Patent Publication Number: US-2013242740-A1

Title: Method and system for controlling communication network and router used in the network

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a division of application Ser. No. 11/783,475 filed on Apr. 10, 2007, which is a division of application Ser. No. 10/056,005 filed on Jan. 28, 2002, which claims foreign priority to Japanese application Nos. 2001-018589, 2001-027048 and 2001-020198 filed on Jan. 26, 2001, Feb. 2, 2001 and Jan. 29, 2001, respectively. The entire content of each of these applications is hereby expressly incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method and a system for controlling a communication network and routers used in the network, and more particularly to a system and method for controlling call to mobile host through a mobile communication hierarchical network as well as another system and method for controlling a mobile communication hierarchical network. 
     2. Description of the Related Art 
       FIG. 1  is a block diagram illustrative of a conventional mobile communication network. This mobile communication network is generally used for a management system for managing positions of mobile telephones or automatic cars. This mobile communication network utilizes transmission control protocol/internet protocol (TCP/IP) for realizing a packet communication. 
     As shown in  FIG. 1 , the mobile communication network includes a host network  1 , plural routers Rn (n=1˜7), base stations BS 1 ˜BS 8 , and a mobile host MH. The host network  1  may comprise a wide area network such as internet. The routers Rn provide multi-point connections between the host network  1  and the base stations BS 1 ˜BS 8 . The routers Rn form a hierarchical network structure between the host network  1  and the base stations BS 1 ˜BS 8 . The router R 1  is highest level router. The routers R 2  and R 3  are middle level routers which are connected to the router R 1  and dominated by the router R 1 . The routers R 4 , R 5 , R 6  and R 7  are lowest level routers, wherein the routers R 4  and R 5  are connected to the router R 2  and dominated by the router R 2 , whilst the routers R 6  and R 7  are connected to the router R 3  and dominated by the router R 3 . The base stations BS 1  and BS 2  are connected to the router R 4  and dominated by the router R 4 . The base stations BS 3  and BS 4  are connected to the router R 5  and dominated by the router R 5 . The base stations BS 5  and BS 6  are connected to the router R 6  and dominated by the router R 6 . The base stations BS 7  and BS 8  are connected to the router R 7  and dominated by the router R 7 . 
     The mobile host MH is connected through radio communication to any one of the base stations BS 1 ˜BS 8  to establish a link to the base station for communication through the host network  1  to other subscriber. 
     In accordance with this mobile communication network, the mobile host MH is managed in the current position thereof in activated state, or the mobile host MH is managed in paging area in inactivated state. 
     The routers R 2  and R 3  manage the respective paging areas. In  FIG. 1 , the mobile host MH is positioned in an area covered by the base stations BS 1 , BS 2 , BS 3  and BS 4 , for which reason the mobile host MH is recorded in the paging area dominated by the router R 2 . If the mobile host MH moves from the first paging area dominated by the base stations BS 1 , BS 2 , BS 3  and BS 4  which are further dominated by the router R 2  into a second paging area dominated by the base stations BS 5 , BS 6 , BS 7  and BS 8  which are further dominated by the router R 3 , then the router R 3  registers the mobile host MH in the second paging area in accordance with a position recording message from the mobile host MH. 
     As shown in  FIG. 1 , it is assumed that the mobile host MH is recorded in the first paging area managed by the router R 2 . If a packet addressed to the mobile host MH for general calling is transmitted from a caller through the host network  1  to the router R 1 , then the router R 1  selectively transfers the packet for the mobile host MH to the router R 2  in the first step ( 1 ). The router R 2  transfers the packet to all of the sub-ordinate routers R 4  and R 5  which are managed or dominated by the router R 2  in the second step ( 2 ). The routers R 4  and R 5  further transfer the packet to all of the base stations BS 1 , BS 2 , BS 3  and BS 4  which are managed by the routers R 4  and R 5  in the third step ( 3 ). 
     The base stations BS 1 , BS 2 , BS 3  and BS 4  perform general calling to the mobile host MH, whereby any connectable one of the base stations BS 1 , BS 2 , BS 3  and BS 4  establishes a link to the mobile host MH in the fourth step ( 4 ). In  FIG. 1 , the base station BS 3  established the link to the mobile host MH. The mobile host MH transmits a position recording message to the base station BS 3  in the fifth step ( 5 ). The base station BS 3  transfers the position recording message to the router R 5  in the sixth step ( 6 ). The router R 5  further transfers the position recording message to the router R 2  as well as updates routing information to the mobile host MH in the seventh step ( 7 ). The router R 2  updates routing information to the mobile host MH. As a result, the communication route of the router R 1 , the router R 2 , the router R 5  and the base station BS 3  is established. The routing information is an information which indicates a route up to a packet-destination. The routing information is recorded on a routing table of the router. 
       FIG. 2  is a sequence diagram illustrative of sequential operations of the above described conventional mobile communication hierarchical network shown in  FIG. 1 . As shown in  FIG. 2 , if the packets are discontinuously transmitted from the host network  1 , then the routers R 1 , R 2 , R 4  and R 5  transfer the received packets to the subordinate routers or the managing base stations BS every time when the packets are transmitted from the host network  1  until any link is established between the base station and the mobile host MH. 
     As described above, in accordance with the conventional mobile communication hierarchical network, if the packet addressed to the mobile host MH in the stand-by state is transmitted from the caller through the host mobile MH, then the router managing the paging area, on which the stand-by state mobile host MH is recorded, performs the general calling the sub-ordinate network managed by this router for calling the host mobile MH, wherein the packet addressed to the mobile host MH is transferred to all of the base stations managed by this router. 
     It is, however, general that the caller transmits the packets through the host network  1  without consideration of loads to the hierarchical network, whereby the packet for general calling to the mobile host MH causes the increase in the load to the hierarchical network. 
       FIG. 3  is a block diagram illustrative of another conventional mobile communication network. This mobile communication network is generally used for a management system for managing positions of mobile telephones or automatic cars. This mobile communication network utilizes transmission control protocol/internet protocol (TCP/IP) for realizing a packet communication. 
     As shown in  FIG. 3 , the mobile communication network includes a host network  1 , plural routers Rn (n=1˜7), base stations BS 1 ˜BS 8 , and a mobile host MH. The host network  1  may comprise a wide area network such as internet. The routers Rn provide multi-point connections between the host network  1  and the base stations BS 1 ˜BS 8 . The routers Rn form a hierarchical network structure between the host network  1  and the base stations BS 1 ˜BS 8 . The router R 1  is highest level router. The routers R 2  and R 3  are middle level routers which are connected to the router R 1  and dominated by the router R 1 . The routers R 4 , R 5 , R 6  and R 7  are lowest level routers, wherein the routers R 4  and R 5  are connected to the router R 2  and dominated by the router R 2 , whilst the routers R 6  and R 7  are connected to the router R 3  and dominated by the router R 3 . The base stations BS 1  and BS 2  are connected to the router R 4  and dominated by the router R 4 . The base stations BS 3  and BS 4  are connected to the router R 5  and dominated by the router R 5 . The base stations BS 5  and BS 6  are connected to the router R 6  and dominated by the router R 6 . The base stations BS 7  and BS 8  are connected to the router R 7  and dominated by the router R 7 . 
     The mobile host MH is connected through radio communication to any one of the base stations BS 1 ˜BS 8  to establish a link to the base station for communication through the host network  1  to other subscriber. 
     The mobile host MH transmits a position recording message to the base station BS 2  in the first step ( 1 ). The routers Rn update the respective routing informations based on the position recording message from the mobile host MH and also transfer the position recording message to the upper level routers in the second, third and fourth steps ( 2 ), ( 3 ) and ( 4 ). The routing information is an information which indicates a route up to a packet-destination. The routing information is recorded on a routing table of the router. 
     When the position recording message reaches the top level router R 1 , a communication route between the host network  1  and the mobile host MH is established. In  FIG. 3 , the communication route as established includes the mobile host MH, the base station BS 2 , the router R 4 , the router R 2  and the router R 1 .  FIG. 4  is a block diagram illustrative of communication processes of the conventional mobile communication network of  FIG. 3 . As shown in  FIG. 4 , the packet addressed to the mobile host MH is transferred from the host network  1  through the router R 1 , the router R 2 , the router R 4  and the base station BS 2  to the mobile host MH sequentially. 
     If, accidentally, at least one router on the established communication route between the host network  1  and the mobile host MH becomes failure, then the communication route becomes disconnect. This conventional communication network has no further available route between the base station BS 2  and the host network  1 . For this reason, it is necessary to reset the failure router and re-establish the communication network between the host network  1  and the mobile host MH before the communication route between the mobile host MH and the host network  1  is established by re-updating process by the routers Rn for re-updating the routing information based on the position record message from the mobile host MH. If at least any one of the router on the established communication route becomes once trouble and the communication route becomes lost, then no communication can be made between the mobile host MH and the host network  1  until the communication route between the mobile host MH and the host network  1  is re-established by re-updating process by the routers Rn for re-updating the routing information based on the position record message from the mobile host MH. 
     In  FIGS. 3 and 4 , only the single mobile host MH is shown, even actually a plurality of the mobile host MH are generally the subject to the communication through the above network. The plural mobile hosts MH transmit respective plural position recording messages which are transferred through the hierarchy-networked routers Rn to the host network  1  for re-establishment of the communication route. The upper level router is likely to receive many position recording messages from the plural mobile hosts MH. This means that the transmissions of the many position recording messages from the many mobile hosts MH increases the load to the upper level router. 
     As described above, if at least any one of the router on the established communication route becomes once trouble and the communication route becomes lost, then no communication can be made between the mobile host MH and the host network  1  until the communication route between the mobile host MH and the host network  1  is re-established by re-updating process by the routers Rn for re-updating the routing information based on the position record message from the mobile host MH. 
     Further, the plural mobile hosts MH transmit respective plural position recording messages which are transferred through the hierarchy-networked routers Rn to the host network  1  for re-establishment of the communication route. The upper level router is likely to receive many position recording messages from the plural mobile hosts MH. This means that the transmissions of the many position recording messages from the many mobile hosts MH increases the load to the upper level router. 
       FIG. 5  is a block diagram illustrative of still another conventional mobile communication network. This mobile communication network is generally used for a management system for managing positions of mobile telephones or automatic cars. This mobile communication network utilizes transmission control protocol/internet protocol (TCP/IP) for realizing a packet communication. 
     As shown in  FIG. 5 , the mobile communication network includes a host network  1 , plural routers Rn (n=1˜7), base stations BS 1 ˜BS 8 , and a mobile host MH. The host network  1  may comprise a wide area network such as internet. The routers Rn provide multi-point connections between the host network  1  and the base stations BS 1 ˜BS 8 . The routers Rn form a hierarchical network structure between the host network  1  and the base stations BS 1 ˜BS 8 . The router R 1  is highest level router. The routers R 2  and R 3  are middle level routers which are connected to the router R 1  and dominated by the router R 1 . The routers R 4 , R 5 , R 6  and R 7  are lowest level routers, wherein the routers R 4  and R 5  are connected to the router R 2  and dominated by the router R 2 , whilst the routers R 6  and R 7  are connected to the router R 3  and dominated by the router R 3 . The base stations BS 1  and BS 2  are connected to the router R 4  and dominated by the router R 4 . The base stations BS 3  and BS 4  are connected to the router R 5  and dominated by the router R 5 . The base stations BS 5  and BS 6  are connected to the router R 6  and dominated by the router R 6 . The base stations BS 7  and BS 8  are connected to the router R 7  and dominated by the router R 7 . 
     The mobile host MH is connected through radio communication to any one of the base stations BS 1 ˜BS 8  to establish a link to the base station for communication through the host network  1  to other subscriber. 
     The mobile host MH transmits a position recording message to the base station BS linked to this mobile host MH in a first step ( 1 ). The position recording message is transferred from the linked base station through the routers from the lowest level to the highest level, thereby establishing the communication route between the host network  1  and the linked base station BS. The routing information is an information which indicates a route up to a packet-destination. The routing information is recorded on a routing table of the router. 
     For example, as shown in  FIG. 5 , a communication route has been established which includes the router R 1 , the router R 2 , the router R 4 , and the base station BS 2  linked to the mobile host MH. The packet addressed to the mobile host  1  is transmitted from the host network  1  to the router R 1 . The router R 1  transfers the received packet to the router R 2  based on the routing information held itself in the first step ( 1 ′). The router R 2  transfers the received packet to the router R 4  based on the routing information held itself in the second step ( 2 ′). The router R 4  transfers the received packet to the base station BS 2  based on the routing information held itself in the third step ( 3 ′). The base station BS 2  transmits the received packet to the mobile host MH. Namely, the packet is transferred from the host network  1  through the router R 1 , the router R 2 , the router R 4  and the base station BS 2  to the mobile host MH. 
       FIG. 6  is a block diagram illustrative of operation of the conventional mobile communication network of  FIG. 5 . The mobile host MH moves from a radio area covered by the base station BS 2  to another radio area covered by the base station BS 3 . Adjacent two radio areas covered by the adjacent two base stations are generally bounded by an overlap boundary area, even this overlap boundary area is not illustrated in  FIG. 6 . The mobile host MH establishes a link to the base station providing a highest radio intensity that is sensed by the mobile host MH. 
