Abstract:
If a network ( 80 ) incurs blockage or if a called subscriber ( 200 ) is unreachable for network blockage or network or inter network errors, the network re-routes the calling subscriber ( 100 ). Instead of merely dropping a call or sending a re-order signal to the calling subscriber, the network automatically reroutes ( 52 ) the calling subscriber to a voice mail system ( 95 ) in the called subscriber&#39;s home service network ( 80 ).

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention pertains to telecommunications networks and more particularly to an arrangement for call forwarding under network control for mobile subscribers.  
           [0002]    Traditional call forwarding depends upon action which may initially be activated by a mobile subscriber. In traditional call processing, incoming calls are routed through the network to the home network of the called subscriber. Calls to the particular subscriber subject to call forwarding are typically rerouted by the home network of the called subscriber to an alternate (pre-specified) telephone number (e.g., Voicemail).  
           [0003]    Often times networks encounter blockage within or among the networks and cannot appropriately route a calling subscriber to the called subscriber. Such call blockage or network failures may leave the calling subscriber with no indication as to the reason the call did not reach the called subscriber. Typical network responses for the network blockage or error situations are to drop the call and/or send a reorder tone back to the calling subscriber.  
           [0004]    Generally, there are four conditions upon which calls may be forwarded. First, a call may be forwarded unconditionally; second, a call may be forwarded upon detection of busy; a call may be forwarded on detection of no reply; and, a call may be forwarded as not reachable. The not reachable basis for call forwarding typically occurs when a mobile subscriber&#39;s handset is in the off condition (detached) or for some other reason fails to respond to paging. Accordingly, it would be highly desirable to have an arrangement for call forwarding controlled by the network for network non-connectivity or network failure situation. This situation is one of the most common occurrences being when network signaling resources are not available end to end for subscribers roaming outside their home network.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0005]    [0005]FIG. 1 is a prior art message flow diagram of an attempted call connection.  
         [0006]    [0006]FIG. 2 is a block diagram of the network controlled call forwarding in accordance with the present invention.  
         [0007]    [0007]FIG. 3 is a message flow diagram of a network controlled call forwarding arrangement in accordance with the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0008]    Referring to FIG. 1, a message flow diagram for a signaling system  7  is shown which depicts the prior art arrangement. System signaling  7  connectivity must exist between gateway MSC  80  and visited MSC  90 . Gateway MSC 80  is located within the home network.  
         [0009]    Mobile Subscriber  100  sends a setup message  10  requesting connection to subscriber  200 . The setup message  10  is transmitted from subscriber  100  to its Visited MSC  75 . The Visited MSC  75  produces the initial address message  12  which is transmitted to the PSTN  65  (Public Switch Telephone Network).  
         [0010]    PSTN  65  propagates message  12  which is transmitted to gateway MSC  80 . The initial address message (IAM) is an out-of-band signaling message which is a part of the ISUP protocol. The ISUP protocol (ISDN User Part) an out-of-band signaling protocol that supports the ISDN interface. The ISUP protocol is used for GSM and UMTS signaling arrangements.  
         [0011]    Upon receipt of the Initial Address Message  12  sent from PSTN  65  to gateway MSC  80 . The Gateway MSC  80  sends the Send Routing Information message  20  to the visited MSC  90  through PSTN  70 . The send routing information message  20  is a GSM/UMTS Mobile Application Part (MAP) message which is sent from the called party&#39;s  200  Home Location Register to the visited MSC  90  when routing information is necessary to attempt to call mobile subscriber  200 .  
         [0012]    As Shown in FIG. 1, this is typically sent through the PSTN  70  where the PSTN represents a network of one or more switches typically that can typically communicate using the ISUP protocol.  
         [0013]    Typically the SRI message would connect through to the visited gateway  90  which would respond back to the Gateway MSC  80  via the PSTN  70  with a Mobile Subscriber Routing Number (a MAP Protocol message). Gateway MSC  80  would then sends an initial address message  32  to visited MSC  90  to complete routing to the called subscriber  200 .  
         [0014]    However, in this situation, due to a lack of end to end ISUP connectivity or some system error or blockage within the PSTN has caused a system error. The PSTN  70  returns back an indication of lack of resources or network blockage, message  30 , to the Gateway MSC  80  which in turn passes it on to the calling subscriber  100  via the PSTN  65  and Calling Party&#39;s Visited MSC  75 . At this point, subscriber  100  may receive reorder tone or some other indication of failure of connection, message  34 . However, subscriber  100  is not aware what failure occurred. Further, subscriber  200  may receive no indication that a call attempt to them failed.  
         [0015]    Referring to FIG. 2, a modern multi-media data network such as UMTS is shown including the present invention. In such a network the home or services network is separated from the visited network. Subscriber  100  originates a call to called subscriber  200 . This may occur through a PSTN  75 . In any event, an initial address message  10  is transmitted to the home services network or CSCF (Call Session Control Function)  80 . This is typical for a UMTS system. However, similar arrangements will apply to CDMA  2000  as well as mobile IP networks.  
         [0016]    As can be seen from FIG. 2, subscriber  200  is in a visited or a proxy network  90 . As a result, gateway MCS or home services network  80  will attempt to establish connection to the visited network proxy agent  90  via PSTN  70  and transmit routing information message  20 .  
         [0017]    The visited network  90  returns an error message  30  to the home services network  80  via the PSTN  70 . Error message  30  indicates that the subscriber  200  was not reachable or busy.  
         [0018]    As a result of message  30 , home services network or gateway MCS  80  diverts or redirects the session or call attempt to a voicemail or messaging system  95  via link  40 . Home services network or gateway MSC  80  then establishes link  50  with subscriber  100 , through PSTN  75 , for example. Then link  50  is coupled through the home network to voicemail  95  through link  52 . Subscriber  100  has been notified of a non-reachable condition of subscriber  200  and is instructed to leave a message. The message is then recorded via link  52  on voicemail system  95 .  
         [0019]    As can be seen from the above explanation, the call was forwarded as a result of the home services network  80  detecting that subscriber  200  was not reachable. As result, subscriber  100  was not returned a reorder tone or simply dropped not knowing why the call to subscriber  200  did not succeed or not have any ability to leave a message.  
         [0020]    This invention allows the ability for the home network to forward for messaging or redirect calls or sessions for a lack of communications between home and visited networks.  
         [0021]    The above invention pertains equally well to session initiation protocol (SIP) signaling in mobile packet networks. A collection of conditions may trigger the return of error message  30  from the visited network to the home network. This collection of conditions includes: the called party is either busy or has rejected the call; a bad or erroneous response from the serving network (bad gateway); the called party simply does not desire to participate or cannot participate; and the called party&#39;s service agent rejects the request because the requested bandwidth or media description is no acceptable.  
         [0022]    The present invention provides the following benefits, namely, increased revenue by generating traffic; terminating calls to voicemail, such calls would otherwise be dropped or unconnected for unexplained reasons. This will increase the customer satisfaction of any network.  
         [0023]    [0023]FIG. 3 is a message flow diagram similar to that of FIG. 1 except that for detection of error message  30  by gateway or home services network  80 , the call is diverted to voicemail  95  via message  40 .  
         [0024]    Although the preferred embodiment of the invention has been illustrated, and that form described in detail, it will be readily apparent to those skilled in the art that various modifications may be made therein without departing from the spirit of the present invention or from the scope of the appended claims.