Abstract:
Telecommunication services are provided to users. User information for a first identity of a user in a first telecommunication network is maintained. An active presence for a mobile device for the user is maintained by means of a second identity in a second telecommunication network. A presence of the user in the first network is emulated using a gateway system that couples the first telecommunication network to the second telecommunication network.

Description:
BACKGROUND  
       [0001]     This description relates to international call and data routing.  
         [0002]     International roaming capabilities allow a cellular subscriber to roam outside of his home country and network and make and receive calls almost as if he were at home. Cellular phone operators both in the subscriber&#39;s home country and abroad charge international long distance and roaming charges for this service.  
         [0003]     Some of the charges can be avoided by renting (at the destination) a local cellular phone or a local GSM SIM card to be inserted into the subscriber&#39;s home GSM phone.  
         [0004]     To receive incoming calls while traveling abroad, a subscriber can leave a message on his voice mail asking callers to dial his overseas cellular number, resulting in long distance charges to the caller, or he can activate call forwarding on his home cellular phone to redirect automatically the call to his local cellular phone. The subscriber must remember to manually activate and deactivate call forwarding before and after overseas travel.  
       SUMMARY  
       [0005]     In general, in one aspect, telecommunication services are provided to users. User information for a first identity of a user in a first telecommunication network is maintained. An active presence for a mobile device for the user is maintained by means of a second identity in a second telecommunication network. A presence of the user in the first network is emulated using a gateway system that couples the first telecommunication network to the second telecommunication network.  
         [0006]     Implementations may include one or more of the following features. An association of the first identity and the second identity is maintained. The first and second telecommunication networks are cellular networks. The gateway system couples the first telecommunication network to the second telecommunication network over an internet. Call traffic addressed to the first identity is forwarded to the second telecommunication network. The call traffic is sound data. The call traffic is text data. The call traffic is image data.  
         [0007]     Advantages of implementations may include one or more of the following. Subscribers can receive their home cellular phone services, including regular voice service as well as other common cellular phone services such as voice mail, SMS and MMS, while traveling overseas without paying roaming charges. Subscribers continue to receive incoming calls to their home mobile phone number when roaming outside their home networks without the manual steps of activating and deactivating call forwarding. No special handsets are required, as subscribers can either use standard rental mobile phones while overseas or insert an overseas SIM card into their GSM phone. No changes are required to current GSM handset designs or current GSM or SIP protocols. The subscriber&#39;s home and foreign cellular phone services do not need to operate on compatible networks; for example, the subscriber&#39;s home cellular phone service could be CDMA and the foreign cellular phone could be GSM or vice-versa.  
         [0008]     Other features and advantages will become apparent from the description and from the claims. 
     
    
     DESCRIPTION OF DRAWINGS  
       [0009]      FIG. 1  and  FIG. 2  show a network.  
         [0010]      FIGS. 3, 4 ,  5 , and  6  show a flow chart. 
     
    
     DETAILED DESCRIPTION  
       [0011]     We describe an international roaming solution that bridges subscribers&#39; home and overseas cellular phone services. Subscribers can receive their home cellular phone services (regular voice service, as well as other common cellular phone services such as voice mail, SMS and MMS) while traveling beyond the service area of their cellular using a foreign (or local) cellular phone, thereby avoiding or reducing roaming charges. The following terms are used in this description:  
                                                       BSC   Base Station Controller           BTS   Base Transceiver Station           CDMA   Code Division Multiple Access           G-MSC   Gateway Mobile Switching Center           GSM   Global System for Mobile communications           GW   meda Gate Way           HLR   Home Location Register           MAP   Mobile Application Parts           MDN   Mobile Directory Number           MSC   Mobile service Switching Center           NCG   Network Convergence Gateway           S-MSC   Serving Mobile Switching Center           SIM   Subscriber Identity Module           SMS   Short Message Service           SMSC   Short Message Service Center           VM   Voice Mail box                      
 
         [0012]     Certain implementations that we describe here are explained in the context of GSM cellular networks but are also useful in the context of CDMA cellular networks, as well as other mobile phone and data standards.  
         [0013]     Referring to  FIG. 1 , a network convergence gateway (NCG)  100  uses a high level network architecture to provide an international roaming feature to networks. In some examples, in actual service deployment, the NCG  100  could comprise a number of physical network elements strategically located for optimal network planning. For example, referring also to  FIG. 2 , NCG  100  could comprise a Home NCG  100 A physically located in a home network  102 A and a World NCG  100 B located elsewhere, for example, in a foreign network  102 B. Wherever located and whether or not comprised of multiple network elements, the NCG  100  functions as a single logical element.  
