Telecommunications – Transmitter and receiver at separate stations
Patent
1995-05-25
1997-12-09
Urban, Edward F.
Telecommunications
Transmitter and receiver at separate stations
455 542, 455 63, H04Q 738
Patent
active
056970587
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a call control method in a transmission trunking radio system.
BACKGROUND OF THE INVENTION
In a trunking radio system, several user groups, even several user organizations, share a common pool of channels. In radio systems like this, a message trunking procedure is usually utilized for call set-up. In this procedure a traffic channel is permanently allocated for one call for the entire duration of the call. The call may consist of various separate call transactions (several pressel activations by separate terminals). The channel is not de-allocated (released) until the call is explicitly terminated or a specific timer expires.
In a transmission trunking procedure, a group of simultaneous calls shares a certain group of traffic channels; for each call, a traffic channel belonging to this group is allocated, separately for each call transaction (each activation of the pressel). The traffic channel is immediately de-allocated at the end of the call transaction, i.e. when the pressel is released and one stops speaking. Between the call transactions, the MS participating in the call goes to listen onto a control channel. It is typical of transmission trunking that allocation of a channel requires only a little signalling during an on-going call.
On account of transmission trunking, for example, more than four calls can, in principle, be allowed simultaneously in a 4-channel system. However, there is no guarantee that a subscriber can be served at the precise moment the service is requested for. Another problem with optimisation of channel utilization is that it is not necessarily possible to make a reliable estimate of the number of calls that can be allowed simultaneously on transmission trunking channels since the amount of traffic may vary from day to day. For example, a very large number of calls by which subscribers give brief instructions to one another relatively seldom (e.g. group call) can be allowed simultaneously. On the other hand, one call with normal conversation occupies an entire traffic channel for a long time.
SUMMARY OF THE INVENTION
An object of the present invention is to optimise the number of simultaneous calls in a transmission trunking radio system.
This is achieved according to the invention with a call control method in a transmission trunking radio system, in which M traffic channels are simultaneously allocated to at most N mobile stations for a call, N and M being positive integers and N>M; and during a call a mobile station is commanded to go onto one of the M traffic channels for the duration of the call transactions only and to go onto a control channel at other times. The method is characterised by collecting data about collisions of call transactions of different calls on said M traffic channels, and automatically adjusting the maximum number N of simultaneously allowable calls in accordance with the collected data.
The invention offers a solution to the problem of optimising the number of calls: the radio system collects collision data about call transactions of different calls, e.g. at a base station or a mobile exchange. On the basis of these traffic and collision data the radio system automatically controls the number of simultaneous calls, increasing the number if no collisions occur and reducing it on certain conditions if collisions occur. It is thus possible to establish several simultaneous calls if traffic is such that the probability of collision is small.
A requirement for collection of collision data is that it is possible to make a relatively reliable estimate of an occurrence of a collision. In one embodiment of the invention, a mobile station sends a channel request to a base station for each service transaction. Each situation where the system is not capable of immediately allocating a traffic channel because no free channels are available is then interpreted as a collision of call transactions.
The maximum number of simultaneous calls can be adaptively adjusted on the basis of the number and frequency
REFERENCES:
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patent: 4612415 (1986-09-01), Zdunek et al.
patent: 4939746 (1990-07-01), Childress
patent: 5239674 (1993-08-01), Comroe et al.
patent: 5355516 (1994-10-01), Herold et al.
patent: 5383185 (1995-01-01), Armbruster et al.
Zdunek: "Design Considerations for Trunked Radio Systems", IEEE, 455, 194-201, 1986, see pp. 194-195.
Nokia Telecommunications Oy
Urban Edward F.
LandOfFree
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