Communication control device and identifier determination method

Abstract

To automatically set optimum cell identifiers in consideration of a plurality of indices.SOLUTION: A communication control apparatus includes a memory, and a processor coupled to the memory. The processor is configured to determine, by using metrics related to a first value and a second value, first remainders of divisions of a cell identifier respectively by the first value and the second value, determine a second remainder of a division of the cell identifier by the least common multiple of the first value and second value, by using the first remainders, determine a third remainder of a division of the cell identifier by the least common multiple of the first value, the second value, and a third value, by using the second remainder and a metric related to the third value, and determine a cell identifier that satisfies the third remainder.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a communication control device and an identifier determination method. [Background technology]

[0002] Generally, cells constituting a wireless communication system are assigned identifiers to identify each other. One example of such a cell identifier is the PCI (Physical Cell ID). For example, in a fifth-generation mobile communication system (5G), each cell is assigned 1008 PCIs, each consisting of a combination of three PSSs (Primary Synchronization Signals) and 336 SSSs (Secondary Synchronization Signals).

[0003] Since PCI is an identifier for identifying each of multiple cells, it is desirable that the PCIs of adjacent cells are different. Furthermore, if the PCIs of adjacent cells have the same remainder when divided by 3, the PSSs of these cells will be the same, which will reduce the accuracy of channel estimation and delay synchronization. Therefore, it is desirable that the remainders of the PCIs of adjacent cells when divided by 3 are different. In other cases, PCIs are set according to multiple indicators, such as when the PCIs of adjacent cells are divided by 4, it is desirable that the remainders are different so that the subcarrier positions of the DMRS (DeModulation Reference Signal) of the PBCH (Physical Broadcast CHannel) do not overlap. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-167464 [Patent Document 2] Special Publication No. 2018-509858 [Patent Document 3] Special Publication No. 2020-504991 [Non-patent literature]

[0005] [Non-Patent Document 1] Techplayon, "5G NR Physical Cell ID (PCI) Planning", [online], November 18, 2019, Internet<URL: https: / / www.techplayon.com / 5g-nr-physical-cell-id-pci-planning / > Summary of the Invention [Problem to be solved by the invention]

[0006] However, there is a problem that a great deal of effort is required to set a PCI, for example, when a cell is newly established. That is, as described above, the PCI of a cell may be set according to multiple indicators, and manually determining a PCI taking these indicators into consideration increases the time and cost required for PCI setting. Therefore, it is conceivable to automatically determine the PCI of a cell, but for example, for a newly established cell, there is no information on radio quality, and it is not easy to determine a PCI in a situation where there is little information on which to base a decision. Furthermore, when multiple indicators are considered for the surplus related to the PCI of an adjacent cell, it is difficult to automatically set an optimal PCI according to these indicators.

[0007] The disclosed technology has been developed in consideration of these points, and aims to provide a communication control device and an identifier determination method that can automatically set an optimal cell identifier taking into account multiple indicators. [Means for solving the problem]

[0008] In one aspect, the communication control device disclosed in the present application has a memory and a processor connected to the memory, and the processor performs the following processes: using a metric for a first value and a second value to determine a first remainder when a cell identifier is divided by the first value and the second value, respectively; using the first remainder to determine a second remainder when a cell identifier is divided by a least common multiple of the first value and the second value; using a metric for a third value and the second remainder to determine a third remainder when a cell identifier is divided by a least common multiple of the first value, the second value, and the third value; and determining a cell identifier that satisfies the third remainder. [Effects of the Invention]

[0009] According to one aspect of the communication control device and identifier determination method disclosed in the present application, it is possible to automatically set an optimal cell identifier taking into consideration a plurality of indicators. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a communication system. [Figure 2] FIG. 2 is a block diagram showing a configuration of the communication control device according to the first embodiment. [Figure 3] FIG. 3 is a sequence diagram showing a cell identifier initial setting method. [Figure 4] FIG. 4 is a flow diagram showing the cell identifier initial setting process. [Figure 5] FIG. 5 is a block diagram showing a configuration of a communication control device according to the second embodiment. [Figure 6] FIG. 6 is a sequence diagram showing a cell identifier optimization method. [Figure 7] FIG. 7 is a flow diagram showing the cell identifier optimization process. [Figure 8] FIG. 8 is a diagram showing a specific example of the number of HOs between cells with the same remainder. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of a communication control device and an identifier determination method disclosed in the present application will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to these embodiments.

