The present disclosure relates to communication devices, base station devices, communication methods, communication programs and communication systems. More specifically, the present invention relates to switching of a base station device to be connected.
Background technology
[0002]
　Mobile communication using wireless access technology such as cellular communication technology is known. In such a wireless access technology, as the communication device such as a cellular phone moves, the wireless base station (hereinafter referred to as a base station) to which the communication device is connected is switched.
Prior art literature
Patent documents
[0003]
Patent Document 1: Japanese Patent No. 5182369
Outline of the invention
Problems to be solved by the invention
[0004]
　However, when the base station or communication device moves at high speed, or when the base station is located far away from the communication device, the above-mentioned conventional technology may not always realize high-quality communication. As an example, assume a non-terrestrial network in which a base station is a satellite station. In this case, the communication device will perform satellite communication with the satellite station, but since the satellite station orbits the earth at high speed, it is expected that the relative speed between the base station and the communication device will be high. Moreover, since the satellite station is located in space, it is expected that the distance between the base station and the communication device will be large. If the base station or communication device is moving at high speed, or if the base station is located far away from the communication device, the possibility of frequent base station switching or base station switching failure increases. Is assumed. In this case, the communication quality may be low.
[0005]
　Therefore, the present disclosure proposes a communication device, a base station device, a communication method, a communication program, and a communication system capable of realizing high-quality communication.
Means to solve problems
[0006]
　In order to solve the above problems, the communication device of one form according to the present disclosure is information used for wireless communication from a connected base station device to a movable base station device which is a candidate for switching destination. When the acquisition unit that acquires switching information including the above, the determination unit that determines whether to switch the connection destination base station device, and the determination unit determines that the connection destination base station device is to be switched, the switching information is used. It has a connection unit that executes a connection to a base station device that is a candidate for switching destination based on the above.
[0007]
(Action) In one form of communication device according to the present disclosure, the acquisition unit acquires switching information from the connected base station device. Then, the determination unit determines whether or not to switch the base station device of the connection destination. Since the communication device has a connection unit for connecting to the switching destination candidate base station device based on the switching information acquired by the acquisition unit, whether or not there is an instruction to switch the connection destination from the connection destination base station device. Regardless, the connection to the switching destination candidate base station device can be executed based on its own judgment.
The invention's effect
[0008]
　According to the present disclosure, high quality communication can be realized. The effects described here are not necessarily limited, and may be any of the effects described in the present disclosure.
A brief description of the drawing
[0009]
FIG. 1 is a diagram showing a configuration example of a communication system according to the first embodiment of the present disclosure.
[Fig. 2] Fig. 2 is a diagram showing an example of a wireless network provided by a communication system.
[Fig. 3] Fig. 3 is a diagram showing an outline of satellite communication provided by a communication system.
[Fig. 4] Fig. 4 is a diagram showing an example of cells configured by a satellite station device.
FIG. 5 is a diagram showing a configuration example of a management device according to the first embodiment of the present disclosure.
FIG. 6 is a diagram showing a configuration example of a non-ground base station apparatus according to the first embodiment of the present disclosure.
FIG. 7 is a diagram showing a configuration example of a ground base station apparatus according to the first embodiment of the present disclosure.
FIG. 8 is a diagram showing a configuration example of a relay device according to the first embodiment of the present disclosure.
FIG. 9 is a diagram showing a configuration example of a communication device according to the first embodiment of the present disclosure.
[Fig. 10] Fig. 10 is a flowchart showing an example of initial connection processing.
[Fig. 11] Fig. 11 is a diagram showing a contention-based random access procedure.
[Fig. 12] Fig. 12 is a diagram showing a non-contention-based random access procedure.
[Fig. 13] Fig. 13 is a diagram showing how the connection-destination base station device is switched.
FIG. 14 is a sequence diagram showing an example of a handover process with a handover command according to the first embodiment of the present disclosure.
FIG. 15 is a sequence diagram showing an example of a handover process without a handover command according to the first embodiment of the present disclosure.
FIG. 16 is a flowchart showing an example of switching information transmission processing according to the first embodiment of the present disclosure.
FIG. 17 is a sequence diagram showing an example of handover processing according to the second embodiment of the present disclosure.
FIG. 18 is a sequence diagram showing an example of handover processing according to the third embodiment of the present disclosure.
FIG. 19 is a diagram showing an example in which a plurality of base station devices cooperate to form one cell.
Mode for carrying out the invention
[0010]
　Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each of the following embodiments, the same parts are designated by the same reference numerals, so that duplicate description will be omitted.
[0011]
　Further, in the present specification and the drawings, a plurality of components having substantially the same functional configuration may be distinguished by adding different numbers after the same reference numerals. For example, a plurality of the configuration, communication as required apparatus 50 having substantially the same functional configuration 1 , 50 2 and 50 3 distinguished as. However, if it is not necessary to distinguish each of the plurality of components having substantially the same functional configuration, only the same reference numerals are given. For example, the communication device 50 1 , 50 2 and 50 3 in the case of there is no particular need to distinguish, simply referred to as a communication device 50.
[0012]
　In addition, the present disclosure will be described according to the order of items shown below.
　　1. 1. Introduction
　　2. First Embodiment
　　　2-1. Overall configuration of communication system
　　　2-2. Configuration of management device
　　　2-3. Configuration of base station equipment
　　　2-4. Configuration of relay device
　　　2-5. Configuration of communication device
　　　2-6. Initial connection process
　　　2-7. Random access procedure
　　　2-8. Handover
　　　2-9. Handover processing (with handover command)
　　　2-10. Handover processing (no handover command)
　　　2-11. Switching information transmission process
　　3. Second Embodiment
　　　3-1. Configuration of communication system
　　　3-2. Handover processing (RACH-less)
　　4. Third Embodiment
　　　4-1. Communication system configuration
　　　4-2. Handover processing (other example)
　　5. Modification
　　　5-1. Modification example regarding system configuration
　　　5-2. Transformation example related to switching information
　　　5-3. Modification example
　　　5-4 regarding transmission timing of switching information . Other modified examples
　　6. Conclusion
[0013]
(1. Introduction)
　Wireless access technologies such as LTE (Long Term Evolution) and NR (New Radio) are being studied by 3GPP (3rd Generation Partnership Project). LTE and NR are a kind of cellular communication technology, and enable mobile communication of a terminal device by arranging a plurality of areas covered by a base station in a cell shape. In the following description, "LTE" includes LTE-A (LTE-Advanced), LTE-A Pro (LTE-Advanced Pro), and EUTRA (Evolved Universal Terrestrial Radio Access). Further, NR shall include NLAT (New Radio Access Technology) and FEUTRA (Further EUTRA).
[0014]
　NR is the next generation (fifth generation) of LTE radio access technology (RAT). NR is a wireless access technology that can support various use cases including eMBB (Enhanced Mobile Broadband), mMTC (Massive Machine Type Communications) and URLLC (Ultra-Reliable and Low Latency Communications). NR is being studied with the aim of creating a technical framework that supports usage scenarios, requirements, and deployment scenarios for these use cases.
[0015]
　Furthermore, in NR, due to increasing demands for wide area coverage and connection stability, studies on non-terrestrial networks (NTN) have begun. In the non-terrestrial network, it is planned that the wireless network will be provided to the terminal device via a base station other than the ground station such as a satellite station or an aircraft station. Base stations other than this ground station are referred to as non-ground stations or non-ground base stations. The wireless network provided by the ground station is called a terrestrial network (TN). By using the same wireless access method for the terrestrial network and the non-terrestrial network, integrated operation of the terrestrial network and the non-terrestrial network becomes possible.
