Master station device, terminal device, wireless communication method, and program

Abstract

To reduce the number of search patterns for appropriately setting the beam direction between a master station device and a terminal device that perform wireless communication via a variable reflector and the shift amount in the reflection direction of the variable reflector.SOLUTION: A master station device 1 transmits a master station scanning radio signal while sequentially changing a beam direction, and the shift amount in the reflection direction of a variable reflector 2. A terminal device 3 uses the received master station scanning radio signal to obtain direction information indicating whether the variable reflector 2 is present in a predetermined beam direction of the master station device 1, and transmits a terminal scanning radio signal including the direction information while sequentially changing the beam direction. The master station device 1 uses the direction information included in the received terminal scanning radio signal to limit the beam direction in which the master station scanning radio signal is to be transmitted.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a master station device, a terminal device, and the like that perform wireless communication via a variable reflector that can electrically change the reflection characteristics of radio waves. [Background technology]

[0002] High-frequency bands such as millimeter waves and terahertz waves are characterized by their large attenuation over distance and their tendency to travel in a straight line. As a result, radio waves between wireless stations (for example, a master station and a terminal device) conducting wireless communication can be blocked by obstacles, potentially creating dead spots (areas where radio waves cannot reach with sufficient strength) in the wireless communication system.

[0003] Therefore, studies have been conducted to control the reflection characteristics of a variable reflector (see Non-Patent Documents 1 and 2), which can electrically change the reflection characteristics of radio waves, to allow radio waves of sufficient strength to reach wireless terminals in dead spots and enable wireless communication. The reflection characteristics of the variable reflector can be controlled, for example, by shifting the reflection direction by a predetermined amount. Note that variable reflectors are also sometimes called, for example, IRS (Intelligent Reflecting Surface) or RIS (Reconfigurable Intelligent Surface). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Q. Wu and R. Zhang, “Towards Smart and Reconfigurable Environment: Intelligent Reflecting Surface Aided Wireless Network,” IEEE Commun. Mag., vol. 58, no. 1, pp. 106?112, 2020. [Non-patent document 2] E. Basar, M. Di Renzo, J. De Rosny, M. Debbah, MS Alouini, and R. Zhang, “Wireless Communications Through Reconfigurable Intelligent Surfaces,” IEEE Access, vol. 7, pp. 116753?116773, 2019. Summary of the Invention [Problem to be solved by the invention]

[0005] To maintain stable wireless communication between a master station and a terminal device, it is necessary to periodically and appropriately set the master station's beam direction, the variable reflector's reflection direction shift amount, and the terminal device's beam direction. Here, assuming that there are M possible beam directions controllable on the master station side, K possible reflection direction shift amounts controllable by the variable reflector, and N possible beam directions controllable on the terminal side, a search of M × K × N possible patterns is required to set these. However, searching all M × K × N possible patterns every time takes too much time. Furthermore, the time required to search for the beam direction and reflection direction shift amount reduces the time available for data communication.

[0006] The present invention has been made to solve the above-mentioned problems, and aims to provide a master station device and a terminal device, etc., which can reduce the number of search patterns for appropriately setting the beam direction of each device and the shift amount of the reflection direction of a variable reflector when the master station device and the terminal device are performing wireless communication via a variable reflector. [Means for solving the problem]

[0007] In order to achieve the above object, a master station device according to one aspect of the present invention is a master station device in a wireless communication system including a master station device, a variable reflector whose shift amount in reflection direction is controlled by the master station device, and a terminal device that performs wireless communication with the master station device via the variable reflector, the master station device comprising: a master station communication unit that is capable of changing a beam direction and that transmits and receives a wireless signal; a master station scanning unit that controls the master station communication unit and the variable reflector so as to transmit a master station scanning wireless signal, the master station scanning signal being a wireless signal that includes a first identifier that identifies the beam direction of the master station communication unit and the shift amount in the reflection direction of the variable reflector, the master station scanning signal being a wireless signal that is transmitted in the beam direction and shift amount identified by the first identifier, while sequentially changing the beam direction and the shift amount; and a master station scanning unit that detects whether a variable reflector is present in a predetermined beam direction of the master station communication unit, based on the first identifier included in the master station scanning wireless signal that is transmitted from the terminal device while sequentially changing the beam direction and that is received by the terminal device at maximum receiving power. and a second identifier that identifies the beam direction of the terminal device, and an identification unit that identifies the second identifier contained in a terminal scanning radio signal received by an omnidirectional master station communication unit with maximum reception power among a plurality of terminal scanning radio signals, which are radio signals transmitted in the beam direction identified by the second identifier; and a response unit that controls the master station communication unit and the variable reflector so as to transmit a response radio signal including the second identifier identified by the identification unit in the beam direction and shift amount identified by the first identifier contained in the terminal scanning radio signal received by the master station communication unit, wherein the master station communication unit performs wireless communication with the terminal device in the beam direction and shift amount identified by the first identifier contained in the received terminal scanning radio signal, and the master station scanning unit limits the beam direction of the master station communication unit that transmits the master station scanning radio signal by using the direction information contained in the terminal scanning radio signal received by the master station communication unit.

[0008] With this configuration, the direction information received from the terminal device can be used to limit the beam direction for transmitting the master station scanning radio signal, which makes it possible to appropriately set the beam direction of each device and the amount of shift in the reflection direction of the variable reflector with a smaller number of search patterns.

[0009] In addition, in a parent station device according to one aspect of the present invention, the parent station scanning radio signal may include a remaining number indicating the number of parent station scanning radio signals to be transmitted in the future, out of the multiple parent station scanning radio signals transmitted while sequentially changing the shift amount of the beam direction of the parent station communication unit and the reflection direction of the variable reflector. With this configuration, the terminal device can determine whether transmission of a set of patterns of the master station scanning radio signal has been completed by referring to the remaining number included in the master station scanning radio signal.

[0010] Furthermore, in a parent station device according to one aspect of the present invention, the parent station scanning unit transmits a parent station scanning radio signal in the specified beam direction when the direction information indicates that a variable reflector is present in the specified beam direction of the parent station communication unit, and does not need to transmit a parent station scanning radio signal in the specified beam direction when the direction information indicates that a variable reflector is not present in the specified beam direction of the parent station communication unit. With this configuration, for example, the number of parent station scanning radio signals to be transmitted can be reduced by transmitting parent station scanning radio signals only in the beam direction in which a variable reflector is present, or by not transmitting parent station scanning radio signals in the beam direction in which no variable reflector is present.

[0011] Furthermore, a terminal device according to one aspect of the present invention is a terminal device in a wireless communication system including a master station device, a variable reflector whose shift amount in reflection direction is controlled by the master station device, and a terminal device that performs wireless communication with the master station device via the variable reflector, the terminal device including a terminal communication unit that can change the beam direction and transmits and receives wireless signals, an identification unit that identifies the first identifier included in a master station scanning wireless signal that is received with the maximum reception power by the non-directional terminal communication unit among a plurality of master station scanning wireless signals that are wireless signals transmitted from the master station device while sequentially changing the beam direction and the shift amount of the reflection direction of the variable reflector, the wireless signals including the first identifier identifying the beam direction and the shift amount, the wireless signals being transmitted with the beam direction and the shift amount identified by the first identifier, and The radio communication device includes an acquisition unit that acquires direction information indicating whether a variable reflector is present in a predetermined beam direction of the master station device using the received master station scanning radio signal, and a terminal scanning unit that controls the terminal communication unit to transmit the terminal scanning radio signal, which is a radio signal including a first identifier identified by the identification unit, the direction information acquired by the acquisition unit, and a second identifier that identifies the beam direction of the terminal communication unit, while sequentially changing the beam direction, and which is transmitted in the beam direction identified by the second identifier.After receiving a response radio signal including the second identifier included in the terminal scanning radio signal transmitted from the master station device and received by the master station device with the maximum reception power, the terminal communication unit performs wireless communication with the master station device in the beam direction identified by the second identifier. With this configuration, by acquiring direction information and transmitting it to the master station, the master station can limit the beam direction in which the master station scan radio signal is transmitted, thereby making it possible to appropriately set the beam direction of each device and the shift amount of the reflection direction of the variable reflector with a smaller number of search patterns.

[0012] In addition, in a terminal device according to one aspect of the present invention, the acquisition unit may acquire directional information indicating that a variable reflector is present in a specified beam direction when the terminal communication unit receives a number of parent station scanning radio signals that are equal to or less than a threshold and transmitted with different shift amounts in a specified beam direction of the parent station device, or when the terminal communication unit receives a number of parent station scanning radio signals that are greater than a threshold and transmitted with different shift amounts in a specified beam direction of the parent station device, and the distribution of the received power of the multiple parent station scanning radio signals exceeds a specified range. With this configuration, it becomes possible to obtain directional information indicating that a variable reflector exists in a predetermined beam direction of the master station device.

[0013] In addition, in a terminal device according to one aspect of the present invention, the acquisition unit may acquire directional information indicating that no variable reflector is present in the specified beam direction when the terminal communication unit receives a number of parent station scanning radio signals exceeding a threshold value transmitted with different shift amounts for a specified beam direction of the parent station device, and the distribution of the received power of the multiple parent station scanning radio signals received is within a specified range. With this configuration, it becomes possible to obtain directional information indicating that no variable reflector exists in the predetermined beam direction of the master station device.