[0012] (Embodiment 1) Fig. 1 is a diagram illustrating a configuration example of a communication system according to embodiment 1. The communication system illustrated in Fig. 1 includes a communication control device 100, a CU / DU (Central Unit / Distributed Unit) 210, an RU (Radio Unit) 220, and a UE (User Equipment: user terminal) 230.

[0013] The communication control device 100 is called, for example, a RAN Intelligent Controller (RIC), and controls the CU / DU 210, which is a base station of a wireless communication system. Specifically, the communication control device 100 determines and assigns a PCI, which is a cell identifier, to a cell 220a under the control of the CU / DU 210. At this time, the communication control device 100 determines the PCI of the cell 220a using the remainders obtained when the PCI of the adjacent cell 220a is divided by three different values ​​as indicators. That is, the communication control device 100 determines the PCI of each cell 220a so that the remainder obtained when the PCI is divided by a first value (e.g., 3), the remainder obtained when the PCI is divided by a second value (e.g., 4), and the remainder obtained when the PCI is divided by a third value (e.g., 30) are as different as possible from the adjacent cells 220a. In this way, the communication control device 100 can automatically set an optimal cell identifier taking multiple indicators into consideration. The configuration and operation of the communication control device 100 will be described in detail later.

[0014] In this embodiment, it is assumed that three indices are used when determining the PCI of cell 220a: the remainder when dividing the PCI by 3, the remainder when dividing the PCI by 4, and the remainder when dividing the PCI of the neighboring cell by 30. That is, it is desirable that the remainders when dividing the PCI by 3, 4, and 30 are as different as possible in neighboring cells. When the remainder when dividing the PCI by 3 differs in neighboring cells, the PSS of the neighboring cells differs, making it possible to suppress a decrease in channel estimation accuracy and a synchronization delay. Furthermore, when the remainder when dividing the PCI by 4 differs in neighboring cells, the subcarrier positions of the DMRS of the PBCH do not overlap, making it possible to reduce interference. Furthermore, since the remainder when dividing PCI by 30 differs between adjacent cells, the basis of the ZC (Zadoff-Chu) sequence used for DMRS and SRS (Sounding Reference Signal) in PUCCH (Physical Uplink Control CHannel) and PUSCH (Physical Uplink Shared CHannel) differs, thereby reducing interference.

[0015] The CU / DU 210 is a baseband device constituting a base station of a wireless communication system. The CU / DU 210 is connected to a core network (not shown) and performs baseband processing on data. The CU / DU 210 is also connected to a plurality of RUs 220 via FH (Front Haul) lines and manages information related to the cells 220a formed by each RU 220. Specifically, the CU / DU 210 sets a cell identifier notified from the communication control device 100 for each cell 220a. The CU / DU 210 then controls the RU 220 to control the transmission power in the cell 220a and transmits and receives data to and from the UE 230 via the RU 220.

[0016] The RU 220 is a radio device that constitutes a base station of a radio communication system. The RU 220 performs radio processing on data, forms a cell 220a, and transmits and receives data wirelessly to and from the UE 230 within the cell 220a.

[0017] The UE 230 is a terminal device capable of wireless communication, and performs wireless communication with the RU 220 that forms the cell 220a in which the UE 230 is located.

[0018] 2 is a block diagram showing the configuration of a communication control device 100 according to Embodiment 1. The communication control device 100 shown in FIG. 2 includes a communication interface unit (hereinafter abbreviated as "communication IF unit") 110, a processor 120, and a memory 130.

[0019] The communication IF unit 110 is connected to the CU / DU 210, and receives information from the CU / DU 210 and transmits information to the CU / DU 210. Specifically, the communication IF unit 110 receives cell information related to cells 220a under the control of the CU / DU 210. The cell information includes location information of the RUs 220 that form each cell 220a and transmission power information of the RUs 220 in each cell 220a. The communication IF unit 110 also transmits cell identifier information of the cell 220a determined by the processor 120 to the CU / DU 210.

[0020] The processor 120 includes, for example, a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), or a DSP (Digital Signal Processor), and performs overall control of the communication control device 100. Specifically, the processor 120 includes a cell information acquisition unit 121, a base remainder determination unit 122, an LCM (Least Common Multiple) remainder determination unit 123, and a cell identifier determination unit 124.

