JPWO2018163230A1 - Mobile terminal, radio base station, and beam transmission / reception method - Google Patents

Abstract

  A mobile terminal that communicates with a radio base station that constitutes a communication range by a set of irradiation ranges of one or more directional beams transmitted in a plurality of directions, and that receives radio signals of directional beams received by an antenna A transmission / reception unit (203) that performs processing and transmission processing of a signal transmitted from an antenna, and a corresponding directional beam based on a reference signal included in the directional beam in each direction that has been received and processed by the transmission / reception unit. A measurement unit (204) that measures the channel quality; and if the measured channel quality is better than the channel quality of the directional beam in the direction used for communication with the radio base station, the measured channel quality is And a control unit (201) that determines to report to the radio base station.

Description

  The present invention relates to a communication technique between a radio base station and a terminal using a beam having directivity to which a beamforming technique is applied.

  In the fifth generation mobile communication system (hereinafter referred to as 5G system), use of a high frequency band such as a millimeter wave is expected in order to expand data communication capacity. Since the propagation loss of radio waves increases as the frequency increases, the 5G system improves the power utilization efficiency by using a directional beam that concentrates radio waves in a specific direction by beam forming technology for signal transmission and reception. Is being considered. By using a directional beam, it is possible to improve antenna gain and reduce interference or interference with other radio waves.

  On the other hand, since the transmission direction of radio waves is determined in a specific direction, there is a problem that the antenna gain attenuation becomes large when the receiving apparatus is out of the transmission direction of the directional beam. In order to keep the reception quality of directional beams transmitted from the base station above a certain level even when the terminal moves, consider beam switching that switches the direction of the beam transmitted from the base station to the terminal according to the movement of the terminal. Has been. In beam switching, the base station transmits directional beams in multiple different directions, and the terminal measures the reception quality (channel quality) of each directional beam transmitted by the base station and transmits the measurement results to the base station. To do. The base station determines the transmission direction of the beam addressed to the terminal based on the quality information of the directional beam transmitted by the terminal.

  In Patent Document 1, as a method for realizing beam switching, the base station transmits a beam including a reference signal, the terminal measures the channel quality of the received beam, and reports the whole or the top several measurement results to the base station. A method is disclosed. Here, the channel quality is at least one of SNR (Signal to Noise Ratio), CINR (Carrier to Interference and Noise Ratio), and RSSI (Receive Signal Strength Ratio).

JP-T-2006-506112

  However, the conventional beam switching described above is based on the premise that the terminal reports the channel quality measured at the time of reception of the beam including the reference signal transmitted by the base station to the base station. Even when there is no problem in channel quality and beam switching is unnecessary, the measurement result is reported to the base station, and there is a problem that unnecessary communication from the terminal to the base station occurs.

  The present invention has been made in view of the above, and provides a mobile terminal, a radio base station, and a beam transmission / reception method capable of reducing reporting of channel quality measurement results to a base station when beam switching is unnecessary. The purpose is to obtain.

  A mobile terminal according to the present invention is a mobile terminal that communicates with a radio base station that constitutes a communication range by a set of irradiation ranges of one or more directional beams transmitted in a plurality of directions, and is received by an antenna Corresponding based on the reference signal included in the directional beam of each direction received and processed in the transceiver unit, and the transceiver unit that performs the reception process of the radio signal of the directional beam and the transmission process of the signal transmitted from the antenna A measurement unit that measures the channel quality of the directional beam to be measured, and the measured channel quality when the measured channel quality is better than the channel quality of the directional beam in the direction used for communication with the radio base station. And a control unit that determines to report the quality to the radio base station.

