System for the Extended Provision of Cellular Mobile Radiotelephone Service

This invention relates to the Cellular Mobile Radiotelephone (CMR) technology and, more particularly, to a system for significantly extending the provision of CMR service by automatically forwarding, to a CMR subscriber outside his home service area, calls placed to the subscriber's Mobile Identification Number (MID) at his home service area.

CMR service is one of the most rapidly growing telecommunication services currently offered. (See, for example, "Surging, Price-Insensitive Demand Over Next Two Years and Strong Five-Year Picture Forecast for Cellular Industry Association, Which Sees Capacity Concerns Validated," TELECOMMUNICATIONS REPORTS, Aug. 15, 1988 (pp. 22, 23).) The technology underlying CMR service is exhaustively documented and well within the understanding of those possessed of ordinary skill in the art. Accordingly, a rigorous description of CMR technology will not be undertaken here, and the reader will be referred to the following representative publications, the contents of which are hereby incorporated by reference:

Arrendondo, G. A., J. C. Feggeler, and J. I. Smith. 1979. AMPS: Voice and Data Transmission, Bell System Technical Journal 58, no. 1 (January): 97.

Bernard, Josef. 1987. The Cellular Connection. Mendocino, Calif.: Quantum Publishing.

Bartee, T. C., ed. 1985. Data Communications, Networks, and Systems. Indianapolis: Howard W. Sams.

Bartee, T. C., ed. 1986. Digital Communications. Indianapolis: Howard W. Sams

Fluhr, Z. C., and P. T. Porter. 1979. AMPS: Control Architecture. Bell System Technical Journal 58, no. 7 (January): 43.

Gibson, Stephen W. 1987. Cellular Mobile Radio Telephones. Englewood Cliffs: Prentice-Hall.

IEEE Journal on Selected Areas in Communications. 1984. Special issue on mobile radio communications. See Hirono et al., Miki and Hata, and Suzuki et al. IEEE Journal on Selected Areas in Communications SAC-2, no. 4 (July).

IEEE Transactions on Communications. 1973. Special joint issue on mobile radio communications. IEEE Transactions on Communications COM-21, no. 11 (November).

Lee, W. C. Y. 1982. Mobile Communications Engineering. New York: McGraw-Hill.

MacDonald, V. H. 1979. AMPS: The Cellular Concept. Bell System Technical Journal 58, no. 7 (January): 15.

Of course, one of the salient attractions of CMR service is that it affords the subscriber enhanced access to the public switched telephone network (PSTN), thereby enabling the subscriber both to place and to receive telephone calls at times when he would otherwise have been inaccessible, that is, at times when he is constrained to the confines of an automobile. The accessibility afforded by CMR technology is further enhanced by the availability of transportable CMR units that may be removed from the automobile and carried by the subscriber.

However, one characteristic of the existing CMR system is that this high degree of accessibility is approachable only when the subscriber is physically present within the range covered by his home service area. The subscriber's ability to receive incoming calls outside his home service area has heretofore been severely restricted in ways that will be described below, but are largely circumvented by the instant invention. (A subscriber using, or attempting to use, his cellular phone in a service area outside his home service area is aid to be "roaming" and is, at least for the purposes of this document, referred to as a "roamer".)

In fact, although it might be assumed that the subscriber will not always be aware that he has travelled beyond the range of his home service area, the cellular system has been designed to detect this situation and to so apprise the subscriber.

Briefly, each cellular system has been uniquely assigned a System ID (SID). Electrical signals corresponding to each cellular system's SID are continually transmitted by that system over a control channel separate from the channel used to provide voice communications. The SID of the system from which a particular subscriber has agreed to acquire CMR services is programmed into a Numerical Assignment Module (NAM) incorporated into the subscriber's mobile unit. When a subscriber's mobile unit is "powered up," it reads a System Parameter Overhead Message that includes the fifteen-bit SID of the system whose signal the mobile unit is receiving. The mobile unit then compares the transmitted SID to the SID programmed in its NAM to determine identically. If the unit determines lack of identicality, a "ROAM" light is activated on the control head associated with the mobile unit. In this manner, the subscriber is made aware that his mobile unit has "seized" a system other than the system on which he is an authorized subscriber.

A roamer who desires to place an outgoing call to the system in the area in which he is roaming need only remember to first dial the area code of that system. Calls placed to the subscriber's home system do not require the dialing of a prefatory area code.

The procedure for receiving incoming calls, however, is substantially more cumbersome. An essential element of the roamer's ability to receive incoming calls is that would-be third-party callers to him need to know in which system the subscriber is physically available. Unanswered calls placed to the subscriber's home number will be answered with a message indicating that the subscriber cannot be found. What the caller needs to know, then, is what CMR system the roamer is using and the procedure for accessing the subscriber through the facilities of that system. That is, the caller must know the roamer's itinerary and the roamer access number of the system the roamer is using. The major service areas each have a ten-digit roamer access number. Areas in which service is provided by both a wireline and a nonwireline carrier, of course, have two roamer access numbers, one corresponding to the wireline carrier and one corresponding to the nonwireline carrier.

Armed with this information, the would-be caller must first dial the ten-digit roamer access number of the system he expects the roamer to be using. After a short pause followed by a tone, the caller must then dial the roamer's home number, including his home area code. In some services areas, this cumbersome and demanding procedure is exacerbated by the need for the subscriber to prearrange, with the CMR service provider in the "foreign" area, the right to have incoming calls delivered.

