JP2014007593A - Parameter adjustment device and parameter adjustment program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a parameter adjustment device and a parameter adjustment program which can prevent degradation in handover performance even after having adjusted parameters of determination conditions used by a terminal to determine whether to transmit a measurement report (MR) to a base station in order to enhance performance other than the handover performance.SOLUTION: A parameter adjustment device comprises a parameter calculation unit 140 which calculates parameter values, which are used by a terminal to determine whether to transmit a measurement report (MR) to a base station 100-1, in order to have a hysteresis value of handover between base stations equal to or more than a predetermined value on the basis of an index of handover between base stations.

Description

  The present invention relates to a parameter adjustment device and a parameter adjustment program in wireless communication.

  In wireless communication such as LTE (Long Term Evolution), an active handover (Active HO) process for switching a base station to which a terminal is connected is a measurement report (Measurement Report: MR) transmitted from the terminal to the base station. Based on this, it is controlled by the base station. Here, the base station designates a determination condition for the terminal to determine whether or not to transmit MR to the base station (hereinafter referred to as “MR transmission condition”) to the terminal. The base station can control the active handover process by adjusting parameters for determining MR transmission conditions (see Non-Patent Documents 1 to 4).

3GPP, TS 36.331, v9.3.0, 2010-06 3GPP, TS 36.304, v9.2.0, 2010-03 3GPP, TS 23.203, v9.9.0, 2011-06 3GPP, TS 36.300, v10.6.0, 2011-12

  However, the parameters for determining the MR transmission conditions include not only handover performance indicators (for example, ping-pong handover occurrence rate and handover failure rate), but also a plurality of parameters other than handover performance (for example, radio resource usage rate). It is a parameter closely related to the indicator. For this reason, when the parameters for determining the MR transmission conditions are adjusted for the purpose of improving other than the handover performance, there is a problem in that the handover performance may be reduced along with this adjustment.

  The present invention has been made in view of the above points, and can prevent handover performance from being degraded even when parameters for determining MR transmission conditions are adjusted for the purpose of improving other than handover performance. It is an object to provide a parameter adjustment device and a parameter adjustment program.

  The present invention has been made in order to solve the above-described problem. A parameter value for a terminal to determine whether or not to transmit a measurement report to a base station is determined based on a handover index between base stations. A parameter adjusting device comprising: a parameter calculating unit that calculates a handover hysteresis value between base stations to be a predetermined value or more.

  The present invention further includes a failure calculation unit that calculates a ping-pong handover occurrence rate or a handover failure rate as the handover index, and the parameter calculation unit includes the ping-pong handover occurrence rate or the handover failure. When the rate is equal to or higher than a threshold, the parameter adjustment device is characterized in that the parameter value is calculated so that the occurrence rate of the ping-pong handover or the failure rate of the handover is less than the threshold.

  Further, according to the present invention, the parameter calculation unit determines at least one of a timing of handover from the own base station to another base station and a timing of handover from the other base station to the own base station as the parameter. The parameter adjustment device is characterized by performing adjustment by calculating a value.

  Further, the present invention is the parameter adjustment device characterized in that the parameter calculation unit calculates the parameter value when receiving an instruction to calculate the parameter value.

  Further, the present invention is the parameter adjustment device, wherein the parameter calculation unit receives the instructions in an order determined by the handover index.

  The present invention also includes a margin calculation unit that calculates a margin value for handover between base stations based on a difference between reception power or reception quality by the own base station and reception power or reception quality by another base station. The parameter calculator is configured to calculate the parameter value so that the hysteresis value determined by the margin value is equal to or greater than the predetermined value.

  Further, the present invention provides a parameter value for a terminal to determine whether or not to transmit a measurement report to a base station to a computer based on a handover index between base stations and a hysteresis of handover between the base stations. It is a parameter adjustment program for executing a procedure for calculating a value to be equal to or greater than a predetermined value.

  According to the present invention, the parameter calculation unit determines the parameter value for the terminal to determine whether or not to transmit the measurement report to the base station, based on the handover index between the base stations. Calculation is performed so that the hysteresis value is equal to or greater than a predetermined value. As a result, the parameter adjustment device can prevent the handover performance from being deteriorated even when the parameter for determining the MR transmission condition is adjusted for the purpose of improving other than the handover performance.

It is a block diagram which shows the structural example of the base station group and the high-order apparatus in one Embodiment of this invention. It is a flowchart which shows the example of the operation | movement procedure of the radio | wireless communications system in one Embodiment of this invention. It is a flowchart which shows the operation | movement procedure of the adjustment method 3 of HO margin value in one Embodiment of this invention. 4 is a table showing a method for expanding or reducing an area of a base station for each HO MR in an embodiment of the present invention. It is a flowchart which shows the example of the operation | movement procedure in which parameter calculation part expands or reduces the area of a base station in one Embodiment of this invention.

An embodiment of the present invention will be described in detail with reference to the drawings.
First, parameters for determining MR transmission conditions will be described. Hereinafter, the parameter for determining the MR transmission condition is referred to as “HO parameter”.

  When receiving the MR, the base station determines based on the received MR whether or not to execute the active handover process for the terminal that has transmitted the MR. Here, the MR includes received power (Reference Signal Received Power: RSRP) and reception quality (RSRP) at a terminal that has received a reference signal transmitted from a currently connected base station (hereinafter referred to as “currently connected base station”). At least one of Reference Signal Received Quality (RSRQ) is included. Furthermore, MR includes at least one of reception power (RSRP) and reception quality (RSRQ) at a terminal that has received a reference signal transmitted from an adjacent base station (hereinafter referred to as “adjacent base station”). include.

  A plurality of types of MR are determined according to transmission conditions (transmission triggers). “A3MR”, “A4MR”, and “A5MR” are defined as MRs for active handover processing (hereinafter referred to as “MR for HO”).

  A3MR is MR that is notified when the difference between the evaluation value of the received power (reception quality) related to the adjacent base station and the evaluation value of the received power (reception quality) related to the currently connected base station exceeds a threshold value. An equation for evaluating the received power (reception quality) for determining whether or not the terminal k connected to the currently connected base station i notifies the A3MR regarding the adjacent base station j is expressed by equation (1). If Equation (1) is satisfied for a certain period of time, the terminal transmits A3MR.