         [0014]     In some examples, the NCG  100  works with media gateways (MGWs)  104 A and  104 B in networks  102 A and  102 B to facilitate call and data transfer over the internet  103 . NCG  100  may also work with other standard network elements in networks  102 A and  102 B, such as mobile service switching centers (MCSs)  108 A and  108 B, home location registers (HLRs)  110 A and  110 B, base station controllers (BSCs)  112 A and  112 B, base transceiver stations (BTSs)  117 A and  117 B, short message service centers (SMSCs)  114 A and  114 B, and voice mail boxes (VMs)  116 A and  116 B.  
         [0015]     In some examples, a subscriber  115  uses one cellular phone  105 A in the home network  102 A and another cellular phone  105 B in the foreign network  102 B. In some examples, the subscriber  115  uses a single GSM cellular phone  105  but replaces a home GSM SIM card  106 A with a foreign SIM card  106 B in his GSM cellular phone  105  to use in the foreign network  102 B.  
         [0016]     In some examples, in home network  102 A, NCG  100  acts as a Serving Mobile Switching Center (S-MSC) for the subscriber  115  in the home network  102 A while the subscriber  115  is active in the foreign network  102 B. NCG  100  performs location registration with home network  102 A using the Home HLR  110 A. When the subscriber  115  is in foreign network  102 B, the home network routes incoming calls to the subscriber&#39;s home cellular phone  105 A to the NCG  100  as the Serving MSC in the home network  102 A, using standard mobile network protocols. The NCG  100  causes the home network  102 A to direct the calls to the Home GW  104 A to be transferred as an SIP message to the foreign GW  104 B in foreign network  102 B.  
         [0017]     In some examples, in the foreign cellular network  102 B, the NCG  100  acts as a Gateway Mobile Switching Center (G-MSC) and routes incoming calls from the home network  102 A for the subscriber  115  to the foreign network  102 B and causes the foreign GW  104 B to direct the calls to cellular phone  105 B through an MSC  108 B using standard MAP protocols. In some examples, the NCG  100  accesses a database  111 B containing identifiers for the subscriber&#39;s home cellular phone  105 A and corresponding foreign cellular phone  105 B to determine how to route incoming calls.  
         [0018]     The call leg  118 A between the home network  102 A and home GW  104 A, as well as the call leg  118 B between the foreign network  102 B and foreign GW  104 B, are local calls, thereby allowing the subscriber  115  to avoid or reduce traditional roaming charges.  
         [0019]     In some examples, a subscriber  115  calls a number in his home network  102 A on his Local SIM  106 B while in foreign network  102 B. To avoid two-stage dialing, the roamed-in carriers (or Local carrier) could establish a Feature Code (FC) as a dialing prefix for calls that could be routed through the Home and Local GWs  104 A and  104 B. FCs are commonly used by the MSCs&#39; data translation tables  501  (referring to  FIG. 5 ), for example, to route calls to special services such as weather reports, traffic, or radio stations. FCs instruct the MSC to route the call to a specific trunk group. Analogous to dialing “9” on a PBX to get an outside line, subscribers using a foreign SIM would use a FC to make calls through an International Roaming service.  
         [0020]     Referring to  FIG. 2 , as an illustration, a Singapore subscriber  115  travels to Korea. The subscriber  115  inserts a Korean SIM  106 B into his GSM cellular phone  105  when he arrives in Korea.  
         [0021]     In some examples, the identifying number ranges of the foreign SIM cards (here, Korean SIM  106 B) are pre-programmed into the Korean HLR  110 B and into a database  111 B for the World NCG  100 B to create an association with the subscriber&#39;s MDN in Singapore. Several mechanisms are possible to program this association. In some examples, the subscriber  115  logs into a self-help website  113  and enters an identifier for his home SIM card  106 A along with identifiers for one or more foreign SIM cards  106 B, possibly one for each country he travels to frequently. In other examples, the subscriber  115  calls a toll free customer care telephone number for operator-assisted provisioning of his foreign SIM/MDN  106 B. The association can also occur by prompting the subscriber  115  to send an SMS to notify the World NCG  100 B of his Home SIM/MDN  106 A.  
