JP2008259046A - Radio controller, radio base station, communication terminal device and forcible handover method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate congestion by efficiently distributing mobile terminals within a cell, in a state where congestion occurs or the occurrence of congestion is predicted. <P>SOLUTION: When the radio controller (RNC) detects a congestion state where calls are concentrated to a cell and a radio channel is being congested, the RNC detects location information and a moving direction of each of mobile terminals under communicating within the cell that is brought into a congested state, determines from among the mobile terminals under communicating a mobile terminal that can be handed over to a radio base station adjacent to the radio base station in the congested state, and forcibly hands the determined mobile terminal to the radio base station adjacent to the radio base station in the congested state. Since only a mobile terminal communicable with an adjacent cell is conducted to implementation of forcible handover, radio cells can be switched efficiently without waste, and processing loads on the side of radio base stations, cellular system and mobile terminals can be reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radio control apparatus, a radio base station, a communication terminal apparatus, and a forced handover method, and more specifically, a plurality of radio base stations constituting a radio communication area and a radio communication area of each radio base station. The present invention relates to a forced handover used in a wireless communication system configured with a communication terminal apparatus that performs wireless communication.

  In a communication network having a small cell configuration such as W-CDMA (Wideband Code Division Multiple Access), so-called inter-cell handover is performed in which communication is performed simultaneously with a plurality of base stations.

  The number of radio base stations (hereinafter abbreviated as BS) is appropriately set according to the size of the area for providing mobile communication services, topographic conditions, etc., constitutes a radio communication area using radio waves, and exists within the radio communication area Communication with a mobile station (hereinafter abbreviated as UE). There is a limit to the number of radio wave channels that can be used for communication within the wireless communication area provided by each BS. Therefore, when a large number of UEs are concentrated in a specific wireless communication area and communication is performed there, a congestion state in which the communication channel is insufficient occurs. In this congested state, when a certain UE makes a priority call transmission requesting communication to the fire department, police, etc., one of the communications in use is forcibly communicated by radio waves emitted by an adjacent BS. A forced handover process is performed in which the channel is switched and a free call channel is assigned to a priority call.

  In the conventional system, for the problem of occurrence of congestion in the mobile communication system, a method of forcibly handing over is used to forcibly move all mobile terminals in a call to adjacent cells. For example, when an emergency call (police, fire fighting, etc.) occurs in a wireless communication area where congestion occurs, all mobile devices that are busy are forcibly handed over in order to assign a call channel to a request for priority call transmission .

In Patent Document 1, in a radio base station area where radio channels are congested, a handover is performed in order to allocate a call channel to a request for a priority call transmission used for contacting a police or a fire department newly generated. There has been disclosed a forced handover method in which a call during a call with the lowest probability of call loss is forcibly switched to a radio channel of an adjacent radio base station promptly.
JP-A-9-135477

However, in such a conventional forced handover method, when an emergency call (police, fire fighting, etc.) occurs in a wireless communication area where congestion has occurred, all the mobile devices in a call are forcibly handed over. Therefore, there were the following problems.
(1) Regardless of whether or not the communication quality with the adjacent radio base station can be ensured, it is not efficient to forcibly hand over all the terminals in communication to the adjacent radio base station.
(2) Even if forcible handover is performed for a mobile terminal that cannot communicate with an adjacent radio base station, communication with the adjacent radio base station cannot be switched. This can be determined before the implementation, and only causes the cellular system and the portable terminal to perform unnecessary processing.
(3) Forcibly handing over all mobile terminals in communication temporarily increases the processing load on the radio base station, cellular system, and mobile terminal, and may further deteriorate the congestion state. There is.

  In this way, when congestion occurs, it is forcibly handed over even to mobile terminals that cannot communicate with adjacent cells, and it is possible to know in advance which mobile terminals cannot be handed over Since it is possible to cause the cellular system and the mobile terminal to perform unnecessary processing, it takes time to determine a handover candidate UE (terminal), and a handover target UE (terminal) Is not necessarily optimally determined.

  The present invention has been made in view of the above, and is capable of efficiently distributing mobile terminals in a cell and eliminating congestion when congestion occurs or when congestion is expected to occur. An object is to provide an apparatus, a radio base station, a communication terminal apparatus, and a forced handover method.

  It is another object of the present invention to provide a radio control apparatus, radio base station, communication terminal apparatus, and forced handover method that can eliminate congestion without performing unnecessary handover processing.

  The radio control apparatus according to the present invention is used in a radio communication system including a plurality of radio base stations constituting a radio communication area and communication terminal apparatuses that perform radio communication within the radio communication area of each radio base station. A wireless control device, a congestion state detecting means for detecting a congestion state where calls are concentrated in a wireless communication area and the wireless channel is congested, and a communication terminal communicating in the wireless communication area in a congested state Based on the position information detecting means for detecting the position information of the apparatus and the detected position information of the communication terminal apparatus, the wireless base station adjacent to the wireless base station in the congested state among the communication terminal apparatuses in communication A determination means for determining a communication terminal device that can be handed over and a communication terminal device that has been determined to be handed over are forcibly A configuration and a forced handover execution means for over.

  The radio base station according to the present invention includes a congestion state detection means for detecting a congestion state in which calls are concentrated in a radio communication area covered by the radio base station and the radio channel is congested, and within the own radio communication area in a congestion state. Based on the detected position information of the communication terminal apparatus, handover is performed to an adjacent radio base station among the communication terminal apparatuses in communication based on the detected position information of the communication terminal apparatus. The configuration includes a determination unit that determines a possible communication terminal device, and a forced handover execution unit that forcibly hands over a communication terminal device that has been determined to be handed over to an adjacent radio base station.

  A communication terminal apparatus according to the present invention is a communication terminal apparatus that performs radio communication with a radio base station in a radio communication area, and forcibly causes a communication terminal apparatus that has been determined to be handed over to be handed over to an adjacent radio base station. A configuration is provided that includes a receiving unit that receives a forced handover request signal and a handover execution unit that executes a handover process when the forced handover request signal is received.

  The forced handover method of the present invention is used in a radio communication system including a plurality of radio base stations that constitute a radio communication area and a communication terminal device that performs radio communication within the radio communication area of each radio base station. A forced handover method for detecting a congestion state in which calls are concentrated in a wireless communication area and a wireless channel is congested, and a communication terminal apparatus communicating in the wireless communication area in a congested state Based on the detected location information of the communication terminal device, and can be handed over to a radio base station adjacent to the congested radio base station among the communication terminal devices in communication The step of determining the communication terminal device and the communication terminal device determined to be able to be handed over to a wireless base station adjacent to a wireless base station in a congested state And a step of command over.

