JP2019033429A - Radio base station device, and radio communication method - Google Patents

Abstract

To provide a radio base station device, and a radio communication method capable of reducing power consumption without changing transmission quantity, even in a situation where the transmission quantity is a certain level or more.SOLUTION: A radio base station device performing radiocommunication with a terminal includes a feedback extraction part receiving feedback information transmitted from the terminal, for a beam search signal that is a signal for determining a beam to be transmitted from the radio base station device to the terminal, an interference amount calculation part calculating the interference amount for the terminal, on the basis of the feedback information, a second electric field strength calculation part for calculating second electric field strength indicating reception electric field strength in the terminal when the number of antennas of the radio base station device is reduced, based on the feedback information, and an antenna state judgement part for changing over the antenna state of the radio base station device from first antenna state to second antenna state, on the basis of the interference amount and the second reception electric field strength.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a radio base station apparatus and a radio communication method.

  In recent years, the number of users who use terminal devices such as smartphones and tablet terminals is increasing. Therefore, attention is paid to a wireless communication system in a higher frequency band (for example, 6 GHz) than a frequency band (for example, 800 MHz to 5 GHz) that has been used so far. As such a wireless communication system, for example, there is a millimeter wave band wireless LAN system based on IEEE (The Institute of Electrical Electronics Engineers, Inc) 802.11ad. Further, in the fifth generation mobile communication system, which has been studied by 3GPP (Third Generation Partnership Project), such a high frequency band is also being studied.

  For example, in the millimeter wave band of 30 GHz or higher, the spatial attenuation of radio waves is large. Therefore, in order to obtain a practical communication distance (for example, 10 m or more), an array antenna may be used in the wireless communication device. An array antenna is, for example, an antenna that obtains a desired radiation directivity (or radiation pattern) by regularly arranging a plurality of antenna elements and feeding them with a constant excitation condition. The array antenna is characterized in that the amplitude and phase of the antenna element can be electrically controlled, and the directivity of the antenna can be easily controlled.

  Examples of the array antenna include a digital synthesis type array antenna and an analog synthesis type array antenna. The digital synthesis type array antenna includes, for example, the same number of radio circuits and AD / DA (Analogue to Digital / Digital to Analogue) conversion circuits as antenna elements. On the other hand, an analog synthesis type array antenna includes, for example, one system of radio circuit and AD / DA conversion circuit for a plurality of antenna elements.

  Compared to an analog synthesis array antenna, a digital synthesis array antenna can easily direct a beam to multiple users at the same time. However, the number of radio circuits and AD / DA conversion circuits is increased, resulting in lower power consumption. Increase. Therefore, in order to increase the number of antenna elements, it is considered that an analog synthesis type array antenna is more suitable than a digital synthesis type array antenna.

  Examples of such technologies related to wireless communication include the following. That is, a wireless transmission device that stops power supply to unused wireless units according to the transmission amount, the number of connected terminals, the set number of MIMO (Multi-Input Multi-Output) signals per hour, the traffic amount per time, etc. There is.

  According to this technique, in the MIMO wireless transmission device, it is possible to reduce power consumption and to simplify the device configuration.

JP 2010-50625 A

  The number of users who use terminal devices is increasing year by year. For this reason, in wireless base station devices, cases of performing wireless communication simultaneously with a plurality of terminal devices are increasing. In the above-described technology for stopping the power supply to the radio units that are not used based on the transmission amount or the like, when the transmission amount continues to be above a certain level, all the radio units may be used. Therefore, in the above-described technique, in such a case, power supply to the wireless unit cannot be stopped, and power consumption of the wireless transmission device cannot be reduced.

  Therefore, one aspect is to provide a radio base station apparatus and a radio communication method capable of reducing power consumption without changing the transmission amount even in a situation where the transmission amount is a certain level or more.

  In one aspect, in a radio base station apparatus that performs radio communication with a terminal apparatus, for the beam search signal that is a signal for determining a beam transmitted from the radio base station apparatus to the terminal apparatus, the terminal A feedback extraction unit that receives feedback information transmitted from a device, an interference amount calculation unit that calculates an interference amount for the terminal device based on the feedback information, and a radio base station device based on the feedback information. Based on a second received electric field strength calculating unit that calculates a second received electric field strength that represents the received electric field strength in the terminal device when the number of antennas is reduced, and based on the interference amount and the second received electric field strength. The antenna state of the radio base station apparatus is changed from the first antenna state to a second power consumption lower than that of the first antenna state. And an antenna state determination unit to switch to antenna state.

  In one aspect, power consumption can be reduced without changing the transmission amount even in a situation where the transmission amount is a certain level or more.

FIG. 1 is a diagram illustrating a configuration example of a wireless communication system. FIG. 2 is a diagram illustrating an example of the position of the terminal viewed from the base station. FIG. 3 is a diagram illustrating a configuration example of a base station. FIG. 4 is a diagram illustrating an example of the antenna state 1. FIG. 5 is a diagram illustrating an example of the antenna state 2. FIG. 6 is a diagram illustrating an example of the antenna state 3. FIG. 7 is a diagram illustrating an example of the antenna state 4. FIG. 8 is a diagram illustrating an example of the antenna state 5. FIG. 9 is a flowchart showing an operation example in the base station. FIG. 10 is a flowchart showing an example of the antenna state setting process. FIG. 11 is a flowchart illustrating an example of the antenna state setting process. FIG. 12 is a diagram illustrating an example of information obtained from feedback information. FIG. 13 is a diagram illustrating a calculation example of the second received electric field strength. FIG. 14 is a diagram illustrating a calculation example of SIR. FIG. 15 is a diagram illustrating a calculation example of the grating angle. FIG. 16 is a diagram illustrating an example of information used for antenna state determination. FIG. 17 is a diagram illustrating a transmission example of the base station. FIG. 18 is a diagram illustrating a configuration example of a base station. FIG. 19 is a diagram illustrating an example of the antenna state 2. FIG. 20 is a diagram illustrating an example of the antenna state 3. FIG. 21 is a diagram illustrating an example of the antenna state 4. FIG. 22 is a diagram illustrating an example of the antenna state 5. FIG. 23 is a flowchart showing an operation example of the base station. FIG. 24 is a flowchart illustrating an example of antenna state setting processing. FIG. 25 is a flowchart illustrating an example of antenna state setting processing. FIG. 26 is a diagram illustrating a configuration example of a wireless communication system.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings. Problems and examples in the present specification are merely examples, and do not limit the scope of rights of the present application. Each embodiment can be combined as appropriate within a range that does not contradict processing contents. In addition, the terms and technical contents described in the specification as communication standards such as 3GPP may be appropriately used as the terms and technical contents described in this specification.

[First Embodiment]
<Configuration example of wireless communication system>
FIG. 1 is a diagram illustrating a configuration example of a wireless communication system 10 according to the first embodiment.

  The radio communication system 10 includes a radio base station apparatus (hereinafter also referred to as “base station”) 100 and terminal apparatuses (hereinafter also referred to as “terminals”) 200-1 and 200-2. Is provided.

  The base station 100 is, for example, a wireless communication device that performs wireless communication with the terminals 200-1 and 200-2 located within the communicable range of the own station. The base station 100 performs scheduling, assigns radio resources and the like to the terminals 200-1 and 200-2, and transmits a control signal including a scheduling result to the terminals 200-1 and 200-2. Base station 100 and terminals 200-1 and 200-2 perform radio communication using radio resources according to the scheduling result.

  In the first embodiment, base station 100 includes an array antenna, and transmits and receives radio signals to terminals 200-1 and 200-2 using beamforming. In the first embodiment, it is assumed that the base station 100 performs wireless communication by a spatial multiplexing method using a maximum of two beams, for example. Therefore, the base station 100 can perform wireless communication simultaneously with a maximum of two users (or two terminals 200-1 and 200-2).

  The terminals 200-1 and 200-2 are wireless communication devices such as feature phones, smartphones, tablet terminals, personal computers, and game devices, for example. The terminals 200-1 and 200-2 can receive various services such as a call service and a web browsing service from the base station 100.

  In FIG. 1, the terminals 200-1 and 200-2 represent two examples, but the number of terminals may be one, or three or more.

  Moreover, in the following, it may be used without distinguishing a terminal and a user. For example, the terminal 200-1 may be referred to as a user A who uses the terminal 200-1. For example, the terminal 200-2 may be referred to as a user B who uses the terminal 200-2. Further, user A may be referred to as terminal A and user B as terminal B.

  Terminals 200-1 and 200-2 are sometimes referred to collectively as terminal 200 because they have the same configuration.

  FIG. 2 is a diagram illustrating an example of the positions of the terminals 200-1 to 200-8 as viewed from the base station 100. FIG. 2 illustrates an example in which the base station 100 has a 90-degree cover area, and eight terminals 200-1 to 200-8 are located in this cover area. Since the base station 100 can perform wireless communication by a spatial multiplexing method using a maximum of two beams, for example, at a certain timing, the base station 100 performs wireless communication simultaneously with the terminals 200-1 and 200-2, and at the next timing, the terminal 200-3. , 200-4 simultaneously with wireless communication. In this manner, the base station 100 can wirelessly communicate with the eight terminals 200-1 to 200-8.

