Abstract:
A simple-structure communication checker capable of detecting the communication state of devices communicating in different communication methods is provided. The communication checker includes an SLPR communication detector that detects the communication state through the SLPR service and a FOMA communication detector that detects the communication state through the FOMA service.

Description:
This application claims priority from Japanese Patent Application 2007-097811, filed on Apr. 3, 2007. The entire content of the aforementioned application is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a communication checker for checking the wireless communication state between devices, a communication-state detection system and a method for checking the communication state, more particularly, to a communication checker for checking the communication state of a master unit communicating with a plurality of slave units or the slave units, a communication-state detection system and a method for checking the communication state. 
     2. Description of the Related Art 
       FIG. 6  is a block diagram showing a structure of a wireless communication system. By referring to  FIG. 6 , this wireless communication system includes slave units  30   a  to  30   c  that are connected to a predetermined measuring instrument and transmits the data from the instrument, a master unit  20  that receives the data transmitted from the slave units  30   a  to  30   c , and a management server  40  that manages the data transmitted from the master unit  20 . The communication between the slave units  30   a  to  30   c  and the master unit  20  can be conducted through specified low power radio (hereinafter referred to as “SLPR”) service, while the communication between the master unit  20  and the management server  40  is conducted through Freedom of Mobile Multimedia Access (hereinafter referred to as “FOMA”) (trademark, the rest is omitted) service, which is a mobile cellular telecommunication system. Thus, the master unit  20  includes an SLPR communication unit  21  to use the SLPR service and a FOMA communication unit  22  to use the FOMA service. 
     Such a communication system using the different communication services requires the master unit  20  to be installed at a position where both services deliver high-performance communication. 
     Conventional apparatuses for evaluating the communication state in wireless communications are disclosed in, for example, Japanese unexamined patent publication Nos. 2004-280793 and 2001-168783. Publication No. 2004-280793 discloses a method in which a personal computer evaluates the strength of signals transmitted from wireless computer peripheral devices. 
     Alternatively, publication No. 2001-168783 discloses an apparatus for checking an error rate to readily locate an installation site for a repeater that makes up a network. 
     There are not any other methods for detecting communication states except for the techniques, as described above, which cannot readily detect positions where both the services deliver high-performance communication with the communication system as shown in  FIG. 6 , thus involving a difficulty in determining where the master unit ought to be set up. 
     SUMMARY OF THE INVENTION 
     The present invention is made in view of the above problem and has an object to provide a communication checker and communication-state detection system capable of readily locating an installation site for devices using different communion services. 
     The communication checker according to the present invention includes a first detector that detects the communication state in a first wireless communication method, and a second detector that detects the communication state in a second wireless communication method which is different from the first wireless communication method. 
     In a wireless communication system using two different communication methods, the communication checker capable of detecting the communication states in both the first wireless communication method and the second wireless communication method which is different from the first wireless communication method can readily locate a site desired for communication. 
     Preferably, the communication checker checks the communication state at a site where a master unit communicating with a plurality of slave units and a management server is planned to be installed. The master unit and the slave units communicate with each other in the first wireless communication method, while the master unit and the management server communicate with each other in the second wireless communication method. 
     The first wireless communication method may be the specified low power radio service, and the second wireless communication method may be a wireless service using a cellular phone communication network. 
     The communication checker can be incorporated in the master unit or can be installed alone. 
     The communication checker can include an automatic communication-state checker for automatically checking the communication states and manners with the plurality of slave units and management server. 
     According to another aspect of the present invention, in a communication-state detection system using the above-described communication checker, the master unit is connected to the management server through the second wireless communication method, and the management server stores the communication states, which are detected by the communication checker, between the plurality of slave units and master unit communicating in the first wireless communication method. The communication-state detection system includes a network accessible through the second wireless communication method and a mobile terminal accessible to the network. The mobile terminal can access to the management server via the network to check the communication states between the plurality of slave units and master unit communicating in the first wireless communication method. 
     Preferably, the communication checker detects only the communication state in the first wireless communication method and second wireless communication method. The mobile terminal has a display to display the communication state in the first wireless communication method and second wireless communication method. 
