Abstract:
In a wireless cell, the potential deterioration in quality is efficiently detected when the indication of abnormalities is weak. Provided are a step of calculating one or more radio qualities for each coverage area of a wireless cell; a step of measuring one or more network statistical qualities for each coverage area of the wireless cell; a step of making a pair of each network statistical quality and one or more radio qualities for each coverage area of each wireless cell; and a step of calculating, based on the pairs of each network statistical quality and one or more radio qualities for the coverage areas of the wireless cells, the correlation between each network statistical quality and one or more radio qualities.

Description:
The present application is the National Phase of PCT/JP2008/053250, filed Feb. 26, 2008, which is based on and claims priority from Japanese Patent Application No. 2007-070620 (filed on Mar. 19, 2007), the entire content of which being incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a method for monitoring a wireless cell in a mobile communication network based on a cellular communication system, a device thereof and a program thereof, and particularly relates to a wireless cell monitoring method, a device thereof and a program thereof which monitor the potential deterioration in quality of the wireless cell using both network planning information and network statistical quality. 
     BACKGROUND ART 
     In the mobile communication network, communication quality is generally monitored based on an indicator (quality indicator) of the network statistical quality acquired from a communication device. For example, the quality indicator includes a call setup success rate, which represents the number of calls successfully set up with respect to the number of requests for setting up a call which occurs when a mobile terminal makes or receives a call, a handover success rate, which represents the number of handover operations successfully performed with respect to the number of requests for handover, and the like. Each mobile carrier uses a combination of the indicators. A network administrator checks the quality indicators and the output of a failure detection mechanism incorporated into the hardware or software of each communication device, thereby making it possible to carry out comprehensive quality and failure management. The general method to detect abnormalities of a network from the quality indicators is to compare the quality indicators with predetermined reference values which are preset for respective quality indicators. One of the conventional methods to set the reference values for respective quality indicators is to use a statistical average value of the past quality indicators (See PTL 1). That is, a statistical average value of the quality indicators during a predetermined period of time in the past when it was assumed that a communication network was normal is regarded as a reference value, the difference between the reference value and the actually measured value is calculated, and it is determined that abnormalities have occurred when the difference exceeds a predetermined threshold. 
     CITATION LIST 
     {Patent Literature}
         {PTL 1} JP-A-2006-094497       

     SUMMARY OF INVENTION 
     Technical Problem 
     The conventional quality monitoring method which uses the statistical average value of the past quality indicators as the reference value is effective in addressing such failures as the malfunction of devices in a network or a wireless base station, which could lead to a steep deterioration in quality. However, when quality is constantly low, or when the indication of abnormalities is weak due to a gradual deterioration in quality, it is difficult to detect potential quality abnormalities. That is, if the difference with respect to the statistical average value of the past quality indicators cannot be confirmed, even a wireless cell with potential abnormalities cannot be detected. For example, according to the conventional method, it is difficult to detect the following wireless cells because the quality does not deteriorate steeply: a wireless cell which has constantly low quality due to the misconfiguration of the network operation parameters, a wireless cell where the radio propagation environment has gradually changed due to the construction of a large structure, and a wireless cell which cannot sufficiently demonstrate the capability because of the partial malfunction of a communication device. 
     The present invention has been made in view of the above problems. The objective of the present invention is to provide a wireless cell monitoring method, a system thereof and a program thereof which efficiently detect the potential deterioration in quality when the indication of abnormalities is weak. 
     Solution to Problem 
     According to the present invention, provided is a wireless cell monitoring method including: a step of calculating one or more radio qualities for each coverage area of a wireless cell; a step of measuring one or more network statistical qualities for each coverage area of the wireless cell; a step of making a pair of each network statistical quality and one or more radio qualities for each coverage area of each wireless cell; and a step of calculating, based on the pairs of each network statistical quality and one or more radio qualities for the coverage areas of the wireless cells, the correlation between each network statistical quality and one or more radio qualities. 
     Moreover, according to the present invention, provided is a wireless cell monitoring device including: a unit for calculating one or more radio qualities for each coverage area of a wireless cell; a unit for measuring one or more network statistical qualities for each coverage area of the wireless cell; a unit for making a pair of each network statistical quality and one or more radio qualities for each coverage area of each wireless cell; and a unit for calculating, based on the pairs of each network statistical quality and one or more radio qualities for the coverage areas of the wireless cells, the correlation between each network statistical quality and one or more radio qualities. 
