JP7220168B2 - Discontinuous coverage detection in overlay cell configuration and wireless network design based on the detection - Google Patents

Description

The present invention relates to a system, management device, method and program for detecting discontinuous service areas in an overlay cell configuration and wireless network design based on the detection.

In recent years, as a countermeasure against disasters and elimination of out-of-service areas, mobile airborne base stations built into flying objects such as aircraft, satellites, HAPS, balloons, helicopters, and drones have been used to transmit data from mobile base stations to the ground, water, or low-altitude air. The expansion of the formed three-dimensional large zone cell (first cell) is validated. In this overlay cell configuration, in which terrestrial cells (second cells) such as normal macrocells and small cells are superimposed on the large zone cells, frequency utilization efficiency is increased by operating the large zone cells using the same frequency as the terrestrial cells. can do.

Non-Patent Documents 1 and 2 describe a procedure for initially connecting (attaching) to a cell from a UE (mobile station) used by a user, and reselecting a cell from an idle state UE (mobile station). The procedure for when to do is disclosed.

3GPP TS 23.401 V16.4.0 (2019-09) 3GPP TS 23.502 V15.2.0 Release 15

The above overlay cell configuration has the following problems. For example, the diameter of a large zone cell (footprint diameter) on the ground is about several tens of kilometers to several hundreds of kilometers, which is about ten times as large as a macrocell, which is a relatively large ground cell with a diameter of several kilometers to ten and several kilometers. In addition, ground base stations (for example, macro cell base stations) cover a wide area with a radius of several hundred meters to tens of kilometers with several hundred to several thousand stations, whereas base stations in the sky form large zone cells. covers a similar wide area with a single station. In this way, since a wide area is covered by a single large zone cell, the amount of communication traffic in the large zone cell is large, but the radio resources used by base stations in the sky for radio communication with UEs are the same as the radio resources of terrestrial base stations. Since they are the same, there is a risk that the radio resources of the large zone cell will be depleted, or that the communication quality (throughput) of UEs residing in the large zone cell will deteriorate. In order to avoid such depletion of radio resources of large zone cells, in areas where terrestrial cells exist in large zone cells, terrestrial cells are preferentially reselected (or handed over between terrestrial cells), and terrestrial cells exist. It is conceivable to design a wireless network with a policy of preferentially reselecting (or handing over to) a large-zone cell in an area where it is not used.

However, in the design of the wireless network based on the above policy, for some reason (for example, the radio waves from the terrestrial base station cannot reach the building), the radio waves of the terrestrial cell frequency cannot be detected even in the area where the terrestrial cells exist. In some cases, only radio waves on the frequency of the zone cell can be detected. In this case, even if radio waves from the terrestrial base station can be detected , the UE does not return to the terrestrial cell and remains connected to the large zone cell, possibly failing to avoid depletion of the radio resources of the large zone cell.

A management device according to an aspect of the present invention sets a frequency priority parameter of the second cell in an overlay cell configuration in which a first cell and a plurality of second cells having a cell size smaller than the first cell coexist. It is a management device that manages. This management device comprises: means for acquiring measurement reports including reception strengths of mobile stations located in the plurality of second cells from the base stations of the plurality of second cells; Based on the obtained measurement report, for each of the plurality of second cells located within the first cell, a discontinuous boundary area in which other second cells are not continuous is detected in the outer boundary area of the second cell. means for determining whether or not to include frequency information of the first cell in setting information of a frequency priority parameter to be set for the second cell based on the detection result of the discontinuous boundary area; Prepare.
A method according to another aspect of the present invention sets a frequency priority parameter of the second cell in an overlay cell configuration in which a first cell and a plurality of second cells having a cell size smaller than the first cell are mixed. How to manage. The method includes obtaining from the plurality of second cell base stations measurement reports including received strengths of mobile stations located in the plurality of second cells; Based on the measurement report, for each of the plurality of second cells located within the first cell, detecting a discontinuous boundary area where other second cells are not continuous in the outer boundary area of the second cell. and, based on the detection result of the discontinuous boundary area, determining whether or not to include the frequency information of the first cell in the setting information of the frequency priority parameter to be set for the second cell. include.
A program according to still another aspect of the present invention sets a frequency priority parameter of the second cell in an overlay cell configuration in which a first cell and a plurality of second cells having a cell size smaller than the first cell coexist. is a program executed by a computer or processor provided in a management device that manages This program includes: program code for acquiring measurement reports including received strength of mobile stations located in the plurality of second cells from the base stations of the plurality of second cells; Based on the measurement report obtained from, for each of the plurality of second cells located in the first cell, a discontinuous boundary area in which other second cells are not continuous in the outer boundary area of the second cell Based on the program code for detection and the detection result of the discontinuous boundary area, it is determined whether or not the frequency information of the first cell is included in the setting information of the frequency priority parameter set for the second cell. and program code for determining.

