Abstract:
Efficient paging control is achieved in a communication system that selectively provides one of communication services implemented by integrating a plurality of communication systems. Before transmitting a downlink signal to a terminal, a gateway requests each of the communication systems to transmit a paging signal to the terminal. Receiving the paging signals transmitted from the communication systems, the terminal selects a communication system A with the lowest communication cost in accordance with communication cost information contained in the paging signal. The terminal sends a request for connection to the selected communication system A. As a result, the communication system A transmits the downlink signal to the terminal.

Description:
This application claims priority under 35 U.S.C. 119 to Patent Application No. 2000-340973 filed Nov. 8, 2000 in Japan, the content of which is incorporated hereinto by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a paging control method, a paging control system and a recording medium recording a paging control program in a communication system that provides a terminal with communication services via a radio communication channel or a wire communication channel. 
   2. Description of the Related Art 
   A terminal such as a mobile station in a mobile communication system, the battery of which is limited in its capacity, so a terminal is usually in the battery saving mode so-called idle mode that halts transfer of information to save power of the battery. When a base station transmits a downlink information signal to the terminal in the idle mode, it transmits a paging signal before transmitting an actual information signal to enable the terminal to shift from the idle mode to a receivable mode (standby mode). Such control is called paging control. 
   Since each conventional communication system offers closed independent services of its own, the paging control is also carried out by each communication system independently. 
   In contrast with this, a virtual communication system, which integrates multiple communication systems with different features and provides the terminal with a communication service selected from the multiple communication systems, is considered to be a very efficient system because it can handle various requests of the terminal flexibly. 
   However, efficient paging control for such a communication system that integrates multiple communication systems has not yet been conceived. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to implement efficient paging control for a communication system that can offer any one of communication services that are provided by integrating a plurality of communication systems. 
   To accomplish the object, according to a first aspect of the present invention, there is provided a paging control method of a communication system that selectively provides one of communication services implemented by integrating a plurality of communication systems, the paging control method comprising: a first step of transmitting a paging signal from each of the plurality of communication systems to a terminal; and a second step of receiving the plurality of paging signals by the terminal, and of selecting a desired communication system for use by the terminal from the plurality of communication systems in accordance with information contained in the plurality of paging signal received. 
   The paging control method may further comprise a third step of transmitting a connection request signal from the terminal to the desired communication system selected at the second step. 
   According to a second aspect of the present invention, there is provided a paging control method of a communication system that selectively provides one of communication services implemented by integrating a plurality of communication systems, and includes a paging agent for managing paging signals, the paging control method comprising: a first step of transmitting previously a request for a communication system a terminal wishes to use, and terminal location information of the terminal from the terminal to the paging agent, and of registering the received request and the terminal location information in the paging agent; a second step of selecting an optimum communication system from among the plurality of communication systems by the paging agent in accordance with the registered request and the terminal location information in the paging agent; and a third step of transmitting the paging signal from the optimum communication system to the terminal. 
   The paging control method may further comprise a fourth step of transmitting a connection request signal from the terminal to the optimum communication system. 
   According to a third aspect of the present invention, there is provided a paging control method of a communication system that selectively provides one of communication services implemented by integrating a plurality of communication systems, and includes a paging agent for managing paging signals, the paging control method comprising: a first step of transmitting previously a request for a communication system a terminal wishes to use, and terminal location information of the terminal from the terminal to the paging agent, and of registering the received request and the terminal location information in the paging agent; a second step of selecting an optimum communication system from among the plurality of communication systems by the paging agent in accordance with the registered request and the terminal location information in the paging agent; and a third step of transmitting a paging signal including a name of the communication system selected at the second step from a given communication system predetermined from among the plurality of communication systems to carry out transmission to the terminal. 
   The paging control method may further comprise a fourth step of transmitting a connection request signal from the terminal to the given communication system, and of waiting for an information signal from the optimum communication system contained in the paging signal. 
   The second step may use one of a communication cost, a transmission rate, a transmission quality and a combination of at least two of them as a selection index of the optimum communication system. 
   According to a fourth aspect of the present invention, there is provided a paging control system of a communication system that selectively provides one of communication services implemented by integrating a plurality of communication systems, the paging control system comprising: communication control means for causing each of the plurality of communication systems to transmit a paging signal via an external network; and a terminal for receiving the plurality of paging signals, and for selecting a desired communication system for use from the plurality of communication systems in accordance with information contained in the plurality of paging signal received. 
   The terminal may transmit a connection request signal to the desired communication system selected. 