  According to the present invention, mobile terminals in communication are forcibly handed over to adjacent radio base stations based on movement status and location information, thereby efficiently distributing mobile terminals in a cell and eliminating congestion. can do. Specifically, the following effects can be obtained.

  (1) When congestion occurs or in a state where congestion is expected to occur, by handing over to the adjacent radio base station based on the position of the mobile terminal, the mobile terminals in the cell are efficiently distributed , Congestion can be solved.

  (2) By performing forced handover only on portable terminals close to adjacent radio base stations, congestion can be eliminated without performing unnecessary handover processing.

  (3) By determining the mobile terminal to be handed over according to the position and moving direction of the mobile terminal and forcibly performing the handover, the processing load on the entire cellular system including the mobile terminal can be minimized. it can.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a radio communication system according to an embodiment of the present invention. As a wireless network architecture, an example applied to a cellular mobile wireless telephone system and a multi-network wireless network architecture capable of communication with a wireless LAN is shown.

  In FIG. 1, a radio network system 100 includes a core network (CN) 101 and a radio access network (RAN) 102. The radio access network (RAN) 102 controls a plurality of base stations. RNC) 103 and a plurality of nodes (B) 104 having a plurality of cells 105. The radio network controller (RNC) 103 is connected to a core network (CN) 101 that is an exchange network via an Iu interface 106, and the radio network controller (RNC) 103 is connected via an Iur interface 107. A radio network controller (RNC) 103 and a plurality of nodes (B) 104 constitute a radio network subsystem (RNS) 109 as one set of base stations.

  In the 3rd Generation Partnership Project (3GPP), the radio access network (RAN) 102 is called a UTRAN (Universal Terrestrial Radio Access Network).

  A radio network controller (RNC) 103 performs radio resource management and Node B control.

  The Node B 104 means a logical node that performs radio transmission / reception, and is specifically a radio base station apparatus. Node B 104 covers one or more cells. Node refers to each element constituting a network.

  The cell 105 has a communication area with a radius of several kilometers to several tens of kilometers.

  An Iu interface 106 is defined as an interface between the core network (CN) 101 and the radio network controller (RNC) 102. An Iur interface 107 is defined as an interface between the radio network controller (RNC) 107. An Iub interface 108 is defined as an interface between the radio network controller (RNC) and the Node B.

  FIG. 2 is a configuration block diagram of the communication terminal apparatus according to the embodiment of the present invention. In this example, the radio communication system is applied to a communication system including a base station shown in Node B of FIG. 1 and a plurality of communication terminal devices existing in the radio communication cover area of the base station. Moreover, it is an example applied to a mobile phone provided with a GPS positioning function as a communication terminal device.

  In the figure, solid arrows indicate control signal lines, and thick solid arrows indicate power supply lines from the power supply unit.

  In FIG. 2, a mobile phone 200 is a mobile communication terminal having a function of connecting to the base station shown in Node B of FIG. 1 and a positioning function by a GPS system, and stores a CPU (not shown) and a control program. The storage block such as a ROM, a working memory such as a RAM, and a communication circuit as existing hardware are implemented, and the function of each functional block is realized by the CPU executing a control program. In addition, the mobile phone 200 performs positioning by capturing GPS signals transmitted from each of four GPS satellites (not shown) and extracting information from each GPS signal. This GPS signal is obtained by superimposing a PRN code such as a C / A code or a P code, which differs for each GPS signal, on a carrier wave having the same frequency of 1,57542 GHz.

  The mobile phone 200 includes an antenna 201, a radio unit 202, a GPS antenna 203, a GPS signal receiving unit 204, a cellular system communication unit 206, a GPS position measurement unit 207, and a communication unit 205 including a communication control unit 208, A terminal control unit 209, a storage unit 210, a power supply unit 211, a display unit 212, and an input unit 213 are provided.

  The radio unit 202 transmits and receives radio signals to and from the radio base station by transmitting and receiving radio waves via the antenna 201.

  The GPS antenna 203 receives radio waves from GPS satellites. The GPS signal receiving unit 204 receives a radio wave from a GPS satellite, searches for the GPS signal, captures it, and acquires information included in the GPS signal. Then, the GPS positioning unit 207 performs a calculation for positioning based on the acquired information.

  The communication unit 205 controls the cellular system communication unit 206, the GPS position positioning unit 207, and the communication control unit 208.

  The cellular system communication unit 206 performs protocol control for performing communication with a cellular communication system (specifically, its radio base station).

  The GPS position measurement unit 207 analyzes a signal from a GPS satellite and measures the position of the mobile terminal. The GPS positioning unit 207 performs a positioning calculation based on satellite acquisition information such as code phase, frequency, signal level, etc. during code synchronization for a plurality of channels performed by the GPS signal receiving unit 204, and outputs a positioning result.

  The communication control unit 208 performs communication control on the cellular system communication unit 206 and the GPS position measurement unit 207.

  The terminal control unit 209 controls each functional block of the mobile terminal 200 except the communication unit 205, determines whether handover control is possible, and issues an instruction to the cellular system communication unit 206. Also, the positional information from the GPS positioning unit 207 is notified to the cellular communication system.

  In particular, when the terminal control unit 209 receives a forced handover request signal for forcibly handing over its own terminal to an adjacent radio base station, the terminal control unit 209 executes a handover process.

  The storage unit 210 includes a ROM that stores control programs, fixed data, and the like, a semiconductor memory such as a RAM that is a working storage area of the CPU, and a hard disk. The storage unit 210 stores character information, image information, and audio signals that are received or input. . The ROM is a read-only semiconductor memory that stores fixed data such as programs and communication control data required when the CPU operates. The RAM is used as a so-called working memory that temporarily stores data related to display and communication, data used for calculation, calculation results, and the like. A program processed by the portable terminal 200 is expanded in the RAM and executed. Further, a part of the RAM includes a flash memory that is an electrically rewritable nonvolatile memory, and various specifications, particularly in the mobile phone 200, can be changed by changing a program written in the flash memory.

  The power supply unit 211 supplies power to each functional block of the mobile terminal 200.

