JP6761010B2 - Communications system - Google Patents

Description

The present invention relates to a communication system.

In recent years, as a countermeasure against disasters and out-of-service areas, it has been formed from mobile mobile base stations incorporated in aircraft, artificial satellites, HAPS, balloons, drones, etc. toward the ground, water, or low altitude air. It is said that the expansion of the three-dimensional large zone cell (first cell) to be performed is effective. In an overlay cell configuration in which a normal ground cell is superimposed in this large zone cell, the frequency utilization efficiency can be expanded by operating the large zone cell using the same frequency as the ground cell.

In the overlay cell configuration, when the mobile station connected to the large zone cell hands over to the ground cell (second cell) in the large zone cell, the base station of the large zone cell identifies the ground cell of the handover destination. Need to be identified. A physical cell identifier (PCI: Physical Cell ID) included in a measurement report (Measurement Report) received from a mobile station connected to a large zone cell can be used to identify the ground cell of the handover destination. The PCI is defined by, for example, 504 numerical values (0 to 503), but if a large number of ground cells are included in the large zone cell, the PCI may overlap between the ground cells. The base station may not be able to identify and identify the ground cell of the handover destination.

In Patent Document 1, a physical cell identifier for each adjacent cell, position information, and transmission power are managed as adjacent cell information, and when a measurement report prompting a handover from a mobile station (mobile device), a handover candidate cell is used. When the physical cell identifiers are duplicated, the position information of the mobile station included in the measurement report of the mobile station, the received power of the handover candidate cell, and the position information and the transmission power of the adjacent cell are acquired and calculated based on the position information. A handover control method for specifying as a handover destination a cell in which the distance obtained and the distance calculated based on the information regarding the electric power match is disclosed. According to the handover control method of Patent Document 1, it is said that the handover destination can be specified when the physical cell identifiers are duplicated.

Japanese Unexamined Patent Publication No. 2016-208101

However, in the handover control method of Patent Document 1, the mobile station is provided with a function different from the standard function of measuring the position information of the mobile station and the received power of the handover candidate cell and reporting it to the base station of the connected cell. It is necessary to modify the mobile station for this.

The communication system according to one aspect of the present invention includes a first cell base station forming a first cell and a plurality of second cells having a cell size smaller than that of the first cell and arranged in the first cell. It is equipped with a second cell base station of. Each of the plurality of second cell base stations is classified into a plurality of distance division areas in which the area of the first cell is divided according to the distance from the reference position in the first cell, and within the same distance division area. And the physical cell identifiers are assigned so as not to overlap within the same distance division area between the adjacent distance division areas and between the adjacent distance division areas. The first cell base station holds second cell station information including information on the physical cell identifier of the second cell base station classified into the distance division area for each of the plurality of distance division areas. Information on the distance from the reference position in the first cell is acquired for the mobile station to be handed over in one cell, and the mobile station among the plurality of distance division areas is based on the distance information. Is specified, a measurement report including the physical cell identifier of the handover destination candidate cell is received from the mobile station to be handed over, and the specified distance dividing area and the physical cell of the handover destination candidate cell are received. The second cell of the handover destination is specified based on the identifier and the second cell station information.
In the communication system, the distance information may be acquired based on the control value of Timing Advance transmitted to the mobile station in the first cell.

The communication system according to another aspect of the present invention forms a first cell base station forming a first cell and a second cell having a cell size smaller than that of the first cell and is arranged in the first cell. It includes a plurality of second cell base stations. Each of the plurality of second cell base stations is arranged so that a plurality of second cells to which the same physical cell identifier is assigned in the first cell are not adjacent to each other. The first cell base station has a correspondence relationship between the physical cell identifier of the second cell base station and the physical cell identifiers of peripheral cells located around the second cell base station for each of the plurality of second cell base stations. The peripheral cell environment information including the above information is retained, and a measurement report including the handover destination candidate cell and the physical cell identifier of the peripheral cell is received from the mobile station located in the first cell, and the handover destination candidate cell is received. The second cell of the handover destination is specified based on the physical cell identifier of the peripheral cell and the peripheral cell environment information.

