Tracking mobile radio telephone across cellular networks and call routing thereto

The present invention, however, by requiring the new visited system to order the home system to store a temporary location for the mobile upon call access allows the mobile to be paged within the new visited system. The temporary location is stored within the home system for the duration of the call, as is shown further in FIG. 5.

Returning to block 64, if the visited system determines that the signal it received is not a call access from a new visitor, it makes one last check to determine whether the signal was a call release from a non-registered visiting mobile phone at block 72. If a determination is made that the signal comprises a call release from a non-registered visiting mobile phone, the visited system continues to block 74 wherein it sends an order to the visiting mobile's home system to delete the previously stored temporary location ordered at block 70. Thus, upon call release, the visited system informs the home system of the release so that the home system can erase the temporary location. And finally, at block 76, the temporary location data is deleted from within the visited system; whereupon the process terminates at end block 18.

If at block 72, the home system determines that the signal was not a call release from a non-registered

-22visitor, the signal falls outside of the parameters of the present invention and the process returns to block 50 and a signal is awaited from a visiting mobile.

It should be noted that a temporary location could be stored with the home system, using the process described immediately above, upon call initiation. This would not, however, provide protection against multiple call accesses. A better solution, however, is to wait for a successful connection of the mobile subscriber to a voice channel or to a digital traffic channel. While the initial call access might be detected by more than one radio base station connection to more than one system, the voice channel connection criteria greatly diminishes the likelihood 'of a false call detection and thus increases the probability that the temporary location will permit routing of terminating calls to the mobile phone's actual physical location.

Referring now to FIG. 5, there is shown the process undertaken by a mobile's home system when the home system receives location data pertaining to one of its mobile subscribers. Beginning at block 80, the home system receives data concerning a mobile phone's location. At block 82, the home system ascertains whether the information received was registration location information. If the information is registration location information transmitted pursuant to block 58 of FIG. 4, the home system transmits a signal to the system last visited by the mobile. The signal transmitted at block 84 informs the last visited system that the mobile has vacated that visited system and proceeded on to another system. This information allows the last visited system to clear its records of the mobile. Next, at block 86, the mobile' s home system updates its own location data to indicate that the mobile subscriber is in a new visited

-23system. This step is necessary so that the home system may page the mobile when calls are received and directed to that mobile. Once the home system updates its own data regarding the mobile subscriber, there remains nothing further to do and the process is terminated at end block 18.

Returning to block 82 of FIG. 5, if the information received by the home system is not registration location information pertaining to one of its mobile subscribers, the process proceeds to block 88 where it is determined if the data received at block 80 was an order to store a temporary location for one of its subscribers. As will be recalled from the description of FIG. 4, an order to store a temporary location is received when the mobile subscriber initiates a call from within a visited system but does not register within that system. The visited system then transmits a signal to the mobile's home system, which signal corresponds to an order requiring the home system to store a temporary location for the mobile subscriber. The analysis performed within block 88 determines whether the signal received is such a temporary location order from a visited system. If the home system concludes that it has received an order to store a temporary location, the home system will not change the existing registration location data for that particular mobile subscriber, as illustrated by block 90. The home system retains the existing location data because the temporary location information is valid only for the duration of the subscriber's call. Once the subscriber terminates its call, the temporary location data is deleted. Upon completion of the temporary location call, the mobile phone rescans control channels. After rescanning the control channels the mobile may learn that it is located in a system to which ι

-24it has not registered and then the registration process of FIG. 4 will proceed.

Still referring to FIG. 5, after block 90, the home system stores the temporary location of its mobile subscriber; this occurs at block 92. The temporary location data enables the home system to forward calls received for the mobile, while the mobile is not within the home system. If the mobile subscriber has been provided with services such as call waiting or transfer upon busy, these services can be implemented in conjunction with the temporary location procedure. Since the temporary location data remains active only for the duration of the mobile's call, if the services described above are not provided to ’the mobile, the calling party hears a busy tone indicating that the mobile subscriber is presently occupied with another call. Thus, once the home system stores the temporary location for its mobile subscriber, it will have completed its tasks, at least until the mobile completes its call, and thus, proceed to the end block 18.

Still referring to FIG. 5, and returning to block 88, if the home system concludes that the signal received at block 80 is not an order to store a temporary location, it next considers whether the signal comprises an order to delete a temporary location at block 94. If the home system determines that the signal is an order to delete a temporary location, the process advances to block 96 where the temporary location is deleted. This completes the process and the home system finishes at end block 18. If the home system, at block 94 concludes that the signal was not an order to delete a temporary lo.cation, the home system returns to block 80 to await receipt of another signal.

-25Referring now to FIG. 6, there is shown the steps taken by a mobile phone's home system, pursuant to the principles of the present invention, when a call is received -for the subscriber while the subscriber has a temporary location assigned to it. At block 100, the mobile's home system receives data indicative of a call for the mobile. At block 102 the home system determines whether the call is to be routed to one of its subscribers. If the call is to be routed, the home system proceeds to block 104 where it ascertains whether or not a temporary location exists for the mobile subscriber to which the call is directed. If a temporary location does exist for the mobile subscriber, at block 106, the home system routes the call to the visited system indicated by the temporary location. If the mobile subscriber utilizes services such as call waiting or transfer upon busy, the visited system acts as appropriate, if the mobile does not avail itself to such services, a busy signal will be generated to the calling party. It should be stressed, that while the calling party may not be able to set up a voice channel with the mobile subscriber, by way of the temporary location, the home system is able to accurately locate the mobile subscriber so that the calling party can at least learn that the mobile subscriber is currently occupied with a different call.

Returning to block 104, if no temporary location exists for the mobile subscriber to which the call is to be routed, then the home system looks to block 108 and routes the call to the location indicated within the home system' s registration location data storage. This situation arises when the mobile subscriber's location data was generated through the process described in FIG. 4, i.e., registration access transmissions. Once the

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-26call is routed to the mobile subscriber the process is completed, as indicated by end block 18.

Thus, there has been described and illustrated herein, a method and apparatus for using temporary location for call routing in mobile telephone systems. However, those skilled in the art will recognize that many modifications and variations besides those specifically mentioned may be made in the techniques described herein without departing substantially from the concept of the present invention. Accordingly, it should be clearly understood that the form of the invention as described herein is exemplary only and is not intended as a limitation on the scope of the invention.

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