Abstract:
Media gateways operate under the control of an intelligent node or switch associated with a wiretap party and are configured on a per call basis to establish multicasting communication links to law enforcement authorities while simultaneously supporting the end-to-end telephony services elected by the calling and/or called party. The multicasting communication links supply law enforcement authorities with communications generated by the calling party and the terminating party.

Description:
This application claims the benefit of provisional application No. 60/451,764, filed Mar. 4, 2003. 

   BACKGROUND 
   This invention is generally directed to the implementation of a wiretap (a legally authorized interception of communications) and is more specifically directed to the use multicasting by a media gateway to facilitate wiretaps including, but not limited to, situations in which the wiretap party employs enhanced telephony services such as call forwarding. 
   The use of conventional wiretaps by law enforcement authorities is well-known. In its most basic form, a wiretap can be accomplished by a splice of a wire telephone line used by the wiretap party where the splice consists of a parallel telephone line connected to a telephone and/or recording device operated by law enforcement authorities. With the evolution of more sophisticated telephony equipment and services, providing facilities to accommodate a legally authorized interception of communications to and from a wiretap party has become increasingly difficult. For example, cellular telephone subscribers may place and receive telephone calls from different locations that are supported by different infrastructure equipment. Advanced call services such as three-way conferencing and call forwarding provide varied circumstances that need to be addressed to support a comprehensive wiretapping capability. Thus, there exists a need for improved wiretap support capability. 
   SUMMARY OF THE INVENTION 
   It is an object to the present invention to provide an improved wiretap support capability that is suited, but not exclusively suited, for use in wireless telephony environments where call forwarding services may be elected. 
   In an embodiment of the present invention, media gateways operate under the control of an intelligent node, e.g. a switch, associated with a wiretap party and are configured on a per call basis to establish multicasting communication links to law enforcement authorities while simultaneously supporting the end-to-end communications sought in accordance with the telephony services elected by the calling and/or called party. The multicasting communication links provide the means of supplying law enforcement authorities with communications generated by the calling party and the terminating party. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram of a telecommunication network that incorporates an embodiment of the present invention. 
       FIG. 2  is a logical diagram illustrating communication paths created through the media gateways in accordance with an embodiment of the present invention. 
       FIGS. 3 and 4  show a flow diagram illustrating steps in accordance with an exemplary method of the present invention. 
   

   DETAILED DESCRIPTION 
   The exemplary network shown in  FIG. 1  supports an embodiment of the present invention. A subscriber associated with wireless communication device  10 , such as a cellular telephone, is supported with wireless telecommunications by radio access network (RAN)  12  and mobile switching center (MSC)  14 . Similarly, subscribers associated with wireless communication devices  16  and  22  are supported with wireless telecommunications by radio access networks  18  and  24  and mobile switching centers  20  and  26 , respectively. A media gateway (MGW)  28 , such as a Cisco Systems Inc. MGX-8850 multiservice switch, is connected to the RANs, mobile switching centers  14 ,  20  and  26 , and to the public switched telephone network (PSTN)  30  that includes media gateway (MGW)  32 . A central office telecommunications switch  34  is also coupled to the PSTN  30  and supports a telephone line connected to telephone  36 . A call collection data unit (CCDU)  38  connected to MGW  28  receives and stores communications associated with party subject to the wiretap. 
   In accordance with an embodiment of the present invention, a wiretap as will be explained below is supported by the network shown in FIG.  1 . The subscriber associated with the wireless device and the wireless device itself will be referred to by the reference numeral associated with the wireless device; it will be apparent from the context whether the subscriber or the device is intended. In an illustrative example, law enforcement authorities associated with telephone  36  have obtained legal authority to intercept and record communications to and from subscriber  16 . The law enforcement authorities have contacted the telecommunications service provider for subscriber  16  and requested that calls to and from the telephone number associated with subscriber  16  be intercepted and that any communications resulting from such calls be routed to and stored in CCDU  38 . It is also requested that all calls intended for subscriber  16  be intercepted even where enhanced telecommunication services are utilized for subscriber  16  to reroute an incoming call, such as by utilizing call forwarding, to another telephone number. Assume that the telecommunications service provider has taken steps in accordance with the present invention as will be described below to carry out these requests. 
