JP2011130354A - Base station apparatus and cell identifier assignment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically form unique cell identifiers for peripheral cells of a neighbor base station apparatus, and to assign the formed cell identifiers, concerning a base station apparatus and a cell identifier assignment method in a mobile communication system. <P>SOLUTION: A base station apparatus 100 includes a cell identifier management section 54 configured to manage cell identifiers of peripheral cells of a neighbor base station apparatus. The cell identifier management section 54 obtains cell identifiers of peripheral cells of a neighbor base station apparatus from the neighbor base station apparatus, and when a duplicate cell identifier is detected among cell identifiers of peripheral cells of the neighbor base station apparatus, an instruction to change the cell identifier of lower priority to a different cell identifier is notified to the base station apparatus of lower priority based on a predetermined priority of the base station apparatus or each cell to which the duplicate cell identifier is assigned. On receipt of the notification, the base station apparatus changes the duplicated cell identifier to a different cell identifier according to the instruction, and assigns the changed cell identifier to the peripheral cell. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a base station apparatus and a cell identifier allocation method in a mobile communication system.

  A mobile communication service area is formed by a set of cells (small radio zones) covered by each base station. When a user terminal moves between cells, handover is performed between the base stations covering the cells. Through this process, the mobile communication service without interruption is provided to the user terminal.

  Each base station is laid so as not to cause radio wave interference and inconsistencies in setting values with neighboring cells of adjacent base stations. Therefore, in the past, after designing the arrangement of each base station in advance and determining various setting values such as the identifier (PCID: Physical Cell ID) of each cell in advance, experimentally check the radio wave interference situation at the actual installation location. It is common to measure and tune and lay.

  Such new establishment of base stations and cell layout design are not simple and require a lot of time and labor for work. As an improvement measure, 3GPP (3rd Generation Partnership Project) recommendation recommends that it can be set by plug-and-play, but cells with the same cell identifier are generated in neighboring cells of neighboring base stations. There is a problem such as that may be.

  In addition, when there are a plurality of manufacturers / distributors who provide base stations to telecommunications carriers, duplicate cell identifiers are not generated between neighboring cells of neighboring base stations even in base stations of different manufacturers / distributors. The operation of automatically assigning the cell identifier is required. In addition, since roaming operation across different carriers is normally performed, cell identifiers are automatically generated between neighboring carriers without causing duplicate cell identifiers in neighboring cells. A method of allocating automatically is required.

  The 3GPP LTE (3rd Generation Partnership Project Long Term Evolution) standard refers to automatic allocation of cell identifiers as a SON (Self Organized Network) function, but a specific implementation method is not yet defined. Therefore, each telecommunications carrier and each manufacturer / distributor aim to realize a unique SON function. However, when each manufacturer / distributor provides the SON function, the cell identifier according to each manufacturer / distributor's own method. Will be automatically assigned.

  In this case, if each base station apparatus rewrites the cell identifier by a unique method based on the cell identifier information from the mobile terminal, the cell identifier may be allocated in duplicate. That is, the same cell identifier may be assigned to the neighboring cells of two base station devices adjacent to a certain base station device.

  In order to solve this problem, a function of automatically installing a server that automatically performs the work that has been done manually, accessing the server, and exchanging information between base station apparatuses is implemented. However, since a server such as an EMS (Element Management System) is installed for each telecommunications carrier, the base station apparatus performs a cell identifier assignment operation when straddling the telecommunications carrier.

  The case of overlapping cell identifiers can be broadly divided into the following two cases. In the first case, a cell that has not been recognized as a neighboring cell of an adjacent base station until then becomes a neighboring cell of the neighboring base station due to the newly installed base station apparatus, and the same cell identifier is duplicated. is there.

  In the second case, the base station apparatus or cell is reduced due to a failure or the like, so that the adjacent cell expands the cover area, and the cell that has not been recognized as the neighboring cell of the adjacent base station until then is the adjacent base station. This is a case where the same cell identifier is duplicated.

