Abstract:
A controller for use with a radiocommunications system includes a control slot frequency management section  12  which manages the frequency of a control slot assigned to each of the base stations; a broadcast call area number management section  16  which manages broadcast call area numbers registered for the purpose of preventing the positions of the mobile stations from being registered in the adjacent base stations in an overlapping manner; and a control slot frequency allocation section  17  which sets the details of the control slot frequency management section in such a way that control channels of different frequencies are allocated to a plurality of base stations assigned the same broadcast area number.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a controller for use with a radiocommunications system which controls a plurality of base stations connected to mobile telephones via a radio channel within a business establishment, and more particularly, to a control operation for the purpose of allocating control slots to the base stations, respectively. 
     2. Description of the Related Art 
     FIG. 6 is a block diagram showing an existing radiocommunications system used in a business establishment, wherein a PBX (private branch exchange) main unit  1  is connected to a plurality of base stations  2  and to a personal computer PC  3  used for customizing the PBX  1 . 
     The PBX main unit  1  comprises a PBX control section  11  for controlling the overall PBX main unit  1 , a control slot frequency management section  12  which manages the frequency of a control slot assigned to each of the base stations  2 , a control slot period management section  13  for managing a period of the control slot during which a radio frequency signal is transmitted from the base station  2 , a base station interface  14  which serves as an interface between the PBX main unit  1  and the base stations  2 , a PC interface  15  which serves as an interface between the PBX unit  1  and the PC  3 , and a broadcast call area number management section  16  which manages a broadcast call area number registered for the purpose of preventing the positions of mobile stations from being registered in the adjacent base stations  2  in an overlapping manner. 
     Each of the base stations  2  comprises a PBX interface  21  which serves as an interface between the PBX main unit  1  and the base station  1 , a base station control section  22  for controlling the entire base station  2 , a control slot management section  23  which stores the frequency and period of the control slot assigned to each of the base stations  2 , and a radio section  24  which emits a radio frequency signal. 
     At the time of designing of the base stations, with regard to the adjacent base stations  2 , the PC  3  sets an identical broadcast call area number in the broadcast call area number management sections  16  by way of the PC interface  15 . In a case where a mobile station is handed over from one zone to another zone of the base stations  2  assigned the same broadcast call area number, the position of the mobile station is not registered in the base station. 
     The PBX control section  11  allocates control slots to the base stations  2  in numerical order of ports of the PBX main unit  1  and thus-allocated control slots are stored in the control slot frequency management section  12  and the control slot period management section  13 . Details of allocation of the control slots are stored in the control slot management section  23  of each base station  2  by way of the base station interface  14  and the PBX interface  21 . Depending on the settings of the control slot management section  23 , each base station  2  determines the frequency and period of the control slot during which a radio frequency signal is transmitted from the base station  2 . 
     FIG. 7 is a table showing broadcast call area numbers respectively assigned to base stations CS 1  to CS 8 , frequencies (i.e., the details of the control slot frequency management section  12 ) f 1  and f 2 , periods (i.e., details of the control slot period management section  13 ) “a”-“d” of the respective control slots, and control slots A through H. 
     FIG. 8 is a schematic representation showing the control slots A to H allocated respectively to the four periods “a” to “d” during one cycle of control channels of two frequencies f 1  and f 2 . 
     FIG. 7 shows base stations CS 1  and CS 2  assigned the same broadcast call area number, i.e., 1, and base stations CS 5  and CS 6  assigned the same broadcast call area number, i.e., 4. The base stations assigned the same broadcast area number are positioned in close proximity to each other. Other base stations CS 3 , CS 4 , CS 7 , and CS 8  are not positioned in close proximity to one another, and hence they are respectively assigned individual broadcast call area numbers 2, 3, 5, and 6. 
     The base stations CS 1  to CS 4  are allocated a control channel of frequency f 1 , and the base stations CS 5  to CS 8  are allocated a control channel of frequency f 2 . The base stations CS 1  to CS 4  are respectively sequentially assigned the four periods “a” to “d” into which one cycle of the control channel of frequency f 1  is divided. Similarly, the base stations CS 5  to CS 8  are sequentially and respectively assigned the four periods “a” to “d” into which one cycle of the control signal of frequency f 2  is divided. Consequently, as shown in FIG. 8, the base stations CS 1  to CS 4  are respectively allocated the control slots A to D, and the base stations CS 5  to CS 8  are respectively allocated the control slots E to H. 
