JP5119951B2 - Mobile communication system, handover performance monitoring method, and management apparatus - Google Patents

Description

  The present invention relates to a mobile communication system, a handover performance monitoring method, and a management apparatus, and more particularly to management of handover performance between radio cells in a mobile communication network based on a cellular system.

  In a mobile communication network based on a cellular system, a large number of radio base stations are arranged in a wide area, and each radio base station covers a small zone called about 1 to 10 radio cells. When the user moves, the communication can be continued by performing a handover for sequentially switching the connection destination radio cells.

  The main reasons for the failure of the handover include a failure of the network device, a shortage of communication resources of the handover destination radio cell, and deterioration of the quality of the radio channel. Specific examples of radio channel quality degradation include lack of radio field strength, radio wave interference between radio cells, lack of overlap between radio cells for the user's moving speed, and neighboring radio cell information as handover candidates. The setting omission is mentioned.

  In general, mobile communication networks define various communication quality monitoring items, calculate KPI (Key Performance Indicator) from the combination of these monitoring items, and identify areas where failure occurs or quality improvement is required due to deterioration of KPI values. Detected.

  The handover characteristic (handover performance) is one of the monitoring items. For example, in the case of a mobile communication network based on the specifications of 3GPP (3rd Generation Partnership Project), as a soft handover monitoring item to be collected periodically for each radio cell, Radio link active link set addition attempts (SHO.AttRLAddUESide), radio link active link set addition success count (SHO.SuccRLAddUESide), radio link active link set addition failure count (SHO.FailRLAddUESide.Cause), radio link Non-Patent Document 1 defines the active link set deletion trial count (SHO.AttRLDelUESide) and the radio link active link set deletion success count (SHO.SuccRLDelUESide).

From the counter described in Non-Patent Document 1, for example, the soft handover failure rate Fsho for each radio cell is obtained by subtracting the soft handover success rate (= success count / trial count) from 1 to the following formula (1 ).
Fsho = 1-SHO.SuccRLAddUESide / SHO.AttRLAddUESide (1)

  According to the technique described in Non-Patent Document 1, it is possible to determine whether or not the quality of handover of the entire cell has deteriorated, and it is possible to detect a problem caused by a failure of a network device. A problem caused by a shortage of communication resources in the handover destination radio cell is also detected as quality degradation of the entire handover destination cell by monitoring the resource utilization rate for each radio cell.

  Further, as a technique for facilitating the deterioration of the quality of a radio channel, particularly the addition or deletion of adjacent cell settings, the method described in Patent Document 1 is known. In the method described in Patent Document 1, neighboring cells that are candidates for handover with respect to a radio cell are grasped in advance by a network monitoring system, and the number of handover trials and neighboring cells are determined for each combination of a radio cell and neighboring neighboring cells. The number of times determined as the best candidate cell is monitored. The best candidate cell is a radio cell having the best radio channel quality at the time of handover. When both the number of handover attempts and the best candidate count are lower than the threshold value, they are deleted from the neighboring cell setting. When the neighbor cell setting is deleted, the number of radio cells that the mobile terminal should search for as a handover candidate decreases, and the handover time can be shortened.

  Further, in the method described in Patent Document 1, if the adjacent cell setting is not performed and the best candidate count is higher than the threshold value, it is added to the setting of the adjacent cell. The radio cell having the best candidate count number higher than the threshold value is likely to have missed the setting of the neighboring cell, and by adding this to the neighboring cell, the handover execution can be stabilized.

JP-T-2005-522156 3GPP TS 32.403, "Telecommunication management; Performance Management (PM); Performance measurements-UMTS and combined UMTS / GSM (Release 5)", 2005.09

  The technique described in Non-Patent Document 1 has a problem that it is difficult to isolate the problem of the entire radio cell and the quality degradation of the radio channel that occurs in a concentrated manner between specific radio cells. The reason is that the monitoring items described in Non-Patent Document 1 are limited to one monitoring target for each wireless cell, and problems that occur in a concentrated manner between specific wireless cells cannot be detected. However, quality degradation of the radio channel rarely occurs over the entire radio cell, and it occurs in a concentrated manner between specific radio cells, making it difficult to detect these problems.

