Patent Publication Number: US-6216005-B1

Title: Cellular-fixed call completion and call transfer service from a cellular network provider

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is related to U.S. application Ser. No. 09/224,236 filed on Dec. 30, 1998, entitled “Establishing Calls and Processing On-Going Calls in Fixed and Cellular Networks”, Ser. No. 09/223,286 filed on Dec. 30, 1998, entitled “Establishing Calls and Processing On-Going Calls in Fixed and Cellular Networks”, Ser. No. 09/223,287 filed on Dec. 30, 1998, entitled “Establishing Calls and Processing On-Going Calls in Fixed and Cellular Networks”, Ser. No. 09/223,463 filed on Dec. 30, 1998, entitled “Establishing Calls and Processing On-Going Calls in Fixed and Cellular Networks”, Ser. No. 09/223,464 filed on Dec. 30, 1998, entitled “Establishing Calls and Processing On-Going Calls in Fixed and Cellular Networks”, Ser. No. 09/223,465 filed on Dec. 30, 1998, entitled “Cellular Fixed Call Completion and Call Transfer Service From a Cellular Network Provider”, and Ser. No. 09/223,466 filed on Dec. 30, 1998, entitled “Cellular Fixed Call Completion and Call Transfer Service From a Cellular Network Provider”, all of which are assigned to the assignee of the present invention. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to telecommunications services and, more particularly, to incorporating a cellular-fixed call transfer service into the conventional public switched telephone network in combination with the conventional cellular network. 
     BACKGROUND OF THE INVENTION 
     Most individuals now, or in the near future will, have at least two telephone numbers through which they make or receive calls on a regular basis. One of these telephone numbers is usually associated with a local access provider while the other is usually associated with a cellular service provider. The connectivity from the local access provider is to the traditional fixed telephone network (oftentimes referred to as the Public Switched Telephone Network (PSTN)) while the connectivity from the cellular service provider is to the cellular network (CN). For discussion purposes below, let N f  and N c  respectively denote the telephone number for a particular user to the fixed and cellular network. 
     The calls made from N f  are usually of lower cost than those made or received from N c  because the call is routed over the fixed network and therefore does not make use of the limited wireless bandwidth. However, once a call has been initiated on the fixed network, the user has very little mobility; a cordless phone may allow the user to move 50-100 meters from the base of the phone without significant deterioration in the voice quality. However, a user can move in a wide geographical area if a user could transfer an on-going call originated over the fixed network to the cellular network. A point of departure from the prior art in accordance with the present invention is a new call transfer service called the Cellular-Fixed Call Transfer Service (CFCTS) which can be offered by the cellular network provider to allow users to transfer on-going calls between the his/her fixed and cellular telephone numbers. 
     The CFCTS service benefits both the user and the service provider. The user benefits because he/she can use the lower cost calls through the fixed network whenever possible without sacrificing mobility. The service provider also benefits because as users switch over to fixed network from cellular whenever possible, the limited capacity of the cellular network can support other users. More customers will also be attracted to this lower cost service with full support for mobility. Also, when a user transfers a call from his/her N f  to N c  the cellular network provider gains additional business. 
     Heuristic Example 1 
     Suppose that a user receives a call at home on N f  just as she is about to leave for work. At present, the user has only one of the following two options. Either complete the call before starting the commute to work or terminate the conversation and restart it using the cellular phone. Terminating the conversation and restarting it using the cellular phone requires all parties in the call to hangup and reestablish the necessary connections. This is clearly troublesome. 
     However, if the user can transfer the call over to her cellular telephone without disrupting the conversation, then the call can be continued while the user is in commute. 
     In this example, the user benefits because she gets mobility while using the lower cost of the fixed network for as long as possible. The cellular network provider also benefits because a call has been transferred to it from another service provider. 
     Heuristic Example 2 
     Suppose that a user makes a call using his cellular telephone while away from home and comes back home while the call is in progress. There will be no degradation in the voice quality and the user can continue using the more expensive cellular network while at home. However, if the user can transfer the call to his fixed telephone, the cost of the rest of call will be lower. The service provider will also benefit because as users switch over to the fixed network, the limited capacity of the cellular network can be used to support other users. In this example, the reason for the transfer capability is reduced cost to the user. 
     The prior art does not allow transfer of on-going calls from a fixed network to a cellular network and vice versa. Some service providers offer forwarding of calls from the fixed to the cellular network prior to the establishment of a call, such as by conventional call-forwarding. Similarly, some fixed network service providers offer transfer of on-going calls from one fixed telephone number to another, typically at the request/intervention of the called party. 
     SUMMARY OF THE INVENTION 
     These shortcomings and other limitations and deficiencies of the prior art are obviated, in accordance with the present invention, by a methodology and concomitant circuitry effected by introducing a Fixed-Cellular Mobility Agent (FCMA) into the cellular network, the FCMA having at least the functionality of a PSTN central office for interconnecting incoming/outgoing calls to the MSC as outgoing/incoming calls to the CN or the PSTN and which, in addition, monitors each call connection to carry out call transfers between the CN and the PSTN. 
     In accordance with a broad method aspect of the call completion aspect of the present invention, a method for establishing a call path from a calling party to a called party utilizing the functionality of the Public Switched Telephone Network (PS TN) and the Cellular Network (CN), the PSTN including a central office (CO) serving the called party, the CN including a mobile switching center (MSC) serving the called party, the called party having a conventional telephone number N f  for accessing the called party through the serving CO, includes: (a) assigning another PSTN telephone number N fc  to the called party for directing each call to the called party via the N fc  to the serving MSC, and associating the N f with the N fc ; (b) when the calling party initiates an incoming call to the called party using the N fc , directing the incoming call to the MSC; (c) initiating an outgoing call from the MSC to the called party using the N f  associated with the N fc ; and (d) when the called party answers the outgoing call, switching the MSC to interconnect the incoming call with the outgoing call to thereby establish the call path. 