Even when the above-mentioned procedural hurdles have been surmounted, the foreign-area service provider may be disinclined to have (or technically incapable of having) the applicable service charges applied to the subscriber's home service area bill, and the charge will need to be prepaid or applied to an acceptable credit card.

In a manner that will be made clear by the detailed Description set forth below, the above-indicated limitation of the CMR system, as it has been heretofore implemented, is cured by the invention underlying the Follow-Me-Roaming (SM) Cellular Mobile Radiotelephone Service. ("Follow-Me-Roaming" is a service mark of GTE Mobilnet Incorporated. At appropriate occurrences throughout the remainder of this document, various constituent elements of the combined hardware and software system that implements that service are referred to in conjunction with the use of the acronym "FMR".)

The above and other objects, advantages and capabilities are achieved in one aspect of the invention by a method for enabling a roaming CMR subscriber to automatically receive, in a foreign service area, calls placed to his home service area. The method comprises the steps: (a) receiving, at a foreign service area MTSO, information indicating that the roaming CMR subscriber desires to receive, in the foreign service area, calls placed to his home service area; (b) validating the roaming subscriber; (c) upon validation of the roaming subscriber, assigning the roaming subscriber a temporary directory number (TDN) for use in the foreign service area; and (d) providing information to the roaming CMR subscriber's home service area MTSO so as to enable the roaming CMR subscriber's home service area MTSO to call forward, to the TDN, calls placed to the roaming CMR subscriber's MID in his home service area.

In another aspect, the invention comprises an apparatus for enabling a roaming CMR subscriber to automatically receive, in a foreign service area, calls placed to this home service area. The apparatus comprises a computer for coupling both to a switch associated in the home service area and to a switch associated with the foreign service area. The computer is programmed to: (1) receive information indicating that calls placed to the home service area are to be forwarded to the foreign service area; (2) assign the subscriber a temporary directory number (TDN) in the foreign switch; and (3) command the home switch to forward, to the TDN, calls placed to the home service area.

In a further aspect, the invention comprises a CMR system that automatically forwards, to a foreign service area outside a CMR subscriber's home service area, calls placed to the subscriber's home service area. The system comprises a home MTSO that is associated with the home service area and includes a home switch for receiving calls placed to the subscriber's MID. A foreign MTSO is associated with a foreign service area and includes a foreign switch. A control computer is coupled to the home switch and to the foreign switch for (1) receiving information indicating that calls placed to the CMR subscriber's home MTSO are to be forwarded to the foreign MTSO; (2) assigning the CMR subscriber a temporary directory number (TDN) in conjunction with the foreign switch for use in the foreign service area; and (3) providing information to the home switch that enables the home switch to forward, to the TDN at the foreign switch, calls placed to the CMR subscriber's MID in the home service area.

In yet another aspect of the invention, a method for activating a process that enables calls placed to a CMR subscriber's home service area to be automatically forwarded to a foreign service area outside the CMR subscriber's home service area includes, as a step, determining whether an activation request is a duplicate request and, further, determining whether a duplicate request is a valid duplicate request or an invalid duplicate request. Duplicate activation requests are detected by searching existing TNUM records (Temporary Number Records) in order to identify a match, if any, between the requesting CMR subscriber's MID and the MID in each of the respective TNUM records. (A complete functional definition of the TNUM records appears in narrative form, and in tabular form, under the Description of a Preferred Embodiment of the Invention. If a match is identified, a determination is made that the activation request is a duplicate request. The duplicate request is determined to be a valid duplicate request if the time of activation contained in the TNUM record that resulted in the identification of a match is at least a predetermined length of time earlier than the time of the then-pending activation request. If the duplicate request is determined to be a valid duplicate request, the subscriber is re-activated in him home service area, and, if the duplicate request is determined to be an invalid duplicate request, the duplicate request is substantially discarded.

FIG. 1.1 is a system diagram of conventional a CMR system, depicting the constituent cell sites, MTSOs (Mobile Telephone Switching Offices), and corresponding MTSO cellular switches. FIG. 1.1 additionally depicts the manner in which two independent CMR systems are coupled via the PSTN (Public Switched Telephone Network).

FIG. 1.2 depicts, in block form, the constituent elements of a CMR mobile unit: the transceiver unit, the control unit, and the handset.

FIG. 1.3 is a pictorial representation of the handset and shows, particularly, the keypad through which activation or deactivation codes may be entered.

FIGS. 2.1 through 2.15 constitute a detailed and comprehensive flow diagram of the operational steps, primarily software-driven, that represent a fundamental aspect of the invention. Each of FIGS. 2.1 through 2.15 comprises several steps to which are attached individual reference designations. For example, in FIG. 2.10, the step labeled "SET PROCESS STATE VALUE=TO 5" has been assigned reference designation 1012. In addition, a directional bubble labeled "E2-9" is attached to step 1012. The prefix portion, "E2" is intended to indicate that step 1012 is connected to a step bearing the identical prefix (E2) on the Figure associated with the suffix, "9", that is, on FIG. 2.9. Therefore, the bubble "E2-9" on FIG. 2.10 is to be connected to the bubble "E2-10" on FIG. 2.9.

FIG. 3 is a diagram of the subject system for the Extended Provision of Cellular Mobile Radiotelephone Service. The diagram depicts a "home" MTSO and associated home switch, and a "foreign" MTSO and associated foreign switch. An FMR processor, programmed with the software disclosed in this patent document, is appended to the foreign switch and is coupled to the home switch via, for example, a private data network. The home MTSO and the foreign MTSO are conventionally interconnected via the PSTN.