The communication system according to still another aspect of the present invention forms a first cell base station forming a first cell and a second cell having a cell size smaller than that of the first cell and is arranged in the first cell. It also has a plurality of second cell base stations. Each of the plurality of second cell base stations divides the area of the first cell according to the rotation angle about the reference position so that the outward directions from the reference position in the first cell are different from each other. It is classified into a plurality of angle division areas, and physical cell identifiers are assigned so as not to overlap in the angle division area. The first cell base station holds second cell station information including information on the physical cell identifier of the second cell base station classified into the angle division area for each of the plurality of angle division areas. For the mobile station to be handed over in one cell, information on the direction from the reference position in the first cell is acquired, and based on the information in the direction, the mobile station among the plurality of angle division areas. Is specified, a measurement report including the physical cell identifier of the handover destination candidate cell is received from the mobile station to be handed over, and the specified angle dividing area and the physical cell of the handover destination candidate cell are received. The second cell of the handover destination is specified based on the identifier and the second cell station information.

At least two of the plurality of methods for specifying the second cell of the handover destination in the communication system of the plurality of aspects may be combined.

In the communication system, the second cell base station is a macro cell base station or a small cell base station installed on a ground, water, or low altitude flying object, and the first cell base station is the second cell base. It may be a base station located at the same position as or higher than the station. Further, the first cell base station may be a macro cell base station installed on the ground, on the water, or on a low-altitude flying object.

According to the present invention, even when a large number of second cells are formed in the first cell of the overlay cell configuration and the physical cell identifiers of the plurality of second cells overlap with each other, the first cell is not modified without modifying the mobile station. When the cell is handed over to the second cell, the second cell of the handover destination can be reliably identified and specified.

The explanatory view which shows an example of the schematic structure of the mobile communication system which has the overlay cell structure in which a plurality of ground cells are arranged in the large zone cell which concerns on embodiment of this invention. The explanatory view which shows an example of the method of specifying the handover destination cell which concerns on embodiment. The flowchart which shows an example of the process of specifying the handover destination cell in the large zone cell base station which concerns on embodiment. The explanatory view which shows another example of the method of specifying the handover destination cell which concerns on embodiment. The flowchart which shows the other example of the process which specifies the handover destination cell in the large zone cell base station which concerns on embodiment. The explanatory view which shows still another example of the method of specifying the handover destination cell which concerns on embodiment. FIG. 5 is a flowchart showing still another example of the process of specifying the handover destination cell in the large zone cell base station according to the embodiment. The sequence diagram which shows an example of the handover processing which concerns on embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, an embodiment of the present invention will be described on the premise of application to LTE / LTE-Advanced, but the concept of the present invention can be applied to any system as long as it is a system using a similar cell configuration and physical channel configuration. Applicable.

Further, in the following embodiment, an overlay cell configuration in which a plurality of ground cells (macro cells and small cells) are superimposed in a large thorn cell formed by a base station incorporated in an air vehicle in the sky will be described. The invention is also applicable to other types of overlay cell configurations. For example, the present invention can be applied to an overlay cell configuration in which a plurality of small cells are superimposed in a macro cell, and the handover destination cell can be specified by the method illustrated in the following embodiment.