     If existing radiocommunications systems are provided in close proximity to each other, and if control slots which one of the systems attempts to use have already been used by the other system, it becomes impossible for the former system to control mobile stations existing in a service area covered by base stations of the former system. 
     FIG. 9 shows a schematic layout showing an example of the adjacent radiocommunications systems and their base stations. Base stations CS 1 , CS 2 , and CS 3  are connected to one PBX main unit  1 A. Base stations CSa and CSb are connected to another PBX main unit B. In this example, the base stations CS 1 , CS 2 , and CSa are positioned in close proximity to one another. In this layout, the rate of connection between the mobile station and the base station CS 1  or CS 2  is decreased by interference from the base station CSa. 
     SUMMARY OF THE INVENTION 
     The present invention has been conceived to solve the aforementioned drawback in the prior art, and an object of the present invention is to provide a controller for use with a radiocommunications system which prevents a decrease in the rate of connection among mobile stations and base stations of the system, which would otherwise be caused by interference resulting from another adjacent radiocommunications system using the same frequency band as that of the system. 
     To achieve the above object, a controller for use with a radiocommunications system according to the present invention, comprises: 
     a control slot frequency management section which manages the frequency of a control slot allocated to each of base stations; 
     a broadcast call area number management section which manages broadcast call area numbers registered for the purpose of preventing the position of a mobile station from being registered in the adjacent base stations; and 
     a control slot frequency allocation section which sets the details of the control slot frequency management section in such a way that control channels of different frequencies are allocated to a plurality of base stations assigned the same broadcast area number. 
     The present invention is capable of providing a controller for use with a radiocommunications system which prevents a decrease in the rate of connection among mobile stations and base stations of the system, which would otherwise be caused by interference from another adjacent radiocommunications system which uses the same frequency band as that of the system. 
     A first aspect of the present application is directed to a controller for use with a radiocommunications system which controls a plurality of base stations connected to mobile stations by way of radio channels, the controller comprising: 
     a control slot frequency management section which manages the frequency of a control slot assigned to each of the base stations; 
     a broadcast call area number management section which manages broadcast call area numbers registered for the purpose of preventing the positions of the mobile stations from being registered in the adjacent base stations in an overlapping manner; and 
     a control slot frequency allocation section which sets the details of the control slot frequency management section in such a way that control channels of different frequencies are allocated to a plurality of base stations assigned the same broadcast area number. 
     According to the present invention, if a decrease arises in the rate of connection among the mobile stations and the base stations of one radiocommunications system by interference from another adjacent radiocommunications system using the same frequency band as that of the system, control channels of different frequencies are allocated to the base stations assigned the same broadcast area number. 
     A second aspect of the present application is directed to a controller for use with a radiocommunications system which controls a plurality of base stations connected to mobile stations by way of radio channels, the controller comprising: 
     a control slot period management section which manages the period of the control slot allocated to each base station during which a radio frequency signal is transmitted; 
     a broadcast call area number management section which manages broadcast call area numbers registered for the purpose of preventing the positions of the mobile stations from being registered in the adjacent base stations in an overlapping manner; and 
     a control slot period allocation section which sets the details of the control slot period management section in such a way that control slots spaced intervals apart from one another are allocated to the plurality of base stations assigned the same broadcast area number. 
     According to the present invention, if a decrease arises in the rate of connection among the mobile stations and the base stations of one radiocommunications system by interference from another adjacent radiocommunications system using the same frequency band as that of the system, control channels spaced at timing apart from one another are allocated to the base stations assigned the same broadcast area number. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing a first embodiment of a radiocommunications system to which the present invention is applied; 
     FIG. 2 is a schematic representation showing the positional relationship between the PBX main unit and base stations; 
     FIG. 3 is a table showing broadcast area numbers assigned respectively to base stations, frequencies assigned to control slots, transmission periods allocated to the control slots, and the control slots; 
     FIG. 4 is a block diagram showing a second embodiment of a radiocommunications system to which the present invention is applied; 
     FIG. 5 is a table showing broadcast area numbers assigned respectively to base stations, frequencies assigned to control slots, transmission periods allocated to the control slots, and the control slots; 
     FIG. 6 is a block diagram showing an existing communications system; 
     FIG. 7 is a table showing broadcast area numbers assigned respectively to existing base stations, frequencies assigned to control slots, transmission periods allocated to the control slots, and the control slots; 
     FIG. 8 is a schematic representation showing allocation of control slots to two control channels: and 
     FIG. 9 is a schematic representation showing the positional relationship between a PBX main unit and base stations. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will be described by reference to FIGS. 1 to  5 . 