     In accordance with the broad aspect of the call transfer aspect of the present invention, the method to further transfer an established call path, the established call path including a first call connection between the calling party and the MSC and a second connection between the called party and the MSC, includes: (a) monitoring the second call connection to detect a request for a call transfer from the called party; (b) initiating by the MSC an outgoing call to a cellular telephone number N c  assigned to the called party upon the call transfer request; (c) whenever the outgoing call to a cellular telephone assigned the N c  is answered, establishing a third call connection between the MSC and the cellular telephone; and (d) bridging the first call connection and the third call connection and terminating the second call connection. 
     In accordance with broad system aspects of the present invention, concomitant circuitry effects the aforementioned methodology. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a high-level block diagram a network arrangement of a conventional public switched telephone network as well as an exemplary, conventional cellular network integrated with the public switched telephone network; 
     FIG. 2 is a high-level block diagram of the Fixed-Cellular Mobility Agent (FCMA) in accordance with the present invention network arrangement shown incorporated into the arrangement of FIG. 1; 
     FIG. 3 depicts in more detail certain elements of FIG. 2, including the call connections for completing a call from a calling party on the fixed network to a called party on the fixed network in accordance with the present invention; 
     FIG. 4 depicts an arrangement equivalent in operation to the arrangement of FIG. 3 wherein the FCMA is co-located with the mobile switching center; 
     FIG. 5 depicts a preferred arrangement of the FCMA which is fully integrated into the structure and operation of the mobile switching center; 
     FIG. 6 is a flow diagram for processing a call to a called party on a fixed network using the CFCTS service in accordance with FIGS. 2-5; 
     FIG. 7 depicts an illustrative arrangement for transferring an established incoming call from the fixed network to the cellular network; 
     FIG. 8 is a flow diagram for processing the transfer of an established incoming call from the fixed network to the cellular network; 
     FIG. 9 depicts an illustrative arrangement for completing an incoming call from a remote calling party to the cellular network; 
     FIG. 10 is a flow diagram for processing a call to a called party on a cellular network using the CFCTS service in accordance with FIG. 9; 
     FIG. 11 depicts an illustrative arrangement for transferring an established incoming call from the cellular network to the fixed network; 
     FIG. 12 is a flow diagram for processing the transfer of an established incoming call from the cellular network to the fixed network; 
     FIG. 13 depicts an illustrative arrangement for completing an outgoing call from the fixed phone of a subscriber/user of the cellular-fixed call transfer service; and 
     FIG. 14 is a flow diagram for processing an outgoing call from the fixed phone of a subscriber/user of the cellular-fixed call transfer service. 
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. 
     DETAILED DESCRIPTION 
     It is instructive to first consider the conventional operation of the Public Switched Telephone Network (PSTN) working in conjunction with the Cellular Network (CN) in exemplary scenarios, namely, when handling (1) a telephone call from a calling party (designated R for “remote”) to a called party (designated U f  for “fixed user”) solely over the PSTN; and (2) a telephone call from calling party R to a called party (designated U c  for “cellular user”) on the CN. The primary purpose for elucidating this conventional operation is that of highlighting the functionalities of the PSTN and the CN which are utilized in accordance with the various aspects of the present invention. 
     FIG. 1 depicts a high-level block diagram of an exemplary network infrastructure  100  composed of PSTN  110  and CN  150 . 
     Public Switched Telephone Network 
     The exemplary PSTN  110  is composed of: (a) end central office (CO)  121  which is the serving office for user  101 , and end central office  122  which is the serving office for user  103 , and end central office  123 ; (b) access tandem (AT) office  131  connected to COs  121 - 123 ; and (c) Signaling System 7 (SS7) network  141  which is connected to COs  121 - 123  as well as AT  131  via channels  142 ,  144 ,  145 , and  143 , respectively, and which is used for call setup and call completion signaling messages. The conventional SS7 protocol is used for signaling messages processed and generated by SS7 network  141 . 
     The interconnection of CO  121  to AT  131  via trunk  126  exemplifies the so-called two-level hierarchy of modem local access providers oftentimes referred to as local exchange carrier (LEC) service providers. CO  121  provides the basic access to the users of PSTN  110  in a pre-determined geographical area; for instance, it is CO  121  which provides the basic “dial-tone” to subscribers/users of a given service provider. CO  121  may be directly linked to other end central offices (not shown) within the same local calling areas to handle “local” calls. On the other hand, “toll” calls are routed through AT  131  for transport to the LEC or an Interexchange Carrier (IC) depending upon the destination of the call. In the exemplary network of FIG. 1, COs  122  and  123  are presumed (without loss of generality but to simplify the description) to be within the same LEC as CO  121 . (In general, COs  122  and  123  could be located anywhere within PSTN  110 —from local to world-wide.) 
     The reasons for the existence of AT  131  are both historical and technical. Historically, so-called service areas known as local exchange and transport areas (LATAs) were established, and because LECs&#39; business was confined to intraLATA operations, access tandems were created to serve as entry points in LATAs by the ICs. The import of this hierarchy on cellular network  150  will be discussed below. In addition, AT  131  provides more rigid transmission characteristics needed for “long distance” type calls. 
     COs  121 - 123  provide both line-side and trunk-side connections, whereas AT  131  provides only trunk-side connections, both for central offices and inter-exchange carriers. In brief, line-side connections (e.g., wire pairs  124  and  125 ) interface directly to the subscribers of a telephone service provided by COs  121  and  122 . Trunk-side connections (e.g., trunks  126 - 128 ) couple switching facilities to each other. Each trunk  126 - 128  is composed, when required, of both trunks used for “talking paths” and trunks used for signaling. Again, the import of these types of connections will be further elucidated once CN  150  is introduced. 