     In another aspect of the present invention, a method for checking communication states at a site where a master unit communicating with a plurality of slave units and a management server is planned to be installed includes a step of detecting the communication state with the slave units in the first wireless communication method by a communication checker at a site where the master unit is planned to be installed, and a step of detecting the communication state with the management server in the second wireless communication method by the communication checker at the site where the master unit is planned to be installed. The second wireless communication method is different from the first wireless communication method. 
     Preferably, the method further includes a step of storing the communication states, between the plurality of slave units and master unit communicating in the first wireless communication method, detected by the communication checker in the management server, and a step of allowing a mobile terminal to access the management server via a network to check the communication states between the plurality of slave units and master unit communicating in the first wireless communication method. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing the entire structure of a wireless communication system according to an embodiment of the invention. 
         FIG. 2  is a block diagram showing the structure of a communication checker. 
         FIG. 3  is a flow chart showing the operation of the controller of the communication checker. 
         FIG. 4  is a block diagram showing the entire structure of a master unit according to an embodiment of the invention. 
         FIG. 5  is a block diagram showing another embodiment of the present invention. 
         FIG. 6  is a block diagram showing the entire structure of a conventional wireless communication system. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An embodiment of the present invention will be described below with reference to the drawings.  FIG. 1  is a block diagram showing the structure of a wireless communication system in which a communication checker according to the embodiment is used, and corresponds to  FIG. 6  described in Background Art. Referring to  FIG. 1 , the wireless communication system in this embodiment includes a communication checker  10  placed at a site corresponding to the site where the master unit is installed in  FIG. 6 . The communication checker  10  can check the communication state via both the SLPR service and FOMA service and locate a site desired for both the communication services. 
       FIG. 2  is a block diagram showing the structure of the communication checker  10 . Referring to  FIG. 2 , the communication checker  10  includes a controller  11  that controls the entire communication checker  10 , an SLPR field-strength detector (first detector)  12  that detects the electric field strength of radio waves through the SLPR service (first wireless communication method), a FOMA field-strength detector (second detector)  13  that detects the electric field strength of radio waves through the FOMA service (second wireless communication method), and a display  14  that displays the electric field strength detected by the SLPR field-strength detector  12  and FOMA field-strength detector  13 . 
     The communication checker  10  enables simultaneous detection of the electric field strength of the radio waves through the FOMA service and the SLPR service at the site where the master unit  20  is supposed to be installed, and therefore the installation site of the master unit  20  can be readily determined. 
     Next, a description will be made about the process of detecting the electric field strength by the communication checker  10 . The detection process can be started by operating a switch on the communication checker  10  or upon receipt of a start-up instruction transmitted through communication channels. The communication checker  10  has information, such as the number of the slave units and IDs, registered therein in advance.  FIG. 3  is a flow chart showing the procedural steps of the detection process of the electric field strength performed by the controller  11 . Referring to  FIG. 3 , the communication checker  10  operates the step to sequentially detect the electric field strength of radio waves from the slave units  30   a  to  30   c  communicating through the SLPR service (step S 11 , hereinafter “step” is omitted). After the electric field strength of all slave units is detected (“YES” in S 12 ), detection of electric field strength of radio waves from the management server  40  through the FOMA service is performed (S 13 ). Upon completion of all detecting operations, the communication checker  10  makes determination based on the detected results (S 14 ), and the determination results are displayed on the display  14  (S 15 ). 
     In the case where the communication checker  10  detects reduction of the electric field strength during communication with the slave units, the communication checker  10  can issue an alarm or display the detected results on the display  14 . 
     Next, a description will be made about the method for determining the installation site shown in S 14 . First, the slave units  30   a  to  30   c  are set up at predetermined sites. Next, the communication checker  10 , situated at a place where the master unit  20  is planned to be set up, checks the electric field strength (communication level) of radio waves from each of the slave units  30   a  to  30   c  communicating through the SLPR service and from the management server  40  communicating through the FOMA service. Specifically, the communication checker  10  detects the electric field strength of the radio waves from the slave units  30   a ,  30   b  and  30   c , in this order, through the SLPR service, and then switches to the FOMA service to detect the electric field strength of radio waves from the management server  40 . Subsequently, the position of the master unit is determined according to Table 1 shown below. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Site A 
                 Site B 
                 Site C 
                 Site D 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 SLPR service 
                 FAIL 
                 PASS 
                 FAIL 
                 PASS 
               