[0021] The cell information acquisition unit 121 acquires cell information related to the cell 220a from the communication IF unit 110. That is, the cell information acquisition unit 121 acquires cell information including location information of the RUs 220 that form each cell 220a and transmission power information of the RUs 220 in each cell 220a.

[0022] The base remainder determination unit 122 calculates a metric for a remainder obtained by a modulo operation using a first value (here, 3) and a second value (here, 4), which is a remainder that serves as an index for determining a cell identifier, and determines a remainder (hereinafter referred to as a "base remainder") for each of the first value and the second value that minimizes the metric. Specifically, when determining the cell identifier of cell #i, the base remainder determination unit 122 calculates a metric for each remainder k obtained by a modulo operation using a value m, m (i, k) is calculated using the following formula (1).

number

[0023] In the above formula (1), C update indicates a set of cells 220a in the target range for which cell identifiers are to be set, and C outside is C update UE 230 can be handed over to a cell 220a belonging to PCI. j indicates the cell identifier of cell #j, and % is the operator symbol for modulo operation. j %m=k indicates that the remainder when the cell identifier of cell #j is divided by the value m is k. j denotes the transmission power of cell #j, and d i,j indicates the distance from the RU 220 in cell #i to the RU 220 in cell #j. θ is a predetermined attenuation coefficient that is set in advance depending on the radio environment. The metric w m (i, k) is the cell identifier PCI of the already set cell #j j is calculated for each remainder k when dividing by the value m, and the metric w m The smaller (i, k) is, the smaller the interference from cell #j corresponding to remainder k to cell #i is. Therefore, the cell identifier of cell #i is expressed as the metric w m By using a cell identifier corresponding to a remainder k that reduces (i, k), there will be fewer cells in the vicinity of cell #i that have the same remainder k when dividing the cell identifier by the value m.

[0024] Here, since metrics for the first value and the second value are calculated, the base remainder determination unit 122 calculates the metric w3(i,k) and the metric w4(i,k) for each remainder k. Then, the base remainder determination unit 122 determines the remainder k that minimizes the metric w3(i,k) and the metric w4(i,k) as the base remainder. That is, the base remainder determination unit 122 determines the remainder k that minimizes the metric w3(i,k) as the base remainder k for the first value. i,3 The remainder k that minimizes the metric w4(i,k) is determined as the base remainder K for the second value. i,4 In other words, the base remainder determination unit 122 determines the base remainder K when determining the cell #i. i,3 , K. i,4 is determined by the following equations (2) and (3).

number

number

[0025] In the above equations (2) and (3), argmin(x) is a function that returns the value that minimizes x.

[0026] The LCM remainder determination unit 123 determines a remainder (hereinafter referred to as "LCM remainder") corresponding to the cell identifier to be determined, which is obtained by a remainder calculation using the least common multiple of a first value (here, 3), a second value (here, 4), and a third value (here, 30). Specifically, the LCM remainder determination unit 123 first calculates an LCM remainder obtained by a remainder calculation using the least common multiple of the first and second values, and then uses the calculated LCM remainder to determine an LCM remainder obtained by a remainder calculation using the least common multiple of the first to third values. That is, the LCM remainder determination unit 123 determines the LCM remainder obtained by a remainder calculation using the least common multiple of the first to third values ​​using the base remainder K corresponding to 3 and 4. i,3 , K. i,4 Using this, the LCM remainder K corresponding to 12, which is the least common multiple of 3 and 4, is i,12 is calculated using the following formula (4).

number

[0027] Then, the LCM remainder determination unit 123 determines the LCM remainder K i,12 Using this, the LCM remainder K corresponding to 60, which is the least common multiple of 3, 4 and 30, is i,60 That is, the LCM remainder determination unit 123 determines the LCM remainder K i,12 Among the values ​​k that satisfy 30 The value k that minimizes (i, k) is the LCM surplus K i,60 is decided.

number

[0028] The cell identifier determination unit 124 determines the cell identifier of the determination target cell 220a based on the LCM remainder for the least common multiple of the first to third values. Specifically, the cell identifier determination unit 124 determines the cell identifier of the determination target cell 220a based on the LCM remainder K i,60 Based on the cell identifier PCI of cell #i i That is, the cell identifier determination unit 124 determines the LCM remainder K as follows: i,60 The cell identifier PCI of cell #i is i is decided.

number

[0029] In the above equation, R(0, x) represents a random integer between 0 and x. i,60 By branching the condition depending on the size of the cell identifier PCI that does not exceed 1008 i Then, the cell identifier determination unit 124 determines the cell identifier PCI of the determined cell #i. i and transmits the cell identifier information including the cell identifier from the communication IF unit 110 to the CU / DU 210.

