Base station device, communication method, and communication system

Abstract

Provided is a base station device that performs normal communication in which the base station device establishes a direct radio connection with a terminal device or reflection communication in which the base station device communicates with the terminal device by using a radio wave reflected by a reflection device and includes: a notification unit that when detecting that the terminal device is performing the reflection communication, notifies a reflection communication handover condition during the reflection communication to the terminal device; and a control unit that when the terminal device performing the reflection communication with a source base station device is handed over to the base station device, performs control to prevent the terminal device from being handed over to the source base station device.

Description

[Technical field]

[0001] The present invention relates to a base station device, a communication method, and a communication system. [Background technology]

[0002] 2. Description of the Related Art In recent years, communication systems using wireless communication have come into use. In a wireless communication system, for example, wireless communication is realized by transmitting and receiving radio waves between a base station device and a terminal device.

[0003] When a base station device has an obstruction such as a building within its own communication area, the base station device may not be able to transmit radio waves to a terminal device located within its own communication area. In this case, the terminal device may not be able to wirelessly connect to the base station device even if it is within the communication area of ​​the base station device. There is a technology that uses a reflector to reflect radio waves to blind areas within such communication areas where radio waves cannot reach.

[0004] Techniques relating to radio wave reflectors are described in the following prior art documents. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2017 / 077898 [Patent Document 2] International Publication No. 2013 / 031114 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the reflected waves from the reflector are merely radio waves intended to rescue terminal devices in blind areas. Therefore, the reflected waves are not, for example, supplied stably over a wide area, and the number of terminal devices that can handle them may be limited. Therefore, it is preferable for the terminal devices to keep communication using the reflected waves as short as possible.

[0007] Therefore, one disclosure provides a base station device, a communication method, and a communication system that reduce communication time caused by reflected waves of a terminal device in a communication system that uses reflected waves from a reflector. [Means for solving the problem]

[0008] A base station device that performs normal communication by directly connecting wirelessly with a terminal device, or reflective communication by communicating with a terminal device using radio waves reflected by a reflection device, has a notification unit that, when it detects that the terminal device is performing the reflective communication, notifies the terminal device of handover conditions for reflective communication when the reflective communication is being performed, and a control unit that performs control to suppress handover of the terminal device to the source base station device when the terminal device that was performing the reflective communication with the source base station device performs handover. Effect of the Invention

[0009] One disclosure is capable of reducing communication time due to reflected waves of a terminal device in a communication system that utilizes waves reflected by a reflector. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a wireless communication system 10. As shown in FIG. [Diagram 2] FIG. 2 illustrates an example of the configuration of the base station device 200. As shown in FIG. [Diagram 3] FIG. 3 is a diagram illustrating an example of the configuration of the terminal device 100. As shown in FIG. [Figure 4] FIG. 4 is a diagram illustrating an example of the configuration of the reflecting device 300. As shown in FIG. [Diagram 5] FIG. 5 is a diagram showing an example of handover of the terminal device 100 during reflective communication. [Figure 6] FIG. 6 is a diagram showing an example of a sequence of handover processing of the terminal device 100 during reflective communication. [Figure 7] FIG. 7 is a diagram showing an example of a sequence of handover processing of the terminal device 100 during reflective communication. [Figure 8] FIG. 8 is a diagram showing an example of a processing flowchart of the HO process S1000 for reflective communication. [Figure 9] FIG. 9 is a diagram showing an example of a process flowchart of the HO request reception process S2000 for reflected communication. [Figure 10] FIG. 10 is a diagram showing an example of a processing flowchart of the ping-pong avoidance processing S3000. [Figure 11] FIG. 11 is a diagram illustrating an example of a wireless connection sequence. [Figure 12] FIG. 12 is a diagram illustrating an example of a sequence for notifying reflective communication after a wireless connection is established. [Figure 13] FIG. 13 is a diagram showing an example of conditions (events) for which the terminal device 100 issues a report in the RRC connection reconfiguration procedure. [Figure 14] FIG. 14 is a diagram showing an example of information elements (IEs) and group names in a handover process. [Figure 15] FIG. 15 is a diagram showing an example of whether or not handover is performed for each reception level. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [First embodiment] A first embodiment will be described. Fig. 1 is a diagram showing a configuration example of a wireless communication system 10. The wireless communication system 10 includes a reflecting device 300, a terminal device 100, and base station devices 200-1 and 200-2. In the wireless communication system 10, a shielding object 400 exists within the communication area of ​​the base station device 200-1.

