Beam determination method

Abstract

Provided is a technique with which communication can be carried out between a base station and a terminal in a wireless communication system that includes a reflection plate together with the base station and the terminal. A beam determination method according to one aspect of the present disclosure in which, for a wireless communication system in which a base station and a terminal communicate with each other by using a plurality of subarrays and along a path in a direct wave direction and / or a path via a reflection plate, carried out are: a first process for allocating a subarray from among the plurality of subarrays to the path in the direct wave direction or the path via the reflection plate; a second process for selecting, on the basis of the power received from candidate beams formed by said subarray, an intermediate beam formed by the subarray; a third process for measuring the communication quality level of the intermediate beam; and a fourth process for, as a result of the first process, the second process, and the third process being carried out at least once for each among the plurality of subarrays, determining, on the basis of the plurality of communication quality levels, a plurality of final beams respectively formed by the plurality of subarrays from the plurality of intermediate beams.

Description

Beam determination method

[0001] The present disclosure relates to a beam determination method.

[0002] For NR (New Radio) (also called "5G"), the successor system to LTE (Long Term Evolution), technologies are being considered that meet the requirements of a large-capacity system, high-speed data transmission speed, low latency, simultaneous connection of a large number of terminals, low cost, low power consumption, etc. (see, for example, Non-Patent Document 1).

[0003] As a technology for realizing ultra-wideband transmission in high frequency bands, there is Massive MIMO technology, which expands the MIMO (Multiple-Input Multiple-Output) technology, which was originally intended to use several tens of antenna elements, to, for example, several hundred to several thousand antenna elements. MIMO technology is a technology in which a base station (also referred to as BS (Base Station)) and a terminal (also referred to as MS (Mobile Station)) each use multiple antenna elements to perform spatial multiplexing, thereby increasing the communication capacity.

[0004] High-frequency bands have radio wave characteristics that are more susceptible to attenuation and diffraction than low-frequency bands, so reception quality is significantly degraded in high-frequency bands due to short transmission distances and obstructions.

[0005] In order to compensate for radio wave attenuation, beamforming (BF) using multiple antenna elements as described above in the base station and terminal is effective. For example, a base station using massive MIMO forms a beam that increases the received power in a specific direction by beamforming using multiple antenna elements. By compensating for radio wave attenuation using beamforming gain, the transmission distance can be extended.

[0006] When transmitting a signal using beamforming, a base station or a terminal selects a beam to be applied to data communication from among multiple candidate beams, for example by performing beam search, so that the reception quality at the communication partner side is good. For example, the base station applies multiple predetermined beam candidates to downlink reference signals (e.g., SSBs (Synchronization Signal Blocks)) and transmits them. The terminal reports the received power for each beam measured based on the received downlink reference signals to the base station. Then, the base station determines a beam to be applied to the terminal based on the received power from each terminal.

[0007] Furthermore, as a technique for reducing the amount of calculation required for MIMO signal processing when MIMO is performed using a massively multi-element antenna, a method called hybrid beamforming is used in which part of the MIMO signal processing is performed by an analog circuit.

[0008] In order to improve the deterioration of reception quality due to obstructions or non-line-of-sight, a method of installing a large number of transmission points is available. From the viewpoint of installing a large number of transmission points, it is also effective to use reflectors, which have small installation scale and restrictions. The reflectors may be intentionally installed or may be objects that are not intentionally installed, such as ordinary buildings or natural objects.

[0009] In recent years, a reflector capable of controlling directivity by dynamically controlling the reflection direction using a metamaterial / metasurface (RIS: Reconfigurable Intelligent Surface) has been developed (see, for example, Patent Document 1).

[0010] Japanese Patent Application Laid-Open No. 2021-141359

[0011] It is conceivable to install a RIS in order to avoid obstructions or to form multiple paths to reduce spatial correlation and improve MIMO capacity. By installing a RIS in this way, even when beamforming is performed between a base station and a terminal, multiple different propagation paths (hereinafter simply referred to as paths) can be formed. The base station and terminal can realize spatial multiplexing by performing transmission and reception signal processing while understanding the status of each path.

[0012] However, there is room for further study on spatial multiplexing using paths via RIS.

[0013] An object of one aspect of the present disclosure is to provide a technology that enables a base station and a terminal to communicate appropriately in a wireless communication system that includes a reflector as well as the base station and the terminal.

[0014] A beam determination method according to one aspect of the present disclosure, in a wireless communication system in which a base station and a terminal communicate using multiple subarrays via a path in the direct wave direction and / or a path via a reflector, performs a first process of assigning a subarray from among the multiple subarrays to the path in the direct wave direction or the path via the reflector, performs a second process of selecting an intermediate beam formed by the subarray based on the received power of a candidate beam formed by the subarray, performs a third process of measuring the communication quality of the intermediate beam, and performs a fourth process of determining each of multiple final beams formed by the multiple subarrays from the multiple intermediate beams based on the multiple communication qualities by performing the first process, the second process, and the third process at least once for each of the multiple subarrays.

[0015] According to one aspect of the present disclosure, in a wireless communication system including a reflector as well as a base station and a terminal, the base station and the terminal can communicate appropriately.

[0016] 1 is a diagram illustrating an example of a wireless communication system according to a first embodiment of the present disclosure. FIG. 1 is a block diagram illustrating an example of an antenna configuration of a base station according to the first embodiment. FIG. 2 is a block diagram illustrating an example of an antenna configuration of a terminal according to the first embodiment. FIG. 3 is a block diagram illustrating an example of a configuration of a reflector according to the first embodiment. FIG. 4 is a block diagram illustrating an example of a configuration of a base station according to the first embodiment. FIG. 5 is a block diagram illustrating an example of a functional configuration of a base station according to the first embodiment. FIG. 6 is a block diagram illustrating an example of a configuration of a terminal according to the first embodiment. FIG. 7 is a block diagram illustrating an example of a functional configuration of a terminal according to the first embodiment. FIG. 8 is a diagram illustrating a first example of beam searching and beam forming according to the first embodiment. FIG. 9 is a diagram illustrating a second example of beam searching and beam forming according to the first embodiment. FIG. 10 is a flowchart illustrating a first operation example of a wireless communication system according to the first embodiment. FIG. 11 is a flowchart illustrating a second operation example of a wireless communication system according to the first embodiment. FIG. 12 is a flowchart illustrating a second operation example of a wireless communication system according to the first embodiment. FIG. 13 is a diagram illustrating conditions for a simulation example using the technology according to the first embodiment. FIG. 14 is a diagram illustrating a result of a simulation example using the technology according to the first embodiment. FIG. 15 is a diagram illustrating an example of a change in the number of beams allocation according to the second embodiment. FIG. 16 is a block diagram illustrating an example of a functional configuration of a base station according to the second embodiment. FIG. 17 is a flowchart illustrating an operation example of a wireless communication system according to the second embodiment. FIG. 10 is a diagram showing the results of a simulation example using the technology according to embodiment 2. FIG. 11 is a diagram showing an example of the hardware configuration of a base station and a terminal according to an embodiment. FIG. 12 is a diagram showing an example of the configuration of a vehicle according to an embodiment. FIG. 13 is a diagram showing an example of spatial multiplexing using a path that goes through a reflector. FIG. 14 is a diagram showing an example of spatial multiplexing using a path that does not go through a reflector.

[0017] (Background to the present disclosure) By installing a RIS as described above, even when beamforming is performed between a base station and a terminal, multiple different paths can be formed, and the base station and the terminal can realize spatial multiplexing. Figure 23 is a diagram showing an example of spatial multiplexing using paths via a RIS, in which a subarray #1 provided in the base station and a subarray #1 provided in the terminal form a path of a direct wave (or LOS (loss of sight)) (i.e., a path that does not pass through the RIS), and a subarray #2 provided in the base station and a subarray #2 provided in the terminal form a path that passes through the RIS.

[0018] However, since the terminal position is unknown to the base station, as described above, it is necessary to perform analog beam search in each subarray. In beam search, the base station generally searches for a beam that maximizes the terminal's received power (i.e., performs beam search based on the terminal received power maximization criterion). In this case, since the path via the RIS has a larger propagation loss than the direct wave path, the direct wave path is selected during beam search, and even if the RIS is installed, it is highly likely that the RIS cannot actually be used (i.e., the path shown in Figure 23 is not formed). Figure 24 is a diagram showing an example of spatial multiplexing using a path that does not go through the RIS, in which a direct wave path is formed by the subarray #1 provided in the base station and the subarray #1 provided in the terminal, and a direct wave path is formed by the subarray #2 provided in the base station and the subarray #2 provided in the terminal. Figure 24 shows a case where the RIS cannot actually be used even if it is installed.

[0019] The present inventors have come up with a technology for selecting a path via a RIS even when performing a beam search based on the terminal received power maximization criterion. This technology will be described in detail in the following first embodiment.

[0020] Furthermore, even when spatial multiplexing is achieved using the above technology with a path that passes through a reflector, changing the allocation of beams or the number of beams depending on the situation may improve the MIMO capacity effect.

[0021] The present inventors have conceived a technology for adaptively changing the allocation of beams or the number of beams between direct waves and waves that pass through a reflector depending on the situation. This technology will be described in detail in the following second embodiment.

[0022] By using the techniques according to the first and second embodiments, it becomes possible for a base station and a terminal to communicate appropriately in a wireless communication system that includes a reflector as well as the base station and the terminal.

[0023] Hereinafter, an embodiment according to one aspect of the present disclosure will be described with reference to the drawings. Note that the embodiment described below is an example, and the embodiment to which the present disclosure is applied is not limited to the following embodiment.

[0024] (First Embodiment) <Wireless Communication System> Fig. 1 is a diagram illustrating an example of a wireless communication system according to a first embodiment of the present disclosure. As illustrated in Fig. 1, the wireless communication system 1 includes a base station (BS) 10, a terminal (MS) 20, and a directivity-controllable reflector (RIS) 30. While Fig. 1 illustrates one BS 10, one MS 20, and one RIS 30, this is merely an example, and multiple BSs, multiple MSs, and / or multiple RISs may exist. Note that, in this embodiment, the reflector is described as being the RIS, but as described above, the reflector may be an intentionally installed object, or may be an object that is not intentionally installed, such as an ordinary building or natural object.

[0025] The BS 10 is a communication device that provides one or more cells and performs wireless communication with the MS 20. The physical resources of a wireless signal are defined in the time domain and the frequency domain. The time domain may be defined by the number of Orthogonal Frequency Division Multiplexing (OFDM) symbols. The frequency domain may be defined by the number of subcarriers or the number of resource blocks.

[0026] The BS 10 transmits DL signals such as control information, configuration information, and data to the MS 20 via a downlink (DL). The BS 10 receives UL signals such as control information, information related to the processing capability of the MS 20 (capability information: UE capability), and data from the MS 20 via an uplink (UL).

[0027] The MS 20 is a communication device equipped with a wireless communication function, such as a smartphone, a mobile phone, a tablet, a wearable device, an M2M (Machine-to-Machine) communication module, etc. The MS 20 wirelessly connects to the BS 10 and uses various communication services provided by the wireless communication system 1.

[0028] The MS 20 receives DL signals such as control signals, setting information, and data from the BS 10 via the DL, and transmits UL signals such as control signals, capability information of the MS 20, and data to the BS 10 via the UL.