  The display unit 212 includes a dot matrix LCD display, a backlight, and various drivers, and displays each information to the user of the portable terminal 200.

  The input unit 213 inputs and generates key operation information from a user of the mobile terminal 200. The input unit 213 includes telephone function keys for incoming / outgoing calls, telephone function switching, operation determination, mode keys for switching various functions, cursor keys for moving a selection target in the up / down / left / right directions, and telephone number input. Consists of dial keys consisting of membrane keys for dialing.

  FIG. 3 is a diagram illustrating a coverage area of a wireless base station (BS) and a cell (wireless communication area).

  In FIG. 3, the cellular system includes a plurality of radio base stations 310 (radio base stations BS-1 to BS7) and cells (radio communication areas) having a radius of several kilometers to several tens of kilometers that each of the radio base stations BS-1 to BS7 has. ) 320 and the radio base stations BS-1 to BS7 are connected to each other, and a radio network controller (RNC) 330 for controlling the radio base stations BS-1 to BS7 and a fixed communication network connected to the radio network controller (RNC) 330 340.

  The mobile terminal is, for example, the mobile phone 200 shown in FIG. The mobile phone 200 performs call control and communication with a radio base station (BS) 310. In addition, the base station (BS) 310 is periodically notified of the location information of the mobile terminal itself. During communication, a handover is performed to an adjacent cell in accordance with an instruction from the radio base station (BS) 310.

  The radio base station (BS) 310 performs call control and communication with the mobile terminal (mobile phone 200) in the cell 320.

  Each radio base station BS-1 to BS7 is connected to a fixed communication network 340 via a radio network controller (RNC) 330. Each radio base station BS-1 to BS7 monitors the position and movement status of the mobile terminal in the cell 320.

  The radio network controller (RNC) 330 supervises the radio base stations BS-1 to BS7 and monitors the position and movement status of the mobile terminal (cell phone 200) in each cell (radio communication area). In addition, the radio network controller (RNC) 330 monitors the congestion state of each of the radio base stations BS-1 to BS7, and when congestion occurs or is predicted to occur, the radio controller (RNC) 330 gives an instruction for eliminating the congestion to the corresponding cell time. Do.

  FIG. 4 is a diagram showing a coverage area of a radio base station (BS) and a cell (radio communication area), taking the communication area of the radio base station BS-1 as an example.

  In FIG. 4, the communication control area is a cover area of a cell (wireless communication area) 320.

  The cell (radio communication area) 320 of the radio base station BS-1 is arranged so as to overlap with the cell of the adjacent radio base station.

  The cell (radio communication area) 320 of the radio base station BS-1 has an area capable of communicating with an adjacent radio base station.

  The radio network controller (RNC) 330 (FIG. 3) has position information that allows communication with an adjacent radio base station.

  In FIG. 4, in the cell (radio communication area) 320 of the radio base station BS-1, an area 320A in which communication with an adjacent cell is possible, and an adjacent cell on the inner side near the radio base station BS-1, There is a non-communication area 320B.

  A mobile terminal in the area 320A in which communication with an adjacent cell is possible is a terminal on which handover is performed.

  Hereinafter, an operation of the wireless communication system including the mobile phone 200 configured as described above will be described. First, an outline of the operation of the mobile phone 200 will be described.

The mobile phone 200 has a communication function with a wireless network system and a GPS positioning function for receiving radio waves from GPS satellites, and can notify the wireless base station (BS) 310 of its own location information. Specifically, the mobile phone 200 performs the following operations.
(1) The position of the portable terminal is measured using radio waves received from GPS satellites, and the position information of the portable terminal is notified to the wireless network side.
(2) In accordance with an instruction from the radio base station (BS) 310, the location information is notified to the radio network side.
(3) Carry out handover led by the wireless communication system.

Next, the congestion control of the cellular system will be described.
When users with mobile terminals concentrate in the same area and calls within a cell increase, congestion or the occurrence of congestion is expected. Mobile terminals that are close to adjacent cells and capable of communicating with adjacent cells are forcibly handed over to distribute the mobile terminals in the cell and eliminate congestion state or congestion state. Deter.

<Congestion factors in cellular systems>
(1) Concentration of users with mobile terminals in the same area ・ Many calls are made in the same cell ・ Many UEs are concentrated in the same cell (2) Concentration of communication traffic (due to disasters, etc.) Sudden increase in calls)
・ The number of calls in the cellular system increases ・ The number of calls on the wired network side increases and failures occur on the calls on the cellular system side (3) Increase in communication volume ・ Congestion due to a large number of packets ・ Congestion due to broadband such as audio / video communication

  In performing a forced handover, a mobile terminal and a cell to be handed over are determined according to the position, moving speed, and moving direction of the mobile terminal in the cell.

  As described above, in the cellular system, (1) users with mobile terminals concentrate in the same area, (2) concentration of communication traffic (sudden increase in calls due to disasters, etc.), (3) communication Congestion occurs due to the increase in volume.

In the present embodiment, as a solution to the above case (1), mobile terminals in a cell are distributed. Specifically, the following methods (a) to (c) are adopted.
(A) When congestion occurs, in a cell in which congestion occurs, only the mobile terminal located near the adjacent radio base station performs forced handover, thereby eliminating the congestion.
(B) When congestion occurs, the handover target radio base station is selected according to the moving direction of the mobile terminal, and by performing forced handover, the processing load on the entire cellular system including the mobile terminal is reduced, Eliminate congestion.
(C) The cellular system (radio base station and radio base station apparatus) has a range of cells of each radio base station and position information of a range in which communication with an adjacent radio base station is possible, and a specific radio When congestion occurs or is expected to occur in the base station, the mobile terminal in a position where communication with the adjacent radio base station can be forcibly handed over to eliminate congestion or to generate congestion Deter.

  In this way, in the radio base station, the position and moving direction of the mobile terminal in the cell are monitored, and when congestion occurs or is expected to occur in the cell, the location of the position close to the adjacent radio base station Specify a mobile terminal and perform a forced handover. Thereby, only the portable terminal close to the adjacent radio base station performs the forced handover, thereby eliminating the congestion without performing an unnecessary handover process.

  In the present embodiment, when congestion occurs, a portable terminal close to an adjacent radio base station is designated and forced handover is performed. An example of the optimum forced handover is the pattern shown in FIGS. 9 and 10 to be described later, but will be described in order from a simpler example for convenience of explanation.