[0016]
　In the embodiment of the present disclosure, the ground station (also referred to as a ground base station) means a base station (including a relay station) installed on the ground. "Ground" is not only the ground (land) but also the ground in a broad sense including underground, water, and water.
[0017]
(2. First Embodiment)
　Hereinafter, the communication system 1 according to the first embodiment will be described. The communication system 1 includes a non-terrestrial base station and provides a communication device with wireless communication using a non-terrestrial network. The non-terrestrial network included in the communication system 1 is not limited to a wireless network using a wireless access method defined by NR. The non-terrestrial network included in the communication system 1 may be a wireless network of a wireless access system other than NR, such as LTE, W-CDMA (Wideband Code Division Multiple Access), cdma2000 (Code Division Multiple Access 2000), and the like.
[0018]
　In the following description, the concept of a base station (hereinafter, also referred to as a base station device) includes a relay station (hereinafter, also referred to as a relay device). Further, the concept of a base station includes not only a structure having a function of a base station but also a device installed in the structure. The structure is, for example, a building such as a high-rise building, a house, a steel tower, a station facility, an airport facility, a port facility, or a stadium. The concept of structure includes not only buildings but also non-building structures such as tunnels, bridges, dams, walls, and iron pillars, and equipment such as cranes, gates, and windmills. The concept of structures includes not only structures on the ground (land) or underground, but also structures on the water such as piers and mega floats, and underwater structures such as ocean observation facilities.
[0019]
　Further, the base station device may be a base station device configured to be movable. For example, the base station device may be a device installed on the mobile body or may be the mobile body itself. The moving body may be a mobile terminal such as a smartphone, a moving body moving on the ground (land) (for example, a vehicle such as a car, a bus, a truck, a train, or a linear motor car), or in the ground (for example, a vehicle such as a linear motor car). It may be a moving body (for example, a subway) that moves (in a tunnel). Further, the moving body may be a moving body moving on the water (for example, a ship such as a passenger ship, a cargo ship, a hovercraft, etc.), or a moving body moving underwater (for example, a submersible, a submarine, an unmanned submarine, etc.). Submersible). Further, the moving body may be a moving body moving in the atmosphere (for example, an aircraft such as an airplane, an airship, or a drone), or a space moving body moving outside the atmosphere (for example, an artificial satellite, a spaceship, or space). It may be an artificial celestial body such as a station or a spacecraft).
[0020]
　The LTE base station may be referred to as eNodeB (Evolved Node B) or eNB. Further, the base station of NR may be referred to as gNodeB or gNB. Further, in LTE and NR, a terminal device (also referred to as a mobile station, mobile station device, or terminal) may be referred to as a UE (User Equipment). The terminal device is a kind of communication device, and is also referred to as a mobile station, a mobile station device, or a terminal. In the embodiments of the present disclosure, the concept of a communication device includes not only a portable terminal device such as a mobile terminal, but also a device installed in a structure or a mobile body, for example. Further, the concept of a communication device includes not only a terminal device but also a base station device and a relay device.
[0021]
[2-1. Overall Configuration of Communication System]
　FIG. 1 is a diagram showing a configuration example of the communication system 1 according to the first embodiment of the present disclosure. The communication system 1 includes a management device 10, a non-ground base station device 20, a ground base station device 30, a relay device 40, and a communication device 50. The communication system 1 provides a user with a wireless network capable of mobile communication by operating the wireless communication devices constituting the communication system 1 in cooperation with each other. The wireless communication device is a device having a wireless communication function, and in the example of FIG. 1, the non-ground base station device 20, the ground base station device 30, the relay device 40, and the communication device 50 correspond to each other.
[0022]
　The communication system 1 may include a plurality of management devices 10, a non-ground base station device 20, a ground base station device 30, a relay device 40, and a communication device 50, respectively. In the example of FIG. 1, the communication system 1 includes management devices 10 1 , 10 2 and the like as the management device 10 . The communication system 1 is non as terrestrial base station device 20 non-terrestrial base station apparatus 20 1 , 20 2 has a like, a terrestrial base station apparatus 30 as a terrestrial base station apparatus 30 1 , 30 2 and a like .. The communication system 1, the relay device 40 as the relay apparatus 40 1 , 40 2 has a like, the communication device 50 as the communication device 50 1 , 50 2 , 50 3 and a like.
[0023]
　The management device 10 is a device that manages a wireless network. For example, the management device 10 is a device that functions as an MME (Mobility Management Entity) or an AMF (Access and Mobility Management Function). The management device 10 constitutes the core network CN. The core network CN is, for example, EPC (Evolved Packet Core) or 5GC (5G Core network). The management device 10 is connected to each of the plurality of non-ground base station devices 20 and the plurality of ground base station devices 30. The management device 10 manages the communication between the non-ground base station device 20 and the ground base station device 30.
[0024]
　The non-ground base station device 20 is a base station device that wirelessly communicates with the communication device 50. In the example of FIG. 1, the non-terrestrial base station apparatus 20 1 , the relay apparatus 40 1 is connected to the relay device 40 1 can be wireless communication and a communication device 50 via the. In the present embodiment, the non-ground base station device 20 is a base station device capable of floating in the air or in space. For example, the non-ground base station device 20 is a non-ground station device such as an aircraft station device or a satellite station device.
[0025]
　The aircraft station device is a wireless communication device capable of floating in the atmosphere such as an aircraft. The aircraft station device may be a device mounted on an aircraft or the like, or may be an aircraft itself. The concept of an aircraft includes not only heavy aircraft such as airplanes and gliders, but also light aircraft such as balloons and airships. The concept of an aircraft includes not only heavy aircraft and light aircraft, but also rotary-wing aircraft such as helicopters and autogyros. The aircraft station device (or the aircraft on which the aircraft station device is mounted) may be an unmanned aerial vehicle such as a drone. The concept of unmanned aerial vehicle also includes unmanned aircraft systems (UAS) and tethered UAS (tethered UAS). In addition, the concept of unmanned aerial vehicle includes a light unmanned aerial vehicle system (LTA: Lighter than Air UAS) and a heavy unmanned aerial vehicle system (HTA: Heavier than Air UAS). In addition, the concept of unmanned aerial vehicles also includes High Altitude UAS Platforms (HAPs).
[0026]
　The satellite station device is a wireless communication device capable of floating outside the atmosphere. The satellite station device may be a device mounted on a space mobile body such as an artificial satellite, or may be a space mobile body itself. The satellites that serve as satellite station equipment are low orbit (LEO: Low Earth Orbiting) satellites, medium earth orbit (MEO: Medium Earth Orbiting) satellites, geostationary (GEO: Geostationary Earth Orbiting) satellites, and high elliptical orbit (HEO: Highly Elliptical Orbiting). It may be any satellite. Of course, the satellite station device may be a device mounted on a low earth orbit satellite, a medium earth orbit satellite, a geostationary satellite, or a high elliptical orbit satellite.
[0027]
　The ground base station device 30 is a base station device that wirelessly communicates with the communication device 50. In the example of FIG. 1, a terrestrial base station apparatus 30 1 , the relay device 40 2 is connected to the relay device 40 2 It is also possible to communicate wirelessly with the communication device 50 via the. The ground base station device 30 may be a base station device arranged on a structure on the ground, or may be a base station device installed on a mobile body moving on the ground. For example, the ground base station device 30 is an antenna installed in a structure such as a building and a signal processing device connected to the antenna. Of course, the ground base station device 30 may be a structure or a moving body itself.
[0028]
　The relay device 40 is a device that serves as a relay station for the base station. The relay device 40 is a type of base station device. The relay device 40 relays communication between the non-ground base station device 20 and the communication device 50, or communication between the ground base station device 30 and the communication device 50. The relay device 40 may be a ground station device or a non-ground station device. The relay device 40 constitutes a radio access network RAN ​​together with the non-ground base station device 20 and the ground base station device 30.