   According to a fifth object of the present invention, there is provided a paging control system of a communication system that selectively provides one of communication services implemented by integrating a plurality of communication systems, and includes a paging agent for managing paging signals, the paging control system comprising: a terminal for transmitting previously a request for a communication system a terminal wishes to use, and terminal location information of the terminal from the terminal to the paging agent; registering means in the paging agent for registering the received request and the terminal location information; selecting means in the paging agent for selecting an optimum communication system from among the plurality of communication systems in accordance with the registered request and the terminal location information in the registering means; and communication control means for causing the optimum communication system selected by the selecting means to transmit the paging signal to the terminal. 
   The terminal may transmit a connection request signal to the optimum communication system. 
   According to a sixth aspect of the present invention, there is provided a paging control system of a communication system that selectively provides one of communication services implemented by integrating a plurality of communication systems, and includes a paging agent for managing paging signals, the paging control system comprising: a terminal for transmitting previously a request for a communication system a terminal wishes to use, and terminal location information of the terminal to the paging agent; storing means in the paging agent for registering the received request and the terminal location information; selecting means in the paging agent for selecting an optimum communication system from among the plurality of communication systems in accordance with the registered request and the terminal location information in the storing means; and communication control means for transmitting a paging signal including a name of the optimum communication system selected by the selecting means from a given communication system predetermined from among the plurality of communication systems to the terminal. 
   The terminal may transmit a connection request signal to the given communication system, and wait for an information signal from the optimum communication system contained in the paging signal. 
   The selecting means may use one of a communication cost, a transmission rate, a transmission quality and a combination of at least two of them as a selection index of the optimum communication system. 
   The selecting means may carry out the selection of the optimum communication system in response to a query about the optimum communication system from the communication control means. 
   According to a seventh aspect of the present invention, there is provided a recording medium recording a paging control program in a communication system that selectively provides one of communication services implemented by integrating a plurality of communication systems, and includes a paging agent for managing paging signals, the paging control program, which is used by a computer for controlling the paging agent, causing the computer to: receive from a terminal a request for a communication system the terminal wishes to use, and terminal location information of the terminal; to register the received request and the terminal location information; to select an optimum communication system from among the plurality of communication systems in accordance with the registered request and the terminal location information; and to cause the optimum communication system selected to transmit the paging signal to the terminal. 
   According to an eighth aspect of the present invention, there is provided a recording medium recording a paging control program in a communication system that selectively provides one of communication services implemented by integrating a plurality of communication systems, and includes a paging agent for managing paging signals, the paging control program, which is used by a computer for controlling the paging agent, causing the computer to: receive from a terminal a request for a communication system the terminal wishes to use, and terminal location information of the terminal; register the received request and the terminal location information; select an optimum communication system from among the plurality of communication systems in accordance with the registered request and the terminal location information; and cause a given communication system, which is predetermined in advance from among the plurality of communication systems communication control means for carrying out transmission to the terminal, to transmit to the terminal a paging signal including a name of the optimum communication system selected. 
   With the foregoing configurations, the present invention can implement efficient paging control in the communication system that can offer any one of communication services that are provided by integrating the plurality of communication systems. 
   The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing a configuration of a first embodiment of the communication system in accordance with the present invention; 
       FIG. 2  is a signal format diagram illustrating an example of a paging signal transmitted from individual communication systems  3 - 5  of  FIG. 1 ; 
       FIG. 3  is a block diagram showing a configuration of a second embodiment of the communication system in accordance with the present invention; 
       FIG. 4A  is a signal format diagram illustrating an example of a signal format of a request signal S 11  of  FIG. 3 ; 
       FIG. 4B  is a signal format diagram illustrating an example of a signal format of a query signal S 12  of an optimum system of  FIG. 3 ; 
       FIG. 4C  is a signal format diagram illustrating an example of a signal format of a reply signal S 13  of  FIG. 3 ; 
       FIG. 5  is a block diagram showing a configuration of a third embodiment of the communication system in accordance with the present invention; 
       FIG. 6A  is a signal format diagram illustrating an example of a signal format of a request signal S 11  of  FIG. 5 ; 
       FIG. 6B  is a signal format diagram illustrating an example of a signal format of a query signal S 12  of an optimum system of  FIG. 5 ; 
       FIG. 6C  is a signal format diagram illustrating an example of a signal format of a reply signal S 13  of  FIG. 5 ; and 
       FIG. 6D  is a signal format diagram illustrating an example of a signal format of a paging signal of FIG.  5 . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   The configurations and operations of some communication systems according to the embodiments of the present invention will be described below with reference to the drawings. 
