Enhanced call delivery system for roaming cellular subscribers

We claim:

1. An enhanced call delivery system, Follow Me Roaming Plus (FMR Plus), for delivering telephone calls to a roaming cellular subscriber, enabling said subscriber to receive calls placed to his MIN in his home system service area, said enhanced system having seamless interoperability with call delivery systems which do not participate in said enhanced call delivery system, comprising:

a central telecommunications system processor capable of handling network applications for said enhanced call delivery system;

a plurality of mobile telephone switches located in the service areas of a plurality of cellular telephone systems which participate in said enhanced call delivery system, each of said mobile telephone switches connected via a direct communications link to said central telecommunications system processor;

a plurality of registers in said central telecommunications system processor for storing data bases of system information, individual switch information, and subscriber information, said registers including:

a general location register in said central telecommunications system processor, said general location register containing a data base of all information necessary for validation of known roamers, whereby validation and registration is accomplished without reference to the home switch;

a home location register within said general location register containing a data base of all information necessary for communication with all cellular switches of all cellular providers in said network;

a visiting location register within said general location register containing a data base of all information necessary for communication with all roaming cellular subscribers registered in said system;

a data base of routing information for location of home carriers in said general location register, whereby end-to-end validation and registration can be accomplished for previously unknown roamers;

an Input/Output Gateway (FIG) to and from said central telecommunications system processor for translation of messages and inter-system communication with the host processor of cellular systems which participate in a second call delivery system, Follow Me Roaming (FMR), having a subset of the features of said enhanced system;

at least one intersystem gateway to and from said central telecommunications system processor for translation of messages and inter-system communication with cellular systems which participate in at least one third call delivery system;

means to enable said central telecommunications system processor of said enhanced call delivery system to communicate with each of said switches of said enhanced system, and through said gateways to the central processors of said second and third call delivery systems, and through said central processors to individual switches of said second and third call delivery systems, to provide to the switches of the home and visited service areas of a roaming cellular subscriber:

(1) the identity of the current visited system switch of a roaming cellular subscriber known to his home system;

(2) the financial responsibility of the roaming cellular subscriber;

(3) a valid roamer service profile in said visited system; and

(4) call delivery to a validated roaming cellular subscriber in the service area of said visited switch.

2. The system of claim 1 wherein said means to communicate with each of said switches in each of said call delivery systems comprises:

a database having information about each switch in each call delivery system, including the type of switch, which messages are supported by said switch, how each switch handles messages;

a set of Mobile Application Part (MAP) messages to control transaction flow processing within said enhanced call delivery system, and between said enhanced call delivery system and said second and third call delivery systems;

means to interpret each of said MAP messages and to discover its origin and destination; and

means to encode/decode messages to/from said second and third call delivery systems through said gateways;

whereby said enhanced call delivery system communicates seamlessly with said second and third call delivery systems.

3. A method for enhanced call delivery, for delivering telephone calls to a roaming cellular subscriber, enabling said subscriber to receive calls placed to his MIN in his home system service area, having seamless interoperability with call delivery systems which do not participate in an enhanced call delivery system, comprising:

connecting a plurality of mobile telephone switches located in the service areas of a plurality of cellular telephone systems which participate in an enhanced call delivery system, via a direct communications link to a central telecommunications system processor;

storing in said central telecommunications system processor for storing data bases of system information, individual switch information, and subscriber information;

storing a data base of routing information for location of home carriers in a general location register in said database, whereby end-to-end validation and registration can accomplished for previously unknown roamers;

providing an Input/Output Gateway to and from said central telecommunications system processor for translation of messages and intersystem communication with the host processor of cellular systems which participate in a second call delivery system, having a subset of the features of said enhanced system;

providing at least one intersystem gateway to and from said central telecommunications system processor for translation of messages and intersystem communication with cellular systems which participate in at least one third call delivery system;

enabling said central telecommunications system processor of said enhanced call delivery system to communicate with each of said switches of said enhanced system, and through said gateways to the central processors of said second and third call delivery systems, and through said central processors to individual switches of said second and third call delivery systems, to provide to the switches of the home and visited service areas of a roaming cellular subscriber:

(1) the identity of the current visited system switch of a roaming cellular subscriber known to his home system;

(2) the financial responsibility of the roaming cellular subscriber;

(3) a valid roamer service profile in said visited system; and

(4) call delivery to a validated roaming cellular subscriber in the service area of said visited switch.

