PROVIDING SERVICE IN MOBILE COMMUNICATION SYSTEM

Abstract: The invention relates to a method, a mobile communication system and a base station for providing service in a mobile communication system comprising an exchange (X, 112), base stations (BS1, BS2, 109) with coverage areas, mobile stations (MS1, MS2), and a centralized database (110) for storing subscriber data (111) of mobile stations (MS1, MS2) located within the service area of the system. In order for the connection establishment to be expedited, the base station (BS1) maintains a database (100) containing the subscriber data (101) of mobile stations (MS1, MS2) registered at the base station by fetching the subscriber data of the mobile station from said centralized database (110) when the mobile station registers at the base station (BS1); the mobile station (MS1) sends a service request to the base station; the base station verifies the access right of said mobile station from the database (100) maintained at said base station; if said mobile station has the right of use, the base station (BS1) provides (102) the service requested by the service request.

Description: Providing service in mobile communication system The invention relates to a method, a mobile communication system and a base station for providing service in a mobile communication system comprising an exchange, base stations with coverage areas, mobile stations, and a centralized database for storing sub¬ scriber data of mobile stations located within the service area of the system. In some mobile communication and mobile tele¬ phone networks of the prior art, subscriber information, i.e. the subscriber database, is stored in a centralized manner in one network element, usually in an exchange or a subscriber database connected to it. In a larger network, the subscriber data may also be stored in a decentralized manner in so-called home mobile telephone exchanges and visited mobile telephone exchanges or visitor databases. This is the case, for example, in GSM mobile communication systems. The drawback of such a system based on central¬ ized registers is that it takes a very long time to establish a connection between mobile stations located within the coverage area of one base station. This is because the location data of the mobile stations must be requested and their subscriber data must be checked from a centralized register located far from the base station within whose area the mobile stations or sub¬ scriber stations between which the connection is to be established are located. Interrogation of data from a register located at a great distance, even behind other exchanges or network elements, is slow and uncertain, as the telecommunication connections may be broken. In the above-described large mobile telephone networks, where the subscriber data are stored in separate, centralized home and visitor location registers or corresponding exchanges, interrogation of subscriber data from the centralized subscriber database takes a considerable amount of the call establishment time. The interrogation time becomes easily longer than 1 s. However, authorities using mobile telephone systems, for example, require that the entire call establishment procedure within the area of one base station must not take longer than 300 ms even though the subscriber data of the subscriber are verified. In this kind of prior art solution, the subscriber data interrogation time is considerably prolonged by the data transmission delay between the exchange and the base station, as it is often not economically possible to use sufficient trans¬ mission capacity between them. Interrogation of sub- scriber data is particularly important, as it involves authentication of the subscriber. Authentication of the subscriber means that it is examined whether the sub¬ scriber and/or the mobile station are/is allowed to use the network services. Another solution of the prior art is that in small systems comprising one base station, the sub¬ scriber data are stored in the base station. This is implemented in such a manner, however, that base stations possibly interconnected via speech paths cannot exchange subscriber data with each other. The drawback of this solution is that when subscriber data are to be updated, they cannot be updated at each base station of the network. In addition, it is not possible to construct larger networks by this technology: if base stations are inter¬ connected directly without any exchanges, communication between the base stations takes up more interface capacity of the base stations than maintenance of the actual radio channels. The problem is even more serious when a larger number of base stations are interconnected. Yet another solution of the prior art is a so- called fallback function of the base station. This kind of a base station does not have a subscriber database of its own, but it can switch calls between subscribers located within its coverage area. The disadvantage of this solution is that the subscriber data of subscribers or mobile stations which are about to register at the base station or wish to establish a call cannot be verified or authenticated. It is therefore possible that an illegal subscriber starts to communicate using the resources of this base station. The prior art solutions described above