First, the overall configuration of a mobile communication system to which the present invention can be applied will be described.
FIG. 1 is an explanatory diagram showing an example of a schematic configuration of a mobile communication system having an overlay cell configuration in which a plurality of ground cells 10A are arranged in a large zone cell 15A according to an embodiment of the present invention. As a measure against disasters and elimination of out-of-service areas, a large zone cell (first cell) formed from an aerial floating communication relay device 15 in which a base station is incorporated in an air vehicle that can move over the sky toward the ground or water is formed. ) The deployment of 15A is effective. As a countermeasure against the rapidly increasing mobile communication traffic in the large zone cell 15A, it is effective to apply an overlay cell configuration in which a plurality of ground cells (second cells) 10A are superimposed in the large zone cell 15A. In this overlay cell configuration, the frequency utilization efficiency can be expanded by using the same frequency band between the large zone cell 15A and the ground cell 10A, and the user terminal device (hereinafter, also referred to as "UE") which is a mobile station (mobile device) can be expanded. It is possible to increase the communication quality (for example, throughput) in 30 and 31.

In FIG. 1, the mobile communication system of the present embodiment is a communication system conforming to next-generation standard specifications such as LTE (Long Term Evolution) / LTE-Advanced or 5th generation, and is mounted on the communication relay device 15. A mobile large zone cell base station 150 as a second base station (another base station) and a fixed arrangement in the cell (hereinafter referred to as "large zone cell") 15A which is a wireless communication area of the large zone cell base station 150. It includes a ground cell base station 10 as a plurality of first base stations. The ground cell base station 10 is, for example, a normal macro cell base station or a small cell base station. The cell (hereinafter, appropriately referred to as “ground cell”) 10A, which is the wireless communication area of the ground cell base station 10, is included inside the large zone cell 15A of the large zone cell base station 150. The number of ground cells 10A arranged in the large zone cell 15A is not limited to the number shown in the figure. As the size of the large zone cell 15A increases, the number of ground cells 10A arranged in the large zone cell 15A may reach hundreds, thousands or tens of thousands. Further, the first base station located in the large zone cell 15A may be a small cell base station that forms a small cell smaller than the macro cell.

The large zone cell base station 150 is a base station (for example, eNodeB, gNodeB) as a mobile relay communication station mounted on a levitation type communication relay device 15 composed of an air vehicle that can move in the sky, and is a mobile communication. It is possible to relay the wireless communication of the feeder link FL on the network side and the wireless communication of the service link SL on the mobile station side.

Note that FIG. 1 shows an example in which the communication relay device 15 equipped with the large zone cell base station 150 is an airship as an aircraft capable of moving in the sky, but the communication relay device 15 is designed to move in the sky. It may be another aircraft such as a flyable aircraft, a solar plane, a drone, or a helicopter. The air vehicle may be controlled to fly and position in a high altitude airspace of 100 [km] or less from the ground, sea surface, or water surface such as a river or lake by autonomous control or external control. Further, the flight airspace of the flying object may be a stratospheric airspace having an altitude of 11 [km] or more and 50 [km] or less. Further, the flight airspace of the air vehicle may be an airspace having an altitude of 15 [km] or more and 25 [km] or less in which the weather conditions are relatively stable, and particularly an airspace having an altitude of approximately 20 [km]. May be good.

Further, the large zone cell base station 150 is installed at the same position as or higher than the second cell base station such as the ground cell base station 10 (including the position in the atmosphere and the position in outer space outside the atmosphere). It may be a base station.

The ground cell base station 10 is, for example, a normal macro cell base station or a small cell base station. A macrocell base station is a high-power base station that covers a ground cell that is usually installed outdoors in a mobile communication network and is a wide area with a radius of several hundred meters to several kilometers. The macrocell base station is connected to another base station by, for example, a wired communication line, and can communicate with a predetermined communication interface. In addition, the macro cell base station is connected to the core network of the mobile communication network via a communication line such as a line termination device and a dedicated line, and communicates with various nodes such as a server on the core network by a predetermined communication interface. It is possible. Unlike wide-area macrocell base stations, small cell base stations have a wireless communication range of several meters to several hundreds of meters, and have a small output that can be installed inside buildings such as ordinary homes, stores, and offices. Base station. Small cell base stations are also connected to the core network of mobile communication networks via line termination devices and communication lines such as ADSL (Asymmetric Digital Subscriber Line) lines and broadband public communication lines such as optical lines, and are on the core network. It is possible to communicate with various nodes such as server devices by a predetermined communication interface.

