JP7105839B2 - Mobile communication system and inter-base station coordinated control device - Google Patents

Description

The present invention relates to inter-base-station cooperative beamforming control.

Conventionally, coordinated beamforming between two adjacent base stations with multi-element (total of 128 elements) antennas is realized by digital signal processing, and multiple (8) users located in the cell boundary area ( A mobile communication system is known in which beamforming is cooperatively controlled so as to reduce interference in terminals) (see, for example, Non-Patent Document 1).

NEC Corporation, NTT Docomo, Inc., "(Announcement) Realization of 5G wireless communication for multiple mobile stations by interference reduction using inter-base-station coordinated beamforming -Interference reduction utilizing beam control by digital signal processing-" , [online], press release, May 23, 2018, [searched on August 21, 2020], Internet <https://www.nttdocomo.co.jp/info/news_release/2018/05/23_00. html>

In the above-described conventional beamforming cooperative control, multi-element antennas with high gain in beams formed by each base station are used, so there is a risk of interference occurring between non-adjacent base stations. Considering such interference between non-adjacent base stations, the problem is to greatly improve the cell boundary throughput without degrading the total throughput of all terminals located in multiple cells in a wide target area. There is

A mobile communication system according to an aspect of the present invention is arranged to form a plurality of cells within a target area, and defines a plurality of beams in advance for each of a plurality of mobile terminals within the cell. A mobile communication system comprising: a plurality of base stations having multi-element antennas that perform codebook-type beamforming control; and an inter-base-station cooperative control device that controls the plurality of base stations. The inter-base-station coordinated control apparatus of this mobile communication system measures, for each of the plurality of base stations, a plurality of reception qualities that are measured by a plurality of terminals corresponding to a plurality of beams in the cell and fed back to the base station. and a plurality of reception qualities fed back from the plurality of terminals for each of a plurality of combinations of the plurality of base stations and the plurality of beams. Throughput calculation means for calculating a plurality of throughputs for the plurality of terminals based on the feedback information of the plurality of and information transmission means for transmitting information about the selected combination to each of the plurality of base stations. Each of the plurality of base stations controls its own plurality of beams based on the information regarding the selected combination.

In the mobile communication system, the inter-base-station coordinated control device selects, from among the plurality of combinations, a combination that maximizes the minimum throughput of the plurality of throughputs for the plurality of terminals calculated for each of the plurality of combinations. You may choose.

In the mobile communication system, the inter-base-station coordinated control device selects a combination that maximizes the minimum throughput among the plurality of throughputs for the plurality of terminals calculated for each of the plurality of combinations, out of the plurality of combinations. , provisionally selecting one or a plurality of combinations in which the minimum throughput is equal to or higher than the allowable lower limit throughput lower than the maximum value by a predetermined value, and from among the plurality of provisionally selected combinations, the plurality of throughputs for the plurality of terminals You may select the combination that maximizes the sum of

In the mobile communication system, the inter-base-station coordinated control device calculates, from among the plurality of combinations, the minimum throughput and the plurality of throughputs for the plurality of terminals calculated for each of the plurality of combinations. The combination that maximizes the product with the sum may be selected.

In the mobile communication system, the reception quality is the reception power measured at the terminal, and the plurality of throughputs are for each of a plurality of combinations of the plurality of base stations and the plurality of beams, Based on the feedback information of the received power fed back from the plurality of terminals, a plurality of SINRs (signal-to-noise and interference power ratios) for the plurality of terminals are calculated, and a plurality of SINRs calculated based on the plurality of SINRs It may be a Shannon capacitance.

An inter-base-station coordinated control apparatus according to another aspect of the present invention is arranged to form a plurality of cells in a target area, and provides a plurality of beams in advance to each of a plurality of mobile terminals in the cell. This is an inter-base-station cooperation control apparatus that controls a plurality of base stations having multi-element antennas that perform codebook-type beamforming control that is defined and used. This inter-base-station cooperation control apparatus, for each of the plurality of base stations, transmits feedback information of a plurality of received qualities measured by a plurality of terminals corresponding to a plurality of beams in the cell and fed back to the base station. an information acquiring means for acquiring information from a base station; and based on the plurality of reception quality feedback information fed back from the plurality of terminals for each of a plurality of combinations of the plurality of base stations and the plurality of beams. a throughput calculation means for calculating a plurality of throughputs for the plurality of terminals; and based on the calculation results of the plurality of throughputs for the plurality of terminals calculated for each of the plurality of combinations, any one of the plurality of combinations A selection means for selecting one combination, and an information transmission means for transmitting information on the selected combination to each of the plurality of base stations.