     Moreover, according to the present invention, provided is a program that causes a computer to function as a wireless cell monitoring device including: a unit for calculating one or more radio qualities for each coverage area of a wireless cell; a unit for measuring one or more network statistical qualities for each coverage area of the wireless cell; a unit for making a pair of each network statistical quality and one or more radio qualities for each coverage area of each wireless cell; and a unit for calculating, based on the pairs of each network statistical quality and one or more radio qualities for the coverage areas of the wireless cells, the correlation between each network statistical quality and one or more radio qualities. 
     Advantageous Effects of Invention 
     According to the present invention, the reference value of the network statistical quality is estimated based on the radio quality. Since this reference value is used to analyze the abnormalities in quality of the wireless cell, the abnormalities in quality can be detected even when the network statistical quality does not deteriorate steeply. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  A diagram illustrating the configuration of a mobile communication network according to a first embodiment of the present invention. 
         FIG. 2  A explanatory diagram illustrating an example of a radio quality kept by a wireless network planning system. 
         FIG. 3  An explanatory diagram illustrating an example of wireless base station information kept by the wireless network planning system. 
         FIG. 4  A diagram illustrating the configuration of a wireless cell monitoring system according to the first embodiment. 
         FIG. 5  An explanatory diagram illustrating an example of data in a network statistical quality storage section. 
         FIG. 6  An explanatory diagram illustrating an example of data in a network planning information storage section. 
         FIG. 7  A flowchart illustrating an example of the operation of a wireless cell monitoring system according to the first embodiment. 
         FIG. 8  A flowchart illustrating an example of the operation of a radio quality calculation unit according to the first embodiment. 
         FIG. 9  A flowchart illustrating an example of the operation of a quality abnormality analysis unit according to the first embodiment. 
         FIG. 10  An explanatory diagram illustrating an example of what a quality display unit displays. 
         FIG. 11  An explanatory diagram illustrating an example of what the quality display unit displays. 
         FIG. 12  An explanatory diagram illustrating an example of what the quality display unit displays. 
         FIG. 13  A flowchart illustrating an example of the operation of a quality abnormality analysis unit according to a second embodiment of the present invention. 
         FIG. 14  A diagram illustrating the configuration of a wireless cell monitoring system according to a third embodiment of the present invention. 
         FIG. 15  A flowchart illustrating an example of the operation of a wireless cell monitoring system according to the third embodiment. 
     
    
    
     REFERENCE SIGNS LIST 
     
         
         
           
               10 ,  11 : Wireless base stations 
               20 : Wireless base station controller 
               30 : Mobile communication core network 
               40 : External network 
               50 : Wireless network planning system 
               60 : Wireless cell monitoring system 
               61 : Wireless cell monitoring system 
               70 ,  71 : Wireless cells 
               80  to  82 : Mobile terminals 
               90  to  95 : Wired links 
               600 : Network statistical quality collection unit 
               601 : Network statistical quality storage section 
               602 : Network planning information collection unit 
               603 : Radio quality calculation section 
               604 : Network planning information storage section 
               605 : Quality abnormality analysis unit 
               606 : Quality display unit 
               610 : Wireless cell grouping unit 
           
         
       
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     An example of the configuration of a first embodiment of the present invention will be described. 
       FIG. 1  is a block diagram illustrating an entire mobile communication network according to the first embodiment. As shown in  FIG. 1 , according to the present embodiment, the mobile communication network includes wireless base stations  10  and  11 , a wireless base station controller  20 , a mobile communication core network  30 , an external network  40 , a wireless network planning system  50 , and a wireless cell monitoring system  60 . 
     The wireless base stations  10  and  11  respectively form wireless cells  70  and  71  in which radio waves can be transmitted between the wireless base stations and mobile terminals. Mobile terminals  80  and  81  in the wireless cell  70  wirelessly communicate with the wireless base station  10 . A mobile terminal  82  in the wireless cell  71  wirelessly communicates with the wireless base station  11 . 
     The wireless base station controller  20  is connected to the wireless base stations  10  and  11  and the mobile communication core network  30  via wired links  90 ,  91  and  92 , respectively, and performs a management process of resources in subordinate wireless cells, a transmitting and receiving process of control traffic and a transferring process of communication traffic. Moreover, the wireless base station controller  20  measures the quality of a communication network and transmits the measurement result to the wireless cell monitoring system  60  as a network statistical quality at regular intervals. 
