Patent Publication Number: US-2017359742-A1

Title: Monitoring apparatus, wireless communication apparatus, communication system, line use rate calculation method, data transmission method, monitoring method, and computer-readable medium

Description:
TECHNICAL FIELD 
     The present invention relates to calculation of a line use rate and, for example, to a monitoring apparatus, a wireless communication apparatus, a communication system, a line use rate calculation method, a data transmission method, a monitoring method, and a program that calculate a line use rate of a wireless section. 
     BACKGROUND ART 
     In recent years, there have been an increasing number of communication carriers who construct a communication network between apparatuses using a wireless communication line. For example, the wireless communication line is used between base stations in a mobile phone network. A system can be constructed inexpensively in a short time period regardless of terrains between the apparatuses by using the wireless communication line between the apparatuses, such as the base stations. 
     In a case of using the wireless communication line between the apparatuses, it is necessary to grasp fluctuations etc. in a traffic amount between the apparatuses, and to apply an appropriate line capacity according to the traffic amount. For grasping the fluctuations in the traffic amount between the apparatuses, calculation methods of a use rate of the wireless communication line are disclosed in Patent Literatures 1 and 2. 
     Patent Literature 1 describes calculating a use rate of a wireless channel using the number of used time slots. In addition, Patent Literature 2 describes a method of measuring a wireless use rate for each terminal in a wireless communication system using a CDMA (Code Division Multiple Access) scheme. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1 
     Japanese Unexamined Patent Application Publication No. 2007-074239 
     Patent Literature 2 
     Japanese Unexamined Patent Application Publication No. 2013-021503 
     SUMMARY OF INVENTION 
     Technical Problem 
     In a case of applying the appropriate line capacity according to the traffic amount, a monitoring apparatus that monitors a communication system desirably measures traffic of all wireless communication lines in real time. However, the monitoring apparatus needs to collect traffic information from a number of apparatuses, in a case of measuring the traffic of all the wireless communication lines in real time. In a case where the monitoring apparatus collects the traffic information from a number of apparatuses, there arises a problem that the traffic information transmitted and received in the communication system increases, and thus the communication system is congested. 
     An object of the present invention is to provide a monitoring apparatus, a wireless communication apparatus, a communication system, a line use rate calculation method, a data transmission method, a monitoring method, and a program that can efficiently collect traffic information of a wireless communication line in a communication system. 
     Solution to Problem 
     A monitoring apparatus according to a first aspect of the present invention includes: a first data collection unit that collects log information including information indicating change in a modulation scheme within a previously fixed first time period, from a wireless communication apparatus that changes the modulation scheme in conformity with a change in environment of a wireless section; an analysis unit that fixes as a monitored apparatus the wireless communication apparatus that transmitted the log information, in a case where the number of changes in the modulation scheme exceeds a first threshold value in the first time period; a second data collection unit that collects information on a modulation scheme applied when wireless communication is performed for each second time period shorter than the first time period, and information on a data amount transmitted and received by applying the modulation scheme in the second time period, from the wireless communication apparatus specified as the monitored apparatus; and a line use rate calculation unit that calculates a line use rate of a wireless line in the wireless section using the information collected in the second data collection unit. 
     A wireless communication apparatus according to a second aspect of the present invention includes: a log information generation unit that generates log information that indicates information indicating change in a modulation scheme and information on a data amount transmitted and received by applying the modulation scheme, when the modulation scheme was changed in conformity with a change in environment of a wireless section; and a communication unit that transmits to a monitoring apparatus the log information generated within a previously fixed first time period. 
     A communication system according to a third aspect of the present invention includes: a wireless communication apparatus that generates log information indicating information on a data amount transmitted and received by applying a modulation scheme before changed, when the modulation scheme was changed in conformity with a change in environment of a wireless section; and a monitoring apparatus that collects the log information generated in the wireless communication apparatus within a previously fixed first time period, fixes as a monitored apparatus the wireless communication apparatus that transmitted the log information in a case where the number of changes in the modulation scheme exceeds a first threshold value, collects information on a modulation scheme applied when wireless communication is performed for each second time period shorter than the first time period, and information on a data amount transmitted and received by applying the modulation scheme in the second time period, from the wireless communication apparatus specified as the monitored apparatus, and calculates a line use rate of a wireless line in the wireless section. 
