Abstract:
A communication control apparatus that controls a wireless communication between a base station and a terminal, the communication control apparatus including: a memory configured to store combinations of each of threshold values, each of areas, and each of realtimenesses, and a processor configured to obtain a specified threshold value of the threshold values by referring the combinations in accordance with a specified area and a specified realtimeness, the specified area being one of the areas where the terminal is located, the specified realtimeness being one of the realtimenesses and being information which indicates how long a delay time from requesting a data communication to performing the data communication is acceptable, and to permit the terminal the data communication, when a channel quality between the terminal and the base station is better than the specified threshold value.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2012-148937 filed on Jul. 2, 2012, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The present invention relates to a communication control apparatus, a communication control system and a communication control method that control communication with respect to a mobile terminal located within a communication area. 
     BACKGROUND 
     Recently, the traffic of the mobile communication system is increasing continuously in line with the distribution of a multifunctional mobile terminal called a smart phone. As a countermeasure for such an increase in traffic, a policy measure is being proposed in which the communication channel capacity between a base station and a mobile terminal is increased to increase the communication capability of the entire mobile communication system. As such, even if a service provider increases the communication capacity, the location of a mobile terminal of a user frequently changes, and thus, the number of mobile terminals located at a certain area frequently varies. As a result, an imbalance in the number of mobile terminals (frequency utilization efficiency in communication) occurs. In an effort to resolve problems related to such variation in the number of mobile terminals in each area, there is a technology in which data communication (download transmission) from a base station for a mobile terminal is controlled. 
     For example, there is a technology in which a movement path of a mobile terminal is estimated and variation in wireless resources in each area is predicted along the estimated movement path in order to perform a communication control in accordance with the wireless resources conditions. See, for example, Japanese Laid-Open Patent Publication No. 2009-188883. For example, in an area where a wireless resource is congested, communication may not be allowed for the mobile terminal until the mobile terminal moves to a next area where the mobile terminal would not experience the wireless resource congestion, so that it is possible to efficiently utilize the wireless resources. 
     As another example, there is a technology in which a base station receives a report from a mobile terminal regarding the channel quality of a downlink communication directed from the base station to the mobile terminal, and the base station acquires a temporal distribution of the channel quality to equally allot channels for transmission with respect to a plurality of mobile terminals. See, for example, Japanese Laid-Open Patent Publication No. 2003-152630. In addition, there is a technology in which a mobile terminal investigates a path appropriate for a destination information and an intended communication condition (e.g., a real time nature, or a bit rate), and performs a communication when the location of the mobile terminal which has moved is in conformity with the communication condition. As a result, the channel quality and communication efficiency may be improved. See, for example, Japanese Laid-Open Patent Publication No. 2008-236381. 
     SUMMARY 
     According to an aspect of the invention, a communication control apparatus that controls a wireless communication between a base station and a terminal, the communication control apparatus including: a memory configured to store combinations of each of threshold values, each of areas, and each of realtimenesses, and a processor configured to obtain a specified threshold value of the threshold values by referring the combinations in accordance with a specified area and a specified realtimeness, the specified area being one of the areas where the terminal is located, the specified realtimeness being one of the realtimenesses and being information which indicates how long a delay time from requesting a data communication to performing the data communication is acceptable, and to permit the terminal the data communication, when a channel quality between the terminal and the base station is better than the specified threshold value. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating an exemplary configuration of a communication control system according to a first embodiment. 
         FIG. 2  is a block diagram illustrating an example of the functions of a communication control apparatus. 
         FIG. 3  is a view illustrating information stored in a geographic information database. 
         FIGS. 4A and 4B  are views illustrating information stored in a channel quality database. 
         FIG. 5  is a graph illustrating a SINR threshold value calculated by a cumulative probability distribution. 
         FIG. 6  is a block diagram illustrating an exemplary hardware configuration of the communication control apparatus. 
         FIG. 7  is a sequence diagram illustrating the processing contents of a communication control processing performed by the communication control apparatus according to the first embodiment. 
         FIG. 8  is a view for explaining an effect of an improvement of frequency utilization efficiency according to the first embodiment. 
         FIG. 9  is a sequence diagram illustrating the processing contents of a communication control processing performed by the communication control apparatus according to a second embodiment. 
         FIGS. 10A and 10B  are views explaining a re-set state of a threshold value according to a third embodiment. 
         FIG. 11  is a sequence diagram illustrating the processing contents of a communication control processing performed by the communication control apparatus according to the third embodiment. 