  M (j, k) −M (i, k)> HOM (i, j) (1)

  Here, M (j, k) represents an evaluation value of received power (reception quality) regarding the adjacent base station j at the terminal k. M (i, k) represents an evaluation value of received power (reception quality) regarding the currently connected base station i at the terminal k. HOM (i, j) is a power offset parameter (hereinafter referred to as “HO margin value”) for each base station pair (currently connected base station i and adjacent base station j). A predetermined first power threshold value for the base station j is shown.

A4MR is MR notified when the evaluation value of the received power (reception quality) regarding the adjacent base station exceeds the threshold Th _A4 . An equation for evaluating the received power (reception quality) for determining whether or not the terminal k connected to the currently connected base station i notifies the A4MR related to the adjacent base station j is expressed by equation (2). If Equation (2) is satisfied for a certain period of time, the terminal transmits A4MR.

M (j, k)> Th _A4 (i, j) (2)

Here, M (j, k) represents an evaluation value of received power (reception quality) related to the adjacent base station j at the terminal k. Further, Th _A4 (i, j) represents a second power threshold that is predetermined for the currently connected base station i and the adjacent base station j.

The A5MR is notified when the evaluation value of the received power (reception quality) regarding the currently connected base station is less than the threshold Th _{A5_1 and} the evaluation value of the reception power (reception quality) regarding the adjacent base station exceeds the threshold Th _{A5_2.} MR. The expression for evaluating the received power (reception quality) for the terminal k connected to the currently connected base station i to notify the A5MR related to the adjacent base station j is expressed by Expression (3) and Expression (4). When Equation (3) and Equation (4) are satisfied for a certain time, the terminal transmits A5MR.

M (i, k) <Th _{A5_1} (i, j) (3)
M (j, k)> Th _{A5_2} (i, j) (4)

Here, M (i, k) represents an evaluation value of received power (reception quality) regarding the currently connected base station i at the terminal k. M (j, k) represents an evaluation value of received power (reception quality) related to the adjacent base station j at the terminal k. Further, Th _{A5_1} (i, j) represents a third power threshold value that is predetermined for the currently connected base station i and the adjacent base station j. Further, Th _{A5_2} (i, j) represents a fourth power threshold that is predetermined for the currently connected base station i and the adjacent base station j.

  Next, a value (hereinafter referred to as “HO hysteresis value”) obtained by evaluating a shift (hysteresis) of a handover (HO) boundary between base stations based on received power (reception quality) will be described.

The HO hysteresis value (HO _hys (s, n)) between the base station s (any one of s = 1 to S) and the base station n (any one excluding s of n = 1 to S) is expressed by the formula ( 5).

HO _hys (s, n) = HOM (s, n) + HOM (n, s) (5)

Occurrence of ping-pong handover (Ping-Pong HO) is suppressed as the HO hysteresis value (= HO _hys (s, n)) between the base station s and the base station n increases.

When A3MR, A4MR, or A5MR is notified, the base station s executes active handover processing. The notification condition of A3MR is changed by adjusting the HO margin value. Also, the A4MR notification condition is changed by adjusting the HO margin value with the base station n by adjusting the power threshold Th _A4 . Also, the notification condition of A5MR is changed by adjusting the HO margin value with the base station n by adjusting at least one of the power threshold Th _{A5_1} and the power threshold Th _{A5_2} .

Next, handover (HO) failure detection will be described.
The base station 100-1 can detect and count events generated due to handover, that is, success or failure of handover, for each factor (see Non-Patent Document 4).

l Cause 1: Successful handover Notification information indicating that the terminal has successfully connected to the handover destination base station.

l Factor 2: Too Late HO
A radio link failure (Radio Link Failure: RLF) occurs in the terminal until the terminal has successfully connected to the adjacent base station (handover destination base station). After the radio link disconnection, the adjacent base station ( Notification information indicating that the terminal is connected to the handover destination base station).

l Factor 3: Too Early HO
After the terminal transmits the HO MR, that is, A3MR, A4MR or A5MR, to the currently connected base station and the handover process is started, a radio link disconnection occurs in the terminal, and after the radio link disconnection, the current connected base Notification information indicating that the terminal has reconnected to the station.

lFactor 4: HO to Wong Cell
After the terminal transmits the HO MR, that is, A3MR, A4MR, or A5MR, to the currently connected base station and the handover process is started, a radio link disconnection occurs in the terminal, and after the radio link disconnection, the current connection Notification information indicating that the terminal is connected to a base station that is neither a base station nor an adjacent base station (handover destination base station).

l Factor 5: Ping-Pong HO
After the handover process from the current connection base station to the adjacent base station (handover destination base station) is executed for the terminal, the current connection from the adjacent base station within a certain time (for example, 1 [second]). Notification information indicating that handover processing to the base station has been executed.

Next, a configuration example of the wireless communication system will be described.
FIG. 1 is a block diagram illustrating a configuration example of a base station group and a host device. Hereinafter, as an example, the wireless communication system will be described as performing wireless communication based on the LTE standard. The wireless communication system includes a base station 100-1 to a base station 100-S (S is an integer of 2 or more) and a higher-level device 200. A terminal (not shown) can be handed over from a currently connected base station (eg, base station 100-s) to an adjacent base station (eg, base station 100-n). Below, about the structure of base station 100-1-base station 100-S, only base station 100-1 is demonstrated as what has the same structure, respectively.

  The base station 100-1 includes a margin calculation unit 110, a failure calculation unit 120, a hysteresis calculation unit 130, a parameter calculation unit 140 (parameter adjustment device), and a setting unit 150. The host apparatus 200 includes a margin totaling unit 210, a failure totaling unit 220, a trigger unit 230, and a parameter totaling unit 240.

  The margin calculation unit 110 receives the HO MR based on the evaluation value of the received power (reception quality) regarding the own base station as the currently connected base station and the evaluation value of the reception power (reception quality) regarding the adjacent base station. Each time it is input from a terminal (not shown). The margin calculating unit 110 receives the HO margin every time it receives the HO MR based on the evaluation value of the received power (reception quality) related to its own base station and the evaluation value of the received power (reception quality) related to the adjacent base station. (HOM) value is calculated. Further, the margin calculation unit 110 outputs information indicating the HO margin value of the own base station to the hysteresis calculation unit 130 and the margin totaling unit 210.