<Configuration example of radio base station device>
FIG. 3 is a diagram illustrating a configuration example of the base station 100. Base station 100 includes antenna elements (or antennas; hereinafter referred to as “antennas”) 101-1 to 101-6, amplifiers 102-1 to 102-6, and combiners 103-1 to 103-6. Phase shifters 104-1 to 104-12 are provided. The base station 100 includes distributors 105-1 and 105-2, T / R (Transmission and Reception) switches 106-1 and 106-2, transmission radio units 107-1 and 107-2, and reception radio unit 108-. 1, 108-2, DAC (Digital to Analogue Converter) 109-1 and 109-2, and ADC (Analogue to Digital Converter) 110-1 and 110-2. Furthermore, the base station 100 includes a digital signal processing unit 111 and a memory unit 120.

  The digital signal processing unit 111 includes a beam search processing unit 112, a signal transmission unit 113, a signal reception unit 114, a feedback extraction unit 115, a SIR (Signal to Interference Ratio) calculation unit 116, a second received electric field strength calculation unit 117, and an antenna. A state determination unit 118 and an antenna control unit 119 are provided.

  In FIG. 3, distributor 105-1, T / R switch 106-1, transmission radio unit 107-1, reception radio unit 108-1, DAC 109-1, ADC 110-1, and digital signal processing unit 111 are: For example, a wireless unit that performs processing related to wireless communication for the user A may be used. The distributor 105-2, the T / R switch 106-2, the transmission radio unit 107-2, the reception radio unit 108-2, the DAC 109-2, the ADC 110-2, and the digital signal processing unit 111 are, for example, user B May be a wireless unit that performs processing related to wireless communication. As described above, the base station 100 has two systems, and by these two systems, it is possible to simultaneously form two beams at the maximum for the user A and the user B.

  The beam is, for example, a single radio signal or a bundle of a plurality of radio signals. In the following, a beam and a radio signal may be used without being distinguished.

  Each antenna 101-1 to 101-6 transmits the radio signal output from each amplifier 102-1 to 102-6 to terminal 200. In addition, each antenna 101-1 to 101-6 receives a radio signal transmitted from terminal 200, and outputs the received radio signal to each of amplifiers 102-1 to 102-6.

  Each amplifier 102-1 to 102-6 amplifies the radio signal output from each combiner 103-1 to 103-6, and outputs the amplified radio signal to each antenna 101-1 to 101-6. . In addition, each of the amplifiers 102-1 to 102-6 amplifies the radio signal output from each of the antennas 101-1 to 101-6, and transmits the amplified radio signal to each of the combiners 103-1 to 103-6. Output each.

  Each amplifier 102-1 to 102-6 is controlled to be turned on or off by the antenna control unit 119. For example, each of the amplifiers 102-1 to 102-6 turns on when receiving a power-on signal from the antenna control unit 119, and turns off when receiving a power-off signal.

  The combiner 103-1 combines the wireless signals output from the phase shifters 104-1 and 104-2, and outputs the combined wireless signal to the amplifier 102-1. Similarly, the other synthesizers 103-2 to 103-6 synthesize the radio signals output from the subordinate phase shifters 104-3 to 104-12, and combine the synthesized radio signals with the amplifiers 102-2 to 102-6. Output to.

  The combiner 103-1 outputs the radio signal output from the amplifier 102-1 to the phase shifters 104-1 and 104-2. In this case, for example, the combiner 103-1 outputs a radio signal for the user A to the phase shifter 104-1 and outputs a radio signal for the user B to the phase shifter 104-2. Similarly, the other synthesizers 103-2 to 103-6 output radio signals for the user A to the phase shifters 104-3, 104-5, 104-7, 104-9, and 104-11, respectively. Radio signals are output to phase shifters 104-4, 104-6, 104-8, 104-10, and 104-12, respectively.

  Each of the phase shifters 104-1, 104-3, 104-5, 104-7, 104-9, 104-11 adjusts (or shifts) the phase of the radio signal output from the distributor 105-1. And outputs the radio signals after phase adjustment (or phase shift) to the combiners 103-1 to 103-6. Each phase shifter 104-2, 104-4, 104-6, 104-8, 104-10, 104-12 also adjusts the phase of the radio signal output from the distributor 105-2. The radio signal after the phase adjustment is output to each of the combiners 103-1 to 103-6. The phase adjustment is controlled by the digital signal processing unit 111, for example. Thereby, the direction of the transmission beam formed by the radio signal transmitted from each of the antennas 101-1 to 101-6 is controlled.

  Further, each of the phase shifters 104-1, 104-3, 104-5, 104-7, 104-9, and 104-11 outputs radio signals output from the combiners 103-1 to 103-6, respectively. The phase is adjusted, and the radio signal after the phase adjustment is output to distributor 105-1. In addition, the phase shifters 104-2, 104-4, 104-6, 104-8, 104-10, and 104-12 also respond to radio signals output from the combiners 103-1 to 103-6, respectively. The phase is adjusted, and the phase-adjusted radio signal is output to distributor 105-2. These phase adjustments are also controlled by, for example, the digital signal processing unit 111, and the direction of the reception beam formed by each of the antennas 101-1 to 101-6 is controlled.

  The distributor 105-1 distributes the radio signal output from the T / R switch 106-1 to each of the phase shifters 104-1, 104-3, 104-5, 104-7, 104-9, and 104-11. To do. The distributor 105-2 also distributes the radio signal output from the T / R switch 106-2 to the phase shifters 104-2, 104-4, 104-6, 104-8, 104-10, and 104-12. To do.

  The distributor 105-1 combines the radio signals output from the phase shifters 104-1, 104-3, 104-5, 104-7, 104-9, and 104-11, respectively, Output to the T / R switch 106-1. The distributor 105-2 also synthesizes the radio signals output from the phase shifters 104-2, 104-4, 104-6, 104-8, 104-10, and 104-12, respectively. Output to the R switch 106-2.

  Each of the T / R switches 106-1 and 106-2 is a switch for switching between transmission and reception. In the case of transmission, the T / R switches 106-1 and 106-2 output the radio signals output from the transmission radio units 107-1 and 107-2 to the distributors 105-1 and 105-2, respectively. To do. Further, in the case of reception, the T / R switches 106-1 and 106-2 receive the radio signals output from the distributors 105-1 and 105-2 to the reception radio units 108-1 and 108-2, respectively. Output each. Each of the T / R switches 106-1 and 106-2 may be switched between transmission and reception under the control of the digital signal processing unit 111, for example.

  Each of the transmission radio units 107-1 and 107-2 performs frequency conversion processing on the baseband signal of the baseband band output from each of the DACs 109-1 and 109-2, so that the radio signal of the radio band is obtained. Convert to Each transmission radio section 107-1 and 107-2 outputs the converted radio signal to each T / R switch 106-1 and 106-2, respectively.

  Receiving radio units 108-1 and 108-2 perform frequency conversion processing and the like on the radio signals output from T / R switches 106-1 and 106-2, respectively, to generate basebands of basebands. Convert to signal. Receiving radio units 108-1 and 108-2 output the converted baseband signals to ADCs 110-1 and 110-2, respectively.

  Each of the DACs 109-1 and 109-2 converts the digital baseband signal output from the signal transmission unit 113 into an analog baseband signal. Each DAC 109-1, 109-2 outputs the converted baseband signal to each transmission radio section 107-1, 107-2.

  Each of the ADCs 110-1 and 110-2 converts an analog baseband signal output from each of the reception radio units 108-1 and 108-2 into a digital baseband signal. Each ADC 110-1 and 110-2 outputs the converted baseband signal to the signal receiving unit 114.

  Note that the transmission control unit 107-2, the reception wireless unit 108-2, the DAC 109-2, and the ADC 110-2 on the user B side are turned on or off by the antenna control unit 119.

  For example, the beam search processing unit 112 performs a beam search for the terminal 200. Specifically, the beam search processing unit 112 generates a beam search signal and outputs the beam search signal to the signal transmission unit 113 during the beam search period. The beam search signal is, for example, a signal that the base station 100 transmits to the terminal 200, and is a signal for determining a beam to be transmitted to the terminal 200. Hereinafter, the beam search signal may be referred to as a beam search packet, for example.

  Further, the beam search processing unit 112 receives transmission data from another processing unit or the like of the base station 100 and generates a data packet including the transmission data. Beam search processing section 112 outputs the data packet to signal transmission section 113 during the transmission time slot period.

  The signal transmission unit 113 performs error correction coding processing, modulation processing, and the like on packet data such as a beam search packet and a data packet output from the beam search processing unit 112, and converts the packet data into a baseband signal. When the packet data is packet data to be transmitted to user A, the signal transmission unit 113 outputs the converted baseband signal to the DAC 109-1. Further, when the packet data is packet data to be transmitted to the user B, the signal transmission unit 113 outputs the converted baseband signal to the DAC 109-2.

  The signal receiving unit 114 performs demodulation processing, error correction decoding processing, and the like on the baseband signals output from the ADCs 110-1 and 110-2, and converts them into packet data. The signal reception unit 114 outputs the converted packet data to the feedback extraction unit 115.

  The feedback extraction unit 115 extracts feedback information from the packet data output from the signal reception unit 114. The feedback information is, for example, information transmitted from the terminal 200 in response to the beam search packet transmitted from the base station 100. The feedback information includes, for example, received field strength measured by the terminal 200 when the terminal 200 receives the beam search packet, identification information of the terminal 200, and the like. For example, the feedback extraction unit 115 extracts the received electric field strength from the feedback information, and outputs the extracted received electric field strength to the second received electric field strength calculation unit 117.

  In the first embodiment, for example, the received electric field strength measured by the terminal 200 is the first received electric field strength, and the received electric field strength calculated by the second received electric field strength calculating unit 117 is the second received electric field strength. Sometimes referred to as received electric field strength.