     When the mobile host MH moves from the area covered by the base station BS 2  to the other area covered by the base station BS 3 , then the mobile host MH has lost the link to the base station BS 2  and establishes a link to the base station BS 3 . The mobile host MH further transmits a new position recording message to the base station BS 3 . The base station BS 3  transfers the received new position recording message to the router R 5 . The router R 5  further transfers the received new position recording message to the router R 2 . The router R 2  further transfers the received new position recording message to the router R 1 . As a result, a new communication route is established which includes the host network  1 , the router R 1 , the router R 2 , the router R 5  and the base station BS 3  to the mobile host MH. 
     If the mobile host MH moves from the radio area covered by the base station BS 2  to the other radio area covered by the base station BS 3  during the transfer of the packet through the hierarchical-structure of the routers Rn, then the packet is transferred through the old communication route including the router R 4  and the base station BS 2 , because a newly communication route including the router R 5  and the base station BS 3  could not be established. Since the mobile host MH has lost the old link to the base station BS 2  and has already established a new link to the base station BS 3 , then the mobile host MH could not receive the packet from by the base station BS 2 . 
     Accordingly, in accordance with the conventional mobile communication network, if the base station having the current link to the mobile host MH is changed to the other base station establishing a new link to the mobile host MH, during the transfer of the packet through the mobile communication network, then the mobile host MH could not receive the packet. Namely, a problem with the packet loss is raised. It is desirable to reduce the probability of rising the problem with the packet loss. 
     In the above circumstances, the development of novel method and system for controlling the mobile communication hierarchical network free from the above problems is desirable. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a novel method for controlling the mobile communication hierarchical network free from the above problems. 
     It is a further object of the present invention to provide a novel method for controlling the mobile communication hierarchical network which reducing a load to the network. 
     It is a still further object of the present invention to provide a novel method for controlling the mobile communication hierarchical network which reducing a load to the network in general calling. 
     It is yet a further object of the present invention to provide a novel system for controlling the mobile communication hierarchical network free from the above problems. 
     It is a further more object of the present invention to provide a novel system for controlling the mobile communication hierarchical network which reducing a load to the network. 
     It is still more object of the present invention to provide a novel system for controlling the mobile communication hierarchical network which reducing a load to the network in general calling. 
     It is more over object of the present invention to provide a novel method for controlling the mobile communication hierarchical network which allows continuation in communication between the mobile host and the host network even if at least one router or line has become trouble and the established communication route has lost. 
     It is another object of the present invention to provide a novel method for controlling the mobile communication hierarchical network which temporary generates a by-pass route to the communication route for allowing continuation in communication between the mobile host and the host network after at least one router or line has become trouble and the established communication route has lost and until the communication route is re-established. 
     It is still another object of the present invention to provide a novel system for controlling the mobile communication hierarchical network which allows continuation in communication between the mobile host and the host network even if at least one router or line has become trouble and the established communication route has lost. 
     It is yet another object of the present invention to provide a novel system for controlling the mobile communication hierarchical network which temporary generates a by-pass route to the communication route for allowing continuation in communication between the mobile host and the host network after at least one router or line has become trouble and the established communication route has lost and until the communication route is re-established. 
     It is further another object of the present invention to provide a novel method for controlling the mobile communication hierarchical network which is capable of reducing the probability of packet loss. 
     It is further more another object of the present invention to provide a novel method for controlling the mobile communication hierarchical network which allows a mobile host to receive a packet from a new base station newly linked to the mobile host even if the mobile host MH moves from an old radio area covered by an old base station to a new radio area covered by the new base station during transfer of the packet through the mobile communication network. 
     It is an additional object of the present invention to provide a novel method for controlling the mobile communication hierarchical network which is capable of reducing a traffic of the host network. 
     It is a further additional object of the present invention to provide a novel method for controlling the mobile communication hierarchical network which is capable of reducing a traffic of the hierarchical network of routers. 
     It is a still further additional object of the present invention to provide a novel method for controlling the mobile communication hierarchical network which is capable of managing receipts of packets. 
     It is a yet further additional object of the present invention to provide a novel method for controlling the mobile communication hierarchical network which allows the hierarchical network of routers to exhibit a high performance. 
     It is furthermore additional object of the present invention to provide a novel method for controlling the mobile communication hierarchical network which improves a transfer efficiency of the packets with avoiding duplicate receipts of the packets by the mobile host. 
     It is also an object of the present invention to provide a novel system for controlling the mobile communication hierarchical network which is capable of reducing the probability of packet loss. 
     It is also an object of the present invention to provide a novel system for controlling the mobile communication hierarchical network which allows a mobile host to receive a packet from a new base station newly linked to the mobile host even if the mobile host MH moves from an old radio area covered by an old base station to a new radio area covered by the new base station during transfer of the packet through the mobile communication network. 
     It is also an object of the present invention to provide a novel system for controlling the mobile communication hierarchical network which is capable of reducing a traffic of the host network. 
     It is also an object of the present invention to provide a novel system for controlling the mobile communication hierarchical network which is capable of reducing a traffic of the hierarchical network of routers. 
     It is also an object of the present invention to provide a novel system for controlling the mobile communication hierarchical network which is capable of managing receipts of packets. 
     It is also an object of the present invention to provide a novel system for controlling the mobile communication hierarchical network which allows the hierarchical network of routers to exhibit a high performance. 
     It is also an object of the present invention to provide a novel system for controlling the mobile communication hierarchical network which improves a transfer efficiency of the packets with avoiding duplicate receipts of the packets by the mobile host. 
     It is also an object of the present invention to provide a novel router included in a hierarchical network of the mobile communication hierarchical network which is capable of reducing the probability of packet loss. 
     It is also an object of the present invention to provide a novel router included in a hierarchical network of the mobile communication hierarchical network which allows a mobile host to receive a packet from a new base station newly linked to the mobile host even if the mobile host MH moves from an old radio area covered by an old base station to a new radio area covered by the new base station during transfer of the packet through the mobile communication network. 
     It is also an object of the present invention to provide a novel router included in a hierarchical network of the mobile communication hierarchical network which is capable of reducing a traffic of the host network. 
     It is also an object of the present invention to provide a novel router included in a hierarchical network of the mobile communication hierarchical network which is capable of reducing a traffic of the hierarchical network of routers. 
     It is also an object of the present invention to provide a novel router included in a hierarchical network of the mobile communication hierarchical network which is capable of managing receipts of packets. 
     It is also an object of the present invention to provide a novel router included in a hierarchical network of the mobile communication hierarchical network which allows the hierarchical network of routers to exhibit a high performance. 
     It is also an object of the present invention to provide a novel router included in a hierarchical network of the mobile communication hierarchical network which improves a transfer efficiency of the packets with avoiding duplicate receipts of the packets by the mobile host. 
     The present invention provides a communication network comprising: a host network; a plurality of base stations; at least a mobile host capable of establishing links to the base stations; and a hierarchy-network of plural routers providing multiple-point routings between the base stations and the host network, and the routers including at least a page-area managing router for managing at least a page area for recording the mobile host, wherein the page-area managing router limits, within a predetermined number, the number of transfer-acceptable packets in packets received in a predetermined time period, so that the page-area managing router transfers only the transfer-acceptable packets to sub-ordinate routers managed by the page-area managing router, and the page-area managing router does not transfer exceeding transfer-requested packets received additionally to the transfer-acceptable packets in the predetermined time period. 
     The present invention also provides a communication network comprising: a host network; a plurality of base stations; at least a mobile host capable of establishing links to the base stations; and a hierarchy-network of plural router-sets providing multiple-point routings between the base stations and the host network, wherein each of the router-sets further includes plural associated routers which provide the same communication route and which have the same routing informations, and normally selected one of the associated routers in each router set is operational to provide the communication route, and if the normally selected one of the associated routers becomes trouble or inoperational, then other of the associated routers is alternatively selected to be operational to provide the communication route, thereby allowing continuous communication between the at least mobile host and the host network. 
     The present invention also provides a communication network comprising: a host network; a plurality of base stations; at least a mobile host capable of establishing links to the base stations; and a hierarchy-network of plural routers providing multiple-point routings between the base stations and the host network, wherein at least one of the routers becomes selectively performing as a multicast router for transferring a packet to not only a first base station which has currently been linked to the mobile host but also at least a second base station adjacent to the first base station, and the second base station has currently been unlinked to the mobile host. 
     The above and other objects, features and advantages of the present invention will be apparent from the following descriptions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. 
         FIG. 1  is a block diagram illustrative of a conventional mobile communication network. 
         FIG. 2  is a sequence diagram illustrative of sequential operations of the above described conventional mobile communication hierarchical network shown in  FIG. 1 . 
         FIG. 3  is a block diagram illustrative of another conventional mobile communication network. 
         FIG. 4  is a block diagram illustrative of communication processes of the conventional mobile communication network of  FIG. 3 . 
         FIG. 5  is a block diagram illustrative of still another conventional mobile communication network. 
         FIG. 6  is a block diagram illustrative of operation of the conventional mobile communication network of  FIG. 5 . 
         FIG. 7  is a block diagram illustrative of a novel mobile communication network in a first embodiment in accordance with the present invention. 
         FIG. 8  is a sequence diagram illustrative of sequential operations of the above described novel mobile communication hierarchical network shown in  FIG. 7 . 
         FIG. 9  is a block diagram illustrative of a novel mobile communication network in a second embodiment in accordance with the present invention. 
         FIG. 10  is a block diagram illustrative of operations of the novel mobile communication network of  FIG. 9 . 
         FIG. 11  is a block diagram illustrative of operations of the novel mobile communication network of  FIG. 9 . 
         FIG. 12  is a block diagram illustrative of operations of the novel mobile communication network of  FIG. 9 . 
         FIG. 13  is a block diagram illustrative of operations of the novel mobile communication network of  FIG. 9 . 
         FIG. 14  is a block diagram illustrative of a novel mobile communication network in a third embodiment in accordance with the present invention. 
         FIG. 15  is a block diagram illustrative of operation of the novel mobile communication network of  FIG. 14 . 
         FIG. 16  is a block diagram illustrative of a novel mobile communication network in a fourth embodiment in accordance with the present invention. 
         FIG. 17  is a block diagram illustrative of operations of the packet transfer in the mobile communication network of  FIG. 16 . 
         FIG. 18  is a block diagram illustrative of a novel mobile communication network in a fifth embodiment in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first aspect of the present invention is a communication network comprising: a host network; a plurality of base stations; at least a mobile host capable of establishing links to the base stations; and a hierarchy-network of plural routers providing multiple-point routings between the base stations and the host network, and the routers including at least a page-area managing router for managing at least a page area for recording the mobile host, wherein the page-area managing router limits, within a predetermined number, the number of transfer-acceptable packets in packets received in a predetermined time period, so that the page-area managing router transfers only the transfer-acceptable packets to sub-ordinate routers managed by the page-area managing router, and the page-area managing router does not transfer exceeding transfer-requested packets received additionally to the transfer-acceptable packets in the predetermined time period. 
     It is possible that the page-area managing router discards the exceeding transfer-requested packets. 
     It is also possible that the page-area managing router is capable of optionally setting the predetermined number for the transfer-acceptable packets. It is also possible that the predetermined number is a natural number. 
     It is also possible that the page-area managing router is capable of optionally setting the predetermined time period. 
     It is also possible that the page-area managing router transmits, through the host network to a caller, a second packet-transmission suppression request which requests the caller to widen a time interval of discontinuous transmission of the packets. 
     It is also possible that the page-area managing router transmits, through the host network to a caller, a second packet-transmission suppression request which requests the caller to stop transmission of the packet until the predetermined time period has passed, and re-start the packet transmission thereafter. 
     A second aspect of the present invention is a method of controlling a communication network comprising: a host network; a plurality of base stations; at least a mobile host capable of establishing links to the base stations; and a hierarchy-network of plural routers providing multiple-point routings between the base stations and the host network, and the routers including at least a page-area managing router for managing at least a page area for recording the mobile host, wherein the page-area managing router limits, within a predetermined number, the number of transfer-acceptable packets in packets received in a predetermined time period, so that the page-area managing router transfers only the transfer-acceptable packets to sub-ordinate routers managed by the page-area managing router, and the page-area managing router does not transfer exceeding transfer-requested packets received additionally to the transfer-acceptable packets in the predetermined time period. 
     It is also possible that the page-area managing router discards the exceeding transfer-requested packets. 
     It is also possible that the page-area managing router is capable of optionally setting the predetermined number for the transfer-acceptable packets. It is also possible that the predetermined number is a natural number. 
     It is also possible that the page-area managing router is capable of optionally setting the predetermined time period. 
     It is also possible that the page-area managing router transmits, through the host network to a caller, a second packet-transmission suppression request which requests the caller to widen a time interval of discontinuous transmission of the packets. 
     It is also possible that the page-area managing router transmits, through the host network to a caller, a second packet-transmission suppression request which requests the caller to stop transmission of the packet until the predetermined time period has passed, and re-start the packet transmission thereafter. 