   Assume subscriber  10  places a telephone call to subscriber  16 . Prior to this incoming telephone call, subscriber  16  has enabled unconditional call forwarding of all incoming calls and directed that all such calls be routed to subscriber  22 . The subscriber  16  may desire that all calls be directed for answering by the subscriber normally associated with telephone  22  or may anticipate himself using telephone  22  to receive incoming calls originally directed to telephone  16 . Regardless of the motive, call forwarding has been initiated to reroute calls from telephone  16  to telephone  22 . The handling of such calls that are subject to a wiretap of the subscriber&#39;s telephone  16  as will be described below. 
   Before beginning a description of the exemplary steps utilized to connect such a call including the wiretap implementation to monitor the call, an overview of  FIG. 2  will be of assistance. Logical media gateway elements  50 ,  52  and  54  could be realized in physically separate media gateway nodes but in the illustrative embodiment are implemented within MGW  28 . Logical media gateway element  56  is implemented as part of MGW  32  that is part of the PSTN  30 . The media gateways  28  and  32  contain a plurality of input/output ports, including ports that support time division multiplex (TDM) communications and packet based Internet protocol communications. In accordance with ITU-T H.248 standards these ports can be interconnected in accordance with requests received from an intelligent node, e.g. MSC  20 , to form a logical network. In accordance with this embodiment these ports are configured on a per call request. Further details concerning  FIG. 2  will be provided as part of the discussion of the exemplary flow diagram. 
   Referring to  FIGS. 3 and 4 , the flow diagram illustrates the handling of a call from subscriber  10  to subscriber  16  where subscriber  16  has unconditional call forwarding activated to telephone  22  and the call is forwarded without being offered to telephone  16 . Subscriber  16  is the target of an interception of communications by law enforcement authorities in which communications to and from telephone  16  are to be routed to telephone  36 ; therefore, this call must be tapped. 
   In step  100  subscriber  10  originates a call to subscriber  16  by dialing the corresponding telephone number of subscriber  16  and requests the establishment of the call by radio access network  12  and mobile switching center  14 . Following normal authentication and security procedures, the call request is relayed to mobile switching center  20  in step  102 . The MSC  20  is the terminating MSC for subscriber  16 . In step  104  a determination is made of whether a wiretap is required. A NO determination by step  104  results in the call request being subject to normal call handling procedures at step  106 . A YES determination by step  104  results in the MSC  20  utilizing wiretap handling call procedures at step  108  as will be explained. 
   Having determined that wiretap procedures are to be utilized, MSC  20  requests a new context (C 1 ) at logical media gateway  50  (MGW  28 ) in step  110 . This request is accomplished by sending H.248 Add commands indicating the assignment of two terminations: TDM termination  58  and IP termination  60 . The TDM termination  58  is coupled to the calling party&#39;s (subscriber  10 ) communication channel and the IP termination  60  is a network facing termination. The logical MGW  50  connects the TDM termination  58  and the IP termination  60 , and provides the appropriate protocol interface to facilitate TDM information to be translated into IP packets and vice versa. The logical MGW  50  returns a transaction reply to MSC  20  that includes a context identification, C 1 , and the associated IP address and port number of IP termination  60  to support real-time packet transmission. This completes the configuration of logical MGW  50 . 
   In step  112 , the MSC  20  queries the home location register (HLR) to obtain the mobile station routing number (MSRN) of telephone  16  and determines that call forwarding unconditional (CFU) is active and that the call is to be forwarded to subscriber telephone  22 . In step  114  the MSC  20  creates a new context C 2  to facilitate the wiretap. The MSC  20  requests a new context C 2  at logical MGW  52  creating four new IP terminations  62 ,  64 ,  66 , and  68 . The logical MGW  52  returns to MSC  20  a context identification, C 2 , and the allocated IP address and port numbers for each termination. In the initial request from MSC  20  for a new context C 2 : routing information for IP termination  60  of logical MGW  50  is provided and assigned as part of the C 2  context to IP termination  62 ; another IP termination  66  is requested to be assigned for two-way communications with IP termination  62 ; IP termination  64  is requested to receive one-way communications from IP termination  62 ; IP termination  66  is requested to receive one-way communications from IP termination  66 . In step  116 , MSC  20  sends route information to MGW  50  by providing the IP address and port information for IP termination  62  which is coupled for two-way communications with IP termination  60 . 