4. The system of claim 3 wherein the step of enabling said central telecommunications system processor of said enhanced call delivery system to communicate with each switch in each call delivery system further comprises:

storing a database having information about each switch in each call delivery system, including the type of switch, which messages are supported by said switch, how each switch handles messages;

providing a set of Mobile Application Part (MAP) messages to control transaction flow processing within said enhanced call delivery system, and between said enhanced call delivery system and said second and third call delivery systems;

interpreting each of said MAP messages to discover its origin and destination; and

encoding/decoding messages to/from said second and third call delivery systems through said gateways;

whereby said enhanced call delivery system communicates seamlessly with said second and third call delivery systems.

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to cellular telephone communication systems, and more particularly to a system and method that provides for enhanced transparent call delivery to roaming subscribers of cellular telephone services and the interoperability of differing call delivery systems and communications among mobile telephone switching offices.

2. Description of the Prior Art

Cellular telephone service is widely available, and the operational capabilities of the systems, switching equipment and computer software utilized to provide cellular telephone service are well known and documented. The product literature of companies selling cellular switches and cellular software is readily available and contains full descriptions of the equipment and software capabilities available today. U.S. Pat. No. 4,901,340, System for the Extended Provision of Cellular Mobile Radiotelephone Service, Parker et al, issued Feb. 13, 1990, discloses a system for call delivery to a cellular telephone service subscriber who has roamed outside the service area of the home cellular system, utilizing a temporary local directory number and a call delivery processor functioning at each mobile telephone switch site. U.S. Pat. No. 5,142,654, Cellular Telephone System And Method For Dynamically Switching Between Call Routing Options, Sonberg et al, issued Aug. 25, 1992, discloses a system and method that provides for dynamic switching between call handling options such as caller notification and call forwarding. U.S. Pat. No. 5,282,240, Apparatus and Method for Directing Calls to Mobile Station Subscribers, Buhl et al, discloses a page first system. U.S. Pat. No. 5,282,250, Method of Carrying Out an Authentication Check Between a Base Station and a Mobile Station in a Mobile Radio System, Dent et al, discloses a pre-call validation system.

The systems for call delivery disclosed in the first two referenced patents are available to cellular telephone systems operators and, through said operators, to cellular subscribers under the trade names and trademarks Follow Me Roaming.RTM., Phone Me Anywhere.RTM., for the system of the Parker et al patent operated by GTE Telecommunications Services Incorporated (GTE TSI), and NationLink.RTM. and RoamAmerica.RTM. for the system of the Sonberg patent operated by Electronic Data Systems (EDS). The Follow Me Roaming.RTM. system is the most widely used and will be designated hereinafter as the FMR system.

Essential to the prior art call delivery systems is that each mobile telephone switching office (MTSO) has its own computer system, or site processor, for setting up fixed delivery of calls to a roaming cellular subscriber. Most of these individual computer systems communicate with a host processor at a clearinghouse operated by GTE EDS.

The Electronic Industries Association (EIA) and the Telecommunications Industry Association (TIA) have published a number of joint standards which pertain to cellular service and which are incorporated herein by reference. EIA/TIA Standard 533, Mobile Station--Land Station Compatibility Specification, applies to the system of this invention. The EIA/TIA Subcommittee TR45.2 has published a series of recommendations entitled Cellular Radiotelecommunications Intersystem Operations, which describe procedures necessary to provide cellular telephone service requiring interaction between different cellular systems and dissimilar switch types. Interim Standard IS-41, Rev. A, (hereinafter "Rev. A"), of said series Cellular Radiotelecommunications Intersystem Operations is currently being implemented at the time of filing of this Application. Further standards (Rev. B and C) have been announced for future implementation. Neither of the prior art call delivery systems conform to IS-41 Rev. A.