     A third aspect of the present invention is a page-area managing router included a hierarchy-network of plural routers providing multiple-point routings between a host network and plural base stations capable of links to at least a mobile host in a communication network, and the page-area managing router managing at least a page area for recording the mobile host, wherein the page-area managing router limits, within a predetermined number, the number of transfer-acceptable packets in packets received in a predetermined time period, so that the page-area managing router transfers only the transfer-acceptable packets to sub-ordinate routers managed by the page-area managing router, and the page-area managing router does not transfer exceeding transfer-requested packets received additionally to the transfer-acceptable packets in the predetermined time period. 
     It is also possible that the page-area managing router discards the exceeding transfer-requested packets. 
     It is also possible that the page-area managing router is capable of optionally setting the predetermined number for the transfer-acceptable packets. It is also possible that the predetermined number is a natural number. 
     It is also possible that the page-area managing router is capable of optionally setting the predetermined time period. 
     It is also possible that the page-area managing router transmits, through the host network to a caller, a second packet-transmission suppression request which requests the caller to widen a time interval of discontinuous transmission of the packets. 
     It is also possible that the page-area managing router transmits, through the host network to a caller, a second packet-transmission suppression request which requests the caller to stop transmission of the packet until the predetermined time period has passed, and re-start the packet transmission thereafter. 
     A fourth aspect of the present invention is a communication network comprising: a host network; a plurality of base stations; at least a mobile host capable of establishing links to the base stations; and a hierarchy-network of plural router-sets providing multiple-point routings between the base stations and the host network, wherein each of the router-sets further includes plural associated routers which provide the same communication route and which have the same routing informations, and normally selected one of the associated routers in each router set is operational to provide the communication route, and if the normally selected one of the associated routers becomes trouble or inoperational, then other of the associated routers is alternatively selected to be operational to provide the communication route, thereby allowing continuous communication between the at least mobile host and the host network. 
     It is also possible that the associated routers in each router set comprise a primary router and a secondary router, and the primary router is normally selected and operational to provide the communication route, and if the primary router becomes trouble or inoperational, then the secondary router is alternatively selected and operational to provide the communication route. 
     It is also possible that selection to one of the associated routers in each router set is made by a selected higher level router which manages the associated routers. It is also possible that originally selected one of the associated routers in each router set sends the selected higher level router a message indicating that the originally selected one of the associated routers is operational, and if the selected higher level router has not received the message from the originally selected one of the associated routers in a predetermined time period, then the selected higher level router judges that the originally selected one of the associated routers has become inoperational, and the selected higher level router selects other of the associated routers to provide the same communication route alternative to the originally selected one of the associated routers. 
     It is also possible that all of the associated routers update the same routing information themselves based on a position recording message of the at least mobile host which has been transferred through a selected lower level router which is managed by selected one of the associated routers, and the selected one of the associated routers further transfers the position recording message to all of higher level associated routers which are capable of managing the associated routers. 
     A fifth aspect of the present invention is a method of controlling a communication network comprising: a host network; a plurality of base stations; at least a mobile host capable of establishing links to the base stations; and a hierarchy-network of plural router-sets providing multiple-point routings between the base stations and the host network, each of the router-sets further including plural associated routers which provide the same communication route and which have the same routing informations, wherein normally selected one of the associated routers in each router set is operational to provide the communication route, and if the normally selected one of the associated routers becomes trouble or inoperational, then other of the associated routers is alternatively selected to be operational to provide the communication route, thereby allowing continuous communication between the at least mobile host and the host network. 
     It is also possible that the associated routers in each router set comprise a primary router and a secondary router, and the primary router is normally selected and operational to provide the communication route, and if the primary router becomes trouble or inoperational, then the secondary router is alternatively selected and operational to provide the communication route. 
     It is also possible that selection to one of the associated routers in each router set is made by a selected higher level router which manages the associated routers. It is also possible that originally selected one of the associated routers in each router set sends the selected higher level router a message indicating that the originally selected one of the associated routers is operational, and if the selected higher level router has not received the message from the originally selected one of the associated routers in a predetermined time period, then the selected higher level router judges that the originally selected one of the associated routers has become inoperational, and the selected higher level router selects other of the associated routers to provide the same communication route alternative to the originally selected one of the associated routers. 
     It is also possible that all of the associated routers update the same routing information themselves based on a position recording message of the at least mobile host which has been transferred through a selected lower level router which is managed by selected one of the associated routers, and the selected one of the associated routers further transfers the position recording message to all of higher level associated routers which are capable of managing the associated routers. 
     A sixth aspect of the present invention is a hierarchy-router-network of plural router-sets providing multiple-point routings between a plurality of base stations establishing links to at least a mobile host and a host network, wherein each of the router-sets further includes plural associated routers which provide the same communication route and which have the same routing informations, and normally selected one of the associated routers in each router set is operational to provide the communication route, and if the normally selected one of the associated routers becomes trouble or inoperational, then other of the associated routers is alternatively selected to be operational to provide the communication route, thereby allowing continuous communication between the at least mobile host and the host network. 
     It is also possible that the associated routers in each router set comprise a primary router and a secondary router, and the primary router is normally selected and operational to provide the communication route, and if the primary router becomes trouble or inoperational, then the secondary router is alternatively selected and operational to provide the communication route. 
     It is also possible that selection to one of the associated routers in each router set is made by a selected higher level router which manages the associated routers. 
     It is also possible that originally selected one of the associated routers in each router set sends the selected higher level router a message indicating that the originally selected one of the associated routers is operational, and if the selected higher level router has not received the message from the originally selected one of the associated routers in a predetermined time period, then the selected higher level router judges that the originally selected one of the associated routers has become inoperational, and the selected higher level router selects other of the associated routers to provide the same communication route alternative to the originally selected one of the associated routers. 
     It is also possible that all of the associated routers update the same routing information themselves based on a position recording message of the at least mobile host which has been transferred through a selected lower level router which is managed by selected one of the associated routers, and the selected one of the associated routers further transfers the position recording message to all of higher level associated routers which are capable of managing the associated routers. 
     A seventh aspect of the present invention is a communication network comprising: a host network; a plurality of base stations; at least a mobile host capable of establishing links to the base stations; and a hierarchy-network of plural routers providing multiple-point routings between the base stations and the host network, wherein at least one of the routers becomes selectively performing as a multicast router for transferring a packet to not only a first base station which has currently been linked to the mobile host but also at least a second base station adjacent to the first base station, and the second base station has currently been unlinked to the mobile host. 
     It is also possible that the router selected as the multicast router is positioned at a branch point of both a currently designated communication route between the host network and the first base station and a currently undesignated adjacent communication route between the host network and the second base station. 
     It is also possible that the selection of the multicast router is made by a retrieval to the branch point based on a position recording message from the mobile host and a last-updated routing information stored on a routing table of each of the routers, wherein the routing information is updated based on the position recording message from the mobile host. It is also possible that the retrieval to the branch point is made, every when the mobile host moves to an adjacent radio area to the last-existed radio area, based on a new position recording message from the mobile host and a newly-updated routing information. 
     It is also possible that the router selected as the multicast router has a lowest level in the hierarchy-network of plural routers and is positioned on a currently designated communication route between the host network and the first base station. It is also possible that the multicast router transfers the packet to the first base station and also to the second base station through a higher level router which is higher in level of the hierarchy-network of plural routers, provided that the higher level router is positioned at a branch point of both the currently designated communication route between the host network and the first base station and a currently undesignated adjacent communication route between the host network and the second base station. 
     It is also possible that the second base station is selected to be a base station which transmits a most intensive radio wave to the mobile host except for the first base station. 
     It is also possible that the multicast router adds the packet with a label value which indicates a sequence in transmission of the packet before transferring the packet with the label value. It is also possible that lowest level routers at the lowest level of the hierarchy-network of plural routers are capable of queuing the packet. It is also possible that after the mobile host entered into the adjacent radio area and established a new link to the second base station, then the mobile host sends the second base station the label value which had been last-received from the first base station, and the second base station transfers the label value to the lowest level router, and the lowest level router selects at least one packet from queuing packets by comparing respective label values of the queuing packets with reference to the last label value, and the lowest level router sends the selected at least one packet of the packets to the mobile host through the second base station. 
     It is also possible that the mobile host compares a just-received label value of the packet just received from the second base station to the last-received label value, and if the just-received label value is identical with the last-received label value, then the mobile host discards the packet just received from the second base station. 
     It is also possible that the second base station queues the packet. It is also possible that after the mobile host entered into the adjacent radio area and established a new link to the second base station, then the mobile host sends the second base station the label value which had been last-received from the first base station, and the second base station selects at least one packet from queuing packets by comparing respective label values of the queuing packets with reference to the last label value, and the second base station sends the selected at least one packet to the mobile host. 
     It is also possible that the multicast router is a bicast router. 
     An eighth aspect of the present invention is a communication network comprising: a host network; a plurality of base stations; at least a mobile host capable of establishing links to the base stations; and a hierarchy-network of plural routers providing multiple-point routings between the base stations and the host network, wherein the hierarchy-network of plural routers establishes not only a currently designated communication route between the host network and a first base station which has currently been linked to the mobile host but also a currently undesignated adjacent communication route between the host network and a second base station adjacent to the first base station, and the second base station has currently been unlinked to the mobile host, and wherein the hierarchy-network of plural routers transfers a packet not only through the currently designated communication route to the first base station but also through the currently undesignated adjacent communication route to the second base station. 
     It is also possible that a router positioned at a branch point of both the currently designated communication route and the currently undesignated adjacent communication route is selected to perform as a multicast router. It is also possible that the selection of the multicast router is made by a retrieval to the branch point based on a position recording message from the mobile host and a last-updated routing information stored on a routing table of each of the routers, wherein the routing information is updated based on the position recording message from the mobile host. It is also possible that the retrieval to the branch point is made, every when the mobile host moves to an adjacent radio area to the last-existed radio area, based on a new position recording message from the mobile host and a newly-updated routing information. 
     It is also possible that the router selected as the multicast router has a lowest level in the hierarchy-network of plural routers and is positioned on a currently designated communication route between the host network and the first base station. It is also possible that the multicast router transfers the packet to the first base station and also to the second base station through a higher level router which is higher in level of the hierarchy-network of plural routers, provided that the higher level router is positioned at a branch point of both the currently designated communication route between the host network and the first base station and a currently undesignated adjacent communication route between the host network and the second base station. 
     It is also possible that the second base station is selected to be a base station which transmits a most intensive radio wave to the mobile host except for the first base station. 
     It is also possible that the multicast router adds the packet with a label value which indicates a sequence in transmission of the packet before transferring the packet with the label value. It is also possible that lowest level routers at the lowest level of the hierarchy-network of plural routers are capable of queuing the packet. It is also possible that after the mobile host entered into the adjacent radio area and established a new link to the second base station, then the mobile host sends the second base station the label value which had been last-received from the first base station, and the second base station transfers the label value to the lowest level router, and the lowest level router selects at least one packet from queuing packets by comparing respective label values of the queuing packets with reference to the last label value, and the lowest level router sends the selected at least one packet of the packets to the mobile host through the second base station. 
     It is also possible that the mobile host compares a just-received label value of the packet just received from the second base station to the last-received label value, and if the just-received label value is identical with the last-received label value, then the mobile host discards the packet just received from the second base station. 
     It is also possible that the second base station queues the packet. It is also possible that after the mobile host entered into the adjacent radio area and established a new link to the second base station, then the mobile host sends the second base station the label value which had been last-received from the first base station, and the second base station selects at least one packet from queuing packets by comparing respective label values of the queuing packets with reference to the last label value, and the second base station sends the selected at least one packet to the mobile host. 
     It is also possible that the multicast router is a bicast router. 
     A ninth aspect of the present invention is a method of controlling a communication network comprising: a host network; a plurality of base stations; at least a mobile host capable of establishing links to the base stations; and a hierarchy-network of plural routers providing multiple-point routings between the base stations and the host network, wherein at least one of the routers becomes selectively performing as a multicast router for transferring a packet to not only a first base station which has currently been linked to the mobile host but also at least a second base station adjacent to the first base station, and the second base station has currently been unlinked to the mobile host. 
     It is also possible that the router selected as the multicast router is positioned at a branch point of both a currently designated communication route between the host network and the first base station and a currently undesignated adjacent communication route between the host network and the second base station. It is also possible that the selection of the multicast router is made by a retrieval to the branch point based on a position recording message from the mobile host and a last-updated routing information stored on a routing table of each of the routers, wherein the routing information is updated based on the position recording message from the mobile host. It is also possible that the retrieval to the branch point is made, every when the mobile host moves to an adjacent radio area to the last-existed radio area, based on a new position recording message from the mobile host and a newly-updated routing information. 
     It is also possible that the router selected as the multicast router has a lowest level in the hierarchy-network of plural routers and is positioned on a currently designated communication route between the host network and the first base station. It is also possible that the multicast router transfers the packet to the first base station and also to the second base station through a higher level router which is higher in level of the hierarchy-network of plural routers, provided that the higher level router is positioned at a branch point of both the currently designated communication route between the host network and the first base station and a currently undesignated adjacent communication route between the host network and the second base station. 
     It is also possible that the second base station is selected to be a base station which transmits a most intensive radio wave to the mobile host except for the first base station. 