[0014] In addition, in a terminal device according to one aspect of the present invention, the parent station scanning radio signal includes a remaining number indicating the number of parent station scanning radio signals to be transmitted in the future, among the multiple parent station scanning radio signals transmitted while sequentially changing the beam direction of the parent station device and the shift amount of the reflection direction of the variable reflector, and the acquisition unit may acquire the direction information when a parent station scanning radio signal with a remaining number of 0 is received by the terminal communication unit, or when a parent station scanning radio signal including the same first identifier is received twice by the terminal communication unit. With this configuration, the direction information can be obtained after the transmission of a set of patterns of the master station scanning radio signal is completed, so that the direction information becomes more accurate.

[0015] Furthermore, a wireless communication method according to one aspect of the present invention is a wireless communication method executed in a master station device in a wireless communication system including a master station device, a variable reflector whose shift amount in reflection direction is controlled by the master station device, and a terminal device that performs wireless communication with the master station device via the variable reflector, the method including the steps of: transmitting a master station scanning radio signal, the master station scanning radio signal being a radio signal including a first identifier that identifies the beam direction of the master station device and the shift amount of the reflection direction of the variable reflector, the radio signal being transmitted in the beam direction and shift amount identified by the first identifier, while sequentially changing the beam direction and the shift amount; and receiving the first identifier included in the master station scanning radio signal that has been transmitted from the terminal device while sequentially changing the beam direction and received at the terminal device with maximum reception power, and direction information indicating whether a variable reflector is present in a predetermined beam direction of the master station device. the step of omnidirectionally receiving one or more terminal scanning radio signals from among a plurality of terminal scanning radio signals, the radio signals including a first identifier and a second identifier that identifies the beam direction of the terminal device, the radio signals being transmitted in the beam direction identified by the second identifier; the step of identifying the second identifier included in the terminal scanning radio signal received with the maximum reception power; the step of transmitting a response radio signal including the identified second identifier in the beam direction and shift amount identified by the first identifier included in the received terminal scanning radio signal; the step of performing wireless communication with the terminal device in the beam direction and shift amount identified by the first identifier included in the received terminal scanning radio signal; and the step of limiting the beam direction in which the master station scanning radio signal is transmitted using direction information included in the received terminal scanning radio signal.

[0016] Furthermore, a wireless communication method according to one aspect of the present invention is a wireless communication method executed in a terminal device in a wireless communication system including a master station device, a variable reflector whose shift amount in reflection direction is controlled by the master station device, and a terminal device that performs wireless communication with the master station device via the variable reflector, the method including the steps of: receiving, in an omnidirectional manner, one or more master station scanning wireless signals out of a plurality of master station scanning wireless signals, the master station scanning wireless signals being wireless signals that include a first identifier that identifies the beam direction and the shift amount and that are transmitted from the master station device while sequentially changing the beam direction and the shift amount in the reflection direction of the variable reflector; and identifying the first identifier included in the master station scanning wireless signal received with the maximum reception power. The method includes the steps of: acquiring direction information indicating whether a variable reflector is present in a predetermined beam direction of the master station device using the received master station scanning radio signal; transmitting a terminal scanning radio signal, which is a radio signal including the specified first identifier, the acquired direction information, and a second identifier that identifies the beam direction of the terminal device, and which is transmitted in the beam direction identified by the second identifier, while sequentially changing the beam direction; receiving a response radio signal that includes the second identifier included in the terminal scanning radio signal transmitted from the master station device and received at the master station device with the maximum reception power; and performing wireless communication with the master station device in the beam direction identified by the second identifier included in the received response radio signal. [Effects of the Invention]

[0017] According to one aspect of the present invention, a master station device and a terminal device can reduce the number of search patterns required to appropriately set the beam direction of each device and the shift amount of the reflection direction of the variable reflector in wireless communication via a variable reflector. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a wireless communication system according to an embodiment of the present invention; [Figure 2] FIG. 2 is a functional block diagram showing the configuration of a master station device according to the embodiment; [Figure 3] FIG. 2 is a functional block diagram showing the configuration of a terminal device according to the embodiment; [Figure 4] FIG. 10 is a diagram showing an example of a time chart according to the embodiment; [Figure 5] A flowchart showing the operation of the master station device according to the embodiment. [Figure 6] A flowchart showing the operation of the terminal device according to the embodiment. [Figure 7] FIG. 2 shows an example of the configuration of a computer system according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a master station device, a terminal device, and a wireless communication method according to the present invention will be described using embodiments. In the following embodiments, components and steps denoted by the same reference numerals are identical or equivalent, and repeated description may be omitted. The master station device and terminal device according to this embodiment perform wireless communication via a variable reflector capable of controlling the amount of shift in the reflection direction. The master station device transmits a master station scanning radio signal while sequentially changing the beam direction and the amount of shift in the reflection direction of the variable reflector. Furthermore, the terminal device uses the received master station scanning radio signal to obtain direction information indicating whether a variable reflector is present in a predetermined beam direction of the master station device, and transmits a terminal scanning radio signal including the direction information while sequentially changing the beam direction. The master station device then uses the direction information included in the received terminal scanning radio signal to limit the beam direction in which the master station scanning radio signal is transmitted.

[0020] FIG. 1 is a schematic diagram showing the configuration of a wireless communication system 100 according to this embodiment, FIG. 2 is a functional block diagram showing the configuration of a master station device 1, and FIG. 3 is a functional block diagram showing the configuration of a terminal device 3. As shown in FIG. 1, the wireless communication system 100 includes the master station device 1, a variable reflector 2, and the terminal device 3. The master station device 1 and the terminal device 3 perform wireless communication via the variable reflector 2. If there is no obstacle between the master station device 1 and the terminal device 3, the two may transmit and receive wireless signals directly without using the variable reflector 2. The wavelength and frequency of the radio waves used in the wireless communication are not particularly limited, and may be, for example, millimeter waves, submillimeter waves, terahertz waves, or other radio waves with a wavelength of 10 mm or less.

[0021] The master station device 1 may be, for example, an access point (AP). The master station device 1 may be, for example, installed at a fixed location. The terminal device 3 may be, for example, a terminal (STA) that performs wireless communication with an access point. The terminal device 3 may be, for example, mobile. Note that while FIG. 1 shows a case where the wireless communication system 100 includes only one terminal device 3, the wireless communication system 100 may include, for example, two or more terminal devices 3 that perform wireless communication with the master station device 1.

[0022] The variable reflector 2 can change the amount of shift in the reflection direction of radio waves, and may be, for example, what is called an IRS or RIS as described above. In this embodiment, the amount of shift in the reflection direction of the variable reflector 2 is controlled by the master station device 1. Therefore, the master station device 1 and the variable reflector 2 may communicate with each other, for example, wired or wirelessly. In this embodiment, as an example, a case where the master station device 1 and the variable reflector 2 communicate with each other wiredly will be mainly described. When the master station device 1 and the variable reflector 2 communicate wirelessly, the wireless communication may be performed using a lower frequency band than the wireless communication performed by the master station communication unit 11 described later. The variable reflector 2 may be installed at a fixed position, for example.

[0023] Here, in this embodiment, it is assumed that there are M beam directions controllable by the parent station device 1, K shift amounts of the reflection direction controllable by the variable reflector 2, and N beam directions controllable by the terminal device 3. The M beam directions controllable by the parent station device 1 and the N beam directions controllable by the terminal device 3 each include an omnidirectional beam. The omnidirectional beam may be, for example, a completely omnidirectional beam, or a beam that is close to omnidirectional enough to be considered omnidirectional. M and N may each be an integer of 3 or greater. The K shift amounts of the reflection direction controllable by the variable reflector 2 include 0 degrees (i.e., there is no shift amount of the reflection direction and the variable reflector functions simply as a reflector). K may be an integer of 2 or greater, or an integer of 3 or greater.

[0024] In this embodiment, the shift amount of the reflection direction of the variable reflector 2 is identified by an index k. This index k is an identifier for the shift amount of the reflection direction of the variable reflector 2, and is assumed to be k={0, 1, ..., K-1}. k=0 indicates that the shift amount of the reflection direction of the variable reflector 2 is 0 degrees.

[0025] In this embodiment, the beam direction of the master station device 1 is identified by an index m. This index m is an identifier of the beam direction of the master station device 1, and is assumed to be m={0, 1, ..., M-1}. m=0 indicates an omnidirectional beam.

[0026] In this embodiment, the beam direction of the terminal device 3 is identified by an index n. This index n is an identifier of the beam direction of the terminal device 3, and is assumed to be n={0, 1, ..., N-1}. n=0 indicates an omnidirectional beam.

[0027] The master station sector ID and terminal sector ID are defined as follows: The master station sector ID is an identifier that identifies the beam direction of the master station device 1 and the shift amount of the reflection direction of the variable reflector 2, and corresponds to the first identifier described later. The master station sector ID = {0, 1, ..., M × K-1}. The terminal sector ID is an identifier that identifies the beam direction of the terminal device 3, and corresponds to the second identifier described later. The terminal sector ID = {0, 1, ..., N-1}. Parent station sector ID = m + (k × M) Terminal sector ID=n

[0028] Here, it is preferable that the master station device 1 knows the values ​​of K and N, and the terminal device 3 knows the value of M. For example, this information may be preset in each device, or may be notified by communication. In the latter case, for example, the value of M may be included in a master station scanning radio signal, which will be described later.