[0012] Each of the base station devices 200-1 and 2 (hereinafter, sometimes referred to as base station device 200) has a communication area. The base station device 200 wirelessly connects to and communicates with the terminal devices 100-1 and 100-2 within the communication area. The base station device 200 also has a directional antenna, and can control the transmission direction of radio waves by changing the multi-level modulation method or using the directional antenna.

[0013] The terminal device 100 is a communication device that is wirelessly connected to the base station device 200 and performs wireless communication with other terminal devices, and is, for example, a smartphone or a tablet terminal.

[0014] The reflection device 300 is a device that reflects radio waves transmitted by the base station device 200 and the terminal device 100 and transmits the reflected waves. The reflection device 300 reflects the received radio waves, for example, under the control of the base station device 200. The reflected waves include, for example, notification information transmitted by the base station device 200. The reflected waves also include communication or control signals transmitted and received in wireless communication between the base station device 200 and the terminal device 100.

[0015] The reflecting device 300 is, for example, a RIS (Reconfigurable Intelligent Surface). The RIS is a reflecting plate using a metasurface. The metasurface is a material that realizes electromagnetic properties (dielectric constant, magnetic permeability, etc.) that do not exist in nature by arranging structures smaller than the wavelength of radio waves on a reflecting device like atoms or molecules. By using the metasurface, the RIS can reflect each of the multiple radio waves in a desired direction. In addition, the RIS can, for example, manipulate information contained in the reflected waves, and may be able to add or update specified information.

[0016] The shield 400 is an object that blocks radio waves. Due to the presence of the shield 400, the base station device 200 cannot directly (without going through the reflecting device 300) transmit and receive radio waves to and from the terminal device 100 located in a specific area (non-serviceable area). The base station device 200 uses the reflecting device 300 to transmit reflected waves to the non-serviceable area in order to complement wireless communication with the terminal device 100 located in the non-serviceable area.

[0017] 1, the terminal device 100 is located in an area where direct wireless connection to the base station device 200-1 is not possible. The terminal device 100 wirelessly connects to the base station device 200-1 using a reflected wave W2 that is generated by a reflecting device 300 reflecting a radio wave W1 transmitted by the base station device 200-1.

[0018] In the wireless communication system 10, the terminal device 100 performing communication by reflected waves (hereinafter, sometimes referred to as reflected communication) is set with handover (Hand Over) conditions that make it easier (relaxed) to perform handover than the handover conditions in normal communication (communication by normal radio waves other than reflected waves). Also, in the wireless communication system 10, the terminal device 100 performing reflected communication but performing handover is set with handover conditions that make it harder (strengthened) to perform handover to the base station device 200 that originally transmitted the reflected waves than the handover conditions in normal communication. In the wireless communication system 10, the terminal device 100 is set to be easy to handover when performing reflected communication, and is set to be hard to handover to the base station device 200 that transmitted the reflected waves when performing handover from reflected communication. This allows the terminal device 100 to reduce the time during which reflected communication is performed.

[0019] In Fig. 1, the number of base station devices 200 is two, but may be three or more. In Fig. 1, the number of terminal devices 100 is two, but may be one or three or more. Furthermore, the reflection device 300 may be controlled by either one of the base station devices 200-1 and 200-2, or both.

[0020] <Example of configuration of base station device 200> 2 is a diagram illustrating an example of the configuration of the base station device 200. The base station device 200 includes a CPU (Central Processing Unit) 210, a storage 220, a memory 230, a communication circuit 240, a wireless communication circuit 250, and an antenna 251.

[0021] The storage 220 is an auxiliary storage device that stores programs and data, such as a flash memory, a hard disk drive (HDD), or a solid state drive (SSD), etc. The storage 220 stores a wireless communication program 221, a reflection device control program 222, a handover program 223, and a handover program 224 for reflection communication.

[0022] The memory 230 is an area into which the programs stored in the storage 220 are loaded. The memory 230 may also be used as an area in which the programs store data.

[0023] The communication circuit 240 is a device that communicates with other base station devices 200 and the reflection device 300. The communication circuit 240 may be, for example, a wired communication circuit such as an NI (Network Interface), or may be a communication circuit that supports wireless connection.

[0024] The wireless communication circuit 250 is a device that performs wireless communication with the terminal device 100, or performs wireless communication with the terminal device 100 via the reflecting device 300. The wireless communication circuit 250 wirelessly connects to the terminal device 100 via the reflecting device 300 or directly, and realizes wireless communication. The wireless communication circuit 250 has an antenna 251. The antenna 251 includes, for example, a directional antenna that can control the direction of transmission and reception of radio waves.