[0030] The memory 130 includes, for example, a random access memory (RAM) or a read only memory (ROM), and stores information used in processing by the processor 120.

[0031] Next, a cell identifier initial setting method in the communication system configured as described above will be described with reference to the sequence diagram shown in Fig. 3. This cell identifier initial setting method is a method for initially setting a cell identifier for new cell 220a when, for example, a new RU 220 is installed to connect to CU / DU 210 and this RU 220 forms a new cell 220a.

[0032] The CU / DU 210 transmits cell information of the cells 220a, including the new cell 220a, to the communication control device 100 (step S101). This cell information includes location information of the RU 220 and transmission power information of the RU 220. The cell information is acquired by the cell information acquisition unit 121, and the base remainder determination unit 122, the LCM remainder determination unit 123, and the cell identifier determination unit 124 initially set the cell identifier of the new cell 220a (step S102).

[0033] That is, the base remainder determiner 122 calculates the metric of the above formula (1) by using the location information and transmission power information of the RU 220, and determines the base remainder that minimizes the metrics for the first value and the second value as shown in the above formulas (2) and (3). Then, the LCM remainder determiner 123 determines the LCM remainder corresponding to the least common multiple of the first to third values ​​by the above formulas (4) and (5) based on the base remainder. Furthermore, the cell identifier determiner 124 determines the cell identifier of the new cell 220a based on the LCM remainder.

[0034] Information about the determined cell identifier is transmitted from the communication IF unit 110 to the CU / DU 210 (step S103). Then, the CU / DU 210 sets the cell identifier of the newly established RU 220 (step S104), and the RU 220 broadcasts the cell identifier, for example, via a broadcast channel, thereby starting communication between the CU / DU 210, the RU 220, and the UE 230 (step S105).

[0035] In this way, when a new cell 220a is formed, an optimal cell identifier that takes multiple indicators into consideration can be automatically set for the new cell 220a.

[0036] Next, the cell identifier initial setting process in the communication control device 100 will be described with reference to the flowchart shown in Fig. 4. This cell identifier initial setting process is mainly executed by the base remainder determination unit 122, the LCM remainder determination unit 123, and the cell identifier determination unit 124.

[0037] When the cell information acquisition unit 121 acquires cell information (step S201), a cell identifier is randomly set for the cell 220a to which a cell identifier has not been assigned (step S202). That is, for example, a random cell identifier is set for the cell 220a formed by the newly installed RU 220 for convenience. Then, a set C of cells 220a within a target range including the cell 220a for which a cell identifier is to be initially assigned is set. update The following process is repeated for

[0038] That is, it is determined whether or not a cell identifier has been initially set for the cell 220a (step S203). In this determination, it is determined whether or not a cell identifier other than the randomly set cell identifier has been assigned to the cell 220a. If the cell identifier has been initially set (step S203 Yes), the set C update The same determination is repeated for the other cells 220a included in the table.

[0039] If the cell identifier has not been initially set in the cell 220a (step S203 No), the base remainder determination unit 122 determines the base remainder for the first value and the second value (step S204). Specifically, for the first value 3 and the second value 4, the metrics w3(i,k) and w4(i,k) in the above formula (1) are calculated for each remainder k, and the base remainder K that minimizes the metrics w3(i,k) and w4(i,k) is determined. i,3 , K. i,4 is determined.

[0040] Then, the LCM remainder determination unit 123 determines the LCM remainder corresponding to the least common multiple of the first value and the second value (step S205). Specifically, for 12, which is the least common multiple of the first value and the second value, the base remainder K i,3 , K. i,4 is used and the LCM surplus K is calculated using the above equation (4). i,12 Furthermore, the LCM remainder determination unit 123 determines the LCM remainder corresponding to the least common multiple of the first value, the second value, and the third value (step S206). Specifically, for 60, which is the least common multiple of the first value, the second value, and the third value, the LCM remainder K i,12 is used and the LCM surplus K is calculated using the above equation (5). i,60 is determined.

