Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-11-28
2002-10-01
Trost, William (Department: 2683)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S447000, C455S449000, C455S524000, C455S561000
Reexamination Certificate
active
06459900
ABSTRACT:
The invention relates to a plurality of arrangements of base transceiver stations of an area-covering radio network and to a method of operating such an arrangement.
FIELD OF THE INVENTION
The invention further comprises base transceiver stations adapted to the new arrangements and a method of subsequently compressing an existing continuous radio network.
DESCRIPTION OF RELATED ART
In order to operate radio telephones, in addition to the respective mobile stations, an area-covering network of fixed transmission stations is necessary in order to ensure interference-free radio operation at any location within the area of coverage.
In order to permit a large number of mutually independent radio participants to use their telephones simultaneously, the region of coverage is divided into a plurality of individual cells, each allocated with its own base transceiver station. By giving adjacent zones different frequencies, it is possible to identify a particular radio telephone with a respective base transceiver station. If the radio telephone is set to a special frequency of the current cells, radio communication is oriented to precisely one fixed transmission station, from which the conversation is forwarded to a base station controller. By the possibility of allocating one and the same transmission frequency to a plurality of zones which are relatively remote from one another, a very large number of conversations can be transmitted simultaneously, using a limited number of transmission frequencies.
If one ignores interference (caused by topographical irregularities etc., a radio network can be put together from a plurality of base transceiver stations arranged in a specified structure, their mutual distance being determined by the range afforded by the transmission power. On the other hand, the spatial sequence of different transmission frequencies is on the one hand such that adjacent, base transceiver stations are allocated different frequencies and furthermore a minimum distance is retained in base transceiver stations using the same transmission frequencies in order to eliminate reliably any interference.
From these peripheral conditions, certain structures arise which can be linked together in lines to form a continuous grid. In establishing the basic structure of such a radio network, the following parameters need to be optimised:
On the one hand, the number of cells should be as large as possible without increasing the number of base transceiver stations. With the large number of cells, a large number of conversations can be transmitted simultaneously. On the other hand, any conventional base transceiver station requires a high level of investment, which considerably increases the cost of the radio network. It has been proposed in the prior art to provide at each base transceiver station, instead of one non-directional aerial, three directional aerials, each covering a transmission or reception angle of approximately 120°, so that the number of cells can be tripled, but such a modus operandi involves heavily increased aerial and installation costs.
Furthermore, the participant capacity to be handled can be increased if the number of channels per cell is increased. The more channels there are available in one cell, the more participants can telephone simultaneously from this cell. On the other hand, however, the total number of frequencies should not be increased, since the transmission frequencies available are limited by a number of other data transmission systems. In order to achieve a large number of channels per cell, the frequencies must be capable of being repeated: at the minimum possible distance from one another. In order to meet this requirement, according to the prior art a hexagonal grid is used, in which the base transceiver stations are arranged in parallel columns, the transceiver stations of adjacent columns being staggered relative to one another by half a distance in the direction of the column. This gives the associated cells a hexagonal shape, a large number of which are joined together like honeycomb cells in order to form a continuous network. In many applications, these basic areas are further subdivided by the above-mentioned allocation of sectors to different aerials. With the hexagonal structure, an elementary system composed of seven base transceiver stations is put together, each station requiring a different transmission frequency, since each cell abuts six further cells.
Where such grid structures known from the prior art are used for the base transceiver stations of an area-covering radio network, the two above-mentioned optimisation criteria, in particular the product of the radio cell area and the number of fixed stations (which are cost-intensive due to being coupled to a base station controller) and the ratio of the number of channels per cell to the total number of transmission frequencies, cannot be varied. Although the area per cell per area can be reduced by reducing the transmission power, which means simultaneously increasing the number of fixed stations, because on the other hand the minimum number of cells is specified by different transmission frequencies (e.g. seven structure), the number of channels per cell can only be increased by increasing the number of frequencies as a whole.
SUMMARY OF THE INVENTION
The problem of the invention arises from these disadvantages of known arrangements of base transceiver stations of an area-covering radio network, and consists in changing the basic structure of the network in such a manner that, without increasing the number of cost-intensive base transceiver stations coupled to a base station controller, the number of cells per area is increased and/or without increasing the total number of frequencies of the network, the number of channels per cell can be increased.
To this end, the invention provides, in a first arrangement of base transceiver stations of an area-covering radio network which are coupled at least in part to base station controllers, that each base transceiver station coupled to a base station controller is surrounded by a plurality of further, decentral transceiver stations which are coupled to the central transceiver station and form one or more cell areas each having a different transmission frequency. The advantage of this arrangement is that the area of coverage of a base transceiver station coupled to a base station controller is increased by the decentral transceiver stations without increasing the transmission power of the central transceiver station coupled to a base station controller. Since cell areas having different transmission frequencies are coupled to the decentral transceiver station, the number of cells per unit area can be increased without having to raise the number of fixed stations coupled to a base station controller. Since the decentral transceiver stations are not coupled to a base station controller but to a central transceiver station, they can be manufactured very simply and cheaply, as will be explained more fully below. By a favourable arrangement of the base stations and the decentral transceiver stations, the number of frequencies required for the basic coverage (1 channel per cell) is reduced (e.g. 2×1+4×1), so that within an elementary base cell (of approx. 9 times' the area of a single base transceiver station) it is even possible to use all frequencies. Thus the number of channels per unit area can be increased.
It has proved advantageous if the decentral cell area(s) as a whole completely surround the central cell(s). This ensures on the one hand an arrangement with an optimum coverage area, which may be approximately four to ten times as large as the original or central cell area. Thus the number of base stations coupled to a base station controller is reduced by a corresponding factor. On the other hand, the central cell area is completely surrounded by the decentral cell areas, so that the transmission frequencies of the central cell(s) can already be used in the adjacent transceiver station coupled to a base stati
Gray Cary Ware & Freidenrich
Littlefeet, Inc.
Sobutka Philip
Trost William
LandOfFree
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