In the management device, the method, and the program, for each of the plurality of second cells located within the first cell, the ratio of the circumference of the discontinuous boundary area to the circumference of the outer boundary area of the second cell is greater than or equal to a predetermined threshold, and the frequency of the first cell is included in the setting information of the frequency priority parameter for the second cell in which the ratio of the perimeter of the discontinuous boundary area is greater than or equal to the threshold Even if the frequency information of the first cell is not included in the setting information of the frequency priority parameter for the second cell in which the ratio of the circumferential length of the discontinuous boundary area is smaller than the threshold value, good.
The management device may be a network management system (NMS) that manages a mobile communication network including the first cell base station and the plurality of second cell base stations.
The management device may be an MME (Mobility Management Entity) connected to a core network to which the base station of the first cell is connected, or the It may be an AMF (Access and Mobility Management Function) to which the base station of the first cell is connected, or a core network device other than the AMF.

A communication system according to still another aspect of the present invention includes any one of the management devices, a first cell base station forming the first cell, and a plurality of second cell bases forming the plurality of second cells. stations.
In the communication system, the first cell base station may be a base station having at least an antenna installed on a flying object capable of moving or flying in the sky.
In the communication system, all or some of the plurality of second cell base stations may use different frequencies.
In the communication system, the plurality of second cell base stations include a second cell base station using the same frequency as the first cell base station and a different frequency using a different frequency from the first cell base station. and a second cell base station.
In the communication system, the second cell base station of the same frequency is a small cell base station installed on the ground or on the water, or has at least an antenna installed on an aircraft flying at a lower altitude than the first cell base station. It is a small cell base station, and the second cell base station of a different frequency is a macrocell base station installed on the ground or on the water, or has at least an antenna installed in an aircraft flying at a lower altitude than the first cell base station. The first cell base station may be a base station having at least an antenna located at the same or higher position than the second cell base station.
In the communication system, the first cell base station may be a macro cell base station, and the same-frequency second cell base station and the different-frequency second cell base station may be small cell base stations.

According to the present invention, a change in the operational status of a wireless network is estimated by detecting a discontinuous boundary area in which other second cells of a plurality of small-sized second cells are not continuous in an overlay cell configuration. be able to. Moreover, based on the detection result of the discontinuous boundary area from which changes in the operation status of the wireless network can be estimated, only the second cell that includes the discontinuous boundary area among the plurality of second cells is given frequency priority in the second cell. The setting information of the frequency parameter can include the information of the frequency of the large size first cell. Therefore, it is possible to prevent depletion of radio resources in the large-sized first cell even when the operational status of the radio network in the overlay cell configuration changes.

BRIEF DESCRIPTION OF THE DRAWINGS 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 large zone cell and a plurality of terrestrial cells are arranged according to an embodiment of the present invention; FIG. 4 is a sequence diagram showing an example of control of frequency priority parameters set for terrestrial cells in the overlay cell configuration of the communication system according to the embodiment; (a) to (c) are explanatory diagrams showing an example of creation of a coverage area estimation map by a plurality of terrestrial cells using mutually different frequencies. FIG. 4 is an explanatory diagram showing an example of a calculation method of the ratio of the perimeter of the discontinuous boundary area to the total perimeter of the outer perimeter boundary area of the ground cell.

Embodiments of the present invention will be described below with reference to the drawings. Here, the embodiment of the present invention will be described on the premise of application to a mobile communication system that conforms to next-generation standard specifications such as LTE / LTE-Advanced and 5th generation, but similar cell configurations and physical channel configurations The concept of the present invention can be applied to any system as long as it is used.

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 large zone cell 10A and a plurality of terrestrial cells 20A are arranged according to an embodiment of the present invention. As a countermeasure against disasters and out-of-service areas, it is effective to deploy a large zone cell 10A as a large-sized first cell formed from the floating communication relay device 15 toward the ground or water. In addition, as a countermeasure against rapidly increasing mobile communication traffic in the large zone cell 10A, it is effective to apply an overlay cell configuration in which a plurality of terrestrial cells 20A are superimposed within the large zone cell 10A.

In FIG. 1, a terrestrial cell 20A as a plurality of second cells uses a frequency (frequency band) A (f _HAPS ) of the large zone cell 10A for wireless communication with a user terminal device (hereinafter also referred to as "UE") which is a mobile station. ) is used (frequency band) B(f ₁ ). The plurality of terrestrial cells 20A may be a plurality of cells using a plurality of mutually different frequencies B (f ₁ , f ₂ , f ₃ , . . . ). Also, the plurality of terrestrial cells 20A includes a plurality of cells using a plurality of mutually different frequencies B (f ₁ , f ₂ , f ₃ , . . . ) formed in the same area by a single terrestrial cell base station. It's okay. In addition, the plurality of ground cells 20A use a ground cell (for example, a small cell) with the same frequency (frequency band) as the large zone cell 10A for wireless communication with the UE, and a frequency (frequency band) different from that of the large zone cell 10A for wireless communication with the UE. different frequency terrestrial cells (for example, macrocells) in which different frequency bands are used.

In the illustrated example, the cell configuration is such that each of the plurality of ground cells 20A is entirely included in the large zone cell 10A. May be duplicated.