[0041] LCM surplus K i,60 Once determined, the cell identifier determination unit 124 determines the LCM remainder K i,60 In other words, the remainder when dividing the first to third values ​​by the least common multiple 60 is the LCM remainder K i,60 The value that becomes the cell identifier of cell 220a is determined. This cell identifier is the cell identifier that minimizes the metric related to the first to third values, and therefore there are few nearby cells with cell identifiers that give the same remainder when divided by the first to third values.

[0042] The initial settings of the above cell identifiers are set C updateWhen the initial setting of the cell identifiers for all the cells 220a is completed, the cell identifier information is transmitted from the communication IF unit 110 to the CU / DU 210 (step S208).

[0043] As described above, according to this embodiment, when the remainders obtained by modular arithmetic using three values ​​are used as multiple indicators for determining a cell identifier, a base remainder is determined using a metric corresponding to each value, and an LCM remainder related to the least common multiple of each value is determined based on the base remainder. Then, a cell identifier is determined using the LCM remainder. Therefore, when initially setting a cell identifier, an optimal cell identifier can be automatically set taking multiple indicators into consideration.

[0044] (Embodiment 2) The second embodiment is characterized in that the cell identifiers are updated and optimized during operation of the communication system.

[0045] The configuration of the communication system according to the second embodiment is the same as that of the first embodiment (FIG. 1), and therefore a description thereof will be omitted.

[0046] Fig. 5 is a block diagram showing the configuration of a communication control device 100 according to embodiment 2. In Fig. 5, the same components as those in Fig. 2 are denoted by the same reference numerals, and their description will be omitted. The communication control device 100 shown in Fig. 5 has a handover information (hereinafter abbreviated as "HO information") acquisition unit 301 instead of the cell information acquisition unit 121 shown in Fig. 2.

[0047] The HO information acquisition unit 301 acquires HO information related to handovers between cells 220a by the UE 230 from the communication IF unit 110. In this embodiment, the CU / DU 210 monitors handovers of the UE 230 between the cells 220a formed by each RU 220, and tallies the number of handovers between the cells 220a. Then, the CU / DU 210 transmits HO information including information on the tallied number of handovers to the communication control device 100. For this reason, the HO information acquisition unit 301 acquires the HO information transmitted by the CU / DU 210. The HO information stores the number of times the UE 230 has performed handovers, in association with the combination of the handover source cell 220a and the handover destination cell 220a.

[0048] In this embodiment, since HO information is acquired while the communication system is in operation, the base remainder determination unit 122 calculates a metric using the number of handovers and determines a base remainder that minimizes the metrics for each of the first value and the second value. Specifically, when determining the cell identifier of cell #i, the base remainder determination unit 122 calculates the metric w for each remainder k obtained by a remainder calculation using the value m. m (i, k) is calculated using the following equation (6).

number

[0049] In the above equation (6), C update indicates a set of cells 220a in the target range for which cell identifiers are to be set, and C outside is C update UE 230 can be handed over to a cell 220a belonging to PCI. j indicates the cell identifier of cell #j, and % is the operator symbol for modulo operation. j %m=k indicates that when the cell identifier of cell #j is divided by the value m, the remainder is k. HO,i,j indicates the number of handovers from cell #i to cell #j, and N HO,j,i indicates the number of handovers from cell #j to cell #i. The metric wm (i,k) is the cell identifier PCI of cell #j j is calculated for each remainder k when dividing by the value m, and the metric w m The smaller (i, k) is, the less handovers there are between cell #j and cell #i corresponding to the remainder k. Therefore, the cell identifier of cell #i is expressed as the metric w m By using a cell identifier corresponding to the remainder k that reduces (i, k), the possibility of handover by UE 230 occurring between cells 220a with the same remainder k when dividing the cell identifier by the value m is reduced.

[0050] Next, a cell identifier optimization method in the communication system configured as above will be described with reference to the sequence diagram shown in Fig. 6. This cell identifier optimization method is a method for optimizing the cell identifier assigned to each cell 220a during operation of the communication system in which cell identifiers have already been assigned to all cells 220a.

