WO2014024439A1 - Procédé et dispositif de commande de communications sans fil dans un système de communications sans fil - Google Patents

Procédé et dispositif de commande de communications sans fil dans un système de communications sans fil Download PDF

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Publication number
WO2014024439A1
WO2014024439A1 PCT/JP2013/004669 JP2013004669W WO2014024439A1 WO 2014024439 A1 WO2014024439 A1 WO 2014024439A1 JP 2013004669 W JP2013004669 W JP 2013004669W WO 2014024439 A1 WO2014024439 A1 WO 2014024439A1
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Prior art keywords
handover
cell
mobile terminal
communication control
suppression
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PCT/JP2013/004669
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English (en)
Japanese (ja)
Inventor
吉則 渡邉
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日本電気株式会社
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Priority to JP2014529286A priority Critical patent/JPWO2014024439A1/ja
Publication of WO2014024439A1 publication Critical patent/WO2014024439A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0083—Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
    • H04W36/00837—Determination of triggering parameters for hand-off
    • H04W36/008375—Determination of triggering parameters for hand-off based on historical data

Definitions

  • the present invention relates to a radio communication system having a plurality of cells, and more particularly to a radio communication control method and apparatus in a radio communication system having a handover control function.
  • a connection destination called a handover (hereinafter abbreviated as HO as appropriate) is used.
  • a cell switching process is performed, whereby the communication of the mobile terminal can be continued between the cells.
  • measurement is first performed when a base station that manages a connected cell (hereinafter referred to as a source cell) generates a predetermined event for the mobile terminal. Instruct them to send a report.
  • the predetermined event there is, for example, deterioration of the radio quality of the source cell.
  • the measurement report by the mobile terminal includes the measurement results of the radio quality of the source cell and its neighboring cells.
  • the base station determines a switching destination cell (hereinafter referred to as a target cell) based on the measurement report, and includes a handover procedure including signaling between the mobile terminal and the target cell. To start.
  • Non-Patent Document 1 An example of an event that triggers measurement report transmission is specified in Non-Patent Document 1 by LTE (Long Term Evolution) / E-UTRAN (Evolved UTRAN).
  • LTE Long Term Evolution
  • E-UTRAN Evolved UTRAN
  • the essential part of a report event defined as Event A3 ⁇ (Neighbor comes offset better than serving) in Non-Patent Document 1 is expressed by the following equation (1).
  • P s + O s ⁇ P t + O t P s + O s ⁇ P t + O t (1)
  • P s is the measurement result of the radio quality of the source cell
  • P t is the measurement result of the radio quality of the neighboring cell
  • O s is the offset value for the radio quality of the source cell
  • O t is the offset value for the radio quality of the neighboring cell. It is.
  • LTE employed is the received power RSRP of P s and P t are the downlink reference signal (Reference Signal Received Power) or reference signal received quality RSRQ (Reference Signal Received Quality).
  • RSRQ is the ratio of RSRP to the total received power RSSI (Received Signal Strength Indicator).
  • O s in Equation (1) affects the radio quality of the downlink reference signal of the source cell
  • O t affects the radio quality of the downlink reference signal of the adjacent cell.
  • O t is generally a handover parameter called cell individual offset (CIO), and a different offset value can be set for each neighboring cell registered in the neighboring list.
  • CIO cell individual offset
  • the CIO is included in the neighbor list notified by the base station to the mobile terminal connected to the cell managed by the base station.
  • the operating condition of Equation (1) is set in the base station, the operating condition of Equation (1) is notified to the mobile terminal connected to the cell managed by the base station. If the measurement results P s and P t of the radio quality of the source cell and the radio quality of the neighboring cell satisfy the condition of the formula (1), the mobile terminal triggers to the base station that manages the source cell. Send measurement report.
  • the base station determines a target cell based on the measurement report and starts a handover process to the target cell.
  • the wireless quality of the source cell falls below the required quality before the handover to the target cell is completed, and an abnormal disconnection of communication occurs.
  • the start of the handover is too late, the radio quality of the target cell falls below the required quality immediately after the handover to the target cell is completed, and an abnormal disconnection of communication occurs.
  • the handover condition for the original cell is satisfied again immediately after completing the handover to the target cell, and repetitive handover (hereinafter referred to as ping-pong HO as appropriate) occurs. There is.
  • the handover timing is increased by increasing the CIO (ie, the offset value O t in equation (1)).
  • the success rate of handover can be improved early.
  • the handover success rate can be improved by reducing the CIO and thereby delaying the handover timing. Therefore, it is possible to reduce handover failures by dynamically adjusting handover parameters such as the offset value O t (CIO) described above.
  • HO failure (Too Late HO, Too Early HO) is performed by dynamically adjusting HO parameters such as TTT (Time-To-Trigger) and CIO on a cell basis based on a measurement report of a terminal. ) Has been disclosed.
  • Non-Patent Document 2 only detects terminals that have detected ping-pongpHO based on handover history information and determined to be stationary based on fluctuations in arrival times of control signals from neighboring base stations. A method for suppressing handover is disclosed.
  • FIG. 1 is a schematic cell configuration diagram for explaining handover
  • FIG. 2 is a graph showing temporal changes in reception quality of a source cell and a target cell in handover of a mobile terminal.
  • a mobile terminal MS1 moving at a high speed and a mobile terminal MS2 having a lower speed are mixed in the source cell.
  • FIG. 2A there is a case where the CIO is increased so as not to cause Too Late ⁇ HO failure in the high-speed terminal MS1, and control is performed so as to advance the timing of the measurement report by the terminal.