         [0022]     Referring to  FIG. 3 , in some examples, the World NCG  100 B asks the Local HLR  110 B to notify it when the Local SIM  106 B becomes active in the network (Step  300 ). The World NCG  100 B in essence is acting as an SMSC in this case, using a common MAP method to tell the Local HLR  110 B that an SMS message is waiting for the subscriber  115  (Step  300 A). The Local HLR  110 B issues an acknowledgment when it receives the SMS (Step  300 B). When the local SIM  106 B becomes active, the normal registration with the Local HLR  110 B occurs (Step  302 ). In some instances, the SIM  106 B registers with the Local MSC  108 B (Step  302 A), the Local MSC updates the location of SIM  106 B at Local HLR  110 B (Step  302 B), the Local HLR  110 B sends a profile message back to the Local MSC  108 B, establishing that the World NCG  100 B will serve as the MSC for the Local SIM  106 B (Step  302 C), and the Local MSC sends an acknowledgement back to the Local SIM  106 B (Step  302 D). The Local HLR  110 B then notifies the World NCG  100 B that the SIM  106 B is active, using a Service Center Alert that contains the Local SIM&#39;s  106 B MDN (Mobile Directory Number) and the ID of its serving MSC (Step  304 ).  
         [0023]     The World NCG  100 B launches an SMS to the subscriber  115  asking the subscriber  115  for his Home MDN (Step  306 ), which is delivered to SIM  106 A by the Local SMSC  114 B using standard methods (Step  308 ). The subscriber  115  responds to the Local SMSC  114 B with text that includes his Home MDN, which is the home telephone number he would like associated with his foreign telephone number (Step  310 ). The local SMSC sends the SMS response back to the World NCG  100 B (Step  312 ).  
         [0024]     The World NCG  100 B maps the home MDN to the matching Home NCG  100 A. It then sends a Register message to the Home NCG  100 A that contains the Home MDN it received from the subscriber  115  via SMS (Step  314 ).  
         [0025]     The Home NCG  100 A then updates the location of the Home MDN with the Home HLR  110 A, establishing that the Home NCG  100 A will serve as the MSC in the home network  102 A for that number (Step  316 ). The Home HLR  110 A sends a profile for the subscriber&#39;s Home MDN back to the Home NCG  100 A (Step  318 ).  
         [0026]     Referring to  FIG. 4 , in some examples, a caller  401  attempts to call the subscriber  115  by dialing the subscriber&#39;s Home MDN, although the subscriber  115  is in a foreign network  102 B. In this instance, normal call setup occurs within the Home domain (Step  400 ). The call comes in to the Home MSC  108 A (Step  400 A), which sends the routing information to the home HLR  110 A (Step  400 B). The Home HLR  110 A looks up the subscriber&#39;s Home MDN and notes that Home NCG  100 A is operating as the serving MSC for that number. The Home HLR  110 A provides roaming information for the call to the Home NCG  100 A (Step  400 C). The Home NCG  100 A informs the Home HLR  110 A that the call should be routed through the Home GW  104 A (Step  400 D). The Home HLR  110 A passes this information back to the Home MSC  108 A (Step  400 E), which then routes the call to the Home GW  104 A (Step  400 F).  
         [0027]     The Home GW  104 A extends an Invite to the Home NCG  100 A to request information in SIP format about where the Home GW  104 A should route the call (Step  402 ). The Home NCG  100 A passes the Invite to the World NCG  100 B, which looks up the Home MDN in a database  111 B to determine that the Local SIM  106 B is associated with that Home MDN (Step  404 ).  
         [0028]     The World NCG, now acting as the Local G-MSC for Local SIM  106 B, launches standard “incoming call” MAP messages to the Local HLR  110 B with the corresponding Local MDN routing information for Local SIM  106 B (Step  406 ). The Local HLR  110 B provides roam information to the Local MSC  108 B (Step  408 ), which replies with a message confirming that the Local SIM  106 B is within its service area (Step  410 ). The Local HLR  110 B sends an SRI Response back to the World NCG  100 B, indicating that the proper Local MSC  108 B for Local SIM  106 B has been located (Step  412 ). The World NCG  100 B passes an OK message back to the Home NCG  100 A with the identity of the Local GW  104 B to which the Home GW  104 A should route the call (Step  414 ). The Home NCG  100 A forwards the OK message on to the Home GW  104 A (Step  416 ).  
         [0029]     The Home GW  104 A then extends the call to the correct Local GW  104 B in an RTP session (Step  418 ). Upon receipt of the call, the Local GW  104 B queries the World NCG  100 B to determine where to route the call. The World NCG  100 B responds with the appropriate Local MSC  108 B servicing the Local SIM  106 B. The Local GW  104 B routes the call to that Local MSC  108 B (Step  424 ), which sends an alert to the Local SIM  106 B (Step  426 ). The subscriber&#39;s phone abroad  106 B therefore rings in response to the call to his local MDN.  