According to the present invention, in a mobile communication system including a plurality of base stations arranged to form a plurality of cells in a target area and performing codebook-type beamforming control for terminals using multi-element antennas, a plurality of Throughput at the cell boundary can be greatly improved without deteriorating the total throughput of all terminals in the cell.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing an example of the overall configuration of a mobile communication system according to one embodiment of the present invention; 4 is a flowchart showing an example of inter-base-station cooperative BF control according to the present embodiment; 4 is a flowchart showing an example of beam combination selection processing; 8 is a flowchart showing another example of beam combination selection processing; 9 is a flowchart showing still another example of beam combination selection processing;

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an explanatory diagram showing an example of a cell configuration in a mobile communication system according to one embodiment of the present invention. In FIG. 1, the mobile communication system of this embodiment comprises a plurality of base stations 20 arranged to form a plurality of cells 20A within a target area. Although FIG. 1 shows a case where the number of base stations is 5, the number of base stations may be 2 to 4, or 6 or more.

Each base station 20 has a multi-element antenna 201 in order to improve the throughput, which is the communication quality within its own cell 20A, and has relatively high power for each of the plurality of mobile terminals 10 within the cell 20A. Beamforming control can be performed to direct multiple beams 20B with narrow beam widths. Although FIG. 1 shows the case where each base station 20 has four beams, the number of beams may be two to three, or five or more. A beam 20B indicated by a solid line in FIG. 1 is a beam that is actually selected and used for communication with the terminal 10 from among multiple beam candidates that can be selected and formed by the base station 20. , and a beam 20B indicated by a dashed line is a beam that is not used for communication with the terminal 10. FIG.

The beamforming control in this embodiment is codebook-type beamforming control that controls a plurality of beams based on a codebook. The codebook includes information of multiple sets of precoding weight matrix candidates for multiple sets of beam candidates whose directivity directions are determined for each of the multiple base stations 20 . The precoding weight matrix is a matrix that indicates phase and amplitude control amounts to be set for the multi-element antenna 201 when transmitting or receiving radio signals.

The base station 20 forms a macrocell. It may be a macro cell base station or a base station forming a cell of another size such as a small cell base station. Also, the base station 20 may be a wireless communication device called eNodeB (evolved Node B: eNB), gNodeB (gNB), en-NodeB (en-gNB), access point, or the like.

A wireless network configuration including the base station 20 of this embodiment is not limited to a specific configuration. For example, the radio network configuration illustrated in FIG. 1 is a D-RAN (distributed radio access network) configuration, and each base station 20 in the figure includes a multi-element antenna 201, a radio transceiver, and a baseband signal processor. Prepare. The baseband signal processing apparatus has, for example, a configuration for performing downlink Massive MIMO transmission with a plurality of terminals 10 using a plurality of beams formed by codebook beamforming control. For example, the baseband signal processing device includes a serial-to-parallel conversion unit, a precoding unit that performs precoding processing based on the codebook information, a codebook storage unit that stores the codebook information, and a control unit that controls each unit. and so on.

Note that the radio network configuration may be a C-RAN (Centralized Radio Access Network) configuration. In this case, a plurality of RRHs (remote radio headers) having multi-element antennas and radio transmitting/receiving devices (also referred to as "extended base stations" or "optical extended units") are arranged at the positions of the plurality of base stations 20 in the figure. be done. A plurality of RRHs share a common BBU that performs baseband signal processing of each base station 20 via a communication line such as an optical fiber, an interface between base stations (for example, x2 interface in LTE) or a wired communication line or a wireless communication line. (baseband unit).

The terminal 10 is a mobile phone, a smart phone, a mobile personal computer having a mobile communication function, or the like, and is also called a user equipment (UE), a mobile station, a mobile device, or a portable communication terminal. The terminal 10 may be a modular mobile station incorporated in a moving body such as an automobile or drone, or may be a terminal device of a device for IoT (Internet of Things).

The terminal 10 is configured using hardware such as a computer device having a CPU, a memory, etc., and a wireless communication unit, for example, and can perform wireless communication with the base station 20 by executing a predetermined program. can.