  Specifically, the margin calculation unit 110, based on the received power information included in the HO MR, receives power (reception quality) by the own base station as the currently connected base station, and received power (reception by the adjacent base station). Difference (quality), that is, the HO margin value HOM is calculated (see, for example, equation (1)).

The margin calculating unit 110 includes the RSRP information RSRP _s of the own base station s included in the i-th HO MR “MR (s, n, i)” regarding the adjacent base station nεNeighbor (s) in the own base station _s. (s, n, i) and RSRP information RSRP _n (s, n, i) of adjacent base station n are tabulated for each base station pair (s, n) of own base station s and adjacent base station n To do. Here, Neighbor (s) is an index set of an adjacent base station adjacent to the own base station s.

  The margin calculation unit 110 calculates the HO margin value between the base station s and the adjacent base station n by, for example, any one of [HO margin value calculation method 1] to [HO margin value calculation method 3]. can do.

[HO Margin Value Calculation Method 1] (Average Value)
When the i-th MR is received, the margin calculation unit 110 calculates the average value using the iterative formula (6).

HOM (s, n, i) = {(RSRP n (s, n, i) -RSRP s (s, n, i)) + (i-1) × HOM (s, n, i-1)} / i (6)

Here, i = 1 to I. HOM (s, n, 0) is an initial value of the HO margin value and is an arbitrary constant.
The above is the calculation method 1 of the HO margin value.

[HO Margin Value Calculation Method 2] (Average value using the latest P RSRP histories)
The margin calculation unit 110 calculates the HO margin value when the i-th MR is received based on the P RSRP (RSRQ) histories received most recently, using Expression (7).

HOM (s, n, i) = 1 / P {Σ_ {j = i−P + 1} ^ {i} (RSRP _n (s, n, j) −RSRP _s (s, n, j))} (7 )

  The above is the calculation method 2 of the HO margin value.

[HO margin value calculation method 3] (weighted average)
When the i-th MR is received, the margin calculation unit 110 calculates the weighted average value using the iterative formula (8).

HOM (s, n, i) = (1-w) × (RSRP n (s, n, i) -RSRP s (s, n, i)) + w × HOM (s, n, i-1) ... ( 8)

Here, i = 1 to I. Further, w is a predetermined real number having a value of 0 or more and 1 or less.
The above is the calculation method 3 of the HO margin value.

  The margin calculation unit 110 is a hysteresis calculation unit that receives information indicating the HO margin value calculated by these calculation methods every time the HO MR is received, every certain time period, or every time the HO margin value is updated a certain number of times. 130 and margin totaling section 210.

  Notification information (successful handover) indicating a successful handover is input to the failure calculating unit 120 from a terminal (not shown) every time the handover is successful. In addition, notification information (“Too Late HO”, “Too Early HO”, “HO to Wong Cell”, “Ping-Pong HO”) indicating the cause of the handover failure is displayed in the failure calculation unit 120. Each time it is input, it is input from a terminal (not shown).

  The failure calculation unit 120 indicates an event (“handover success”, “Too Late HO”, “Too Early HO”, “HO to Wong Cell”, or “Ping-Pong HO”) caused by the handover. Based on the information, the number of occurrences for each event caused by the handover of the own base station is calculated for each base station pair of the own base station and an adjacent base station (handover destination base station).

  The failure calculation unit 120 includes the number of occurrences for each event caused by the handover of the own base station in information indicating a handover index (hereinafter referred to as “HO index information”), and the own base station and the adjacent base station. HO index information is output to the parameter calculation unit 140 and the failure counting unit 220 for each base station pair.

  Specifically, the failure calculation unit 120 calculates the evaluation value of the number of occurrences for each event by, for example, any one of the calculation methods 1 to 3 for the number of occurrences for each event. Calculate for each pair. Note that the calculation methods 1 to 3 for the number of occurrences for each event are examples of the method for calculating the number of occurrences for each event, and the method is not limited to these methods.

[Calculation method 1 for the number of occurrences for each event]
The failure calculation unit 120 aggregates the number of occurrences for each event in a certain period for each base station pair of the base station and the adjacent base station, and uses the result of the aggregation as an evaluation value.
The above is calculation method 1 of the number of occurrences for each event.

[Calculation method 2 for each event] (Forgetting factor)
The failure calculation unit 120 includes the i-th handover success evaluation value N _i (s, n, handover success) included in the HO index information and the i-th Too Late HO evaluation value N _i (s, n, included in the HO index information. n, Too Late HO), the i-th Too Early HO evaluation value N _i (s, n, Too Early HO) included in the HO index information, and the i-th HO to Wong Cell evaluation value included in the HO index information N _i (s, n, HO to Wong Cell) and i-th Ping-Pong HO evaluation value N _i (s, n, Ping-Pong HO) included in the HO index information Based on the evaluation value N _i−1 and the number of occurrences of the event X, it is calculated by the equation (9).

N _i (s, n, X) = w × N (s, n, X) + (1-w) × N _i−1 (s, n, X) (9)

Here, X is an event (factor), that is, “handover success”, “Too Late HO”, “Too Early HO”, “HO to Wong Cell”, or “Ping-Pong HO”. Further, w is a predetermined real number having a value of 0 or more and 1 or less. N (s, n, X) is the number of occurrences of event X related to handover from the currently connected base station s to the adjacent base station n.
The above is calculation method 2 of the number of occurrences for each event.

[Calculation method 3 for each event] (Slide average)
The failure calculation unit 120 stores the number of occurrences of each event in a certain period for each base station pair of the base station and the adjacent base station for the latest P times. The failure calculation unit 120 calculates the average value (slide average value) of the number of occurrences for each event in the latest P times.
The above is calculation method 3 of the number of occurrences for each event.

  Information indicating the HO margin value for each base station pair is input from the margin calculation unit 110 of each base station 100 to the margin totalization unit 210 of the host device 200. The margin totalization unit 210 totalizes the latest HO margin value for each base station pair. Hereinafter, the HO margin value for each base station pair of the adjacent base station is referred to as “adjacent base station HO margin value”.