The present invention is directed to an enhanced version of the FMR system of Parker et al, hereinafter FMR Plus, whereby not only are the requirements of each increment of IS-41 met as required, but they are met faster and more efficiently utilizing one central computer, or host processor, serving a multiplicity of Mobile Telephone Switching Offices (MTSOs), eliminating the site processors, while having the capability of interoperability with the older FMR system and IS-41 Rev. A systems using X.25 or Signaling System 7 (SS7) transport. FMR Plus implements IS-41 Rev. A automatic roaming, which includes making the identity of the visited system known to the home system (automatic registration), transparent call delivery to the roaming subscriber, and allowing the roamer's service profile features to be changed remotely.

The principal object of the present invention is to provide a cellular call delivery system for automatically delivering calls to roaming cellular subscribers meeting the standards of IS-41 Rev. A while maintaining connectivity with non-IS-41 systems.

It is a further object of the invention to provide an enhanced cellular call delivery system utilizing IS-41 Rev. A with seamless interoperability among Mobile Switching Centers utilizing IS-41 Rev. A via a single switch connection, between MSCs using IS-41 and MSCs which have not implemented IS-41, and the provision of connectivity via the FMR host processor to FMR site processors which reside at cellular switches which have not implemented IS-41, Rev. A.

It is still a further object of this invention to provide an input/output gateway between the FMR host processor and the FMR Plus host processor, enabling message translation between the two systems.

Other objects, features and advantages of the invention will become apparent by reading the enclosed specification with the accompanying drawings.

SUMMARY OF THE INVENTION

In a first aspect of the invention, a system for enhanced call delivery to a roaming cellular subscriber, enabling said subscriber to receive calls placed to his MIN in his home system service area, comprises a central telecommunications system processor capable of handling network applications, directly connected to a plurality of mobile telephone switches located in the service areas of a plurality of cellular telephone systems. A plurality of registers in said central telecommunications system processor are provided for storing data bases of system information, individual switch information, and subscriber information. The central telecommunications system processor is programmed to communicate with said switches, and to provide to the switches of the home and visited service areas of a roaming cellular subscriber: (1the identity of the current visited system switch of a roaming cellular subscriber known to his home system; (2) the financial responsibility of the roaming cellular subscriber; (3) the valid roamer service profile in a visited system; and (4call delivery to a validated roaming cellular subscriber in the service area of a visited switch.

The system further comprises a general location register in said central telecommunications system processor containing a data base of all information necessary for validating and locating known roamers, and a data base of routing information for location of home carriers, whereby end-to-end validation and registration is accomplished for previously unknown roamers. The system provides call delivery information to the home switch of a roamer, routing information for forwarding calls to said roamer; and a temporary directory number as needed for forwarding calls to said roamer over the Public Switched Telephone Network (PSTN).

In a second aspect of the invention, a method for enhanced call delivery to a roaming cellular subscriber, whose presence with an active cellular telephone in a foreign service area having been detected by the MTSO of said area, enabling said subscriber to receive calls placed to his home service area, comprising the steps of notifying said home service area MTSO of the presence of said roaming cellular subscriber in said foreign service area; validating and completing the registration of said roaming cellular subscriber in said foreign service area and enabling call delivery to said roaming cellular subscriber according to his service profile. The step of notifying said home service area MTSO of the presence of said roaming cellular subscriber in said foreign service area comprises the steps of: sending a registration notification to a central network telecommunications computer; and storing said registration notification in central network telecommunications computer; and relaying said registration notification from said central network telecommunications computer to the home MTSO of said roaming cellular subscriber.

In yet another aspect of the invention, a method for enhanced call delivery to a registered roaming cellular subscriber, enabling said subscriber to receive calls placed to his MIN in his home service area, includes the steps of: receiving a call at the home MTSO of said registered roaming cellular subscriber; determining the location of said registered roaming cellular subscriber by reference to a location register; requesting a temporary directory number (TDN) (sometims referred to as a temporary local directory number (TLDN) for delivery of said call from the MTSO of said roaming cellular subscriber; delivering a TDN to said home MTSO; upon receipt of said TDN, delivering said call to said TDN; and releasing said TDN for further use upon termination of said call. For some call delivery functions, the method further comprising the step of verifying the presence of said registered roaming cellular subscriber by reference to a visiting location register.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the architecture of the Follow Me Roaming Plus system of the present invention.