     A line use rate calculation method according to a fourth aspect of the present invention is for: collecting log information including information indicating change in a modulation scheme within a previously fixed first time period, from a wireless communication apparatus that changes the modulation scheme in conformity with a change in environment of a wireless section; fixing as a monitored apparatus the wireless communication apparatus that transmitted the log information, in a case where the number of changes in the modulation scheme exceeds a first threshold value in the first time period; collecting information on a modulation scheme applied when wireless communication is performed for each second time period shorter than the first time period, and information on a data amount transmitted and received by applying the modulation scheme in the second time period, from the wireless communication apparatus specified as the monitored apparatus; and calculating a line use rate of a wireless line in the wireless section using the information collected for each the second time period. 
     A data transmission method according to a fifth aspect of the present invention is for: generating log information that indicates information indicating change in a modulation scheme and information on a data amount transmitted and received by applying the modulation scheme, when the modulation scheme was changed in conformity with a change in environment of a wireless section; and transmitting to a monitoring apparatus the log information generated within a previously fixed first time period. 
     A monitoring method according to a sixth aspect of the present invention is for: generating log information indicating information on a data amount transmitted and received by applying a modulation scheme before changed, when the modulation scheme was changed in conformity with a change in environment of a wireless section; collecting the log information generated in a wireless communication apparatus within a previously fixed first time period; fixing as a monitored apparatus the wireless communication apparatus that transmitted the log information, in a case where the number of changes in the modulation scheme exceeds a first threshold value; collecting information on a modulation scheme applied when wireless communication is performed for each second time period shorter than the first time period, and information on a data amount transmitted and received by applying the modulation scheme in the second time period, from the wireless communication apparatus specified as the monitored apparatus; and calculating a line use rate of a wireless line in the wireless section using the information collected for each the second time period. 
     A program according to a seventh aspect of the present invention makes a computer execute: collecting log information including information indicating change in a modulation scheme within a previously fixed first time period, from a wireless communication apparatus that changes the modulation scheme in conformity with a change in environment of a wireless section; fixing as a monitored apparatus the wireless communication apparatus that transmitted the log information, in a case where the number of changes in the modulation scheme exceeds a first threshold value in the first time period; collecting information on a modulation scheme applied when wireless communication is performed for each second time period shorter than the first time period, and information on a data amount transmitted and received by applying the modulation scheme in the second time period, from the wireless communication apparatus specified as the monitored apparatus; and calculating a line use rate of a wireless line in the wireless section using the information collected for each the second time period. 
     Advantageous Effects of Invention 
     According to the present invention, there can be provided a monitoring apparatus, a wireless communication apparatus, a communication system, a line use rate calculation method, a data transmission method, a monitoring method, and a program that can efficiently collect traffic information of a wireless communication line in a communication system. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a configuration diagram of a monitoring apparatus according to an embodiment 1. 
         FIG. 2  is a configuration diagram of a communication system according to an embodiment 2. 
         FIG. 3  is a configuration diagram of an NE according to the embodiment 2. 
         FIG. 4  is a table showing log information according to the embodiment 2. 
         FIG. 5  is a configuration diagram of a monitoring apparatus according to the embodiment 2. 
         FIG. 6  shows graphs explaining a calculation method of a line use rate according to the embodiment 2. 
         FIG. 7  is a flow chart showing a flow of information collection processing between the monitoring apparatus and the NE according to the embodiment 2. 
         FIG. 8  is a flow chart showing a flow of information collection processing in the monitoring apparatus according to the embodiment 2. 
         FIG. 9  is a flow chart showing a flow of log information generation processing in the NE according to the embodiment 2. 
         FIG. 10  is a flow chart showing a flow of information collection processing between a monitoring apparatus and an NE according to an embodiment 3. 
         FIG. 11  is a flow chart showing a flow of information collection processing in the monitoring apparatus according to the embodiment 3. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiment 1 
     Hereinafter, embodiments of the present invention will be explained with reference to drawings. A monitoring apparatus  10  of  FIG. 1  communicates with a wireless communication apparatus  20 . The monitoring apparatus  10  may be a computer apparatus that operates by a CPU (Central Processing Unit) executing a program stored in a memory. The monitoring apparatus  10  has: a data collection unit  11 ; a data collection unit  12 ; an analysis unit  13 ; and a line use rate calculation unit  14 . 
     The wireless communication apparatus  20  may be, for example, an apparatus that performs microwave communication with an opposed apparatus. In addition, a wired communication line may be used between the monitoring apparatus  10  and the wireless communication apparatus  20 , or a wireless communication line may be used therebetween. 