[0025] The CPU 210 is a processor that loads programs stored in the storage 220 into the memory 230, executes the loaded programs, configures each unit, and realizes each process.

[0026] The CPU 210 performs wireless communication processing by executing the wireless communication program 221. The wireless communication processing is processing for wirelessly connecting to the terminal device 100 and realizing communication executed by the terminal device 100.

[0027] The CPU 210 executes the reflection device control program 222 to construct a reflection control unit and perform reflection device control processing. The reflection device control processing is processing for causing the reflection device 300 to execute reflection control. The base station device 200 instructs the reflection device 300 on the reflection angle of the reflected wave, the transmission output, information to be added to the reflected wave (for example, information indicating that it is a reflected wave), and the like.

[0028] The CPU 210 establishes a normal control unit and performs handover processing by executing the handover program 223. The handover processing is processing for executing a handover of the terminal device 100 performing normal communication.

[0029] The CPU 210 executes the handover program 224 for reflective communication to construct a control unit and a notification unit and perform handover processing for reflective communication. The handover processing for reflective communication is processing to execute handover of the terminal device 100 performing reflective communication. The handover processing for reflective communication includes processing to set handover conditions for reflective communication (reception level threshold, offset value, etc.) for the terminal device 100 performing reflective communication. The handover processing for reflective communication also includes processing to receive a handover request (a report that a base station device satisfying the handover conditions for reflective communication has been detected) from the terminal device 100 performing reflective communication, and transmit handover permission to the terminal device 100 when the handover is permitted from the base station device 200 of the handover destination. The handover processing for reflective communication also includes detection that the terminal device 100 is performing reflective communication, and notification that the terminal device 100 is performing reflective communication at the time of detection. In addition, the handover process for reflective communication includes a process of transmitting to the destination base station device 200 an instruction that the handed over terminal device 100 was performing reflective communication or an instruction to avoid (suppress) handover to the original base station device 200.

[0030] <Configuration Example of Terminal Device 100> 3 is a diagram illustrating an example of the configuration of the terminal device 100. The terminal device 100 includes a CPU 110, a storage 120, a memory 130, a wireless communication circuit 150, and an antenna 151.

[0031] The storage 120 is an auxiliary storage device such as a flash memory, an HDD, or an SSD that stores programs and data. The storage 120 stores a terminal wireless communication program 121, a terminal handover program 122, and a terminal handover program 123 for reflected communication.

[0032] The memory 130 is an area into which the programs stored in the storage 120 are loaded. The memory 130 may also be used as an area in which the programs store data.

[0033] The wireless communication circuit 150 is a device that performs wireless communication with the base station device 200. The wireless communication circuit 150 wirelessly connects to the base station device 200 directly or via the reflecting device 300 to achieve wireless communication. The wireless communication circuit 150 has an antenna 151. The antenna 151 includes, for example, a directional antenna that can control the direction of transmission and reception of radio waves.

[0034] The CPU 110 is a processor that loads a program stored in the storage 120 into the memory 130, executes the loaded program, configures each unit, and realizes each process.

[0035] The CPU 110 performs terminal wireless communication processing by executing the terminal wireless communication program 121. The terminal wireless communication processing is processing for wirelessly connecting to the base station device 200 and realizing wireless communication with other terminal devices 100 and the base station device 200.

[0036] The CPU 110 performs a terminal handover process by executing the terminal handover program 122. The terminal handover process is a process in which, during normal communication, permission for handover is received from the base station device 200 and handover is performed to the destination base station device 200.

[0037] The CPU 110 executes the handover program for terminal reflective communication 123 to perform handover processing for terminal reflective communication. The handover processing for terminal reflective communication is a process of receiving a handover permission from the base station device 200 when reflective communication is being performed, and performing a handover to the destination base station device 200. The handover processing for terminal reflective communication includes detecting that reflective communication is being performed, and notifying the base station device 200 that reflective communication is being performed when the handover processing for terminal reflective communication includes a process of requesting the base station device 200 to perform a handover for reflective communication when a base station device 200 that satisfies the handover condition for reflective communication is detected.

[0038] <Configuration Example of Reflection Device 300> 4 is a diagram illustrating an example of the configuration of the reflection device 300. The reflection device 300 includes a CPU 310, a storage 320, a memory 330, a communication circuit 340, and a reflection structure 370.