  The margin totalization unit 210 of the higher-level device 200 outputs information indicating the adjacent base station HO margin value to the hysteresis calculation unit 130 of each base station 100. That is, the margin totalization unit 210 calculates the HO margin value (= HOM (n, s)) related to the handover from the adjacent base station nεNeighbor (s) to the base station s for all base stations (s = 1 to S). Notify Here, the margin totalization unit 210 notifies the base station s only of the HO margin value related to the handover from the adjacent base station n to the base station s. That is, the margin totalization unit 210 does not notify the base station s of the HO margin value not related to the base station s.

  HO index information for each base station pair is input from the failure calculation unit 120 of each base station 100 to the failure counting unit 220 of the host device 200. The failure counting unit 220 stores the latest HO index information for each base station pair (base station s and adjacent base station n) of the adjacent base station. Hereinafter, the HO index information for each base station pair of the adjacent base station is referred to as “adjacent base station HO index information”.

The failure counting unit 220 outputs the adjacent base station HO index information to the parameter calculation unit 140 and the trigger unit 230 of each base station 100. That is, the failure counting unit 220 uses the evaluation value N _M (n, s, X) of the number of occurrences of the event X related to the handover from the adjacent base station nεNeighbor (s) to the base station s for each base station 100. The parameters are output to the parameter calculation unit 140 and the trigger unit 230. Here, M is an index of an evaluation value included in the latest HO index information.

The trigger unit 230 of the higher-level device 200 includes adjacent base station HO index information, that is, a handover success evaluation value N _i (s, n, handover success), a Too Late HO evaluation value N _i (s, n, Too Late HO). , Too Early HO evaluation value _{n i (s, n, Too} Early HO), HO to Wrong Cell evaluation value _{n i (s, n, HO} to Wrong Cell), and, Ping-Pong HO evaluation value _{n i} (s, n, Ping-Pong HO) is input from the failure counting unit 220 for all base stations s = 1 to S.

  The trigger unit 230 outputs instruction information indicating whether the parameter is adjusted (whether the HO parameter value is calculated) to the parameter calculation unit 140 of each base station 100. Here, the trigger unit 230 indicates to the parameter calculation unit 140 of the base station selected based on the adjacent base station HO index information (for example, in descending order of the adjacent base station HO index) whether to adjust the parameter. Output information.

Information indicating the HO margin value of the own base station s is input from the margin calculation unit 110 to the hysteresis calculation unit 130. In addition, information indicating the adjacent base station HO margin value (a result of counting the HO margin values) is input from the margin totaling unit 210 to the hysteresis calculating unit 130. The hysteresis calculation unit 130 calculates the HO hysteresis value based on the information indicating the HO margin value of the own base station s and the information indicating the adjacent base station HO margin value, and calculates the parameter indicating the information indicating the HO hysteresis value. Output to the unit 140. Here, the hysteresis calculation unit 130 calculates the HO hysteresis value HO _hys (s, n) between the own base station s and the adjacent base station nεNeighbor (s) according to Expression (5).

The parameter calculation unit 140 (parameter adjustment device) includes HO index information for each base station pair of the own base station s and the neighboring base station n regarding the handover from the own base station s to the neighboring base station n. 120 is input. Further, the parameter calculation unit 140 receives, from the failure counting unit 220, the adjacent base station HO index information related to the handover from the adjacent base station n to the own base station s. Further, information indicating the HO hysteresis value (HO _hys (s, n)) between the own base station s and the adjacent base station n is input to the parameter calculation unit 140 from the hysteresis calculation unit 130. In addition, instruction information indicating whether to adjust the parameter is input to the parameter calculation unit 140 from the trigger unit 230 of the higher-level device 200.

  When the instruction information indicating whether or not to adjust the parameter indicates that the parameter is adjusted, the parameter calculation unit 140 indicates information indicating the HO margin value of the own base station and the adjacent base station, and information indicating the HO hysteresis value. HO parameter value based on the HO index information for each base station pair of the own base station s and the adjacent base station n regarding the handover from the own base station s to the adjacent base station n, and the adjacent base station HO index information Is calculated. Thereby, the parameter calculation unit 140 can prevent the handover performance from being deteriorated even when the HO parameter is adjusted for the purpose of improving other than the handover performance. The parameter calculation unit 140 outputs information indicating the HO parameter value to the setting unit 150 and the parameter totaling unit 240.

  Information indicating the HO parameter value for each base station pair is input from the parameter calculation unit 140 of each base station 100 to the parameter totaling unit 240 of the host device 200. The parameter totaling unit 240 totals information indicating the HO parameter value for each base station pair, and outputs the totaling result to the setting unit 150 of each base station 100.

  Information indicating the HO parameter value is input from the parameter calculation unit 140 to the setting unit 150. In addition, information indicating the HO parameter value for each base station pair (a result of counting the HO parameter values) is input from the parameter counting unit 240 to the setting unit 150. The setting unit 150 executes the active handover process based on at least one of information indicating the HO parameter value and information indicating the HO parameter value for each base station pair (a total result of the HO parameter value).

Next, an example of an operation procedure of the wireless communication system will be described.
In order to suppress ping-pong handover, the wireless communication system adjusts the HO parameter value according to the following operation procedure.

The trigger unit 230 includes HO index information (N _i (s, n, handover success), N _i (successful handover) for each adjacent base station n (for each base station pair) regarding handover from the base station s to the adjacent base station n. s, n, Too Late HO) , N i (s, n, Too Early HO), N i (s, n, HO to Wrong Cell), _{and, N i (s, n,} Ping-Pong HO)) is , Input for all base stations. The trigger unit 230 outputs instruction information indicating whether to adjust the parameter to the parameter calculation unit 140 of each base station 100.

Information (HO _hys (s, n)) indicating the HO hysteresis value between the own base station s and the adjacent base station n is input to the parameter calculation unit 140. Further, the parameter calculation unit 140 includes HO index information (N _i (s, n, successful handover)) for each adjacent base station n (for each base station pair) regarding handover from the own base station s to the adjacent base station n, N _{i (s, n, Too Late} HO), N i (s, n, Too Early HO), N i (s, n, HO to Wrong Cell), _{and, N i (s, n,} Ping-Pong HO) ) Is entered.

Also, the parameter calculation unit 140 includes adjacent base station HO index information (N _i (n, s, successful handover), _Ni (n, s, Too Late HO) regarding handover from the adjacent base station n to the own base station s. ), N _i (n, s, Too Early HO), N _i (n, s, HO to Wong Cell), and N _i (n, s, Ping-Pong HO)).