  In addition, in the technique described in Patent Document 1, it is possible to detect the problem of setting omission of neighboring cells, but wireless quality such as lack of electric field strength, interference, and lack of overlap occurring between specific radio cells can be detected. There is a problem that the deterioration of the handover performance due to the problem cannot be grasped. This is because only the number of handover attempts is evaluated, and the handover failure rate is not evaluated. Furthermore, since not only neighboring cells set as handover candidates for wireless cells in advance, but also neighboring wireless cells discovered by the terminal are monitored, the number of monitoring items increases, and wireless to wireless cells other than neighboring cells increases. There is also a problem that a special function of measuring and collecting quality is required in the mobile terminal and the radio base station control station.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems, and to easily separate the handover performance degradation between specific radio cells and the handover performance degradation of the entire cell, a handover performance monitoring method, and a management apparatus. Is to provide.

The mobile communication system according to the present invention includes, for each adjacent cell adjacent to an evaluation target radio cell, the number of handover attempts from the evaluation target cell to the adjacent cell and the number of handover attempts from the adjacent cell to the evaluation target cell. Measuring means for measuring the number of successful handovers from the evaluation target cell to the neighboring cell and the number of successful handovers from the neighboring cell to the evaluation target cell, and the evaluation target based on the measurement result of the measuring means Calculating a handover failure rate between a cell and the neighboring cell for each of the neighboring cells, calculating a bias of the handover failure rate calculated for each of the neighboring cells, and based on the bias determination of determining whether the deterioration of the handover failure rate between the evaluation target cell with a particular cell among the neighbor cells occurs and concentrated Characterized in that it comprises a stage.

A handover performance monitoring method according to the present invention is a handover performance monitoring method of a mobile communication system, and for each adjacent cell adjacent to an evaluation target radio cell, the number of handover attempts from the evaluation target cell to the adjacent cell, A measurement step of measuring the number of handover attempts from the neighboring cell to the evaluation target cell, the number of successful handovers from the evaluation target cell to the neighboring cell, and the number of successful handovers from the neighboring cell to the evaluation target cell; The handover failure rate between the evaluation target cell and the neighboring cell is calculated for each neighboring cell based on the measurement result of the measuring step, and the handover failure rate bias calculated for each neighboring cell is calculated. A calculating step of calculating a specific cell and the evaluation target cell among the adjacent cells based on the bias. Characterized in that it comprises a determination step of degradation of the handover failure rate is determined whether or not the generated concentrated between.

The management apparatus according to the present invention is a management apparatus for a radio access network in a mobile communication system, for each adjacent cell adjacent to an evaluation target radio cell, the number of handover attempts from the evaluation target cell to the adjacent cell, Measuring means for measuring the number of handover attempts from the neighboring cell to the evaluation target cell, the number of successful handovers from the evaluation target cell to the neighboring cell, and the number of successful handovers from the neighboring cell to the evaluation target cell; The handover failure rate between the evaluation target cell and the neighboring cell is calculated for each neighboring cell based on the measurement result of the measuring unit, and the handover failure rate bias calculated for each neighboring cell is calculated. a calculating means for calculating, handover failure between the evaluation target cell with a particular cell among the neighbor cells based on the deviation Characterized in that it comprises a judgment means for degradation of determining whether occurring concentrated.

  According to the present invention, it is possible to easily separate the handover performance degradation between specific radio cells and the handover performance degradation of the entire cell.

  Before describing embodiments of the present invention, the principle of the present invention will be described with reference to the drawings in order to help understanding of the present invention. FIG. 1 is a schematic functional block diagram of a mobile communication system for explaining the principle of the present invention.

  The mobile communication system shown in FIG. 1 includes a measurement unit 501, a calculation unit 502, and a determination unit 503. The measuring unit 501 includes, for each adjacent cell adjacent to the evaluation target radio cell, the number of handover attempts from the evaluation target cell to the adjacent cell, the number of handover attempts from the adjacent cell to the evaluation target cell, and the adjacent from the evaluation target cell. The number of successful handovers to the cell and the number of successful handovers from the neighboring cell to the evaluation target cell are measured.