[0039] The storage 320 is an auxiliary storage device that stores programs and data, such as a flash memory, a HDD, or an SSD. The storage 320 stores a reflex control program 321.

[0040] The memory 330 is an area into which the programs stored in the storage 320 are loaded. The memory 330 may also be used as an area in which the programs store data.

[0041] The communication circuit 340 is a device that communicates with the base station device 200. The communication circuit 340 may be, for example, a wired communication circuit such as an NI, or may be a communication circuit that supports wireless connection.

[0042] The reflecting structure 370 is an assembly of a plurality of structures that receive radio waves transmitted by the base station device 200 and the terminal device 100 and transmit them at a desired angle. The reflecting structure 370 is capable of receiving and transmitting (reflecting) radio waves on a structure-by-structure basis.

[0043] The CPU 310 is a processor that loads programs stored in the storage 320 into the memory 330, executes the loaded programs, configures each unit, and realizes each process.

[0044] The CPU 310 executes the reflection control program 321 to perform reflection control processing. The reflection control processing is processing for controlling the reflection of the received radio wave. In the reflection control processing, the reflection device 300 performs reflection control in accordance with an instruction from the base station device 200. Furthermore, the reflection device 300 performs reflection control so that the reflected wave reaches a specific area (for example, an area where the radio wave from the base station device 200 does not reach). Furthermore, the reflection device 300 can adjust the angle, frequency, beam width, etc. of the reflected wave. Furthermore, the reflection device 300 may be able to include predetermined information in the reflected wave and change (update) some of the information.

[0045] <Handover processing during reflected communication> The handover process of the terminal device 100 during the reflective communication will be described.

[0046] 5 is a diagram showing an example of handover of the terminal device 100 during reflected communication. The terminal device 100 is in wireless communication with the base station device 200-1 via a reflected wave W2.

[0047] The terminal device 100 moves in a direction D1 toward the base station device 200-2. The terminal device 100 moves to a position where it can receive (detect) radio waves transmitted from the base station device 200-2.

[0048] Here, the terminal device 100 measures the reception level of radio waves transmitted from the base station device 200-2. For example, even if the HO condition for normal communication is not satisfied, the terminal device 100 performs handover to the base station device 200-2 when the HO condition for reflective communication is satisfied.

[0049] Furthermore, the base station device 200-2 recognizes that the terminal device 100 has been performing reflected communication with the base station device 200-1, and controls the terminal device 100 so as to make it difficult (not difficult) for the terminal device 100 to perform handover to the base station device 200-1.

[0050] 6 is a diagram showing an example of a sequence of handover processing of the terminal device 100 during reflection communication. The terminal device 100 is in reflection communication with the base station device 200-1 via the reflection device 300 (S100).

[0051] The terminal device 100 detects that the device itself is performing reflective communication (S101). The detection of reflective communication will be described in detail later.

[0052] When the terminal device 100 detects that it is performing reflective communication (S101), it transmits a reflective communication notification indicating that it is performing reflective communication to the base station device 200-1 (S102). The method of notifying that reflective communication is being performed will be described later in detail.

[0053] The base station device 200-1 receives a reflected communication notification from the terminal device 100 (S102), and upon detecting that the terminal device 100 is performing reflected communication (S103), transmits an HO condition notification for reflected communication to the terminal device 100 (S104).

[0054] The HO condition notification for reflective communication includes HO conditions in reflective communication (HO conditions for reflective communication). The HO conditions for reflective communication are conditions that make handover easier (more relaxed) than the HO conditions for normal communication (HO conditions for normal communication). The HO conditions for reflective communication are, for example, a reception level (reflected HO reception level) lower than the reception level (normal HO reception level) of radio waves (signals) transmitted from a neighboring base station device that is the HO destination in the HO conditions for normal communication. By lowering the reception level of radio waves transmitted from the HO destination base station device, it becomes easier for the terminal device 100 in reflective communication to hand over to a neighboring base station device. Details of the method of notifying the HO conditions for reflective communication will be described later.

[0055] 7 is a diagram showing an example of a sequence of handover processing of the terminal device 100 during reflective communication. The terminal device 100 and the base station device 200-1 recognize that the terminal device 100 is in reflective communication.

[0056] The terminal device 100 moves toward the base station device 200-2 (S105). Then, the terminal device 100 receives radio waves transmitted by the base station device 200-2 (S106).

[0057] When the terminal device 100 receives radio waves from the base station device 200-2 (adjacent base station device) (S106), it performs HO processing for reflected communication (S1000).

