Network management device and network management method

Abstract

In the present invention, an acquisition unit acquires a plurality of pieces of base station position information and a plurality of pieces of representative position information. Each of the plurality of pieces of base station position information indicates the position of a base station corresponding thereto. Each of the plurality of pieces of representative position information indicates the representative position of a group corresponding thereto. A determination unit divides a plurality of base stations into a plurality of groups such that the sum of distances between each of the plurality of base stations and the representative position of a group to which each of the plurality of base stations belongs is minimized. An output control unit outputs belonging information relating to base stations belonging to each of the plurality of groups.

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. As a result, a so-called "enclave problem" may occur, where geographically distant base stations S are assigned to the same tracking area list or the same tracking area. When enclaves occur within a tracking area list or tracking area, problems such as an increase in location registration signals, a decrease in the efficiency of paging signals, and a decline in communication quality may occur.

[0005] The present invention aims to suppress the occurrence of isolated areas when optimizing tracking area lists and the like.

[0006] A network management device according to one aspect of the present invention includes: an acquisition unit that acquires a plurality of base station location information and a plurality of representative location information; a determination unit that divides the plurality of base stations into a plurality of groups such that each of the plurality of base station location information indicates the location of a corresponding base station and each of the plurality of representative location information indicates the representative location of a corresponding group, and minimizes the sum of the distances between each of the plurality of base stations and the representative location of the group to which each of the plurality of base stations belongs; and an output control unit that outputs membership information relating to the base stations belonging to each of the plurality of groups.

[0007] A computer-based network management method according to one aspect of the present invention acquires a plurality of base station location information and a plurality of representative location information, each of the plurality of base station location information indicates the location of a corresponding base station, the plurality of base stations are divided into a plurality of provisional groups, each of the plurality of representative location information indicates the representative location of the corresponding provisional group, the plurality of base stations are divided into a plurality of groups so as to minimize the sum of the distances between each of the plurality of base stations and the representative location of the corresponding provisional group, and membership information is output indicating which of the plurality of groups each of the plurality of base stations belongs to.

[0008] This invention can suppress the occurrence of isolated areas when optimizing tracking area lists and the like.

[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 first determination information. This is a schematic diagram showing the distribution of the tracking area list TL. This is a schematic diagram showing the distribution of the tracking area list TL. This is a block diagram showing the configuration of the network management device 10. This is a diagram showing an example of table TB. This is a flowchart showing the operation of the processing device 105.

[0010] [First 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 the 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" or "second paging." "Second paging signal" may also be referred to as "retransmission paging signal" or "second 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 area E4 to E6 of base stations S4 to S6, so the incoming call request via 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" or "third paging." "Third paging signal" may also be referred to as "re-retransmission paging signal" or "third 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 the communication area E1 of the base station S1, so the incoming call request is successful due to 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] In this embodiment, "optimization" refers to changing 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, optimization is determining 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. The membership status before optimization may be referred to as the "first status," and the membership status after optimization may be referred to as the "second status."

[0027] Another problem is the so-called "enclave problem," where some tracking areas TA within a tracking area list TL, or some base stations S within a tracking area TA, are located in geographically separated locations. Conventional optimization is mainly based on the movement history of communication terminals 20 between base stations S. Therefore, geographically separated base stations S may be assigned to the same tracking area list TL or the same tracking area TA.

[0028] Figures 6A and 6B are schematic diagrams showing the distribution of tracking area lists TL. Figure 6A shows three tracking area lists TL1 to TL3. Within each tracking area list TL1 to TL3, each region enclosed by a line segment is a tracking area TA belonging to that tracking area list TL. In Figure 6A, tracking area list TL3 includes the main tracking area list TL3-1 and the detached tracking area list TL3-2. Tracking area lists TL3-1 and TL3-2 are separated by tracking area list TL2.

[0029] Similar problems can also arise with tracking area TA. In this case, the tracking area list TL in Figures 6A and 6B should be read as tracking area TA, and the tracking area TA as base station S (more specifically, the communication area of ​​base station S).