[0051] During operation of the communication system, communication is performed among the CU / DU 210, the RU 220, and the UE 230 (step S301). During this time, the CU / DU 210 monitors handover of the UE 230 and counts the number of handovers between the cells 220a (step S302). That is, the CU / DU 210 counts the number of handovers by the UE 230 for each combination of the handover source cell 220a and the handover destination cell 220a. Then, the CU / DU 210 transmits HO information including the count result of the number of handovers to the communication control device 100 (step S303).

[0052] The HO information acquisition unit 301 acquires the HO information, and the base remainder determination unit 122, the LCM remainder determination unit 123, and the cell identifier determination unit 124 optimize the cell identifier of each cell 220a (step S304). That is, the base remainder determination unit 122 uses the number of handovers to calculate the metric of the above formula (6), and determines the base remainder that minimizes the metric for the first value and the second value as shown in the above formulas (2) and (3). Then, the LCM remainder determination unit 123 determines the LCM remainder corresponding to the least common multiple of the first to third values ​​using the above formulas (4) and (5) based on the base remainder. Furthermore, the cell identifier determination unit 124 determines the cell identifier of the cell 220a based on the LCM remainder.

[0053] Information about the determined cell identifier is transmitted from the communication IF unit 110 to the CU / DU 210 (step S305). Then, the CU / DU 210 updates the cell identifier of the cell 220a formed by each RU 220 (step S306).

[0054] In this way, when the cell identifier of each cell 220a is updated during operation of the communication system, an optimal cell identifier that takes into consideration a plurality of indicators can be automatically set to the new cell 220a.

[0055] Next, the cell identifier optimization process in the communication control device 100 will be described with reference to the flow diagram shown in Fig. 7. In Fig. 7, the same parts as in Fig. 4 are assigned the same reference numerals, and detailed description thereof will be omitted. This cell identifier optimization process is mainly executed by the base remainder determination unit 122, the LCM remainder determination unit 123, and the cell identifier determination unit 124.

[0056] When the HO information acquisition unit 301 acquires the HO information (step S401), parameters for optimizing the cell identifier are initialized (step S402). Specifically, the minimum value L of the evaluation value L for determining whether to update the cell identifier of the cell 220a is set to L. min is the current set of cell identifiers PCI now The evaluation value L(PCInow ) is set. Also, the set of cell identifiers after the update is set to PCI update and a set of update candidate cell identifiers PCI candidate All of these are the current set of cell identifiers PCI now is initialized to

[0057] Here, the evaluation value L is calculated by the following formula (7): update metric w for the first, second, and third values ​​in m It is defined using (i,k).

number

[0058] In the above formula (7), α, β, and γ are weighting coefficients for the first value, the second value, and the third value, respectively. Therefore, the evaluation value L is calculated by multiplying the metrics w m The smaller the evaluation value L, the greater the value of the set C of cells 220a in the target range. update It can be said that a desirable cell identifier is assigned in consideration of multiple indicators.

[0059] Once the parameters are initialized, a set C of cells 220a within the target range for which the cell identifiers are to be optimized is update The following process is repeated for

[0060] That is, the base remainder determination unit 122 determines a base remainder for the first value and the second value (step S204). Then, the LCM remainder determination unit 123 determines an LCM remainder corresponding to the least common multiple of the first value and the second value (step S205). Furthermore, the LCM remainder determination unit 123 determines an LCM remainder corresponding to the least common multiple of the first value, the second value, and the third value (step S206).

[0061] LCM surplus K i,60 Once determined, the cell identifier determination unit 124 determines the LCM remainder Ki,60 The cell identifier based on the PCI is determined, and the set of update candidates is PCI candidate is updated (step S403). That is, the remainder when dividing the first to third values ​​by the least common multiple 60 is the LCM remainder K i,60 The value is determined as the cell identifier of the cell 220a, and the set of update candidates PCI is updated to include this cell identifier. candidate will be updated.