  A radio base station according to the present invention is a radio base station that communicates with a mobile terminal by composing a communication range by a set of irradiation ranges of one or more directional beams transmitted in a plurality of directions, and is received by an antenna. A transmission / reception unit and a transmission / reception unit that perform reception processing of a received radio signal, transmission processing of a signal transmitted from an antenna with a directional beam, and a generation unit that generates a reference signal transmitted with a directional beam in each direction The channel quality of the directional beam measured based on the reference signal at the mobile terminal is extracted from the signal received and processed by the transmission / reception unit, and the beam control information is transmitted to the mobile terminal at a predetermined transmission timing as a response. And a control unit for generating.

  In the beam transmission / reception method according to the present invention, a radio base station forms a communication range by a set of irradiation ranges of one or more directional beams transmitted in a plurality of directions, and communicates with mobile terminals located in the communication range. A beam transmission / reception method in a communication system, wherein a radio base station transmits a reference signal with a directional beam, and a mobile terminal measures channel quality of a corresponding directional beam based on the reference signal; The mobile terminal, when the measured channel quality is better than the channel quality corresponding to the directional beam being used, reporting the measured channel quality to the radio base station. is there.

  According to the present invention, when beam switching is unnecessary, it is possible to reduce the report of channel quality measurement results to the base station.

It is a block diagram which shows an example of a structure of the radio | wireless communications system which concerns on Embodiment 1 of this invention. It is a block diagram which shows an example of a function structure of the wireless base station which concerns on Embodiment 1 of this invention. It is a block diagram which shows an example of the hardware constitutions of the radio base station which concerns on Embodiment 1 of this invention. It is a block diagram which shows an example of a function structure of the mobile terminal which concerns on Embodiment 1 of this invention. It is a block diagram which shows an example of the hardware constitutions of the mobile terminal which concerns on Embodiment 1 of this invention. It is a sequence diagram which shows an example of the procedure of the channel quality measurement of the wireless base station and mobile terminal which concern on Embodiment 1 of this invention. It is a flowchart which shows an example of the flow of the report necessity judgment process of the channel quality measurement result of the mobile terminal which concerns on Embodiment 1 of this invention. It is a format figure which shows an example of a structure of the beam control information notification which the wireless base station which concerns on Embodiment 1 of this invention transmits. It is a flowchart which shows an example of the flow of a reception process of the beam control information notification of the mobile terminal which concerns on Embodiment 1 of this invention. It is a sequence diagram which shows an example of a procedure in case a radio base station cannot receive the measurement result which a mobile terminal transmits in the channel quality measurement of the radio base station and mobile terminal which concerns on Embodiment 1 of this invention. It is a sequence diagram which shows an example of a procedure in case the mobile terminal cannot receive the beam control information notification transmitted by the radio base station in the channel quality measurement of the radio base station and the mobile terminal according to Embodiment 1 of the present invention. It is a sequence diagram which shows the modification of the procedure of the channel quality measurement of the radio base station and mobile terminal which concern on Embodiment 1 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings referred to below, the same or corresponding parts are denoted by the same reference numerals. The present invention is not limited to the following embodiments.

  FIG. 1 is a block diagram showing a configuration example of a radio communication system 10 using a radio base station 100 and a mobile terminal 200 according to this embodiment. The radio base station 100 irradiates one or more directional beams simultaneously in a plurality of different directions, and a communication range (cell) with the mobile terminal 200 is configured by combining the irradiation ranges of the respective directional beams. In FIG. 1, a broken line and a solid line ellipse indicate an irradiation range of one directional beam. When the directional beam 20 is irradiated on the irradiation range 30 and the directional beam 21 is irradiated on the irradiation range 31, and the mobile terminal 200 moves from the irradiation range 30 to the irradiation range 31, the radio base station 100 and the mobile terminal The beam used for communication 200 is switched from the directional beam 20 to the directional beam 21 by beam switching. Here, it is assumed that the directional beam irradiated to each irradiation range can be identified by an identifier (beam ID) for identifying the directional beam.

  FIG. 2 is a block diagram illustrating an example of a functional configuration of the radio base station 100 according to this embodiment. The radio base station 100 includes a control unit 101, a transmission / reception unit 103, a generation unit 104, and an antenna 105.