[0030] The occurrence of an exclave within a Tracking Area List (TL) or Tracking Area TA can lead to the following problems: 1. Increase in location registration signals (RS): Even when a communication terminal 20 moves between two base stations S belonging to the same Tracking Area List (TL), a location registration signal (RS) may be generated, increasing traffic. Specifically, when a communication terminal 20 moves between a base station S located in the main body of the Tracking Area List (TL) and a base station S located in an exclave, a total of two location registration signals (RS) will be generated. 2. Decreased efficiency of paging signals: Because paging signals are transmitted over a wide area spanning both the main body and the exclave, unnecessary paging signals increase, reducing efficiency. 3. Decreased communication quality: The increase in location registration signals (RS) and the decreased efficiency of paging signals may lead to a decrease in communication quality.

[0031] In this embodiment, the network management device 10 optimizes at least one of the tracking area list TL and tracking area TA to suppress the occurrence of isolated areas. Specifically, as shown in Figure 6B, for example, the organization of base stations S is determined such that the outer edge of each of the tracking area lists TL1 to TL3 is indicated by a single closed line segment.

[0032] The following explanation describes the optimization of the tracking area list TL, but the tracking area TA can also be optimized using a similar process. In other words, the multiple groups described later may be multiple tracking area TAs.

[0033] [Network Management Device] Figure 7 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. The network management device 10 may also 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.

[0034] 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.

[0035] 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.

[0036] 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, map data DB1, and base station data DB2.

[0037] Program PG1 is a program for operating the network management device 10. Map data DB1 stores a map (map image) that includes the communication area of ​​the communication system 1. Map data DB1 includes latitude and longitude information that uniquely identifies each point on the map. Base station data DB2 stores the location information of each of the multiple base stations S (hereinafter referred to as "base station location information") and base station identification information that identifies each of the multiple base stations S in association with each other. In this embodiment, the base station location information is latitude information and longitude information. By combining map data DB1 and base station data DB2, the locations of the base stations S can be displayed as points (or arbitrary marks), for example, superimposed on a map displayed on the display device 101.

[0038] The processing unit 105 includes one or more CPUs (Central Processing Units). One or more CPUs are examples of one or more processors. Each of the processors and CPUs is an example of a computer. The processing unit 105 reads program PG1 from the storage device 104. By executing program PG1, the processing unit 105 functions as an acquisition unit 111, a determination unit 112, and an output control unit 113.

[0039] At least a portion of the acquisition unit 111, the determination unit 112, and the output control unit 113 may be composed of circuits such as a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), and an FPGA (Field Programmable Gate Array).

[0040] The acquisition unit 111 acquires multiple base station location information and multiple representative location information. Each of the multiple base station location information indicates the location of the corresponding base station S. The acquisition unit 111 acquires base station location information by, for example, reading the base station data DB2 stored in the storage device 104. The base stations S whose location information is to be acquired are, for example, the base stations S that are to be optimized. The base stations S that are to be optimized may be specified, for example, using base station identification information, or they may be specified by the location of the base station S.

[0041] Furthermore, each of the multiple representative location information points indicates the representative location of the corresponding group. Each group comprises one or more base stations S. In this embodiment, a group is a tracking area list TL. Each of the multiple base stations S belongs to one of the multiple groups.

[0042] The acquisition unit 111 accepts, for example, the designation of multiple points P on a map and acquires the location information of multiple points P as multiple representative location information. The acquisition unit 111 displays the map on, for example, the display device 101 and accepts the designation of points P from the user of the network management device 10 via the input device 102. The user is, for example, the administrator of the communication system 1 (or an operator instructed by the administrator). The number of points designated by the user becomes the number of groups. In addition, the map may display marks indicating the location of base stations S.