     (First Embodiment) 
     FIG. 1 is a block diagram showing a first embodiment of a radiocommunications system to which the present invention is applied. In the drawing, the same reference numerals are assigned to constituent elements which are the same as those shown in FIG. 6, and their detailed explanations will be omitted here. 
     In the first embodiment, the control slot frequency allocation section  17  is newly provided in the PBX main unit  1 . If there are the base stations  2  assigned the same broadcast area number stored in the broadcast area number management section  16 , the control slot frequency allocation section  17  sets the details of the control slot frequency management section  12  so as to allocate control slots of different frequencies to these base stations  2 . The PBX main unit  1  constitutes the controller for use with a radiocommunications system according to the present invention. In other respects, the PBX main unit  1  is the same in structure as that previously shown in FIG.  6 . 
     The details of settings of the control slot frequency management section  12  are stored in the control slot management section  23  by way of the base station interface  14  and the PBX interface  21 , together with the details of the control slot period management section  13  set by the PBX control section  11 . The base station  2  determines a period of the control slot during which the radio section  24  transmits a radio frequency signal. 
     FIG. 2 is a schematic representation showing the positional relationship between the PBX main unit  1  and the base stations CS 1  to CS 8 . In this example, the base stations CS 1  and CS 2  are positioned in close proximity to each other, and the base stations CS 5  and CS 6  are also positioned in close proximity to each other. The other base stations are positioned independently of one another. Here, the base stations CS 4 , CS 7 , and CS 8  are omitted from the drawing. 
     FIG. 3 is a table showing broadcast area numbers assigned respectively to the base stations CS 1  to CS 8  thus arranged, the frequencies f 1  and f 2  assigned to the control slots, the transmission periods “a” to “d” allocated to the control slots, and the control slots A to H. 
     As shown in FIG. 3, since the base stations CS 1  and CS 2  are positioned in close proximity to each other, they are assigned the same broadcast call area number 1, and the base station CS 3  is assigned broadcast call area number 2. The base station CS 4  is assigned broadcast call area number 3. Since the base stations CS 5  and CS 6  are positioned in close proximity to each other, they are assigned the same broadcast call area number 4, and the base station CS 7  is assigned broadcast call area number 5. The base station CS 8  is assigned the broadcast call area number 6. 
     In principle, the base stations CS 1  to CS 4  are assigned a control channel of frequency f 1 . However, since the base stations CS 1  and CS 2  are positioned in close proximity to each other, the base stations CS 2  is assigned a control channel of frequency f 2 . 
     In principle, the base stations CS 5  to CS 8  are assigned the control channel of frequency f 2 . However, since the base stations CS 5  and CS 6  are positioned in close proximity to each other, the base stations CS 5  is assigned the control channel of frequency f 1 . 
     With regard to assignment of the periods “a” to “d” in the control channel of frequency f 1 , the period “a” is assigned to the base station CS 1 , and the period “b” is assigned to the base station CS 3 . The period “c” is assigned to the base station CS 4 , and the period “d” is assigned to the base station CS 5 . With regard to assignment of the periods in the control frequency of frequency f 2 , the period “a” is assigned to the base station CS 2 , and the period “b” is assigned to the base station CS 5 . The period “c” is assigned to the base station CS 7 , and the period “d” is assigned to the base station CS 8 . 
     As a result, the control slots A to H are allocated to the base stations CS 1  to CS 8  as follows: Namely, the base station CS 1  is allocated the control slot A, and the base station CS 2  is allocated the control slot E. The base station CS 3  is allocated the control slot B, and the base station CS 4  is allocated the control slot C. The base station CS 5  is allocated the control slot D, and the base station CS 6  is allocated the control slot F. The base station CS 7  is allocated the control slot G, and the base station CS 8  is allocated the control slot H. 
