Network management device and network management method

Abstract

An acquisition unit according to the present invention acquires advance notice information for giving advance notice of a state transition from a first state in which an Nth base station and an N-1th base station, from among N base stations (where N is an integer of 2 or more), are associated with a first tracking area that is assigned a first tracking area code, to a second state in which the Nth base station is associated with a second tracking area and the N-1th base station is associated with a third tracking area. A code determination unit according to the present invention references to the acquired advance notice information, and on the basis of a tracking area code of a tracking area with which at least one base station including the Nth base station is associated in the first state, said at least one base station being associated with the second tracking area in the second state, and on the basis of a tracking area code of a tracking area with which at least one base station including the N-1th base station is associated in the first state, said at least one base station being associated with the third tracking area in the second state, determines a second tracking area code to be assigned to the second tracking area and a third tracking area code to be assigned to the third tracking area. An output control unit according to the present invention outputs information related to the second tracking area code and the third tracking area code determined by the code determination unit.

Description

Network management device and network management method

[0001] The present invention relates to a network management device and a network management method.

[0002] Conventionally, communication terminals have been called (paging) using tracking areas (TAs) and tracking area lists (TA-Lists). For example, Patent Document 1 below enables the provision of a tracking area list to a communication terminal according to its movement characteristics. Area number acquisition means refers to history information storage means and acquires the number of tracking areas in which the terminal was present within a predetermined time. Determination means determines whether the acquired number of tracking areas is equal to or greater than a threshold. If the list generation means determines that the number of tracking areas is less than or equal to the threshold, it generates a first tracking area list based on the tracking areas stored in the history information storage means. If the transmission means determines that the number of tracking areas is less than or equal to the threshold, it transmits the first tracking area list to the terminal. If the transmission means determines that the number of tracking areas is greater than the threshold, it transmits a second tracking area list to the terminal.

[0003] Japanese Patent Publication No. 2022-003719

[0004] Telecommunications carriers may optimize the tracking areas and tracking area lists to which their subordinate base stations belong. This optimization is performed, for example, based on the movement status of communication terminals between base stations. Telecommunications carriers need to assign tracking area codes to the optimized tracking areas and tracking area list codes to the optimized tracking area lists. In this case, it is preferable that the tracking area codes and tracking area list codes assigned to each base station before optimization are highly consistent with the tracking area codes and tracking area list codes assigned to each base station after optimization, as this reduces the need to change network settings.

[0005] The present invention aims to efficiently assign tracking area codes to optimized tracking areas.

[0006] A network management device according to one aspect of the present invention includes: an acquisition unit that acquires notification information that foretells a transition in state from a first state in which the Nth base station and the (N-1)th base station belong to a first tracking area to which a first tracking area code has been assigned, to a second state in which the Nth base station belongs to a second tracking area and the (N-1)th base station belongs to a third tracking area, among N (N is an integer of 2 or more) base stations; a code determination unit that, referring to the acquired notification information, determines a second tracking area code to be assigned to the second tracking area and a third tracking area code to be assigned to the third tracking area based on the tracking area code of the tracking area to which at least one base station, including the Nth base station, belonged in the first state and which belongs to the second tracking area in the second state, and the tracking area code of the tracking area to which at least one base station, including the (N-1)th base station, belonged in the first state and which belongs to the third tracking area in the second state; and an output control unit that outputs information relating to the second tracking area code and the third tracking area code determined by the code determination unit.

[0007] A network management method performed by a computer according to one aspect of the present invention acquires notification information that foretells a transition in state from a first state in which the Nth base station and the (N-1)th base station belong to a first tracking area to which a first tracking area code has been assigned, to a second state in which the Nth base station belongs to a second tracking area and the (N-1)th base station belongs to a third tracking area, and, referring to the acquired notification information, determines a second tracking area code to be assigned to the second tracking area and a third tracking area code to be assigned to the third tracking area based on the tracking area code of the tracking area to which at least one base station, including the Nth base station, belonged in the first state and which belongs to the second tracking area in the second state, belonged in the first state, and the tracking area code of the tracking area to which at least one base station, including the (N-1)th base station, belonged in the first state and which belongs to the third tracking area in the second state, and outputs information relating to the second tracking area code and the third tracking area code.

[0008] The present invention aims to efficiently assign tracking area codes to optimized tracking areas.

[0009] This is a schematic diagram showing the communication system 1 managed by the network management device 10 according to the embodiment. This is a schematic diagram showing the paging method in the communication system 1. This is a schematic diagram showing the paging method in the communication system 1. This is a schematic diagram showing the paging method in the communication system 1. This is a schematic diagram showing the location registration signal RS. This is a schematic diagram showing an example of the first determination information. This is a block diagram showing the configuration of the network management device 10. This is a schematic diagram showing the status of the base station S belonging to the tracking area TA in the first state. This is a schematic diagram showing the status of the base station S belonging to the tracking area TA in the second state. This is a schematic diagram showing the first example of assigning the tracking area code TAC to the tracking area TA. This is a schematic diagram showing the second example of assigning the tracking area code TAC to the tracking area TA. This is a schematic diagram showing the advance information JY1. This is a table showing the count value of the status of belonging to the old TAC for each new TA. This is a schematic diagram showing the status of the base station S belonging to the tracking area list TL in the first state. This diagram schematically shows the status of a base station S's affiliation with the tracking area list (TL) in the second state. This is a schematic diagram showing advance information JY2. This is a table showing the count value of a base station whose TL has been changed when each TLC is assigned to each new TL. This is a schematic diagram showing advance information JY3. This is a schematic diagram showing advance information JY4. This is a table showing the density of affiliated base stations U. This is a flowchart showing the operation of the processing unit 105.

[0010] [Embodiment] [Overall Configuration] Figure 1 is a schematic diagram showing a communication system 1 managed by a network management device 10 according to an embodiment. The communication system 1 is a wireless communication system using, for example, LTE (Long Term Evolution). The communication system 1 includes a communication terminal 20, an MME (Mobility Management Entity) 30, and a plurality of base stations S (S1 to S5 are shown in Figure 1).

[0011] The communication terminal 20 is a mobile terminal such as a smartphone, an in-vehicle device, or an IoT (Internet of Things) device. The communication terminal 20 may also be referred to as User Equipment (UE).

[0012] Base station S constitutes a Radio Access Network (RAN) within the communication system 1, which performs wireless communication with communication terminals 20. Base station S may also be referred to as eNB (evolved Node B). The base stations S (S1 to S5) shown in Figure 1 communicate wirelessly with communication terminals 20 located within their respective communication areas E (E1 to E5), called cells. In a RAN, the communication areas E of numerous base stations S form the communication area of ​​the network. In this embodiment, only a few base stations S are shown, but in reality, hundreds to thousands of base stations S are deployed in the communication system 1.

[0013] MME30 is a node that constitutes the control plane (C-plane) of the core network (CN) of communication system 1. MME30 and each base station S are connected by a line called a backhaul. In Figure 1, the connection between MME30 and each base station S is not shown. MME30 performs various controls in communication system 1, such as registering communication terminals 20 in the core network and managing the movement of communication terminals 20.

[0014] Figures 2 to 4 are schematic diagrams showing the paging method in communication system 1. The upper part of Figures 2 to 4 schematically shows the communication areas E1 to E9 of base stations S1 to S9. As shown by the dotted line, it is assumed that the communication terminal 20 was located in the communication area E5 of base station S5 when the previous incoming call ended (end of call). In other words, the base station S that the communication terminal 20 last accessed was base station S5. On the other hand, as shown by the solid line, it is assumed that the communication terminal 20 is currently located in the communication area E1 of base station S1.

[0015] The lower section of Figures 2 to 4 schematically shows the tracking area TA to which base stations S1 to S9 belong. In the example shown, tracking area list TL1 (indicated as "TL1" in the figure) includes tracking areas TA1 to TA3. Tracking area TA1 accommodates base stations S1 to S3. In other words, base stations S1 to S3 belong to tracking area TA1. Base stations S1 to S3 belong to tracking area list TL1. Furthermore, tracking area TA2 accommodates base stations S4 to S6. Tracking area TA3 accommodates base stations S7 to S9.

[0016] Here, we consider the case where there is an incoming call request to the communication terminal 20. An incoming call request includes, for example, the reception of a message using a messaging application, and push notifications from SNS (Social Networking Service) applications, etc. When there is an incoming call request to the communication terminal 20, the MME 30 first causes the base station S5 that the communication terminal 20 last accessed to transmit a paging signal (see Figure 2). Hereinafter, the transmission of the paging signal by the base station S that the communication terminal 20 last accessed will be referred to as "first paging," and the paging signal transmitted in the first paging will be referred to as "first paging signal." "First paging" may also be referred to as "initial paging (first paging)." "First paging signal" may also be referred to as "initial paging signal." In the example shown in Figure 2, the communication terminal 20 is not located in the communication area E5 of base station S5, so the incoming call request via the first paging signal fails.

[0017] If the incoming call request using the first paging signal fails, the MME 30 causes all base stations S belonging to the tracking area TA to which base station S5 (the base station S that transmitted the first paging signal) belongs to transmit paging signals (see Figure 3). Hereinafter, the transmission of paging signals from all base stations S in the tracking area TA to which base station S that transmitted the first paging signal belongs will be called "second paging," and the paging signal transmitted in second paging will be called the "second paging signal." "Second paging" may also be referred to as "retransmission paging." "Second paging signal" may also be referred to as "retransmission paging signal." In the example shown in Figure 3, base station S5 belongs to tracking area TA2. Therefore, the second paging signal is transmitted to the communication areas E4 to E6 of base stations S4 to S6. In the example shown in Figure 3, the communication terminal 20 is not located in the communication areas E4 to E6 of base stations S4 to S6, so the incoming call request using the second paging signal fails.