     The data collection unit  11  collects log information including information indicating a change in a modulation scheme within a previously fixed time period T 1 , from the wireless communication apparatus  20  that changes the modulation scheme in conformity with a change in environment of a wireless section. In order to change the modulation scheme in conformity with the change in environment of the wireless section, an AMR (Adaptive Modulation Radio) function using multiple levels QAM may be used. The wireless section is, for example, a section between the wireless communication apparatus  20  and the other wireless communication apparatus that perform communication with each other through the wireless communication line. The wireless communication apparatus  20  may apply 32QAM as the modulation scheme, for example, in a case where communication quality of the wireless section is good, and may apply 16QAM decreased in multiple levels in a case where the communication quality of the wireless section is deteriorated. The communication quality of the wireless section may be determined using a previously fixed reference value of the communication quality. The communication quality may be, for example, fixed based on the number of discarded packets, a data rate, etc. 
     The previously fixed time period T 1  may be, for example, fixed as a fifteen-minute period or the like. The log information is information regularly generated by the wireless communication apparatus  20 . The log information may be statistical information generated using information accumulated in the memory. The information indicating the change in the modulation scheme, the information being included in the log information, may be information on the number of changes in the modulation scheme or a timing at which the modulation scheme was changed. 
     The analysis unit  13  fixes as a monitored apparatus the wireless communication apparatus  20  that transmitted the log information, in a case where the number of changes in the modulation scheme exceeds a threshold value. The monitored apparatus transmits information to the monitoring apparatus  10  more frequently compared with an unmonitored apparatus. The analysis unit  13  specifies the number of changes in the modulation scheme from the information indicating the change in the modulation scheme, the information being included in the log information. The analysis unit  13  determines whether or not the specified number of times exceeds the threshold value by comparing the specified number of times with the previously fixed threshold value. 
     The data collection unit  12  collects information on a modulation scheme applied when wireless communication is performed for each time period T 2  shorter than the time period T 1 , and information on a transmitted and received data amount, from the wireless communication apparatus  20  specified as the monitored apparatus in the analysis unit  13 . For example, in a case where the time period T 1  is set to be fifteen minutes, the time period T 2  may be set to be one minute or the like. The information collected by the data collection unit  12  may be the log information generated by the wireless communication apparatus  20 , or may be the information accumulated in the memory, the information being used by the wireless communication apparatus  20  in order to generate the log information. In addition, although the data collection unit  11  and the data collection unit  12  are shown as different functional blocks in  FIG. 1 , they may be realized by the same functional block or hardware. 
     The line use rate calculation unit  14  calculates a line use rate of the wireless communication line in the wireless section managed by the wireless communication apparatus  20 , using the information collected in the data collection unit  12 . For example, the line use rate calculation unit  14  calculates a line use rate in the time period T 2  using a line capacity fixed by the applied modulation scheme, and the transmitted and received data amount. 
     As explained above, the monitored apparatus can be fixed using the information on the number of changes in the modulation scheme by using the monitoring apparatus  10  of  FIG. 1 . Generally, in a case where communication quality is stable, it is considered that there is small number of changes in the modulation scheme. In other words, in a case where the number of changes in the modulation scheme exceeds the threshold value, it can be regarded that the communication quality is unstable. Therefore, the monitoring apparatus  10  can fix as a monitored apparatus a wireless communication apparatus that manages a wireless section in which communication quality is unstable. 
     Further, the monitoring apparatus  10  can collect data from the monitored apparatus for each time period T 2  shorter than the time period T 1 . That is, the monitoring apparatus  10  limits wireless communication apparatuses to which the time period T 2  is applied, and thereby a data amount transmitted and received in the entire communication system can be decreased compared with a case where the time period T 2  is applied to all the wireless communication apparatuses. Hereby, congestion can be prevented from occurring in the communication system. 
     Embodiment 2 
     Subsequently, using  FIG. 2 , there will be explained a configuration example of a communication system according to an embodiment 2 of the present invention. The communication system of  FIG. 2  has the monitoring apparatus  100  and NEs (Network Elements)  30  to  90 . The NE corresponds to the wireless communication apparatus  20  of  FIG. 1 . The NE  30  wirelessly communicates with the NE  60 . The NE  40  wirelessly communicates with the NE  70 . The NE  50  wirelessly communicates with the NEs  80  and  90 . In addition, the NEs  60  to  90  may wirelessly communicate with other NEs that are not shown. 