         FIGS. 12A and 12B  are views illustrating another example of an area division. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Even if the communication from a base station to a mobile terminal is controlled by predicting a channel quality, the channel quality varies for each timing and location of the mobile terminal within a specific area of a predetermined range. The channel quality such as a SINR (Signal-to-Interference-plus-Noise Ratio) value or throughput varies with being affected by an increase or decrease of the number of mobile terminals within the area, the reflection of radio wave by a mountain or a building, or an interference such as a noise. Therefore, it is difficult to accurately predict the channel quality in a predetermined area, and the communication efficiency has not been improved in a conventional communication control (download control). 
     For example, when it is assumed that a communication is not performed until a mobile terminal reaches an area where wireless resources are not congested, a plurality of mobile terminals that arrived the area perform communications concurrently and thus, a new problem arises in that the wireless resources in the area are consumed quickly and the communications by other mobile terminals cannot be performed. Also, in the conventional technology, when each mobile terminal is under a different communication condition, it may be difficult to perform communications satisfying the communication condition of each mobile terminal and to utilize the wireless resources efficiently. 
     According to one aspect, the present disclosure intends to perform a communication control corresponding to the channel quality of a mobile terminal thereby enhancing the communication efficiency. 
     First Embodiment 
     Overall Configuration of the System 
     Hereinafter, an embodiment appropriate for the disclosed technology will be described with reference to the accompanying drawings.  FIG. 1  is a block diagram illustrating an exemplary configuration of a communication control system according to a first embodiment. The communication control system  100  may be applied to a mobile communication in which a mobile station (mobile terminal)  102  performs a communication with a base station  101  using radio waves. 
     The base station  101  includes a wireless communication unit that performs a wireless communication with the mobile terminal  102  using wireless channel (wireless resources) by radio waves, and a network communication unit that performs a communication with a communication control apparatus  104  via a network  103 . Further, the control unit (not illustrated) controls a data transmission (download) from the base station  101  to the mobile terminal  102  based on a communication control performed by the communication control apparatus  104 . 
     When communicating with the base station  101 , the mobile terminal  102  reports to the base station  101  with various information including location information, channel quality information and communication service information. The base station  101  transmits (transfers) these information reported from the mobile terminal  102  to the communication control apparatus  104 . The mobile terminal  102  may be equipped with functions that generate the location information, the channel quality information and the communication service information. 
     The mobile terminal  102  of the present embodiment includes, for example, a location information detection unit that receives radio waves from a GPS  105  and detects location information of the mobile terminal  102 , and a channel quality measurement unit that measures the channel quality when communicating with the base station  101 . The channel quality parameters to be utilized may include, but not limited to, a signal to interference plus noise ratio (SINR) value received by the mobile terminal, a throughput (communication speed), a reception strength, and a bit error rate. The SINR value will be used as the channel quality parameter in the following description. These channel quality parameters may be readily detected in the mobile terminal  102 . 
     The communication service information is largely divided into two types of information depending on the real time nature (a realtimeness) of data transmission and includes information regarding whether the service requested by the mobile terminal  102  needs to be provided instantly or not by the base station  101 . The realtimeness corresponds to a period of time counted from the time when a user starts to manipulate to the time when the download of data is actually started. For example, a web browsing or moving picture streaming reproduction falls within a real time service which requires an instant data transmission. In the meantime, a non-real time service includes, for example, downloading of an updated application file, or downloading of a document or periodical subscription information that do not need an instant data transmission. 
     In the mobile terminal  102 , data to be handled and data to be downloaded from the base station  101  are determined for each application being activated. Therefore, the mobile terminal  102  can detect a communication service type (the real time nature of data transmission requested to the base station  101 ) based on the data type requested for a download transmission or an application type being activated. Also, the mobile terminal  102  reports the communication service information to the communication control apparatus  104  via the base station  101 . 
     For example, a server may be utilized for the communication control apparatus  104 . In the present embodiment, the communication control for the mobile terminal is not limited to the utilization of a specific single communication control apparatus (server)  104 , but may include the utilization of a cloud computing. The communication control apparatus  104  performs the communication control for the plurality of base stations  101  (and mobile terminals  102 ) via the network  103 . Further, the functions of the communication control apparatus  104  may be provided in the base station  101 . 
     Exemplary Configuration of Communication Control Apparatus 
       FIG. 2  is a block diagram illustrating an example of the functions of a communication control apparatus. The communication control apparatus (server)  104  includes a communication unit  201 , a database unit  202 , and a control unit  203 . The communication unit  201  performs a transmission/reception of data to/from the mobile terminal  102  via the base station  101 . The database unit  202  includes a geographic information database  211  and a channel quality database  212 . The setting unit (not illustrated) stores these information in the database unit  202 . 