are not suitable for use in mobile telephone networks where calls must be established rapidly but where a large number of subscriber data are needed, e.g. in private mobile radio (PMR) networks used by authorities. The subscriber data include subscriber-specific information on the rights of each subscriber to the network services, on priorities, security codes, operating state, group call groups, and other data. Furthermore, it should be possible to provide a very large permitted operating area for a subscriber in such a PMR network used by authorities: e.g. a whole country or even a larger area. On the basis of the above, it is thus evident that the prior art solutions described do not meet the requirements set by large mobile communication networks or mobile telephone networks, typically PMR networks used by autorities, which require rapid establishment of connection and rapid verification of subscriber data. The object of the present invention is to solve the problems associated with the above-described solutions of the prior art. It is an object of the present invention to provide a mobile telephone network which is capable of rapid establishment of connection and verification of subscriber data and which may be extremely large, covering for example a whole country. In addition, it must be possible to update the sub- scriber data of such a network flexibly and in a centralized manner. This new type of method for providing service in a mobile communication system is achieved with a method according to the invention, which is character- ized in that the base station maintains a database containing the subscriber data of mobile stations registered at the base station by fetching the subscriber data of a mobile station from said central¬ ized database when the mobile station registers at the base station; the mobile station sends a service request to the base station; the base station verifies the access right of said mobile station from the database maintained at said base station; if said mobile station has the access right, the base station provides the service requested by the service request. The invention also relates to a base station comprising a transceiver unit, an interface unit for connecting the base station through telecommunication connections to the exchange of the mobile communication system. The base station according to the invention comprises a database for storing subscriber data of mobile stations registered at the base station, means for verifying from said database the access right of a mobile station which sent the service request to the base station. The invention further relates to a mobile com¬ munication system comprising: base stations, an exchange, a database for storing, in a centralized manner, subscriber data of mobile stations located within the service area of the system. The mobile com- munication system according to the invention is charac¬ terized in that said base station comprises a database for storing the subscriber data of mobile stations registered at the base station, means for verifying from said database the access right of a mobile station which has sent a service request to the base station. The invention is based on the idea that in a mobile communication system comprising a centralized database containing subscriber data, the base stations maintain smaller databases for storing the subscriber data of the mobile stations registered at the base station in question. When a mobile station wishes to use a telecommunications service offered by the system, e.g. to establish a call, the subscriber data of this mobile station are checked from the database of the base station in question, whereafter the base station sets up the connection. The connection establishment is expedited particularly in a situation where a connection is to be set up to a mobile station registered at the same base station. An advantage of such a method for providing service in a mobile communication system, a mobile com¬ munication system and a base station is that when a call is made within the area of one base station, it is not necessary to request the subscriber data needed for establishing the call from the exchange or, via the exchange, from the centralized database of the system. Particularly most of the connections which are estab¬ lished between authorities and require rapid communica- tion fall within the area of one base station. Examples of such connections are those needed by a police patrol on duty, by a fire brigade in the event of a fire, and by an ambulance on the scene of an accident. The invention allows a call to be established within the area of one base station more rapidly than if the subscriber data had to be requested every time from a centralized database. This advantage is particularly apparent in systems where most of the traffic takes place within the area of one base station. An example of such a system is the police radio system, in which the police make a large number of calls in quick succession within the area of only one base station. The fastness of connection establishment is naturally very significant in police use and other emergency use. Another advantage of the method according to the invention is that the base station is able to serve subscribers remaining within its area even when