Beam determination method

Abstract

Provided is a technology whereby a base station and a terminal can appropriately communicate in a wireless communication system including the base station, the terminal, and a reflective plate. A beam determination method according to one embodiment of the present disclosure includes performing a first process in a wireless communication system in which a base station and a terminal communicate through a path in a direct wave direction and / or a path through a reflective plate using a plurality of sub-arrays, assigning a sub-array of the plurality of sub-arrays to a path in the direct wave direction or a path through the reflective plate; performing second processing, and selecting an intermediate beam formed by the sub-array based on the receiving power of the candidate beam formed by the sub-array; performing third processing, and measuring the communication quality of the intermediate beam; and performing a fourth process by performing the first process, the second process, and the third process at least once on each of the plurality of sub-arrays, and determining each of a plurality of final beams formed by each of the plurality of sub-arrays from among the plurality of intermediate beams on the basis of the plurality of communication qualities.

Description

Technical Field

[0001] This disclosure relates to a beam determination method. Background Technology

[0002] In NR (New Radio) (also known as "5G"), which is the successor system to LTE (Long Term Evolution), technologies that meet requirements such as high-capacity systems, high-speed data transmission, low latency, simultaneous connection of multiple terminals, low cost, and power saving are being researched (for example, see Non-Patent Literature 1).

[0003] As a technology for achieving ultra-wideband transmission in high-frequency bands, there exists a technology that extends MIMO (Multiple-Input Multiple-Output) technology, which envisions having around tens of antenna elements, to Massive MIMO technology, which uses hundreds to thousands of antenna elements. MIMO technology is a technology in which the base station (BS) and the terminal (MS) each use multiple antenna elements to achieve spatial multiplexing and realize high-capacity communication.

[0004] Compared to low-frequency bands, high-frequency bands experience greater radio wave attenuation and possess radio wave characteristics that are difficult to diffract. Therefore, in the high-frequency band, due to shorter transmission distances and blockages, the reception quality deteriorates significantly.

[0005] To compensate for radio wave attenuation, beamforming (BF) using multiple antenna elements, as described above, is effective in base stations and terminals. For example, base stations using Massive MIMO (MIMO) utilize beamforming with multiple antenna elements to create beams with increased received power in specific directions. By compensating for radio wave attenuation through beamforming gain, transmission distance can be extended.

[0006] When beamforming is used to transmit signals, the base station or terminal, for example, performs a beam search to select a beam from multiple candidate beams for data communication, thereby improving reception quality at the communication target. For instance, the base station applies and transmits multiple pre-determined beam candidates to a downlink reference signal (e.g., an SSB (Synchronization Signal Block)). The terminal reports the received power of each beam, measured based on the received downlink reference signal, to the base station. The base station then determines the beam to apply to the terminal based on the received power from each terminal.

[0007] Furthermore, as a technique to reduce the computational load of MIMO signal processing when using a multi-element antenna for MIMO, a method called hybrid beamforming is being used, in which a portion of the MIMO signal processing is handled by analog circuitry.

[0008] To improve reception quality from obstructions and beyond line-of-sight, methods exist for setting up multiple transmitting points. Within this approach, using reflectors with small installation sizes and limitations is also effective. Furthermore, the reflector can be an intentionally placed object or a non-intentionally placed object such as a building or natural feature.

[0009] In recent years, the use of metamaterials and metasurfaces has been developed to dynamically control the direction of reflection, thereby enabling the control of directional reflectors (RIS: Reconfigurable Intelligent Surface) (for example, see Patent Document 1).

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Application Publication No. 2021-141359 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] To avoid obstructions or to create multiple paths to reduce spatial correlation and increase MIMO capacity, a Replication Path System (RIS) is considered. Thus, by setting up the RIS, multiple different propagation paths (hereinafter referred to as paths) can be formed even when beamforming occurs between the base station and the terminal. The base station and the terminal can achieve spatial multiplexing by simultaneously processing transmitted and received signals while knowing the status of each path.

[0015] However, there is room for research regarding spatial reuse using paths via RIS.

[0016] One of the objectives of this disclosure is to provide a technique that enables the base station and the terminal to communicate appropriately in a wireless communication system comprising a base station, a terminal, and a reflector.

[0017] Methods for solving problems

[0018] The beam determination method disclosed herein includes: in a wireless communication system in which a base station and a terminal use multiple subarrays to communicate via a path in the direct wave direction and / or via a path through a reflector, performing a first process that assigns a subarray among the multiple subarrays to the path in the direct wave direction or the path through the reflector; performing a second process that selects an intermediate beam formed by the subarrays based on the received power of candidate beams formed by the subarrays; performing a third process that measures 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 performing a fourth process based on the multiple communication qualities, the fourth process determining each of a plurality of final beams formed by the multiple subarrays from the multiple intermediate beams.

[0019] Invention Effects

[0020] According to one aspect of this disclosure, in a wireless communication system comprising a base station, a terminal, and a reflector, the base station and the terminal are able to communicate appropriately. Attached Figure Description

[0021] Figure 1 This is a diagram illustrating an example of a wireless communication system according to Embodiment 1 of this disclosure.

[0022] Figure 2 This is a block diagram illustrating an example of the antenna structure of the base station according to Embodiment 1.

[0023] Figure 3 This is a block diagram illustrating an example of the antenna structure of the terminal according to Embodiment 1.

[0024] Figure 4 This is a block diagram illustrating an example of the structure of the reflector according to Embodiment 1.

[0025] Figure 5 This is a block diagram illustrating an example of the structure of the base station according to Embodiment 1.

[0026] Figure 6 This is a block diagram illustrating an example of the functional structure of the base station according to Embodiment 1.

[0027] Figure 7 This is a block diagram illustrating an example of the structure of the terminal according to Embodiment 1.

[0028] Figure 8 This is a block diagram illustrating an example of the functional structure of the terminal according to Embodiment 1.

[0029] Figure 9This is a diagram illustrating a first example of beam search and beamforming according to Embodiment 1.

[0030] Figure 10 This is a diagram illustrating a second example of beam search and beamforming according to Embodiment 1.

[0031] Figure 11 This is a flowchart illustrating a first operational example of the wireless communication system according to Embodiment 1.

[0032] Figure 12A This is a flowchart illustrating a second operational example of the wireless communication system according to Embodiment 1.

[0033] Figure 12B This is a flowchart illustrating a second operational example of the wireless communication system according to Embodiment 1.

[0034] Figure 13 This is a diagram illustrating the conditions of a simulation example using the technology described in Implementation 1.

[0035] Figure 14 This is a diagram showing the results of a simulation example using the technology involved in Implementation 1.

[0036] Figure 15 This is a diagram showing the results of a simulation example using the technology involved in Implementation 1.

[0037] Figure 16A This is a diagram illustrating an example of beam number allocation change involved in Implementation 2.

[0038] Figure 16B This is a diagram illustrating another example of the beam number allocation change involved in Implementation 2.

[0039] Figure 17 This is a block diagram illustrating an example of the functional structure of the base station according to Embodiment 2.

[0040] Figure 18A This is a flowchart illustrating an operational example of the wireless communication system according to Embodiment 2.

[0041] Figure 18B This is a flowchart illustrating an operational example of the wireless communication system according to Embodiment 2.

[0042] Figure 19 This is a diagram showing the results of a simulation example using the technology involved in Implementation 2.

[0043] Figure 20 This is a diagram showing the results of a simulation example using the technology involved in Implementation 2.

[0044] Figure 21This is a diagram illustrating an example of the hardware structure of the base station and terminal involved in the implementation method.

[0045] Figure 22 This is a diagram illustrating an example of the structure of the vehicle involved in the embodiment.

[0046] Figure 23 This is a diagram illustrating an example of spatial multiplexing using a path via a reflector.

[0047] Figure 24 This is a diagram illustrating an example of spatial multiplexing using a path that does not pass through a reflector. Detailed Implementation

[0048] (How this disclosure came about)

[0049] As mentioned above, by setting up RIS, multiple different paths can be formed even when beamforming is performed between the base station and the terminal, and the base station and the terminal can achieve spatial multiplexing. Figure 23 This is a diagram illustrating an example of spatial multiplexing using a path via RIS, where the subarray #1 of the base station and the subarray #1 of the terminal form a direct wave (or LOS (loss of sight)) path (i.e., a path not via RIS), and the subarray #2 of the base station and the subarray #2 of the terminal form a path via RIS.

[0050] However, the location of the terminal is unknown to the base station, therefore, as mentioned above, simulated beam search needs to be performed in each subarray. In beam search, generally, the base station searches for the beam with the highest received power at the terminal (i.e., a beam search based on the terminal received power maximization criterion). In this case, the propagation loss of the path via the RIS is greater than that of the direct wave path, therefore the direct wave path will be selected during beam search, and even if the RIS is set, it may actually be unusable (i.e., no beam is formed). Figure 23 The path shown). Figure 24 This is a diagram illustrating an example of spatial multiplexing using a path that does not pass through RIS, where a direct wave path is formed by subarray #1 of the base station and subarray #1 of the terminal, and a direct wave path is formed by subarray #2 of the base station and subarray #2 of the terminal. Figure 24 This illustrates a situation where RIS cannot actually be utilized even if it is set up.

[0051] The inventors of this invention conceived of a technique that selects a path via RIS even when performing beam search based on a terminal receive power maximization specification. This technique will be described in detail in the following Embodiment 1.

[0052] Furthermore, even when spatial multiplexing is achieved using the path via the reflector through the aforementioned techniques, changing the allocation of beams or the number of beams depending on the situation may improve the MIMO capacity effect.

[0053] The inventors of this invention conceived of a technique for adaptively altering the distribution of beams or the number of beams between direct waves and waves transmitted via a reflector, depending on the circumstances. This technique will be described in detail in Embodiment 2 below.

[0054] By using the techniques described in Embodiments 1 and 2, in a wireless communication system including a base station, a terminal, and a reflector, the base station and the terminal can communicate appropriately.

[0055] Hereinafter, with reference to the accompanying drawings, an embodiment of one aspect of this disclosure will be described. Furthermore, the embodiment described below is an example, and the application of this disclosure is not limited to the following embodiment.

[0056] (Implementation Method 1)

[0057] <Wireless Communication Systems>

[0058] Figure 1 This is a diagram illustrating an example of a wireless communication system according to Embodiment 1 of this disclosure. (See diagram below.) Figure 1 As shown, the wireless communication system 1 includes a base station (BS) 10, a terminal (MS) 20, and a reflector (RIS) 30 capable of controlling directionality. Figure 1 In this embodiment, one BS 10, one MS 20, and one RIS 30 are shown, but this is just one example; multiple BSs, multiple MSs, and / or multiple RISs may also exist. Furthermore, in this embodiment, a reflector is used as the RIS for explanation, but as mentioned above, a reflector can be an intentionally placed object or a general building, natural object, or other unintentionally placed object.

[0059] BS 10 is a communication device that provides one or more cells and communicates wirelessly with MS 20. The physical resources of the wireless signal are defined in the time and frequency domains. The time domain can also be defined by the number of OFDM (Orthogonal Frequency Division Multiplexing) symbols. The frequency domain can also be defined by the number of subcarriers or resource blocks.