     The geographic information database  211  stores information (e.g., a latitude and a longitude) of each of a plurality of partitioned areas formed by dividing the geographic information. The channel quality database  212  stores the channel quality of radio waves (SINR value) and a SINR threshold value for each partitioned area. The setting unit stores the area information divided from outside of the communication control apparatus  104  in the geographic information database  211  of the database unit  202 . Further, the setting unit may perform a processing that divides the geographic information into multiple areas. 
     The control unit  203  includes a location determination unit  221 , a threshold value determination unit  222 , and a communication determination unit  223 . The location determination unit  221  refers to the geographic information database  211  using the location information of the mobile terminal  102  received by the communication unit  201  from the mobile terminal  102 , and determines where the mobile terminal  102  is located on a map. 
     The threshold value determination unit  222  reads and determines the SINR threshold value of the area where the mobile terminal  102  is determined to be located by the location determination unit  221 , from the database unit  202  (channel quality database  212 ). The communication determination unit  223  compares the SINR threshold value determined by the threshold value determination unit  222  with the SINR value reported from the mobile terminal  102 , and according to the comparison result, determines whether the starting of download from the base station  101  is permitted for the mobile terminal  102 . 
     In the following description, when the SINR value equals to or more than the SINR threshold value, it is assumed that the download from the base station  101  is started to the mobile terminal  102 . The determination result regarding whether the communication is allowed or disallowed is transmitted to the base station  101  via the communication unit  201 , and the base station  101  controls the starting of the communication (download) to the mobile terminal  102  in response to the determination result. 
       FIG. 3  is a view illustrating the information stored in a geographic information database. In  FIG. 3 , although a planar image of a map is represented for the convenience of explanation, the information stored in the geographic information database  211  is not limited to an image, and the geographic information database  211  may also store numerical values representing data for a latitude and longitude and data for a structure. In an example represented in  FIG. 3 , the geographic information is partitioned into a plurality of areas a to p by being equally divided into vertically and horizontally. Further, the latitude and longitude ranges for each of the areas a to p are stored as information. Further, the dotted lines in the map represent a topography (altitude line). 
       FIG. 4  is a view representing information stored in the channel quality database. In  FIG. 4 , information about the area c of  FIG. 3  is represented. A channel quality information  212   a  represented in  FIG. 4A  and a threshold value information  212   b  represented in  FIG. 4B  are stored in the channel quality database  212 . The channel quality information  212   a  represented in  FIG. 4A  includes latitudes and longitudes of a plurality of locations in a predetermined range of the area c illustrated in  FIG. 3  and the SINR values of each location. When viewed from  FIG. 3 , the SINR values of each location are distributed in a plurality of locations within the area c. The results of SINR values measured in an area in advance are stored in the channel quality information  212   a . For example, all of the SINR values for each location (latitude and longitude) reported from the mobile terminal  102  may be maintained, and a cumulative probability distribution of the SINR value may be acquired. 
     Additionally, the corresponding location of the channel quality database  212  may always be updated using the SINR value every time when the mobile terminal  102  reports. In this case, the value stored in the channel quality database  212  may be given a weight, and the stored value and the SINR value of the same locations (latitude and longitude) reported from the mobile terminal  102  are added and averaged. That is, the SINR value instantly detected by the mobile terminal  102  is not used as it is, thereby increasing the reliability of the SINR value. 
     The threshold values information  212   b  represented in  FIG. 4B  are SINR threshold values corresponding to the cumulative probability values at the area c. The SINR threshold values corresponding to each of the cumulative probability values of 0% to 100% are acquired in advance. These values are referenced when setting the SINR threshold value with respect to the cumulative probability values according to the communication service of the mobile terminal  102  using the communication service information reported from the mobile terminal  102 . 
     Calculation Example of SINR Threshold Value 
       FIG. 5  is a graph illustrating the SINR threshold values calculated by a cumulative probability distribution. In the graph, the axis of abscissas indicates SINR values and the axis of ordinates indicates cumulative probability values.  FIG. 5  corresponds to a graph on which the threshold value information  212   b  represented in  FIG. 4B  is charted. 
     The SINR threshold values are calculated from the channel quality information  212   a  represented in  FIG. 4A  using the cumulative probability distribution. Specifically, the threshold value determination unit  222  prepares a cumulative probability distribution for the channel quality information  212   a  at each of the areas a to p. In the preparation of the cumulative probability distribution, for example, all of the SINR values of an area (e.g., area c) intended to be prepared are extracted from the database of the channel quality information  212   a  in  FIG. 4A  and the SINR values are listed in an ascending order, such that the SINR values are determined with respect to the cumulative probability value. The prepared cumulative probability distribution becomes the SINR values according to the cumulative probability value as illustrated in  FIG. 5 . 
