Abstract:
Call content may be intercepted for law enforcement purposes by detecting subscriber status and then routing the relevant media streams to a conferencing means such as a conference bridge or a media server. The target subscriber and others in conversation with the target may be provisioned on the same switch as the monitoring agency seeking to intercept the call content or may be distributed over multiple, discrete networks and switches.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is related to and claims the benefit of commonly-owned U.S. Provisional Application no. 60/681,608, filed May 17, 2005 and titled “Seamless Verifiability of Subscribers on a Next Generation Network,” incorporated by reference herein. It is also related to U.S. Application Ser. No. 10/356,299, filed Nov. 27, 2003 and titled “Call-Content Determinative Selection of Interception Access Points, in a Soft Switch Controlled Network,” incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The invention described and claimed here concerns law enforcement monitoring of telephone conversations under the Communications Assistance for Law Enforcement Act of 1994 (CALEA), 47 U.S.C. §§1001-1010, mandating that telecommunications carriers provide law enforcement agencies with access to the telecommunications networks to enable lawfully-ordered intercept of the voice content of telecommunications. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0003]      FIG. 1  is a block diagram of a telecommunications system incorporating a softswitch and the logical connections for call interception;  
         [0004]      FIG. 2  is a call flow diagram of a subscriber status determination process; and  
         [0005]      FIG. 3  is a call flow diagram of a call interception process.  
     
    
     DESCRIPTION OF THE INVENTION  
       [0006]     The interception of a telephone may be accomplished in two steps: (1) determination of the status of a target subscriber; and (2) call interception. The latter enables an authorized law enforcement representative to monitor the call.  
         [0007]     Architecture  
         [0008]     A telecommunications system, shown in  FIG. 1 , illustrates the components relevant to this discussion. An IP network  100 ,,depicted as a cloud, is managed in part by a softswitch  200 . The softswitch  200  contains a call control engine  210 , gateway controller call agents  220 , a CALEA call agent  230 , a subscriber status call agent  240 , and a CALEA database  250 .  
         [0009]     The call control engine  210  is responsible for setting up and tearing down connections generally and, in this context, it also oversees the determination of subscriber status and interception of call content. While the gateway controller call agents  220  carry out the call setup and tear down functions, the subscriber status call agent  240  described here is tasked solely with determining the status of a subscriber, although it too could have other functions and capabilities. For this purpose, the subscriber status call agent  240  may have a database containing subscriber status information or it may relay on a database located elsewhere in the softswitch  200  or the network.  
         [0010]     The system shown in  FIG. 1  also illustrates subscribers identified as “Subscriber A”  310  and “Subscriber B”  320 , which access the IP network  100  through respective gateways  330 . These gateways  330  may interact with the gateway controller call agents  220  in a peer-to-peer or a master-slave relationship.  
         [0011]     “Subscriber A” is the target—the party of interest, whose telephone conversations the law enforcement agency or “monitoring agency”  400  wishes to intercept. The subscribers may be conventional landline telephones (PSTN), cellular telephones, VoIP devices, or any other devices that can access the network  100 , utilizing any desired compatible protocol (e.g., H.323, MGCP, SIP, etc.). Although individual access gateways  330  are provided in  FIG. 1  for Subscribers A and B, if appropriate, these two subscribers could access the network  100  through the same gateway.  
         [0012]     In the arrangement shown in  FIG. 1 , both subscribers (A and B) are controlled by the same switch, implying that they are both provisioned (i.e., registered) on this switch. However, one or both of the subscribers may be located in remote networks, e.g., the networks of other service providers, or under the control of other switches. In such a case, the procedures described here will involve the active participation of those remote networks and switches.  
         [0013]     An access gateway  410  provides the monitoring agency  400  with access to the softswitch  200  through the network  100  and specifically the CALEA call agent  230 . The monitoring agency  400  may access the switch  200  utilizing any desired protocol or device (e.g., H.323, MGCP, SIP, etc.; landline, cellular telephone, VoIP device, etc.) through a protocol-appropriate gateway.  
