JP2015211282A - Base station, control method of the same, and wireless communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain high reception quality and achieve high throughput by properly selecting an antenna for performing BF (Beam Forming) and MIMO (Multiple-Input Multiple-Output) multiplexing out of a number of antennas of a base station with respect to a terminal movement.SOLUTION: The base station for communicating with a terminal by including a plurality of antennas includes: a mobile speed estimate part for estimating a moving speed of the terminal in horizontal/vertical directions; and a BF antenna determination part for determining an antenna combination for performing BF on the basis of the estimated moving speed from the plurality of antennas.

Description

  The present invention relates to a base station, a control method thereof, and a radio communication system.

  In a wireless communication system, it is important to improve throughput in order to cope with an increase in traffic. In order to improve the throughput, a MIMO (Multiple-Input Multiple-Output) technique for multiplexing and transmitting different signals from different antennas using the same time and frequency is widely used. For example, in LTE (Long Term Evolution) of cellular systems that are currently widely used, MIMO transmission using a maximum of 8 antennas is defined. In MIMO transmission, it is necessary to maintain high reception quality in order to multiplex a large number of signals. In other words, it is important to maintain high reception quality in order to cope with high traffic.

  On the other hand, as a technique for achieving high reception quality, BF (Beamforming), which improves reception quality by transmitting the same signal with different antennas, is widely known. In the case of having multiple antennas, in order to improve the reception quality, BF that transmits the same signal through the multiple antennas should be applied, but since the same signal is transmitted through the multiple antennas, Achieving high throughput is difficult.

  As described above, in order to cope with high traffic, high throughput is required while maintaining high reception quality. Currently, as a technology to achieve high reception quality and high throughput, MIMO and BF are performed simultaneously using more antennas (for example, 10 or more) arranged in two dimensions (4 antennas x 4 antennas square arrangement, etc.). 3D MIMO (also called Full Dimension MIMO) has been studied. In 3D MIMO, since the number of usable antennas is larger than in the past, MIMO transmission and BF can be performed simultaneously. The area of high reception quality can be expanded by the effect of BF, and the area of high throughput in which MIMO can be performed is expanded. That is, BF technology that expands the area where MIMO transmission is possible is important in 3D MIMO.

  For example, Patent Document 1 discloses a technique for determining a BF pattern by estimating a position of a terminal from an uplink signal in a MIMO system.

JP 2013-005379 A

  When performing BF using a large number of antennas, it is possible to improve the reception quality of the terminal by narrowing the beam width, and at the same time reduce the interference given to adjacent cells. However, the narrower the beam width, the more difficult it is to follow the movement of the terminal, and the throughput is degraded due to the inability to form a correct beam.

  Therefore, an object of the present invention is to select an appropriate antenna for performing BF and MIMO multiplexing from among a large number of antennas of a base station for the movement of a terminal, and achieve high throughput while maintaining high reception quality. There is to do.

  A representative base station according to the present invention is a base station that includes a plurality of antennas and communicates with a terminal, and a moving speed estimation unit that estimates a moving speed in a horizontal direction and / or a vertical direction of the terminal; And a BF antenna determining unit that determines a combination of antennas for performing BF based on the estimated moving speed from the plurality of antennas.

  The present invention is also understood as a base station control method and a radio communication system.

  According to the present invention, an appropriate antenna selection for performing BF and MIMO multiplexing is performed from among a large number of antennas of a base station with respect to movement of a terminal, and high reception quality is maintained and high throughput is achieved. Can do.

It is a figure which shows the example of the network structure of a radio | wireless communications system. It is a figure which shows the example of the cell structure by a base station. It is a figure which shows the example of an antenna structure. It is a figure which shows the example of the flame | frame communicated wirelessly between a base station and a terminal. It is a figure which shows the example of the processing sequence in a terminal and a base station. It is a figure which shows the example of the process part which a base station has. It is a figure which shows the example of the process part which a BF possible pattern determination part has. It is a figure which shows the example of the process flowchart of a moving speed estimation part. It is a figure which shows the example of the antenna group for estimating a moving speed. It is a figure which shows the example of another process flowchart of a moving speed estimation part. It is a figure which shows the example of the process flowchart of a BF antenna determination part. It is a figure which shows the example of a BF antenna reference table. It is a figure which shows the example of a BF antenna group. It is a figure which shows the example of the relationship between a moving speed and a BF antenna group. It is a figure which shows the example of the process flowchart of a DL reference signal information generation part. It is a figure which shows the example of a DL reference signal. It is a figure which shows the 1st example of the antenna structure which transmits DL reference signal. It is a figure which shows the 2nd example of the antenna structure which transmits DL reference signal. It is a figure which shows the example of the relationship between a moving speed and the antenna structure which transmits DL reference signal. It is a figure which shows the example of the process flowchart of 3D MIMO determination part. It is a figure which shows the example of grouping of RS antenna group. It is a figure which shows the example of the antenna structure used for transmission of 3D MIMO. FIG. 10 is a diagram illustrating an example of a processing sequence according to the second embodiment. 6 is a diagram illustrating an example of an antenna configuration of Example 3. FIG. It is a figure which shows the example of a division | segmentation of the horizontal direction of the antenna structure of Example 3. FIG. It is a figure which shows the example of a division | segmentation of the perpendicular direction of the antenna structure of Example 3. FIG. It is a figure which shows the example of a division | segmentation of the horizontal direction of the antenna structure of Example 3, and a vertical direction.

  The base station in the wireless communication system according to the first embodiment includes a plurality of antennas arranged two-dimensionally in the horizontal direction and the vertical direction, and moves the terminal in the horizontal direction and the vertical direction from a UL (Uplink) reference signal from the terminal. After estimating the speed, determining a combination of antennas capable of BF, and setting a DL (Downlink) reference signal based on the combination of the antennas, the terminal transmits the number of MIMO multiplexing available from the DL reference signal to the base station. The antenna to be used for BF and MIMO is determined from the combination of the reported spatial multiplexing number, the UL reference signal, and the antenna capable of BF, and DL transmission is performed. Hereinafter, a wireless communication system according to the first embodiment and a base station in the wireless communication system will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating an example of a network configuration of a wireless communication system. The wireless communication system is implemented, for example, by the network configuration shown in FIG. That is, the wireless communication system includes a plurality of base stations 20 (20a, 20b,...), A plurality of terminals 21 (21a, 21b,...), And a backhaul 305. The wireless communication system is connected to the network 203.

  The base station 20 is a device that transfers a signal received from the terminal 21 to the router 201 and further transfers a signal received from the router 201 to the terminal 21. The base station 20 is a computer having a processor and a memory. The base station 20 can communicate with the terminal 21 included in the cell 22 by radio. For example, the base station 20a can communicate with the terminals 21a and 21b included in the cell 22a. Here, the cell 22 is a communication range of the base station 20. The terminal 21 is a device having an interface to the user. In general, the position of the base station 20 is fixed, but the terminal 21 moves.