  Further, when receiving the feedback information, the feedback extraction unit 115 acquires the direction (or angle) in which the terminal 200 that transmitted the feedback information is located to the base station 100 based on the feedback information. This direction may be referred to as a terminal angle or a terminal direction, for example. There are various methods for acquiring the terminal angle. For example, the feedback extraction unit 115 may acquire the terminal angle by the following method. In other words, the feedback extraction unit 115 includes the phase shifters 104-1, 104-3, 104-5, 104-7, 104-9, 104-11 (or the phase shifters 104-2, 104-4, 104-6, 104). −8, 104-10, 104-12), the angle when the reception beam is formed by performing the phase control is acquired from the phase control unit (not shown) of the digital signal processing unit 111. The feedback extraction unit 115 extracts the terminal angle of the terminal 200 by binding the identification information of the terminal 200 included in the feedback information with the angle at that time as the terminal angle. The feedback extraction unit 115 outputs the terminal angle to the SIR calculation unit 116. For example, the feedback extraction unit 115 extracts the terminal angle and the first received electric field strength based on the feedback information.

  FIG. 12 is a diagram illustrating an example of the terminal angle and the first received electric field strength extracted by the feedback extraction unit 115, for example. As shown in FIG. 12, the terminal angle and the first received electric field strength are extracted for each terminal 200. Details of FIG. 12 will be described in an operation example.

  Returning to FIG. 3, the feedback extraction unit 115 extracts received data from the packet data output from the signal receiving unit 114, and extracts the extracted received data, for example, other processing units of the base station 100. Output to.

  The SIR calculation unit 116 is an interference amount calculation unit that calculates the amount of interference with the terminal 200 based on feedback information, for example. Specifically, the SIR calculation unit 116 calculates SIR as the interference amount based on the terminal angle received from the feedback extraction unit 115. For example, the SIR calculating unit 116 calculates the difference between the received power of the user A in the terminal angle θa direction and the received power of the user B in the terminal angle θa direction as the SIR. The SIR calculation unit 116 calculates the gain difference on the assumption that the terminal angle θa direction of the user A is a desired direction and the terminal angle θa direction with respect to the user B is an interference component. The calculation method will be described in an operation example. The SIR is an example of the interference amount, and may be SINR (Signal to Interference plus Noise Ratio).

  For example, the second received electric field strength calculation unit 117 calculates the second received electric field strength based on the feedback information. Specifically, the second received electric field strength calculation unit 117 calculates the second received electric field strength based on the first received electric field strength received from the feedback extraction unit 115. The second received electric field strength represents, for example, the received electric field strength at the terminal 200 when the number of antennas of the base station 100 is reduced. A method for calculating the second received electric field strength will be described in an operation example.

  The antenna state determination unit 118 changes the antenna state of the antennas 101-1 to 101-6 from the first antenna state to the power consumption more than the first antenna state based on the interference amount and the second received electric field strength. Switch to the lower second antenna state. Specifically, the antenna state determination unit 118 determines that the antenna state is any one of the antenna state 1 to the antenna state 3 based on the interference amount and the second received electric field strength. The antenna state will be described later. Details of the determination method will be described in an operation example. The antenna state determination unit 118 outputs the determination result to the antenna control unit 119.

  According to the determination result, the antenna control unit 119 includes the phase shifters 104-1 to 104-12 and the amplifiers 102-1 to 102-6, the transmission radio unit 107-2, the reception radio unit 108-2, the DAC 109-2, and the ADC 110. -2, control power on and off. Thereby, the antenna control unit 119 controls the antenna states of the antennas 101-1 to 101-6. In this case, the antenna control unit 119 refers to, for example, a table stored in the memory unit 120 and turns off or on the power of which phase shifters 104-1 to 104-12 according to the determination result, and which amplifier 102 Controls whether the power of -1 to 102-6 is turned off or turned on. Also, the antenna control unit 119 refers to the table, for example, turns on or off the power of the transmission radio unit 107-2, the reception radio unit 108-2, the DAC 109-2, and the ADC 110-2 according to the determination result. Control what to do. Specifically, the antenna control unit 119 controls on or off by, for example, outputting a power on signal indicating power on or a power off signal indicating power off to each amplifier 102-1. To do.

  The memory unit 120 stores the above-described table. In the table, for example, information indicating which amplifier 102-1 or the like of the amplifier 102-1 or the like is to be turned on or off corresponding to the antenna state is stored.

  In FIG. 3, each function of the digital signal processing unit 111 may be executed by a DSP (Digital Signal Processor), for example.

  For example, the DSP can realize the functions of the beam search processing unit 112, the signal transmission unit 113, the signal reception unit 114, and the feedback extraction unit 115 by executing a program. Also, the DSP can realize the functions of the SIR calculation unit 116, the second received electric field strength calculation unit 117, the antenna state determination unit 118, and the antenna control unit 119 by executing a program, for example. The DSP includes, for example, a beam search processing unit 112, a signal transmission unit 113, a signal reception unit 114, a feedback extraction unit 115, an SIR calculation unit 116, a second received electric field strength calculation unit 117, an antenna state determination unit 118, and antenna control. Corresponds to portion 119.

  Instead of the DSP, a processor or controller such as a CPU (Central Processing Unit), an MPU (Micro Processing Unit), or an FPGA (Field Programmable Gate Array) may be used.

<Antenna state>
Base station 100 can set antenna states from antenna state 1 to antenna state 5. Hereinafter, each antenna state from antenna state 1 to antenna state 5 will be described.

<1.1 Antenna state 1>
FIG. 4 is a diagram illustrating an example of the antenna state 1.

  The antenna state 1 is an antenna state called a full array, for example. In antenna state 1, all amplifiers 102-1 to 102-6 and phase shifters 104-1 to 104-12 are powered on. In the antenna state 1, the powers of the transmission radio units 107-1 and 107-2, the reception radio units 108-1 and 108-2, the DACs 109-1 and 109-2, and the ADCs 110-1 and 110-2 are also turned on. It has become.

  In the antenna state 1, the radio signal for the user A is phase-shifted by the phase shifters 104-1, 104-3, 104-5, 104-7, 104-9, and 104-11, and is combined and transmitted. In the antenna state 1, the radio signal for the user B is synthesized by the phase shifters 104-2, 104-4, 104-6, 104-8, 104-10, and 104-12 and transmitted. In the antenna state 1, the base station 100 can multiplex and transmit radio signals to the two terminals 200-1 and 200-2 in an arbitrary direction when viewed from the own station.

<1.2 Antenna state 2>
FIG. 5 is a diagram illustrating an example of the antenna state 2.

  The antenna state 2 is an antenna state called an interleaved array type, for example. In antenna state 2, radio signals output from transmission radio units 107-1 and 107-2 are fed to alternate antennas 101-1 to 101-6.

  That is, as shown in FIG. 5, the phase shifters 104-1, 104-4, 104-5, 104-8, 104-9, and 104-12 are turned on, and the other phase shifters are turned off. It has become. In the example of the antenna state 2 shown in FIG. 5, the amplifiers 102-1 to 102-6, the transmission radio units 107-1 and 107-2, the reception radio units 108-1 and 108-2, and the DACs 109-1 and 109- 2. The power supplies of the ADCs 110-1 and 110-2 are turned on.

  The antennas 101-1, 101-3, and 101-5 are used for the radio signals for the user A, and the antennas 101-2, 101-4, and 101-6 are used for the radio signals for the user B. Thereby, for example, overlapping portions are generated in each beam formed when transmitting radio signals to the user A and the user B. In the antenna state 2, a fine beam equivalent to the antenna state 1 is formed in the base station 100. It becomes possible to do. In the antenna state 2, for example, as shown in FIG. 5, the antenna 101-2 used for the wireless communication with the user B is located between the antennas 101-1 and 101-3 used for the wireless communication with the user A. It is an antenna state.

  In the antenna state 2, the phase shifters other than the phase shifters 104-1, 104-4, 104-5, 104-8, 104-9, and 104-12 are turned off as compared with the antenna state 1. Therefore, the power consumption in the base station 100 can be reduced.

  However, in the antenna state 2, a grating lobe is generated in the visible region because the antenna interval is wider than in the antenna state 1. The grating lobe is, for example, a pseudo component (or reflection component) that diffuses around the main lobe (or main beam). In general, the wider the interval between the antenna elements, the narrower the interval between the main lobe and the grating lobe. If the distance between the antenna elements is appropriate, no grating lobe is generated in the visible region. As compared with the antenna state 1, the antenna element interval is widened by the antenna state 2, so that the grating lobe may enter the visible region. For example, when the main lobe for the user A is formed by using the antennas 101-1, 101-3, and 101-5, a grating lobe is generated in a certain direction. If the user B's main glove is present in the direction in which the grating lobe is generated (or the grating direction), the grating lobe interferes with the user B.

  In the first embodiment, the base station 100 suppresses the grating lobe by a known method to enable multiplex transmission to the two terminals 200-1 and 200-2. As an example of the known method, for example, the method described in JP-A-2006-201769 may be used. In this method, in a mapping space obtained by sinusoidally mapping the arrival direction of a received signal, users separated from the reference user by a multiple of an interval equally divided by the number of signals that can be transmitted and received simultaneously are grouped into the same group as the reference user. Then, a weighting factor for forming a directional beam in the direction of the user is determined for each group. Thus, by simultaneously directing the beam to the users in the group, the beam power intensity becomes substantially equal, and interference due to the grating lobe is prevented. For example, the digital signal processing unit 111 performs grouping on the phase shifters 104-1, 104-4, 104-5, 104-8, 104-9, and 104-12, so that the above-described known method is performed. Can be realized.

