Telecommunications – Transmitter and receiver at separate stations – Single message via plural carrier wave transmission
Patent
1994-03-31
1997-01-14
Eisenzopf, Reinhard J.
Telecommunications
Transmitter and receiver at separate stations
Single message via plural carrier wave transmission
455 341, 455 561, H04B 726
Patent
active
055949487
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention pertains to a method for realising a group call in a digital radio network wherein a plurality of mobile subscribers participating in the group call roam within the area of at least one base station. The method is specifically designed for a trunking network, which is typically an organisation network in which all channels are in the use of several organisations and in which the subscribers have, in addition to their own subscriber numbers, group numbers indicating the subscriber group the particular subscriber belongs to. According to the method, subscribers participating in the group call are guided one by one to talk on the same radio channel.
In known (analogous) trunking radio networks realisation of a group call is based on the use of the tangent as a switch: by pressing the tangent, the transmitter switches on, and the subscriber may communicate on the channel. Pressing the tangent also mutes the earphone of the subscriber apparatus. Each subscriber may attempt to communicate whenever he or she so wishes, and it is thus possible that several subscribers attempt to communicate simultaneously without one another's knowledge. As a result, everybody's speech becomes blurred. As the earphone of each speaker is mute, he or she does not know that the channel is congested.
SUMMARY OF THE INVENTION
The object of the present invention is thus to obtain a new type of method for realising a group call in digital radio networks without the deficiencies described above. This aim is achieved with a method according to the present invention, which is characterised in that (i) the base station is informed of the subscriber's desire to speak after the subscriber has indicated his or her desire to speak with predetermined signalling, (ii) the next speaker is selected at the base station on the basis of a predetermined algorithm, and (iii) the base station transmits an indication of a turn to speak to the subscriber which at the time is the next speaker.
The basic concept of the invention is to use pressing of the tangent (or other suitable way of signalling) as an indication of the subscriber's desire to speak, and signal an indication of this to the base station, which registers at least part of the indications and selects the speakers in accordance with a predetermined algorithm.
Thanks to the solution of the invention the subscribers can never congest the traffic on the radio channel by talking at the same time, but the traffic is handled in a controlled manner at all times.
According to one preferred embodiment of the invention, the turn to speak is given to the subscriber who was the first to indicate his or her desire to speak. This may be carried out either based on competition, such that the base station receives indications of a wish to speak only after the preceding speaker has finished when the base station has informed the subscribers that the channel is available, or such that the base station receives indications of a wish to speak already during the previous turns to speak. An advantage of the former alternative is that no signalling during speech is required for realisation of the group call.
According to another preferred embodiment of the invention, the next speaker is selected among subscribers registered as wishing to speak by searching for the subscriber with the highest priority. Thus, e.g. the group leader or the person on duty may be given priority over others.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following, the invention will be described in greater detail with reference to the examples of the attached drawings wherein:
FIG. 1 schematically shows a radio network with a plurality of subscribers participating in a group call,
FIG. 2a is a flowchart of channel allocation in regard of the base station when the competition method is used,
FIG. 2b is a flowchart of channel allocation in regard of a mobile station when the competition method is used,
FIG. 3a is a flowchart of channel allocation in regard of the base station when the time-, random-
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Li, Victor O. K., "Multiple Access Communications Networks", IEEE Communications Magazine, Jun. 1987, pp. 41-48.
Brockman Pertti
Talarmo Reino
Eisenzopf Reinhard J.
Nokia Telecommunications Oy
Sobutka Philip J.
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