The second cell base station in the large zone cell 15A may be a base station installed on the ground or on the water, or may be a base station installed on a low-altitude flying object such as a drone or a balloon.

In FIG. 1, the first mobile station, the UE 30, is a user terminal device (MUE) located in the cell 15A of the large zone cell base station 150 and connected to the large zone cell base station 150, and is a large zone cell base station 150. It is in a state where wireless communication for telephone and data communication is possible via. Since the UE 30 is located near the boundary between the large zone cell 15A and the ground cell 10A, it is susceptible to interference from the ground cell 10A.

The second mobile station, UE 31, is a user terminal device (SUE) that is located at the outer edge of cell 10A of the ground cell base station 10 and is connected to the ground cell base station 10. Wireless communication for telephone and data communication is possible via the system. Since the UE 31 is located near the boundary between the ground cell 10A and the large zone cell 15A, the UE 31 is vulnerable to interference from the large zone cell 15A.

When the UEs 30 and 31 are in the large zone cell 15A or the ground cell 10A, they are wirelessly connected to the macro cell base station or the small cell base station corresponding to the cell in the area by using a predetermined communication method and wireless communication resource. Can communicate. The UEs 30 and 31 are configured by using hardware such as a computer device having a CPU and a memory, an external communication interface unit for a core network, and a wireless communication unit, and the base stations 10, 150 are executed by executing a predetermined program. It is possible to perform wireless communication with, etc.

In the present embodiment, the large zone cell base station 150 and the terrestrial cell base station 10 are each configured by using hardware such as a computer device having a CPU and a memory, an external communication interface unit for a core network, and a wireless communication unit. By executing a predetermined program, various processes for suppressing interference described later are executed, and wireless communication with the UEs 30 and 31 is performed using a predetermined communication method and wireless communication resources. Can be done.

Each of the base stations 10 and 150 is a base station capable of wireless communication of an OFDM (Orthogonal Frequency Division Multiplexing) downlink with a UE as a mobile station. The base stations 10 and 150 include, for example, an antenna, a radio signal path switching unit, a transmission / reception duplexer (DUP: Duplexer), a downlink radio reception unit and an OFDM (Orthogonal Frequency Division Multiplexing) demodulation unit, an uplink radio reception unit, and an SC-FDMA ( Single-Carrier Frequency-Division Multiple Access) Equipped with a demodulation unit, etc. Further, each of the base stations 10 and 150 includes an OFDM modulation unit, a downlink radio transmission unit, a control unit, and the like.

The SC-FDMA demodulation unit executes an SC-FDMA demodulation process on the received signal received by the uplink radio reception unit, and passes the demodulated data to the control unit. The OFDM modulation unit modulates the downlink signal data received from the control unit to the UE in the cell of its own station by the OFDM method so that it is transmitted with a predetermined power. Further, when the base station receives information on a subframe to be stopped from transmission, for example, the OFDM modulation unit is controlled to stop downlink transmission only for a specific subframe in the wireless communication frame. The downlink radio transmission unit transmits the transmission signal modulated by the OFDM modulation unit via the transmission / reception duplexer, the radio signal path switching unit, and the antenna.

The control units of the base stations 10 and 150 are composed of, for example, a computer device, and control each unit or execute various processes by reading and executing a predetermined program.

The control unit of the terrestrial cell base station 10 also functions as a control means for controlling the transmission of the downlink wireless communication frame in the terrestrial cell 10A at the corrected transmission timing.