  The antenna 105 transmits a radio signal to the terminal 200 and receives a radio signal transmitted from the mobile terminal 200. Note that the antenna 105 includes one or more antenna elements, and can generate one or more directional beams by beam forming. The transmission / reception unit 103 performs transmission processing on a signal transmitted from the antenna 105 using a directional beam, and performs reception processing on a radio signal received by the antenna 105. Here, the transmission process and the reception process are general processes performed at the time of transmission and reception of radio signals such as encoding, decoding, modulation, demodulation, digital analog conversion, and frequency conversion.

  The control unit 101 extracts channel quality information that is a measurement result of the reception quality (channel quality) of the directional beam transmitted by the radio base station 100 from the radio signal received and processed by the transmission / reception unit 103. Then, it is determined whether beam switching is necessary for the target mobile terminal 200 based on the extracted channel quality information. When it is determined that beam switching needs to be performed, it is determined which directional beam is allocated to the terminal, at what timing beam switching is performed, and the like. The control unit 101 outputs a control signal for causing the mobile terminal 200 to perform beam switching to the transmission / reception unit 103 and transmits the control signal to the mobile terminal 200. The generation unit 104 generates a reference signal to be transmitted with each directional beam in accordance with an instruction from the control unit 101. In addition, as for a specific implementation method of beam switching, an existing method such as the method disclosed in International Publication No. WO2017 / 006470A1 may be used except for the matters described below.

  FIG. 3 is a block diagram illustrating an example of a hardware configuration of the radio base station 100. In FIG. 3, the radio base station 100 includes a processor 110, a memory 111, a transmitter 112, a receiver 113, and an antenna 114. The processor 110 is a general-purpose processor, a DSP (Digital Signal Processor) or the like, and the memory 111 is a volatile or non-volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, A storage medium such as a magnetic disk. The transmitter 112 and the receiver 113 are realized by a circuit including an application specific integrated circuit (ASIC) and a field programmable gate array (FPGA). The processor 110, the memory 111, the transmitter 112, the receiver 113, and the antenna 114 are connected by a system bus 115.

  The control unit 101 and the generation unit 104 of the radio base station 100 are realized by the processor 110 executing a program stored in the memory 111. The transmission / reception unit 103 is realized by the transmitter 112 and the receiver 113. The antenna 105 corresponds to the antenna 114. Note that at least part of the functions of the control unit 101 and the generation unit 104 may be realized by an ASIC or the like, or at least part of the function of the transmission / reception unit 103 may be realized by a program.

  FIG. 4 is a block diagram showing an example of a functional configuration of the mobile terminal 200 according to this embodiment. In FIG. 4, the mobile terminal 200 includes a control unit 201, a transmission / reception unit 203, a measurement unit 204, and an antenna 205. The antenna 205 transmits a radio signal to the radio base station 100 and receives a radio signal transmitted by the radio base station 100. The antenna 205 includes one or more antenna elements, and can generate one or more directional beams by beam forming. The transmission / reception unit 203 performs transmission processing on a signal transmitted from the antenna 205, and performs reception processing on a radio signal received by the antenna 105. Transmission processing and reception processing are general processing performed at the time of transmission and reception of radio signals such as encoding, decoding, modulation, demodulation, digital analog conversion, and frequency conversion. The transmission / reception unit 203 outputs the received signal to the control unit 201 and the measurement unit 204.

  The measurement unit 204 detects the reference signal transmitted from the radio base station 100 from the signal received and processed by the transmission / reception unit 203, measures the reception quality of the detected reference signal as the channel quality of the directional beam, and the measurement result (channel quality) Information) to the control unit 201. The quality to be measured may be any quality that can be used as the quality of a radio signal, such as SNR (Signal to Noise Ratio), CINR (Carrier to Interference and Noise Ratio), RSSI (Receive Signal Strength Ratio). The control unit 201 notifies the notified channel quality information to the transmission / reception unit 203 as information to be transmitted to the radio base station 100, and the channel quality information is transmitted to the radio base station 100. Also, the control unit 201 acquires a control signal related to beam switching transmitted from the radio base station 100 from the signal received and processed by the transmission / reception unit 203.

