Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Patent
1996-07-17
1998-05-12
Mullen, Thomas
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
370340, H04B 100
Patent
active
057521964
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/F195/00640, filed Nov. 21, 1995.
FIELD OF THE INVENTION
The invention relates to a method for maintaining group data relating to a communication group in a mobile communications system comprising a plurality of exchanges having connection through base stations with subscribers at least some of which belong to the communication group, said exchanges incorporating databases.
The invention relates to a mobile communications system in which group communication is to be established when the subscribers are located in the service areas of several exchanges.
BACKGROUND OF THE INVENTION
The invention is specifically intended for use in what are known as trunked networks, which are typically networks of companies or authorities wherein all channels are shared by one or several user organizations. In such networks, the subscribers have individual subscriber numbers and also group numbers indicating the communication group or subscriber group the subscriber belongs to, thus enabling communication intended for members of a given group to be switched to subscribers of that group.
The invention is suitable to be used in mobile communications networks with digital as well as analog radio paths. Digital mobile communications systems may be, for example, in accordance with the TETRA (=Trans European Trunked Radio) standard. Analog mobile communications systems have been described, for instance in MPT 1327, A Signalling Standard for Trunked Private Land Mobile Radio Systems, January 1988, revised and reprinted November 1991, and MPT 1343, Performance Specification, January 1988, revised and reprinted September 1991, United Kingdom Department of Trade and Industry, Radiocommunications Agency.
An essential characteristic of the above mobile communications systems, for example, is that it is possible and desired to implement group communication involving several subscribers therein. Group communication is all-informed communication within predefined groups. Groups are used, for example, to emulate open-channel type of operation or to enable group calls.
In group communication an entire group is addressed by a single calling number. An individual mobile station (e.g. a radio telephone), i.e. subscriber, can belong to several groups that are programmed into the mobile station. The system maintains a data file on the base stations associated with each group number. Group communication can include one, several or all base stations in the service area of a radio telephone exchange or mobile exchange, and also a number of mobile exchanges. In establishing a group call, a traffic channel is allocated at all base stations associated with the group, and each of these base stations sends a group call message, including the group number and information on the traffic channel allocated. If the mobile station recognizes the group number included in the group call message, it switches to the traffic channel indicated in the group call message. Hence, in principle, the mobile station is always available for a group call if it is located within the predetermined operational area of the group, where it is also paged for participation in the call.
Group communication is normally a characteristic of networks intended for special applications. As a rule, such networks have not comprised several exchanges. Furthermore, conventionally it has been possible for example to reserve the service area of one exchange as the area for establishing the group communication. The recent expansion in size of mobile communications systems has resulted in establishment of group communication extending to the service areas of several exchanges, and hence it has become problematic how to maintain group data for group communication established in the service areas of several exchanges.
The group data for a communication group comprise all data relating to a given group. These data include group-related data needed for establishing group communication. The group data include for instance the permit
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MPT 1343, Performance Specification: System Interface Specification for radio units to be used with commerical trunked networks operating in Band III sub-bands 1 and 2, Jan. 1988, revised Sep. 1991.
MPT 1327, A Technical Overview of the United Kingdom PMR Trunking Standards, date unknown.
Ahvenainen Jouko
Sillanpaa Anna
Mullen Thomas
Nokia Telecommunications Oy
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