[0043] Alternatively, the acquisition unit 111 may, for example, apply the k-means method to the locations of multiple base stations S to divide the multiple base stations S into multiple provisional groups, and acquire the location information of the centroid point of each of the multiple provisional groups as multiple representative location information. The k-means method is a clustering method and is an algorithm that classifies multiple data by finding their centroids. The user specifies the number of clusters to classify the multiple base stations S into. The specified number of clusters becomes the number of provisional groups. The acquisition unit 111 divides the multiple base stations S into the specified number of provisional groups (clusters) using the k-means method. The acquisition unit 111 determines the centroid points of the locations of the multiple base stations S belonging to each provisional group as representative location information for the group.

[0044] The determination unit 112 divides the multiple base stations S into multiple groups in such a way that it minimizes the sum of the distances between each of the multiple base stations S and the representative position of the group to which each of the multiple base stations S belongs. As described above, in this embodiment, the multiple groups are multiple tracking area lists TL. Therefore, the representative position of a group is the representative position of the tracking area list TL. In this embodiment, the determination unit 112 determines which of the multiple tracking area lists TL each of the multiple base stations S belongs to by solving an objective function whose objective is to minimize the sum of the distances between each of the multiple base stations S and the representative position of the tracking area list TL to which each of the multiple base stations S belongs.

[0045] The decision unit 112 finds a solution to the objective function, for example, using quantum annealing. Quantum annealing is known to quickly 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 decision unit 112 may perform steps [1] to [3] above. Alternatively, if the network management device 10 is a computer connected to a quantum computer, the decision unit 112 may request the quantum computer to perform step [3] to obtain a solution to the objective function.

[0046] Let e ​​be an integer greater than or equal to 2, among the base stations S in the communication system 1 that are the target of this optimization. Let A = {a, b, ...} be the number of tracking area lists TLs of which two or more are the target of optimization. a, b, etc. represent individual tracking area lists TLs. 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 TLs to be optimized is denoted by |A|. In this embodiment, |A| = V (number of groups). The number of tracking areas TA in each tracking area list TL is denoted by |a|, |b|, ... The total number of tracking areas TA in all tracking area lists TLs to be optimized is f ｓｕｍ It can be shown that (= |a| + |b| + ...).

[0047] The membership 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 equation (A1). The matrix X is e row f ｓｕｍ This is a matrix of columns. Matrix X represents the membership status of each base station S in the tracking area list TL and tracking area TA after optimization. In other words, optimization corresponds to finding matrix X when the objective function is minimized (or maximized). Note that matrix X represents the membership status of each base station S in the tracking area list TL and tracking area TA before optimization. ０ Let's assume that matrix X ０ This is a known matrix.

[0048] In the following equation (A1), 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，ｊdenotes a flag = {1, 0} indicating 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 one tracking area TA (one-hot constraint), as shown in the following formula (A2), the sum of values in the horizontal direction (rows) of the matrix X is constrained to 1.

[0049]

[0050] The matrix X' shown in the following formula (A3) is a matrix with e rows and |A| columns, which indicates which tracking area list TL each base station S belongs to. The following formula (A3) shows a case where |A|=2, similarly to the above formula (A1). The elements of the matrix X' are, for example, x' ａ ｉ expressed as. x' ａ ｉ denotes a flag = {1, 0} indicating whether the i-th base station S belongs to the a-th tracking area list TL. As shown in the following formula (A4), x' ａ ｉ is the number of base stations S belonging to the a-th tracking area list TL.

[0051]

[0052] The position information of e base stations S, that is, e pieces of base station position information, is represented by the matrix X shown in the following formula (B1) ｌａｔｌｏｎ . The matrix X ｌａｔｌｏｎ is a matrix with e rows and 2 columns. Among the elements (components) of the matrix X ｌａｔｌｏｎ , x ｉ ｌａｔ denotes the latitude of the i-th base station S, and x ｉ ｌｏｎ denotes the longitude of the i-th base station S. In addition, the temporary representative positions of V (|A|) tracking area lists TL, that is, V pieces of representative position information, are represented by the matrix C shown in the following formula (B2) ｌａｔｌｏｎ . The matrix C ｌａｔｌｏｎ is a matrix with V rows (|A| rows) and 2 columns. Among the elements (components) of the matrix C ｌａｔｌｏｎ , C ａ ｌａｔThis indicates the latitude of the representative position of the a-th tracking area list TL, and C ａ ｌｏｎ This indicates the longitude of the representative location of the a-th tracking area list TL.