[0029] In the wireless communication system 100, as an example, radio signals may be transmitted and received according to a round interval T, as shown in the time chart of Fig. 4. First, during a period P1 in which scanning on the master station device 1 side is performed, a plurality of master station scanning radio signals, which will be described later, may be transmitted from the master station device 1. Next, during a period P2 in which scanning on the terminal device 3 side is performed, a plurality of terminal scanning radio signals, which will be described later, may be transmitted from the terminal device 3. During a period P3 following the period P2, a response radio signal, which is a response to the terminal scanning radio signal, may be transmitted and received, and data communication may be performed between the master station device 1 and the terminal device 3. In this data communication, channel access may be performed by, for example, CSMA / CA or scheduling by the master station device 1. Furthermore, the periods P1 to P3 may be repeated at every round interval T.

[0030] For example, period P1 may be a period corresponding to BTI in IEEE 802.11ad, period P2 may be a period corresponding to A-BFT in IEEE 802.11ad, and period P3 may be a period corresponding to ATI, CBAP, and SP in IEEE 802.11ad.

[0031] As shown in FIG. 2, the master station device 1 includes a master station communication unit 11, a storage unit 12, a master station scanning unit 13, an identifying unit 14, and a responding unit 15.

[0032] The master station communication unit 11 transmits and receives radio signals. The master station communication unit 11 can change the beam direction. The master station communication unit 11 may transmit and receive radio signals using, for example, an array antenna such as a phased array antenna. In this embodiment, as described above, it is assumed that there are M beam directions for the master station communication unit 11 to transmit and receive radio signals, one of which is omnidirectional. Note that, for example, if the antenna elements constituting the array antenna are omnidirectional, omnidirectional transmission and reception can be performed by selecting any one of the antenna elements. Also, for example, if the antenna elements constituting the array antenna have directionality (for example, if each antenna element has high gain in a different direction), omnidirectional transmission and reception can be performed by combining signals received by multiple antenna elements to be omnidirectional, or by transmitting signals using multiple antenna elements to be omnidirectional.

[0033] The storage unit 12 stores information such as a master station identifier for identifying the master station device 1. The master station identifier may be, for example, a unique ID for identifying the master station device 1. This master station identifier may be, for example, equivalent to a BSSID in a wireless LAN. Information related to a wireless signal received by the master station communication unit 11 and information included in the wireless signal may also be stored in the storage unit 12. The storage unit 12 is preferably realized by a non-volatile recording medium, but may also be realized by a volatile recording medium. The recording medium may be, for example, a semiconductor memory or a magnetic disk.

[0034] The master station scanning unit 13 controls the master station communication unit 11 and the variable reflector 2 so as to transmit a master station scanning radio signal, which is a radio signal including a first identifier that identifies the beam direction of the master station communication unit 11 and the shift amount of the reflection direction of the variable reflector 2, while sequentially changing the beam direction and shift amount. The master station scanning radio signal is transmitted in the beam direction and shift amount identified by the first identifier. The master station scanning radio signal is transmitted with the beam direction of the master station communication unit 11 and the shift amount of the reflection direction of the variable reflector 2 set to the beam direction and shift amount identified by the first identifier included in the master station scanning radio signal. In this embodiment, the case where the first identifier is a master station sector ID will be mainly described. Therefore, hereinafter, the first identifier may also be referred to as a master station sector ID.

[0035] The master station scanning radio signal may include, for example, a master station identifier that identifies the master station device 1 that is the transmitter. The master station scanning radio signal may also include, for example, a remaining number that indicates the number of master station scanning radio signals to be transmitted in the future among the multiple master station scanning radio signals that are transmitted while sequentially changing the shift amount of the beam direction of the master station communication unit 11 and the reflection direction of the variable reflector 2. The remaining number included in a certain master station scanning radio signal indicates the number of master station scanning radio signals to be transmitted after that master station scanning radio signal. Therefore, the remaining number included in the master station scanning radio signal that is transmitted last among the multiple master station scanning radio signals is 0.

[0036] The process of transmitting multiple master station scanning radio signals while sequentially changing the shift amount of the beam direction of the master station communication unit 11 and the reflection direction of the variable reflector 2 is referred to as master station scanning. When transmitting multiple master station scanning radio signals in master station scanning, the signals may be transmitted in omnidirectional or non-omnidirectional directions. In this embodiment, the latter case will be mainly described. When omnidirectional directions are not included, for example, (M-1)×K master station scanning radio signals excluding the omnidirectional beam direction may be transmitted in the first master station scanning. These master station scanning radio signals may be transmitted in the order of the master station sector IDs or randomly. In subsequent master station scanning, the number of master station scanning radio signals transmitted may be reduced by using direction information, which will be described later. It is preferable that a master station scanning radio signal including the same master station sector ID is not transmitted more than once in one master station scanning. As an example of the remaining number, if the number of master station scanning radio signals transmitted in one master station scanning is W, the Vth master station scanning radio signal may include the remaining number "WV".

[0037] Transmission of multiple master station scanning radio signals, i.e., master station scanning, may be performed, for example, in a period P1. Note that if it is not possible to transmit all of the master station scanning radio signals to be transmitted in one master station scanning in one period P1, for example, one master station scanning may be performed using multiple periods P1. In other words, one master station scanning may span multiple rounds.

[0038] The identification unit 14 identifies a second identifier included in the terminal scanning radio signal received with the maximum reception power by the non-directional master station communication unit 11 from among a plurality of terminal scanning radio signals transmitted from the terminal device 3 while sequentially changing the beam direction. The terminal scanning radio signal is a radio signal including a first identifier (master station sector ID) included in the master station scanning radio signal received with the maximum reception power by the terminal device 3, direction information indicating whether the variable reflector 2 is present in a predetermined beam direction of the master station communication unit 11, and a second identifier identifying the beam direction of the terminal device 3, and is transmitted in the beam direction identified by the second identifier. In this embodiment, the case where the second identifier is the terminal sector ID will be mainly described. Therefore, hereinafter, the second identifier may also be referred to as the terminal sector ID. The terminal scanning radio signal may include, for example, a master station identifier identifying the destination master station device 1. The terminal scanning radio signal may also include, for example, a terminal identifier identifying the source terminal device 3. The terminal identifier may be, for example, the MAC address of the terminal device 3.

[0039] The process of transmitting a plurality of terminal scanning radio signals while sequentially changing the beam direction of the terminal device 3 is referred to as terminal scanning. Terminal scanning may be performed, for example, during period P2. When transmitting a plurality of terminal scanning radio signals in terminal scanning, the signals may be transmitted with or without omnidirectionality, for example. In this embodiment, the latter case will be mainly described. When omnidirectionality is not included, for example, N-1 terminal scanning radio signals excluding the omnidirectional beam direction may be transmitted in one terminal scanning. Note that it is preferable that terminal scanning radio signals including the same terminal sector ID are not transmitted more than once in one terminal scanning.

[0040] The determination unit 14 may, for example, associate a second identifier (terminal sector ID) included in a terminal scanning radio signal received by the non-directional master station communication unit 11 with the received power of the terminal scanning radio signal, and store the association data in the storage unit 12. The received power may be, for example, a received signal strength indicator (RSSI). After one terminal scan is completed, the determination unit 14 may identify the second identifier associated with the maximum received power stored in the storage unit 12 as the second identifier included in the terminal scanning radio signal received with the maximum received power. This second identifier may also be referred to as a maximum received second identifier. For example, the determination unit 14 may determine that one terminal scan is completed when the period P2 ends. During terminal scanning, the master station device 1 receives the terminal scanning radio signal non-directionally. The shift amount of the reflection direction of the variable reflector 2 may be set to 0 degrees, i.e., k=0, or the shift amount may be changed for each terminal scan. In the latter case, even if the master station device 1 is unable to receive the terminal scanning radio signal during one terminal scan, it is considered that the master station device 1 will be able to receive the terminal scanning radio signal during any subsequent terminal scan.

[0041] Furthermore, for example, the first identifier and direction information included in the terminal scanning radio signal received by the master station communication unit 11 may also be stored in the storage unit 12. Note that since the first identifier and direction information included in the multiple terminal scanning radio signals transmitted in one terminal scanning are all the same, for example, only the first identifier and direction information included in any one of the multiple terminal scanning radio signals received by the master station device 1 in one terminal scanning may be stored in the storage unit 12. As an example, when the master station communication unit 11 receives a terminal scanning radio signal, the identification unit 14 stores the first identifier and direction information included in the terminal scanning radio signal in the storage unit 12. However, if the same information is already stored in the storage unit 12, this storage may not be performed.

[0042] The direction information may include, for example, information indicating that the variable reflector 2 is present in a predetermined beam direction of the master station communication unit 11, or may include information indicating that the variable reflector 2 is not present in the predetermined beam direction of the master station communication unit 11. The predetermined beam direction of the master station communication unit 11 may be indicated, for example, by an index m that identifies the beam direction of the master station device 1. The direction information may be information that includes, for example, a combination of the index m that identifies the beam direction of the master station device 1 and information such as a flag that indicates whether the variable reflector 2 is present in that beam direction.