     The threshold value determination unit  222  sets a different SINR threshold value according to the communication service. As an example of the SINR threshold value, in a case where the communication service information indicates a real time service, the SINR value bbb[dB] corresponding to the cumulative probability value of 10% is set as the SINR threshold value. In the meantime, in a case where the communication service information indicates a non-real time service, the SINR value ddd[dB] corresponding to the cumulative probability value of 70% is set as the SINR threshold value. 
     Accordingly, in the real time service, since the SINR threshold value is set to a relatively low value, the time exceeding the SINR threshold value also increases so that the delay problem in a communication startup is resolved. Further, in the non-real time service, the SINR threshold value is set to a relatively high value. Accordingly, the starting of download is put on hold until the channel quality (SINR) reaches a good state such that the download is started efficiently (in a short time) when the channel quality becomes a good state. 
     For example, it is assumed that the SINR value reported by the mobile terminal  102  is c[dB]. In this case, if the communication service of the mobile terminal  102  is a real time service, download may be started. In contrast, if the communication service of the mobile terminal  102  is a non-real time service, the starting of download is put on hold. 
     In this manner, the starting of a communication is controlled according to the communication service such that it becomes possible to efficiently utilize the communication frequency and flexibly cope with the communication state (channel quality and communication service). Further, in a case where the communication service information is a real time service, it may be set in such a manner that the download may be allowed at any time without setting a SINR threshold value. 
     Exemplary Hardware Configuration of Communication Control Apparatus 
       FIG. 6  is a block diagram illustrating an exemplary hardware configuration of the communication control apparatus. The communication control apparatus  104  includes a CPU  601 , a ROM  602 , a RAM  603 , and an auxiliary storage device  604  such as, for example, a HDD. Further, the respective components are connected with each other via a bus  606 . 
     Here, the CPU  601  is responsible for the control of the entire communication control apparatus  104 . The ROM  602  stores programs such as, for example, a boot program. The RAM  603  is used as a working area of the CPU  601 . 
     A network I/F  607  is connected to the network  103  (see, for example,  FIG. 1 ), and connected to the base station  101  via the network  103 . The network  103  in  FIG. 6  is, for example, a network communication path such as S1 interface between the base station  101  and the communication control apparatus  104 . In addition, it may be configured that an input/output interface (not illustrated) is installed to connect with an input device such as, for example, a keyboard or an output device such as, for example, a display. 
     The communication unit  201  represented in  FIG. 2  may utilize the network I/F  607  represented in  FIG. 6 . The database unit  202  represented in  FIG. 2  may utilize the auxiliary storage device  604  represented in  FIG. 6 . The control unit  203  represented in  FIG. 2  may utilize the CPU  601 , the ROM  602 , and the RAM  603  as illustrated in  FIG. 6 . The ROM  602  stores programs for executing the respective functional units such as the location determination unit  221 , the threshold value determination unit  222 , and the communication determination unit  223  of the control unit  203  as illustrated in  FIG. 2 , and the CPU  601  executes these programs. 
     Communication Control Processes of Communication Control Apparatus 
       FIG. 7  is a sequence diagram illustrating the processing contents of the communication control performed by the communication control apparatus according to the first embodiment. In addition to the processing performed by the communication control apparatus  104 , the processing performed by the mobile terminal  102  is described. 
     First, the mobile terminal  102  acquires the location information, the channel quality information and the communication service information (step S 701 ), and reports the location information, the channel quality information and the communication service information to the communication control apparatus  104  via the base station  101  (step S 702 ). The base station  101  transmits the location information, the channel quality information and the communication service information reported from the mobile terminal  102  to the communication control apparatus  104 . 
     The communication control apparatus  104  determines an area where the mobile terminal  102  is located using the location information reported from the mobile terminal  102  (step S 703 ). Specifically, the location determination unit  221  refers to the geographic information database  211  using the location information reported from the mobile terminal  102 , determines where the mobile terminal  102  is located on a map, and determines an area where the mobile terminal  102  is currently located. 
     Subsequently, the communication control apparatus  104  determines the SINR threshold value of the area from the communication service information reported from the mobile terminal  102  (step S 704 ). Specifically, the threshold value determination unit  222  acquires information regarding the area where the mobile terminal  102  is currently located from the location determination unit  221 . Further, the threshold value determination unit  222  refers to the threshold value information  212   b  of the database unit  202  based on the communication service information reported from the mobile terminal  102  and determines the SINR threshold value corresponding to the communication service. 
     Subsequently, the communication control apparatus  104  compares the SINR value reported from the mobile terminal  102  with the SINR threshold value determined by the threshold value determination unit  222  (step S 705 ). Specifically, the communication determination unit  223  compares the SINR threshold value determined by the threshold value determination unit  222  with the SINR value reported from the mobile terminal  102 . Also, if the SINR value equals to or more than the SINR threshold value (step S 705 : communication is allowed), the communication control apparatus  104  instructs the mobile terminal  102  to start communication (step S 706 ). Accordingly, the mobile terminal  102  starts to download from the base station  101  (step S 707 ). 