[0058] 8 is a diagram showing an example of a processing flowchart of the HO process S1000 for reflected communication. The terminal device 100 measures radio waves from adjacent base station devices (S1000-1). In the process S1000-1, the terminal device 100 measures, for example, the reception strength and noise (degree of interference) of the radio waves.

[0059] If the measurement result of the radio wave does not satisfy the HO condition for reflective communication (No in S1000-2), the terminal device 100 executes the process S1000-1 again.

[0060] On the other hand, if the radio wave measurement result satisfies the HO condition for reflective communication (Yes in S1000-2), the terminal device 100 transmits an HO request for reflective communication to the communicating base station device 200 to request an HO for reflective communication (S1000-3).

[0061] The terminal device 100 waits for a response to the HO request for reflected communication from the communicating base station device 200, and receives the response. If handover is not permitted (No in S1000-4), the terminal device 100 executes the process S1000-1 again.

[0062] On the other hand, if handover is permitted (Yes in S1000-4), the terminal device 100 executes the HO process (S1000-5) and ends the process.

[0063] Returning to the sequence of FIG. 7, in the HO process for reflective communication S1000, the terminal device 100 determines that the measurement results of the radio waves of the neighboring base station device 200-2 satisfy the HO conditions for reflective communication (S107, Yes in S1000-2 in FIG. 8), and transmits an HO request for reflective communication to the base station device 200-1 (S108, S1000-3 in FIG. 8).

[0064] When the base station device 200-1 receives the HO request for reflected communication (S107), it performs a HO request for reflected communication reception process (S2000).

[0065] 9 is a diagram showing an example of a processing flowchart of the HO request reception process S2000 for reflective communication. The base station device 200 waits to receive an HO request for reflective communication (No in S2000-1). When the base station device 200 receives the HO request for reflective communication (Yes in S2000-1), it queries the target base station device 200 as to whether or not to permit handover of the terminal device 100 (S2000-2).

[0066] If the handover is not permitted (No in S2000-3), the base station device 200 transmits (notifies) an HO rejection (non-permission) to the terminal device 100 (S2000-7), and ends the process.

[0067] On the other hand, if the handover is permitted (Yes in S2000-3), the base station device 200 transmits (notifies) an HO permission to the terminal device 100 (S2000-4). Then, the base station device 200 performs handover processing (S2000-5), transmits a ping-pong avoidance instruction to the handover destination base station device 200 (S2000-6), and ends the processing.

[0068] The processing of the handover source base station device 200 includes, for example, a process of transmitting information about the terminal device 100 (for example, information about the session, information about the edge, etc.) to the handover destination base station device 200. In addition, the processing of the handover source base station device 200 includes, for example, a process of disconnecting the wireless connection with the terminal device 100 and releasing the session after the terminal device 100 has successfully completed the handover.

[0069] The ping-pong avoidance instruction is a message that instructs the terminal device 100 to avoid or suppress ping-pong in which the terminal device 100 performs reflective communication as the handover source to the base station device 200. The ping-pong avoidance instruction will be described in detail later.

[0070] 7, in the HO request reception process S2000 for reflected communication, the base station device 200-1 is permitted to perform handover by the base station device 200-2 (Yes in S2000-3 in FIG. 9), transmits HO permission to the terminal device 100 (S2000-4 in FIG. 9), and performs handover to the base station device 200-2 (SS109, S2000-5 in FIG. 9). The base station device 200-1 then transmits a ping-pong avoidance command to the base station device 200-2 (S110, S2000-6 in FIG. 9).

[0071] When the base station device 200-2 receives the ping-pong avoidance instruction (S110), it executes a ping-pong avoidance process (S3000).

[0072] 10 is a diagram showing an example of a processing flowchart of the ping-pong avoidance process S3000. The base station device 200 waits to receive a ping-pong avoidance instruction (No in S3000-1). Upon receiving the ping-pong avoidance instruction (Yes in S3000-1), the base station device 200 transmits an HO condition notification for ping-pong avoidance including an HO condition for avoiding ping-pong to the terminal device 100 (3000-2), and ends the process. The HO condition notification for ping-pong avoidance will be described in detail later.

[0073] Returning to the sequence in FIG. 7, in the ping-pong avoidance process S3000, the base station device 200-1 transmits a ping-pong avoidance HO condition notification to the terminal device 100 (S111, S3000-2 in FIG. 10).

[0074] <Detection of reflected communication> The fact that the terminal device 100 is performing reflective communication may be detected by either the terminal device 100 or the base station device 200-1.