Next, specific description will be given of the handover destination cell when UE30 residing in large Zonseru 15A that put the mobile communication system of the overlay cell configuration of handover (HO) in the ground cells 10A. As described above, when the UE 30 connected to the large zone cell (first cell) 15A and in the sphere in the overlay cell configuration hands over to the ground cell (second cell) 10A in the large zone cell 15A, the large zone cell The base station 150 of 15A needs to identify and identify the ground cell 10A of the handover destination. A physical cell identifier (PCI) included in the measurement report (MR) received from the UE 30 connected to the large zone cell 15A can be used to identify the ground cell 10A as the handover destination. PCI is defined by, for example, 504 numerical values (0 to 503) in LTE, which is a standard of 3GPP, but when a large number of ground cells 10A are included in a large zone cell, PCI (PCI) between the ground cells 10A ( For example, PCI = 21) in FIG. 1 may overlap. Therefore, the base station 150 of the large zone cell 15A may not be able to identify and identify the ground cell 10A of the handover destination.

Therefore, in the present embodiment, the large zone cell base station 150 performs a process of specifying the ground cell 10A of the handover destination as illustrated below.

[Handover destination cell identification processing example 1]
FIG. 2 is an explanatory diagram showing an example of a method for specifying a handover destination cell according to the present embodiment. FIG. 3 is a flowchart showing an example of a process for specifying a handover destination cell in the large zone cell base station 150 according to the present embodiment.

In Example 1 of the specific processing of the handover destination cell of the present embodiment, the following advance preparations are performed. As shown in FIG. 2, a large number of ground cell base stations (second cell base stations) 10 arranged in the large zone cell 15A are each large according to the distance from the central position 15C as a reference position in the large zone cell 15A. The area of the zone cell 15A is divided into a plurality of concentric annular distance division areas 15T (n) (n = 1 to N). In the illustrated example, the number of divisions N of the large zone cell 15A is 5, but the number of divisions N may be 4 or less or 6 or more.

Further, the same PCI (physical cell identifier) is not assigned between the distance division areas adjacent to each other among the plurality of distance division areas 15T (n). For example, when PCI = 21 is assigned to the ground cell base station 10 in the third distance division area 15T (3) from the center of the large zone cell 15A, the ground in the second distance division area 15T (2). PCI = 21 is not assigned to either the cell base station 10 or the ground cell base station 10 in the fourth distance division area 15T (4).

The large zone cell base station 150 provides second cell station information including the PCI information of the ground cell base station 10 classified into the distance division areas for each of the plurality of distance division areas 15T (n) (n = 1 to N). Hold.

In FIG. 3, the large zone cell base station 150 first acquires information on the distance from the center position 15C of the large zone cell of the UE 30 located in the large zone cell 15A (S101 in FIG. 3). This distance information can be obtained, for example, based on the control value of Timing Advance transmitted to the UE 30 for controlling the transmission timing of the UE 30. The large zone cell base station 150 identifies the distance division area 15T (n) in which the UE 30 is located based on the distance information (S102 in FIG. 3).

Next, the large zone cell base station 150 receives a measurement report (MR) including the PCI of the handover destination candidate cell (PCI = 21 in the example of FIG. 2) and the peripheral cell environment information from the UE 30 to be handover (FIG. 2). 3 S103).

Next, the large zone cell base station 150 stores cell station information in advance for the specified distance division area 15T (n) and the distance division areas 15T (n-1) and 15T (n + 1) adjacent thereto. Reference is made, the referenced cell station information is compared with the peripheral cell environment information included in the MR received from the UE 30, and the handover destination cell is specified based on the comparison result (S104 in FIG. 3). For example, in the example of FIG. 2, the ground cell (PCI = 21) 10A included in the third distance division area 15T (3) is specified as the handover destination.

[Handover destination cell identification processing example 2]
FIG. 4 is an explanatory diagram showing another example of the method of specifying the handover destination cell according to the present embodiment. FIG. 5 is a flowchart showing another example of the process of specifying the handover destination cell in the large zone cell base station 150 according to the present embodiment.