     Signaling in PSTN  110  is dependent primarily upon whether the signaling is line-side or trunk-side. The signaling on the line side is typically associated with the circuit itself, namely, subscriber wire pair  124  coupling CO  121  with user  101  or wire pair  127  coupling CO  122  with user  103 . Such signaling is usually in-band, meaning it uses the associated wire pair. Examples of in-band signaling include taking a telephone handset “off-hook”, placing the handset “on-hook”, “dialing” (e.g., keying digits on a telephone keypad using DTMF tones), “ringing” to alert a user of an incoming call, “flashing”, that is, a momentary disruption in direct current supplied to a telephone on an established connection, and “in-band tone signaling” (e.g., DTMF tones). These types of functions are used in accordance with inventive aspects of the present invention. In general, there are a number of basic types of signaling elements, including addressing, supervisory, alerting, call progress, and control. 
     The type of signaling between central offices and access tandem offices uses a path distinct from the wire pair/voice path; such signaling arrangements are known as common channel signaling (C C S), with the SS7 signaling system being one wellknown signaling system representative of C C S. The utility of C C S is that there is no need to establish a circuit path through PSTN  110  if a called party is not available (thereby freeing the circuit facilities for another call connection)—such information as called party availability can be established via the C C S, as provided by a “busy signal” on the called party&#39;s wire pair, or a “no answer” by the called party. The essential characteristics of C C S used in accordance with the present invention are discussed in detail at the point in the description in which the C C S is invoked. 
     To describe a standard operating scenario, consider a PSTN-to-PSTN call. It is assumed that remote calling party R (in this example, user  101 ) initiates a telephone call to called party U f  (in this example, user  103 ), where U f  is assigned the fixed telephone number 908-555-1111. To establish this call, a signaling message generated by the call initiation actions of calling party R (going off-hook and dialing U f &#39;s telephone number) is launched by CO  121  to SS7  141  over signaling channel  142 . In turn, SS7  141  processes the signaling message, and provides routing and signaling information for the call to CO  121 , AT  131 , and CO  122  over signaling channels  142 - 144  so that a call connection path can be established, in seriatim, over wire pair  124 , CO  121 , trunk  126 , AT  131 , trunk  127 , CO  122 , and wire pair  127  to called party U f  whenever called party U answers the incoming call ringing signal applied to wire pair  127 . Assuming that a call has been established, COs  121  and  122  then monitor the established call for call completion, and upon detection of call completion (e.g., by both parties going on-hook), the established talking path is taken down. 
     Cellular Network  150   
     The exemplary CN  150  is composed of: (a) mobile terminals (MTs)  151  and  152 , with MT  151  serving user (U c )  102 ; (b) base stations (BSs)  161 ,  162 ,  163 , and  164 ; (c) base station controllers (BSCs)  171  and  172 ; (d) mobile switching center (MSC)  181 ; and (e) home location register (HLR)  191  coupled to SS7 network  141  and visitor location register (VLR)  192  coupled to MSC  181 . Focusing on MT  151 , it is served by base station  164  as its home base station over radio channel  165 , and user  102  of MT  151  is free to “roam” so that the user may be handled, in this example, by another base stations  161 - 163 . Base stations  161 - 164  are connected to BSC  171  via trunks trunk  173  is shown as connecting base station  164  to BSC  171 . The primary purpose of each BSC  171  or  172  is to manage the radio resources of its associated base stations, such as by allocating radio channels or performing handoffs. BSC  171  and  172  home on MSC  181  via trunks  183  and  184 , respectively. MSC  181  provides typical switching functions and coordinates location registration of base stations  161 - 164  and call delivery. MSC  181  is connected to AT  131  via trunk  132 , which serves as the backbone communication network, to CO  123  via trunk  129 , and to SS7 network  141 , which serves as the signaling network to CN  150 , via signaling channel  182 . 
     Typically, MSC  181  is a special-purpose switch tailored for mobile applications, and can be viewed as having two ports, namely, a “wireline network” side and a “wireless network” side. On the wireline side, MSC  181  is connected to PSTN  110  with conventional trunking facilities  132  and  129 , such as T1 trunk groups. Call set-up, call connection, and call completion between the CN  150  and the PSTN  110  are handled in a conventional wireline manner by viewing MSC  181  on the wireline side, for example, as a PSTN-like terminating central office. On the wireless side, MSC  181  provides the interface to base station controllers to effect wireless-wireless connections only involving CN  150 , as well as wireless-wireline connections involving PSTN  110 . 
     Thus, MSC  181  provides the telephony functions required for cellular mobile telephone operations and interfaces mobile terminals with PSTN  110 . To reiterate, these functions include: (1) switching facilities for switching of voice channels to accomplish end-to-end conversations for fixed-to-cellular, cellular-to-fixed, and cellular-to-cellular; moreover, the switching facilities engender the handoff process to allow for continuous conversations as mobile terminals travel from cell site to cell site; (2) control and detection signaling to and from PSTN  110 ; (3) control and coordination of information and supervision signaling to mobile terminals; (4) control and coordination of call-processing activities for the mobile switching center and cell sites; (5) control of the links between the mobile switching center and the base stations; and (6) communication with the home location register and control of any associated visitor location register. 
     The following example covers the call setup, call establishment, and call tear-down of a PSTN-originated call from calling party R (user  101 ) to called party U. (user  102 ), assuming that U c  is located in the area served by his/her home base station  164  so that U c  is registered with the same information both in HLR  191  and VLR  192 ; moreover, U c  is presumed to be served by cellular number 908-555-2222. Calling party R initiates a call by going off-hook and dialing U c &#39;s telephone number. CO  121  sends a signaling message to SS7 network  141  for processing; in turn, SS7 network returns signaling messages to CO  121 , AT  131 , and MSC  181  to establish a path, whenever U c  answers an incoming ringing signal, including in seriatim: wire pair  124 , CO  121 , trunk  126 , AT  131 , trunk  132 , MSC  181 , trunk  183 , BSC  171 , trunk  173 , base station  164 , radio path  165 , and mobile terminal  151 . 