[0029] Here, both the BS 10 and the MS 20 can transmit and receive signals by performing beamforming. The BS 10 may be equipped with multiple antenna elements and may use massive MIMO technology to enable high-speed transmission over a wide area even in high frequency bands. The MS 20 may also be equipped with multiple antenna elements and may use massive MIMO technology.

[0030] 2 and 3 are block diagrams showing examples of antenna configurations of the BS 10 and the MS 20 according to the first embodiment, respectively.

[0031] The BS 10 is equipped with an array antenna, and as shown in FIG. 2, the array antenna is divided into a plurality of sub-arrays 11. １ ~11 Ｘ Similarly, the MS 20 may also have an array antenna, and as shown in FIG. 3, the array antenna may be divided into a plurality of sub-arrays 21. １ ~21 Ｙ (Y is an integer of 2 or more). １ ~11 Ｘ may be distributed so that distributed MIMO is applied.

[0032] The BS 10 performs beam search to transmit a signal to the MS 20 using an appropriate beam. For example, the BS 10 transmits signals (such as a synchronization signal, a reference signal, or a synchronization signal block (SSB), referred to as measurement signals) from a subarray using multiple beams (candidate beams) using predetermined radio resources. The MS 20 then receives the measurement signals transmitted from the BS 10 using multiple beams in the subarray, measures the received power (e.g., Reference Signal Received Power (RSRP)) for each measurement signal associated with the candidate beam, and reports (transmits) the measurement results of the received power to the BS 10.

[0033] Note that here (and below), it is assumed that the received power of the beam (measurement signal) transmitted from BS10 is reported from MS20 to BS10, but this is not limited to this, and any indicator that can identify the received strength or reception state of the beam, communication performance or communication quality, such as SNR (Signal-to-Noise Ratio) or throughput, may be used.

[0034] In the first embodiment, the duplex method may be a time division duplex (TDD) method or a frequency division duplex (FDD) method.

[0035] The RIS 30 is a metasurface reflector composed of multiple reflecting elements, and by adjusting the reflection phase of each reflecting element, it forms a reflection pattern with any direction and beam width. The RIS 30 relays wireless signals (from the BS 10 to the MS 20) without decoding user data.

[0036] It should be noted that a wireless repeater that can amplify received signals (and further convert the frequency as necessary) and output them, and that can form beams in any direction and with any beam width using multiple antennas, may be used instead of the RIS 30. The RIS 30 and the wireless repeater may also be referred to as relay devices or the like.

[0037] 4 is a block diagram showing an example of the configuration of the RIS 30 according to the first embodiment. As shown in FIG. 4, the RIS 30 includes one or more RIS 30 １ ~30 Ｚ (Z is an integer of 1 or more). １ (i.e., when Z is 1), RIS30 and RIS30 １ may refer to the same RIS.

[0038] Next, the configurations of the BS 10 and the MS 20 will be described. Note that the configurations of the BS 10 and the MS 20 described below are examples of functions related to the embodiments. The BS 10 and the MS 20 may have functions not shown. Furthermore, the functional divisions and / or names of the functional units are not limited as long as the functions perform the operations related to the embodiments. Furthermore, in the BS 10 and / or the MS 20 described below with reference to Figures 6 and 8, multiple functional units may be integrated into one functional unit, or one functional unit may be divided into multiple functional units.

[0039] 5 is a block diagram showing an example of the configuration of the BS 10 according to embodiment 1. The BS 10 includes, for example, a transmitting unit 101, a receiving unit 102, and a control unit 103.

[0040] The transmitting unit 101 transmits a DL signal to the MS 20. For example, the transmitting unit 101 transmits the DL signal under the control of the control unit 103.

[0041] The DL signal may include, for example, a downlink data signal and control information (e.g., DCI (Downlink Control Information)). The DL signal may also include information indicating scheduling related to signal transmission of the MS 20 (e.g., an UL grant). The DL signal may also include control information of higher layers (e.g., control information of RRC (Radio Resource Control)). The DL signal may also include a reference signal.

[0042] The channels used for transmitting DL signals include, for example, a data channel and a control channel. For example, the data channel may include a PDSCH (Physical Downlink Shared Channel), and the control channel may include a PDCCH (Physical Downlink Control Channel). For example, the BS 10 transmits control information to the MS 20 using the PDCCH and transmits data signals using the PDSCH.

[0043] The reference signal included in the DL signal may include at least one of, for example, a Demodulation Reference Signal (DMRS), a Phase Tracking Reference Signal (PTRS), a Channel State Information-Reference Signal (CSI-RS), a Sounding Reference Signal (SRS), and a Positioning Reference Signal (PRS) for position information. For example, reference signals such as the DMRS and PTRS are used for demodulating downlink data signals and are transmitted using the PDSCH.

[0044] The receiving unit 102 receives the UL signal transmitted from the MS 20. For example, the receiving unit 102 receives the UL signal under the control of the control unit 103.

[0045] The transmitter 101 and receiver 102 (which may be collectively referred to as a communication unit) communicate with the MS 20 .

[0046] The control unit 103 controls the overall operation of the BS 10 including the transmission process of the transmission unit 101 and the reception process of the reception unit 102, as well as the communication operation of the BS 10.

[0047] For example, the control unit 103 acquires information such as data and control information from the upper layer and outputs it to the transmitting unit 101. The control unit 103 also outputs the data, control information, etc. received from the receiving unit 102 to the upper layer.

[0048] For example, the control unit 103 allocates resources (or channels) used for transmitting and receiving DL signals and / or resources used for transmitting and receiving UL signals based on a signal (e.g., data and control information, etc.) received from the MS 20 and / or data and control information, etc. acquired from a higher layer. Information on the allocated resources may be included in control information transmitted to the MS 20.

[0049] Note that the channel used for transmitting the DL signal is not limited to the above example. For example, the channel used for transmitting the DL signal may include a Random Access Channel (RACH) and a Physical Broadcast Channel (PBCH). The RACH may be used to transmit DCI including a Random Access Radio Network Temporary Identifier (RA-RNTI), for example.

[0050] 6 is a block diagram showing an example of the functional configuration of the BS 10 according to embodiment 1. The BS 10 (e.g., the control unit 103) includes, for example, a beam search unit 131, a beam forming unit 132, and a reflector position estimation unit 133.

[0051] The BS 10 transmits measurement signals to the MS 20 using multiple beams and receives measurement results of the received power of the measurement signals from the MS 20. Based on the measurement results of the received power, the BS 10 combines the beams of its subarrays in space to suppress or cancel the direct wave direction (toward the MS) or the direct wave signal so that the MS 20 cannot see at least the direct wave transmitted by the BS 10 (this may also be referred to as "directing a null in the direct wave direction," "nulling the direct wave," "forming a null beam in the direct wave direction," etc.). The BS 10 then selects a beam that propagates a signal between the BS 10 and the MS 20 via the RIS 30. To achieve this, the beam search unit 131, the beam forming unit 132, and the reflector position estimation unit 133 perform the following processes.

[0052] The beam search unit 131 receives from the MS 20 via the receiving unit 102 the measurement results of the received power of the beam transmitted by the BS 10, and based on the received measurement results of the received power, searches for beams of the sub-arrays provided in the BS 10, beams of the sub-arrays provided in the MS 20 and / or beams of the RIS 30, and selects (or determines) a beam to be applied to communication with the MS 20, including a beam through which a signal is propagated via the RIS 30.

[0053] The beam forming unit 132 spatially combines the beams of the sub-arrays provided in the BS 10 to suppress signals in the direction of the direct waves so that the MS 20 cannot see at least the direct waves transmitted by the BS 10 .

[0054] The reflector position estimation unit 133 estimates the position of the RIS 30. For example, if the position of the RIS 30 is fixed, the position of the RIS 30 may be stored as position information (e.g., latitude and longitude) in the BS 10 (e.g., the processor 1001, memory 1002, storage 1003, etc., which will be described later), and the reflector position estimation unit 133 may estimate the position indicated by the stored position information as the position of the RIS 30. Furthermore, for example, if the RIS 30 is mounted on a drone or the like and moves, the reflector position estimation unit 133 may estimate the position of the RIS 30 by communicating with the drone or the like and acquiring position information from the drone or the like. The reflector position estimation unit 133 outputs the estimated position of the RIS 30 to the beam forming unit 132.

[0055] Next, specific examples of processing performed by the beam search unit 131, the beam formation unit 132, and the reflector position estimation unit 133 will be described.

[0056] An example of processing when the number of RISs is one and the number of subarrays in the BS 10 and the MS 20 is two will be described below.

[0057] (Process 1A) The beam search unit 131 receives the subarray 11 transmitted by the BS 10 from the MS 20 via the receiving unit 102. １ The beam search unit 131 receives the measurement result of the received power of the beam (the measurement signal of the direct wave). Based on the measurement result of the received power, the beam search unit 131 searches for the beam of the sub-array included in the BS 10 (the sub-array 11 transmitted by the BS 10).１ Among the beams, the subarray 21 provided in the MS 20 １ (The beam search unit 131 selects a beam (final first BS beam) that maximizes the received power of the first BS beam.) The beam search unit 131 outputs identification information of the final first BS beam selected by the search to the beam forming unit 132. This allows the BS 10 (beam forming unit 132) to form a beam in the direct wave direction (toward the MS 20) using some of the subarrays.

[0058] (Process 1B) The beam search unit 131 receives from the MS 20 via the receiver 102 the subarray 11 that the beam search unit 131 selected immediately before and that the BS 10 transmitted. １ The beam search unit 131 receives the measurement result of the received power of the beam (the measurement signal of the direct wave). Based on the measurement result of the received power, the beam search unit 131 searches for the beam of the sub-array provided in the MS 20 (the sub-array 21 provided in the MS 20). １ (A beam with the maximum reception power (final first MS beam) is selected from the beams.) The beam searcher 131 outputs identification information of the final first MS beam selected by the search to the beam former 132. This allows the MS 20 (for example, a beam former not shown in FIG. 8 , which will be described later) to form a beam in the direct wave direction (toward the BS 10) using some of the subarrays.

[0059] (Process 1C) The beam forming unit 132 calculates the RIS30 output by the reflector position estimation unit 133. １ Based on the position of the sub-array 11 provided in the BS 10, ２ Of the beams, RIS30 １ This allows the BS 10 to form a beam in the direction of the RIS 30 using another sub-array.

[0060] (Process 1D) The beam forming unit 132 determines the subarray 11 included in the BS 10 based on the identification information of the final first BS beam output by the beam search unit 131. １ The final first BS beam is selected.

[0061] (Process 1E) The beam forming unit 132 determines the subarray 21 included in the MS 20 based on the identification information of the final first MS beam output by the beam search unit 131. ２ Among the beams, the subarray 21 provided in the MS 20 １ A beam (intermediate second MS beam) in the same direction as the final first MS beam is selected.