  FIG. 5 is a diagram illustrating a cover area of a cell (wireless communication area) for explaining communication control, and takes call control of the wireless base station BS-1 as an example.

  The cell (wireless communication area) of the radio base station BS-1 is assumed to be cell 1. In the figure, UE-1 to UE-5 are mobile terminals (mobile phone 200).

  Control of the radio base station (BS-1) is as follows.

  A radio network controller (RNC) (see radio network controller (RNC) 330 in FIG. 3; the same applies hereinafter) monitors the position and moving direction of the mobile terminal during communication with the mobile terminals (UE-1 to UE-5). .

  A radio | wireless control apparatus (RNC) requests | requires the notification of a positional information with respect to a portable terminal (UE-1-UE-5).

  The radio network controller (RNC) is accurate from the location information from the mobile terminals (UE-1 to UE-5) and the location information of the mobile terminals (UE-1 to UE5) measured on the radio base station BS-1 side. Determine the location of the mobile device.

  A radio | wireless control apparatus (RNC) also monitors a moving speed and a moving direction with the position of a portable terminal (UE-1-UE-5).

  The radio network controller (RNC) monitors the congestion state of the radio base station BS-1 of the cell 1.

  FIG. 6 is a control sequence diagram showing a call control sequence during communication of the radio base station BS-1 of FIG. UE-1 to UE-5 in FIG. 6 are portable terminals existing in the cell 1 shown in FIG.

  As shown in FIG. 6, after starting communication with each mobile terminal (UE-1 to UE5), the radio network controller (RNC) “location information notification request” to each mobile terminal (UE-1 to UE5). Is transmitted as a control signal message.

  After receiving the “location information notification request” from the radio network controller (RNC), each mobile terminal (UE-1 to UE5) returns Ack to the radio network controller (RNC) via the radio base station BS-1. Then, “location information notification” is periodically transmitted as a control signal message. In FIG. 6, each mobile terminal (UE-1 to UE-5) receives a “location information notification request” from the radio network controller (RNC) and first returns Ack and then “location information” after a predetermined time T1 to T5. Reply "notification".

  FIG. 7 is a diagram illustrating a cell (wireless communication area) cover area for explaining forced handover control when congestion occurs, and a wireless base station BS-2 adjacent to the wireless base station BS-1 of FIG. An example of forced handover control when there is

  The cell (wireless communication area) of the radio base station BS-1 is assumed to be cell 1. In the figure, UE-1 to UE5 are mobile terminals (mobile phone 200).

  The cell (wireless communication area) of the radio base station BS-2 is defined as cell 2. The mobile terminal UE-3 exists not only in the area of the cell 1 but also in the area of the cell 2, and can communicate with the radio base station BS-2.

  In the cellular system, the cell range of each radio base station and position information of a range in which communication with an adjacent radio base station is possible are provided. The position information is acquired by, for example, three-point positioning of three wireless base stations.

  The procedure for performing a forced handover is as follows.

  (1) The mobile terminal UE-3 communicates with the radio base station BS-1.

  (2) The mobile terminal UE-3 is in an area where the communication state (for example, electric field strength) is good with the radio base station BS-1 and in which communication with the radio base station BS-2 is possible.

  (3) When congestion occurs, the standard for carrying out normal handover (electric field strength degradation standard) is not reached, but the mobile terminal UE-3 capable of communicating with the cell 2 of the radio base station BS-2 is adjacent Forced handover is performed to forcibly perform handover to cell 2 to be performed.

  (4) By forcibly handing over the mobile terminal UE-3 to the adjacent radio base station BS-2, the mobile terminals in the cell 1 where calls are concentrated can be distributed to the adjacent cell 2, Eliminate congestion. In other words, the congestion state in the cell is eliminated by designating only the portable terminal located near the adjacent radio base station and performing the forced handover.

  The forced handover may be executed by any control device installed at any place. For example, it may be a control device installed or connected to a radio base station, or a radio control device (RNC) that controls each radio base station. In this embodiment, an example will be described in which the radio network controller (RNC) performs forced handover.

  FIG. 8 is a control sequence diagram showing a call control sequence when congestion occurs during the forced handover control when congestion occurs in FIG. UE-1 to UE-5 in FIG. 8 are mobile terminals existing in the cell 1 shown in FIG. Also, UE-3 in FIG. 8 is a mobile terminal that exists in an area where communication with the radio base station BS-2 is possible.

  As shown in FIG. 8, after starting communication with each mobile terminal (UE-1 to UE-5), the radio network controller (RNC) “location” for each mobile terminal (UE-1 to UE-5). “Information notification request” is transmitted as a message of a control signal.

  After receiving the “location information notification request” from the radio network controller (RNC) side, each mobile terminal (UE-1 to UE-5) periodically transmits to the radio network controller (RNC) via the radio base station BS-1. The “location information notification” is transmitted as a control signal message. In FIG. 8, each mobile terminal (UE-1 to UE-5) receives a “location information notification request” from the radio network controller (RNC) and first returns Ack and then “location information” after a predetermined time T1 to T5. Reply "notification".

  In FIG. 8, congestion has occurred (see number 410). Congestion occurs when a large number of mobile terminals are concentrated in a specific wireless communication area (in this case, cell 1), and when communication is performed there, a congestion state occurs in which the communication channel is insufficient.

  When congestion occurs, the radio network controller (RNC) does not reach the standard for performing a normal handover (electric field strength degradation standard), but is a portable terminal that can communicate with the cell 2 of the radio base station BS-2 Is forcibly handed over to the adjacent cell 2. In this example, the mobile terminal subject to forced handover is the mobile terminal UE-3. The radio network controller (RNC) transmits a “forced handover request” to the mobile terminal UE-3, and the mobile terminal UE-3 returns an Ack for the forced handover request and performs a normal “handover process”. (See reference numeral 420). As a result of the “handover process” by the mobile terminal UE-3, the mobile terminal UE-3 transmits a “call connection request” to the radio network controller (RNC) via the radio base station BS-2. The radio network controller (RNC) receives the “call connection request” from the mobile terminal UE-3, returns Ack, and then returns “location information notification request”. The portable terminal UE-3 receives the “location information notification request” from the radio network controller (RNC), and returns “location information notification” after a predetermined time T3 after returning Ack.