         [0014]     Subscriber Status Determination  
         [0015]     Before setting up the connections necessary to intercept call content, the system first determines the status of Subscriber A, the target subscriber. A signaling scheme for making this determination is set forth in the call flow diagram of  FIG. 2 . In the examples discussed here, there are four possible states for a subscriber—idle, off-hook, call-processing busy (call in progress), and status restricted, although there could be more or fewer such states as dictated by design considerations. The last indicated state, “status restricted,” may result when the queried party may not for whatever reason (e.g., legal) or cannot be monitored (e.g., for technical reasons).  
         [0016]     The monitoring agency  400  sends a request for call interception to the CALEA call agent  230 . The CALEA call agent  230  in turn requests the number of the target subscriber (Subscriber A) from the monitoring agency  400 , if the number has not already been provided with the initial request. The CALEA call agent  230  then sends a request to the call control engine  210 , requesting set up of a status-determination call to Subscriber A to determine subscriber status.  
         [0017]     In the configuration shown here, the call control engine  210  determines whether the monitoring agency  400  is authorized to make this request, challenging the agency  400  for a PIN. This function could have been handled by the CALEA call agent  230  or some other network or switch component. Further, it could occur at a different stage of the procedure. Authorizing information, which may include the telephone numbers of target subscribers and law enforcement identifying information, may be stored in a database such as the exemplary CALEA database  250 . This database  250  may reside in the softswitch  200  or it may be located elsewhere, as desired. Further, the authorization may be blanket or subscriber-specific. In the example of  FIG. 2 , the monitoring agency  400  supplies a PIN.  
         [0018]     Once the authorization clears, the call control engine  210  sets up the status-determination call through the subscriber status call agent  240 , which would query the gateway controller call agent  220  provisioned to the target, Subscriber A. The gateway controller call agent  220  for Subscriber A either has or obtains the information sought by the subscriber status call agent  240 , including its current state and existing connections. The subscriber status call agent  240  returns a status message to the call control engine  210 , which is then passed to the CALEA call agent  230 . The call flow diagram of  FIG. 2  provides that status is indicated by an audible tone, but the status message could assume another form such as data appearing in a display or a pre-recorded verbal announcement. In the case of a remote monitored party, i.e., a subscriber provisioned on another switch or in an entirely different network, the remote switch or network would provide status information to the softswitch  200 .  
         [0019]     Call Interception  
         [0020]     If the target is in conversation with another party (or parties), the call can be intercepted. A suggested signaling procedure for accomplishing call interception is shown in the call flow diagram of  FIG. 3 . A media server  500  ( FIG. 1 ), functioning as a conference bridge, provides a means for acquiring access to the call content (i.e., the call). To intercept call content, the media streams of the monitored parties (the subscriber media streams) are re-routed or translated to ports on the media server  500 .  
         [0021]     The call control engine  210  first requests that the media server  500  create a port for the monitoring agency  400 . A dotted line in the IP network cloud  100  connecting the media server  500  and the access gateway  410  represents the media stream carrying the intercepted call back to the monitoring agency  400 .  
         [0022]     The call control engine  210  then queries the subscriber status call agent  240 , seeking media information about the target Subscriber A and all other participating target subscribers, i.e., Subscriber B, etc. The media information provides the call control engine  210  with the details of the call and the identities of the parties to the call.  
         [0023]     The call control engine  210  then sets up the conference, creating ports on the media server  500  for Subscriber A, Subscriber B, and any others. The respective media streams for each of these subscribers are then rerouted (or translated) to the ports on the media server  500 , as depicted by the dotted lines in the IP network cloud  100  connecting the gateways  330  to the media server  500  (the ports being simply illustrated by arrow heads). If desired, the port for the monitoring agency  400  could be established after the media streams of the target and the other subscribers have been re-routed to the media server  500 . Once all of the target subscribers return to an idle state, the conference can be torn down.  
         [0024]     The status determination and intercept processes can be utilized in a variety of networks. Architectures suitable for such an application include the Siemens SURPASS hiQ8000 softswitch, described in “SURPASS hiQ8000—The Winning Softswitch Strategy for NGN Solutions,” Ref. No. A50001-N2-P121-1-7600, dated 2003, and the systems described in the MultiService Forum Technical Report, “Bandwidth Management in Next Generation Packet Networks,” MSF-TR-ARCH-005-FINAL, dated August 2005, both incorporated by reference herein. Media servers, such as those manufactured by IP Unity, Milpitas, Calif., may be utilized as the media server  500  described here.