  In the antenna state 2, for example, the direction of the main lobe for the user A and the direction of the main lobe for the user B are fixed. Therefore, in the antenna state 2, for example, the grating lobe direction with respect to the user A is also fixed. Thus, antenna state 2 is available when user A is located in the direction of the fixed main lobe and user B is located in the direction of the fixed main lobe in another direction. When the grating lobe direction with respect to the main lobe for user A exists in the direction of user B, base station 100 can prevent interference due to the grating lobe by the method described above.

<Antenna state 3>
FIG. 6 is a diagram illustrating an example of the antenna state 3.

  The antenna state 3 is an antenna state called a localized type, for example. The antenna state 3 is an antenna state in which the antennas 101-1 to 101-6 are subdivided on both sides, and the DACs 109-1 and 109-2 and the transmission radio units 107-1 and 107-2 are connected to the subarray. In antenna state 3, antennas 101-1 to 101-3 used for wireless communication with user A and antennas 101-4 to 101-6 used for wireless communication with user B are as in antenna state 2. It is the state of the antennas that are positioned separately without being crossed. That is, in antenna state 3, like antenna state 2, antenna 101-2 used for wireless communication with user B is located between antennas 101-1 and 101-3 used for wireless communication with user A. Rather, the antennas 101-1 to 101-3 and 101-4 to 101-6 used for wireless communication between the user A and the user B are in an antenna state where they are located separately. As a result, the base station 100 can separately form the beam directed toward the user A and the beam directed toward the user B without overlapping at the same time.

  That is, in the example of the antenna state 3 shown in FIG. 6, the phase shifters 104-1, 104-3, 104-5, and 104-8, 104-10, 104-12 are turned on, and the other phase shifters are turned off. It has become. In the example of antenna state 3 shown in FIG. 6, amplifiers 102-1 to 102-6, transmission radio units 107-1 and 107-2, reception radio units 108-1 and 108-2, DACs 109-1 and 109- 2. The power supplies of the ADCs 110-1 and 110-2 are turned on.

  Therefore, the antennas 101-1, 101-2, and 101-3 are used for the user A, and the antennas 101-4, 101-5, and 101-6 can be used for the user B. . As a result, it becomes possible to form a main lobe in any direction for user A and user B, and multiplex communication with terminals 200-1 and 200-2 becomes possible.

  Also, in the antenna state 3, the phase shifters other than the phase shifters 104-1, 104-3, 104-5, and 104-8, 104-10, 104-12 are turned off as compared with the antenna state 1. Therefore, power consumption in the base station 100 can be reduced.

  However, the antenna state 3 has a narrower antenna opening than the antenna state 1 and the antenna state 2. Therefore, in the antenna state 3, compared with the antenna state 1 and the antenna state 2, the beam width of the antenna is increased, the length of the main lobe formed is shortened, and the array efficiency is lowered.

  FIG. 6 illustrates an example in which antennas 101-1 to 101-6 are divided into half for user A and user B. Therefore, the power consumption does not change between the antenna state 2 and the antenna state 3 shown in FIG.

  In the antenna state 3, for example, the number of antennas 101-1 to 101-6 to be used, such as the antenna 101-1 for the user A and the antenna 101-6 for the user B, may be reduced to half or less. Is possible. In antenna state 3, by further reducing the phase shifters 104-1, 104-3, 104-5 and 104-8, 104-10, 104-12 to be operated, compared to the case shown in FIG. The power consumption in the base station 100 can be further reduced.

<1.4 Antenna state 4>
FIG. 7 is a diagram illustrating an example of the antenna state 4.

  The antenna state 4 is an antenna state in which some DACs 109-1 and the transmission radio unit 107-1 are turned on, and other DACs 109-2 and the transmission radio unit 107-2 are turned off. The antenna state 4 is, for example, an antenna state in which all antennas 101-1 to 101-6 are used for wireless communication with the user A without using all the antennas 101-1 to 101-6 for wireless communication with the user B. It is.

  That is, in the example of FIG. 7, the phase shifters 104-1, 104-3, 104-5, 104-7, 104-9, and 104-11 are turned on, and the other phase shifters are turned off. Yes. Further, the power of the transmission radio unit 107-2, the reception radio unit 108-2, the DAC 109-2, and the ADC 110-2 is turned off. Further, the other transmitting radio section 107-1, receiving radio section 108-1, DAC 109-1, and ADC 110-1 are turned on and connected to the antennas 101-1 to 101-6.

  In the example of FIG. 7, the base station 100 can perform wireless communication with the user A and cannot perform wireless communication with the user B simultaneously with the user A. In antenna state 4, the number of multiplexed terminals is “1”. However, since all antennas 101-1 to 101-6 are used in the antenna state 4, it is possible to form a beam having the same thinness as that in the antenna state 1.

  In the first embodiment, the base station 100 performs a beam search based on the antenna state 4. Therefore, it is possible to reduce the power consumption of the base station 100 as compared with the case where the beam search is performed in the antenna state 1.

<1.5 Antenna state 5>
FIG. 8 is a diagram illustrating an example of the antenna state 5.

  The antenna state 5 is also an antenna state in which the antennas 101-1 to 101-3 are used for wireless communication with the user A without using the antennas 101-1 to 101-6 for wireless communication with the user B, for example. . However, compared to the antenna state 4, the antenna state 5 is an antenna state in which the antennas used are part of all the antennas and the number of antennas 101-1 to 101-3 used is reduced.

  That is, in the example of FIG. 8, the phase shifters 104-1, 104-3, and 104-5 are turned on, and the other phase shifters are turned off. Further, the power sources of the amplifiers 102-1 to 102-3 are turned on, and the power sources of the other amplifiers are turned off. Further, the power of the transmission radio unit 107-2, the reception radio unit 108-2, the DAC 109-2, and the ADC 110-2 is turned off. Further, the other transmitting radio section 107-1, receiving radio section 108-1, DAC 109-1, and ADC 110-1 are turned on and connected to the antennas 101-1 to 101-3.

  Compared with the antenna state 4, the antenna state 5 has a wider beam width for the user A, and the antenna gain also decreases. However, in the antenna state 5, the power consumption of the base station 100 can be further reduced because the phase shifter and the amplifier that are turned off are further present compared to the antenna state 4.

<Operation example>
Next, an operation example will be described. FIG. 9 is a flowchart illustrating an operation example in the base station 100.

  When starting the process (S10), the base station 100 sets the antenna state to the antenna state 4 and transmits a beam search packet (S11). For example, the antenna control unit 119 turns on the power of the phase shifters 104-1, 104-3, 104-5, 104-7, 104-9, 104-11, and turns off the power of the other phase shifters. Thus, the antenna state is set to the antenna state 4 (for example, FIG. 7). Beam search processing section 112 then outputs the beam search packet to signal transmission section 113.

  FIG. 17 is a diagram illustrating a transmission example in the base station 100. As shown in FIG. 17, the base station 100 transmits a beam search packet in the beam search period.

  Returning to FIG. 9, next, the base station 100 receives the feedback information transmitted from the terminal 200 (S12). For example, the feedback extraction unit 115 receives a packet transmitted from the terminal 200 via the signal reception unit 114 or the like, and extracts feedback information from the received packet.

  Next, the base station 100 determines whether or not the number of terminals is “1” or more (S13). For example, the feedback extraction unit 115 counts the identification information of the terminal 200 extracted from the feedback information in the beam search period, and determines whether the count value is “1” or more.

  When the number of terminals is not “1” or more (No in S13), the base station 100 turns off all the power of each wireless unit in the transmission slot (S14). For example, when the identification information of the terminal 200 extracted from the feedback information is “0” in the beam search period, the feedback extraction unit 115 outputs that fact to the power supply control unit in the digital signal processing unit 111. The power control unit includes amplifiers 102-1 to 102-6, phase shifters 104-1 to 104-12, transmission radio units 107-1 and 107-2, reception radio units 108-1 and 108-2, and DAC 109-. 1, 109-2 and ADC 110-1 and 110-2 are turned off.

  And the base station 100 complete | finishes a series of processes (S19).

  On the other hand, when the number of terminals is “1” or more (Yes in S13), the base station 100 performs an antenna state setting process (S15). For example, the feedback extraction unit 115 determines to perform the antenna state setting process when the number of pieces of identification information of the extracted terminal 200 is “1” or more in the beam search period.

  FIG. 12 shows an example of information that the base station 100 can obtain from the feedback information. The example of FIG. 12 represents an example in which feedback information for eight terminals 200-1 to 200-8 is extracted in the beam search period.

  10 and 11 are flowcharts showing an example of the antenna state setting process.

  As illustrated in FIG. 10, when the base station 100 starts the antenna state setting process (S150), the base station 100 calculates the second electric field strength (S151).

  FIG. 13 is a diagram illustrating an example of a second electric field strength calculation method. For example, the second received electric field strength calculation unit 117 calculates the second received electric field strength for the terminal 200-1 using the following equation (1).

  Second received electric field strength of terminal 200-1 = (first received electric field strength of terminal 200-1) − (antenna gain difference when array antennas are reduced) (1)

  FIG. 13 is a graph showing an example of the antenna gain difference when the antenna state is changed from the antenna state 1 to the antenna state 3 at the terminal angle “−42 °” of the terminal 200-1.