  FIG. 2 is a flowchart illustrating an example of an operation procedure of the wireless communication system. When the instruction information indicating whether or not to adjust the parameter indicates that the parameter is adjusted, the parameter calculation unit 140 executes the following operation procedure.

(Step S1) The trigger unit 230 sets the ping-pong handover evaluation value N _i included in the HO index information for each adjacent base station n (for each base station pair) regarding the handover from the own base station s to the adjacent base station n, All base stations s = 1 to S are sorted in descending order. The trigger unit 230, a step S2~ step S4 shown below, the base station pairs of the base station s and the adjacent base station n (s, n) for each execution in descending order of the ping-pong handover evaluation value N _i To do.

(Step S2) The trigger unit 230 determines whether or not the ping-pong / handover evaluation value N _i (s, n, Ping-Pong HO) is equal to or greater than a predetermined threshold value. If ping-pong handover evaluation value _{N i} is equal to or greater than a predetermined threshold value (step S2: Yes), the trigger unit 230 advances the process to step S3. On the other hand, when the ping-pong / handover evaluation value _Ni is not equal to or greater than a certain threshold (step S2: No), the trigger unit 230 advances the process to step S4.

In step S2, the trigger unit 230 determines whether or not the value obtained by dividing the ping-pong / handover evaluation value N _i by the handover success evaluation value N _i (s, n, handover success) is equal to or greater than a certain threshold value. May be.

(Step S3) The trigger unit 230 uses a flag (hereinafter referred to as “MR parameter adjustment flag”) for adjusting the HO MR parameter related to the MR transmission condition, and the ping-pong / handover evaluation value _Ni is equal to or greater than a certain threshold. The base station pair (s, n) of the base station s and the adjacent base station n is set off (the HO hysteresis value HO _hys is not equal to or greater than a predetermined value). And the trigger part 230 advances a process to step S5.

(Step S4) The trigger unit 230 sets the MR parameter adjustment flag between the base station s and the adjacent base station n with the ping-pong / handover evaluation value N _i not equal to or greater than a certain threshold (the HO hysteresis value HO _hys is equal to or greater than a predetermined value). Set to ON for base station pair (s, n). And the trigger part 230 advances a process to step S5.

(Step S5) The parameter calculation unit 140 sets the base station pair (s, n) where the ping-pong handover evaluation value _Ni is not equal to or greater than a certain threshold, that is, the base station pair (s, n) with the MR parameter adjustment flag set to ON. On the other hand, after assuring that the HO hysteresis value HO _hys is a predetermined value, the HO MR parameters related to the MR transmission conditions are adjusted for the purpose of improving other than the handover performance. The operation procedure of this adjustment will be described later with reference to FIG.

(Step S6) The trigger unit 230 sets the base station pair (s, n) in which the ping-pong handover evaluation value _Ni is not equal to or greater than a certain threshold, that is, the base station pair (s, n) in which the MR parameter adjustment flag is set to off. Are sorted in descending order of the Ping-Pong HO evaluation value N _i (s, n, Ping-Pong HO). Then, the trigger unit 230, the MR parameter adjustment flag base station pairs defined off (s, n) of each parameter calculation unit 140, in descending order of the Ping-Pong HO evaluation value _{N i,} to perform the step S7 .

(Step S7) The occurrence of ping-pong handover is suppressed as the HO hysteresis value HO _hys increases. The trigger unit 230 indicates to the parameter calculation unit 140 of the base station whose MR parameter adjustment flag is set to OFF to delay the handover timing according to the type of MR for HO designated by the base station to the terminal. Output instruction information.

Here, the trigger unit 230, the parameter calculating unit 140 of the base station s of MR parameter adjustment flag defined off is assigned, ping-pong handover evaluation value N _i is relatively large base station pair (s, In order from n), instruction information indicating that the handover timing is delayed is transmitted.

When the parameter calculation unit 140 receives instruction information indicating that the handover timing is delayed from the trigger unit 230, the parameter calculation unit 140 ensures that the HO hysteresis value HO _hys is equal to or greater than a predetermined value, and then determines the MR of the HO for the MR transmission condition. Adjust the parameters. The parameter calculation unit 140 can suppress the occurrence of ping-pong handover by delaying the handover timing based on this instruction information.

  Specifically, the parameter calculation unit 140 adjusts the HO MR parameter related to the MR transmission condition by adjusting the HO margin value by any one of the adjustment methods 1 to 4 of the HO margin value. Note that the HO margin value adjustment methods 1 to 4 are examples of the HO margin value adjustment method, and are not limited to these methods.

[HO margin adjustment method 1]
The parameter calculation unit 140 includes the Too Late HO evaluation value N _i (s, n, Too Late HO) included in the HO index information related to the handover from the own base station s to the neighboring base station n, and the neighboring base station n. The Too Late HO evaluation value N _i (n, s, Too Late HO) included in the HO index information related to the handover to the base station s is compared.

When the Too Late HO evaluation value N _i (s, n, Too Late HO) is equal to or greater than the Too Late HO evaluation value N _i (n, s, Too Late HO), the parameter calculation unit 140 determines whether the Too Late HO evaluation value N _i (s, n, Too Late HO) is greater than or equal to It is determined that the HO margin value HOM (n, s) related to the handover to the own base station s is adjusted.

On the other hand, when the Too Late HO evaluation value N _i (s, n, Too Late HO) is less than the Too Late HO evaluation value N _i (n, s, Too Late HO), the parameter calculation unit 140 It is determined that the HO margin value HOM (s, n) related to the handover from s to the adjacent base station n is adjusted.
The above is the adjustment method 1 of the HO margin value.

[HO margin adjustment method 2]
The parameter calculation unit 140 includes a Too Late HO evaluation value _Ni (s, n, Too Late HO) and a Too Early HO evaluation value N included in the HO index information related to the handover from the own base station s to the adjacent base station n. _i (s, n, Too Early HO) and the HO to Wron Cell evaluation value N _i (s, n, HO to Wron Cell) are added. Hereinafter, this addition result is referred to as “first addition result”.

In addition, the parameter calculation unit 140 includes the Too Late HO evaluation value _Ni (n, s, Too Late HO) and the Too Early HO evaluation included in the HO index information related to the handover from the adjacent base station n to the own base station s. The value N _i (n, s, Too Early HO) is added to the HO to Wron Cell evaluation value N _i (n, s, HO to Wron Cell). Hereinafter, this addition result is referred to as “second addition result”.