[0029]
　The communication device 50 is, for example, a mobile phone, a smart device (smartphone or tablet), a PDA (Personal Digital Assistant), or a personal computer. Further, the communication device 50 may be an M2M (Machine to Machine) device or an IoT (Internet of Things) device. Further, the communication device 50 may be a wireless communication device installed on the mobile body, or may be the mobile body itself. The communication device 50 may be a relay station device that relays satellite communication, or may be a base station device that receives satellite communication. The communication device 50 supports both terrestrial networks and non-terrestrial networks. Therefore, the communication device 50 can communicate not only with the ground station device such as the ground base station device 30 but also with the non-ground station device such as the non-ground base station device 20.
[0030]
　FIG. 2 is a diagram showing an example of a wireless network provided by the communication system 1. The non-ground base station device 20 and the ground base station device 30 each constitute a cell. A cell is an area covered by a base station for wireless communication. The cell composed of the non-ground base station device 20 and the ground base station device 30 may be any of a macro cell, a micro cell, a femto cell, and a small cell. The communication system 1 may be configured to manage a plurality of cells by a single base station apparatus, or may be configured to manage one cell by a plurality of base station apparatus.
[0031]
　In the example of FIG. 2, the terrestrial base station apparatus 30 1 , 30 2 constitutes a terrestrial network TN1, terrestrial base station apparatus 30 3 , 30 4 , 30 5 constitute a terrestrial network TN 2. The terrestrial network TN1 and the terrestrial network TN2 are, for example, terrestrial networks operated by a wireless communication carrier such as a telephone company. The terrestrial network TN1 and the terrestrial network TN2 may be operated by different wireless communication carriers or may be operated by the same wireless communication carrier. It is also possible to regard the terrestrial network TN1 and the terrestrial network TN2 as one terrestrial network.
[0032]
　The terrestrial network TN1 and the terrestrial network TN2 are each connected to the core network. In the example of FIG. 2, the terrestrial base station apparatus 30 constituting the terrestrial network TN2, the management apparatus 10 1 is connected to the composed core network CN by like. If the wireless access system of the terrestrial network TN2 is LTE, the core network CN is EPC. If the wireless access system of the terrestrial network TN2 is NR, the core network CN is 5GC. Of course, the core network CN is not limited to EPC and 5GC, and may be a core network of another wireless access method. In the example of FIG. 2, the terrestrial network TN1 is not connected to the core network, but the terrestrial network TN1 may be connected to the core network CN. Further, the terrestrial network TN1 may be connected to a core network (not shown) different from the core network CN.
[0033]
　The core network CN is provided with a gateway device, a barrier exchange, and the like, and is connected to the public network PN via the gateway device. The public network PN is, for example, a public data network such as the Internet, a regional IP network, a telephone network (mobile phone network, fixed telephone network, etc.). The gateway device is, for example, a server device connected to the Internet, a regional IP network, or the like. The barrier exchange is, for example, an exchange connected to the telephone network of a telephone company. The management device 10 1 may have a function as a gateway device or gateway exchange.
[0034]
　The non-ground base station device 20 and the relay device 40 shown in FIG. 2 are both non-ground station devices such as satellite station devices and aircraft station devices. A group of satellite station devices (or satellite station devices) that make up a non-terrestrial network is called a Spaceborne Platform. Further, the aircraft station equipment group (or aircraft station equipment) constituting the non-terrestrial network is referred to as an airborne platform. In the example of FIG. 2, the non-terrestrial base station apparatus 20 2 , relay device 40 1 , and the relay device 40 2 constitute a space bones platform SBP1, non terrestrial base station apparatus 20 1 constitutes a space bones platform SBP2. The non-terrestrial base station apparatus 20 3 constitutes the airborne platform ABP1.
[0035]
　The communication device 50 can communicate with both the ground station device and the non-ground station device. In the example of FIG. 2, a communication device 50 1 can communicate with the ground station apparatus constituting the terrestrial network TN1. The communication device 50 1 can communicate with the non-ground station apparatus constituting the space bones platform SBP1, SBP2. The communication device 50 1 is also non-ground station apparatus constituting the airborne platform ABP1 can communicate. The communication apparatus 50 1 (in the example of FIG. 2 communication device 50 other communication devices 50 2 ) may be capable of communicating directly with.
[0036]
　The non-ground station apparatus connects to the terrestrial network or the core network via the relay station 60. Non ground station apparatus constituting the space bones platform SBP1, SBP2, the relay station 60 1 is connected to the terrestrial network TN1 through. The non-ground station apparatus constituting the space bones platform SBP1, SBP2, and airborne platform ABP1, the relay station 60 2 is connected to the core network CN via. The non-ground station equipment can also directly communicate with each other without going through the relay station 60.
[0037]
　The relay station 60 is, for example, an aviation station or an earth station. The Civil Aviation Bureau is a radio station installed on the ground or on a mobile body moving on the ground in order to communicate with the aircraft station. In addition, an earth station is a radio station located on the earth (including the air) in order to communicate with a satellite station (space station). The earth station may be a large earth station or a small earth station such as VSAT (Very Small Aperture Terminal). The earth station may be a VSAT controlled earth station (also referred to as a master station or a HUB station) or a VSAT earth station (also referred to as a slave station). Further, the earth station may be a radio station installed in a mobile body moving on the ground. For example, as an earth station mounted on a ship, an onboard earth station (ESV: Earth Stations on board Vessels) can be mentioned. In addition, the earth station may include an aircraft earth station installed on an aircraft (including a helicopter) and communicating with a satellite station. Further, the earth station may include an aviation earth station which is installed on a mobile body moving on the ground and communicates with an aircraft earth station via a satellite station. The relay station 60 may be a portable mobile radio station that communicates with a satellite station or an aircraft station. The relay station 60 can be regarded as a part of the communication system 1.
[0038]
　Each device constituting the space bone platforms SBP1 and SBP2 performs satellite communication with the communication device 50. Satellite communication is wireless communication between a satellite station device and a communication device. FIG. 3 is a diagram showing an outline of satellite communication provided by the communication system 1. The satellite station equipment is mainly divided into a geostationary satellite station equipment and a low earth orbit satellite station equipment.
[0039]
　The geostationary satellite station device is located at an altitude of about 35786 km and revolves around the earth at the same speed as the rotation speed of the earth. In the example of FIG. 3, the non-terrestrial base station apparatus 20 constituting the spaces bones platform SBP2 1 is a geostationary satellite station. The geostationary satellite station device has a relative speed of almost 0 with the ground communication device 50, and is observed from the ground communication device 50 as if it were stationary. Non terrestrial base station apparatus 20 1 includes a communication device 50 located on the earth 1 , 50 3 , 50 4 performs like and satellite communications.
[0040]
　The low earth orbit satellite station device is a satellite station device that orbits at a lower altitude than a geostationary satellite station device or a medium earth orbit satellite station device. The low earth orbit satellite station device is, for example, a satellite station device located between an altitude of 500 km and 2000 km. In the example of FIG. 3, the space bones platform SBP1 non terrestrial base station apparatus 20 constituting the 2, 20 3 is at a low orbit satellite station. Incidentally, in FIG. 3, the space bones platform SBP1 non terrestrial base station apparatus 20 as a satellite station apparatus constituting the 2 and non-terrestrial base station apparatus 20 3 Although only two shown. However, in reality, in the satellite station devices constituting the space bone platform SBP1, a low earth orbit satellite constellation is formed by two or more (for example, tens to thousands) of non-ground base station devices 20. Unlike the geostationary satellite station device, the low earth orbit satellite station device has a relative velocity with the ground communication device 50, and is observed as if it is moving from the ground communication device 50. Non terrestrial base station apparatus 20 2, 20 3 constitutes a cell, respectively, the communication device 50 located on the earth 1 , 50 2 , 50 3 performs such a satellite communication.