     The monitoring apparatus  100  communicates with the NEs  30  to  50  through a communication network. For example, the monitoring apparatus  100  collects from the NE  30  information such as a traffic amount between the NE  30  and the NE  60 . Further, the monitoring apparatus  100  collects from the NE  60  information such as a traffic amount between the NE  60  and the other NE. At this time, the monitoring apparatus  100  collects from the NE  60  the information such as the traffic amount through a wireless communication line between the NE  30  and the NE  60 , and the communication network. 
     That is, in a case where the monitoring apparatus  100  collects information on all wireless sections for each time period T 2 , congestion may occur not only in the communication network between the NEs  30  to  50  and the monitoring apparatus  100  but in the wireless sections between the NEs. Therefore, the monitoring apparatus  100  limits the NEs from which information is collected, and thereby congestion can be avoided from occurring, or points where the congestion occurs can be decreased. 
     Subsequently, using  FIG. 3 , there will be explained a configuration example of the NE  30  according to the embodiment 2 of the present invention. The NE  30  has an MIB (Management Information Base) information generation unit  31  and a log information generation unit  32 . 
     The MIB information generation unit  31  generates MIB information. The MIB information includes the traffic amount transmitted and received between the NE  30  and the NE  60 , a modulation scheme applied to wireless communication, timing at which the traffic amount was measured, a data loss amount, etc. In addition, as described above, MIB information on a communication situation may be referred to as RMON (Remote network Monitoring) MIB information. The MIB information generation unit  31  may store the generated MIB information in a memory of the NE  30 , etc. The MIB information may be referred to as memory information. 
     The log information generation unit  32  generates log information that is statistical information using plural pieces of MIB information. For example, the log information generation unit  32  may generate the log information using plural pieces of MIB information collected for a predetermined time period. 
     Here, log information generated by the log information generation unit  32  will be explained using  FIG. 4 . The log information of  FIG. 4  indicates that wireless communication to which 32QAM has been first applied as the modulation scheme is started. Further, it indicates that the modulation scheme is changed to 16QAM after elapse of ten minutes from the communication start. Further, it indicates that in ten minutes after the communication start, the modulation scheme of 32QAM is applied, and that traffic of 1980M Octet is generated. In addition, it indicates that 800 packets are lost in ten minutes after the communication start. 
     Further, the log information of  FIG. 4  indicates that the modulation scheme is changed to 32QAM after elapse of fifteen minutes from the communication start, in five minutes from the elapse of ten minutes to the elapse of fifteen minutes, the modulation scheme of 16QAM is applied, and that traffic of 495M Octet is generated. In addition, it indicates that 400 packets are lost in five minutes from the elapse of ten minutes to the elapse of fifteen minutes. 
     As shown in  FIG. 4 , the log information is generated so that timing at which the modulation scheme was changed, and a traffic amount and a packet loss amount generated before the modulation scheme was changed can be grasped. 
     Subsequently, using  FIG. 5 , there will be explained a detailed configuration example of the monitoring apparatus  100  according to the embodiment 2 of the present invention. The monitoring apparatus  100  has a configuration in which an output unit  15  is added to the monitoring apparatus  10  of  FIG. 1 . In  FIG. 5 , points different from  FIG. 1  will be mainly explained. 
     The data collection unit  11  collects log information regularly generated in the log information generation unit  32 . In addition, the data collection unit  11  collects log information from all the NEs arranged in a monitored area. For example, the data collection unit  11  collects log information from the NEs  30  to  90  of  FIG. 4 . For example, the data collection unit  11  may use a FTP (File Transfer Protocol) in collecting the log information. 
     The data collection unit  12  collects MIB information generated in the MIB information generation unit  31  of a monitored NE. The monitored NE is an NE decided in the analysis unit  13  from the plurality of NEs arranged in the monitored area. For example, in a case where the NE  30  is decided as the monitored NE in the analysis unit  13 , the data collection unit  12  collects MIB information from the NE  30  among the NEs  30  to  90 . The data collection unit  12  collects the MIB information from the monitored NE in a period shorter than a period in which the data collection unit  11  collects the log information. 
     The data collection unit  12  may operate as an SNMP (Simple Network Management Protocol) manager in order to collect the MIB information from the monitored NE. In addition, the MIB information generation unit  31  that transmits the MIB information to the data collection unit  12  may operate as an SNMP agent. 