For a thorough understanding of the subject invention, reference is made to the following Description and appended claims, in conjunction with the above-described Drawings.

Preliminarily, however, in order to arrive at a contextual appreciation of the subject invention, attention is directed to the constituent Drawings of FIG. 1, which depict various conventional aspects of the existing CMR system.

FIG. 1.1 depicts two conventionally configured cellular systems, 2 and 3 respectively, interconnected via. For present purposes, assume that system 2 is a "home" system, that is, a system in which a particular, roaming, CMR customer is an authorized subscriber. Conversely, assume that system 3 is a "foreign" system, that is, a system to which the roaming subscriber may travel and through the facilities of which the subscriber desires to receive CMR telephone calls.

By way of background (and deferring for the moment the discussion of the more pertinent details of the subject invention), it is well understood that the conventional cellular system comprises a Mobile Telephone Switching Office (MTSO), illustrated by reference numerals 21 and 31 in FIG. 1.1, surrounded by an appropriate array of more or less identically equipped cell sites, 22 and 32. Mobile subscribers, 42 and 43, establish an RF communications link with the cell sites. Each of the cell sites is, in turn, coupled to its associated MTSO by a dedicated landline. The MTSOs are coupled by dedicated lines to the PSTN.

A complete description of the fixed and mobile hardware and software necessary to implement a cellular system, such as either system 2 or system 3, would be feckless as an effort to enhance the understanding of the invention by those even modestly acquainted with the U.S. cellular system, inasmuch as practitioners having ordinary skill in the art of CMR system design are well acquainted with the configuration and operation of such systems and will, therefore, be well prepared to apprehend the Description of the invention that follows. However, the conscientious reader is referred to the document entitled "DYNA T.A.C..TM. System Description," Instruction Manual 68P81150E01-A, available from Motorola Inc., Technical Writing Services, 1301 East Algonquin Road, Schaumburg, Ill., 60196, hereby incorporated reference.

Suffice it to say, however, that incorporated into each MTSO is a software-driven, computer-based cellular switch that performs various functions, including but not limited to:

(1) Providing switched interconnection between the MTSO and the PSTN.

(2) Providing switched connections between mobile subscribers served by the MTSO.

(3) Administering the usage of RF voice channels available to the associated cellular system.

(4) Providing control over signaling with the mobile units. (Some specifics regarding the configuration and operation of the mobile units are forthcoming below.)

(5) Providing control of the intercell location process and control of the resulting "handoff" of calls between cells.

(6) Recording billing information, including, inter alia, the generation of Call Records.

(7) Providing custom service to mobile users.

A specific example of a cellular switch that has been used in connection with the subject invention is the EMX 2500, available from Motorola, Inc. Literature describing that switch has in the past been available from Motorola, Inc., at the address provided above.

Turning now to the mobile unit, depicted in FIG. 1.2 with reliance on functional block diagrams, it is well understood that installed within each cellular subscriber's vehicle is a mobile unit that includes a transceiver unit, a control unit (including a cradle and a handset), a cellular antenna, and associated control, power, and antenna cables. A detailed description of one embodiment of such a mobile unit is found in the document "GTE METAL SERIES CELLULAR MOBILE TELEPHONE (MT930)," Publication Reference GTE-MN 1176, available from GTE Mobilnet Incorporated, 616 FM 1960 West, Suite 400, Houston, Tex., 77373, hereby incorporated by reference.

As alluded to above, included with each mobile unit is a handset, such as the handset depicted in FIG. 1.3. The handset includes a keypad that operates in some ways like the keypad of a standard push button residential telephone set. However, the handset provides many functions uncommon to residential telephones. These functions are described in operating manuals available from vendors of the mobile units. In the context of the subject invention, however, the handset (specifically, the keypad) will be seen as a suggested preferred mechanism by which the roaming subscriber may indicate a desire to receive the FMR cellular service.

With the above backgroun in grasp, it will be seen that the FMR system, in most respects, may be viewed as an "overlay" on the CMR system depicted in FIG. 1.1. As may be seen in FIG. 3, the FMR system includes an FMR processor 5 that is coupled to the foreign MTSO 31. Specifically, processor 5 is coupled, in a manner described below, to the cellular switch 33 resident within the foreign MTSO 31. The FMR processor is also coupled to the home cellular switch 21 through, preferably, a dedicated network 6. (The use of a dedicated network is suggested; however, those skilled in the art will recognize that numerous telecommunication facilities exist for establishing a communication channel between two computer-based devices such as the FMR processor 5 and the home MTSO 21 switch.)

The FMR processor 5 may be implemented in one form by a Compaq Portable II (Model 2) computer, available from Compaq Computer Corporation 20555 FM 149, Houston, Tex., 77070. The processor is equipped with 64K bytes internal RAM (Random Access Memory) and a 20M byte hard disk and may be upgraded with a communication port, also available from Compaq Corporation Computer. The FMR processor 5 is also enhanced with a "WATSON" voice communication card (provided by Natural Microsystems Corporation, Natick, Mass.) and a four-port communications card (such as the product designated Asynchronous Cluster Adapter Communication Board and available from AST Research Incorporated, Irvine, Calif.) that provides four communication ports on a single, pluggable circuit board.

The processor 5 is coupled to the "foreign" switch 33 (the switch resident in the foreign MTSO 31) at one port. Another communications port is used for remote maintenance by a central monitoring center that dials into the processor. The voice card is used to communicate with the switch via the software modules referred to as "ROAMERHOME" and "HOME.x," described below. Additionally, the voice card allows the FMR system to place a voice call (colloquially referred to as a "Watson") to the subscriber in order to announce to the subscriber that, for example, an FMR activation process has been successfully completed. The remaining communications ports may be used to monitor callers so that Call Records can be tracked and so that an activation or deactivation code may be detected.