  The first case will be specifically described with reference to FIG. 9. For example, the local cell of the first base station apparatus eNB # 1 includes cell identifier 1 (PCID = 1), cell identifier 2 (PCID = 2) Cell identifier 3 (PCID = 3) is assigned. Then, across the out-of-service area, the cell of the second base station apparatus eNB # 2 has cell identifier 1 (PCID = 1), cell identifier 2 (PCID = 2), cell identifier 3 (PCID = 3) Is assigned. In this case, since the own station cells of the first and second base station apparatuses eNB # 1 and # 2 are not adjacent to each other, there is no problem even if the same cell identifier (PCID) is assigned.

  Also, the cell identifier 4 (PCID = 4) is allocated to the own station cell of the third base station apparatus eNB # 3, and the cell identifier 5 (PCID = 4) is assigned to the own station cell of the fourth base station apparatus eNB # 4. PCID = 5) is allocated, the cell identifier 6 (PCID = 6) is allocated to the own station cell of the fifth base station apparatus eNB # 5, and the own station cell of the sixth base station apparatus eNB # 6 is allocated. Is assigned a cell identifier 7 (PCID = 7).

  Here, when a new base station apparatus is newly installed in the out-of-service area, the cells of the first and second base station apparatuses eNB # 1 and # 2 adjacent to the newly installed base station apparatus installed in the out-of-service area are newly installed. The same cell identifier 1 (PCID = 1), cell identifier 2 (PCID = 2), and cell identifier 3 (PCID = 3) are allocated adjacent to the neighboring cells of the base station apparatus. Then, for a newly installed base station apparatus installed in an out-of-service area, duplicate cell identifier 1 (PCID = 1), cell identifier 2 (PCID = 2), cell identifier 3 (PCID = PCID = 3) will exist.

  The second case will be specifically described with reference to FIG. In FIG. 10, for example, cell identifier 1 (PCID = 1), cell identifier 2 (PCID = 2), and cell identifier 3 (PCID = 3) are allocated to the own station cell of the first base station apparatus eNB # 1. Yes. And the cell identifier 11 (PCID = 11) and the cell identifier 12 (PCID = 12) are allocated to the own station cell of the seventh base station device eNB # 7 adjacent to the first base station device eNB # 1. Yes.

  Moreover, the cell identifier 8 (PCID = 8), the cell identifier 9 (PCID = 9), and the cell identifier 10 are assigned to the own cell of the second base station device eNB # 2 adjacent to the seventh base station device eNB # 7. (PCID = 10) is assigned. The cell identifier 4 (PCID = 4) is assigned to the own cell of the third base station device eNB # 3 adjacent to the second base station device eNB # 2, and the own cell of the fourth base station device eNB # 4. Cell identifier 5 (PCID = 5), and cell identifier 6 (PCID = 6) is allocated to the own cell of the fifth base station apparatus eNB # 5.

  Further, the cell identifier 7 (PCID = 7) is assigned to the own station cell of the sixth base station apparatus eNB # 6 adjacent to the fourth base station apparatus eNB # 4, and the own station of the eighth base station apparatus eNB # 8. Assume that a cell identifier 11 (PCID = 11) is assigned to a cell.

  Here, if the cell of the cell identifier 10 (PCID = 10) of the second base station apparatus eNB # 2 is removed, the area of the cell of the cell identifier 10 (PCID = 10) is set to the adjacent cell identifier 11. (PCID = 11), cell identifier 12 (PCID = 12), and cell identifier 5 (PCID = 5) are expanded and covered.

  Then, the cell identifier 11 (PCID = 11) of the seventh base station device eNB # 7 adjacent to the fourth base station device eNB # 4 and the cell identifier 11 (PCID = 8) of the eighth base station device eNB # 8. 11) will overlap.