The parameter calculation unit 140 determines that the HO margin value HOM (n, s) related to the handover from the adjacent base station n to the own base station s is adjusted when the first addition result is greater than or equal to the second addition result. On the other hand, when the first addition result is not equal to or greater than the second addition result, the parameter calculation unit 140 determines that the HO margin value HOM (s, n) related to the handover from the own base station s to the adjacent base station n is adjusted.
The above is the adjustment method 2 of the HO margin value.

[HO margin adjustment method 3]
FIG. 3 is a flowchart showing an operation procedure of the HO margin value adjusting method 3.
(Step Sa1) The parameter calculation unit 140 adds the first addition to the handover success HO evaluation value N _i (s, n, handover success) included in the HO index information related to the handover from the own base station s to the adjacent base station n. Add the results. Hereinafter, this addition result is referred to as “third addition result”. The parameter calculation unit 140 divides the first addition result by the third addition result. Hereinafter, this division result is referred to as “handover failure rate related to handover from the own base station s to the adjacent base station n”.

In addition, the parameter calculation unit 140 adds the second addition result to the handover success HO evaluation value N _i (n, s, handover success) included in the HO index information related to the handover from the adjacent base station n to the own base station s. to add. Hereinafter, this addition result is referred to as a “fourth addition result”. The parameter calculation unit 140 divides the second addition result by the fourth addition result. Hereinafter, this division result is referred to as “handover failure rate related to handover from the adjacent base station n to the own base station s”.

  The parameter calculation unit 140 has both a handover failure rate relating to a handover from the own base station s to the adjacent base station n and a handover failure rate relating to a handover from the adjacent base station n to the own base station s being equal to or greater than a predetermined allowable threshold. It is determined whether or not. When the handover failure rates are both equal to or greater than the predetermined allowable threshold (step Sa1: Yes), the parameter calculation unit 140 proceeds with the process to step Sa2. On the other hand, when at least one of the handover failure rates is not equal to or greater than the predetermined allowable threshold (step Sa1: No), the parameter calculation unit 140 proceeds with the process to step Sa3.

  (Step Sa2) The parameter calculation unit 140 adjusts the HO MR parameter related to the MR transmission condition by adjusting the HO margin value in order to reduce the handover failure rate according to the cause of the handover failure. For example, the parameter calculation unit 140 performs parameter adjustment so as to reduce the handover failure rate according to the cause of the handover failure. Here, the parameter calculation unit 140 performs parameter adjustment by a method disclosed in Non-Patent Document 1, for example. Then, the parameter calculation unit 140 ends the process related to the HO margin value adjustment method 3.

(Step Sa3) The parameter calculation unit 140 determines that the Too Late HO evaluation value _Ni (s, n, Too Late HO) included in the HO index information related to the handover from the own base station s to the adjacent base station n It is determined whether or not the Too Late HO evaluation value N _i (n, s, Too Late HO) is greater than or equal to the HO index information related to the handover from the station n to the own base station s.

When the Too Late HO evaluation value N _i (s, n, Too Late HO) is greater than or equal to the Too Late HO evaluation value _Ni (n, s, Too Late HO) (step Sa3: Yes), the parameter calculation unit 140 is Then, the process proceeds to step Sa4. On the other hand, if the Too Late HO evaluation value N _i (s, n, Too Late HO) is not equal to or greater than the Too Late HO evaluation value N _i (n, s, Too Late HO) (step Sa3: No), the parameter calculation unit 140 Advances the process to step Sa5.

(Step Sa4) The parameter calculation unit 140 determines to increase the HO margin value HOM (n, s) in order to increase the HO hysteresis value HO _hys . Then, the parameter calculation unit 140 ends the process related to the HO margin value adjustment method 3.

(Step Sa5) The parameter calculation unit 140 determines that the HO margin value HOM (s, n) is increased in order to increase the HO hysteresis value HO _hys . Then, the parameter calculation unit 140 ends the process related to the HO margin value adjustment method 3.
The above is the adjustment method 3 of the HO margin value.

Returning to FIG. 2, the description of the operation in step S7 is continued.
[HO margin adjustment method 4]
The parameter calculation unit 140 includes the number of occurrences of radio link disconnection (RLF) (hereinafter referred to as “first radio link disconnection count”) included in the HO index information related to the HO handover from the own base station s to the adjacent base station n. The number of occurrences of radio link disconnection (RLF) (hereinafter referred to as “second radio link disconnection count”) included in the HO index information related to the HO handover from the adjacent base station n to the own base station s is compared.

The parameter calculation unit 140 relates to the HO handover from the adjacent base station n to the own base station s in order to increase the HO hysteresis value HO _hys when the first radio link disconnection count is equal to or greater than the second radio link disconnection count. It is determined that the HO margin value HOM (n, s) is adjusted. On the other hand, when the first radio link disconnection count is not equal to or greater than the second radio link disconnection count, the parameter calculation unit 140 increases the HO hysteresis value HO _hys to increase the HO handover value from the own base station s to the adjacent base station n. It is determined that the HO margin value HOM (s, n) relating to is adjusted.
The above is the adjustment method 4 of the HO margin value.

The parameter calculation unit 140 increases the HO margin value HOM (see Equation (5)) by a predetermined first value when the base station designates A3MR to the terminal as the MR transmission condition. As a result, the HO hysteresis value HO _hys increases.

In addition, when the base station designates A4MR to the terminal as the MR transmission condition, parameter calculation section 140 increases power threshold Th _A4 (see equation (2)) by a predetermined second value. As a result, the HO margin value, that is, the HO hysteresis value HO _hys increases.

Also, the parameter calculation unit 140 decreases the power threshold Th _{A5_1} (see Equation (3)) by a predetermined third value when the own base station specifies A5MR for the terminal as the MR transmission condition, or The power threshold Th _{A5 —} 2 (see formula (4)) is increased by a predetermined fourth value. As a result, the HO margin value, that is, the HO hysteresis value HO _hys increases. In addition, the minimum parameter setting granularity (refer nonpatent literature 1) may be sufficient as each adjustment range by these 1st value-4th value.

