Telecommunications – Transmitter and receiver at separate stations
Patent
1993-10-14
1996-04-02
Urban, Edward F.
Telecommunications
Transmitter and receiver at separate stations
455 334, 455 561, H04Q 730
Patent
active
055049370
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates generally to a method for controlling of local traffic capacity in a cellular radio network.
BACKGROUND OF THE INVENTION
In cellular mobile radio networks, the geographical area covered by the network is divided into smaller radio coverage areas, i.e. radio cells, each comprising at least one base station. In each cell, a certain number of frequency channels are assigned to the base station, and the frequency channels, in turn, may be time-division multiplexed into several traffic channels on the TDMA principle. Typically, the size and density of the radio cells as well as the number of frequency channels assigned to them are determined by the traffic capacity requirements in each particular area. The cellular mobile radio network may, however, comprise radio cells or larger areas in which the traffic capacity requirements may increase temporarily to a very high degree, e.g. at certain hours of the day. If the number of channels assigned to the radio cell is now determined on the basis of this instantaneous maximum capacity, the number of channels will be high, resulting in a higher number of radio equipments at the base station and therefore higher costs. Such an arrangement does not either enable efficient utilization of radio frequencies in the network. On the other hand, if the number of channels and the base station equipment are not dimensioned on the basis of the peak traffic in a service area, the number of rejected calls will be very high within that service area at peak hours.
In certain prior art networks, attempts have been made to alleviate the capacity problem by increasing transmitting powers in the network. In GB Patent Specification 1562963, the mobile radios are able to increase the coverage area (transmitting power) of their transmissions when adjacent base stations are overloaded in order to establish a connection to less loaded, more remote base stations. U.S. Patent Specification 4435840, in turn, teaches a cellular system in which the cell size of an overloaded base station is temporarily decreased by reducing its transmitting power while correspondingly increasing the transmitting power and the cell size of a neighbouring base station. Changes in transmitting powers may, however, cause interference elsewhere in the network and complicate the design of the network.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an arrangement of a new type for alleviating the capacity problem.
To this end, a base station according to the invention for a digital cellular radio system comprises at least one radio transmitter and radio receiver, an antenna means having a predetermined radio coverage area, and at least one frequency channel assigned to the base station, the frequency channel being divided into several traffic channel time slots on the TDMA principle. In the base station according to the invention, at least one radio transmitter is permanently connected or temporarily connectable to an additional antenna means in addition to the antenna means so that the joined radio coverage area of the two antenna means is variable, in order to control the local traffic capacity of the cellular radio network, between a first radio coverage area substantially corresponding to the predetermined radio coverage area and a second radio coverage area deviating substantially from the predetermined radio coverage area by adjusting the mutual phase difference and/or transmitting power ratio of the two antenna means. In this embodiment, the base station may divide the capacity of the same frequency channel between its own cell and an adjacent radio cell and adjust the division of the capacity into these cells.
The invention further relates to a cellular radio network, comprising several base stations each having one or more assigned frequency channels for establishing radio connections with active mobile radio stations presently located within a predetermined radio coverage area thereof, the assigned frequency channels being different
REFERENCES:
patent: 4144496 (1979-03-01), Cunningham et al.
patent: 4435840 (1984-03-01), Kojima et al.
patent: 4759051 (1988-07-01), Han
patent: 5048116 (1991-09-01), Schaeffer
patent: 5119501 (1992-06-01), Perry et al.
patent: 5276907 (1994-01-01), Meidan
patent: 5303240 (1994-04-01), Borras et al.
Nokia Telecommunications Oy
Urban Edward F.
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