[0043] The first identifier included in the terminal scanning radio signal is the first identifier included in the master station scanning radio signal received at the terminal device 3 with the maximum reception power. Therefore, this first identifier is sometimes referred to as the maximum reception first identifier. Furthermore, it is considered that a radio signal is transmitted using the beam direction of the master station communication unit 11 and the shift amount of the reflection direction of the variable reflector 2 identified by this maximum reception first identifier, and the radio signal is transmitted from the variable reflector 2 to the terminal device 3. Therefore, it is preferable that the master station communication unit 11 performs wireless communication with the terminal device 3 using the first identifier included in the received terminal scanning radio signal, i.e., the beam direction and shift amount identified by the maximum reception first identifier. For example, during period P3, when transmitting a radio signal from the master station device 1 to the terminal device 3, the beam direction of the master station communication unit 11 and the shift amount of the reflection direction of the variable reflector 2 may be set to the beam direction and shift amount identified by the maximum reception first identifier.

[0044] The response unit 15 controls the master station communication unit 11 and the variable reflector 2 so as to transmit a response radio signal including the second identifier identified by the identification unit 14, i.e., the maximum receivable second identifier, in the beam direction and shift amount identified by the first identifier, i.e., the maximum receivable first identifier, included in the terminal scanning radio signal received by the master station communication unit 11. For example, the quotient obtained by dividing the master station sector ID, which is the maximum receivable first identifier, by M becomes index k, which identifies the shift amount, and the remainder becomes index m, which identifies the beam direction. The second identifier included in the response radio signal indicates the beam direction that the master station 1 wants the terminal device 3 to use when wirelessly communicating with the master station 1. The response radio signal may include, for example, a master station identifier that identifies the master station 1, which is the source of the response radio signal, or a terminal identifier that identifies the terminal device 3, which is the destination of the response radio signal. The terminal identifier that identifies the terminal device 3, which is the destination of the response radio signal, may be, for example, the one included in the terminal scanning radio signal.

[0045] The master station scanning unit 13 may use direction information included in the terminal scanning radio signal received by the master station communication unit 11 to limit the beam direction of the master station communication unit 11 transmitting the master station scanning radio signal. For example, the master station scanning unit 13 may use direction information included in the terminal scanning radio signal received in a terminal scan after a master station scan to limit the beam direction in the next master station scan. More specifically, when the direction information indicates that a variable reflector 2 is present in a predetermined beam direction of the master station communication unit 11, the master station scanning unit 13 may transmit the master station scanning radio signal in the predetermined beam direction, and when the direction information indicates that a variable reflector 2 is not present in the predetermined beam direction of the master station communication unit 11, the master station scanning unit 13 may not transmit the master station scanning radio signal in the predetermined beam direction. This reduces the number of master station scanning radio signals transmitted in master station scanning, enabling master station scanning to be performed in a shorter period of time. In addition, when the parent station scanning unit 13 transmits (or does not transmit) a parent station scanning radio signal in a predetermined beam direction, it may mean, for example, controlling the parent station communication unit 11 to perform (or not perform) such transmission.

[0046] For example, the master station scanning unit 13 may not transmit a master station scanning radio signal for a beam direction in which the direction information does not indicate the presence or absence of a variable reflector 2, i.e., for a beam direction in which it is unclear whether a variable reflector 2 exists in that direction. By doing so, the number of master station scanning radio signals transmitted in a master station scan can be further reduced, and the master station scanning period can be further shortened. In this case, if a miss occurs, it may be impossible to achieve appropriate wireless communication between the master station device 1 and the terminal device 3. Therefore, when not transmitting a master station scanning radio signal for a beam direction in which it is unclear whether a variable reflector 2 exists, the master station scanning unit 13 may perform a full search, i.e., transmit a master station scanning radio signal for all beam directions of the master station device 1 and all shift amounts of the reflection direction of the variable reflector 2, for example, every predetermined number of master station scans (e.g., every five master station scans).

[0047] Note that the master station scanning unit 13 may transmit a master station scanning radio signal for a specific shift amount of the reflection direction of the variable reflector 2, for example, a shift amount identified by index k=0, for all beam directions of the master station device 1 for each master station scan. This is because there is a possibility that the master station device 1 and the terminal device 3 can communicate wirelessly without going through the variable reflector 2.

[0048] As an example, when direction information is received indicating that the variable reflector 2 does not exist in the beam direction of the master station device 1 identified by index m1, the master station scanning unit 13 may transmit a master station scanning radio signal excluding the next master station sector ID in the next master station scan. m1+M, m1+2×M, …, m1+(K-1)×M

[0049] As another example, when direction information indicating that the variable reflector 2 is present in the beam direction of the master station device 1 identified by index m2 is received, the master station scanning unit 13 may transmit a master station scanning radio signal only to the next master station sector ID in the next master station scan. Note that the following example shows a case where, for the shift amount identified by index k=0, a master station scanning radio signal is transmitted in all beam directions except for the omnidirectional beam of the master station device 1. 1,2,…,M-1,m2+M,m2+2×M,…,m2+(K-1)×M

[0050] When the master station scanning unit 13 performs a full search, for example, (M-1) x K master station scanning radio signals are transmitted. On the other hand, when the direction information indicates that the variable reflector 2 is present in a specific beam direction of the master station device 1, the number of master station scanning radio signals to be transmitted can be reduced to (M-1) + (K-1) = M + K-2, for example. Here, M-1 is the number of master station scanning radio signals transmitted for all beam directions of the master station device 1 for a specific shift amount in the reflection direction of the variable reflector 2. Also, K-1 is the number of master station scanning radio signals transmitted for all shift amounts in the reflection direction of the variable reflector 2 (excluding the specific shift amount) in the beam direction of the master station device 1 facing the variable reflector 2.

[0051] As shown in FIG. 3, the terminal device 3 includes a terminal communication unit 31, a storage unit 32, an identification unit 33, an acquisition unit 34, and a terminal scanning unit 35.

[0052] The terminal communication unit 31 transmits and receives radio signals. The terminal communication unit 31 is capable of changing the beam direction. The terminal communication unit 31 may transmit and receive radio signals using, for example, an array antenna such as a phased array antenna. In this embodiment, as described above, it is assumed that there are N beam directions in which the terminal communication unit 31 transmits and receives radio signals, one of which is omnidirectional.

[0053] The storage unit 32 stores information such as a terminal identifier for identifying the terminal device 3. Information related to a wireless signal received by the terminal communication unit 31 and information included in the wireless signal may also be stored in the storage unit 32. The storage unit 32 is preferably realized by a non-volatile recording medium, but may also be realized by a volatile recording medium. The recording medium may be, for example, a semiconductor memory or a magnetic disk.

[0054] The identification unit 33 identifies the first identifier included in the master station scanning radio signal received with the maximum reception power by the non-directional terminal communication unit 31, i.e., the maximum received first identifier, among multiple master station scanning radio signals transmitted from the master station device 1 while sequentially changing the beam direction and the shift amount of the reflection direction of the variable reflector 2. As described above, the master station scanning radio signal is a radio signal including a first identifier that identifies the beam direction and the shift amount, and is transmitted in the beam direction and shift amount identified by the first identifier. The master station scanning radio signal may include, for example, the master station identifier, the remaining number, etc.

[0055] For example, the specifying unit 33 may associate a first identifier (master station sector ID) included in a master station scanning radio signal received by the non-directional terminal communication unit 31 with the reception power of the master station scanning radio signal, and store the associated information in the storage unit 12. After one master station scan is completed, the specifying unit 33 may then specify the first identifier associated with the maximum reception power stored in the storage unit 12 as the first identifier included in the master station scanning radio signal received with the maximum reception power, i.e., the maximum reception first identifier.

[0056] It may be determined that one master station scan has ended, for example, when a master station scanning radio signal with a remaining number of 0 is received, or when a master station scanning radio signal including the same first identifier is received twice. A master station scanning radio signal with a remaining number of 0 is a master station scanning radio signal including a remaining number of 0. When a master station scanning radio signal including the same first identifier is received twice, the first identifier, i.e., the master station sector ID, has gone around once, so at least one master station scan has ended.

[0057] The acquisition unit 34 acquires direction information indicating whether the variable reflector 2 is present in a predetermined beam direction of the master station device 1, using the master station scanning radio signal received by the terminal communication unit 31. As described above, the terminal communication unit 31 receives the master station scanning radio signal by using the non-directional terminal communication unit 31. Using the received master station scanning radio signal may mean, for example, using a first identifier included in the received master station scanning radio signal, or may also mean using the reception power of the received master station scanning radio signal. The acquisition unit 34 may acquire direction information including information indicating that the variable reflector 2 is present in the predetermined beam direction of the master station communication unit 11, or may acquire direction information including information indicating that the variable reflector 2 is not present in the predetermined beam direction of the master station communication unit 11.

[0058] For example, when the terminal communication unit 31 receives a first threshold or less of master station scanning radio signals transmitted with different shift amounts for a predetermined beam direction of the master station device 1, the acquisition unit 34 may acquire direction information indicating that the variable reflector 2 is present in the predetermined beam direction. This is referred to as a first acquisition method. Note that the master station scanning radio signals transmitted with different shift amounts for the predetermined beam direction of the master station device 1 may be master station scanning radio signals including a first identifier that identifies one beam direction and different shift amounts.

[0059] Furthermore, for example, when the terminal communication unit 31 receives a number of master station scanning radio signals that exceed a first threshold and are transmitted with different shift amounts in a predetermined beam direction of the master station device 1, and the distribution of the received power of the plurality of master station scanning radio signals exceeds a predetermined range (for example, 6 dB), the acquisition unit 34 may acquire direction information indicating that the variable reflector 2 is present in the predetermined beam direction. This is referred to as a second acquisition method.