     In the meantime, if the SINR value is less than the SINR threshold value (step S 705 : communication is disallowed), the communication control apparatus  104  does not instruct the mobile terminal  102  to start communication, and the processing returns to step S 703  and the operations after step S 703  are repeated again. In this case, the download from the base station  101  by the mobile terminal  102  is put on hold until the SINR value becomes the SINR threshold value or more. 
     After the mobile terminal  102  starts a download processing at step S 707 , the processing returns to step S 701 . Accordingly, the processing described above are continued during the period between download start and download end, and the channel quality and the threshold value are always compared with each other to determine whether the download is to be continued or temporarily stopped. 
     With the communication control described above, it becomes possible to control the starting of data transmission (download) from the base station  101  to the mobile terminal  102  in response to the variation of the channel quality in each area. Moreover, the threshold value of the channel quality is changed depending on the realtimeness (the real time nature) of the communication service in the mobile terminal  102  such that the starting of the download is controlled according to the realtimeness (a real time nature) of each communication service. Accordingly, an instant download may be started for the mobile terminal  102  being serviced with the communication service which requires an instant download. Further, the download may be put on hold for the mobile terminal  102  being serviced with the communication service which does not require an instant download thereby making a wireless resources occupation time to be different. 
     Accordingly, the wireless resources between the base station  101  and the mobile terminal  102  may be utilized efficiently such that the delay in wireless communication between the base station  101  and the mobile terminal  102  can be prevented from being increased and the frequency utilization efficiency also can be enhanced. Conventionally, the threshold value is set to be constant regardless of the communication service type, so that the download has not been started when the channel quality equals to or less than the threshold value and the delay time increases. In contrast, according to the communication control described above, when the communication service type is a real time service, the download can be started while suppressing the delay as much as possible. Further, when the communication service type is a non-real time service, the download is performed at a timing when the channel quality is good, so that the frequency of wireless resources can be efficiently (less occupation time) utilized at the period when the channel quality is good. 
     Regarding Frequency Utilization Efficiency 
       FIG. 8  is a view for explaining the effect of improving the frequency utilization efficiency according to the first embodiment. The axis of ordinates represents the channel quality such as the SINR and the axis of abscissas represents times (and places). The axis of abscissas indicates the moving state of the mobile terminal  102 , and is represented by times (and places) in order to represent the channel quality at a specific place as the mobile terminal  102  is located at different places at different times. 
     In  FIG. 8 , it is assumed that there are two download periods a and b, and the mobile terminal  102  performs a download for t seconds in each of the periods a and b. When comparing the downloaded amount between the download periods a and b, the channel quality during the download period b is better than that of the download period a. In this case, the downloaded amount (the area depicted by inclined lines in  FIG. 8 ) during the download period b becomes larger than that of the download period a. As a result, the frequency utilization efficiency may be enhanced from the result that the download amount for the same t seconds is increased when the download is started at a time when the channel quality becomes in a better state. 
     Second Embodiment 
     Another Example of Acquiring Channel Quality of Mobile Terminal 
     In the first embodiment, the communication control apparatus  104  determines the SINR threshold value using the channel quality (e.g., SINR value) reported from the mobile terminal  102  and determines whether communication is to be allowed or disallowed. Alternatively, without being limited to this, the mobile terminal  102  may be configured to report information regarding the location and the communication service only, and not to report the channel quality (e.g., SINR value). In this case, the location determination unit  221  of the communication control apparatus  104  retrieves the SINR value at the reported location of the mobile terminal  102  or at a location close to the reported location in the channel quality database  212 , and sets the retrieved result as the SINR value. Also, the threshold value determination unit  222  determines the SINR threshold value using the retrieved SINR value in order to determine whether a communication is to be allowed or disallowed. The configuration of the communication control apparatus  104  in the second embodiment is substantially similar to that in  FIG. 2 , but the processing for determining the location of the mobile terminal  102  in the location determination unit  221  is different from that in the first embodiment. 
       FIG. 9  is a sequence diagram illustrating the processing contents of a communication control performed by the communication control apparatus according to a second embodiment. First, the mobile terminal  102  acquires the location information, the channel quality information and the communication service information (step S 901 ), and reports the location information, the channel quality information and the communication service information to the communication control apparatus  104  via the base station  101  (step S 902 ). The base station  101  transmits the location information, the channel quality information and the communication service information reported from the mobile terminal  102  to the communication control apparatus  104 . 
