Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Patent
1996-06-18
1999-07-27
Eisenzopf, Reinhard J.
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
455519, 455520, H04Q 738
Patent
active
059307234
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method for establishing an expanded group call in a mobile communication system comprising group call groups formed by mobile stations, a network infrastructure comprising at least one exchange, base stations and the telecommunication connections between them, and a group call database for maintaining data concerning group calls.
The invention relates to mobile communication systems, especially mobile communication systems which comprise exchanges, base stations and radio phones, and which have a cellular structure and in each cell at least one base station communicating with at least one mobile station by means of one or more radio channels. One or several of the channels are typically used for signalling and the rest are utilized as traffic channels. The channels may be either time division or frequency division multiple access channels.
BACKGROUND OF THE INVENTION
The method according to the invention is intended for use especially in trunked networks, which are typically networks of companies or authorities wherein all channels are used by one or several user organizations. In addition to their own subscriber numbers, the subscribers in these networks also have group numbers, which indicate the group call group or subscriber group the subscriber belongs to, so that calls intended for subscribers of a particular group can be forwarded to the subscribers in question.
The invention is applicable in both mobile communication systems with a digital radio path and systems with an analog radio path. Analog mobile communication systems are described for example in the following publications by the British Department of Trade and Industry: "MPT 1327, January 1988, Revised and reprinted November 1991, A Signalling Standard for Trunked Private Land Mobile Radio Systems, Radio-communications Agency" and "MPT 1343, January 1988, Revised and reprinted September 1991, Performance Specification, Radiocommunications Agency".
A group call is one of the central functions of a private mobile radio communication system. A group call is used, for example, in all kinds of operations with several participants, especially when an entire group must be continuously kept up to date in regard to certain events. A group call is a conference call wherein all participants can speak in their turn and also hear each other. In group calls, the entire group is called by using a single call number. An individual radio unit, such as a mobile station or a radio phone, i.e. a subscriber station, may belong to several groups that are programmed into the radio unit. The programming may be fixed, but the user of the mobile station may also change it. The system stores a file of the base stations associated with each group number. A group call may cover one, several or all base stations within the area of a mobile exchange, or several mobile exchanges. When a group call is being established, a traffic channel is reserved from all base stations belonging to the group, and each of these base stations transmits a group call message comprising a group number and information about the reserved traffic channel. If the mobile station identifies the group number contained in the group call message, it moves to the traffic channel indicated in the group call message. Therefore it is in principle always possible to engage a mobile station in a group call if the mobile station is within the area of operation predetermined for the group and if it is not already engaged in another group call.
In the following, the operation of a mobile communication system employing group calls is illustrated in a normal situation by means of FIG. 1. In a normal situation, mobile stations must be able to communicate in a group call group comprising all radio phones and the dispatcher of the dispatching area (FIG. 1). For example, radio phones 111, 112 and 113 and dispatcher A in AREA 1 belong to group call group R1, and when they call each other they use the identifier of the group call group R1, i.e. they dial the number
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Heiskari Mika
Lehmusto Mika
Eisenzopf Reinhard J.
Nokia Telecommunications Oy
Orgad Edan
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