[0075] In one detection method, the terminal device 100 judges whether or not the communication is reflective based on whether or not the decision bit included in the predetermined message can be recognized (whether or not the message was received without error). The base station device 200-1 transmits a message multiplexed with decision bits at a power lower than a predetermined value. A power lower than a predetermined value is, for example, a power as high as possible among the powers at which the reflection device 300 cannot reflect. In other words, the decision bits transmitted at a power lower than a predetermined value are information elements that can be recognized by the terminal device 100 that communicates on the base station device 200-1 side of the reflection device 300, but cannot be recognized by the terminal device 100 that performs reflective communication. When the terminal device 100 cannot recognize the decision bit, it judges that reflective communication is being performed.

[0076] In one detection method, the terminal device 100 determines whether or not reflective communication is occurring based on the location of the terminal device 100. The terminal device 100 stores in advance in a memory information on a location where a reflected wave arrives with a predetermined power or more (a location where radio waves from the base station device 200-1 do not directly arrive). The terminal device 100 then acquires the location of the terminal device 100 using, for example, a Global Positioning System (GPS), compares the acquired location with the information stored in the memory, and determines whether or not the terminal device 100 is performing reflective communication. The base station device 200-1 may store location information where a reflected wave arrives with a predetermined power or more, acquire location information of the terminal device 100 from the terminal device 100, and determine whether or not the terminal device 100 is performing reflective communication.

[0077] In one detection method, the terminal device 100 determines whether or not the communication is a reflected communication based on whether or not it has acquired information contained only in the reflected wave. The reflection device 300, for example, receives a radio wave from the base station device 200-1, and adds information indicating that the received radio wave is a reflected wave to generate a reflection.

[0078] <How to notify that reflective communication is in progress> In the sequence of Fig. 6, the terminal device 100 notifies the base station device 200-1 that the terminal device is performing reflective communication by a reflective communication notification. The reflective communication notification may be a newly defined message or may be included as part of a conventional message. An example of a method of notifying that reflective communication is being performed is shown below.

[0079] The notification that reflective communication is being performed may be implemented, for example, in a series of procedures for starting a wireless connection. Fig. 11 is a diagram showing an example of a wireless connection sequence. In the explanation of Fig. 11, a message name in fifth generation communication is used as an example, but the embodiment is not limited to this message. The same applies to the following explanation.

[0080] The base station device 200-1 notifies the terminal device 100 of system information in System Information (S200).

[0081] The terminal device 100 transmits a preamble signal in an RA (Random Access) Preamble to the base station device 200-1 (S201).

[0082] The base station device 200-1 transmits a response to the preamble signal in the form of an RA Response to the terminal device 100 (S202).

[0083] The terminal device 100 transmits an RRC Connection Request requesting a connection in RRC (Radio Resource Control) to the base station device 200-1 (S203).

[0084] The base station device 200-1 transmits an RRC Connection Setup including setting information related to a connection in RRC to the terminal device 100 (S204).

[0085] The terminal device 100 establishes an RRC connection, and transmits an RRC Connection Setup Complete indicating completion of the RRC connection to the base station device 200-1.

[0086] The base station device 200-1 may notify a setting value (such as a threshold value of a reception level) indicating reflected communication, for example, in an information element (such as EstablishmentCause) included in the RA Response. The terminal device 100 detects reflected communication according to the setting value and reports it to the base station device 200-1.

[0087] Furthermore, the terminal device 100 may add an information element indicating that reflective communication is being performed to a message (for example, an RA Preamble, an RRC Connection Request, or an RRC Connection Setup Complete) transmitted to the base station device 200-1.

[0088] In addition, in the communication system 10, a new information element (IE) indicating that reflective communication is being performed may be added.

[0089] Furthermore, the notification that reflective communication is being performed may be made after a wireless connection is established, for example.

[0090] 12 is a diagram showing an example of a sequence for notifying reflective communication after wireless connection is established. In the communication system 10, a new RRC message (RIS Notification Message) is defined, and information about the reflective communication and the fact that reflective communication is being performed are transmitted and received between the terminal device 100 and the base station device 200-1 (S300).

[0091] Also, by using RRC Reconfiguration, the terminal device 100 and the base station device 200-1 transmit and receive information about the reflected communication and that the reflected communication is being performed (S301).

[0092] The base station device 200-1 notifies the terminal device 100 of a setting value indicating reflective communication, for example, by using an RRC message. The terminal device 100 measures radio waves from the base station device 200-1, and if a condition based on the setting value indicating reflective communication is satisfied (for example, if it is lower than the setting value), it detects that reflective communication is being performed, and transmits a Measurement Report including information indicating that reflective communication is being performed to the base station device 200-1 (S302).