[0053]

[0054] The squared error between the latitude and longitude of the i-th base station S and the latitude and longitude of the representative location of the tracking area list TL to which the i-th base station S belongs is given by equation (B3) below. Equation (B4) below shows the sum of the squared errors shown in equation (B3) for all base stations S. The squared error in equation (B3) below is proportional to the distance between the location of the i-th base station S and the representative location of the tracking area list TL to which the i-th base station S belongs. Therefore, by finding the solution (X or X') that minimizes equation (B4) below, a base station S that is close to the representative location of a tracking area list TL can be assigned to that tracking area list TL. That is, D shown in equation (B4) below ｄｉｓｔ This is the objective function for minimizing the sum of the distances between each of the multiple base stations S and the representative location in the tracking area list TL.

[0055]

[0056] The output control unit 113 outputs membership information for each of the multiple groups to which the base station S belongs. Membership information is information that can identify, for example, which of the multiple groups (in this embodiment, the tracking area list TL) each of the multiple base station S belongs. In other words, membership information is information that can identify, for example, which of the multiple base station S belongs to each of the multiple tracking area list TLs.

[0057] The output control unit 113 may output a table TB as belonging information, which associates the identification information of multiple tracking area lists TL with the identification information of the base stations S belonging to each of the multiple tracking area lists TL. Outputting the table TB may mean displaying the table TB on the display device 101, or transmitting the data of the table TB to another information processing device using the communication device 103.

[0058] Figure 8 shows an example of a table TB. The table TB shown in Figure 8 includes group identification information 811 (indicated as "group ID" in the figure) that identifies the tracking area list TL, and base station identification information 812 (indicated as "base station ID" in the figure) of the base stations S belonging to the tracking area list TL. The table TB may also include, for example, the latitude and longitude information of each base station S, or distance information between each base station S and a representative point of the tracking area list TL.

[0059] [Flowchart] Figure 9 is a flowchart showing the operation of the processing unit 105. The processing unit 105 functions as an acquisition unit 111 and acquires multiple base station location information by reading the base station data DB2 from the storage device 104 (step S100). The processing unit 105 also functions as an acquisition unit 111 and acquires multiple representative location information (step S102). The acquisition of representative location information is performed, for example, by displaying a map on the display device 101 based on the map data DB1 and accepting the user to specify a representative location, or by calculating the representative location of a provisional group by applying the k-means method to the locations of multiple base stations S.

[0060] The processing unit 105 functions as a determination unit 112 and divides the multiple base stations S into multiple groups such that the sum of the distances between each of the multiple base stations S and the representative position of the group to which each base station S belongs is minimized (step S104). The processing unit 105 functions as an output control unit 113 and outputs membership information indicating which of the multiple groups each of the multiple base stations S belongs to (step S106), thereby ending the processing of this flowchart.

[0061] [Summary of the First Embodiment] As described above, the network management device 10 according to the first embodiment divides the multiple base stations S into multiple groups in such a way as to minimize the sum of the distances between each of the multiple base stations S and the representative location of the group to which each of the multiple base stations S belongs. Therefore, the geographical locations of base stations S belonging to the same group can be consolidated, and the occurrence of enclaves within the same group can be suppressed.

[0062] In particular, in this embodiment, multiple groups are multiple tracking area lists TL. Therefore, the occurrence of isolated areas within the tracking area lists TL is suppressed, and it is possible to prevent an increase in the position registration signal RS, a decrease in the efficiency of the paging signal, and a decrease in communication quality.

[0063] Furthermore, the network management device 10 accepts the user's specification of multiple points on a map and acquires the location information of multiple points as multiple representative location information. Therefore, the user can arbitrarily determine the representative location of the group.

[0064] Furthermore, the network management device 10 applies the k-means method to the locations of multiple base stations S, dividing the multiple base stations S into multiple provisional groups, and acquires the location information of the centroid point of each of the multiple provisional groups as multiple representative location information. Therefore, representative locations are set at appropriate locations based on the geographical distribution of the base stations S, enabling efficient optimization.