  FIG. 5 is a block diagram illustrating an example of a hardware configuration of the mobile terminal 200. The mobile terminal 200 includes a processor 210, a memory 211, a transmitter 212, a receiver 213, and an antenna 214, which are connected to each other via a system bus 215. These are the same as the processor 110, the memory 111, the transmitter 112, the receiver 113, and the antenna 114 shown in FIG. The control unit 201 and the measurement unit 204 of the mobile terminal 200 are realized by the processor 210 executing a program stored in the memory 211. The transmission / reception unit 203 is realized by the transmitter 212 and the receiver 213. The antenna unit 205 corresponds to the antenna 214.

  Next, the beam switching operation in this embodiment will be described. Since beam switching is related between the radio base station 100 and the mobile terminal 200, description will be made with reference to a sequence diagram between apparatuses shown in FIG.

  In the radio base station 100, the control unit 101 determines the timing for transmitting the reference signal with a directional beam, and the generation unit 104 generates a control signal according to the determination of the control unit 101 (S100). And the transmission / reception part 103 performs the transmission process of the produced | generated control signal, and the antenna 105 transmits a reference signal by a directional beam (S101). Note that the radio base station 100 performs the processes of S100 and S101 in a plurality of different directions in order to cover the cell of the own device. At this time, if the radio base station 100 can simultaneously transmit a plurality of directional beams, the processes of S100 and S101 may be performed for each directional beam. The directional beam that transmits the reference signal includes an identifier (beam ID) that can identify the directional beam according to the transmission direction.

  Note that the radio base station 100 may notify the mobile terminal 200 in advance of the timing for transmitting the reference signal and information on channel quality measurement as broadcast information or as signaling information by RRC (Radio Resource Control) or the like. Here, the information on the channel quality measurement specifically includes a report method of the channel quality measurement result (report by opportunity, periodic report), report cycle, and the like.

  In the mobile terminal 200, the antenna 205 receives the directional beam transmitted from the radio base station 100, and the received signal is received and processed by the transmission / reception unit 203. Then, the measurement unit 204 detects a reference signal included in the received signal, and measures the channel quality of the received directional beam based on the detected reference signal (S102). The measurement unit 204 notifies the control unit 201 of the measurement result together with the beam ID. Note that the measurement unit 204 measures the channel quality for each received directional beam and notifies the control unit 201 of the channel quality. When receiving the notification of the channel quality measurement result from the measurement unit 204, the control unit 201 determines whether or not it is necessary to report the received measurement result to the radio base station 100 (S103).

  FIG. 7 is a flowchart illustrating an example of a detailed flow of the determination process in S103. Upon receiving the measurement result notification from the measurement unit 204, the control unit 201 identifies the beam with the best channel quality from among the beams receiving the measurement result notification (S201). Then, the control unit 201 determines whether or not the identified beam is a beam currently in use (S202). If the identified beam is a beam currently in use, the process is terminated. On the other hand, when the identified beam is not a currently used beam, it is determined to report the channel quality of the identified beam to the radio base station 100 (S203). Note that the process of S103 may be performed periodically instead of being triggered by the notification of the channel quality from the measurement unit 204.

  When it is determined to report the channel quality measured to the radio base station 100 in the process of S103, the control unit 201 notifies the transmission / reception unit 203 of the channel quality measurement result of the directional beam to be reported as channel quality information. Then, the transmission / reception unit 203 transmits the channel quality information, and the channel quality information is wirelessly transmitted from the antenna 205 to the radio base station 100 (S104). The channel quality information notified in S104 may include the corresponding beam ID, or the beam ID is not necessarily included as long as the directional beam corresponding to the channel quality information can be specified. Good. In addition, although an example in which channel quality information is reported for a beam with the best channel quality has been described here, a plurality of higher ranks with good channel quality may be reported.