Also, the plurality of terrestrial cells 20A may be a mixture of small cells and macro cells. In this case, part of the small cell may overlap with the macro cell, or the entire small cell may be located within the macro cell.

The frequencies A and B used in the cells 10A and 20A may be, for example, frequencies in the microwave band of 300 MHz to 30 GHz, or frequencies in the millimeter wave band higher than 30 GHz. Further, frequency A may be between 700 MHz and 1 GHz, and frequency B may be a frequency higher than 1 GHz.

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 installed in the communication relay device 15 A movable large zone cell base station (air base station) 10 as a first cell base station, and a plurality of second cell base stations fixedly arranged in a large zone cell 10A, which is a radio communication area of the large zone cell base station 10. It comprises a terrestrial cell base station 20 as a. The large zone cell base station 10 and the terrestrial cell base station 20 are eNodeB (eNB) or gNodeB (gNB), for example.

A plurality of terrestrial cell base stations 20 use, for example, a frequency B(f ₁ ) different from the frequency A(f _HAPS ) of the large zone cell base station 10 for wireless communication with UEs. A plurality of terrestrial cell base stations 20 may use a plurality of different frequencies B (f ₁ , f ₂ , f ₃ , . . . ). Also, the terrestrial cell base station 20 may form a plurality of terrestrial cells with a plurality of different frequencies (f ₁ , f ₂ , f ₃ , . . . ) in the same area. In addition, the plurality of terrestrial cell base stations 20 are terrestrial cell base stations (for example, small cell base stations) that form terrestrial cells of the same frequency (frequency band) as the large zone cell 10A for wireless communication with the UEs, and UEs. A terrestrial cell base station (for example, a macrocell base station) that forms a different frequency terrestrial cell that uses a different frequency (frequency band) from the large zone cell 10A for wireless communication may also be included.

In this embodiment, the mobile communication network of frequency A and the mobile communication network of frequency B are operated and managed by the same carrier (carrier) to provide mobile communication services. In order to mutually identify the mobile communication network of frequency A and the mobile communication network of frequency B of the same carrier (carrier), different mobile communication network identification information ( PLMN (Public Land Mobile Network Number) is assigned and configured.

The large zone cell base station 10 is a base station (e.g., eNodeB, gNodeB) as a relay communication station installed in a floating communication relay device 15 composed of a flying object capable of moving in the sky, and serves as a feeder on the mobile communication network side. Radio communication on the link FL and radio communication on the service link SL on the mobile station side can be relayed.

Although FIG. 1 shows an example in which the relay communication station mounted on the communication relay device 15 in the sky is the large zone cell base station 10, the large zone cell base station 10 is provided in the gateway station 70 on the ground side. Alternatively, it may be provided in a device connected to the gateway station 70 on the ground side. In this case, the relay communication station installed in the communication relay device 15 performs radio communication with the large zone cell base station 10 on the feeder link FL and radio communication with the UE (mobile station) on the service link SL. Acts as a relaying repeater.

Further, among the constituent elements of the large zone cell base station 10, at least the antenna and the radio equipment of the service link SL for radio communication with the UE may be mounted on the communication relay device 15, and the baseband processing section may be provided on the ground side.

Also, FIG. 1 shows an example in which the communication relay device 15 on which the large zone cell base station 10 is mounted is an airship as a flying object capable of moving in the sky. drones, balloons, aircraft, helicopters, solar plane type HAPS (“High Altitude Platform Station” or “High Altitude Pseudolite”) or LAPS (“Low Altitude Platform Station” or “Low Altitude Pseudolite”), airship type It may be HAPS or LAPS, other unmanned or manned air vehicles such as satellites. In addition, after moving to a predetermined position in the sky where the communication relay device 15 is located during wireless relay operation, the communication relay device 15 is controlled so as to remain at that position or to fly in a circular flight within a predetermined range of flight space including that position. You may

An aircraft is positioned by flying in an airspace at an altitude of 100 km or less above the ground, sea surface, or water surface such as a river or lake, under autonomous control, external control, or operation by an operator on board the aircraft. may be controlled as follows. Also, the flight airspace of the flying object may be a stratospheric airspace with an altitude of 11 [km] or more and 50 [km] or less. Furthermore, the flight airspace of the aircraft may be an airspace at an altitude of 15 [km] or more and 25 [km] or less where weather conditions are relatively stable, and in particular an airspace at an altitude of approximately 20 [km]. good too.

Also, the large zone cell base station 10 is a base station installed at a position higher than the ground cell base station (second base station) 20 (including a position in the atmosphere and a position in outer space). may The terrestrial cell base station 20 may be installed on the ground or on the water, or may be installed in an air vehicle flying at a lower altitude than the large zone cell base station 10 . Also, the first cell base station (large zone cell base station) 10 may be a macrocell base station, and the second cell base station 20 having a frequency different from that of the macrocell base station may be a small cell base station.