When the terminal 10 is located within the cell 20A, the terminal 10 communicates with the mobile communication network through the base station 20 corresponding to the cell 20A. Also, when the terminal 10 moves to a cell boundary area where a plurality of cells 20A overlap, the terminal 10 communicates with the mobile communication network side via the base station 20 of one of the plurality of cells 20A.

The terminal 10 includes, for example, an antenna for performing downlink MIMO transmission with the base station 20 of the serving cell 20A, a radio transmitting/receiving device, a distributor, a data decoder, a parallel-to-serial converter, and a channel estimator. , a feedback information generator, a controller, and the like. The feedback information is, for example, information such as the received power (RSRP) of the radio signal received by the terminal 10 from the base station 20 . Feedback information is transmitted from the terminal 10 to the base station 20 of the cell 20A to which the terminal 10 is connected as a measurement report (MR) measured by the terminal 10 .

The same radio transmission method and the same frequency band are used for radio communication between each base station 20 and the terminal 10 . Examples of wireless transmission methods include LTE (Long Term Evolution) and LTE-Advanced communication methods, fourth generation mobile communication system (4G) communication methods, fifth generation mobile communication system (5G) communication methods, and so on. A communication method of the next-generation mobile communication system (5G) or the like can be adopted.

Each base station 20 is configured using hardware such as a computer device having a CPU, a memory, etc., an external communication interface unit for the core network, and a wireless communication unit. communication can be performed. For example, each base station 20 performs wireless communication with the terminal 10 and communication with the core network side. Also, each base station 20 communicates with an inter-base-station cooperative beamforming controller (hereinafter referred to as "inter-base-station cooperative controller") 30 via a wired or wireless control communication network. Also, each base station 20 communicates with other base stations other than its own via a wired or wireless inter-base station communication network.

In the mobile communication system configured as described above, since the multi-element antenna 201 having a high gain in the beam 20B formed by each base station 20 is used, interference may occur between non-adjacent base stations. Considering such interference between non-adjacent base stations (interference from distant cells), the total throughput of all terminals located in a plurality of cells 20A in a wide target area is not degraded. A technique that can greatly improve throughput is desired.

Therefore, in the present embodiment, in order to solve the above problem, the inter-base-station cooperation control device 30 performs inter-base-station cooperation beamforming control in which a plurality of base stations 20 forming a plurality of cells 20A in a target area cooperate with each other. (hereinafter also referred to as “inter-base-station cooperation BF control”).

In the case of the D-RAN (distributed radio access network) configuration of FIG. 1, the inter-base station cooperation control device 30 is connected to each base station 20 via the communication line 40 of the inter-base station network. In the case of a C-RAN (Centralized Radio Access Network) configuration, the inter-base-station coordinated control device 30 is connected to a BBU common to each base station 20 via a communication line, for example.

The inter-base-station cooperation control device 30 is composed of, for example, a single or a plurality of computer devices, and functions as means A to D below by executing a predetermined program.
A. For each of the plurality of base stations 20, feedback information of reception power (for example, RSRP) as a plurality of reception qualities measured by a plurality of terminals 10 corresponding to a plurality of beams 20B in the cell 20A and fed back to the base station 20 from the base station 20.
B. For each of a plurality of beam combinations consisting of a combination of a plurality of base stations 20 and a plurality of beams 20B, based on feedback information of received power (for example, RSRP) fed back from a plurality of terminals 10, for a plurality of terminals 10 Throughput calculation means for calculating multiple throughputs.
C. selection means for selecting any one beam combination from the plurality of beam combinations based on a plurality of throughput calculation results for a plurality of terminals 10 calculated for each of the plurality of beam combinations;
D. Information transmission means for transmitting information on the selected beam combination to each of the plurality of base stations 20 .

The information about the selected beam combination to be transmitted to each of the plurality of base stations 20 is, for example, the selected beam among multiple sets of precoding weight matrix candidates included in the codebook stored in the base station 20 This is information specifying precoding weight matrices for forming multiple sets of beams for the base station 20 corresponding to the combination.

FIG. 2 is a flowchart showing an example of inter-base-station cooperation BF control according to this embodiment. In FIG. 2 , first, the inter-base-station cooperative control apparatus 30 measures a plurality of terminals 10 corresponding to a plurality of beams 20B in a cell 20A and feeds back to the base station 20 for each of the plurality of base stations 20 . receive power (RSRP) feedback information (S101).