  For transmission of channel quality information to the radio base station 100, a channel similar to PUCCH (Physical Uplink Control Channel) defined in LTE (Long Term Evolution) or PUSCH (Physical Uplink Shared Channel) is used. Also good. Note that PUSCH is a data channel for transmitting uplink data, which is a direction from a mobile terminal to a radio base station, and PUCCH notifies uplink radio resource allocation requests, downlink channel quality information, and the like. Control channel.

  In the radio base station 100, the antenna 105 receives a radio signal transmitted from the mobile terminal 200, and the received signal is subjected to reception processing by the transmission / reception unit 103 and input to the control unit 101. Then, the control unit 101 acquires channel quality information from the signal input from the transmission / reception unit 103. And the control part 101 determines the directional beam used for communication with the mobile terminal 200 based on the acquired channel quality information (S105). As a method for determining a directional beam in the process of S105, for example, when channel quality information of one beam is received, the beam is determined as a communication beam, and channel quality information of a plurality of beams is received. In such a case, a method of determining the beam with the best quality can be considered. The present invention does not limit the method of determining the directional beam to be used, but may be determined by a method different from the above method.

  Next, the control unit 101 of the radio base station 100 creates a message (beam control information notification) for notifying the terminal 200 of the beam ID of the directional beam to be used determined in the process of S105 and notifies the transmission / reception unit 103 of the message. The beam control information notification corresponds to the control signal related to the beam switching described above. The beam control information notification is transmitted by the transmitting / receiving unit 103 and transmitted from the antenna 105 to the terminal 200 (S106). Depending on the directional beam determination method in the process of S105, there is a possibility that the determined directional beam is a directional beam in use. Even in such a case, the beam control is performed in the process of S106. An information notification is transmitted, and the directional beam used for the mobile terminal 200 is notified. The beam control information notification may be a message transmitted as a response to the received channel quality information. If the directional beam to be used is not changed, the current directional beam is measured and used, and the change is made. You may make it notify that it does not.

  In the processing of S106, the beam control information notification is transmitted at the timing of the subframe after offset k from the timing when the radio base station 100 receives the channel quality information from the mobile terminal 200. Here, k is a predetermined integer of 1 or more. A subframe is a unit obtained by further dividing a radio frame constituting a radio resource in the frequency and time directions in the time direction. In the case of LTE, it corresponds to 1 subframe = 1 millisecond, and in a 5G system, further than LTE. A short time length is assumed. As a result, the mobile terminal 200 can predict the timing for receiving the beam control information notification from the radio base station 200, and performs the beam control information notification analysis processing as receiving the beam control information notification at the predicted timing. Is possible. Note that the radio base station 100 may notify the mobile terminal 200 of the offset k by broadcast information or an RRC message.

  FIG. 8 is a format diagram showing an example of the configuration of the beam control information notification. The beam control information notification is composed of an 8-bit communication beam ID field. In the communication beam ID, the beam ID of the directional beam to be used determined in the process of S105 is set. Note that the message configuration shown in FIG. 8 is an example, the communication beam ID is not limited to 8 bits, and the beam control information notification may include fields other than the communication beam ID.

  For transmission of the beam control information notification to the mobile terminal 200, a channel similar to PDCCH (Physical Downlink Control Channel) or PDSCH (Physical Downlink Shared Channel) defined in LTE may be used. The PDSCH is a data channel that transmits data in the downlink direction, which is a direction from the radio base station to the mobile terminal, and the PDCCH is a control channel that notifies allocation information of uplink radio resources and the like.