  The backhaul 305 is a system that relays communication between a plurality of base stations 20 and relays communication between the terminal 21 and the network 203. The backhaul 305 includes a router 201 and a gateway (GW) 202. The router 201 is a device that communicates with the base station 20 wirelessly or by wire. The router 201 is a device that distributes signals according to the destination of the received signal. For this reason, the router 201 may be an L3 switch. The GW 202 is a device that relays communication between the router 201 and the network 203. The network 203 is, for example, the Internet. Base station 20 is connected to network 203 via router 201 and GW 202.

  FIG. 2 is a diagram illustrating an example of a cell configuration by the base station 20. The base station 20 may be installed so as to constitute a cell as shown in FIG. The three base stations 20 (20c, 20d, and 20e) shown in FIG. 2 are installed so as to constitute three cells. The base stations 20c, 20d, and 20e include antennas having directivity, and can communicate with the terminals 21 in the ranges of the cells 22c, 22d, and 22e, respectively. A cell is sometimes called a sector. However, the base station 20 of this example does not need to have a sector configuration, and is limited to this as long as the base station 20 covers a certain range, such as an omnicell configuration in which a single base station 20 covers a circular range. Not what you want.

  FIG. 3 is a diagram illustrating an example of an antenna configuration included in the base station 20 according to the first embodiment. As shown in FIG. 3, the antenna of the base station 20 includes a plurality of antenna elements 301, and each antenna element 301 is arranged in a grid pattern in the horizontal direction and the vertical direction. FIG. 3 shows an example of a total of 16 antenna elements with 4 antenna elements in the horizontal direction and 4 antenna elements in the vertical direction, but the invention is not limited to this as long as the antenna elements are arranged in the horizontal and vertical directions. . For example, instead of the square arrangement, the antennas may be arranged in a rectangle such as 4 antenna elements in the horizontal direction and 8 antenna elements in the vertical direction according to the distribution of the terminals 21 and the frequency in the moving direction. Further, the antenna elements may be arranged in a curved shape instead of on a plane. Each antenna element 301 may be a so-called patch antenna, but is not limited to a patch antenna, and may be another type of antenna. As described below, for a horizontal antenna and a vertical antenna as shown in FIG. 3, an antenna combination to which BF is applied and an antenna combination to which MIMO multiplexing is applied are adaptively selected. Perform DL transmission.

  FIG. 4 is a diagram illustrating an example of a frame wirelessly communicated between the base station 20 and the terminal 21. The base station 20 allocates radio resources having a frequency domain and a time domain to the frame. In one frame, information is included in a frequency region of a predetermined frequency bandwidth 404. Also, in one frame, information is included in the time domain of Downlink (DL) 405 and Uplink (UL) 406. The frequency bandwidth 404 includes a plurality of subchannels 401. One frame includes a plurality of subframes 402 in the time direction. A PRB (Physical Resource Block) 403 is a frequency domain delimited by one subchannel 401 and a time domain delimited by one subframe 402.

  The control channel 407 is a time domain included in at least one subframe 402. In the frame in which the frame shown in FIG. 4 is transmitted from the base station 20 to the terminal 21, the control channel 407 includes allocation information related to radio resources allocated to the frame transmitted and received by the terminal, configuration information of the radio communication system including the terminal, and the like. Control information. Control messages in DL 405 and UL 406 are included in PRBs 403 other than control channel 407 in each subframe 402. The frame configuration shown in FIG. 4 is, for example, a frame configuration used in OFDMA (Orthogonal Frequency Division Multiple Access) of TDD (Time Division Duplex). Note that one subframe 402 includes a plurality of symbols, and one subchannel includes a plurality of subcarriers. The base station 20 performs DL transmission by transmitting control information indicating a DL transmission configuration of BF and MIMO and a DL signal determined by processing to be described later to the terminal 21 using a frame as illustrated in FIG.

  FIG. 5 is a diagram illustrating an example of a processing sequence in the base station 20 and the terminal 21. First, the terminal 21 transmits a UL reference signal to the base station 20 in step 501. The UL reference signal is a signal transmitted in the UL subframe, and information such as a radio resource to be used is set in advance at the time of handover or the like at the time of connection. If not set, the base station 20 notifies the terminal 21 of the setting information of the UL reference signal. For example, in the case of LTE (Long Term Evolution), SRS (Sounding Reference Signal) corresponds to the UL reference signal. The UL reference signal is a signal transmitted using a specific symbol or frequency of the UL subframe, and may be a signal that is known between the base station 20 and the terminal 21. The information such as the radio resource to be used may include a frequency to be used, a symbol, a transmission cycle, a UL reference signal sequence number, and antenna information to be used.

  The base station 20 that has received the UL reference signal estimates the moving speed of the terminal 21 in step 502. This estimation process will be described later. In accordance with the moving speed estimated in step 502, in step 503, a combination of antennas used for BF is determined from horizontal and vertical antennas as shown in FIG. This determination process will be described later. Further, a DL reference signal for the terminal to estimate the MIMO multiplexing number is generated from the combination of antennas used for the BF determined in step 503. The DL reference signal generation process will be described later.

  The DL reference signal setting information generated in step 504 is notified to the terminal 21 in step 505, and the DL reference signal is transmitted to the terminal 21 in step 506. Information notified to the terminal 21 in step 505 includes information such as resource allocation information of the DL reference signal, modulation scheme, and transmission timing. However, the information is not limited to this as long as the terminal 21 can identify the DL reference signal. Further, the DL reference signal transmitted to the terminal in step 506 may be transmitted only at this timing, or may be transmitted periodically.

  The terminal 21 that has received the DL reference signal estimates the MIMO spatial multiplexing number in step 507, and notifies the base station 20 in step 508. The spatial multiplexing number is a number that can be received by the terminal separately even if the base station 20 multiplexes and transmits different signals according to MIMO at the same time and frequency, and can be estimated from the radio propagation path. For example, the radio channel may be estimated from the DL reference signal and estimated from the Rank information of the channel matrix. However, the MIMO spatial multiplexing number estimation process is not limited to this as long as the multiplexing number is estimated from the DL reference signal. The notification process to the base station in step 508 may be performed only at this timing or periodically.

  The base station 20 simultaneously determines the antenna used for BF and the antenna used for MIMO multiplexing at step 509 from the combination of the MIMO multiplexing number notified at step 508 and the BF-capable antenna determined at step 503. Finally, DL data transmission is performed in step 510 using the antenna usage configuration determined in step 509.

  FIG. 6 is a diagram illustrating an example of a processing unit included in the base station 20. The plurality of processing units included in the base station 20 include a line interface 601, an upper layer control unit 602, a scheduling unit 603, a Downlink baseband processing unit 604, an Uplink baseband processing unit 605, a transmission RF (Radio Frequency) unit 606, and a reception RF. A unit 607, a switch 608, a controller 610, a BF possible pattern determination unit 611, a 3D MIMO determination unit 612, and a BF processing unit 613. The base station 20 includes an antenna 609. The antenna 609 is a device that transmits and receives a radio signal to communicate with the terminal 21 by radio waves, and has an antenna configuration as shown in FIG.

