Abstract:
A network hub interconnects a public access cellular telephone network transceiving signals according to a SS 7  protocol with a wireless office environment transceiving signals according to a TCP/fP protocol. The wireless office environment comprises a TCP/IP network interconnecting a plurality of private wireless networks. A processor within the hub converts received signals between being carried by the SS 7  and TCP/IP protocols. The conversions are assisted by a translation table including active mobile identification numbers and IP addresses within the wireless office environment and a second table listing all signal point codes for nodes within the public access cellular telephone network.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     The present invention relates to the interconnection of wireless office environments with a public cellular telephone network, and more particularly, to a network hub providing for transmission of messages from the hub to the public cellular telephone network using the SS 7  protocol and the transmission of messages from the hub to the wireless office environment using the TCP/IP protocol. 
     2. Description of Related Art 
     Public access cellular telephone systems are currently available for use throughout the world. As a result of the success of such systems in providing mobile telecommunication services to the public, considerable interest has arisen in the corporate sector to provide a wireless communication feature add on to conventional private wireline telephone systems. Such a feature is typically implemented through the use of a private cellular telephone system. 
     Due to the costs of mobile terminals, it is preferable in any private cellular telephone system established by a business to utilize the same type of mobile terminals as are used within public access cellular telephone systems. Furthermore, because many employees already own mobile terminals and have subscriptions with a public access telephone system, it is preferable that the utilized mobile stations be capable of operating with and between each of the systems. At a minimum, this requires that the private cellular telephone system operate within the same cellular frequency band as the public access cellular telephone system, and use the same type or compatible switching equipment and base stations. It is also likely that the radio frequency coverage regions of the private cellular telephone system and the public access cellular telephone system may at least partially overlap. Furthermore, the private cellular telephone system and the public access cellular telephone system must communicate with each other regarding the servicing of mobile stations, the allocation of channels (frequencies) for communication, the routing of communications, and the handing off of mobile station communications. 
     It is preferred that the wireless offices be connected to an existing home location register (HLR) of the cellular network to enable automatic roaming between the cellular network and the wireless office. As the popularity of wireless offices increases, each new wireless offices must be connected to the signaling system no.  7  (SS 7 ) network that forms the backbone of existing public access cellular telephone systems. Each additional connection of a wireless office adds an additional node to the cellular network and requires a great deal of work to update each node within the cellular network with knowledge of a new wireless office node. This work level is repeated by each wireless office that is added to the network creating a huge task for the cellular network provider. 
     Furthermore, when a private network is added as a node to the public access cellular telephone system, the wireless office nodes will not be owned by the cellular network providers. This raises several security concerns, and cellular network operators are not keen on adding nodes that are not under their total control. Nodes not controlled by the cellular network provider raise a serious security risk due to unscrupulous third parties access to the private nodes. Additionally, nodes not under the control of the cellular network operators may often be restarted which raises the number of management messages which must be transmitted by the network. Thus, a great many problems and concerns arise in the direct connection of a number of new wireless office nodes directly to a public access cellular network. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the foregoing and other problems with an improved communications system utilizing a network hub. A first public access cellular telephone network operates according to the signaling system no.  7  (SS 7 ) protocol for transmitting signals between various nodes and the public access network. A second communications system comprises a TCP/IP network utilizing the TCP/IP protocol. The second network is interconnected with a plurality of private wireless networks and transmits signals via the TCP/IP protocol. 
     A network hub interconnects the first and second communications networks and enables the transfer of signals therebetween. The network includes processing means for converting signals from being carried by the SS 7  protocol to the TCP/IP protocol and vice versa. This is accomplished by replacing the MTP and SSCP layers of an SS 7  protocol signal with a TCP/IP layer for transmissions from the SS 7  network to the TCP/IP network, and for replacing a TCP/IP layer with MTP and SSCP layers for transmissions from the TCP/IP network to the SS 7  network. 
     A translation table within the network hub enables the location of mobile stations being served by wireless networks connected to the network hub to be determined. The translation table includes the mobile identification numbers of registered mobile stations. Each mobile identification number entry further includes an associated IP address for the wireless network serving the mobile station. This enables calls from the public network to be directed to the wireless office serving a mobile station. A North American Cellular Network address table provides the signaling control points (addresses) for all nodes within the public access cellular telephone network. This enables transmissions from the wireless networks to be directed to any location within the public access cellular telephone network once the communication reaches the network hub. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a schematic diagram of a public access cellular telephone network; 
     FIG. 2 is a schematic diagram of a wireless communication system including a wireless office environment private cellular telephone network, a public access cellular telephone network and a network hub for interconnecting the public and private networks; 
     FIGS. 3 a  and  3   b  illustrate the signaling system no.  7  (SS 7 ) protocols and TCP/IP protocols for transporting IS-41 messages according to the present invention; 
     FIG. 4 is a signal flow and node operation diagram illustrating the adding of a mobile to a translation table within the network hub; 
     FIG. 5 is a signal flow and node operation diagram illustrating the receipt of a message from the HLR by the wireless office/VLR; and 
     FIG. 6 is a signal flow and node operation diagram illustrating the removal of a mobile identification number from the translation table of the network hub. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the Drawings, and more particularly to FIG. 1, there is illustrated a schematic diagram of a public access cellular telephone network  12  (such as a known public land mobile network—PLMN). The public access cellular telephone network  12  includes a plurality of interconnected switching nodes  14  commonly referred to as mobile switching centers (PLMN-MSCs)  14 . Although only three mobile switching centers  14  are shown, it will be understood that the system  12  likely includes many more interconnected nodes. The mobile switching centers  14  may comprise any one of a number of known telecommunication switching devices, including those commonly used and known in the art of providing either digital or analog cellular telephone services to a plurality of mobile stations (not shown). 