[0060] BS 10 transmits control information, configuration information, data, and other DL signals to MS 20 via the downlink (DL). BS 10 receives control information, information related to the processing capabilities of MS 20 (capability information; UE capability) and data, and other UL signals from MS 20 via the uplink (UL).

[0061] MS 20 is a communication device with wireless communication capabilities, such as a smartphone, mobile phone, tablet computer, wearable terminal, or M2M (machine-to-machine) communication module. MS 20 is wirelessly connected to BS 10 and utilizes various communication services provided by the wireless communication system 1.

[0062] MS 20 receives control signals, setting information, data and other DL signals from BS 10 via DL, and sends control signals, MS 20 capability information, data and other UL signals to BS 10 via UL.

[0063] Both BS 10 and MS 20 are capable of beamforming for signal transmission and reception. BS 10 can also have multiple antenna elements, enabling high-speed transmission over a wide area, even in high-frequency bands, through the use of Massive MIMO technology. Similarly, MS 20 can also have multiple antenna elements, employing Massive MIMO technology.

[0064] Figure 2 as well as Figure 3 These are block diagrams illustrating an example of the antenna structure of BS 10 and MS 20 according to Embodiment 1.

[0065] BS 10 is equipped with an array antenna, such as Figure 2 As shown, it can have multiple subarrays 111~11 obtained by dividing the array antenna. X (X is an integer greater than or equal to 2). Similarly, the MS 20 also features an array antenna, such as... Figure 3 As shown, it can have multiple subarrays 211~21 obtained by dividing the array antenna. Y (Y is an integer greater than or equal to 2). Additionally, the subarrays 111~11 of BS 10... X It can also be configured in a distributed manner to apply distributed MIMO.

[0066] In order to use an appropriate beam to transmit signals to MS10, BS 10 performs beam search. For example, BS 10 uses specific radio resources to transmit signals (synchronization signals, reference signals, or synchronization signal blocks (SSBs), etc.; referred to as measurement signals) from the subarray through multiple beams (candidate beams). Then, MS 20 receives the measurement signals transmitted from BS 10 through multiple beams in the subarray, measures the received power (e.g., Reference Signal Received Power (RSRP)) for each measurement signal associated with a candidate beam, and reports (transmits) the measurement results of the received power to BS 10.

[0067] Additionally, here (and below), it is assumed that the MS 20 reports the received power of the beam (measurement signal) transmitted from the BS 10 to the BS 10, but it is not limited to this. For example, any indicator that can determine the received strength or reception status, communication performance or communication quality of the beam, such as SNR (Signal-to-Noise Ratio) or throughput, can also be used.

[0068] In implementation method 1, the duplex mode can be either TDD (Time Division Duplex) or FDD (Frequency Division Duplex).

[0069] The RIS 30 is a metasurface reflector composed of multiple reflective elements. By adjusting the reflection phase of each reflective element, a reflection pattern with arbitrary direction and beamwidth can be formed. The RIS 30 relays wireless signals (from BS 10 to MS 20) without decoding user data.

[0070] Alternatively, a wireless repeater can be used as an alternative to the RIS 30. This repeater amplifies the received signal (and further converts the frequency as needed) and outputs it, and can use multiple antennas to form beams of arbitrary direction and beamwidth. The RIS 30 and the wireless repeater can also be referred to as repeater devices, etc.

[0071] Figure 4 This is a block diagram illustrating an example of the structure of the RIS 30 according to Embodiment 1. Figure 4 As shown, RIS 30 can also consist of more than one RIS 301~30. Z (Z is an integer greater than or equal to 1). In the case where RIS 30 consists of only one RIS 301 (i.e., when Z is 1), RIS 30 and RIS 301 can refer to the same RIS.

[0072] Next, the structures of BS 10 and MS 20 will be described. Furthermore, the structures of BS 10 and MS 20 described below represent one example of the functions associated with the implementation. BS 10 and MS 20 may also have functions not shown. Moreover, the functional divisions and / or names of functional units are not limited as long as they perform the operations involved in the implementation. Furthermore, in reference to... Figure 6 as well as Figure 8 In the BS 10 and / or MS 20 described below, multiple functional units may be integrated into one functional unit, or one functional unit may be divided into multiple functional units.

[0073] Figure 5 This is a block diagram illustrating an example of the structure 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.

[0074] The transmitting unit 101 transmits the DL signal to the MS 20. For example, the transmitting unit 101 transmits the DL signal under the control of the control unit 103.

[0075] The DL signal may include, for example, downlink data signals and control information (e.g., DCI (Downlink Control Information)). Furthermore, the DL signal may include scheduling information related to the signal transmission of MS 20 (e.g., UL authorization). Additionally, the DL signal may also include higher-layer control information (e.g., RRC (Radio Resource Control) control information). Furthermore, the DL signal may also include reference signals.

[0076] The channels used for transmitting DL signals may include, for example, data channels and control channels. For instance, 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, BS 10 uses the PDCCH to send control information to MS 20 and uses the PDSCH to send data signals to MS 20.

[0077] The reference signals included in the DL signal may include at least one of the following: DMRS (Demodulation Reference Signal), PTRS (Phase Tracking Reference Signal), CSI-RS (Channel State Information-Reference Signal), SRS (Sounding Reference Signal), and PRS (Positioning Reference Signal) for location information. For example, reference signals such as DMRS and PTRS are used for demodulation of downlink data signals and are transmitted using PDSCH.

[0078] 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.

[0079] The transmitting unit 101 and the receiving unit 102 (which may also be collectively referred to as the communication unit) communicate with the MS 20.

[0080] The control unit 103 controls the overall operation including the transmission processing of the transmission unit 101 and the reception processing of the reception unit 102, and the communication operation of the BS 10.

[0081] For example, control unit 103 acquires data and control information from higher layers and outputs it to transmitting unit 101. Furthermore, control unit 103 outputs data and control information received from receiving unit 102 to higher layers.

[0082] For example, the control unit 103 allocates resources (or channels) used for transmitting and receiving DL signals and / or UL signals based on signals received from the MS 20 (e.g., data and control information) and / or data and control information obtained from higher layers. Information related to the allocated resources may be included in the control information transmitted to the MS 20.

[0083] Furthermore, the channels used for transmitting DL signals are not limited to the examples described above. For instance, the channels used for transmitting DL signals may include RACH (Random Access Channel) and PBCH (Physical Broadcast Channel). RACH, for example, can be used for transmitting DCIs that include RA-RNTI (Random Access Radio Network Temporary Identifier).

[0084] Figure 6 This is a block diagram illustrating an example of the functional structure of the BS 10 according to Embodiment 1. The BS 10 (e.g., control unit 103) includes, for example, a beam search unit 131, a beamforming unit 132, and a reflector position estimation unit 133.

[0085] BS 10 transmits measurement signals to MS 20 via multiple beams and receives measurement results of the received power of the measurement signals from MS 20. Based on the received power measurement results, BS 10 spatially synthesizes the beams of the subarrays it possesses, suppressing or canceling signals in the direct wave direction (MS direction) or direct wave direction, so that MS 20 at least cannot see the direct wave transmitted by BS 10 (this can also be referred to as "or ..." and "" and in" ("in"" ," "","and"","and,""""and """"generating " ' ' ' in ' or " beams,," "" " or " or " or " or " " or " " " or " " or " " " " ' ' or " or " " ) "" "" "" " " " " " "" " " " " " " " " "" " " "

[0086] The beam search unit 131 receives the measurement results of the received power of the beam transmitted by the BS 10 from the MS 20 via the receiving unit 102. Based on the received received power measurement results, it searches for the beams of the subarrays of the BS 10, the beams of the subarrays of the MS 20, and / or the beams of the RIS 30, and selects (or determines) the beam that includes the beam that propagates the signal via the RIS 30 and is used for communication with the MS 20.

[0087] The beamforming unit 132 spatially synthesizes the beams of the subarrays of BS 10 to suppress signals in the direction of the direct wave, so that MS 20 can at least not see the direct wave transmitted by BS 10.

[0088] 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 can also be stored as position information (e.g., latitude and longitude) in the BS 10 (e.g., processor 1001, memory 1002, storage 1003, etc., described later), and the reflector position estimation unit 133 can also estimate the position of the RIS 30 from the position represented by the stored position information. Furthermore, for example, if the RIS 30 is mounted on a drone or the like and moves, the reflector position estimation unit 133 can also estimate the position of the RIS 30 by communicating with the drone or the like and obtaining position information from the drone or the like. The reflector position estimation unit 133 outputs the estimated position of the RIS 30 to the beamforming unit 132.

[0089] Next, specific processing examples of the beam search unit 131, beam forming unit 132, and reflector position estimation unit 133 described above will be explained.

[0090] The following describes a processing example with a RIS number of 1 and a BS 10 and MS 20 subarray number of 2.

[0091] (Processing 1A) Beam search unit 131 receives, via receiving unit 102, the measurement result of the received power of the beam (direct wave measurement signal) of subarray 111 transmitted by BS 10. Based on the received received power measurement result, beam search unit 131 searches for the beams of the subarrays possessed by BS 10 (among the beams of subarray 111 transmitted by BS 10, the beam with the highest received power of subarray 211 possessed by MS 20 is selected (final first BS beam)). Beam search unit 131 outputs the identification information of the final first BS beam selected through the search to beamforming unit 132. Thus, BS 10 (beamforming unit 132) can use a portion of the subarrays to form a beam in the direct wave direction (MS 20 direction).

[0092] (Process 1B) Beam search unit 131 receives, via receiving unit 102, the measurement result of the received power of the beam (direct wave measurement signal) of subarray 111 selected by beam search unit 131 and transmitted by BS 10 from MS 20. Based on the received received power measurement result, beam search unit 131 searches for beams of subarrays 211 of MS 20 (selecting the beam with the highest received power among the beams of subarray 211 of MS 20 (final first MS beam)). Beam search unit 131 outputs the identification information of the final first MS beam selected through the search to beamforming unit 132. Thus, MS 20 (e.g., described later) Figure 8 The beamforming unit (not shown) can use a portion of the subarray to form a beam in the direct wave direction (BS 10 direction).

[0093] (Process 1C) Based on the position of RIS 301 output by the reflector position estimation unit 133, the beamforming unit 132 selects the beam in the direction of RIS 301 (the final second BS beam) from the beams of the subarray 112 provided by the BS 10. Thus, the BS 10 can use other subarrays to form a beam in the direction of RIS 30.

[0094] (Processing 1D) Beamforming unit 132 selects the final first BS beam of subarray 111 of BS 10 based on the identification information of the final first BS beam output by beam search unit 131.

[0095] (Processing 1E) Based on the identification information of the final first MS beam output by the beam search unit 131, the beamforming unit 132 selects a beam (the middle second MS beam) that is in the same direction as the final first MS beam of the subarray 211 of the MS 20 from the beams of the subarray 212 of the MS 20.