     The wireless network planning system  50  is equipped with a radio propagation simulator which estimates the radio quality around each region where each wireless base station is installed, and the like. The wireless network planning system  50  is generally used to determine wireless parameters such as the location of each wireless base station, an antenna power, and a tilting angle of each antenna. The information to be input into the radio propagation simulator includes map information, building information and setting information of the wireless base stations. The radio quality to be estimated includes distribution of the received signal code power (RSCP) representing the received signal strength from the wireless base station, and distribution of the received energy per chip divided by the power density in the band (Ec/N0) representing the amount of radio interference around an arbitrary point in planning areas.  FIGS. 2A and 2B  show an example of how to hold the estimation result of radio quality. As shown in  FIG. 2A , the planning area is divided in a lattice pattern. As shown in  FIG. 2B , at each lattice point which is obtained as a result of dividing, the received signal code power (RSCP) and the received energy per chip divided by the power density in the band (Ec/N0) received from each adjacent wireless base station are estimated. Moreover,  FIG. 3  shows an example of how to hold wireless base station information. As shown in  FIG. 3 , longitude and latitude information, the height of an antenna, the angles of an antenna, transmission power, wireless base station installation location information and the like for each wireless base station are associated with wireless base station identification information and are kept. In the wireless network planning system  50 , not only the information as shown in  FIGS. 2A and 2B  but the information as shown in  FIG. 3  are kept as the network planning information. 
     The following describes the wireless cell monitoring system  60  with reference to the accompanying diagrams. 
       FIG. 4  is a block diagram illustrating an example of the configuration of the wireless cell monitoring system  60 . The wireless cell monitoring system  60  monitors, based on the reference value of the network statistical quality which is statistically estimated based on the radio quality, the potential abnormalities in quality of the wireless cells. The wireless network planning system  50  and the wireless cell monitoring system  60  are not necessarily connected to each other through wired links, as long as a means has been prepared for transferring network planning information from the wireless network planning system  50  to the wireless cell monitoring system  60 . 
     A network statistical quality collection unit  600  collects an measured value of the network statistical quality from the wireless base station controller  20  via the wired link  94  at regular intervals. The collected information is stored in a network statistical quality storage section  601 . 
     The network statistical quality storage section  601  stores the measured value of the network statistical quality collected by the network statistical quality collection unit  600 . As illustrated in  FIG. 5 , wireless cell identification information and the measured value of the network statistical quality associated with the wireless cell identification information are stored. 
     A network planning information collection unit  602  collects the network planning information from the wireless network planning system  50  via the wired link  95 . The collected information is stored in a network planning information storage section  604 . 
     Moreover, a radio quality calculation unit  603  reads out the network planning information from the network planning information storage section  604 , and calculates the radio quality for each wireless cell. For example, as illustrated in  FIG. 2(   b ), based on the distribution information about the received signal code power (RSCP) and the distribution information about the amount of the received energy per chip divided by the power density in the band (Ec/N0) at each lattice point which is obtained as a result of dividing, a coverage area of the wireless cell, and the strong signal area ratio and the average amount of radio interference of each wireless cell are calculated. The definition of the strong signal area ratio will be described later. 
     The results of the above calculation are stored in the network planning information storage section  604 . 
     Incidentally, the radio quality calculation unit  603  can be omitted. If the radio qualities collected for each wireless cell can be acquired from the wireless network planning system  50  or the like, the radio qualities may be directly stored in the network planning information storage section  604 . 
     The network planning information storage section  604  stores the network planning information collected by the network planning information collection unit  602  and the radio qualities of each wireless cell calculated by the radio quality calculation unit  603 . For example, the network planning information illustrated in  FIGS. 2(   b ) and  3  and the strong signal area ratio and the average amount of radio interference of each wireless cell illustrated in  FIG. 6  are stored. 
     A quality abnormality analysis unit  605  estimates, based on the radio qualities, the reference value of the network statistical quality for each wireless cell and compares the estimated reference value and the actually measured value to analyze the potential abnormalities in quality of the wireless cell. The quality abnormality analysis unit  605  acquires the network statistical quality and the radio quality from the network statistical quality storage section  601  and the network planning information storage section  604 , analyzes the abnormalities in quality of the wireless cell, and outputs the result of analysis to a quality display unit  606 . 