  As a method of centrally managing network identifiers by the identifier management device and assigning network identifiers to each base station device, the result of investigation for the base station device that can autonomously investigate the network identifier being used by the peripheral base station device There is known an identifier assigning method for selecting one of unused network identifiers from a group of network identifiers based on the above and setting it as the network identifier of the own station (see, for example, Patent Document 1).

  In addition, in the base station ID assignment, a technique for assigning an arbitrary ID from the ID table and then searching for and assigning an unused ID in the neighboring base station is known, for example, from Patent Document 2 below.

JP 2001-69151 A Japanese Patent Laid-Open No. 4-8022

  Manual setting work for assigning cell identifiers when newly installing or removing a base station device in a mobile communication system is not easy, requiring a lot of time and labor, and assigning the same cell identifier to neighboring cells of an adjacent base station device There is a possibility that. The present invention makes it possible to automatically generate and assign non-overlapping cell identifiers to neighboring cells of an adjacent base station device when a base station device is newly installed or removed.

  A base station apparatus as an embodiment for solving the above problem includes a cell identifier management unit that manages cell identifiers of neighboring cells of the neighboring base station apparatus, and the cell identifier managing unit includes cells of neighboring cells of the neighboring base station apparatus. When an identifier is obtained from the adjacent base station device and a duplicate cell identifier is detected among cell identifiers of neighboring cells of the neighboring base station device, the base station device or cell to which the duplicate cell identifier is assigned Based on the predetermined priority, an instruction to change the cell identifier having the lower priority to a different cell identifier is notified to the base station apparatus having the lower priority.

  Cell identifiers that overlap between neighboring cells of adjacent base station devices when the coverage area of the cell is changed when a new base station device or cell is installed, or when a cell is removed due to a failure or cell failure of the base station device. When this occurs, it becomes possible to automatically generate and assign cell identifiers without duplication, thereby reducing cell design work and simplifying maintenance.

It is a figure which shows the structural example of a base station apparatus. It is a figure which shows the example of allocation of the cell identifier at the time of the new installation of a base station apparatus. It is a figure which shows the operation | movement sequence example of the cell identifier allocation at the time of the new installation of a base station apparatus. It is a figure which shows the example of allocation of the cell identifier at the time of cell reduction. It is a figure which shows the example of an operation | movement sequence of the cell identifier allocation at the time of cell reduction. It is a figure which shows the example of an operation | movement sequence of the cell identifier allocation at the time of cell reduction. It is a figure which shows an example of the priority determination at the time of the duplicate cell identifier detection. It is a figure which shows the example of a sequence of the operation | movement which received the change instruction | indication of the cell identifier, and the response. It is a figure which shows the case of cell identifier duplication at the time of the new installation of a base station apparatus. It is a figure which shows the case of cell identifier duplication at the time of cell reduction.

  A configuration example of the disclosed base station apparatus is shown in FIG. The base station apparatus (eNB) 100 includes a remote radio unit (RRH: Remote RF Head) 1, a baseband signal processing unit (BB) 2, a wired transmission path interface unit (HWY-IF) 3, a switch unit (SW) 4, A main control unit (CNT) 5 and a memory 6 are provided. The main control (CNT) unit 5 includes a radio protocol termination unit 51, a call processing control unit 52, an interface termination unit 53, and a cell identifier (PCID) management unit 54.

  The cell identifier (PCID) management unit 54 is connected to a wired transmission line interface unit (e.g., a peripheral base station device (eNB), a maintenance management system (OPS), an EMS (Element management System), or an MME (Mobility Management Entity). The peripheral base station apparatus (eNB) list (white list) is acquired via the (HWY-IF) 3 and the interface termination unit 53.

  In addition, the cell identifier (PCID) management unit 54, when the mobile terminal is handed over, from the mobile terminal to a remote radio unit (RRH) 1, a baseband signal processing unit (BB) 2, a radio protocol termination unit 51, a call processing control unit Via 52, cell information including the cell identifier of the cell in which the mobile terminal was located is received.