[0041]
　FIG. 4 is a diagram showing an example of cells configured by the satellite station device. Figure 4 is a non-terrestrial base station apparatus 20 is a low orbit satellite station device 3 has a cell C2 which is formed is shown. The satellite station device orbiting in low earth orbit communicates with the ground communication device 50 with a predetermined directivity on the ground. For example, the angle R1 shown in FIG. 4 is 40 °. For Figure 4, the non-terrestrial base station apparatus 20 3 radius D1 of the cell C2 which is formed, for example, 1000km. The low earth orbit satellite station device moves at a constant speed. When it becomes difficult for the low earth orbit satellite station device to provide satellite communication to the terrestrial communication device 50, the subsequent low earth orbit satellite station device provides satellite communication. For example in FIG. 4, the non-terrestrial base station apparatus 20 3 If the became difficult to provide a satellite communications to the ground of the communication device 50, a subsequent non-terrestrial base station apparatus 20 4 to provide a satellite communications .. The values ​​of the angle R1 and the radius D1 described above are merely examples and are not limited to the above.
[0042]
　As described above, the communication device 50 is capable of wireless communication using a non-terrestrial network. Further, the non-terrestrial base station device 20 and the relay device 40 of the communication system 1 form a non-terrestrial network. This makes it possible for the communication system 1 to extend the service to the communication device 50 located in an area that cannot be covered by the terrestrial network. For example, the communication system 1 can provide public safety communication and critical communication to communication devices such as IoT (Internet of Things) devices and MTC (Machine Type Communications) devices. Further, since the service reliability and recoverability are improved by using the non-terrestrial network, the communication system 1 can reduce the vulnerability of the service to physical attacks or natural disasters. Further, the communication system 1 can realize a service connection to an aircraft terminal device such as an airplane passenger or a drone, or a service connection to a mobile terminal device such as a ship or a train. In addition, the communication system 1 can provide A / V content, group communication, IoT broadcast service, software download service, high-efficiency multicast service such as emergency message, high-efficiency broadcast service, and the like. Further, the communication system 1 can also realize traffic offload between a terrestrial network and a non-terrestrial network. In order to realize these, it is desirable that the non-terrestrial network provided by the communication system 1 be integrated with the terrestrial network provided by the communication system 1 in the upper layer. Further, it is desirable that the non-terrestrial network provided by the communication system 1 has the same wireless access method as the terrestrial network provided by the communication system 1.
[0043]
　In the case of communication using a non-terrestrial network, as in the case of communication using a terrestrial network, switching of the base station device to be connected (for example, from the non-terrestrial base station device 20 to another non-terrestrial base station device) Handover to 20) occurs. However, in communication using a non-terrestrial network, the distance between the communication device 50 and the base station device may increase depending on the mode of the base station device. Therefore, in the case of communication using a non-terrestrial network, the signal propagation delay may increase depending on the mode of the base station device. In this case, the communication device 50 may take time for the switching process (for example, the handover process) of the base station device to be connected. In this case, it is assumed that there is a high possibility that the process of switching the connection destination base station device will fail.
[0044]
　For example, if the signal propagation delay is large, it takes time to send and receive information for handover processing between the base station device and the communication device 50 (for example, information required for the base station device to determine the handover). there is a possibility. Depending on the type of the non-ground base station device 20, it is expected that the moving speed relative to the communication device 50 will increase. Further, since the moving speed of the communication device 50 itself is high, the moving speed of the non-ground base station device 20 with respect to the communication device 50 may be high. If the relative movement speed is high, the communication device 50 already receives a switching instruction (for example, a handover command) for switching the connection destination base station device from the connected base station device. The communication range of the connected base station device may be out of range. If this happens, the communication device 50 fails the handover.
[0045]
　Further, as described above, it is assumed that the non-ground station device has a high moving speed relative to the communication device 50 depending on the type of the non-ground station device. Therefore, in the case of communication using a non-terrestrial network, there is a possibility that switching of base stations will occur more frequently than in communication using a terrestrial network. For example, when a non-terrestrial network is composed of a low earth orbit satellite constellation composed of hundreds to thousands of low earth orbit satellites, the connection destination of the communication device 50 is connected regardless of whether the communication device 50 is moving or not. There is a possibility that switching of the base station device will occur repeatedly in a short time.
[0046]
　Further, even in the case of communication using a terrestrial network, the relative speed between the base station device and the communication device 50 may be high depending on the mode of the ground station device or the communication device 50. For example, when one or both of the ground station device and the communication device 50 are located inside a moving body that moves at high speed, the relative speed between the base station device and the communication device 50 becomes high. In this case as well, switching of the base station device to which the communication device 50 is connected may occur repeatedly in a short time.
[0047]
　If the possibility of failure in the switching process of the base station device increases, or if the switching of the base station device to be connected occurs frequently, the communication quality may deteriorate. For example, it takes time to acquire data, packet loss occurs, seamless communication cannot be performed, or the communication speed fluctuates greatly.
[0048]
　Therefore, in the present embodiment, high-quality communication is realized by enabling the switching process of the connection-destination base station device to be completed in a short procedure or a short time. Specifically, the communication device 50 acquires switching information from the connected base station device before receiving a switching instruction (for example, a handover command) of the connected base station device from the connected base station device. do. The switching information is information used for switching the connection to the base station device which is a candidate for the switching destination of the connection. The switching information includes, for example, information used for wireless communication with a base station device as a switching destination candidate. Then, the communication device 50 determines whether or not the base station needs to be switched by itself before receiving the switching instruction from the connected base station device. When it is determined that switching is necessary, the communication device 50 switches the connection destination by itself using the switching information.
[0049]
　For example, as shown in FIG. 4, the communication device 50 3 is non-terrestrial base station apparatus 20 3 is connected to the base station apparatus as the switching destination candidate non terrestrial base station apparatus 20 4 and a. In this case, the communication device 50 3 is non-terrestrial base station apparatus 20 3 before receiving the handover command from the non-terrestrial base station apparatus 20 3 from the non-terrestrial base station apparatus 20 4 switching information used to switch the connection to the To get.
[0050]
　At this time, the switching information may be information related to handover. For example, switching information, the communication device 50 3 is non-terrestrial base station apparatus 20 4 may be information includes information about radio resources used for radio communication with (resource information). In this case, the resource information, the communication device 50 3 may include information dedicated radio resources allocated to the dedicated is. For example, the resource information, the communication device 50 3 is non-terrestrial base station apparatus 20 4 for transmitting a random access preamble to the communication unit 50 3 assigned time dedicated to - information dedicated physical resources such as the frequency May be included. Or, in the resource information, the communication device 50 3 may include information of the dedicated preamble sequences allocated to the exclusively is.
[0051]
　The communication device 50 3 is non-terrestrial base station apparatus 20 3 or without receiving a handover command from the performs themselves handover decision, the obtained switching information beforehand (e.g., resource information) the destination using To switch.
[0052]
　Thus, the communication device 50 3 from the non-terrestrial base station apparatus 20 3 information for handover determination to (e.g., measurements of received power) transmission step and the non-terrestrial base station apparatus 20 3 communication device 50 from 3 to The step of transmitting the handover command of is omitted. Therefore, while performing these steps, the communication device 50 3 is non-terrestrial base station apparatus 20 3 can be reduced a situation that deviates from the coverage area. Further, since these steps are omitted, the time required for the entire handover process is shortened. As a result, the number of failures in the handover process is reduced. Alternatively, the time for temporarily interrupting communication due to the handover process is reduced. As a result, the communication system 1 can realize high-quality communication.