Directing attention now to FIGS. 2.1 through 2.15, set forth therein is a comprehensive flow diagram describing in detail the operation of the software-driven FMR system according to which the subject invention is realized. The complete FMR software package includes an executive or background program, FMR.EXEC, and a basic program, FMR.BAS.

However, the keystone, and central software component, of the FMR system is the FMR.BAS program. Accordingly, the complete source code listing of FMR.BAS is set forth in Appendix A. (It will be recognized by programmers of any meaningful experience, that FMR.BAS is written in the Advanced Basic language.) As is immediately apparent from an inspection of FMR.BAS, as well as from an inspection of the flow diagram constituted by FIGS. 2.1 through 2.15, FMR.BAS utilizes in its operation a number of software flags, variables and subroutines. The descriptions and definitions of those many of these flags, variables, and subroutines are set forth in Appendix B. "FMR.BAS Glossary," which is provided to assist in the intimate and comprehensive understanding of the software-related aspects of the invention. In addition, FMR.BAS utilizes in its operation a number of subroutines of varying length. These subroutines are set forth in Appendix C. For completeness, Appendix D contains the FMR.EXEC software which is written in assembly language.

What will be described immediately below are the operational steps required to "activate" a roaming subscriber. In this context, to "activate" a roaming subscriber means to perform all the functions performed by the subject invention in the context of the FMR system in order that the roaming subscriber might receive, in a "foreign" service area (that is, a service area outside his home service area), calls placed in his home service area to his MID. (It is understood that such calls may originate with callers outside the subscriber's home service area. These calls, however, will be routed through the PSTN, perhaps by interexchange carriers, but will ultimately be delivered to the end office connected to the subscriber's home MTSO.)

It will be appreciated that some of the necessary operations are purely software operations, some are purely hardware operations, and some are hybrid. A "hybrid" operation is, for example, an operation that involves hardware operating under the control of or in response to a stimulus provided by the software, or software operating in response to a stimulus provided by the hardware. Furthermore, a number of the functions described below are performed by conventional cellular systems and are known to those familiar with the operation of cellular systems. To the extent that such functions are implicated in, or assist in an understanding of, the invention, they are included in the Description, infra. However, the comprehension and implementation of such functions are well understood by those having ordinary skill in the art of cellular communications.

In addition, a number of functions conventionally performed by cellular systems are deemed ancillary or collateral to the operation of the subject invention. Such functions have not been described in detail, but their comprehension and understanding are likewise understood by those having ordinary skill in the art of cellular communications.

In order to assure an intimate understanding of a roamer activation process, a software "map" is provided in tabular form below. The map sequentially traces the operational steps encountered according to the subject invention in order to activate a roaming CMR subscriber. The steps set forth below refer, of course, to the software-driven steps illustrated in FIGS. 2.1 through 2.15. A narrative description of those step appears immediately infra.

Operation may be assumed to begin when a Call Record is received, in Step 011, by the MTSO in the foreign service area. The FMR processor coupled to the foreign switch monitors all Call Records (regardless whether the corresponding call represents a request for FMR service) and, in Step 012, increments a variable whose value represent the total number of calls received. In Step 013, a determination is made as to whether the Call Record represents a roamer Call Record. The specific manner or logical method by which this determination is made depends on the particular characteristics of the foreign switch to which the FMR processor is coupled. Uniformly, however, the software driving the foreign switch must be adapted so as to provide some form of indication in the Call Record that a request for an FMR activation or FMR deactivation, usually a call class 67, has been received. This is conveniently accommodated in the Dial Digit field or the Roamer Home field in the Call Record. Alternatively, the determination may be derived from the call class failure indicator.

If the Call Record is, in fact, determined to be a roamer Call Record, the total number of roamer calls is incremented in an associated register. In Step 015, a determination is made whether the call class indicator associated with the then current Call Record is 67, 69, or 70. It should be understood that the call class indicator field of the Call Record indicates the manner in which the call was handled. For example, the call class indicator may designate a dropped call, a completed call, a call routed to a message or recording, or a call diverted to special handling trunks. If the call class indicator gives reason to suspect that the call might be a roamer call, a subsequent determination is made to see whether the subscriber has transmitted an FMR activation code, that is, the digits "211." The code, 211, is, of course, the code indicating to the foreign MTSO that the call being processed has been placed by a subscriber who is a roamer in that system. The code represents a request that calls placed to the roamer's home service area be forwarded to the foreign system that serves the location in which the roamer is now present. If it is determined that the code digits (i.e., 211) have in fact been dialed, the Call Record is stored in a call buffer (Step 018) and a flag, ROAMER CALL, is set (Step 019).

At this point it is useful to introduce the reader to the structure of the "TNUM" file and corresponding records entered into that file in response to the receipt, by the FMR system, of the activation code that represents a request for FMR service by a CMR subscriber. The TNUM file comprises a number of TNUM records containing information in the format set forth in the table below. Notice that a TNUM record includes a "TDN" field that contains the temporary directory numbers (TDNs) available for use with the associated foreign switch. The "USED" field indicates whether the TDN has been (tentatively or finally) assigned to a roaming subscriber. The mobile identification number (MID) of the requesting subscriber is indicated in the "MID" field. Other information in a TNUM record includes the roamer's electronic serial number (ESN), time and date of activation, and the roamer's feature package in his home switch. The "Sent" field indicates whether the activation has been completed (SENT=Y) or is merely in process (SENT=N).