  The base station apparatus exchanges cell information of neighboring cells with neighboring base station apparatuses. If a cell identifier that overlaps the cell identifiers of neighboring cells covered by a plurality of adjacent base station devices and the own base station device exists, a cell identifier different from the cell identifier is generated and assigned to the neighboring cell.

  The cell identifier assignment triggers are as follows: (1) When cell information is notified from a mobile terminal, (2) When a base station device is installed (at power-on), (3) Base station device due to cell failure or base station device failure, etc. (4) When a cell identifier exchange instruction is received from another base station apparatus, or the like.

  As a method of automatically assigning cell identifiers, each base station device communicates with neighboring base station devices and cell identifiers of neighboring cells of each base station device, and cell identifiers that overlap the cell identifiers of neighboring cells of neighboring base stations are If it exists, a cell identifier to be allocated is determined based on a predetermined priority.

  Cell identifiers are automatically allocated by a combination of the above-described allocation trigger and automatic allocation method. In this embodiment, a procedure for changing the duplicate cell identifier when the duplicate of the cell identifier is detected mainly at the above-described triggers (2) and (3) will be described.

  FIG. 2 shows an example of a cell identifier (PCID) assignment operation when a base station apparatus is newly installed. FIG. 3 shows an operation sequence of this operation example. This operation example shows a case where the seventh base station apparatus eNB # 7 is newly installed in the out-of-service area in the example of the cell arrangement shown in FIG. 9 described above. In this case, the cell identifiers 1, 2, and 3 (PCID = 1, 2, 3) of the neighboring cells of the second base station device eNB # 2 are changed to the first by setting the seventh base station device eNB # 7. It overlaps with cell identifiers 1, 2, 3 (PCID = 1, 2, 3) of neighboring cells of the base station apparatus eNB # 1.

  Therefore, first, the seventh base station apparatus (eNB # 7) randomly assigns a temporary cell identifier (temporary PCID) to its neighboring cells at the time of installation (power on) (3-1). The seventh base station apparatus (eNB # 7) acquires a peripheral base station apparatus (eNB) list from the maintenance management system (OPS) as the peripheral information (3-2). Thereby, the 7th base station apparatus (eNB # 7) acquires the information on the 1st and 2nd base station apparatuses (eNB # 1, # 2).

  The seventh base station apparatus (eNB # 7) is an identifier of the own station cell of the base station apparatus (eNB # 1, # 2, # 5) listed in the acquired neighboring base station apparatus (eNB) list, Exchange of additional information such as cell identifiers and priorities of neighboring cells of the base station apparatus (eNB) is performed (3-3, 3-4, 3-5). At this time, not only the list of cell identifiers (PCID) of the own station cell covered by itself (hereinafter referred to as “cell list”) but also the cell list of its own neighboring base station apparatus (eNB) is exchanged. .

  The seventh base station apparatus (eNB # 7) determines a non-overlapping cell identifier (PCID) based on the cell list exchanged with the neighboring base station apparatuses (eNB # 1, # 2, # 5), and The cell identifier (PCID) of the cell covered by is assigned. In this example, 11 and 12 are assigned as cell identifiers (PCID) (3-6).

  As the seventh base station device (eNB # 7) newly generates a cell, the base station devices (eNB # 1, # 2, # 5) adjacent to the seventh base station device (eNB # 7) The same cell identifier (PCID) may occur in the cell identifiers (PCID) of neighboring cells. In this example, the duplication of the cell identifiers 1, 2, 3 (PCID = 1, 2, 3) is detected in the neighboring cells of the cell identifiers 11, 12 (PCID = 11, 12) (3-7).

When duplication of the cell identifier (PCID) is detected, the priority of the cell identifier to be changed is determined based on priority information such as a priority determination element as shown in Table 1, for example, and the cell identifier (PCID) to be assigned is determined. (3-8). This priority determining element can be appropriately customized by a communication carrier operating the mobile communication system.

