Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-09-23
2001-01-30
Nguyen, Lee (Department: 2746)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S432300, C455S435100
Reexamination Certificate
active
06181939
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of processing mobile station data in a mobile communication system which comprises at least a first and a second mobile services switching centre, in which method: the subscriber data of a mobile station is registered in a visitor location register which corresponds to the mobile services switching centre the coverage area of which the mobile station enters, and the subscriber data of the mobile station are deleted from said visitor location register after the mobile station has left the coverage area of the mobile services switching centre which corresponds to the visitor location register. Furthermore, the invention relates to a mobile communication system comprising: a mobile station, at least a first and a second mobile services switching centre, and a visitor location register which corresponds to the first mobile services switching centre, comprising register means for registering in a memory means the subscriber data of the mobile station having entered the coverage area of the first mobile services switching centre, and deletion means for deleting the subscriber data of said mobile station from the memory means after the mobile station has left the coverage area of the first mobile services switching centre.
The present invention relates to maintaining the subscriber data of mobile stations, or subscriber stations, in a mobile communication system in a visitor location register which corresponds to the mobile services switching centre in the coverage area of which the mobile station is located. The invention is therefore suitable for use in a mobile communication system comprising at least two mobile services switching centres and visitor location registers corresponding thereto. In this context, the concept subscriber data refers to both the subscriber data of an individual mobile station and the data of a subscriber group.
DESCRIPTION OF RELATED ART
In a prior art mobile communication system, the subscriber data of a mobile station is stored in a home location register specified for the mobile station in question and, in addition thereto, in the visitor location register of the mobile services switching centre in the coverage area of which the mobile station is located at that time. When moving in the coverage area of the system, the mobile station of the prior art system continuously follows the location area indicated by the base station whose signals are best received by the mobile station. If the mobile station detects when moving from the radio coverage area of the base station to the radio coverage area of another base station that the location area of the new base station differs from that of the previous base station, then the mobile station performs a location update by sending a message via a radio path to the new base station. If the new location area belongs to the coverage area of a new mobile services switching centre, the visitor location register of the new mobile services switching centre sends a message to the home location register of the mobile station in question, notifying the home location register that the mobile station in question has entered the coverage area of the new mobile services switching centre. The subscriber data of the mobile station are in that case also registered in the new visitor location register. Furthermore, the home location register sends a message to the previous visitor location register (the coverage area of the mobile services switching centre the mobile station in question has left), reporting that the mobile station has entered the coverage area of the other mobile services switching centre. After receiving the message in question, the previous visitor location register deletes from its memory the subscriber data of the mobile station indicated in the message. If the mobile station in question belongs to a specific subscriber group, then the visitor location register does not delete the subscriber group data until the last mobile station belonging to the subscriber group leaves the coverage area of the mobile services switching centre in question.
It is a disadvantage of the above-described prior art solution that the subscriber data are deleted from the visitor location register almost immediately after the mobile station in question has left the coverage area of the mobile services switching centre which corresponds to the visitor location register. This means that when the same mobile station re-enters the coverage area of the mobile services switching centre in question, its subscriber data have been deleted from the visitor location register, in consequence of which the data have to be re-registered therein. Copying the subscriber data in question requires a relatively large amount of data transmission capacity. The situation is particularly problematic in a special network, such as a network used by authorities. For example, a police patrol may continuously patrol a specific area possibly composed of coverage areas of several different mobile services switching centres. In that case, the mobile station of the police patrol in question repeatedly leaves and re-enters the coverage area of a given mobile services switching centre.
In the prior art, an attempt is made to solve the above-described problem by storing the subscriber data in the visitor location register for a given period of time of a constant length, for example 10 minutes, from the moment the subscriber has left the coverage area of the mobile services switching centre corresponding to the visitor location register. However, this kind of time period of a constant length is not useful, since it alleviates the situation only in some cases, i.e. when the mobile station leaves the coverage area of the mobile services switching centre only for a short period of time (in this case, for less than 10 minutes). In addition, the prior art solution of the type is not able to adapt to the special needs of an individual mobile station.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above-mentioned problem by providing a solution by means of which it is easier to delete subscriber data in a more flexible manner from a visitor location register and take subscriber-specific differences into account. This objective is achieved by the method of the invention, which is characterized by comprising the steps of: defining an algorithm by means of which a storage time for the subscriber data of a given mobile station can be determined, the storage time indicating how long the subscriber data of the mobile station have to be stored after the mobile station has left the coverage area of the mobile services switching centre, storing in a memory means information on at least the entries of said mobile station into the coverage area of said mobile services switching centre, determining by means of said algorithm and information stored in the memory means the storage time for the subscriber data of said mobile station, and after the mobile station has left the coverage area of said mobile services switching centre, deleting the subscriber data of said mobile station from the visitor location register after the expiration of the storage time unless the mobile station has re-entered the coverage area of said mobile services switching centre.
The invention also relates to a mobile communication system to which the method of the invention can be applied. The mobile communication system of the invention is characterized in that the system comprises: monitor means storing in a memory information on at least the entries of said mobile station into the coverage area of the first mobile services switching centre, and control means determining, on the basis of the information stored in the memory by the monitor means, the storage time for the subscriber data of the mobile station, the storage time indicating how long the subscriber data of said mobile station have to be stored from the moment the mobile station has left the coverage area of the mobile services switching centre and controllin
Altera Law Group LLC
Nguyen Lee
Nokia Networks Oy
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