[0062] (Process 1F) The beam forming unit 132 performs the beamforming for the selected subarray 11 １ The final first BS beam, subarray 11 ２ RIS30 １ The final second BS beam in the direction and the subarray 21 ２ Based on the intermediate second MS beam, the subarray 11 １ and Subarray 21 ２ Between and Sub-array 11 ２ and Subarray 21 ２ The channel estimation is performed between the sub-array 11 and the sub-array 12. １ and Subarray 21 ２ and the sub-array 11 ２ and Subarray 21 ２ The channels between １１ and h １２ (all complex numbers), the beam forming unit 132 １ The beam is a complex number -(h １１ ＊ h １２ ) / (|h １１ | ２ +σ ｎ ２ ) multiplied by (h １１ ＊ Hah １１ complex conjugate of |h １１ | ２ Hah １１ The square of the absolute value of σ ｎ ２ and are fixed parameters that represent the variance of noise power.) The beam forming unit 132 outputs the multiplied subarrays 11 １ and subarray 11 ２ The transmitting unit 101 transmits the beams of and simultaneously.

[0063] (Process 1G) The beam search unit 131 receives from the MS 20 via the receiver 102 the measurement result of the received power of the beam formed by the beam forming unit 132 and transmitted by the BS 10 after process 1F. Based on the received measurement result of the received power, the beam search unit 131 calculates the received power of the beam from the RIS 30. １ Search for the beam (RIS30 １ Among the beams (to the MS 20), the subarray 21 provided in the MS 20 ２ (The beam search unit 131 selects a beam (final first RIS beam) that maximizes the received power of the first RIS beam.) The beam search unit 131 outputs identification information of the final first RIS beam selected by the search to the beam forming unit 132. This allows the RIS 30 (for example, a beam forming unit not shown) to form a beam in the direction of the MS 20.

[0064] (Process 1H) The beam search unit 131 receives from the MS 20, via the receiver 102, the measurement result of the received power of the beam formed by the beam forming unit 132 and transmitted by the BS 10 after Process 1F. Based on the received measurement result of the received power, the beam search unit 131 searches for a beam of the subarray included in the MS 20 (the subarray 21 included in the MS 20). ２ (Among the beams, the beam with the maximum received power (final second MS beam) is selected.) The beam searcher 131 outputs identification information of the final second MS beam selected by the search to the beam former 132. This enables the MS 20 to form a beam in the direction of the RIS 30 using another subarray.

[0065] 9 is a diagram showing a first example of beam search and beam forming according to the first embodiment, and is a diagram showing the above-mentioned processing example in the case where the number of RISs is 1 and the number of subarrays in the BS 10 and the MS 20 is 2. As shown in FIG. １ and subarray 11 ２ By combining the beams and forming a null beam in the direct wave direction to the MS 20, the RIS 30 １ It becomes possible to select the beam (propagation path) via

[0066] Next, a processing example will be described in which the number of RISs is N (N is an integer equal to or greater than 2) and the number of subarrays in the BS 10 and the MS 20 is (N+1) or greater. ｎ When searching for a beam via the direct wave and the first RIS30 １ to (n-1)th RIS30 ｎ－１ All waves passing through and need to be nulled.

[0067] (Process 2A) The BS 10 performs the above-described processes 1A to 1G. The BS 10 sets n to 2.

[0068] (Process 2B) The beam forming unit 132 calculates the RIS30 output by the reflector position estimating unit 133. ｎ Based on the position of the sub-array 11 provided in the BS 10, ｎ＋１ Of the beams, RIS30 ｎ By this, the BS 10 selects a beam in the direction (the final n+1 BS beam) by using some of the subarrays. ｎ It is possible to form a directional beam.

[0069] (Process 2C) The beam forming unit 132 determines the subarrays 11 included in the BS 10 based on the identification information of the final first BS beam to the final n-th BS beam output by the beam search unit 131. １ ~11 ｎ The BS 10 selects the final first BS beam to the final n-th BS beam. The BS 10 sets p to 1.

[0070] (Process 2D) The beam forming unit 132 determines the beam number of the subarray 21 included in the MS 20 based on the identification information of the pth MS beam output by the beam search unit 131. ｐ＋１ Among the beams, the subarray 21 provided in the MS 20 ｐ The BS 10 selects a beam (intermediate p+1th MS beam) in the same direction as the final pth MS beam.

[0071] (Process 2E) The beam forming unit 132 performs the beamforming for the selected subarray 11. ｑ The final qth BS beam, subarray 11 ｑ＋１ RIS30 ｑ＋１The final q+1th BS beam in the direction and the subarray 21 ｐ＋１ The channel estimation is performed based on the intermediate (p+1)th MS beam of the sub-array 11. ｑ and Subarray 21 ｐ＋１ The channel between ｐｑ (complex number). Increment q by 1.

[0072] (Process 2F) The beam forming unit 132 repeats processes 2D and 2E until channel estimation for q = n is performed. The BS 10 increments p by one.

[0073] (Process 2G) The beam forming unit 132 repeats processes 2D to 2F until channel estimation for the case where p=n is performed.

[0074] (Process 2H) The beam forming unit 132 performs the ｐｑ ] is an n × (n + 1) matrix with elements H, and the singular value decomposition is calculated (H = UΣV Ｈ The beam forming unit 132 converts the (n+1)-th row (n+1)-order column vector of V into v ｎ＋１ and the sub-array 11 provided in the BS 10 ｑ (1≦q≦n) beams, and a complex number (v ｎ＋１ (n+1) ＊ v ｎ＋１ (q)) / (|v ｎ＋１ (n+1) | ２ +σ ｎ ２ ) multiplied by (v ｎ＋１ (n+1) ＊ is v ｎ＋１ complex conjugate of (n+1), |v ｎ＋１ (n+1) | ２ is v ｎ＋１ the square of the absolute value of (n+1), σ ｎ ２ and are fixed parameters that represent the variance of noise power.) The beam forming unit 132 outputs the multiplied subarrays 11 １ ~11 ｎ and subarray 11 ｎ＋１ The transmitting unit 101 transmits the beams of and simultaneously.

[0075] (Process 2I) The beam search unit 131 receives from the MS 20 via the receiver 102 the measurement result of the received power of the beam formed by the beam forming unit 132 and transmitted by the BS 10 after process 2H. Based on the received measurement result of the received power, the beam search unit 131 calculates the received power of the beam from the RIS 30. ｎ Search for the beam (RIS30 ｎ Among the beams (to the MS 20), the subarray 21 provided in the MS 20 ｎ＋１ The beam search unit 131 outputs the identification information of the final n-th RIS beam selected by the search to the beam forming unit 132. ｎ can form a beam in the direction of MS 20.

[0076] (Process 2J) The beam search unit 131 receives from the MS 20, via the receiver 102, the measurement result of the received power of the beam formed by the beam forming unit 132 and transmitted by the BS 10 after process 2H. Based on the received measurement result of the received power, the beam search unit 131 determines the received power of the subarray 21 included in the MS 20. ｎ＋１ (sub-array 21 provided in MS 20) ｎ＋１ The beam search unit 131 outputs the identification information of the final n+1th MS beam selected by the search to the beam forming unit 132. The BS 10 increments n by 1. As a result, the MS 20 uses some of the subarrays to form the RIS 30 ｎ It is possible to form a directional beam.

[0077] (Process 2K) The BS 10 repeats processes 2B to 2J until the beam for n=N is searched.

[0078] 10 is a diagram showing a second example of beam search and beam forming according to the first embodiment, and is a diagram showing the above-mentioned processing example in the case where the number of RISs is N (N is an integer equal to or greater than 2) and the number of subarrays in the BS 10 and the MS 20 is (N+1) or more. As shown in FIG. 10, the subarrays 11 of the BS 10 １ ~11 ｎ The beam is transmitted to the subarray 21 of the MS 20.ｎ＋１ In addition to forming a null beam in the direct wave direction to the MS 20 so that the １ ~30 ｎ－１ By forming a null beam in a direction passing through the RIS 30 (called the selected RIS), the RIS 30 is selected based on the received power of the measurement signal. ｎ It becomes possible to select the beam (propagation path) via

[0079] As described above, BS10 (beam search unit 131, beam forming unit 132, reflector position estimation unit 133) can select or determine a beam (propagation path) that passes through RIS30 based on the received power of the measurement signal by forming a null beam at least in the direct wave direction to MS20.

[0080] 7 is a block diagram showing an example of the configuration of the MS 20 according to embodiment 1. The MS 20 includes, for example, a receiving unit 201, a transmitting unit 202, and a control unit 203.

[0081] The receiving unit 201 receives a DL signal transmitted from the BS 10. For example, the receiving unit 201 receives the DL signal under the control of the control unit 203.

[0082] The transmitting unit 202 transmits the UL signal to the BS 10. For example, the transmitting unit 202 transmits the UL signal under the control of the control unit 203.

[0083] The UL signal may include, for example, an uplink data signal and control information (e.g., UCI (Uplink Control Information)). For example, information related to the processing capability of the MS 20 (e.g., UE capability) may be included. The UL signal may also include a reference signal.

[0084] The channels used for transmitting UL signals include, for example, a data channel and a control channel. For example, the data channel may include a PUSCH (Physical Uplink Shared Channel), and the control channel may include a PUCCH (Physical Uplink Control Channel). For example, the MS 20 transmits control information using the PUCCH and transmits data signals using the PUSCH.

[0085] The reference signal included in the UL signal may include, for example, at least one of a DMRS, a PTRS, a CSI-RS, an SRS, and a PRS. For example, the reference signal such as the DMRS or the PTRS is used for demodulating an uplink data signal and is transmitted using an uplink channel (for example, a PUSCH).

[0086] The receiving unit 201 and the transmitting unit 202 (which may be collectively referred to as a communication unit) communicate with a network such as the BS 10 .

[0087] The control unit 203 controls the overall operation of the MS 20 including the receiving process in the receiving unit 201 and the transmitting process in the transmitting unit 202, as well as the communication operation.

[0088] For example, the control unit 203 acquires information such as data and control information from the upper layer and outputs it to the transmitting unit 202. Also, the control unit 203 outputs, for example, the data and control information received from the receiving unit 201 to the upper layer.

[0089] For example, the control unit 203 controls transmission of information to be fed back to the BS 10. The information to be fed back to the BS 10 may include, for example, HARQ ACK / NACK, Channel State Information (CSI), or a Scheduling Request (SR). The information to be fed back to the BS 10 may be included in UCI. The UCI is transmitted, for example, in PUCCH resources.

[0090] Note that the channel used for transmitting the UL signal is not limited to the above example.

[0091] 8 is a block diagram showing an example of the functional configuration of the MS 20 according to embodiment 1. The MS 20 (for example, the control unit 203) includes, for example, a received power measuring unit 231 and a received power reporting unit 232.

[0092] The received power measurement unit 231 measures the received power of the subarray #21. １ ~#21 Ｙ For each of the above, the received power measurement unit 231 measures the power of the beam (measurement signal) transmitted from BS 10. For example, the received power measurement unit 231 measures the reference signal transmitted from BS 10 and acquires the reference signal received power (RSRP). The received power measurement unit 231 measures the received power of the beam directly from BS 10 and the beam transmitted from BS 10 via RIS 30. The received power measurement unit 231 outputs the measurement result of the received power to the received power reporting unit 232.

[0093] The reception power reporting unit 232 reports (feeds back) the measurement result of the reception power output by the reception power measuring unit 231 (information indicating the measured reception power) to the BS 10 via the transmission unit 202. １ ~#21 Ｙ For each of the beams, the measurement results of the received power of all beams may be reported, or the measurement results of the received power of the top x best beams may be reported.

[0094] <Example of Operation of Wireless Communication System> Next, an example of operation of the wireless communication system 1 will be described with reference to FIG. 11 and FIGS. 12A to 12B.

