Patent Publication Number: US-2009221328-A1

Title: Method for operating a mobile communications system and corresponding system mobile communications system

Description:
The invention relates to a method for operating a mobile communications system, which comprises a multitude of radio cells and at least one mobile communications terminal with a subscriber identification module, the operation ensuing according to the whereabouts of the communications terminal. The invention additionally relates to a mobile communications system for implementation of this method. 
     In mobile radio communications, it is known to assign to the mobile telephone subscribers an individual subscriber area, the so-called home zone. The home zone corresponds to a defined geographic area, usually the immediate environs of the subscriber&#39;s place of residence, in which the subscriber can make telephone calls at particularly favorable conditions. Provision is made in this context to indicate to the subscriber on the communications terminal when he located is within the home zone, for example in the form of a home-zone symbol. When this home-zone symbol is displayed on the communications terminal, the subscriber knows that he can make telephone calls at a more favorable tariff. The known methods are based on geographic data, which are broadcast via CBC (cell broadcast), analyzed in the communications terminal, and compared with the geographic location of the subscriber&#39;s place of residence. Geographic location data is being broadcast by base stations (fixed radio stations) of the mobile radio communications system. This solution is technically complex, as a check must be performed in the communications terminal, as to whether the geographic location of the base station corresponds with the area, data of the home zone. 
     It is the object of the invention to provide a mobile communications system and method for operating the same that permits a simple and reliable verification whether a communications terminal is located within a certain subscriber area, at which time corresponding actions may be initiated if appropriate. 
     This object is met according to the invention with a method having the characteristics of claim  1  and a device having the characteristics of claim  13 . 
     Preferred embodiments and advantageous improvements of the invention are disclosed in the dependent claims. 
     In accordance with the invention. at least one subscriber area is established within a total geographic area covered by the mobile communications system, and those radio cells are determined that are located at least partially within the subscriber region. The cell identifications of the determined radio cells are transmitted to the communications terminal and subscriber identification module of the subscriber and stored there. A comparison then takes place to determine whether the cell identifications of the radio cells that currently serve the communications terminal correspond with the cell identifications stored in the subscriber identification module, at which time, if appropriate, a special operating mode is switched on that is assigned to the subscriber area. 
     The invention permits the visualization on a mobile communications terminal of its location within certain freely definable geographic areas—also called subscriber areas—of a mobile communications network, without using the cell broadcast service. No broadcast of special geographic location data of the base stations is needed, like it is the case with other known methods, e.g., broadcasting of the geographic location of the base station via cell broadcast. 
     Additionally, it is possible with the invention to establish any desired number of geographically different subscriber areas without additional technical expenditure, as the base stations do not need to be located in a contiguous area. With the conventional technology by means of cell broadcasting and transmission of geographic coordinates, this is possible only if the program code (applet) on the communications terminal or subscriber identification module supports multiple geographic zones. 
    
    
     
       A simple exemplary embodiment of the invention will be described in more detail below, in conjunction with the drawings. 
         FIG. 1  shows a block diagram of the inventive system and of its most significant components. 
         FIG. 2  shows a schematic depiction of a section of the cell structure of a cellular mobile communications network with two defined subareas. 
     
    
    
     As one can see from  FIG. 2 , a cellular mobile communications system comprises a multitude of radio cells C 1 -C 11 . Each radio cell C 1 -C 11  is supplied with radio signals by at least one base station (fixed radio station). The base stations are represented by a black dot in each radio cell. 
     The inventive solution essentially consists of two parts: 
     1. Advance Calculation of the Required Geographic Data:
         An advance calculation of geographic locations, i.e., a calculation as to which terminal is to display a geographic visualization in which cell region, is performed per subscriber. The cell regions do not need to be contiguous.       

     2. Visualization on the Communications Terminal:
         The location of the communications terminal within a defined subscriber area is verified and displayed to the subscriber.       

     1. Calculation of the Geographic Data 
     Reference now being made to  FIG. 1  the required geographic calculations are performed offline in a network element  1  of the communications system. Each mobile telephone subscriber can define personal subscriber areas in which he can communicate at special rates or table advantage of special communications services. A subscriber area of this type is intended to be created, for example, around a subscriber&#39;s place of residence. 
     Reference now being made to  FIG. 2 , the place of residence of a subscriber is defined by the geographic point P 1 . The associated subarea is then established by the network operator as a circular area with the center point P 1  and specified radius r 1 . In the network element  1 , relevant mobile radio cells for the desired subscriber area, i.e., those radio cells that are located at least partially within the circular area P 1 , r 1 , are now identified with the aid of network planning maps. In the depicted example, these are the radio cells C 2 , C 4  and C 5 . Then the associated cell identifications (cell IDs) CID 2  CID 4 . and CID 5  are determined. The subscriber region that was determined for the subscriber, as defined by the radio cells C 2 , C 4 , and C 5  with the cell identifications CID 2 , CID 4 , and CID 5 , is stored together with other subscriber data in a database  2 . The determined cell identifications CID 2 , CID 4  and CID 5  are then transmitted via the base station subsystem  3  (BSS) of the mobile communications network via the air interface (OTA: over the air) to the communications terminal  4  and subscriber identification module  5  (SIM card) of the subscriber and stored there. 
     The database  2  contains data of all subscribers for whom a subscriber region was established, the associated cell identifications. and information as to whether the download to the SIM card  5  of the subscriber was successful. 
     Transmission of the cell identifications can be repeated if the communications terminal  4  or SIM card  5  can temporarily not be reached. The base station subsystem  3  receives an acknowledgement from the SIM card  5  if the download was successful, which is then transmitted to the network element  1 . 
     Before the service can be used, a one-time download of a SIM application is required per subscriber for the display of geographic information. This application is transmitted in the form of an executable pro-ram code from the network element  1  via the base station subsystem  3  to the communications terminal  4  and SIM card  5  and executed there. 
     2. Visualization 
     On the SIM card  5  the SIM application continually checks, in which radio cell the communications terminal  4  is currently located. In a manner known per se each base station continually sends out a unique cell identification in the radio cell that it supplies, which can be received and analyzed by the communications terminal  4 . The SIM card  5  then checks whether the cell identification of the current radio cell, for example radio cell C 2  with CID 2 , corresponds with one of the stored cell identifications CID 2 , CID 4 , CIDS assigned to the subscriber area. If a correspondence is determined, a visualization takes place in the form of a symbol  6  and/or text  7  on the display of the communications terminal  4  ( FIG. 2 ). The subscriber is thus being informed that he is located within his personal subscriber area. In addition to, or alternatively to the visualization an acoustic signal  8  may be emitted to the subscriber as well. 
     The SIM application compares, both during every log-in of the communications terminal to the communications network as well as during each change of location of the communications terminal  4 , the respective current cell identifications to which the terminal is currently logged-in with the cell identifications that are stored on the SIM card  5 . If they correspond, the visualization begins. If they no longer correspond, the visualization ends (in the example: in cells C 2 , C 4 , C 5  the symbol lights up, in the other cells it is switched off). 
     In accordance with the invention, it is possible to define not only one subscriber area per subscriber, but multiple subscriber areas as well. In  FIG. 2 , an additional subscriber area P 2 , r 2  is depicted, which is assigned to the radio cell C 11  with the cell identification CID 11 . 
     All of the utilized functions are standard SIM toolkit functions, so that no technical changes to the communications terminal or SIM card need to be made.