METHOD OF DETECTING TERMINAL MOVEMENT, AND CELLULAR RADIO NETWORK

Abstract: The invention relates to a method of detecting terminal (130) movement, and a cellular radio network. The terminal (130) is a wireless subscriber terminal (210) or a home repeater (220). The method comprises the following steps: the terminal (130) stores a cell list at given intervals; the terminal (130) compares the cell lists stored at given intervals; in case a sufficient number of changes has occured in the cell lists, the terminal (130) concludes that it is moving; the terminal (130) sends an alarm regarding its movement to the network part. By using terminals implementing the method, operators may supply subscribers with cost-effective subscriber interfaces.

Description: METHOD OF DETECTING TERMINAL MOVEMENT, AND CELLULAR RADIO NETWORK FIELD OF TECHNOLOGY The invention relates to a method of detecting terminal movement in a cellular radio network comprising a network part and at least one terminal, the network part comprising base stations, and a base station having a coverage area, or cell, and the terminal having a bi-directional radio connection to the base station of the home cell, and the terminal keeping a cell list over the identities of the base stations it hears. PRIOR ART Cellular radio networks are used to replace a public fixed telephone network, the system comprising a terminal which is in connection with what is known as the home cell base station. Such a system is called a wireless subscriber interface (Wireless Local Loop). As the telephone operator monopolies break down, the new operators joining the competition may offer a subscriber a competitively priced interface by means of such a system. Cables do not have to be laid at the customers premises and this causes savings in building the infrastructure of the network. This kind of a technology provides a good chance to supply subscribers with cost-effective subscriber interfaces also in sparsely inhabited areas. Figure 2 shows two different ways to implement a wireless subscriber interface. A base station 120 has a bi-directional radio connection 122 to a terminal 210, 220. The terminal may be a wireless subscriber terminal 210 or a home repeater 220. The home repeater 220 transmits the bi-directional radio connection 122 to a mobile station 230 by using a bi-directional radio connection 202. Usually the mobile station 230 is a mobile telephone. In both implementations a user 204, 206 may take along the wireless subscriber terminal 210 or the mobile station 230 in a restricted area, e.g. in the home yard or the home block, and pay for the connection according to the tariffs of a pub- lie fixed telephone network. A major problem with the use of such systems is preventing misuse of the interface. It is known that the services of a fixed telephone network are considerably less expensive than those of a cellular radio network. A terminal of the system is comparable with a device connected to a fixed telephone net- work: it only operates at the site where it is installed. A subscriber might find it tempting to take along the terminal and use it outside the area of the home cell. This means that the subscriber can utilize the mobility of the terminal, but at the prices of a fixed telephone network. In order to prevent misuse, the terminal has to be able to detect its movements and to prevent misuse. In accordance with prior art, a GPS receiver may be installed in the terminal for easy detection of movement. A major drawback of this solution are the extra costs incurred. CHARACTERISTICS OF THE INVENTION It is the object of the present invention to provide a cost-effective method of detecting terminal movement and preventing misuse of the terminal. This is achieved by means of the method described in the preamble, characterized in that the method comprises the following steps: A) the terminal stores a cell list at given intervals, B) the terminal compares the cell lists stored at given intervals, C) in case a sufficient number of changes has occurred in the cell lists, the terminal concludes that it is moving, D) the terminal sends an alarm regarding its movement to the network part. The invention also relates to a system of detecting terminal move- ment in a cellular radio network comprising a network part and at least one terminal, the network part comprising base stations, and a base station having a coverage area, or cell, and the terminal having a bi-directional radio connection to the base station of the home cell, and the terminal keeping a cell list over the identities of the base stations it hears. The system is characterized in that the terminal comprises means for storing a cell list at given intervals, means for comparing the cell lists stored at given intervals, means for detecting its movement in case a sufficient number of changes has occurred in the cell lists, means for sending an alarm regarding its movement to the network part. The method according to the invention provides a plurality of significant advantages. The method does not cause expensive extra costs in the equipment used. The method provides efficient means for detecting terminal movement and preventing its misuse either by changing the price of the service or by terminating the connection. According to the method, the user is, however, warned if inadvertent movement outside the agreed operation range is taking place. The method allows the user to move e.g. in the home yard or the home block. The method provides advantages both to the subscribers and to the operators: The subscribers get cheaper calls and can move in a restricted area, the operators again can offer new competitive services without fear of misuse. The system according to the invention provides the same advantages as have been described above in connection with the method. The preferred embodiments of the invention and other more detailed embodiments emphasize the advantages of the invention. DESCRIPTION OF THE DRAWINGS In the following the invention will be described in more detail with reference to examples according to the attached drawings, in which Figure 1 shows a cellular radio network of the invention, Figure 2 shows the different types of the terminal of the invention already described above, Figure 3 shows the parts of the terminal of the invention that are relevant to the implementation of the method according to the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 shows the parts of the cellular radio network of the invention that are relevant to the invention. The network comprises a network part and at least one terminal 130. As stated above, the terminal 130 may be a wireless subscriber terminal or a home repeater. In this description a network part refers to all other parts of a cellular radio network expect for the terminal. The network part comprises base stations 120, 172 to 186. Each base station 120, 172 to 186 has a coverage area, or cell, 100 to 116. The terminal 130 has a bi-directional radio connection 122 to the base station 120 of the home cell 100. In addition the terminal 130 keeps a cell list over the identities of the base stations 120, 172, 174, 178, 180, 184, 186 it hears. The terminal 130 does not hear the base stations 176, 182, because their cells are too far from the terminal 130. If the terminal 130 moves to the area of e.g. the cell 106, the list over the base stations it hears changes, and this is detected when carrying out the steps of the method. The method of detecting movement comprises the following steps: A) the terminal 130 stores the cell list at given intervals, B) the terminal 130 compares the cell lists stored at given intervals, C) in case a sufficient number of changes have occurred in the cell lists, the terminal 130 concludes that it is moving, D) the terminal 130 sends an alarm regarding its movement to the network part. In a preferred embodiment of the method, the changes in the cell list during a given period of time are compared. A given time period may show very different values. It may be an hour, for example, or it may be said given interval at which the cell lists are stored. This means that in the latter case the new and previous cell lists stored are compared. If desired, the method may be modified by adding the following step: B') the terminal 130 issues a warning of excessive movement in good time before the alarm regarding movement is sent to the network part. When the user moves outside the agreed area of use in spite of a warning, misuse is prevented by having the network part terminate a bi-direc- tional radio connection 122 in which one of the parties is a terminal 130 of whose movement an alarm has been received. However, the procedure in certain situations is that the network changes the pricing of the use of a bi-directional radio connection 122 in which one of the parties is a terminal 130 of whose movement an alarm has been received. Figure 3 shows the essential parts of the terminal of the system of the invention shown in Figure 1 : an antenna 300, a duplex filter 310, a transmitter 320, a receiver 330, a control unit 340, a memory means 350, and a user interface 360. The structure and operation of the terminal are known from prior art and not described here in more detail. The terminal 130 comprises means 350 for storing a cell list at given intervals. The terminal also comprises means 340 for comparing the cell lists stored at given intervals, and means 340 for concluding its movement in case a sufficient number of changes have occurred in the cell lists. The terminal further comprises means 350, 340, 320, 310, 300 for sending an alarm regarding its movement to the network part. In a preferred embodiment the terminal 130 comprises means 360 for issuing a warning of excessive movement in good time before the alarm regarding its movement is sent to the network part. The warning may be issued e.g. as text, a light signal, or voice. The simplest way of implementing the invention is to convert the steps of the method, carried out in the described means, into executable soft- ware. The software may be stored in the memory means 350 and executed in the control unit 340. Thus the software controls the operation of the means 300, 310, 320, 330, 350, and 360. The equipment required by the invention may also be realized by general or signal processors or by independent logic. Even though the invention has been explained in the above with reference to the example in accordance with the accompanying drawings, it is obvious that the invention is not restricted to it but can be modified in a variety of ways within the scope of the inventive idea disclosed in the attached claims.