[0053]
　Hereinafter, the configuration of each device constituting the communication system 1 according to the first embodiment will be specifically described.
[0054]
[2-2. Configuration of
　management device ] The management device 10 is a device that manages a wireless network. For example, the management device 10 is a device that manages communication between the non-ground base station device 20 and the ground base station device 30. If the core network is an EPC, the management device 10 is, for example, a device having a function as an MME (Mobility Management Entity). If the core network is 5GC, the management device 10 is, for example, a device having a function as an AMF (Access and Mobility Management Function). The management device 10 may have a gateway function. For example, if the core network is an EPC, the management device 10 may have a function as an S-GW (Serving Gateway) or a P-GW (Packet Data Network Gateway). Further, if the core network is 5GC, the management device 10 may have a function as an UPF (User Plane Function). The management device 10 does not necessarily have to be a device that constitutes the core network. For example, if the core network is a W-CDMA or cdma2000 core network, the management device 10 may be a device that functions as an RNC (Radio Network Controller).
[0055]
　FIG. 5 is a diagram showing a configuration example of the management device 10 according to the first embodiment of the present disclosure. The management device 10 includes a communication unit 11, a storage unit 12, and a control unit 13. The configuration shown in FIG. 5 is a functional configuration, and the hardware configuration may be different from this. Further, the functions of the management device 10 may be distributed and implemented in a plurality of physically separated configurations. For example, the management device 10 may be composed of a plurality of server devices.
[0056]
　The communication unit 11 is a communication interface for communicating with another device. The communication unit 11 may be a network interface or a device connection interface. For example, the communication unit 11 may be a LAN (Local Area Network) interface such as a NIC (Network Interface Card), or a USB interface composed of a USB (Universal Serial Bus) host controller, a USB port, and the like. May be good. Further, the communication unit 11 may be a wired interface or a wireless interface. The communication unit 11 functions as a communication means of the management device 10. The communication unit 11 communicates with the ground base station device 30 and the relay station 60 under the control of the control unit 13.
[0057]
　The storage unit 12 is a data readable / writable storage device such as a DRAM (Dynamic Random Access Memory), a SRAM (Static Random Access Memory), a flash memory, and a hard disk. The storage unit 12 functions as a storage means for the management device 10. The storage unit 12 stores, for example, the connection state of the communication device 50. For example, the storage unit 12 stores the RRC (Radio Resource Control) state and the ECM (EPS Connection Management) state of the communication device 50. The storage unit 12 may function as a home memory for storing the position information of the communication device 50.
[0058]
　The control unit 13 is a controller that controls each unit of the management device 10. The control unit 13 is realized by, for example, a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). For example, the control unit 13 is realized by the processor executing various programs stored in the storage device inside the management device 10 using a RAM (Random Access Memory) or the like as a work area. The control unit 13 may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). The CPU, MPU, ASIC, and FPGA can all be regarded as controllers.
[0059]
[2-3. Configuration of base station equipment]
　Next, the configuration of the base station equipment will be described. The communication system 1 includes, as a base station device, a non-terrestrial base station device 20 that constitutes a non-terrestrial network and a ground base station device 30 that constitutes a terrestrial network. All of the non-terrestrial base station devices 20 constituting the non-terrestrial network are movable. First, the configuration of the non-ground base station device 20 will be described.
[0060]
[Non-ground base station device]
　FIG. 6 is a diagram showing a configuration example of the non-ground base station device 20 according to the first embodiment of the present disclosure. The non-ground base station device 20 includes a wireless communication unit 21, a storage unit 22, and a control unit 23. The configuration shown in FIG. 6 is a functional configuration, and the hardware configuration may be different from this. Further, the functions of the non-ground base station apparatus 20 may be distributed and implemented in a plurality of physically separated configurations.
[0061]
　The wireless communication unit 21 is a wireless communication interface that wirelessly communicates with another wireless communication device (for example, a communication device 50, a relay station 60). The wireless communication unit 21 corresponds to one or a plurality of wireless access methods. For example, the wireless communication unit 21 supports both NR and LTE. The wireless communication unit 21 may support W-CDMA and cdma2000 in addition to NR and LTE. The wireless communication unit 21 includes a reception processing unit 211, a transmission processing unit 212, and an antenna 213. The wireless communication unit 21 may include a plurality of reception processing units 211, transmission processing units 212, and antennas 213, respectively. When the wireless communication unit 21 supports a plurality of wireless access methods, each unit of the wireless communication unit 21 may be individually configured for each wireless access method. For example, the reception processing unit 211 and the transmission processing unit 212 may be individually configured by LTE and NR.
[0062]
　The reception processing unit 211 processes the uplink signal received via the antenna 213. The reception processing unit 211 includes a wireless reception unit 211a, a multiple separation unit 211b, a demodulation unit 211c, and a decoding unit 211d.
[0063]
　The radio receiver 211a performs down-conversion, removal of unnecessary frequency components, control of amplification level, orthogonal demodulation, conversion to digital signal, removal of guard interval, and fast Fourier transform of the frequency domain signal for the uplink signal. Extract, etc. The multiplex separation unit 211b separates uplink channels such as PUSCH (Physical Uplink Shared Channel) and PUCCH (Physical Uplink Control Channel) and uplink reference signals from the signal output from the radio reception unit 211a. The demodulation unit 211c demodulates the received signal with respect to the modulation symbol of the uplink channel by using a modulation method such as BPSK (Binary Phase Shift Keying) or QPSK (Quadrature Phase shift Keying). The modulation method used by the demodulation unit 211c may be 16QAM (Quadrature Amplitude Modulation), 64QAM, or 256QAM. The decoding unit 211d performs decoding processing on the coded bits of the demodulated uplink channel. The decoded uplink data and uplink control information are output to the control unit 23.
[0064]
　The transmission processing unit 212 performs transmission processing of downlink control information and downlink data. The transmission processing unit 212 includes a coding unit 212a, a modulation unit 212b, a multiplexing unit 212c, and a wireless transmission unit 212d.
[0065]
　The coding unit 212a encodes the downlink control information and the downlink data input from the control unit 23 by using a coding method such as block coding, convolutional coding, or turbo coding. The modulation unit 212b modulates the coding bits output from the coding unit 212a by a predetermined modulation method such as BPSK, QPSK, 16QAM, 64QAM, 256QAM and the like. The multiplexing unit 212c multiplexes the modulation symbol of each channel and the downlink reference signal and arranges them in a predetermined resource element. The wireless transmission unit 212d performs various signal processing on the signal from the multiplexing unit 212c. For example, the radio transmitter 212d converts to the time domain by fast Fourier transform, adds a guard interval, generates a baseband digital signal, converts to an analog signal, quadrature modulation, up-conversion, removes an extra frequency component, and so on. Performs processing such as power amplification. The signal generated by the transmission processing unit 212 is transmitted from the antenna 213.
[0066]
　The storage unit 22 is a data-readable / writable storage device such as a DRAM, SRAM, flash memory, and hard disk. The storage unit 22 functions as a storage means for the non-ground base station device 20. The storage unit 22 stores the switching information. The switching information is information used by the communication device 50 to switch the base station. The switching information includes, for example, information such as resource information, trigger information, and timing advance information.
[0067]
　The resource information is information about a wireless resource used by the connected communication device 50 to wirelessly communicate with a movablely configured switching destination candidate base station device. Further, the trigger information is information used for determining whether or not the communication device 50 switches the connection destination base station. Further, the timing advance information is information regarding the timing advance for the communication device 50 to connect to the switching destination candidate base station. Resource information, trigger information, and timing advance information will be described in detail later.