[0018] If the incoming call request using the second paging signal fails, the MME 30 causes all base stations S in the tracking area list TL that includes tracking area TA2 (the tracking area TA that transmitted the second paging signal) to transmit paging signals (see Figure 4). Hereinafter, the transmission of paging signals from all base stations S in the tracking area list TL that includes the tracking area TA that transmitted the second paging signal will be referred to as "third paging," and the paging signal transmitted in third paging will be referred to as "third paging signal." "Third paging" may also be referred to as "re-retransmission paging." "Third paging signal" may also be referred to as "re-retransmission paging signal." In the example shown in Figure 4, tracking area TA2 is included in tracking area list TL1. Therefore, the third paging signal is transmitted to communication areas E1 to E9 of base stations S1 to S9 belonging to tracking area list TL1. In the example shown in Figure 4, the communication terminal 20 is located in communication area E1 of base station S1, so the incoming call request is successful with the third paging signal.

[0019] If the incoming call request also fails with the third paging signal, the MME 30 will cause the base stations S in the tracking area list TL1, as well as base stations S belonging to other tracking area lists TLs adjacent to tracking area list TL1 (for example, tracking area list TL2 shown in Figure 5), to transmit paging signals.

[0020] Thus, if the incoming call request at the communication terminal 20 fails, the range of paging signals transmitted expands, increasing the processing load at each base station S. For example, considering the number of paging signals transmitted by base stations S1 to S9, if the incoming call is successful in the first paging, the total number of paging signals transmitted is 1 (the first paging signal from base station S5). If the incoming call is successful in the second paging, the total number of paging signals transmitted is 4 (the first paging signal from base station S5 + the second paging signals from base stations S4 to S6). If the incoming call is successful in the third paging, the total number of paging signals transmitted is 13 (the first paging signal from base station S5 + the second paging signals from base stations S4 to S6 + the third paging signals from base stations S1 to S9).

[0021] Furthermore, as the number of communication terminals 20 in the communication system 1 increases, the number of paging signals transmitted increases, and the processing load at each base station S increases. If the processing load exceeds the processing capacity of base station S, communication failures may occur, and it is desirable to reduce the number of paging signals transmitted throughout the entire communication system 1. One example of a measure to reduce the number of paging signals transmitted is to set the tracking area TA such that even when a communication terminal 20 moves, it is more likely to be located within the same tracking area TA before and after the move.

[0022] Another signal generated by the communication system 1 is the location registration signal RS. The location registration signal RS is transmitted to the MME 30 when the communication terminal 20 moves between communication areas E of base stations S belonging to different tracking area lists TL.

[0023] Figure 5 is a schematic diagram showing the location registration signal RS. In addition to the base stations S1 to S9 belonging to tracking area list TL1 shown in Figure 2, etc., Figure 5 also shows base stations S10 to S14 belonging to tracking area list TL2 (indicated as "TL2" in the figure). Tracking area list TL2 includes tracking areas TA4 to TA5. Tracking area TA4 accommodates base stations S10 to S12. In other words, base stations S10 to S12 belong to tracking area TA4. Also, tracking area TA5 accommodates base stations S13 to S14.

[0024] As shown in Figure 5, when a communication terminal 20 moves from the communication area E9 of base station S9, which belongs to tracking area list TL1, to the communication area E10 of base station S10, which belongs to tracking area list TL2, the communication terminal 20 transmits a location registration signal RS to the MME 30. The location registration signal RS is transmitted to the MME 30 via base station S. Therefore, an increase in the number of location registration signals RS transmitted contributes to an increase in the processing load of base station S.

[0025] One possible strategy for transmitting the location registration signal RS is to increase the number of base stations S belonging to a single tracking area list TL. On the other hand, since the third paging signal is transmitted to all base stations S belonging to a single tracking area list TL, it is expected that the number of paging signals transmitted will increase as the number of base stations S belonging to a single tracking area list TL increases. In other words, there is a trade-off relationship between the number of location registration signals RS transmitted and the number of paging signals transmitted.

[0026] [Network Management Device] Figure 6 is a block diagram showing the configuration of the network management device 10. The network management device 10 is, for example, an information processing terminal owned by a business operator (telecommunications carrier) that manages and operates the communication system 1. If the optimization processing unit 111, which will be described later, is included in the network management device 10, the network management device 10 may be, for example, a quantum computer. Alternatively, the network management device 10 may be a computer that is connected to a quantum computer and capable of having the quantum computer execute specific processes.

[0027] The network management device 10 includes a display device 101, an input device 102, a communication device 103, a storage device 104, a processing device 105, and a bus 120 that connects these devices to each other.

[0028] The display device 101 is a display device that displays information to the outside (for example, various display panels such as a liquid crystal display panel or an organic EL display panel). The input device 102 is an input device that accepts input from the outside (for example, a keyboard, mouse, microphone, switch, button, or sensor). The display device 101 and the input device 102 may be configured as an integrated unit (for example, a touch panel). The communication device 103 has an interface that can connect to a network and communicates with other devices connected to the network using wireless or wired communication.

[0029] The storage device 104 is a recording medium that can be read by the processing device 105. The storage device 104 includes, for example, non-volatile memory and volatile memory. Non-volatile memory includes, for example, ROM (Read Only Memory), EPROM (Erasable Programmable Read Only Memory), and EEPROM (Electrically Erasable Programmable Read Only Memory). Volatile memory includes, for example, RAM (Random Access Memory). The storage device 104 stores program PG1. Program PG1 is a program for operating the network management device 10.

[0030] The processing unit 105 includes one or more CPUs (Central Processing Units). One or more CPUs are an example of one or more processors. Each of the processors and CPUs is an example of a computer. The processing unit 105 reads the program PG1 from the storage device 104. By executing the program PG1, the processing unit 105 functions as an optimization processing unit 111 (first belonging determination unit 111A, second belonging determination unit 111B), an acquisition unit 112, a code determination unit 113 (first code determination unit 113A, second code determination unit 113B), and an output control unit 114.

[0031] At least a portion of the optimization processing unit 111, acquisition unit 112, code determination unit 113 (first code determination unit 113A, second code determination unit 113B), and output control unit 114 may be composed of circuits such as a DSP (Digital Signal Processor), ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), and FPGA (Field Programmable Gate Array).

[0032] The optimization processing unit 111 optimizes the membership status of each of the N base stations S included in the communication system 1 to the tracking area TA and the tracking area list TL. In other words, the optimization processing unit 111 determines which of the multiple tracking area TAs and multiple tracking area list TLs each of the N base stations S belongs to. Hereinafter, when simply referred to as "membership status," it means the membership status of each of the N base stations S included in the communication system 1 to the tracking area TA and the tracking area list TL. Membership status is an example of a status.

[0033] The belonging state before optimization by the optimization processing unit 111 is called the first state, and the belonging state after optimization is called the second state. The optimization processing unit 111 generates notification information JY that foreshadows the transition of the belonging state from the first state to the second state. It can also be said that the notification information JY is output by the first belonging determination unit 111A and the second belonging determination unit 111B, which constitute the optimization processing unit 111. The notification information JY includes second belonging information that indicates which tracking area TA and tracking area list TL each of the N base stations S belongs to in the second state. Furthermore, the first belonging information that indicates which tracking area TA and tracking area list TL each of the N base stations S belongs to in the first state is known and is stored, for example, in the storage device 104 (not shown). Details of the processing of the optimization processing unit 111 will be described later.

[0034] In this embodiment, the network management device 10 includes an optimization processing unit 111, but other information processing devices other than the network management device 10 may also include an optimization processing unit 111. In this case, the network management device 10 acquires advance information JY from other information processing devices using an acquisition unit 112, which will be described later.

[0035] The acquisition unit 112 acquires notification information JY that indicates a transition in the belonging status from the first state to the second state. As described above, in this embodiment, the network management device 10 is equipped with an optimization processing unit 111, so the acquisition unit 112 acquires the notification information JY from the optimization processing unit 111. Also, if an information processing device other than the network management device 10 is equipped with an optimization processing unit 111, the acquisition unit 112 acquires the notification information JY from the other information processing device. The notification information JY includes, for example, notification information JY1 shown in Figure 9 and notification information JY2 shown in Figure 12. Details of the notification information JY will be described later.

[0036] The code determination unit 113 (first code determination unit 113A, second code determination unit 113B) assigns identification information to the tracking area TA and the tracking area list TL. The first code determination unit 113A and the second code determination unit 113B are examples of code determination units. In this embodiment, the identification information for identifying the tracking area TA in the network is called the "tracking area code TAC," and the identification information for identifying the tracking area list TL in the network is called the "tracking area list code TLC." The first code determination unit 113A determines the tracking area code TAC. The second code determination unit 113B determines the tracking area list code TLC.

[0037] First, the determination of the tracking area code TAC by the first code determination unit 113A will be explained. Figure 7 is a schematic diagram showing the status of a base station S's affiliation with a tracking area TA in the first state. Note that Figure 7 and others show a very simplified representation of the state of base station S in the communication system 1. As described above, the communication system 1 actually includes hundreds to thousands of base stations S, and tracking area TAs and tracking area lists TL are also formed in units of tens to hundreds.

[0038] Figure 7 schematically shows the tracking area TA to which each of the base stations S1 to S24 belongs. In the first state, base stations S1 to S6 belong to tracking area TA_101. In other words, tracking area TA_101 is composed of base stations S1 to S6. "TA_101" is not information that identifies a tracking area TA in the network (tracking area code TAC), but rather a convenient code for identifying multiple tracking area TAs in this embodiment. Similarly, base stations S7 to S12 belong to tracking area TA_102, base stations S13 to S18 belong to tracking area TA_103, and base stations S19 to S24 belong to tracking area TA_104.

[0039] Furthermore, in the first state, tracking area TA_101 is assigned the tracking area code TAC of "001" (hereinafter referred to as "TAC_001"). The tracking area code TAC is identification information that identifies tracking area TA in the network. The tracking area code TAC used in the network (the string used as the tracking area code TAC; the string may consist only of numbers) is maintained before and after optimization. That is, if "001" was used as the tracking area code TAC before optimization, "001" will be used as the tracking area code TAC after optimization, except in cases such as when the number of tracking area TAs decreases.