     As mentioned previously, according to the first embodiment, if a decrease arises in the rate of connection among mobile stations and base stations of one radiocommunications system by interference from another adjacent radiocommunications system using the same frequency band as that of the system, control channels of different frequencies are allocated to the base stations assigned the same broadcast area number. 
     (Second Embodiment) 
     FIG. 4 is a block diagram showing a second embodiment of the radiocommunications system to which the present invention is applied. In the drawing, the same reference numerals are assigned to constituent elements which are the same as those shown in FIG. 6, and their detailed explanations will be omitted here. 
     In the second embodiment, the control slot period allocation section  18  is newly provided in the PBX main unit  1 . If there are the base stations  2  assigned the same broadcast area number stored in the broadcast area number management section  16 , the control slot period allocation section  18  sets the details of the control slot period management section  13  so as to allocate control slots spaced at timing apart from one another to these base stations  2 . The PBX main unit  1  constitutes the controller for use with a radiocommunications system according to the present invention. In other respects, the PBX main unit  1  is the same in structure as that previously shown in FIG.  6 . 
     The details of settings of the control slot period management section  13  are stored in the control slot management section  23  by way of the base station interface  14  and the PBX interface  21 , together with the details of the control slot period management section  12  set by the PBX control section  11 . The base station  2  determines the period of the control slot during which the radio section  24  transmits a radio frequency signal. 
     FIG. 5 is a table showing broadcast area numbers assigned respectively to the base stations CS 1  to CS 8  thus arranged, the frequencies f 1  and f 2  assigned to the control slots, the periods “a” to “d” allocated to the control slots, and the control slots A to H, provided that the PBX main unit  1  and the base stations CS 1  to CS 8  are arranged in a manner as shown in FIG.  2 . 
     The broadcast call area numbers provided in FIG. 5 are the same as those previously used in the first embodiment. The base stations CS 1  to CS 4  are assigned the control channel of frequency f 1 , and the base stations CS 5  through CS 8  are assigned the control channel of frequency f 2 . 
     In principle, the periods “a” to “d” are assigned to the base stations CS 1  to CS 4  in that order, as well as to the base stations CS 5  to CS 8  in that order. Since the base stations CS 1  and CS 2  are positioned in close proximity to each other, the base station CS 1  is assigned the period “a,” and the base station CS 2  is assigned the period “c” in order to assign transmission periods spaced apart from each other to the base stations CS 1  and CS 2 . Similarly, since the base stations CS 5  and CS 6  are positioned in close proximity to each other, the base station CS 5  is assigned the period “a,” and the base station CS 6  is assigned the period “c.” 
     With regard to the assignment of periods to the remaining base stations, the period “b” in the control channel of frequency f 1  is assigned to the base station CS 3 , and the period “d” in the control channel of frequency f 1  is assigned to the base station CS 4 . The period “b” in the control channel of frequency f 2  is assigned to the base station CS 7 , and the period “d” in the control channel of frequency f 2  is assigned to the base station CS 8 . 
     As a result, the control slots A to H are allocated to the base stations CS 1  to CS 8  as follows: Namely, the base station CS 1  is allocated the control slot A, and the base station CS 2  is allocated the control slot C. The base station CS 3  is allocated the control slot B, and the base station CS 4  is allocated the control slot D. The base station CS 5  is allocated the control slot E, and the base station CS 6  is allocated the control slot G. The base station CS 7  is allocated the control slot F, and the base station CS 8  is allocated the control slot H. 
     As mentioned previously, according to the second embodiment, if a decrease arises in the rate of connection among mobile stations and base stations of one communications system by interference from another adjacent radiocommunications system using the same frequency band as that of the system, control slots spaced at timing apart from each other are allocated to the radiocommunications systems assigned the same broadcast area call number, thus enabling an increase in the rate of connection among the mobile stations and the base stations of the system in its area. 
     As was described above, according to the present invention, if a decrease arises in the rate of connection among mobile stations and base stations of one radiocommunications system by interference from another radiocommunications system using the same frequency band as that of the system, the base stations assigned the same broadcast call area number are allocated control channels of different frequencies or control channels spaced at timing from one another, enabling an increase in the rate of connection among the mobiles stations and the base stations of the system in its area.