     The quality display unit  606  reads out the analysis result from the quality abnormality analysis unit  605 , and uses a display unit such as a display to display the quality state of the wireless cell along with the information stored in the network statistical quality storage section  601  and the network planning information storage section  604 . 
     The example of the configuration of the first embodiment of the present invention has been described above. Since the wireless base stations  10  and  11 , the wireless base station controller  20  and the mobile terminals  80  to  82  are well known among those skilled in the art and are not directly related to the present invention, the structures are not detailed here. 
     The following describes the operation of the wireless cell monitoring system  60  according to the present embodiment, with reference to a flowchart of  FIG. 7 . 
     When a wireless cell monitoring process starts at a predetermined timing (S 1101 ), the network statistical quality collection unit  600  collects the measured value (the call setup success rate, the handover success rate, a call termination success rate, a packet transfer throughput, a packet loss rate or a packet transfer delay, for example) of the network statistical quality using the wireless base station controller  20  via the wired link  94 , and stores the measured value in the network statistical quality storage section  601  (S 1102 ). For example, the operations done at regular intervals or the operations done by a maintenance worker trigger the wireless cell monitoring process. 
     Then, the network planning information collection unit  602  collects the network planning information (the radio quality distribution of each wireless base station as illustrated in  FIG. 2 , for example) from the wireless network planning system  50  via the wired link  95 , and stores the network planning information in the network planning information storage section  604  (S 1103 ). Then, the radio quality calculation unit  603  reads out the network planning information from the network planning information storage section  604 , calculates the radio quality of each wireless cell (the strong signal area ratio and the average amount of radio interference, for example), and stores the radio quality in the network planning information storage section  604  (S 1104 ). 
     Also referring to  FIG. 8 , an example of the operation of a radio quality calculation process by the radio quality calculation unit  603  will be described. 
     When the radio quality calculation process starts (S 1201  in  FIG. 8 ), an area where the received signal code power (RSCP) from a certain wireless base station is stronger than the received signal code powers (RSCP) from the other wireless base stations is defined as a coverage area (s 1 ) of the certain wireless base station. In this manner, the coverage area is defined for each wireless base station (S 1202  in  FIG. 8 ). Then, the area (s 2 ) where the received signal code power (RSCP) from the wireless base station is greater than or equal to a predetermined threshold in the coverage area of the wireless base station is calculated, and the ratio of the calculated size of s 2  to the calculated size of s 1  is regarded as the strong signal area ratio (S 1203  in  FIG. 8 ). Subsequently, the average value of the received energy per chip divided by the power density in the band (Ec/N0) from the wireless base station in the coverage area of the wireless base station is calculated and regarded as the average amount of radio interference (S 1204  in  FIG. 8 ). Then, the strong signal area ratio and the average amount of radio interference are associated with the wireless cell identification information on a per wireless base station basis, and then output to the network planning information storage section  604  (S 1205  in  FIG. 8 ). Then, the process ends (S 1206  in  FIG. 8 ). Incidentally, only one of the calculation of the strong signal area ratio (S 1203 ) and the calculation of the average amount of radio interference (S 1204 ) may be performed. 
     Then, the quality abnormality analysis unit  605  analyzes the abnormalities in quality of the wireless cell based on the information stored in the network statistical quality storage section  601  and the network planning information storage section  604  (S 1105 ). 
     Also referring to  FIG. 9 , the operation of a quality abnormality analysis process by the quality abnormality analysis unit  605  will be described. 
     When the quality abnormality analysis process starts at a predetermined timing (S 1301  in  FIG. 9 ), the measured network statistical quality and the calculated radio quality of each wireless cell are respectively acquired from the network statistical quality storage section  601  and the network planning information storage section  604  (S 1302  in  FIG. 9 ). In the case described below, an indicator of the network statistical quality is the call setup success rate, and an indicator of the radio quality is the strong signal area ratio. 
     Then, based on many pairs of the values of the strong signal area ratio and the call setup success rate acquired on a per wireless cell basis, the value of the call setup success rate that can be expected in accordance with the value of the strong signal area ratio is statistically estimated, and the estimated value is regarded as a reference value of the call setup success rate (S 1303  in  FIG. 9 ). That is, for each wireless cell, a pair of the calculated strong signal area ratio and the measured call setup success rate is created, and many pairs are accumulated (for many wireless cells). Based on the pairs, the correlation (a linear regression equation, for example) between the strong signal area ratio and the call setup success rate is calculated. 