In step S3, the ping-pong handover is already suppressed for the base station pair (s, n) whose MR parameter adjustment flag is set to ON. For this reason, the parameter calculation unit 140 secures the current value of the HO hysteresis value HO _hys and adjusts the HO MR parameter related to the MR transmission condition, thereby suppressing the occurrence of ping-pong handover. Parameter adjustment can be performed for the purpose of improving other than handover performance.

  The parameter calculation unit 140 adjusts the HO margin value HOM within a range where Expression (10) is satisfied.

HO _hys (s, n) ≦ HOM (n, s) + HOM (s, n) (10)

  Here, the parameter calculation unit 140 increases the HOM (s, n) by a certain value when the own base station designates the terminal to notify the A3MR, and satisfies the equation (10), and the HOM (n, n Reduce s). In addition, the parameter calculation unit 140 may increase HOM (n, s) by a certain value and decrease HOM (s, n) within a range that satisfies Equation (10). The parameter calculation unit 140 may increase at least one of HOM (s, n) and HOM (n, s) by a certain value.

Further, the parameter calculation unit 140 increases the power threshold Th _A4 (s, n) by a certain value and sets the power threshold Th _A4 (n, s) when the own base station designates the terminal to notify A4MR. Decrease by a constant value (see equation (2)). In addition, the parameter calculation unit 140 may increase at least one of the power threshold Th _A4 (s, n) and the power threshold Th _A4 (n, s) by a certain value.

Also, the parameter calculation unit 140 decreases the threshold Th _{A5_1} by a certain value when the base station designates the terminal to notify _A5MR (see equation (3)). In addition, the parameter calculation unit 140 may increase the threshold Th _{A5_2} by a certain value (see formula (4)).
The above is an example of the operation procedure of the wireless communication system.

Next, a description will be given of a case where parameters for determining MR transmission conditions are adjusted for the purpose of improving other than the handover performance (see step S5 in FIG. 2).
For the purpose of improving other than handover performance, for example, for the purpose of smoothing the radio resource usage rate between base stations (load distribution), the trigger unit 230 is configured to calculate each parameter 140 of each base station pair (s, n). In addition, it is necessary to enlarge or reduce each area.

  FIG. 4 is a table showing, for each HO MR, a method for expanding or reducing the area of the base station. The trigger unit 230 compares the radio resource usage rate of the base station s with the radio resource usage rate of the base station n. The trigger unit 230 requests a base station with a relatively high radio resource usage rate to expand the area. On the other hand, the trigger unit 230 requests a base station with a relatively low radio resource usage rate to reduce the area. The parameter calculation unit 140 selects a method for expanding or reducing the area of the own base station according to the type of MR for HO designated by the own base station to the terminal.

The parameter calculation unit 140 increases the HO margin value (HOM) when the MR for HO designated by the base station as the terminal is A3MR and it is requested to expand the area. As a result, the HO hysteresis value HO _hys increases. On the other hand, when the MR for HO designated by the base station as the terminal is A3MR and the parameter calculation unit 140 is requested to reduce the area, the parameter calculation unit 140 decreases the HO margin value. As a result, the HO hysteresis value HO _hys decreases. Here, when the expression (10) is not satisfied due to the decrease in the HO margin value, the parameter calculation unit 140 may decrease the HO margin value within a range that satisfies the expression (10). The parameter calculation unit 140 may cancel the process (procedure) for reducing the HO margin value.

Also, the parameter calculation unit 140 increases the power threshold Th _A4 by a certain value when the HO MR designated by the base station as a terminal is A4MR and when it is requested to expand the area. As a result, the HO margin value, that is, the HO hysteresis value HO _hys increases. On the other hand, when the HO MR designated by the base station as the terminal is A4MR and it is requested to reduce the area, the power threshold Th _A4 is decreased by a certain value. As a result, the HO margin value, that is, the HO hysteresis value HO _hys decreases.

Also, the parameter calculation unit 140, when the HO MR specified by the base station as the terminal is A5MR and when it is requested to expand the area, the parameter Th ₁₄₀ decreases the threshold Th _{A5_1} , and the threshold Th _At least one of the processes of increasing _{A5_2} by a certain value is executed. As a result, the HO margin value, that is, the HO hysteresis value HO _hys increases. On the other hand, the parameter calculation unit 140 increases the threshold Th _{A5_1} by a certain value when the HO MR specified by the base station is A5MR and the area is requested to be reduced, and the threshold Th _At least one of the processes of decreasing _{A5_2} by a certain value is executed. As a result, the HO margin value, that is, the HO hysteresis value HO _hys decreases.

FIG. 5 is a flowchart illustrating an example of an operation procedure in which the parameter calculation unit enlarges or reduces the area of the base station.
(Step Sb1) The parameter calculation unit 140 determines to adjust the HO margin value HOM (s, n) related to the HO handover from the own base station s to the adjacent base station n (HO margin value adjustment methods 1 to 4 are performed). (See), it is determined whether the trigger unit 230 has requested the maintenance, expansion, or reduction of the area of the base station s.

  When the maintenance is requested (step Sb1: maintenance), the parameter calculation unit 140 proceeds with the process to step Sb4. When enlargement is requested (step Sb1: enlargement), the parameter calculation unit 140 proceeds to step Sb2. If reduction is requested (step Sb1: reduction), the parameter calculation unit 140 proceeds to step Sb3.

(Step Sb2) The parameter calculation unit 140 increases the HO margin value HOM (s, n) related to the HO handover from the own base station s to the adjacent base station n, and advances the process to step Sb4.
(Step Sb3) The parameter calculation unit 140 decreases the HO margin value HOM (s, n) related to the HO handover from the own base station s to the adjacent base station n, and proceeds to step Sb4.

  (Step Sb4) The parameter calculation unit 140 determines to adjust the HO margin value HOM (n, s) related to the HO handover from the adjacent base station n to the own base station s (HO margin value adjustment methods 1 to 4 are performed). (See), it is determined whether the trigger unit 230 has requested the maintenance, expansion, or reduction of the area of the base station s.

  When the maintenance is requested (step Sb4: maintenance), the parameter calculation unit 140 ends the process of adjusting the HO margin value. When enlargement is requested (step Sb4: enlargement), the parameter calculation unit 140 proceeds to step Sb5. If reduction is requested (step Sb4: reduction), the parameter calculation unit 140 proceeds to step Sb6.