     PSTN-CN Interconnection 
     With reference to FIG. 1, AT  131  and MSC  181  are coupled via connection  132 . In this technology art, this connection is known as a “Type 2A’ connection which allows MSC  181  to connect to PSTN  110  like any other central office, such as COs  121 - 123 . A Type 2A connection is a true trunk-side connection that employs trunk signaling protocols. 
     MSC  181  also connects to CO  123  via connection  129 ; this type of connection is a so-called Type 1 connection, which has characteristics of both line-side and trunk-side connections. In essence, the Type 1 connection is a trunk-side connection to a central office that uses trunk signaling protocols in conjunction with a feature generically called “trunk with line treatment” (TWLT). Basically, the TWLT feature allows the end office to combine some line-side and trunk-side features; for example, while trunk-side signaling protocols are used, a call is recorded for billing purposes as if the call was made by a line-side connection. In addition, the use of TWLT enables the central office switch to return answer supervision to MSC  181 . Using a Type 1 connection, MSC  181  can access any valid telephone number. The full import of depicting CO  123  as being connected to MSC  181  by a Type 1 connection will be detailed shortly. 
     Typically, a Type 2A connection or a Type 1 connection uses a four-wire circuit for two-way communications, that is, transmit and receive, as well as E&amp;M supervision well-known in the art. 
     Network Management Functions of CN  150   
     In the fixed-to-cellular phone call example above, it was assumed that U was located in his/her home serving region. One major function of MSC  181  is to control the tracking of a user as the user roams throughout CN  150 , and beyond to other cellular network providers. Network management functions of CN  150 , such as call processing and location registration, are achieved by the exchange of signaling messages through SS7 network  141 . 
     One standard location management technique to register MT  151 , both in its home region as well as when the user of MT  151  roams, is based on a two-level data hierarchy such that the two types of databases—HLR  191  and VLR  192 —are invoked in tracking a mobile terminal. In this example, user of MT  151  is presumed to be permanently associated with HLR  191  (there may be other HLRs homing on SS7 network  141  as accessed by users of the services of other cellular providers). Information about each user, such as the types of services subscribed to, billing information, and location information, is stored in a user profile located in HLR  191 . Generally, there may be a plurality of visitor location registers, and there placement may vary among service providers. In this example, VLR  192  is shown as being associated with MSC  181 . VLR  192  stores the information about MTs  151  and  152 , as well as other mobile terminals not shown (as downloaded from HLR  191 ) visiting the geographical region served by VLR  192 . 
     Location Registration 
     In order to correctly deliver a call, CN  150  must keep track of the location of each mobile terminal. As a user of MT  151  moves around the coverage area of CN  150 , data stored in HLR  191  and VLR  192  may no longer be accurate. To ensure that calls can be delivered successfully, an update technique must be applied—the process is called location registration. Locations registration is initiated by MT  151  when it reports its current location to CN  150 . One conventional cellular network arrangement, discussed for expository purposes, adopts the approach such that the coverage area of CN  150  is partitioned into registrations areas (RAs), and each mobile terminal performs a location update when it enters a new RA. Each RA includes a number of cells and, in general, all base stations belonging to the same RA are connected to the same MSC. 
     When a mobile terminal enters a RA, if the new RA belongs to the same VLR as the old RA, the record of the VLR is updated to record an identifier (ID) on the new RA. Otherwise, if the new RA belongs to a different VLR, a number of extra steps are required to: (a) register the mobile terminal at the new serving VLR; (b) update the HLR to record the ID of the new serving VLR; and (c) de-register the mobile terminal at the old serving VLR. 
     To give a concrete example of this process, the following is a list of tasks that are performed during location registration: 
     (i) MT  151  enters the new RA and transmits a location message to the new base station. In FIG. 1, suppose one registration area encompasses BSs  161  and  162 , and a second registration area encompasses BSs  163  and  164 . Thus, when MT  151  moves from the cell covered by BS  164  to the cell covered by BS  163 , a registration boundary has been crossed. 
     (ii) new BS  162  forwards the location update message through BSC  171  to MSC  181 , which launches a registration query to its associated VLR  192 ; and 
     (iii) VLR  192  updates its record on the location of MT  151  to complete location registration. 
     Call Delivery 
     Two major steps are involved in call delivery, namely, determining the VLR of the called MT, and locating the visiting cell for the called MT. Locating the serving VLR of the serving MT involves the following lookup procedure, assuming the calling MT is MT  151  and the called MT is MT  152 : 
     (i) calling MT  151  sends a call initiation signal to MSC  181  through BS  164  and BSC  171 ; 
     (ii) MSC  181  determines the address of the HLR of called MT  152  by table lookup procedure called global title translation, and sends a location request message to the HLR. In the network of FIG. 1, there is only one HLR  191 , so HLR  191  is identified as the address of the HLR associated with MT  152 ; 
     (iii) HLR  191  determines the serving VLR of called MT  152  and sends a route request message to this serving VLR. In the network of FIG. 1, there is only one VLR  192 , so VLR  192  then forwards the message to MSC  181  serving VLR  192 ; 
     (iv) MSC  181  allocates a temporary identifier to MT  152  and sends a reply to HLR  191  together with the temporary identifier; 
     (v) HLR  191  returns this information to MSC  181  of calling MT  151 ; and 
     (vi) MSC  181  initiates a call setup based upon the VLR information of called MT  152 . (Note: in a more complex network than depicted by FIG. 1, wherein there is a MSC associated with the MT  151  and another MSC associated with MT  152 , then a call setup between the two MSCs is requested via SS7 network  141 .) 