     The reason why the measured value of the call setup success rate (including that of a malfunctioning wireless cell) can be input to calculate the correlation is that many samples are prepared. 
     Moreover, the effect of the temporary deterioration in quality caused by a malfunctioning device or the like can be eliminated by calculating the long-term average of the network statistical quality. The objective of the present invention is not to detect the temporary deterioration in quality caused by a malfunctioning device or the like but to detect a wireless cell that constantly demonstrates lower performance as compared with the expected quality. Moreover, the temporary deterioration in quality can be excluded in advance by a conventional quality monitoring method (the comparison with the past statistical average value, for example). 
     In one example, when a multivariate analysis, which is for example a regression analysis, is used, a regression equation to the reference value of the call setup success rate from the strong signal area ratio can be calculated with the strong signal area ratio and the call setup success rate being set as a explanatory variable s and a objective variable p, respectively. That is, when the linear regression equation is used, with the use of the appropriately set coefficients a and b, the correlation between the strong signal area ratio and the reference value of the call setup success rate can be expressed as follows:
 
 p=a*s+b  
 
     Moreover, in another example, the strong signal area ratio is discretized at predetermined intervals. Based on a pair of the average value of the strong signal area ratio which is calculated for each discretization segment and the average value of the call setup success rate, the correlation between the strong signal area ratio and the reference value of the call setup success rate can be expressed. 
     Then, for each wireless cell, the difference between the reference value of the call setup success rate that can be expected in accordance with the value of the strong signal area ratio of the wireless cell and the measured value of the call setup success rate of the wireless cell is calculated (S 1304  in  FIG. 9 ). That is, the difference represents a gap between the quality that the wireless cell is expected to demonstrate and the actual quality. 
     If the correlation between the network statistical quality and the radio quality is weak, the variance of the difference which is calculated for each wireless cell increases. Therefore, it is difficult to appropriately evaluate the abnormalities in quality of the wireless cells by simply comparing the differences. To solve the problem, the statistical significance of the calculated difference is evaluated, and the degree of quality abnormality (the degree of gap) is calculated as a barometer of the statistical significance (S 1305  in  FIG. 9 ). For example, in the case of regression analysis, a standard residual obtained by normalizing the difference using a standard deviation thereof, and the like can be used as the degree of quality abnormality. In one example, the difference is normalized with the standard deviation; the difference is generally normalized based on the degree of statistical reliability of the correlation. Incidentally, a predetermined threshold may be set for the difference or the degree of quality abnormality; only the wireless cells the quality abnormality of which exceed a predetermined limitation may be detected. 
     After the operations described above, the quality abnormality analysis process of the wireless cell ends (S 1306  in  FIG. 9 ). 
     According to another embodiment, a plurality of indicators of the radio quality are used for one indicator of the network statistical quality to analyze the quality abnormalities. For example, the indicator of the network statistical quality may be the call setup success rate, while the indicators of the radio quality may be the strong signal area ratio and the average amount of radio interference. In this way, using a plurality of indicators of the radio quality leads to the highly reliable analysis of the quality abnormalities for one indicator of the network statistical quality. Incidentally, in this case, the multivariate analysis such as the multiple regression analysis, and the like can be used to perform the same operations as those described above. Therefore, the operations are not detailed here. 
     Then, the quality display unit  606  displays, based on the result of analysis by the quality abnormality analysis unit  605 , the quality state of the wireless cell using a display unit (S 1106 ). 
       FIGS. 10 to 12  show examples of how to display the quality state of the wireless cells.  FIG. 10  is a table in which the wireless cell identification information, the strong signal area ratios, the reference values of the call setup success rates that can be expected from the strong signal area ratios, the measured values, and the degrees of quality abnormality are displayed; the quality state of each wireless cell is quantitatively listed. Moreover,  FIG. 11  is a bar graph where the degrees of quality abnormality of the wireless cells are displayed from the highest to the lowest; the degree and distribution of quality abnormality of the wireless cell can be visually checked.  FIG. 12  is a scatter diagram where the strong signal area ratios and the call setup success rates of the wireless cells are displayed; one dot corresponds to one wireless cell. In the scatter diagram of  FIG. 12 , the solid line represents a regression line from the strong signal area ratio to the reference value of the call setup success rate; a dashed line represents the threshold thereof. The quality state of a specific wireless cell can be checked in comparison with the overall trend. 