[0095] 11 is a flowchart showing a first operation example of the wireless communication system 1 according to embodiment 1. The first operation example corresponds to a case where the number of RISs is one and the number of subarrays of the BS 10 and the MS 20 is two.

[0096] In step S11, the BS 10 estimates the position of the first RIS. Step S11 may be executed by the reflector position estimation unit 133. The first RIS is the RIS 30. １ may correspond to.

[0097] In step S12, the BS 10 performs a beam search for the first subarray of the BS 10 and the first subarray of the MS 20. Step S12 may be executed by the beam search unit 131 and may correspond to, for example, the above-described processes 1A and 1B. The first subarray of the BS 10 and the first subarray of the MS 20 are respectively subarrays 11 and 12. １ and subarray 21 １ It is assumed that step S12 involves the BS 10 transmitting a measurement signal and the MS 20 measuring and reporting the received power of the measurement signal.

[0098] In step S13, the BS 10 suppresses the signal in the direct wave direction to the MS 20. Step S13 may be performed by the beam forming unit 132, and may correspond to, for example, the above-mentioned processes 1C to 1F.

[0099] In step S14, the BS 10 performs a beam search for the first RIS. Step S14 may be executed by the beam search unit 131 and may correspond to, for example, process 1G described above. Note that step S14 involves the BS 10 transmitting a measurement signal and the MS 20 measuring and reporting the received power of the measurement signal.

[0100] In step S15, the BS 10 performs a beam search for the second subarray of the MS 20. Step S15 may be executed by the beam search unit 131 and may correspond to, for example, the above-mentioned process 1H. The second subarray of the MS 20 is the subarray 21. ２ It should be noted that step S15 involves the BS 10 transmitting a measurement signal, and the MS 20 measuring and reporting the received power of the measurement signal.

[0101] 12A and 12B are flowcharts showing a second operation example of the wireless communication system 1 according to embodiment 1. The second operation example corresponds to a case where the number of RISs is N (N is an integer equal to or greater than 2) and the number of subarrays of the BS 10 and the MS 20 is (N+1) or greater.

[0102] Steps S11 to S15 shown in FIGS. 12A and 12B are the same as steps S11 to S15 shown in FIG. 11, respectively.

[0103] In step S16, the BS 10 sets n=2.

[0104] In step S21, the BS 10 estimates the position of the n-th RIS. Step S21 may be executed by the reflector position estimation unit 133. The n-th RIS is the RIS 30. ｎ may correspond to.

[0105] In step S22, the BS 10 suppresses signals in the direct wave direction to the MS 20 and signals in the direction via the selected first to (n-1)th RISs. Step S22 may be executed by the beam forming unit 132 and may correspond to, for example, the above-described processes 2B to 2H.

[0106] In step S23, the BS 10 performs a beam search for the n-th RIS. Step S23 may be executed by the beam search unit 131 and may correspond to, for example, the above-mentioned process 2I. Note that step S23 involves the BS 10 transmitting a measurement signal and the MS 20 measuring and reporting the received power of the measurement signal.

[0107] In step S24, the BS 10 performs a beam search for the (n+1)-th subarray of the MS 20. Step S24 may be executed by the beam search unit 131 and may correspond to, for example, the above-mentioned process 2J. The (n+1)-th subarray of the MS 20 is the subarray 21. ｎ＋１ It should be noted that step S24 involves the BS 10 transmitting a measurement signal, and the MS 20 measuring and reporting the received power of the measurement signal.

[0108] In step S25, the BS 10 increments n by one.

[0109] In step S26, BS 10 determines whether n is equal to or greater than (N+1). If n is equal to or greater than (N+1) (step S27; YES), the flow ends, and if n is not equal to or greater than (N+1) (step S27; NO), the flow returns to step S21, and the process is repeated.

[0110] In summary, the BS 10 and the MS 20 search (select or determine) a beam in the direct wave direction among some of the subarrays, and thereby form a beam in the direct wave direction using some of the subarrays (Procedure 1). Next, the BS 10 forms a beam in the direction of the RIS 30 using another subarray (Procedure 2). Procedure 2 can be performed as a result of beamforming performed in Procedure 1. Next, the RIS 30 forms a beam in the direction of the MS 20 by the BS 10 suppressing signals in the direct wave direction to the MS 20 (Procedure 3). Next, the MS 20 forms a beam in the direction of the RIS 30 using another subarray (Procedure 4). Procedures 3 and 4 can be performed as a result of beamforming performed in Procedure 2. These procedures enable the selection of a beam via the RIS 30, reducing spatial correlation between subarrays and improving MIMO capacity. Note that Procedure 3 may also be performed by the MS 20. That is, in procedure 3, RIS 30 may form a beam in the direction of BS 10 or MS 20 by MS 10 suppressing signals in the direction of direct waves to BS 20. Also, if the number of RISs is two or more and the number of subarrays in BS 10 and MS 20 is three or more, it is possible to similarly select a beam that passes through RIS 30 by repeating procedures 2 to 4. In this case, BS 30 also suppresses signals in the direction that passes through the selected RIS 30 in procedure 3.

[0111] As described above, the wireless communication system 1 (BS 10, MS 20, RIS 30) can select or determine the beam (propagation path) along which the signal will propagate via RIS 30 based on the received power of the measurement signal by forming a null beam at least in the direct wave direction to MS 20.

[0112] <Simulation> Next, a description will be given of a simulation using the technology according to embodiment 1. This simulation was carried out under the conditions shown in FIG.

[0113] 14A, 14B, 14C, and 14D are diagrams showing the results of this simulation (beam selection by maximum power search). (A), (B), (C), and (D) in FIG. 14 show the first subarray (subarray 11) of the BS when null beamforming according to the first embodiment is used. １ ), the first subarray of the MS (corresponding to subarray 21 １ ), the second subarray of the RIS and MS (subarray 21 ２ 14A, 14B, 14C, and 14D show beam selection by the first subarray of the BS, the first subarray of the MS, and the second subarrays of the RIS and MS, respectively, when the null beamforming according to the first embodiment is not used (comparison example).

[0114] In both the case where the null beam forming according to embodiment 1 is used and the case where the null beam forming according to embodiment 1 is not used, as shown in (A) and (a) of Figure 14, it can be seen that for the first subarray of the BS, the beam is directed toward the MS, and as shown in (B) and (b) of Figure 14, it can be seen that for the first subarray of the MS, the beam is directed toward the BS.

[0115] For the RIS, when null beamforming according to embodiment 1 is used, it can be seen that the beam is directed in the intended direction (i.e., toward the MS), as shown in Figure 14(C). On the other hand, when null beamforming is not used, the power appears to be minimum when the beam is directed toward the MS, as shown in Figure 14(c). Under the conditions of this simulation example, the LOS beam and the beam in the RIS direction are in opposite phase, and it is thought that as the power of the beam via the RIS increases, it cancels out with the LOS beam, resulting in a lower power at the MS end.

[0116] Also, for the second subarray of the MS, when null beamforming according to embodiment 1 is used, it can be seen that the beam is directed in the intended direction (the RIS direction) as shown in Fig. 14(D). On the other hand, when null beamforming is not used, the power is maximized when the beam is directed toward the BS as shown in Fig. 14(d).

[0117] Figure 15 shows the results of this simulation (throughput simulation results). "Beam #1" shown in Figure 15 represents the beam of the first subarray of the BS and the beam of the first subarray of the MS. Also, "Beam #2" shown in Figure 15 represents the beam of the second subarray of the BS and the beam of the second subarray of the MS.

[0118] When the null beam forming according to the first embodiment is used, it can be seen that two-stream transmission (LOS transmission and transmission via RIS) can be performed, as shown in FIG.

[0119] <Modification of First Embodiment> In the above, an example of a method for suppressing signals by combining beams emitted from multiple array antennas (sub-arrays) has been described. However, the present disclosure is not limited to this example. For example, a method of suppressing signals may be used in which a single array antenna does not emit a beam in a specific direction. Specifically, well-known techniques using a Butler matrix or DFT (Discrete Fourier Transformation) may be used to perform beamforming so that a single array antenna does not emit a beam in a specific direction. In other words, suppressing signals in the direct wave direction or the direction via a selected RIS may be achieved by signal processing using multiple array antennas of the BS 10 and / or the MS 20, or by directivity shaping of any array antenna of the BS 10 and / or the MS 20.

[0120] In the above description, it has been assumed that the subarrays of the BS 10, the MS 20, and the RIS 30 perform beam selection (beam search). １ ~11 Ｘ and sub-array 21 of MS 20 １ ~21Ｙ The beam selections (and the RIS 30) may be performed sequentially or simultaneously. These beam selections can be performed simultaneously by (1) suppressing signals in the direct wave direction or the direction via the selected RIS by synthesizing reference signals of the same frequency through signal processing using multiple array antennas of the BS 10 and / or the MS 20, and (2) multiplexing the reference signals in the frequency direction. This can speed up the beam selection.

[0121] Some or all of the above-described processes of the BS 10 and the MS 20 may alternatively or additionally be performed in the other device. For example, beam search (beam selection) may be performed by the MS 20.

[0122] As described above, according to the first embodiment, it is possible to select a path that passes through a reflector even when performing a beam search based on a terminal received power maximization criterion. As a result, in a wireless communication system that includes a reflector as well as a base station and a terminal, the base station and the terminal can communicate appropriately via a path that passes through the reflector, and the base station and the terminal can communicate appropriately.

[0123] (Embodiment 2) In embodiment 1, it is arbitrary to allocate (distribute) which subarray (i.e., beam) to which RIS (or direct wave). However, in the following situations, adaptively changing the allocation of beams (or the number of beams) may improve the MIMO capacity effect: - When an obstruction is present and the loss of the direct wave or the path via RIS is very large - When multiple spatial multiplexing is possible in one direction (direct wave direction or RIS direction) (when so-called LOS-MIMO is possible)

[0124] Therefore, in the second embodiment, a method for determining which subarray is assigned to which RIS (or direct wave) will be described, assuming that a path via RIS is selected using the technique described in the first embodiment.

[0125] In the second embodiment, the description will focus on the parts that are different from the first embodiment, and the description of the parts that are the same as or in common with the first embodiment may be omitted.

[0126] 16A is a diagram showing an example of beam number allocation change according to embodiment 2. In the example shown in FIG. 16A, as shown in (a), in the initial stage, two beams are equally allocated to each of paths that go through a RIS and paths that do not go through a RIS. Depending on the situation, using the technology described below, as shown in (b), one beam may be allocated to a path that goes through a RIS, and three beams may be allocated to a path that does not go through a RIS. Depending on the situation, as shown in (c), three beams may be allocated to a path that goes through a RIS, and one beam may be allocated to a path that does not go through a RIS.

[0127] 16B is a diagram showing another example of changing the allocation of the number of beams according to the second embodiment. In the example shown in FIG. 16B, it is assumed that, in the initial stage, one beam is allocated equally to each of the paths that go through the RIS and the paths that do not go through the RIS. Here, it is assumed that an obstruction is present on the path formed between the subarray #1 included in the BS and the subarray #1 included in the MS, as shown in (a). Then, as shown in (b), two beams can be allocated to the path that goes through the RIS so that the subarray #1 included in the BS and the subarray #1 included in the MS form a path that goes through the RIS.

