Beam transmission-reception method, base station, terminal, and wireless communication system

A base station, which is to be applied to a wireless communication system in which a beam is used for communication to and from a terminal, the base station comprising:

• a controller to control, when a random access channel signal transmitted as a connection request from the terminal is to be received, a beam direction of an antenna unit by combining a main beam direction, which is determined as suitable for reception of the random access channel signal, with one or more beam directions adjacent to the main beam direction, and thus grouping a plurality of beam directions;
• a transmitter/receiver to receive, via the antenna unit, the random access channel signal transmitted from the terminal;
• and
• a detector to detect whether the random access channel signal has been received by the transmitter/receiver,
• wherein the controller groups beam directions, when one group formed by combining the plurality of beam directions into a group is insufficient to cover entirety of a service area of the base station, and the service area is required to be divided into a plurality of groups, by combining a plurality of beam directions adjacent to one another in directions of edges of the service area, as at least one of the plurality of groups,
• wherein the base station is one of a current communication partner base station, which is holding communication to and from the terminal, and a nearby base station, which is a handover destination, and
• wherein the nearby base station:
• groups the plurality of beam directions and execute first-time reception processing of receiving the random access channel signal;
• and
• regroups beam directions, when the nearby base station fails to receive the random access channel signal in the first-time reception processing, by increasing a number of beam directions from a number of already grouped beam directions, and re-execute reception processing of receiving the random access channel signal as second-time reception processing.

A wireless communication system, comprising:

• a base station, which is to be applied to a wireless communication system in which a beam is used for communication to and from a terminal, the base station comprising:
• a controller to control, when a random access channel signal transmitted as a connection request from the terminal is to be received, a beam direction of an antenna unit by combining a main beam direction, which is determined as suitable for reception of the random access channel signal, with one or more beam directions adjacent to the main beam direction, and thus grouping a plurality of beam directions;
• a transmitter/receiver to receive, via the antenna unit, the random access channel signal transmitted from the terminal;
• and
• a detector to detect whether the random access channel signal has been received by the transmitter/receiver;
• and
• a terminal comprising
• a transmitter/receiver that receives, from the nearby base station, a broadcast signal containing information about timing at which reception of a random access channel signal is possible in a grouped plurality of beam directions;
• a quality measurement device that measures, when the transmitter/receiver receives as the broadcast signal a plurality of broadcast signals associated with different groups, for each of the plurality of broadcast signals, a communication quality of the each of the plurality of broadcast signals from a reception state of the each of the plurality of broadcast signals, and identifies, for each of the plurality of broadcast signals, timing at which reception of a random access channel signal corresponding to the each of the plurality of broadcast signals is possible;
• and
• a controller that controls, when two or more broadcast signals determined as having a suitable communication quality are included among the plurality of broadcast signals, transmission of a random access channel signal for each of the two or more broadcast signals so that the random access channel signal is transmitted at timing indicated by the each of the two or more broadcast signals,
• wherein, when the base station includes a current communication partner base station, which is holding communication to and from the terminal, and a nearby base station, which is a handover destination, the controller of the nearby base station groups the plurality of beam directions, generates, for each group of the plurality of beam directions, a broadcast signal containing first information and second information, and transmits the broadcast signal via the transmitter/receiver of the nearby base station, the first information being about shared timing at which reception of a random access channel signal is possible, the second information defining a number of beam direction groups, and
• wherein, when the broadcast signal is received from the nearby base station, the controller of the terminal identifies timing at which reception of a random access channel signal is possible from the first information contained in the broadcast signal, identifies, as a transmission count of the random access channel signal, a count matching the number of beam direction groups in the second information, the transmission count being a number of times the random access channel signal is transmitted, and transmits the random access channel signal as many times as the identified transmission count at the identified timing.