FIGS. 2a and 2b are diagrammatic presentations of the registration and call delivery processes for roaming cellular subscribers in cases in which the home and visited cellular systems subscribe to the Follow Me Roaming Plus service of the present invention.

FIGS. 3a and 3b are diagrammatic presentations of the registration and call delivery processes for roaming cellular subscribers in cases in which the home cellular system utilizes Follow Me Roaming Plus and the visited cellular system utilizes an older Follow Me Roaming service.

FIGS. 4a and 4b are diagrammatic presentations of the call delivery process for roaming cellular subscribers in cases in which the visited cellular system utilizes a Follow Me Roaming Plus service, while the home cellular system utilizes an older Follow Me Roaming service.

FIG. 5 is a simplified block diagram of the system of FIG. 1 showing the FMR Plus system of the present invention.

FIG. 6 is a diagrammatic representation of the process of registration of a Rev. A roamer in a Rev. A visited cellular system.

FIG. 7 is a diagrammatic representation of the process of registration of a roamer from a Rev 0 home system in a Rev. A visited cellular system.

FIG. 8 is a diagrammatic representation of the process of registration of a roamer from a non-IS-41 home system in a Rev. A visited cellular system.

FIG. 9 is a diagrammatic representation of the process of call delivery for a FMR Plus Rev. A roamer in a FMR Plus Rev. A visited cellular system.

FIG. 10 is a diagrammatic representation of the process of call delivery for a FMR Plus Rev. A roamer in an FMR visited cellular system.

FIG. 11 is a diagrammatic representation of the process of call delivery for a FMR roamer in an FMR Plus visited cellular system.

FIG. 12 is a diagrammatic representation of the process of cancellation of registration when a roamer returns to a home system utilizing FMR Plus.

FIG. 13 is a diagrammatic representation of the process of call delivery for a FMR Plus Rev. A roamer in a FMR Plus Rev. A visited cellular system with the home system restricted.

FIG. 14 is a diagrammatic representation of the process of registration of a FMR Plus Rev. A roamer in a newly visited FMR Plus Rev. A visited cellular system with cancellation of registration in a previously visited system.

FIG. 15 is a block diagram of the interoperability gateway of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 presents an overview of the FMR Plus system according to the present invention in an operational context. Only those functions relevant to the present invention are discussed in this specification. FMR Plus is a service of GTE Telecommunications Services, Incorporated, Tampa, Fla.

Referring now to FIG. 1, the FMR Plus system 10 is built on a host processor 11, which is produced by Tandem Telecommunication Systems Inc. (TTSI) for network applications. FMR Plus 10 includes the Call Processor 12, and the FMR I/O Gateway (FIG) 14. The Call Processor 12 is a software application running on host processor 11 which provides the call validation and call delivery functionality for GTE TSI's FraudManager.sup.sm 16 and FMR Plus.sup.sm 10 products. FraudManager 16 is GTE TSI's pre-call validation product supporting the IS-41 protocol, but is not included in this invention. FMR Plus 10 is an automatic call delivery product supporting the IS-41 protocol for cellular subscribers roaming in other markets. IS-41 is the cellular industry standard designed to facilitate intersystem operation between dissimilar switch types. As will be explained later, Call Processor 12 maintains a number of data bases on the host processor 11, including the General Location Register (GLR) 18, and within the GLR 18 registers which were formerly called a Home Location Register (HLR) 20, and a Visitor Location Register (VLR) 22. The Call Processor 12 also interfaces with a Positive Validation System (PVS) 24. Through a port 26 on host processor 11, Call Processor 12 interfaces directly with Mobile Telephone Switching Office (MTSO) cellular switches 34 that can communicate using the IS-41 Rev. A standard, which is a point-to-point protocol. However, there are at least seven manufacturers of IS-41 switches, and each manufacturer has configured its hardware and software slightly differently, thus making point-to-point communication among switches cumbersome. To an individual IS-41 Rev. A cellular switch 34, the host processor 11 running Call Processor 12 appears to be another IS-41 Rev. A switch with which the switch can communicate using its own variation of Rev. A message formats. Call Processor 12 can recognize the variations among switch types and forward messages to diverse types of switches. This communication may follow an SS7 or X0.25 transport protocol. FMR Plus 10 connects to the older central FMR host processor 28 via FMR I/O Gateway 14. The FMR host processor 28 is connected, in turn, to FMR site processors 30, which interface directly with MTSO switches 32.