In Example 2 of the specific processing of the handover destination cell of the present embodiment, the following advance preparations are performed. As shown in FIG. 4, a large number of ground cell base stations (second cell base stations) 10 arranged in the large zone cell 15A include a plurality of ground cells 10A to which the same PCI is assigned in the large zone cell 15A. They are arranged so that they are not adjacent to each other.

The large zone cell base station 150 includes peripheral cell environment including information on the correspondence between the PCI of the ground cell base station 10 and the PCI of the peripheral cells located around the ground cell base station 10 for each of the plurality of ground cell base stations 10. Hold information.

In FIG. 5, the large zone cell base station 150 first includes the PCI of the handover destination candidate cell (PCI = 21 in the example of FIG. 4) and the peripheral cell environment information from the handover target UE 30 located in the large zone cell 15A. Receive the measurement report (MR) (S201 in FIG. 5).

Next, the large zone cell base station 150 refers to the peripheral cell environment information held in advance based on the PCI of the handover destination candidate cell (S202 in FIG. 5). Here, when there are a plurality of ground cells of the PCI of the handover destination candidate cell (PCI = 21 in the example of FIG. 4), the peripheral cell PCI in the peripheral cell environment information held in advance for the PCI of the handover destination candidate cell. Refer to. Then, the peripheral cell PCI in the peripheral cell environment information received from the UE 30 is compared with the peripheral cell PCI in the peripheral cell environment information held in advance for the PCI of the handover destination candidate cell, and the handover is performed based on the comparison result. The destination cell is specified (S203 in FIG. 5).

For example, in the example of FIG. 4, there are a plurality of ground cells 10A (1) and 10A (2) of the PCI of the handover destination candidate cell (PCI = 21 in the example of FIG. 4), and as peripheral cell PCIs corresponding to them. The following PCI is retained.
Ground cell 10A (1): Peripheral cell PCI = 22, 23, 24
Ground cell 10A (2): Peripheral cell PCI = 32, 33, 34

Here, since the peripheral cell PCIs included in the MR received from the UE 30 are 22, 23, 24, the ground cell (PCI = 21) 10A corresponding to the peripheral cells PCI 22, 23, 24 is specified as the handover destination. To.

[Handover destination cell identification processing example 3]
FIG. 6 is an explanatory diagram showing still another example of the method of specifying the handover destination cell according to the present embodiment. FIG. 7 is a flowchart showing still another example of the process of specifying the handover destination cell in the large zone cell base station 150 according to the present embodiment.

In Example 3 of the specific processing of the handover destination cell of the present embodiment, the following advance preparations are performed. As shown in FIG. 6, a large number of ground cell base stations (second cell base stations) 10 arranged in the large zone cell 15A are oriented outward from the central position 15C as a reference position in the large zone cell 15A. Differently, the area of the large zone cell 15A is divided into a plurality of angle division areas (sectors) 15S (n) (n = 1 to N) according to the rotation angle centered on the center position 15C. In the illustrated example, the number of divisions N of the large zone cell 15A is 6, but the number of divisions N may be 5 or less or 7 or more.

Also a PCI as a plurality of angles divided areas 15S (n) the same within an angular division area 15S (n) in each PCI (physical cell ID) is not duplicated assignment has. For example, in each of the six angle division areas 15S (n) of the large zone cell 15A of FIG. 6, PCI = 21 is assigned only to one ground cell base station 10 in the angle division area 15S (n).

The large zone cell base station 150 provides second cell station information including the PCI information of the ground cell base station 10 classified into the angle division areas for each of the plurality of angle division areas 15S (n) (n = 1 to N). Hold.

In FIG. 7, the large zone cell base station 150 first acquires information in the direction from the center position 15C of the large zone cell of the UE 30 located in the large zone cell 15A (S301 in FIG. 7). The information in this direction is, for example, whether the UE 30 has the highest input level to the antenna in which direction among the plurality of antennas included in the large zone cell 15A, or whether the antenna in which direction is used for communication. Can be obtained based on. The large zone cell base station 150 identifies the angle division area 15S (n) where the UE 30 is located based on the information in the direction (S302 in FIG. 7).