The FMR processing indicated above has been performed by the background or execution program, FMR.EXEC, which runs in a continuous loop. However, once the Flag ROAMER CALL is detected by FMR.BAS, FMR.BAS begins to process the call as indicated below.

Specifically, in Step 021, the FMR processor examines the ROAMER CALL flags to determine whether any of those flags are set. Because a ROAMER CALL flag had been set in Step 019, the determination is positive, and the system proceeds, in Step 023, to remove the corresponding Call Record from the call buffer and store the Call Record on a RAM, disk storage medium. This procedure is done primarily as a backup, precautionary, measure.

Next, in Step 024, the ROAMER CALL flag that had been set in Step 019, the buffer flag, and pointers are all reset.

In Step 025, the flag BUFFLAG is set. The setting of BUFFLAG occurs as part of the operation of the subroutine PEEKCALL. (See Appendix C.13) Specifically, BUFFLAG is set whenever Call Record data is passed by FMR.EXEC to a predetermined buffer, e.g., the RAM disk.

After Step 025, the FMR processing system loops back to Step 021. If any other ROAMER CALL flags have been or remain raised (i.e., set) (which would be true if there were, at the time, at least one other roaming subscriber who was simultaneously requesting FMR service), the processing of Steps 023 through 026 would be repeated until all ROAMER CALL flags have been cleared. Assuming the pending request is the only, or the last, request to be served, the FMR system proceeds to Step 041. Subsequently, in Step 042, a determination is made as to whether the two-second timer has timed out. If it is determined that the two-second timer has timed out, a routine is called to check the operation of the FMR system. For example, the "heartbeat" incorporated into the background program is examined for continuity. In addition, it may be possible for FMR.BAS to become "stuck" in one module for an excessive duration. If not, BUFFER is reset in Step 42, and the system jumps to step 052.

In Step 052, information related to the call is retrieved from the Call Buffer. Recall that information had been previously stored in the Call Buffer in Step 18. In Step 053, relevant information (MID, ESN, dialed digits) accumulated in the original request for FMR service is extracted. In Step 054, 055, and 056, a determination is made whether or not to "validate" the roaming subscriber's home switch. This determination is based on the information extracted in Step 052. Specifically, the FMR processing system determines: (1) whether the NPA NXX associated with the subscriber's request is in the validation file; (2) whether the subscriber's home switch is a "valid" switch. The determinants here are, inter alia, whether or not the switch is part of the FMR system and whether or not the switch is operating.

Once the roaming subscriber's home switch has been "validated," the digits dialed by the subscriber are examined in Step 0511 to determine whether those digits constitute an "activation" code. The activation code is, to a degree, arbitrarily chosen and may, for example, correspond, as suggested above, to the selection, by the subscriber, of the three keys on the control unit keypad corresponding to the digits 211. (The converse "deactivation" code and attendant processing by the FMR system will be described below.)

Once it has been determined that an activation code has been received, an ACTIVE FILE is created (Step 058), and the MID and ESN associated with the subscriber's mobile unit, as well as information identifying his home switch site, are stored (Step 059). In Step 0510 the ACTR flag is incremented, indicating that an activation request has been received. FMR.BAS then returns to Step 051 in order to determine whether the last Call Record has been stored. If there are no remaining Call Records to be stored, the FMR processing jumps to Step 045, where a determination is made whether ACTR is equal to ZERO. Inasmuch as, in this instance, ACTR cannot be equal to ZERO because it had, in Step 0510, been incremented, the program jumps to Step 061.

In Step 061, FMR.BAS determines the total number of temporary directory numbers (TDNs) provided for or allocated by the switch in the foreign MTSO. This value is stored in the variable LC (Last TDN Count). Subsequent to Step 062, in which it is determined that an activation is pending, the Call Record is retrieved (Step 063) from the ACTIVE file, and the value of ACTR is decremented by one. Assuming the current Call Record is not the last record in the file, the first record is retrieved from TNUM file (Step 074), and first record indicator LTRI (Step 071) is set to ONE.

Steps 072 through 075 comprise a looping routine that examines all TDN records in the TNUM file. In so doing, FMR.BAS searches for the first unused TDN or attempts to determine whether the roamer has previously requested the FMR activation. At Step 078, after all temporary number records in the TNUM file have been examined, the variable "R" will equal the record number in TNUM file of the first unused temporary number or the record number associated with a temporary number already allocated to the roamer. If `R` is equal to ZERO, all temporary numbers have been used, and a message is sent to the daily transaction file (Step 0715) to indicate this condition. Assuming that an unused temporary number has been found or that the roamer has already been assigned a TDN, the program flow continues with Step 072.

If, during Steps 072 through 077, the roamer was found to already have a TDN assigned to him, the flag DUPFLG will be set equal to ONE (Step 0714), and program flow continues with Step 082. A determination is made at Step 084 whether the roamer's initial request for an activation has been completed or whether FMR.BAS is in the process of activating the roamer. Because we have assumed the presently described operation to be an activation, and because DUPFLG will be ZERO, FMR.BAS proceeds to Step 0815, where the then-present data is stored in the ACTSND file and SNDF (SeND Flag) is set.

At this point (Step 0816), an examination of DDUP is undertaken to determine if the roamer has already been assigned a temporary number in the foreign MTSO and three hours have elapsed since his first activation. If so, the value of the variable PROCESS STATE is set to 3, indicating a re-activation in the local switch only, else the value of PROCESS STATE is set to ONE (Normal Activation).