[0062] The above cell identifiers are determined as set C update is repeated for the cells 220a included in the set of update candidates PCI candidate When is updated, the set of update candidates PCI candidate The evaluation value L(PCI candidate ) is calculated, and the evaluation value L min As a result of this determination, it is determined whether the evaluation value L(PCI candidate ) is the evaluation value L min If it is smaller than (Yes in step S404), there is a possibility that the evaluation value L can be further reduced, so the minimum evaluation value L min is the set of update candidates PCI candidate The evaluation value L(PCI candidate ) and the updated cell identifier set PCI update is the set of update candidates PCI candidate (Step S407). Then, the set C of cells 220a in the target range is set as follows: update For the set of update candidates PCI candidate The process of updating is repeated.

[0063] On the other hand, as a result of the determination in step S404, the evaluation value L(PCI candidate ) is the evaluation value L min In the above case (No in step S404), the evaluation value L is sufficiently small, so the set of cell identifiers PCI after update is update Then, using the evaluation value L, it is determined whether or not to actually update the cell identifier of the cell 220a (step S405).

[0064] Specifically, the set of updated cell identifiers PCI update The evaluation value L(PCI update ) is the current set of cell identifiers before updating PCI now The evaluation value L(PCI now ) is determined. At this time, since changing the cell identifier involves a load on the communication system, the evaluation value L(PCI update ) includes aggregate PCI update The number N of cells 220a whose cell identifiers are changed by the update to change The evaluation value L(PCI now ) is subtracted by a predetermined value ε. This allows the cell identifier of cell 220a to actually be updated if the evaluation value L is significantly improved.

[0065] As a result of the determination in step S405, the evaluation value L(PCI update ) is the evaluation value L(PCI now ) is not significantly improved (step S405 No), the set PCI of cell identifiers of the cell 220a update Updates to the Collective PCI were cancelled. update is not notified to the CU / DU 210. update ) is the evaluation value L(PCI now ) is significantly improved (step S405 Yes), update is notified to the CU / DU 210 (step S406), and the cell identifier of the cell 220a is actually updated.

[0066] As described above, according to this embodiment, when remainders obtained by modular arithmetic using three values ​​are used as multiple indicators for determining a cell identifier, a base remainder is determined using a metric corresponding to each value, and an LCM remainder related to the least common multiple of each value is determined based on the base remainder. Then, a cell identifier is determined using the LCM remainder, and if the determined cell identifier improves the evaluation value, the cell identifier is updated. Therefore, when optimizing cell identifiers during operation of a communication system, an optimal cell identifier taking multiple indicators into consideration can be automatically set.

[0067] In the second embodiment, the metric w m (i, k) is calculated, but for example, the metric w m In this case, when determining the cell identifier of cell #i, the base remainder determination unit 122 calculates the metric w (i, k) for each remainder k obtained by a remainder calculation using the value m. m (i, k) is calculated using the following equation (8).

number

[0068] In the above equation (8), N Edge,i,j indicates the number of UEs 230 located in the cell #i near the boundary with the cell #j, and N Edge,j,i indicates the number of UEs 230 located in the cell #j near the boundary with the cell #i. m (i,k) is the cell identifier PCI of cell #j j is calculated for each remainder k when dividing by the value m, and the metric w m The smaller (i, k) is, the fewer UEs 230 are near the boundary between cell #j and cell #i corresponding to the remainder k. Therefore, the cell identifier of cell #i is expressed as the metric w mBy using a cell identifier corresponding to the remainder k that reduces (i, k), the possibility of handover by UE 230 occurring between cells 220a with the same remainder k when dividing the cell identifier by the value m is reduced.

[0069] The number of UEs 230 near the boundary of a cell 220a can be counted by determining that a UE 230 is near the boundary of a cell 220a formed by two RUs 220 when the difference in the received power (e.g., RSRP (Reference Signal Received Power)) from two RUs 220 at the UE 230 is less than a predetermined threshold.

[0070] Furthermore, the above-mentioned first and second embodiments can be implemented in combination. That is, when a communication system is operated with a cell identifier initially set as in the above-mentioned first embodiment, the cell identifier may be periodically optimized as in the above-mentioned second embodiment. Fig. 8 is a diagram showing the difference in effect between a case where only the initial setting of the first embodiment is implemented and a case where the optimization of the second embodiment is implemented. That is, Fig. 8 shows the number of times that handover of the UE 230 occurs between cells 220a having the same remainder when the cell identifier is divided by a first value (i.e., 3), a second value (i.e., 4), and a third value (i.e., 30).