[0040] Tracking area TA_102 is assigned the tracking area code TAC "002" (hereinafter referred to as "TAC_002"). Tracking area TA_103 is assigned the tracking area code TAC "003" (hereinafter referred to as "TAC_003"). Tracking area TA_104 is assigned the tracking area code TAC "004" (hereinafter referred to as "TAC_004"). "TA_101", etc. can be rephrased as relative tracking area codes, and "TAC_001", etc. can be rephrased as absolute tracking area codes. The relative tracking area code identifies which group (tracking area TA) N base stations S belong to. The absolute tracking area code is the group name assigned to the group (tracking area TA) to which the base stations S belong.

[0041] For example, base station S1 belongs to tracking area TA with tracking area code TAC_001, and base station S24 belongs to tracking area TA with tracking area code TAC_004. This membership status is known to each base station S and the MME 30, as well as other components of the communication system 1.

[0042] Figure 8A is a schematic diagram showing the status of the base stations S's affiliation with the tracking area TA in the second state. The advance information JY acquired by the acquisition unit 112 includes information on which of the base stations S1 to S24 belong to the same tracking area TA in the second state. Specifically, as shown in Figure 8A, for example, in the second state, base stations S1 to S8 and S10 to S11 belong to tracking area TA_201. In other words, tracking area TA_201 is composed of base stations S1 to S8 and S10 to S11. Similarly, base stations S9, S12, S21, and S24 belong to tracking area TA_202, base stations S13 to S14 and S16 to S17 belong to tracking area TA_203, and base stations S15, S18 to S20 and S22 to S23 belong to tracking area TA_204.

[0043] For example, in Figures 7 and 8A, we focus on base station S24, which is the 24th base station S, and base station S23, which is the 23rd base station S, out of 24 base stations. In the first state shown in Figure 7, base stations S24 and S23 belong to tracking area TA_104, which is assigned tracking area code TAC_004. In the second state shown in Figure 8A, base station S24 belongs to tracking area TA_202, and base station S23 belongs to tracking area TA_204. 24 is just one example of N. Tracking area code TAC_004 is just one example of a first tracking area code. Tracking area TA_104 is just one example of a first tracking area. Tracking area TA_202 is just one example of a second tracking area. Tracking area TA_204 is just one example of a third tracking area.

[0044] In the example shown in Figure 8A, the number of tracking areas TA in the second state is four, which is the same as the number of tracking areas TA in the first state shown in Figure 7 (four). However, the number of tracking areas TA may increase or decrease between the first and second states as needed. If the number of tracking areas TA increases, tracking area codes TAC that were not used in the first state are added by the same number. Conversely, if the number of tracking areas TA decreases, tracking area codes TAC that were used in the first state are no longer used by the same number of times they were decreased.

[0045] The tracking areas TA_201 to TA_204 shown in Figure 8A do not have tracking area codes TAC assigned to them. Therefore, the first code determination unit 113A determines the tracking area codes TAC to be assigned to the tracking areas TA_201 to TA_204. More specifically, the first code determination unit 113A determines the tracking area codes TAC such that the number of base stations S1 to S24 in which the tracking area codes TAC in the first state differ from the tracking area codes TAC in the second state is minimized. This is because the more base stations S in which the tracking area codes TAC do not change between the first and second states, the higher the network stability. In other words, the higher the consistency of the tracking area codes TAC between the first and second states, the higher the network stability.

[0046] Figure 8B schematically shows a first example of assigning tracking area codes TAC to tracking area TA. In the example in Figure 8B, tracking area TA_201 is assigned tracking area code TAC_001, tracking area TA_202 is assigned tracking area code TAC_002, tracking area TA_203 is assigned tracking area code TAC_003, and tracking area TA_204 is assigned tracking area code TAC_004.

[0047] Comparing Figure 7 with Figure 8B, of the base stations S1 to S24, the tracking area code TAC to which the base station belongs changed for eight base stations S7 to S8, S10 to S11, S15, S18, S21, and S24, while the tracking area code TAC of the remaining 16 base stations S did not change.

[0048] Figure 8C schematically shows a second example of assigning tracking area codes TAC to tracking area TA. In the example in Figure 8C, tracking area TA_201 is assigned tracking area code TAC_004, tracking area TA_202 is assigned tracking area code TAC_003, tracking area TA_203 is assigned tracking area code TAC_002, and tracking area TA_204 is assigned tracking area code TAC_001.

[0049] Comparing Figure 7 and Figure 8C, the tracking area code TAC to which all 24 base stations S1 to S24 belong has changed. Therefore, comparing the assignment shown in Figure 8B with the assignment shown in Figure 8C, the assignment shown in Figure 8B is preferable. The first code determination unit 113A assigns the tracking area code TAC to each tracking area TA so that the assignment shown in Figure 8B is obtained. The processing of the first code determination unit 113A will be described in more detail below.

[0050] Figure 9 is a schematic diagram showing the notification information JY1. The notification information JY1 shown in Figure 9 is information concerning the tracking area TA from the notification information JY, and it notifies of the transition from the first state shown in Figure 7 to the second state shown in Figure 8A. The notification information JY1 includes base station identification information H11 that identifies the base station S, identification information (referred to as "newly assigned TA") H12 that provisionally identifies the tracking area TA to which the base station S belongs in the second state, and tracking area code TAC (referred to as "old TAC") H13 that was assigned to the tracking area TA to which the base station S belonged in the first state. For example, a base station S with a newly assigned TA of "201" indicates that in the second state it belongs to tracking area TA_201. Also, a base station S with an old TAC of "001" indicates that in the first state it belongs to the tracking area TA to which tracking area code TAC_001 was assigned.

[0051] The first code determination unit 113A first counts which old TAC each new TA belongs to for the same base station S. Figure 10 is a table showing the count values ​​for the old TACs each new TA belongs to. For example, of the base stations S whose new TA is "201", there are 6 base stations S whose old TAC is "001", 4 base stations S whose old TAC is "002", and 0 base stations S whose old TAC is "003" and 0 base stations S whose old TAC is "004".

[0052] Similarly, among the base stations S whose new assigned TA is "202", there are 0 base stations S whose former TAC was "001" and "003", 2 base stations S whose former TAC was "002", and 2 base stations S whose former TAC was "004". Also, among the base stations S whose new assigned TA is "203", there are 0 base stations S whose former TAC was "001", "002", and "004", and 4 base stations S whose former TAC was "003". Also, among the base stations S whose new assigned TA is "204", there are 0 base stations S whose former TAC was "001" and "002", 2 base stations S whose former TAC was "003", and 4 base stations S whose former TAC was "004".

[0053] Next, the first code determination unit 113A focuses on the tracking area code TAC with the largest count value for the base station S. In the example above, the largest count value is "6," which is the number of base stations S with the old TAC "001" in the base station S whose new assigned TA is "201." The first code determination unit 113A then assigns the tracking area code TAC to the new assigned TA whose count value was found. Specifically, the first code determination unit 113A assigns the tracking area code TAC "001" (TAC_001) to the new assigned TA "201" (TA_201). This completes the processing for the new assigned TA "201" and the tracking area code TAC "001." Tracking area TAs and tracking area code TACs that have already been processed are excluded from further processing to prevent duplicate assignments.

[0054] Next, the first code determination unit 113A focuses on the tracking area code TAC with the second largest count value for the base station S. In the example above, the second largest count values ​​are "4", which is the number of base stations S with the old TAC "002" in the base station S with the new assigned TA "201", "4", which is the number of base stations S with the old TAC "003" in the base station S with the new assigned TA "203", and "4", which is the number of base stations S with the old TAC "004" in the base station S with the new assigned TA "204". Of these, processing for the new assigned TA "201" has been completed, so it is excluded from processing.

[0055] The first code determination unit 113A assigns the tracking area code TAC "003" (TAC_003) to the base station S of the newly assigned TA "203" (TA_203), and the tracking area code TAC "004" (TAC_004) to the newly assigned TA "204" (TA_204). This completes the processing for the newly assigned TAs "203" and "204" and the tracking area codes TAC "003" and "004".

[0056] Furthermore, if, for example, there are multiple newly assigned TAs with the same count value for the same tracking area code TAC, the first code determination unit 113A may assign the tracking area code TAC to the newly assigned TA that has a larger number of affiliated base stations S.

[0057] Finally, the first code determination unit 113A assigns the tracking area code TAC "002" (TAC_002) to the remaining base station S of the newly assigned TA "202" (TA_202). This completes the processing for all newly assigned TAs and all tracking area codes TAC. The processing by the first code determination unit 113A can also be described as an algorithm using a greedy method.

[0058] In this way, the first code determination unit 113A assigns a tracking area code TAC to each tracking area TA in the second state based on the advance information JY1. For example, focusing on base station S24, which is the 24th base station S, and base station S23, which is the 23rd base station S, the first code determination unit 113A refers to the acquired advance information JY1 and determines the tracking area code TAC to be assigned to tracking area TA_204 and the tracking area code TAC to be assigned to tracking area TA_202 based on the tracking area code TAC of the tracking area TA to which at least one base station S, including base station S24, which belongs to tracking area TA_202 in the second state (in other words, all base stations S that belong to tracking area TA_202 in the second state) belonged in the first state, and the tracking area code TAC of the tracking area TA to which at least one base station, including base station S23, which belongs to tracking area TA_204 in the second state (in other words, all base stations S that belong to tracking area TA_204 in the second state) belonged in the first state.