  In Table 1, since an element having a low priority has little influence on the communication service even if the cell identifier (PCID) is changed, it is determined to change the cell identifier (PCID) of a cell having a low priority. On the other hand, for the element having a high priority, if the cell identifier (PCID) is changed, the influence is large. Therefore, the cell identifier (PCID) of the cell having the high priority is determined to maintain the current value.

  In order to change the value of the duplicate cell identifier (PCID), the base station apparatus (eNB) that needs to be changed based on the priority is notified to the duplicate cell identifier (PCID) and the change notification or the cell identifier after the change ( PCID) candidate list or non-permissible cell identifier (PCID) list. In the example of FIG. 3, the example which notifies the change instruction | indication of cell identifier 1,2,3 (PCID = 1,2,3) to a 2nd base station apparatus (eNB # 2) is shown (3-9) .

  The second base station apparatus (eNB # 2) that has received the notification of the change instruction uses the cell identifier (for example, PCID = 8, 9, 10) changed according to the change instruction as the seventh base station apparatus (eNB # 7). ) (3-10). The seventh base station apparatus (eNB # 7) exchanges again the cell list including the changed cell identifier (PCID) value with the neighboring base station apparatuses (eNB # 1, # 2, # 5) (3 -11, 3-12, 3-13).

  If the same cell identifier (PCID) does not exist in the exchanged cell list, the seventh base station apparatus (eNB # 7) determines the temporarily assigned cell identifier (temporary PCID) as the cell identifier. After the cell identifier is changed, the cell list is exchanged with neighboring base station apparatuses at regular intervals to check whether the cell identifier has been changed.

  In addition, if the cell identifier change operation is simultaneously executed in each base station device, it becomes impossible to change the cell identifier normally, so during the execution of the cell identifier change operation in the surrounding base station device, It is configured to wait for the execution of the cell identifier change operation in the own base station apparatus.

  Next, an example of the cell identifier assignment operation at the time of cell reduction will be described with reference to FIGS. This operation example is an example in the case where the neighboring cell (PCID = 10) of the second base station apparatus eNB # 2 is reduced in the cell arrangement example shown in FIG. In this case, the cell with the cell identifier 11 (PCID = 11), the cell identifier 12 (PCID = 12), and the cell identifier 5 (PCID = 5) is expanded to cover the reduced area.

  Thereby, the cell identifier 11 (PCID = 11) of the seventh base station device eNB # 7 adjacent to the fourth base station device eNB # 4 and the cell identifier 11 (PCID of the eighth base station device eNB # 8) = 11) will overlap.

  The second base station apparatus eNB # 2 notifies the neighboring base station apparatuses eNB # 4, eNB # 3, eNB # 5, eNB # 7 of the occurrence of a failure in its own neighboring cell (PCID = 10) (FIG. 5-5-1,5-2,5-3,5-4). The fourth base station apparatus (eNB # 4) that has received the notification of the occurrence of the failure acquires a neighboring base station apparatus (eNB) list from the maintenance management system (OPS) (5-5). Thereby, the 4th base station apparatus (eNB # 4) is the 2nd, 3rd, 5th, 6th, 7th, 8th base station apparatus (eNB # 2, # 3, # 5, # 6). , # 7, # 8).

  The fourth base station apparatus (eNB # 4) is a base station apparatus (eNB # 2, # 3, # 5, # 6, # 7, # 8) that is listed in the acquired neighboring base station apparatus (eNB) list. ) And additional information such as cell identifiers and priorities of neighboring cells of the base station apparatus (eNB) are exchanged (5-6 to 5-11).

  The 4th base station apparatus (eNB # 4) updates the cell list of the surrounding cell of the cell of the cell identifier 5 (PCID = 5) by said exchange (5-12). In the fourth base station apparatus (eNB # 4), based on the updated cell list, the same cell identifier 11 (PCID = 11) is duplicated in the cell identifier 5 (PCID = 5) neighboring cell. Is detected (5-13).