  • an object of the present invention is to provide a radio communication control method and apparatus in a radio communication system that can effectively suppress frequent occurrence of handover of a mobile terminal.
  • a radio communication control apparatus is a radio communication control apparatus in a radio communication system that includes a plurality of cells and has a function of recording a history of inter-cell handover by a mobile terminal.
  • History analysis means for obtaining a handover frequency between the first cell and the second cell, and a mobile terminal that selects a mobile terminal that should suppress a handover between the first cell and the second cell based on the handover frequency It comprises: selection means; and handover suppression means for suppressing handover between the first cell and the second cell for a mobile terminal selected as a handover suppression target.
  • a radio communication control method is a radio communication control method in a radio communication system that includes a plurality of cells and has a function of recording a history of inter-cell handover by a mobile terminal. Frequency between the first cell and the second cell is calculated, and based on the handover frequency, a mobile terminal that should suppress handover between the first cell and the second cell is selected and selected as a handover suppression target A handover between the first cell and the second cell is suppressed for the mobile terminal that has been made.
  • a base station is a base station that manages a cell in a radio communication system having a function of recording a history of inter-cell handover by a mobile terminal, and includes a first cell and a second cell based on a handover history of the mobile terminal.
  • a handover history analyzing means for obtaining a handover frequency between the mobile terminals, a mobile terminal selection means for selecting a mobile terminal that should suppress a handover between the first cell and the second cell based on the handover frequency, and a handover suppression Handover suppressing means for suppressing a handover between the first cell and the second cell for a mobile terminal selected as a target.
  • a radio communication system includes a base station that manages a cell and a mobile terminal, and has a function of recording a history of handover between cells by the mobile terminal, wherein the base station is a mobile terminal
  • a handover history analysis means for obtaining a handover frequency between the first cell and the second cell from the handover history of the handover, and handover between the first cell and the second cell should be suppressed based on the handover frequency
  • Mobile terminal selection means for selecting a mobile terminal, and handover suppression means for suppressing a handover between the first cell and the second cell for a mobile terminal selected as a handover suppression target.
  • FIG. 1 is a schematic cell configuration diagram for explaining handover.
  • FIG. 2A is a graph showing temporal changes in the reception quality of the source cell and the target cell in the handover of the high-speed terminal
  • FIG. 2B is the reception quality of the source cell and the target cell in the handover of the low-speed to medium-speed terminal. It is a graph which shows the time change of.
  • FIG. 3 is a schematic configuration diagram showing an example of a wireless communication system to which the wireless communication control according to the present invention is applied.
  • FIG. 4 is a block diagram showing a schematic configuration of a base station in the wireless communication system according to the first embodiment of the present invention.
  • FIG. 5 is a flowchart showing the operation of the base station in the first embodiment.
  • FIG. 1 is a schematic cell configuration diagram for explaining handover.
  • FIG. 2A is a graph showing temporal changes in the reception quality of the source cell and the target cell in the handover of the high-speed terminal
  • FIG. 2B is the reception quality of the source
  • FIG. 6 is a schematic diagram showing an example of the HO history analysis in the first embodiment.
  • FIG. 7 is a block diagram showing a schematic configuration of a base station in the wireless communication system according to the second embodiment of the present invention.
  • FIG. 8 is a flowchart showing a first example of the operation of the base station in the second embodiment.
  • FIG. 9 is a flowchart showing a second example of the operation of the base station in the second embodiment.
  • FIG. 10 is a block diagram showing a schematic configuration of a base station in the wireless communication system according to the third embodiment of the present invention.
  • FIG. 11 is a flowchart showing the operation of the base station in the third embodiment.
  • FIG. 11 is a flowchart showing the operation of the base station in the third embodiment.
  • FIG. 12 is a block diagram showing a schematic configuration of a base station and a network management system in a wireless communication system according to the fourth embodiment of the present invention.
  • 13A is a sequence diagram showing TooToLate HO
  • FIG. 13B is a sequence diagram showing Too Early HO
  • FIG. 13C is a sequence diagram showing HO to Wrong Cell.
  • FIG. 14 is a flowchart showing the operation of the base station in the fourth embodiment.
  • FIG. 15 is a flowchart showing a first example of HO failure detection in the fourth embodiment.
  • FIG. 16 is a flowchart showing a case of Incoming HO failure in the second example of HO failure detection in the fourth embodiment.
  • FIG. 17 is a flowchart showing a case of Outgoing HO failure in the second example of HO failure detection in the fourth embodiment.
  • FIG. 18 is a flowchart showing a case of Incoming HO failure in the third example of HO failure detection in the fourth embodiment.
  • FIG. 19 is a flowchart showing a case of Outgoing HO failure in the third example of HO failure detection in the fourth embodiment.
  • FIG. 20 is a flowchart showing the HO optimization operation in the fourth embodiment.
  • a mobile terminal that should suppress handover is selected based on the most recent handover frequency between cells experienced by the mobile terminal, and handover is suppressed for the selected mobile terminal.
  • unnecessary handover between cells is effectively suppressed.
  • base stations (eNBs) 30A and 30B manage a cell 35A and a cell 35B, respectively, there is a cell 35B in the cell 35A, and the cell 35B serves as a mobile terminal (UE) 10 (FIG. 3).
  • UE mobile terminal
  • FIG. 3 base stations (eNBs) 30A and 30B manage a cell 35A and a cell 35B, respectively, there is a cell 35B in the cell 35A, and the cell 35B serves as a mobile terminal (UE) 10 (FIG. 3).