     The communication control apparatus  104  determines an area where the mobile terminal  102  is located using the location information reported from the mobile terminal  102  (step S 903 ). Specifically, the location determination unit  221  refers to the geographic information database  211  using the location information reported from the mobile terminal  102 , determines where the mobile terminal  102  is located on a map, and determines an area where the mobile terminal  102  is currently located. 
     Subsequently, using the location information reported from the mobile terminal  102 , the communication control apparatus  104  retrieves a SINR value stored in the channel quality database  212  corresponding to the same location as the mobile terminal  102  (step S 904 ). Alternatively, without being limited to this, the communication control apparatus  104  may be configured to retrieve the SINR value at a location close to the location reported from the mobile terminal  102 , and determine a SINR threshold value of an area from the communication service information using the retrieved SINR value (step S 905 ). Specifically, the threshold value determination unit  222  acquires the area information where the mobile terminal  102  is currently located from the location determination unit  221 . Moreover, the threshold value determination unit  222  refers to the threshold value information  212   b  of the database unit  202  based on the communication service information reported from the mobile terminal  102  in order to determine the SINR threshold value which corresponds to the communication service. 
     Subsequently, the communication control apparatus  104  compares the SINR value corresponding to a location reported from the mobile terminal  102  with the SINR threshold value determined by the threshold value determination unit  222  (step S 906 ). Specifically, the communication determination unit  223  compares the SINR value of the location reported from the mobile terminal  102  acquired by retrieving the channel quality database  212  with the SINR threshold value determined by the threshold value determination unit  222 . Also, if the SINR value equals to or larger than the SINR threshold value (step S 906 : communication is allowed), the communication control apparatus  104  instructs the mobile terminal  102  to start communication (step S 907 ). Accordingly, the mobile terminal  102  starts download from the base station  101  (step S 908 ). 
     In the meantime, if the SINR value is less than the SINR threshold value (step S 906 : communication is disallowed), the communication control apparatus  104  does not instruct the mobile terminal  102  to start communication, and the processing is returned to step S 903 , and the operations after step S 903  are repeated again. In this case, the download from the base station  101  by the mobile terminal  102  is put on hold until the SINR value becomes larger than or equal to the SINR threshold value. 
     After the mobile terminal  102  starts download at step S 908 , the processing returns to step S 901 . Accordingly, the processing described above continues during the period between download start and download end, and the channel quality and the threshold value are always compared with each other to determine whether download is to be continued or temporarily stopped. 
     As described above, the similar effects as in the first embodiment can be acquired in the second embodiment. According to the second embodiment, the reporting of the channel quality (SINR value) from the mobile terminal  102  may be unnecessary, and also the function of measuring the channel quality in the mobile terminal  102  may be omitted. Further, the transmission of the channel quality information from the mobile terminal  102  to the communication control apparatus  104  may be omitted, thereby reducing the amount of data. 
     Third Embodiment 
     Example of Providing an Upper Limit to Threshold Value 
     The configuration of the communication control apparatus  104  in the third embodiment is substantially similar to that in  FIG. 2 , but the processing of location determination of the threshold value in the threshold value determination unit  222  is different from that in the second embodiment. In the third embodiment, an upper limit value (or a ceiling value) of SINR is provided in the threshold value determination unit  222  for re-setting the SINR threshold value. Also, when the SINR threshold value is higher than the upper limit value of SINR, the upper limit value of SINR is re-set as the SINR threshold value. 
       FIG. 10  is a view explaining a re-set state of the threshold value according to the third embodiment. In  FIG. 10 , the axis of abscissas indicates the areas and the axis of ordinates indicates the SINR, and three areas a, b, and c are depicted. In  FIG. 10A , the SINR threshold value and the upper limit value of SINR for each of areas a, b and c are depicted. For the areas a and c, the SINR threshold values are lower than the upper limit value of the SINR and thus, the SINR threshold values are used as they are, as illustrated in  FIG. 10B . 
     In the meantime, for the area b illustrated in  FIG. 10A , the SINR threshold value has exceeded the upper limit value of the SINR. In this case, the threshold value determination unit  222  sets the SINR threshold value of the area b as the upper limit value of the SINR as illustrated in  FIG. 10B . In this case, the SINR threshold value of the area b is made to be lowered to the upper limit value of the SINR. As described above, a similar download control is performed to the first embodiment using the re-set SINR threshold value. 
     Accordingly, as compared to the time before the SINR threshold value is changed in the area b, the downloaded amount (an area depicted by inclined lines in  FIG. 10 ) may be made larger along with the increasing of the size of the area b in which the download is performed, at the time after the SINR threshold value has been changed. 