the connection to the exchange is broken for one reason or another. This is a very important feature especially in PMR networks used by authorities, where it may be of utmost significance to have functioning connections, and where attempts may be made to intentionally disturb or even disconnect data link connections between, for instance, the base station and other parts of the system. Yet another advantage of the method according to the invention is that the decentralized databases at the base stations of the mobile communication system can be maintained so that they constantly contain the new subscriber data of the mobile stations registered at these base stations. Still a further advantage of the invention is that it renders it possible to construct larger networks than the prior art solution in which the base stations did have databases, but the base stations where inter¬ connected through telecommunication connections. This enables the construction of extremely large mobile tele¬ phone networks for the use of national authorities. Yet another advantage of the invention is that it allows the subscriber data of mobile stations com¬ municating within the area of the base station to be verified and authenticated, and safe connections between mobile stations located within the coverage area of the base station to be established even in cases where the telecommunication connections between the base station and the exchange are broken. In the following, the invention will be described in greater detail with reference to the accom¬ panying drawings, in which Figure 1 is a block diagram of a mobile com¬ munication system according to the invention with sub¬ scriber databases, Figure 2 is a signalling and event diagram of the registration of a mobile station at a base station, Figure 3 is a signalling and event diagram of connection establishment withi the service area of a base station. Figure 1 is a block diagram of a mobile com¬ munication system according to the invention with sub¬ scriber databases. The mobile communication system comprises a base station BSl, at which a mobile station MSI, which is a subscriber station (i.e. a mobile or radio telephone, for example), is registered. The base station BSl, BS2, 109 comprises a database 100 for storing the subscriber data 101 of subscribers registered at the base station BSl. The subscriber data may include, for example, the number or other identifier of the subscriber, the rights belonging to the subscriber, i.e. mainly information on the functions and services which the mobile station in question is entitled to use. In addition, these services or some of them are associated with a certain priority. The subscriber data further include encryption keys, used in the communication between the base station and a mobile station for encrypting traffic taking place on a radio path. The subscriber data also include the location of the mobile station, e.g. with an accuracy of a base station or a location area. In addition, the subscriber data include information on the state of the mobile station, i.e. on whether the subscriber station in question is switched on, and whether the mobile station communicates on a traffic channel or whether it only listens to a control channel. The state information also includes, for example, information on ongoing group calls. The base station BSl further comprises switch¬ ing means 102 for establishing connections between mobile stations MSI, MS2 registered at the base station. The base station BSl, BS2 also comprises at least one transceiver unit 105 connected to an antenna. The trans¬ ceiver unit 105 communicates with mobile stations MSI, MS2 via a radio path. The base station also comprises means 104 for verifying, from the database 100 of the base station, the access right of the mobile station MSI that sent the service request to the base station, said database con¬ taining the subscriber data 101 of the mobile stations MSI, MS2 registered at the base station. In addition, the base station BSl, BS2 comprises means 106 for requesting the subscriber data 111 of a mobile station MSI registered at the base station from a centralized database 110. The base station BSl, BS2 further comprises an interface unit 103 for connecting the base station through telecommunication connections 108 to the exchange 112, X of the mobile communication system. The exchange 112 shown in Figure 1 comprises a database 110 for storing, in a centralized manner, the subscriber data 111 of mobile stations located within the service area of the mobile communication system. The mobile communication system may comprise means 113 for erasing the subscriber data of a mobile station from the database of the base station BS2, 120 at which the mobile station MSI is no longer registered, responsive to the request 106 for subscriber data made by the base station BSl, 100 at which the mobile station MSI is registered. The means 113 are located, for example, at the exchange 112 of the mobile communication system or in connection with the above-mentioned centralized data¬ base 110. Figure 2 is a signalling and event diagram of the registration of a mobile station MSI at a base station BSl. The MSI is a new subscriber registering at the area of the base station BSl by transmitting a registration message 