  The calculation unit 502 calculates the handover performance between the evaluation target cell and the neighboring cell for each neighboring cell based on the measurement result of the measuring unit 501, and calculates the handover performance bias calculated for each neighboring cell. . The determination unit 503 determines whether or not handover performance degradation is concentrated between a specific cell and an evaluation target cell among neighboring cells based on the deviation in handover performance calculated by the calculation unit 502. To do.

  In this way, since the handover performance for each adjacent cell is calculated and the bias is evaluated, it is possible to easily distinguish between the degradation of the handover performance between specific radio cells and the degradation of the handover performance of the entire cell. it can.

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

  FIG. 2 is a diagram showing the configuration of the mobile communication system according to the first embodiment of the present invention. In FIG. 2, the part excluding the core network 40 is a radio access network. The entire area is divided into small zones of wireless cells 1 to 12, the wireless base station 20 is wireless cells 4 and 5, the wireless base station 21 is wireless cells 6, 11 and 22, the wireless base station 22 is wireless cells 1 to 3, The radio base station 23 covers the radio cells 7, 9 and 10. The radio base stations 20 to 23 are connected to the radio base station control station 30 via wired links 60 to 63. The radio base station control station 30 is connected to the core network 40 via a wired link 64 and is connected to the radio access network management device 50 via a wired link 65.

  FIG. 3 is a diagram showing an internal configuration of the radio access network management apparatus 50 of FIG. The data transmitter / receiver 51 collects network monitoring data from the wireless access network via the wired link 65. The failure management unit 52 processes a failure message issued when a wireless base station, a wireless base station control station, or a wired link fails.

  The quality monitoring unit 53 has functions corresponding to the measurement unit 501, the calculation unit 502, and the determination unit 503 described above, and processes monitoring data of communication quality for each input wireless cell or wired link. Of these, the statistical information regarding the performance of the handover is output to the handover performance storage unit 55, and is notified to the handover performance display unit 57 when significant degradation of the handover performance is observed between specific cells.

  In addition, the configuration management unit 54 manages the network configuration of the radio access network, and retains in the neighboring cell configuration storage unit 56 setting information of neighboring cells that are candidates for handover destinations for each radio cell. The quality monitoring unit 53 and the configuration management unit 54 perform management other than information related to handover, but functions other than management of handover performance are well known to those skilled in the art and are omitted because they are not directly related to the present invention.

  FIG. 4 is a diagram showing a configuration of information held in the adjacent cell configuration storage unit 56 of FIG. The radio cell identifier column 100 of the radio access network holds radio cell identifiers in the radio access network to be managed. The adjacent cell identifier column 110 corresponding to this indicates an adjacent cell as a handover destination candidate in each radio cell. For example, six wireless cells of cells 2, 3, 4, 5, 6, and 7 are defined as adjacent cells to the cell 1.

  FIG. 5 is a diagram showing a configuration of information held by the handover performance storage unit 55 of FIG. The radio cell identifier column 120 holds a set of radio cell identifiers of a handover source and a handover destination. For each set of radio cell identifiers, statistics of monitoring items such as the number of handover attempts 121, the number of successful handovers 122, and the handover failure rate 123 are held. The number of handover trials 121 and the number of successful handovers 122 are cumulative count values in the target period for evaluating the handover performance. When the handover performance is evaluated in a plurality of target periods, the statistical information on the handover performance is held separately for each evaluation period.

  Next, the overall operation of the present embodiment will be described in detail with reference to the flowcharts of FIGS. FIG. 6 is a flowchart showing the handover performance evaluation operation according to the first embodiment of the present invention. In FIG. 6, when the handover performance evaluation operation is started, the quality monitoring unit 53 acquires the handover performance statistical information from the handover performance storage unit 55 (step S201).