     The analysis unit  13  decides an NE to be monitored using the collected log information. For example, assume that the analysis unit  13  has received the log information shown in  FIG. 4  from the NE  30 . The log information shown in  FIG. 4  indicates that the number of changes in the modulation scheme is twice. For example, in a case where a threshold value is fixed as once, the analysis unit  13  determines that communication quality of the wireless section managed by the NE  30  is unstable, since the number of changes in the modulation scheme indicated in the received log information is twice. In this case, the analysis unit  13  sets the NE  30  as a monitoring target. That is, in a case where the number of changes in the modulation scheme exceeds the threshold value, the analysis unit  13  sets the NE having transmitted the log information as the monitoring target. 
     Alternatively, the analysis unit  13  may decide the NE set as the monitoring target using the number of times the modulation scheme was changed in order to decrease modulation multiple levels among the number of changes in the modulation scheme. For example, in the log information of  FIG. 4 , the modulation scheme is changed once from 32QAM to 16QAM, and is changed once from 16QAM to 32QAM. 
     In the case where the modulation scheme is changed from 32QAM to 16QAM, the analysis unit  13  determines that the modulation scheme is changed in order to decrease the modulation multiple levels. In this case, the analysis unit  13  compares the number of times the modulation scheme was changed in order to decrease the modulation multiple levels, i.e. once, with the number of times fixed as the threshold value, and determines whether or not the communication quality of the wireless section managed by the NE  30  is unstable. The AMR function generally changes the modulation scheme so as to decrease the modulation multiple levels, in a case where the communication quality is lowered. Therefore, it can be estimated whether or not the communication quality of the wireless section managed by the NE is deteriorated, by using only the number of times the modulation scheme was changed so that the multiple levels may be decreased, among the number of changes in the modulation scheme. 
     The output unit  15  may be, for example, an LCD (Liquid Crystal Display) or the like. The output unit  15  displays the line use rate calculated in the line use rate calculation unit  14 . In addition, the output unit  15  may transmit to the other apparatus information on the line use rate calculated in the line use rate calculation unit  14 . The monitoring apparatus  100  may make a display unit of the other apparatus display the line use rate calculated in the monitoring apparatus  100  by transmitting the information on the line use rate to the other apparatus. The monitoring apparatus  100  may transmit the line use rate to the other apparatus through a wireless communication line or a wired communication line. 
     Subsequently, a calculation method of the line use rate in the line use rate calculation unit  14  will be explained using  FIG. 6 . Note that in  FIG. 6 , a generally used calculation method of a line use rate will also be explained as a comparative example. An upper graph of  FIG. 6  shows results of having applied the generally used calculation method of the line use rate, and a lower graph of  FIG. 6  shows results of the line use rates calculated using the line use rate calculation unit  14  of  FIG. 5 . 
     A general line use rate is, for example, calculated using regularly collected log information. For example, a case will be explained where log information is collected for each fifteen minutes. Assume that traffic of 2475M Octet has occurred in fifteen minutes. In addition, information on the applied modulation scheme is not shown in general log information. Therefore, the line use rate is calculated assuming that a particular modulation scheme is used without consideration for the AMR function. In the upper graph of  FIG. 6 , a case will be explained where 16QAM is applied as the modulation scheme. 
     In a case of applying the generally used calculation method of the line use rate, a line speed (Mbps) is calculated by the following formula: 2475M×8/60 s/15 m=22 Mbps. In addition, in a case where a line capacity when 16QAM is applied as the modulation scheme is set to be 22 Mbps, the line use rate is calculated by the following formula: 22 Mbps/22 Mbps=100%. That is, the upper graph of  FIG. 6  shows that the line use rate is 100% until elapse of fifteen minutes from measurement start. 
     Meanwhile, in a case of using the line use rate calculation unit  14  of  FIG. 5 , the line use rate can be calculated in consideration of change in the modulation scheme. Specifically, there will be explained a case of using the log information shown in  FIG. 4 .  FIG. 4  shows that the modulation scheme is changed from 32QAM to 16QAM after elapse of ten minutes from measurement start. In addition, it shows that traffic of 1980M Octet has occurred in ten minutes after the measurement start. Hereby, a line speed for ten minutes after the measurement start is calculated by the following formula: 1980M×8/60 s/15 m=26.4 Mbps. In addition, in a case where a line capacity when 32QAM is applied as the modulation scheme is set to be 28 Mbps, the line use rate is calculated by the following formula: 22 Mbps/28 Mbps=approximately 94%. 