[0060] The first threshold may be a small number, such as two. Furthermore, the acquisition unit 34 may determine that the beam directions of the master station devices 1 identified by the master station sector IDs are the same, for example, if the remainders obtained by dividing the master station sector ID, which is the first identifier, by M are the same. The acquisition unit 34 may acquire the direction information using, for example, one of the first and second acquisition methods, or may acquire the direction information using both. As an example, when acquiring the direction information using the first acquisition method, the acquisition unit 34 may identify the beam direction of the master station device 1 corresponding to the first identifier included in the received master station scanning radio signal, which is stored in the storage unit 32, and acquire direction information indicating that the variable reflector 2 is present in that beam direction when the number of different first identifiers corresponding to a certain beam direction is equal to or less than the first threshold.

[0061] When the beam direction of the master station device 1 is directed toward the variable reflector 2, the beam of the radio signal reaches the variable reflector 2, and the direction of the beam of the radio signal reflected by the variable reflector 2 changes according to the shift amount of the reflection direction of the variable reflector 2. Therefore, since the number of radio signals received by the terminal device 3 is usually considered to be small, the direction information can be acquired by the first acquisition method. Furthermore, even if a large number of radio signals are received by the terminal device 3, the difference between the peak received power (i.e., the received power when the reflection direction of the radio signal by the variable reflector 2 is directed toward the terminal device 3) and the non-peak received power (i.e., the received power when the reflection direction of the radio signal by the variable reflector 2 is shifted from the terminal device 3) is considered to be large. Therefore, the direction information can be acquired by the second acquisition method.

[0062] Furthermore, for example, when the terminal communication unit 31 receives a number of master station scanning radio signals that exceed a second threshold and are transmitted with different shift amounts in a predetermined beam direction of the master station device 1, and the distribution of the received power of the plurality of master station scanning radio signals is within a predetermined range (for example, 6 dB), the acquisition unit 34 may acquire direction information indicating that the variable reflector 2 is not present in the predetermined beam direction. The second threshold may be, for example, a value obtained by multiplying M by a positive real number that is less than 1 (for example, a value close to 1, such as 0.75).

[0063] When the beam direction of the master station device 1 is not directed toward the variable reflector 2, the radio signal beam does not reach the variable reflector 2, and therefore the direction of the radio signal reflected by the variable reflector 2 does not change significantly according to the amount of shift in the reflection direction of the variable reflector 2. Therefore, direction information can be obtained in this way.

[0064] The acquisition unit 34 may acquire the direction information, for example, when the terminal communication unit 31 receives a master station scanning radio signal with a remaining number of 0, or when the terminal communication unit 31 receives a master station scanning radio signal including the same first identifier twice. In this way, the acquisition unit 34 can acquire the direction information after the master station scanning is completed, and can acquire more accurate direction information. As an example, the acquisition unit 34 may receive from the identification unit 33 or another component information that the terminal communication unit 31 has received a master station scanning radio signal with a remaining number of 0, or that the terminal communication unit 31 has received a master station scanning radio signal including the same first identifier twice.

[0065] The terminal scanning unit 35 controls the terminal communication unit 31 to transmit a terminal scanning radio signal, which is a radio signal including the first identifier identified by the identification unit 33, i.e., the maximum received first identifier, the direction information acquired by the acquisition unit 34, and a second identifier (terminal sector ID) that identifies the beam direction of the terminal communication unit 31, while sequentially changing the beam direction. The terminal scanning radio signal is transmitted with the beam direction of the terminal communication unit 31 set to the beam direction identified by the second identifier included in the terminal scanning radio signal.

[0066] The terminal scanning radio signal may include, for example, a terminal identifier that identifies the terminal device 3 that is the source of the signal. The terminal scanning radio signal may also include, for example, a master station identifier that identifies the master station device 1 that is the destination of the signal. This master station identifier may be, for example, the master station identifier that was included in the master station scanning radio signal received by the terminal communication unit 31.

[0067] In response to the transmission of the multiple terminal scanning radio signals by the terminal scanning unit 35, the terminal communication unit 31 may omnidirectionally receive a response radio signal that includes the second identifier included in the terminal scanning radio signal transmitted from the master station device 1 and received at the master station device 1 with the maximum reception power, i.e., the maximum reception second identifier. After receiving the response radio signal, the terminal communication unit 31 may perform wireless communication with the master station device 1 in a beam direction identified by the second identifier included in the response radio signal. For example, during period P3, when transmitting a radio signal from the terminal device 3 to the master station device 1, the beam direction of the terminal communication unit 31 may be set to the beam direction identified by the maximum reception second identifier included in the response radio signal.

[0068] During period P3, data communication may be performed by wireless communication between the master station device 1 and the terminal device 3. In this data communication, channel access may be performed, for example, as follows.

[0069] When channel access is performed by CSMA / CA, it is preferable to use an omnidirectional beam direction for carrier sensing. Note that, in the terminal device 3, carrier sensing may be performed using a beam direction identified by the maximum received second identifier.

[0070] When channel access is performed by scheduling by the master station device 1, scheduling may be performed first by the master station device 1, and wireless communication may be performed between the master station device 1 and the terminal device 3 according to the scheduling. The radio signal for scheduling that the master station device 1 transmits to the terminal device 3 may include, for example, a terminal identifier for identifying the terminal device 3, and information indicating the period during which wireless communication with the terminal device 3 is performed (for example, the start and end times of wireless communication, the number of the time slot for wireless communication, etc.).

[0071] In data communication, it is preferable that the transmitting side transmits a radio signal using a beam direction and a shift amount identified by the maximum reception first identifier or the maximum reception second identifier. On the other hand, it is preferable that the receiving side receives a radio signal transmitted from the other side in an omnidirectional manner. In data communication, for example, the receiving side may also receive a radio signal using a beam direction and a shift amount identified by the maximum reception first identifier or the maximum reception second identifier. In other words, the master station device 1, the variable reflector 2, and the terminal device 3 may use the same beam direction and shift amount for both transmitting and receiving radio signals in data communication.

[0072] Next, the operation of the master station device 1 will be described with reference to the flowchart of FIG. (Step S101) The master station scanning unit 13 determines whether or not it is the transmission period of the master station scanning radio signal, i.e., period P1. If it is the transmission period of the master station scanning radio signal, the process proceeds to step S102; if not, the process proceeds to step S105.

[0073] (Step S102) The master station scanning unit 13 sets the beam direction of the master station communication unit 11 to the beam direction identified by the first identifier included in the master station scanning radio signal to be transmitted, and sets the reflection direction of the variable reflector 2 to the shift amount identified by the first identifier. If a processing delay occurs in setting the shift amount, the master station scanning unit 13 may, for example, issue an instruction to change the shift amount in advance, taking that delay into consideration.

[0074] (Step S103) The master station scanning unit 13 causes the master station communication unit 11 to transmit the master station scanning radio signal to be transmitted. This master station scanning radio signal is received by the terminal device 3, for example, when the beam direction of the master station device 1 is directed toward the variable reflector 2 and the master station scanning radio signal is reflected by the variable reflector 2 in the direction of the terminal device 3;

[0075] (Step S104) The master station scanning unit 13 determines whether or not to end the transmission of the master station scanning radio signal. If it is to end, the process returns to step S101, and if not, the process returns to step S102.

[0076] In step S104, the master station scanning unit 13 may determine to end the transmission of the master station scanning radio signal when, for example, all of the master station scanning radio signals to be transmitted in one master station scanning have been transmitted, or may determine to end the transmission of the master station scanning radio signal when the transmission period of the master station scanning radio signal has ended. In the latter case, when the transmission period of the master station scanning radio signal starts again, transmission may be resumed from the next master station scanning radio signal. Also, for example, a full search may be performed in the first master station scanning, and in subsequent master station scanning, searches may be performed only in the beam directions limited in step S112, which will be described later.

[0077] (Step S105) The master station communication unit 11 determines whether it is the reception period of the terminal scanning radio signal, i.e., period P2, or not. If it is the reception period of the terminal scanning radio signal, the process proceeds to step S106; if not, the process returns to step S101.

[0078] (Step S106) The master station communication unit 11 determines whether or not it has received a terminal scanning radio signal. If it has received a terminal scanning radio signal, it proceeds to step S107; if not, it proceeds to step S108. Note that the terminal scanning radio signal is received non-directionally.

[0079] (Step S107) The identifying unit 14 associates the second identifier included in the received terminal scanning radio signal with the reception power of the terminal scanning radio signal, and stores them in the storage unit 12. The identifying unit 14 may also store, for example, a maximum received first identifier, which is a first identifier included in the received terminal scanning radio signal, and direction information in the storage unit 12. Then, the process returns to step S106.

[0080] (Step S108) The identification unit 14 determines whether reception of the terminal scanning radio signal has ended, i.e., whether one terminal scan has ended. If reception of the terminal scanning radio signal has ended, the process proceeds to step S109; otherwise, the process returns to step S106. The identification unit 14 may determine that reception of the terminal scanning radio signal has ended, for example, when the period P2 has ended.