  Then, the quality monitoring unit 53 sequentially extracts radio cells of the radio access network to be evaluated (step S202), and determines whether or not the handover failure rate of the entire evaluation target cell has deteriorated beyond the threshold (step). S203). Usually, as described in Non-Patent Document 1, management items for acquiring the number of handover attempts and the number of successful handovers of the entire cell are prepared in the management system of the mobile communication network, and the above-described formula (1) By performing the calculation as described above, the handover failure rate of the entire cell can be obtained.

  If the handover failure rate of the entire evaluation target cell is good, the process returns to step S202. If the handover failure rate of the entire evaluation target cell has deteriorated beyond the threshold, the quality monitoring unit 53 performs the handover performance storage unit 55. The handover failure rate between the evaluation target cell and the neighboring cell is calculated for each neighboring cell from the number of handover attempts and the number of successful handovers for each neighboring cell obtained from (1).

  Next, the quality monitoring unit 53 calculates a handover performance bias calculated for each neighboring cell (step S205). If the handover performance bias exceeds a threshold (step S206), a specific wireless cell is calculated. It is determined that the handover performance has deteriorated, and the determination result, the number of handover attempts for each neighboring cell, and the handover failure rate for each neighboring cell are output to the handover performance display unit 57 (step S207).

  On the other hand, if the bias in the handover performance is equal to or less than the threshold, the quality monitoring unit 53 determines that the handover performance of the entire evaluation target cell is deteriorated, the determination result, the number of handover attempts for each adjacent cell, and the adjacent The handover failure rate for each cell is output to the handover performance display unit 57 (step S208). When the handover performance of all wireless cells is evaluated (step S202), the evaluation operation is terminated.

  FIG. 7 is a flowchart showing an example of handover performance bias calculation operation for each neighboring cell in step S205 of FIG. In FIG. 7, first, the handover failure rate {pij} for each adjacent cell defined in the wireless cell i to be evaluated is input (step S301). When i = 1, for example, as shown in FIG. 8, handover failure rates p12 (4%) and p13 (5%) flowing out from the wireless cell 1 to the wireless cells 2, 3, 4, 5, 6, 7 , P14 (6%), p15 (7%), p16 (70%), p17 (3%), and the failure rate of handover flowing from the wireless cells 2, 3, 4, 5, 6, 7 to the wireless cell 1 p21 (2%), p31 (6%), p41 (4%), p51 (7%), p61 (60%), and p71 (8%) are input. In this case, it is assumed that the handover performance between the radio cell 1 and the radio cell 6 is significantly deteriorated.

Next, the failure rate concentration for each adjacent cell is calculated according to the following equation (step S302).

  This equation indicates the degree to which deterioration of handover performance is concentrated between a specific cell and an evaluation target cell i among neighboring cells. If the degree of concentration is low, the value becomes a small value close to 0. The index is close to 1 if it is high. In the case of the example in FIG. 8, the degree of concentration C (1) = 0.266. The degree of concentration C (i) calculated in this way is output as a handover performance bias (step S303), and the calculation of the handover performance bias for each neighboring cell is terminated.

  FIG. 9 is a diagram showing an example of display on the handover performance display unit 57 of FIG. In FIG. 9, each wireless cell is indicated by a circle on the map along with the identifier of the wireless cell near the center of the wireless cell. At this time, the color or pattern of the circle may be changed according to the determination result in step S206 of FIG. 6 so that the handover performance degradation of the entire radio cell and the handover performance degradation between specific radio cells can be identified.

  If the radio cell to be evaluated is cell 1, the line thickness is changed according to the number of handover attempts from the evaluation target cell 1 to each of the adjacent cells 2 to 7, and the handover from the evaluation target cell 1 to each of the adjacent cells 2 to 7 is performed. When the failure rate is good, the cells are connected by a solid line, and when the failure rate exceeds the threshold, the cells are connected by a broken line. By drawing such a diagram about the handover inflow from the adjacent cell to the evaluation target cell and the handover outflow from the evaluation target cell to the adjacent cell, it is possible to grasp at a glance the deterioration of the handover performance between specific cells.