Because, again, the system is undergoing an activation process, processing proceeds to Step 063 where, inter alia, ACTR is caused to be decremented. Because, during Step 065, the then-current record is determined to be the last record and, in fact, an activation (Step 066), ACTR is set to ZERO, and the file is cleared. That is, all necessary information is at the time extracted from the file as the file is being processed. Consequently, the file can be used for another activation while this processing takes place. FMR.BAS then jumps to Step 046.

Because SNDF is set (recall Step 0815), FMR.BAS skips to Step 091. At Step 091, a determination is made that the processing then encountered is an activation. Accordingly, at Step 092, File is set to indicate an activation. Because (1) the then-present record is not the last record (Step 095), (2) the value of PROCESS STATE is ONE, and (3) all the ACTSND variables, roamer ESN and MID, are valid, FMR.BAS then determines which switch to call (Step 0910). This determination is made based on data in the ACTSND file. Specifically, data identifying the roamer's home switch is stored in ACTSND, and this data can be matched against the NPA file to retrieve the telephone number (that is, the number assigned to the switch in the private data network) of the home switch. In Step 0912, FMR.BAS calls the roamer's home switch. The roamer's home switch is then interrogated to determine:

Step 0913: Is the roamer a "homer" in the switch called?

Step 0914: Has there been no denial of services to the ESN corresponding to the roamer's equipment?

Step 0915: Do the ESN and the MID match in the data base?

If the results of the interrogation are all affirmative and the value of PROCESS STATE is not equal to 3 (Recall: PROCESS STATE was set to ONE in Step 0817), then, according to Step 102, the subscriber's feature package is retrieved from the home switch and stored in the assigned record in the TNUM file. (As an aside, the subscriber's feature package is evaluated to determine whether the subscriber has Call Forwarding in his home service area. If not, FMR.BAS will give the subscriber Call Forwarding in conjunction with the command to the home switch, set forth below.) Because the file is an ACTSND (Step 103), the FMR processor, in Step 104, issues a command to the roamer's home switch to call forward all calls placed the roamer's MID in his home service area to the assigned TDN.

The command, sent from the FMR processor to the roamer's home MTSO switch is a central component of the invention. This command, as well as ancillary and penumbral operations associated with it, form the contents of a subroutine referred to as ROAMERHOME. The specific processing steps undertaken by ROAMERHOME will vary in their detail in order to accommodate the command structure of the home switch with which ROAMERHOME is, at the time, interacting. The complete source listing of an exemplary form ROAMERHOME follows. ##SPC1##

After the command has been issued by the FMR processor to the roamer's home switch, the FMR processor continues to monitor the switch's response to all issued commands in order to assure that proper responses to those commands have been received. This operation is illustrated as Step 106.

Assuming proper responses are obtained, the system then determines that the value of PROCESS STATE is not equal to 2 or 3. (A value of PROCESS STATE equal to 2 would indicate that the roamer was found to have had his ESN denied in his home switch. A value of 3 indicates that a reactivation is in progress.) The value of PROCESS STATE is then set to 4, at which point the program jumps to Step 094.

At step 094, the Call Record is pulled from the file and, because this is not the last record (Step 095) and the value of PROCESS STATE is equal to 4 (Steps 096 and 097), the program jumps to step 111.

At step 111, a determination is made that the then-ongoing process is an activation. As a result, file is set to ACTSND in Step 112. In step 114, the next record is retrieved, and, because (1) that record is determined not to be the last record (Step 115), (2) the SKIP flag is not set (Step 116), (3) the value of PROCESS STATE is equal to 4 (Step 117 and 1112), and (4) all command parameters are determined to be valid (Step 1113), the program jumps to step 121.

At step 121, a determination is made that the HOME flag is not set. The HOME flag would be set if the FMR system were at this time simultaneously processing several requests for activation. In Step 122, the FMR processor obtains all parameters necessary to establish a communications link with the local switch. The link may be established through the PSTN or through a private network such as is available through Telenet Corporation. This information is then stored in the HOME file, and the FMR processor calls the local switch. This processing is done in one of several subroutines generically referred to as HOME.x.

The word "HOME" in the subroutine name denotes the FMR processor's perspective rather than the perspective of a CMR subscriber. Thus, HOME.X is used to communicate with the local (i.e. HOME) switch, which is a foreign switch for FMR service purposes. Each of the HOME.x subroutines will vary in its particulars in order to accommodate the specific command structure of the local switch to which the FMR processor is, at the time, coupled. (HOME.2500, for example, is the version of HOME.x currently used in conjunction with the EMX 2500, available from Motorola, Inc.) The command structure of the switch dictates the specific code required to "tell" the local switch to validate the roaming subscriber's TDN. In addition, the format of the Call Record generated by each model of switch can be expected to vary so the EXEC software may need to be modified as well. The complete source code listing of HOME.2500 follows. ##SPC2##

The HOME flag is then set in Step 123, and after a determination is made, in Step 124, that the ongoing process is an activation, the TDN is validated, and the roamer is included in the list of TDNs (Step 125).

In Step 127 a test is undertaken to confirm that correct responses have been received to all commands. If so, the TNUM file is updated with date and time of activation, and the SND is set to ONE. In Step 1214, the roamer's TDN is entered into the TEST.TXT file, in preparation for a callback that will be transmitted to the roamer. This callback is colloquially referred to as a "WATSON."

In Step 1215, the CALL flag is set; and in Step 1216 PROCESS STATE is set to 9. The program then jumps to Step 114, where the next record is obtained. If this record is determined to have been the last record, the program jumps to Step 131.

