Ntt Docomo, Inc.

Tokyo Institute of Technology

Yusuke Ohwatari

Yukihiko Okumura

Yousuke Sano

Kazuaki Takeda

Satoshi Nagata

Nobuhiko Miki

Tetsushi Abe

Anass Benjebbour

Junichiro Hagiwara

Yoshihisa Kishiyama

Takahiro Asai

Yuta Sagae

Akihito Morimoto

Tomoyuki Ooya

Hiroki Harada

Hiroyuki Ishii

Hiroshi Suzuki

Satoshi Suyama

Naoto Okubo

Kazuhiko Fukawa

A user apparatus, in a radio communication system including a plurality of base stations, including a reception unit configured to receive, from a connecting base station, control information to be used for reducing an interference signal sent from an interference base station for the user apparatus; and an interference reducing unit configured to reduce the interference signal by using the control information to obtain a desired signal sent from the connecting base station.

User apparatus, base station, interference reducing method and interference reducing control information notification method

A user apparatus in a radio communication system including a plurality of base stations, including a reception unit that receives, from a connecting base station, control information to be used for reducing a signal of a control channel, that causes interference, sent from an interference base station for the user apparatus, and an interference reducing unit that reduces the signal of the control channel that causes the interference by using the control information to obtain a desired signal sent from the connecting base station.

A base station, according to received qualities at user devices, allocates a downlink transmission power to each user device. The base station transmits a mixed data signal in which data signals mutually not orthogonal and each addressed to a corresponding user device are mixed. Control signals are transmitted to user devices to enable each user device to decode a data signal addressed to the user device using a control signal corresponding to the user device. Each control signal is scrambled by the identifier of the corresponding user device. A control signal for a first user device to which a first data signal is addressed includes information indicating the identifier of a second user device to which a second data signal mixed with the first data signal is addressed. The first user device is thus enabled to descramble a control signal for the second user device.

Base station and user device for reducing amount of information for interference canceller in radio communication system

A base station allocates downlink transmission powers to user equipments according to the reception qualities of the user equipments. The base station transmits a mixed data signal in which multiple data signals that are addressed to multiple user equipments and are not orthogonal to each other are mixed, and transmits multiple control signals to the multiple user equipments such that each user equipment can decode the data signal addressed to that user equipment using the control signal corresponding to that user equipment. Each control signal is scrambled using the identifier of the user equipment corresponding to that control signal. With a period longer than the transmission period for the control signal, the base station notifies the multiple user equipments of identifier information indicating multiple identifiers, and thus the user equipment can descramble a control signal for another user equipment to which an interference data signal with a higher transmission power is addressed.

Base station and user equipment

From a base station, a user equipment receives a mixed data signal transmitted in a format in which multiple data signals are transmitted with different downlink transmission powers such that the multiple data signals are not orthogonal to each other, multiple control signals corresponding to multiple user equipments, and information indicating an identifier of another user equipment. The user equipment determines an aggregation level of the subject user equipment. The user equipment uses the identifier of the other user equipment to attempt descrambling of one control signal among multiple control signals corresponding to an aggregation level higher than or equal to the aggregation level of the user equipment, and if the descrambling is successful, the user equipment uses the control signal to demodulate the non-orthogonal data signal.

User equipment

Some OFDM symbols transmitted temporally continuously by a base station include data signals that are not orthogonal to each other and are directed to user devices. A reference signal is arranged in the OFDM symbols temporally intermittently. The base station determines, according to reception qualities at user devices, downlink data signal transmission powers for transmitting downlink data signals. The base station reduces a downlink data signal transmission power in an OFDM symbol in which the reference signal is arranged to be lower than a downlink data signal transmission power in an OFDM symbol in which the reference signal is not arranged. The base station determines a downlink reference signal transmission power to be higher than the downlink data signal transmission power of a data signal in the OFDM symbol in which the reference signal is not arranged.

Base station

A user device receives, from a base station, a radio signal in which non-orthogonal signals are mixed. The user device recognizes, based on information transmitted from the base station, a parameter associated with the location of the user device. When the user device is at the edge of the cell area of the base station, a demodulator of the user device demodulates, as a signal directed to the user device, the radio signal in which an interference signal component has been suppressed by an interference rejection combining processor of the user device and a non-orthogonal signal canceller of the user device does not operate. When the user device is within the cell area and is not at the edge of the cell area, until the demodulator demodulates the signal directed to the user device, the interference rejection combining processor suppresses an interference signal component in a non-orthogonal signal outputted from the non-orthogonal signal canceller and the demodulator demodulates the non-orthogonal signal in which the interference signal component has been suppressed by the interference rejection combining processor.

