Group call method, a system controller and a subscriber station

Details Group call method, a system controller and a subscriber station Group call method, a system controller and a subscriber station

1995-12-12

1998-09-15

Chin, Wellington

Multiplex communications

Communication over free space

Having a plurality of contiguous regions served by...

34082544, 34082536, 370261, 370384, 455422, H04Q 700, G08B 522

Patent

active

058090185

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention relates to a group call method, a subscriber station and a system controller in a radio system comprising a plurality of base stations and subscriber stations.


BACKGROUND OF THE INVENTION

The method according to the invention is designed particularly for use in so-called trunking networks, which are typically radio networks for companies or authority organizations where all channels are shared by several companies or authority organizations and where the subscribers, in addition to subscriber numbers, have group numbers indicating to which group call group or subscriber group the subscribers belong; thus it is possible to switch calls directed to the members of a certain group to the subscribers of this group.
A group call is one of the key functions in a dedicated radio network. A group call is used in various activities in which several people participate, particularly when a whole group must continuously be aware of the progress of events. A group call is a conference call, in which all participants can in turn talk and listen to each other. In group calls the whole group is called by one radio identity code. An individual radio unit (e.g. a mobile phone), i.e. a subscriber station, may belong to several groups programmed to the radio unit. The system stores a file on the base stations associated with the number of each group. A group call may cover one, several or all base stations in the area of a mobile exchange, or several mobile exchanges. When a group call is established,, all base stations associated with the group call allocate a traffic channel for the group call, and each of these base stations sends a group call request which includes the group number and information on the allocated traffic channel. If the mobile phone identifies the group number included in the group call request, it moves to the traffic channel indicated by the group call request. In principle, a mobile phone can thus always be engaged in a group call if it is located in a predetermined area of operation of the group and if it is not already participating in another group call.
In trunking networks of the prior art, subscribers are not aware of other calls which are ongoing in the location area of the subscriber and in which the subscriber station could participate. Therefore the subscriber station participates merely in one group call, typically the one in which it is first requested to participate, as the subscriber does not know that there are also other ongoing group calls in the location area of the subscriber station in which it could participate.
In prior art systems it has been possible to release the call in which the subscriber has first participated if the system has observed that the subscriber station is wanted to participate in a call with a high priority. A high priority call is a so-called pre-emptive call, typically an emergency call. In such calls, an overriding priority has been used, and the user has not been given a possibility to select the call directly, but the call has been selected on the basis of the system parameterization. When pre-emptive calls are used, a subscriber station cannot select the call that is the most important to it from among the group calls in which it in principle could participate.
A simple prior art solution to this problem of selecting group calls has been that all users of a system have used the same channel. This solution does not, of course, satisfy users of modern trunking networks, or PMR (Private Mobile Radio) networks, as there are many problems pertaining to the use of one channel open to all users owing to the privacy and secrecy requirements set for a private mobile radio system. Thus, as the traffic within organizations has been divided between different channels, the problem caused by the fact that, during a call, the user of a subscriber station does not receive information on other ongoing calls in which the subscriber/subscriber station could participate, still remains unsolved. The subscriber/subscriber station partic

REFERENCES:
patent: 5117501 (1992-05-01), Childress et al.
patent: 5404571 (1995-04-01), Makowski
patent: 5465391 (1995-11-01), Toyryla
Patent Abstracts of Japan, vol. 9, No. 154, E-325, Abstract of JP, A, 60-32441 (Nippon Denki K.K.), 19 Feb. 1985.

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