At Step 131, a determination is made that the SKIP flag is not set. The SKIP flag would be set, for example, when multiple activations are pending or when the initial attempt to establish a communications link with the home switch had failed. Such failure might be attributable to several causes, including, for example, blockage of the switch. The SKIP flag is then set to ZERO in Step 133, and in Step 134 all records in the ACTSND file are cleared. Because the HOME flag is determined in Step 135 to be equal to ONE, the FMR processor logs off the home switch (Step 136), clears all appropriate flags, updates and counters (Step 137).

In Step 138 a determination is made whether AUTO FLAG is greater than 2 and whether BUSY FLAG equals ZERO. Because this condition is not satisfied, FMR processing then returns to FMR.EXEC.

The FMR system also provides a unique feature, alluded to above, in that it is capable of detecting and appropriately processing a "duplicate activation request". A first type of "duplicate activation request" would occur, for example, when the roaming subscriber repeatedly enters an activation code through the keypad on his handset, without allowing the FMR system sufficient time to process the request, or on any other occasion when the subscriber initially enters an activation code and then re-enters the code, prematurely, before the FMR systems has completed processing of the initial activation request.

A second type of duplicate activation request arises when, for example, a CMR subscriber roams into a foreign service area and is provided FMR service in that area. Should the subscriber, on the same day, leave and then return to a local service area, he would need to be "re-activated" in this local area. Otherwise, of course, although this local MTSO would consider him active, calls placed to his home MID might be forwarded to the TDN in another foreign service area or not forwarded at all. Throughout the remainder of this document the second type of duplicate application request will be denominated a "valid" duplicate application, and the first type (described in the paragraph immediately above) will be denominated an "invalid" duplicate activation. In order to understand the manner in which either type of the duplicate activation request is handled, the flow of FMR.BAS will be re-traced, beginning with Step 0511.

Again, at Step 0511, FMR.BAS detects that an activation code, 211, has been received by the foreign switch. In response, an ACTIVE file is created in Step 058. In Step 059, the subscriber's MID and ESN are stored, and his home switch is identified and stored. The ACTR flag is incremented in Step 0510, indicating that an activation process is pending. At Step 051 a determination is made that the pending call is the last call stored, and processing is routed to Step 045. Because, at this point, ACTR is set (an activation is in process), processing jumps to Step 061. At this point a determination is made as to the exact number of TDNs allocated to the foreign switch, and this value is stored in LC. Because the pending process is an activation, in Step 063 the record is retrieved from the ACTIVE file, the ACTR is decremented. The pending record is not the last record (Step 065). (The effective last record is a dummy record.) Processing continues at Step 071, where LTRI is set to ONE, that is, a limit is imposed on the number of attempts that will be allowed to complete this activation. At Step 074, the record is recalled from TNUM. At this point, the FMR system is reading a TDNs in the TNUM file and attempting to assign a TDN to the requesting subscriber.

At Step 075, the last try (LTRI) is not equal to LC. That is, the FMR system determines that it has not exhausted all the TDNs available for assigning to the requesting subscriber. At Step 076, a determination is made that the "USED" field of the temporary number does not contain an "N" (=No).

At Step 077, the system compares the requesting roamer's MID to the MID field of the TNUM record. That is, FMR.BAS attempts to determine whether this roamer has previously been assigned a TDN. The process of comparing (i) MIDs that have already been assigned to TDN to (ii) the requesting MID is repeated for every TDN record. That is, a determination is made whether the requesting roamer has already been assigned any of the foreign switch's TDNs. If, in any one case, a match is found between the roamer's MID and the MID field of any TNUM record, that match indicates a duplicate activation, DUPFLG is set (Step 0714), and processing continues at Step 082. At Steps 082 and 084 a determination is made whether (1) this activation has actually been sent to ROAMERHOME or (2) whether the FMR system is simply in the process of activating this subscriber. To reiterate, if the "SENT" field in TNUM is equal to "Y" (=YES), then the requesting roamer has already been activated. If the SENT field is equal to "N" (=No), the FMR system has not completed the initial request for activation.

Assuming the response in Step 084 was N, then at Step 085 the system determines whether more than three hours have elapsed since the preceding activation. If three hours have elapsed, a "local" re-activation is indicated. That is to say, the subscriber travelled, for example, from a foreign service area in Houston to a service area in Austin, and then returned to Houston. He therefore needs to be "locally re-activated" in the foreign switch. The local re-activation is initiated in Step 0812. In addition, the Step 0812 the flag DUPFLG is reset, and the flag DDUPFLG is set. Setting DDUPFLG is an indication to the FMR system that a valid duplicate activation request is being processed.

If three hours have not elapsed, the FMR system effectively decides that it is encountering an "invalid" duplicate activation, and FMR.BAS sets LTRI (last try) to LC (last temporary number) plus 6. In essence, this step discards or ignores the invalid duplicate activation request. This is because LC is the last record FMR.BAS will complete and, as a result, there is no mechanism for arriving at LC+6. To apprehend the manner in which the discard is effected, we pick up the processing sequence at Step 074, where the next TDN record is extracted from the TNUM file. At Step 075, LTRI will be equal to LC+7 (because LTRI was incremented in Step 074). At Step 078, we assume that all TDNs are not in use.

Because at Step 079 DUPFLG is detected to be set (see Step 0813) and LTRI=LC+7, processing returns to Step 062. At this point, the FMR system undertakes to process the TDN record acquired immediately above in Step 074, having effectively discarded the invalid duplicate activation request.