     The mobile switching centers  14  are interconnected with each other for communications via both voice trunks and signaling links  20  together providing a known ISUP (RI or RII) type connection. The trunks provide voice and data communication paths used to carry subscriber communications between the mobile switching centers  14 . The signaling links carry command signals (such as IS-41 or other signaling system no.  7  (SS 7 ) messages) between the mobile switching centers  14 . These signals may be used, for example, in setting up and tearing down voice and data communication links over the voice trunks and controlling the provision of calling services to mobile stations. 
     The mobile switching centers  14  are also connected to data bases comprising a home location register (PLMN-HLR)  22  by means of signaling links  20  providing a known MAP type connection (IS-41, MAP for GSM, MAP for PDC, or other SS 7  type connection). The HLRs  22  store data for each mobile station, including the location of the mobile station, which comprises a direct or indirect SS 7  address (signaling point code) to the VLR (or VLR/MSC) where the mobile station last provided a registration. 
     Since each node is a part of the SS 7  network, the nodes will further include associated signaling points (SP)  24  and signaling transfer points (STP)  26 . Within an SS 7  network each node essentially comprises a signaling point  24 . Signaling transfer points  26  provide packet switching of IS-41 message based signaling protocols within the SS 7  network. 
     The VLRs of FIG. 1 are illustrated as being co-located with the MSCs  14 . However, it should be realized that the VLRs may comprise separate logical nodes located at a different position within the network. The VLRs includes a listing of mobile station mobile identification numbers currently registered within the service area of the associated MSC  14 . For routing purposes, all of the VLRs include a table  30  of all nodes included within the network. The table  30  enables mapping of the mobile identification number (MIN) of a mobile station to the address of the HLR with which the mobile station is associated when the used mobile station registers with the VLR. 
     Referring now to FIG. 2, there is illustrated the present invention wherein a network hub  38  is utilized to interconnect a public access cellular telephone network  12  with wireless office environment (private cellular telephone system)  40 . The network hub  38  is capable of operating in systems using IS-41 signaling, MAP for GSM signaling, MAP for PDC signaling or other types of SS 7  signaling. For purposes of discussion, the following description shall be with respect to a system using IS-41 signaling but it should be realized that the system is applicable to systems using other types of signaling. The public access cellular telephone network  12  consists of a number of mobile switching centers  14  and home location registers  22  which are interconnected with the network hub  38  via the SS 7  signaling protocol links  20  and associated signaling points  25  and signaling transfer points  26  as described previously with respect to FIG.  1 . 
     Communications between the network hub  38  and the public access cellular network  12  are accomplished through the exchange of IS-41 messages  50  using well-known SS 7  messaging protocols as illustrated in FIG.  3 A. According to this protocol, the signal connection control part (SCCP) layer  52  is used with the message transfer part (MTP) layer  54  to route transaction capability application part (TCAP) layer  56  formatted IS-41 messages  50  from the network hub  38  to HLR  22  and MSC  14  nodes within the public access cellular telephone system  12 . The TCP/IP network  45  connecting the wireless offices  40  to the network hub  38  is not capable of providing a transport medium for IS-41 messages in accordance with the SS 7  messaging protocols. The SCCP layer  52  and the MTP layer  54  thus cannot be used for end-to-end routing of the TCAP layer  56  formatted IS-41 messages  50 . 
     In accordance with the present invention, as illustrated in FIG. 3B, the TCP/IP layer  60  replaces the MTP layer  54  and the SSCP layer  52  of the SS 7  protocol while the TCAP layer  56  remains intact for transportation of the IS-41 messages  50 . To allow communications between the TCAP layer  56  and the TCP/IP layer  60 , an adaptation layer  58  must exist between the TCAP layer and the TCP/IP layer. The adaption layer  58  acts as a translation interface between the different protocols. The conversion between transportation of the IS-41 messages  50  by the SS 7  protocol or the TCP/IP protocol is performed by processing means within the network hub  38  and enables interconnection of the public network  12  to the wireless offices  40 . The network hub  38  includes an IP address for communications using the TCP/IP protocol and a signal point code (address) for communications with respect to the SS 7  protocol. 
