SYSTEM AND METHOD FOR RESTRICTING MOBILITY OF CELLULAR TELEPHONES

Abstract: A cellular telephone is restricted to using only predetermined cells. The first time (306) the telephone is used, it learns (308) the identity of the cell which services it and stores that identity in the telephone. Thereafter, a request (314) to be serviced by a cell whose identity is not stored in the telephone will be denied (316) unless it is to the service provider or to emergency personnel. If it is to the service provider, then the service provider can determine (318) whether the requested cell should be in the telephone as an approved cell.

Description: SYSTEM AND METHOD FOR RESTRICTING MOBILITY OF CELLULAR TELEPHONES BACKGROUND OF THE INVENTION I. Field of the Invention The present invention relates to cellular telephone service, and more particularly, to controlling the effective mobility of a cellular telephone. II. Related Art A significant advantage to cellular telephone technology is that it gives a user mobility. The user can travel about and use a cellular telephone in any area serviced by a cellular service provider. In some situations, such as for every remote locations or in newly developing nations with minimal existing phone service, cellular technology is selected because it is less expensive to install than a traditional land-line system which requires extensive installation of copper wiring. In such a situation, the cellular service provider intends for the cellular telephone to be used in the same manner as a conventional wireline telephone, that is, in a fixed location. However, there is little that can be done to prevent the use of such a cellular telephone as a mobile device. If the telephone can be given a suitable power source, the user can travel with the telephone and use it freely because the device uses cellular technology. Nonetheless, the telephone is intended for use as a wireline telephone in a fixed location, and the subscriber is billed only for such use. Typically, wireline rates are lower than cellular (mobile) rates. Mobile operation is not envisioned by the cellular service provider, and the subscriber is not billed at cellular rates. Hence there is a need for a system and method for restricting the mobility of such a telephone, so that a user can only use the device in a relatively limited geographical area, as intended by the cellular service provider. This would prevent use of the device in a mobile manner for which the subscriber is not billed. SUMMARY OF THE INVENTION The present invention provides a system and method through which a cellular service provider can control the mobility of a cellular telephone that is normally treated as a wireline telephone for billing purposes. The cellular telephone must identify which cells it can access directly from some fixed location, such as the home of a user. For purposes of this discussion, a cellular telephone can directly access a cell if the telephone can establish usable radio frequency (RF) contact with the cell without requiring any intervening relays. The identities of the directly accessible cells are recorded in a section of the memory of the cellular telephone known hereinafter as the cell buffer. Subsequent use of the cellular telephone at wireline rates can only take place if the cellular telephone is in a geographic region determined by these cells, known hereinafter as the home region of the telephone. In one embodiment of the invention, for example, the home region comprises those locations from which the cellular telephone has direct access to any of the cells listed in its cell buffer. If the cellular telephone is not in the home region, use of the cellular telephone at wireline billing rates is prevented. In an embodiment of the invention, operation of the cellular telephone is permitted outside the home region, but only at cellular billing rates. In another embodiment of the invention, operation of the cellular telephone outside the home region is prevented entirely. Features and advantages The present invention has the feature of enabling a cellular telephone to identify and record the cells which it can access directly. The present invention has the additional feature of enabling determination of a home region for the cellular telephone. The present invention has the additional feature of affecting the operability of the cellular telephone or changing its billing rate outside the home region. The present invention has the advantage of allowing a cellular service provider to control the effective mobility of a cellular telephone. The present invention has the further advantage of having flexibility of implementation. The invention can be implemented in software, hardware, or a combination thereof. BRIEF DESCRIPTION OF THE FIGURES The foregoing and other features and advantages of the invention will be apparent from the following, more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings. FIG. 1 illustrates a portion of an exemplary cellular communications system. FIG. 2 illustrates an exemplary cell buffer, according to an embodiment of the invention. FIG. 3 is a flow chart illustrating the processing of a cellular telephone call and the decision process regarding permissibility of the call, according to an embodiment of the invention. FIG. 4 illustrates a cellular telephone in contact with one of the cells identified in its cell buffer, according to an embodiment of the invention. FIG. 5 illustrates a cellular telephone in contact with a cell not identified in its cell buffer, according to an embodiment of the invention. FIG. 6 is a flow chart illustrating the process of identifying directly accessible cells and recording their identities, according to an embodiment of the invention. FIG. 7 is a flow chart illustrating the processing of a cellular handoff, according to an embodiment of the invention. FIG. 8 illustrates a generic computer system which may be used to perform the operations of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS I. Overview The present invention provides a system and method through which a cellular service