  • UE mobile terminal
  • the present invention is not limited to the system configuration shown in FIG. 3 and can be applied to inter-cell handover in an arbitrary cell arrangement.
  • the target cell of IncomingInHO and the source cell of Outgoing HO are referred to as own cells as appropriate.
  • the radio communication control apparatus of the base station that manages the own cell It is determined whether or not handover (Incoming HO) of the mobile terminal should be suppressed based on the handover history of the mobile terminal, and if it is a suppression target, a response rejecting the handover of the mobile terminal is returned to the handover request source base station . Thereby, unnecessary handovers such as repeated handovers can be suppressed.
  • FIG. 4 is a block diagram showing a schematic configuration of a base station in the wireless communication system according to the present embodiment.
  • a cell 35A is a source cell and a cell 35B is a target cell.
  • the base station 30B that manages the target cell 35B responds with a handover permission / rejection. return it.
  • FIG. 4 shows only the portions related to the description of the present embodiment.
  • the base station 30A includes a handover control unit 101A that performs handover control
  • the base station 30B includes a handover control unit 101B.
  • the radio communication control apparatus of the base station 30B that manages the cell 35B includes a handover history analysis unit 102, a mobile terminal selection unit 103, and a handover suppression unit 104 as functions related to the operation of this embodiment.
  • FIG. 5 is a flowchart showing the operation of the base station in this embodiment.
  • the handover history analysis unit 102 acquires the handover history of the mobile terminal 10 (Operation S102).
  • the handover history can be received from the base station 30A.
  • the handover history analysis unit 102 analyzes the handover history and counts the frequency of ping-pong HO between the cell 35B and the cell 35A (operation S103).
  • the mobile terminal selection unit 103 selects a mobile terminal that should suppress the handover between the cell 35B and the cell 35A based on the analysis result (frequency of ping-pong HO) (operation S104).
  • the handover suppressing unit 104 determines whether or not the mobile terminal to be handed over is selected as a handover suppressing target (operation S105). If it is not a handover suppression target (operation S105; NO), the handover suppression unit 104 returns a handover permission response to the base station 101A of the cell 35A (operation S106). A rejection response is returned (operation S107).
  • UE History Information defined in 3GPP TS36.423 v9.5.0 (Non-Patent Document 3) (from the base station 30A on the source side at the time of a handover request) Can be used).
  • UE History Information records up to 16 cells where the mobile terminal stayed during communication, and the history is discarded when the mobile terminal transitions to the idle state. Therefore, the latest handover history is recorded in UE History Information.
  • a list in which cell IDs and stay periods are recorded for handovers executed within a predetermined period in the past may be used.
  • FIG. 6 is a schematic diagram showing an example of the HO history analysis in the present embodiment.
  • the handover history analysis unit 102 can count the number N of ping-pong HO between the cell 35B and the cell 35A by tracing the handover history to the end in the order from the newest record. Specifically, the handover history is traced to the end in order from the newest record, and the count N is incremented by one every time the following ping-pong HO count conditions 1 and 2 are satisfied.
  • MTS Minimum Time of Stay
  • Condition 2 The cell staying next to the own cell is the handover request source cell (cell 35A).
  • Mobile terminal selection unit 103 if the ping-pong HO number N exceeds a predetermined value N TH, to select a mobile terminal handover target as a mobile terminal that requires reduced handover between cells 35B and the cell 35A. If the mobile terminal to be handed over is a selected terminal, the handover suppressing unit 104 returns a response rejecting the handover in response to the handover request from the base station that manages the cell 35A. For other terminals, a response permitting handover is returned in response to the handover request.
  • the handover history analysis unit 102 may be configured to count the frequency of ping-pong HO generated between the cell 35B and the cell 35A per unit time in units of cell pairs.
  • the mobile terminal selection unit 103 performs all handover attempts between the cell 35B and the cell 35A when the frequency of ping-pong HO in units of cell pairs between the cell 35B and the cell 35A exceeds a predetermined value. You may select a mobile terminal as a mobile terminal which should suppress the hand-over between the cell 35B and the cell 35A.
  • a handover selected from another cell is performed in the same manner as in the first embodiment without suppressing a handover from another cell (that is, Incoming HO).
  • a terminal completes Incoming HO, if there is a measurement report from the mobile terminal, it excludes other cells connected immediately before from the target cell candidate for handover (ie, Outgoing HO) of the mobile terminal Determine the target cell. That is, unnecessary handovers such as repeated handovers can be suppressed by avoiding handovers to other cells that have frequently caused unnecessary handovers in the past, and the possibility of handover failures can be further reduced. .
  • FIG. 7 is a block diagram showing a schematic configuration of a base station in the wireless communication system according to the present embodiment.
  • the wireless communication system according to the present embodiment is the same as the system configuration according to the first embodiment, but is not connected to the cell 35B in that it does not suppress incoming HOs from other cells.
  • the difference is that measurement information is acquired from the mobile terminal 10 that is being used and used for controlling the handover suppressing unit 104. Therefore, the same functional blocks and operation steps as those in the first embodiment shown in FIGS. 4 and 5 are denoted by the same reference numerals, and the description will be simplified, and functions different from those in the first embodiment will be mainly described.
  • FIG. 8 is a flowchart showing a first example of the operation of the base station in the present embodiment.
  • the handover control unit 101B receives a handover request (incoming HO) regarding the mobile terminal 10 (operation S101; YES)
  • the normal handover process is completed.
  • the handover history analysis unit 102 analyzes the handover history of the mobile terminal (operations S102 and S103), and the mobile terminal selection unit 103 determines whether the cell is based on the analysis result of the handover history (frequency of ping-pong HO).