Here, the macrocell base station is a high-output base station that covers a terrestrial cell that is a wide area with a radius of several hundred meters to several kilometers, which is usually installed outdoors in a mobile communication network. The macrocell base station 30 is connected to other base stations by, for example, a wired communication line, and is capable of communicating with a predetermined communication interface. In addition, the macro cell base station is connected to the core network of the mobile communication network via communication lines such as line termination equipment and dedicated lines, and can communicate with various nodes such as servers on the core network through a predetermined communication interface. It has become.

Unlike wide-area macrocell base stations, small cell base stations have a wireless communication range of several meters to several hundred meters, and have a low output that can be installed inside buildings such as general homes, stores, and offices. is the base station of Small cell base stations are also connected to the core network of the mobile communication network via communication lines such as line termination equipment and broadband public communication lines such as ADSL (Asymmetric Digital Subscriber Line) lines and optical lines, and servers on the core network It is possible to communicate with various nodes such as devices through a predetermined communication interface.

The ground cell base station 20 in the large zone cell 10A may be a base station installed on the ground or on the water, or may be a low-altitude flying object such as a drone or balloon that flies at a lower altitude than the large zone cell base station 10. It may be an installed base station.

In FIG. 1, UE 41, which is the first mobile station, is a user terminal equipment (MUE) located in large zone cell 10A on frequency A and connected to large zone cell base station 10. is ready for wireless communication for phone calls, data communication, etc.

A second mobile station, UE 42, is a user terminal equipment (SUE) located in the terrestrial cell 20A of frequency B and connected to the terrestrial cell base station 20. It is in a state in which wireless communication for communication or the like is possible.

UE41 is located in the large zone cell 10A and is connected to the cell 10A. The UE 42 is located in the terrestrial cell 20A and is connected to the cell 20A. UE 42' sets the ratio [%] of discontinuous boundary areas in which other terrestrial cells located around the outer boundary area of a terrestrial cell (to be described later) are discontinuous among the plurality of terrestrial cells 20A to a predetermined threshold value (Z [ %]), and the frequency information of the large zone cell 10A is included in the setting information of the frequency priority parameter. and is connected to the ground cell 20A'.

Note that the ratio [%] of the discontinuous boundary area among the plurality of terrestrial cells 20A is smaller than a predetermined threshold (Z [%]), and the frequency information of the large zone cell 10A is not included in the setting information of the frequency priority parameter. Terrestrial cell 20A is also referred to as a "large zone cell frequency deactivated cell". In addition, in the description of this document, when the terrestrial cell 20A and the terrestrial cell 20A' are not distinguished, it is described as "terrestrial cell 20A", and when the terrestrial cell base station 20 and the terrestrial cell base station 20A' are not distinguished, It is described as "terrestrial cell base station 20". When UE42 and UE42' are not distinguished from each other, they are referred to as "UE42".

When UEs 41 and 42 are located in the large zone cell 10A and the terrestrial cell 20A, respectively, the UE 41 and 42 communicate with the large zone cell base station 10 and the terrestrial cell base station 20 corresponding to the cell in which they are located, using a predetermined communication scheme and radio communication resources. can be used for wireless communication. Each of the UEs 41 and 42 is configured using hardware such as a computer device having a CPU, a memory, etc., an external communication interface unit for the core network, and a wireless communication unit. 20, etc., can be performed.

In this embodiment, the large zone cell base station 10 and the terrestrial cell base station 20 are respectively configured using hardware such as a computer device having a CPU, memory, etc., an external communication interface unit for the core network, a wireless communication unit, etc. By executing a predetermined program, various processes for controlling and managing connection and disconnection of UEs to cells 10A and 20A are executed, and various processes such as handover of UEs 41 and 42 are executed. , to the UEs 41 and 42, control information including frequency priority parameter setting information, and wireless communication with the UEs 41 and 42 using a predetermined communication scheme and wireless communication resources.

Each of the base stations 10 and 20 is a base station capable of downlink wireless communication with a mobile station, UE, using OFDM (Orthogonal Frequency Division Multiplexing). The base stations 10 and 20 include, for example, an antenna, a radio signal path switching unit, a duplexer (DUP: Duplexer), a downlink radio reception unit and an OFDM (Orthogonal Frequency Division Multiplexing) demodulation unit, an uplink radio reception unit, SC-FDMA ( Single-Carrier Frequency-Division Multiple Access) demodulator, etc. Further, each base station 10, 20 has an OFDM modulation section, a downlink radio transmission section, a control section, and the like.

The SC-FDMA demodulation section performs SC-FDMA demodulation processing on the reception signal received by the uplink radio reception section, and passes the demodulated data to the control section. The OFDM modulation unit modulates the data of the downlink signal received from the control unit and transmitted to the UE located in the cell of the own station using the OFDM method so that the data is transmitted with a predetermined power. Further, when the base station receives, for example, information about a subframe to stop transmission from the server, the OFDM modulation section is controlled to stop downlink transmission only for a specific subframe in the radio communication frame. The downstream radio transmission section transmits the transmission signal modulated by the OFDM modulation section via the duplexer, the radio signal path switching section and the antenna.