[0059] More specifically, the first code determination unit 113A assigns the tracking area code TAC_004 to the tracking area TA (in this embodiment, tracking area TA_204) that has a larger number of base stations S belonging to tracking area TA_104 in the first state, out of tracking area TA_202 and tracking area TA_204. Furthermore, if tracking area code TAC_004 is assigned to tracking area TA_204, the first code determination unit 113A assigns to tracking area TA_202 the tracking area code TAC (in this embodiment, tracking area code TAC_002) that has the highest number of tracking area codes other than tracking area code TAC_004 among the tracking area codes TAC of the tracking area TA to which at least one base station S belonging to tracking area TA_202 belonged in the first state (in other words, all base stations S belonging to tracking area TA_202).

[0060] Next, the second code determination unit 113B will be described. As described above, the second code determination unit 113B determines the tracking area list code TLC. The determination of the tracking area list code TLC by the second code determination unit 113B will be described below.

[0061] Figure 11A schematically shows the status of a base station S's membership in the tracking area list TL in the first state. In the first state, tracking area TA_101, to which base stations S1 to S6 belong, and tracking area TA_102, to which base stations S7 to S12 belong, belong to tracking area list TL_101. In other words, tracking area list TL_101 is composed of base stations S1 to S12 (or tracking areas TA_101 and TA_102). "TL_101" is not information that identifies the tracking area list TL in the network (tracking area list code TLC), but rather a convenient code for identifying multiple tracking area lists TL in this embodiment. Similarly, tracking area TA_103, to which base stations S13 to S18 belong, and tracking area TA_104, to which base stations S19 to S24 belong, belong to tracking area list TL_102.

[0062] Furthermore, in the first state, tracking area list TL_101 is assigned the tracking area list code TLC of "001" (hereinafter referred to as "TLC_001"). Tracking area list TL_102 is assigned the tracking area list code TLC of "002" (hereinafter referred to as "TLC_002"). "TL_101", etc. can be rephrased as relative tracking area codes, and "TLC_001", etc. can be rephrased as absolute tracking area codes. The relative tracking area list code identifies which group (tracking area list TL) base station S belongs to. The absolute tracking area list code is the group name assigned to the group (tracking area list TL) to which base station S belongs.

[0063] For example, base station S1 belongs to tracking area list TL_101 with tracking area list code TLC_001, and base station S24 belongs to tracking area list TL_102 with tracking area list code TLC_002. This membership status is known to each base station S and the MME 30, as well as other components of the communication system 1.

[0064] Figure 11B schematically shows the status of a base station S's affiliation with the tracking area list TL in the second state. The advance information JY acquired by the acquisition unit 112 also includes information on which of the base stations S1 to S24 belong to the same tracking area list TL in the second state. Specifically, as shown in Figure 11B, for example, in the second state, tracking area TA_201 to which base stations S1 to S8 and S10 to S11 belong, and tracking area TA_202 to which base stations S9, S12, S21, and S24 belong, belong to tracking area list TL_201. In other words, tracking area list TL_201 is composed of base stations S1 to S8, S10 to S11, S9, S12, S21, and S24 (tracking areas TA_201 and TA_204). Similarly, tracking area TA_203, to which base stations S13-S14 and S16-S17 belong, and tracking area TA_204, to which base stations S15, S18-S20 and S22-S23 belong, belong to tracking area list TL_202.

[0065] For example, in Figure 11A, we focus on base station S24, which is the 24th base station S, and base station S23, which is the 23rd base station S, out of 24 base stations. In the first state shown in Figure 11A, base stations S24 and S23 belong to tracking area list TL_102, which is assigned tracking area list code TLC_002. On the other hand, in the second state shown in Figure 11B, base station S24 belongs to tracking area list TL_201, and base station S23 belongs to tracking area list TL_202. Tracking area list code TLC_002 is an example of a first tracking area list code. Tracking area list TL_102 is an example of a first tracking area list. Tracking area list TL_201 is an example of a second tracking area list. Tracking area list TL_202 is an example of a third tracking area list.

[0066] In the example shown in Figure 11B, the number of tracking area lists TL in the second state is two, which is the same as the number of tracking area lists TL in the first state shown in Figure 11A (two). However, the number of tracking area lists TL may be increased or decreased between the first and second states as needed. If the number of tracking area lists TL increases, tracking area list codes TLC that were not used in the first state are added by the same number. Conversely, if the number of tracking area lists TL decreases, the same number of tracking area list codes TLC that were used in the first state are no longer used.

[0067] The tracking area lists TL_201 and TL_202 shown in Figure 11B do not have tracking area list codes TLC assigned to them. Therefore, the second code determination unit 113B determines the tracking area list code TLC to be assigned to the tracking area lists TL_201 and TL_202. More specifically, the second code determination unit 113B determines the tracking area list code TLC by considering the following first and second conditions.

[0068] The first condition is to minimize the number of base stations S whose tracking area list code TLC is changed, similar to the tracking area TA. That is, the second code determination unit 113B determines the tracking area list code TLC such that the number of base stations S1 to S24 whose tracking area list code TLC in the first state is different from the tracking area list code TLC in the second state is minimized. This is because the network stability is higher when there are many base stations S whose tracking area list code TLC does not change between the first and second states.

[0069] The second condition is that the size of the tracking area list TL to which tracking area list code TLC (e.g., TLC_001) is assigned does not change significantly between the first state and the second state. For example, if there is a large difference between the size of the tracking area list TL to which tracking area list code TLC_001 was assigned in the first state and the size of the tracking area list TL to which tracking area list code TLC_001 is assigned in the second state, the network may become unstable. Therefore, the second code determination unit 113B determines the tracking area list code TLC such that the size of the tracking area list TL in the first state and the size of the tracking area list TL in the second state are approximately the same.

[0070] More specifically, the second code determination unit 113B determines the objective function X shown in the following formula (A1). Ｑ X is the smallest value ｉｊ We seek X. ｉｊ This is an f-row, h-column matrix indicating which tracking area list code TLC is assigned to each tracking area list TL. f is the number of tracking area lists TL in the second state, and h is the number of tracking area list codes TLC in the first state (equivalent to the number of tracking area lists TL in the first state). If the number of tracking area lists TL does not change between the first and second states, then f = h.

[0071] As shown in the following formula (A2), X ｉｊ The elements (components) are denoted as Xi and j. i is a natural number from 1 to f, and j is a natural number from 1 to h. The elements Xi and j become "1" when the "i"-th tracking area list TL among the f tracking area lists TL in the second state is assigned the "j"-th tracking area list code TLC among the h tracking area list codes TLC. ｉｊThe following one-hot constraints are set: (A3) and (A4) below. (A3) is a row-direction one-hot constraint, and (A4) is a column-direction one-hot constraint. The one-hot constraint indicates that one tracking area list code TLC is always assigned to one tracking area list TL.

[0072]

[0073] Next, we will explain Q1 and Q2 in the above equation (A1). Q1 is given by the following equation (A5). Q1 is the term corresponding to the first condition. Q2 is given by the following equation (A6). Q2 is the term corresponding to the second condition. The coefficients ε attached to Q1 and ζ attached to Q2 are coefficients for weighting Q1 and Q2, respectively.

[0074]

[0075] First, let's explain Q1 (the first condition). Figures 11A and 11B only show the ranges of two tracking area lists TL (base stations S1 to S24), but as mentioned above, many tracking area lists TL are actually set in the communication system 1. In the following explanation, we will assume that three or more tracking area lists TL are set.

[0076] Figure 12 is a schematic diagram showing the advance information JY2. The advance information JY2 shown in Figure 12 shows information related to the tracking area list TL from the advance information JY. The advance information JY2 includes base station identification information H21 that identifies the base station S, identification information (referred to as "newly assigned TL") H22 that provisionally identifies the tracking area list TL to which the base station S belongs in the second state, and tracking area list code TLC (referred to as "old TLC") H23 that was assigned to the tracking area list TL to which the base station S belonged in the first state. For example, a base station S with a newly assigned TL of "201" indicates that in the second state, it belongs to the tracking area list TL_201. Also, a base station S with an old TLC of "001" indicates that in the first state, it belongs to the tracking area list TL to which the tracking area list code TLC_001 was assigned.

[0077] When the second code determination unit 113B acquires the advance information JY2, it counts the number of base stations S (hereinafter referred to as "TL change base stations") that need to change their tracking area list code TLC when one of several old TLCs (hereinafter referred to as "new TLC") is assigned to the new TLC for base stations S with the same new TL. Figure 13 is a table showing the count values ​​of TL change base stations when each TLC is assigned to each new TL. For example, among base stations S with the new TL "201", there are 3 base stations S that need to change their tracking area list code TLC when "001" is assigned as the new TLC. Also, among base stations S with the new TL "201", there are 2 base stations S that need to change their tracking area list code TLC when "002" is assigned as the new TLC. Also, among base stations S with the new TL "202", there is 1 base station S that needs to change its tracking area list code TLC when "001" is assigned as the new TLC.

[0078] The matrix Q1 shown in equation (A5) above is obtained by converting the table in Figure 13 into a matrix. The elements (components) of matrix Q1 are denoted as Ti and j. i is a natural number from 1 to f, and j is a natural number from 1 to h. The elements Ti and j represent the number of base stations S whose new assigned TL is "i" and which need to change their tracking area list code TLC (TL change base stations) when "j" is assigned as the new TLC.

[0079] Next, we will explain Q2 (the second condition). Figure 14 is a schematic diagram showing the advance information JY3. The advance information JY3 includes a new belonging TL H31 that provisionally identifies the tracking area list TL to which the base station S belongs in the second state, and the number of base stations S belonging to that new belonging TL H32. For example, there are 100 base stations S whose new belonging TL is 201 (TL_201). In other words, there are 100 base stations S included in the tracking area list TL_201 in the second state.

[0080] The advance information JY3 is information compiled from the base station identification information H21 and the new assigned TL H22 of the advance information JY2. The second code determination unit 113B may acquire the advance information JY3 from the acquisition unit 112, or it may create the advance information JY3 based on the advance information JY2.