[0093] <How to notify HO conditions for reflective communication> In the sequence of Fig. 6, the base station device 200-1 notifies the terminal device 100 of the HO condition for the terminal device 100 during reflective communication by using the HO condition notification for reflective communication. The HO condition notification for reflective communication may be a newly defined message or may be included as part of a conventional message. An example of a method for notifying the HO condition for reflective communication is shown below.

[0094] FIG. 13 is a diagram showing an example of conditions (events) under which the terminal device 100 issues a report in the RRC connection reconfiguration procedure. Event A3 is an event that instructs the terminal device 100 to issue a report when the reception level of radio waves from the adjacent base station device 200 becomes better (stronger) by an offset value than that of the base station device 200 currently communicating. Event A3 is, for example, a conventional event. The base station device 200-1 sets the offset of event A3 for the terminal device 100 performing reflective communication to a value smaller than the offset of the terminal device 100 performing normal communication. As a result, the terminal device 100 performing reflective communication will perform a handover even if the reception level from the adjacent base station device is such that the terminal device 100 would not perform a handover in normal communication.

[0095] Also, the offset value of the conventional event A3 may not be changed, and a new event A7 may be set. Event A7 is an event for terminal devices performing reflective communication. The base station device 200-1 sets the offset of event A7 to a value smaller than the offset of the terminal device 100 performing normal communication. When performing reflective communication, the terminal device 100 uses the offset value of event A7 instead of the offset value of event A3, and thus performs handover even if the reception level from a neighboring base station device that would not perform handover in normal communication is low.

[0096] When the terminal device 100 detects a neighboring base station device with a reception level that satisfies the offset value of event A3 or event A7, the terminal device 100 transmits, for example, an MR to the base station device 200-1 to notify that it has detected a neighboring base station device that satisfies the HO condition during reflection communication.

[0097] <Regarding ping-pong avoidance instructions> The ping-pong avoidance instruction is a message that the handover source base station device 200-1 notifies the handover destination base station device 200-2 that the terminal device 100 has performed reflective communication. The ping-pong avoidance instruction may be a newly defined message or may be included in a conventional message. The ping-pong avoidance instruction may be transmitted after the handover is completed, as in the sequence of FIG. 7.

[0098] Furthermore, the ping-pong avoidance instruction may be transmitted in handover processing. Fig. 14 is a diagram showing examples of information elements (IEs) and group names in handover processing. The base station device 200-1 sets, for example, an RRC message to be notified to the terminal device 100 by the handover destination base station device 200-2 in the RRC Context. In the RRC message, a ping-pong avoidance HO condition is set.

[0099] The handover condition for avoiding ping-pong is a stricter condition for handing over to the handover source base station device 200-1. The HO condition for avoiding ping-pong is, for example, a condition for suppressing handover to the handover source base station device 200-1, and a value (offset value) is set to the base station device 200-2 so that handover is not performed unless the reception level is higher than the reception level for normal handover. The handover condition for avoiding ping-pong may be, for example, a condition for prohibiting handover to the handover source base station device 200-1. Note that the prohibition or suppression of handover to the base station device 200-1 may be released after a predetermined time has elapsed or when a predetermined condition is satisfied.

[0100] Also, a new information element (IE) may be defined to notify that the terminal device 100 has performed reflective communication or a handover condition for avoiding ping-pong.

[0101] <Example of whether or not handover is performed> By performing the handover control in the first embodiment, the terminal device 100 performing the reflective communication can easily perform a handover and can hardly perform a handover (ping-pong) to the original base station device 200.

[0102] Fig. 15 is a diagram showing an example of whether or not handover is to be performed for each reception level. In Fig. 15, the reception level is indicated by RSRP (Reference Signal Received Power) in dBm units.

[0103] For example, a case will be described in which the signal reception level of the communicating base station is −90 dBm and the signal reception level of the adjacent base station is −100 dBm.

[0104] When the terminal device 100 is in normal communication, it does not perform handover at this reception level.

[0105] Furthermore, after a handover from the adjacent base station device with which the terminal device 100 has performed reflective communication, the terminal device 100 does not perform a handover, as in the case of normal communication.

[0106] However, when the terminal device 100 is in reflective communication, the conditions for handover are low, so the terminal device 100 performs handover to an adjacent base station device.