  The controller 610 is a processing unit that notifies processing timings to a plurality of processing units included in the base station 20 and inputs instructions according to predetermined setting values. When the base station 20 receives DL data from the backhaul 305, the line interface 601 receives the data. The upper layer control unit 602 receives data from the line interface 601 and performs header processing for communicating with the GW 202 on the received data. The scheduling unit 603 receives the header-processed data from the upper layer control unit 602.

  When the antenna 609 receives UL data, the switch 608 switches itself to a receiving switch. The reception RF unit 607 performs RF processing on the data input from the switch 608. The UL data subjected to the RF processing is processed by the Uplink baseband processing unit 605, and the information is transmitted to the scheduling unit 603, the BF possible pattern determination unit 611, and the upper layer control unit 602. The UL data received by the upper layer control unit 602 is transmitted to the backhaul 305 via the line interface 601.

  The BF possible pattern determination unit 611 receives the information of the UL reference signal transmitted in Step 501 of FIG. 5 from the Uplink baseband processing unit 605, estimates the moving speed of the terminal 21, and determines a combination of BF-capable antennas. To do. After determining the combination of antennas, information for generating a DL reference signal is transmitted to the upper layer control unit 602, and a request to generate a notification message to the terminal 21 is made. Upon receiving information for generating a DL reference signal from the BF possible pattern determining unit 611, the upper layer control unit 602 notifies the scheduling unit 603 of the information in order to transmit the DL reference signal to the terminal. Also, the BF possible pattern determination unit 611 notifies the 3D MIMO determination unit 612 of the determined antenna combination information.

  The 3D MIMO determination unit 612 receives the information on the MIMO multiplexing number notified in step 508 of FIG. 5 from the Uplink baseband processing unit 605 or the upper layer control unit 602, and receives the combination of antennas received from the BF possible pattern determination unit 611. Together with the information, the combination of the antenna that performs BF and the antenna that performs MIMO multiplexing is determined for each antenna. The determined BF antenna information is notified to the BF processing unit 613, and the BF processing unit 613 performs weight calculation for performing BF. The content of the weight calculation is a general technique of BF. For example, a weight calculation formula based on MMSE (Minimum Mean Square Error) may be used, or a different weight calculation formula for performing BF may be used.

  The scheduling unit 603 receives service information input from the higher layer control unit 602, information input from the reception RF unit 607, information input from the Uplink baseband processing unit 605, and input from the 3D MIMO determination unit 612. Based on the information, the base station 20 determines radio resources to be allocated to the DL 405 and UL 406 of the frame to be transmitted to the terminal 21, and the configuration of BF and MIMO transmission. The data input from the higher layer control unit 602 is transmitted to the terminal 21 by a frame to which radio resources are allocated. However, the information used by the scheduling unit 703 to allocate radio resources is not limited to the information as described above, and the scheduling unit 603 determines radio resource allocation using information input from other processing units. Also good.

  Thereafter, the Downlink baseband processing unit 604 performs encoding, modulation, and the like on the data input from the scheduling unit 603. Here, the Downlink baseband processing unit 604 performs BF processing by multiplying the MIMO-processed signal by the BF weight determined by the BF processing unit 613. Processing for applying a BF weight to a signal is also a general technique of BF.

  The transmission RF unit 606 performs RF processing on the data input from the Downlink baseband processing unit 604. When data is input from the transmission RF unit 606, the switch 608 switches itself to a transmission switch. When data is input from the switch 608, the antenna 609 transmits the input data from the antenna 609 by a radio signal.

  Each processing unit operates in accordance with a control signal from the controller 610 so as to perform the processing described above. Each processing unit illustrated in FIG. 6 may be implemented by software, or may be implemented by a physical device such as an integrated circuit. When the processing unit illustrated in FIG. 6 is implemented by software, software corresponding to the processing unit is executed by a processor included in the base station 20. When the base station 20 includes a physical transceiver and a network interface, the transmission RF unit 606, the reception RF unit 607, the switch 608, the antenna 609, the BF pattern determination unit 611, and the 3D MIMO determination unit are stored in the transceiver. May be. The line interface 601 may be stored in a network interface. The other processing units may be implemented as software.

  FIG. 7 is a diagram illustrating an example of a processing unit included in the BF possible pattern determination unit 611. The BF possible pattern determining unit 611 includes a moving speed estimating unit 701 that estimates the moving speed of the terminal, a BF antenna determining unit 702 that determines a combination of BF capable antennas, and a BF antenna reference table 704 that is referred to by the BF antenna determining unit. And a DL reference signal information generation unit 703 that determines a DL reference signal and generates related setting information.

  The moving speed estimation unit 701 receives information on the UL reference signal received from the Uplink baseband processing unit 605 or information on the moving speed transmitted from the upper layer control unit 602, and moves each terminal 21 in the horizontal and vertical directions. Estimate speed. The process of the moving speed estimation unit 701 corresponds to the process of step 502 in FIG. The BF antenna determining unit 702 determines the combination of antennas that can perform BF from the horizontal and vertical moving speeds determined by the moving speed estimating unit 701, and notifies the 3D MIMO determining unit 612 of the determined antenna combinations. To do. The process of the BF antenna determination unit 702 corresponds to the process of step 503 in FIG. Based on the antenna combination determined by the 3D MIMO determination unit 612, the DL reference signal information generation unit 703 determines DL reference signal information for spatial multiplexing, and provides information for notifying the terminal 21 of the information. Generate the information and notify the higher layer control unit 602 of the information. The process of the DL reference signal information generation unit 703 corresponds to the process of step 504 in FIG.

  FIG. 8 is a diagram illustrating an example of a processing flowchart of the moving speed estimation unit 701. The moving speed estimation unit 701 uses the UL reference signal information received from the Uplink baseband processing unit 605 to estimate the moving speed in the horizontal direction from the information in the horizontal antenna, and in the vertical direction from the information in the vertical antenna. Estimate the moving speed of. In step 801, the moving speed estimation unit 701 acquires horizontal UL reference signal information.

  The horizontal UL reference signal information indicates information of each antenna calculated from the UL reference signals received by the base station 20 using the horizontal antennas A1, A2, A3, and A4 as shown in FIG. 9A. . In the case of a 4 × 4 antenna configuration as shown in FIG. 9A, there are four combinations of antenna groups 901, 902, 903, and 904 in the horizontal direction. In step 801, information on any one or a plurality of antenna groups 901, 902, 903, and 904 in FIG. 9A is acquired.