  By changing the antenna state from antenna state 1 to antenna state 3, the antennas used for terminal 200-1 (one user) are changed from antennas 101-1 to 101-6 to antennas 101-1 to 101-3. The number of antennas is reduced. This reduction in the number of antennas also reduces the antenna gain, resulting in a gain difference. For example, the difference in antenna gain when the number of antennas of the base station 100 is reduced with respect to the first received electric field strength measured by the terminal 200-1 is the terminal 200-1 when the number of antennas of the base station 100 is reduced. It is expressed as the received electric field strength at.

  For example, the second received electric field strength calculation unit 117 calculates the second received electric field strength as follows. That is, the second received electric field strength calculation unit 117 receives the terminal angle θa of the terminal A from the feedback extraction unit 115 and calculates the antenna gain of the antenna state 1 at the received terminal angle θa. Further, the second received electric field strength calculation unit 117 calculates the antenna gain of the antenna state 3 at the terminal angle θa. The second received electric field strength calculation unit 117 may hold a calculation formula in the internal memory and use the calculation formula to calculate an antenna gain corresponding to the terminal angle θa in each antenna state. The second received electric field strength calculating unit 117 calculates the difference between the two calculated antenna gains, and the calculation result is the right side of the expression (1) read from the internal memory (“antenna gain when array antennas are reduced”). Substituting for the difference "). In addition, the second received electric field strength calculation unit 117 reads the first received electric field strength of the terminal A received from the feedback extraction unit 115 from the internal memory (the right side of the terminal 200-1 The first received electric field strength ") is substituted. Then, second received electric field strength calculating section 117 calculates equation (1) to calculate the second received electric field strength when the number of antennas is reduced from antenna state 1 to antenna state 3.

  In the first embodiment, the second received electric field strength when the number of antennas is reduced is, for example, the second received electric field strength in the antenna state 3 and the second received electric field strength in the antenna state 5. And the received electric field strength. Therefore, the second received electric field strength calculating unit 117 calculates the second received electric field strength in the antenna state 3 when the number of antennas is reduced from the antenna state 1 to the antenna state 3. The second received electric field strength calculating unit 117 calculates the second received electric field strength in the antenna state 5 when the number of antennas is reduced from the antenna state 1 to the antenna state 5. In the latter case, the second received electric field strength calculation unit 117 uses the calculation formula when “directivity of antenna state 3” in FIG. In this case, it is possible to calculate the second received electric field strength.

  Returning to FIG. 10, next, the base station 100 determines whether or not the number of terminals is “2” or more (S152). For example, the feedback extraction unit 115 determines whether or not the number of identification information of the terminal 200 extracted from the feedback information is “2” or more in the beam search period.

  When the number of terminals is not “2” or more (when No in S152), the base station 100 determines that the second received electric field strength of the terminal 200-1 is greater than or equal to a predetermined value (or received electric field strength threshold) in the case of the antenna state 5 Is detected (S164 in FIG. 11).

  For example, the base station 100 performs the following processing. That is, the antenna state determination unit 118 receives the number of pieces of identification information of the terminal 200 from the feedback extraction unit 115 via the SIR calculation unit 116 or the second received electric field strength calculation unit 117 in the beam search period. When the number of pieces of identification information of the received terminal 200 is “1”, the antenna state determining unit 118 receives the second received electric field strength of the terminal 200-1 received from the second received electric field strength calculating unit 117 as a predetermined value. It is detected whether it is above.

  When the number of terminals is “1” (No in S152), the base station 100 only needs to use one of the two systems, and does not need to use the other one. Among the antenna states 1 to 5, the antenna state 4 or the antenna state 5 uses one system. The base station 100 determines whether or not the antenna state 5 is usable by this process (S164).

  When the second received electric field strength in the antenna state 5 is larger than the predetermined value (Yes in S164), the base station 100 sets the antenna state to the antenna state 5 (S165). On the other hand, the base station 100 sets the antenna state to the antenna state 4 when the second received electric field strength in the case of the antenna state 5 is equal to or lower than the predetermined value (No in S164) (S166).

  For example, the base station 100 performs the following processing. That is, when the second received electric field strength in the case of the antenna state 5 received from the second received electric field strength calculating unit 117 is larger than a predetermined value (Yes in S164), the antenna state determining unit 118 determines the antenna state. Decide to be in antenna state 5. The antenna state determination unit 118 determines that the terminal 200-1 can receive a data packet transmitted from the base station 100 with a constant reception field strength even when the antenna state of the base station 100 is changed to the antenna state 5. It is. On the other hand, the antenna state determination unit 118 determines to set the antenna state to the antenna state 4 when the second received electric field strength is equal to or lower than the predetermined value (No in S164). In this case, when antenna state determining section 118 enters antenna state 5, there is a possibility that the received electric field strength of terminal 200-1 will be as low as a predetermined value or less, and that data packets transmitted from base station 100 cannot be received normally. This is because it is determined that there is.

  When the base station 100 ends the process of S165 or S165, the base station 100 ends the antenna state setting process and proceeds to S17 (FIG. 10).

  On the other hand, when the number of terminals is “2” or more (Yes in S152), the base station 100 creates a combination of the terminals 200 (S153). For example, as shown in FIG. 12, when the number of terminals is “8”, the base station 100 creates a combination of the terminals 200 as follows.

  That is, the feedback extraction unit 115 includes terminal # 1 (200-1) and terminal # 2 (200-2), terminal # 1 and terminal # 3 (200-3),..., Terminal # 7 (200-7). A combination of terminal # 8 (200-8) is created. And the feedback extraction part 115 allocates the combination number s in the order which produced the combination. That is, the feedback extraction unit 115 is from the combination of terminal # 1 (200-1) and terminal # 2 (200-2) to the combination of terminal # 7 (200-7) and terminal # 8 (200-8). The combination numbers from “1” to “28” are assigned in order. Feedback extraction unit 115 outputs the combination of terminal 200 and the combination number to SIR calculation unit 116.

  Returning to FIG. 10, next, the base station 100 calculates an SIR between the terminal A and the terminal B in the antenna state 3 (hereinafter also referred to as “SIR between the terminals A and B”). (S154).

  FIG. 14 is a diagram illustrating an example of a SIR calculation method. For example, the SIR calculation unit 116 calculates the SIR between the terminals A and B using the following formula.

  SIR between terminals A and B = (gain in terminal angle θa direction of beam for terminal A in antenna state 3) − (gain in terminal angle θa direction of beam for terminal B in antenna state 3) ... (2)

  FIG. 14 illustrates an example in which terminal A is terminal # 1 (200-1) and terminal B is terminal # 3 (200-3). In the example of FIG. 14, the gain at the terminal angle “−42 °” of the terminal # 1 (200-1) and the gain at the angle “−42 °” of the beam for the terminal # 3 (200-3). The difference is the SIR between the terminal # 1 (200-1) and the terminal # 3 (200-3). The feedback extraction unit 115 creates a combination of the terminals 200, and the SIR calculation unit 116 uses the combination of the terminals 200 to calculate SIRs for all combinations using Equation (2).

  For example, the SIR calculation unit 116 may calculate the SIR between the terminals A and B as follows. That is, when the SIR calculation unit 116 receives the terminal angle θa of the terminal A from the feedback extraction unit 115, the SIR calculation unit 116 reads the gain Ga in the terminal angle θa direction in the antenna state 3 from the internal memory. In addition, when the SIR calculation unit 116 receives the terminal angle θb of the terminal B that is the combination target of the terminal A from the feedback extraction unit 115, the SIR calculation unit 116 internally represents an expression that represents the beam for the terminal B including the terminal angle θb as a main lobe. Read from memory. The SIR calculation unit 116 substitutes the terminal angle θa of the terminal A into the equation representing the beam for the terminal B, and calculates the gain Gb of the beam for the terminal B at the angle θa. The SIR calculating unit 116 calculates the SIR between the terminals A and B by subtracting the gain Gb of the beam for the terminal B at the angle θa from the gain Ga in the terminal angle θa direction in the antenna state 3. The SIR calculation unit 116 calculates the SIR between the terminals A and B for all combinations, and outputs the calculated SIR to the antenna state determination unit 118.

  Returning to FIG. 10, the base station 100 further calculates the grating angle of the terminal A in the antenna state 2 (S154).

  FIG. 15 is a diagram illustrating an example of a grating angle (or a grating lobe angle or a grating direction. Hereinafter, it may be referred to as a “grating angle”). That is, FIG. 15 shows that when the terminal angle of terminal A (terminal # 1) is “−42 °”, the grating angle of the beam for terminal # 1 (200-1) in antenna state 2 is “3 °”. Represents an example.

  As described above, in the antenna state 2 (for example, FIG. 5), since the distance between the antenna elements is narrower than that in the antenna state 1 (for example, FIG. 4), a grating lobe is generated within the viewing angle. For example, the SIR calculation unit 116 calculates the grating angle θg of the beam for each terminal in the antenna state 2 based on the terminal angle θa of the terminal A received from the feedback extraction unit 115.

  Here, an example of calculating the grating angle θg will be described.

  As the simplest example of a linear array antenna, when each antenna element is excited at equal intervals and in common phase, the array factor F (u) is expressed by the following equation.

  However, the following u is used instead of θ as a variable representing the angle.