201. After that, the base station BSl may check 202 whether its database 100 already contains the subscriber data of the subscriber MSI. If the database does not 203 contain these subscriber data, the base station BSl sends 204 a registration message to the exchange X of the mobile communication system. The exchange fetches 205 the data of the mobile station or subscriber from the centralized database 110 and simultaneously checks the location of the mobile station. If the mobile station has changed its base station, i.e. moved away from the service area of a base station BS2 to the service area of a new base station BSl, the exchange X sends 206 a remove message to the old base station BS2. Responsive to this message, the old base station BS2 removes 207 the subscriber data of the mobile station MSI from its database. On receiving a registration message from the (new) base station BSl and verifying 205 the subscriber data of the mobile station, the exchange sends 208 the subscriber data of the mobile station as a data message to the (new) base station BSl which sent the registra¬ tion message. The base station BSl stores the subscriber data 101 of the mobile station in its database 100. Thereafter the base station BSl sends 209 an acknowledge message to the mobile station. By this message, the base station informs that the registration of the mobile station has succeeded at the base station. Figure 3 is a signalling and event diagram of connection establishment within the service area of the base station BSl. A mobile station MSI, e.g. a mobile telephone, wishes to establish a telecommunication con¬ nection, e.g. a call, to a B-subscriber, i.e. to another mobile station MS2. The mobile station MSI sends a con- nection establishment request 302, comprising the identifier of the B-subscriber, i.e. the identifier of the other mobile station. The base station BSl receives this connection establishment request 302 and checks 303 the subscriber data 101 of the calling subscriber, i.e. the mobile station MSI, from its database 100 according to the invention, and performs the necessary verifica¬ tions, and authentication and authorization of the sub¬ scriber. At the same time, the subscriber data of the receiving B-subscriber can also be checked from the database 100. If the base station BSl has 304 a free channel which the mobile station can use, it sends a channel command 305, by which it commands the mobile stations MSI, MS2 to move to the desired channel(s). Thereafter the base station BSl sends 306 information to the exchange X on the allocation of the channel(s). The exchange X stores 307 these data in its database or in the centralized database of the system. When the above-described method of the invention is used, the time it takes to establish a call is shortened approximately from a few seconds to a few milliseconds. Such an improvement is possible, as data can be very rapidly retrieved from the relatively small subscriber data table in the database 100 of the base station BSl, implemented e.g. by means of a rapid RAM memory, as compared with fetching the subscriber data from a large centralized subscriber database over an uncertain data link, in which case transmission errors and transmission delays, for example, cause a significant additional delay. The drawings and the description relating to them are intended merely to illustrate the inventive concept. In its details, the method for providing service in a mobile communication system, the mobile communication system and the base station according to the invention can be modified within the scope of the claims. Although the invention has been described above mainly in connection with mobile telephone systems, it may also be used in other kinds of mobile communication systems.

Claims: Claims 1. A method for providing service in a mobile communication system comprising an exchange (X, 112), base stations (BSl, BS2, 109) with coverage areas, mobile stations (MSI, MS2), and a centralized database (110) for storing subscriber data (111) of mobile stations (MSI, MS2) located within the service area of the system, c h a r a c t e r i z e d in that the base station (BSl) maintains (Fig.2) a database (100) containing the subscriber data ( 101 ) of mobile stations (MSI) registered at the base station by fetching (204) the subscriber data of a mobile station from said centralized database (110) when the mobile station registers (201) at the base station (BSl); the mobile station (MSI) sends a service request (302) to the base station; the base station verifies (303) the access right of said mobile station from the database (100) maintained at said base station; if said mobile station has the access right, the base station (BSl) provides the service requested by the service request (302) . 2. A method according to claim l, c h a r a c - t e r i z e d in that the step in which the base station maintains (Fig. 2) a database (100) comprises the following steps: if the subscriber data of the mobile station which sent the registration message are not (203) contained in the database (100) of the base station, the base station (BSl) requests (204) the subscriber data (111) of said mobile station from the centralized data¬ base (110) of the system, responsive to this request, said subscriber data are sent (208) to said base station (BSl), said base station (BSl) stores said subscriber data in its database (100). 