Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Patent
1995-12-18
1998-06-23
Eisenzopf, Reinhard J.
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
455524, H04B 700, H04Q 720
Patent
active
057714606
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT FI95/00062, filed Feb. 13, 1995.
FIELD OF THE INVENTION
The invention relates to a method of processing signalling messages in a mobile communication system comprising mobile stations and base stations, the receiver units of the base stations being tuned to the same channel, in which method more than one mobile station transmits a signalling message to the base stations on the same channel in such a way that the signalling messages are received at the base stations so that they overlap at least partly in time.
BACKGROUND OF THE INVENTION
In radio networks comprising several base stations and repeating the same frequencies at determined intervals, it is possible to optimize the re-use of the frequencies very effectively, if there are enough available channels, i.e. radio frequencies. Problems begin to occur when there are too few available channels. Such a situation occurs often in private mobile radio networks (PRM). One solution to this problem is to use the same frequency at adjacent base stations and to synchronize the base stations in such a way that the mobile stations can understand the shared signal of both base stations. Such a method is called the use of quasi-synchronized base stations or a simulcast system. "Simulcast" refers to a method of increasing a cell by using on the same radio channel two or more base stations, which have at least one radio transmitter/receiver pair. The receivers of all base stations listen to the same channel.
The pocket phones used in mobile communication systems have a lower power and a weaker antenna, i.e. a smaller antenna gain, than the base station has, wherefore the pocket phone can hear the transmission of the base station without problems, but since the power of the pocket phone or some other radio phone is a lot lower than that of the base station, the base station can hear the transmission of the mobile station, i.e. the radio phone, poorly or not at all. To eliminate this problem, it is possible to use in the terrain additional receivers connected to the main base station. These are positioned in such a way that the transmission of a pocket phone, or some other low-power radio phone, reaches one of these additional receivers, even though it does not reach the actual base station, i.e. the one which comprises both a transmitter and a receiver.
These arrangements of the prior art are characterized in that in both of them at least two geographically closely positioned receivers listen to the signalling of the mobile stations on the same channel. Thus, when the mobile stations transmit in a place where the coverage areas of the base stations overlap, the control unit of the mobile communication system receives the same information from several base stations. The control unit selects for processing one of the messages transmitted by the mobile stations to the base stations and rejects the other messages.
The problems of the prior art arrangements also occur in a situation where two or more mobile stations transmit uplink signalling substantially simultaneously in the coverage area of different receivers, i.e. base stations. FIG. 1 shows this situation. In the figure, the mobile stations x and y transmit signalling 110, 112 simultaneously. Thus the control unit simultaneously receives, from two or more different radio phones, signalling which has not been mixed on the radio path. If, on the other hand, more mobile stations transmit signalling in the coverage area of the same receiver, the transmissions are mixed together in the receiver of the base station and they cannot be interpreted.
In the above-described situation according to the prior art, the prior art systems may operate, for example, in such a way that they directly add together the signalling messages from the different receivers before the processing, whereupon the messages interfere with each other and none of them can be interpreted. The other alternative is that the systems of the prior art select one of the signalling messages
REFERENCES:
patent: 4866788 (1989-09-01), Mouly et al.
patent: 5054109 (1991-10-01), Blackburn
patent: 5109528 (1992-04-01), Uddenfeldt
patent: 5287552 (1994-02-01), Sasuta et al.
patent: 5442807 (1995-08-01), Takayama
Heiskari Mika
Vaitovirta Hannu
Bhattacharya Sam
Eisenzopf Reinhard J.
Nokia Telecommunications Oy
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