Softbank Corporation

Atsushi Nagate

Mitsukuni Konishi

Teruya Fujii

Kenji Hoshino

Yoshichika Ota

Koji Tashiro

Daigo Ogata

Sho Nabatame

Noboru Kanazawa

In an upper-airspace staying type communication relay apparatus that performs an MU-MIMO radio communication with plural terminal apparatuses located in a cell, it is intended to improve the communication quality of the entire cell and enhance the system capacity, while suppressing an increase in overhead in the terminal apparatus and the communication relay apparatus even if the number of terminal apparatuses located in the cell increases. The communication relay apparatus receives an uplink signal from each of plural terminal apparatuses via an array antenna, estimates angle information indicating a direction of the terminal apparatus for each of the plural terminal apparatuses, selects a terminal apparatus to be assigned to each of plural radio resources used for a downlink based on the estimation result of the angle information, calculates a downlink beamforming weight based on the estimation result of the angle information, and transmits a downlink signal to the terminal apparatus via the array antenna based on the beamforming weight corresponding to the terminal apparatus and the radio resources assigned to the terminal apparatus.

Massive MIMO for HAPS based on angle information on user apparatus

It is suppressed of a deterioration of a communication quality of a service link (SL), which is caused by an increase of signal attenuation in a propagation path of a feeder link (FL) between an aerial-staying type communication relay apparatus and a gateway (GW) station. A relay communication station of the communication relay apparatus comprises a FL communication section that performs a feeder-link radio communication with each of a first gateway station and a second gateway station corresponding to a first cell and a second cell which are adjacent to each other, a SL communication section that performs a radio communication with a terminal apparatus in each SL of the first cell and the second cell, and a control section that controls the SL communication section so that a shape of the second cell is changed to include a part or a whole of the first cell, when a radio communication quality in the FL propagation path with the first gateway station corresponding to the first cell is deteriorated or when the deterioration of the radio communication quality is predicted.

Multi-feeder link configuration in haps communication system and control therefor

When there is a movement or attitude change of an upper-airspace staying type communication relay apparatus, it is suppressed of an increase in control signals and disconnection of communication with a terminal apparatus in a cell configuring a service area, and it is reduced of a circuit scale and power consumption of a base-station processing section. The base-station processing section of the communication relay apparatus performs, with respect to a radio resource part for control communication by which a communication is performed with plural terminal apparatuses located in a cell via a single or plural beams for control among downlink and uplink radio resources used for service links, a footprint fixation control for performing a precoding and a postcoding so as to fix a position of a footprint corresponding to the beam for control, based on information on at least one of a position and attitude of the communication relay apparatus, and does not perform the footprint fixation control on the basis of the information on the at least one of the position and attitude, with respect to downlink and uplink radio resource parts other than the radio resource part for control communication.

Footprint fixation control limited to specific channels considering movement and rotation of HAPS

In a mobile communication system using a mobile-type radio relay apparatus that forms a plurality of cells toward the ground or the sea while moving in an upper airspace, a deterioration in communication quality, which is caused by a Doppler shift of a reception signal due to a relative movement of a radio relay apparatus with respect to a terminal apparatus of each of a plurality of cells or a feeder station on the ground or on the sea, is suppressed. The communication system comprises a mobile-type radio relay apparatus that is disposed movably by flying in an upper airspace, forms a plurality of cells from an antenna at a predetermined altitude toward the ground or the sea, and performs a radio communication with a terminal apparatus located in each of the plurality of cells. The communication system comprises an estimation section for estimating a Doppler shift in at least one of a radio communication of a service link between the terminal apparatus located in the cell and the radio relay apparatus and a radio communication of a feeder link between the radio relay apparatus and a feeder station on the ground or on the sea, and a correction section for correcting a frequency of the at least one radio communication based on an estimation result of the Doppler shift.

Doppler shift correction in three-dimensional network

A base station, a communication system and a time synchronization method between base stations are provided, which are capable of performing a time synchronization with another base station using a downlink signal of the other base station cell in which the own cell is located, without stopping transmission of the own base station even during operation. A base station receives a downlink signal that includes a downlink signal including a synchronization signal transmitted from the other base station and a downlink wraparound signal transmitted from own base station, removes an interference of the wraparound signal from the downlink received signal, with respect to a predetermined subframe in which the downlink wraparound signal from own base station interferes with the synchronization signal of the base station, among subframes of the downlink signal including the synchronization signal of the base station, performs a time synchronization processing with the base station by detecting a synchronization signal timing of the base station based on the downlink received signal from which the interference of wraparound signal is removed.

Base station, communication system and time synchronization method between base stations

A base station, a mobile communication system and a handover control method are provided, which are capable of preventing a handover failure and a ping-pong handover phenomenon which are caused by an interference from a neighboring cell to a serving cell. When a received power difference (S&#x2212;S) between a received power Sfrom a neighboring second base station, which is fed back from a mobile station, and a received power Sfrom first base station, becomes larger than a predetermined threshold value, the first base station to which the mobile station is connected requests the second base station to stop a transmission of a downlink signal including at least one of a data signal and a control signal. In response to the transmission-stop request, the second base station performs a determination of a radio resource in which the transmission of the downlink signal is to be stopped and a notification of the radio resource to the first base station, and stops a transmission of a downlink signal. The first base station allocates the radio resource notified from the second base station or a radio resource partially including the notified radio resource, as a radio resource used for the downlink signal to the mobile station.

Base station, mobile communication system and handover control method

A base station apparatus capable of preventing occurrence of a communication delay when performing an inter-cell interference control using an ABS is provided. The base station apparatus is capable of performing an inter-cell interference control by setting an ABS pattern with one cycle of a predetermined number of subframes, and when the ABS pattern is to be switched, changes an MCS (Modulation and Coding Scheme) index value to be determined by an adaptive modulation control, for a communication within a predetermined period of time on or before a switching time of the switching, with respect to a subframe in which a communication with a mobile station apparatus is allowed before switching the ABS pattern.

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Tokyo, Japan

Atsushi Nagate