By way of synthesization with respect to the detailed processing steps disclosed above, the FMR system uniquely processes activation requests by determining, initially, whether the request represents a duplicate activation request. This determination is made by comparing the then-requesting subscriber's MID to the MIDs in all the then-existing TNUM records. A match indicates a duplicate activation request and thereby gives rise to the need to discriminate between invalid and valid duplicate requests.

The duplication request is judged to be a valid request if the time of activation in the earlier TNUM record that formed the basis for the match is at least a predetermined length of time, for example, three hours, earlier than the then-requested activation. In this instance, it is assumed that the CMR subscriber has left the local foreign service area, been provided FMR service in another foreign service area, or had FMR service removed while in his home service area, and then returned to the local service area. A local re-activation is required, and the system sets DDUPFLG to signal this condition. The predetermined length of time is accordingly chosen to be the anticipated minimum time of travel between contiguous CMR service areas.

Conversely, if the duplicate activation request is determined to be an invalid request, because, for example, the earlier activation request occurred less than the predetermined length of time prior to the pending request, the request is substantially discarded.

What has been described above represents, in detailed form, the processing steps required to "activate" an FMR roamer. An analogous process is, of course, undertaken in order to "deactivate" the roamer once the FMR service is no longer required. The sequence of these steps is in some respects similar to and suggested by the steps encountered in the activation process.

However, in order to assure an intimate understanding of a roamer deactivation process, a software "map", similar to the one above, is provided in tabular form below. The map sequentially traces the operational steps encountered according to the subject invention in order to deactivate a roaming CMR subscriber.

By way of summarization, the subject System for the Provision of Extended Cellular Mobile Radiotelephone Service substantially enhances that value of CMR service to the subscriber by overcoming one of the limiting aspects of the existing system and permitting the subscriber to receive CMR calls, in a very convenient manner, beyond his home service area.

The underlying invention includes a method for enabling a roaming CMR subscriber to automatically receive, in a foreign service area, calls placed to his home service area. The method comprises the steps: (a) receiving at a foreign service area MTSO request information indicating that the roaming CMR subscriber desires to receive, in the foreign service, calls placed to his home service area; (b) validating the roaming subscriber; (c) upon validation of the roaming subscriber, assigning the roaming subscriber a temporary directory number (TDN) for use in the foreign service area; and (d) providing command information to the roaming CMR subscriber's home service area MTSO so as to enable the roaming CMR subscriber's home service area MTSO to call forward, to the TDN, calls placed to the roaming CMR subscriber's MID in his home service area. The request information may be delivered to the foreign MTSO by virtue of an activation code entered by the subscriber through the control unit (specifically, the handset keypad) of the subscriber's mobile unit. However, other approaches to logging the request for CMR service are contemplated by the invention. It is not necessary that the request be initiated through the mobile unit; and the subscriber himself may, on occasion, be not involved.

In addition, the subject system has been described as including a "validation" process prior to the grant of FMR service. Validation is granted according to a number of criteria. One of these criteria is that CMR system, or CMR carrier, that provides the subscriber service in his home service area be part of the "FMR network." This determination is made by examining the NPA NXX file to determine whether the subscriber's home NPA NXX are listed as part of the FMR network. In this sense, validation is directed, not primarily to the subscriber's entitlement, but to whether the subscriber's home system is entitled to participate in the provision of FMR service. It is contemplated that, in some configurations, validation, whether of the subscriber or of his home system, may be circumvented.

In another aspect, the subject System embodies an apparatus for enabling a roaming CMR subscriber to automatically receive, in a foreign service area, calls placed to his home service area. The apparatus comprises a computer for coupling both to a switch associated with the home service area and to a switch associated with the roaming service area. This switch is programmed to (1) receive information indicating that calls placed to the home service area are to be forwarded to the foreign service area; (2) assign the subscriber a temporary directory number (TDN) in the foreign switch; and (3) command the home switch to forward, to the TDN, calls place to the home service area. The apparatus, as described herein, assumes the form of a "control computer," namely, FMR processor 5. Although a specific model computer (the Compaq computer identified above) has been described for enablement purposes, various hardware configurations, including the computer and supplemental or peripheral equipment, are contemplated by the invention.

The FMR processing system, additionally, includes software means, in the form of FMR.BAS, its associated subroutines, and FMR.EXEC, all associated with the foreign MTSO (by virtue of the coupling and information exchange between the cellular switch resident in the foreign MTSO, and the FMR processor) for performing the FMR system functions described above.

Finally, the FMR processor is described in an environment that is characterized by the physical collocation of that processor with the foreign switch. At present this configuration is deemed preferred. However, given the comprehensive Description of the invention set forth above, it seems clear that the functions of that processor are susceptible of performance by or integration into a cellular switch.

Correspondingly, although the FMR processor may be coupled to the foreign and home switches by any appropriate telecommunications transmission media, transfer of calls between the home and foreign systems are presently performed, because of external constraints, through the PSTN. It is possible, however, that at some time these constraints, whether technological or regulatory, will be mitigated, and substitute forms of call transfer will be permitted. It is submitted beyond peradventure that such substitute forms will reside within the scope of this invention as claimed below.

Accordingly, although there has been disclosed and described what at present is considered to be a preferred embodiment of a CMR system for automatically forwarding, to a foreign service area, calls placed to a roaming subscriber's home service area, it will be apparent to those having ordinary skill in the art that various modifications can be made to the described system without departure from the concept of the subject invention or the scope of the appended claims. ##SPC3##