[0128] In this way, in the second embodiment, beam allocation (allocation of the number of beams) is optimized depending on the situation.

[0129] 17 is a block diagram showing an example of the functional configuration of the BS 10 according to embodiment 2. The BS 10 (e.g., the control unit 103) includes, for example, an allocation unit 134, a selection unit 135, and a measurement unit 136 in addition to the beam search unit 131, the beam formation unit 132, and the reflector position estimation unit 133 described in embodiment 1.

[0130] As an initial allocation, the allocation unit 134 arbitrarily allocates the number of beams (or beams or subarrays; hereinafter, the number of beams) to the direct wave (or direct wave direction) and the RIS (or RIS via direction). For example, if the number of RIS is 1 and the number of subarrays of the BS 10 and the MS 20 is 2, the allocation unit 134 allocates the number of beams to the subarray 11. １ and subarray 21 １ is assigned to the direct wave direction, and the subarray 11 ２ and subarray 21 ２ The allocation unit 134 outputs the initial allocation result to the selection unit 135.

[0131] The allocation unit 134 changes the allocation of the number of beams and outputs the allocation result to the selection unit 135 .

[0132] The above process by the allocation unit 134, the following process by the selection unit 135, and the following process by the measurement unit 136 are repeated.

[0133] The allocating unit 134 searches for a combination of beam number allocations that will result in the best communication quality, based on the communication quality output by the measuring unit 136. Note that the allocating unit 134 may use well-known methods such as a greedy search method or a local search method to search for a combination. The allocating unit 134 determines the combination of beam number allocations that will result in the best communication quality as the final allocation.

[0134] The selector 135 performs beam selection based on the allocation result output by the allocator 134. For example, similar to the beam searcher 131 in the first embodiment, the selector 135 receives from the MS 20 via the receiver 102 the measurement result of the received power of the subarray beam (measurement signal) transmitted by the BS 10, and searches for the beam of the subarray provided in the BS 10, the beam of the subarray provided in the MS 20, and the beam of the RIS 30 based on the received measurement result of the received power. The beam searcher 131 outputs identification information of the beam selected by the search to the measurer 136. Note that the selector 135 may be the beam searcher 131.

[0135] The measurement unit 136 measures the communication quality of the beam (channel) indicated by the identification information output by the selection unit 135. Any index may be used as the communication quality, such as the physical throughput of the channel, SNR, or bit error rate. For example, the measurement unit 136 may directly measure the physical throughput of the channel as the communication quality, or may measure the communication quality by estimating the communication quality from the singular values ​​of the channel. The measurement unit 136 outputs the measured communication quality to the allocation unit 134.

[0136] A specific example of processing according to the second embodiment will be described below. In this example, the singular values ​​of the channel are used to measure the communication quality, and a greedy search method is used for the search. Also, in this example, the number of subarrays in the BS 10 is M (X=M), the number of subarrays in the MS 20 is N (Y=N), and the number of RISs is K (Z=K), where M≧N≧K. Therefore, in this example, the number of groups of beam directions is a group of "direct waves" (called "group 1") and a group of "RIS 30" (called "group 2"). ｋ (k is an integer between 1 and K) (referred to as "Group 2" (k=1) to "Group K+1" (k=K)).

[0137] (Process 1C) The allocation unit 134 allocates the subarray 11 of the BS 10. １ and sub-array 21 of MS 20 １ to the direct wave group ("Group 1"), thereby making an initial allocation.

[0138] (Process 2C) The selector 135 selects a beam based on the received power, similar to the beam selection by the beam searcher 131 in the first embodiment.

[0139] (Process 3C) The measurement unit 136 performs singular value decomposition on the inter-subarray channel matrix H (H=UΣV Ｈ ).

[0140] (Process 4C) The allocation unit 134 calculates the diagonal elements σ of Σ. ｎ (Here, n=1) and calculate the evaluation function S (S=Σlog ２ (1 + σ ｎ )). The BS 10 sets n to 2 and k to 1.

[0141] (Process 5C) The BS 10 performs the following process to the subarray 11 of the BS 10. ｎ and sub-array 21 of MS 20 ｎ Determine group assignments.

[0142] (Process 5-1C) The allocation unit 134 allocates the sub-array 11 of the BS 10. ｎ and sub-array 21 of MS 20 ｍ is distributed (assigned) to group k.

[0143] (Process 5-2C) The selector 135 selects a beam based on the received power, similar to the beam selection by the beam searcher 131 in the first embodiment.

[0144] (Process 5-3C) The measurement unit 136 performs singular value decomposition on the inter-subarray channel matrix H (H=UΣV Ｈ ).

[0145] (Process 5-4C) The allocation unit 134 calculates the diagonal elements σ of Σ. ｎ Calculate the evaluation function S (S = Σ log ２ (1 + σ ｎ )) Increment k by 1.

[0146] (Process 5-5C) The BS 10 repeats processes 5-1C to 5-4C until the evaluation function S for k=K+1 is calculated.

[0147] (Process 5-6C) The allocation unit 134 selects the kth value for which the evaluation function S has the maximum value within 1≦k≦K+1. ｍａｘ and the subarray 11 of the BS 10 is selected. ｎ and sub-array 21 of MS 20 ｍ Group k ｍａｘ The BS 10 increments n by one.

[0148] (Process 5-7C) BS10 calculates k when n=N. ｍａｘ The processes 5-1C to 5-6C are repeated until the node number m is selected. The BS 10 sets m to N+1 and k to 1.

[0149] (Process 6C) The BS 10 performs the following process to the subarray 11 of the BS 10.ｍ Determine group assignments.

[0150] (Process 6-1C) The allocation unit 134 allocates the sub-array 11 of the BS 10. ｍ is distributed (assigned) to group k.

[0151] (Process 6-2C) The selector 135 selects a beam based on the received power, similar to the beam selection by the beam searcher 131 in the first embodiment.

[0152] (Process 6-3C) The measurement unit 136 performs singular value decomposition on the inter-subarray channel matrix H (H=UΣV Ｈ ).

[0153] (Process 6-4C) The allocation unit 134 calculates the diagonal elements σ of Σ. ｍ Calculate the evaluation function S (S = Σ log ２ (1 + σ ｍ )) The BS 10 increments k by one.

[0154] (Process 6-5C) The BS 10 repeats processes 6-1C to 6-4C until the evaluation function S for k=K+1 is calculated.

[0155] (Process 6-6C) The allocation unit 134 selects the kth parameter in which the evaluation function S has the maximum value within 1≦k≦K+1. ｍａｘ and the subarray 11 of the BS 10 is selected. ｍ Group k ｍａｘ To allocate (assign) to.

[0156] (Process 6-7C) The BS 10 increments m by 1 and calculates k when m=M. ｍａｘ Steps 6-1C to 6-6C are repeated until the item is selected.

[0157] Next, with reference to Figures 18A and 18B, an operation example of the wireless communication system 1 will be described. Figures 18A and 18B are flowcharts showing an operation example of the wireless communication system 1 according to embodiment 2. In this example, it is assumed that the number of subarrays of the BS 10 and the number of subarrays of the MS 20 are M, and the number of RISs is K.

[0158] In step S31, the BS 10 performs an initial allocation of the number of beams. Step S31 may be executed by the allocation unit 134 and may correspond to, for example, process 1C described above.

[0159] In step S32, the BS 10 performs beam selection for the subarray of the BS 10, the subarray of the MS 20, and the RIS 30. Step S32 may be executed by the selection unit 135 and may correspond to, for example, the above-mentioned process 2C. Note that step S32 involves the BS 10 transmitting a measurement signal and the MS 20 measuring and reporting the received power of the measurement signal.

[0160] In step S33, the BS 10 measures the communication quality of the selected beam. Step S33 may be performed by the measurement unit 136 and may correspond to, for example, process 3C described above.

[0161] In step S34, the BS 10 calculates an evaluation function for the selected beam. Step S34 may be performed by the allocation unit 134 and may correspond to, for example, process 4C described above.

[0162] In step S35, the BS 10 sets n=2.

[0163] In step S36, the BS 10 sets k=1.

[0164] In step S37, the BS 10 changes the beam allocation. Step S37 may be executed by the allocation unit 134 and may correspond to, for example, the above-mentioned process 5-1C.

[0165] In step S38, the BS 10 performs beam selection for the subarray of the BS 10, the subarray of the MS 20, and the RIS 30. Step S38 may be executed by the selection unit 135 and may correspond to, for example, the above-mentioned process 5-2C. Note that step S38 involves the BS 10 transmitting a measurement signal and the MS 20 measuring and reporting the received power of the measurement signal.

[0166] In step S39, the BS 10 measures the communication quality of the selected beam. Step S39 may be performed by the measurement unit 136 and may correspond to, for example, process 5-3C described above.

[0167] In step S40, the BS 10 calculates the evaluation function of the selected beam. Step S40 may be performed by the allocation unit 134 and may correspond to, for example, process 5-4C described above.

[0168] In step S41, the BS 10 increments k by one.

[0169] In step S42, BS 10 determines whether k is equal to or greater than (K+2). If k is equal to or greater than (K+2) (step S42; YES), the flow proceeds to step S43, and if k is not equal to or greater than (K+2) (step S42; NO), the flow returns to step S37, and the process is repeated.

[0170] In step S43, the BS 10 assigns a beam to the group k for which the evaluation function calculated in step S40 has a maximum value, based on the communication quality measured in step S39.

[0171] In step S44, the BS 10 increments n by one.

[0172] In step S45, BS 10 determines whether n is equal to or greater than (M+1). If n is equal to or greater than (M+1) (step S45; YES), the flow ends, and if n is not equal to or greater than (M+1) (step S45; NO), the flow returns to step S36, and the process is repeated.

[0173] In summary, BS10 assigns subarrays from among multiple subarrays to paths in the direct wave direction or paths via reflectors (Step 1). Next, BS10 selects intermediate beams formed by the subarrays based on the received power of candidate beams formed by the subarrays (Step 2). Next, BS10 measures the communication quality of the intermediate beams (Step 3). BS10 performs Steps 1 to 3 at least once for each of the multiple subarrays, and determines each of multiple final beams formed by the multiple subarrays from the multiple intermediate beams based on the measured communication qualities (Step 4).

[0174] As described above, BS10 (allocation unit 134, selection unit 135, measurement unit 136) can perform optimal beam allocation according to the channel conditions by searching (beam determination) until it finds the beam number allocation that results in the best communication quality.

[0175] Next, a description will be given of a simulation using the technology according to embodiment 2. This simulation was carried out under the conditions shown in Tables 5 to 8 below.

[0176] 19A, 19B, 19C, and 19D are diagrams showing the results of this simulation (beam selection by maximum power search). (A), (B), (C), and (D) in FIG. 19 show the results of the first subarray (subarray 21) of the MS when beam reselection (beam number allocation change) according to the second embodiment is used. １ ), the second subarray (corresponding to subarray 21 ２ ), the third subarray (corresponding to subarray 21 ３ ) and the fourth subarray (corresponding to subarray 21 ４19A, 19B, 19C, and 19D show beam selection for the first subarray, the second subarray, the third subarray, and the fourth subarray of the MS, respectively, when beam reselection (changing the allocation of the number of beams) according to the second embodiment is not used. As shown in FIG. 19A, 19B, 19C, and 19D, when beam reselection is not used, the four beams are allocated evenly (two beams each) between the LOS and RIS directions.

