the best reception quality in the user apparatus UE is selected from among tried reception BF weight vectors.

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Tokyo, Japan

Tatsunori Obara