[0071] In Fig. 8, the white graph indicates the number of handovers when cell identifiers are set randomly, the diagonally hatched graph indicates the number of handovers when only the initial setting of the first embodiment is performed, and the horizontally hatched graph indicates the number of handovers when the optimization of the second embodiment is performed. As shown in Fig. 8, the number of times handovers occur between cells 220a that give the same remainder when dividing by a first value (i.e., 3) and a second value (i.e., 4) ("mod3" and "mod4" in the figure) is reduced by performing the initial setting of the first embodiment, and is further reduced significantly by performing the optimization of the second embodiment. It can also be seen that the number of times handovers occur between cells 220a that give the same remainder when dividing by a third value (i.e., 30) ("mod30" in the figure) is 0.

[0072] In this way, by determining the cell identifier as in the above-mentioned first and second embodiments, it is possible to automatically set the optimum cell identifier in consideration of multiple indicators from the viewpoint of the remainder when dividing by the first to third values. [Explanation of symbols]

[0073] 110 Communication IF section 120 processors 121 Cell information acquisition unit 122 Base remainder determination part 123 LCM remainder determination unit 124 Cell identifier determination unit 130 memory 301 HO Information Acquisition Department

Claims

1. Memory and a processor coupled to the memory; The processor: using a metric for the first value and the second value to determine a first remainder when dividing a cell identifier by the first value and a first remainder when dividing the cell identifier by the second value; determining a second remainder when a cell identifier is divided by the least common multiple of the first value and the second value using a first remainder when the cell identifier is divided by the first value and the second value; determining a third remainder when a cell identifier is divided by the least common multiple of the first value, the second value, and the third value using a metric for a third value and the second remainder; determining a cell identifier that satisfies the third remainder; A communication control device that executes processing.

2. The processor: further performing a process of acquiring location information and transmission power information of wireless devices forming a cell; The metric is: Calculated based on the location information and the transmission power information 2. The communication control device according to claim 1.

3. The processor: further performing a process of acquiring handover information indicating the number of times the terminal device performs handover between cells; The metric is: Calculated based on the handover information 2. The communication control device according to claim 1.

4. The process of determining the first remainder comprises: For the first value, a value that minimizes the metric is determined to be a first remainder when the value is divided by the first value, and for the second value, a value that minimizes the metric is determined to be a first remainder when the value is divided by the second value.

2. The communication control device according to claim 1.

5. The process of determining the third remainder comprises: A value that minimizes a metric for the third value among values ​​that satisfy the second remainder is determined as the third remainder.

2. The communication control device according to claim 1.

6. The process of determining a cell identifier includes: determining a value obtained by adding the third remainder to a multiple of the least common multiple of the first value, the second value, and the third value as a cell identifier; 2. The communication control device according to claim 1.

7. The processor: comparing evaluation values ​​before and after changing the cell identifier to the determined cell identifier, the evaluation values ​​corresponding to the sums of metrics for the first value, the second value, and the third value; If the evaluation value is improved after changing the cell identifier, an update to the determined cell identifier is performed.

2. The communication control device according to claim 1, further comprising: a processor for executing a process;

8. The comparing process includes: A value obtained by subtracting a predetermined value from the evaluation value before the change of the cell identifier is compared with the evaluation value after the change of the cell identifier; The process to be performed is: If the evaluation value after changing the cell identifier is smaller, the cell identifier is updated.

8. The communication control device according to claim 7.

9. The comparing process includes: The evaluation value before the change of the cell identifier is compared with the evaluation value after the change of the cell identifier plus a value corresponding to the number of cells whose cell identifiers are changed. The process to be performed is: If the added value is smaller, the cell identifier is updated.

8. The communication control device according to claim 7.

10. An identifier determination method for determining a cell identifier of a cell used in wireless communication, comprising: using a metric for the first value and the second value to determine a first remainder when dividing a cell identifier by the first value and a first remainder when dividing the cell identifier by the second value; determining a second remainder when a cell identifier is divided by the least common multiple of the first value and the second value using a first remainder when the cell identifier is divided by the first value and the second value; determining a third remainder when a cell identifier is divided by the least common multiple of the first value, the second value, and the third value using a metric for a third value and the second remainder; determining a cell identifier that satisfies the third remainder; 10. A method for determining an identifier, comprising the steps of:

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