   (First Embodiment) 
     FIG. 1  is a block diagram showing a configuration of a first embodiment of the communication system in accordance with the present invention. In this figure, the reference numeral  1  designates an external network;  2  designates a gateway (GW);  3 ,  4  and  5  designate a communication system A, a communication system B and a communication system C, respectively; and  6  designates a terminal. It is assumed in the present embodiment that the signal from the external network  1  is transmitted to the individual communication systems  3 - 5  via the gateway  2 . Although the communication systems  3 - 5  are different communication systems, they can be a wired or wireless system, and are integrated via the gateway  2 . 
     FIG. 2  is a signal format diagram illustrating an example of a paging signal transmitted from each of the communication systems  3 - 5  of FIG.  1 . Reference symbols S 1 , S 2  and S 3  designate paging signals of the communication systems A, B and C respectively. They each include their own terminal address, system name field and communication cost information field. In the example of  FIG. 2 , the communication cost of the communication systems satisfies the relationship of S 1 &lt;S 2 &lt;S 3 . Accordingly, it is obvious that the communication cost of the communication system A is cheapest. 
   In the first embodiment in accordance with the present invention, when there is a downlink signal from an external network to a terminal (the terminal  6 , for example) among a plurality of terminals, the gateway  2  requests the communication systems  3 - 5  to transmit the paging signals S 1 -S 3  to the terminal. Receiving the paging signals transmitted from the communication systems  3 - 5 , the terminal  6  selects a communication system with the lowest communication cost (in the present example, the communication system A  3 ) in accordance with the communication cost information contained in the paging signals S 1 -S 3 . 
   Subsequently, the terminal  6  sends a request for connection to the selected communication system. Here, the terminal  6  selects the communication system A. As a result, the downlink signal is transmitted to the terminal  6  via the communication system A. 
   Although the communication cost of the present embodiment is based on a measured rate charge system, it can be based on a connect time charge system. In addition, although the present embodiment uses the communication cost as the selection index of the communication system, other selection indices are also applicable. For example, it is possible to use a transmission rate, a transmission quality or a combination of the communication cost and the transmission rate or the like as the selection index for selecting the communication system. In this case, these pieces of information used as the communication system selection index must be contained in the paging signals transmitted from the individual communication systems. 
   (Second Embodiment) 
     FIG. 3  is a block diagram showing a configuration of a second embodiment of the communication system in accordance with the present invention. In this figure, the reference numeral  7  designates a paging agent connected between the gateway  2  and the terminal  6 . The paging agent  7  can recognize communication systems available for the use of each terminal  6  from the terminal location information of the terminal  6 , and obtain information such as communication cost and transmission rate about the individual communication system at the terminal location. Since the remaining components are the same as those of the first embodiment described above in connection with  FIG. 1 , the description thereof is omitted here. 
     FIG. 4A  illustrates an example of a signal format of a request signal S 11  a terminal  6  among a plurality of terminals transmits to the paging agent  7 . The request signal S 11  includes a destination address field (paging agent address), a source address field (terminal address), a terminal location field (terminal terminal location information) and a request field (such as the lowest communication cost). 
   The terminal  6  previously sends the information about the request (such as the lowest communication cost) for the communication system to be connected to the paging agent  7 , by using the signal format of FIG.  4 A. 
   According to the terminal location information and the request from the terminal, the paging agent  7  selects the optimum communication system (communication system A  3 , for example), and stores it in its internal memory (not shown in this figure). 
   Subsequently, before transmitting a downlink signal to the terminal  6 , the gateway  2  inquires of the paging agent  7  which one of the communication systems the terminal  6  wishes to be connected with, by using a query signal S 12  with the signal format of FIG.  4 B. The query signal S 12  includes a destination address field (paging agent address), a source address (gateway address) and a terminal address. 
   The paging agent  7  replies the gateway  2  by the reply signal S 13  with the signal format of FIG.  4 C. The reply signal S 13  includes a destination address field (gateway address), a source address field (paging agent address), a terminal address and an optimum communication system name (communication system A  3 , for example). 
   The gateway  2  request the communication system (optimum communication system) associated with the reply to transmit the paging signal to the terminal by using a request for transmission of paging signal S 14 . Here, the communication system A  3  is assumed to be selected as the optimum communication system. 
   Receiving the paging signal transmitted from the communication system A, the terminal  6  sends a request for connection back to the communication system A. As a result, the downlink signal is transmitted to the terminal  6  via the communication system A. 