  • a mobile terminal that should suppress handover between 35B and the cell 35A is selected (operation S104). If a handover request related to the mobile terminal 10 is not received (operation S101; NO), operations S102 to S104 are not executed. When there is no handover request (operation S101; NO) or when the operation S104 is completed, the subsequent operation S201 is executed.
  • the handover suppressing unit 104 determines whether the mobile terminal is the mobile terminal selected in operation S104 (operation S202). If it is not the selected mobile terminal (operation S202; NO), the handover control unit 101B starts normal handover processing, determines the target cell of the mobile terminal (operation S203), and transmits a handover request to the target cell. (Operation S204), the process ends.
  • the handover suppressing unit 104 excludes the cell 35A from the handover candidate cell of the handover control unit 101B (operation S205), and the handover control unit 101B If handover candidate cells remain (operation S206; YES), the target cell of the mobile terminal is determined (operation S203), and a handover request is transmitted to the target cell (operation S204). If there is no handover candidate cell (operation S206; NO), the process ends.
  • FIG. 9 is a flowchart showing a second example of the operation of the base station in this embodiment. The difference from the first example described above is that the determination of operation S207 in FIG. 9 is made. That is, whether to perform the operation (S205) of excluding the previous connected cell from the handover candidate cell depends on the radio quality of the cell 35B.
  • operations S101 to S104 and operation S201 are the same as the flow of the first example shown in FIG.
  • the handover suppressing unit 104 determines whether or not the radio quality Q self of the cell 35B is smaller than a predetermined value Qmin (operation).
  • operation S207 RSRP or RSRQ can be used as the radio quality Q self of the cell 35B.
  • the handover control unit 101B starts normal handover processing, determines the target cell of the mobile terminal (operation S203), and transmits a handover request to the target cell. (Operation S204), the process ends. If the radio quality Q self of the cell 35B is equal to or greater than the predetermined value Q min (operation S207; NO), the handover suppressing unit 104 determines whether or not the mobile terminal is the mobile terminal selected in operation S104 (operation S202). . If it is not the selected mobile terminal (operation S202; NO), operations S203 and S204 are executed as described above.
  • the handover suppressing unit 104 excludes the cell 35A from the handover candidate cell of the handover control unit 101B (operation S205), and the handover control unit 101B If handover candidate cells remain (operation S206; YES), the target cell of the mobile terminal is determined (operation S203), and a handover request is transmitted to the target cell (operation S204). If there is no handover candidate cell (operation S206; NO), the process ends.
  • Third Embodiment According to the third embodiment of the present invention, only a mobile terminal selected in the same manner as in the above-described first embodiment is performed without performing suppression for handover (Incoming HO) from another cell. In addition, a handover parameter for suppressing unnecessary handover such as ping-pong HO with another cell is notified. As a result, it is possible to suppress handovers to other cells (Outgoing HO) that frequently caused unnecessary handovers in the past, and to suppress unnecessary measurement reports from mobile terminals.
  • a handover parameter for suppressing unnecessary handover such as ping-pong HO with another cell is notified.
  • FIG. 10 is a block diagram illustrating a schematic configuration of a base station in the wireless communication system according to the present embodiment.
  • the radio communication system according to the present embodiment is basically the same as the system configuration according to the first embodiment, except that no suppression is performed on incoming HOs from other cells. The difference is that the handover parameter is acquired from the base station that manages the cell. Therefore, the same functional blocks and operation steps as those in the first embodiment shown in FIGS. 4 and 5 are denoted by the same reference numerals, and the description will be simplified, and functions different from those in the first embodiment will be mainly described.
  • FIG. 11 is a flowchart showing the operation of the base station in this embodiment.
  • the handover control unit 101B receives a handover request (incoming HO) related to the mobile terminal 10 (operation S101; YES)
  • the handover control unit 101B starts a normal handover process, and further from the base station that manages the handover request source cell.
  • the handover parameter notified to the mobile terminal is acquired.
  • the handover history analysis unit 102 acquires and analyzes the handover history of the mobile terminal (operations S102 and S103), and the mobile terminal selection unit 103 performs the handover history analysis result (ping ⁇ Based on the frequency of pong HO), a mobile terminal that should suppress handover between the cell 35B and the cell 35A is selected (operation S104).
  • the handover suppressing unit 104 determines whether the mobile terminal is the mobile terminal selected in operation S104 (operation S301). ). If it is not the selected mobile terminal (operation S301; NO), the handover control unit 101B notifies the mobile terminal of the handover parameters common to the cell 35B (operation S302).
  • the handover suppressing unit 104 calculates a handover parameter for suppressing ping-pong HO, as will be described later (operation S303).
  • the mobile terminal is notified (operation S304). In this way, only the mobile terminal selected by the mobile terminal selection unit 103 is notified of a handover parameter that suppresses ping-pong HO with the cell 35A, so that an unnecessary measurement report from the mobile terminal can be obtained.
  • the battery consumption of the mobile terminal and the processing load on the base station and the mobile terminal can be suppressed.
  • Handover suppression unit 104 receives a handover request from the cell 35A, the mobile terminal the mobile terminal selected by the selection unit 103 (e.g., mobile terminals ping-pong HO number N between cell 35A exceeds a predetermined value N TH) Is notified of the CIO value that suppresses the ping-pong HO with the cell 35A (operations S303 and S304 in FIG. 11), and other mobile terminals are notified of the CIO value managed in units of cells (FIG. 11). Operation S302).