[0107] In this way, the terminal device 100 in the reflective communication performs a handover to an adjacent base station device even if the reception level is such that a handover would not be performed during normal communication.

[0108] Also, for example, a case will be described in which the signal reception level of the communicating base station is −100 dBm and the signal reception level of the adjacent base station is −80 dBm.

[0109] When the terminal device 100 is in normal communication, it performs handover to an adjacent base station device.

[0110] Furthermore, when the terminal device 100 is in reflective communication, it performs handover to an adjacent base station device in the same manner as during normal communication.

[0111] However, if the terminal device 100 has just performed a handover from a neighboring base station device with which it was performing reflective communication, the handover conditions are high due to ping-pong avoidance processing, or handover to the neighboring base station device is prohibited, so the terminal device 100 does not perform a handover to the neighboring base station device.

[0112] In this way, the terminal device 100 that has been handed over from the adjacent base station device with which it was performing reflective communication does not hand over to the adjacent base station device even if the reception level is such that a handover would be performed during normal communication.

[0113] [Other embodiments] The method of detecting reflective communication, the method of notifying the HO condition for reflective communication, and the method of issuing a ping-pong avoidance instruction shown in the first embodiment may be combined with each other. [Explanation of symbols]

[0114] 10: Wireless communication systems 100: Terminal device 110: CPU 120: Storage 121: Terminal wireless communication program 122: Terminal handover program 123: Handover program for terminal reflective communication 130: Memory 150: Wireless communication circuit 151: Antenna 200:Base station equipment 210: CPU 220: Storage 221: Wireless communication program 222: Reflector control program 223: Handover program 224: Handover program for reflex communication 230: Memory 240: Communication circuit 250: Wireless communication circuit 251: Antenna 300:Reflector 310: CPU 320: Storage 321: Reflex control program 330: Memory 340: Communication circuit 370:Reflection structure 400: Shield

Claims

1. A base station device that performs normal communication by directly connecting wirelessly with a terminal device, or reflection communication by communicating with a terminal device using radio waves reflected by a reflection device, a notification unit that notifies the terminal device of a handover condition for reflective communication when the terminal device detects that the reflective communication is being performed; a control unit that, when the terminal device that has been performing the reflective communication with the source base station device performs handover, performs control to suppress handover of the terminal device to the source base station device; A base station device having the above configuration.

2. The handover condition for the reflective communication is a condition that makes handover easier than the handover condition for the normal communication. The base station apparatus according to claim 1.

3. The handover condition includes a reception level of a signal transmitted from a base station device, and the reception level of the handover condition for the reflective communication is lower than the reception level of the handover condition for the normal communication. The base station apparatus according to claim 2.

4. The control unit acquires from the source base station device information that the terminal device has performed the reflective communication with the source base station device. The base station apparatus according to claim 1.

5. The control unit prohibits handover of the terminal device to the source base station device. The base station apparatus according to claim 1.

6. The control unit sets a source handover condition for the terminal device to the source base station device so that the terminal device is less likely to be handed over than a handover condition for the terminal device to a base station device other than the source base station device. The base station apparatus according to claim 1.

7. The handover conditions include a reception level of a signal transmitted from a base station device, and the reception level of the handover condition of the terminal device to the source base station device is higher than the reception level of the handover condition of the terminal device to a base station device other than the source base station device. The base station apparatus according to claim 6.

8. The control unit acquires the source handover condition from the source base station device. The base station apparatus according to claim 6.

9. The control unit transmits the source handover condition to the terminal device. The base station apparatus according to claim 6.

10. A communication method in a base station device that performs normal communication by directly wirelessly connecting with a terminal device, or reflection communication by communicating with a terminal device using radio waves reflected by a reflection device, comprising: a notification step of notifying the terminal device of a handover condition for reflective communication when the terminal device detects that the reflective communication is being performed; a control step of performing control to suppress handover of the terminal device to the source base station device when the terminal device that has been performing the reflective communication with the source base station device has performed handover; A communication method comprising:

11. A communication system having a terminal device, a reflector device, and a base station device, the reflection device transmits a reflected wave that reflects a radio wave transmitted by the base station device or the terminal device, the terminal device performs reflected communication using the reflected wave or normal communication by directly wirelessly connecting to the base station device; The base station device is configured to: notifying the terminal device of a handover condition for reflective communication when the reflective communication is being performed, when the reflective communication is being performed; When a handover is made from the source base station device with which the reflective communication has been performed, the terminal device is prevented from being handed over to the source base station device. Communication systems.

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