Next, the large zone cell base station 150 receives a measurement report (MR) including the PCI of the handover destination candidate cell (PCI = 21 in the example of FIG. 6) and the peripheral cell environment information from the UE 30 to be handover (FIG. 6). 7 S303).

Next, the large zone cell base station 150 stores cell station information in advance for the specified angle division area 15S (n) and the angle division areas 15S (n-1) and 15S (n + 1) adjacent thereto. Reference is made, the referenced cell station information is compared with the peripheral cell environment information included in the MR received from the UE 30, and the handover destination cell is specified based on the comparison result (S304 in FIG. 7). For example, in the example of FIG. 6, the ground cell (PCI = 21) 10A (1) included in the first angle division area 15S (1) is specified as the handover destination.

FIG. 8 is a sequence diagram showing an example of the handover process according to the embodiment.
In FIG. 8, first, prior to the handover processing, the above-mentioned handover destination cell identification processing example 1 is performed between the large zone cell base station 150 and the ground cell base stations 10 of a large number of ground cells 10A included in the large zone cell 15A. At least one advance preparation (PCI allocation, retention of cell station information or peripheral cell environment information, etc.) of to 3 is performed (S401). In the illustrated example, the large number of ground cell base stations 10 includes a plurality of ground cell base stations 10 (1) and 10 (2) in which PCI = 21 overlaps.

Next, the large zone cell base station 150 receives from the UE 30 a measurement report including peripheral cell environment information including the PCI of the adjacent cell measured by the UE 30 located in the large zone cell 15A and the reception level corresponding to the PCI. (S402). In the illustrated example, since the reception level of PCI = 21 is high, PCI = 21 is set as the PCI of the handover destination candidate cell.

Next, the large zone cell base station 150 executes at least one of the above-mentioned handover destination cell identification processing examples 1 to 3 to specify the handover destination cell (S403). In the illustrated example, since cell 10A (1) of the ground cell base station 10 (1) is specified as the handover destination cell, the large zone cell base station 150 makes a handover request to the ground cell base station 10 (1). Transmit (S404).

When the ground cell base station 10 (1) receives the handover request from the large zone cell base station 150, the ground cell base station 10 (1) transmits "RRC CONNECTION RECONFIGURATION" for starting the handover process to the UE 30, and the ground cell base station 10 (1) and the UE 30 Processing for subsequent handover is executed between and.

As described above, according to the present embodiment, a large number of ground cells (macro cells, small cells, etc.) as second cells are formed in the large zone cell 15A as the first cell of the overlay cell configuration, and physical cells of a plurality of ground cells are formed. Even when the identifiers overlap with each other, the ground cell of the handover destination can be reliably identified and specified when the handover is performed from the large zone cell to the ground cell without modifying the UE (mobile station).

It should be noted that any two or three of the handover destination cell identification processing examples 1 to 3 described in the above embodiment may be combined. By combining in this way, it is possible to improve the accuracy when specifying the ground cell of the handover destination as compared with the case where any one of the handover destination cell identification processing examples 1 to 3 is performed alone, and the large zone cell can be obtained. The number of PCIs that can be accommodated can be further increased.

Further, in the above embodiment, the case of the overlay configuration of the ground cell 10A and the large zone cell 15A has been described, but the present invention is not limited to this configuration, and the present invention is applied to an overlay configuration of a plurality of cells having different sizes. be able to.

Further, in the present embodiment, the description has been made on the premise of application to LTE / LTE-Advanced, but downlink wireless communication, wireless communication frame, and OFDM of the OFDM (Orthogonal Frequency Division Multiplexing) method similar to LTE / LTE-Advanced. The concept of the present invention can be applied to any system as long as it is a system using symbols and the like, and is not limited to the transmitter and receiver configurations shown in the present embodiment.