  By forcibly handing over the mobile terminal UE-3 to the adjacent radio base station BS-2, the mobile terminals in the cell 1 where calls are concentrated can be distributed to the adjacent cell 2, and the congestion state can be reduced. Can be resolved.

  FIG. 9 is a diagram illustrating a cell (radio communication area) cover area for explaining forced handover control when congestion occurs, and radio base station BS-2 adjacent to radio base station BS-1 in FIG. In addition, an example of forced handover control when there is a radio base station BS-3 adjacent to the radio base station BS-1 is shown.

  The cell (wireless communication area) of the radio base station BS-1 is assumed to be cell 1. In the figure, UE-1 to UE5 are mobile terminals (mobile phone 200).

  The cell (wireless communication area) of the radio base station BS-2 is defined as cell 2. The mobile terminal UE-3 exists not only in the area of the cell 1 but also in the area of the cell 2, and can communicate with the radio base station BS-2. In addition, the mobile terminal UE-2 is about to move in the communication area direction of the cell 2.

  The cell (wireless communication area) of the wireless base station BS-3 is assumed to be cell 3. The mobile terminal UE-5 is about to move in the communication area direction of the cell 3. In the cellular system, it is used that the position information of the range of the cell of each radio base station and the range in which communication with the adjacent radio base station can be acquired.

  The procedure for performing a forced handover is as follows.

  (1) The mobile terminal UE-2, the mobile terminal UE-3, and the mobile terminal UE-5 are communicating with the radio base station 1 (BS-1).

  (2) The mobile terminal UE-2 has moved to an area where the communication status (electric field strength) with the radio base station BS-1 is good and communication with the radio base station BS-2 is possible.

  (3) The mobile terminal UE-3 is in a state where the communication status (electric field strength) with the radio base station BS-1 is good and communication with the radio base station BS-2 is possible.

  (4) The mobile terminal UE-5 has moved to an area where the communication status (electric field strength) with the radio base station BS-1 is good and communication with the radio base station BS-3 is possible.

  (5) A mobile terminal capable of communicating with the cell 2 (radio communication area) of the radio base station BS-2, although it does not reach the standard for carrying out normal handover (electric field strength degradation standard) when congestion occurs Forced handover is performed to forcibly hand over UE-3 to the adjacent cell 2.

  (6) By forcibly handing over the mobile terminal UE-3 to the adjacent radio base station BS-2, the mobile terminals in the cell 1 where calls are concentrated can be distributed to the adjacent cell 2, Eliminate congestion.

  (7) When congestion occurs, the radio base station BS-1 does not reach the standard for performing normal handover (electric field strength degradation standard), but can communicate with the radio base station cell 2 (radio communication area) Forced handover is performed in which the mobile terminal UE-2 moving to a certain position is forcibly handed over to the adjacent cell 2.

  (8) By forcibly handing over the mobile terminal UE-2 to the adjacent radio base station BS-2, the mobile terminals in the cell 1 where calls are concentrated can be distributed to the adjacent cell 2, Eliminate congestion.

  (9) When congestion occurs, the radio base station BS-1 does not reach the standard for carrying out normal handover (electric field strength degradation standard), but the cell 3 (radio communication area) of the radio base station BS-3 The mobile terminal UE-5 moving to a position where communication can be forcibly handed over to the adjacent cell 3 is performed.

  (10) By forcibly handing over the mobile terminal UE-5 to the adjacent radio base station (BS-3), the mobile terminals in the cell 1 where calls are concentrated can be distributed to the adjacent cell 3 Yes, to eliminate congestion.

  In the example of FIG. 9, the mobile terminal UE-3 in a position close to the radio base stations BS-2 and BS-3 adjacent to the radio base station BS-1 moves to the cell 2 and cell 3 adjacent to each other and can talk. By specifying only the portable terminals UE-2 and UE-5 and performing forced handover, the congestion state in the cell 1 is eliminated.

  FIG. 10 is a control sequence diagram showing a call control sequence when congestion occurs during forced handover control when congestion occurs in FIG. UE-1 to UE-5 in FIG. 10 are mobile terminals existing in the cell 1 shown in FIG. Also, UE-3 in FIG. 10 is a mobile terminal that exists in an area where communication with the radio base station BS-2 is possible.

  As shown in FIG. 10, after starting communication with each mobile terminal (UE-1 to UE-5), the radio network controller (RNC) “location” for each mobile terminal (UE-1 to UE-5). “Information notification request” is transmitted as a message of a control signal.

  After receiving the “location information notification request” from the radio network controller (RNC) side, each mobile terminal (UE-1 to UE-5) periodically transmits to the radio network controller (RNC) via the radio base station BS-1. The “location information notification” is transmitted as a control signal message. In FIG. 10, each mobile terminal (UE-1 to UE-5) receives a “location information notification request” from the radio network controller (RNC) and first returns Ack and then “location information” after a predetermined time T1 to T5. Reply "notification".

  When congestion occurs (see number 510), the radio network controller (RNC) does not reach the standard for performing a normal handover (electric field strength degradation standard), but communicates with the cell 2 of the radio base station BS-2. Forcible handover is performed for forcibly handing over a portable terminal capable of performing handover to the adjacent cell 2. In this example, the mobile terminal subject to forced handover is the mobile terminal UE-3. The radio network controller (RNC) transmits a “forced handover request” to the mobile terminal UE-3, and the mobile terminal UE-3 returns an Ack for the forced handover request and performs a normal “handover process”. (See number 520). As a result of the “handover process” by the mobile terminal UE-3, the mobile terminal UE-3 transmits a “call connection request” to the radio network controller (RNC) via the radio base station BS-2. The radio network controller (RNC) receives the “call connection request” from the mobile terminal UE-3 and returns Ack.

  In the case of FIG.9 and FIG.10, unlike the case of FIG.7 and FIG.8, portable terminal UE-2 moves to the area which can communicate with wireless base station BS-2, portable terminal UE-5, It has moved to an area where communication with the radio base station BS-3 is possible. For this reason, the radio network controller (RNC) performs the same forced handover as that of the mobile terminal UE-3 on the mobile terminals UE-2 and UE-5. Since the forced handover is performed for the mobile terminal UE-2 and the mobile terminal UE-5 following the mobile terminal UE-3, the radio network controller (RNC) in FIG. After returning “call connection request” Ack, the “location information notification request” that has been made to the mobile terminal UE-3 is not issued.