[0096] (Processing 1F) Beamforming unit 132 performs channel estimation between subarrays 111 and 212, and between subarrays 111 and 212, based on the final first BS beam of selected subarray 111, the final second BS beam of subarray 112 in the RIS 301 direction, and the intermediate second MS beam of subarray 212. 11 and h 12 (All are complex numbers) are used to represent the beam of the beamforming unit 132 to the subarray 111 multiplied by the complex number - ( h 12 ) / (|h 11 | 2 +σ n 2 )(set up h 11 The complex conjugate of |h 11 | 2 h 11 The square of the absolute value, σ n 2 (This represents a fixed parameter indicating the variance of the noise power). The beamforming unit 132 simultaneously transmits the multiplied beams of subarray 111 and subarray 112 to the transmitting unit 101.

[0097] (Processing 1G) Beam search unit 131 receives, via receiving unit 102, the measurement result of the received power of the processed 1F beam formed by beamforming unit 132 and transmitted by BS 10 from MS 20. Based on the received received power measurement result, beam search unit 131 searches for the beam of RIS 301 (among the beams of RIS 301 (towards MS 20), selecting the beam with the highest received power of the subarray 212 of MS 20 (final first RIS beam)). Beam search unit 131 outputs the identification information of the final first RIS beam selected through the search to beamforming unit 132. Thus, RIS 30 (e.g., beamforming unit not shown) is able to form a beam in the direction of MS 20.

[0098] (Processing 1H) Beam search unit 131 receives, via receiving unit 102, the measurement result of the received power of the beam formed by beamforming unit 132 and transmitted by BS 10 after processing 1F from MS 20. Based on the received received power measurement result, beam search unit 131 searches for beams of the subarrays of MS 20 (selecting the beam with the highest received power among the beams of subarray 212 of MS 20 (the final second MS beam)). Beam search unit 131 outputs the identification information of the final second MS beam selected through the search to beamforming unit 132. Thus, MS 20 can use other subarrays to form a beam in the RIS 30 direction.

[0099] Figure 9 This diagram illustrates a first example of beam search and beamforming according to Embodiment 1, and also illustrates the above-described processing example when the number of RIS is 1 and the number of subarrays of BS 10 and MS 20 is 2. Figure 9 As shown, by synthesizing the beams of subarrays 111 and 112 of BS 10 and forming a null beam in the direct wave direction toward MS 20, it is possible to select the beam (propagation path) via RIS 301 based on the received power of the measurement signal.

[0100] Next, a processing example will be explained when the number of RIS is N (N is an integer greater than or equal to 2), and the number of subarrays of BS 10 and MS 20 is (N+1) or more. In this example, the search is performed via the nth RIS 30 n In the case of beamforming, it is necessary to combine the direct wave with the waves transmitted via the first RIS 301 to the (n-1)th RIS 301. n-1 All waves are nullified.

[0101] (Process 2A) BS 10 performs the above processes 1A to 1G. BS 10 sets n to 2.

[0102] (Process 2B) Beamforming unit 132 is based on RIS 30 output by reflector position estimation unit 133. n The position is within subarray 11 of BS 10. n+1 Among the beams, select RIS 30 n The beam in the direction (finally the (n+1)th BS beam). Thus, BS 10 can use a portion of the subarray to form the beam in the RIS 30n direction.

[0103] (Processing 2C) Based on the identification information of the final first BS beam to the final nth BS beam output by the beam search unit 131, the beamforming unit 132 selects the subarrays 111 to 112 of BS 10. n The final first BS beam ~ the final nth BS beam. BS 10 sets p to 1.

[0104] (Processing 2D) Beamforming unit 132, based on the identification information of the p-th MS beam output by beam searching unit 131, performs beamforming on the subarray 21 of MS 20. p+1 Among the beams, select the subarray 21 that is available on the MS 20. p The beam in the same direction as the final p-th MS beam (the middle p+1 MS beam). BS 10 sets q to 1.

[0105] (Processing 2E) Beamforming unit 132 based on selected subarray 11 q The final q-th BS beam, subarray 11 q+1 RIS 30 q+1 The final q+1th BS beam in the direction, and subarray 21 p+1 Channel estimation is performed on the (p+1)th MS beam in the middle. Let h be the path... pq (Complex number) to represent subarray 11 q AND subarray 21 p+1 The channel between them. Increment q by 1.

[0106] (Process 2F) Beamforming unit 132 repeatedly performs Process 2D and Process 2E until channel estimation for q=n is performed. BS 10 increments p by 1.

[0107] (Processing 2G) Beamforming unit 132 repeatedly performs processing 2D to processing 2F until channel estimation is performed for p=n.

[0108] (Processing 2H) Beamforming unit 132 will use [h pq Let H be an n×(n+1) matrix with elements, and calculate the singular value decomposition (H=UΣV).H The beamforming unit 132 sets the (n+1)th row of V as the (n+1)th dimension column vector of V. n+1 For the subarray 11 of BS 10 q (1≤q≤n) beam multiplied by a complex number (set up Indicates v n+1 The complex conjugate of (n+1), |v n+1 (n+1)| 2 Indicates v n+1 The square of the absolute value of (n+1), σ n 2 (This represents a fixed parameter indicating the variance of the noise power). Beamforming unit 132 multiplies the subarrays 111-11... n Beams and subarrays 11 n+1 The beam is simultaneously transmitted to the transmitting unit 101.

[0109] (Processing 2I) Beam search unit 131 receives, via receiving unit 102, the measurement result of the received power of the beam formed by beamforming unit 132 and transmitted by BS 10 after processing 2H from MS 20. Based on the received received power measurement result, beam search unit 131 searches for RIS 30. n The beam (in RIS 30) n In the beam (towards MS 20), select the subarray 21 provided by MS 20. n+1 The received power becomes the largest beam (the final nth RIS beam). The beam search unit 131 outputs the identification information of the final nth RIS beam selected through the search to the beamforming unit 132. Thus, RIS30 n It can form a beam in the MS 20 direction.

[0110] (Processing 2J) Beam search unit 131 receives, via receiving unit 102, the measurement result of the received power of the beam formed by beamforming unit 132 and transmitted by BS 10 after processing 2H from MS 20. Based on the received received power measurement result, beam search unit 131 searches for the subarray 21 of MS 20. n+1 The beam (in the subarray 21 of the MS 20) n+1 Among the beams, the beam with the highest received power (the final (n+1)th MS beam) is selected. The beam search unit 131 outputs the identification information of the final (n+1)th MS beam selected through the search to the beamforming unit 132. BS 10 increments n by 1. Thus, MS 20 can use a portion of the subarray to form RIS 30. n directional beam.

[0111] (Process 2K) BS 10 repeatedly performs Process 2B~Process 2J until the beam with n=N is searched.

[0112] Figure 10 This diagram illustrates a second example of beam search and beamforming according to Embodiment 1, and also illustrates the above-described processing example when the number of RIS is N (N is an integer greater than or equal to 2) and the number of subarrays of BS 10 and MS 20 is (N+1) or more. Figure 10 As shown, in addition to forming a null beam in the direct wave direction towards MS 20 to make the subarray 21 of MS 20 n+1 The subarrays 111~11 of BS 10 are not visible. n In addition to the beam, it also passes through RIS 301~30 n-1 The direction of the RIS (referred to as the selected RIS) forms a null beam, thereby enabling selection of the beam via the RIS 30 based on the received power of the measurement signal. n The beam (propagation path).

[0113] As explained above, BS 10 (beam search unit 131, beamforming unit 132, reflector position estimation unit 133) can select or determine the beam (propagation path) via RIS 30 based on the received power of the measurement signal by forming a null beam at least in the direct wave direction toward MS 20.

[0114] <Terminal Structure>

[0115] Figure 7 This is a block diagram illustrating an example of the structure 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.

[0116] The receiving unit 201 receives the DL signal transmitted from BS 10. For example, the receiving unit 201 receives the DL signal under the control of the control unit 203.

[0117] The transmitting unit 202 transmits a UL signal to BS 10. For example, the transmitting unit 202 transmits a UL signal under the control of the control unit 203.

[0118] The UL signal may include, for example, uplink data signals and control information (e.g., UCI (Uplink Control Information)). For instance, it may include information related to the processing capabilities of the MS 20 (e.g., UE capability). Furthermore, the UL signal may also include reference signals.

[0119] The channels used for transmitting UL signals may include, for example, data channels and control channels. For instance, 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, MS 20 uses the PUCCH to transmit control information and the PUSCH to transmit data signals.

[0120] The reference signals included in the UL signal may include, for example, at least one of DMRS, PTRS, CSI-RS, SRS, and PRS. For example, reference signals such as DMRS and PTRS are used for demodulation of uplink data signals and are transmitted using an uplink channel (e.g., PUSCH).

[0121] The receiving unit 201 and the transmitting unit 202 (which can also be collectively referred to as the communication unit) communicate with the network of BS 10, etc.

[0122] The control unit 203 controls the overall operation including the receiving process in the receiving unit 201 and the transmitting process in the transmitting unit 202, as well as the communication operation of the MS 20.

[0123] For example, control unit 203 acquires data and control information from higher layers and outputs it to transmitting unit 202. Furthermore, control unit 203 may output data and control information received from receiving unit 201 to higher layers, for example.

[0124] For example, control unit 203 controls the transmission of information fed back to BS 10. The information fed back to BS 10 may include, for example, HARQ-ACK / NACK, Channel State Information (CSI), and Scheduling Request (SR). The information fed back to BS 10 may also be included in UCI. UCI is transmitted, for example, within the resources of PUCCH.

[0125] Furthermore, the channels used for transmitting UL signals are not limited to the examples mentioned above.

[0126] Figure 8 This is a block diagram illustrating an example of the functional structure of the MS 20 according to Embodiment 1. The MS 20 (e.g., control unit 203) includes, for example, a received power measurement unit 231 and a received power reporting unit 232.

[0127] Received power measurement unit 231 for subarrays #211~#21Y Each of these units measures the power of the beam (measurement signal) transmitted from BS 10. For example, the receive power measurement unit 231 measures the reference signal transmitted from BS 10 and obtains the reference signal received power (RSRP). The receive power measurement unit 231 measures the received power of the direct beam from BS 10 and the beam from BS 10 via RIS 30. The receive power measurement unit 231 outputs the received power measurement results to the receive power reporting unit 232.

[0128] The received power reporting unit 232, via the transmitting unit 202, reports (feeds back) the received power measurement result (information representing the measured received power) output by the received power measurement unit 231 to BS 10. The received power reporting unit 232 is for subarrays #211~#21. Y Each of these can report the measured power of all beams, or the measured power of the best beams up to the first x.

[0129] <Operating Examples of Wireless Communication Systems>

[0130] Next, refer to Figure 11 as well as Figures 12A-12B An operational example of wireless communication system 1 will be explained.

[0131] Figure 11 This is a flowchart illustrating a first operating example of the wireless communication system 1 according to Embodiment 1. The first operating example corresponds to the case where the number of RIS is 1 and the number of subarrays of BS 10 and MS 20 is 2.

[0132] In step S11, BS 10 estimates the position of the first RIS. Step S11 can be performed by the reflector position estimation unit 133. The first RIS can correspond to RIS 301.