[0065] [Second Embodiment] In the first embodiment, an example was described in which optimization is performed by considering only the geographical positional relationship between the base station S and the representative point of the tracking area list TL so that no enclaves occur within the tracking area list TL. On the other hand, in practice, optimization is performed based on various factors, such as the number of paging signals generated and the number of location registration signals RS transmitted. In the second embodiment, a case in which optimization is performed by considering not only the geographical positional relationship but also various other factors will be described.

[0066] In the second embodiment, in addition to minimizing the sum of distances as described in the first embodiment, the determination unit 112 divides the multiple base stations S into multiple tracking area list TLs such that it satisfies at least one of the following: smoothing the sum of the initial paging signals received by each of the multiple tracking area list TLs; minimizing the number of location registration signals RS transmitted when the communication terminal 20 moves between base stations S belonging to different tracking area list TLs; minimizing the sum of the second and subsequent paging signals generated in each of the multiple tracking area list TLs; and smoothing the number of base stations S belonging to each of the multiple tracking area list TLs.

[0067] Hereinafter, "Smoothing the sum of the initial paging signals generated in each of the multiple tracking area lists TL" will be referred to as "A. Smoothing the initial paging signals," "Minimizing the number of location registration signals RS transmitted when the communication terminal 20 moves between base stations S belonging to different tracking area lists TL" will be referred to as "B. Minimizing the location registration signals RS," "Minimizing the sum of the second and subsequent paging signals generated in each of the multiple tracking area lists TL" will be referred to as "C. Minimizing the second and subsequent paging signals," and "Smoothing the number of base stations S belonging to each of the multiple tracking area lists TL" will be referred to as "D. Smoothing the number of base stations S."

[0068] 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 subsequent retransmissions (fourth paging) and beyond 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.

[0069] First, let's explain the data used for the simulation. 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 MＰ This is an e-row, e-column matrix as shown in equation (C1) 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.

[0070]

[0071] 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 M Ｌ This is an e-row, e-column matrix as shown in equation (C2) 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.

[0072]

[0073] A. If A is the set of tracking area lists TL that are subject to smoothing optimization of the initial paging signal, then A = {a, b, ...} = {A １ , A ２ ,...A ｖ}. Of the |A| (V) tracking area lists TLs that are to be optimized, the k-th tracking area list TL is A ｋ This is how it is written.

[0074] The total number of initial paging signals received at base stations S belonging to the nth tracking area list TL, D ｎ This is represented by the following formula (D1). ｎ Parameters related to (p ｋ ) is represented by the following formula (D2). p 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 initial paging signals generated targeting the k-th base station S.

[0075]

[0076] Similarly, D is the total number of initial paging signals received at base stations S belonging to the (n+1)th tracking area list TL. ｎ＋１ Let n = 1 to |A|-1, (D ｎ -D ｎ＋１ ) ２ The solution that minimizes the sum of these values ​​is the solution that satisfies the "uniformity of the initial paging signals". In other words, the objective function for smoothing the number of initial paging signals received in each of the multiple tracking area lists TL is given by the following equation (D3).

[0077]

[0078] B. 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 (E3). G Ｌ The parameters related to are shown by the following equations (E1) to (E2). The R shown in equation (E1) 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 equation (E2) shows 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 "minimization of the position registration signal RS". In other words, the objective function for minimizing the number of position registration signals RS is given by the following equation (E3).

[0079]

[0080] C. Minimizing the second and subsequent paging signals First, we consider the second paging signal (retransmitted paging signal). 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 (F7). D' ａ The parameters related to are shown by the following equations (F1) to (F8). The R shown in equation (F1) 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 (F2) 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.

[0081] P' shown in equation (F3) 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 the second paging signal is generated, targeting the k-th base station S.