[0068]
　The control unit 23 is a controller that controls each unit of the non-ground base station device 20. The control unit 23 is realized by, for example, a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). For example, the control unit 23 is realized by the processor executing various programs stored in the storage device inside the non-ground base station device 20 using a RAM (Random Access Memory) or the like as a work area. The control unit 23 may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). The CPU, MPU, ASIC, and FPGA can all be regarded as controllers.
[0069]
　As shown in FIG. 6, the control unit 23 includes an acquisition unit 231, a reception unit 232, a discrimination unit 233, a selection unit 234, and a transmission unit 235. Each block (acquisition unit 231 to transmission unit 235) constituting the control unit 23 is a functional block indicating the function of the control unit 23, respectively. These functional blocks may be software blocks or hardware blocks. For example, each of the above-mentioned functional blocks may be one software module realized by software (including a microprogram), or may be one circuit block on a semiconductor chip (die). Of course, each functional block may be one processor or one integrated circuit. The method of configuring the functional block is arbitrary. The control unit 23 may be configured in a functional unit different from the above-mentioned functional block. The operation of each block (acquisition unit 231 to transmission unit 235) constituting the control unit 23 will be described in detail in the description of the handover process (without the handover command) described later.
[0070]
[Ground Base Station Device]
　Next, the configuration of the ground base station device 30 will be described. FIG. 7 is a diagram showing a configuration example of the ground base station device 30 according to the first embodiment of the present disclosure. The ground base station device 30 includes a wireless communication unit 31, a storage unit 32, a network communication unit 33, and a control unit 34. The configuration shown in FIG. 7 is a functional configuration, and the hardware configuration may be different from this. Further, the functions of the ground base station apparatus 30 may be distributed and implemented in a plurality of physically separated configurations.
[0071]
　The wireless communication unit 31 is a wireless communication interface that wirelessly communicates with another wireless communication device (for example, a communication device 50). The wireless communication unit 31 includes a reception processing unit 311, a transmission processing unit 312, and an antenna 313. The configurations of the wireless communication unit 31, the reception processing unit 311, the transmission processing unit 312, and the antenna 313 are the same as those of the wireless communication unit 21, the reception processing unit 211, the transmission processing unit 212, and the antenna 213 of the non-ground base station apparatus 20. ..
[0072]
　The storage unit 32 is a data-readable / writable storage device such as a DRAM, SRAM, flash memory, and hard disk. The storage unit 32 functions as a storage means for the ground base station device 30. The configuration of the storage unit 32 is the same as that of the storage unit 22 of the non-ground base station device 20.
[0073]
　The network communication unit 33 is a communication interface for communicating with other devices. For example, the network communication unit 33 is a LAN interface such as a NIC. The network communication unit 33 may be a wired interface or a wireless interface. The network communication unit 33 functions as a network communication means for the ground base station device 30. The network communication unit 33 communicates with the management device 10 and the relay station 60 under the control of the control unit 34.
[0074]
　The control unit 34 is a controller that controls each unit of the ground base station device 30. The configuration of the control unit 34 is the same as that of the control unit 23 of the non-ground base station device 20.
[0075]
[2-4. Configuration of Relay Device]
　Next, the configuration of the relay device 40 will be described. FIG. 8 is a diagram showing a configuration example of the relay device 40 according to the first embodiment of the present disclosure. The relay device 40 includes a wireless communication unit 41, a storage unit 42, a network communication unit 43, and a control unit 44. The configuration shown in FIG. 8 is a functional configuration, and the hardware configuration may be different from this. Further, the functions of the relay device 40 may be distributed and implemented in a plurality of physically separated configurations.
[0076]
　The wireless communication unit 41 is a wireless communication interface that wirelessly communicates with other wireless communication devices (for example, a non-ground base station device 20, a ground base station device 30, and a communication device 50). The wireless communication unit 41 includes a reception processing unit 411, a transmission processing unit 412, and an antenna 413. The configurations of the wireless communication unit 41, the reception processing unit 411, the transmission processing unit 412, and the antenna 413 are the same as those of the wireless communication unit 21, the reception processing unit 211, the transmission processing unit 212, and the antenna 213 of the non-ground base station apparatus 20. ..
[0077]
　The storage unit 42 is a storage device capable of reading and writing data such as a DRAM, SRAM, flash memory, and hard disk. The storage unit 42 functions as a storage means for the relay device 40. The configuration of the storage unit 42 is the same as that of the storage unit 22 of the non-ground base station device 20.
[0078]
　The network communication unit 43 is a communication interface for communicating with other devices. For example, the network communication unit 43 is a LAN interface such as a NIC. The network communication unit 43 may be a wired interface or a wireless interface. The network communication unit 43 functions as a network communication means of the relay device 40. The network communication unit 43 communicates with the non-ground base station device 20 and the ground base station device 30 under the control of the control unit 44.
[0079]
　The control unit 44 is a controller that controls each unit of the relay device 40. The configuration of the control unit 44 is the same as that of the control unit 23 of the non-ground base station device 20.
[0080]
[2-5. Configuration of Communication Device]
　Next, the configuration of the communication device 50 will be described. FIG. 9 is a diagram showing a configuration example of the communication device 50 according to the first embodiment of the present disclosure. The communication device 50 includes a wireless communication unit 51, a storage unit 52, a network communication unit 53, an input / output unit 54, and a control unit 55. The configuration shown in FIG. 9 is a functional configuration, and the hardware configuration may be different from this. Further, the functions of the communication device 50 may be distributed and implemented in a plurality of physically separated configurations.
[0081]
　The wireless communication unit 51 is a wireless communication interface that wirelessly communicates with other wireless communication devices (for example, non-ground base station device 20, ground base station device 30, relay device 40). The wireless communication unit 51 corresponds to one or a plurality of wireless access methods. For example, the wireless communication unit 51 corresponds to both NR and LTE. The wireless communication unit 51 may support W-CDMA and cdma2000 in addition to NR and LTE. The wireless communication unit 51 includes a reception processing unit 511, a transmission processing unit 512, and an antenna 513. The wireless communication unit 51 may include a plurality of reception processing units 511, transmission processing units 512, and antennas 513, respectively. When the wireless communication unit 51 supports a plurality of wireless access methods, each unit of the wireless communication unit 51 may be individually configured for each wireless access method. For example, the reception processing unit 511 and the transmission processing unit 512 may be individually configured by LTE and NR.
[0082]
　The reception processing unit 511 processes the downlink signal received via the antenna 513. The reception processing unit 511 includes a wireless reception unit 511a, a multiple separation unit 511b, a demodulation unit 511c, and a decoding unit 511d.
[0083]
　The radio receiver 511a performs down-conversion, removal of unnecessary frequency components, control of amplification level, orthogonal demodulation, conversion to digital signal, removal of guard interval, and fast Fourier transform of the frequency domain signal for the downlink signal. Extract, etc. The multiplex separation unit 511b separates the downlink channel, the downlink synchronization signal, and the downlink reference signal from the signal output from the radio reception unit 511a. The downlink channel is, for example, a channel such as PBCH (Physical Broadcast Channel), PDSCH (Physical Downlink Shared Channel), PDCCH (Physical Downlink Control Channel), or the like. The demodulation unit 211c demodulates the received signal with respect to the modulation symbol of the downlink channel by using a modulation method such as BPSK, QPSK, 16QAM, 64QAM, 256QAM. The decoding unit 511d performs decoding processing on the coded bits of the demodulated downlink channel. The decoded downlink data and downlink control information are output to the control unit 23.