[0081] Here, the number of base stations S indicates the trend in the number of paging signals (more specifically, initial paging signals) generated. In this embodiment, it is assumed that the number of base stations S and the number of initial paging signals transmitted are proportional. As the advance information JY3, instead of the number of base stations S H32, the number of initial paging signals transmitted by base stations S belonging to the new TL during a predetermined period of the first state may also be included.

[0082] Figure 15 is a schematic diagram showing the advance information JY4. The advance information JY4 indicates the number of tracking areas TA belonging to the tracking area list TL indicated by the old TLC in the first state (hereinafter referred to as "TLC-belonging TA count"). For example, there are 2 tracking areas TA belonging to the tracking area list TL where the old TLC is "001". In this embodiment, it is assumed that the more tracking area TAs a tracking area list TL has, the more initial paging signals are transmitted.

[0083] The notification information JY4 can be created based on past notification information JY1 and notification information JY2 (when transitioning to the first state). The second code determination unit 113B may acquire the notification information JY4 from the acquisition unit 112, or it may create the notification information JY4 based on past notification information JY1 and notification information JY2.

[0084] The second code determination unit 113B calculates the base station density U by dividing the number of base stations S belonging to one new TL by the number of TAs belonging to the TLC. Figure 16 is a table showing the base station density U. For example, there are 100 base stations S in the new TL "201". Also, there are 2 tracking area TAs belonging to the tracking area list TL where the old TLC is "001". Therefore, the base station density U for the combination of new TL "201" and old TLC "001" is "100 / 2". Also, there are 6 tracking area TAs belonging to the tracking area list TL where the old TLC is "002". Therefore, the base station density U for the combination of new TL "201" and old TLC "002" is "100 / 6".

[0085] The matrix Q2 shown in equation (A6) above is obtained by converting the table in Figure 16 into a determinant. The elements (components) of matrix Q2 are denoted as Ui and j. i is a natural number from 1 to f, and j is a natural number from 1 to h. The elements Ui and j are the values ​​obtained by dividing the number of base stations S whose new assigned TL is "i" by the number of tracking area TAs belonging to the old TLC "j" (assigned base station density U).

[0086] Thus, the second code determination unit 113B refers to the acquired advance information JY2, (Q1 × X ｉｊ) and (Q2×X ｉｊ ), determines the tracking area list code TLC to be assigned to the tracking area list TL in the second state. More specifically, the second code determination unit 113B refers to the acquired advance notice information JY2, and based on (Q1×X ｉｊ ) and (Q2×X ｉｊ ), determines the tracking area list code TLC (second tracking area list code) to be assigned to the tracking area list TL_201 and the tracking area list code TLC (third tracking area list code) to be assigned to the tracking area list TL_203. (Q1×X ｉｊ ) is an example of a first parameter, and (Q2×X ｉｊ ) is an example of a second parameter.

[0087] Focus is placed on the 24th base station S, which is base station S24, and the 23rd base station S, which is base station S23, among the 24 base stations. (Q1×X ｉｊ ) is a parameter based on: the tracking area list code TLC of the tracking area list TL to which at least one base station including the 24th base station S24 belonging to the tracking area list TL_201 in the second state (in other words, all base stations S belonging to the tracking area list TL_201 in the second state) belonged in the first state; and the tracking area list code TLC of the tracking area list TL to which at least one base station including the 23rd base station S23 belonging to the tracking area list TL_202 in the second state (in other words, all base stations S belonging to the tracking area list TL_202 in the second state) belonged in the first state.

[0088] More specifically, (Q1×X ｉｊThis can be expressed as a first objective function whose purpose is to assign the tracking area list code TLC_002 to the tracking area list TL whichever has more base stations S belonging to tracking area list TL_102 in the first state, among at least one base station S belonging to tracking area list TL_201 in the second state (in other words, all base stations S belonging to tracking area list TL_201 in the second state) and at least one base station S belonging to tracking area list TL_202 in the second state (in other words, all base stations S belonging to tracking area list TL_202 in the second state).

[0089] (Q2 x X ｉｊ This parameter is based on the ratio of the number of base stations S belonging to tracking area list TL_201 in the second state to the number of tracking areas TA belonging to tracking area list TL_101 in the first state, and the ratio of the number of base stations S belonging to tracking area list TL_202 in the second state to the number of tracking areas TA belonging to tracking area list TL_102 in the first state.

[0090] For more details, see (Q2 x X ｉｊ This is represented by a second objective function that compares the ratio of the number of base stations S included in tracking area list TL_201 in the second state to the number of tracking areas TA belonging to tracking area list TL_102 in the first state with the ratio of the number of base stations S included in tracking area list TL_202 in the second state to the number of tracking areas TA belonging to tracking area list TL_102 in the first state, and assigns the tracking area list code TLC_002 to the tracking area list TL with the smaller ratio.

[0091] The code determination unit is (Q1 × X ｉｊ ) and (Q2 x X ｉｊBy finding the solution that minimizes the sum of ), we determine the tracking area list code TLC (second tracking area list code) to be assigned to tracking area list TL_201 and the tracking area list code TLC (third tracking area list code) to be assigned to tracking area list TL_202.

[0092] The output control unit 114 outputs information regarding the tracking area code TAC and tracking area list code TLC determined by the code determination unit 113. The output control unit 114 may, for example, cause the display device 101 to display a list showing the tracking area code TAC and tracking area list code TLC in the second state. The output control unit 114 may also transmit print control information to, for example, a printer (not shown) for printing a list showing the tracking area code TAC and tracking area list code TLC in the second state. The output control unit 114 may also transmit the tracking area code TAC and tracking area list code TLC in the second state to, for example, another information processing terminal via the communication device 103.

[0093] Next, the optimization processing unit 111 will be described. The optimization processing unit 111 optimizes a plurality of tracking area TAs that include the communication area E of at least one base station S among the N base stations S, and a plurality of tracking area lists TLs that each include at least one of the plurality of tracking area TAs.

[0094] Taking the base station S shown in Figures 2 to 5 as an example, the communication system 1 has at least two tracking area lists TL1 and L2. Tracking area list TL1 includes tracking areas TA1 to TA3. Tracking area TA1 includes communication areas E1 to E3 of base stations S1 to S3. Tracking area TA2 includes communication areas E4 to E6 of base stations S4 to S6. Tracking area TA3 includes communication areas E7 to E9 of base stations S7 to S9. In addition, tracking area list TL2 includes tracking areas TA4 to TA5. Tracking area TA4 includes communication areas E10 to E12 of base stations S10 to S12. Tracking area TA5 includes communication areas E13 to E14 of base stations S13 to S14. The optimization processing unit 111 optimizes these tracking area lists TL1 to L2 and tracking areas TA1 to T5.

[0095] The optimization processing unit 111 includes a first membership determination unit 111A and a second membership determination unit 111B. The first membership determination unit 111A determines which of the plurality of tracking area lists TL each of the N base stations S belongs to. In this embodiment, the first membership determination unit 111A finds a first solution that satisfies at least one of the following: minimizing the number of paging signals transmitted in each of the plurality of tracking area lists TL, and minimizing the number of location registration signals RS transmitted when the communication terminal 20 moves between tracking areas TA belonging to different tracking area lists TL. Based on the first solution obtained, the first membership determination unit 111A determines which tracking area list TL each of the N base stations S belongs to. In this embodiment, the first membership determination unit 111A determines which tracking area list TL each of the N base stations S belongs to by finding a first solution that satisfies minimizing the number of paging signals transmitted in each of the plurality of tracking area lists TL and minimizing the number of location registration signals transmitted. Alternatively, the first assignment determination unit 111A may determine the tracking area list TL to which each of the N base stations S belongs by finding a solution that further satisfies the requirement of equalizing the number of initial paging signals transmitted in each of the multiple tracking area list TLs as a first solution.

[0096] Hereafter, "minimizing the number of paging signals transmitted in each of the multiple tracking area lists (TLs)" may be referred to as "minimizing all paging signals." "minimizing the number of location registration signals (RS) transmitted" may be referred to as "minimizing location registration signals (RS)." "Equalizing the number of initial paging signals transmitted in each of the multiple tracking area lists (TLs)" may be referred to as "equalizing the first paging signal."

[0097] The second belonging determination unit 111B determines which of the at least one tracking area TA included in the tracking area list TL a base station belonging to one of the multiple tracking area list TLs belongs to. The second belonging determination unit 111B determines the tracking area TA to which the base station S belonging to the tracking area list TL belongs by finding a second solution that satisfies the minimization of the number of paging signals transmitted in the tracking area list TL.

[0098] The first and second assignment determination units 111A and 111B obtain the first and second solutions, for example, using quantum annealing. Quantum annealing is known to be a fast way to find good solutions in combinatorial optimization problems. Quantum annealing is performed in the following steps: [1] conversion of the objective function to QUBO (Quadratic Unconstrained Binary Optimization) form, [2] mapping to the circuit, and [3] execution of quantum annealing. If the network management device 10 is a quantum computer, the first and second assignment determination units 111A and 111B may perform steps [1] to [3] above. Alternatively, if the network management device 10 is a computer connected to a quantum computer, the first and second assignment determination units 111A and 111B may request the quantum computer to perform step [3] to obtain the first and second solutions.

[0099] In the mapping to the circuit in step [2], when there is a problem in which multiple variables are all related to each other, it is necessary to generate a topology in which the qubits that embed each variable are connected to all other qubits. However, due to the current limitations of the machine configuration, one variable is made up of multiple qubits to realize the topology. In the optimization problem of the base station S dealt with in this embodiment, for example, the number of base stations S is 300, the number of tracking area TAs is 10, the number of tracking area lists TLs is 3, etc., making the problem scale large. Therefore, there are not enough qubits, and it is not possible to map at once.

[0100] Therefore, in this embodiment, the process is divided into two stages: the first belonging determination unit 111A determines the belonging of each base station S to the tracking area list TL, and the second belonging determination unit 111B determines the belonging of each base station S to the tracking area TA. This allows the problem to be divided into units that can be solved by a quantum computer.