[0081] In addition, if the terminal scanning radio signal has not been received at all by the master station device 1 even after the period P2 has ended, for example, if the shift amount of the variable reflector 2 is inappropriate and the terminal scanning radio signal transmitted from the terminal device 3 while sequentially changing the beam direction has not been received at all by the master station device 1, the processing of steps S109 to S112 may be skipped.

[0082] (Step S109) The identifying unit 14 identifies the second identifier associated with the maximum received power stored in the storage unit 12.

[0083] (Step S110) The response unit 15 sets the parent station communication unit 11 so that the beam direction is identified by the maximum received first identifier, and sets the reflection direction of the variable reflector 2 so that the shift amount is identified by the maximum received first identifier.

[0084] (Step S111) The response unit 15 causes the master station communication unit 11 to transmit a response wireless signal including the maximum receivable second identifier identified in step S109.

[0085] (Step S112) The master station scanning unit 13 uses the direction information included in the received terminal scanning radio signal to limit the beam direction of the master station device 1 for the master station scanning radio signal to be transmitted in the next master station scanning. Then, the process returns to step S101. In the next master station scanning, a smaller number of master station scanning radio signals will be transmitted than in the full search, according to this limitation.

[0086] Although not included in the flowchart of Fig. 5, wireless signals may be transmitted and received with the terminal device 3 during period P3. In this case, as described above, wireless signals may be transmitted with the beam direction identified by the maximum received first identifier and the amount of shift in the reflection direction of the variable reflector 2. The order of processing in the flowchart of Fig. 5 is an example, and the order of each step may be changed as long as the same results are obtained. In the flowchart of Fig. 5, processing may be terminated by power-off or an interrupt to end processing.

[0087] Next, the operation of the terminal device 3 will be described with reference to the flowchart of FIG. (Step S201) The terminal communication unit 31 determines whether or not a master station scanning radio signal has been received. If a master station scanning radio signal has been received, the process proceeds to step S202; if not, the process proceeds to step S203. Note that the master station scanning radio signal is received non-directionally.

[0088] (Step S202) The identifying unit 33 associates the first identifier included in the received master station scanning radio signal with the reception power of the master station scanning radio signal, and stores them in the storage unit 32. Then, the process returns to step S201.

[0089] (Step S203) The terminal scanning unit 35 determines whether to transmit a terminal scanning radio signal. If the terminal scanning radio signal is to be transmitted, the process proceeds to step S204; if not, the process returns to step S201. The terminal scanning unit 35 may determine to transmit a terminal scanning radio signal, for example, when a master station scanning radio signal with a remaining number of 0 is received, or when a master station scanning radio signal including the same first identifier is received twice, or may further determine to transmit a terminal scanning radio signal after the start of period P2. The start point of period P2 may be indicated, for example, by information included in the master station scanning radio signal.

[0090] (Step S204) The identifying unit 33 identifies the maximum received first identifier, which is the first identifier associated with the maximum received power stored in the storage unit 32.

[0091] (Step S205) The acquisition unit 34 acquires direction information using the first identifier included in the master station scanning radio signal received by the terminal communication unit 31 and, if necessary, the reception power of the master station scanning radio signal.

[0092] (Step S206) The terminal scanning unit 35 sets the beam direction of the terminal communication unit 31 to the beam direction identified by the second identifier included in the terminal scanning radio signal to be transmitted.

[0093] (Step S207) The terminal scanning unit 35 causes the terminal communication unit 31 to transmit the terminal scanning radio signal to be transmitted. The terminal scanning radio signal may include, for example, a maximum reception first identifier, direction information, and a second identifier. This terminal scanning radio signal is received by the master station device 1 when, for example, the beam direction of the terminal device 3 is directed toward the variable reflector 2 and the terminal scanning radio signal is reflected by the variable reflector 2 toward the master station device 1, but is not received by the master station device 1 otherwise.

[0094] (Step S208) The terminal scanning unit 35 determines whether to end the transmission of the terminal scanning radio signals. If it has ended, the process proceeds to step S209, and if not, the process returns to step S206. For example, the terminal scanning unit 35 may determine to end the transmission of the terminal scanning radio signals when M-1 terminal scanning radio signals have been transmitted, and may otherwise determine not to end the transmission of the terminal scanning radio signals.

[0095] (Step S209) The terminal communication unit 31 determines whether or not a response wireless signal has been received. If a response wireless signal has been received, the process proceeds to step S210; if not, the process of step S209 is repeated until a response wireless signal is received. Note that the response wireless signal is received omnidirectionally.

[0096] (Step S210) The terminal communication unit 31 sets the beam direction of the terminal communication unit 31 so that it becomes the beam direction identified by the maximum received second identifier, which is the second identifier included in the received response radio signal. Subsequent transmission of radio signals from the terminal device 3 to the master station device 1 may be performed using this beam direction until the next terminal scan is performed. Then, the process returns to step S201.

[0097] Although not included in the flowchart of Fig. 6, wireless signals may be transmitted and received with the master station device 1 during period P3. In this case, as described above, the wireless signals may be transmitted in the beam direction identified by the maximum received second identifier. The order of the processing in the flowchart of Fig. 6 is an example, and the order of the steps may be changed as long as the same results are obtained. In the flowchart of Fig. 6, the processing may be terminated by power-off or an interrupt to terminate the processing.

[0098] Next, a specific example will be used to explain the operation of the wireless communication system 100 according to this embodiment. In this specific example, it is assumed that the master station device 1 first performs a full search, and then the search range is limited.

[0099] First, when period P1 begins, the master station scanning unit 13 of the master station device 1 determines that it is time to transmit a master station scanning radio signal (step S101), and causes the master station communication unit 11 to transmit (M-1) x K master station scanning radio signals for performing a full search while sequentially changing the beam direction of the master station device 1 and the shift amount of the reflection direction of the variable reflector 2 (steps S102 to S104). Note that the master station scanning radio signal includes a first identifier that identifies the beam direction and shift amount used in the transmission.

[0100] Some of the multiple master station scanning radio signals transmitted in this manner are sequentially received by the non-directional terminal device 3, and the first identifiers included in the master station scanning radio signals are associated with the received power and stored in the storage unit 32 (steps S201 and S202). Furthermore, when the terminal device 3 receives a master station scanning radio signal with a remaining number of 0, or when the terminal device 3 receives a master station scanning radio signal containing the same first identifier twice, it is determined to transmit a terminal scanning radio signal after the start of the period P2, and a maximum received first identifier, which is a first identifier corresponding to the maximum received power, is identified (steps S203 and S204). Furthermore, direction information is acquired using the first identifier and the received power stored in the storage unit 32 (step S205). The terminal scanning unit 35 then causes the terminal communication unit 31 to transmit N-1 terminal scanning radio signals, each including the identified maximum received first identifier and the acquired direction information, while sequentially changing the beam direction of the terminal device 3 (steps S206 to S208). It is assumed that the terminal scanning radio signal includes a second identifier that identifies the beam direction used in the transmission.

[0101] Some of the multiple terminal scanning radio signals transmitted in this manner are sequentially received by the non-directional master station device 1, and the second identifiers included in the terminal scanning radio signals are associated with the received power and stored in the storage unit 12. The maximum received first identifier, which is the first identifier included in the terminal scanning radio signals, and direction information are also stored in the storage unit 12 (steps S105 to S107). Furthermore, when the period P2 ends, it is determined that reception of the terminal scanning radio signals has ended, and the maximum received second identifier, which is the second identifier corresponding to the maximum received power, is identified (steps S108 and S109). The responding unit 15 then transmits a response radio signal including the identified maximum received second identifier, with the beam direction of the master station device 1 and the amount of shift in the reflection direction of the variable reflector 2 identified by the maximum received first identifier stored in the storage unit 12 (steps S110 and S111). Furthermore, the master station scanning unit 13 uses the direction information stored in the memory unit 12 to limit the beam direction of the master station device 1 to be scanned in the next master station scan (step S112). As a result, in the next and subsequent master station scans, fewer master station scanning radio signals are transmitted, enabling master station scans to be completed in a shorter time. Furthermore, the transmission of radio signals from the master station communication unit 11 to the terminal device 3 is performed using the beam direction of the master station device 1 identified by the maximum received first identifier and the shift amount of the reflection direction of the variable reflector 2.

[0102] The response wireless signal transmitted from the master station device 1 is received by the non-directional terminal device 3 (step S209). Then, subsequent transmission of wireless signals from the terminal communication unit 31 to the master station device 1 is performed in the beam direction identified by the maximum received second identifier, which is the second identifier included in the response wireless signal (step S210). In this way, wireless communication can be performed between the master station device 1 and the terminal device 3 via the variable reflector 2.

[0103] As described above, according to the master station device 1 of this embodiment, the beam direction for transmitting the master station scanning radio signal can be limited using the direction information received from the terminal device 3. As a result, it is possible to complete the search for the beam direction of the master station device 1 and the terminal device 3 and the shift amount of the reflection direction of the variable reflector 2 with a smaller number of search patterns. Furthermore, according to the terminal device 3 of this embodiment, by using the master station scanning radio signal transmitted from the master station device 1, it is possible to obtain direction information indicating whether the variable reflector 2 is present in a predetermined beam direction of the master station device 1 and transmit the information to the master station device 1. As a result, it is possible to reduce the number of patterns for searching the beam direction in the master station device 1. Furthermore, the positional relationship between the terminal device 3 and the master station device 1 or the variable reflector 2 changes as the terminal device 3 moves. However, it is generally considered that the positional relationship between the master station device 1 and the variable reflector 2 does not change. Therefore, if the beam direction from the master station device 1 to the variable reflector 2 can be properly obtained, the interval between full searches can be lengthened.