[0133] In step S12, BS 10 performs beam search for the first subarray of BS 10 and the first subarray of MS 20. Step S12 can be executed by beam search unit 131, for example, corresponding to processes 1A to 1B described above. The first subarray of BS 10 and the first subarray of MS 20 can correspond to subarray 111 and subarray 211, respectively. Furthermore, step S12 is assumed to include the transmission of measurement signals based on BS 10, the measurement and reporting of the received power of measurement signals based on MS 20.

[0134] In step S13, BS 10 suppresses the signal in the direct wave direction toward MS 20. Step S13 can be performed by beamforming unit 132, for example, corresponding to processes 1C to 1F described above.

[0135] In step S14, BS 10 performs a beam search for the first RIS. Step S14 can be executed by the beam search unit 131, for example, corresponding to the process 1G described above. Furthermore, step S14 is assumed to be accompanied by the transmission of a measurement signal based on BS 10, the measurement of the received power of the measurement signal based on MS 20, and a report.

[0136] In step S15, BS 10 performs a beam search for the second subarray of MS 20. Step S15 can be executed by beam search unit 131, for example, it can correspond to the process 1H described above. The second subarray of MS 20 can correspond to subarray 212. In addition, step S15 is accompanied by the transmission of measurement signals based on BS 10, the measurement of the received power of measurement signals based on MS 20, and reporting.

[0137] Figures 12A-12B This is a flowchart illustrating a second operating example of the wireless communication system 1 according to Embodiment 1. The second operating example corresponds to the case where the number of RIS is N (N is an integer greater than or equal to 2) and the number of subarrays of BS 10 and MS 20 is (N+1) or more.

[0138] Figures 12A-12B Steps S11 to S15 shown are respectively with Figure 11 Steps S11 to S15 shown are the same.

[0139] In step S16, BS 10 is set to n=2.

[0140] In step S21, BS 10 estimates the position of the nth RIS. Step S21 can be performed by the reflector position estimation unit 133. The nth RIS can correspond to RIS 30. n .

[0141] In step S22, BS 10 suppresses signals in the direct wave direction toward MS 20 and signals in the directions via the selected first RIS to (n-1)th RIS. Step S22 can be performed by beamforming unit 132, for example, corresponding to processes 2B to 2H described above.

[0142] In step S23, BS 10 performs a beam search for the nth RIS. Step S23 can be executed by beam search unit 131, for example, corresponding to the process 2I described above. Furthermore, step S23 is assumed to be accompanied by the transmission of a measurement signal based on BS 10, the measurement of the received power of the measurement signal based on MS 20, and a report.

[0143] In step S24, BS 10 performs a beam search for the (n+1)th subarray of MS 20. Step S24 can be executed by beam search unit 131, for example, it can correspond to the process 2J described above. The (n+1)th subarray of MS 20 can correspond to subarray 21. n+1 Additionally, step S24 is configured to include the transmission of a measurement signal based on BS 10, the measurement of the received power of the measurement signal based on MS 20, and a report.

[0144] In step S25, BS 10 increments n by 1.

[0145] In step S26, BS 10 determines whether n is (N+1) or greater. If n is (N+1) or greater (step S27; Yes), the process ends; if n is not (N+1) or greater (step S27; No), the process returns to step S21, and the process is repeated.

[0146] In summary, BS 10 and MS 20 search (select or determine) the beam in the direct wave direction among a subset of subarrays, thereby forming a beam in the direct wave direction using a subset of subarrays (process 1). Next, BS 10 uses the other subarrays to form a beam in the RIS 30 direction (process 2). Process 2 can be performed as a result of beamforming in process 1. Next, BS 10 suppresses signals in the direct wave direction toward MS 20, thereby allowing RIS 30 to form a beam in the MS 20 direction (process 3). Next, MS 20 uses the other subarrays to form a beam in the RIS 30 direction (process 4). Processes 3 and 4 can be performed as results of beamforming in process 2. Through these processes, the beam via RIS 30 can be selected, spatial correlation between subarrays can be reduced, and MIMO capacity can be improved. Alternatively, process 3 can also be performed by MS 20. That is, in process 3, MS 10 can also suppress signals in the direct wave direction of BS 20, thereby RIS 30 forming a beam in the direction of BS 10 or MS 20. Furthermore, when the number of RIS is 2 or more and the number of subarrays of BS 10 and MS 20 is 3 or more, by repeatedly performing processes 2 to 4, the beam passing through RIS 30 can also be selected. In this case, BS 30 also suppresses signals in the direction passing through the selected RIS 30 in process 3.

[0147] As explained above, the wireless communication system 1 (BS 10, MS 20, RIS 30) forms a null beam at least in the direct wave direction toward MS 20, thereby enabling the selection or determination of the beam (propagation path) through RIS 30 to propagate the signal based on the received power of the measurement signal.

[0148] <Simulation>

[0149] Next, a simulation using the technology described in Implementation Method 1 will be explained. This simulation is in... Figure 13 Implemented under the conditions shown in Tables 1 to 4 below.

[0150] [Table 1]

[0151]

[0152] [Table 2]

[0153]

[0154] [Table 3]

[0155]

[0156] [Table 4]

[0157]

[0158] Figure 14 This is a graph showing the results of this simulation (the case of beam selection based on maximum power search). Figure 14 (A), (B), (C), and (D) show the beam selection of the first subarray of the BS (corresponding to subarray 111), the first subarray of the MS (corresponding to subarray 211), the RIS, and the second subarray of the MS (corresponding to subarray 212) when using the null beamforming involved in Embodiment 1. Figure 14 (a), (b), (c), and (d) show the beam selection of the first subarray of the BS, the first subarray of the MS, the RIS, and the second subarray of the MS without using the null beamforming involved in Embodiment 1 (comparative examples).

[0159] In either the case of using null beamforming according to Embodiment 1, or the case of not using null beamforming according to Embodiment 1, such as Figure 14 As shown in (A) and (a), for the first subarray of BS, it can be seen that the beam is oriented towards the MS direction, as follows. Figure 14 As shown in (B) and (b), for the first subarray of MS, it can be seen that the beam is oriented in the direction of BS.

[0160] For RIS, when using the null beamforming described in Implementation 1, such as Figure 14 As shown in (C), the beam is oriented in the desired direction (i.e., the MS direction). On the other hand, without using null beamforming, as... Figure 14As shown in (c), the power appears to be minimum when the beam is directed towards the MS direction. Under the conditions of this simulation example, it is assumed that the beam of LOS is out of phase with the beam of RIS. The higher the power of the beam through RIS, the more it cancels out the beam of LOS, and the lower the power at the MS end.

[0161] Furthermore, for the second subarray of the MS, when using the null-beamforming described in Implementation 1, it is also as follows... Figure 14 As shown in (D), the beam is oriented in the desired direction (RIS direction). On the other hand, without using null beamforming, as... Figure 14 As shown in (d), the power is maximized when the beam is directed toward the BS direction.

[0162] Figure 15 This is a graph showing the results of this simulation (throughput simulation results). Figure 15 The "beam #1" shown indicates the beam of the first subarray of the BS and the beam of the first subarray of the MS. Furthermore, Figure 15 The “beam #2” shown indicates the beam of the second subarray of the BS and the beam of the second subarray of the MS.

[0163] When using the null beamforming described in Implementation 1, such as Figure 15 As shown, two streams were transmitted (LOS transmission and transmission via RIS).

[0164] <Modifications of Implementation Method 1>

[0165] In the above, an example of using a method to synthesize beams radiated from multiple array antennas (subarrays) was described as a method for suppressing signals, but this disclosure is not limited to this example. For example, as a method for suppressing signals, a method that does not radiate beams from a single array antenna in a specific direction can also be used. Specifically, beamforming can also be performed in a manner that does not radiate beams from a single array antenna in a specific direction by using known techniques such as the Butler matrix and DFT (Discrete Fourier Transform). In other words, suppressing signals toward the direct wave direction or the direction via the selected RIS can be achieved either by signal processing using multiple array antennas of BS 10 and / or MS 20, or by directivity formation of any array antenna of BS 10 and / or MS 20.

[0166] The above describes the beam selection (beam search) of the BS 10 subarray, the MS 20 subarray, and the RIS 30 subarray, but these processes (e.g., subarrays 111-11 of the BS 10) are not described in detail.X And the subarrays 211~21 of MS 20 Y (Beam selection of RIS 30) can be performed sequentially or simultaneously. These beam selections (1) use multiple array antennas of BS 10 and / or MS 20 to synthesize reference signals of the same frequency through signal processing, thereby suppressing signals toward the direct wave direction or the direction via the selected RIS, and (2) multiplex the aforementioned reference signals in the frequency direction, thus enabling simultaneous selection. As a result, beam selection can be accelerated.

[0167] Some or all of the processes described above in BS 10 and MS 20 may also be performed alternatively or additionally in the other party's device. For example, beam search (beam selection) may also be performed by MS 20.

[0168] According to Embodiment 1, even when performing beam search based on the terminal received power maximization criterion, the path via the reflector can be selected. Therefore, in a wireless communication system including a base station, a terminal, and a reflector, the base station and the terminal can communicate appropriately via the path via the reflector.

[0169] (Implementation Method 2)

[0170] In Implementation 1, the allocation (assignment) of which subarray (i.e., beam) to which RIS (or direct wave) is arbitrary. However, adaptively changing the allocation of beams (or the number of beams) may improve MIMO capacity performance in situations where the allocation is modified.

[0171] • In cases where there are obstructions, the loss of the direct wave or the path via RIS is very large;

[0172] • The case where multiple spatial multiplexing can be performed in one direction (direct wave direction or RIS direction) (the case where so-called LOS-MIMO can be performed).

[0173] Therefore, in Embodiment 2, the method for determining which subarray to assign to which RIS (or direct wave) is described, based on the premise of selecting the path via RIS using the technology described in Embodiment 1.

[0174] Furthermore, in Embodiment 2, the description focuses on the parts that are different from Embodiment 1, while the description of the parts that are the same as or common to Embodiment 1 is sometimes omitted.

[0175] Figure 16A This is a diagram illustrating an example of beam number allocation change involved in Implementation 2. Figure 16AIn the example shown, as in (a), in the initial stage, it is assumed that two beams are equally allocated to each path via the RIS and each path not via the RIS. Using the techniques described below, depending on the situation, as in (b), sometimes one beam is allocated to the path via the RIS and three beams are allocated to the path not via the RIS. Furthermore, depending on the situation, as in (c), sometimes three beams are also allocated to the path via the RIS and one beam is allocated to the path not via the RIS.

[0176] Figure 16B This diagram illustrates another example of the beam number allocation change involved in Implementation 2. Figure 16B In the example shown, in the initial stage, it is assumed that one beam is equally allocated to each path via the RIS and the path not via the RIS. Here, as shown in (a), it is assumed that there is an obstruction in the path formed between the subarray #1 of the BS and the subarray #1 of the MS. Thus, as shown in (b), two beams can be allocated to the path via the RIS so that the subarray #1 of the BS and the subarray #1 of the MS form the path via the RIS.

[0177] In this way, in implementation 2, beam allocation (beam number allocation) is optimized according to the situation.