               
                   
                 FOMA service 
                 FAIL 
                 FAIL 
                 PASS 
                 PASS 
               
               
                   
                 Determination 
                 FAIL 
                 FAIL 
                 FAIL 
                 PASS 
               
               
                   
                   
               
             
          
         
       
     
     In Table 1, “PASS” in the field of the services denotes that the electric field strength through the service exceeds a predetermined threshold, while “FAIL” denotes that the strength does not reach the threshold. On the other hand, “PASS” in the field of determination denotes that the master unit  20  can be installed at the site without problems, while “FAIL” denotes that the master unit  20  should not be installed at the site. Only when the site has no problem in communication through both the SLPR service and FOMA service, as shown in Table 1, it is determined that the master unit  20  can be installed at the site. 
     Although, in this embodiment, the evaluation of the communication state and the determination of the installation site are made on a two-scale with the threshold, as an example, the present invention is not limited thereto. The evaluation can be made through a scale of three, such as A, B and C, or can be made with the values of the electric field strength as they are. 
     Although, in the above embodiment, the communication checker  10  measures the electric field strength of radio waves emitted from each of the slave units  30   a  to  30   c  as an example, the present invention is not limited thereto; the communication checker  10  can transmit an inquiry signal to each of the slave units  30   a  to  30   c  and receive responses from the slave units  30   a  to  30   c . Alternatively, the communication checker  10  can be provided with an automatic communication-state checking device that automatically checks the communication states and manners with the plurality of slave units and with the management server  40 . In this case, the controller  11  serves as an automatic communication-state checker together with the SLPR field-strength detector  12  and FOMA field-strength detector  13 . 
     Based on the displayed results, it is possible to relocate the slave unit or master unit whose electric field strength failed to reach the predetermined threshold, thereby readily setting the position of the slave units and the master unit. 
     Next, another embodiment of the present invention will be described. Although the communication checker  10  is used as a single unit in the above embodiment, the present invention is not limited thereto; the communication checker  10  can be incorporated in the master unit  20 . The structure of a master unit  25  having the function of the communication checker is illustrated in a block diagram of  FIG. 4 . Referring to  FIG. 4 , the master unit  25  includes, in addition to an SLPR communication unit  21  and a FOMA communication unit  22 , an electric field strength detector  23  that is functionally the same as the communication checker  10 , in other words, that can detect the electric field strength of radio waves through both the SLPR service and FOMA service, a display  24  that displays the communication results, and a controller  26  that controls the entire master unit  25 . 
     As with the above embodiment, the controller  26  of the master unit  25  can automatically detect the electric field strength of a plurality of slave units  30   a  to  30   c  and management server  40  to determine the installation site for the master unit  25  or slave units  30   a  to  30   c.    
     Next, yet another embodiment of the present invention will be described. In this embodiment, the electric field strength detected by the communication checker is used via the management server  40 .  FIG. 5  illustrates the embodiment of the present invention.  FIG. 5A  is a block diagram showing the structure of a communication checker  35  in the embodiment, while  FIG. 5B  illustrates a method for checking the electric field strength by the communication checker  35 . The communication checker  35  in this embodiment is not provided with a display but uses a display of a cellular phone connected to the management server  40  through the FOMA service as a substitute of the display of the communication checker. 
     Referring to  FIG. 5B , in this embodiment, the management server  40  is connected to a network like the Internet  41  and is accessible by an external cellular phone  50  or other communication tools. The connected relationship of the management server  40 , slave units  30   a  to  30   c  and communication checker  35  is shown in  FIG. 1 . 
     As the communication checker  35  that is temporarily placed at a candidate site for the master unit installation is turned on, the process shown in  FIG. 3  is executed. Then, the detection data obtained from the communication between the communication checker  35  and the slave units  30   a  to  30   c  and the communication between the communication checker  35  and the management server  40  are held in the management server  40 , and the detection data is available to view on the display screen of the cellular phone  50 . It is also possible to display only the determination results without displaying the detected data in process. 
     The cellular phone can be a mobile terminal such as a PDA (Personal Data Assistant) but must have Internet access. 
     The embodiment, described above, allowing the detected data to be viewed by using a cellular phone over the FOMA service network accessible to the Internet  41  eliminates the need for a display to be provided on the communication checker  35 . 
     Although the communication checker in the above-described embodiments detects the communication states through the SLPR service and in the FOMA service, the present invention is not limited thereto; the communication checker can be adapted to detect the communication states through a plurality of any types of wireless services. 
     There exists a call-originating type slave unit that transmits data by itself in its own cycle without reference to a master unit and a slave unit employing a master-unit centralized system that transmits the data in response to the instruction from the master unit. The slave unit according to the embodiment can be either one. 
     The foregoing has described the embodiments of the present invention by referring to the drawings. However, the invention should not be limited to the illustrated embodiments. It should be appreciated that various modifications and changes can be made to the illustrated embodiments within the scope of the appended claims and their equivalents.