The control units of the base stations 10 and 20 are composed of, for example, computer devices, and control each unit and execute various processes by reading and executing a predetermined program. Further, the control unit includes an external communication interface unit for the core networks 51 and 52, core network devices 61 and 62 such as an MME (mobility management entity) device, an AMF (access and mobility management function) device, and a network management system (NMS). In cooperation with the management device 30 such as, a means for performing processing for controlling and managing initial connection, reselection and disconnection of the UE to the cells 10A and 20A, and handover of the UE 41 and 42 It also functions as a means of processing. The MME device and the AMF device accommodate base stations (e.g., eNodeB, gNodeB) 10, 20, function as gateways for control signals between the base stations, and perform UE mobility control.

In this embodiment, the first core network 51 for the large zone cell base station 10 and the second core network 52 for the terrestrial cell base station 20 are provided separately. A common core network may be provided for the cell base stations 20, and a core network device accommodating the large zone cell base stations 10 and a core network device accommodating the terrestrial cell base stations 20 may be separately provided in the common core network. . A common core network is provided for the large zone cell base station 10 and the terrestrial cell base station 20, and a common core network device accommodating the large zone cell base station 10 and the terrestrial cell base station 20 is provided in the common core network. good too.

Each of the base stations 10 and 20 can communicate with the management device 30 via core network devices 61 and 62 such as MME devices of each of the core networks 51 and 52, respectively. For example, the large zone cell base station 10 can communicate with the management device 30 via the gateway station 70 and the core network device 61 of the first core network 51 . The terrestrial cell base station 20 can communicate with the management device 30 via a predetermined interface and the core network device 62 of the second core network 52 .

The communication system of the present embodiment includes at least a management device 30 and may include base stations 10 and 20 . The management device 30 is composed of, for example, a single or a plurality of computer devices, and performs processing for managing or controlling base stations and UEs in a mobile communication system with an overlay cell configuration by reading and executing a predetermined program. Execute. The management device 30 also functions as means for the following (1) to (3).

(1) Means for acquiring measurement reports (MR) including the reception strength of UEs (mobile stations) 42 located in a plurality of terrestrial cells (second cells) 20A from the terrestrial cell base stations 20 of the plurality of terrestrial cells 20A.
(2) Based on the measurement reports obtained from the terrestrial cell base stations 20 of the terrestrial cells 20A, for each of the terrestrial cells 20A located in the large zone cell (first cell) 10A, in the outer boundary area of the terrestrial cell 20A Means for detecting discontinuous border areas where other second cells are not continuous.
(3) Means for determining whether or not to include information on frequency A of the large zone cell 10A in the frequency priority parameter setting information to be set in the terrestrial cell 20A, based on the detection result of the discontinuous boundary area.

The management device 30 also functions as means for the following (4) and (5).
(4) For each of the plurality of ground cells 20A located within the large zone cell 10A, whether the ratio of the perimeter L2 of the discontinuous boundary area to the perimeter L of the outer perimeter boundary area of the ground cell 20A is equal to or greater than a predetermined threshold value Z Means for determining whether or not
(5) including information on the frequency A (f _HAPS ) of the large zone cell 10A in the setting information of the frequency priority parameter for the ground cell 20A' in which the ratio of the perimeter L2 of the discontinuous boundary area is equal to or greater than the threshold Z, Means for not including information on the frequency A(f _HAPS ) of the large zone cell 10A in the setting information of the frequency priority parameter for the terrestrial cell 20A in which the ratio of the perimeter L2 of the discontinuous boundary area is smaller than the threshold Z.

In the communication system with the overlay cell configuration, the diameter of the large zone cell 10A on the ground (footprint diameter) is about several tens of kilometers to several hundreds of kilometers. It is about ten times as large as one macrocell 30A. In addition, while the macro cell base station 30 covers a wide area with a radius of several tens of kilometers with several hundred to several thousand stations, the large zone cell base station 10 in the sky forming the large zone cell 10A covers a similar wide area. Cover in one go. Since a wide area is covered by one large zone cell in this way, the amount of communication traffic in the large zone cell 10A increases, but the radio resources used by the large zone cell base station 10 in the sky for radio communication with the UE 41 are limited to terrestrial cell bases. Since it is the same as the radio resource of the station 20, the radio resource in the large zone cell 10A may run out. In addition, there is a possibility that the communication quality (throughput) of UE 41 residing in large zone cell 10A may deteriorate. Also, when the amount of communication traffic in the large zone cell 10A exceeds the processing capability of the radio equipment of the large zone cell base station 10, handover to the large zone cell 10A fails, or reselection of the large zone cell 10A by an idle UE fails. There is also a possibility that

Therefore, in this embodiment, as described below, only UEs that are located in a terrestrial cell that satisfies a predetermined condition among the plurality of terrestrial cells 20A can be handed over to the large zone cell 10A (or the large zone cell 10A). can be reselected). Specifically, for example, among the plurality of cells 20A, the large zone cell frequency activated cell 20A in which the ratio of the discontinuous boundary area in which the other second cells are not continuous in the outer boundary area of the terrestrial cell 20A is equal to or greater than a predetermined threshold Only UE 42' located in 'can be handed over to the large zone cell 10A (or can be reselected to the large zone cell 10A). As a result, it is possible to prevent depletion of radio resources in the large zone cell 10A even when the operational status of the radio network in the overlay cell configuration changes, and to suppress deterioration in communication quality (for example, throughput) in the large zone cell 10A.