[0178] Figure 17 This is a block diagram illustrating an example of the functional structure of the BS 10 according to Embodiment 2. In addition to the beam search unit 131, beamforming unit 132, and reflector position estimation unit 133 described in Embodiment 1, the BS 10 (e.g., control unit 103) also includes, for example, an allocation unit 134, a selection unit 135, and a measurement unit 136.

[0179] As an initial allocation, allocation unit 134 arbitrarily assigns the number of beams (or beams or subarrays; hereinafter referred to as beam number) to the direct wave (or direct wave direction) and RIS (or direction via RIS). For example, when the number of RIS is 1 and the number of subarrays of BS 10 and MS 20 is 2, allocation unit 134 may also assign subarray 111 and subarray 211 to the direct wave direction and subarray 112 and subarray 212 to the direction via RIS. Allocation unit 134 outputs the allocation result of the initial allocation to selection unit 135.

[0180] The allocation unit 134 changes the beam number allocation and outputs the allocation result to the selection unit 135.

[0181] The above-described processing performed by the allocation unit 134, the following processing performed by the selection unit 135, and the following processing performed by the measurement unit 136 are repeatedly performed.

[0182] Based on the communication quality output by the measurement unit 136, the allocation unit 134 searches for the combination of beam number allocations that provides the best communication quality. Furthermore, known methods such as greedy algorithms and local search methods can be used in the search for combinations performed by the allocation unit 134. The allocation unit 134 determines the beam number allocation of the combination that provides the best communication quality as the final allocation.

[0183] Selection unit 135 performs beam selection based on the allocation result output by allocation unit 134. For example, similar to beam search unit 131 in Embodiment 1, selection unit 135 receives the measurement result of the received power of the subarray beam (measurement signal) transmitted by BS 10 from MS 20 via receiving unit 102, and searches for the beams of the subarrays of BS 10, the subarrays of MS 20, and the beams of RIS 30 based on the received received power measurement result. Beam search unit 131 outputs the identification information of the beam selected through the search to measurement unit 136. Alternatively, selection unit 135 can also be beam search unit 131.

[0184] Measurement unit 136 measures the communication quality of the beam (channel) indicated by the identification information output by selection unit 135. Communication quality can be any indicator, such as the channel's physical throughput, SNR, or bit error rate. For example, measurement unit 136 can directly measure the channel's physical throughput as communication quality, or it can estimate the communication quality based on the channel's singular values. Measurement unit 136 outputs the measured communication quality to allocation unit 134.

[0185] The following describes a specific processing example related to Implementation Method 2. In this example, the singular value of the channel is used in the measurement of communication quality, and a greedy algorithm is used in the search. Furthermore, in this example, the number of subarrays of BS 10 is set to M (X=M), the number of subarrays of MS 20 is set to N (Y=N), and the number of RIS is set to K (Z=K), where M≥N≥K. Therefore, in this example, the number of groups in the beam direction is the group of "direct wave" (referred to as "group 1") and the group of "via RIS 30". k The K+1 groups of waves (where k is an integer between 1 and K) are called "group 2" (k=1) to "group K+1".

[0186] (Processing 1C) The allocation unit 134 performs initial assignment by allocating (assigning) the subarray 111 of BS 10 and the subarray 211 of MS 20 to the group of direct waves ("Group 1").

[0187] (Process 2C) Similar to the beam selection performed by the beam search unit 131 in Embodiment 1, the selection unit 135 performs beam selection based on the received power.

[0188] (Processing 3C) Measurement unit 136 performs singular value decomposition (H=UΣV) on the inter-array channel matrix H. H ).

[0189] (Processing 4C) Allocation unit 134 based on the diagonal element σ of Σ n (Here, n=1), calculate the evaluation function S (S=Σlog2(1+σ n BS 10 sets n to 2 and k to 1.

[0190] (Process 5C) BS 10 determines its subarray 11 through the following process. n And subarray 21 of MS 20 n Group assignment.

[0191] (Processing 5-1C) Allocation unit 134 allocates subarray 11 of BS 10 n And subarray 21 of MS 20 m Assign (distribute) to group k.

[0192] (Process 5-2C) Similar to the beam selection performed by the beam search unit 131 in Embodiment 1, the selection unit 135 performs beam selection based on the received power.

[0193] (Processing 5-3C) Measurement unit 136 performs singular value decomposition (H=UΣV) on the inter-array channel matrix H. H ).

[0194] (Process 5-4C) Allocation unit 134 based on the diagonal element σ of Σ n Calculate the evaluation function S (S=Σlog2(1+σ)). n Increment k by 1.

[0195] (Process 5-5C) BS 10 repeats the process from process 5-1C to process 5-4C until the evaluation function S for the case of k=K+1 is calculated.

[0196] (Processing 5-6C) In allocation unit 134, the evaluation function S is selected to be the k that has the maximum value in the range of 1 ≤ k ≤ K+1. max Subarray 11 of BS10 n And subarray 21 of MS 20 m Assigned (allocated) to group k max BS 10 increments n by 1.

[0197] (Processing 5-7C) BS 10 repeatedly processes 5-1C to 5-6C until k is obtained when n=N. max Until selected. BS 10 sets m to N+1 and k to 1.

[0198] (Process 6C) BS 10 determines its subarray 11 through the following processing. m Group assignment.

[0199] (Processing 6-1C) Allocation unit 134 allocates subarray 11 of BS 10 m Assign (distribute) to group k.

[0200] (Process 6-2C) Similar to the beam selection performed by the beam search unit 131 in Embodiment 1, the selection unit 135 performs beam selection based on the received power.

[0201] (Processing 6-3C) Measurement unit 136 performs singular value decomposition (H=UΣV) on the inter-array channel matrix H. H ).

[0202] (Process 6-4C) Allocation unit 134 based on the diagonal element σ of Σ m Calculate the evaluation function S (S=Σlog2(1+σ)). m )). BS 10 increments k by 1.

[0203] (Process 6-5C) BS 10 repeats processes 6-1C to 6-4C until the evaluation function S for the case of k=K+1 is calculated.

[0204] (Processing 6-6C) In allocation unit 134, the evaluation function S is selected to be the k that has the maximum value in the range of 1 ≤ k ≤ K+1. max Subarray 11 of BS10 m Assigned (allocated) to group k max .

[0205] (Processing 6-7C) BS 10 increments m by 1, repeating processes 6-1C to 6-6C until k is obtained when m=M. max Until selected.

[0206] Next, refer to Figure 18A as well as Figure 18B An operational example of wireless communication system 1 will be explained. Figure 18A as well as Figure 18B This is a flowchart illustrating an operational example of the wireless communication system 1 according to Embodiment 2. In this example, the number of subarrays of BS 10 and MS 20 is set to M, and the number of RIS is set to K.

[0207] In step S31, BS 10 performs the initial allocation of the number of beams. Step S31 can be performed by the allocation unit 134, for example, it can correspond to the process 1C described above.

[0208] In step S32, BS 10 performs beam selection for its subarray, MS 20's subarray, and RIS 30. Step S32 can be executed by selection unit 135, for example, corresponding to the process 2C described above. Furthermore, step S32 is assumed to be accompanied by the transmission of measurement signals based on BS 10, the measurement of the received power of measurement signals based on MS 20, and a report.

[0209] In step S33, BS 10 measures the communication quality of the selected beam. Step S33 can be performed by measurement unit 136, for example, corresponding to the process 3C described above.

[0210] In step S34, BS 10 calculates the evaluation function of the selected beam. Step S34 can be performed by the allocation unit 134, for example, it can correspond to the process 4C described above.

[0211] In step S35, BS 10 is set to n=2.

[0212] In step S36, BS 10 is set to k=1.

[0213] In step S37, BS 10 changes the beam allocation. Step S37 can be performed by allocation unit 134, for example, it can correspond to the process 5-1C described above.

[0214] In step S38, BS 10 performs beam selection for its subarray, MS 20 subarray, and RIS 30. Step S38 can be executed by selection unit 135, for example, corresponding to the process 5-2C described above. Furthermore, step S38 is assumed to be accompanied by the transmission of measurement signals based on BS 10, the measurement of the received power of measurement signals based on MS 20, and a report.

[0215] In step S39, BS 10 measures the communication quality of the selected beam. Step S39 can be performed by measurement unit 136, for example, corresponding to the processes 5-3C described above.

[0216] In step S40, BS 10 calculates the evaluation function of the selected beam. Step S40 can be performed by the allocation unit 134, for example, it can correspond to the processes 5-4C described above.

[0217] In step S41, BS 10 increments k by 1.

[0218] In step S42, BS 10 determines whether k is greater than or equal to (K+2). If k is greater than or equal to (K+2) (step S42; Yes), the process proceeds to step S43. If k is not greater than or equal to (K+2) (step S42; No), the process returns to step S37, and the process is repeated.

[0219] In step S43, BS 10 assigns the beam to the group whose evaluation function, calculated in step S40, has the maximum value k based on the communication quality measured in step S39.

[0220] In step S44, BS 10 increments n by 1.

[0221] In step S45, BS 10 determines whether n is greater than or equal to (M+1). If n is greater than or equal to (M+1) (step S45; Yes), the process ends; if n is not greater than or equal to (M+1) (step S45; No), the process returns to step S36, and the process is repeated.

[0222] In summary, BS 10 assigns the subarrays from the multiple subarrays to paths in the direct wave direction or paths via the reflector (process 1). Next, BS 10 selects an intermediate beam formed by the subarrays based on the received power of the candidate beams formed by the subarrays (process 2). Then, BS 10 measures the communication quality of the intermediate beam (process 3). BS 10 performs processes 1 through 3 at least once for each of the multiple subarrays, thereby determining each of the multiple final beams formed by the multiple subarrays from the multiple intermediate beams based on the measured communication quality (process 4).

[0223] As explained above, BS 10 (allocation unit 134, selection unit 135, measurement unit 136) searches (beam determination) until it finds a beam number allocation that provides the best communication quality, thereby enabling optimal beam allocation based on channel conditions.

[0224] Next, a simulation using the technology described in Embodiment 2 will be described. This simulation was performed under the conditions shown in Tables 5 to 8 below.

[0225] [Table 5]

[0226]

[0227] [Table 6]

[0228]

[0229] [Table 7]

[0230]

[0231] [Table 8]

[0232]

[0233] Figure 19 This is a graph showing the results of this simulation (the case of beam selection based on maximum power search). Figure 19 (A), (B), (C), and (D) show the beam selection of the first subarray (corresponding to subarray 211), second subarray (corresponding to subarray 212), third subarray (corresponding to subarray 213), and fourth subarray (corresponding to subarray 214) of the MS when using the beam reselection (beam number allocation change) involved in Embodiment 2. Figure 19 (a), (b), (c), and (d) respectively show the beam selection of the first, second, third, and fourth subarrays of the MS without using the beam reselection (beam number allocation change) involved in Embodiment 2. Additionally, as... Figure 19 As shown in (a), (b), (c) and (d), without using beam reselection, four beams (two beams each) are evenly distributed between the LOS and the direction via RIS.

