Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-01-24
2002-11-12
Le, Thanh Cong (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S435100, C455S519000, C455S518000
Reexamination Certificate
active
06480715
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method for recovering group data between mobile systems, which incorporate at least one first mobile system, which comprises a first database, at least one second mobile system, which comprises a second database and a service area, and which mobile systems incorporate mobile stations as subscribers, the method comprising the steps of maintaining group data in said first database of said first mobile system, and maintaining group data in said second database of said second mobile system.
The invention relates to a plurality of mobile systems, in particular mobile systems which comprise control centres, one or more databases, base stations and radio telephones, the mobile systems having a cellular structure and each cell having at least one base station which communicates by means of one or more radio connections with at least one mobile station. The radio connection may be established by channels, of which one or more are typically used for signalling and the rest for traffic.
The method of the invention is intended for use particularly in so called trunking mobile systems, which are typically company networks or private mobile radio networks used by authorities, all the channels in these networks being allocated to one or more companies or authority organizations. In these networks, the subscribers have, apart from their own subscriber numbers, group numbers, which indicate to which group call group said subscriber belongs, whereby the calls, particularly the group calls, that are intended for all subscribers of said group, can be switched to said group subscribers.
The invention is applicable to mobile systems with either digital or analogue radio paths. Analogue mobile systems are described, for instance, in the British Department of Trade and Industry publications MPT 1327
, A Signalling Standard for Trunked Private Land Mobile Radio Systems
, January 1988, revised and reprinted November 1991, issued by the Radiocommunications Agency, and MPT 1343
, Performance Specification
, January 1988, revised and reprinted September 1991, issued by the Radiocommunications Agency.
A group call is one of the key functions in a private mobile radio network. A group call is used, among other things, in various operations involving several participants, particularly when an entire group must know all the time how things proceed. A group call is a call in which all participants may take turns to speak and to listen to each other. In group calls the whole group is called by one call number. A single radio unit, for instance, a mobile station or a radio telephone, i.e. a subscriber station, may belong to a plurality of groups which are programmed in the mobile station. Programming can be carried out permanently, but it can also be changed by the user or even by the system. Each mobile system may maintain a file on base stations relating to each group number. A group call may cover one, several or all base stations in the service area of a mobile services switching centre and a plurality of mobile services switching centres, or a group call can be established within the service area of several mobile systems.
When establishing a group call a traffic channel is allocated in all base stations relating to the group, and each of these base stations transmits. a group call request which comprises the group number and information on the allocated traffic channel. If the mobile station identifies the group number included in the group call request, it transfers to the traffic channel indicated by the group call request. Thus the mobile station that is registered in the operating area predetermined to the group, is in principle always available for a group call.
In connection with cellular radio networks it is known that group data of the radio telephones registered in said mobile system are stored in the database of the trunking mobile system, for instance in the switching centre or in its visitor location register or home location register.
The group data (group profile) contain data that inform the subscribers of said group, or some subscribers of the group, of available or activated services, for instance, of supplementary services. The group profile may also contain definition of importance, i.e. priority, of said group or its subset. Moreover, the group profile may contain information which subscribers belong to said group, i.e. a list which includes the identifiers of such subscribers that are allowed to participate in communication within said group, e.g. in a group call, in the service area of said mobile system, in its specific location areas (Location Area) or its specific base stations.
This group profile is stored, for instance, in a volatile RAM memory, wherefrom the data disappears, for instance, when the power supply for the database is switched off, and at regular intervals in a non-volatile memory means, for instance, on a hard disk on which the data are maintained permanently. When the RAM database at times restarts itself, the group profile stored in the volatile memory disappears. Only the group data stored in the non-volatile memory, for instance, on the hard disk; remain.
The disappearance of group data from the databases causes a serious problem in the group of a plurality of mobile systems, since if a given group call extends to the service areas of several mobile systems, group data of the group call are stored in the databases of all said several mobile systems. Hence, if the database of any one of the mobile systems has to be driven down and since the down-driven database cannot continuously update the changes that have taken place in the group's group profile, these data may change in the meantime in the databases of other mobile systems, but remain unchanged in said down-driven database. As a consequence, the group data contained in the databases of different mobile systems become different, on one hand in the down-driven database and on the other hand in other normally functioning databases.
This difference between the group data of the databases may bring about a situation that a given mobile station is allowed to join a group call in a first mobile system, but in a second mobile systems aid mobile station is not allowed to join the same group call, since the data of said group have not been maintained updated in said mobile system, nor in its database.
In accordance with the prior art, it is possible to try to maintain the database contents of various mobile systems consistent by using so called recovery.
The recovery method utilizes a normal inter-network sequence of mobile systems, or the like, by which sequence attachment and detachment requests sent by subscriber terminals operating in the network are processed, the requests being addressed to a group of another network. In the TETRA mobile system this sequence is an ANF-ISIMM sequence; That sequence is described in the TETRA specification ETS 300 392-3-5, Part 3
: Inter
-
working basic operations
; Part 3-5
. Additional Network Feature Inter
-
System Interface for Mobility Management
(
ANF
-
ISIMM
), ETSI, March 1997, 167 pages.
A normal update sequence of group profile starts, when a subscriber terminal sends an attachment request to a mobile system and said mobile system is not the group's home-mobile system. In the TETRA mobile system, the home mobile system is home SwMI, and correspondingly, the visited mobile system is visited SwMI. The visited mobile system thus communicates the attachment request to the group's home mobile system which stores in its database information on the attachment and replies to the visited mobile system by sending it the group profile. The visited mobile system stores the attachment and other group data in its database. The group data are kept stored in the database of the visited mobile system as long as there is at least one valid attachment request for said group.
When the visited mobile system receives an attachment request from the subscriber terminal, any of the following procedures can be applied:
1) If s
Altera Law Group LLC
Cong Le Thanh
Le Lana
Nokia Networks Oy
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