     Further,  FIG. 4  shows that traffic of 495M Octet has occurred in five minutes from elapse of ten minutes to elapse of fifteen minutes. Hereby, a line speed for this five minutes is calculated by the following formula: 495M×8/60 s/5 m=13.2 Mbps. In addition, in a case where the line capacity when 16QAM is applied as the modulation scheme is set to be 22 Mbps, the line use rate is calculated by the following formula: 13.2 Mbps/22 Mbps=60%. 
     As described above, timing at which the modulation scheme was changed is specified, the line use rate is calculated in consideration of the line capacity according to the applied modulation scheme, and thereby an accurate line use rate can be calculated. For example, in a case of using the general calculation method of the line use rate in an example of  FIG. 6 , the line use rate is calculated to be 100% for fifteen minutes after measurement start. In this case, an administrator of a communication network, etc. needs to increase the line capacity, etc. In addition, an amount of capital investment to the communication network also increases along with the increase in line capacity. 
     In contrast with this, in the case of using the line use rate calculation unit  14  of  FIG. 5 , it turns out that the line use rate for fifteen minutes after the measurement start actually has not reached 100%. Therefore, the administrator of the communication network, etc. can determine that there is no need to immediately increase the line capacity. 
     In addition, a modulation scheme with more multiple levels than 16QAM may be used in some cases in the general calculation method of the line use rate of  FIG. 6 . In such a case, the line use rate becomes lower than the case of using 16QAM as the modulation scheme. However, the line use rate using the line use rate calculation unit  14  of  FIG. 5 , which indicates a value near an actual line use rate, may become higher in some cases than the line use rate calculated in accordance with the general calculation method of the line use rate. The administrator of the communication network, etc. will refer to a line use rate lower than the actual line use rate, in deciding a time to increase the line capacity, etc. in accordance with the general calculation method of the line use rate. In this case, it is also considered that the administrator of the communication network, etc. make mistakes in deciding the time to increase the line capacity. 
     Subsequently, using  FIG. 7 , there will be explained a flow of information collection processing between the monitoring apparatus  100  and the NE  30  according to the embodiment 2 of the present invention. First, the monitoring apparatus  100  transmits a log information transmission request message to the NE  30  (S 11 ). Next, the NE  30  transmits to the monitoring apparatus  100  log information generated in the log information generation unit  32  as a response of the log information transmission request message (S 12 ). Next, the analysis unit  13  of the monitoring apparatus  100  analyzes the received log information (S 13 ). Specifically, the analysis unit  13  determines whether or not the number of changes in the modulation scheme in the NE  30  exceeds a previously fixed threshold value. Here, assume that the analysis unit  13  has determined that the number of changes in the modulation scheme in the NE  30  exceeds the previously fixed threshold value. 
     Next, the monitoring apparatus  100  transmits a memory information transmission request message to the NE  30  (S 14 ). Memory information may be information stored in the memory of the NE  30  and, for example, may be MIB information. Next, the NE  30  transmits to the monitoring apparatus  100  the memory information generated in the MIB information generation unit  31  as a response of the memory information transmission request message (S 15 ). Next, the monitoring apparatus  100  and the NE  30  repeats processing similar to that of steps S 14  and S 15 , in steps S 16  and S 17 . In addition, the monitoring apparatus  100  collects the memory information in a period shorter than a period to collect the log information. 
     In addition, a frequency at which the monitoring apparatus  100  collects the memory information may be fixed according to the number of changes in the modulation scheme in the log information analyzed in the analysis unit  13 . For example, the monitoring apparatus  100  estimates that the larger the number of changes in the modulation scheme in the log information is, the more the communication quality in the wireless section is deteriorated, and it may increase the frequency of collecting the memory information. In addition, the less the number of changes in the modulation scheme in the log information is, the more the monitoring apparatus  100  may reduce the frequency of collecting the memory information. 
     Subsequently, using  FIG. 8 , there will be explained a flow of information collection processing in the monitoring apparatus  100  according to the embodiment 2 of the present invention. First, the data collection unit  11  determines whether or not it is an acquisition time in a steady state where log information is collected (S 21 ). The acquisition time in the steady state is set based on the previously fixed time period T 1 . If the data collection unit  11  determines that it is not the acquisition time in the steady state, it repeats processing of step S 21 . 