  A 4th base station apparatus (eNB # 4) starts the operation | movement which changes a cell identifier by the detection of a duplicate cell identifier. However, in order to prevent the cell identifier changing operation from being simultaneously executed in each base station apparatus, for the neighboring base station apparatuses (eNB # 2, # 3, # 5, # 6, # 7, # 8) Then, it is notified that the operation of changing the cell identifier of the neighboring cell is being executed (6-1 to 6-6).

  A 4th base station apparatus (eNB # 4) determines the priority of the cell identifier which needs a change based on the acquired information (6-7). 4 to 6, the cell identifier 11 (PCID = 11) of the seventh base station apparatus (eNB # 7) and the cell identifier 11 (PCID = 11) of the eighth base station apparatus (eNB # 8). ) And, as a result of the determination, an instruction to change the cell identifier 11 (PCID = 11) is given to the eighth base station apparatus (eNB # 8) (6-8).

  In accordance with the change instruction, the eighth base station apparatus (eNB # 8) changes the cell identifier 11 (PCID = 11) to the cell identifier 13 (PCID = 13), and the changed cell identifier 13 (PCID = 13) is notified to the fourth base station apparatus (eNB # 4) (6-9). The fourth base station apparatus (eNB # 4) transmits the cell list including the changed cell identifier 13 (PCID = 13) notified from the eighth base station apparatus (eNB # 8) and the additional information to the periphery. To the base station apparatus (eNB # 2, # 3, # 5, # 6, # 7, # 8) (6-10-6-15).

  FIG. 7 shows an example of priority determination when a duplicate cell identifier (PCID) is detected. For example, the number of calls in a call between the base station apparatus eNB # A and the base station apparatus eNB # B is compared (7-1). When the base station apparatus eNB # A has a larger number of calls during a call, the base station apparatus eNB # A determines that the priority is higher, and sets the cell identifier (PCID) of the base station apparatus eNB # B. Change (7-5).

  Furthermore, operation time is compared with base station apparatus eNB # A and base station apparatus eNB # B (7-2). When the base station apparatus eNB # A has a longer operation time, it is determined that the base station apparatus eNB # A has higher priority, and the cell identifier (PCID) of the base station apparatus eNB # B is changed ( 7-5).

  Furthermore, the number of accommodated cells is compared between the base station apparatus eNB # A and the base station apparatus eNB # B (7-3). When the base station apparatus eNB # A has more cells, the base station apparatus eNB # A determines that the priority is higher and changes the cell identifier (PCID) of the base station apparatus eNB # B ( 7-5).

  Further, the base station apparatus eNB # A and the base station apparatus eNB # B compare the priority determination elements n other than those in Table 1 (7-4). When the priority of the priority determining element n is higher in the base station apparatus eNB # A, the base station apparatus eNB # A determines that the priority is higher, and the cell identifier of the base station apparatus eNB # B ( (PCID) is changed (7-5).

  When it is determined in the above determinations 7-1 to 7-4 that the base station apparatus eNB # B has higher priority, the cell identifier (PCID) of the base station apparatus eNB # A is changed ( 7-6). When the base station apparatus whose cell identifier (PCID) is to be changed is determined, a duplicate list is created or updated (7-7). And the change of a cell identifier (PCID) is instruct | indicated with respect to the base station apparatus which should change a cell identifier (PCID) (7-8).

  FIG. 8 shows a sequence example of an operation in which a cell identifier (PCID) change instruction and a response to the change instruction are received. FIG. 8A shows an example of an operation sequence of the base station apparatus that has received a cell identifier (PCID) change instruction. The base station apparatus receives a cell identifier (PCID) change instruction (8-1), creates or updates a duplicate list (8-2), and updates a cell list of neighboring cells (8-3). A non-overlapping cell identifier (PCID) is selected based on the cell list (8-4).