provider can control the mobility of a cellular telephone. To do this, the cellular telephone must identify which cells it can access directly from some fixed location, such as the home or office of a user. This fixed location is known hereinafter as the home location. The identities of the directly accessible cells are recorded in a portion of the memory of the cellular telephone, known as a cell buffer. Subsequent use of the telephone can take place only if the cellular telephone is in a geographic region determined by these cells. For purposes of this discussion, this geographic region is known as the home region. Methods by which such a home region can be determined are described below. If the cellular telephone is not in its home region, use of the cellular telephone at the usual wireline billing rates is prevented. In an embodiment of the invention, operation of the cellular telephone is permitted outside this region, but only at cellular billing rates. In another embodiment of the invention, operation of the cellular telephone outside this region is prevented completely. II. Apparatus The present invention operates in the context of a cellular telephone system, the general architecture of which is known to persons skilled in the relevant art. A portion of an exemplary cellular telephone system is illustrated in FIG. 1. A cellular telephone 101 is shown in a location where it can reach any one of cells 102, 104, and 106 directly. Once in contact with a cell, cellular telephone 101 can place or receive a call through the cellular system, via that cell. Note that at any given time there will be cells which are not accessible by the cellular telephone 101. A cell 108 is one such cell. As will be described below, the cells which can be accessed directly by cellular telephone 101 from a home location (such as a user's home or office) are used to determine a home region. It is within the home region that cellular telephone 101 may operate at the usual wireline billing rates, according to the present invention. Contained within cellular telephone 101 is a cell buffer which is used to record the identities of cells that are directly accessibleby cellular telephone 101. FIG. 2 illustrates such a buffer. A cell buffer 202 comprises a plurality of memory locations, illustrated as memory locations 204A through 204H. Memory locations 204A through 204C contain identifiers 102, 104, and 106 respectively. These identifiers correspond to the cells directly accessible by cellular telephone 101 from its home location. III. Process The process of the present invention requires a cellular telephone to learn the identities of the cells accessible from a defined location. Use of the cellular telephone at wireline billing rates is permitted only if the cellular telephone is in a home region determined by these cells. If the cellular telephone has moved to a location outside this home region, use of the cellular telephone at wireline billing rates is not permitted. A. Call placement The process of the invention, according to one embodiment, is described in greater detail in FIG. 3. In a step 304, the user attempts to place a call from some location using a cellular telephone. In a step 306, the process asks whether this is the first call originated by the cellular telephone. If so, in a step 308 the cellular telephone must learn the identities of the cells that it can directly access. This learning process is described below. Once the learning process is completed, in a step 310 the user may proceed with the call. Note that in an alternative embodiment of the invention, the learning process may take place as soon as the cellular telephone is powered on, even before any attempt to place a call. If, in step 306, it is determined that this is not the first call, then the learning process must have taken place previously. In this case a set of cell identifiers will already have been stored in the cell buffer of the cellular telephone. In the embodiment of the invention illustrated in FIG.3, operation of the cellular telephone at wireline rates is permitted only if one or more of the cells identified in the cell buffer is directly accessible by the cellular telephone. In a step 312, therefore, the process asks whether any of the cells listed in the cell buffer are accessible by the cellular telephone from its present location. If so, the call may proceed in step 310. If none of the cells listed in the cell buffer are accessible by the cellular telephone, then the cellular telephone must have moved some distance from its home location, where it had initially performed learning step 308. Normally, a call in this situation would be denied by the present invention. In an embodiment of the invention, however, an exception is made for calls to the cellular service provider and for emergency calls, e.g. 911. Therefore, in a step 314 the process asks whether the call is being made to the cellular service provider. If not, then in a step 316 the call is denied, according to an embodiment of the invention. If the call is directed to the cellular service provider, the call is allowed in a step 317. The cellular service provider must then decide, in a step 318, whether the cellular telephone's apparent relocation should be authorized. If the relocation is authorized, then the cellular telephone must undergo a learning process 319, identical to learning process 308, to learn the identities of the cells accessible by the cellular telephone from its new location. If the relocation is not authorized in step 318, then processing halts. FIG. 4 illustrates the situation where one of the cells originally listed in the cell buffer is directly accessible by the cellular telephone. Here cellular telephone 101 can directly access cell 102, which is one of the cells whose identifier is recorded in the cell buffer. In such a situation, a call placed by cellular telephone 101 will be allowed according to the embodiment of the invention illustrated in FIG. 3. FIG. 5 illustrates the situation where none of the cells originally listed in the cell buffer is directly accessible by the cellular