  The radio network controller (RNC) transmits a “forced handover request” to the mobile terminal UE-2, and the mobile terminal UE-2 returns an Ack to the forced handover request and performs a normal “handover process”. (See reference numeral 530). As a result of the “handover process” by the mobile terminal UE-2, the mobile terminal UE-2 transmits a “call connection request” to the radio network controller (RNC) via the radio base station BS-2. The radio network controller (RNC) receives “call connection request” from the mobile terminal UE-2 and returns Ack.

  Further, the radio network controller (RNC) transmits a “forced handover request” to the mobile terminal UE-5, and the mobile terminal UE-5 returns an Ack for the forced handover request, Over processing "(see number 540) is executed. As a result of the “handover process” by the mobile terminal UE-5, the mobile terminal UE-5 transmits a “call connection request” to the radio network controller (RNC) via the radio base station BS-3. The radio network controller (RNC) receives the “call connection request” from the mobile terminal UE-5 and returns Ack.

  Calls are concentrated by forcibly handing over the mobile terminal UE-3, the mobile terminal UE-2, and the mobile terminal UE-5 to the adjacent radio base station BS-2 and radio base station BS-3 in sequence. The mobile terminals in the cell 1 can be distributed to the adjacent cells 2 and 3 and the congestion state can be eliminated.

  11 and 12 are flowcharts showing the congestion control process of the radio network controller (RNC). FIG. 11 shows the congestion control process, and FIG. 12 shows the details of the congestion control process.

  In this Embodiment, since the radio | wireless control apparatus (RNC) is performing the forced handover control at the time of congestion with respect to a portable terminal, the processing flow of a radio | wireless control apparatus (RNC) is shown. This forced handover control is not limited to the radio network controller (RNC), and any device (for example, a radio base station) may perform it. In this case, the flow shown in FIGS. 11 and 12 is a processing flow of the radio base station.

  In FIG. 11, it is determined whether or not there is a location registration request from the portable terminal in step S1. If there is a location registration request from the portable terminal, the location registration processing to the communication system is performed in step S2, and the process proceeds to step S3. If there is no location registration request from the portable terminal, the procedure proceeds to step S3 as it is.

  In step S3, it is determined whether or not there is a communication request from the portable terminal. If there is a communication request from the mobile terminal, the process proceeds to step S6. If there is no communication request, it is determined in step S4 whether there is a communication request to the mobile terminal.

  If there is no communication request to the mobile terminal in step S4, it is determined in step S5 whether there is a mobile terminal in communication. If there is a mobile terminal in communication in step S5, the process proceeds to step S8. If there is no mobile terminal in communication, a communication request from the communication terminal, a communication request to the communication terminal, and a mobile terminal in communication It is determined that there is neither, and this flow ends.

  On the other hand, if there is a communication request from the portable terminal in step S3 or if there is a communication request to the portable terminal in step S4, communication processing is started in step S6, and the “position” to the portable terminal in step S7. Send "Information notification request". For example, in the control sequences of FIGS. 6, 8, and 10, the radio network controller (RNC) sends a “location information notification request” to each mobile terminal (UE-1 to UE-5) as a control signal Message. Send as.

  In step S8, it is determined whether or not there is a location information notification from the portable terminal. If there is a location information notification from the mobile terminal, the location information acquisition process of the mobile terminal is performed in step S9 and the process proceeds to step S10. If there is no location information notification from the mobile terminal, the procedure proceeds to step S10 as it is.

  In step S10, a congestion state monitoring process is performed. In the congestion state monitoring process, the occurrence of a congestion state in which the call channel is insufficient is monitored.

  In step S11, it is determined whether there is a communication disconnection request from the mobile terminal. If there is a communication disconnection request from the mobile terminal, the process proceeds to step S13. If there is no communication disconnection request, it is determined in step S12 whether there is a communication disconnection request to the mobile terminal.

  If there is no communication disconnection request to the mobile terminal in step S12, the flow is terminated. If there is a communication disconnection request to the mobile terminal, a communication end process is performed in step S13 to end the flow.

  In FIG. 12, it is determined in step S21 whether congestion has occurred in the cell. If congestion does not occur in the cell, this flow is terminated without performing congestion control. When congestion occurs in the cell, the number (X) of mobile terminals that perform forced handover is calculated in step S22.

  In step S23, it is determined whether or not there is a mobile terminal in a position where communication with an adjacent cell is possible. If there is a mobile terminal in a position where communication with an adjacent cell is possible, a handover destination cell is determined in step S24, and a handover request to the mobile terminal is transmitted in step S25. For example, in FIG. 7, the mobile terminal UE-3 exists in an area where communication with the radio base station BS-2 is possible. As shown in the control sequence of FIG. 8, the radio network controller (RNC) transmits a “forced handover request” to the mobile terminal UE-3, and the mobile terminal UE-3 sends an Ack for the forced handover request. While replying, the normal “handover process” (see number 420) is executed.

  In step S26, it is determined whether or not the handover is successful. In the example of FIG. 8, “call connection request” transmitted from the mobile terminal UE-3 to the radio network controller (RNC) via the radio base station BS-2 as a result of the “handover process” by the mobile terminal UE-3. Is received to determine the success of the handover. Here, the radio network controller (RNC) receives the “call connection request” from the mobile terminal UE-3, returns Ack, and then returns “location information notification request”. The portable terminal UE-3 receives the “location information notification request” from the radio network controller (RNC), and returns a “location information notification request” after a predetermined time T3 after returning Ack.

  If the handover is successful in step S26, it is determined in step S27 whether or not the handover of all portable terminals has been completed.

  If the handover is not successful in step S26 or if the handover of all mobile terminals is not completed in step S27, the process returns to step S23 and continues the handover process until there is no corresponding mobile terminal. .

  On the other hand, if handover of all mobile terminals is completed in step S27, or if there is no mobile terminal in a position where communication with an adjacent cell is possible in step S23, whether or not congestion has been resolved in step S28. If the congestion is not eliminated, the process returns to step S22. If the congestion is eliminated, the flow is terminated. Therefore, as long as congestion occurs in a cell, a forced handover is performed for a mobile terminal located at a position where communication with an adjacent cell is possible.