Next, the inter-base-station cooperation control apparatus 30 receives the received power (RSRP ), a plurality of received SINRs (signal-to-noise and interference power ratios) for a plurality of terminals 10 are calculated (S102).

Next, the inter-base station cooperation control apparatus 30 calculates multiple throughputs (for example, Shannon capacities) for the multiple terminals 10 based on the multiple SINR calculation results for the multiple terminals 10 (S103).

Next, the inter-base-station cooperation control apparatus 30 selects one beam combination from the plurality of beam combinations based on the calculation results of the plurality of throughputs (for example, Shannon capacities) for the plurality of terminals 10 (S104). .

Next, the inter-base-station cooperative control apparatus 30 transmits information on the selected beam combination (for example, information designating the precoding weight matrix in the codebook) to each of the plurality of base stations 20 (S105).

First, beam combination selection processing in a case where there are two base stations to be linked and each base station forms three beams will be described.

FIG. 3 is a flow chart showing an example of beam combination selection processing (S104 in FIG. 2). FIG. 3 is an example of a beam control algorithm (minimum throughput maximization method) for maximizing the minimum throughput of each terminal 10 .

In the example of FIG. 3, two base stations 20 adjacent to each other and to be linked and located in the target area form three beams 20B, respectively, and the terminal 10 is located in the cell 20A of each base station 20. This is an example of when The same applies to the examples shown in FIGS. 4 and 5, which will be described later.

Table 1 shows numerical examples of throughput calculations and beam combination selection examples for the terminal 10 in the beam control algorithm of FIG. In Table 1 and Tables 2 and 3 described later, the plurality of base stations 20 are denoted as base station #1 and base station #2, and beams 20B in three different directions formed by each base station 20 are beam # 1, beam #2, and beam #3. Terminals 10 located in cell 20A of each base station 20 are denoted as terminal #1 and terminal #2.

In FIG. 3, the inter-base-station cooperative control device 30 calculates the minimum throughput (the rightmost column in Table 1) for each beam combination for all 3 ³ =9 beam combinations 1 to 9 for a plurality of base stations 20. (S201).

Next, the inter-base-station cooperative control device 30 selects the beam combination that maximizes the minimum throughput from all the beam combinations 1 to 9 (S202). In the example of Table 1, the beam combination 6 that maximizes the minimum throughput (14) is selected as surrounded by a thick frame. That is, beam #2 is selected for base station #1, and beam #3 is selected for base station #2.

FIG. 4 is a flow chart showing another example of the beam combination selection process (S104 in FIG. 2). FIG. 4 is an example of a beam control algorithm (modified minimum throughput maximization method) that allows a slight decrease in throughput in the minimum throughput maximization method described above and also maximizes the total throughput of the entire mobile communication system. .

Table 2 shows numerical examples of throughput calculations and beam combination selection examples for the terminal 10 in the beam control algorithm of FIG.

In FIG. 4, the inter-base-station cooperation control device ³⁰ calculates the minimum throughput (second column) and a total throughput (rightmost column of Table 2) obtained by totaling a plurality of throughputs for a plurality of terminals 10 (S301).

Next, the inter-base-station cooperation control device 30 selects the beam combination 6 with the maximum minimum throughput among all the beam combinations 1 to 9, and the A beam combination 2 and 9 having an allowable lower limit throughput (13 in the example of Table 2) lower than the value (14 in the example of Table 2) by a predetermined value ε (1 in the example shown) is provisionally selected (S302). ).

Next, the inter-base-station cooperation controller 30 selects the beam combination that maximizes the total throughput (the rightmost column in Table 2) from among the plurality of provisionally selected beam combinations 2, 6, and 9 (S303). In the example of Table 2, select beam combination 2, which gives the maximum total throughput (31). That is, beam #1 is selected for base station #1, and beam #2 is selected for base station #2.

FIG. 5 is a flow chart showing still another example of the beam combination selection process (S104 in FIG. 2). FIG. 5 shows a beam control algorithm (evaluation value (minimum throughput and total It is an example of throughput product) maximization method).

Table 3 shows numerical examples of throughput calculations and beam combination selection examples for the terminal 10 in the beam control algorithm of FIG.