In step 803, the moving speed in the horizontal direction is estimated from the acquired antenna group information. The UL reference signal information indicates UL propagation path information, and the moving speed estimation unit 701 collects the information for each antenna in the antenna group. For example, the antenna group 901 collects UL propagation path information of the antennas A1, A2, A3, and A4. The direction of arrival is estimated from the collected UL propagation path information. In this direction-of-arrival estimation, the direction of arrival can be estimated from the phase difference, wavelength, and antenna interval of UL propagation path information of each antenna. For example, in the case of a phase difference δ [rad], a wavelength λ [m], and an antenna interval d [m], the arrival direction θ can be obtained by the following equation.
θ = asin (λ (δ + 2πn) / 2πd)
Here, asin (x) is an inverse function of sin, and n is an arbitrary integer.

The estimated direction of arrival may be averaged between the antennas and calculated as the final direction of arrival. Further, it may be calculated as the final direction of arrival by averaging between antenna groups. In step 803, any process may be used as long as the direction of arrival is estimated. For example, MUSIC (Multiple Signal Classification) may be used. In step 803, the arrival direction estimation is performed as described above for a plurality of UL reference signal information separated by time intervals, and the rate of change V in the arrival direction per time is simply calculated by the following equation.
V = Δθ / T
Here, Δθ is the difference between the arrival direction value estimated last time and the arrival direction value estimated this time, and T is the reception interval of the UL reference signal. The change speed V may be obtained by averaging from a plurality of UL reference signal information. The change speed V calculated here is determined as the movement speed V in the estimated direction.

  In addition, the moving speed estimation unit 701 obtains UL reference signal information in the vertical direction in step 802. The UL reference signal information in the vertical direction indicates information on each antenna calculated from the UL reference signals received by the base station 20 with the antennas A1, B1, C1, and D1 in the vertical direction, as shown in FIG. 9B. . In the case of the 4 × 4 antenna configuration as shown in FIG. 9B, there are four combinations of antenna groups 901, 902, 903, and 904 in the vertical direction. In step 802, information on any one or a plurality of antenna groups 901, 902, 903, and 904 in FIG. 9B is acquired.

  In step 804, the moving speed in the vertical direction is estimated from the acquired antenna group information. The content of the moving speed estimation process is the same as the horizontal process in step 803 except that the information to be used is vertical antenna information. In order to estimate the moving speed in both the horizontal direction and the vertical direction, step 801 and step 802 may be executed simultaneously or may be executed based on some order.

  Although it has been described that the moving speed estimation unit 701 estimates the moving speed in the horizontal direction and the vertical direction, only the estimation in the horizontal direction may be performed in order to reduce the processing amount of the base station 20. In general, since the terminals 21 are distributed more widely in the horizontal direction than in the vertical direction, the moving speed in the horizontal direction is faster than in the vertical direction. For this reason, only the horizontal direction may be implemented with emphasis on the estimation accuracy in the horizontal direction. However, when the moving speed in the vertical direction is dominant, such as in the vicinity of an elevator in a high-rise building, only the estimation in the vertical direction may be performed.

  Thus, the direction in which the moving speed is estimated may be limited depending on the environment in which the base station 20 is installed. By limiting the estimated direction of the moving speed, the processing load on the base station 20 can be reduced. Further, in order to reduce the processing amount, the horizontal direction and the vertical direction may be simply estimated as the moving speed without being separated. In this case as well, the processing is advanced assuming that either the horizontal direction or the vertical direction is dominant.

  In addition, the moving speed estimation unit 701 has been described as estimating the moving speed by the arrival direction estimation as shown in FIG. 8, but as shown in FIG. 10, the arrival direction is not estimated directly but from the changing speed of the propagation path. The moving speed may be estimated. In step 1001, propagation path information is acquired from the upper layer control unit 602. For example, CQI (Channel Quality Indicator) information fed back from the terminal 21, SINR (Signal to Interference plus Noise Ratio) calculated from UL reference signal information, or the like may be used. The terminal 21 may be instructed to estimate the moving speed itself, and information fed back to the terminal 21 may be acquired from the upper layer control unit 602.

  In step 1002, the moving speed of the terminal 21 is estimated from the information acquired in step 1001. For example, when the CQI is acquired in step 1001, the CQI variance is calculated and the variance value is estimated as the moving speed. That is, when the moving speed is fast, the dispersion is large, and when the moving speed is slow, the dispersion is regarded as small. In such an example of processing, it may be impossible to distinguish the horizontal direction from the vertical direction. In that case, as described above, the movement of the terminal 21 may be estimated as a horizontal movement speed with a high probability in the horizontal direction. For example, the moving speed in the vertical direction may be zero.

  However, when the installation environment of the base station 21 is in the vicinity of an elevator of a high-rise building or the like and it is known in advance that the movement in the vertical direction is dominant, the movement speed may be estimated as the vertical direction. In addition, as long as the terminal 21 can measure GPS (Global Positioning System), another process such as estimating a moving speed based on position information by GPS may be used. The moving speed estimation unit 701 may operate every time a UL reference signal is received, or may operate at regular time intervals.

  FIG. 11 is a diagram illustrating an example of a process flowchart of the BF antenna determination unit 702. The BF antenna determining unit 702 determines a combination of BF-capable antennas from the moving speed information estimated by the moving speed estimating unit 701. In step 1101, the moving speed information estimated by the moving speed estimation unit 701 is acquired. The moving speed information to be acquired is a moving speed in the horizontal direction and / or a moving speed in the vertical direction.

  In step 1102, a combination of antennas capable of BF is determined from the acquired moving speed information by referring to the table. When the moving speed is high, the BF tracking characteristic deteriorates, so it is determined that BF cannot be performed for the antenna in the direction. When the moving speed is low, it is determined that BF can be performed in order to improve reception power by BF and reduce interference with adjacent cells. That is, when the moving speed in the horizontal direction or the vertical direction is slow, it is determined that BF is possible using antennas arranged in the same direction as the direction. When the moving speed in the horizontal direction or the vertical direction is high, it is determined that BF cannot be performed using the antennas arranged in the same direction as the direction. Further, in step 1102, the determination is made to increase the number of antennas that can be used for BF as the moving speed is low, and the determination is made to decrease the number of antennas that can be used for BF as the moving speed is high.

  FIG. 12 is a diagram showing an example of the BF antenna reference table 704 used in step 1102. In step 1102, an antenna capable of BF is determined by using the BF antenna reference table 704 based on the acquired moving speed information. In a column 1201, the moving speed V_v in the vertical direction is set to threshold values y1, y2,. . . The number of antennas that can be used in the vertical direction is set for each stage. Here, the number of antennas that can be used in the vertical direction is set to decrease as the moving speed V_v in the vertical direction increases. For example, when the vertical moving speed V_v is smaller than the smallest threshold value y1, all the antennas in the vertical direction can be used, and when the vertical moving speed V_v is equal to or higher than y1 and lower than y2, the number of vertical antennas BF can be used by using half of the number of antennas, and when the moving speed V_v in the vertical direction is equal to or larger than the threshold yM having the largest value, the number of antennas that cannot be BF in the vertical direction may be set to 1.