[0234] When using the beam reselection method described in Implementation 2, such as Figure 19 As shown in (A), (B), (C) and (D), adjustments were made to allocate 3 of the 4 beams to LOS and 1 beam to the direction via RIS.

[0235] Figure 20 This is a graph showing the results of this simulation (throughput simulation results). Figure 20 The "w / o reselect, TP" shown corresponds to Figure 19 The cases shown in (a), (b), (c), and (d) are those where beam reselection is not used. Figure 20 The "w / reselect, TP" shown corresponds to Figure 19 The cases shown in (A), (B), (C), and (D) involve beam reselection.

[0236] When using the beam reselection method described in Implementation 2, compared to not using beam reselection, as follows: Figure 20 As shown, throughput was improved in a portion of the SNR range (0~40dB).

[0237] <Modifications of Implementation Method 2>

[0238] Some or all of the processes described above in BS 10 and MS 20 may also be performed alternatively or additionally in the other party's device. For example, beam search (beam selection) may also be performed by MS 20.

[0239] According to Embodiment 2, optimal beam allocation can be performed based on the channel conditions. Therefore, in a wireless communication system including a base station, a terminal, and a reflector, the base station and the terminal can communicate appropriately, with or without using a path via the reflector.

[0240] (Summary of implementation methods)

[0241] The beam determination method disclosed herein includes: in a wireless communication system comprising a base station, a terminal, and a reflector, performing a first process that determines that a beam of an array antenna of the base station is used in the direct wave direction toward the terminal; performing a second process that determines that a beam of an array antenna of the terminal is used in the direct wave direction toward the base station; performing a third process that determines that a beam of an array antenna of the base station is used in the direction toward the reflector; performing a fourth process that determines that a beam of the reflector is used in the direction toward the terminal by suppressing signals in the direct wave direction toward the terminal; and performing a fifth process that determines that a beam of an array antenna of the terminal is used in the direction toward the reflector.

[0242] In one example, in this beam determination method, when there are multiple reflectors, the third process, the fourth process, and the fifth process are performed repeatedly according to the number of reflectors.

[0243] In one example, in this beamforming method, when multiple reflectors are present, signals in the direction via a portion of the reflectors are suppressed during the fourth process.

[0244] In one example, in this beam determination method, multiple subarrays constituting the array antennas of the base station are used to suppress signals in the direct wave direction toward the terminal through signal processing.

[0245] In one example, in this beam determination method, the signal directed toward the terminal in the direct wave direction is suppressed by the directivity formation of any one of the multiple subarrays constituting the array antenna of the base station.

[0246] In one example, in this beam determination method, multiple subarrays constituting the array antenna of the base station are used to suppress signals in the direction of a portion of the reflector through signal processing.

[0247] In one example, in this beamforming method, signals in the direction of a portion of the reflector are suppressed by the directivity formation of any one of the multiple subarrays constituting the array antenna of the base station.

[0248] In one example, in this beam determination method, multiple subarrays constituting the array antenna of the base station are used to synthesize measurement signals of the same frequency through signal processing, thereby suppressing signals in the direct wave direction toward the terminal.

[0249] In one example, in this beam determination method, different measurement signals are multiplexed in the frequency direction for each of the plurality of subarrays constituting the array antenna of the base station, thereby simultaneously determining the beam corresponding to the plurality of subarrays.

[0250] In one example, in this beam determination method, a third process is performed to estimate the position of the reflector and, based on the estimated position of the reflector, to determine the beam toward the reflector.

[0251] According to this beam determination method, by forming a null beam at least in the direct wave direction toward the terminal, it is possible to select the beam through which the signal propagates via the reflector.

[0252] The beam determination method disclosed herein includes: in a wireless communication system in which a base station and a terminal use multiple subarrays to communicate via a path in the direct wave direction and / or via a path through a reflector, performing a first process that assigns a subarray among the multiple subarrays to the path in the direct wave direction or the path through the reflector; performing a second process that selects an intermediate beam formed by the subarrays based on the received power of candidate beams formed by the subarrays; performing a third process that measures the communication quality of the intermediate beam; and performing the first, second, and third processes at least once for each of the multiple subarrays, thereby performing a fourth process based on the multiple communication qualities, the fourth process determining each of a plurality of final beams formed by the multiple subarrays from the multiple intermediate beams.

[0253] In one example, in this beam determination method, during the fourth process, each of the plurality of final beams corresponding to the best plurality of communication qualities is determined.

[0254] In one example, in this beam determination method, during the third processing, the communication quality is estimated based on channel singular values.

[0255] According to this beam determination method, the final beam is determined based on communication quality, and beam allocation can be performed according to the channel conditions.

[0256] The above provides an explanation of this disclosure. Furthermore, the division of items in the above explanation is not essential in this disclosure; items described in two or more items may be combined as needed, and items described in one item may be applied to items described in other items (as long as there is no contradiction).

[0257] <Hardware structure, etc.>

[0258] The block diagrams used in the description of the above embodiments illustrate functional units. These functional blocks (structural units) are implemented through any combination of at least one of hardware and software. Furthermore, the implementation method of each functional block is not particularly limited. That is, each functional block can be implemented using a single device that is physically or logically combined, or it can be implemented by directly or indirectly (e.g., using wired, wireless, etc.) connecting two or more physically or logically separate devices. A functional block can also be implemented by combining one or more of the aforementioned devices with software.

[0259] The functions include judgment, decision, determination, calculation, calculation, processing, derivation, investigation, search, confirmation, receiving, sending, output, access, resolution, selection, choosing, establishment, comparison, assumption, expectation, regard as, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, mapping, and assigning, but are not limited to these. For example, the functional block (structural unit) that implements the sending function is called a transmitting unit or a transmitter. Both are as described above, and the implementation method is not particularly limited.

[0260] For example, the base station, terminal, etc. in one embodiment of this disclosure can also function as a computer for processing the wireless communication method of this disclosure. Figure 21 This diagram illustrates an example of the hardware structure of the base station and terminal involved in the embodiment. The base station 10 and terminal 20 described above can also be physically configured as computer devices including a processor 1001, a memory 1002, a storage device 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007, etc.

[0261] Additionally, in the following description, the term "device" can be replaced with circuit, device, unit, etc. The hardware structure of base station 10 and terminal 20 can be configured to include one or more of the devices shown in the figure, or it can be configured to exclude some of the devices.

[0262] Regarding the various functions in base station 10 and terminal 20, specific software (programs) are read into hardware such as processor 1001 and memory 1002, so that processor 1001 performs calculations and controls communication based on communication device 1004, or controls at least one of reading out and writing data in memory 1002 and storage device 1003, thereby achieving the functions.

[0263] The processor 1001, for example, enables the operating system to operate and control the computer as a whole. The processor 1001 may also be composed of a central processing unit (CPU) that includes interfaces with peripheral devices, control devices, arithmetic units, registers, etc. For example, the control unit 103 and control unit 203 described above may also be implemented by the processor 1001.

[0264] Furthermore, the processor 1001 reads programs (program code), software modules, data, etc., from at least one of the storage 1003 and the communication device 1004 into the memory 1002, and performs various processes accordingly. As a program, a program that causes the computer to perform at least a portion of the operations described in the above embodiments can be used. For example, the control unit 103 of the base station 10 and the control unit 203 of the terminal 20 can also be implemented by control programs stored in the memory 1002 and operated by the processor 1001; similarly, other functional blocks can be implemented. The various processes described above have been explained as being executed by one processor 1001, but they can also be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 can also be implemented using more than one chip. Additionally, the program can also be transmitted from a network via an electrical communication line.

[0265] The memory 1002 is a computer-readable recording medium, and may be composed of at least one of the following: ROM (Read-Only Memory), EPROM (Erasable Programmable ROM), EEPROM (Electrically Erasable Programmable ROM), RAM (Random Access Memory). The memory 1002 may also be referred to as a register, cache, main memory (main storage device), etc. The memory 1002 can store executable programs (program code), software modules, etc., for implementing the wireless communication method according to an embodiment of this disclosure.

[0266] Storage 1003 is a computer-readable recording medium, and may be comprised of at least one of the following: CD-ROM (Compact Disc ROM) or other optical discs; hard disk drives; flexible discs; optical discs (e.g., compact discs, digital multifunction discs, Blu-ray discs); smart cards; flash memory (e.g., cards, sticks, key drives); floppy disks; magnetic stripes; etc. Storage 1003 may also be referred to as an auxiliary storage device. The aforementioned storage medium may also be, for example, a database, server, or other suitable medium including at least one of memory 1002 and storage 1003.

[0267] The communication device 1004 is hardware (transmitting and receiving device) used for communication between computers via at least one of a wired network and a wireless network. It is also referred to as a network device, network controller, network interface card (NIC), communication module, etc. To implement at least one of, for example, Frequency Division Duplex (FDD) and Time Division Duplex (TDD), the communication device 1004 may also be configured to include a high-frequency switch, a duplexer, a filter, a frequency synthesizer, etc. For example, the aforementioned transmitting unit 101, receiving unit 102, receiving unit 201, and transmitting unit 202 can also be implemented using the communication device 1004.

[0268] Input device 1005 is an input device that accepts input from external sources (e.g., keyboard, mouse, microphone, switch, button, sensor, etc.). Output device 1006 is an output device that performs output to external sources (e.g., display, speaker, LED light, etc.). Alternatively, input device 1005 and output device 1006 can also be an integrated structure (e.g., touch panel).

[0269] Furthermore, the processor 1001, memory 1002, and other devices are connected via a bus 1007 for communicating information. The bus 1007 can be configured using a single bus or different buses between the devices.

[0270] Furthermore, the base station 10 and the terminal 20 can also be configured with hardware including microprocessors, digital signal processors (DSPs), ASICs (Application Specific Integrated Circuits), PLDs (Programmable Logic Devices), FPGAs (Field Programmable Gate Arrays), etc., and can also implement some or all of the functional blocks through such hardware. For example, the processor 1001 can also be implemented using at least one of these hardware components.

[0271] <Information notification and signaling>

[0272] The notification of information is not limited to the implementation methods described in this disclosure, and can also be performed by other methods. For example, the notification of information can also be implemented through physical layer signaling (e.g., DCI (Downlink Control Information), UCI (Uplink Control Information)), higher layer signaling (e.g., RRC (Radio Resource Control) signaling, MAC (Media Access Control) signaling, broadcast information (MIB (Master Information Block)), SIB (System Information Block)), other signals, or combinations thereof. In addition, RRC signaling can also be referred to as RRC messages, for example, RRC Connection Setup messages, RRC Connection Reconfiguration messages, etc.

[0273] <Application Systems>

[0274] The implementations described in this disclosure can also be applied to LTE (Long Term Evolution), LTE-A (LTE-Advanced), 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 At least one of 802.20, UWB (Ultra-Wideband), Bluetooth (registered trademark), systems utilizing other suitable systems, and next-generation systems derived from them through extension, modification, fabrication, or specification. Furthermore, multiple systems may be combined (e.g., a combination of LTE and at least one of LTE-A with 5G, etc.) for application.