     Second Embodiment 
     According to a second embodiment of the present invention, the basic configuration thereof is the same as that of the first embodiment, but the quality abnormality analysis unit  605  can analyze the quality abnormalities of the wireless cell using a plurality of indicators of the network statistical quality. 
     In one embodiment, with the use of the weighted sum of the degrees of quality abnormality which is calculated for each indicator of the network statistical quality, the quality abnormalities of the wireless cell can be analyzed. 
       FIG. 13  is a flowchart illustrating one example of the operation of the present embodiment. In  FIG. 13 , the call setup success rate and the handover success rate are used as the indicators of the network statistical quality; the strong signal area ratio is used as the indicator of the radio quality. 
     The operations of S 1403  to S 1405  and S 1406  to S 1408  in  FIG. 13  are the same as those of S 1303  to S 1305  of the operation flow ( FIG. 9 ) of the first embodiment. The difference between the present embodiment and the first embodiment is that a plurality of indicators of the network statistical quality are acquired (S 1402 ) and the weighted sum of the degrees of quality abnormality is calculated for each indicator of the network statistical quality (S 1409 ). 
     In that manner, the quality abnormalities of the wireless cell are analyzed based on a plurality of indicators of the network statistical quality. Therefore, the quality abnormalities of the wireless cell are comprehensively determined. 
     Third Embodiment 
     The configuration of a third embodiment of the present invention will be described.  FIG. 14  is a block diagram illustrating an example of the configuration of a wireless cell monitoring system  61  according to the third embodiment. The wireless cell monitoring system  61  of the third embodiment is different from the wireless cell monitoring system  60  of the first embodiment: The wireless cell monitoring system  61  includes a wireless cell grouping unit  610 . The same components as those of the first embodiment have been designated by the same reference numbers, and are not detailed here. 
     The wireless cell grouping unit  610  groups, based on the information acquired from the network statistical quality storage section  601  and the network planning information storage section  604 , the wireless cells in accordance with a predetermined criterion. In one embodiment, grouping is carried out based on information about where the wireless cell is installed such as information about the wireless cell is installed in a suburban area, a subway or a building, information about what type the wireless base station is, and the like. Such pieces of information can be usually acquired from the wireless network planning system  50 . The information on groups of wireless cells, which are grouped by the wireless cell grouping unit  610 , are, on group by group basis, output to the quality abnormality analysis unit  605  which then performs the analysis process of the quality abnormalities. 
     The following describes the operation of the above-described example of configuration. 
       FIG. 15  is a flowchart illustrating an example of the operation of the example of the configuration of the third embodiment. The same operations as those of the first embodiment have been designated by the same reference symbols as those of  FIG. 7 , and are not detailed here. 
     The difference between the first and third embodiments is that the wireless cells are grouped with the predetermined criterion before the quality abnormality analysis process (S 1501 ). That is, as described above, the wireless cell grouping unit  610  groups the wireless cells in accordance with the predetermined criterion, and the analysis of the quality abnormalities of the wireless cells is carried out by the quality abnormality analysis unit  605  for each group. Since the quality abnormality analysis process of the wireless cells can be performed in the same way as in the first and second embodiments, the quality abnormality analysis process is not detailed here. 
     In one embodiment, grouping is carried out according to where the wireless cell is installed: The wireless cell may be installed in a suburban area, a subway, or a building (the name of the building where the wireless cell is installed, for example). A mobile carrier usually sets a different planning policy in accordance with type of the installation place of the wireless cell whose communication traffic characteristic and radio propagation characteristic are different from those of the other. If the wireless cells are not grouped, then the wireless cells with different characteristics exist together. Therefore, it is difficult to obtain the proper result of the analysis process of the quality abnormalities. According to the present embodiment, this problem is prevented. Since the wireless cells having same planning policies are grouped and handled on group by group basis, the accuracy of the quality abnormality analysis process increases. 
     Incidentally, the wireless cell monitoring system shown in  FIG. 4  may be configured hardware, software or a combination of both. The software, i.e., computer program, is read out from a computer readable medium, such as a hard disk drive and CD-ROM, by CPU of a computer and executed by the CPU to have the computer function as each component of the wireless cell monitoring system. 
     While representative embodiments of the present invention have been described in detail above, various changes, substitutions, and alternatives may be made without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, even if the claims are changed at the time of filing the application, the inventor intends that the scope of the appended claims or the equivalents thereof be maintained. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be applied to a mobile communication network based on a cellular communication system.