[0082] A shown in the following formula (F4) ａ ｊThis 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 equation (F5). ａ ｊ This is the number of times each base station S belonging to the j-th tracking area TA in the a-th tracking area list TL has received its second paging signal. C is shown in the following equation (F6). ａ ｊ This represents 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.

[0083]

[0084]

[0085] Next, we consider the third paging signal (re-retransmitted paging signal). 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 (F12). H ａ The parameters related to are shown by the following equations (F8) to (F11). The R shown in equation (F8) 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 (F9) ａ ｋ，ｉ This 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.

[0086] G shown in formula (F10) 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 (F11) ａ This is the number of base stations S in the a-th tracking area list TL.

[0087]

[0088]

[0089] From the above, the total number of receptions Y of paging signals from the second time onward at the base station S belonging to the a-th tracking area list TL ａ is expressed by the following formula (F13). Then, the total number of receptions Y' of paging signals at all base stations S belonging to the tracking area list TL to be optimized is expressed by the following formula (F14). In other words, the objective function for minimizing the paging signals from the second time onward is expressed by the following formula (F14).

[0090]

[0091] D. Smoothing of the Number of Base Stations S As described above, the number of base stations S targeted for the current optimization is e, and the number of tracking area lists TL (|A|) is V. When e base stations S belong to V tracking area lists TL in equal numbers, that is, the ideal number of affiliated base stations S in one tracking area list TL e ａｖｅ is expressed by the following formula (G1). When the number of base stations S in the a-th tracking area list TL is defined as e ａ , the objective function for smoothing the number of base stations S belonging to each tracking area list TL is expressed by the following formula (G2).

[0092]

[0093] Summarizing the above-described formula (D3) that is the objective function for smoothing the initial paging signal, formula (E3) that is the objective function for minimizing the location registration signal RS, formula (F14) that is the objective function for minimizing the paging signals from the second time onward, formula (G2) that is the objective function for smoothing the number of base stations S, and formula (B4) that is the objective function for preventing enclaves, the result is an objective function Z expressed by the following formula (H1). In formula (H1), the term (δD of formula (B4) ｄｉｓｔ) It is optional whether or not to employ terms other than the above. For example, optimization may be performed using an objective function Z that includes all five terms as shown in formula (H1), or optimization may be performed using only the term (δD ｄｉｓｔ ) of formula (B4) and the term (αH Ｄ１ ) of formula (D3) to constitute the objective function.

[0094]

[0095] In the above formula (H1), α, β, ζ, η, and δ are coefficients for weighting (scaling) each term. Each coefficient is a value obtained by dividing a constant specified for each term by the value of the objective function of each term before optimization. More specifically, for example, δ which is the coefficient of formula (B4) is represented by the following formula (H2). In formula (H2), C １ is a constant specified for the corresponding term, and D ｄｉｓｔ０ represents a value obtained by substituting the elements of the matrix X ０ indicating the affiliation state before optimization into formula (B4). In this way, the coefficient of each term is calculated by dividing the constant specified for each term by the objective function of the corresponding term calculated based on the affiliation state before optimization.

[0096]

[0097] Further, in the above formula (H1), when the term of formula (E3) which is the objective function for minimizing the location registration signal RS is employed, a constraint condition that the number of location registration signals RS after optimization is equal to or less than the number of location registration signals RS before optimization may be imposed. That is, G Ｌ is a value obtained by substituting the elements of the matrix X ０ indicating the affiliation state before optimization into G Ｌ０ , and G Ｌ ≦ G Ｌ０ may be set such that the matrix X satisfying this condition is obtained. Thereby, it is possible to prevent the location registration signals RS after optimization from increasing compared to before optimization.

[0098] In other words, in addition to minimizing the sum of distances, the determination unit 112 may divide the multiple base stations S into multiple tracking area lists TL such that the number of location registration signals RS transmitted when the communication terminal 20 moves between base stations S belonging to different tracking area lists TL is less after optimization (second state) than before optimization (first state).

[0099] In the second embodiment as well, since each base station S belongs to only one tracking area list TL and tracking area TA (one-hot constraint), the sum of the horizontal (row) values ​​of matrix X is constrained to 1, as shown in equation (A2) above.