[0101] The following describes the details of the processing performed by the first affiliation determination unit 111A and the second affiliation determination unit 111B. The processing performed by the first affiliation determination unit 111A may be referred to as "optimization of the tracking area list TL" or simply "optimization." Similarly, the processing performed by the second affiliation determination unit 111B may be referred to as "optimization of the tracking area TA" or simply "optimization."

[0102] The following assumptions apply to the explanation below: [1] Generally, communication at one base station S is composed of multiple sectors, but sectors are not considered in this optimization (sectors within one base station S are assumed to belong to the same tracking area TA). [2] Only the retransmission of the paging signal up to the third paging is considered, and retransmissions from the fourth paging onward are not considered. [3] A data communication paging method is used. [4] Movement of the communication terminal 20 is counted in units of the communication area E of the base station S.

[0103] Let e ​​be an integer greater than or equal to 1, among the base stations S in the communication system 1, to be the target of this optimization. Let A = {a, b, ...} be the number of tracking area lists TL to be optimized, where a, b, etc., represent individual tracking area lists TL. The tracking area list TL indicated by a is called the "a-th tracking area list TL". The tracking area list TL indicated by b is called the "b-th tracking area list TL". The number of tracking area lists TL to be optimized is denoted as |A|. The number of tracking areas in each tracking area list TL is denoted as |a|, |b|, .... The number of tracking areas TA in the tracking area list TL to be optimized is f ｓｕｍ It can be shown that (= |a| + |b| + ...).

[0104] Next, the data for the simulation will be described. In this embodiment, the mobile model M of the communication terminal 20 is used for the simulation of the paging signal. Ｐ Use the following: Movement model M Ｐ This is generated using statistical values ​​that show the hourly movement status of the communication terminal 20. Movement model M Ｐ This is an e-row, e-column matrix as shown in equation (B1) below. Therefore, the moving model M Ｐ This can also be called a movement matrix. Movement model M Ｐ The elements (components) are, ｐ ｋ，ｉ It is written as follows: k and i are integers from 1 to e. ｐ ｋ，ｉ This is the total number of times a communication terminal 20 was located in the communication area E of the k-th base station S at the end of the Nth incoming call (where N is an integer greater than or equal to 1), and moved to the i-th base station S at the (N+1)th incoming call.

[0105]

[0106] Furthermore, in this embodiment, a mobile model M of the communication terminal 20 is used for simulating the position registration signal RS. Ｌ Use the following: Movement model M Ｌ This is generated using statistical values ​​that show the hourly movement status of the communication terminal 20. Movement model MＬ This is an e-row, e-column matrix, as shown in equation (B2) below. Therefore, the moving model M Ｌ This can also be called a movement matrix. Movement model M Ｌ The elements (components) are, Ｌ ｋ，ｉ It is written as follows: k and i are integers from 1 to e. Ｌ ｋ，ｉ This represents the total number of communication terminals 20 that moved from the communication area E of the k-th base station S to the i-th base station S.

[0107]

[0108] The belonging of each of the e base stations S to the tracking area list TL and tracking area TA is shown by the matrix X in the following formula (B3). Matrix X is e row f ｓｕｍ It is a matrix of columns. In the following equation (B3), for the sake of simplicity, we assume that the targets of optimization are two tracking area list TLs, the a-th tracking area list TL and the b-th tracking area list TL. The elements (components) of matrix X are, for example, x ａ ｉ，ｊ It is written as x ａ ｉ，ｊ This indicates a flag = {1, 0} that shows whether the i-th base station S belongs to the j-th tracking area TA of the a-th tracking area list TL. Since each base station S belongs to only one tracking area list TL and tracking area TA, the sum of the horizontal (row) values ​​of matrix X is constrained to 1, as shown in equation (B4) below.

[0109]

[0110] [Processing of the First Membership Determination Unit 111A] [Minimization of all paging signals] The matrix X' shown in the following equation (B5) is an e-row |A| matrix indicating which tracking area list TL each base station S belongs to. As described above, in this embodiment, the targets of optimization are the a-th tracking area list TL and the b-th tracking area list TL, so the following equation (B5) shows the case where |A| = 2. The elements of matrix X' are, for example, x' ａｉ It is written as x'. ａ ｉ This indicates a flag = {1, 0} that shows whether the i-th base station S belongs to the a-th tracking area list TL. As shown in the following equation (B6), x' ａ ｉ This refers to the base station S belonging to the tracking area TA within the a-th tracking area list TL.

[0111]

[0112] The total number of times the first paging signal was received D at base station S belonging to the a-th tracking area list TL. ａ This is represented by the following formula (B8). D ａ Parameters related to (p ｋ ) is shown by the following formula (B7). ｋ This indicates the number of times the location of the communication terminal 20 at the time of the previous call termination was within the communication area E of the k-th base station S. In other words, p ｋ This represents the number of first paging signals generated targeting the k-th base station S.

[0113]

[0114] The total number of receptions D' of the second paging signal at base station S belonging to the a-th tracking area list TL. ａ This is represented by the following formula (B15). D' ａ The parameters related to are shown in the following equations (B9) to (B14). R shown in equation (B9) ２ This is an e-row, e-column matrix that indicates whether each base station S is a different base station S. The r shown in equation (B10) ２ ｋ，ｉ This flag indicates whether the k-th base station S and the i-th base station S are different base stations S. More specifically, it takes a value of 1 if the k-th base station S and the i-th base station S are different base stations S, and a value of 0 if the k-th base station S and the i-th base station S are the same base station S.

[0115] P' shown in equation (B11) ｋThis indicates the number of times the location of the communication terminal 20 at the time of the previous call termination was within the communication area of ​​the k-th base station S, and the location of the communication terminal 20 at the time of the current incoming call is not within the communication area of ​​the k-th base station S. In other words, P' ｋ This represents the number of times a second paging signal is generated targeting the k-th base station S.

[0116] A shown in the following formula (B12) ａ ｊ B is the number of base stations S belonging to the j-th tracking area TA in the a-th tracking area list TL. B is shown in the following formula (B13). ａ ｊ This is the number of second paging signals received per base station S belonging to the j-th tracking area TA in the a-th tracking area list TL. C is shown in the following equation (B14). ａ ｊ This is the total number of times the second paging signal has been received by base station S belonging to the a-th tracking area list TL.

[0117]

[0118]

[0119] The total number of receptions H of the third paging signal at base station S belonging to the a-th tracking area list TL. ａ This is represented by the following formula (B20). H ａ The parameters related to are shown in the following equations (B16) to (B19). R shown in equation (B16) ａ This is an e-row, e-column matrix that indicates whether each base station S belonging to the a-th tracking area list TL belongs to a different tracking area TA. The r shown in equation (B17) ａ ｋ，ｉThis flag indicates whether the k-th base station S and the i-th base station S in the a-th tracking area list TL belong to different tracking area TAs. More specifically, it takes a value of 1 if the k-th base station S and the i-th base station S belong to different tracking area TAs, and a value of 0 if the k-th base station S and the i-th base station S belong to the same tracking area TA.

[0120] G shown in formula (B18) ａ This is the total number of times the third paging signal occurs in the a-th tracking area list TL. e shown in equation (B19) ａ This is the number of base stations S in the a-th tracking area list TL.

[0121]

[0122]

[0123] Based on the above, the total number of paging signals received by base station S belonging to the a-th tracking area list TL Y ａ This is given by equation (B21) below. The total number of paging signals received Y at all base stations S belonging to the tracking area list TL to be optimized is given by equation (B22) below. In equation (B22), α is a weighting coefficient for the number of paging signals in each tracking area list TL, and is specified during the optimization calculation. The solution that minimizes Y is the solution that satisfies "minimization of all paging signals".

[0124]

[0125] [Minimizing the position registration signal RS] Total number of times the position registration signal RS is generated G Ｌ This is represented by the following formula (B25). G Ｌ The parameters related to are shown in the following equations (B23) to (B24). R shown in equation (B23) Ｌ This is an e-row, e-column matrix that indicates whether each base station S belongs to a different tracking area list TL. The following formula (B24) is shown for r Ｌ ｋ，ｉThis flag indicates whether the k-th base station S and the i-th base station S belong to different tracking area lists TLs. More specifically, it takes a value of 1 if the k-th base station S and the i-th base station S belong to different tracking area lists TLs, and a value of 0 if the k-th base station S and the i-th base station S belong to the same tracking area list TL. Ｌ The solution that minimizes this value is the solution that satisfies the condition of "minimizing the position registration signal RS".

[0126]

[0127] [Uniformity of the first paging signal] Total number of receptions D of the first paging signal at base station S belonging to the a-th tracking area list TL ａ This is shown in equation (B8) above. Similarly, D is the total number of receptions of the first paging signal at base stations S belonging to the b-th tracking area list TL. ｂ Let's assume that. (D ａ -D ｂ ) ２ The solution that minimizes this value is the solution that satisfies the "uniformity of the first paging signal".

[0128] Based on the above, the first assignment determination unit 111A finds the solution that minimizes equation f1, shown in the following equation (B26), as the first solution. In equation (B26), Y is a term relating to minimizing the entire paging signal, and G Ｌ This is a term relating to minimizing the position registration signal RS, (D ａ -D ｂ ) ２ is a term relating to the homogenization of the first paging signal. α is the weighting coefficient for the total paging signal term. β is the weighting coefficient for the position registration signal RS term. γ is the weighting coefficient for the first paging signal term.

[0129]

[0130] [Processing of Second Affiliation Determination Unit 111B] The second affiliation determination unit 111B determines which tracking area TA each base station S belongs to. As described above, the second affiliation determination unit 111B determines the tracking area TA to which the base station S belonging to the one tracking area list TL belongs by obtaining a second solution that satisfies the minimization of the total number of paging signal transmissions in the one tracking area list TL.