  And the selected cell identifier (PCID) is notified to an adjacent base station apparatus (eNB) (8-5), and the response with respect to the change instruction | indication of a cell identifier (PCID) is transmitted (8-6). FIG. 8B shows an example of an operation sequence of the base station apparatus that has received the response to the change instruction of the cell identifier (PCID). Upon receiving the cell identifier (PCID) change instruction response (8-7), the base station apparatus updates the cell list of the neighboring cells (8-8).

  As described above, in this base station apparatus, the cell list storing the cell identifier (PCID) of the neighboring cell covered by the own apparatus, the cell list of the neighboring base station apparatus, and its additional information are exchanged with other base station apparatuses. The cell identifier (PCID) is updated. A duplicate cell identifier (PCID) is detected based on the exchanged cell list.

  The cell list includes information on the cell identifier (PCID) of the cell covered by each base station apparatus, but adjacent information indicating which cell identifier (PCID) cell is adjacent to the cell of each cell identifier (PCID). Does not contain. The neighbor information of the cell identifier (PCID) can be updated with the handover information notified from the mobile terminal.

100 Base station apparatus (eNB)
1 Remote radio unit (RRH)
2 Baseband signal processor (BB)
3 Wired transmission line interface (HWY-IF)
4 Switch part (SW)
5 Main controller (CNT)
6 Memory 51 Wireless Protocol Termination Unit 52 Call Processing Control Unit 53 Interface Termination Unit 54 Cell Identifier (PCID) Management Unit

Claims (5)

In a base station apparatus of a mobile communication system,
A cell identifier management unit that manages cell identifiers of neighboring cells of the adjacent base station device,
The cell identifier management unit acquires a cell identifier of a neighboring cell of the neighboring base station device from the neighboring base station device, and detects a cell identifier overlapping between the neighboring cell identifiers of the neighboring base station device, Based on the predetermined priority of the base station apparatus or cell to which the overlapping cell identifier is assigned, an instruction to change the lower-priority cell identifier to a different cell identifier is given. The base station apparatus is notified to the base station apparatus. In the cell identifier allocation method of the neighboring cells of each base station device of the mobile communication system,
Obtaining cell identifiers of neighboring cells of the neighboring base station device from the neighboring base station device;
When a duplicate cell identifier is detected among cell identifiers of neighboring cells of the adjacent base station device, priority is given based on a predetermined priority of the base station device or cell to which the duplicate cell identifier is assigned. An instruction to change the lower cell identifier to a different cell identifier is sent to the lower priority base station apparatus,
A cell identifier assigning method comprising: a base station apparatus that has received an instruction to change to a cell identifier, changing a duplicate cell identifier to another cell identifier according to the instruction, and assigning the cell identifier to a neighboring cell of the base station apparatus.   When a base station device is newly installed in the mobile communication system, the newly installed base station device acquires a peripheral base station device list including information on neighboring base station devices of the base station device from a maintenance management system, and The cell identifier assigning method according to claim 2, wherein a cell identifier of a neighboring cell of an adjacent base station device registered in the neighboring base station device list is acquired from the neighboring base station device.   When a base station device or a cell is removed in the mobile communication system, the base station device that has recognized the removal has a maintenance management system that maintains a list of neighboring base station devices including information on neighboring base station devices of the base station device. The cell identifier assigning method according to claim 2, wherein the cell identifier of the neighboring cell of the neighboring base station device that is obtained from the neighboring base station device list is obtained from the neighboring base station device.   When detecting an overlapping cell identifier between cell identifiers of neighboring cells of the adjacent base station device and starting an operation of changing the cell identifier, the operation of changing the cell identifier is not performed simultaneously with other base station devices, 5. The cell identifier assigning method according to claim 2, wherein a cell identifier change operation is being executed to neighboring base station apparatuses.

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