  As described above, when the channel quality information transmitted from the mobile terminal 200 can be received, the beam control information notification is transmitted from the radio base station 100, but the channel quality information cannot be received by the radio base station 100. The beam control information notification is not transmitted. In addition, the mobile terminal 200 may fail to receive the beam control information notification. Such a phenomenon is caused by, for example, a decrease in radio quality when the mobile terminal 200 rotates or moves, or when there is an obstacle between the mobile terminal 200 and the radio base station 100. Occur. In such a case, the mobile terminal 200 cannot acquire the beam control information notification. FIG. 9 is a flowchart showing a flow of processing related to reception of beam control information notification performed by the mobile terminal 200.

  The control unit 201 of the mobile terminal 200 waits for a beam control information notification that is expected to be received in a subframe after k subframes from the timing at which the channel quality information notification is transmitted, and performs beam control at the scheduled reception timing. It is determined whether an information notification has been received (S301). When the reception of the beam control information notification is determined in the process of S301, the control unit 201 acquires the communication beam ID from the received beam control information notification (S302). Then, the control unit 201 determines whether or not the communication beam ID is the same as the beam ID of the directional beam currently used (S304). If it is determined in step S304 that they are not the same, the control unit 201 ends the beam control information notification reception processing by beam switching processing for changing the directional beam used for communication. If it is determined that the process is the same in step S304, the control unit 201 ends the beam control information notification reception process.

  On the other hand, when it is determined in S301 that the beam control information notification has not been received, the control unit 201 retransmits the channel quality information (S302), and ends the beam control information notification receiving process. The process performed in S302 is the same as the first transmission process (S104). There is a possibility that the beam control information notification corresponding to the retransmitted channel quality information may not be received. In order to cope with this, it is conceivable that the number of retransmissions is determined in advance and the above-described processing is repeated. It is also possible to notify the mobile terminal 200 of the number of retransmissions from the radio base station 100 by broadcast information or an RRC message.

  FIG. 10 is a sequence diagram showing an operation when the channel quality information transmitted by the mobile terminal 200 is not normally received by the radio base station 100 and the beam control information notification is not transmitted. In FIG. 10, when the channel quality information transmitted in the process of S104 is not normally received by the radio base station 100, the radio base station 100 does not perform the processes of S105 and S106, and the mobile terminal 200 notifies the beam control information. Not receive. At this time, according to the flowchart shown in FIG. 9, the mobile terminal 200 performs the process of S302 in S301 (not receiving the beam control information notification). When the radio base station 100 receives the retransmitted channel quality information transmitted in the process of S302, the processes of S105 and S106 are performed, and when the radio terminal 200 receives the beam control information notification normally, the radio base station 100 performs S301 (beam control information). Notification is received) and the processing after S303 is performed.

  The same processing is performed when the beam control information notification transmitted in the processing of S106 is not normally received by the mobile terminal 200. FIG. 11 is a sequence diagram showing an operation when the beam control information notification is not normally received by the mobile terminal 200. If the beam control information notification transmitted in the first process of S106 is unsuccessful, the processes of S301, S302, S105, S106, and S301 are performed as in the sequence diagram of FIG. Here, it is assumed that the radio base station 100 performs the same processing as the first time in the second reception of the channel quality information.

  Further, after the radio base station 100 receives the channel quality information, the beam control information notification is not transmitted to the mobile terminal 200 with a fixed interval (k subframes), but within a predetermined transmission window range. You may make it transmit by. FIG. 12 is a sequence diagram showing an operation when a transmission window of n (n is an integer of 1 or more) subframes is provided. In FIG. 12, after the radio base station 100 determines the directional beam to be used by the process of S105, counting from the timing at which the channel quality information is received, and any one of k subframes to k + n subframes in S106. Processing is performed, and a beam control information notification is transmitted to the mobile terminal 200. In this case, the mobile terminal 200 waits for reception of a beam control information notification by providing a window of n subframes. The determination that the beam control information notification has not been received is performed after k + n subframes from the timing at which the channel quality information is transmitted.