[0104] If the positional relationship between the master station device 1 and the variable reflector 2 in real space is known, it is possible to accordingly limit the beam direction when the master station device 1 transmits a master station scanning radio signal so that it is only in the direction of the variable reflector 2. However, it is very difficult for an ordinary person who has no knowledge of wireless communications to grasp the positional relationship between the master station device 1 and the variable reflector 2 and accordingly limit the pattern to be searched. On the other hand, by using the master station device 1 and the terminal device 3 according to this embodiment, such limitation can be performed automatically.

[0105] Furthermore, if the radio signal for scanning the master station contains a remaining number, the terminal device 3 can know that the master station scanning has ended by receiving a radio signal for scanning the master station whose remaining number is 0, and can then identify the maximum receivable first identifier, obtain direction information, and transmit a radio signal for scanning the terminal including the maximum receivable first identifier and direction information at the appropriate time.

[0106] Furthermore, in this embodiment, the case where one terminal device 3 is included in the wireless communication system 100 has been mainly described, but this is not necessarily the case. When two or more terminal devices 3 are included in the wireless communication system 100, for example, the processing described in this embodiment may be performed for each terminal device 3. Even when two or more terminal devices 3 are included in the wireless communication system 100, the positional relationship between the master station device 1 and the variable reflector 2 does not change for each terminal device 3. Therefore, the master station device 1 may, for example, limit the beam direction of the master station device 1 during a search for a second terminal device 3 by using the beam direction of the orientation of the variable reflector 2 identified by performing a full search for a first terminal device 3.

[0107] Furthermore, in the above embodiments, each process or function may be realized by centralized processing by a single device or a single system, or may be realized by distributed processing by multiple devices or multiple systems.

[0108] Furthermore, in the above embodiments, when two or more components included in the parent station device 1 or the terminal device 3 have a communication device, an input device, etc., the two or more components may physically have a single device, or may have separate devices.

[0109] Furthermore, in the above-described embodiments, each component may be configured by dedicated hardware, or a component that can be realized by software may be realized by executing a program. For example, each component may be realized by a program execution unit such as a CPU reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory. During execution, the program execution unit may execute the program while accessing a storage unit or recording medium. Note that the software that realizes the master station device 1 in the above-described embodiments may be a program such as the following:That is, this program is a program for causing a computer to execute processing of a master station device in a wireless communication system including a master station device, a variable reflector whose shift amount in reflection direction is controlled by the master station device, and a terminal device that performs wireless communication with the master station device via the variable reflector, and includes the steps of transmitting a master station scanning radio signal, which is a radio signal including a first identifier that identifies the beam direction of the master station device and the shift amount of the reflection direction of the variable reflector, and which is transmitted in the beam direction and shift amount identified by the first identifier, while sequentially changing the beam direction and shift amount; and transmitting the first identifier included in the master station scanning radio signal that is transmitted from the terminal device while sequentially changing the beam direction and received at the terminal device with maximum reception power, direction information indicating whether a variable reflector is present in a predetermined beam direction of the master station device, and the beam direction of the terminal device. The program may cause a computer to execute the steps of: receiving one or more terminal scanning radio signals omnidirectionally from among a plurality of terminal scanning radio signals, the radio signals including a second identifier for identifying the direction, and the radio signals being radio signals transmitted in a beam direction identified by the second identifier; identifying the second identifier included in the terminal scanning radio signal received with the maximum reception power; transmitting a response radio signal including the identified second identifier in the beam direction and shift amount identified by the first identifier included in the received terminal scanning radio signal; performing wireless communication with a terminal device in the beam direction and shift amount identified by the first identifier included in the received terminal scanning radio signal; and limiting the beam direction in which the parent station scanning radio signal is transmitted using direction information included in the received terminal scanning radio signal.

[0110] Furthermore, software for realizing the terminal device 3 in the above-described embodiment may be a program as follows: That is, this program is a program for making a computer execute processing of a terminal device in a wireless communication system including a master station device, a variable reflector whose shift amount in the reflection direction is controlled by the master station device, and a terminal device that performs wireless communication with the master station device via the variable reflector, and includes the steps of: receiving, in an omnidirectional manner, one or more master station scanning radio signals among a plurality of master station scanning radio signals, the master station scanning radio signals being radio signals that include a first identifier for identifying the beam direction and the shift amount and that are transmitted from the master station device while sequentially changing the beam direction and the shift amount in the reflection direction of the variable reflector; identifying the first identifier included in the master station scanning radio signal received with the maximum reception power; The program may cause a computer to execute the following steps: using a scanning radio signal to acquire direction information indicating whether a variable reflector is present in a predetermined beam direction of the master station device; transmitting a terminal scanning radio signal, which is a radio signal including the identified first identifier, the acquired direction information, and a second identifier that identifies the beam direction of the terminal device, and which is transmitted in the beam direction identified by the second identifier, while sequentially changing the beam direction; receiving a response radio signal that is transmitted from the master station device and includes the second identifier contained in the terminal scanning radio signal received at the master station device with the maximum reception power; and performing wireless communication with the master station device in the beam direction identified by the second identifier contained in the received response radio signal.

[0111] In the above program, the transmitting step of transmitting a signal and the receiving step of receiving a signal do not include processing that can only be performed by hardware, such as processing that can be performed by a modem or interface card in the transmitting step.

[0112] This program may be executed by being downloaded from a server or the like, or by being read from a predetermined recording medium (for example, an optical disk such as a CD-ROM, a magnetic disk, or a semiconductor memory). This program may also be used as a program constituting a program product.

[0113] Furthermore, the computer that executes this program may be a single computer or multiple computers, and may perform centralized processing or distributed processing.

[0114] 7 is a diagram showing an example of a computer that executes the above program to realize the master station device 1 or the terminal device 3 according to the above embodiment. The above embodiment can be realized by computer hardware and a computer program executed thereon. In FIG. 7, a computer system 900 includes, for example, a computer 901 including a disk drive 905, a keyboard 902, a mouse 903, and a monitor 904.

[0115] In addition to the disk drive 905, the computer 901 includes an MPU (Micro Processing Unit) 911, a ROM 912 for storing programs such as a boot-up program, a RAM 913 connected to the MPU 911 for temporarily storing instructions for application programs and providing temporary storage space, a hard disk 914 for storing application programs, system programs, and data, a communication device 916, and a bus 915 for interconnecting the MPU 911, ROM 912, etc. The computer 901 can transmit and receive radio signals from an antenna via the communication device 916.

[0116] A program that causes the computer system 900 to execute the functions of the master station device 1 or the terminal device 3 according to the above-described embodiment may be stored on a disk 921, such as a CD-ROM or DVD-ROM, inserted into the disk drive 905, and transferred to the hard disk 914, for example. Alternatively, the program may be transmitted to the computer 901 via a network (not shown) and stored on the hard disk 914. The program is loaded into the RAM 913 when executed. The program may also be loaded directly from the disk 921 or the network. Alternatively, a recording medium such as an SSD (Solid State Drive) may be used instead of the hard disk 914, for example.

[0117] The program does not necessarily include an operating system (OS) or a third-party program that causes the computer 901 to execute the functions of the master station device 1 or the terminal device 3 according to the above-described embodiment. The program may include only instructions that call appropriate functions or modules in a controlled manner to achieve the desired results. How the computer system 900 operates is well known, and a detailed description thereof will be omitted.

[0118] Furthermore, the above-described embodiments are merely examples for specifically implementing the present invention, and are not intended to limit the technical scope of the present invention. The technical scope of the present invention is defined by the claims, not by the description of the embodiments, and is intended to include modifications within the literal scope of the claims and within the scope of equivalent meanings. [Explanation of symbols]

[0119] 1 Master station device 2 Variable reflector 3 Terminal Devices 11 Master station communication department 12, 32 Storage section 13 Master station scanning unit 14, 33 Specific part 15 Response section 31 Terminal communication unit 34 Acquisition Department 35 Terminal scanning unit

Claims

1. A master station in a wireless communication system including a master station, a variable reflector whose shift amount in reflection direction is controlled by the master station, and a terminal device that performs wireless communication with the master station via the variable reflector, a master station communication unit that can change the beam direction and transmits and receives wireless signals; a master station scanning unit that controls the master station communication unit and the variable reflector so as to transmit a master station scanning radio signal, the master station scanning radio signal including a first identifier that identifies the beam direction of the master station communication unit and the shift amount of the reflection direction of the variable reflector, in the beam direction and shift amount identified by the first identifier, while sequentially changing the beam direction and shift amount; a determination unit that determines the second identifier included in the terminal scanning radio signal received by the non-directional master station communication unit with the maximum reception power from among a plurality of terminal scanning radio signals, the terminal scanning radio signals being radio signals transmitted from the terminal unit while sequentially changing the beam direction and including a first identifier included in the master station scanning radio signal received by the terminal unit with the maximum reception power, direction information indicating whether the variable reflector is present in a predetermined beam direction of the master station communication unit, and a second identifier that identifies the beam direction of the terminal unit; a response unit that controls the master station communication unit and the variable reflector so as to transmit a response radio signal including the second identifier identified by the identification unit in a beam direction and shift amount identified by a first identifier included in the terminal scanning radio signal received by the master station communication unit, the master station communication unit performs wireless communication with the terminal device using a beam direction and a shift amount identified by a first identifier included in the received terminal scanning wireless signal, The master station scanning unit uses direction information contained in the terminal scanning radio signal received by the master station communication unit to limit the beam direction of the master station communication unit that transmits the master station scanning radio signal.