[0177] When using the beam reselection according to embodiment 2, adjustments are made so that three of the four beams are assigned to the LOS and one beam is assigned to the RIS route, as shown in (A), (B), (C), and (D) of Figure 19.

[0178] Fig. 20 shows the results of this simulation (throughput simulation results). "w / o reselection, TP" shown in Fig. 20 corresponds to the case where beam reselection is not used as shown in Fig. 19(a), (b), (c), and (d), and "w / reselection, TP" shown in Fig. 20 corresponds to the case where beam reselection is used as shown in Fig. 19(A), (B), (C), and (D).

[0179] When beam reselection according to embodiment 2 is used, it can be seen that throughput is improved in some SNR ranges (0 to 40 dB) compared to when beam reselection is not used, as shown in FIG.

[0180] <Modification of Second Embodiment> A part or all of the above-described processes of the BS 10 and the MS 20 may be alternatively or additionally performed by the other device. For example, beam search (beam selection) may be performed by the MS 20.

[0181] As described above, according to the second embodiment, it is possible to perform optimal beam allocation depending on the channel conditions. As a result, in a wireless communication system including a base station, a terminal, and a reflector, the base station and the terminal can communicate appropriately with each other via a path that goes through the reflector or without the path going through the reflector, and the base station and the terminal can communicate appropriately with each other.

[0182] (Summary of embodiment) A beam determination method according to one aspect of the present disclosure, in a wireless communication system including a base station, a terminal, and a reflector, performs a first process of determining a beam in a direct wave direction to the terminal using an array antenna provided in the base station, a second process of determining a beam in a direct wave direction to the base station using an array antenna provided in the terminal, a third process of determining a beam in a direction of the reflector using the array antenna provided in the base station, a fourth process of determining a beam in a direction of the terminal using the reflector by suppressing a signal in the direct wave direction to the terminal, and a fifth process of determining a beam in a direction of the reflector using the array antenna provided in the terminal.

[0183] In one example, in the beam determination method, when there are a plurality of reflectors, the third process, the fourth process, and the fifth process are repeated a number of times equal to the number of reflectors.

[0184] In one example, in this beam determination method, if there are a plurality of reflectors, signals in directions that pass through some of the reflectors are suppressed when the fourth process is performed.

[0185] In one example, in this beam determination method, a plurality of subarrays constituting an array antenna provided in the base station are used to suppress signals in the direct wave direction to the terminal by signal processing.

[0186] In one example, in this beam determination method, a signal in the direction of a direct wave to the terminal is suppressed by forming the directivity of one of a plurality of subarrays that constitute an array antenna provided in the base station.

[0187] In one example, in this beam determination method, a plurality of subarrays constituting an array antenna provided in the base station are used to suppress signals in directions that pass through some of the reflectors by signal processing.

[0188] In one example, in this beam determination method, signals in a direction that passes through some of the reflectors are suppressed by forming the directivity of one of a plurality of subarrays that constitute the array antenna provided in the base station.

[0189] In one example, in this beam determination method, multiple subarrays that make up the array antenna equipped in the base station are used to combine measurement signals of the same frequency through signal processing, thereby suppressing signals in the direct wave direction to the terminal.

[0190] In one example, in this beam determination method, different measurement signals are multiplexed in the frequency direction for each of multiple subarrays that make up the array antenna provided in the base station, thereby simultaneously determining beams corresponding to the multiple subarrays.

[0191] In one example, the beam determination method includes a third process of estimating the position of the reflector and determining the beam in the direction of the reflector based on the estimated position of the reflector.

[0192] According to this beam determination method, by forming a null beam at least in the direction of the direct wave to the terminal, it is possible to select a beam in which a signal propagates via a reflector.

[0193] A beam determination method according to one aspect of the present disclosure, in a wireless communication system in which a base station and a terminal communicate using multiple subarrays via a path in the direct wave direction and / or a path via a reflector, performs a first process of assigning a subarray from among the multiple subarrays to the path in the direct wave direction or the path via the reflector, performs a second process of selecting an intermediate beam formed by the subarray based on the received power of a candidate beam formed by the subarray, performs a third process of measuring the communication quality of the intermediate beam, and performs a fourth process of determining each of multiple final beams formed by the multiple subarrays from the multiple intermediate beams based on the multiple communication qualities by performing the first process, the second process, and the third process at least once for each of the multiple subarrays.

[0194] In one example, in this beam determination method, when the fourth process is performed, each of the plurality of final beams corresponding to the plurality of best communication qualities is determined.

[0195] In one example, in this beam determination method, when the third processing is performed, the communication quality is estimated by estimating the communication quality from a channel singular value.

[0196] According to this beam determination method, the final beam is determined based on communication quality, thereby enabling beam allocation according to channel conditions.

[0197] The present disclosure has been described above. Note that the division of items in the above description is not essential to the present disclosure, and items described in two or more items may be used in combination as needed, and items described in one item may be applied to items described in another item (unless they are inconsistent).

[0198] <Hardware Configuration, etc.> The block diagrams used to explain the above embodiments show functional blocks. These functional blocks (components) are realized by any combination of at least one of hardware and software. Furthermore, the method for realizing each functional block is not particularly limited. That is, each functional block may be realized using a single device that is physically or logically coupled, or may be realized using two or more physically or logically separated devices that are directly or indirectly connected (e.g., using wires, wirelessly, etc.) and these multiple devices. The functional block may also be realized by combining software with the single device or the multiple devices.

[0199] Functions include, but are not limited to, judgment, determination, assessment, calculation, computation, processing, derivation, investigation, search, confirmation, reception, transmission, output, access, resolution, selection, selection, establishment, comparison, assumption, expectation, consideration, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, mapping, and assignment. For example, a functional block (component) that performs transmission is called a transmitting unit or transmitter. As mentioned above, there are no particular limitations on how these functions are implemented.

[0200] For example, a base station, a terminal, or the like according to an embodiment of the present disclosure may function as a computer that performs processing of the wireless communication method of the present disclosure. Fig. 21 is a diagram illustrating an example of the hardware configuration of a base station and a terminal according to an embodiment. The base station 10 and the terminal 20 described above may be physically configured as a computer device including a processor 1001, a memory 1002, a storage 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007, and the like.

[0201] In the following description, the term "apparatus" can be interpreted as a circuit, a device, a unit, etc. The hardware configuration of the base station 10 and the terminal 20 may be configured to include one or more of the apparatuses shown in the drawings, or may be configured to exclude some of the apparatuses.

[0202] Each function in the base station 10 and the terminal 20 is realized by loading specified software (programs) onto hardware such as the processor 1001 and the memory 1002, causing the processor 1001 to perform calculations, control communication by the communication device 1004, and control at least one of reading and writing data in the memory 1002 and the storage 1003.

[0203] The processor 1001 controls the entire computer by running, for example, an operating system. The processor 1001 may be configured by a central processing unit (CPU) including an interface with peripheral devices, a control device, an arithmetic unit, a register, etc. For example, the above-mentioned control unit 103 and control unit 203 may be realized by the processor 1001.

[0204] The processor 1001 also reads programs (program codes), software modules, data, etc. from at least one of the storage 1003 and the communication device 1004 into the memory 1002 and executes various processes in accordance with these programs. The programs used are those that cause a computer to execute at least some of the operations described in the above-described embodiments. For example, the control unit 103 of the base station 10 and the control unit 203 of the terminal 20 may be implemented by a control program stored in the memory 1002 and running on the processor 1001, and similar implementations may be used for other functional blocks. While the above-described various processes have been described as being executed by one processor 1001, they may also be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. The programs may also be transmitted from a network via a telecommunications line.

[0205] The memory 1002 is a computer-readable recording medium and may be configured by, for example, at least one of a read-only memory (ROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), a random access memory (RAM), etc. The memory 1002 may also be called a register, a cache, a main memory (primary storage device), etc. The memory 1002 can store executable programs (program codes), software modules, etc. for implementing a wireless communication method according to an embodiment of the present disclosure.

[0206] Storage 1003 is a computer-readable recording medium, and may be composed of at least one of, for example, an optical disk such as a CD-ROM (Compact Disc ROM), a hard disk drive, a flexible disk, a magneto-optical disk (e.g., a compact disk, a digital versatile disk, a Blu-ray (registered trademark) disk), a smart card, a flash memory (e.g., a card, a stick, a key drive), a floppy (registered trademark) disk, a magnetic strip, etc. Storage 1003 may also be referred to as an auxiliary storage device. The above-mentioned storage medium may be, for example, a database, a server, or other appropriate medium including at least one of memory 1002 and storage 1003.

[0207] The communication device 1004 is hardware (transmission / reception device) for communicating between computers via at least one of a wired network and a wireless network, and is also referred to as, for example, a network device, a network controller, a network card, a communication module, etc. The communication device 1004 may be configured to include a high-frequency switch, a duplexer, a filter, a frequency synthesizer, etc. to realize at least one of frequency division duplex (FDD) and time division duplex (TDD). For example, the above-mentioned transmitter 101, receiver 102, receiver 201, transmitter 202, etc. may be realized by the communication device 1004.

[0208] The input device 1005 is an input device (e.g., a keyboard, a mouse, a microphone, a switch, a button, a sensor, etc.) that receives input from the outside. The output device 1006 is an output device (e.g., a display, a speaker, an LED lamp, etc.) that outputs to the outside. The input device 1005 and the output device 1006 may be integrated into one device (e.g., a touch panel).

[0209] Furthermore, each device, such as the processor 1001 and the memory 1002, is connected by a bus 1007 for communicating information. The bus 1007 may be configured using a single bus, or may be configured using different buses between each device.

[0210] Furthermore, the base station 10 and the terminal 20 may be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA), and some or all of the functional blocks may be realized by the hardware. For example, the processor 1001 may be implemented using at least one of these pieces of hardware.

[0211] <Notification of Information, Signaling> Notification of information is not limited to the embodiments described in the present disclosure and may be performed using other methods. For example, notification of information may be performed by physical layer signaling (e.g., Downlink Control Information (DCI), Uplink Control Information (UCI)), higher layer signaling (e.g., Radio Resource Control (RRC) signaling, Medium Access Control (MAC) signaling, broadcast information (Master Information Block (MIB), System Information Block (SIB))), other signals, or a combination thereof. Furthermore, RRC signaling may be referred to as an RRC message, and may be, for example, an RRC Connection Setup message, an RRC Connection Reconfiguration message, or the like.