In FIG. 5, the inter-base-station cooperative control device 30 calculates the minimum throughput (the ^third column) and a total throughput (the second column from the right in Table 3) obtained by totaling a plurality of throughputs for a plurality of terminals 10 (S401).

Next, the inter-base-station cooperation control device 30 calculates an evaluation value (the rightmost column in Table 3) by multiplying the minimum throughput and the total throughput for each beam combination for all beam combinations 1 to 9 (S402). .

Next, the inter-base-station cooperation control device 30 selects the beam combination that maximizes the evaluation value (the rightmost column in Table 3) from all the beam combinations 1 to 9 (S403). In the example of Table 3, beam combination 9 with the maximum evaluation value (411.75) is selected. That is, beam #3 is selected for base station #1, and beam #3 is selected for base station #2.

According to the example of the beam combination selection process of FIGS. 3 to 5, when two adjacent base stations 20 to be cooperated are arranged in the target area, a plurality of base stations 20 are located in the cell 20A. The cell boundary throughput can be greatly improved without degrading the total throughput of the plurality of terminals 10 .

Next, a description will be given of beam combination selection processing when there are five base stations to be linked and each base station forms five beams. When the number of base stations is 5 and the number of beams of each base station is 5, the total number of beam combinations N is 3125 (=5 ⁵ ). Hereinafter, the five base stations are referred to as base stations #1 to #5, and the five beams formed by each base station are referred to as beams #1 to #5. The terminals are denoted as terminals #1 to #5.

As shown in S101 to S103 in FIG. 2 described above, as preprocessing for the beam combination selection processing, the inter-base station cooperation control device 30 obtains feedback information on received power (RSRP), SINR (signal to noise and interference power ratio) and throughput (Shannon capacity).

First, inter-base station cooperation control apparatus 30 measures terminals #1 to #5 corresponding to beams #1 to #5 for each of base stations #1 to #5 and feeds them back to base stations #1 to #5. receive feedback information of multiple received powers (RSRPs).

Table 4 shows the received power (RSRP) [dBm ] is a numerical example collectively describing the feedback information.

Next, the inter-base-station cooperation control device 30 performs the following for all beam combinations #1 to #N (N=3125) consisting of a plurality of base stations #1 to #5 and a plurality of beams #1 to #5: SINR (signal-to-noise and interference power ratio) for terminals #1 to #5 is calculated based on feedback information of received power (RSRP) fed back from terminals #1 to #5. Table 5 is a numerical example summarizing the calculation results of the SINR (signal-to-noise and interference power ratio) of each terminal #1 to #5 for all beam combinations #1 to #N (N = 3125). be.

Next, the inter-base station cooperation controller 30 calculates multiple throughputs (Shannon capacities) for the multiple terminals 10 based on multiple SINR calculation results for the multiple terminals 10 . Table 6 is a numerical example of calculated throughput (Shannon capacity) [bps] of each terminal #1 to #5 for each beam combination for all beam combinations #1 to #N (N=3125).

Next, as shown in S104 in FIG. 2 described above, the inter-base-station cooperation control apparatus 30 performs all beam combinations #1 to Select any one beam combination from #N (N=3125). The beam control algorithm shown in FIGS. 3 to 5 can be used for this beam combination selection process.

Table 7 shows numerical examples for selecting beam combinations by the beam control algorithm (minimum throughput maximization method) of FIG. 3 described above. In this example, the inter-base-station cooperation controller 30 calculates the minimum throughput (rightmost column in Table 7) for each beam combination for all beam combinations #1 to #N (N=3125) (S201 in FIG. 3). ), from among all the beam combinations #1 to #N, the beam combination #k that maximizes the minimum throughput (2.4 bps) as surrounded by a thick frame is selected (S202 in FIG. 3).