  That is, when the number N of antennas in the horizontal direction or the vertical direction is a power of 2, it may be divided into log 2 (N) stages. If it is determined that the speed is the slowest in such a way, BF is possible with all antennas, and the number of antennas may be halved as the speed increases by one step. When the number of antennas is not a power of 2, it may be reduced to 1/2, 1/3, or 1/4 each time the moving speed increases. In order to reduce the number of antennas, it is desirable to divide the antenna groups so that the number of antennas is the same. However, when the number of antennas cannot be divided, the antenna groups may be divided so that the difference in the number of antennas is minimized. For example, when the number of antennas N = 15, it is divided into 7 antennas and 8 antennas.

  Further, threshold values y1, y2,. . . The operator sets yM in advance. The same applies to the row 1202 of the moving speed V_h in the horizontal direction. From the comparison between the vertical movement speed V_v and each threshold value and the comparison between the horizontal movement speed V_h and each threshold value, the antenna fij1203 usable for the BF is specified as an element (table value) in the BF antenna reference table 704. . Here, i represents the i-th element in the vertical direction, j represents the j-th element in the horizontal direction, and f information includes the number of antennas and the antenna combinations that can be used for the BF as the antenna position. Shown in enumeration or bitmap of all antennas.

  For example, in the case of a 4 × 4 antenna configuration as shown in FIG. 3, there are two threshold values for the moving speed in the horizontal direction and the vertical direction, and the vertical moving speed V_v is If the horizontal movement speed V_h is the first stage, that is, the slowest state, BF is possible using all four antennas in the horizontal direction, but the vertical direction is somewhat lower. Since the moving speed is high, not all antennas can be used, and it is determined that two antennas can be used for BF. An example of this is shown in FIG. Since there are four antennas in the horizontal direction and two antennas in the vertical direction, f21 = (A1, A2, A3, A4, B1, B2, B3, B4), (C1, C2, C3) in the BF antenna reference table 704. C4, D1, D2, D3, D4), and constitutes antenna groups 1301, 1302.

  FIG. 14 shows an example of BF-capable antenna combinations when the antenna combinations are changed in three stages using a 4 × 4 antenna. The BF antenna reference table 704 is set based on, for example, combinations of BF-capable antennas shown in FIG. In FIG. 14, a 4 × 4 antenna is a combination of antennas, and an antenna surrounded by a black frame is a combination of antennas capable of BF. The antenna combination 1401 indicates that all the antennas can be used for BF because the moving speed is low in both the horizontal direction and the vertical direction. With the combination of antennas 1402, the horizontal movement speed is slightly faster, so using two antennas instead of using all horizontal antennas allows BF with a total of eight antennas, two horizontal antennas and four vertical antennas. It is shown that.

  In the antenna combination 1405, since the moving speed is slightly high in both the horizontal direction and the vertical direction, it is shown that BF is possible with a total of four antennas, two horizontal antennas and two vertical antennas. In the antenna combination 1409, since the moving speed in the vertical direction is high in the horizontal direction, there is no combination of antennas capable of BF. Here, when the moving speed estimation unit 701 estimates only the moving speed in the horizontal direction or the vertical direction, a part of the antenna combinations shown in FIG. 14 is selected from the moving speed. When only the horizontal moving speed is estimated, the vertical moving speed is not estimated, and therefore a combination of antennas is selected from the three horizontal sides in FIG.

  For example, when it is assumed that the moving speed in the vertical direction is slow, the antenna combination 1401, 1402, 1403 is selected. When it is assumed that the moving speed in the vertical direction is high, the antenna combination 1407, 1408, or 1409 is selected. If only the vertical movement speed is estimated, the same selection is made from the three in the vertical direction. Here, the moving speed in the direction not estimated may be a preset value or may be changed depending on the installation environment of the base station 20. Hereinafter, the combination of antennas determined by the BF antenna determination unit 702 is referred to as a BF antenna group. The BF antenna determination unit 702 may operate every time the estimated value from the moving speed estimation unit 701 is received or may operate periodically.

  FIG. 15 is a diagram illustrating an example of a processing flowchart of the DL reference signal information generation unit 703. DL reference signal information generation section 703 generates DL reference signal information from BF antenna group information received from BF antenna determination section 702 and antenna number information of terminal 21 for estimating the MIMO multiplexing number. In BF, the same signal is weighted and transmitted from different antennas, but in MIMO multiplexing, different signals are transmitted from different antennas to improve throughput. When performing MIMO multiplexing, the base station 20 needs to estimate whether or not the terminal 21 is in a reception environment that can demultiplex the multiplexed signals. The number of multiplexes that can be separated by the terminal 21 is called Rank. When estimating the Rank, the terminal 21 receives a reference signal from an antenna that transmits a different signal, and estimates whether or not separation is possible by signal processing.

  FIG. 16 shows an example of a DL reference signal when the terminal 21 has 4 antennas and up to 4 multiplexing is possible. Here, the multiplexed signal is called a stream. DL reference signal arrangements 1601 to 1604 shown in FIG. 16 indicate the arrangement of DL reference signals for each stream for an RB composed of 12 subcarriers and 14 symbols. The DL reference signal indicates, for example, LTE UE (User Equipment) Specific RS (Reference Signal). DL reference signal arrangements 1601 and 1602 transmit DL reference signals with the same subcarriers and symbols, but can be separated at terminal 21 because the transmission sequence is changed. DL reference signal arrangements 1601 and 1603 can be separated because they use different subcarriers and symbols. The Rank can be estimated by the terminal 21 receiving and processing these DL reference signals.

  However, as long as the terminal 21 can estimate the Rank, the DL reference signal may use different subcarriers and symbols for all streams, or use the same subcarriers and symbols, and use different sequences. May be. Further, the number of signal points used for the DL reference signal is 12 in FIG. 16, but may be more or less as long as it is 1 or more. Also, the DL reference signal may be set not in units of RBs but in units of multiple RBs. DL reference signal information generation section 703 determines the subcarrier, symbol, sequence, and antenna for transmitting each DL reference signal to be used as shown in FIG. 16 for each stream from the antenna configuration as shown in FIG. Notify the layer controller.

  The DL reference signal information generation unit 703 first acquires the antenna combination information fij determined by the BF antenna determination unit 702 in step 1501. Next, in step 1502, the number of antennas of the terminal 21 is acquired from the upper layer. Here, it is assumed that the number of antennas of the terminal 21 is notified to the base station 20 by the terminal 21 when the base station 20 and the terminal 21 are connected.

  In step 1503, DL reference signal setting information is determined based on the number of antennas of the terminal 21 and the combination information fij of BF-capable antennas. Here, it is assumed that the subcarrier position and symbol position of each stream of the DL reference signal are determined in advance as shown in FIG. For example, when the terminal 21 has two antennas, the DL reference signals of the streams 1 and 2 are used, and the DL reference signals of the streams 3 and 4 are not used. In the case of 4 antennas, DL reference signals of all streams are used.

  Next, it is determined which antenna is used to transmit the DL reference signal of each stream. In the combination of BF-capable antennas, each antenna group classified by the black frame in FIG. 14 may perform BF by transmitting the same signal from each antenna in the antenna group. Conversely, different signals are transmitted because BF is not performed between antenna groups. That is, since there is a possibility that different MIMO multiplexed streams may be transmitted between different antenna groups, the DL reference signals of different streams are set to be transmitted.