  As described above, according to the radio base station and the mobile terminal of this embodiment, the reference signal transmitted by the radio base station in which the mobile terminal transmits directional beams in a plurality of different directions using the respective directional beams. If the other directional beam has a better quality than the current directional beam, the measurement result of the directional beam with the higher quality is transmitted to the radio base station, and the mobile terminal transmits Since the radio base station that has received the measurement result transmits a response to the received measurement result, the mobile terminal does not notify the unnecessary measurement result when the quality of the current directional beam is good, Further, the mobile terminal can wait for a response transmitted by the radio base station, and can transmit the measurement result again when the response is not received. Thereby, transmission of unnecessary measurement results in the uplink direction can be reduced. Further, by retransmitting, the possibility that the measurement result is not normally received by the radio base station can be reduced. Further, it is possible to reduce the transmission of the downlink control message by notifying the directional beam used by the mobile terminal using the response from the radio base station.

  10 wireless communication system, 20, 21 directional beam, 30, 31 irradiation range, 100 wireless base station, 101 control unit, 103 transmission / reception unit, 104 generation unit, 105 antenna, 110 processor, 111 memory, 112 transmitter, 113 reception Unit, 114 antenna, 115 system bus, 200 mobile terminal, 201 control unit, 203 transceiver unit, 204 measurement unit, 205 antenna, 210 processor, 211 memory, 212 transmitter, 213 receiver, 214 antenna, 215 system bus.

A mobile terminal according to the present invention is a mobile terminal that communicates with a radio base station that constitutes a communication range by a set of irradiation ranges of one or more directional beams transmitted in a plurality of directions, and is received by an antenna Corresponding based on the reference signal included in the directional beam of each direction received and processed in the transceiver unit, and the transceiver unit that performs the reception process of the radio signal of the directional beam and the transmission process of the signal transmitted from the antenna A measurement unit that measures the channel quality of the directional beam to be measured, and the measured channel quality when the measured channel quality is better than the channel quality of the directional beam in the direction used for communication with the radio base station. those to and a control unit that determines to report the channel quality information including information capable of identifying the quality and the directional beam to the wireless base station A.

A radio base station according to the present invention is a radio base station that communicates with a mobile terminal by composing a communication range by a set of irradiation ranges of one or more directional beams transmitted in a plurality of directions, and is received by an antenna. A transmission / reception unit and a transmission / reception unit that perform reception processing of a received radio signal, transmission processing of a signal transmitted from an antenna with a directional beam, and a generation unit that generates a reference signal transmitted with a directional beam in each direction , When the mobile terminal is measured based on a reference signal and the measured result is better than the measured result with the directional beam in the direction used for communication with the mobile terminal. the channel quality information including the results measured by sexual beam extracted from the received signal processed by the transceiver unit, directional Bee to be used to communicate with the mobile terminal based on the channel quality information It determines, in which as and a control unit for generating a beam control information notification transmitted to the mobile terminal at a predetermined transmission timing as a response, the.

In the beam transmission / reception method according to the present invention, a radio base station forms a communication range by a set of irradiation ranges of one or more directional beams transmitted in a plurality of directions, and communicates with mobile terminals located in the communication range. A beam transmission / reception method in a communication system, wherein a radio base station transmits a reference signal with a directional beam, and a mobile terminal measures channel quality of a corresponding directional beam based on the reference signal; When the mobile terminal has a measured channel quality better than the channel quality corresponding to the directional beam in use, the mobile terminal wirelessly transmits the channel quality information including the measured channel quality and information capable of identifying the directional beam. And reporting to the base station.

The measurement unit 204 detects the reference signal transmitted from the radio base station 100 from the signal received and processed by the transmission / reception unit 203, measures the reception quality of the detected reference signal as the channel quality of the directional beam, and the measurement result (channel quality) Information) to the control unit 201. The quality to be measured may be any quality that can be used as the quality of the radio signal, such as SNR (Signal to Noise Ratio), CINR (Carrier to Interference and Noise Ratio), RSSI (Receive Signal Strength Indicator ). The control unit 201 notifies the notified channel quality information to the transmission / reception unit 203 as information to be transmitted to the radio base station 100, and the channel quality information is transmitted to the radio base station 100. Also, the control unit 201 acquires a control signal related to beam switching transmitted from the radio base station 100 from the signal received and processed by the transmission / reception unit 203.