  In the example of FIG.7 and FIG.8, the portable terminal in the position which can communicate with an adjacent cell is portable terminal UE-3, Compulsory handover of portable terminal UE-3 to adjacent radio base station BS-2 I was letting. In this embodiment, a mobile terminal in a position where communication with an adjacent cell can be performed is forcibly handed over to an adjacent radio base station, while moving to a position where communication with the adjacent cell is possible. A certain mobile terminal is continuously monitored, and when the mobile terminal being monitored moves to an area where communication with an adjacent cell is possible, the mobile terminal is forcibly handed over to an adjacent radio base station. In the above processing, in step S22 of FIG. 12, when calculating the number (X) of mobile terminals that perform forced handover, the mobile terminal that is moving to a position where communication with an adjacent cell can be performed is performed. May be included in the number (X) of mobile terminals that implement the above. For example, in the examples of FIG. 9 and FIG. 10, the mobile terminal UE-3 located near the radio base station BS-2 adjacent to the radio base station BS-1 and the radio base station BS adjacent to the radio base station BS-1 -Forcible handover is performed for mobile terminals UE-2 and UE-5 that can move to cell 2 and cell 3 adjacent to mobile terminal UE-3 located near BS-2 and BS-3 and can talk to each other. Thus, the congestion state in the cell 1 is eliminated.

As described above in detail, according to the present embodiment, the radio network controller (RNC) is in a congestion state when it detects a congestion state in which calls are concentrated in the cell and the radio channel is congested. Detects location information and moving direction of a mobile terminal in communication within a cell, and determines a mobile terminal that can be handed over to a radio base station adjacent to a radio base station in a congested state among the mobile terminals in communication The determined portable terminal is forcibly handed over to a radio base station adjacent to the radio base station in a congested state. That is, when congestion occurs or is expected to occur, only the mobile terminal located near the adjacent radio base station is forcibly handed over. Since only mobile terminals that can communicate with adjacent cells are the target terminals for forced handover, switching between wireless cells is efficient and efficient without causing the cellular system and mobile terminals to perform unnecessary handover processing. It is possible to reduce the processing load on the radio base station, cellular system, and portable terminal side. In addition, by forcibly handing over a mobile terminal in a position where communication with an adjacent radio base station is possible, the congestion state is eliminated or the occurrence of congestion is suppressed. The above effects are summarized as follows.
(1) When congestion occurs or in a state where congestion is expected to occur, by handing over to the adjacent radio base station based on the position of the mobile terminal, the mobile terminals in the cell are efficiently distributed , Congestion can be solved.
(2) By performing forced handover only on portable terminals close to adjacent radio base stations, congestion can be eliminated without performing unnecessary handover processing.
(3) By determining the mobile terminal to be handed over according to the position and moving direction of the mobile terminal and forcibly performing the handover, the processing load on the entire cellular system including the mobile terminal can be minimized. it can.

  Further, in the present embodiment, in a cell of a wireless base station in a congested state, a moving state including the moving direction of a mobile terminal that is communicating is detected, and the moving direction is adjacent to the wireless base station in a congested state. When the mobile terminal approaches the cell of the other radio base station, monitoring is performed even if the corresponding mobile terminal does not yet exist in the cell of the other radio base station, and forced handover is performed immediately after reaching the area of the cell Therefore, the mobile terminals in the cell can be more efficiently distributed and congestion can be eliminated. For example, as shown in FIG. 9, in addition to performing a forced handover for the mobile terminal UE-3 that is also present in the area of the cell 2, the mobile terminal UE3 moves to the adjacent cell 2 and the cell 3, Congestion within the cell 1 by performing a forced handover to the mobile terminals UE-2 and UE-5 that would be able to talk to the base stations BS-2 and BS-3 The state can be resolved more quickly.

  From another viewpoint, among the mobile terminals determined to be handed over, the mobile terminals that are closer to the radio base station adjacent to the congested radio base station are sequentially forced to be handed over sequentially. .

  Further, when a mobile terminal that is a target of forced handover can perform forced handover to any cell of a plurality of adjacent radio base stations, forced handover may be performed on either side. In this case, it is preferable for the portable terminal that is the target of forced handover that a forced handover instruction is issued to a closer radio base station in order to reduce handover processing time and frequency. Furthermore, if the radio network controller (RNC) can predict the congestion state or the tendency of congestion occurrence to a certain extent to each radio base station, if a forced handover is instructed to the radio base station where the next congestion occurrence is predicted to be smaller More preferred.

  It is also possible to notify each radio base station of the relationship between the corresponding mobile terminal and the radio base station so that the mobile terminal instructed to perform a forced handover will not return to the cell of the radio base station in a congested state again. is there.

  The above description is an illustration of a preferred embodiment of the present invention, and the scope of the present invention is not limited to this.

  In the above embodiment, the communication terminal device such as a PHS or a mobile phone has been described. However, this is an example, and any device that performs wireless communication via a base station can be applied. Yes, the type and number of communication methods are not limited. The same applies to the number of radio base stations and communication terminal devices.

  In the above embodiment, an example has been described in which the radio network controller (RNC) performs forced handover control when the mobile terminal is congested. However, this forced handover control is limited to the radio network controller (RNC). Instead, any device (for example, a radio base station) may perform.

  In the above embodiment, the names wireless communication system, communication terminal device, wireless base station, and forced handover method are used. However, this is for convenience of explanation, and a portable wireless terminal, mobile communication device, and mobile communication are used. Of course, a system, a forced handover method, or the like may be used.

  Further, the units constituting the radio control device, the radio base station, and the communication terminal device, for example, the types of transmission units, reception units, storage units, the number thereof, and connection methods may be any.

  The radio control apparatus, radio base station, and communication terminal apparatus described above are also realized by a program for causing the radio control apparatus, radio base station, and communication terminal apparatus to function. This program is stored in a computer-readable recording medium.

  In the radio control apparatus, radio base station, communication terminal apparatus and forced handover method according to the present invention, users with mobile terminals concentrate in the same area, and the number of calls in the cell increases, thereby causing congestion or When the occurrence of congestion is predicted, the mobile terminal in communication is forcibly handed over to an adjacent radio base station based on the movement status and location information, thereby canceling the congestion state or suppressing the congestion state. This is useful for a communication system having a handover method.