     The determination method of the upper limit value of the SINR may specify a single upper limit value for the entire country regardless of the areas. In addition, districts, metropolis or administrative districts (e.g., prefectures in Japan), or the earth may be assumed as a big area and a certain percentage value of the cumulative probability distribution in a database for that area may be set as the upper limit value of the SINR. For example, an area with many mountains and an area of the level ground are defined as separate areas such that a predetermined upper limit value of the SINR is set for each of the areas, based on the fact that the channel quality (SINR) is different depending on, for example, a topography. Similarly, an urban area with many buildings and a suburban area are defined as separate areas, such that a predetermined upper limit value of the SINR is set for each of the areas. 
       FIG. 11  is a sequence diagram illustrating the processing contents of the communication control performed by the communication control apparatus according to the third embodiment. First, the mobile terminal  102  acquires location information, channel quality information and communication service information (step S 1101 ), and reports the location information, the channel quality information and the communication service information to the communication control apparatus  104  via the base station  101  (step S 1102 ). The base station  101  transmits the location information, the channel quality information and the communication service information reported from the mobile terminal  102  to the communication control apparatus  104 . 
     The communication control apparatus  104  determines an area where the mobile terminal  102  is located using the location information reported from the mobile terminal  102  (step S 1103 ). Specifically, the location determination unit  221  refers to the geographic information database  211  using the location information reported from the mobile terminal  102 , determines where the mobile terminal  102  is located on a map, and determines an area where the mobile terminal  102  is currently located. 
     Subsequently, the communication control apparatus  104  determines a SINR threshold value of the area from the communication service information reported from the mobile terminal  102  (step S 1104 ). Specifically, the threshold value determination unit  222  acquires the area information regarding where the mobile terminal  102  is currently located from the location determination unit  221 . Further, the threshold value determination unit  222  refers to the threshold value information  212   b  of the database unit  202  based on the communication service information reported from the mobile terminal  102 , and determines a SINR threshold value corresponding to the communication service. 
     Subsequently, the threshold value determination unit  222  of the communication control apparatus  104  compares the SINR threshold value set for the area with a preset upper limit value of SINR, and if necessary, re-sets the SINR threshold value (step S 1105 ). Specifically, if the SINR threshold value equals to or less than the upper limit value of SINR, the threshold value determination unit  222  uses the SINR threshold value as it is. In the meantime, if the SINR threshold value is larger than the upper limit value of the SINR, the threshold value determination unit  222  re-sets the upper limit value of SINR as a SINR threshold value. 
     Thereafter, the communication control apparatus  104  compares the SINR value reported from the mobile terminal  102  with the SINR threshold value determined by the threshold value determination unit  222  (step S 1106 ). Specifically, the communication determination unit  223  compares the SINR threshold value determined by the threshold value determination unit  222  with the SINR value reported from the mobile terminal  102 . Also, if the SINR value equals to or larger than the SINR threshold value (step S 1106 : communication is allowed), the communication control apparatus  104  instructs the mobile terminal  102  to start communication (step S 1107 ). Accordingly, the mobile terminal  102  starts the download from the base station  101  (step S 1108 ). 
     In the meantime, if the SINR value is less than the SINR threshold value (step S 1106 : communication is disallowed), the communication control apparatus  104  does not instruct the mobile terminal  102  to start communication, and the processing returns to step S 703 , and the operations after step S 1103  are repeated again. In this case, the download from the base station  101  by the mobile terminal  102  is put on hold until the SINR value becomes larger than or equal to the SINR threshold value. 
     After the mobile terminal  1108  starts the download at step S 707 , the processing returns to step S 1101 . Accordingly, the processing described above continues during the period between the download start and the download end, and the channel quality and the threshold value are always compared with each other in order to determine whether the download is to be continued or temporarily stopped. 
     According to the third embodiment described above, substantially similar effects to the first embodiment may be obtained. In addition, since an upper limit for the SINR threshold value is set to re-set the SINR threshold value for each area, an appropriate value may be set as the SINR threshold value, thereby enhancing the frequency utilization efficiency. 
     Other Example of Area Division 
     In a method of dividing a map into multiple areas as described above, the map is divided into a checkerboard (matrix) type areas arranged at regular intervals along the east, the west, the north, and the south (latitude and longitude) directions in the example illustrated in  FIG. 3 . Alternatively, without being limited to dividing the map on the basis of the direction, a map may be divided into multiple areas according to the channel quality. For example, the size and shape of the area may be made to vary according to the channel quality (SINR value) or information obtained from the mobile terminal  102 . Another method of dividing the map into multiple areas corresponding to the channel quality may regard neighboring places having approximately the same SINR values stored in the channel quality database  212  as an area, and the map may be divided into these areas. 