Thus, cellular switches 34 operating at the level of IS-41 Rev. A and higher connect directly by a single switch connection to the central mobile telecommunications system 10 known as Follow Me Roaming Plus (hereinafter FMR Plus), which is operated by a cellular clearinghouse for call delivery to roaming cellular subscribers and associated services for cellular carriers. If either the home service area (switch) or the visited service area (switch) of a roaming cellular subscriber is non-IS-41 or IS-41 Rev. O, and utilizes the FMR system, the FMR Plus system 10 interfaces through a site processor 30 at the FMR non-IS-41 Rev. A switch. The communications between the FMR Plus host 11 and the MTSO 30 site processor running FMR passes through an FMR I/O Gateway 14 (hereinafter FIG), then through a central FMR host processor 28 to the FMR site processor 30 providing FMR service. FMR Plus 10 is the subject of the present invention, and the two unique features of FMR Plus are its Call Processor 12 and the FIG. 14. The Call Processor 12 eliminates the need for FMR site processors 30 for switches at IS-41 Rev. A or higher, while providing for seamless interoperability among diverse switch types and call processing systems. The FIG. 14 permits the FMR Plus system 10 to communicate with the older FMR systems. Each of these unique features will be described in detail.

A single switch connection from an IS-41 switch 34 to Follow Me Roaming Plus host processor 11 provides connectivity with all other Follow Me Roaming Plus markets, as well as connectivity to all Follow Me Roaming and Phone me Anywhere markets in the United States, Canada and Mexico. Therefore, many call delivery scenarios encountered will be hybrid in nature, in which the home or serving switch utilizes FMR Plus 10 service, while the other switch utilizes Follow Me Roaming service.

The full set of call delivery scenarios are as follows:

1. FMR Plus Serving Market--FMR Plus Home Market;

2. FMR Serving Market--FMR Plus Home Market;

3. FMR Plus Serving Market--FMR Home Market; and

4. FMR Serving Market--FMR Home Market. (This scenario does not involve FMR Plus, and will not be discussed.)

FMR Plus Serving Market--FMR Plus Home Market--Scenario 1

Activation and Setup Process For Scenario 1

FIG. 2a illustrates the activation and set up of call delivery of a roaming subscriber 40 (roamer) from an FMR Plus Home market 36 roaming in an FMR Plus Serving or visited market 38. The FMR+host processor 11 sends and receives IS-41 Rev. A messages through the same IS-41 switch port 26 used by the FraudManager 14 service, to facilitate call delivery to both IS-41 Rev. A and non-IS-41 markets. When a subscriber with FMR Plus service roams into a FMR Plus served market, the following occurs:

1. The roamer first registers in the serving market 38 (after the mobile telephone is turned on). Autonomous registration may take place in a IS-41 Rev. A market when a cellular phone unit is powered on. The local switch 38 periodically sends out a canvassing signal asking for a response from any cellular units in the area. The roamer's phone's response begins the registration process. Once a phone is registered in a Rev. A market, the switch 38 instructs it not to respond to the canvassing signal until a future point in time. (See FIG. 6, and the discussion of registration below.)

2. At the time of registration, the home switch 36 is notified of the roamer's location, and the roamer's service profile is passed from the home switch 36 to the serving switch 38. (See FIGS. 6 and 12 also.)