Claims: CLAIMS 1. A method of detecting terminal movement in a cellular radio network comprising a network part and at least one terminal (130), the network part comprising base stations (120, 172 to 186), and a base station (120, 172 to 186) having a coverage area, or cell (100 to 116), and the terminal having a bi-directional radio connection (122) to the base station (120) of the home cell (100), and the terminal (130) keeping a cell list over the identities of the base stations (120, 172, 174, 178, 180, 184, 186) it hears, characterized in that the method comprises the following steps: A) the terminal (130) stores a cell list at given intervals, B) the terminal (130) compares the cell lists stored at given intervals, C) in case a sufficient number of changes has occurred in the cell lists, the terminal (130) concludes that it is moving, D) the terminal (130) sends an alarm regarding its movement to the network part. 2. A method as claimed in claim ^characterized in that the terminal (130) is a wireless subscriber terminal (210). 3. A method as claimed in claim ^characterized in that the terminal (130) is a home repeater (220). 4. A method as claimed in claim ^characterized in that the method also comprises the following step: B') the terminal (130) issues a warning of excessive movement in good time before the alarm regarding movement is sent to the network part. 5. A method as claimed in claim ^characterized in that the network part terminates a bi-directional radio connection (122) in which one of the parties is a terminal (130) of whose movement an alarm has been received. 6. A method as claimed in claim ^characterized in that the network changes the pricing of the use of a bi-directional radio connection (122) in which one of the parties is a terminal (130) of whose movement an alarm has been received. 7. A method as claimed in claim ^characterized in that the changes in the cell list during a given period of time are compared. 8. A method as claimed in claim 7, characterized in that the given period of time is an hour. 9. A method as claimed in claim 7, characterized in that the given period of time is said given interval at which the cell lists are stored. 10. A system of detecting terminal movement in a cellular radio network comprising a network part and at least one terminal (130), the network part comprising base stations (120, 172 to 186), and a base station having a coverage area, or cell (100 to 116), and the terminal having a bi-directional radio connection (122) to the base station (120) of the home cell (100), and the terminal (130) keeping a cell list over the identities of the base stations (120, 172, 174, 178, 180, 184, 186) it hears, characterized in that the terminal (130) comprises means (350) for storing a cell list at given intervals, means (340) for comparing the cell lists stored at given intervals, means (340) for detecting its movement in case a sufficient number of changes has occurred in the cell lists, means (300, 310, 320, 340, 350) for sending an alarm regarding its movement to the network part. 11. A system as claimed in claim 10, characterized in that the terminal (130) is a wireless subscriber terminal (210). 12. A system as claimed in claim 10, characterized in that the terminal (130) is a home repeater (220). 13. A system as claimed in claim 10, characterized in that the terminal (130) comprises means (360) for issuing a warning of excessive movement in good time before the alarm regarding its movement is sent to the network part.

Inventors: MAENNISTOE HARRI, MAENNISTOE, HARRI
Applicants: MAENNISTOE HARRI, NOKIA TELECOMMUNICATIONS OY, MAENNISTOE, HARRI
Application year: 1997
Main classification: H04Q7
IPC codes: H04W84