  In addition to the example of FIG. 9, a graph of handover performance for each adjacent cell as shown in FIG. 8 or FIG. 11 described later may be displayed. In this case, if there is a significant bias in handover performance, it may be highlighted by changing the color or pattern of the bar graph corresponding to the adjacent cell.

  As described above, in the first embodiment of the present invention, handover performance is evaluated for each adjacent cell, and degradation of handover performance between specific cells is evaluated using an index of concentration. Therefore, it is possible to easily distinguish between handover performance degradation between specific radio cells and handover performance degradation of the entire cell. Further, in the first embodiment of the present invention, information indicating whether or not degradation of handover performance is concentrated between specific radio cells is displayed. Deterioration of handover performance can be grasped at a glance.

  Next, a second embodiment of the present invention will be described with reference to the drawings. An index other than the degree of concentration can also be used as an index representing the handover performance bias for each neighboring cell. FIG. 10 is a flowchart showing a handover performance bias calculation operation according to the second embodiment of the present invention.

  In step S205 of FIG. 6, first, the number of handover attempts {aij} for each adjacent cell for the radio cell i to be evaluated is input from the handover performance storage unit 55 (step S401). When i = 1, for example, as shown in FIG. 11, the number of handover attempts a12 (90 times) and a13 (70 times) flowing out from the wireless cell 1 to the wireless cells 2, 3, 4, 5, 6, and 7 , A14 (120 times), a15 (20 times), a16 (35 times), a17 (60 times), and the number of handover attempts that flow into the wireless cell 1 from the wireless cells 2, 3, 4, 5, 6, 7 a21 (87 times), a31 (7 times), a41 (105 times), a51 (22 times), a61 (39 times), and a71 (58 times) are input.

Next, the handover outflow / inflow ratio Rij (= Rji) is calculated for each adjacent cell according to the following equation (step S402).
Rij = Rji = min (aij, aji) / max (aij, aji)
Here, min (x, y) represents the smaller of x and y, and max (x, y) represents the larger of x and y.

  Next, of Rij and Rji calculated in this way, the smallest value for all neighboring cells is output as the bias of handover performance (step S403), and the calculation of the bias of handover performance for each neighboring cell is terminated. As is clear from the above equation, the greater the Rij, the greater the bias between inflow and outflow of handover. This is because when a long time is accumulated, it is known that the inflow and outflow of users to a limited area such as a radio cell balance, so if this ratio is extremely large, the handover performance deteriorates. You can think that you are.

  As described above, in the second embodiment of the present invention, the number of handover attempts from the evaluation target cell to the adjacent cell and the number of handover attempts from the adjacent cell to the evaluation target cell are used instead of the concentration index. By evaluating the deterioration of handover performance between specific cells using the ratio, it is possible to easily distinguish between the deterioration of handover performance between specific wireless cells and the deterioration of handover performance of the entire cell.

  The first and second embodiments of the present invention can be applied to applications such as a handover performance monitoring system in mobile communication based on a cellular system.

1 is a schematic functional block diagram of a mobile communication system for explaining the principle of the present invention. It is a figure which shows the structure of the mobile communication system by the 1st Embodiment of this invention. It is a figure which shows the internal structure of the radio | wireless access network management apparatus of FIG. It is a figure which shows the structure of the information which the adjacent cell structure storage part of FIG. 3 hold | maintains. It is a figure which shows the structure of the information which the handover performance memory | storage part of FIG. 3 hold | maintains. 4 is a flowchart showing a handover performance evaluation operation according to the first embodiment of the present invention. 7 is a flowchart illustrating an example of a handover performance bias calculation operation in step S205 of FIG. 6. FIG. 3 is a diagram illustrating a handover failure rate for each neighboring cell when the evaluation target cell is the wireless cell 1 of FIG. 2. It is a figure which shows an example of a display of the hand-over performance display part of FIG. 7 is a flowchart showing another example of a handover performance bias calculation operation in step S205 of FIG. 6. FIG. 3 is a diagram illustrating the number of handover attempts for each neighboring cell when the evaluation target cell is the wireless cell 1 in FIG. 2.