     If the data collection unit  11  determines that it is the acquisition time in the steady state, it collects the log information from the NE  30  (S 22 ). Specifically, the data collection unit  11  transmits a log information transmission request message to the NE  30 , and receives the log information as a response of the message. 
     Next, the analysis unit  13  specifies the number of changes in the modulation scheme from the log information, and determines whether or not the number of changes in the modulation scheme exceeds a threshold value (S 23 ). If the analysis unit  13  determines that the number of changes in the modulation scheme does not exceed the threshold value, it repeats the processing of step S 21 . If the analysis unit  13  determines that the number of changes in the modulation scheme exceeds the threshold value, it changes a period to acquire information from the NE  30  (S 24 ). In addition, the analysis unit  13  changes the period to acquire the information, and also changes information to be acquired. Specifically, although the analysis unit  13  collects the log information from the NE  30  in a period of the time period T 1 , it decides to collect memory information from the NE  30  in a period of the time period T 2 . Time information set based on the period of the time period T 2  indicates an acquisition time at the time of line deterioration. The line deterioration means that communication quality in the wireless section is deteriorated. 
     Next, the data collection unit  12  determines whether or not now is the acquisition time at the time of line deterioration (S 25 ). If the data collection unit  12  determines that now is not the acquisition time at the time of line deterioration, it repeats processing of step S 25 . If the data collection unit  12  determines that now is the acquisition time at the time of line deterioration, it acquires the memory information from the NE  30  (S 26 ). Specifically, the data collection unit  12  transmits a memory information transmission request message to the NE  30 , and receives the memory information as a response of the message. 
     Next, the line use rate calculation unit  14  calculates a line use rate of a line managed by the NE  30  using the acquired memory information (S 27 ). Next, the data collection unit  12  determines whether to end processing to acquire the memory information (S 28 ). Acquisition processing of the memory information may be ended, for example, in a case where information indicating processing end from a user is input, or in a case where the previously fixed number of times of processing to acquire the memory information is carried out. 
     If the data collection unit  12  determines that the processing to acquire the memory information is not ended, it repeats the processing of step S 25 . If the data collection unit  12  determines that the processing to acquire the memory information is ended, it ends the processing. 
     Subsequently, using  FIG. 9 , there will be explained a flow of log information generation processing in the NEs according to the embodiment 2 of the present invention. First, the log information generation unit  32  determines whether or not the modulation scheme was changed in the MIB information generated in the MIB information generation unit  31  (S 101 ). Next, if the log information generation unit  32  determines that the modulation scheme was changed, it updates or generates the log information (S 102 ). The log information generation unit  32  repeats processing of step S 101  or later, after updating the log information. 
     In step S 101 , if the log information generation unit  32  determines that the modulation scheme was not changed, it determines whether or not it is a time or timing to generate the log information (S 103 ). If the log information generation unit  32  determines that it is the time to generate the log information, it updates or generates the log information (S 102 ). If the log information generation unit  32  determines that it is not the time to generate the log information, it repeats the processing of step S 101  or later. 
     As explained above, the monitoring apparatus  100  can grasp the number of changes in the modulation scheme between the NEs that communicate with each other through the wireless communication line, by using the communication system according to the embodiment 2 of the present invention. Hereby, the monitoring apparatus  100  can estimate whether or not communication quality between the NEs is deteriorated. In addition, the monitoring apparatus  100  can specify the NE that manages the wireless section in which communication quality is deteriorated. Further, the monitoring apparatus  100  can acquire information on a generated traffic amount and an applied modulation scheme only from the specified NE in a short period. As described above, a load of the entire communication system can be prevented from increasing by limiting the NE from which the information is acquired in the short period. 
     Embodiment 3 
     Subsequently, using  FIG. 10 , there will be explained a flow of information collection processing between the monitoring apparatus  100  and the NE  30  according to an embodiment 3 of the present invention. Since steps S 31  to S 33  are similar to steps S 11  to S 13  of  FIG. 7 , detailed explanation thereof is omitted. 
     Assume that in step S 33 , the analysis unit  13  of the monitoring apparatus  100  has determined that the number of changes in the modulation scheme in the NE  30  exceeds a previously fixed threshold value. In this case, the data collection unit  11  transmits a change request message of a log information recording period (S 34 ). In the change request message of the log information recording period, there is set a content to instruct the log information generation unit  32  of the NE  30  to make a period to generate log information using MIB information shorter than a current period. That is, the monitoring apparatus  100  collects the log information generated by the log information generation unit  32  as information acquired in a short period from the NE  30  in which communication quality is deteriorated. 