When a roaming subscriber is validated (registered) in another, later visited switch or is detected back in his home switch 36, registration is automatically cancelled in the previous visited switch.

Call Delivery Process For Scenario #1

FIG. 2b illustrates the process of call delivery. Once the roamer 40 is registered and validated, Follow Me Roaming Plus 10 provides call delivery as follows (if the roamer is valid and the call delivery bit is turned on):

1. Home switch 36 receives an incoming call for the roamer 40.

2. Home switch 36 sends an IS-41 Route Request message to Follow Me Roaming Plus 10, asking for a Temporary Local Directory Number (TDN) to which the call will be routed.

3. Follow me Roaming Plus 10 sends the Route Request to the serving switch 38.

4. The Serving switch 38 responds with the appropriate TDN, before or after paging the roamer's mobile phone 40, or:

a) If the mobile 40 is busy or does not answer, the serving switch 38 responds with a return result indicating a busy mobile or inactive mobile status, or:

b) If the mobile's service profile (provided earlier upon registration) indicates that either Busy Transfer or No Answer Transfer is active, then a REDIRECT message is returned (to redirect the call to the transfer phone number).

5. Follow Me Roaming Plus 10 passes the results back to the home switch 36.

6. The home switch 36 routes the call if a TDN is received. If a busy/idle return result or REDIRECT message is received, the incoming call may be routed to voice mail, to another phone number (i.e., home or office landline phone) or to an announcement.

The TDN provided by the serving switch 38 is only used in routing that one call to the roamer 40. Once the call is connected, the TDN is then freed up to be used by another roamer. The TDN is dynamic. In the older call delivery systems, each FMR switch must have a single TDN assigned to every roamer receiving call delivery in its market. That particular TDN will be unavailable for other roamers until that roamer deactivates call delivery or FMR automatically deactivates at midnight.

FMR Serving Market FMR Plus Home Market

FIG. 3a illustrates the activation and set up of call delivery of a roaming subscriber 40 from an FMR Plus Home market 36 roaming in an FMR Serving or visited market 42. FIG. 3b illustrates the call delivery of a subscriber from an FMR Plus Home market 36 roaming in an FMR Serving market 42.

Call Delivery Overview

The *18 SEND command is the only event that will permit call delivery to the roamer 40 in this scenario. The roamer from a FMR Plus home market must execute the *18 activation command in all FMR visited markets to initiate call delivery. When the roamer 40 executes a *18 SEND command, his call delivery feature will be activated at the home switch 36. The call delivery feature will remain active until it is turned off by a *19 SEND command form the subscriber. However, the TDN for the serving FMR market 42 will be released at midnight through the normal FMR midnight deactivation process, so the roamer 40 will be required to re-activate using the *18 SEND command after midnight each day and when entering each new FMR market to receive call delivery. The reason for this is that even though the Call Delivery bit will remain on indefinitely, the FMR system must be triggered to assign a new TDN each day and in each new serving market through the *18 SEND command.

Activation & Setup Process For Scenario #2

1. The roamer 40 enters an FMR market 42 and executes a *18 command. The visited switch's FMR site processor 30 sends an activation request back to the FMR host processor 28.

2. The FMR host processor 28 recognizes that the roamer 40 belongs to an FMR Plus home switch 36 (by analyzing the Mobile Identification Number or MID) and sends the transaction to the FMR Plus host processor 11.

3. The FMR Plus host processor 11 records the serving location of the roamer 40, and turns the call delivery feature active in the subscriber's home switch 36, if necessary.

4. The FMR host processor 28 assigns the appropriate TDN for call delivery, based on the serving market 42 where the *18 command was executed, and passes this TDN to the FMR Plus host 11, where it is recorded.

Call Delivery Process For Scenario #2

1. A phone call is received at the FMR Plus home switch 36 for the roaming subscriber 40.

2. A ROUTE REQUEST message is sent from the home switch 36 to FMR Plus 10, requesting a TDN to route the call.

3. FMR Plus 10 replies to the ROUTE REQUEST message with the appropriate TDN (previously assigned by FMR 28 and recorded by FMR Plus 10).