     It is also possible that the multicast router adds the packet with a label value which indicates a sequence in transmission of the packet before transferring the packet with the label value. It is also possible that lowest level routers at the lowest level of the hierarchy-network of plural routers are capable of queuing the packet. It is also possible that after the mobile host entered into the adjacent radio area and established a new link to the second base station, then the mobile host sends the second base station the label value which had been last-received from the first base station, and the second base station transfers the label value to the lowest level router, and the lowest level router selects at least one packet from queuing packets by comparing respective label values of the queuing packets with reference to the last label value, and the lowest level router sends the selected at least one packet of the packets to the mobile host through the second base station. 
     It is also possible that the mobile host compares a just-received label value of the packet just received from the second base station to the last-received label value, and if the just-received label value is identical with the last-received label value, then the mobile host discards the packet just received from the second base station. 
     It is also possible that the second base station queues the packet. It is also possible that after the mobile host entered into the adjacent radio area and established a new link to the second base station, then the mobile host sends the second base station the label value which had been last-received from the first base station, and the second base station selects at least one packet from queuing packets by comparing respective label values of the queuing packets with reference to the last label value, and the second base station sends the selected at least one packet to the mobile host. 
     It is also possible that the multicast router is a bicast router. 
     A tenth aspect of the present invention is a method of controlling a communication network comprising: a host network; a plurality of base stations; at least a mobile host capable of establishing links to the base stations; and a hierarchy-network of plural routers providing multiple-point routings between the base stations and the host network, wherein the hierarchy-network of plural routers establishes not only a currently designated communication route between the host network and a first base station which has currently been linked to the mobile host but also a currently undesignated adjacent communication route between the host network and a second base station adjacent to the first base station, and the second base station has currently been unlinked to the mobile host, and wherein the hierarchy-network of plural routers transfers a packet not only through the currently designated communication route to the first base station but also through the currently undesignated adjacent communication route to the second base station. 
     It is also possible that a router positioned at a branch point of both the currently designated communication route and the currently undesignated adjacent communication route is selected to perform as a multicast router. 
     It is also possible that the selection of the multicast router is made by a retrieval to the branch point based on a position recording message from the mobile host and a last-updated routing information stored on a routing table of each of the routers, wherein the routing information is updated based on the position recording message from the mobile host. It is also possible that the retrieval to the branch point is made, every when the mobile host moves to an adjacent radio area to the last-existed radio area, based on a new position recording message from the mobile host and a newly-updated routing information. It is also possible that the router selected as the multicast router has a lowest level in the hierarchy-network of plural routers and is positioned on a currently designated communication route between the host network and the first base station. It is also possible that the multicast router transfers the packet to the first base station and also to the second base station through a higher level router which is higher in level of the hierarchy-network of plural routers, provided that the higher level router is positioned at a branch point of both the currently designated communication route between the host network and the first base station and a currently undesignated adjacent communication route between the host network and the second base station. 
     It is also possible that the second base station is selected to be a base station which transmits a most intensive radio wave to the mobile host except for the first base station. 
     It is also possible that the multicast router adds the packet with a label value which indicates a sequence in transmission of the packet before transferring the packet with the label value. It is also possible that lowest level routers at the lowest level of the hierarchy-network of plural routers are capable of queuing the packet. It is also possible that after the mobile host entered into the adjacent radio area and established a new link to the second base station, then the mobile host sends the second base station the label value which had been last-received from the first base station, and the second base station transfers the label value to the lowest level router, and the lowest level router selects at least one packet from queuing packets by comparing respective label values of the queuing packets with reference to the last label value, and the lowest level router sends the selected at least one packet of the packets to the mobile host through the second base station. 
     It is also possible that the mobile host compares a just-received label value of the packet just received from the second base station to the last-received label value, and if the just-received label value is identical with the last-received label value, then the mobile host discards the packet just received from the second base station. 
     It is also possible that the second base station queues the packet. It is also possible that after the mobile host entered into the adjacent radio area and established a new link to the second base station, then the mobile host sends the second base station the label value which had been last-received from the first base station, and the second base station selects at least one packet from queuing packets by comparing respective label values of the queuing packets with reference to the last label value, and the second base station sends the selected at least one packet to the mobile host. 
     It is also possible that the multicast router is a bicast router. 
     First Embodiment 
     A first embodiment according to the present invention will be described in detail with reference to the drawings.  FIG. 7  is a block diagram illustrative of a novel mobile communication network in a first embodiment in accordance with the present invention. This mobile communication network is generally used for a management system for managing positions of mobile telephones or automatic cars. This mobile communication network utilizes transmission control protocol/internet protocol (TCP/IP) for realizing a packet communication. 
     As shown in  FIG. 7 , the mobile communication network includes a host network  1 , plural routers Rn (n=1˜7), base stations BS 1 ˜BS 8 , and a mobile host MH. The host network  1  may comprise a wide area network such as internet. The routers Rn provide multi-point connections between the host network  1  and the base stations BS 1 ˜BS 8 . The routers Rn form a hierarchical network structure between the host network  1  and the base stations BS 1 ˜BS 8 . The router R 1  is highest level router. The routers R 2 ′ and R 3 ′ are middle level routers which are connected to the router R 1  and dominated by the router R 1 . The routers R 4 , R 5 , R 6  and R 7  are lowest level routers, wherein the routers R 4  and R 5  are connected to the router R 2 ′ and dominated by the router R 2 ′, whilst the routers R 6  and R 7  are connected to the router R 3 ′ and dominated by the router R 3 ′. The base stations BS 1  and BS 2  are connected to the router R 4  and dominated by the router R 4 . The base stations BS 3  and BS 4  are connected to the router R 5  and dominated by the router R 5 . The base stations BS 5  and BS 6  are connected to the router R 6  and dominated by the router R 6 . The base stations BS 7  and BS 8  are connected to the router R 7  and dominated by the router R 7 . 
     The mobile host MH is connected through radio communication to any one of the base stations BS 1 ˜BS 8  to establish a link to the base station for communication through the host network  1  to other subscriber. 
     In accordance with this mobile communication network, the mobile host MH is managed in the current position thereof in activated state, or the mobile host MH is managed in paging area in inactivated state o stand-by state. 
     The routers R 2 ′ and R 3 ′ manage the respective paging areas. In  FIG. 7 , the mobile host MH is positioned in an area covered by the base stations BS 1 , BS 2 , BS 3  and BS 4 , for which reason the mobile host MH is recorded in the paging area dominated by the router R 2 ′. If the mobile host MH moves from the first paging area dominated by the base stations BS 1 , BS 2 , BS 3  and BS 4  which are further dominated by the router R 2 ′ into a second paging area dominated by the base stations BS 5 , BS 6 , BS 7  and BS 8  which are further dominated by the router R 3 ′, then the router R 3 ′ registers the mobile host MH in the second paging area in accordance with a position recording message from the mobile host MH. 
     The routers R 2 ′ and R 3 ′ are adjusted to reduce the load to the sub-ordinate network managed by the routers R 2 ′ and R 3 ′ in the general calling process if the package addressed to the mobile host MH is in the stand-by state is received. Each of the routers R 2 ′ and R 3 ′ has a limiting function for limiting the number of transfer-requested packets in a predetermined time period “T” within a predetermined number, for example, 1, wherein the transfer-requested packets are the packets requested to be transferred to the sub-ordinate routers R 4 , R 5 , R 6  and R 7 . 
     If the number of the transfer-requested packets received by each of the routers R 2 ′ and R 3 ′ in the predetermined time period “T” is within the predetermined number, then each of the routers R 2 ′ and R 3 ′ normally transfers the received packet to the sub-ordinate routers R 4 , R 5 , R 6  and R 7 . If, however, the number of the transfer-requested packets received by each of the routers R 2 ′ and R 3 ′ in the predetermined time period “T” exceeds the predetermined number, then each of the routers R 2 ′ and R 3 ′ transfers transfer-acceptable packets of the predetermined number to the sub-ordinate routers R 4 , R 5 , R 6  and R 7 , and discard exceeding transfer-requested packets in addition to the transfer-acceptable packets. The transfer-acceptable packets are the packets of the predetermined number, whilst the exceeding transfer-requested packets are the packets of the exceeding number over the predetermined number. 
     If the predetermined number is set  1 , then first one of the received packets corresponds to the transfer-acceptable packet, and any further ones of the packets received in the predetermined time period correspond to the exceeding transfer-requested packets, for which reason each of the routers R 2 ′ and R 3 ′ transfers only the first one packet as the transfer-acceptable packet and discard the further packets received in the predetermined time period as the exceeding transfer-requested packets. 
       FIG. 8  is a sequence diagram illustrative of sequential operations of the above described novel mobile communication hierarchical network shown in  FIG. 7 . As shown in  FIG. 8 , the router R 2 ′ receives four packets, for example, a first-received packet, a second-received packet, a third-received packet, and a fourth-received packet in the predetermined time period “T”. The predetermined number for the transfer-acceptable packet is set  1  in the router R 2 ′. The router R 2 ′ transfers only the first-received packet to the routers R 4  and R 5  and discard the remaining second-received, third-received and fourth-received packets without transfer. As a result, in the predetermined time period “T”, no link can be established between the base station BS 3  and the mobile host MH. 
     After the predetermined time period “T” has passed, then the router R 2  becomes able to transfer but only one packet in the next predetermined time period “T”. As shown in  FIG. 8 , the second-transfer of the packet from the router R 2 ′ to the routers R 4  and R 5  results in the establishment between the base station BS 3  and the mobile host MH. 
     As described above, in accordance with the novel mobile communication hierarchical network, the routers R 2 ′ and R 3 ′ for managing the respective paging areas for recording the mobile host MH are improved to reduce or control a packet traffic in the predetermined time period in the sub-ordinate network managed by the routers R 2 ′ and R 3 ′, whereby the improved routers R 2 ′ and R 3 ′ reduce the load to the mobile communication hierarchical network. 
     The above-described predetermined time period “T”, the throughput of the network and the predetermined number for the transfer-acceptable packets may optionally be decided. The number of hierarchy of the routers in the mobile communication network, the number of the base stations BS, and the number of the mobile host MH may be optional. 
     The following modification to the first embodiment is optionally possible. If the number of the transfer-requested packets received by each of the routers R 2 ′ and R 3 ′ in the predetermined time period “T” exceeds the predetermined number, then each of the routers R 2 ′ and R 3 ′ further sends the caller of a packet-transmission suppression request which requests the caller to widen the time interval of discontinuous transmission of the packets or which requests the caller to stop the transmission of the packet until the predetermined time period “T” has passed, and re-start the packet transmission thereafter. 
     If, for example, the predetermined number is set  1 , then after the router R 2 ′ received the first-received packet, then the router R 2 ′ sends the caller of a packet-transmission suppression request which requests the caller to widen the time interval of discontinuous transmission of the packets or which requests the caller to stop the transmission of the packet until the predetermined time period “T” has passed, and re-start the packet transmission thereafter. 
     Second Embodiment 
     A second embodiment according to the present invention will be described in detail with reference to the drawings.  FIG. 9  is a block diagram illustrative of a novel mobile communication network in a second embodiment in accordance with the present invention. This mobile communication network is generally used for a management system for managing positions of mobile telephones or automatic cars. This mobile communication network utilizes transmission control protocol/internet protocol (TCP/IP) for realizing a packet communication. 
     As shown in  FIG. 9 , the mobile communication network includes a host network  1 , plural pairs of primary routers Rnp (n=1˜7) and secondary routers Rns (n=1˜7), base stations BS 1 ˜BS 8 , and a mobile host MH. The host network  1  may comprise a wide area network such as internet. The plural pairs of primary routers Rnp (n=1˜7) and secondary routers Rns (n=1˜7) provide multi-point connections between the host network  1  and the base stations BS 1 ˜BS 8 . The plural pairs of primary routers Rnp (n=1˜7) and secondary routers Rns (n=1˜7) form a hierarchical network structure between the host network  1  and the base stations BS 1 ˜BS 8 . 
     The primary router R 1   p  and the secondary router R 1   s  make a first pair providing a first point at highest level of the hierarchical routes. The primary router R 1   p  and the secondary router R 1   s  provide the same route and have the same routing information. 
     The primary router R 2   p  and the secondary router R 2   s  make a second pair providing a second point at middle level of the hierarchical routes. The primary router R 2   p  and the secondary router R 2   s  provide the same route and have the same routing information. The primary router R 2   p  is connected to both the primary router R 1   p  and the secondary router R 1   s  in parallel, so that the primary router R 2   p  is managed by each of the primary router R 1   p  and the secondary router R 1   s . The secondary router R 2   s  is also connected to both the primary router R 1   p  and the secondary router R 1   s  in parallel, so that the secondary router R 2   s  is managed by each of the primary router R 1   p  and the secondary router R 1   s . The primary router R 2   p  and the secondary router R 2   s  have the same connection routes to the primary router R 1   p  and the secondary router R 1   s.    