     Further, in another method of dividing the map into multiple areas, the map may be divided into the areas that follow a movement direction of the mobile terminal  102  when the moving state can be presupposed. For example, the method may be applied when the mobile terminal  102  moves along a fixed traffic route such as a train or a bus. On the map, it may be understood beforehand that the movement path of the mobile terminal  102  of a user who is in the train follows the track of the train. In this case, the map is divided into multiple areas along the track. For example, neighboring areas are aggregated with reference to the direction of the track. Accordingly, the mobile terminal  102  of the user moves between the presupposed neighboring areas following the movement of the train. 
     The shape of each area may have an angle with respect to the latitude and longitude directions without following the latitude and longitude (east, west, south, north) directions. The size of each area may be lengthened along the track or curve points may be transformed. Further, within the areas of the divided map, an area itself where the mobile terminal  102  cannot enter may not be set for a zone, and the determination process of whether communication is allowed or disallowed may not be performed for the unnecessary area. 
     Accordingly, the communication control apparatus  104  may prevent a frequent area change as the mobile terminal  102  sequentially moves between the predetermined areas, even without analyzing the movement pattern of the mobile terminal  102 . Also, since the mobile terminal  102  remains at an area for a predetermined time before passing through the area, the processing load may be reduced according to the communication control in the communication control apparatus  104 , and a stable communication control (download control) may be performed at a high precision. The method of dividing the map may not be limited to the train track but may also be applied similarly to a bus route since the bus route is predefined as well. 
     Further, in another method of dividing the map into multiple areas, the map may be divided into areas according to a download size (transmission data size requested to the base station  101 ) received by the mobile terminal  102  from the base station  101 . The area size may be changed in response to the download size of the mobile terminal  102 , such that the download control may be performed at a higher precision. An area size change unit (not illustrated) may be provided inside or outside of the location determination unit  221  to change the size of the area. Upon receipt of a report regarding the download size from the mobile terminal  102 , the area size change unit may change the size of the area of the geographic information database  211  in response to the download size. 
       FIG. 12  is a view illustrating another example of the method of dividing the map into multiple areas.  FIG. 12A  is substantially similar to  FIG. 3 . It is assumed that the size of an area used for dividing the map is initially set as the size of area represented in  FIG. 12A . After the initial setting of the size, it is assumed that the area size is changed when the download size of the mobile terminal  102  becomes smaller. In this case, the time needed for the download is also reduced correspondingly. For this reason, the area size change unit of the communication control apparatus  104  changes the size of the area to allow the map to be more finely divided as illustrated in  FIG. 12B . As a result, the number of the areas on the map increases after the size of the area is changed, and also the number of the SINR threshold values increases as well by the number of the areas. 
     Further, the SINR threshold value corresponding to the area after being changed may be obtained using each SINR value of the plurality of locations within one area in response to the change of the area. Accordingly, the determination process whether a communication is allowed or disallowed may be performed during the download for each of the finely divided areas, and the download control may be performed at a higher precision. 
     According to each embodiment described above, the frequency utilization efficiency of wireless channels (wireless resources) may be improved even without predicting the movement path of the mobile terminal or the variation of the SINR value. In particular, since different threshold values are set for each of the various communication services type, it is possible to perform a flexible download control appropriate for the real time nature requested by the communication service. An instant data transmission is ensured for the communication that requires a real time nature to meet the requirement. In the meantime, for a communication type with a non-real time nature, a communication start may be put on hold until the channel quality is improved to a good state, and the download amount increases by communicating in a good state, thereby enhancing the communication efficiency. Further, the change of channel quality such as the change to a good state in channel quality, as described above, occurs from either one of the cases where there is an elapse of time in the same area or where the mobile terminal moves to other areas. 
     Accordingly, the wireless resources are efficiently utilized and, as a result, the frequency utilization efficiency is enhanced. Further, since the mobile terminal may be able to receive download data for a short time in a good state in channel quality, the power consumption required for the download may be reduced and the life of the power supply (battery) of the mobile terminal may be lengthened as well. 
     Further, in each embodiment described above, the type of communication service is divided into two of a real time service and a non-real time service. However, the type of communication service may be more finely divided into, for example, three or more types, and the determination regarding whether the communication is allowed or disallowed may be performed using the number of threshold value corresponding to the number of finely divided areas. Accordingly, the start timing of download may be controlled finely depending on the type of communication service. 
     Further, the communication control method explained in the present embodiment may be implemented by executing a program provided in advance with a personal computer or a workstation. Further, the program is recorded on a computer readable recording medium such as, for example, a hard disc, a flexible disc, a CD-ROM, a MO, a DVD, and the program may be executed through the read-out from the recording medium by the computer. Further, the program may be distributed through a network such as the Internet. 
     According to one aspect, it is possible to perform a communication control according to the channel quality of a mobile terminal, thereby enhancing the communication efficiency. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment(s) of the present invention has (have) been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.