  • the CIO value that suppresses ping-pong HO is set to a value that satisfies the condition of the following equation (2) (a necessary condition for ensuring handover hysteresis).
  • a3offset s a3-offset of cell 35A
  • a3offset t a3-offset of cell 35B
  • CIO st CIO from cell 35A to cell 35B
  • CIO ts CIO from cell 35B to cell 35A
  • CIO ts Min (CIO ts , a3offset s + a3offset t ⁇ CIO st ⁇ ) (3)
  • ⁇ is a predetermined margin value for the hysteresis of handover.
  • the setting value of the handover parameter (a3-offset, CIO) of the cell 35A can be obtained from, for example, HandoverPreparationInformation a AS-Config a sourceMeasConfig IE defined in Non-Patent Document 1.
  • the IE is notified from the base station that manages the source cell when Incoming HO requests.
  • the handover suppressing unit 104 can also notify the mobile terminal after adjusting the CIO value of the cell 35B so as not to excessively increase the handover margin of the cell 35B.
  • the CIO value of the cell 35B is set to a value satisfying the condition of the following expression (4).
  • CIO ts CIO from cell 35B to cell 35A
  • CIO ts Max (CIO ts, PingPong , a3offset t -MaxHoMargin) (5)
  • CIO ts and PingPong are the CIO values determined in the first example.
  • the CIO value of the cell 35B can be adjusted so as not to become excessively small. Note that the reason why the Max value is employed in the equation (5) is because priority is given to prevention of handover failure over suppression of ping-pong HO.
  • a mobile terminal that suppresses handover is selected based on the frequency of the latest ping-pong HO between cells experienced by the mobile terminal, and the selected mobile terminal
  • unnecessary handover is further effectively adjusted by adjusting the degree of handover suppression according to handover quality such as handover failure rate. Can be suppressed.
  • FIG. 12 is a block diagram showing a schematic configuration of a base station and a network management system in the wireless communication system according to the present embodiment.
  • base stations (eNBs) 31A and 31B manage a cell 35A and a cell 35B, respectively, and there is a cell 35B in the cell 35A. Further, it is assumed that another cell 35C is arranged adjacent to the cells 35A and 35B, and the base station 31C manages the cell 35C.
  • a network management system 20 is provided to perform optimization control of inter-cell handover.
  • the present invention is not limited to the system configuration shown in FIG. 12, and can be applied to inter-cell handover in an arbitrary cell arrangement.
  • the mobile terminal 10 enters the cell 35B from the cell 35A, passes through the cell 35B, fails in handover to the cell 35A, enters the other cell 35C as it is, and enters the base station 31C.
  • the case of reconnecting will be described.
  • the cell 35B becomes the source cell and the cell 35B becomes the target cell.
  • the mobile terminal 10 leaves the cell 35B to the cell 35A / 35C (Outgoing) HO)
  • the cell 35B becomes the source cell and the cell 35A / 35C becomes the target cell.
  • the base station 31A includes a handover control unit 101A that performs handover control
  • the base station 31B includes a handover control unit 101B
  • the base station 31C includes a handover control unit 101C.
  • the base station 31B that manages the cell 35B includes a handover history analysis unit 102, a mobile terminal selection unit 103, a handover suppression unit 104, and a handover failure detection unit 105 as functions related to the operation of this embodiment.
  • the network management system 20 includes a handover optimization unit 201 and a quality statistics storage unit 202, and the handover optimization unit 201 is provided with a handover suppression optimization unit 203.
  • the quality statistics storage unit 202 acquires handover statistical information from each base station, and the handover optimization unit 201 sets a handover suppression threshold N TH for the base station.
  • the base station 31C When the mobile terminal 10 reconnects with the base station 31C in the cell 35C, the base station 31C notifies the base station 31B of handover failure information described later.
  • the handover failure detection unit 105 of the base station 31B acquires the handover failure information from the cell 35C, the handover failure detection unit 105 determines whether or not the handover has failed due to handover suppression, and obtains the handover statistical information including the number of handover failures from the network management system 20. Report to The handover suppression optimization unit 203 of the network management system 20 adjusts for each cell by sequentially increasing / decreasing the handover suppression threshold based on the handover statistical information reported from the base station.
  • Types of handover failure 3GPP TS36.300 v.9.7.0 has three types of handover failure with abnormal radio link failure (RLF), namely “Too Late Handover” and “Too Early”. “Handover” and “Handover to Wrong Cell” are defined as follows (22.4.2). In the present embodiment, these three types of handover failures are handled as handover failures (HO failures).
  • RLF radio link failure
  • ⁇ Too Late HO> Too Late Handover is when a mobile terminal (UE) that has experienced RLF at the source cell during the handover process tries to re-establish connection (including re-establishment of radio link) to the target cell (target). , Handover from the source cell to the target cell. Or it is RLF which arises in a source cell when the mobile terminal which experienced RLF in the source cell before the start of a handover tries to reestablish connection to a cell different from the source cell.
  • UE mobile terminal
  • RLF Radio Link
  • Too Early Handover is a handover from a source cell to a target cell when a mobile terminal that has experienced RLF in the target cell during execution of the handover process or immediately after completion of the handover attempts to reestablish connection to the source cell.
  • Handover to Wrong Cell is a mobile terminal that has experienced RLF in the source cell or target cell during the handover process or immediately after the handover is completed, and tries to reestablish connection to a cell (neighbor) different from both the source cell and the target cell. Is a handover from the source cell to the target cell.