Further, the processing process and the components of the mobile communication system, the large zone cell base station 150, the ground cell base station 10, and the user terminal devices (mobile stations) 30 and 31 described in the present specification shall be implemented by various means. Can be done. For example, these steps and components may be implemented in hardware, firmware, software, or a combination thereof.

Regarding hardware implementation, means such as a processing unit used to realize the above steps and components in an entity (for example, various wireless communication devices, Node B, terminal, hard disk drive device, or optical disk drive device) One or more application-specific ICs (ASICs), digital signal processors (DSPs), digital signal processors (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors , Controllers, microcontrollers, microprocessors, electronic devices, other electronic units designed to perform the functions described herein, computers, or combinations thereof.

Also, for firmware and / or software implementation, means such as processing units used to implement the above components are programs (eg, procedures, functions, modules, instructions) that perform the functions described herein. , Etc.) may be implemented. In general, any computer / processor readable medium that clearly embodies the firmware and / or software code is a means such as a processing unit used to implement the steps and components described herein. May be used to implement. For example, the firmware and / or software code may be stored in memory and executed by a computer or processor, for example, in a control device. The memory may be implemented inside the computer or processor, or may be implemented outside the processor. The firmware and / or software code includes, for example, random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), programmable read-only memory (PROM), and electrically erasable PROM (EEPROM). ), FLASH memory, floppy (registered trademark) discs, compact discs (CDs), digital versatile discs (DVDs), magnetic or optical data storage devices, etc., even if they are stored on a computer- or processor-readable medium. Good. The code may be executed by one or more computers or processors, or the computers or processors may be made to perform the functional embodiments described herein.

Further, the medium may be a non-temporary recording medium. In addition, the code of the program may be read and executed by a computer, a processor, or another device or device machine, and the format is not limited to a specific format. For example, the code of the program may be any of source code, object code, and binary code, or may be a mixture of two or more of these codes.

Also, the description of the embodiments disclosed herein is provided to allow one of ordinary skill in the art to manufacture or use the disclosure. Various amendments to this disclosure will be readily apparent to those skilled in the art, and the general principles defined herein are applicable to other variations without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not limited to the examples and designs described herein, but should be accepted in the broadest range consistent with the principles and novel features disclosed herein.

10 Ground cell base station (second base station)
10A ground cell (second cell)
15 Communication relay device (aircraft)
15A large zone cell (1st cell)
30 Mobile stations (user terminal devices, UEs) connected to ground cells
31 Mobile stations (user terminal devices, UEs) connected to large zone cells
150 large zone cell base station (second base station, relay communication station)

Claims (3)

A communication system including a first cell base station forming a first cell and a plurality of second cell base stations forming a second cell having a cell size smaller than that of the first cell and arranged in the first cell. And
Each of the plurality of second cell base stations is arranged so that the plurality of second cells to which the same physical cell identifier is assigned in the first cell are not adjacent to each other.
The first cell base station is
Peripheral cell environment information including information on the correspondence between the physical cell identifier of the second cell base station and the physical cell identifier of the peripheral cell located around the second cell base station for each of the plurality of second cell base stations. Hold and
A measurement report including the physical cell identifiers of the handover destination candidate cell and the peripheral cells is received from the handover target mobile station located in the first cell.
A communication system characterized in that a second cell of a handover destination is specified based on physical cell identifiers of the handover destination candidate cell and peripheral cells and the peripheral cell environment information . In the communication system of 請Motomeko 1,
The second cell base station is a macro cell base station or a small cell base station installed on the ground, water, drone, or balloon, and the first cell base station is located at the same position as or higher than the second cell base station. A communication system characterized by being an arranged base station. In the communication system of claim 1 ,
The first cell base station is a communication system characterized in that it is a base station located in outer space in the atmosphere or outside the atmosphere.