4. The call is routed over the PSTN to the TDN by the home switch 36.

FMR Plus Serving Market--FMR Home Market--Scenario #3

FIG. 3a illustrates the activation and set up of call delivery of a roaming subscriber 40 from an FMR Home market 44 roaming in an FMR Plus Serving or visited market 38. FIG. 3b illustrates the call delivery of a subscriber from an FMR Home market 44 roaming in an FMR Serving market 38.

Call Delivery Overview

The *18 SEND command is the only event that will permit call delivery to the roamer 40 in this scenario. The roamer from a FMR home market must execute the *18 activation command in all FMR visited markets to initiate call delivery. When the roamer 40 executes a *18 SEND command, standard FMR call forwarding will be setup at the home switch 44. FMR call forwarding will remain active until midnight deactivation or until it is turned off by a *19 SEND command from the subscriber 40.

Activation & Setup Process For Scenario #3

1. The roamer enters an FMR Plus market 38 and executes a *18 command. This registers the roamer 40 for validation and call delivery.

2. The FMR Plus processor 11 recognizes that this roamer 40 is from an FMR market and forwards the activation request to the FMR Host Processor 28. The FMR Host 28 initiates activation processing and sets up call forwarding in the home switch 44 to the appropriate TDN for the serving switch 38.

3. The home switch 44 responds back with confirmation and is ready to forward calls.

4. The FMR Plus host processor 11 records both the MID of the roamer 40 and the associated TDN.

5. Roamer 40 is now ready for call delivery.

Call Delivery Process For Scenario #3

1. A phone call is received at the FMR home switch 44 for the roaming subscriber 40.

2. The phone call is directly forward through the PSTN to the assigned TDN.

3. The serving switch 38 receives the call via the TDN and sends a message to the FMR Plus Host 11, requesting the correct roamer 40 mobile phone MID to page so that the call may be delivered.

4. The FMR Plus host 11 responds to the serving switch 38 with the correct MID of the roaming mobile 40.

5. The mobile phone is paged and the call is delivered.

CALL PROCESSOR

FIG. 5 is a simplified block diagram of the system of FIG. 1 showing the functional features relevant to the invention. The FMR Plus system 10 is built on the Tandem Telecommunication Systems Inc. (TTSI) platform for network applications, which is the host processor 11. FMR Plus 10 includes the Call Processor 12 and the FMR I/O Gateway (FIG) 14. The Call Processor 12 provides the call validation and call delivery functionality for GTE TSI's FraudManager.sup.sm 16 and FMR Plus.sup.sm 10 products. Referring to FIG. 5, the Call Processor 12 is a software system which operates on the host processor 11. This host system software platform 11 distributes incoming messages and their responses, provides the signaling and connection interfaces, and collects information for alarms, and exception and statistics reporting.

Call Processor 12 interfaces with IS-41 Rev. A cellular switches 34, 35, 36 that can communicate using the IS-41 Rev. A standard. This communication may follow an SS7 or X0.25 protocol. The Call Processor also interfaces with FIG. 14 in the Tandem host processor 11, which in turn interfaces with older FMR systems via the FMR host processor 28. Call Processor 12 also interfaces with Inter-Clearinghouse Exchange/Inter-System Gateway (ICE/ISG) 48, through which it interfaces with the EDS clearinghouse system 50 and the MTSOs connected therewith 51-53. All interaction between the Call Processor 12 and PVS 24 is handled by ICE/ISG 48. The seamless interoperability of the Call Processor 12 between diverse switch types and between diverse call delivery systems is the subject of this invention.

The Call Processor 12 performs two primary functions:

Call delivery to a roaming subscriber; and

Pre-call validation of a roaming subscriber.

Call Delivery

A cellular subscriber who is in a market other than his/her home market and who attempts to send or receive a call is referred to as a roamer. Automatic roaming is the process by which a cellular telephone system responds to the presence of a roamer by informing the home system of its presence; determines the roamer's credit worthiness; obtains the roamer's service profile; permits a roamer to originate calls and operate subscribed features; and provides information needed for routing calls to the roaming subscriber in question. Call delivery with automatic roaming includes automatic mechanisms for the following:

Making the identify of the current serving, i.e. visited system, known to the home system;

Establishing financial responsibility for the roaming subscriber;

Establishing a valid roamer service profile in a visited system;

Providing for call delivery to the roaming subscriber.

