Telecommunications – Transmitter and receiver at separate stations
Patent
1991-10-25
1994-03-08
Eisenzopf, Reinhard J.
Telecommunications
Transmitter and receiver at separate stations
455 62, 455 63, 379 59, H04B 1500
Patent
active
052936406
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for planning radio cells, particularly planning cells with control over the interaction between the cells in the system and the capability of channel allocations which vary in accordance with the traffic demand. The method utilizes field strength measurements and an allocating algorithm, which permits a simple adaptation of the cell system, that is to say increasing or decreasing the number of cells with altered traffic demand. In particular, the invention relates to the planning of mobile radio cells. The changes in the traffic demand can relate to diurnal variations in the traffic and more long-term variations due to changes in the route network and so forth.
The present invention also relates to a method for constructing an exclusion matrix for resource allocation in a radio system. The radio system can be unidirectional with communication in only one direction, for example a paging system, or bidirectional, for example a mobile radio system. In the application, a mobile radio system is preferably considered, but it is understood that the invention is also applicable to a unidirectional system. In a mobile radio system, it is of importance that the available frequence resources are used in such a manner that the system capacity is optimized under the condition that the customers obtain an acceptable quality. In a microcell system in a densely populated area, it is desirable that the channel allocation can be tailored to the actual traffic distribution. Such planning is a very demanding task and there are great gains to be made if the operator of the system has full control over the inherent interferences in the system. An improved quality and traffic handling in a given frequency range is, moreover, equivalent to an increased frequency economy.
The following prerequisites are given: a distribution of traffic demand over, for example, Stockholm, system parameters which define which C/I (carrier to interference) interference ratio is required for good reception and how much interference a receiver tolerates in adjoining channels, and a frequency band for the system with a limited number of channels. It is the object to distribute the channels to the different base stations in the given frequency range so that the quality of connection experienced by the customers satisfies the given minimum requirements.
The present invention further relates to a method for determining uplink interferences in a mobile radio system, that is to say determining the degree of interference in a cell with respect to interfering mobile units in another cell. STATE OF THE ART
Earlier mobile radio cell planning methods were static methods, that is to say all cells are always operating with one and the same channel allocation. Since direct field strength measurements have not been utilized previously, there has been no check of the factual interference ratios and it has been difficult to make new channel allocations. It is an uneconomical utilization of the resources for all cells to be operating at all times.
In the art, the problem of resource allocation has been solved essentially as follows: a systematic description is given of all the restrictions which apply to channel distribution in the form of a so-called exclusion matrix. An exclusion matrix provides a description in symbolic form of how different base stations, or alternatively mobile units in different coverage areas, can coexist with respect to the same channel and with respect to the adjacent channel. Then allocation algorithms are used for finding exactly which channels the different base stations should have for the minimum requirements for the connection quality to be satisfied. The method is used little since it is difficult to characterize a large city with respect to wave propagation in such a manner that a useful field strength and interference field strengths can be predicted within a few dB at relevant points, for example along the main traffic routes. There are examples of attempts made with l
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Gunmar Krister
Tegth Ulf
Eisenzopf Reinhard J.
Faile Andrew
Televerket
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