FIG. 2 is a sequence diagram showing an example of control of frequency priority parameters set for the terrestrial cell 20A in the overlay cell configuration of the communication system according to this embodiment.
2, the terrestrial cell base station 20 receives frequencies B (f ₁ , f ₂ , f ₃ , _. ) is received and collected (S101), and the measurement report (MR) collected from each UE 42 is reported to the management device (NMS) 30 (S102).

The management device 30 receives the direction of arrival of the MR of each UE (for example, the azimuth of the direction of arrival of the MR based on the position of the antenna of the ground cell base station 20) received from the plurality of ground cell base stations 20 in the large zone cell 10A, and Based on the reception intensity, the area of the terrestrial cell 20A of each terrestrial cell base station 20 is estimated, and a coverage area estimation map of the entire terrestrial cell formed by a plurality of terrestrial cells 20A in the large zone cell 10A is created (S103). . The direction of arrival of the MR of each UE can be calculated, for example, based on the location information of the antenna of the terrestrial cell base station 20 and the location information of the current location of each UE (for example, GNSS location information).

Next, based on the coverage area estimation map of the entire ground cell, management device 30 determines whether other ground cells are continuous in the outer boundary area of ground cell 20A for each of a plurality of ground cells 20A located within large zone cell 10A. A non-continuous boundary area is detected, the ratio of the circumference L2 of the discontinuous boundary area to the circumference L of the outer boundary area of the ground cell 20A is determined, and the ground cell ( A large zone cell (frequency activated cell) 20A' is identified (S104).

Next, the management device 30 instructs the terrestrial cell base station 20' of the large zone cell frequency activated cell 20A ' having the discontinuous boundary area of the predetermined ratio to select the large zone cell frequency activated cell 20A' as the frequency to be searched. Information on the frequency A (large zone cell frequency f _HAPS ) of the located large zone cell 10A is transmitted (S105).

Next, when the management device 30 receives the reception result of the signal of the large zone cell frequency f _HAPS from the terrestrial cell base station 20' that received the information of the large zone cell frequency f _HAPS (S106), Decide to include the information of the large zone cell frequency f _HAPS in the setting information to the frequency priority parameter of 20', and make an additional request requesting the addition of the information of the large zone cell frequency f _HAPS to the setting information to the frequency priority parameter. , to the terrestrial cell base station 20' (S108).

On the other hand, for the large zone cell frequency-inactivated cells 20A (terrestrial cells other than the large zone cell frequency-activated cells 20A') that do not have a predetermined ratio of discontinuous boundary areas, the management device 30 sets the frequency priority parameter to It decides not to include the information of the large zone cell frequency f _HAPS in the configuration information. By not including the information of the large zone cell frequency f _HAPS , it is possible to avoid unnecessary frequency searches by the UE and prevent the occurrence of a measurement gap that stops radio communication with the terrestrial cell in which the UE is located.

When the terrestrial cell base station 20' receives the request to add the information of the large zone cell frequency f _HAPS from the management device 30, it adds the information of the large zone cell frequency f _HAPS to the setting information of the frequency priority parameter (S109), and The control information including the setting information of the frequency priority parameter is notified to the UE 42' (S110).

Upon receiving the above control information from the terrestrial cell base station 20', the UE 42' receives signals from surrounding base stations for multiple frequencies including the large zone cell frequency f _HAPS based on the setting information for the frequency priority parameter. do. Then, the UE 42' is handed over from the large zone cell frequency-activated cell 20A' to the large zone cell or another terrestrial cell 20A with respect to the large zone cell base station 10 based on the signal reception results from the surrounding base stations. processing (S111), or reselection processing for reselecting the large zone cell frequency activated cell 20A' with the terrestrial cell base station 20 of the large zone cell frequency activated cell 20A' (S111 ) . ' ).

Note that in the control sequence of FIG. 2, steps S101 to S110 may be repeatedly executed at regular intervals. For example, at regular intervals, the MR of the terrestrial cell 20A of a specific frequency is aggregated, based on the aggregated result, the terrestrial cell 20A' having a discontinuous boundary area of a predetermined ratio is identified, and the frequency of the terrestrial cell 20A' is identified. Information on the large zone cell frequency f _HAPS may be added to the priority parameter setting information.

Table 1 shows an example of frequency priority parameters and UE 42, 42' behavior in the large zone cell frequency deactivated cell 20A and the large zone cell frequency activated cell 20A' respectively. In the example of Table 1, large zone cell frequency deactivated cell 20A and large zone cell frequency activated cell 20A′ each include two frequency f ₁ and f ₂ cells and are adjacent to a terrestrial cell at frequency f ₃ . . Also, the frequency priority parameter when the UEs 42 and 42' are connected is the handover parameter (MeasConfig). A frequency priority parameter (SIB5) is a frequency priority parameter during idle when the wireless connection is disconnected.