  On the other hand, different antennas within the antenna group are set to transmit the same DL reference signal because the same signal is transmitted by BF. However, when there are more antenna groups than the number of streams, for example, in the case of the antenna combinations 1406, 1408, and 1409 in FIG. 14, DL reference signals exceeding the number of streams cannot be transmitted. A signal is transmitted so that the DL reference signal has a maximum of 4 streams. For example, in the case of the antenna combination 1408, the same DL reference signal may be set to be transmitted with four horizontal antennas as shown in FIG. 17A, or the same DL reference signal may be transmitted with four square antennas. You may set as shown in FIG.17 (b) so that it may transmit.

  On the other hand, when the number of antenna groups is less than the number of streams, for example, in the case of the antenna combinations 1401, 1402, and 1404 in FIG. 14, the terminal 21 can perform the maximum number of streams for MIMO multiplexing. Set to send a reference signal. In that case, it sets so that the same DL reference signal may not be transmitted between several BF antenna groups. For example, in the case of the antenna combination 1402, it may be set as shown in FIG. 18A so that the same DL reference signal is transmitted with four vertical antennas, or the same DL reference signal is transmitted with four square antennas. In this way, the setting may be made as shown in FIG. When there are a plurality of combinations of antennas that transmit DL reference signals, which combination is selected may be set in advance or may be set at random.

  When BF is possible both in the horizontal direction and in the vertical direction as in the combination 1401 of antennas, it is better to perform BF using an antenna in the horizontal direction in consideration of the effect of reducing interference with adjacent cells. That is, it is preferable to select as shown in FIG. Also, assuming that the moving speed in the horizontal direction is more likely to change than in the vertical direction, the BF transmits the same signal as the DL reference signal using the vertical antenna so that the vertical antenna is preferentially used. You may set as follows. That is, it may be set as shown in FIG. Here, it is assumed that the setting is made in advance as in the example shown in FIG.

  In the example of FIG. 19, in order to suppress interference with adjacent cells, it is assumed that BF is performed using a horizontal antenna as much as possible. That is, in the case of an antenna combination 1401 capable of BF with all antennas, the same DL reference signal is set to be transmitted with the horizontal antenna as in the antenna combination 1901 so that BF can be performed using the horizontal antenna. Further, when the moving speed in the horizontal direction is fast and all the horizontal antennas cannot be used for the BF, the vertical antenna is used for the BF. That is, in the case of a combination 1408 of antennas, a DL reference signal is transmitted using a combination of two antennas in the horizontal direction and two antennas in the vertical direction as in the combination 1908 of antennas.

  Even in the case of a combination of antennas 1409 that cannot perform BF, there are cases where MIMO multiplexing is possible, so it is necessary to transmit DL reference signals for 4 streams. In that case, since only one antenna can be used for the BF in the horizontal direction, the antenna combination 1909 is set so that the same DL reference signal is transmitted in the vertical direction. Further, since the DL reference signal is a reference signal specific to the terminal 21, the subframe, frame, and frequency position (RB position) to be transmitted are designated, and the terminal 21 in the subframe, frame, and RB position A DL reference signal is received and Rank estimation is performed. Therefore, the base station 20 determines subframes, frames, and RB positions at which DL reference signals are transmitted simultaneously.

  Note that the number of RBs to be used is set in advance. The RB positions are assigned in the order of each terminal 21 from the smallest RB number. Also, subframe numbers and frame numbers are assigned to RB numbers in order from each terminal 21 in ascending order. Here, it is assumed that the allocation period is set in advance. Here, the number of RBs may be changed for each terminal 21. Further, the subframes, frames, and RB positions to be assigned may be randomly distributed rather than assigned in order if all the subcarriers, symbols, and sequences of the DL reference signal are set so as not to overlap.

  Hereinafter, the combination of antennas that transmit the same DL reference signal determined in step 1503 is referred to as an RS (Reference Signal) antenna group. The RS antenna group is configured so that the antennas in the RS antenna group span a plurality of BF antenna groups and each antenna in the BF antenna group is not set across a plurality of RS antenna groups. That is, a plurality of RS antenna groups exist in one BF antenna group, and antennas of different BF antenna groups are not used, or one RS antenna group includes a plurality of BF antenna groups, and the BF antenna In this state, the antennas of different RS antenna groups are not used. In addition to the above description, the BF antenna group and the RS antenna group may be the same antenna group.

  In step 1504, the DL reference signal setting information determined in step 1503 is notified to the upper layer control section 602. Since the DL reference signal is transmitted from the Downlink baseband processing unit 604, the setting information is necessary. Therefore, the upper layer control unit 602 notifies the information to the Downlink baseband processing unit 604 through the scheduling unit 603.

  In the terminal 21 that has received the DL reference signal, the Rank is estimated in Step 507 in FIG. 5, and the Rank information is fed back to the base station 20. The base station 20 that has received the Rank information notifies the 3D MIMO determination unit 612 of the information. Note that the DL reference signal generation unit 703 may operate every time information is received from the BF antenna determination unit 702, or may operate periodically.

  FIG. 20 is a diagram illustrating an example of a processing flowchart of the 3D MIMO determination unit 612. The 3D MIMO determination unit 612 determines the antenna used for BF and the antenna used for MIMO multiplexing from the BF antenna group information, the RS antenna group information, and the Rank information fed back from the terminal 21 notified from the BF possible pattern determination unit 611. decide. In step 2001, BF antenna group information, RS antenna group information, and Rank information are acquired. Here, G is the total number of RS antenna groups.

  MIMO multiplexing multiplexes the number of rank (R) streams. That is, the MIMO multiplexing number = R. When R <G, it is necessary to transmit signals of the same stream between a plurality of RS antenna groups. For this reason, first, in step 2002, the floor (G / R) RS antenna groups are grouped as one group, and RG mod (R) groups are generated. Here, floor (x) is a function that returns the maximum integer that does not exceed x, and x mod (y) is a function that returns the remainder when x is divided by y. Further, for the remaining RS antenna groups, in step 2003, floor (G / R) +1 RS antenna groups are grouped into one group, and G mod (R) groups are generated.

  Here, when grouping, it groups by adjacent RS antenna group. That is, RS antenna groups are grouped into a total of R so that the difference in the number of antenna groups to be integrated becomes 1. However, when RS antenna groups are grouped, the BF antenna groups that are different from each other should not be crossed as much as possible. For example, when the BF antenna group is an antenna combination 1402, the RS antenna group is an antenna combination 1902, and R = 2, two RS antenna groups are grouped into one. In this case, either one of the two types of FIG. 21A or FIG. 21B is used, but in FIG. 21A, the BF antenna group shown in the antenna combination 1402 is straddled. (B).