In Equation (4) (Equation 2), k ₀ represents the wave number, d represents the antenna element spacing, θ ₀ represents the beam direction or terminal angle, and θ represents the angle. The wave number k ₀ has a relationship of k ₀ = 2π / λ where λ is the wavelength of the radio wave radiated from the antenna element.

となり、式（５）（数３）を変形すると、

を得る。 The grating lobe is generated at an angle θ after m = ± 1 (u = ± 2π) with a period of u = 2mπ (m = 0, ± 1, ± 2,...) In the equation (4). When equation (4) is transformed,

When Equation (5) (Equation 3) is transformed,

Get.

For example, the base station 100 calculates the grating angle θg as follows. That is, the SIR calculation unit 116 reads the equation (6) (equation 4) held in the internal memory, and substitutes the terminal angle θa of the terminal A into “θ ₀ ” of the equation (6), whereby the grating for the terminal A The angle θg is calculated. λ and d may be fixed values and assigned to the equation (6). In this case, the SIR calculation unit 116 calculates the grating angle θg of the terminal A for the combination of the terminal A and the terminal B. The SIR calculation unit 116 outputs the calculated grating angle θg to the antenna state determination unit 118.

  FIG. 16 is a diagram illustrating an example of terminal combination, the first and second received electric field strengths, the SIR between the terminal A and the terminal B, and the grating angle θg of the terminal A when the number of terminals is “8”. It is. In FIG. 16, the left end represents the combination number s. There is a first received electric field strength of each terminal 200 and a second received electric field strength calculated by the second received electric field strength calculating unit 117 in the order of the combination number, and the terminal calculated by the SIR calculating unit 116 for each combination. There is an SIR between A and B and a grating angle of terminal A. For example, it may be stored in the internal memory of the antenna state determination unit 118 in the table format shown in FIG.

  Returning to FIG. 10, next, the base station 100 substitutes “1” for the combination number s (S155), and performs the following processing in the order of the combination number.

  That is, base station 100 determines whether or not the second received electric field strength of the combination of terminal A and terminal B with combination number s is larger than a predetermined value (or second received electric field strength threshold) in the case of antenna state 3 Is determined (S156). For example, in the terminal A and the terminal B with the combination number “1”, the antenna state determination unit 118 determines whether both the second received electric field strength of the terminal A and the second received electric field strength of the terminal B are larger than a predetermined value. Determine whether.

  For example, as shown in FIG. 6, the antenna state 3 is an antenna state when the number of antennas is reduced for both the terminal A and the terminal B with respect to the antenna state 1. For example, even if the antenna state determination unit 118 reduces the number of antennas and changes to the antenna state 3 in this way, both the terminal A and the terminal B are larger than a predetermined value with respect to the radio signal transmitted from the base station 100. In this process (S156 in FIG. 10), it is determined whether or not reception with the received electric field strength is possible.

  The predetermined value used in S156 and the predetermined value used in S164 may be the same value or different values.

  Returning to FIG. 10, when the second received electric field strength of the combination of the combination number s is larger than the predetermined value (Yes in S156), the base station 100 sets the SIR of the combination of the combination number s in the case of the antenna state 3 It is determined whether or not the value is greater than the value (or interference amount threshold value) (S157). For example, the antenna state determination unit 118 determines whether or not the SIR between the terminals A and B in the case of the antenna state 3 calculated in S154 is larger than a predetermined value.

  The base station 100 sets the antenna state to the antenna state 3 (S158) when the SIR of the combination of the combination number s is larger than a predetermined value in the case of the antenna state 3 (Yes in S157). For example, the antenna state determination unit 118 determines that the antenna state is the antenna state 3 when the SIR between the terminals A and B in the antenna state 3 is larger than a predetermined value in the combination number “1”. In this case, even if the antenna state 3 is set, the second received electric field strength is larger than the predetermined value (Yes in S156), and the SIR between the terminals A and B is also larger than the predetermined value (Yes in S157). Therefore, it is considered that both the terminal A and the terminal B can obtain a received signal whose interference is in an allowable range and whose quality is a certain level or higher. Therefore, for example, the antenna state determination unit 118 can set the antenna state for the terminals A and B to the antenna state 3.

  For example, if the predetermined value of S156 is “−70 dBm” and the predetermined value of S157 is “16 dB”, in the example of FIG. 16, the terminal # 1 (200-1) and the terminal # 5 (200− For 5), antenna state 3 is set.

  Returning to FIG. 10, next, the base station 100 increments the combination number s (S159). Then, the base station 100 determines whether or not the combination number s is larger than the maximum value S of the combination number s (S160). When the combination number s is larger than the maximum value S (Yes in S160), the base station 100 ends the antenna state setting process and proceeds to S17 in FIG. On the other hand, when the combination number s is equal to or less than the maximum value S (No in S160), the base station 100 proceeds to S156.

  For example, when the antenna state determination unit 118 ends the process for the combination number “1”, the antenna state determination unit 118 performs the process for the combination number “2”, and combines each combination up to the maximum combination number S = 28. On the other hand, the process after S156 is performed.

  On the other hand, in the combination of the combination number s, when the second received electric field strength is equal to or lower than the predetermined value (No in S156), the base station 100 determines that the terminal angle direction of the user B (terminal B) is It is determined whether the user A (terminal A) is in the grating angle direction (S161). For example, the antenna state determination unit 118 determines whether or not the grating angle θg of the terminal A calculated in S154 matches the terminal angle θb of the terminal B.

  In addition, in the combination of the combination number s, when the SIR between the terminals A and B is equal to or less than the predetermined value (No in S157), the base station 100 also determines the terminal angle direction of the user B (terminal B). Determines whether the user A (terminal A) is in the grating angle direction (S161). For example, the antenna state determination unit 118 determines that the terminal A of the combination number s calculated in S154 even when both of the terminals A and B of the combination number s have the second received electric field strength greater than a predetermined value (Yes in S156). When the SIR between -B is equal to or less than the predetermined value (No in S157), the process of S161 is performed.

  When the second received electric field strength is less than or equal to a predetermined value in the antenna state 3 (No in S156), even if the base station 100 transmits a radio signal in the antenna state 3, both the terminals A and B receive at a certain level or more. A radio signal cannot be received with electric field strength. Further, when the SIR between the terminals A and B is equal to or less than the predetermined value (No in S157), even if the base station 100 transmits a radio signal in the antenna state 3, the terminals A and B can transmit the terminal A and the terminal B. These beams interfere with each other and cannot receive radio signals with sufficient quality. In such a case, the base station 100 gives up setting the antenna state 3 and determines whether or not the antenna state 2 can be set.

  As described above, in the antenna state 2, the terminal angles of the terminal A and the terminal B are fixed. When the grating angle of terminal A matches the terminal angle of terminal B, base station 100 can cancel the grating lobe that exists in the grating angle direction of terminal A. In this process (S161), the base station 100 determines that a radio signal can be transmitted to the terminal A and the terminal B according to the antenna state 2 if the grating angle of the terminal A matches the terminal angle of the terminal B. .

  When the terminal angle direction of the user B is the grating direction of the user A (Yes in S161), the base station 100 sets the antenna state to the antenna state 2 (S162). For example, when the grating angle θg of the terminal A matches the terminal angle θb of the terminal B, the antenna state determination unit 118 determines that the condition of the antenna state 2 is satisfied and sets the antenna state to the antenna state 2. Set to.

  On the other hand, when the terminal angle direction of the user B is not the grating direction of the user A (No in S161), the base station 100 sets the antenna state to the antenna state 1 (S163). For example, when the grating angle θg of the terminal A and the terminal angle θb of the terminal B do not match, the antenna state determination unit 118 determines that the conditions of the antenna states 2 and 3 are not satisfied, and sets the antenna state to the antenna state. State 1 is set (S163), or the antenna state is maintained as antenna state 1.

  And the base station 100 will increment a combination number, after complete | finishing the process of S162 or S163 (S159), and repeats the process mentioned above.

  In the example of FIG. 16, since the combination number “3” matches the terminal angle “3 °” of the terminal B (terminal 200-5) and the grating angle “3 °” of the terminal A (terminal 200-1), Antenna state 2 is set for terminals 200-1 and 200-5.

  In the example of FIG. 16, for example, the combination of terminal # 2 (200-2) and terminal # 4 (200-4), or the combination of terminal # 6 (200-6) and terminal # 7 (200-7) On the other hand, antenna state 1 is set.

  Thus, the antenna state setting process ends.

  Returning to FIG. 9, next, the base station 100 sets a transmission time slot of the terminal 200 (S17).

  Then, the base station 100 starts transmission to the terminal 200 in the set transmission time slot (S18).

  FIG. 17 is a diagram illustrating an example of transmission to terminal 200 in the set transmission time slot. For example, the base station 100 performs the following processing. That is, antenna state determination section 118 outputs a determination result for antenna state 3 to antenna control section 119 for the combination of terminal # 3 (200-3) and terminal # 8 (200-8). In addition, the antenna state determination unit 118 outputs a determination result for the antenna state 2 to the antenna control unit 119 for the combination of the terminal # 1 (200-1) and the terminal # 4 (200-4). Furthermore, the antenna state determination unit 118 includes a combination of the terminal # 2 (200-2) and the terminal # 4 (200-4), a combination of the terminal # 6 (200-6) and the terminal # 7 (200-7), On the other hand, the determination result of the antenna state 1 is output to the antenna control unit 119. The antenna control unit 119 controls the power on and off of the amplifier 102-1 or the like so that the set antenna state is obtained for each combination of terminals 200 during the transmission time slot period according to the determination process. As a result, as shown in FIG. 17, wireless communication is performed in the antenna state set by the combination of each terminal 200 in the transmission time slot period.