  • Handover failure information for example, RLF Indication and Handover Report defined in 3GPP TS36.423 v.9.5.0 can be used (9.1.2.18 and 9.2.119).
  • the RLF Indication includes identification information of a mobile terminal that has caused an abnormal disconnection, identification information of a cell that was connected immediately before the abnormal disconnection, and identification information of a cell that has been reconnected after the abnormal disconnection.
  • the Handover Report includes the identification information of the source cell and the target cell and the type of handover failure.
  • the base station of the source cell can detect the handover failure type as described below by referring to the handover failure information (that is, RLF Indication and Handover Report).
  • the base station of the source cell receives the RLF-Indication message from the target cell (when handover is started) or a cell different from the source cell (when handover is not started). And the Too Late HO can be detected on the condition that the UE Context Release message has not been transmitted to another cell within a predetermined period ( Tstore_UE_cntxt ) prior to the reception of RLF-Indication.
  • ⁇ Too Early HO> As shown in FIG. 13B, when the base station of the target cell receives the RLF-Indication message from the base station of the source cell, the UE Context Release message is received within a predetermined period (T store_UE_cntxt ) prior to the reception of the RLF-Indication. If already transmitted to the base station of the source cell, a Handover Report message indicating Too Early HO is transmitted to the base station of the source cell. Therefore, the base station of the source cell can detect Too Early HO on condition that the Handover Report message is received and Handover Report Type IE indicates Too Early HO.
  • ⁇ HO to Wrong Cell> As shown in FIG. 13C, when the base station of the target cell receives the RLF-Indication message from the adjacent cell, the UE Context Release message is received from the source cell within a predetermined period (T store_UE_cntxt ) prior to the reception of the RLF-Indication. If it has already been transmitted to the base station, a Handover Report message indicating HO to Wrong Cell is transmitted to the base station of the source cell. Therefore, the base station of the source cell can detect the HO to Wrong Cell on condition that the Handover Report message is received and that the Handover Report Type IE indicates HO to Wrong Cell.
  • FIG. 14 is a flowchart showing the operation of the base station in this embodiment.
  • the handover suppression unit 104 of the base station 31B acquires a handover suppression threshold from the network management system 20 (operation S401).
  • the handover control unit 101B receives the handover request (operation S402; YES), as described above, the handover history analysis unit 102 and the mobile terminal selection unit 103 select the mobile terminal that suppresses the handover (operation S403). ), The handover suppressing unit 104 suppresses the handover of the selected mobile terminal (operation S404).
  • the operation of the handover suppressing unit 104 may employ any of the operations in the first to third embodiments described above. Subsequently, the handover suppressing unit 104 records the identification information of the mobile terminal that has suppressed the handover (Operation S405), and counts the number of times of handover suppression (Operation S406).
  • the handover failure detection unit 105 analyzes the handover failure as described later (operation S407), and the number of Incoming HO failures and Outgoing HO failures due to handover suppression.
  • the numbers are totaled (operations S408 and S409), and the handover statistical information is reported to the network management system 20 (operation S410).
  • the handover statistical information includes the number of handover suppressions counted in operation S406 and the number of Incoming HO failures and the number of Outgoing HO failures respectively counted in operations S408 and S409.
  • a specific example of handover failure detection will be described in detail.
  • Handover failure detection due to handover suppression (first example)
  • the first example of handover failure detection is applied when the handover suppressing unit 104 performs the operation according to the first embodiment.
  • mobile terminals that are handed over from other cells that meet the predetermined criteria reject the handover, so detection of Outgoing HO failure due to handover suppression is unnecessary, and Incoming Too Since Early HO and Incoming HO to Wrong Cell do not occur, only Incoming Too Late HO needs to be detected.
  • the handover failure detection unit 105 detects Incoming Too Late HO caused by handover suppression.
  • the fact that handover suppression is the cause of handover failure can be determined in consideration of the identity of the mobile terminal identification information and the elapsed time since handover suppression, as described below. Details will be described below.
  • the handover failure detection unit 105 of the base station 31B determines whether or not there is a mobile terminal that has attempted reconnection to the cell 35B (operation S501), and the mobile terminal that has attempted reconnection (hereinafter referred to as terminal UEa). .) (Operation S501; YES), the identification information of the terminal UEa is acquired (operation S502). Subsequently, the handover failure detection unit 105 determines whether or not the terminal UEa is a mobile terminal that should suppress handover (that is, a HO suppression target selected by the mobile terminal selection unit 103) (Operation S503).
  • UEa is a HO suppression target (operation S503; YES)
  • the identification information of the cell X to which the terminal UEa is connected immediately before is acquired (operation S504).
  • the handover failure detection unit 105 determines whether or not the handover request of the terminal UEa has been received from the cell X within a predetermined period (operation S505). If it has been received (operation S505; YES), IncomingoToo Late HO is detected (operation S506), and the process is terminated.
  • Handover failure detection due to handover suppression (second example)
  • the second example of the handover failure detection is applied when the handover suppressing unit 104 performs the operation according to the second or third embodiment.
  • Incoming HOs from other cells are not suppressed, and when a mobile terminal that is a HO suppression target performs Outgoing HO, it is not in the cell other than the cell connected immediately before.
  • To determine the handover destination the handover HO is not suppressed for incoming HOs from other cells, and only the mobile terminal targeted for HO suppression suppresses outgoing HO to the cell connected immediately before. Suppress ping-pong HO between cells by reporting parameters.
  • the handover suppression unit 104 When the handover suppression unit 104 performs the operation according to the second or third embodiment, the influence of the handover suppression extends to both Incoming HO and Outgoing HO. Therefore, the handover failure detection unit 105 detects both Incoming HO failure and Outgoing HO failure due to handover suppression.