FIGS. 3(a) to 3(c) show the creation of a coverage area estimation map by a plurality of ground cells 20A using mutually different frequencies (f ₁ , f ₂ , f ₃ ) (see step S103 of the control in FIG. 2 described above). ) is an explanatory diagram showing an example. In this example, as shown in FIG. 3A, a plurality of terrestrial cells 20A with three mutually different frequencies (f ₁ , f ₂ , f ₃ ) are formed in the same area 200 . Each terrestrial cell 20A is an area where the reception strength is equal to or greater than a predetermined out-of-range threshold value X [dBm], as shown in FIG. 3(c). It is composed of an area 20A(2) and a weak electric field area 20A(3). The weak electric field area 20A(3) corresponds to the outer boundary area of the ground cell 20A described above, and the area outside thereof is the out-of-service area 20A(4). By superimposing the terrestrial cells 20A of the three frequencies (f ₁ , f ₂ , f ₃ ) in FIG. An area estimation map can be created.

FIG. 4 is an explanatory diagram showing an example of a calculation method of the ratio (L2/L) of the perimeter L2 of the discontinuous boundary area to the total perimeter L of the outer perimeter boundary area 20C of the ground cell 20. As shown in FIG. Of the entire peripheral length L of the outer perimeter boundary area 20C of the ground cell 20A in the figure, the portion of length L1 where the other adjacent ground cells 20A overlap is the continuous boundary area, and the other ground cells 20A overlap. The portion of length L2 that is not covered is the discontinuous boundary area. The ratio [%] of the perimeter L2 of the discontinuous boundary area to the perimeter L of the outer boundary area of the ground cell 20A in step S104 of the control in FIG. 2 can be estimated by calculating, for example, L2/L. .

It should be noted that the determination of whether or not the terrestrial cell includes a predetermined ratio of discontinuous boundary areas is based on a specific index value in the KPI (Key Performance Indicator ) such as the HO success rate and throughput obtained for the terrestrial cell. you can go

As described above, according to the present embodiment, by detecting a discontinuous boundary area where other terrestrial cells are not continuous among a plurality of small-sized terrestrial cells (second cells) 20 in the overlay cell configuration, Changes in operational status can be estimated. Moreover, only the terrestrial cell 20' including the discontinuous boundary area among the plurality of terrestrial cells 20 based on the detection result of the discontinuous boundary area that can estimate the change in the operation status of the wireless network Information about the frequency A (f _HAPS ) of the large zone cell 10A can be included in the setting information of the frequency priority parameter. Therefore, it is possible to prevent depletion of radio resources in the large zone cell 10A even when the operational status of the radio network in the overlay cell configuration changes.

In this embodiment, the case of the overlay configuration of the large zone cell 10A and the terrestrial cell 20A has been described, but the present invention is not limited to this configuration, and can be applied to an overlay configuration of a plurality of cells of different sizes. be able to.

Further, in the present embodiment, although described on the premise of application to LTE / LTE-Advanced, OFDM (orthogonal frequency division multiplexing) downlink wireless communication similar to LTE / LTE-Advanced, wireless communication frame, OFDM The concept of the present invention can be applied to any system as long as it uses symbols and the like, and is not limited to the configurations of the transmitter and receiver shown in this embodiment.

Also, the processing steps and components of the mobile communication system, large zone cell base station (first cell base station), terrestrial cell base station (second cell base station) and user terminal equipment (mobile station) described herein. can be implemented by various means. For example, these processes and components may be implemented in hardware, firmware, software, or any combination thereof.

For hardware implementation, means such as processing units used to implement the above steps and components in an entity (e.g., various wireless communication devices, Node Bs, terminals, hard disk drives, or optical disk drives) are: One or more of an application specific integrated circuit (ASIC), digital signal processor (DSP), digital signal processor (DSPD), programmable logic device (PLD), field programmable gate array (FPGA), processor , 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 implementations, means such as processing units used to implement the above components may be programs (e.g., procedures, functions, modules, instructions) that perform the functions described herein. , etc.). In general, any computer/processor readable medium tangibly embodying firmware and/or software code means, such as a processing unit, used to implement the above steps and components described herein. may be used to implement For example, firmware and/or software code may be stored in memory and executed by a computer or processor, such as in a controller. The memory may be implemented within the computer or processor, or external to the processor. The firmware and/or software code may also be, for example, random access memory (RAM), read only memory (ROM), non-volatile random access memory (NVRAM), programmable read only memory (PROM), electrically erasable PROM (EEPROM). ), FLASH memory, floppy disk, compact disk (CD), digital versatile disk (DVD), magnetic or optical data storage devices, etc. good. The code may be executed by one or more computers or processors and may cause the computers or processors to perform certain aspects of the functionality described herein.