The registration of a roaming cellular subscriber 40 from a Rev. A home switch 36 in a visited Rev. A switch 38 and normal call delivery is diagrammatically illustrated in FIGS. 2a and 2b, and will be again discussed later. FIGS. 3a and 3b are diagrammatic presentations of the registration and call delivery processes for roaming cellular subscribers in cases in which the home cellular system 36 utilizes Follow Me Roaming Plus and the visited cellular system 42 utilizes an older Follow Me Roaming serrvice. FIGS. 4a and 4b are diagrammatic presentations of the call delivery process for roaming cellular subscribers in cases in which the visited cellular system 38 utilizes a Follow Me Roaming Plus service, while the home cellular system 44 utilizes an older Follow Me Roaming sservice. The home switch 36 for a roaming subscriber is notified to deliver calls to the subscriber's current location after the Call Processor 12 validates that the roaming subscriber is not fraudulent.

Pre-call Validation/Registration

Pre-call validation provides protection against roamer fraud by performing roamer validation prior to connecting the first call and stopping known fraudulent roamers, and tumbling ESN and tumbling MIN users prior to their first call. Through the call teardown process, fraudulent users are disconnected when they are identified. Various techniques and systems for pre-call validation are known in the prior art and available commercially.

Upon inquiry from a visited switch 38, Call Processor 12 returns to the visited switch the status of a roaming subscriber 40 within six seconds of receiving an IS-41 message from the visited switch due to autonomous registration or a call attempt from or to a roaming subscriber. The Call Processor 12 maintains a General Location Register (GLR) 18 containing all information necessary for validation of known roamers. It also contains routing files 54 used by Call Processor 12 to locate the Home Carrier 36, for validation when roamer is unknown. The pre-call validation operation of the Call Processor 12 conforms to the guidelines established by the IS-41 series (Rev. 0 and Rev. A) of recommendations on Cellular Radiotelecommunications Intersystem Operations. A request sent to an IS-41 home switch 36 usually receives a response within one second. In the FMR Plus system of the present invention, the visited carrier may choose among five optional call validation features, which are part of the Fraud Manager 16 software.

Transaction Processing Flow in Call Processor

Transaction processing flow is a high level representation of the functions performed in the Call Processor 12. In this section, the transaction processing flow for each relevant Mobile Application Part (MAP) message is described, and illustrated in FIGS. 6 through 14 inclusive. Steps related to pre-call validation are not presented in detail.

The MAP messages, their acronyms (and the drawing Figures in which they appear), and usage are as follows:

Call Validation:

__________________________________________________________________________ REGNOT Registration Generated when a roaming subscriber is Notification 60 detected through autonomous registration, FIGS. 6-14 call origination, call termination, or other mechanism QUALREQ Qualification To retrieve a subscriber's qualification Request 64 information QUALDIR Qualification To update a subscriber's qualification Directive 68 information in the current visited location FIGS. 7-9 REGCAN Registration To cancel a subscriber's registration in a Cancellation 70 previously visited VLR FIGS. 12, 14 __________________________________________________________________________

Call Delivery:

__________________________________________________________________________ FIGS. 9-11 ROUTREQ Routing Request To provide a temporary number in the 72 current visited system so the subscriber's FIGS. 9-11 home market can deliver a call FEATREQ Remote Feature To request a remote feature control Control Request function FIGS. 10, 11 74 PROFDIR Service Profile To update a subscriber's service profile Directive 62 information in the current visited system FIG. 10 CSSINACT CSS Inactive 76 A visited system detects a roaming subscriber is no longer active in its service area PROFREQ Service Profile To retrieve a subscriber's service profile Request 66 information REDREQ Redirection A call cannot be delivered to a roaming Request 78 subscriber that does n