Explanation of symbols

1 to 12 Radio cell 20 to 23 Radio base station 30 Radio base station control station 40 Core network 50 Radio access network management device 51 Data transmission / reception unit 52 Fault monitoring unit 53 Quality monitoring unit 54 Configuration management unit 55 Hander performance storage unit 56 Adjacent cell Configuration storage unit 57 Handover performance display unit 60 to 65 Wired link 501 Measurement unit 502 Calculation unit 503 Determination unit

Claims (9)

For each adjacent cell adjacent to the evaluation target radio cell, the number of handover attempts from the evaluation target cell to the adjacent cell, the number of handover attempts from the adjacent cell to the evaluation target cell, and the evaluation target cell to the Measuring means for measuring the number of successful handovers to neighboring cells and the number of successful handovers from the neighboring cells to the evaluation target cell;
A handover failure rate between the evaluation target cell and the neighboring cell is calculated for each of the neighboring cells based on a measurement result of the measuring unit, and a deviation of the handover failure rate calculated for each of the neighboring cells is calculated. A calculating means for calculating;
And determining means for determining whether or not deterioration of a handover failure rate is concentrated between a specific cell among the adjacent cells and the evaluation target cell based on the bias. Mobile communication system. 2. The operation of the calculating unit and the determining unit is performed when a handover failure rate between the evaluation target cell and the entire neighboring cell is deteriorated exceeding a predetermined threshold. Mobile communication system. 2. The display device according to claim 1 , further comprising display means for displaying information indicating whether or not handover performance deterioration is concentrated between a specific cell of the neighboring cells and the evaluation target cell. Or the mobile communication system according to 2 ; A method for monitoring handover performance of a mobile communication system, comprising:
For each adjacent cell adjacent to the evaluation target radio cell, the number of handover attempts from the evaluation target cell to the adjacent cell, the number of handover attempts from the adjacent cell to the evaluation target cell, and the evaluation target cell to the A measurement step of measuring the number of successful handovers to neighboring cells and the number of successful handovers from the neighboring cells to the evaluation target cell;
Based on the measurement result of the measurement step, a handover failure rate between the evaluation target cell and the neighboring cell is calculated for each neighboring cell, and the deviation of the handover failure rate calculated for each neighboring cell is calculated. A calculating step for calculating;
A determination step of determining whether or not deterioration of a handover failure rate is concentrated between a specific cell among the neighboring cells and the evaluation target cell based on the bias. Handover performance monitoring method. The operation of the calculation step and the determination step is performed when a handover failure rate between the evaluation target cell and the entire neighboring cell is deteriorated exceeding a predetermined threshold. Handover performance monitoring method. The display step of displaying information indicating whether or not deterioration of handover performance is concentrated between a specific cell and the evaluation target cell among the adjacent cells is further included. Or the handover performance monitoring method according to 5 . A radio access network management apparatus in a mobile communication system, comprising:
For each adjacent cell adjacent to the evaluation target radio cell, the number of handover attempts from the evaluation target cell to the adjacent cell, the number of handover attempts from the adjacent cell to the evaluation target cell, and the evaluation target cell to the Measuring means for measuring the number of successful handovers to neighboring cells and the number of successful handovers from the neighboring cells to the evaluation target cell;
A handover failure rate between the evaluation target cell and the neighboring cell is calculated for each of the neighboring cells based on a measurement result of the measuring unit, and a deviation of the handover failure rate calculated for each of the neighboring cells is calculated. A calculating means for calculating;
And determining means for determining whether or not deterioration of a handover failure rate is concentrated between a specific cell among the adjacent cells and the evaluation target cell based on the bias. Management device. 8. The operation of the calculating unit and the determining unit is performed when a handover failure rate between the evaluation target cell and the entire neighboring cell is deteriorated exceeding a predetermined threshold. Management device. 8. The information processing apparatus according to claim 7, further comprising display means for displaying information indicating whether or not handover performance degradation is concentrated between a specific cell of the neighboring cells and the evaluation target cell. Or the management apparatus of 8.

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