     Overview in Accordance with Present Invention 
     Operation from User&#39;s Perspective 
     A user who subscribes to the Cellular-Fixed Call Transfer Service (CFCTS) in accordance with the present invention must have his/her cellular network provider assign a new number, say N fc , to the user. With reference to FIG. 1, it is now assumed that a user of CFCTS, previously identified by reference numerals  102  and  103  to distinguish separate parties generally, are now the same party (referred to as user  102 - 3 ), that is, user  102 - 3  has both a fixed phone served by PSTN  110  (e.g., CO  122  and wire pair  125 ) and a cellular phone served by CN  150  (e.g., MT  151  coupled by radio channel  165  to BS  164 ). Calls made to N fc  will be received by user  102 - 3  on his/her fixed telephone while those made N c  will still be received on his/her cellular telephone. User  102 - 3  must still subscribe to the fixed network service from the local access provider and keep N f  active. Although user  102 - 3  can receive calls made to N f  on his/her fixed telephone, these calls cannot be transferred to his cellular telephone. Therefore, from user  102 - 3 &#39;s perspective, it is better to receive all calls to the fixed telephone on N fc  instead of N f . This can be accomplished by keeping N f  private and using N fc  and N c  as user  102 - 3 &#39;s telephone numbers made known to the public. 
     In addition, the cellular network provider gives user  102 - 3  a special access number, say N a , for use in making outgoing calls. Whenever the user wants to make a call from either the fixed or the cellular telephone, he/she first dials N a . User  102 - 3  user is then be prompted to dial the telephone number to be called. A call is then established to the desired telephone number. 
     To transfer an on-going call from either the fixed telephone to the cellular telephone or vice versa, user  102 - 3  initiates a call transfer signaling action, such as keying in a tone sequence using touch-tone keys, i.e., DTMF tones. When the other, nearby telephone rings, user  102 - 3  picks up and resumes the conversation. 
     Implementation Details 
     The key constraint in implementing CFCTS as described below is effecting a service which is completely transparent to the local access provider. However, if the cellular service provider and local service provider are the same entity, the methodology is also transparent to the coalescing of the providers. 
     The following discussion references FIG. 2, which is essentially the network arrangement of FIG. 1 with an interposed intelligent agent, referred to as the Fixed Cellular Mobility Agent (FCMA)  210 , cooperatively arranged with MSC  181  to handle the functions related to CFCTS. Each mobile switching center in the cellular network now has an associated FCMA. 
     FCMA  210 , for purposes of the immediate discussion, is presumed to be a PSTN-type central office. To accomplish this in a practical sense, one can visualize CO  123  in FIG. 1 being been re-located to CN  150  and re-named FCMA  210 . Accordingly, trunk  212  (formerly trunk  129 ) is a Type 1 connection and signaling trunk  213  (formerly trunk  145 ) connects to SS7 network  141 . In all respects, FCMA  210  of FIG. 2 functions like a PSTN central office, complete with switching and signaling functionalities. 
     In addition, the cellular network provider of CN  150  maintains a look-up table  211  as a data structure in FCMA  210  which identifies the three telephone numbers N f , N c , and N fc  (e.g., from the discussions above, 908-555-1111, 908-555-2222, and as used later, 908-555-3333, respectively) for every user who has subscribed to CFCTS. Table  211  for a particular user can also be maintained as part of the user profile in the Home Location Registry (HLR). For clarity of presentation, this table is referred to as CFCTS-table  211  and it is assumed to be part of FCMA  210  for the expository purposes. 
     In the following sections, the actions required to implement CFCTS for several different scenarios are described. In the descriptions, the focus is on a particular user (U now in place of user  102 - 3 ) who has subscribed to CFCTS. 
     1.1 Incoming call to N fc    
     Reference is now made to FIG. 3, which shows the pertinent subcomponents of FIG. 2 in some detail, to describe the operation of FCMA  210  in completing a call from calling party  101  (R) to called party  103  (U). R keys in N fc  (e.g., 908-555-3333) to call U. The circuit arrangement in accordance with the present invention is such that CO  121 , in a network sense, treats FCMA  210  as the central office serving U based upon the assigned N fc , whereas U is actually served by CO  122 . CO  121  sends a call setup signaling message to SS7  141  which processes the signaling message to arrange for a call connection path composed of, in seriatim: wire pair  124 , CO  121 , talking trunk  126 , AT  131 , talking trunk  132 - 1 , MSC  181  (including switching point  181 -A), talking trunk  212 - 1 , and FCMA  210  (including switching point  210 -A)—this path is designated C R  in the sequel. User  103 - 1 , shown in phantom connected to FCMA  210 , is the surrogate for U (user  103 ). (It is as if user  103 - 1  is assigned an equipment location in FCMA  210 , but there is no wire pair connected to the line side of the equipment to complete a call.) 
     FCMA  210 , upon detecting the incoming call to N fc , now acts as a calling party by initiating a call to U via a look-up in table  211  to obtain N f . FCMA  210  is, in a logic sense, acting as a surrogate to R by placing the call to N f . This call initiation action is indicated by showing user  101 - 1 , in phantom, as the logical initiator of the call to N f . FCMA  210  initiates a call setup message to SS7  141  to set-up a call path when U answers the call to N f , the path being composed of, in seriatim: FCMA  210  (including switching point  210 -B), talking trunk  212 - 2 , MSC  181  (including switching point  181 -B), talking trunk  132 - 2 , AT  131  (including switching point  131 -B), trunk  127 , CO  122 , and wire pair  125 —this path is designated C U  in the sequel. 
     When U answers the incoming call to N f , U&#39;s call-answer is detected by FCMA  210  acting in its surrogate capacity as user  101 - 1 . Then FCMA  210  answers the incoming call on N fc  as the call-answering surrogate to user  103 - 1 . Now FCMA can bridge R to U by closing switching point  210 -C to interconnect switched points  210 -A and  210 -B. In practice, one way to accomplish this bridging function is to bridge the equipment location associated with surrogate  103 - 1  to the equipment location associated with surrogate  101 - 1 . 
     From R&#39;s viewpoint, the call to U has been transparent in terms of the additional call set-up and talking path routing, and R is unaware that U may be at a location different than the surrogate of U that is served by FCMA  210 . 