Also, the medium may be a non-temporary recording medium. Also, the code of the program is not limited to a specific format as long as it can be read and executed by a computer, processor, or other device or machine. For example, the program code may be source code, object code, or binary code, or may be a mixture of two or more of these codes.

Moreover, the description of the embodiments disclosed herein is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications 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. This disclosure, therefore, is not to be limited to the examples and designs described herein, but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

10 large zone cell base station (first base station, relay communication station)
10A large zone cell (first cell)
15 communication relay device 20, 20' terrestrial cell base station (second base station)
20A ground cell (second cell)
20A' terrestrial cell having a discontinuous border area with a predetermined ratio 30 management device 41, 42, 42' UE (mobile station)
51, 52 core network 61, 62 core network device 70 gateway station

Claims (12)

A management device for managing setting of a frequency priority parameter of the second cell in an overlay cell configuration in which a first cell and a plurality of second cells having a cell size smaller than the first cell are mixed,
means for obtaining from base stations of the plurality of second cells measurement reports including received strengths of mobile stations located in the plurality of second cells;
Based on the measurement reports obtained from the base stations of the plurality of second cells, for each of the plurality of second cells located within the first cell, another second cell is located in the outer boundary area of the second cell. means for detecting non-contiguous discontinuous boundary areas;
means for determining whether or not to include information about the frequency of the first cell in the setting information of the frequency priority parameter to be set for the second cell, based on the detection result of the discontinuous boundary area. A management device characterized by: The management device of claim 1,
For each of the plurality of second cells located within the first cell, determining whether or not a ratio of the circumference of the discontinuous boundary area to the circumference of the outer boundary area of the second cell is equal to or greater than a predetermined threshold. judge,
Including the frequency information of the first cell in the setting information of the frequency priority parameter for the second cell in which the ratio of the perimeter of the discontinuous boundary area is equal to or greater than the threshold,
The management device, wherein information about the frequency of the first cell is not included in the setting information of the frequency priority parameter for the second cell in which the ratio of the perimeter of the discontinuous boundary area is smaller than the threshold value. 3. The management device according to claim 1, wherein said management device is a network management system (NMS) for managing a mobile communication network including said first cell base station and said plurality of second cell base stations. A management device characterized by: A communication system,
A management device according to any one of claims 1 to 3, a first cell base station forming said first cell, and a plurality of second cell base stations forming said plurality of second cells. communication system. In the communication system of claim 4,
A communication system, wherein the first cell base station is a base station in which at least an antenna is installed on a flying object capable of moving or flying in the sky. In the communication system according to claim 4 or 5,
A communication system, wherein the second cell base station forms a plurality of second cells using a plurality of mutually different frequencies in the same area. In the communication system according to any one of claims 4 to 6,
A communication system, wherein all or some of the plurality of second cell base stations use different frequencies. In the communication system according to any one of claims 4 to 7,
The plurality of second cell base stations are a second cell base station on the same frequency that uses the same frequency as the first cell base station, and a second cell base station on a different frequency that uses a frequency different from that of the first cell base station. and a communication system. In the communication system of claim 8,
The second cell base station of the same frequency is a small cell base station installed on the ground or on the water, or a small cell base station having at least an antenna installed on an aircraft flying at a lower altitude than the first cell base station. can be,
The second cell base station with a different frequency is a macrocell base station installed on the ground or on the water, or a macrocell base station having at least an antenna installed in an aircraft flying at a lower altitude than the first cell base station,
A communication system, wherein the first cell base station is a base station in which at least an antenna is arranged at the same or higher position than the second cell base station. In the communication system of claim 8,
The communication system, wherein the first cell base station is a macro cell base station, and the second cell base station of the same frequency and the second cell base station of the different frequency are small cell base stations. A method for managing setting of frequency priority parameters of the second cell in an overlay cell configuration in which a first cell and a plurality of second cells having a cell size smaller than the first cell are mixed, the method comprising:
obtaining measurement reports including received strengths of mobile stations located in the plurality of second cells from the base stations of the plurality of second cells;
Based on the measurement reports obtained from the base stations of the plurality of second cells, for each of the plurality of second cells located within the first cell, another second cell is located in the outer boundary area of the second cell. detecting a discontinuous boundary area that is not continuous;
determining whether or not to include frequency information of the first cell in frequency priority parameter setting information to be set in the second cell, based on the detection result of the discontinuous boundary area. A method characterized by A computer or processor provided in a management device for managing setting of frequency priority parameters of said second cells in an overlay cell configuration in which first cells and a plurality of second cells having a cell size smaller than said first cells coexist A program that runs in
program code for obtaining measurement reports including received strengths of mobile stations located in the plurality of second cells from the base stations of the plurality of second cells;
Based on the measurement reports obtained from the base stations of the plurality of second cells, for each of the plurality of second cells located within the first cell, another second cell is located in the outer boundary area of the second cell. program code for detecting discontinuous discontinuous boundary areas;
a program code for determining whether or not to include frequency information of the first cell in setting information of a frequency priority parameter to be set in the second cell based on the detection result of the discontinuous boundary area; A program characterized by comprising:

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