[0084]
　The transmission processing unit 512 performs the transmission processing of the uplink control information and the uplink data. The transmission processing unit 512 includes a coding unit 512a, a modulation unit 512b, a multiplexing unit 512c, and a wireless transmission unit 512d.
[0085]
　The coding unit 512a encodes the uplink control information and the uplink data input from the control unit 55 by using a coding method such as block coding, convolutional coding, or turbo coding. The modulation unit 512b modulates the coding bits output from the coding unit 512a by a predetermined modulation method such as BPSK, QPSK, 16QAM, 64QAM, 256QAM. The multiplexing unit 512c multiplexes the modulation symbol of each channel and the uplink reference signal and arranges them in a predetermined resource element. The wireless transmission unit 512d performs various signal processing on the signal from the multiplexing unit 512c. For example, the radio transmitter 512d converts to the time domain by inverse fast Fourier transform, adds a guard interval, generates a baseband digital signal, converts to an analog signal, orthogonal modulation, up-converts, and removes extra frequency components. , Power amplification, etc. The signal generated by the transmission processing unit 512 is transmitted from the antenna 513.
[0086]
　The storage unit 52 is a data-readable / writable storage device such as a DRAM, SRAM, flash memory, and hard disk. The storage unit 52 functions as a storage means for the communication device 50. The storage unit 52 stores the switching information. The switching information is information acquired from the non-ground base station device 20, the ground base station device 30, or the relay device 40, and is used by the communication device 50 for switching the base station. The switching information includes, for example, information such as resource information, trigger information, and timing advance information. Resource information, trigger information, and timing advance information will be described in detail later.
[0087]
　The network communication unit 53 is a communication interface for communicating with other devices. For example, the network communication unit 53 is a LAN interface such as a NIC. The network communication unit 53 may be a wired interface or a wireless interface. The network communication unit 53 functions as a network communication means of the communication device 50. The network communication unit 53 communicates with other devices according to the control of the control unit 55.
[0088]
　The input / output unit 54 is a user interface for exchanging information with the user. For example, the input / output unit 54 is an operation device for the user to perform various operations such as a keyboard, a mouse, operation keys, and a touch panel. Alternatively, the input / output unit 54 is a display device such as a liquid crystal display (Liquid Crystal Display) or an organic EL display (Organic Electroluminescence Display). The input / output unit 54 may be an audio device such as a speaker or a buzzer. Further, the input / output unit 54 may be a lighting device such as an LED (Light Emitting Diode) lamp. The input / output unit 54 functions as an input / output means (input means, output means, operation means, or notification means) of the communication device 50.
[0089]
　The control unit 55 is a controller that controls each unit of the communication device 50. The control unit 55 is realized by, for example, a processor such as a CPU or MPU. For example, the control unit 55 is realized by the processor executing various programs stored in the storage device inside the communication device 50 with the RAM or the like as a work area. The control unit 55 may be realized by an integrated circuit such as an ASIC or FPGA. The CPU, MPU, ASIC, and FPGA can all be regarded as controllers.
[0090]
　As shown in FIG. 9, the control unit 55 includes an acquisition unit 551, a determination unit 552, a connection unit 553, an update unit 554, a reception unit 555, and a transmission unit 556. Each block (acquisition unit 551 to transmission unit 556) constituting the control unit 55 is a functional block indicating the function of the control unit 55. These functional blocks may be software blocks or hardware blocks. For example, each of the above-mentioned functional blocks may be one software module realized by software (including a microprogram), or may be one circuit block on a semiconductor chip (die). Of course, each functional block may be one processor or one integrated circuit. The method of configuring the functional block is arbitrary. The control unit 55 may be configured in a functional unit different from the above-mentioned functional block. The operation of each block (acquisition unit 551 to transmission unit 556) constituting the control unit 55 will be described in detail in the description of the handover process (without the handover command) described later.
[0091]
[2-6. Initial connection processing]
　Next, the operation of the communication system 1 will be described. First, the initial connection process will be described. The initial connection process is a process for transitioning from an idle state (RRC_IDLE) in which the communication device 50 is not connected to any cell to a connection state (RRC_CONNECTED) in which a connection with any cell is established. FIG. 10 is a flowchart showing an example of the initial connection process. Hereinafter, the initial connection process will be described with reference to FIG. The initial connection process shown below is executed, for example, when the communication device 50 is turned on.
[0092]
　First, the idle communication device 50 performs a cell search. The cell search of the present embodiment includes a step of detecting a synchronization signal and decoding a PBCH. The receiving unit 555 of the communication device 50 detects the cell synchronization signal (step S101). The receiving unit 555 synchronizes the cell with the downlink based on the detected synchronization signal. Then, after establishing the downlink synchronization, the receiving unit 555 attempts to decode the PBCH and acquires the MIB (Master Information Block) which is a part of the system information (step S102).
[0093]
　The system information is information that notifies the setting in the cell that transmits the system information. The system information includes, for example, information on access to cells, information on cell selection, information on other RATs and other systems, and the like. The system information includes MIB and SIB (System Information Block). The MIB is information on the physical layer required to receive the SIB and the like, and is information on a fixed payload size notified by the PBCH. The MIB includes downlink system bandwidth, part of the system frame number, SIB scheduling information, and the like. The SIB is system information other than the MIB, and is notified by the PDSCH.
[0094]
　The system information can be classified into a first system information, a second system information, and a third system information. The first system information and the second system information include information on access to cells, information on acquisition of other system information, and information on cell selection. In LTE, the information contained in the MIB is the first system information. Further, the information included in SIB1 and SIB2 among the SIBs is the second system information. The remaining system information is the third system information.
[0095]
　Also in NR, system information is transmitted from the NR cell. The physical channel carrying system information may be transmitted in slots or minislots. A minislot is defined by a number of symbols that is less than the number of symbols in the slot. By transmitting the physical channel that carries system information in the minislot, the time required for beam sweeping can be reduced and the overhead can be reduced. In the case of NR, the first system information is transmitted on the NR-PBCH and the second system information is transmitted on a physical channel different from the NR-PBCH.
[0096]
　The acquisition unit 551 of the communication device 50 acquires the second system information based on the MIB (that is, the first system information) (step S103). As described above, the second system information is composed of SIB1 and SIB2. SIB1 is cell access regulation information and scheduling information of system information other than SIB1. SIB1 includes cell access information, cell selection information, maximum uplink transmission power information, TDD setting information, system information cycle, system information mapping information, SI (System Information) window length, and the like. Further, SIB2 includes connection prohibition information, cell-common radio resource setting information (radioResourceConfigCommon), uplink carrier information, and the like. The radio resource setting information common to cells includes setting information of PRACH (Physical Random Access Channel) and RACH (Random Access Channel) common to cells.
[0097]
　If the acquisition unit 551 cannot acquire the system information necessary for establishing the link, the control unit 55 of the communication device 50 determines that access to the cell is prohibited. For example, if all of the first system information and the second system information cannot be acquired, the control unit 55 determines that access to the cell is prohibited. In this case, the control unit 55 ends the initial connection process.
[0098]
　When the system information can be acquired, the control unit 55 executes a random access procedure (Random Access Procedure) based on the first system information and / or the second system information (step S104). Random access procedures are sometimes referred to as RACH procedures (Random Access Channel Procedures) or RA procedures (RA Procedures). Upon completion of the random access procedure, the communication device 50 transitions from the idle state (RRC_IDLE) to the connected state (RRC_CONNECTED).
[0099]
[2-7. Random access procedure]
　Next, the random access procedure will be described. The random access procedure is executed for the purpose of "RRC connection setup" from the idle state to the connected state (or inactive state), "request for state transition" from the inactive state to the connected state, and the like. The random access procedure is also used for the purpose of "scheduling request" for requesting resources for uplink data transmission and "timing advance adjustment" for adjusting uplink synchronization. In addition, the random access procedure is executed in the case of "on-demand SI request" for requesting system information that has not been transmitted, "beam recovery" for restoring a broken beam connection, "handover" for switching connection cells, and the like.