[0131] [Minimization of Total Paging Signals] Hereinafter, description will be given taking the a-th tracking area list TL as an example. A matrix X'' represented by the following formula (B27) is a matrix with e rows and |a| columns indicating which tracking area TA each base station S belongs to. In the present embodiment, for convenience of description, it is assumed that there are two tracking areas TA, c and d (hereinafter referred to as the c-th tracking area TA and the d-th tracking area TA) in the a-th tracking area list TL. Therefore, the following formula (B27) shows the case where |a|=2. The elements of the matrix X'' are, for example, x'' ｃ ｉ is expressed as. x'' ｃ ｉ represents a flag={1,0} indicating whether or not the i-th base station S belongs to the c-th tracking area TA.

[0132]

[0133] Total number of receptions D of first paging signals in base stations S belonging to the c-th tracking area TA ｃ is represented by the following formula (B29). D ｃ parameter related to (p ｋ ) is represented by the following formula (B28). p ｋ indicates the number of times the position of the communication terminal 20 at the end of the previous call was within the communication area of the k-th base station S. In other words, p ｋ is the number of first paging signals generated targeting the k-th base station S.

[0134]

[0135] The total number of receptions D' of the second paging signal at base station S belonging to the c-th tracking area TA. ｃ This is shown by the following equation (B36). In equation (B36), |c| is the number of base stations belonging to the c-th tracking area TA. D' ｃ The parameters related to are shown in the following equations (B30) to (B35). R shown in the following equation (B30) ２ This is an e-row, e-column matrix that indicates whether each base station S is a different base station S. The following equation (B31) shows r ２ ｋ，ｉ This flag indicates whether the k-th base station S and the i-th base station S are different base stations S. More specifically, it takes a value of 1 if the k-th base station S and the i-th base station S are different base stations S, and a value of 0 if the k-th base station S and the i-th base station S are the same base station S.

[0136] P' shown in the following formula (B32) ｋ This indicates the number of times the location of the communication terminal 20 at the time of the previous call termination was within the communication area of ​​the k-th base station S, and the location of the communication terminal 20 at the time of the current incoming call is not within the communication area of ​​the k-th base station S. In other words, P' ｋ This represents the number of times a second paging signal is generated targeting the k-th base station S.

[0137] A shown in the following formula (B33) ｃ ｊ B is the number of base stations S belonging to the c-th tracking area TA. B is shown in the following formula (B34) ｃ ｊ This is the number of second paging signals received per base station S belonging to the c-th tracking area TA. C is shown in the following equation (B35). ｃ ｊ This represents the total number of times the second paging signal has been received by base station S belonging to the c-th tracking area TA.

[0138]

[0139]

[0140] The total number of receptions H of the third paging signal at base station S belonging to the c-th tracking area TA. ｃ This can be expressed as shown in the following formula (B39). The total number of receptions of the third paging signal will be the same among base stations S belonging to the same tracking area list TL. However, if there is a base station S with a high incoming call failure rate (described later) within the tracking area list TL, and if the number of base stations S within the tracking area list TL is relatively large (if the size of the tracking area list TL is large), the number of receptions of the third paging signal will be relatively higher compared to base stations S within the tracking area list TL that do not have this problem.

[0141] H ｃ The parameters related to this are shown in the following equations (B37) to (B38). M' shown in the following equation (B37) Ｐ This is a mobile model of the communication terminal 20. Mobile model M' Ｐ This is generated using statistical values ​​that show the movement status of the communication terminal 20 within the tracking area TA. Movement model M' Ｐ The elements (components) are m' ｐ ｋ，ｉ It is written as follows: k and i are integers from 1 to e. m' ｐ ｋ，ｉ This is the total number of times a communication terminal 20 was located in the communication area E of the k-th base station S at the end of the Nth incoming call, and moved to the i-th base station S at the (N+1)th incoming call. e is shown in the following formula (B38). ａ This is the number of base stations S in the c-th tracking area TA (a constant).

[0142]

[0143] From the above, the total number of paging signals received Y at base station S belonging to the c-th tracking area TA is ｃThis is given by equation (B40) below. The total number of paging signals received Yt at all base stations S belonging to the a-th tracking area list TL is given by equation (B41) below. δ in equation (B41) is a weighting coefficient for the number of paging signals in each tracking area TA, and is specified during the optimization calculation. The solution that minimizes Yt is the second solution that satisfies "minimization of all paging signals".

[0144]

[0145] Furthermore, the optimization processing unit 111 may determine the membership status in the second state based, for example, on the membership status of each base station S in the tracking area list TL and tracking area TA in the first state.

[0146] Specifically, the first affiliation determination unit 111A determines the current affiliation status and the movement model M Ｐ and M Ｌ Based on this, the number of paging signals and the number of position registration signals are calculated. The first belonging determination unit 111A then calculates a first solution, with the constraint that one of the number of paging signals and the number of position registration signals is minimized, and the other of the number of paging signals and the number of position registration signals is kept at approximately the same level as the current belonging status.

[0147] First, we consider the case where the number of position registration signals transmitted is minimized and the number of paging signals transmitted is kept at approximately the same level as the current belonging state, as a constraint. When only the number of position registration signals transmitted is minimized, the coefficients α and γ in the above equation (B26) are set to 0. As for the constraint, for example, a solution is sought in which the number of paging signals transmitted after optimization is less than the number of paging signals transmitted in the current belonging state. The number of paging signals transmitted in the current belonging state is determined by the current belonging state and the movement model M. Ｐ This can be obtained by substituting the above formula (B21). Furthermore, the number of paging signals transmitted after optimization is determined by the membership state (matrix X) after optimization and the movement model M Ｐ This can be obtained by substituting the above formula (B21).

[0148] Next, we consider the case where the constraint is set to minimize the number of paging signals transmitted and to keep the number of position registration signals transmitted at approximately the same level as the current affiliation state. When only the number of paging signals transmitted is minimized, the coefficients β and γ in the above equation (B26) are set to 0. As for the constraint, for example, a solution is sought in which the number of position registration signals transmitted after optimization is less than the number of position registration signals transmitted in the current affiliation state. The number of position registration signals transmitted in the current affiliation state is determined by the current affiliation state and the movement model M. Ｌ This can be obtained by substituting the above equation (25). Furthermore, the number of position registration signals transmitted after optimization is determined by the membership status (matrix X) after optimization and the movement model M Ｌ This can be obtained by substituting and into the above formula (25).

[0149] In other words, the first assignment determination unit 111A determines the provisional assignment status of each of the N base stations S to the tracking area TA and tracking area list TL, and uses the number of paging signals transmitted and the number of location registration signals transmitted in each of the multiple tracking area list TLs in that provisional assignment to determine the movement status of the communication terminal 20 in the movement model M Ｐ and M Ｌ The calculation is performed based on the above. The first affiliation determination unit 111A determines the tracking area list TL to which each of the N base stations S belongs by finding a solution in which one of the number of paging signals transmitted or the number of location registration signals transmitted in each of the multiple tracking area list TLs is minimized, and the other of the number of paging signals transmitted or the number of location registration signals transmitted is at the same level as the number of transmissions in the provisional affiliation. The provisional affiliation state is, for example, the current affiliation state.

[0150] This method allows for the optimization of each base station S's assignment to the tracking area TA and tracking area list TL based on its current assignment status. This reduces the processing load on the network management device 10 and improves the processing efficiency of the communication system 1 without requiring large-scale assignment changes.

[0151] The processing performed by the optimization processing unit 111 described above is just one example, and the optimization of the tracking area TA and the tracking area list TL can be performed in any way.

[0152] [Flowchart] Figure 17 is a flowchart showing the operation of the processing unit 105. The processing unit 105 functions as an optimization processing unit 111 and optimizes the tracking area TA and tracking area list TL of the communication system 1 (step S100). The optimization processing unit 111 generates and outputs preliminary information JY indicating the optimization result. The processing unit 105 functions as an acquisition unit 112 and acquires the preliminary information JY output from the optimization processing unit 111 (step S102).

[0153] The processing unit 105 functions as a code determination unit 113 (first code determination unit 113A) and determines the tracking area code TAC to be assigned to the tracking area TA after optimization (second state) (step S104). The processing unit 105 also functions as a code determination unit 113 (second code determination unit 113B) and determines the tracking area list code TLC to be assigned to the tracking area list TL after optimization (second state) (step S106).

[0154] The processing unit 105 functions as an output control unit 114 and outputs information regarding the tracking area code TAC determined in step S104 and the tracking area list code TLC determined in step S106 (indicated as "code information" in the figure) (step S108), thereby terminating the processing of this flowchart.

[0155] [Summary of Embodiments] As described above, the network management device 10 according to the embodiment determines the tracking area code TAC to be assigned to the tracking area TA in the second state and the tracking area list code TLC to be assigned to the tracking area list TL when the belonging status of a base station S in the communication system 1 transitions from the first state to the second state. When determining the tracking area code TAC, the network management device 10 determines the tracking area code TAC in such a way that the number of base stations S whose tracking area code TAC changes between the first state and the second state is minimized. This ensures network stability.

[0156] Furthermore, when determining the tracking area list code TLC, the network management device 10 determines the tracking area list code TLC in such a way that the number of base stations S whose tracking area list code TLC is changed between the first and second states is reduced, and the size of the tracking area list TL to which a single tracking area list code TLC is assigned does not change significantly between the first and second states. This further enhances network stability.

[0157] Furthermore, when the network management device 10 optimizes the tracking area TA and tracking area list TL to which each base station S belongs, it first determines the tracking area list TL to which each base station S belongs, and then determines the tracking area TA to which each base station S belongs. By dividing the process into two stages, a solution can be obtained even when the number of base stations S is large and the scale of the problem is large.

[0158] Furthermore, the network management device 10 uses quantum annealing to determine the tracking area list TL and tracking area TA to which each base station S belongs. Therefore, the computation time can be drastically reduced compared to classical computers, and problems that are practically unsolvable by classical computers can be solved.