telephone. Here cellular telephone 101 can directly access only cell 108, which is not one of the cells whose identifier was recorded in its cell buffer. In such a situation, a call placed by cellular telephone 101 will not be allowed unless the call is directed to the cellular service provider, according to the embodiment of the invention illustrated in FIG. 3. Note that in other embodiments of the invention, an unauthorized call (that is, a call placed by the cellular telephone while outside the home region and directed to a party other than the cellular service provider) will not be denied. In an alternative embodiment, such a call will be permitted, but will be billed at cellular rates, rather than wireline rates. Moreover, in alternative embodiments of the invention, the home region may be determined in ways other than what is described above with respect to FIG. 3. For example, the home region may comprise the locations from which all the cells identified in the cell buffer, rather than just one cell, are directly accessible. In this case, unrestricted operation at wireline rates is only permitted if all cells in the cell buffer are directly accessible by the cellular telephone. Alternatively, the home region may comprise the locations from which some predetermined subset of cells is directly accessible. Direct access to any two of the cells identified in the cell buffer, for example, might be required before unrestricted operation at wireless rates is permitted. In another alternative embodiment, a cellular telephone is considered to be in the home region unless a cell not listed in the cell buffer is directly accessible. In this case, direct access to some other cell not listed in the cell buffer implies that the cellular telephone is no longer in the home region. In yet another alternative embodiment, a cellular telephone is considered to be in the home region as long as signals from cells identified in the cell buffer are sufficiently strong. Here, receiving a weak signal from a cell identified in the cell buffer implies that the cellular telephone has strayed outside the home region, and unrestricted operation at wireless rates will not be permitted. B. Call receipt Processing for call receipt is entirely analogous to that of call placement. Receiving a call at wireline billing rates is permitted if the cellular telephone is in a home region determined by the cells identified in the cell buffer. If the cellular telephone has moved to a location outside this home region, receipt of a call at wireline billing rates is not permitted. Note that in an embodiment of the invention, an exception is made for calls originating from the cellular service provider. Here, receipt of such calls will be permitted at wireline rates regardless of the location of the cellular telephone. C. Learning The invention requires the cellular telephone to be able to record the identities of cells which can be directly accessed from a given location. This learning process is illustrated in FIG. 6. In a step 604, the cell buffer of a cellular telephone is cleared. In a step 606, the process asks whether any new cell, that is, one not currently listed in the cell buffer, is directly accessibleby the cellular telephone. If there are no such cells, then processing ends at a step 607. If there is such a cell, then in a step 608 the process asks whether the cell buffer is currently full. If the cell buffer is full, then no more cell identifiers can be added to the cell buffer, and processing ends at step 607. If the cell buffer is not full, then, in a step 610, the identifier of the cell is added to the cell buffer. The process then repeats with step 606. The learning process continues until either no more accessible cells are found or the cell buffer becomes full. D. Handoff A special problem may arise if the cellular telephone originates a call from a location in the home region, then moves to another location during the call, such that a cell handoff is required. The invention handles this by either ending the call or changing to cellular billing rates if the new cell (to which the handoff is to be made) is not identified in the cell buffer. The process for dealing with such a handoff problem is illustrated in FIG. 7. In a step 704 the process asks whether a handoff is required. If so, in a step 706 the process asks whether the identifier of the newly accessible cell (to which the connection is about to be handed) is listed in the cell buffer. If this cell is not listed in the cell buffer, then the call is terminated in a step 708. In an alternative embodiment, the call will proceed in this situation, but at cellular rates. If, as determined in step 706, the newly accessible cell is listed in the cell buffer, then the handoff proceeds in a step 710. In a step 712, the call proceeds. IV. Environment The present invention is preferably implemented in software. Alternatively, the invention may be implemented using hardware or a combination of hardware and software. Consequently, the invention may be implemented in a computer system or other processing system. An example of such a computer system 800 is shown in FIG. 8. The computer system 800 includes one or more processors, such as processor 804. The processor 804 is connected to a communication infrastructure 806 (for example, a bus or network). Various software implementations are described in terms of this exemplary computer system. After reading this description, it will become apparent to a person skilled in the relevant art how to implement the invention using other computer systems and/or computer architectures. Computer system 800 also includes a main memory 808, preferably random access memory (RAM), and may also include a secondary memory 810. The secondary memory 810 may include, for example, a hard disk drive 812 and/or a removable storage drive 814, representing a floppy disk drive, a magnetic tape drive, an optical disk drive, etc. The removable storage drive 814 reads from and/or writes to a removable storage unit 818 in a well known manner. Removable storage unit 818, represents a floppy