Table 8 shows a numerical example of selecting beam combinations by the beam control algorithm (modified minimum throughput maximization method) of FIG. 4 described above. In this example, the inter-base-station cooperation control device 30, for all beam combinations #1 to #N (N=3125), for each beam combination, the minimum throughput (the second column from the right in Table 8) and a plurality of A total throughput (rightmost column in Table 8) is calculated by summing a plurality of throughputs for terminals #1 to #5 (S301 in FIG. 4). Next, the inter-base-station cooperation control apparatus 30 selects the beam combination # that maximizes the minimum throughput among all the beam combinations #1 to #N (N=3125), as surrounded by a thick frame in Table 8. k and the allowable lower limit throughput (1.9 bps in the example of Table 8) lower than the maximum value (2.4 bps in the example of Table 8) by a predetermined value ε (0.5 bps in the example shown in the figure). The above beam combinations #1, #2, #l, #m, and #n are tentatively selected (S302 in FIG. 4). Then, the inter-base-station cooperation control device 30 determines that the total throughput (the rightmost column in Table 8) is the maximum from among the plurality of temporarily selected beam combinations #1, #2, #k, #l, #m, and #n. (18.9 bps) is selected (S303 in FIG. 4).

Table 9 shows numerical examples for selecting beam combinations by the beam control algorithm of FIG. 5 described above. In this example, the inter-base-station cooperation control device 30, for all beam combinations #1 to #N (N=3125), for each beam combination, the minimum throughput (the third column from the right in Table 9), the terminal # A total throughput (the second column from the right in Table 9) is calculated by summing a plurality of throughputs for 1 to #5 (S401 in FIG. 5). Furthermore, the inter-base-station cooperation control device 30 multiplies the minimum throughput by the total throughput for each beam combination for all beam combinations #1 to #N (N=3125) (the rightmost column in Table 9). is calculated (S402 in FIG. 5). Then, the inter-base-station cooperation control apparatus 30 selects the beam combination #m with the maximum evaluation value (rightmost column in Table 9) (41.1 bps) from among all the beam combinations #1 to #N (N=3125). is selected (S403 in FIG. 5).

According to the example of the beam combination selection process in Tables 4 to 9, when the base stations #1 to #5 to be linked are located in the target area, the base stations #1 to #5 are located in the cell. Throughput at the cell boundary can be greatly improved without deteriorating the total throughput of terminals #1 to #5.

と定義する。また、各基地局で利用可能なビーム数をＬとし、選択可能なビームの組み合わせ数を

とし、ビームの全組み合わせの集合を

と定義する。 Next, the inter-base-station cooperation BF control of this embodiment can be explained using the following generalized model. Here, the number of base stations is _NBS , and the set of base stations to be linked (collaborating base stations) is

defined as Let L be the number of beams available at each base station, and let the number of selectable beam combinations be

and let the set of all combinations of beams be

defined as

Assuming that a terminal located in each base station can ideally measure the received power of all beams from the associated base station, the received SINR of the i-th terminal #i in the k-th beam combination is given by the following equation ( 1) can be calculated.

は、ｋ番目のビーム組み合わせを選択した場合の基地局＃ｊからの端末＃ｉの受信電力であり、ｎ_ｉは、端末＃ｉにおける雑音電力である。 Here, in formula (1)

is the received power of terminal _#i from base station #j when the k-th beam combination is selected, and ni is the noise power at terminal #i.

は、次式（２）を用いて推定（計算）することができる。

Based on the received SINR, the throughput of the i-th terminal #i in the k-th beam combination (Shannon capacity)

can be estimated (calculated) using the following equation (2).

Here, the throughput of each terminal greatly differs depending on the combination of beams. The beam combination selection algorithm is a beam control algorithm that maximizes the minimum throughput of each terminal (minimum throughput maximization method), and allows a slight decrease in the minimum throughput maximization method to maximize the throughput of the entire system. A beam control algorithm that increases together (modified minimum throughput maximization method) and a beam control algorithm that maximizes the evaluation value of minimum throughput multiplied by total throughput (estimation value maximization method) can be used.

For example, the minimum throughput maximization method described above can be implemented in step 1 below.

Step 1: For the set S, the beam combination k _Final that maximizes the lowest estimated throughput among the terminals located in the cell of the base station to be coordinated is selected using the following equations (3) and (4). The throughput _Cmaxmin after maximizing the minimum throughput at that time is given by the following equation (5).

Also, the above modified minimum throughput maximization method can be realized by the formulas (3) and (4) of step 1 above and step 2 below.

Step 2: Set a throughput _C'maxmin that is lower than the throughput _Cmaxmin after maximizing the minimum throughput by ε in order to allow a slight decrease in throughput. A beam combination S' that makes the minimum throughput higher than the set minimum throughput is determined, and from among the beam combinations S', a beam combination k _Final that maximizes the total throughput of the terminal is determined.

