Telecommunications – Transmitter and receiver at separate stations
Patent
1993-06-03
1995-07-25
Urban, Edward F.
Telecommunications
Transmitter and receiver at separate stations
455 561, 455 671, H04Q 700
Patent
active
054370566
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a radio channel allocation method for a radio system comprising several fixed radio stations located apart from each other in a geographical area covered by the radio system, remote radio stations, and a control center for dynamically allocating radio channels to the fixed radio stations from a predetermined pool of radio channels independently for each call.
BACKGROUND OF THE INVENTION
In a multiple access type mobile radio system, a large number of subscribers share the same group or pool of radio channels. In the call setup, the system checks the user authorization of an individual subscriber and allocates radio channel resources to the subscriber by automatically selecting a free radio channel from the pool. Dynamic allocation or control of the radio channels aims at increasing the efficiency of the utilization of radio channels within areas where the traffic intensity is relatively low, where there occurs coverage problems or where the traffic moves from one area to another at different times of the day, for instance. The mobile exchange thereby allocates radio channels to the base stations within its area on the basis of the call requests so that the same frequencies are not used simultaneously at adjacent base stations which might interfere with each other.
In the fallback state of the base station, there is a line failure in the transmission line between the base station and the mobile exchange. In the fallback state, the base station is not, however, controlled by the associated mobile exchange, but the base station configuration is usually such that the base station is able to switch calls between the mobile radios located within its radio coverage area. As a result, it may independently use the same radio channels which the mobile exchange has at the same time allocated to an adjacent base station. Such simultaneous calls or the same radio channels interfere with each other.
In one prior art arrangement, to solve this problem, base stations in the fallback state use special fallback radio channels which the system does not use in normal operation. This, however, requires more channels in the system and is uneconomical in terms of the utilization of the channels.
SUMMARY OF THE INVENTION
The object of the invention is to provide a method which avoids the above-mentioned problems and disadvantages.
This is achieved by means of a radio channel allocation method, which according to the invention is characterized in that when any of the fixed stations detects a line failure in the transmission line between the fixed station and the control center, the fixed station starts to use only specific fallback radio channels assigned to it in advance from the pool of radio channels; and when the control center detects a line failure in the transmission line between the control center and any of the fixed stations, the control center removes specific fallback radio channels assigned in advance to the particular fixed station from the pool of radio channels available to the neighboring fixed stations of the particular fixed station.
According to the invention, a fixed radio station, i.e. a base station, does not disturb the rest of the radio system when it operates independently. Further according to the invention, the same radio channels can be used both in normal operation and in fallback state. Accordingly, the utilization ratio of the radio channels is higher and the remote radio stations need not register separately at a base station which is in the fallback state, which improves the efficiency of the fallback operation.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following the invention will be described in greater detail by means of illustrating embodiments with reference to the attached drawings, in which:
FIG. 1 illustrates a radio system in which the invention is applicable;
FIG. 2 illustrates a switching arrangement between a mobile exchange and a base station;
FIG. 3 is a flow chart of the preferred embodiment of the process.
DETAILED DESCRIPT
REFERENCES:
patent: 4686671 (1987-08-01), Burian et al.
patent: 5117501 (1992-05-01), Childress et al.
patent: 5239682 (1993-08-01), Strawcynski et al.
patent: 5241686 (1993-08-01), Charbonnier
Nokia Telecommunications Oy
Urban Edward F.
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