     The network hub  38  further includes a translation table  70  for storing the mobile identification numbers (MIN) of mobile stations  41  being serviced by a wireless office  40  interconnected with the network hub  38 . Associated with the stored MIN are the IP address of the wireless office  40  in which a mobile station is registered. The translation table  70  enables the location of mobile stations according to the IP address of its serving wireless office  40 . A network table  72  (NACN) addressing table, is also included within the hub  38  and includes a listing of all nodes and signaling point codes (addresses) within the public access cellular network  12 . The table  72  also includes a list of all mobile identification numbers and their corresponding HLR. The Network table  72  enables location and addressing of messages to all nodes in the public cellular telephone network  12 . 
     As an interface between the public access cellular telephone network  12  and the wireless offices  40 , the network hub  38  will include a signaling point code (address) and an IP address. Nodes within the public access cellular telephone network  12  will see the network hub  38  as a single node within the public access cellular telephone system and access the hub by the signaling point code. Thus, additions of wireless offices  40  to the hub  38  does not require additional maintenance for updating nodes within the public access telephone network  12  since the wireless office does not comprise a new node. 
     The network hub  38  may also include functionalities to enable restriction of the total number of active users within a wireless office or to restrict particular users from accessing a wireless office. In this manner, the network hub  38  will be able to act as a firewall between the SS 7  (public) network and the wireless office (private) networks to provide security along with the reliability of the SS 7  network. 
     While the network hub  38  within the foregoing description has been illustrated as a separate node, it should be realized that the hub is a logical node which may be physically co-located with other cellular nodes such as an HLR, VLR, MSC or a wireless office. Furthermore, while the foregoing description has been made with respect to the public access cellular system using a SS 7  network, it is also possible to utilize an X. 25  network in place of the SS 7  network. 
     Referring now to FIG. 4, there is illustrated a signal and node diagram illustrating the process for when the Network hub  38  receives a registration of a mobile station  41  from a wireless office  40 . The mobile station  41  transmits a registration message  100  to the wireless office/VLR  40  within whose service area the mobile station is currently located. The wireless office  40  forwards the registration request message  102  to the Network hub  38 . In response to receipt of this message  102 , the Network hub  38  adds the mobile identification number of the mobile station  41  to the translation table  70  within the hub together with the IP address of the wireless office  40  forwarding the message. The network hub  38  then utilizes the Network table  72  to determine the address of the home location register  22  (also identified in the registration request message) of the mobile station  41  and forwards the registration request message  104  to the HLR such that the location and status of the mobile station  41  may be updated by the HLR. Responses ( 106 ,  108 ,  110 ) are then returned to the network hub  38 , wireless office  40  and mobile station  41 . 
     Referring now to FIG. 5, there is a signal and node diagram illustrating the receipt by the network hub  38  of a message from the HLR  22  via the SS 7  network for the wireless office  40 . The HLR  22  generates an IS-41 message  112  to the wireless office/VLR  40 , for example, the roaming routing request message. The destination address of the roaming routing request  112  is the signaling point code (address) of the network hub  38  within the SS 7  network. Upon delivery of the roaming routing request  112  to the network hub  38 , the hub utilizes the mobile identification number stored within the message in accordance with IS-41 protocol standards to find the IP address of the wireless office with which the mobile station associated with the mobile identification number is registered. This is accomplished by accessing the translation table  70 . The roaming routing request is then forwarded to the identified IP address at  114 . The wireless office  40  provides a response to the request at  116  to the Network hub  38 , and the hub  38  forwards the response to the HLR  22  at  118 . 
     Referring now to FIG. 6, there is illustrated the receipt by the network hub  38  of a message indicating that the mobile station  41  is no longer registered with the wireless office. The HLR  22  initially generates a registration cancelization message  120  to the network hub  38 . At the network hub  38 , the translation table  70  is utilized to find the IP address of the wireless office/VLR  40  associated with the mobile  41 . The request cancellation is then forwarded to the wireless office at  122 , and a response is received at  124 . The network hub  38  then removes the mobile identification number for the mobile from the translation table  70  and notifies the HLR  22  of this at step  126 . The network hub  38  could also remove the mobile identification number for the mobile  41  from the translation table  70 , if the wireless office  40  sends an CCS-inactive message to the HLR  22 . In this way, the updating of the translation table  70  is done automatically. 
     While the concept of the network hub  38  has been discussed with respect to the use of the hub as a bridge between an SS 7  network and a wireless office, TCP/IP network, the hub could be useful in a variety of other applications. For example, the hub concept with automatic update of mobile registration is also applicable for the similar map protocols of GSM and PDC. The concept would also be useful for applications attempting to avoid the connection of several different types of small nodes, e.g., MSC/VLR to an SS 7 /CC 7  network using an IP network. Similarly, the network hub concept would be useful for mapping between other types of protocols using E. 164  type addressers (normal telephone numbers) to SS 7  networks. For example, if the WO/VLR is using ISDN, the network hub  38  could provide the bridge to the cellular network with the added advantage that the HLR is unaware of the ISDN type of bearer for the WO/VLR. 
     Although a preferred embodiment of the method and apparatus of the present invention has been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it is understood that the invention is not limited to the embodiment disclosed, but is capable of numerous rearrangements, modifications, and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.