Radio communication system and user device

A base station connected to a user apparatus in a radio communication system is provided. The base station includes a receiving unit configured to receive from an interference base station first control information which is used by the user apparatus for reducing an uplink interference signal from one or more cells formed by the interference base station or from another user apparatus, a generation unit configured to generate second control information based on one or more pieces of the first control information received from the interference base station, and a transmitting unit configured to transmit the second control information to the user apparatus by a downlink control signal.

Base station, user apparatus and interference reduction method

A mobile communication terminal calculates an interference rejection combining reception weight matrix so as to reduce interference with a desired beam by another beam, in which the desired beam is a beam of radio waves transmitted from a desired base station. The mobile communication terminal estimates an interference and noise power expected when the IRC is implemented based on the interference rejection combining reception weight matrix and calculates a signal-to-interference-plus-noise ratio expected when the IRC is implemented based on the interference and noise power. The mobile communication terminal measures or calculates received signal qualities relative to radio waves received from a plurality of base stations, to compensate for the signal-to-interference-plus-noise ratio or the interference and noise power.

Mobile communication terminal

The present invention provides a base station apparatus, a mobile terminal apparatus and a communication control method which can improve the accuracy of channel quality estimation. A communication control method includes the steps of: allocating a CSI-RS (Channel State Information-Reference Signal), which is a reference signal for downlink channel estimation, in resources for the CSI-RS that are defined for CSI-RS transmission; setting muting resources in the resources for the CSI-RS; and reporting parameters to specify the CSI-RS, including at least a transmitting subframe cycle, a subframe offset and transmission power, to a mobile terminal apparatus.

Base station apparatus, mobile terminal apparatus and communication control method

A radio communication system includes a user device, base stations, and a communication control device. The communication control device generates and reports, to the user device, selection information that is used to select base stations with which the user device should maintain synchronization. The user device selects, based on the selection information, base stations with which the user device should maintain synchronization. The user device reports, to the communication control device, identifiers of the selected base stations and received levels of radio waves transmitted from the base stations corresponding to the identifiers. The user device maintains synchronization with each of the selected base stations.

Radio communication system and communication control method

A user apparatus for use in a radio communication system, including: an interference reduction process unit configured to reduce, from a received signal received by the user apparatus, an interference signal that becomes interference to a desired signal so as to obtain the desired signal; an interference reduction process execution determination unit configured to measure reception quality of the interference signal, and to determine whether to regard the interference signal as a target of interference reduction processing based on the reception quality, wherein the interference reduction process execution determination unit determines whether to regard the interference signal as the target of interference reduction processing by comparing a first indicator value of the interference signal that is estimated from the reception quality with a second indicator value that is used for transmission of the interference signal.

User apparatus and interference reduction process method

A user apparatus in a radio communication system including a plurality of base stations, including: a reception unit configured to receive, from a connecting base station, control information to be used for reducing an interference signal sent from an interference base station for the user apparatus; and an interference reducing unit configured to reduce the interference signal by using the control information to obtain a desired signal sent from the connecting base station, wherein the reception unit receives a part of the control information as a part of downlink control information that is transmitted by a downlink physical layer signaling channel from the connecting base station, and receives the other part of the control information by RRC signaling.

A mobile communication terminal calculates an interference rejection combining reception weight matrix based on a vector representing a reference signal transmitted from a desired base station so as to reduce interference with a desired beam of radio waves. The mobile communication terminal estimates, from the interference rejection combining reception weight matrix and the reference signal, an all received power expected when an IRC is implemented, and estimates, from an interference rejection combining weight vector, a channel matrix, and a reference signal sequence, a desired reference signal power expected when an IRC is implemented. The mobile communication terminal subtracts the desired reference signal power from the all received power, thereby estimating an interference and noise power expected when an IRC is implemented, and calculates an SINR expected when an IRC is implemented from the estimated interference and noise power.

A user apparatus for use in a radio communication system, including: an successive interference cancelling reception unit configured to obtain a desired signal by successively canceling an interference signal that becomes interference to the desired signal from a received signal that the user apparatus receives; and an ordering determination unit configured to determine an order of interference signals to be successively canceled by the successive interference cancelling reception unit, wherein the ordering determination unit determines the order based on reception quality for each interference signal.

Growing community of inventors

Tokyo, Japan

Yusuke Ohwatari