[0100] [Summary of the Second Embodiment] As described above, the network management device 10 according to the second embodiment optimizes by considering, in addition to the positional relationship between the base station S and the representative location, at least one of the following: the number of paging signals (initial paging signal and subsequent paging signals), the number of location registration signals RS, and the number of base stations S belonging to each tracking area list TL. This makes it possible to further improve the communication quality in the communication system 1.

[0101] [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.

[0102] (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.

[0103] (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.

[0104] (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).

[0105] (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.

[0106] (6) Each function illustrated in Figure 7 is realized by any combination of at least one of hardware and software. Furthermore, the method of realizing each functional block is not particularly limited. That is, each functional block may be realized using one device that is physically or logically coupled, or it may be realized using two or more physically or logically separated devices that are directly or indirectly connected (for example, using wired, wireless, etc.). A functional block may also be realized by combining the one or more devices with software.

[0107] (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.

[0108] 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.

[0109] (8) In each of the above-mentioned forms, the terms “system” and “network” shall be used interchangeably.

[0110] (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.

[0111] (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.

[0112] (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.

[0113] (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".

[0114] (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."

[0115] (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.

[0116] (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.

[0117] (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.”

[0118] (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).

[0119] 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...Acquisition unit, 112...Decision unit, 113...Output control unit, S...Base station.

Claims

1. A network management device comprising: an acquisition unit that acquires multiple base station location information and multiple representative location information; each of the multiple base station location information indicates the location of a corresponding base station; each of the multiple representative location information indicates the representative location of a corresponding group; a determination unit that divides the multiple base stations into the multiple groups in such a way as to minimize the sum of the distances between each of the multiple base stations and the representative location of the group to which each of the multiple base stations belongs; and an output control unit that outputs membership information relating to the base stations belonging to each of the multiple groups.

2. The network management device according to claim 1, wherein the acquisition unit accepts the designation of multiple points on a map and acquires the location information of the multiple points as the multiple representative location information.

3. The network management device according to claim 1, wherein the acquisition unit divides the plurality of base stations into a plurality of provisional groups by applying the k-means method to the locations of the plurality of base stations, and acquires the location information of the centroid point of each of the plurality of provisional groups as the plurality of representative location information.

4. The network management device according to claim 1, wherein the plurality of groups are a plurality of tracking area lists.

5. The network management device according to claim 4, wherein the determination unit divides the plurality of base stations into the plurality of tracking area lists such that, in addition to minimizing the sum of the distances, it satisfies at least one of the following: smoothing the sum of the initial paging signals received in each of the plurality of tracking area lists; minimizing the number of location registration signals transmitted when a communication terminal moves between base stations belonging to different tracking area lists; minimizing the sum of the second and subsequent paging signals received in each of the plurality of tracking area lists; and smoothing the number of base stations belonging to each of the plurality of tracking area lists.

6. The network management device according to claim 4, wherein the belonging information indicates which of the plurality of tracking area lists each of the plurality of base stations belongs to when a first base station, which is one of the plurality of base stations, transitions from a first state, in which it belongs to a first tracking area list, which is one of the plurality of tracking area lists, to a second state, in which it belongs to a second tracking area list, which is one of the plurality of tracking area lists, and the determination unit divides the plurality of base stations into the plurality of tracking area lists such that, in addition to minimizing the sum of the distances, the number of location registration signals transmitted when a communication terminal moves between base stations belonging to different tracking area lists is less in the second state than in the first state.

7. The network management device according to claim 1, wherein the plurality of groups are the plurality of tracking areas.

8. A network management method performed by a computer, comprising: acquiring multiple base station location information and multiple representative location information; each of the multiple base station location information indicates the location of a corresponding base station; each of the multiple representative location information indicates the representative location of a corresponding group; dividing the multiple base stations into multiple groups such that the sum of the distances between each of the multiple base stations and the representative location of the group to which each of the multiple base stations belongs is minimized; and outputting membership information relating to the base stations belonging to each of the multiple groups.

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