disk, magnetic tape, optical disk, etc. which is read by and written to by removable storage drive 814. As will be appreciated, the removable storage unit 818 includes a computer usable storage medium having stored therein computer software and/or data. In alternative implementations, secondary memory 810 may include other similar means for allowing computer programs or other instructions to be loaded into computer system 800. Such means may include, for example, a removable storage unit 822 and an interface 820. Examples of such means may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an EPROM, or PROM) and associated socket, and other removable storage units 822 and interfaces 820 which allow software and data to be transferred from the removable storage unit 822 to computer system 800. Computer system 800 may also include a communications interface 824. Communications interface 824 allows software and data to be transferred between computer system 800 and external devices. Examples of communications interface 824 may include a modem, a network interface (such as an Ethernet card), a communications port, a PCMCIA slot and card, etc. Software and data transferred via communications interface 824 are in the form of signals 828 which may be electronic, electromagnetic, optical or other signals capable of being received by communications interface 824. These signals 828 are provided to communications interface 824 via a communications path 826. Communications path 826 carries signals 828 and may be implemented using wire or cable, fiber optics, a phone line, a cellular phone link, an RF link and other communications channels. In this document, the terms "computer program medium" and "computer usable medium" are used to generally refer to media such as removable storage drive 814, a hard disk installed in hard disk drive 812, and signals 828. These computer program products are means for providing software to computer system 800. Computer programs (also called computer control logic) are stored in main memory 808 and/or secondary memory 810. Computer programs may also be received via communications interface 824. Such computer programs, when executed, enable the computer system 800 to implement the present invention as discussed herein. In particular, the computer programs, when executed, enable the processor 804 to implement the process of the present invention. Accordingly, such computer programs represent controllers of the computer system 800. In a preferred embodiment of the invention, the processes in which a cellular telephone is permitted (or denied) the placement or receipt of a call, learns and records the identities of the accessible cells, and performs cell handoff s, are all performed by computer control logic. Where the invention is implemented using software, the software may be stored in a computer program product and loaded into computer system 800 using removable storage drive 814, hard drive 812 or communications interface 824. V. Conclusion While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in detail can be made therein without departing from the spirit and scope of the invention. Thus the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. We claim:

Claims: CLAIMS 1. A method of restricting the mobility of a cellular telephone in a cellular communications system, the method comprising the steps of: (a) identifying cells that are directly accessible by the cellular telephone when the cellular telephone is in a home location; (b) recording identities of said cells in a cell buffer internal to the cellular telephone; and (c) preventing the cellular telephone from operating at predetermined wireline rates when the cellular telephone is outside a home region determined by said cells. 2. The method of claim 1, wherein step (c) comprises: (i) preventing placement of outgoing calls to parties other than a cellular service provider or emergency agency when the cellular telephone is outside said home region; (ii) preventing reception of incoming calls from parties other than said cellular service provider or from an emergency agency when the cellular telephone is outside said home region; (iii) allowing placement of said outgoing calls when the cellular telephone is in said home region; and (iv) allowing reception of said incoming calls when the cellular telephone is in said home region. 3. The method of claim 1, wherein step (c) comprises: (i) allowing placement of said outgoing calls regardless of a location of the cellular telephone; (ii) billing at said predetermined wireline rates for said outgoing calls placed when the cellular telephone is in said home region; (iii) billing at predetermined cellular rates for said outgoing calls placed when the cellular telephone is not in said home region; (iv) allowing receipt of said incoming calls regardless of a location of the cellular telephone; (v) billing at said predetermined wireline rates for said incoming calls received when the cellular telephone is in said home region; and (vi) billing at said predetermined cellular rates for said incoming calls received when the cellular telephone is not in said home region. 4. The method of claim 1, wherein step (c) comprises terminating an ongoing call when the cellular telephone attempts to handoff to a cell not identified in said cell buffer. 5. The method of claim 1, wherein step (c) comprisesbilling for said ongoing call at said predetermined cellular rates when the cellular telephone attempts to handoff to said cell not identified in said cell buffer. 6. The method of claim 1, wherein said home region comprises geographic locations from which the cellular telephone can directly access a subset of said cells whose identities are recorded in said cell buffer, wherein said subset is of a predetermined size that is less than the total number of operating cells in a cellular communications system. 7. The method of claim 1, wherein said home region comprises geographic locations from which the cellular telephone can directly access all of said cells whose identities are recorded in said cell buffer. 