[0159] [Other] (1) In the embodiments described above, ROM and RAM were given as examples of the storage device 104, but the storage device 104 may be a flexible disk, magneto-optical disk (e.g., compact disk, digital multipurpose disk, Blu-ray® disk), smart card, flash memory device (e.g., card, stick, key drive), CD-ROM (Compact Disc-ROM), register, removable disk, hard disk, floppy® disk, magnetic strip, database, server, or other suitable storage medium.

[0160] (2) In the embodiments described above, the information, signals, etc. may be represented using any of the various different techniques. For example, the data, instructions, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description may be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or photons, or any combination thereof.

[0161] (3) In the embodiments described above, the input and output information may be stored in a specific location (e.g., memory) or managed using a management table. The input and output information may be overwritten, updated, or appended to. The output information may be deleted. The input information may be transmitted to other devices.

[0162] (4) In the embodiments described above, the determination may be made by a value represented by one bit (0 or 1), by a Boolean value (true or false), or by a numerical comparison (for example, a comparison with a predetermined value).

[0163] (5) The processing procedures, sequences, flowcharts, etc., exemplified in the embodiments described above may be rearranged in order, as long as there is no inconsistency. For example, in the methods described herein, various step elements are presented using an exemplary order and are not limited to the specific order presented.

[0164] (6) Each function illustrated in Figure 6 is implemented by any combination of at least one of hardware and software. Furthermore, the method of implementing each function block is not particularly limited. That is, each function block may be implemented using one device that is physically or logically coupled, or it may be implemented using two or more physically or logically separated devices that are directly or indirectly connected (for example, using wired, wireless, etc.). A function block may also be implemented by combining the one or more devices with software.

[0165] (7) The programs illustrated in the embodiments described above should be broadly interpreted to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, functions, etc., whether they are called software, firmware, middleware, microcode, hardware description languages ​​or by any other name.

[0166] Furthermore, software, instructions, information, etc., may be transmitted and received via a transmission medium. For example, if software is transmitted from a website, server, or other remote source using at least one of wired technology (such as coaxial cable, fiber optic cable, twisted pair, or digital subscriber line (DSL)) and wireless technology (such as infrared or microwave), then at least one of these wired and wireless technologies is included in the definition of a transmission medium.

[0167] (8) In each of the above-mentioned forms, the terms “system” and “network” shall be used interchangeably.

[0168] (9) The information, parameters, etc. described in this disclosure may be expressed using absolute values, relative values ​​from a given value, or other corresponding information.

[0169] (10) In the embodiments described above, the portable device may be a Mobile Station (MS). A Mobile Station may also be referred to by those skilled in the art as a subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handset, user agent, mobile client, client, or several other appropriate terms. In this disclosure, terms such as “mobile station,” “user terminal,” “user equipment (UE),” and “terminal” may be used interchangeably.

[0170] (11) In the embodiments described above, the terms “connected,” “coupled,” or any variation thereof means any direct or indirect connection or coupling between two or more elements, and may include the presence of one or more intermediate elements between two elements that are “connected” or “coupled” with each other. The coupling or connection between elements may be physical, logical, or a combination thereof. For example, “connection” may be read as “access.” As used in the present disclosure, two elements may be considered to be “connected” or “coupled” with each other using at least one of one or more wires, cables, and printed electrical connections, and, in some non-limiting and non-exclusive examples, electromagnetic energy having wavelengths in the radio frequency domain, microwave domain, and optical (both visible and invisible) domain.

[0171] (12) In the embodiments described above, the phrase "based on" does not mean "based solely on" unless otherwise specified. In other words, the phrase "based on" means both "based solely on" and "based at least on".

[0172] (13) The terms “determinating” and “deciding” as used in this disclosure may encompass a wide variety of actions. “Determinating” and “deciding” may include, for example, judging, calculating, computing, processing, deriving, investigating, looking up, search, inquiry (for example, searching in a table, database or other data structure), and confirming. Furthermore, "judgment" and "decision" may include considering something as a "judgment" or "decision" based on actions such as receiving (e.g., receiving information), transmitting (e.g., sending information), input, output, and access (e.g., accessing data in memory). Additionally, "judgment" and "decision" may include considering something as a "judgment" or "decision" based on actions such as resolving, selecting, choosing, establishing, and comparing. In short, "judgment" and "decision" may include considering something as a "judgment" or "decision" based on some action. Furthermore, "judgment (decision)" may be reinterpreted as "assuming," "expecting," or "considering."

[0173] (14) Where the terms “include,” “including,” and variations thereof are used in the embodiments described above, these terms are intended to be inclusive, as is the term “comprising.” Furthermore, the term “or” as used in this disclosure is not intended to be exclusive OR.

[0174] (15) In the present disclosure, if articles are added by translation, for example, a, an, and the in English, the present disclosure may include the fact that the noun following these articles is plural.

[0175] (16) In this disclosure, the term “A and B are different” may mean “A and B are different from each other.” The term may also mean “A and B are each different from C.” Terms such as “separate” and “combine” may be interpreted in the same way as “different.”

[0176] (17) Each aspect / embodiment described herein may be used individually, in combination, or switched between as needed during implementation. Furthermore, notification of certain information (e.g., notification that "it is X") is not limited to explicit notification, but may also be implicit (e.g., by not providing such notification).

[0177] 1...Communication system, 10...Network management device, 20...Communication terminal, 101...Display device, 102...Input device, 103...Communication device, 104...Storage device, 105...Processing device, 111...Optimization processing unit, 111A...First affiliation determination unit, 111B...Second affiliation determination unit, 112...Acquisition unit, 113...Code determination unit, 113A...First code determination unit, 113B...Second code determination unit, 114...Output control unit, S (S1 to S24)...Base station.

Claims

1. Network management device comprising: an acquisition unit that acquires notification information for announcing a state transition from a first state in which the Nth base station and the (N-1)th base station belong to a first tracking area to which a first tracking area code has been assigned, to a second state in which the Nth base station belongs to a second tracking area and the (N-1)th base station belongs to a third tracking area; a code determination unit that, referring to the acquired notification information, determines a second tracking area code to be assigned to the second tracking area and a third tracking area code to be assigned to the third tracking area based on the tracking area code of the tracking area to which at least one base station, including the Nth base station, belonged in the first state and which belongs to the second tracking area in the second state, belonged in the first state, and the tracking area code of the tracking area to which at least one base station, including the (N-1)th base station, belonged in the first state and which belongs to the third tracking area in the second state; and an output control unit that outputs information relating to the second tracking area code and the third tracking area code determined by the code determination unit.

2. The network management device according to claim 1, wherein the code determination unit assigns the first tracking area code to the tracking area, whichever of the second tracking area and the third tracking area has a larger number of base stations belonging to the first tracking area in the first state.

3. The network management device according to claim 2, wherein, when the code determination unit is assigned the first tracking area code to the third tracking area, it assigns to the second tracking area the tracking area code that has the highest number of tracking area codes other than the first tracking area code among the tracking area codes to which the at least one base station belonging to the second tracking area belonged in the first state.

4. Each of the N base stations belongs to one of a plurality of tracking areas, and each of the plurality of tracking areas belongs to one of a plurality of tracking area lists. The system further comprises: a first belonging determination unit that determines which of the plurality of tracking area lists each of the N base stations belongs to; and a second belonging determination unit that determines which of the at least one tracking area belonging to one of the plurality of tracking area lists a base station belonging to belongs to. The first belonging determination unit finds a first solution that satisfies at least one of the following: minimizing the number of paging signals transmitted in each of the plurality of tracking area lists, and minimizing the number of location registration signals transmitted when a communication terminal moves between base stations belonging to different tracking area lists. Based on the first solution found, the system determines which of the N base stations belongs to the tracking area list. The network management device according to claim 1, wherein the second belonging determination unit finds a second solution that minimizes the number of paging signals transmitted in the first tracking area list, determines the tracking area to which the base station belonging to the first tracking area list belongs based on the second solution obtained, and the advance information is output by the first belonging determination unit and the second belonging determination unit.

5. The network management device according to claim 4, wherein the first membership determination unit determines the tracking area list to which each of the N base stations belongs by finding a solution that, as the first solution, satisfies the minimization of the number of paging signals transmitted in each of the plurality of tracking area lists and the minimization of the number of location registration signals transmitted.

6. The network management device according to claim 5, wherein the first belonging determination unit determines the tracking area list to which each of the N base stations belongs by finding a solution that further satisfies the requirement of equalizing the number of initial paging signals transmitted in each of the plurality of tracking area lists as the first solution.

7. The network management device according to claim 4, wherein the first assignment determination unit determines the provisional assignment status of each of the N base stations to a tracking area and a tracking area list, calculates the number of paging signals transmitted and the number of location registration signals transmitted in each of the plurality of tracking area lists in the provisional assignment based on a movement model showing the movement status of the communication terminal, and determines the tracking area list to which each of the N base stations belongs by finding a solution as the first solution in which one of the number of paging signals transmitted or the number of location registration signals transmitted in each of the plurality of tracking area lists is minimized and the other of the number of paging signals transmitted or the number of location registration signals transmitted in each of the plurality of tracking area lists is at the same level as the number of transmissions in the provisional assignment.

8. A network management method performed by a computer, comprising: obtaining notification information that foretells a transition in state from a first state in which the Nth base station and the (N-1)th base station belong to a first tracking area to which a first tracking area code has been assigned, to a second state in which the Nth base station belongs to a second tracking area and the (N-1)th base station belongs to a third tracking area; referring to the obtained notification information, determining a second tracking area code to be assigned to the second tracking area and a third tracking area code to be assigned to the third tracking area based on the tracking area code of the tracking area to which at least one base station, including the Nth base station, belonged in the first state and which belongs to the second tracking area in the second state and which belonged to the first state and which belonged to at least one base station, including the (N-1)th base station, belonged in the first state; and outputting information relating to the second tracking area code and the third tracking area code.

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