         [0030]     If the subscriber  115  doesn&#39;t answer or is busy, the World NCG  100 B can use a SIP message ( 302  Redirect, see  FIG. 3  ) to redirect the call back to the Home NCG  100 A, which continues to operate as the Serving MSC. The Home NCG  100 A can interact with the Home HLR  110 A for routing instructions based on the failure reason. In some examples, when the subscriber does not answer the call, the caller can be routed to the subscriber&#39;s voicemail box  116 A in home network  102 A (see  FIG. 1 ). Using standard methods, the Home NCG  100 A instructs the Home GW  104 A to forward the call through the Home MSC  108 A to the Home Voice Mail Box  116 B, where the caller  401  can leave a message. A “voice mail message waiting” indicator arrives at the Home NCG  100 A as an SMS message. The Home NCG  100 A can pass the message on to the World NCG  100 B, which in turn forwards the SMS to Local SIM  106 B as explained below. In some examples, the subscriber  115  calls his Home Voice Mail Box  116 A from his Local SIM  106 B in foreign network  102 B to check this message. In some examples, the subscriber  115  calls his Home Voice Mail Box  116  from his Home SIM  106 A upon his return to his home country.  
         [0031]     Referring to  FIG. 5 , in some examples, on his Local SIM  106 B, the subscriber  115  makes an outbound call to an entity in the home network  102 A. The subscriber  115  dials a FC followed by a country code and desired DN in the home network  102 A (Step  500 ). The foreign MSC  108 B recognizes that the subscriber  115  has entered a FC and routes the call to the foreign GW  104 B (Step  502 ). The Local GW  104 B sends an Invite to the World NCG  100 B, as its serving MSC, to determine where to route the call (Step  504 ). The World NCG  100 B performs digit analysis and determines that the call should be extended to the Home NCG  100 A (Step  506 ). In some examples, the Home NCG  100 A performs steps similar to Steps  406 - 412 , as described above, to determine where to route the call. The Home NCG  100 A forwards an OK message with the identity of the appropriate home GW  104 A back to the World NCG  100 B (Step  508 ), which forwards the message back to the foreign GW  104 B (Step  510 ).  
         [0032]     The NCG  100 A sets up the call between the foreign GW  104 B and the Home GW  104 A (Step  512 ). The Home GW  104 A then follows standard outgoing routing procedures to the appropriate Home Serving MSC  108 A (Step  514 ). In some examples, where the DN is not a cellular number, the Home Media Gateway routes the call to the Home PSTN using standard methods.  
         [0033]     A subscriber  115  in foreign network  102 B can also receive SMS messages on his Local SIM  106 B that are addressed to his home SIM  106 A. Referring to  FIG. 6 , in some examples, another user or a device such as a computer program  601  sends an SMS containing voice or image data to the subscriber&#39;s Home MDN. In some examples, the Home MSC  108 A sends the subscriber  115  a “voice mail message waiting” notice  603  using SMS. In other examples, there will be a similar data flow for MMS (Multimedia Messaging Service) because MMS notification is done via SMS.  
         [0034]     Using normal MAP methods, the Home SMSC  114 A receives an SMS message (Step  600 ) and queries the Home HLR  110 A for the appropriate routing information (Step  602 ). The Home HLR  110 A informs the Home SMSC  114 A that the Home NCG  100 A is acting as the subscriber&#39;s Home MDN&#39;s Service MSC (Step  604 ). The Home SMSC  114 A delivers the message to the Home NCG  100 A (Step  606 ). The Home NCG  100 A converts the SMS message to a SIP format and extends the message to the World NCG  100 B (Step  608 ). The World NCG  100 B looks up the Home MDN in its translation table to map the number to the subscriber&#39;s Local MDN, and converts the SIP message back to P2P format to forward it to the appropriate Local SMSC  114 B (Step  610 ).  
         [0035]     The Local SMSC  114 B delivers the message to the subscriber  115  at his Local SIM  106 B using normal MAP methods. The Local SMSC  114 B queries the Local HLR  110 B for the appropriate routing information (Step  612 ). The Local HLR  110 B responds with the identity of the Local MSC serving the subscriber&#39;s Local MDN (Step  614 ). The Local SMSC  114 B forwards the message accordingly to the Local MSC  108 B (Step  616 ), who delivers it to the Local SIM  106 B using standard methods (Step  618 ). The Local SIM  106 B acknowledges receipt of the message to the Local MSC  108 B (Step  620 ), who forwards the acknowledgement to the Local SMSC (Step  622 ).  
         [0036]     In some examples, a subscriber&#39;s response  624  to the SMS would follow a similar path in the reverse direction.  
         [0037]     Other embodiments are within the scope of the following claims.