8. The method of claim 1, wherein said home region comprises geographic locations from which the cellular telephone can directly access at least one of said cells whose identities are recorded in said cell buffer. 9. The method of claim 1, wherein said home region comprises geographic locations where: (i) all of said cells whose identities are recorded in said cell buffer are directly accessible by the cellular telephone; and (ii) signals coming from said cells and received by the cellular telephone have a signal strength greater than or equal to a predetermined minimum signal strength. 10. The method of claim 1, wherein said home region comprises geographic locations where, apart from said cells whose identities are recorded in said cell buffer, no other cells are directly accessibleby the cellular telephone. 11. A system for restricting the mobility of a cellular telephone in a cellular communications system, the system comprising: (i) identifying means for identifying cells that are directly accessible by the cellular telephone when the cellular telephone is in a home location; (ii) recording means for recording identities of said cells in a cell buffer internal to the cellular telephone; and (iii) preventing means for preventing the cellular telephone from operating at predetermined wireline rates when the cellular telephone is outside a home region determined by said cells. 12. The system of claim 11, wherein said preventing means comprises: (i) placement preventing means for preventing placement of outgoing calls to parties other than a cellular service provider or 911 when the cellular telephone is outside said home region; (ii) reception preventing means for preventing reception of incoming calls from parties other than said cellular service provider and 911 when the cellular telephone is outside said home region; (iii) home region placement allowing means for allowing placement of said outgoing calls when the cellular telephone is in said home region; and (iv) home region reception allowing means for allowing reception of said incoming calls when the cellular telephone is in said home region. 13. The system of claim 11, wherein said preventing means comprises: (i) placement allowing means for allowing placement of said outgoing calls regardless of a location of the cellular telephone; (ii) outgoing wireline billing means for billing at said predetermined wireline rates for said outgoing calls placed when the cellular telephone is in said home region; (iii) outgoing cellular billing means for billing at predetermined cellular rates for said outgoing calls placed when the cellular telephone is not in said home region; (iv) receipt allowing means for allowing receipt of said incoming calls regardless of a location of the cellular telephone; (v) incoming wireline billing means for billing at said predetermined wireline rates for said incoming calls received when the cellular telephone is in said home region; and (vi) incoming cellular billing means for billing at said predetermined cellular rates for said incoming calls received when the cellular telephone is not in said home region. 14. The system of claim 11, wherein said preventing means comprises handoff terminating means for terminating an ongoing call when the cellular telephone attempts to handoff to a cell not identified in said cell buffer. 15. The system of claim 11, wherein said preventing means comprises cellular handoff billing means for billing for said ongoing call at said predetermined cellular rates when the cellular telephone attempts to handoff to said cell not identified in said cell buffer. 16. The system of claim 11, wherein said home region comprises geographic locations from which the cellular telephone can directly access a subset of said cells whose identities are recorded in said cell buffer, wherein said subset is of a predetermined size that is less than the total number of operating cells in a cellular communications system. 17. The system of claim 11, wherein said home region comprises geographic locations from which the cellular telephone can directly access all of said cells whose identities are recorded in said cell buffer. 18. The system of claim 11, wherein said home region comprises geographic locations from which the cellular telephone can directly access at least one of said cells whose identities are recorded in said cell buffer. 19. The system of claim 11, wherein said home region comprises geographic locations where: (i) all of said cells whose identities are recorded in said cell buffer are directly accessible by the cellular telephone; and (ii) signals coming from said cells and received by the cellular telephone have a signal strength greater than or equal to a predetermined minimum signal strength. 20. The system of claim 11, wherein said home region comprises geographic locations where, apart from said cells whose identities are recorded in said cell buffer, no other cells are directly accessibleby the cellular telephone. 21. A computer program product comprising a computer usable medium having computer readable program code means embodied in said medium for causing an application program to execute on a computer that restricts the mobility of a cellular telephone in a cellular communications system, computer readable program code means comprising: (a) a first computer readable program code means for causing the computer to identify cells that are directly accessible by the cellular telephone when the cellular telephone is in a home location; (b) a second computer readable program code means for causing the computer to record identities of said cells in a cell buffer internal to the cellular telephone; and (c) a third computer readable program code means for causing the computer to prevent the cellular telephone from operating at predetermined wireline rates when the cellular telephone is outside a home region determined by said cells.

Inventors: HOLCMAN ALEJANDRO R, KAPLAN DIEGO A, HOLCMAN, ALEJANDRO, R., KAPLAN, DIEGO, A.
Applicants: QUALCOMM INC, QUALCOMM INCORPORATED
Application year: 2000
Main classification: H04Q7
IPC codes: H04M3, H04M15, H04W4