[0212] <Applicable Systems> The embodiments described in the present disclosure are applicable to LTE (Long Term Evolution), LTE-Advanced (LTE-A), SUPER 3G, IMT-Advanced, 4G (4th generation mobile communication system), 5G (5th generation mobile communication system), 6th generation mobile communication system (6G), xth generation mobile communication system (xG) (xG (x is, for example, an integer or a decimal)), FRA (Future Radio Access), NR (new Radio), New radio access (NX), Future generation radio access (FX), W-CDMA (registered trademark), GSM (registered trademark), CDMA2000, UMB (Ultra Mobile Broadband), IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.17 (WiMAX (registered trademark)), IEEE 802.19 (WiMAX (registered trademark)), IEEE 802.20 (WiMAX (registered trademark)), IEEE 802.21 (Wi-Fi (registered trademark)), IEEE 802.22 (WiMAX (registered trademark)), IEEE 802.23 (WiMAX (registered trademark)), IEEE 802.24 (WiMAX (registered trademark)), IEEE 802.25 (WiMAX (registered trademark)), IEEE 802.26 (WiMAX (registered trademark)), IEEE 802.27 (WiMAX (registered trademark)), IEEE 802.28 (WiMAX (registered trademark)), IEEE 802.29 (WiMAX (registered trademark)), IEEE 802.30 (WiMAX (registered trademark)), IEEE 802.31 (Wi-Fi (registered trademark)), IEEE 802.32 (WiMAX (registered trademark)), IEEE 802.33 (WiMAX (registered trademark)), IEEE 802.34 (WiMAX (registered trademark The present invention may be applied to at least one of systems using 802.20, UWB (Ultra-Wide Band), Bluetooth (registered trademark), or other suitable systems, and next-generation systems that are extended, modified, created, or defined based on these systems. The present invention may also be applied to a combination of multiple systems (e.g., a combination of LTE and / or LTE-A with 5G).

[0213] <Processing Procedures, etc.> The processing procedures, sequences, flowcharts, etc. of each aspect / embodiment described in this disclosure may be rearranged unless inconsistent. For example, the methods described in this disclosure present elements of various steps using an example order, and are not limited to the particular order presented.

[0214] <Operation of Base Station> In the present disclosure, specific operations described as being performed by a base station may also be performed by its upper node in some cases. In a network consisting of one or more network nodes having a base station, it is clear that various operations performed for communication with a terminal may be performed by at least one of the base station and another network node other than the base station (for example, an MME or an S-GW, etc., but are not limited to these). Although the above example illustrates a case where there is one other network node other than the base station, a combination of multiple other network nodes (for example, an MME and an S-GW) may also be used.

[0215] <Direction of Input / Output> Information, etc. (see <Information, Signal>) can be output from a higher layer (or a lower layer) to a lower layer (or a higher layer). It may also be input / output via multiple network nodes.

[0216] <Handling of Input / Output Information, etc.> Input / output information, etc. may be stored in a specific location (for example, memory) or may be managed using a management table. Input / output information, etc. may be overwritten, updated, or added. Output information, etc. may be deleted. Input information, etc. may be sent to another device.

[0217] <Determination method> The determination may be made based on a value represented by one bit (0 or 1), a Boolean value (true or false), or a numerical comparison (e.g., comparison with a predetermined value).

[0218] <Variations of Aspects, etc.> Each aspect / embodiment described in the present disclosure may be used alone, in combination, or switched depending on the implementation. In addition, notification of predetermined information (e.g., notification that "X is true") is not limited to being done explicitly, but may be done implicitly (e.g., by not notifying the predetermined information).

[0219] Although the present disclosure has been described in detail above, it is clear to those skilled in the art that the present disclosure is not limited to the embodiments described herein. The present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the present disclosure as defined by the claims. Therefore, the description of the present disclosure is intended to be illustrative and does not have any limiting meaning on the present disclosure.

[0220] <Software> Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0221] Software, instructions, information, etc. may also be transmitted or received over a transmission medium. For example, if software is transmitted from a website, server, or other remote source using wired technologies (such as coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL)), and / or wireless technologies (such as infrared, microwave), then these wired and / or wireless technologies are included within the definition of transmission media.

[0222] Information, Signals, etc., described in this disclosure may be represented using any of a variety of different technologies. For example, data, instructions, commands, information, signals, bits, symbols, chips, etc., which may be referred to throughout the above description, may be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or photons, or any combination thereof.

[0223] Note that terms described in this disclosure and terms necessary for understanding this disclosure may be replaced with terms having the same or similar meanings. For example, at least one of a channel and a symbol may be a signal (signaling). Furthermore, a signal may be a message. Furthermore, a component carrier (CC) may be called a carrier frequency, a cell, a frequency carrier, etc.

[0224] <System, Network> As used in this disclosure, the terms "system" and "network" are used interchangeably.

[0225] <Parameter and Channel Names> Furthermore, the information, parameters, and the like described in the present disclosure may be expressed using absolute values, relative values ​​from a predetermined value, or other corresponding information. For example, a radio resource may be indicated by an index.

[0226] The names used for the above-described parameters are not intended to be limiting in any way. Furthermore, the mathematical expressions using these parameters may differ from those explicitly disclosed in this disclosure. The various channels (e.g., PUCCH, PDCCH, etc.) and information elements may be identified by any suitable names, and therefore the various names assigned to these various channels and information elements are not intended to be limiting in any way.

[0227] <Base Station> In the present disclosure, terms such as "base station (BS)," "radio base station," "fixed station," "NodeB," "eNodeB (eNB)," "gNodeB (gNB)," "access point," "transmission point," "reception point," "transmission / reception point," "cell," "sector," "cell group," "carrier," and "component carrier" may be used interchangeably. A base station may also be referred to by terms such as a macrocell, a small cell, a femtocell, and a picocell.

[0228] A base station can accommodate one or more (e.g., three) cells. When a base station accommodates multiple cells, the overall coverage area of ​​the base station can be partitioned into multiple smaller areas, and each smaller area can also be provided with communication services by a base station subsystem (e.g., a remote radio head (RRH)). The terms "cell" or "sector" refer to part or the entire coverage area of ​​a base station and / or base station subsystem that provides communication services within that coverage area.

[0229] In the present disclosure, the base station transmitting information to a terminal may be interpreted as the base station instructing the terminal to control or operate based on the information.

[0230] Mobile Station In this disclosure, the terms "Mobile Station (MS)," "user terminal," "User Equipment (UE)," "terminal," and the like may be used interchangeably.

[0231] A mobile station may also be referred to by those skilled in the art as a subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handset, user agent, mobile client, client, or some other suitable terminology.

[0232] <Base Station / Mobile Station> At least one of the base station and the mobile station may be referred to as a transmitting device, a receiving device, a communication device, etc. At least one of the base station and the mobile station may be a device mounted on a mobile object, the mobile object itself, etc. The mobile object refers to a movable object, and may move at any speed. Naturally, this also includes cases where the mobile object is stationary. Examples of the mobile object include, but are not limited to, vehicles, transport vehicles, automobiles, motorcycles, bicycles, connected cars, excavators, bulldozers, wheel loaders, dump trucks, forklifts, trains, buses, handcars, rickshaws, ships and other watercraft, airplanes, rockets, satellites, drones (registered trademark), multicopters, quadcopters, balloons, and objects mounted thereon. The mobile object may also be an autonomous mobile object operating based on an operational command. It may be a vehicle (e.g., a car, an airplane, etc.), an unmanned mobile object (e.g., a drone, an autonomous vehicle, etc.), or a robot (manned or unmanned). At least one of the base station and the mobile station may be a device that does not necessarily move during communication operations. For example, at least one of the base station and the mobile station may be an IoT (Internet of Things) device such as a sensor.

[0233] Furthermore, a base station in the present disclosure may be read as a terminal. For example, the embodiments of the present disclosure may be applied to a configuration in which communication between a base station and a terminal is replaced with communication between multiple terminals (which may be called, for example, D2D (Device-to-Device) or V2X (Vehicle-to-Everything)). In this case, the terminal 20 may be configured to have the functions of the base station 10 described above. Furthermore, terms such as "uplink" and "downlink" may be read as terms corresponding to communication between terminals (for example, "side"). For example, terms such as an uplink channel and a downlink channel may be read as a side channel.

[0234] Similarly, the term "terminal" in the present disclosure may be read as "base station." In this case, the base station 10 may be configured to have the functions of the terminal 20 described above.

[0235] Fig. 22 shows an example configuration of a vehicle 2001. As shown in Fig. 22, the vehicle 2001 includes a drive unit 2002, a steering unit 2003, an accelerator pedal 2004, a brake pedal 2005, a shift lever 2006, front wheels 2007, rear wheels 2008, an axle 2009, an electronic control unit 2010, various sensors 2021 to 2029, an information service unit 2012, and a communication module 2013. Each aspect / embodiment described in the present disclosure may be applied to a communication device mounted on the vehicle 2001, and may be applied to the communication module 2013, for example.

[0236] The drive unit 2002 is configured, for example, by an engine, a motor, or a hybrid of an engine and a motor. The steering unit 2003 includes at least a steering wheel (also called a handle) and is configured to steer at least one of the front wheels and the rear wheels based on the operation of the steering wheel operated by the user.

[0237] The electronic control unit 2010 is composed of a microprocessor 2031, a memory (ROM, RAM) 2032, and a communication port (IO port) 2033. Signals are input to the electronic control unit 2010 from various sensors 2021 to 2029 provided in the vehicle 2001. The electronic control unit 2010 may also be called an ECU (Electronic Control Unit).

[0238] The signals from the various sensors 2021 to 2029 include a current signal from a current sensor 2021 that senses the current of the motor, a rotation speed signal of the front and rear wheels obtained by a rotation speed sensor 2022, an air pressure signal of the front and rear wheels obtained by an air pressure sensor 2023, a vehicle speed signal obtained by a vehicle speed sensor 2024, an acceleration signal obtained by an acceleration sensor 2025, an accelerator pedal depression amount signal obtained by an accelerator pedal sensor 2029, a brake pedal depression amount signal obtained by a brake pedal sensor 2026, a shift lever operation signal obtained by a shift lever sensor 2027, and a detection signal for detecting obstacles, vehicles, pedestrians, etc. obtained by an object detection sensor 2028.

[0239] The information service unit 2012 is composed of various devices, such as a car navigation system, an audio system, speakers, a television, and a radio, for providing (outputting) various types of information, such as driving information, traffic information, and entertainment information, and one or more ECUs that control these devices. The information service unit 2012 provides various types of multimedia information and multimedia services to the occupants of the vehicle 2001 by using information acquired from external devices via the communication module 2013, etc.

[0240] The information service unit 2012 may include input devices (e.g., keyboards, mice, microphones, switches, buttons, sensors, touch panels, etc.) that accept input from the outside, and may also include output devices (e.g., displays, speakers, LED lamps, touch panels, etc.) that output to the outside.

[0241] The driving assistance system unit 2030 is composed of various devices that provide functions for preventing accidents and reducing the driving burden on the driver, such as millimeter-wave radar, LiDAR (Light Detection and Ranging), cameras, positioning locators (e.g., GNSS, etc.), map information (e.g., high-definition (HD) maps, autonomous vehicle (AV) maps, etc.), gyro systems (e.g., IMU (Inertial Measurement Unit), INS (Inertial Navigation System), etc.), AI (Artificial Intelligence) chips, and AI processors, as well as one or more ECUs that control these devices. In addition, the driving assistance system unit 2030 transmits and receives various information via the communication module 2013 to realize the driving assistance function or the autonomous driving function.

[0242] The communication module 2013 can communicate with the microprocessor 2031 and components of the vehicle 2001 via the communication port. For example, the communication module 2013 transmits and receives data via the communication port 2033 to and from the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, front wheels 2007, rear wheels 2008, axle 2009, microprocessor 2031 and memory (ROM, RAM) 2032 in the electronic control unit 2010, and sensors 2021 to 29, which are provided in the vehicle 2001.

[0243] The communication module 2013 is a communication device that can be controlled by the microprocessor 2031 of the electronic control unit 2010 and can communicate with an external device. For example, it transmits and receives various information to and from the external device via wireless communication. The communication module 2013 may be located either inside or outside the electronic control unit 2010. The external device may be, for example, a base station, a mobile station, or the like.