The block diagram which shows the structure of the radio | wireless communications system which concerns on one embodiment of this invention Configuration block diagram of communication terminal apparatus of radio communication system according to the present embodiment The figure which shows the cover area of the radio | wireless base station (BS) and cell (wireless communication area) of the radio | wireless communications system which concerns on this Embodiment. The figure which shows the cover area of the radio | wireless base station (BS) and cell (wireless communication area) of the radio | wireless communications system which concerns on this Embodiment. The figure which shows the cover area of the cell (radio | wireless communication area) for demonstrating the communication control of the radio | wireless communications system which concerns on this Embodiment. Control sequence diagram showing a call control sequence during communication of the radio base station BS-1 of the radio communication system according to the present embodiment The figure which shows the cover area of the cell (radio communication area) for demonstrating forced handover control at the time of congestion generation of the radio | wireless communications system which concerns on this Embodiment. Control sequence diagram showing a call control sequence when congestion occurs during forced handover control when congestion occurs in the wireless communication system according to the present embodiment The figure which shows the cover area of the cell (radio communication area) for demonstrating forced handover control at the time of congestion generation of the radio | wireless communications system which concerns on this Embodiment. Control sequence diagram showing a call control sequence when congestion occurs during forced handover control when congestion occurs in the wireless communication system according to the present embodiment The flowchart which shows the process of the congestion control of the radio | wireless control apparatus (RNC) of the radio | wireless communications system which concerns on this Embodiment The flowchart which shows the detail of the process of the congestion control of the radio | wireless control apparatus (RNC) of the radio | wireless communications system which concerns on this Embodiment

Explanation of symbols

100 Wireless network system 101 Core network (CN)
102 Radio Access Network (RAN)
103,330 Radio Control Unit (RNC)
104 nodes (B)
105,320 cells 106 Iu interface 107 Iur interface 108 Iub interface 109 Radio network subsystem (RNS)
DESCRIPTION OF SYMBOLS 200 Cellular phone 201 Antenna 202 Radio | wireless part 203 GPS antenna 204 GPS signal receiving part 205 Communication part 206 Cellular system communication part 207 GPS position positioning part 208 Communication control part 209 Terminal control part 210 Storage part 211 Power supply part 212 Display part 213 Input part 310 wireless base station 340 fixed communication network

Claims (14)

A radio control device used in a radio communication system including a plurality of radio base stations constituting a radio communication area and a communication terminal device that performs radio communication within the radio communication area of each radio base station,
A congestion state detection means for detecting a congestion state where calls are concentrated in the wireless communication area and the wireless channel is congested;
Position information detecting means for detecting position information of a communication terminal device in communication in a wireless communication area in a congested state;
Determining means for determining a communication terminal apparatus that can be handed over to a radio base station adjacent to a radio base station in a congested state among the communication terminal apparatuses in communication based on the detected position information of the communication terminal apparatus; ,
A radio control apparatus comprising: a forced handover execution means for forcibly handing over a communication terminal apparatus determined to be handed over to a radio base station adjacent to a radio base station in a congested state.   The radio control apparatus according to claim 1, wherein the congestion state detection unit detects a congestion occurrence in which calls are concentrated in a radio communication area and a radio channel is congested or a state in which a congestion occurrence is expected.   The radio control apparatus according to claim 1, wherein the position information detection unit detects position information of a communication terminal within a radio communication area. The position information detecting means detects a moving state including a moving direction of a communication terminal device that is communicating in a wireless communication area in a congested state,
Based on the detected position state of the communication terminal device, the determination means includes a communication terminal device that can be handed over to a wireless base station adjacent to a wireless base station in a congested state among the communication terminal devices that are in communication. The wireless control device according to claim 1 for determination.   2. The forced handover execution unit sends a forced handover request signal for instructing an adjacent radio base station to execute a handover to a communication terminal apparatus determined to be handed over. Wireless control device.   2. The forced handover execution means forcibly performs handover sequentially from communication terminal devices adjacent to a radio base station adjacent to a radio base station in a congested state among communication terminal devices determined to be capable of handover. The wireless control device described. Congestion state detection means for detecting a congestion state in which calls are concentrated in the wireless communication area covered by itself and the wireless channel is congested;
Position information detecting means for detecting position information of a communication terminal device that is communicating in a local wireless communication area in a congested state;
Based on the detected location information of the communication terminal device, among the communication terminal devices in communication, a determination unit that determines a communication terminal device that can be handed over to an adjacent radio base station;
A radio base station comprising forced handover execution means for forcibly handing over a communication terminal apparatus determined to be handed over to an adjacent radio base station.   8. The radio base station according to claim 7, wherein the congestion state detection unit detects a congestion occurrence in which calls are concentrated in a radio communication area and a radio channel is congested or a state in which congestion is expected to occur.   The radio base station according to claim 7, wherein the position information detection means detects position information of a communication terminal within a radio communication area. The position information detecting means detects a moving state including a moving direction of a communication terminal device that is communicating in a congested state of the own wireless communication area,
Based on the detected position state of the communication terminal device, the determination means includes a communication terminal device that can be handed over to a wireless base station adjacent to a wireless base station in a congested state among the communication terminal devices that are in communication. The radio base station according to claim 7 for determination.   8. The forced handover execution means sends a forced handover request signal for instructing an adjacent radio base station to execute a handover to a communication terminal apparatus determined to be handed over. Radio base station.   8. The forced handover execution means forcibly performs handover sequentially from communication terminal devices closer to a radio base station adjacent to a radio base station in a congested state among communication terminal devices determined to be capable of handover. The radio base station described. A communication terminal apparatus that performs radio communication with a radio base station in a radio communication area,
Receiving means for receiving a forced handover request signal for forcibly handing over a communication terminal apparatus determined to be handed over to an adjacent radio base station;
A communication terminal apparatus comprising: a handover execution unit that executes a handover process when the forced handover request signal is received. A forced handover method used in a radio communication system including a plurality of radio base stations constituting a radio communication area and a communication terminal device performing radio communication within the radio communication area of each radio base station,
Detecting a congestion state where calls are concentrated in a wireless communication area and a wireless channel is congested;
Detecting the position information of the communication terminal device in communication in the wireless communication area in a congested state;
Determining a communication terminal apparatus that can be handed over to a radio base station adjacent to a radio base station in a congested state among the communication terminal apparatuses in communication based on the detected position information of the communication terminal apparatus; ,
Forcibly handing over a communication terminal apparatus determined to be handed over to a radio base station adjacent to a radio base station in a congested state.

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