[0275] <Processing procedures, etc.>

[0276] The processing procedures, sequences, flowcharts, etc., of the various methods / implementations described in this disclosure may be rearranged as long as they do not contradict each other. For example, for the methods described in this disclosure, an exemplary order is used to indicate the elements of various steps, but the order in which they are indicated is not limited.

[0277] <Base Station Operation>

[0278] In this disclosure, specific operations purported to be performed by a base station may sometimes be performed by its upper node, depending on the circumstances. Clearly, in a network consisting of one or more network nodes having a base station, various operations for communication with a terminal can also be performed by at least one of the base station and other network nodes besides the base station (e.g., considering MME or S-GW, but not limited to these). The above example illustrates a case where there is only one other network node besides the base station; it could also be a combination of multiple other network nodes (e.g., MME and S-GW).

[0279] <Direction of input / output>

[0280] Information (see the items under "Information, Signals") can also be output from higher (or lower) layers to lower (or higher) layers. It can also be input and output via multiple network nodes.

[0281] <Processing of input and output information>

[0282] Input and output information can be stored in a specific location (e.g., memory) or managed using a management table. Input and output information can be overwritten, updated, or appended. Output information can also be deleted. Input information can also be sent to other devices.

[0283] <Judgment Method>

[0284] The determination can be made by a value represented by a single bit (0 or 1), by a true or false value (Boolean: true or false), or by a numerical comparison (e.g., a comparison with a specific value).

[0285] <Changes in methods, etc.>

[0286] The various methods / implementations described in this disclosure can be used individually or in combination, and can be switched as needed during execution. Furthermore, notification of specific information (e.g., a "It is X" notification) is not limited to explicit notification, but can also be done implicitly (e.g., without notifying the recipient of that specific information).

[0287] The present disclosure has been described in detail above, but it will be apparent to those skilled in the art that the present disclosure is not limited to the embodiments described herein. The present disclosure can be implemented with modifications and variations without departing from the spirit and scope defined by the claims. Therefore, the description in this disclosure is for illustrative purposes only and is not intended to be restrictive in any way.

[0288] <Software>

[0289] Whether software is called software, firmware, middleware, microcode, hardware description language, or any other name, it should be broadly interpreted to refer to instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, functions, etc.

[0290] Furthermore, software, instructions, and information can also be sent and received via a transmission medium. For example, when software is sent from a website, server, or other remote source using at least one of wired technologies (coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), etc.) and wireless technologies (infrared, microwave, etc.), at least one of these wired and wireless technologies is included within the definition of transmission medium.

[0291] <Information, Signals>

[0292] The information, signals, etc., described in this disclosure can also be represented using any of a variety of different technologies. For example, data, instructions, commands, information, signals, bits, symbols, chips, etc., which may be mentioned throughout the above description, can also be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light fields or photons, or any combination thereof.

[0293] Furthermore, the terms described in this disclosure, as well as those necessary for understanding this disclosure, may be replaced with terms that have the same or similar meanings. For example, at least one of the channel and the symbol may also be a signal (signaling). Additionally, a signal may also be a message. Furthermore, a component carrier (CC) may also be referred to as a carrier frequency, cell, frequency carrier, etc.

[0294] <Systems, Networks>

[0295] The terms “system” and “network” are used interchangeably in this disclosure.

[0296] <Parameters, Channel Name>

[0297] Furthermore, the information, parameters, etc., described in this disclosure can be represented by absolute values, relative values ​​with respect to a specific value, or other corresponding information. For example, wireless resources can also be indicated by an index.

[0298] The names used for the parameters described above are not limiting names in any respect. Furthermore, the mathematical expressions using these parameters sometimes differ from those explicitly disclosed in this disclosure. Various channels (e.g., PUCCH, PDCCH, etc.) and information elements can be identified by any suitable name; therefore, the various names assigned to these various channels and information elements are not limiting names in any respect.

[0299] <Base Station>

[0300] In this disclosure, the terms "base station (BS)," "wireless 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" are used interchangeably. There are also instances where terms such as macro cell, small cell, femtocell, and picocell are used to refer to base stations.

[0301] 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 divided into multiple smaller areas, each of which can also provide communication services through a base station subsystem (e.g., a small indoor base station (Remote Radio Head (RRH))). Terms such as "cell" or "sector" refer to a portion or all of the coverage area of ​​at least one of the base station and base station subsystem providing communication services within that coverage area.

[0302] In this disclosure, the information sent by the base station to the terminal can also be rewritten as the base station instructing the terminal to perform information-based control and operation.

[0303] <Mobile Station>

[0304] In this disclosure, the terms “Mobile Station (MS),” “user terminal,” “user equipment (UE),” and “terminal” are used interchangeably.

[0305] There are also instances where a mobile station is 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, hand set, user agent, mobile client, client, or several other appropriate terms.

[0306] <Base station / Mobile station>

[0307] At least one of the base station and the mobile station can also be referred to as a transmitting device, a receiving device, a communication device, etc. Furthermore, at least one of the base station and the mobile station can also be a device mounted on a mobile body, the mobile body itself, etc. The mobile body refers to a movable object whose speed of movement is arbitrary. This also includes situations where the mobile body is stationary. Examples of mobile bodies include vehicles, transport vehicles, automobiles, autonomous two-wheelers, bicycles, connected cars, excavators, bulldozers, wheel loaders, dump trucks, forklifts, trains, buses, trailers, rickshaws, ships (boats and other watercraft), airplanes, rockets, artificial satellites, drones (registered trademark), multi-rotor aircraft, quadcopter aircraft, balloons, and objects mounted on them, and are not limited to these. Furthermore, the mobile body can also be a mobile body that moves autonomously based on operating commands. It can be a means of transportation (e.g., vehicles, airplanes, etc.), a mobile body that moves unmanned (e.g., drones, autonomous vehicles, etc.), or a robot (humanized or unmanned). In addition, at least one of the base station and the mobile station also includes a device that is not necessarily mobile during communication operations. For example, at least one of the base station and the mobile station can also be an Internet of Things (IoT) device such as a sensor.

[0308] Furthermore, the base station in this disclosure can also be rewritten as a terminal. For example, embodiments of this disclosure can also be applied to structures where communication between the base station and the terminal is replaced by communication between multiple terminals (e.g., also referred to as D2D (Device-to-Device), V2X (Vehicle-to-Everything), etc.). In this case, it can also be configured such that the terminal 20 has the functions of the base station 10 described above. In addition, terms such as "uplink" and "downlink" can also be rewritten as terms corresponding to inter-terminal communication (e.g., "side"). For example, uplink channel, downlink channel, etc., can also be rewritten as side channel.

[0309] Similarly, the terminal in this disclosure can also be rewritten as a base station. In this case, it can also be configured such that the base station 10 has the functions of the terminal 20 described above.

[0310] Figure 22 An example of the structure of vehicle 2001 is shown. For example... Figure 22 As shown, the vehicle 2001 includes a drive unit 2002, a steering unit 2003, an accelerator pedal 2004, a brake pedal 2005, a gear shift lever 2006, front wheels 2007, rear wheels 2008, axles 2009, an electronic control unit 2010, various sensors 2021-2029, an information service unit 2012, and a communication module 2013. The various methods / implementations described in this disclosure can also be applied to a communication device mounted on the vehicle 2001, for example, to the communication module 2013.

[0311] The drive unit 2002 is configured, for example, as an engine, a motor, or a combination of an engine and a motor. The steering unit 2003 is configured to include at least a steering wheel (also called a handlebar) and to steer at least one of the front and rear wheels based on the operation of the steering wheel by the user.

[0312] The electronic control unit 2010 consists of a microprocessor 2031, a memory (ROM, RAM) 2032, and a communication port (IO port) 2033. The electronic control unit 2010 receives signals from various sensors 2021-2029 of the vehicle 2001. The electronic control unit 2010 can also be referred to as an ECU (Electronic Control Unit).

[0313] The signals from various sensors 2021 to 2029 include current signals from current sensor 2021 that senses the current of the motor, speed signals of the front and rear wheels obtained by speed sensor 2022, air pressure signals of the front and rear wheels obtained by air pressure sensor 2023, vehicle speed signals obtained by vehicle speed sensor 2024, acceleration signals obtained by acceleration sensor 2025, accelerator pedal depress amount signals obtained by accelerator pedal sensor 2029, brake pedal depress amount signals obtained by brake pedal sensor 2026, gear shift lever operation signals obtained by gear shift lever sensor 2027, and detection signals obtained by object detection sensor 2028 for detecting obstacles, vehicles, pedestrians, etc.

[0314] The information service unit 2012 consists of various devices such as a car navigation system, audio system, speakers, television, and radio, used to provide (output) various information such as driving information, traffic information, and entertainment information, as well as one or more ECUs that control these devices. The information service unit 2012 uses information obtained from external devices via the communication module 2013, etc., to provide various multimedia information and multimedia services to the occupants of the vehicle 2001.

[0315] The information service unit 2012 may include input devices (e.g., keyboard, mouse, microphone, switch, button, sensor, touch panel, etc.) that accept input from the outside, and output devices (e.g., display, speaker, LED light, touch panel, etc.) that implement output to the outside.

[0316] The driver assistance system unit 2030 comprises various devices used to provide functions such as preventing accidents or reducing the driver's workload, including millimeter-wave radar, LiDAR (Light Detection and Ranging), cameras, locators (e.g., GNSS), map information (e.g., high-definition (HD) maps, autonomous vehicle (AV) maps), gyroscope systems (e.g., IMU (Inertial Measurement Unit), INS (Inertial Navigation System)), AI (Artificial Intelligence) chips, and AI processors, as well as one or more ECUs that control these devices. Furthermore, the driver assistance system unit 2030 sends and receives various information via a communication module 2013 and implements driver assistance or autonomous driving functions.

[0317] The communication module 2013 can communicate with the microprocessor 2031 and the constituent elements of the vehicle 2001 via the communication port. For example, the communication module 2013 sends and receives data between the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, gear shift lever 2006, front wheel 2007, rear wheel 2008, axle 2009, microprocessor 2031 in the electronic control unit 2010, and memory (ROM, RAM) 2032 and sensors 2021-29 in the vehicle 2001 via the communication port 2033.

[0318] The communication module 2013, controlled by the microprocessor 2031 of the electronic control unit 2010, is a communication device capable of communicating with external devices. For example, it enables the transmission and reception of various information between external devices via wireless communication. The communication module 2013 can be located either inside or outside the electronic control unit 2010. External devices can be, for example, base stations, mobile stations, etc.

[0319] The communication module 2013 can also wirelessly transmit to an external device at least one of the signals input to the electronic control unit 2010 from the various sensors 2021-2029 described above, information obtained based on these signals, and information based on input from an external source (user) obtained via the information service unit 2012. The electronic control unit 2010, the various sensors 2021-2029, and the information service unit 2012 can also be referred to as input units that receive input. For example, the PUSCH transmitted via the communication module 2013 can also include information based on the aforementioned input.