     The primary router R 3   p  and the secondary router R 3   s  make a third pair providing a third point at middle level of the hierarchical routes. The primary router R 3   p  and the secondary router R 3   s  provide the same route and have the same routing information. The primary router R 3   p  is connected to both the primary router R 1   p  and the secondary router R 1   s  in parallel, so that the primary router R 3   p  is managed by each of the primary router R 1   p  and the secondary router R 1   s . The secondary router R 3   s  is also connected to both the primary router R 1   p  and the secondary router R 1   s  in parallel, so that the secondary router R 3   s  is managed by each of the primary router R 1   p  and the secondary router R 1   s . The primary router R 3   p  and the secondary router R 3   s  have the same connection routes to the primary router R 1   p  and the secondary router R 1   s.    
     The primary router R 1   p  is connected to the primary router R 2   p  and the secondary router R 2   s  as well as connected to the primary router R 3   p  and the secondary router R 3   s  for managing the primary router R 2   p  and the secondary router R 2   s  as well as the primary router R 3   p  and the secondary router R 3   s . The secondary router R 2   s  is also connected to the primary router R 2   p  and the secondary router R 2   s  as well as connected to the primary router R 3   p  and the secondary router R 3   s  for managing the primary router R 2   p  and the secondary router R 2   s  as well as the primary router R 3   p  and the secondary router R 3   s.    
     The primary router R 4   p  and the secondary router R 4   s  make a fourth pair providing a fourth point at lowest level of the hierarchical routes. The primary router R 4   p  and the secondary router R 4   s  provide the same route and have the same routing information. The primary router R 4   p  is connected to both the primary router R 2   p  and the secondary router R 2   s  in parallel, so that the primary router R 4   p  is managed by each of the primary router R 2   p  and the secondary router R 2   s . The secondary router R 4   s  is also connected to both the primary router R 2   p  and the secondary router R 2   s  in parallel, so that the secondary router R 4   s  is managed by each of the primary router R 2   p  and the secondary router R 2   s . The primary router R 4   p  and the secondary router R 4   s  have the same connection routes to the primary router R 2   p  and the secondary router R 2   s . The primary router R 4   p  is further connected to the base stations BS 1  and BS 2  in parallel for managing the base stations BS 1  and BS 2 . The secondary router R 4   s  is also connected to the base stations BS 1  and BS 2  in parallel for managing the base stations BS 1  and BS 2 . The primary router R 4   p  and the secondary router R 4   s  have the same connection routes to the base stations BS 1  and BS 2 . 
     The primary router R 5   p  and the secondary router R 5   s  make a fifth pair providing a fifth point at lowest level of the hierarchical routes. The primary router R 5   p  and the secondary router R 5   s  provide the same route and have the same routing information. The primary router R 5   p  is connected to both the primary router R 2   p  and the secondary router R 2   s  in parallel, so that the primary router R 5   p  is managed by each of the primary router R 2   p  and the secondary router R 2   s . The secondary router R 5   s  is also connected to both the primary router R 2   p  and the secondary router R 2   s  in parallel, so that the secondary router R 5   s  is managed by each of the primary router R 2   p  and the secondary router R 2   s . The primary router R 5   p  and the secondary router R 5   s  have the same connection routes to the primary router R 2   p  and the secondary router R 2   s . The primary router R 5   p  is further connected to the base stations BS 3  and BS 4  in parallel for managing the base stations BS 3  and BS 4 . The secondary router R 5   s  is also connected to the base stations BS 3  and BS 4  in parallel for managing the base stations BS 3  and BS 4 . The primary router R 5   p  and the secondary router R 5   s  have the same connection routes to the base stations BS 3  and BS 4 . 
     The primary router R 2   p  is connected to the primary router R 4   p  and the secondary router R 4   s  as well as connected to the primary router R 5   p  and the secondary router R 5   s  for managing the primary router R 4   p  and the secondary router R 4   s  as well as the primary router R 5   p  and the secondary router R 5   s . The secondary router R 2   s  is also connected to the primary router R 4   p  and the secondary router R 4   s  as well as connected to the primary router R 5   p  and the secondary router R 5   s  for managing the primary router R 4   p  and the secondary router R 4   s  as well as the primary router R 5   p  and the secondary router R 5   s.    
     The primary router R 6   p  and the secondary router R 6   s  make a sixth pair providing a sixth point at lowest level of the hierarchical routes. The primary router R 6   p  and the secondary router R 6   s  provide the same route and have the same routing information. The primary router R 6   p  is connected to both the primary router R 3   p  and the secondary router R 3   s  in parallel, so that the primary router R 6   p  is managed by each of the primary router R 3   p  and the secondary router R 3   s . The secondary router R 6   s  is also connected to both the primary router R 3   p  and the secondary router R 3   s  in parallel, so that the secondary router R 6   s  is managed by each of the primary router R 3   p  and the secondary router R 3   s . The primary router R 6   p  and the secondary router R 6   s  have the same connection routes to the primary router R 3   p  and the secondary router R 3   s . The primary router R 6   p  is further connected to the base stations BS 5  and BS 6  in parallel for managing the base stations BS 5  and BS 6 . The secondary router R 6   s  is also connected to the base stations BS 5  and BS 6  in parallel for managing the base stations BS 5  and BS 6 . The primary router R 6   p  and the secondary router R 6   s  have the same connection routes to the base stations BS 5  and BS 6 . 
     The primary router R 7   p  and the secondary router R 7   s  make a seventh pair providing a seventh point at lowest level of the hierarchical routes. The primary router R 7   p  and the secondary router R 7   s  provide the same route and have the same routing information. The primary router R 7   p  is connected to both the primary router R 3   p  and the secondary router R 3   s  in parallel, so that the primary router R 7   p  is managed by each of the primary router R 3   p  and the secondary router R 3   s . The secondary router R 7   s  is also connected to both the primary router R 3   p  and the secondary router R 3   s  in parallel, so that the secondary router R 7   s  is managed by each of the primary router R 3   p  and the secondary router R 3   s . The primary router R 7   p  and the secondary router R 7   s  have the same connection routes to the primary router R 3   p  and the secondary router R 3   s . The primary router R 7   p  is further connected to the base stations BS 7  and BS 8  in parallel for managing the base stations BS 7  and BS 8 . The secondary router R 7   s  is also connected to the base stations BS 7  and BS 8  in parallel for managing the base stations BS 7  and BS 8 . The primary router R 7   p  and the secondary router R 7   s  have the same connection routes to the base stations BS 7  and BS 8 . 
     The primary router R 3   p  is connected to the primary router R 6   p  and the secondary router R 6   s  as well as connected to the primary router R 7   p  and the secondary router R 7   s  for managing the primary router R 6   p  and the secondary router R 6   s  as well as the primary router R 7   p  and the secondary router R 7   s . The secondary router R 3   s  is also connected to the primary router R 6   p  and the secondary router R 6   s  as well as connected to the primary router R 7   p  and the secondary router R 7   s  for managing the primary router R 6   p  and the secondary router R 6   s  as well as the primary router R 7   p  and the secondary router R 7   s . Each of the base stations BS 1 , BS 2 , BS 3 , BS 4 , BS 5 , BS 6 , BS 7  and BS 8  is capable of establishing the link to the mobile host MH. 
     As described above, the primary set of the primary routers Rnp and the secondary set of the secondary routers Rns provide the same hierarchical routes between the host network  1  and the base stations BS 1 , BS 2 , BS 3 , BS 4 , BS 5 , BS 6 , BS 7  and BS 8 . The reason why the secondary routers Rns are additionally provided to the primary routers Rnp are as follows. In normal, the primary set of the primary routers Rnp is used to provide the hierarchical routes between the host network  1  and the base stations BS 1 , BS 2 , BS 3 , BS 4 , BS 5 , BS 6 , BS 7  and BS 8  for implementation of the communication through the mobile communication hierarchical network. If the primary router Rnp becomes trouble, then the paired secondary router Rns making the pair with the troubled primary router Rnp is selected and used alternative to the troubled primary router Rnp. The secondary router Rns has the same routing information and provides the same route as the troubled primary router Rnp, for which reason the same communication route can be maintained. 
     If at least any one of the primary routers Rnp on the established communication route becomes once trouble and the communication route becomes lost, then the paired secondary router Rns making the pair with the troubled primary router Rnp is selected and used alternative to the troubled primary router Rnp, whereby the secondary router Rns provides the same communication route for allowing continuation of the current communication between the mobile host MH and the host network  1 . 
       FIG. 10  is a block diagram illustrative of operations of the novel mobile communication network of  FIG. 9 . A communication route has been established between the first pair of the primary router R 1   p  and the secondary router R 1   s  and the fourth pair of the primary router R 4   p  and the secondary router R 4   s  through the second pair of the primary router R 2   p  and the secondary router R 2   s.    
     The primary router R 2   p  and the secondary router R 2   s  are sub-ordinate routers to the primary router R 1   p  and the secondary router R 1   s , so that the primary router R 2   p  and the secondary router R 2   s  are managed by the primary router R 1   p  and the secondary router R 1   s . Each of the primary router R 2   p  and the secondary router R 2   s  periodically sends informations of whether the router function is effective or ineffective to each of the primary router R 1   p  and the secondary router R 1   s , so that the primary router R 1   p  and the secondary router R 1   s  can periodically manage that the functions of the primary router R 2   p  and the secondary router R 2   s  would be currently effective. 
     The primary router R 4   p  and the secondary router R 4   s  are sub-ordinate routers to the primary router R 2   p  and the secondary router R 2   s , so that the primary router R 4   p  and the secondary router R 4   s  are managed by the primary router R 2   p  and the secondary router R 2   s . Each of the primary router R 4   p  and the secondary router R 4   s  periodically sends informations of whether the router function is effective or ineffective to each of the primary router R 2   p  and the secondary router R 2   s , so that the primary router R 2   p  and the secondary router R 2   s  can periodically manage that the functions of the primary router R 4   p  and the secondary router R 4   s  would be currently effective. 
     The primary router R 1   p  and the secondary router R 1   s  are manager routers to the primary router R 2   p  and the secondary router R 2   s , so that the primary router R 1   p  and the secondary router R 1   s  manage the primary router R 2   p  and the secondary router R 2   s . Each of the primary router R 1   p  and the secondary router R 1   s  periodically sends the following respective informations to each of the primary router R 2   p  and the secondary router R 2   s . The respective informations from the primary router R 1   p  and the secondary router R 1   s  to the primary router R 2   p  and the secondary router R 2   s  include respective primary flags which separately indicate that the primary router R 2   p  should be selected or not and that the secondary router R 2   s  should be selected or not. If the primary flag is ON, this means that the router be selected. If the primary flag is OFF, this means that the router be unselected. 
     The primary router R 2   p  and the secondary router R 2   s  are manager routers to the primary router R 4   p  and the secondary router R 4   s , so that the primary router R 2   p  and the secondary router R 2   s  manage the primary router R 4   p  and the secondary router R 4   s . Each of the primary router R 2   p  and the secondary router R 2   s  periodically sends the following respective informations to each of the primary router R 4   p  and the secondary router R 4   s . The respective informations from the primary router R 1   p  and the secondary router R 1   s  to the primary router R 2   p  and the secondary router R 2   s  include respective primary flags which separately indicate that the primary router R 2   p  should be selected or not and that the secondary router R 2   s  should be selected or not. If the primary flag is ON, this means that the router be selected. If the primary flag is OFF, this means that the router be unselected. 
     For example, the primary router R 1   p  periodically sends the primary router R 2   p  the information that the primary flag is ON, whereby the primary router R 2   p  is selected to provide the communication route. The primary router R 1   p  also periodically sends the secondary router R 2   s  the information that the primary flag is OFF, whereby the secondary router R 2   s  is unselected to provide no communication route. The selected primary router R 2   p  further periodically sends the primary router R 4   p  the information that the primary flag is ON, whereby the primary router R 4   p  is selected to provide the communication route. The selected primary router R 2   p  further periodically sends the secondary router R 4   s  the information that the primary flag is OFF, whereby the secondary router R 4   s  is unselected to provide no communication route. The unselected secondary router R 2   s  periodically sends the primary router R 4   s  and the secondary router R 4   s  the information that the primary flag is OFF. The unselected secondary router R 1   s  periodically sends the primary router R 2   s  and the secondary router R 2   s  the information that the primary flag is OFF. 
     The informations including the primary flag are transmitted between the upper level routers and the lower level routers for selecting the routers which provide the communication route between the host network  1  and the base stations BS, whereby the available communication route can be established based on the informations including the primary flags. 
     The mobile host MH establishes a link to any one of the base stations BS 1 ˜BS 8 , and then sends the position recording message to the linked base station, so that the position recording message is transferred from the linked base station through the routers from the lowest level to the highest level, thereby establishing the communication route between the host network  1  and the linked base station. The lower level routers send the same position recording message to all of the paired higher level routers which manage the lower level routers and provide the same communication route. 
       FIG. 11  is a block diagram illustrative of operations of the novel mobile communication network of  FIG. 9 , wherein all of the primary and secondary routers are operational. The mobile host MH has established a link to the base station BS 2 , and the mobile host MH sends the position recording message to the base station BS 2  in a first step ( 1 ). The base station BS 2  transfers the position recording message to both the primary router R 4   p  and the secondary router R 4   s  which provides the same communication route in a second step ( 2 ) and ( 2 ′). The primary router R 4   p  and the secondary router R 4   s  update the routing information themselves based on the received position recording message. 