  Similarly, FIG. 21C shows the case of R = 3, and FIG. 21D shows the case of R = 1. In the case of FIG. 21C, the position where two RS antenna groups are grouped may be determined in advance or may be set at random. Although the number of ranks of streams is multiplexed here, the reported number of ranks may not match the number of streams to be multiplexed. For example, when it is determined that the BLER (Block Error Rate) is high when multiplexing is performed with the reported number of Ranks, the BLER can be decreased by reducing the number of stream multiplexing. Conversely, when it is determined that the BLER is low, the throughput can be improved by increasing the number of multiplexed streams.

  If signals of the same MIMO stream are transmitted within an antenna obtained by grouping the RS antenna groups determined in steps 2002 and 2003, the determination is made in step 2004. That is, in the case of FIG. 21 (c), stream 1 is transmitted in A1, B1, C1, and D1, stream 2 is transmitted in A2, B2, C2, and D2, and A3, A4, B3, B4, C3, C4, Stream 3 is transmitted in D3 and D4.

  In step 2005, it is determined that BF is performed using the antennas of the determined BF antenna group in the antenna group that transmits the signal of the same stream determined in step 2004. When it is determined in step 2004 as shown in FIG. 21C, BF cannot be performed between antennas that transmit signals of different streams in step 2005. Therefore, the black frame of the antenna combination 1402 in FIG. Again, the antenna to be BF is determined as shown by the dotted line in FIG. In other words, stream 1 is BF with A1, B1, C1, and D1, stream 2 is BF with A2, B2, C2, and D2, and stream 3 is BF with A3, A4, B3, B4, C3, C4, D3, and D4. To do.

  Similarly, when it is determined in step 2004 as shown in FIG. 21 (d), the stream 1 is BF with A1, A2, B1, B2, C1, C2, D1, D2 as shown by the dotted line in FIG. 22 (b). , A3, A4, B3, B4, C3, C4, D3, and D4 are BF. That is, for example, when performing BF using a horizontal antenna, MIMO multiplexing is performed in the vertical direction, and when performing BF using a vertical antenna, MIMO multiplexing is performed in the horizontal direction. When R = G, a stream may be allocated to each RS antenna group.

  The base station 20 notifies the BF processing unit 613 of the information to generate the BF weight from the UL reference signal using the combination information of the antenna that performs the BF determined in Step 2005. Also, the information on the MIMO multiplexing number determined in step 2004 is notified to the scheduling unit 603 and used for scheduling of radio resources.

  As described above, according to the first embodiment, the direction and the number of antennas to be BF are changed according to the moving speeds in the horizontal direction and the vertical direction, and further, MIMO multiplexing according to the BF is performed, thereby moving the terminal. It is possible to improve the throughput by MIMO multiplexing while performing suitable BF.

  Hereinafter, Example 2 will be described with reference to the drawings. In the second embodiment, DL data transmission in the case of BF in the horizontal direction and DL data transmission in the case of BF in the vertical direction are both performed at different times or at different frequencies, and a horizontal or vertical antenna with high throughput is given priority. Appropriate 3D MIMO is performed by repeating the operation of selecting the above.

  FIG. 23 shows an example of a processing sequence of the second embodiment. First, in step 2302, the moving speed is temporarily estimated. The temporarily estimated moving speed is the same as the value estimated in step 502 of FIG. 5, but an arbitrary value is given instead of calculation based on the UL reference signal. The arbitrary value given here may be a preset value or a random value. Steps 2303 to 2310 determine 3D MIMO processing in the same manner as steps 503 to 510 in FIG.

  In step 2311, the throughput when DL data is transmitted in the determined 3D MIMO transmission process is measured. The throughput measured here is used in step 2312 to determine which is superior to the 3D MIMO transmission process when different moving speeds are estimated. In step 2312, 3D MIMO transmission using a moving speed different from the moving speed (pattern 1) used up to step 2311 is attempted. The moving speed used here is selected so that one or both of the moving speeds in the horizontal direction and the vertical direction are different from those in pattern 1 and the combination of antennas capable of BF is different from pattern 1.

  For example, if it is determined that the moving speed is such that the BF antenna group of the antenna combination 1405 shown in FIG. 14 is selected in pattern 1, the antenna moving speed is compared with the case where the horizontal moving speed is slower than pattern 1. Select a combination 1404, select an antenna combination 1406 to compare with the case where the horizontal movement speed is faster than pattern 1, or select an antenna combination to compare with the case where the vertical movement speed is slower than pattern 1. Either the combination 1402 is selected, or the antenna combination 1408 is selected for comparison with the case where the moving speed in the vertical direction is faster than the pattern 1.

  After transmission with two different BF antenna groups, the throughput is compared in step 2313, and the moving speed with the higher throughput is selected. For the selected moving speed, 3D MIMO transmission using different moving speeds is attempted based on the selected moving speed in the same manner as in Step 2312. Hereinafter, this operation is repeated and updated to a suitable 3D MIMO transmission process.

  Here, the step 2312 of trying the new moving speed may be performed periodically, or is performed when it is determined that the wireless quality is deteriorated, such as when the result of the throughput measurement 2311 falls below a predetermined threshold. May be. Until step 2312 is performed, 3D MIMO may be executed from the UL reference signal using the transmission processing of 3D MIMO determined so far. Further, the moving speed to be compared may be two or more patterns. Furthermore, although the movement speed patterns to be compared are executed at different times in FIG. 23, they may be executed using different frequencies. For example, pattern 1 may be executed by using half of RB and pattern 2 by using half of RB, and may be compared.

  According to the second embodiment, the UL reference signal for estimating the moving speed becomes unnecessary. In addition, even when there is an error in the moving speed estimation itself, it is possible to select a BF antenna group corresponding to a different moving speed, and thus it is highly possible that a suitable 3D MIMO transmission process can be selected.

  Hereinafter, Example 3 will be described with reference to the drawings. In the third embodiment, the BF antenna group is formed when the antenna elements are not uniformly arranged such as a square or a rectangle. Since the antenna configuration is different from that of the first embodiment, the antenna grouping process is different from that of the first embodiment.

  FIG. 24 shows an example of the antenna configuration of the third embodiment. In the example of FIG. 24, the antenna elements are not arranged in a lattice pattern but are unevenly arranged. This occurs, for example, when each antenna element 2401 is not a manufacturing process in which the antenna elements 2401 are arranged in advance on a certain plane, but when each antenna element is individually generated and later arranged according to the installation requirements of the antenna. . In such a case, the antennas are not necessarily arranged in a lattice shape, and thus may be non-uniform as shown in FIG. Moreover, although the example shown in FIG. 24 is on a plane, it may be arranged in a curved shape.