  And the base station 100 complete | finishes a series of processes (S19).

  Thus, in the first embodiment, the base station 100 can set the antenna state to the antenna state 2 or the antenna state 3 based on the interference amount and the second received electric field strength. (S158, S162 in FIG. 10).

  In base station 100, since the amount of interference and the second received electric field strength are considered, the number of terminals is large (Yes in S152), and the reception quality on terminal 200 side is high even when the transmission amount is a certain level or more. It is possible to determine whether or not it is sufficient.

  The base station 100 can also set the antenna state 2 and the antenna state 3 that consume less power than the antenna state 1. For example, the base station 100 is set as the antenna state 1 before the start of this operation (S10 in FIG. 9), and then can be set to the antenna states 2 to 5 by the antenna state setting process (FIG. 10). Become. Therefore, in the base station 100, the antenna state can be switched from the antenna state 1 to the antenna states 2 to 5 having lower power consumption than the antenna state 1. Accordingly, the base station 100 can reduce power consumption without changing the transmission amount.

  From the above, the base station 100 according to the first embodiment reduces the power consumption of the base station 100 without changing the transmission amount even when the transmission amount is more than a certain level for a plurality of terminals 200. Is possible.

  Note that the base station 100 can set the antenna state to the antenna state 4 or the antenna state 5 when the number of terminals is “1” (FIG. 11). Compared to antenna state 1, antenna state 4 and antenna state 5 consume less power. Therefore, even if the number of terminals is “1”, the base station 100 can reduce the power consumption of the base station 100 compared to the case of the antenna state 1.

  In the first embodiment, the antennas 101-1 to 101-6 have been described using six examples. For example, the number of antennas may be three or more in consideration of the antenna state 2.

[Second Embodiment]
Next, a second embodiment will be described. FIG. 18 is a diagram illustrating a configuration example of the base station 100 in the second embodiment.

  The base station 100 further includes switches (SW) 130-1 to 130-6 between the phase shifters 104-1 to 104-6 and the distributors 105-1 and 105-2.

  Each switch 130-1 to 130-6 connects each phase shifter 104-1 to 104-6 to either the user A side (distributor 105-1) or the user B side (distributor 105-2). It is possible to switch as described above. Further, each switch 130-1 can be configured such that the power is turned off and the phase shifters 104-1 to 104-6 are not connected to both the user A side and the user B side. Such switching and power on / off can be controlled by a switching control signal from the antenna control unit 119, a power on signal, a power off signal, or the like.

  The base station 100 illustrated in FIG. 18 can set the antenna state 5 to the antenna state 2 described in the first embodiment. However, the base station 100 illustrated in FIG. 18 cannot set the antenna state 1 by switching with the switches 130-1 to 130-6. 19 to 22 are diagrams illustrating examples of the antenna state 2 to the antenna state 5, respectively.

  FIG. 23 is a flowchart illustrating an operation example in the base station 100 according to the second embodiment. FIG. 24 and FIG. 25 are flowcharts showing an example of the antenna state setting process in the second embodiment.

  In the second embodiment, when the direction of the user B is not the grating direction of the user A (No in S161), since the antenna state 1 does not exist, the determination of the antenna state 5 is performed (S164 in FIG. 25). I have to. When the base station 100 cannot set the antenna state 2 or the antenna state 3, the base station 100 sets the antenna state 5 or the antenna state 4 (S165, S166).

  In the second embodiment, as in the first embodiment, the base station 100 changes the antenna state to the antenna state 2 or the antenna state 3 based on the interference amount and the second received electric field strength. It is possible to set (S158, S162 in FIG. 24). Therefore, as in the first embodiment, the base station 100 reduces the power consumption of the base station 100 without changing the transmission amount even when the transmission amount is a certain level or more with respect to the terminal 200. Is possible.

[Third Embodiment]
FIG. 26 is a diagram illustrating a configuration example of the wireless communication system 10 according to the third embodiment. The radio communication system 10 includes a radio base station device 100 and a terminal device 200. Radio base station apparatus 100 also includes feedback extraction section 115, interference amount calculation section 116, second received electric field strength calculation section 117, and antenna state determination section 118.

  Note that the interference amount calculation unit 116 corresponds to, for example, the SIR calculation unit 116 in the first embodiment.

  The feedback extraction unit 115 receives feedback information transmitted from the terminal apparatus 200 in response to a beam search signal that is a signal for determining a beam transmitted from the radio base station apparatus 100 to the terminal apparatus 200. The interference amount calculation unit 116 calculates an interference amount for the terminal device 200 based on the feedback information. Based on the feedback information, the second received electric field strength calculation unit 117 calculates a second received electric field strength that represents the received electric field strength in the terminal device 200 when the number of antennas of the radio base station device 100 is reduced.

  The antenna state determination unit 118 changes the antenna state of the radio base station apparatus 100 from the first antenna state, which has lower power consumption than the first antenna state, based on the interference amount and the second received electric field strength. Switch to 2 antenna state.

  Thus, in the third embodiment, radio base station apparatus 100 switches the antenna state based on the interference amount and the second received electric field strength. For this reason, the radio base station apparatus 100 can detect that the transmission amount at the time of radio communication with the terminal apparatus 200 is under a certain condition, and can switch the antenna state in such a situation. Become.

  Further, in the third embodiment, radio base station apparatus 100 can switch the antenna state from the first antenna state to the second antenna state. For this reason, the radio base station apparatus 100 can reduce power consumption without changing the transmission amount.

  In summary, the radio base station apparatus 100 switches from the antenna state 1 to the antenna state 2 based on the interference amount and the second received electric field strength, so that the transmission amount with respect to the radio communication with the terminal device 200 is a certain amount or more. Even in the situation, it is possible to reduce power consumption without changing the transmission amount.

  The above is summarized as an appendix.

(Appendix 1)
In a wireless base station device that performs wireless communication with a terminal device,
For a beam search signal that is a signal for determining a beam to be transmitted to the terminal device transmitted from the radio base station device, a feedback extraction unit that receives feedback information transmitted from the terminal device;
An interference amount calculation unit that calculates an interference amount for the terminal device based on the feedback information;
Based on the feedback information, a second received electric field strength calculating unit that calculates a second received electric field strength that represents the received electric field strength in the terminal device when the number of antennas of the radio base station device is reduced;
Based on the amount of interference and the second received electric field strength, the antenna state of the radio base station apparatus is changed from the first antenna state to a second antenna state with lower power consumption than the first antenna state. An antenna state determination unit for switching,
A radio base station apparatus comprising:

(Appendix 2)
The feedback extraction unit detects a direction in which the terminal apparatus is located with respect to the radio base station apparatus based on the feedback information, and when the terminal apparatus receives the beam search signal from the feedback information Extract the measured first received electric field strength,
The interference amount calculation unit calculates the interference amount based on a direction in which the terminal device is located,
The second received electric field strength calculating unit calculates the second received electric field strength based on the first received electric field strength;
The radio base station apparatus according to supplementary note 1, wherein:

(Appendix 3)
The feedback extraction unit receives first and second feedback information respectively transmitted from the first and second terminal apparatuses with respect to the beam search signal, and based on the first and second feedback information , Detecting first and second directions in which the first and second terminal apparatuses are respectively located with respect to the radio base station apparatus, and determining the first and second from the first and second feedback information. Extracting the third and fourth received electric field strengths measured when the terminal device receives the beam search signal,
The interference amount calculation unit is configured to perform the first reception power in the first direction of the first terminal device based on the first and second directions with respect to the first received power in the first terminal device. Calculating the difference of the second received power in the direction of 1 as the amount of interference,
The second received electric field strength calculating unit is configured to perform a first operation on the first and second terminal devices when the number of antennas of the radio base station device is reduced with respect to the third and fourth received electric field strengths. And the difference between the second antenna gain and the received electric field strength at the first and second terminal devices when the number of antennas of the radio base station device is reduced are calculated as the fifth and sixth received electric field strengths, respectively. ,
The antenna state determination unit switches from the first antenna state to the second antenna state based on the interference amount and the fifth and sixth received electric field strengths.
The radio base station apparatus according to supplementary note 1, wherein:

(Appendix 4)
The first antenna state is an antenna state in which all antennas are used in wireless communication with the first and second terminal devices,
The second antenna state is:
A third antenna state in which an antenna used for wireless communication with the second terminal device is located between antennas used for wireless communication with the first terminal device; or
The antenna used for wireless communication with the first terminal apparatus and the antenna used for wireless communication with the second terminal apparatus are between the antennas used for wireless communication with the first terminal apparatus. It is a fourth antenna state where the antenna used for wireless communication with the terminal device of 2 is located separately without being located.
The radio base station apparatus according to supplementary note 1, wherein:

(Appendix 5)
The antenna state determination unit is configured such that the second received electric field strength is a second received electric field strength threshold when the amount of interference is larger than an interference amount threshold and the number of antennas is reduced to the third antenna state. Is greater than the second antenna state, the interference amount is less than or equal to the interference amount threshold value, or the second reception field strength is less than or equal to the second reception field strength threshold value. 4. The radio base station apparatus according to appendix 4, wherein the radio base station apparatus is switched to the antenna state of 3.

(Appendix 6)
The feedback extraction unit detects a direction in which the first and second terminal devices are located with respect to the radio base station device based on the feedback information,
The interference amount calculation unit detects a direction in which a grating lobe with respect to the main lobe exists based on the direction in which the first terminal device is located, with the direction as the main lobe,
The antenna state determination unit is configured to detect a grating lobe of the first terminal apparatus when the interference amount is equal to or less than the interference amount threshold value or when the second reception electric field strength is equal to or less than the second reception electric field strength. When the direction in which the second terminal apparatus is located and the direction in which the second terminal apparatus is located are switched to the third antenna state, the direction in which the grating lobe of the first terminal apparatus exists and the second terminal apparatus The radio base station apparatus according to appendix 5, wherein the first antenna state is maintained when the direction in which the radio wave is located does not match.

(Appendix 7)
Furthermore,
First and second phase shifters for adjusting the phases of the first and second radio signals transmitted to the first and second terminal devices for each antenna, and the first and second phase shifters An amplifier for amplifying the first and second radio signals output from
According to the switching by the antenna state determination unit, the power supply of the first and second phase shifters and the amplifier is controlled to be switched on and off to switch from the first antenna state to the second antenna state. The radio base station apparatus according to appendix 4, further comprising: an antenna control unit.

(Appendix 8)
Furthermore,
A first wireless unit that converts first transmission data to be transmitted to the first terminal device into a first wireless signal in a wireless band and outputs the first wireless signal to the antenna; and a second terminal device A second wireless unit for converting second transmission data to be transmitted to a second wireless signal in a wireless band and outputting the second wireless signal to the antenna;
The radio base station apparatus according to appendix 1, wherein the radio base station apparatus performs radio communication simultaneously with the first and second terminal apparatuses by the first and second radio units.

(Appendix 9)
The radio base station apparatus according to appendix 8, further comprising a switch for switching connection between the antenna and the first radio unit or between the antenna and the second radio unit for each antenna.

(Appendix 10)
The first antenna state is an antenna state in which all antennas are used in wireless communication with the first and second terminal devices,
The second antenna state is:
A third antenna state in which an antenna used for wireless communication with the second terminal device is located between antennas used for wireless communication with the first terminal device;
The antenna used for wireless communication with the first terminal apparatus and the antenna used for wireless communication with the second terminal apparatus are between the antennas used for wireless communication with the first terminal apparatus. A fourth antenna state where the antenna used for wireless communication with the two terminal devices is located without being located, or
A fifth antenna state in which the antenna is used for wireless communication with the first terminal device without being used for wireless communication with the second terminal device;
The feedback extraction unit detects a direction in which the first and second terminal devices are located with respect to the radio base station device based on the feedback information,
The interference amount calculation unit detects a direction in which a grating lobe with respect to the main lobe exists based on the direction in which the first terminal device is located, with the direction as the main lobe,
The antenna state determination unit switches to the fourth antenna state when the amount of interference is larger than an interference amount threshold and the second received electric field strength is larger than a second received electric field strength threshold, When the interference amount is less than or equal to the interference amount threshold value, or when the second received electric field strength is less than or equal to the second received electric field strength, the direction in which the grating lobe of the first terminal device exists and the second Switch to the third antenna state when the direction in which the terminal device is located matches the direction in which the grating lobe of the first terminal device exists and the direction in which the second terminal device is located does not match The radio base station apparatus according to appendix 9, wherein the radio base station apparatus is switched to the fifth antenna state.

(Appendix 11)
The second antenna state is:
The sixth antenna state in which all of the antennas are used for wireless communication with the first terminal device without being used for wireless communication with the second terminal device, and wireless communication with the second terminal device A seventh antenna state in which a part of the antenna is used for wireless communication with the first terminal device without being used for communication;
When the radio base station apparatus performs radio communication with the first terminal apparatus without performing radio communication with the second terminal apparatus, the second number when the number of antennas is reduced to the seventh antenna state. When the received electric field strength is larger than the second received electric field strength threshold, the second received electric field strength when switching to the seventh antenna state and reducing the number of antennas to the seventh antenna state is the second The radio base station apparatus according to supplementary note 4, wherein the radio base station apparatus switches to the sixth antenna state when the received electric field intensity threshold value is less than or equal to.

(Appendix 12)
A wireless communication method in a wireless base station device that performs wireless communication with a terminal device,
Receiving feedback information transmitted from the terminal device with respect to a beam search signal that is a signal for determining a beam to be transmitted to the terminal device transmitted from the radio base station device;
Based on the feedback information, calculate the amount of interference for the terminal device,
Based on the feedback information, a second received electric field strength representing a received electric field strength in the terminal device when the number of antennas of the radio base station device is reduced is calculated,
Based on the amount of interference and the second received electric field strength, the antenna state of the radio base station apparatus is changed from the first antenna state to a second antenna state with lower power consumption than the first antenna state. Switch,
A wireless communication method.

10: Radio communication system 100: Radio base station apparatuses 101-1 to 101-6: Antenna elements 102-1 to 102-6: Amplifiers 103-1 to 103-6: Synthesizers 104-1 to 104-12: Phase shifters 105-1 and 105-2: Distributors 106-1, 106-2: T / R switches 107-1 and 107-2: Transmission radio units 108-1 and 108-2: Reception radio units 109-1 and 109- 2: DAC 110-1, 110-2: ADC
111: Digital signal processing unit 112: Beam search processing unit 113: Signal transmission unit 114: Signal reception unit 115: Feedback extraction unit 116: SIR calculation unit 117: Second received electric field strength calculation unit 118: Antenna state determination unit 119: Antenna control unit 120: memory units 130-1 to 130-6: switch 200 (200-1 to 200-8): terminal device

Claims (7)

In a wireless base station device that performs wireless communication with a terminal device,
For a beam search signal that is a signal for determining a beam to be transmitted to the terminal device transmitted from the radio base station device, a feedback extraction unit that receives feedback information transmitted from the terminal device;
An interference amount calculation unit that calculates an interference amount for the terminal device based on the feedback information;
Based on the feedback information, a second received electric field strength calculating unit that calculates a second received electric field strength that represents the received electric field strength in the terminal device when the number of antennas of the radio base station device is reduced;
Based on the amount of interference and the second received electric field strength, the antenna state of the radio base station apparatus is changed from the first antenna state to a second antenna state with lower power consumption than the first antenna state. An antenna state determination unit for switching,
A radio base station apparatus comprising: The feedback extraction unit detects a direction in which the terminal apparatus is located with respect to the radio base station apparatus based on the feedback information, and when the terminal apparatus receives the beam search signal from the feedback information Extract the measured first received electric field strength,
The interference amount calculation unit calculates the interference amount based on a direction in which the terminal device is located,
The second received electric field strength calculating unit calculates the second received electric field strength based on the first received electric field strength;
The radio base station apparatus according to claim 1. The first antenna state is an antenna state in which all antennas are used in wireless communication with the first and second terminal devices,
The second antenna state is:
A third antenna state in which an antenna used for wireless communication with the second terminal device is located between antennas used for wireless communication with the first terminal device; or
The antenna used for wireless communication with the first terminal apparatus and the antenna used for wireless communication with the second terminal apparatus are between the antennas used for wireless communication with the first terminal apparatus. It is a fourth antenna state where the antenna used for wireless communication with the terminal device of 2 is located separately without being located.
The radio base station apparatus according to claim 1.   The antenna state determination unit is configured such that the second received electric field strength is a second received electric field strength threshold when the amount of interference is larger than an interference amount threshold and the number of antennas is reduced to the third antenna state. Is greater than the second antenna state, the interference amount is less than or equal to the interference amount threshold value, or the second reception field strength is less than or equal to the second reception field strength threshold value. The radio base station apparatus according to claim 3, wherein the radio base station apparatus is switched to an antenna state of 3. The feedback extraction unit detects a direction in which the first and second terminal devices are located with respect to the radio base station device based on the feedback information,
The interference amount calculation unit detects a direction in which a grating lobe with respect to the main lobe exists based on the direction in which the first terminal device is located, with the direction as the main lobe,
The antenna state determination unit is configured to detect a grating lobe of the first terminal apparatus when the interference amount is equal to or less than the interference amount threshold value or when the second reception electric field strength is equal to or less than the second reception electric field strength. When the direction in which the second terminal apparatus is located and the direction in which the second terminal apparatus is located are switched to the third antenna state, the direction in which the grating lobe of the first terminal apparatus exists and the second terminal apparatus The radio base station apparatus according to claim 4, wherein the first antenna state is maintained when the direction in which the radio wave is located does not match. Furthermore,
A first wireless unit that converts first transmission data to be transmitted to the first terminal device into a first wireless signal in a wireless band and outputs the first wireless signal to the antenna; and a second terminal device A second wireless unit for converting second transmission data to be transmitted to a second wireless signal in a wireless band and outputting the second wireless signal to the antenna;
The radio base station apparatus according to claim 1, wherein the radio base station apparatus performs radio communication simultaneously with the first and second terminal apparatuses by the first and second radio units. A wireless communication method in a wireless base station device that performs wireless communication with a terminal device,
In response to a beam search signal that is a signal for determining a beam to be transmitted to the terminal device transmitted from the radio base station device, the feedback information transmitted from the terminal device is received,
Based on the feedback information, calculate the amount of interference for the terminal device,
Based on the feedback information, a second received electric field strength representing a received electric field strength in the terminal device when the number of antennas of the radio base station device is reduced is calculated,
Based on the amount of interference and the second received electric field strength, the antenna state of the radio base station apparatus is changed from the first antenna state to a second antenna state with lower power consumption than the first antenna state. Switch,
A wireless communication method.

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