     While the foregoing description of FIG. 3 is helpful in visualizing the manner in which a call to U is completed in terms of conventional PSTN and CN elements, it is apparent that it is possible to co-locate FCMA  210  with MSC  181  for increased efficiency by reducing the use of trunk facilities and switching points. Such a co-located arrangement for FCMA  210  is shown in FIG. 4, and is now referred to by reference numeral  410  to evidence the co-located nature of the Fixed-Cellular Mobility Agent. FCMA  410 , in this embodiment, is implemented essentially in software which may be an applique to the generic program executing MSC  181 . Basically, FCMA  410  has the characteristics of an embedded central office, meaning trunk-side properties when interfaced with the standard functionality of MSC  181 , and line-side properties when interfaced to the surrogates of calling and called parties. 
     From the arrangement of FIG. 4, it is further apparent that even more efficiencies can be realized if FCMA  410  is integrated with MSC  181  so as to control the switching action of MSC  181  to eliminate unnecessary switching points; such an arrangement is shown in FIG. 5, wherein the FCMA is now identified by reference numeral  510  to highlight the added functionality. In particular, FCMA  510  is arranged with control function  511  which controls switching point  181 -C to cross-connect incoming talking trunk  132 - 1  from R with outgoing talking trunk  132 - 2  to U. (In the following, “H-MSC” designates the mobile switching center serving closest to U&#39;s home location.) Broadly, to reiterate the operating characteristics of FCMA  510 , user U is assigned the telephone number N fc  by the cellular network provider for receiving calls on U&#39;s fixed telephone. N fc  for U is chosen such that PSTN  110  routes the call to the H-MSC from calling party R. From the entry for U in CFCT-Stable  211 , the H-MSC&#39;s FCMA  510  determines the telephone number N f  of U. FCMA  510  then initiates a call to N f  via the H-MSC. This call will be routed through PSTN  110  to the user&#39;s fixed telephone. When U answers the phone, FCMA  510  then, in effect, answers the call made to N fc , and directs that the H-MSC, in turn, establishes a call path, via the switching capabilities of the H-MSC, to U&#39;s fixed telephone. 
     It is noted now that, in addition, FCMA  510  also monitors C U  to detect if U wants to transfer the call to his/her cellular telephone. Recall, for example, that the user can communicate this intention by dialing a DTMF sequence. The actions taken by FCMA  510  to complete the transfer are discussed shortly. 
     Summary of the flow of a call from R to U via N fc : 
     With reference to flow diagram  600  of FIG. 6, the program flow effected by FCMA  510  is as follows (note that the telephony-type functionality required of FCMA  510  is shown in parentheses after each step): 
     1.) block  605 —R calls U on N fc  (908-555-3333) via R&#39;s CO  121   
     2.) block  610 —FCMA is alerted to incoming call from R directed to 908-555-3333 via standard SS7 signaling (signaling) 
     3.) block  615 —FCMA cross-references incoming call to 908-555-3333 in CFCTS lookup table to obtain N f  of 908-555-1111 
     4.) block  620 —FCMA initiates a call set-up to 908-555-1111 via signaling messages to SS7 network (call initiation) 
     5.) block  625 —U answers FCMA-initiated call, e.g. by picking up handset 
     6.) block  630 —FCMA receives information that U has answered FCMA-initiated call (call answered) 
     7.) block  635 —Standard call connection C U  is established between U and MSC through AT  131  and CO  122  by U answering incoming call 
     8.) block  640 —Once U answers the FMCA-initiated call, the incoming call from R to FCMA is used by FCMA to establish a call connection C R  established between R and MSC via AT  131  and CO  121  (call answering) 
     9.) block  645 —MSC C onnects C U  and C R  via standard switching to complete of the overall path between R and U (switching) 
     10.) block  650 —FCMA monitors C U  to detect call transfer request by U, if any (call monitoring, e.g., by a pattern of DTMF digits) 
     1.2 Transfer of Incoming call to N fc    
     It is now supposed that user U desires to transfer the already established incoming call to N fc  from party R to his/her cellular telephone/mobile terminal  151  from his/her fixed telephone  103 . The arrangement for accomplishing the desired transfer is shown in FIG.  7 . The starting point for the description of FIG. 7 is the call completion description of the arrangement of FIG. 3, which has been re-drawn in FIG. 7 along with the overlay required to effect the desired transfer. In particular, original talking paths C R  and C U  are shown connected via FCMA  710 . Now, in addition, FCMA  710  includes monitor circuit  712  to monitor that part of talking path C U  emanating from FCMA  710 , namely, path  212 - 2 , and switching point controller  711  to open/close switching points to incoming/outgoing talking paths. Whenever monitor circuit  712  detects U&#39;s desire to transfer the established incoming call, for instance by detecting a sequence of DTMF tones (e.g., *1#1) on path  212 - 2 , FCMA  710  acts as a surrogate call initiator by dialing the U&#39;s telephone number N c  as a conventional cellular network-type call. This is shown in FIG. 7 wherein surrogate user  701  dials N c  through switching point  710 -D as closed by controller  711 . When U answers cellular telephone  151 , which is presumably at the same physical location as user U, a new talking path is established from FCMA  710  to MT  151 , the new path being composed of talking path  212 - 3 , MSC  181  via switching point  181 -C, trunk  183 , base station controller  171 , talking path  173 , base station  164 , and radio path  165 —this connection is denoted C C . Once talking path C C  is established, then (a) controller  711  closes switching point  710 -E to bridge talking path C C  to talking path C R , and (b) controller  711  opens switching points  210 -B and  210 -C so that talking path C U  may be torn down by the usual call termination procedures. 
     It is noted that now U&#39;s fixed phone  103  is again available for receiving another incoming call and, moreover, since monitor circuit  712  now monitors talking path  212 - 3 , it is possible to re-transfer a connection between user U&#39;s fixed telephone and U&#39;s cellular telephone—this is discussed in more detail in section 2.2 below after the discussion of section 2.1 below. 