     The primary router R 4   p  has already received, from the primary router R 2   p , the information that the primary flag is ON, whereby the primary router R 4   p  has already been selected. The secondary router R 4   s  has already received, from the primary router R 2   p , the information that the primary flag is OFF, whereby the secondary router R 4   s  has been unselected. 
     The primary router R 4   p  transfers the position recording message to both the primary router R 2   p  and the secondary router R 2   s  which provides the same communication route in a third step ( 3 ) and ( 3 ′). Since the secondary router R 4   s  has been unselected, then the secondary router R 4   s  does not transfer the position recording message. The primary router R 2   p  and the secondary router R 2   s  update the routing information themselves based on the received position recording message. 
     The primary router R 2   p  has already received, from the primary router R 1   p , the information that the primary flag is ON, whereby the primary router R 2   p  has already been selected. The secondary router R 2   s  has already received, from the primary router R 1   p , the information that the primary flag is OFF, whereby the secondary router R 2   s  has been unselected. 
     The primary router R 2   p  transfers the position recording message to both the primary router R 1   p  and the secondary router R 1   s  which provides the same communication route in a fourth step ( 4 ) and ( 4 ′). Since the secondary router R 2   s  has been unselected, then the secondary router R 2   s  does not transfer the position recording message. The primary router R 1   p  and the secondary router R 1   s  update the routing information themselves based on the received position recording message. 
     As a result, a primary communication route can be established which includes the primary router R 1   p , the primary router R 2   p , the primary router R 4   p , and the base station BS 2 . 
       FIG. 12  is a block diagram illustrative of operations of the novel mobile communication network of  FIG. 9 , wherein one of the primary routers becomes trouble and inoperational. If the primary router R 2   p  becomes trouble and inoperational, then the troubled primary router R 2   p  does not transfer the messages to the upper level primary and secondary routers R 1   p  and R 1   s  and the lower level primary and secondary routers R 4   p  and R 4   s , whereby the above primary communication route becomes no longer available. 
       FIG. 13  is a block diagram illustrative of operations of the novel mobile communication network of  FIG. 9 , wherein one of the secondary routers is selected alternative to the troubled primary router for allowing continuous communication. The troubled primary router R 2   p  does not transfer the message, and the unselected secondary router R 2   s  does not transfer the message. After the selected primary router R 1   p  has not received any messages from the troubled primary router R 2   p  and the unselected secondary router R 2   s  during a predetermined time period, then the selected primary router R 1   p  judges that the primary router R 2   p  has been troubled and inoperational. The selected primary router R 1   p  starts to periodically send the unselected secondary router R 2   s  the information that the primary flag is ON, whereby the secondary router R 2   s  is selected and becomes operational to provide the communication route instead of the troubled primary router R 2   p . Since the secondary router R 2   s  have already had the same routing information as the primary router R 2   p , the secondary router R 2   s  is operational to provide the communication route immediately after the secondary router R 2   s  has been selected by the primary router R 1   p . As a result, an alternating communication route can immediately be established which includes the primary router R 1   p , the secondary router R 2   s , the primary router R 4   p  and the base station BS 2 , whereby the continuous communication between the mobile host MH linked to the base station BS 2  and the host network  1  can be realized. 
     As described above, in accordance with the second embodiment of the present invention, if at least any one of the primary routers Rnp on the already established communication route becomes once trouble and inoperational and the communication route becomes lost, then the paired secondary router Rns making the pair with the troubled primary router Rnp is selected by the upper level selected router managing those routers and becomes operational alternative to the troubled primary router Rnp, whereby the newly selected secondary router Rns provides the same communication route for allowing the continuation of the current communication between the mobile host MH and the host network  1 . 
     Further, it is not required that the plural mobile hosts MH transmit respective plural position recording messages which are transferred through the hierarchy-networked routers Rn to the host network  1  for re-establishment of the communication route. It appear that the upper level router does not receive many position recording messages from the plural mobile hosts MH for re-establishment of the communication route, resulting in no problem with the increase in the load to the upper level router. 
     The number of hierarchy of the routers in the mobile communication network, the number of the base stations BS, and the number of the mobile host MH may be optional. 
     Third Embodiment 
     A third embodiment according to the present invention will be described in detail with reference to the drawings.  FIG. 14  is a block diagram illustrative of a novel mobile communication network in a third embodiment in accordance with the present invention. This mobile communication network is generally used for a management system for managing positions of mobile telephones or automatic cars. This mobile communication network utilizes transmission control protocol/internet protocol (TCP/IP) for realizing a packet communication. 
     As shown in  FIG. 14 , the mobile communication network includes a host network  1 , plural routers Rn′ (n=1˜7), base stations BS 1 ˜BS 8 , and a mobile host MH. The host network  1  may comprise a wide area network such as internet. The routers Rn′ provide multi-point connections between the host network  1  and the base stations BS 1 ˜BS 8 . The routers Rn′ form a hierarchical network structure between the host network  1  and the base stations BS 1 ˜BS 8 . The router R 1 ′ is highest level router. The routers R 2 ′ and R 3 ′ are middle level routers which are connected to the router R 1 ′ and dominated by the router R′ 1 . The routers R 4 ′, R 5 ′, R 6 ′ and R 7 ′ are lowest level routers, wherein the routers R 4 ′, R 5 ′, R 6 ′ and R 7 ′ are bicast routers. The bicast routers R 4 ′ and R 5 ′ are connected to the router R 2 ′ and dominated by the router R 2 ′, whilst the bicast routers R 6 ′ and R 7 ′ are connected to the router R 3 ′ and dominated by the router R 3 ′. The base stations BS 1  and BS 2  are connected to the bicast router R 4 ′ and dominated by the bicast router R 4 ′. The base stations BS 3  and BS 4  are connected to the bicast router R 5 ′ and dominated by the bicast router R 5 ′. The base stations BS 5  and BS 6  are connected to the bicast router R 6 ′ and dominated by the bicast router R 6 ′. The base stations BS 7  and BS 8  are connected to the bicast router R 7 ′ and dominated by the bicast router R 7 ′. 
     Each of the bicast routers R 4 ′, R 5 ′, R 6 ′ and R 7 ′ also has additional informations about adjacent base stations to the corresponding base station managed by them. For example, the bicast router R 4 ′ manages the base stations BS 1  and BS 2 . The bicast router R 4 ′ has informations that the base station BS 2  is adjacent to the base station BS 1 , and the base stations BS 1  and BS 3  are adjacent to the base station BS 2 . The bicast router R 5 ′ manages the base stations BS 3  and BS 4 . The bicast router R 5 ′ has informations that the base stations BS 2  and BS 4  are adjacent to the base station BS 3 , and the base stations BS 3  and BS 5  are adjacent to the base station BS 4 . The bicast router R 6 ′ manages the base stations BS 5  and BS 6 . The bicast router R 6 ′ has informations that the base stations BS 4  and BS 6  are adjacent to the base station BS 5 , and the base stations BS 5  and BS 7  are adjacent to the base station BS 6 . The bicast router R 7 ′ manages the base stations BS 7  and BS 8 . The bicast router R 7 ′ has informations that the base stations BS 6  and BS 8  are adjacent to the base station BS 7 , and the base station BS 7  is adjacent to the base station BS 8 . 
     Each of the bicast routers R 4 ′, R 5 ′, R 6 ′ and R 7 ′ transmits the packet not only to the base station BSn which has been linked to the mobile host MH at a time when the packet has been transmitted from the host network  1  but also one or more unlinked base stations BSn adjacent to the above linked base station BSn, wherein the unlinked base station BSn has been unlinked at the above time. Namely, not only the linked base stations BSn but also the unlinked base stations BSn adjacent to the linked base station BSn have the same packet from the bicast router Rn′. If the mobile host MH moves from the radio area managed by the linked base station BSn to an adjacent radio area managed by the unlinked base station adjacent to the linked base station BSn, then the mobile host MH loses the link to the originally linked base station BSn and establishes a new link to the adjacent base station BSn to the originally linked base station BSn. As described above, however, not only the past-linked base station BSn but also the newly linked base station BSn have the same packet from the bicast router Rn. For this reason, the mobile host MH could receive the packet from the newly linked base station BSn but not from the past-linked base station BSn. 
     For example, as shown in  FIG. 14 , the mobile host MH has originally been linked to the base station BS 2 , and the original communication route has been established which includes the host network  1 , the router R 1 ′, the router R 2 ′, the router R 4 ′, and the base station BS 2 . In this state, the packet is transferred from the host network  1  through the router R 1 ′, the router R 2 ′, and the bicast router R 4 ′ to the base station BS 2  linked to the mobile host MH in the sequential steps ( 1 ′), ( 2 ′), ( 3 ′) and ( 4 ′) and further the packet is transferred from the bicast router R 4 ′ through the router R 2 ′ and the router R 5 ′ to the base station BS 3  in the sequential steps ( 5 ′) and ( 6 ′). 
     In detail, the router R 1 ′ receives the packet from the host network  1 . The router R 1 ′ transfers the packet to the router R 2 ′ in the first step ( 1 ′). The router R 2 ′ transfers the packet to the bicast router R 4 ′ in the second step ( 2 ′). The bicast router R 4 ′ transfers the packet to the base station BS 2  in the third step ( 3 ′). The base station BS 2  transmits the packet to the mobile host MH in the fourth step ( 4 ′). The bicast router R 4 ′ further transfers the packet through the router R 2 ′ to the router R 5 ′ in the fifth step ( 5 ′). The router R 5 ′ transfers the packet to the base station BS 3  in the sixth step ( 6 ′), wherein the base station BS 3  is adjacent to the base station BS 2  linked to the mobile host MH. The base station BS 3  transmits the received packet to the mobile host MH in the seventh step ( 7 ′). 
       FIG. 15  is a block diagram illustrative of operation of the novel mobile communication network of  FIG. 14 , when the mobile host MH moves to the adjacent radio area. If the mobile host MH moves from the original radio area managed by the base station BS 2  to an adjacent radio area managed by the adjacent base station BS 3  to the base station BS 2 , whereby the base station BS 3  establishes a link to the mobile host MH based on the received position recording massage from the mobile host MH. 
     The base station BS 2 , which has received the packet from the bicast router R 4 ′, has already been unavailable to transmit the received packet to the mobile host MH since the mobile host MH has already been absent in the radio area managed by the base station BS 2 . The base station BD 3 , which has received the packet from the bicast router R 5 ′, has already been available to transmit the received packet to the mobile host MH since the mobile host MH has already been present in the radio area managed by the base station BS 3 , and has already established the link to the mobile host MH. 
     Even if the movement of the mobile host MH from the radio area managed by the base station BS 2  to the adjacent radio area managed by the base station BS 3  appears during the transfer of the packet through the mobile communication network or after the packet has been transmitted from the host network  1  and before the packet reaches the base station BS 2 , then the mobile host MH surely receives the packet from the base station BS 3  because the bicast router R 4 ′ not only has transferred the packet to the base station BS 2  managed by the bicast router R 4 ′ but also has transferred the packet through the router R 2 ′ and the router R 5 ′ to the base station BS 3  adjacent to the base station BS 2 . 
     Accordingly, the above novel mobile communication network including the bicast routers in the lowest level in hierarchical network structure of the routers always transfers the packet to not only the originally-linked base station BS 2  but also the originally-unlinked base station BS 3  adjacent to the originally-linked base station BS 2 , whereby if the movement of the mobile host MH from the radio area managed by the base station BS 2  to the adjacent radio area managed by the base station BS 3  appears during the transfer of the packet through the mobile communication network or after the packet has been transmitted from the host network  1  and before the packet reaches the base station BS 2 , then the mobile host MH surely receives the packet from the base station BS 3  because the bicast router R 4 ′ not only has transferred the packet to the base station BS 2  managed by the bicast router R 4 ′ but also has transferred the packet through the router R 2 ′ and the router R 5 ′ to the base station BS 3  adjacent to the base station BS 2 . 
     In accordance with the above-described novel mobile communication network, the bicast routers are selectively provided only at the lowest level of the hierarchical network structure of the routers, wherein the routers connected directly to the base stations become the bicast routers, so that the bicast operations of the packets are conducted only at the lowest level of the hierarchical network structure of the routers. This makes the host network  1  free from the requirement for controlling the bicast operations, whereby the load to the host network  1  can be reduced. 
     The hierarchical network structure of the routers simples the routing informations and inter-relationship between adjacent base stations and respective hierarchical levels of the routers. Respective loads to the routers for managing those informations can be reduced. 
     The hierarchical-level of the bicast or multicast routers would basically be optional. Notwithstanding, in accordance with the embodiment described above, the bicast routers are selectively provided only at the lowest level of the hierarchical network structure of the routers. Thus, the bicast router R 4 ′ additionally transfers the packet through the higher level router R 2 ′ and the bicast router R 5 ′ to the base station BS 3  adjacent to the base station BS 2  managed by the bicast router R 4 ′. In view of possible reduction to the traffic mount of the packets, it is possible that the middle level routers R 2 ′ and R 3 ′ become the bicast routers in place of the lowest level routers R 4 ′, R 5 ′, R 6 ′ and R 7 ′, because the middle level router R 2 ′ indirectly mages both the adjacent two radio areas directly covered by the adjacent two base stations BS 2  and BS 3 . 
     The mobile communication network of this third embodiment is free from any requirement for complicated control processes to the communication routing, for which reason the load to the each router can be reduced. 
     The number of hierarchy of the routers in the mobile communication network, the number of the base stations BS, and the number of the mobile host MH may be optional. 
     Fourth Embodiment 
     A fourth embodiment according to the present invention will be described in detail with reference to the drawings.  FIG. 16  is a block diagram illustrative of a novel mobile communication network in a fourth embodiment in accordance with the present invention. This mobile communication network is generally used for a management system for managing positions of mobile telephones or automatic cars. This mobile communication network utilizes transmission control protocol/internet protocol (TCP/IP) for realizing a packet communication. 
     As shown in  FIG. 16 , the mobile communication network includes a host network  1 , plural routers Rn″ (n=1˜7), base stations BS 1 ˜BS 8 , and a mobile host MH. The host network  1  may comprise a wide area network such as internet. The routers Rn″ provide multi-point connections between the host network  1  and the base stations BS 1 ˜BS 8 . The routers Rn″ form a hierarchical network structure between the host network  1  and the base stations BS 1 ˜BS 8 . The router R 1 ″ is highest level router. The routers R 2 ″ and R 3 ″ are middle level routers which are connected to the router R 1 ″ and dominated by the router R 1 ″. The routers R 2 ″ and R 3 ″ are bicast routers. The routers R 4 ″, R 5 ″, R 6 ″ and R 7 ″ are lowest level routers. The routers R 4 ″ and R 5 ″ are connected to the bicast router R 2 ″ and dominated by the bicast router R 2 ″, whilst the routers R 6 ″ and R 7 ″ are connected to the bicast router R 3 ″ and dominated by the bicast router R 3 ″. The base stations BS 1  and BS 2  are connected to the router R 4 ″ and dominated by the router R 4 ″. The base stations BS 3  and BS 4  are connected to the router R 5 ″ and dominated by the router R 5 ″. The base stations BS 5  and BS 6  are connected to the router R 6 ″ and dominated by the router R 6 ″. The base stations BS 7  and BS 8  are connected to the router R 7 ″ and dominated by the router R 7 ″. 
     In this fourth embodiment, the bicast routers are the routers which indirectly manage both the originally linked base station BSn to the mobile host MH and the originally unlinked base station BSn adjacent to the originally linked base station BSn, wherein each of the bicast routers is positioned on a branch point of both an original communication route between the host network  1  and the originally linked base station BSn and an adjacent communication route between the host network  1  and the originally unlinked base station BSn adjacent to the originally linked base station BSn. 
     In this embodiment, each of the middle level routers R 2 ″ and R 3 ″ is positioned on a branch point of both an original communication route between the host network  1  and the originally linked base station BSn and an adjacent communication route between the host network  1  and the originally unlinked base station BSn adjacent to the originally linked base station BSn. For this reason, the middle level routers R 2 ″ and R 3 ″ become the bicast routers. 
     Therefore, a retrieval is made to the router which is positioned at the branch point of both the original communication route between the host network  1  and the originally linked base station BSn and the adjacent communication route between the host network  1  and the originally unlinked base station BSn adjacent to the originally linked base station BSn. The retrieved router acts as the bicast router which performs the bicast of the received packet, wherein the bicast router transfers the packet not only to the originally linked base station BSn which has already been linked to the mobile host MH but also to the originally unlinked base station BSn adjacent to the originally linked base station BSn. 
     The detailed descriptions will be made with reference to  FIG. 16 . The mobile host MH is present in the radio area covered by the base station BS 2  which has originally been linked to the mobile host MH. The base station BS 2  corresponds to the originally linked base station. The base station BS 3  is positioned adjacent to the originally linked base station BS 2 . This base station BS 3  has been unlinked to the mobile host MH. This base station BS 3  corresponds to the originally unlinked base station adjacent to the originally linked base station BS 2 . 
     The mobile host MH transmits a position recording message to the originally linked base station BS 2  in the first step ( 1 ). The originally linked base station BS 2  transmits the received position recording message to the router R 4 ″ which manages the originally linked base station BS 2  in the second step ( 2 ). The router R 4 ″ updates the routing information itself based on the received position recording message. The router R 4 ″ also confirm whether the router R 4 ″ is available or unavailable to manage the originally unlinked base station BS 3  adjacent to the originally linked base station BS 2  based on the received position recording message. Since the router R 4 ″ is unavailable to manage the originally unlinked base station BS 3 , the router R 4 ″ sends the bicast router R 2 ″ not only the received position recording message but also a branch point retrieving message for retrieving a branch point of both an original communication route between the host network  1  and the originally linked base station BS 2  and an adjacent communication route between the host network  1  and the originally unlinked base station BS 3  adjacent to the originally linked base station BS 2  in the third step ( 3 ). 
     The bicast router R 2 ″ updates the routing information itself based on the received position recording message. The bicast router R 2 ″ also confirm whether the bicast router R 2 ″ is available or unavailable to manage the originally unlinked base station BS 3  adjacent to the originally linked base station BS 2  based on the received position recording message. Since the bicast router R 2 ″ is available to manage the originally unlinked base station BS 3 , the bicast router R 2 ″ incorporates the routing information with the effect that the bicast router R 2 ″ performs the bicast operation. The bicast router R 2 ″ transfers the position recording message to the router R 1 ″ in the fourth step ( 4 ). The bicast router R 2 ″ further sends an adjacent communication route establishing message to the router R 5 ″ managing the originally unlinked base station BS 3  adjacent to the originally linked base station BS 2 , wherein the adjacent communication route establishing message is to additionally establish an adjacent communication route between the host network  1  and the originally unlinked base station BS 3  adjacent to the originally linked base station BS 2  in the fifth step ( 5 ). 
     The router R 1 ″ updates the routing information itself based on the received position recording message, whereby an original communication route as a primary communication route is established, which includes the router R 1 ″, the bicast router R 2 ″, the router R 4 ″ and the originally linked base station BS 2 . The router R 5 ″ newly establishes a new communication route to the originally unlinked base station BS 3  adjacent to the originally linked base station BS 2 , based on the received adjacent communication route establishing message. As a result, the adjacent communication route is established which includes the router R 1 ″, the bicast router R 2 ″, the router R 5 ″ and the originally unlinked base station BS 3  adjacent to the originally linked base station BS 2 . 
       FIG. 17  is a block diagram illustrative of operations of the packet transfer in the mobile communication network of  FIG. 16 . Since both the original communication route and the adjacent communication route have been established, then the packet supplied from the host network  1  is transferred through both the original communication route and the adjacent communication route to the originally linked base station BS 2  and the originally unlinked base station BS 3  respectively. 
     The router R 1 ″ receives the packet from the host network  1  and transfers the received packet to the bicast router R 2 ″ in the first step ( 1 ′). The bicast router R 2 ″ transfers the received packet to both the router R 4 ″ and the router R 5 ″ through the original communication route and the adjacent communication route respectively in the second and firth steps ( 2 ′) and ( 5 ′). The router R 4 ″ transfers the received packet to the originally linked base station BS 2  linked to the mobile host MH through the original communication route in the third step ( 3 ′). The router R 5 ″ transfers the received packet to the originally unlinked base station BS 3  through the adjacent communication route in the sixth step ( 6 ′). 
     If the mobile host MH moves from the original radio area managed by the originally linked base station BS 2  to the adjacent radio area managed by the originally unlinked base station BS 3  adjacent to the originally linked base station BS 2 , then the originally linked base station BS 2  loses the link to the mobile host MH, whereby the originally linked base station BS 2  becomes the past-linked base station or the currently unlinked base station. The originally unlinked base station BS 3  establishes a new link to the mobile host MH, whereby the originally unlinked base station BS 3  becomes the newly linked base station. The base station BS 2  has become unavailable to transmit the packet to the mobile host MH because the mobile host MH has already been absent in the original radio area managed by the base station BS 2 . However, the base station BS 3  adjacent to the base station BS 2  has the link to the mobile host MH which has been present in the adjacent radio area managed by the base station BS 3 . The adjacent base station BS 3  has already become available to transmit the packet to the mobile host MH. For this reason, the mobile host MH present in the adjacent radio area could receive the packet from the adjacent base station BS 3 . 
     The original communication route, which includes the router R 1 ″, the bicast router R 2 ″, the router R 4 ″ and the base station BS 2 , has become the subordinate or secondary communication path. The adjacent communication route, which includes the router R 1 ″, the bicast router R 2 ″, the router R 5 ″ and the base station BS 3 , has become the main or primary communication path. 
     Even if the movement of the mobile host MH from the radio area managed by the base station BS 2  to the adjacent radio area managed by the base station BS 3  appears during the transfer of the packet through the mobile communication network or after the packet has been transmitted from the host network  1  and before the packet reaches the base station BS 2 , then the mobile host MH surely receives the packet from the base station BS 3  because the bicast router R 2 ′ not only has transferred the packet to the base station BS 2  managed by the router R 4 ′ but also has transferred the packet to the base station BS 3  adjacent to the base station BS 2 . 
     Accordingly, the above novel mobile communication network includes the bicast routers which are positioned at the branch points of both the original communication route between the host network  1  and the originally linked base station BSn and the adjacent communication route between the host network  1  and the originally unlinked base station BSn adjacent to the originally linked base station BSn. The bicast router positioned at the communication route branch point always transfers the packet to not only the originally-linked base station BS 2  but also the originally-unlinked base station BS 3  adjacent to the originally-linked base station BS 2 , whereby if the movement of the mobile host MH from the radio area managed by the base station BS 2  to the adjacent radio area managed by the base station BS 3  appears during the transfer of the packet through the mobile communication network or after the packet has been transmitted from the host network  1  and before the packet reaches the base station BS 2 , then the mobile host MH surely receives the packet from the base station BS 3  because the bicast router R 2 ″ not only has transferred the packet to the base station BS 2  but also has transferred the packet to the base station BS 3  adjacent to the base station BS 2 . 
     The bicast router positioned at the communication route branch point reduces the probability of packet loss. The bicast router positioned at the communication route branch point also reduces the amount of traffic of the packet as compared to the above-described third embodiment. 
     In accordance with this fourth embodiment, as described above, the bicast router further sends an adjacent communication route establishing message to the lower level router managing the originally unlinked base station adjacent to the originally linked base station, in order to additionally establish the adjacent communication route between the host network and the originally unlinked base station adjacent to the originally linked base station. Notwithstanding, it is possible modify the above structure as follows. 
     The bicast router does not establish the above adjacent communication route. The bicast router adds the received packet addressed to the mobile host MH with an adjacent address to the adjacent base station for changing a destination of the packet in order to transfer the destination-changed packet to the adjacent base station only without transferring the packet to the originally linked base station. This modification may reduce the traffic amount. It is effective to design this modified communication network optionally in consideration of the acceptable traffic capacity of the network. 
     Further, the lowest level router R 4 ″ sends the higher level router R 2 ″ the branch point retrieving message for retrieving the branch point of both the original communication route between the host network  1  and the originally linked base station BS 2  and the adjacent communication route between the host network  1  and the originally unlinked base station BS 3  adjacent to the originally linked base station BS 2 . 
     It is possible as a modification that the mobile host MH transmits the branch point retrieving message through the base station BSn to the routers Rn. In this modification, the mobile host MH measures the intensity of each of respective radio waves transmitted from the other base stations than the originally linked base station BS 2 , so that the base station transmitting the most intensive radio wave is defined to be the adjacent base station. The mobile host MH transmits a branch point retrieving message for retrieving a branch point of both the original communication route between the host network  1  and the originally linked base station and an adjacent communication route between the host network  1  and the defined adjacent base station. 
     If the mobile host further moves and other base station than the defined adjacent base station becomes transmitting the most intensive radio wave, then the mobile host MH further transmits a new branch point retrieving message for newly retrieving a new branch point of both the current communication route between the host network  1  and the currently linked base station and a new adjacent communication route between the host network  1  and the newly defined adjacent base station, instead of the past-defined adjacent base station. 
     In addition to the above transmission of the new branch point retrieving message, the mobile host MH furthermore transmits a bicast release message to the currently bicast router R 2 ″. The currently bicast router R 2 ″ receives the bicast release message from the mobile host MH, and the currently bicast router R 2 ″ becomes normal or unicast router which transfers the packet along the primary communication route only, unless the currently bicast router R 2 ″ remains still positioned at the new branch point of the current communication route and the new adjacent communication route. If the currently bicast router R 2 ″ remains still positioned at the new branch point of the current communication route and the new adjacent communication route, then, of course, the currently bicast router R 2 ″ remains acting as the bicast router even receipt of the bicast release message from the mobile host MH. This modified structure is effective in case that the adjacent base station is likely to be changed frequently. 
     The number of hierarchy of the routers in the mobile communication network, the number of the base stations BS, and the number of the mobile host MH may be optional. 
     Fifth Embodiment 
     A fifth embodiment according to the present invention will be described in detail with reference to the drawings. As described in the third and fourth embodiments, the bicast system is effective to reduce the probability of the packet loss upon the movement of the mobile host MH to the adjacent radio area. However, the problem with the packet loss may be raised if the same packets are transmitted from the adjacent two base stations at the timing when the mobile host MH moves across the boundary area between the adjacent radio areas, whereby the packet-transport performance of the network is reduced. The present fifth embodiment is to solve these problem and surely prevent the packet loss even if the same packets are transmitted from the adjacent two base stations at the timing when the mobile host MH moves across the boundary area between the adjacent radio areas. 