  • the fact that handover suppression is the cause of handover failure can be determined in consideration of the identity of the mobile terminal identification information and the elapsed time since handover suppression, as described below. Details will be described below.
  • FIG. 16 is a flowchart showing a case of Incoming HO failure in the second example of HO failure detection in the present embodiment.
  • the handover failure detection unit 105 determines whether or not an RLF Indication message has been received (Operation S601). If the RLF Indication message is received (operation S601; YES), the identification information of the terminal that has caused the abnormal disconnection (hereinafter referred to as terminal UEa) is acquired (operation S602). Subsequently, the handover failure detection unit 105 determines whether or not the terminal UEa is a mobile terminal that should suppress handover (that is, a HO suppression target selected by the mobile terminal selection unit 103) (Operation S603).
  • the handover failure detection unit 105 determines whether or not the handover completion message of the terminal UEa has been transmitted to the cell X within a predetermined period (operation S605), and if it has transmitted (operation S605; YES), Incoming HO failure is detected (operation S606), and the process is terminated.
  • the handover failure detection unit 105 of the base station 31B determines whether there is a mobile terminal that has attempted reconnection to the cell 35B (operation S607), and reconnection is performed. If there is a mobile terminal that has tried (hereinafter referred to as terminal UEb) (operation S607; YES), identification information of the terminal UEb is acquired (operation S608). Subsequently, the handover failure detection unit 105 determines whether or not the terminal UEb is a mobile terminal that should suppress handover (that is, a HO suppression target selected by the mobile terminal selection unit 103) (Operation S609).
  • the handover failure detection unit 105 determines whether or not the HO Report message of the terminal UEb has been received from the cell Y (Operation S611). If the HO Report message has not been received from the cell Y (Operation S611; NO) Further, it is determined whether or not the handover request of the terminal UEb has been received from the cell Y within a predetermined period in the past from the reconnection attempt (operation S612).
  • the handover failure detection unit 105 detects Incoming HO failure (Operation S606) and ends the process.
  • operation S607; NO when there is no terminal UEb that has attempted reconnection (operation S607; NO), when the terminal UEb is not a HO suppression target (operation S609; NO), when a HO-Report message of the terminal UEb is received from the cell Y (operation) (S611; YES), or if the handover request of the terminal UEb has not been received from the cell Y within a predetermined period (operation S612; NO), the process is terminated as it is.
  • FIG. 17 is a flowchart showing a case of Outgoing HO failure in the second example of HO failure detection in the present embodiment.
  • operations S601 to S604 are the same as the flow of FIG.
  • the handover failure detection unit 105 acquires the identification information of the cell X to which the terminal UEa has just connected (operation S604), it determines whether or not the handover completion message of the terminal UEa has been transmitted to the cell X within a predetermined period. If it is determined (operation S620) and not transmitted (operation S620; NO), Outgoing HO failure is detected (operation S621), and the process is terminated.
  • the handover failure detection unit 105 determines whether or not a HO Report message has been received (operation S622).
  • operation S622 When the HO Report message indicating the handover failure is received (operation S622; YES), identification information of the handover destination cell (cell Z) of the failed handover is acquired (operation S623), and the mobile terminal subject to HO suppression within a predetermined period. Is handed over to cell Z (operation S624). If handed over to cell Z (operation 624; YES), Outgoing HO failure is detected (operation S621), and the process ends. If the HO Report message is not received (operation S622; NO), or if the HO suppression target terminal has not handed over to the cell Z within a predetermined period (operation S624; NO), the processing is terminated as it is.
  • Handover failure detection due to handover suppression (third example)
  • the third example of handover failure detection is applied when the handover suppressing unit 104 performs the operation according to the second or third embodiment, and the handover failure detecting unit 105 determines the type of incoming HO failure caused by handover suppression and the outgoing HO. Detect the failure type.
  • FIG. 18 is a flowchart showing a case of Incoming HO failure in the third example of HO failure detection in this embodiment.
  • the operations S601 to S605 are the same as those described in the second example (FIG. 16) described above, and thus the description thereof is omitted.
  • the handover failure detection unit 105 sets the source cell of the RLF Indication message and the transmission destination of the handover completion message. It is determined whether or not the cell X is the same (operation S640).
  • operation S640 If the source cell of the RLF Indication message and the destination cell X of the handover complete message are the same (operation S640; YES), the incoming Too Early HO is detected (operation) as shown in FIG. If they are different (operation S640; NO), the incoming HO to Wrong Cell is detected (operation S642) as shown in FIG. 13C.
  • operation S601; NO If no RLF Indication message is received (operation S601; NO), operations S607 to S612 are executed as described in the second example (FIG. 16), and a handover request from the terminal UEb is sent from the cell Y within a predetermined period. If received (operation S612; YES), as shown in FIG. 13A, the handover failure detection unit 105 detects Incoming ⁇ ⁇ Too Late HO (operation S643), and ends the process.
  • FIG. 19 is a flowchart showing a case of Outgoing HO failure in the third example of HO failure detection in the present embodiment.
  • operations S601 to S604, S620, and S622 to S624 are the same as the flow of FIG.
  • the handover failure detection unit 105 does not transmit a handover completion message of the terminal UEa to the cell X within a predetermined period (operation S620; NO)
  • the handover failure detection unit 105 detects Outgoing Too Late HO (operation S630) and ends the process. .