   Although the present embodiment uses the communication cost as the selection index of the communication system just as the foregoing first embodiment, this is not essential. For example, it can use other selection index such as a transmission rate, a transmission quality or a combination of the communication cost and the transmission rate as the selection index to select the communication system. In this case, the terminal  6  must specify its own request (transmission rate, for example) in the request field of the request signal S 11  of  FIG. 4A  to be transmitted to the paging agent  7 . 
   (Third Embodiment) 
     FIG. 5  is a block diagram showing a configuration of a third embodiment of the communication system in accordance with the present invention. The present embodiment is a variation of the foregoing second embodiment. Since the components of  FIG. 5  are nearly the same as those of  FIG. 3 , the description thereof is omitted here. 
   The third embodiment differs from the second embodiment in that one of the communication systems is specified in advance as a system (called paging system) for transmitting a paging signal S 25  to the terminal  6  as shown in  FIG. 5  (in this case the communication system B  4 ). The paging system sends to the terminal  6  the optimum communication system name selected by the paging agent  7 , that is, the communication system name (communication system A  3 , for example) to be used for actually transmitting the information signal, with containing in the paging signal S 25 . The remaining operation is nearly the same as that of the second embodiment. 
     FIG. 6A  illustrates a format of a request signal S 11  the terminal  6  transmits to the paging agent  7 ;  FIG. 6B  illustrates a format of a signal S 12  the gateway  2  transmits to the paging agent  7 ; and  FIG. 6C  illustrates a format of a signal S 13  the paging agent  7  sends back to the gateway. These formats are the same as those of the second embodiment as shown in  FIGS. 4A-4C . 
   The operation of the present embodiment will now be described. 
   The terminal  6  notifies the paging agent  7  of the request (such as the lowest communication cost) for the communication system to be connected with, by using the signal format of  FIG. 6A  in advance. 
   The paging agent  7  selects the optimum communication system (communication system A  3 , for example) in accordance with the terminal location information and request of the terminal  6 , and stores it in the internal memory (not shown in the drawings). 
   Subsequently, before transmitting the downlink signal to the terminal  6 , the gateway  2  inquires of the paging agent  7  which one of the communication systems the terminal  6  wishes to be connected with, by using the query signal S 12  with the signal format of FIG.  6 B. 
   The paging agent  7  replies the gateway  2  using the reply signal S 13  with the signal format of FIG.  6 C. 
   Receiving the reply signal S 13 , the gateway  2  requests the predetermined paging system (communication system B  4  in the present embodiment) to transmit the paging signal S 25  to the terminal  6 . Here, the paging signal S 25  includes the name of the communication system, that is, the optimum communication system selected by the paging agent  7 , which is used for the actual transmission of the information signal. 
     FIG. 6D  illustrates a format of the paging signal S 25 . It includes a terminal address and a system name field (that designates the communication system A  3 , for example). As a criterion for determining the paging system, among the communication systems, the minimum intermittent receiving ratio or the lowest communication cost will be applicable. 
   Receiving the paging signal S 25  transmitted from the paging system  4 , the terminal  6  sends a request for connection to the paging system B  4  using the connection request signal S 26 , and waits for the information signal from the communication system (communication system A  3 , for example) specified by the paging signal S 25 . Thus, the downlink signal is transmitted to the terminal  6  via the communication system A. 
   Although the present embodiment uses the communication cost as the selection index of the communication system just as the foregoing second embodiment, this is not essential. For example, it can use other selection index such as a transmission rate, a transmission quality or a combination of the communication cost and the transmission rate as the selection index to select the communication system. In this case, the terminal  6  must specify its own request (transmission rate, for example) in the request field of the request signal S 11  of  FIG. 6A  to be transmitted to the paging agent  7 . 
   It will be obvious to those skilled in the art of the present invention that the object of the present invention can be accomplished by providing a system or apparatus with a recording medium (storing medium) that records a program code of software for implementing the functions of the foregoing embodiments, and by reading and executing the program code stored in the recording medium by a computer (or CPU or MPU) of the system or apparatus. In this case, the program code itself read from the recording medium can implement the functions of the foregoing embodiments, and hence the recording medium recording the program code constitutes the present invention. As the recording medium for recording the program code and variable data such as tables, such media as a floppy disk, hard disk, optical disk, magneto-optical disk, and nonvolatile memory card are available. 
   The present invention has been described in detail with respect to preferred embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspect, and it is the intention, therefore, in the apparent claims to cover all such changes and modifications as fall within the true spirit of the invention.