     Next, the NE  30  changes the recording period of the log information in accordance with the change request message of the log information recording period (S 35 ). In other words, the NE  30  changes it so that a time between log information generation times may become shorter. 
     Next, the monitoring apparatus  100  transmits a log information transmission request message to the NE  30  (S 36 ). Next, the NE  30  transmits log information as a response of the log information transmission request message (S 37 ). The log information transmitted by the NE  30  is information generated in a period changed in accordance with the change request message of the log information recording period. Also in steps S 38  and S 39 , processing of steps S 36  and S 37  is repeated. In addition, the monitoring apparatus  100  makes an interval to transmit the log information transmission request message of step S 36  or later shorter than an interval to transmit the log information transmission request message in step S 31   
     Subsequently, using  FIG. 11 , there will be explained a flow of information collection processing in the monitoring apparatus  100  according to the embodiment 3 of the present invention. Since steps S 41  to S 44  are similar to steps S 21  to S 24  of  FIG. 8 , detailed explanation thereof is omitted. In step S 44 , the analysis unit  13  changes a time period to collect log information from the NE  30  from the time period T 1  to the time period T 2 . However, in processing in step S 44 , information to be acquired is not changed to memory information unlike step S 24  of  FIG. 8 . That is, the analysis unit  13  collects the log information, even after the period to acquire the information is changed. 
     Next, the analysis unit  13  transmits a change request message of a log information recording period to the NE  30  through the data collection unit  11  (S 45 ). Since steps S 46 , S 48 , and S 49  are similar to steps S 25 , S 27 , and S 28  of  FIG. 8 , detailed information thereof is omitted. Step S 47  is different from step S 26  of  FIG. 8  in that the monitoring apparatus  100  acquires the log information. 
     As explained above, by using the communication system according to the embodiment 3 of the present invention, the monitoring apparatus  100  can acquire the log information from the NE that manages the wireless section in which the communication quality is deteriorated, after the period to acquire the information is shortened. Hereby, the monitoring apparatus  100  need not be equipped with a function to collect the MIB information from the NE  30 , and can be equipped with only a function to collect the log information. Hereby, a processing load in the monitoring apparatus  100  can be reduced. 
     Although the present invention has been explained as a configuration of hardware in the above-mentioned embodiments, the present invention is not limited to this. In the present invention, the processing in  FIGS. 8, 9, and 11  can also be realized by making a CPU (Central Processing Unit) execute a computer program. 
     In the above-mentioned examples, the program is stored using various types of non-transitory computer-readable media, and can be supplied to a computer. The non-transitory computer-readable media include various types of tangible storage media. Examples of the non-transitory computer-readable media include: a magnetic recording medium (for example, a flexible disk, a magnetic tape, a hard disk drive); a magnetic optical recording medium (for example, a magnetic optical disk); a CD-ROM (Read Only Memory); a CD-R; a CD-R/W; and a semiconductor memory (for example, a mask ROM, a PROM (Programmable ROM), an EPROM (Erasable PROM), a flash ROM, an RAM (Random Access Memory)). In addition, the program may be supplied to the computer by various types of transitory computer-readable media. Examples of the transitory computer-readable media include an electrical signal, an optical signal, and an electromagnetic wave. The transitory computer-readable medium can supply the program to the computer through a wired communication path, such as an electric wire and an optical fiber, or a wireless communication path. 
     Note that the present invention is not limited to the above-described embodiments, and that they can be appropriately changed without departing from the scope of the invention. 
     Hereinbefore, although the invention in the present application has been explained with reference to the embodiments, it is not limited by the above. Various changes that can be understood by those skilled in the art can be made to the configurations and the details of the invention in the present application within the scope of the invention. 
     This application claims priority based on Japanese Patent Application No. 2015-000181 filed on Jan. 5, 2015, and the entire disclosure thereof is incorporated herein. 
     REFERENCE SIGNS LIST 
     
         
           10  monitoring apparatus 
           11  data collection unit 
           12  data collection unit 
           13  analysis unit 
           14  line use rate calculation unit 
           15  output unit 
           20  wireless communication apparatus 
           30  NE 
           30  to  90  NE 
           31  MIB information generation unit 
           32  log information generation unit 
           100  monitoring apparatus