[0320] The communication module 2013 receives various information (traffic information, signal information, vehicle-to-vehicle information, etc.) sent from external devices and displays it on the information service unit 2012 of the vehicle 2001. The information service unit 2012 can also be referred to as an output unit that outputs information (for example, outputs information to devices such as displays and speakers based on the PDSCH received through the communication module 2013 (or data / information decoded from the PDSCH).

[0321] Furthermore, the communication module 2013 stores various information received from external devices in a memory 2032 that can be utilized by the microprocessor 2031. Based on the information stored in the memory 2032, the microprocessor 2031 can also control the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, gear shift lever 2006, front wheels 2007, rear wheels 2008, axles 2009, sensors 2021-2029, etc., provided by the vehicle 2001.

[0322] <Meaning and Explanation of Terms>

[0323] The terms "determining" and "determining" as used in this disclosure encompass a wide variety of actions. For example, "determining" and "determining" can include actions such as judging, calculating, computing, processing, deriving, investigating, searching (e.g., searching in a table, database, or other data structure), and ascertaining. Furthermore, "determining" and "determining" can include actions such as receiving (e.g., receiving information), transmitting (e.g., sending information), inputting, outputting, and accessing (e.g., accessing data in memory). Additionally, "determining" and "determining" can include actions such as resolving, selecting, choosing, establishing, and comparing. That is, "judgment" and "decision" can include situations where certain actions are regarded as having been "judged" or "decided". In addition, "judgment (decision)" can also be rewritten as "assuming", "expecting", "considering", etc.

[0324] The terms “connected,” “coupled,” or any variations thereof, refer to all direct or indirect connections or combinations between two or more elements, and can include cases where there is one or more intermediate elements between two mutually “connected” or “coupled” elements. The connection or combination between elements can be physical, logical, or a combination thereof. For example, “connected” can also be rewritten as “access.” In the context of this disclosure, it is possible to consider two elements being mutually “connected” or “coupled” using at least one or more wires, cables, or printed electrical connections, and as several non-limiting and non-exclusive examples, using electromagnetic energy with wavelengths in the wireless frequency domain, microwave region, and light (both visible and invisible) region.

[0325] <Reference Signal>

[0326] The reference signal can also be simply referred to as RS (Reference Signal), or it can be called a pilot depending on the standard applied.

[0327] <The meaning of "based on">

[0328] As used in this disclosure, the term "based on" does not mean "based on only" unless otherwise specified. In other words, the term "based on" means both "based on only" and "based on at least".

[0329] <"First", "Second">

[0330] Any reference to elements using the designations "first," "second," etc., as used in this disclosure does not comprehensively limit the quantity or order of these elements. These designations may be used in this disclosure as a convenient method of distinguishing between two or more elements. Therefore, references to the first and second elements do not imply that only two elements may be used, or that the first element must precede the second element in some form.

[0331] <Unit>

[0332] Alternatively, the term "unit" in the structure of the above devices can be replaced with "section", "circuit", "equipment", etc.

[0333] <Open format>

[0334] In this disclosure, the terms "include," "including," and variations thereof, as well as the term "comprising," refer to inclusion. Furthermore, the term "or" as used in this disclosure does not mean XOR.

[0335] <Time units such as TTI, frequency units such as RB, and radio frame structure>

[0336] A wireless frame can also consist of one or more frames in the time domain. These frames can also be referred to as subframes in the time domain. Furthermore, a subframe can also consist of one or more time slots in the time domain. A subframe can also be a fixed time length (e.g., 1 ms) independent of the parameter set (numerology).

[0337] A parameter set can also be a set of communication parameters applied in at least one of the transmission and reception of a signal or channel. For example, a parameter set can also represent at least one of the following: subcarrier spacing (SCS), bandwidth, symbol length, cyclic prefix length, transmission time interval (TTI), number of symbols per TTI, radio frame structure, specific filtering processing performed by the transmitter and receiver in the frequency domain, and specific windowing processing performed by the transmitter and receiver in the time domain.

[0338] In the time domain, a time slot can also be composed of one or more symbols (OFDM (Orthogonal Frequency Division Multiplexing) symbols, SC-FDMA (Single Carrier Frequency Division Multiple Access) symbols, etc.). A time slot can also be a time unit based on a set of parameters.

[0339] A time slot can also comprise multiple mini-time slots. Each mini-time slot can also consist of one or more symbols in the time domain. Furthermore, a mini-time slot can also be called a sub-time slot. A mini-time slot can also consist of fewer symbols than a time slot. PDSCH (or PUSCH) transmitted in a time unit larger than a mini-time slot can also be called PDSCH (or PUSCH) mapping type A. PDSCH (or PUSCH) transmitted using mini-time slots can also be called PDSCH (or PUSCH) mapping type B.

[0340] Radio frames, subframes, time slots, mini-time slots, and symbols all represent time units for transmitting signals. Radio frames, subframes, time slots, mini-time slots, and symbols can also be referred to by their respective other names.

[0341] For example, a subframe can also be called a Transmission Time Interval (TTI), multiple consecutive subframes can also be called a TTI, and a time slot or a mini-time slot can also be called a TTI. That is, at least one of a subframe and a TTI can be a subframe in existing LTE (1ms), a period shorter than 1ms (e.g., 1-13 symbols), or a period longer than 1ms. In addition, the unit representing TTI may not be called a subframe, but a time slot, mini-time slot, etc.

[0342] Here, TTI refers, for example, to the smallest unit of time for scheduling in wireless communication. For instance, in an LTE system, the base station schedules radio resources (frequency bandwidth, transmit power, etc., available to each user terminal) in TTI units. However, the definition of TTI is not limited to this.

[0343] TTI can also be a unit of time for transmitting channel-coded data packets (transmission blocks), code blocks, codewords, etc., and can also be a unit of processing such as scheduling and link adaptation. In addition, when a TTI is given, the actual time interval (e.g., the number of symbols) mapped to transmission blocks, code blocks, codewords, etc. can be shorter than the TTI.

[0344] Additionally, where a time slot or a mini-time slot is referred to as a TTI, more than one TTI (i.e., more than one time slot or more than one mini-time slot) can also serve as the minimum time unit for scheduling. Furthermore, the number of time slots (mini-time slots) constituting the minimum time unit of the schedule can also be controlled.

[0345] A TTI with a duration of 1ms can also be referred to as a normal TTI (TTI in LTE Rel.8-12), standard TTI, long TTI, normal subframe, standard subframe, long subframe, time slot, etc. A TTI shorter than a normal TTI can also be referred to as a shortened TTI, short TTI, partial TTI (partial or fractional TTI), shortened subframe, short subframe, mini time slot, sub-time slot, time slot, etc.

[0346] In addition, a long TTI (e.g., a normal TTI, a subframe, etc.) can also be rewritten as a TTI with a duration of more than 1 ms, and a short TTI (e.g., a shortened TTI, etc.) can also be rewritten as a TTI with a duration of less than a long TTI but more than 1 ms.

[0347] A resource block (RB) is a unit of resource allocation in both the time and frequency domains. In the frequency domain, it can also include one or more consecutive subcarriers. The number of subcarriers included in an RB can be the same regardless of the parameter set, for example, it can be 12. The number of subcarriers included in an RB can also be determined based on the parameter set.

[0348] Furthermore, the time domain of an RB can also include one or more symbols, or it can be the length of a time slot, a mini-time slot, a subframe, or a TTI. A TTI, a subframe, etc., can also be composed of one or more resource blocks.

[0349] In addition, one or more RBs can also be referred to as Physical Resource Blocks (PRBs), Sub-Carrier Groups (SCGs), Resource Element Groups (REGs), PRB pairs, RB pairs, etc.

[0350] Furthermore, a resource block can also consist of one or more resource elements (REs). For example, an RE can also be a radio resource area consisting of a subcarrier and a symbol.

[0351] The Bandwidth Part (BWP) (also known as partial bandwidth, etc.) can also represent a subset of consecutive common resource blocks (RBs) used for a certain parameter set in a certain carrier. Here, common RBs can also be determined by the index of RBs based on the common reference point of that carrier. PRBs can also be defined in a BWP and appended with numbers within that BWP.

[0352] A BWP can also include a UL BWP and a DL BWP. For a UE, one or more BWPs can also be set within a single carrier.

[0353] At least one of the configured BWPs can be active, and the UE may not intend to transmit or receive specific signals / channels outside of the active BWPs. Furthermore, the terms "cell," "carrier," etc., in this disclosure can be rewritten as "BWP."

[0354] The structures described above, such as radio frames, subframes, time slots, mini-time slots, and symbols, are merely illustrative. For example, the number of subframes included in a radio frame, the number of time slots in each subframe or radio frame, the number of mini-time slots included in a time slot, the number of symbols and RBs included in a time slot or mini-time slot, the number of subcarriers included in an RB, and the number of symbols in a TTI, symbol length, and cyclic prefix (CP) length can be varied in many ways.

[0355] <Maximum Transmit Power>

[0356] The term "maximum transmit power" as used in this disclosure may refer to the maximum value of the transmit power, the nominal maximum transmit power (the nominal UE maximum transmit power), or the rated maximum transmit power (the rated UE maximum transmit power).

[0357] <Article>

[0358] In this disclosure, for example, in cases where articles are added through translation, such as in English (a, an, and the), this disclosure may also include cases where the noun following these articles is in a plural form.

[0359] <"Differences">

[0360] In this disclosure, the term "A is different from B" can also mean "A and B are different from each other." Additionally, the term can also mean "A and B are each different from C." Terms such as "separate" and "combined" can also be interpreted in the same way as "different."

[0361] The entire contents of the specification, drawings and abstract contained in Japanese Application No. 2024-025702, filed on February 22, 2024, are incorporated herein by reference.

[0362] Industrial availability

[0363] One aspect of this disclosure is useful for wireless communication systems.

[0364] Explanation of reference numerals in the attached figures

[0365] 1. Wireless communication system; 10. Base stations (BS); 20. Terminals (MS); 30. Directional reflectors (RIS); 111~11 X Subarray; 211~21 Y Subarray; 301~30 Z RIS; 101, 202 Transmitting Unit; 102, 201 Receiving Unit; 103, 203 Control Unit; 131 Beam Searching Unit; 132 Beamforming Unit; 133 Reflector Position Estimation Unit; 134 Allocation Unit; 135 Selection Unit; 136 Measurement Unit; 231 Received Power Measurement 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, comprising: In wireless communication systems where multiple subarrays are used at the base station and the terminal to communicate via a direct wave path and / or a path via a reflector, The first process involves assigning the subarrays of the plurality of subarrays to the path of the direct wave direction or the path via the reflector. The second processing step involves selecting the intermediate beam formed by the subarray based on the received power of the candidate beams formed by the subarray. A third processing step is performed to measure the communication quality of the intermediate beam; as well as A fourth process is performed by performing the first, second, and third processes on each of the plurality of subarrays at least once, thereby determining each of the plurality of final beams formed by the plurality of subarrays from the plurality of intermediate beams based on the plurality of communication qualities.

2. The beam determination method as described in claim 1, wherein, During the fourth process, each of the plurality of final beams corresponding to the best plurality of communication qualities is determined.

3. The beam determination method as described in claim 1, wherein, During the third processing, the communication quality is estimated based on the channel singularity value.

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