The beam combination k _Final can be obtained by the following equations (6) to (8).

Further, in the evaluation value maximization method, the optimum beam combination k _Final can be determined by the following equation (9).

As described above, according to the present embodiment, in consideration of not only interference between adjacent base stations but also interference between non-adjacent base stations (interference from distant cells), a plurality of cells 20A in a wide target area Throughput at the cell boundary can be greatly improved without degrading the total throughput of all terminals located in the area.

It should be noted that the processing steps and components of communication systems, wireless devices, base stations and terminals (user equipment, mobile stations, mobile stations) described herein may be implemented by various means. For example, these processing steps and components may be implemented in hardware, firmware, software, or any combination thereof.

For hardware implementation, in order to implement the above processes and components in entities (for example, various wireless communication devices, wireless relay devices, NodeBs, servers, gateways, exchanges, computers, hard disk drives, or optical disk drives) The means such as processing units used in the Programmable Gate Arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, electronic devices, other electronic units designed to perform the functions described herein, computers, or combinations thereof may be implemented in

Also, for firmware and/or software implementations, the means used to implement the above components may comprise programs (e.g., procedures, functions, modules, instructions, etc. code) that perform the functions described herein. ) may be implemented. In general, any computer/processor readable medium tangibly embodying firmware and/or software code means, such as a processing unit, used to implement the above steps and components described herein. may be used to implement For example, firmware and/or software code may be stored in memory and executed by a computer or processor, such as in a controller. The memory may be implemented within the computer or processor, or external to the processor. The firmware and/or software code may also be, for example, random access memory (RAM), read only memory (ROM), non-volatile random access memory (NVRAM), programmable read only memory (PROM), electrically erasable PROM (EEPROM). ), flash memory, floppy disk, compact disk (CD), digital versatile disk (DVD), magnetic or optical data storage devices, etc. good. The code may be executed by one or more computers or processors and may cause the computers or processors to perform certain aspects of the functionality described herein.

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

Moreover, the description of the embodiments disclosed herein is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to this disclosure will be readily apparent to those skilled in the art, and the general principles defined herein are applicable to other variations without departing from the spirit or scope of this disclosure. This disclosure, therefore, is not to be limited to the examples and designs described herein, but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

10 terminal (mobile station)
20 Base station 20A Cell 20B Beam 30 Coordination control device between base stations 40 Communication line

Claims (6)