In the radio base station 100, the control unit 101 determines the timing for transmitting a reference signal with a directional beam, and the generation unit 104 generates the reference signal according to the determination of the control unit 101 (S100). Then, the transmission / reception unit 103 performs transmission processing of the generated reference signal , and the antenna 105 transmits the reference signal using a directional beam (S101). Note that the radio base station 100 performs the processes of S100 and S101 in a plurality of different directions in order to cover the cell of the own device. At this time, if the radio base station 100 can simultaneously transmit a plurality of directional beams, the processes of S100 and S101 may be performed for each directional beam. The directional beam that transmits the reference signal includes an identifier (beam ID) that can identify the directional beam according to the transmission direction.

Claims (10)

A mobile terminal that communicates with a radio base station that constitutes a communication range by a set of irradiation ranges of one or more directional beams transmitted in a plurality of directions,
A transmission / reception unit that performs reception processing of a radio signal of the directional beam received by an antenna and transmission processing of a signal transmitted from the antenna;
A measurement unit that measures the channel quality of the corresponding directional beam based on a reference signal included in the directional beam in each direction received and processed in the transmission / reception unit;
Reporting the measured channel quality to the radio base station when the measured channel quality is better than the channel quality of the directional beam in the direction used for communication with the radio base station A control unit for determining
A mobile terminal comprising:   The control unit receives a control signal from the radio base station transmitted at a predetermined transmission timing as a response to the report of the channel quality, and when the control signal is not received, The mobile terminal according to claim 1, wherein the report is performed again.   The mobile terminal according to claim 2, wherein the transmission timing includes a window having a predetermined time length.   The mobile terminal according to claim 1, wherein the control unit determines whether or not to report the channel quality every predetermined period.   The mobile terminal according to claim 1, wherein the control unit reports a plurality of the channel qualities respectively corresponding to the directional beams in a plurality of directions to the radio base station. A radio base station that configures a communication range by a set of irradiation ranges of one or more directional beams transmitted in a plurality of directions and communicates with a mobile terminal,
A transmission / reception unit that performs reception processing of a radio signal received by an antenna and transmission processing of a signal transmitted from the antenna by the directional beam;
A generator for generating a reference signal transmitted by the directional beam in each direction;
The channel quality of the directional beam measured based on the reference signal in the mobile terminal is extracted from the signal received and processed by the transmission / reception unit, and is transmitted to the mobile terminal as a response at a predetermined transmission timing A controller that generates a beam control information notification;
A radio base station comprising:   When determining that the directional beam used for communication with the mobile terminal is changed based on the received channel quality, the control unit includes an identifier indicating the changed directional beam in the beam control information notification. The radio base station according to claim 6, wherein the radio base station is included.   The radio base station according to claim 6, wherein the transmission timing has a window having a predetermined time length. A beam transmission / reception method in a communication system in which a radio base station forms a communication range by a set of irradiation ranges of one or more directional beams transmitted in a plurality of directions and communicates with a mobile terminal located in the communication range. And
The radio base station transmitting a reference signal with the directional beam;
The mobile terminal measuring the channel quality of the corresponding directional beam based on the reference signal;
The mobile terminal reporting the measured channel quality to the radio base station if the measured channel quality is better than the channel quality corresponding to the directional beam in use;
A beam transmission / reception method comprising: The radio base station transmits a beam control information notification at a predetermined transmission timing as a response to the received channel quality;
If the wireless terminal does not receive the beam control information notification transmitted from the wireless base station at the predetermined timing, the step of transmitting the measured channel quality again;
The beam transmitting / receiving method according to claim 9, further comprising:

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