2. 2. The master station device according to claim 1, wherein the master station scanning radio signal includes a remaining number indicating the number of master station scanning radio signals to be transmitted in the future, among the plurality of master station scanning radio signals transmitted while sequentially changing the beam direction of the master station communication unit and the shift amount of the reflection direction of the variable reflector.

3. 3. The master station device according to claim 1, wherein the master station scanning unit transmits a master station scanning radio signal in a predetermined beam direction of the master station communication unit when the direction information indicates that the variable reflector is present in the predetermined beam direction of the master station communication unit, and does not transmit a master station scanning radio signal in the predetermined beam direction when the direction information indicates that the variable reflector is not present in the predetermined beam direction of the master station communication unit.

4. A terminal device in a wireless communication system including a master station device, a variable reflector whose shift amount in reflection direction is controlled by the master station device, and a terminal device that performs wireless communication with the master station device via the variable reflector, a terminal communication unit that can change the beam direction and transmits and receives wireless signals; a specifying unit that specifies the first identifier included in a master station scanning radio signal that is received with maximum reception power by the non-directional terminal communication unit from a plurality of master station scanning radio signals, the master station scanning radio signals being radio signals that include a first identifier that identifies the beam direction and the shift amount and are transmitted from the master station device while sequentially changing the beam direction and the shift amount of the reflection direction of the variable reflector, and that are transmitted with the beam direction and the shift amount identified by the first identifier; an acquisition unit that acquires direction information indicating whether the variable reflector is present in a predetermined beam direction of the master station device, using the master station scanning radio signal received by the terminal communication unit; a terminal scanning unit that controls the terminal communication unit to transmit a terminal scanning radio signal, which is a radio signal including a first identifier identified by the identification unit, direction information acquired by the acquisition unit, and a second identifier that identifies a beam direction of the terminal communication unit, while sequentially changing the beam direction, the radio signal being transmitted in the beam direction identified by the second identifier; The terminal communication unit of the terminal device receives a response radio signal including a second identifier contained in a terminal scanning radio signal transmitted from the parent station device and received at the parent station device with maximum reception power, and then performs wireless communication with the parent station device in a beam direction identified by the second identifier.

5. 5. The terminal device according to claim 4, wherein the acquisition unit acquires direction information indicating that the variable reflector is present in a predetermined beam direction when the terminal communication unit receives a number of parent station scanning radio signals that are equal to or less than a threshold and that are transmitted with different shift amounts in a predetermined beam direction of the parent station device, or when the terminal communication unit receives a number of parent station scanning radio signals that are greater than the threshold and that are transmitted with different shift amounts in a predetermined beam direction of the parent station device and a distribution of the received powers of the received parent station scanning radio signals exceeds a predetermined range.

6. The terminal device according to claim 4, wherein the acquisition unit acquires directional information indicating that the variable reflector is not present in a predetermined beam direction when the terminal communication unit receives a number of parent station scanning radio signals exceeding a threshold value transmitted with different shift amounts for a predetermined beam direction of the parent station device, and when the distribution of the received power of the received plurality of parent station scanning radio signals is within a predetermined range.

7. the master station scanning radio signal includes a remaining number indicating the number of master station scanning radio signals to be transmitted in the future, among the plurality of master station scanning radio signals transmitted while sequentially changing the beam direction of the master station device and the shift amount of the reflection direction of the variable reflector; The terminal device according to claim 5 or claim 6, wherein the acquisition unit acquires direction information when a parent station scanning radio signal with a remaining number of 0 is received by the terminal communication unit, or when a parent station scanning radio signal including the same first identifier is received twice by the terminal communication unit.

8. A wireless communication method executed in a master station in a wireless communication system including a master station, a variable reflector whose shift amount in reflection direction is controlled by the master station, and a terminal device that performs wireless communication with the master station via the variable reflector, comprising: a step of transmitting a master station scanning radio signal, which is a radio signal including a first identifier that identifies the beam direction of the master station device and the shift amount of the reflection direction of the variable reflector, and which is transmitted in the beam direction and shift amount identified by the first identifier, while sequentially changing the beam direction and shift amount; a step of omnidirectionally receiving one or more terminal scanning radio signals among a plurality of terminal scanning radio signals, the radio signals including a first identifier included in a master station scanning radio signal transmitted from the terminal device while sequentially changing the beam direction and received at the terminal device with maximum reception power, direction information indicating whether the variable reflector is present in a predetermined beam direction of the master station device, and a second identifier identifying the beam direction of the terminal device, the plurality of terminal scanning radio signals being radio signals transmitted in the beam direction identified by the second identifier; Identifying a second identifier included in the terminal scanning radio signal received with the maximum reception power; transmitting a response radio signal including the identified second identifier in a beam direction and shift amount identified by the first identifier included in the received terminal scanning radio signal; performing wireless communication with the terminal device using a beam direction and a shift amount identified by a first identifier included in the received terminal scanning radio signal; and limiting the beam direction for transmitting the master station scanning radio signal using direction information included in the received terminal scanning radio signal.

9. A wireless communication method executed in a terminal device in a wireless communication system including a master station device, a variable reflector whose shift amount in reflection direction is controlled by the master station device, and a terminal device that wirelessly communicates with the master station device via the variable reflector, comprising: a step of omnidirectionally receiving one or more master station scanning radio signals among a plurality of master station scanning radio signals, the master station scanning radio signals being radio signals including a first identifier for identifying the beam direction and the shift amount, the radio signals being transmitted from the master station device while sequentially changing the beam direction and the shift amount of the reflection direction of the variable reflector, the radio signals being transmitted in the beam direction and the shift amount identified by the first identifier; identifying a first identifier included in the master station scanning radio signal received with the maximum reception power; obtaining direction information indicating whether the variable reflector is present in a predetermined beam direction of the master station device using the received master station scanning radio signal; a step of transmitting a terminal scanning radio signal, which is a radio signal including the specified first identifier, the acquired direction information, and a second identifier that identifies the beam direction of the terminal device, and which is transmitted in the beam direction identified by the second identifier, while sequentially changing the beam direction; receiving a response radio signal including a second identifier contained in the terminal scanning radio signal transmitted from the master station and received at the maximum reception power by the master station; and performing wireless communication with the master station device in a beam direction identified by a second identifier included in the received response wireless signal.

10. A program for causing a computer to execute processing of a master station in a wireless communication system including a master station, a variable reflector whose shift amount in reflection direction is controlled by the master station, and a terminal device that performs wireless communication with the master station via the variable reflector, the program comprising: a step of transmitting a master station scanning radio signal, which is a radio signal including a first identifier that identifies the beam direction of the master station device and the shift amount of the reflection direction of the variable reflector, and which is transmitted in the beam direction and shift amount identified by the first identifier, while sequentially changing the beam direction and shift amount; a step of omnidirectionally receiving one or more terminal scanning radio signals among a plurality of terminal scanning radio signals, the radio signals including a first identifier included in a master station scanning radio signal transmitted from the terminal device while sequentially changing the beam direction and received at the terminal device with maximum reception power, direction information indicating whether the variable reflector is present in a predetermined beam direction of the master station device, and a second identifier identifying the beam direction of the terminal device, the plurality of terminal scanning radio signals being radio signals transmitted in the beam direction identified by the second identifier; Identifying a second identifier included in the terminal scanning radio signal received with the maximum reception power; transmitting a response radio signal including the identified second identifier in a beam direction and shift amount identified by the first identifier included in the received terminal scanning radio signal; performing wireless communication with the terminal device using a beam direction and a shift amount identified by a first identifier included in the received terminal scanning radio signal; and limiting the beam direction for transmitting the master station scanning radio signal using direction information included in the received terminal scanning radio signal.

11. A program for causing a computer to execute processing of a terminal device in a wireless communication system including a master station device, a variable reflector whose shift amount in reflection direction is controlled by the master station device, and a terminal device that performs wireless communication with the master station device via the variable reflector, the program comprising: a step of omnidirectionally receiving one or more master station scanning radio signals among a plurality of master station scanning radio signals, the master station scanning radio signals being radio signals including a first identifier for identifying the beam direction and the shift amount, the radio signals being transmitted from the master station device while sequentially changing the beam direction and the shift amount of the reflection direction of the variable reflector, the radio signals being transmitted in the beam direction and the shift amount identified by the first identifier; identifying a first identifier included in the master station scanning radio signal received with the maximum reception power; obtaining direction information indicating whether the variable reflector is present in a predetermined beam direction of the master station device using the received master station scanning radio signal; a step of transmitting a terminal scanning radio signal, which is a radio signal including the specified first identifier, the acquired direction information, and a second identifier that identifies the beam direction of the terminal device, and which is transmitted in the beam direction identified by the second identifier, while sequentially changing the beam direction; receiving a response radio signal including a second identifier contained in the terminal scanning radio signal transmitted from the master station and received at the maximum reception power by the master station; and performing wireless communication with the master station device in a beam direction identified by a second identifier included in the received response wireless signal.

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