   In step  118  the MSC  20  requests a new context, C 3 , at logical MGW  56  (PSTN MGW  32 ) to establish a TDM termination  72  to receive one-way communications from an IP termination  70  that will be coupled to IP termination  64  wherein the IP address and port assignment associated with IP termination  64  is provided to MGW  56  for association with IP termination  70 . In step  120  the MSC  20  requests a new context, C 4 , at logical MGW  56  to establish another TDM termination  76  to receive one-way communications from an IP termination  74  wherein the IP address and port assignment associated with IP termination  68  is provided to MGW  56  for association with IP termination  74 . In response to the request for each new context C 3  and C 4 , logical MGW  56  returns a transaction reply to MSC  20  that includes the context identification and associated addresses and ports for the newly created terminations. In step  122  the MSC  20  sends routing information to MGW  52  providing the addressing of IP termination  70  to be associated with IP termination  64 , and the addressing of IP termination  74  to be associated with IP termination  68 . 
   In step  124  the MSC  20  forwards the call request to MSC  26 , the terminating MSC for subscriber  22 . The MSC  26  makes a query of the HLR to obtain the MSRN of subscriber  22  in step  126  and determines that the subscriber  22  is available (active) to receive the call. This information is conveyed to MSC  20  wherein a request for a new context, C 5 , at MGW  54  is made in step  128 . This request seeks the assignment of two terminations: an IP termination  78  and a TDM termination  80  that will support communications with a telephone  22 . The request also includes addressing information for IP termination  66  to facilitate communications with IP termination  78 . Two-way communications are supported between terminations  78  and  80 . The MSC  20  receives a transaction reply from MGW  54  providing the termination addresses and ports associated with terminations  78  and  80 . In step  130  MSC  20  sends routing information to MGW  52  that includes the IP addressing and port of IP termination  78  to be utilized in conjunction with IP termination  66  for communications there between. 
   In step  132  a traffic channel is enabled from subscriber  10  to subscriber  22 . Two-way TDM communications are supported for subscriber  10  and subscriber  22  by TDM termination  58  and  80 , respectively. The TDM terminations  58  and  80  are coupled by IP terminations  60 ,  62 ,  66 , and  78 . 
   The call is established with typical call setup messages at step  134 . For example, a call connect alerting message is transmitted by telephone  22  that is relayed by the MSC to telephone  10 . An audible ringing tone may be transmitted to telephone  10  that ends upon the called party (subscriber  22 ) answering which causes a connect message to be relayed to the MSC. The MSC generates a connect message to telephone  10 . Upon the MSC receiving a connect acknowledgment from telephone  10  and telephone  22 , the previously established communication path (bearer path) between telephones  10  and  22  is enabled at step  134 . Also, concurrent communications generated by subscribers  10  and  22  are relayed to CCDU  38  by one-way TDM terminations  72  and  76 , respectively, in step  136 . The call connection process terminates at END  138 . 
   TDM terminations  72  and  76  are connected to dedicated trunks assigned for wire tapping the wire tape party implemented by the service provider pursuant to a request of the law enforcement agency. CCDU  38  records communications incoming and outgoing relative to the wiretap party via these dedicated trunks. 
   It will be apparent to those skilled in the art based on the description of the above embodiment that the present invention is not limited to the specific call request described. For example, the logical diagram shown in  FIG. 2  is also suited for supporting a wiretap between a calling and a called party where one of these parties is subject to monitoring even if call forwarding is not utilized. A wiretap of a three-way or conference call can also be accommodated in a similar manner by establishing three concurrent 1-way communication channels routed to law enforcement authorities in a similar manner explained with regard to FIG.  2 . Although three mobile switching centers are shown in  FIG. 1 , it will be apparent that subscribers  10 ,  16  and  22  could all the supported by a single MSC. The logical media gateways  50 ,  52  and  54  could be implemented more than one physical media gateway. 
   Assuming a media gateway is available with the required types of terminations, a single media gateway could be utilized to implement all of the logical media gateways illustrated in FIG.  2 . The calling and called party subscribers may utilize wireless services, wireline services, or a combination of these services. Although the intelligence associated with controlling and establishing the logical media gateways is illustrated in the current example as residing in the terminating MSC of the monitored party, this intelligence can be distributed to more than one node or transferred to a different intelligent node. If desired, the wiretap communications concurrently delivered to the law enforcement authority line can be in a format other than traditional TDM communications, e.g. IP packets. Although the internal communication paths within the media gateway are described as using IP packets, it will be apparent that other communication protocols could be utilized. Also the external communication ports provided by the media gateway could be other than TDM protocol depending on the protocol employed in the subject telecommunication network, e.g. ATM ports would be used to support ATM channels. 
   Although an embodiment of the present invention has been described above and shown in the drawings, the scope of the invention is defined by the claims that follow.