Multi-elements arranged to form a plurality of cells in a target area and performing codebook-type beamforming control using a plurality of beams defined in advance for each of a plurality of mobile terminals in the cells. A mobile communication system comprising: a plurality of base stations having antennas; and an inter-base-station cooperation control device for controlling the plurality of base stations,
The inter-base-station cooperation control device,
an information acquiring means for acquiring, from each of the plurality of base stations, feedback information of a plurality of reception qualities measured by a plurality of terminals corresponding to a plurality of beams in the cell and fed back to the base station; ,
A plurality of throughputs for the plurality of terminals based on the plurality of reception quality feedback information fed back from the plurality of terminals for each of a plurality of combinations of the plurality of base stations and the plurality of beams. a throughput calculation means for calculating
selection means for selecting one of the plurality of combinations based on the calculation results of the plurality of throughputs for the plurality of terminals calculated for each of the plurality of combinations;
information transmission means for transmitting information about the selected combination to each of the plurality of base stations;
Each of the plurality of base stations controls a plurality of beams of its own station based on information regarding the selected combination ,
The inter- base-station cooperation control device selects, from among the plurality of combinations, the combination that maximizes the minimum throughput among the plurality of throughputs for the plurality of terminals calculated for each of the plurality of combinations, and the combination that maximizes the minimum throughput. provisionally selecting one or a plurality of combinations equal to or higher than the allowable lower limit throughput lower by a predetermined value from the maximum value, and from among the plurality of provisionally selected combinations, the sum of the plurality of throughputs for the plurality of terminals becomes the maximum. A mobile communication system characterized by selecting a combination. Multi-elements arranged to form a plurality of cells in a target area and performing codebook-type beamforming control using a plurality of beams defined in advance for each of a plurality of mobile terminals in the cells. A mobile communication system comprising: a plurality of base stations having antennas; and an inter-base-station cooperation control device for controlling the plurality of base stations,
The inter-base-station cooperation control device,
an information acquiring means for acquiring, from each of the plurality of base stations, feedback information of a plurality of reception qualities measured by a plurality of terminals corresponding to a plurality of beams in the cell and fed back to the base station; ,
A plurality of throughputs for the plurality of terminals based on the plurality of reception quality feedback information fed back from the plurality of terminals for each of a plurality of combinations of the plurality of base stations and the plurality of beams. a throughput calculation means for calculating
selection means for selecting one of the plurality of combinations based on the calculation results of the plurality of throughputs for the plurality of terminals calculated for each of the plurality of combinations;
information transmission means for transmitting information about the selected combination to each of the plurality of base stations;
Each of the plurality of base stations controls a plurality of beams of its own station based on information regarding the selected combination,
The inter-base-station cooperation control device determines, from among the plurality of combinations, that the product of the minimum throughput in the plurality of throughputs for the plurality of terminals calculated for each of the plurality of combinations and the total of the plurality of throughputs is the maximum. A mobile communication system characterized by selecting a combination of In the mobile communication system according to claim 1 or 2 ,
The reception quality is the reception power measured at the terminal,
The plurality of throughputs are calculated for each of the plurality of combinations of the plurality of base stations and the plurality of beams based on the feedback information of the received power fed back from the plurality of terminals. calculating a plurality of SINRs (signal-to-noise-and-interference power ratios) for each of the plurality of Shannon capacities calculated based on the plurality of SINRs. Multi-elements arranged to form a plurality of cells in a target area and performing codebook-type beamforming control using a plurality of beams defined in advance for each of a plurality of mobile terminals in the cells. An inter-base station cooperation control device for controlling a plurality of base stations having antennas,
an information acquiring means for acquiring, from each of the plurality of base stations, feedback information of a plurality of reception qualities measured by a plurality of terminals corresponding to a plurality of beams in the cell and fed back to the base station; ,
A plurality of throughputs for the plurality of terminals based on the plurality of reception quality feedback information fed back from the plurality of terminals for each of a plurality of combinations of the plurality of base stations and the plurality of beams. a throughput calculation means for calculating
selection means for selecting one of the plurality of combinations based on the calculation results of the plurality of throughputs for the plurality of terminals calculated for each of the plurality of combinations;
information transmission means for transmitting information about the selected combination to each of the plurality of base stations ;
The selecting means selects, from among the plurality of combinations, a combination that maximizes the lowest throughput among the plurality of throughputs for the plurality of terminals calculated for each of the plurality of combinations, and the lowest throughput from the maximum value. tentatively selecting one or a plurality of combinations equal to or higher than an allowable lower limit throughput lower by a predetermined value, and selecting a combination that maximizes the sum of the plurality of throughputs for the plurality of terminals from the plurality of tentatively selected combinations. , an inter-base-station coordinated control device characterized by: Multi-elements arranged to form a plurality of cells in a target area and performing codebook-type beamforming control using a plurality of beams defined in advance for each of a plurality of mobile terminals in the cells. An inter-base station cooperation control device for controlling a plurality of base stations having antennas,
an information acquiring means for acquiring, from each of the plurality of base stations, feedback information of a plurality of reception qualities measured by a plurality of terminals corresponding to a plurality of beams in the cell and fed back to the base station; ,
A plurality of throughputs for the plurality of terminals based on the plurality of reception quality feedback information fed back from the plurality of terminals for each of a plurality of combinations of the plurality of base stations and the plurality of beams. a throughput calculation means for calculating
selection means for selecting one of the plurality of combinations based on the calculation results of the plurality of throughputs for the plurality of terminals calculated for each of the plurality of combinations;
information transmission means for transmitting information about the selected combination to each of the plurality of base stations;
The selecting means selects, from among the plurality of combinations, a combination that maximizes the product of the minimum throughput in the plurality of throughputs for the plurality of terminals calculated for each of the plurality of combinations and the sum of the plurality of throughputs. An inter-base-station coordinated control device, characterized by: In the inter-base-station cooperation control device according to claim 4 or 5,
The reception quality is the reception power measured at the terminal,
The plurality of throughputs are calculated for each of the plurality of combinations of the plurality of base stations and the plurality of beams based on the received power feedback information fed back from the plurality of terminals. and a plurality of Shannon capacities calculated based on the plurality of SINRs.

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