  The configuration of the BF possible pattern determination unit 611 is the same as that in FIG. 7, but the processing is different in the following points. In the movement speed estimation when arranged as shown in FIG. 24, since antenna elements are not arranged strictly in the horizontal direction and the vertical direction, antenna elements having a small horizontal spread and antenna elements having a small vertical spread are used. Are grouped to estimate the moving speed. The movement speed estimation unit 701 first groups the antenna elements in the horizontal direction as shown in FIG. 25 in order to estimate the movement speed in the horizontal direction and the vertical direction. Here, an example of dividing into four as shown by a dotted line is shown. The surface on which the antenna elements are arranged is divided into N parts in the vertical direction, and the antenna elements included in the divided parts are grouped. The number of divisions N is set in advance, and how to divide may be set in advance, or may be changed depending on the location where the antenna is installed. For example, in the case of FIG. 25, each antenna element 2501 indicated by A, each antenna element 2502 indicated by B, each antenna element 2503 indicated by C, and each antenna element 2504 indicated by D are grouped. Using these antenna elements, the moving speed in the horizontal direction is estimated in the same manner as in the first embodiment. Similarly, they are grouped in the vertical direction as shown in FIG. Here, an example of dividing into four as shown by a dotted line is shown. The surface on which the antenna elements are arranged is divided into M parts in the horizontal direction, and the antenna elements included in the divided parts are grouped. The division number M is set in advance, and how to divide may be set in advance, or may be changed depending on the place where the antenna is installed. For example, in the case of FIG. 26, each antenna element 2601 indicated by 1, each antenna element 2602 indicated by 2, each antenna element 2603 indicated by 3, and each antenna element 2604 indicated by 4 are grouped. Using these antenna elements, the moving speed in the vertical direction is estimated as in the first embodiment. However, the antenna element may be divided not by a straight line as shown by dotted lines in FIGS. 25 and 26 but by a curved line.

  The antenna division used for the setting of the BF antenna group and the antenna element used for the setting of the RS antenna group uses the antenna division described above with reference to FIGS. For example, in the case of division as shown in FIGS. 25 and 26, these are integrated and divided as shown in FIG. That is, it is divided into four parts A, B, C, and D in the vertical direction and four parts 1, 2, 3, and 4 in the horizontal direction. Such division may be defined in the BF antenna reference table 704. For the antennas thus divided, a BF antenna group and an RS antenna group are determined in the same manner as in the first embodiment, and a 3D MIMO transmission process is determined.

  As described above, according to the third embodiment, it is possible to select an appropriate 3D MIMO transmission process even in an environment in which it is difficult to uniformly arrange antennas.

20 base station 21 terminal 22 cell 611 BF possible pattern determining unit 612 3D MIMO determining unit 701 moving speed determining unit 702 BF antenna determining unit 703 DL reference signal information generating unit 704 BF antenna reference table

Claims (15)

A base station comprising a plurality of antennas and communicating with a terminal,
A moving speed estimator for estimating a moving speed in a horizontal direction and / or a vertical direction of the terminal;
A BF antenna determining unit that determines a combination of antennas that perform BF (beamforming) based on the estimated moving speed from the plurality of antennas;
A base station characterized by comprising: The base station comprises a plurality of antennas in the horizontal direction as the plurality of antennas,
The BF antenna determining unit determines a smaller number of horizontal antennas for performing BF as the estimated horizontal moving speed is faster, and as the estimated horizontal moving speed is slower, the BF antenna determining unit determines the horizontal direction for performing BF. The base station according to claim 1, wherein a large number of antennas are determined. The base station further comprises a plurality of antennas in the vertical direction as the plurality of antennas,
The BF antenna determination unit determines a smaller number of vertical antennas for performing BF as the estimated vertical movement speed is faster, and as the estimated vertical movement speed is slower, the BF antenna determination unit determines the vertical direction for performing BF. The base station according to claim 2, wherein a large number of antennas are determined. The base station further includes a table of the number of antennas for performing BF according to a combination of moving speeds in the horizontal direction and the vertical direction,
The base station according to claim 3, wherein the BF antenna determining unit determines the number of antennas with reference to the table based on the estimated combination of the moving speeds in the horizontal direction and the vertical direction. The base station further includes a 3D MIMO determination unit,
The BF antenna determination unit divides the plurality of antennas into antenna groups each performing BF,
The base station according to claim 4, wherein the 3D MIMO determination unit allocates a MIMO stream to each of the antenna groups when the number of MIMO multiplexing and the number of antenna groups are the same. The base station further includes a 3D MIMO determination unit,
The BF antenna determination unit divides the plurality of antennas into antenna groups each performing BF,
The base station according to claim 5, wherein the 3D MIMO determination unit allocates one MIMO stream to a plurality of the antenna groups when the number of antenna groups is larger than the number of MIMO multiplexing. The moving speed estimation unit estimates a plurality of moving speeds,
The 3D MIMO determination unit measures communication throughput between the base station and the terminal by a combination of antennas that perform BF for the plurality of estimated moving speeds, and uses a combination of antennas that perform BF with the highest throughput. The base station according to claim 5 or 6, wherein a MIMO stream is allocated. The base station comprises a plurality of antennas in the horizontal direction and / or vertical direction as the plurality of antennas,
The moving speed estimation unit estimates a moving speed in a horizontal direction or a vertical direction based on an interval between two antennas in a horizontal direction or a vertical direction and a phase difference between signals received by the respective antennas. The base station according to 1. The base station according to claim 1, wherein the plurality of antennas are arranged in a grid pattern in a horizontal direction and a vertical direction. The plurality of antennas are non-uniformly arranged in a horizontal direction and a vertical direction,
The base station according to claim 1, wherein the BF antenna determination unit divides the plurality of non-uniformly arranged antennas in a horizontal direction and a vertical direction in a pseudo manner. A control method of a base station that comprises a plurality of antennas and communicates with a terminal,
Estimating the horizontal and / or vertical movement speed of the terminal;
Determining a combination of antennas that perform BF (beamforming) based on the estimated moving speed from the plurality of antennas;
A control method for a base station, comprising: The base station comprises a plurality of antennas in the horizontal direction as the plurality of antennas,
The determining step determines a smaller number of horizontal antennas for performing BF as the estimated horizontal movement speed is faster, and determines a horizontal antenna for performing BF as the estimated horizontal movement speed is slower. The base station control method according to claim 11, wherein a large number is determined. The base station further comprises a plurality of antennas in the vertical direction as the plurality of antennas,
In the determining step, the faster the estimated vertical movement speed is, the smaller the number of vertical antennas for performing BF is. The slower the estimated vertical movement speed is, the lower the vertical antenna for performing BF is. The base station control method according to claim 12, wherein a large number is determined. Dividing the plurality of antennas into antenna groups each performing BF;
Allocating a MIMO stream to each of the antenna groups when the number of MIMO multiplexing and the number of antenna groups are the same;
The base station control method according to claim 13, further comprising: A wireless communication system in which a terminal and a base station communicate wirelessly,
The terminal moves horizontally and / or vertically,
The base station
Multiple antennas,
A moving speed estimator for estimating a moving speed in a horizontal direction and / or a vertical direction of the terminal;
A BF antenna determining unit that determines a combination of antennas that perform BF (beamforming) based on the estimated moving speed from the plurality of antennas;
A wireless communication system comprising:

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