  • the handover failure detection unit 105 executes operations S622 to S624 as described above, and the mobile terminal subject to HO suppression has handed over to the cell Z within a predetermined period. If there is (Operation 624; YES), Outgoing Too Early HO or Outgoing HO to Wrong Cell is detected depending on whether the type of handover failure is Too Early (Operation S631) (Operations S632, S633). If the HO Report message is not received (operation S622; NO), or if the mobile terminal subject to HO suppression has not been handed over to the cell Z within a predetermined period (operation S624; NO), the processing ends.
  • FIG. 20 is a flowchart showing the HO optimization operation in this embodiment.
  • the network management system 20 acquires handover statistical information from the base station and stores it in the quality statistical storage unit 202 (operation S701).
  • the handover statistical information includes the number of handover suppressions counted at each base station and both the number of incoming HO failures or the number of incoming HO failures and the number of outgoing HO failures.
  • the handover suppression optimization unit 203 calculates a handover failure rate Rf caused by handover suppression based on the acquired handover statistical information (operation S702).
  • the handover failure rate Rf can be defined as follows according to the embodiment described above.
  • Rf (Incoming Too Late HO number due to suppression) / (HO suppression number)
  • Rf (Number of Outgoing HO failures due to suppression + Number of Incoming HO failures due to suppression) / (Number of HO suppression)
  • Rf (Outgoing Too Late HO number due to suppression + Incoming Too Early HO number due to suppression + Incoming HO to Wrong Cell number due to suppression) / (HO suppression number)
  • the handover suppression optimizing unit 203 reads the handover statistical information stored in the quality statistics storage unit 202 and performs the handover compared to before changing the handover suppression threshold (N TH or N TH and Q min ). It is determined whether or not the failure rate has increased (operation S703). If the handover failure rate has increased from before the handover suppression threshold is changed (operation S703; YES), the handover suppression threshold is changed in a direction to mitigate handover suppression (operation S704). Handover suppression is mitigated by increasing the handover suppression thresholds N TH and Q min , and is enhanced by reducing the thresholds N TH and Q min .
  • the handover suppression optimization unit 203 reduces the ping-pong handover rate compared to before changing the handover suppression threshold. It is determined whether or not (Operation S705). If the ping-pong handover rate has decreased (operation S705; YES), the handover suppression threshold is changed in a direction to strengthen handover suppression (operation S706). If the ping-pong handover rate has not decreased (operation S705; NO), the threshold value for handover suppression is not changed. In this way, the handover suppression threshold value determined in operation S704 or S706 is notified to the base station (operation S707).
  • the handover optimization unit 201 sequentially changes the handover suppression threshold and notifies the base station based on the handover failure rate before and after the change of the handover suppression threshold and the amount of change in the ping-pong handover rate. To do.
  • the threshold value for handover suppression can be adjusted for each cell based on the results of handover suppression. It is possible to suppress handover failure due to suppression.
  • the present invention can be used for inter-cell handover control in a mobile communication system.
  • Handover suppression optimization unit 10, 10a, 10b Mobile terminal 20 Network management system 30, 30A, 30B Base station (eNB) 101, 101A, 101B, 101C Handover control unit 102 Handover history analysis unit 103 Mobile terminal selection unit 104 Handover suppression unit 105 Handover failure detection unit 201 Handover optimization unit 202 Quality statistics storage unit 203 Handover suppression optimization unit

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

La présente invention a pour objet un procédé et un dispositif de commande de communications sans fil, dans un système de communications sans fil, qui sont capables de supprimer efficacement l'occurrence fréquente de transferts intercellulaires d'un terminal mobile ayant de nombreuses vitesses de déplacement. L'objectif est résolu par un système de communications sans fil comprenant : une unité d'analyse d'historique de transferts intercellulaires (102) qui, à partir de l'historique de transferts intercellulaires du terminal mobile, trouve la fréquence des transferts intercellulaires entre une première cellule (35B) et une seconde cellule (35A) subits par un terminal mobile (10) ; une unité de sélection de terminal mobile (103) qui sélectionne des terminaux mobiles pour lesquels un transfert intercellulaire entre la première cellule et la seconde cellule devrait être supprimé, sur la base de la fréquence des transferts intercellulaires ; et une unité de suppression de transfert intercellulaire (104) qui supprime un transfert intercellulaire entre les première et seconde cellules pour le terminal mobile sélectionné pour la suppression du transfert intercellulaire.
PCT/JP2013/004669 2012-08-06 2013-08-01 Procédé et dispositif de commande de communications sans fil dans un système de communications sans fil WO2014024439A1 (fr)

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RU2681198C2 (ru) * 2016-11-21 2019-03-05 Бейдзин Сяоми Мобайл Софтвэр Ко., Лтд. Способ и устройство для перевыбора соты
WO2021226985A1 (fr) * 2020-05-15 2021-11-18 Qualcomm Incorporated Interdiction de transfert intercellulaire vers une cellule permettant d'éviter le ping-pong entre des cellules d'évolution à long terme en mode non autonome

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WO2017170011A1 (fr) * 2016-03-30 2017-10-05 日本電気株式会社 Terminal sans fil, station sans fil et procédé de commande d'un terminal sans fil
RU2681198C2 (ru) * 2016-11-21 2019-03-05 Бейдзин Сяоми Мобайл Софтвэр Ко., Лтд. Способ и устройство для перевыбора соты
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WO2021226985A1 (fr) * 2020-05-15 2021-11-18 Qualcomm Incorporated Interdiction de transfert intercellulaire vers une cellule permettant d'éviter le ping-pong entre des cellules d'évolution à long terme en mode non autonome

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