(Step Sb5) The parameter calculation unit 140 increases the HO margin value HOM (n, s) related to the HO handover from the adjacent base station n to the own base station s, and ends the process of adjusting the HO margin value.
(Step Sb6) The parameter calculation unit 140 decreases the HO margin value HOM (n, s) related to the HO handover from the adjacent base station n to the own base station s, and ends the process of adjusting the HO margin value.

As described above, the parameter adjustment apparatus determines the parameter value (HO parameter value) for the terminal (not shown) to determine whether or not to transmit the measurement report (HO MR) to the base station 100-1. A hysteresis value (HO hysteresis value) of handover between base stations (for example, base station 100-s and base station 100-n) based on an index of handover between stations (for example, ping-pong handover occurrence rate, handover failure rate) ) Includes a parameter calculation unit 140 that calculates the value to be equal to or greater than a predetermined value.
With this configuration, the parameter calculation unit 140 determines a parameter value for the terminal to determine whether or not to transmit a measurement report to the base station, based on a handover index between the base stations. Calculation is performed so that the hysteresis value is equal to or greater than a predetermined value. As a result, the parameter adjustment device can prevent the handover performance from being deteriorated even when the parameter for determining the MR transmission condition is adjusted for the purpose of improving other than the handover performance.

  In addition, the parameter adjustment apparatus includes a failure calculation unit 120 that calculates a ping-pong handover occurrence rate or a handover failure rate as the handover index. When the ping-pong handover occurrence rate or the handover failure rate is greater than or equal to a threshold, the parameter calculation unit 140 may cause the ping-pong handover occurrence rate or the handover failure rate to be less than the threshold. A value (HO parameter value) is calculated.

  Further, the parameter calculation unit 140 determines at least one of the timing of handover from the own base station s to another base station n and the timing of handover from the other base station n to the own base station s as the parameter. Adjustment is performed by calculating a value (HO parameter value).

In addition, when the parameter calculation unit 140 receives an instruction (instruction information) for calculating the parameter value (HO parameter value), the parameter calculation unit 140 calculates the parameter value.
The parameter calculation unit 140 receives the instructions in an order (for example, descending order) determined by the handover index (for example, ping-pong / handover occurrence rate, handover failure rate).

  In addition, the parameter adjustment apparatus can perform a handover margin between base stations based on the difference between the received power (RSRP) or received quality (RSRQ) by the base station s and the received power or received quality by another base station n. A margin calculation unit 110 that calculates a value (HO margin value) is provided. The parameter calculation unit 140 calculates the parameter value so that the hysteresis value (HO hysteresis value) determined by the margin value is equal to or greater than the predetermined value.

  The parameter adjustment program also sets a parameter value (HO parameter value) for a terminal (not shown) to determine whether or not to send a measurement report (MR for HO) to the base station 100-1 to the computer. A hysteresis value (HO hysteresis value) of handover between base stations (for example, base station 100-s and base station 100-n) based on an index of handover between stations (for example, ping-pong handover occurrence rate, handover failure rate) ) Is executed so as to be equal to or greater than a predetermined value.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

  For example, the wireless communication system may execute wireless communication based on other than the LTE standard. Further, for example, the base station may exchange the HO index information and the like with other base stations and aggregate the information. In this case, the wireless communication system may not include a host device.

  In addition, by recording the program for realizing the parameter adjusting apparatus and the base station described above on a computer-readable recording medium, causing the computer system to read and execute the program recorded on the recording medium, Execution processing may be performed. Here, the “computer system” may include an OS and hardware such as peripheral devices.

  Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used. The “computer-readable recording medium” means a flexible disk, a magneto-optical disk, a ROM, a writable nonvolatile memory such as a flash memory, a portable medium such as a CD-ROM, a hard disk built in a computer system, etc. This is a storage device.

Further, the “computer-readable recording medium” means a volatile memory (for example, DRAM (Dynamic) in a computer system which becomes a server or a client when a program is transmitted through a network such as the Internet or a communication line such as a telephone line. Random Access Memory)) that holds a program for a certain period of time.
The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.
The program may be for realizing a part of the functions described above.
Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

DESCRIPTION OF SYMBOLS 100 ... Base station, 110 ... Margin calculation part, 120 ... Failure calculation part, 130 ... Hysteresis calculation part, 140 ... Parameter calculation part, 150 ... Setting part, 200 ... Host apparatus, 210 ... Margin total part, 220 ... Failure total part , 230 ... trigger part, 240 ... parameter totaling part

Claims (7)

Based on a parameter value for the terminal to determine whether or not to transmit a measurement report to the base station, based on a handover index between the base stations, the hysteresis value of the handover between the base stations is greater than or equal to a predetermined value. A parameter adjustment device comprising: a parameter calculation unit for calculating. A failure calculation unit for calculating a ping-pong handover occurrence rate or a handover failure rate as the handover index,
The parameter calculation unit is configured such that when the ping-pong handover occurrence rate or the handover failure rate is greater than or equal to a threshold, the ping-pong handover occurrence rate or the handover failure rate is less than the threshold. The parameter adjustment device according to claim 1, wherein a value is calculated.   The parameter calculation unit calculates at least one of a timing of handover from the own base station to another base station and a timing of handover from the other base station to the own base station by calculating the parameter value. The parameter adjusting device according to claim 1, wherein the parameter adjusting device adjusts the parameter.   The parameter adjustment device according to any one of claims 1 to 3, wherein the parameter calculation unit calculates the parameter value when receiving an instruction to calculate the parameter value.   The parameter adjustment apparatus according to claim 4, wherein the parameter calculation unit receives the instructions in an order determined by the handover index. A margin calculation unit for calculating a margin value for handover between base stations based on a difference between reception power or reception quality by the own base station and reception power or reception quality by another base station;
6. The parameter calculation unit according to claim 1, wherein the parameter calculation unit calculates the parameter value such that the hysteresis value determined by the margin value is equal to or greater than the predetermined value. 7. Parameter adjustment device. On the computer,
Based on a parameter value for the terminal to determine whether or not to transmit a measurement report to the base station, based on a handover index between the base stations, the hysteresis value of the handover between the base stations is greater than or equal to a predetermined value. Parameter adjustment program for executing the calculation procedure.

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