[0100]
　The “RRC connection setup” is an operation executed when the communication device 50 connects to the base station device in response to the generation of traffic or the like. Specifically, it is an operation of passing information about the connection (for example, UE context) from the base station device to the communication device 50. The UE context is managed by predetermined communication device identification information (for example, C-RNTI) instructed by the base station device. When the communication device 50 finishes this operation, the state transitions from the idle state to the inactive state or from the idle state to the connected state.

The scope of the claims
[Claim 1]

　Whether to switch between 　the acquisition unit that acquires switching information including information used for wireless communication from the connected base station device and the movable base station device that is a switch destination candidate, and the connection destination base station device.
　A connection unit that executes a connection to the switching destination candidate base station device based on the switching information when the determination unit determines whether or not to switch the connection destination base station device. And,
　a communication device having.
[Claim 2]
　The acquisition unit acquires the switching information including resource information related to the wireless resource used for wireless communication with the switching destination candidate base station device, and the
　connection unit uses the wireless resource to acquire the switching destination candidate.
　The communication device according to claim 1 , which executes a connection to a base station device.
[Claim 3]
　The acquisition unit acquires the resource information including the information of the dedicated radio resource dedicated to the communication device from the connected base station device, and the
　connection unit uses the dedicated radio resource.
　The communication device according to claim 2, wherein the connection to the switching destination candidate base station device is executed .
[Claim 4]
　The acquisition unit acquires the resource information including the information of the radio resource shared by the plurality of selected wireless communication devices including the communication device from the connected base station device, and the
　connection unit is the shared device.
　The communication device according to claim 2, wherein the wireless resource is used to connect to the switching destination candidate base station device.
[Claim 5]
　The acquisition unit acquires the switching information including the timing advance information regarding the timing advance for connecting to the switching destination candidate base station device from the connected base station device, and the connection unit obtains the
　timing advance information.
　The communication device according to claim 1, wherein the connection to the switching destination candidate base station device is executed based on the above .
[Claim 6]
　The acquisition unit acquires the switching information used for handover from the connected base station device to the switching destination candidate base station device from the connected base station device, and the
　determination unit performs the handover. When it is determined whether or not
　to execute the handover, and the determination unit determines that the handover is to be executed, the connection unit uses the switching information to determine the base of the switching destination candidate from the connected base station device.
　The communication device according to claim 1 , which executes the handover to the station device .
[Claim 7]
　The acquisition unit uses the switching information used for wireless communication with the switching destination candidate base station device among the plurality of base station devices constituting one cell in cooperation with each other.
　The communication device according to claim 1, which is acquired from the connected base station device.
[Claim 8]
　The acquisition unit acquires the switching information including the trigger information for determining whether or not to switch the base station device from the connected base station device, and the
　determination unit obtains the base station based on the trigger information.
　The communication device according to claim 1 , wherein the switching of the device is determined .
[Claim 9]
　The acquisition unit acquires the switching information of each of a plurality of base station devices that are candidates for switching destinations, and the
　connection unit is based on the switching information when it is determined by the determination unit that the base station devices are to be switched.
　The communication device according to claim 1 , wherein the connection to the base station device selected from the plurality of base station devices as the switching destination candidates is executed .
[Claim 10]
　The
　acquisition unit further has an update unit for updating the switching information, the acquisition
　unit acquires the switching information including the update information regarding the update condition of the switching information, and the update unit satisfies the update condition.
　The communication device according to claim 1 , wherein the switching information is updated with new switching information acquired from the connected base station device.
[Claim 11]
　The acquisition unit receives the first switching information used for switching the connection to the movablely configured first base station device which is a candidate for the switching destination, and the switching destination after connecting to the first base station device.
　The communication device according to claim 1, wherein the second switching information used for switching the connection to the candidate second base station device configured to be movable is acquired from the connected base station device. ..
[Claim 12]
　The communication device being connected
　transmits the switching information to the communication device and an acquisition unit that acquires switching information including information used for wireless communication with a movably configured base station device that is a candidate for a connection switching destination. The
　switching unit includes a transmission unit, and the switching information includes trigger information used for determining whether or not the connected communication device switches the connection-destination base station device, and the
　transmission unit uses the trigger information. A
　base station device that transmits the switching information including the above .
[Claim 13]
　The base station device is configured to be
　movable, and a determination is made to determine whether or not the current time is the timing to transmit the switching information based on at least one information of the current position, the moving direction, and the moving speed of the base station device.
　12.
　The base station apparatus according to claim 12 , wherein the transmission unit transmits the switching information when it is determined that the current time is the timing for transmitting the switching information .
[Claim 14]
　It further has a selection unit for selecting the switching destination candidate base station device from a plurality of base station devices configured to be movable, and the
　selection unit includes the current position, movement direction, and movement of the base station device. The movement information including at least one information of the speed, the base station device of the switching destination candidate is selected based on the movement information of each of the plurality of base station devices configured to be movable, and the
　acquisition unit The base station apparatus according to
　claim 12, wherein the switching information used for wireless communication with the base station apparatus selected by the selection unit is acquired .
[Claim 15]
　The connected communication device further includes a discriminating unit for determining whether or not the connected communication device is a communication device to which the switching information is transmitted. The
　transmitting unit further switches the connected communication device by the discriminating unit.
　The base station device according to claim 12 , wherein when it is determined that the communication device is the target of information transmission, the switching information is transmitted to the connected communication device.
[Claim 16]

　Whether or not to switch the connection destination base station device by 　acquiring switching information including information used for wireless communication with the movable base station device which is a switching destination candidate from the connected base station device. A 　communication method
　for executing a connection to the switching destination candidate base station device based on the switching information when the determination is made and it is determined to switch the connection destination base station device
.
[Claim 17]
　A movably configured base station device in which the communication device is a candidate for connection switching destination, including trigger information used to determine whether or not the connected communication device switches the connection destination base station device. A communication method in which switching information including information used for wireless communication is acquired and the
　switching information including the trigger information is transmitted to the
　communication device.
[Claim 18]

　An acquisition unit that acquires switching information including information used for wireless communication between a base station device that is connected 　to a computer of a communication device and a base station device that is movably configured as a switching destination candidate, and a
　connection destination. A determination unit that determines whether or not to switch the base station device, and when the determination unit
　determines that the connection destination base station device is to be switched, the connection to the switching destination candidate base station device is based on the switching information.
　A communication program to function as a connection, which executes .
[Claim 19]
　The computer of
　the base station device can be moved so that the communication device is a connection switching destination candidate, including trigger information used for determining whether or not the connected communication device switches the connection destination base station device. 　A communication program for functioning as an acquisition unit for acquiring switching information including information used for wireless communication with a base station device configured in the
　above, and a transmission unit for transmitting the switching information including the trigger information to the communication device
.
[Claim 20]
　It has a plurality of base station devices configured to be movable and
　a communication device connected to at least one of the plurality of base station devices, and the
　plurality of base station devices are each
　connected to a communication device. The communication device has a transmission unit that transmits switching information including information used for wireless communication with a movable base station device that is a candidate for a connection switching destination to the connected communication device, and the
　communication device has the
　switching. an acquisition unit that acquires information from the base station apparatus during connection of said plurality of base stations,
　and a determination section for determining whether or not to switch the base station apparatus of a connection destination,
　the base station apparatus by the determination unit A
　communication system including a connection unit that executes a connection to the switching destination candidate base station device based on the switching information when it is determined to switch .