     The mobile communication network of this fifth embodiment is different from the mobile communication network of the above fourth embodiment only in the base stations.  FIG. 18  is a block diagram illustrative of a novel mobile communication network in a fifth embodiment in accordance with the present invention. This mobile communication network is generally used for a management system for managing positions of mobile telephones or automatic cars. This mobile communication network utilizes transmission control protocol/internet protocol (TCP/IP) for realizing a packet communication. 
     As shown in  FIG. 18 , the mobile communication network includes a host network  1 , plural routers Rn″ (n=1˜7), base stations BS 1 ′˜BS 8 ′, and a mobile host MH. The host network  1  may comprise a wide area network such as internet. The routers Rn″ provide multi-point connections between the host network  1  and the base stations BS 1 ′˜BS 8 ′. The routers Rn″ form a hierarchical network structure between the host network  1  and the base stations BS 1 ′˜BS 8 ′. The router R 1 ″ is highest level router. The routers R 2 ″ and R 3 ″ are middle level routers which are connected to the router R 1 ″ and dominated by the router R 1 ″. The routers R 2 ″ and R 3 ″ are bicast routers. The routers R 4 ″, R 5 ″, R 6 ″ and R 7 ″ are lowest level routers. The routers R 4 ″ and R 5 ″ are connected to the bicast router R 2 ″ and dominated by the bicast router R 2 ″, whilst the routers R 6 ″ and R 7 ″ are connected to the bicast router R 3 ″ and dominated by the bicast router R 3 ″. The base stations BS 1 ′ and BS 2 ′ are connected to the router R 4 ″ and dominated by the router R 4 ″. The base stations BS 3 ′ and BS 4 ′ are connected to the router R 5 ″ and dominated by the router R 5 ″. The base stations BS 5 ′ and BS 6 ′ are connected to the router R 6 ″ and dominated by the router R 6 ″. The base stations BS 7 ′ and BS 8 ′ are connected to the router R 7 ″ and dominated by the router R 7 ″. 
     In this fifth embodiment, the bicast routers are the routers which indirectly manage both the originally linked base station BSn′ to the mobile host MH and the originally unlinked base station BSn′ adjacent to the originally linked base station BSn′, wherein each of the bicast routers is positioned on a branch point of both an original communication route between the host network  1  and the originally linked base station BSn′ and an adjacent communication route between the host network  1  and the originally unlinked base station BSn′ adjacent to the originally linked base station BSn′. 
     In this embodiment, each of the middle level routers R 2 ″ and R 3 ″ is positioned on a branch point of both an original communication route between the host network  1  and the originally linked base station BSn′ and an adjacent communication route between the host network  1  and the originally unlinked base station BSn′ adjacent to the originally linked base station BSn′. For this reason, the middle level routers R 2 ″ and R 3 ″ become the bicast routers. 
     Therefore, a retrieval is made to the router which is positioned at the branch point of both the original communication route between the host network  1  and the originally linked base station BSn′ and the adjacent communication route between the host network  1  and the originally unlinked base station BSn′ adjacent to the originally linked base station BSn′. The retrieved router acts as the bicast router which performs the bicast of the received packet, wherein the bicast router transfers the packet not only to the originally linked base station BSn′ which has already been linked to the mobile host MH but also to the originally unlinked base station BSn′ adjacent to the originally linked base station BSn′. 
     Each of the base stations BS 1 ′˜BS 8 ′ further has an additional function of queuing the packet, provided that the base station BSn′ is positioned on at a terminal of the adjacent communication route, in order to prevent the originally linked base station and the adjacent base station from concurrently transmitting the same packets. The adjacent base station queues the packet until the mobile host MH has become present in the adjacent radio area and sends the adjacent base station a notice that the mobile host MH has become present in the adjacent radio area. After the adjacent base station receives this notice from the mobile host MH, then the adjacent base station transmits the packet to the mobile host MH. As a result, the mobile host MH could surely receive the packet from the adjacent base station after the mobile host MH has entered into the adjacent radio area, even the packet was also transmitted from the originally linked base station at the timing when the mobile host MH moved across the boundary area between the adjacent radio areas. 
     In this embodiment, each of the middle level routers R 2 ″ and R 3 ″ is positioned on a branch point of both an original communication route between the host network  1  and the originally linked base station BSn′ and an adjacent communication route between the host network  1  and the originally unlinked base station BSn′ adjacent to the originally linked base station BSn′. For this reason, the middle level routers R 2 ″ and R 3 ″ become the bicast routers. 
     Therefore, a retrieval is made to the router which is positioned at the branch point of both the original communication route between the host network  1  and the originally linked base station BSn′ and the adjacent communication route between the host network  1  and the originally unlinked base station BSn′ adjacent to the originally linked base station BSn′. The retrieved router acts as the bicast router which performs the bicast of the received packet, wherein the bicast router transfers the packet not only to the originally linked base station BSn′ which has already been linked to the mobile host MH but also to the originally unlinked base station BSn′ adjacent to the originally linked base station BSn′. 
     The mobile host MH transmits a position recording message to the originally linked base station BS 2 ′. The originally linked base station BS 2 ′ transmits the received position recording message to the router R 4 ″ which manages the originally linked base station BS 2 ′. The router R 4 ″ updates the routing information itself based on the received position recording message. The router R 4 ″ also confirms whether the router R 4 ″ is available or unavailable to manage the originally unlinked base station BS 3 ′ adjacent to the originally linked base station BS 2 ′ based on the received position recording message. Since the router R 4 ″ is unavailable to manage the originally unlinked base station BS 3 , the router R 4 ″ sends the bicast router R 2 ″ not only the received position recording message but also a branch point retrieving message for retrieving a branch point of both an original communication route between the host network  1  and the originally linked base station BS 2 ′ and an adjacent communication route between the host network  1  and the originally unlinked base station BS 3 ′ adjacent to the originally linked base station BS 2 ′. 
     The bicast router R 2 ″ updates the routing information itself based on the received position recording message. The bicast router R 2 ″ also confirm whether the bicast router R 2 ″ is available or unavailable to manage the originally unlinked base station BS 3 ′ adjacent to the originally linked base station BS 2 ′ based on the received position recording message. Since the bicast router R 2 ″ is available to manage the originally unlinked base station BS 3 ′, the bicast router R 2 ″ incorporates the routing information with the effect that the bicast router R 2 ″ performs the bicast operation. The bicast router R 2 ″ transfers the position recording message to the router R 1 ″. The bicast router R 2 ″ further sends an adjacent communication route establishing message to the router R 5 ″ managing the originally unlinked base station BS 3 ′ adjacent to the originally linked base station BS 2 ′, wherein the adjacent communication route establishing message is to additionally establish an adjacent communication route between the host network  1  and the originally unlinked base station BS 3 ′ adjacent to the originally linked base station BS 2 ′. 
     The router R 1 ″ updates the routing information itself based on the received position recording message, whereby an original communication route as a primary communication route is established, which includes the router R 1 ″, the bicast router R 2 ″, the router R 4 ″ and the originally linked base station BS 2 ′. The router R 5 ″ newly establishes a new communication route to the originally unlinked base station BS 3 ′ adjacent to the originally linked base station BS 2 ′, based on the received adjacent communication route establishing message. As a result, the adjacent communication route is established which includes the router R 1 ″, the bicast router R 2 ″, the router R 5 ″ and the originally unlinked base station BS 3 ′ adjacent to the originally linked base station BS 2 ′. 
     Since both the original communication route and the adjacent communication route have been established, then the packet supplied from the host network  1  is transferred through both the original communication route and the adjacent communication route to the originally linked base station BS 2 ′ and the originally unlinked base station BS 3 ′ respectively, wherein the originally unlinked base station BS 3 ′ positioned at the terminal of the adjacent communication route queues the packet. 
     In addition to the above description about operation of the above bicast router R 2 ″, the bicast router R 2 ″ further adds the received packet with a transmission sequence label which indicates a sequence of transmission of the packet, before the bicast router R 2 ″ sends the packet with the transmission sequence label to the routers R 4 ″ and R 5 ″. The bicast router R 2 ″ puts a label value as the transmission sequence label on a flow label field or an option field of a header format of the packet. The label value distinguishes the sequence in transmission of the packet. The label values may comprise continuous values, for example, 100, 101, 102, - - - or discontinuous values 100, 105, 110, 1150, - - - . 
     If the mobile host MH moves from the original radio area managed by the originally linked base station BS 2 ′ to the adjacent radio area managed by the originally unlinked base station BS 3 ′ adjacent to the originally linked base station BS 2 ′, then the originally linked base station BS 2 ′ loses the link to the mobile host MH, whereby the originally linked base station BS 2 ′ becomes the past-linked base station or the currently unlinked base station. The originally unlinked base station BS 3 ′ establishes a new link to the mobile host MH, whereby the originally unlinked base station BS 3 ′ becomes the newly linked base station. The base station BS 2 ′ has become unavailable to transmit the packet to the mobile host MH because the mobile host MH has already been absent in the original radio area managed by the base station BS 2 ′. However, the base station BS 3 ′ adjacent to the base station BS 2 ′ has the link to the mobile host MH which has been present in the adjacent radio area managed by the base station BS 3 ′. The adjacent base station BS 3 ′ has already become available to transmit the packet to the mobile host MH. For this reason, the mobile host MH present in the adjacent radio area could receive the packet from the adjacent base station BS 3 ′. 
     After the mobile host MH has established the link to the base station BS 3 ′, then the mobile host MH sends the base station BS 3 ′ not only the position recording message but also the last-received label value which had, in the past, been received from the past-linked base station BS 2 ′. The base station BS 3 ′ receives the last-received label value from the mobile host MH, wherein the base station BS 3 ′ has currently queuing packets. The base station BS 3 ′ discards all of the packets having label values which are lower than the last-received label value from the mobile host MH, and the base station BS 3 ′ sends the mobile host MH the residual queuing packets having label values equal to or higher than the last-received label value after the mobile host MH has entered into the radio area managed by the newly linked base station BS 3 . 
     As a result, even if the movement of the mobile host MH from the radio area managed by the base station BS 2 ′ to the adjacent radio area managed by the base station BS 3 ′ appears during the transmission of the packet from the originally linked base station BS 2 , then the base station BS 3 ′ queues the received packet. After the mobile host MH has entered into the adjacent radio area managed by the base station BS 3 ′, then the base station BS 3 ′ receives the label value from the mobile host MH, whereby the base station BS 3 ′ selectively discards the queuing packets based on the received label value, so that the base station BS 3 ′ sends the residual queuing packet to the mobile host MH. Therefore, no packet loss appears in any conditions, and a desirable high throughout of the mobile communication hierarchical network can be obtained. 
     In accordance with the above fifth embodiment, the base station BSn′ at the terminal of the adjacent communication route performs queuing the packet. It is also possible as a modification that the lowest level router on the adjacent communication route would perform queuing the packet. For example, in place of the base station BS 3 ′, then the router  5 ″ queues the packet. After the mobile host MH has entered into the adjacent radio area managed by the base station BS 3 ′, then the base station BS 3 ′ receives the label value from the mobile host MH and transfers the received label value to the router  5 ″, whereby the router  5 ″ selectively discards the queuing packets based on the received label value, so that the router  5 ″ sends the residual queuing packet to the base station BS 3 ′ and the base station BS 3 ′ transmits the packet to the mobile host MH. Therefore, no packet loss also appears in any conditions, and a desirable high throughout of the mobile communication hierarchical network can also be obtained. 
     The adjacent radio areas are, in general, bounded through the overlap boundary area. It is possible that the mobile host MH being just present in the overlap boundary area between the adjacent radio areas could receive the duplications of the same packet from both the adjacent base stations managing the adjacent radio areas. In this case, it is preferable that the packet has the label value which indicates the transmission sequence of the packet, so that the mobile host MH receives the packet with the label value, so that the mobile host MH verifies whether the just received packet is identical with the already-received packet with reference to the label value. If the just received packet is identical with the already-received packet, then it is possible that the mobile host MH discards the duplicate packet. 
     In this fifth embodiment, the hierarchical network of the routers is identical with that of the fourth embodiment, wherein the bicast routers are the routers R 2 ″ and R 3 ″ which are higher in level than the lowest level routers R 4 ″, R 5 ″, R 6 ″ and R 7 ″. It is also possible that the hierarchical network of the routers is identical with the third embodiment, wherein the bicast routers are the lowest level routers R 4 ″, R 5 ″, R 6 ″ and R 7 ″. 
     The number of hierarchy of the routers in the mobile communication network, the number of the base stations BS, and the number of the mobile host MH may be optional. 
     Although the invention has been described above in connection with several preferred embodiments therefor, it will be appreciated that those embodiments have been provided solely for illustrating the invention, and not in a limiting sense. Numerous modifications and substitutions of equivalent materials and techniques will be readily apparent to those skilled in the art after reading the present application, and all such modifications and substitutions are expressly understood to fall within the true scope and spirit of the appended claims.