[0244] The communication module 2013 may transmit at least one of signals from the above-mentioned various sensors 2021 to 2029 input to the electronic control unit 2010, information obtained based on the signals, and information based on input from the outside (user) obtained via the information service unit 2012 to an external device via wireless communication. The electronic control unit 2010, the various sensors 2021 to 2029, the information service unit 2012, etc. may be referred to as input units that accept input. For example, the PUSCH transmitted by the communication module 2013 may include information based on the above-mentioned input.

[0245] The communication module 2013 receives various information (traffic information, traffic signal information, vehicle distance information, etc.) transmitted from an external device and displays it on the information service unit 2012 provided in the vehicle 2001. The information service unit 2012 may also be called an output unit that outputs information (for example, outputs information to a device such as a display or speaker based on the PDSCH received by the communication module 2013 (or data / information decoded from the PDSCH)).

[0246] Furthermore, the communication module 2013 stores various information received from external devices in a memory 2032 that can be used by the microprocessor 2031. Based on the information stored in the memory 2032, the microprocessor 2031 may control the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, front wheels 2007, rear wheels 2008, axle 2009, sensors 2021 to 2029, and the like provided in the vehicle 2001.

[0247] <Meaning and Interpretation of Terms> As used in this disclosure, the terms "determining" and "determining" may encompass a wide variety of actions. "Determining" and "determining" may include, for example, judging, calculating, computing, processing, deriving, investigating, looking up, searching, inquiring (e.g., searching a table, database, or other data structure), ascertaining something that is considered to be a "judging" or "determining," and the like. "Determining" and "determining" may also include receiving (e.g., receiving information), transmitting (e.g., sending information), input, output, accessing (e.g., accessing data in memory), and the like that are considered to be a "judging" or "determining." Furthermore, "judgment" and "decision" can include regarding resolving, selecting, choosing, establishing, comparing, etc. as having been "judged" or "decided." In other words, "judgment" and "decision" can include regarding some action as having been "judged" or "decided." Furthermore, "judgment (decision)" can be interpreted as "assuming," "expecting," "considering," etc.

[0248] The terms "connected," "coupled," or any variation thereof, refer to any direct or indirect connection or coupling between two or more elements, and may include the presence of one or more intermediate elements between two elements that are "connected" or "coupled" to each other. The coupling or connection between elements may be physical, logical, or a combination thereof. For example, "connected" may be read as "access." As used in this disclosure, two elements may be considered to be "connected" or "coupled" to each other using one or more wires, cables, and / or printed electrical connections, as well as electromagnetic energy having wavelengths in the radio frequency range, microwave range, and optical (both visible and invisible) range, as some non-limiting and non-exhaustive examples.

[0249] <Reference Signal> A reference signal can also be abbreviated as RS (Reference Signal), and may also be called a pilot depending on the applicable standard.

[0250] <Meaning of "based on"> As used in this disclosure, the phrase "based on" does not mean "based only on," unless expressly stated otherwise. In other words, the phrase "based on" means both "based only on" and "based at least on."

[0251] "First," "Second" Any reference to an element using designations such as "first," "second," etc., used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed or that the first element must precede the second element in some way.

[0252] <Means> The "means" in the configuration of each device above may be replaced with "section," "circuit," "device," etc.

[0253] Open Format: When the terms "include," "including," and variations thereof are used in this disclosure, these terms are intended to be inclusive, similar to the term "comprising." Furthermore, when the term "or" is used in this disclosure, it is not intended to be an exclusive or.

[0254] <Time Units such as TTI, Frequency Units such as RB, and Radio Frame Configuration> A radio frame may be composed of one or more frames in the time domain. Each of the one or more frames in the time domain may be called a subframe. A subframe may further be composed of one or more slots in the time domain. A subframe may have a fixed time length (e.g., 1 ms) that is independent of numerology.

[0255] Numerology may be a communication parameter that applies to the transmission and / or reception of a signal or channel, and may indicate, for example, at least one of subcarrier spacing (SCS), bandwidth, symbol length, cyclic prefix length, transmission time interval (TTI), number of symbols per TTI, radio frame structure, specific filtering operations performed by the transceiver in the frequency domain, and specific windowing operations performed by the transceiver in the time domain.

[0256] A slot may be composed of one or more symbols in the time domain (such as an Orthogonal Frequency Division Multiplexing (OFDM) symbol or a Single Carrier Frequency Division Multiple Access (SC-FDMA) symbol). A slot may be a time unit based on numerology.

[0257] A slot may include multiple minislots. Each minislot may consist of one or multiple symbols in the time domain. A minislot may also be called a subslot. A minislot may consist of fewer symbols than a slot. A PDSCH (or PUSCH) transmitted in a time unit larger than a minislot may be called PDSCH (or PUSCH) mapping type A. A PDSCH (or PUSCH) transmitted using a minislot may be called PDSCH (or PUSCH) mapping type B.

[0258] The radio frame, subframe, slot, minislot, and symbol all represent time units for transmitting signals, and may be referred to by other names corresponding to the radio frame, subframe, slot, minislot, and symbol.

[0259] For example, one subframe may be called a transmission time interval (TTI), multiple consecutive subframes may be called a TTI, or one slot or one minislot may be called a TTI. That is, at least one of the subframe and the TTI may be a subframe (1 ms) in existing LTE, a period shorter than 1 ms (for example, 1-13 symbols), or a period longer than 1 ms. Note that the unit representing the TTI may be called a slot, minislot, etc. instead of a subframe.

[0260] Here, TTI refers to, for example, the smallest time unit for scheduling in wireless communication. For example, in an LTE system, a base station performs scheduling to allocate radio resources (such as frequency bandwidth and transmission power that can be used by each user terminal) to each user terminal in TTI units. Note that the definition of TTI is not limited to this.

[0261] The TTI may be a transmission time unit for a channel-encoded data packet (transport block), a code block, a code word, etc., or may be a processing unit for scheduling, link adaptation, etc. When a TTI is given, the time interval (e.g., the number of symbols) to which a transport block, a code block, a code word, etc. is actually mapped may be shorter than the TTI.

[0262] When one slot or one minislot is called a TTI, one or more TTIs (i.e., one or more slots or one or more minislots) may be the minimum time unit for scheduling. Also, the number of slots (minislots) constituting the minimum time unit for scheduling may be controlled.

[0263] A TTI having a time length of 1 ms may be called a regular TTI (TTI in LTE Rel. 8-12), normal TTI, long TTI, regular subframe, normal subframe, long subframe, slot, etc. A TTI shorter than a regular TTI may be called a shortened TTI, short TTI, partial or fractional TTI, shortened subframe, short subframe, minislot, subslot, slot, etc.

[0264] In addition, a long TTI (e.g., a normal TTI, a subframe, etc.) may be interpreted as a TTI having a time length of more than 1 ms, and a short TTI (e.g., a shortened TTI, etc.) may be interpreted as a TTI having a TTI length shorter than the TTI length of a long TTI and greater than or equal to 1 ms.

[0265] A resource block (RB) is a resource allocation unit in the time domain and the frequency domain, and may include one or more consecutive subcarriers in the frequency domain. The number of subcarriers included in an RB may be the same regardless of numerology, for example, 12. The number of subcarriers included in an RB may be determined based on numerology.

[0266] The time domain of an RB may include one or more symbols and may have a length of one slot, one minislot, one subframe, or one TTI. One TTI, one subframe, etc. may each be composed of one or more resource blocks.

[0267] Note that one or more RBs may also be called a physical resource block (PRB), a sub-carrier group (SCG), a resource element group (REG), a PRB pair, an RB pair, etc.

[0268] Furthermore, a resource block may be composed of one or more resource elements (REs). For example, one RE may be a radio resource region of one subcarrier and one symbol.

[0269] A Bandwidth Part (BWP) (which may also be referred to as a fractional bandwidth) may represent a subset of contiguous common resource blocks (RBs) for a given numerology on a given carrier, where the common RBs may be identified by their index relative to a Common Reference Point of the carrier. PRBs may be defined in a BWP and numbered within the BWP.

[0270] The BWP may include a BWP for UL (UL BWP) and a BWP for DL ​​(DL BWP). One or more BWPs may be configured for a UE within one carrier.

[0271] At least one of the configured BWPs may be active, and the UE may not expect to transmit or receive a given signal / channel outside the active BWP. Note that the terms "cell," "carrier," etc. in this disclosure may be read as "BWP."

[0272] The above-described structures of radio frames, subframes, slots, minislots, symbols, etc. are merely examples, and various changes may be made to the number of subframes included in a radio frame, the number of slots per subframe or radio frame, the number of minislots included in a slot, the number of symbols and RBs included in a slot or minislot, the number of subcarriers included in an RB, the number of symbols in a TTI, the symbol length, the cyclic prefix (CP) length, etc.

[0273] <Maximum Transmit Power> The "maximum transmit power" in the present disclosure may refer to the maximum value of transmit power, the nominal UE maximum transmit power, or the rated UE maximum transmit power.

[0274] Articles In this disclosure, where articles are added by translation, such as a, an, and the in English, the disclosure may include that the nouns following these articles are in the plural form.

[0275] <"Different"> In the present disclosure, the term "A and B are different" may mean "A and B are different from each other." Note that the term may also mean "A and B are each different from C." Terms such as "separate" and "coupled" may also be interpreted in the same way as "different."

[0276] The disclosures of the specification, drawings and abstract contained in Japanese Patent Application No. 2024-025702, filed February 22, 2024, are incorporated herein by reference in their entirety.

[0277] One aspect of the present disclosure is useful in wireless communication systems.

[0278] REFERENCE SIGNS LIST 1 Wireless communication system 10 Base station (BS) 20 Terminal (MS) 30 Directivity controllable reflector (RIS) 11 １ ~11 Ｘ Subarray 21 １ ~21 Ｙ Sub-array 30１ ~30 Ｚ RIS 101, 202 Transmitting unit 102, 201 Receiving unit 103, 203 Control unit 131 Beam search unit 132 Beam forming unit 133 Reflector position estimating unit 134 Allocation unit 135 Selection unit 136 Measurement unit 231 Received power measuring unit 232 Received power reporting unit 1001 Processor 1002 Memory 1003 Storage 1004 Communication device 1005 Input device 1006 Output device 1007 Bus

Claims

1. A beam determination method in a wireless communication system in which a base station and a terminal communicate using multiple subarrays via paths in the direct wave direction and / or paths via a reflector, comprising: performing a first process of assigning a subarray from among the multiple subarrays to the path in the direct wave direction or the path via the reflector; performing a second process of selecting an intermediate beam formed by the subarray based on the received power of a candidate beam formed by the subarray; performing a third process of measuring the communication quality of the intermediate beam; and performing the first process, the second process, and the third process at least once for each of the multiple subarrays, thereby determining each of multiple final beams formed by the multiple subarrays from the multiple intermediate beams based on the multiple communication qualities.

2. The beam determination method according to claim 1, wherein when the fourth process is performed, each of the plurality of final beams corresponding to the plurality of best communication qualities is determined.

3. The beam determination method according to claim 1, wherein when the third processing is performed, the communication quality is estimated by estimating the communication quality from a channel singular value.

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