     Summary of the flow of a transfer from C U  to C C    
     With reference to flow diagram  800  of FIG. 8, the program flow effected by FCMA  710  for call transfer is as follows (note that the telephony-type functionality required of FCMA  710  is shown in parentheses after each step): 
     1.) block  805 —U requests a call transfer to cellular phone (monitoring) 
     2.) block  810 —FCMA is alerted to call transfer request by monitor circuit  712   
     3.) block  815 —FCMA obtains U&#39;s cellular number N c  (908-555-2222) in CFCTS look-up table 
     4.) block  820 —FCMA initiates a call set-up to 908-555-2222 via signaling messages to SS7 network (call initiation) 
     5.) block  825 —U answers FCMA-initiated call by answering cellular telephone 
     6.) block  830 —FCMA receives information that U has answered FCMA-initiated call (call answered) 
     7.) block  835 —Standard call connection C C  is established between FCMA and BS through MSC by U answering incoming call 
     8.) block  840 —FCMA connects C C  and C R  to bridge call from R to cellular phone (switching) 
     9.) block  845 —FCMA disconnects C U  from C R  via switching to tear down of the established connection between R and U on the fixed network (switching) 
     2.1 Incoming call to N c    
     When a third party on the fixed network, such as party  101  of FIG. 1 (again designated party R for Remote), wants to call user  102  on his/her cellular telephone/mobile terminal  151 , party R uses the telephone number N c  (e.g., 908-555-2222). If user  102  is NOT a subscriber to the CFCTS, this incoming call will be routed by the public switched telephone network  110  and the cellular network  150  to cellular telephone  151  in the conventional manner as discussed above with respect to FIG.  1 . If user  102  is located within his/her home registration area, this call will go through the user  102 &#39;s H-MSC ( 181  in FIG. 1) via the call registration and call delivery processes effected by HLR  191 . If the user  102  moves from a registration area outside his/her home area into his/her home registration area while the call is in progress, the call will be handed over to the H-MSC as part of the routine handovers in cellular networks, that is, by the call registration, delivery, and handoff procedures effected by the interplay of HLR  191  and VLR  192 . 
     However, if user  102  (now U) is a subscriber of CFCTS, the cellular service provider of cellular network  150  knows U is a subscriber (e.g., by contents of the CFCTS-table) and handles the incoming call to N c  by invoking, in one illustrative arrangement, the processing effected by the FCMA, first discussed with respect to FIG. 3, further described with respect to FIG. 7, and as now further described with reference to FIG.  9 . In the arrangement of FIG. 9, a call set-up and call completion procedure similar to the call set-up and call completion procedure of FIG. 3 is effected when R calls U, the difference being that R now calls U at N c  rather than N fc . Thus, FMCA  710  of FIG. 9 acts as a called party surrogate to process the incoming call by R, and as a calling party surrogate to initiate an outgoing call to U at his/her cellular phone  151 . The components of FIG. 9 depict the final call connection result wherein R is connected to U via two talking paths. The first path (again called C R ) includes in series: talking path  124 , CO  121 , talking trunk  126 , AT  131  including switching point  131 -C, talking trunk  132 - 3 , MSC  181  including switching point  181 -D, and talking trunk  212 - 4 . The second path (again called C C ) includes in series: talking trunk  212 - 5 , MSC  181  including switching point  181 -E, trunk  183 , BSC  171 , trunk  173 , BS  164 , and radio path  165 . In FCMA  710 , the two talking paths are bridged via switching points  710 -F,  710 -G, and  710 -H. 
     Summary of the flow of a call from R to U via N c : 
     With reference to flow diagram  1000  of FIG. 10, the program flow effected by FCMA  710  is as follows (note that the telephony-type functionality required of FCMA  710  is shown in parentheses after each step): 
     1.) block  1005 —R calls U on N c  (908-582-2222) via R&#39;s CO  121   
     2.) block  1010 —FCMA is alerted to incoming call from R directed to 908-555-2222 via standard SS7 signaling (signaling) 
     3.) block  1015 —FCMA initiates a call set-up to 908-555-2222 via signaling messages to SS7 network (call initiation) 
     4.) block  1020 —U answers FCMA-initiated call, e.g. by pressing “ON’ of cellular telephone 
     5.) block  1025 —FCMA receives information that U has answered FCMA-initiated call (call answered) 
     6.) block  1030 —Standard call connection C C  is established between U and FCMA through BS  164 , BSC  171 , and MSC  181  by U answering incoming call 
     7.) block  1035 —Once U answers the FMCA-initiated call, the incoming call from R to FCMA is used by FCMA to establish a call connection C R  established between R and FCMA via MSC  181 , AT  131 , and CO  121  (call answering) 
     8.) block  1040 —FCMA connects C C  and C R  via standard switching to complete the overall path between R and U (switching) 
     9.) block  1045 —FCMA monitors C C  to detect call transfer request by U, if any (call monitoring, e.g., by a pattern of DTMF digits) 
     (It is noted that, in another illustrative embodiment, FCMA  710  may be merged with MSC  181  in the same manner described with respect to FIGS. 4 and 5. One advantage of the arrangement of FIG. 9, from a deployment perspective, is that FCMA  710  is a stand-alone central office-like facility which may deployed as an adjunct to the conventional network with minimal impact, that is, without the need to modify components, such as MSC  181 , of the conventional network.) 
     2.2 Transfer of Incoming call to N c    
     It is now supposed that user U desires to transfer the already established incoming call to N c  from party R to his/her fixed telephone  103  from his/her cellular telephone/mobile terminal  151 . The arrangement for accomplishing the desired transfer is shown in FIG.  11 . The starting point for the description of FIG. 11 is the call completion description of the arrangement of FIG. 9, which has been re-drawn in FIG. 11 along with the overlay required to effect the desired transfer. In particular, original talking paths C R  and C C  are shown connected via FCMA  710 . Now monitor circuit  712  monitors that part of talking path C C  emanating from FCMA  710 , namely, path  212 - 5 . Whenever monitor circuit  712  detects U&#39;s desire to transfer the established incoming call, for instance by detecting a sequence of DTMF tones (e.g., *1#1) on path  212 - 5 , FCMA  710  acts as a surrogate call initiator by dialing the U&#39;s telephone number N f  as a fixed network-type call. This is shown in FIG. 11 wherein surrogate user  1101  dials N f  through switching point  710 -I as closed by controller  711 . When U answers telephone  103 , which is presumably at the same physical location as user U, a new talking path is established from FCMA  710  to telephone  103 , the new path being composed of talking path  214 - 5 , MSC  181  via switching point  181 -F, trunk  132 - 4 , AT  131  including switching point  131 -D, trunk  127 , CO  122 , and talking path  125 —this connection is denoted C U . Once talking path C U  is established, then (a) controller  711  closes switching point  710 -J to bridge talking path C U  to talking path C R , and (b) controller  711  opens switching points  710 -F,  710 -G, and  710 -H so that talking path C C  may be torn down by the usual call termination procedures. 