3. A method according to claim 2, c h a r a c ¬ t e r i z e d in that, responsive to the request (204) made by the base station for subscriber data from the centralized database, another base station (BS2) is requested (206) to remove the subscriber data of said mobile station from its database and, responsive to this request, the other base station (BS2) removes the sub- scriber data of said mobile station from its database. 4. A method according to claim 2 or 3, c h a r a c t e r i z e d in that on receiving the subscriber data of said mobile station, the base station (BSl) sends (209) an acknowledge message to the mobile station (MSI) which sent the registration message (201). 5. A method according to claim 1, c h a r a c ¬ t e r i z e d in that said service request (302) is a connection establishment request, responsive to which the base station switches (102) a telecommunication connection from said mobile station (MSI) to the destination (MS2) defined in the connection establish¬ ment request (302) . 6. A method according to claim 5, c h a r a c ¬ t e r i z e d in that when switching (102) the telecom- munication connection from said mobile station (MSI) to the destination (MS2 ) defined in the connection estab¬ lishment request (302), the base station (BSl) commands (305) said mobile station to move to the desired radio channel. 7. A method according to claim 5 or 6, c h a r a c t e r i z e d in that when switching (102) the telecommunication connection from said mobile station (MSI) to the destination defined in the connection establishment request (302) , the base station (BSl) sends (306) to the exchange (X) information on said mobile station, said destination, and the radio channel to be used. 8. A method according to any one of claims 5 to 7, c h a r a c t e r i z e d in that the destina- tion defined in the connection establishment request (302) is another mobile station (MS2) registered at said base station (BSl). 9. A method according to claim 8, c h a r a c ¬ t e r i z e d by comprising the following steps: a mobile station (MSI) registered at the base station sends (302) a connection establishment request to the base station for requesting establishment of a connection to another mobile station (MS2), the base station verifies the access right of said mobile station (MSI) from the database (100) maintained (Fig. 2) at said base station (BSl), the base station detects that the subscriber data of said other mobile station (MS2) are stored in the base station (100) of said base station (BSl), the base station establishes (102) the desired connection between said one mobile station (MSI) and said other mobile station (MS2). 10. A base station (BSl, BS2, 109) comprising: a transceiver unit (105), an interface unit (103) for connecting the base station through telecommunication connections ( 108) to the exchange (112) of the mobile communication system, c h a r a c t e r i z e d in that the base station comprises a database (100) for storing subscriber data (101) of mobile stations (MS) registered at the base station, means ( 104) for verifying from said database (100) the access right of a mobile station (MSI) which sent the service request to the base station. 11. A base station according to claim 10, c h a r a c t e r i z e d in that it further comprises means (106) for requesting (204) the subscriber data (111) of a mobile station registering at the base station from the centralized database (110) of the mobile communication system. 12. A base station according to claim 10 or 11, c h a r a c t e r i z e d in that it further comprises switching means (102) for establishing connections between mobile stations (MSI, MS2 ) registered at the base station. 13. A mobile communication system comprising: base stations (BSl, BS2), an exchange (X, 112), a database (110) for storing, in a centralized manner, subscriber data (111) of mobile stations located within the service area, of the system, the system being c h a r a c t e r i z e d in that said base station comprises a database (100) for storing the subscriber data (101) of mobile stations (MS) registered at the base station, means ( 104) for verifying from said database (100) the access right of a mobile station (MSI) which has sent a service request to the base station. 14. A mobile communication system according to claim 13, c h a r a c t e r i z e d in that said base station comprises switching means (102) for establishing connections between mobile stations (MSI, MS2) registered at said base station (BSl). 15. A mobile communication system according to claim 13, c h a r a c t e r i z e d in that it further comprises means (113) for erasing the subscriber data (101) of a mobile station from the database (100) of a base station (BS2) at which the mobile station is no longer registered, responsive to the request (204) for subscriber data of the mobile station made (106) by a base station (BSl) at which the mobile station is registered.

Inventors: HELENIUS ALI, TUULOS MATTI, HELENIUS, ALI, TUULOS, MATTI
Applicants: HELENIUS ALI, NOKIA TELECOMMUNICATIONS OY, TUULOS MATTI, HELENIUS, ALI, TUULOS, MATTI
Application year: 1995
Main classification: H04Q7
IPC codes: H04W8, H04W88