     It is noted that now U&#39;s cellular phone  151  is again available for receiving another incoming call and, moreover, since monitor circuit  712  now monitors talking path  214 - 5 , it is possible to re-transfer a connection between user U&#39;s cellular phone telephone and U&#39;s fixed telephone. 
     Summary of the flow of a transfer from C C  to C U    
     With reference to flow diagram  1200  of FIG. 12, the program flow effected by FCMA  710  for call transfer is as follows (note that the telephony-type functionality required of FCMA  710  is shown in parentheses after each step): 
     1.) block  1205 —U requests a call transfer to fixed phone (monitoring) 
     2.) block  1210 —FCMA is alerted to call transfer request by monitor circuit  712   
     3.) block  1215 —FCMA obtains U&#39;s fixed number N f  (908-555-1111) in CFCTS look-up table 
     4.) block  1220 —FCMA initiates a call set-up to 908-555-1111 via signaling messages to SS7 network (call initiation) 
     5.) block  1225 —U answers FCMA-initiated call by answering fixed telephone 
     6.) block  1230 —FCMA receives information that U has answered FCMA-initiated call (call answered) 
     7.) block  1235 —Standard call connection C U  is established between FCMA and CO  122  by U answering incoming call 
     8.) block  1240 —FCMA connects C U  and C R  to bridge call from R to fixed phone (switching) 
     9.) block  1245 —FCMA disconnects C C  from C R  via switching to tear down of the established connection between R and U on the cellular network (switching) 
     3.1) Outgoing calls handled by the FCMA 
     To make an outgoing call from either the fixed telephone  103  or the mobile terminal  151  identified with a particular user (again referred to as U) to a remote party (say to party R at remote telephone  101 ), U f irst dials an access number N a ; N a  is not user specific. All CFCTS users assigned to a given MSC C an access the same N a . When U dials N a , the call is routed to the FCMA. For instance, with reference to FIG. 13, which depicts the arrangement for handling an outgoing call by U from his/her fixed phone  102  to R, the call by U is answered by the called party surrogate to R, namely, phone  101 - 1  shown dashed in FIG. 13, via switching point  710 -K. This call is completed over a call connection path C U  including: wire pair  125 , CO  122 , trunk  127 , AT  131  including switching point  131 -E, trunk path  132 - 5 , MSC  181  including switching point  181 -G, and trunk  214 - 6 . Next, U is prompted by FCMA  710 , via digit collector  1313 , to provide the telephone number of party R. Then FCMA  710 , in its capacity as a surrogate to initiate a call, initiates a call to party R via surrogate phone  103 - 1  through switching point  710 -L. Whenever party R answers phone  101 , then another call connection path C R  is established between FCMA  710  and party R, the path including: trunk  214 - 7 , MSC  181  including switching point  181 -H, trunk  132 - 6 , AT  131  including switching point  131 -F, trunk  126 , CO  121 , and wire pair  124 . FCMA  710  then bridges C U  and C R    
     Summary of the flow of a transfer from C C  to C U    
     With reference to flow diagram  1400  of FIG. 14, the program flow effected by FCMA  710  for an outgoing call by U to R is as follows (note that the telephony-type functionality required of FCMA  710  is shown in parentheses after each step): 
     1.) block  1405 —U initiates an outgoing call by calling N a    
     2.) block  1410 —Standard call connection C U  is established between FCMA and CO  122  by FCMA answering call to N a  (call answer) 
     3.) block  1415 —FCMA prompts U for telephone number of party R (digit collection) 
     4.) block  1420 —FCMA initiates a call set-up to party R via signaling messages to SS7 (call initiation) 
     5.) block  1425 —R answers FCMA-initiated call 
     6.) block  1430 —FCMA receives information that R has answered FCMA-initiated call (call answered) 
     7.) block  1435 —Standard call connection C R  is established between FCMA and CO  121  by R answering incoming call 
     8.) block  1440 —FCMA connects C U  and C R  to bridge call from U to R (switching) 
     9.) block  1445 —FCMA monitors C U  for call transfer (monitoring) 
     Upon comparison of FIG. 13 with FIG. 3, including the description of each, it is clear that the call completion paths are essentially the same. (Although a directional orientation has been shown on the paths by arrows, this designation is only for the purpose of depicting the party initiating or receiving the calls. Call connections in themselves have no directional orientation.). Accordingly, to now effect a call transfer given the circuit state shown in FIG. 13, the arrangement and discussion of FIG. 7 applies equally as well to the arrangement of FIG.  13 . In addition, flow diagram  800  of FIG. 8 applies also to a call transfer. 
     Now, with respect to U completing an outgoing call to party R via U&#39;s cellular phone  151 , the final call completion paths are as shown in FIG.  9 . To arrive at the call paths summarized by FIG. 9 for an outgoing call from U to R, again there is a need to collect digits from U once U&#39;s call to N a  has been completed. Because the outgoing call paths from U to R are those of FIG. 9, then a call transfer can be effected in the same manner as set forth by flow diagram  1200  of FIG. 12 which describes the operation of the arrangement of FIG. 11 for a call transfer. 
     Although various embodiments which incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings.