Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1997-10-03
2004-03-23
Urban, Edward F. (Department: 2685)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S069000, C455S127100
Reexamination Certificate
active
06711415
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a method and system for improving a telephone communications network in general and, in particular, to a method and system for improving a cellular telephone communications network. Still more particularly, the present invention relates to a method and system for minimizing transmitter power levels within a cellular telephone communications network.
2. Description of the Related Art
In order to provide cellular telephone communications service to a populated area, such as the metropolitan area of a city, the service area must be first divided into small honeycomb-patterned units known as “cells.” Each of these cells has a typical radius of about 8 to 12 miles (or 13 to 19 kilometers). If necessary, each cell can be further subdivided into even smaller cells. A cellular base station (or radio transmitter) is then installed in each of these cells within the service area. Each cellular base station within a cell further is connected to a public telephone company via one or more cellular switching networks.
A user within the service area having a widespread range of cellular base stations is able to place and receive telephone calls by utilizing a cellular telephone (or a cellular subscriber unit). Each cellular telephone, which may be portable and mobile, has an assigned cellular telephone number that allows the user to place and receive telephone calls throughout the entire service. As the user is moving from one cell to another, a telephone call currently in-progress is allowed to be handed-over from one cell to another within the service area, without any interruptions. As such, the cellular telephone communications network enables the user to access a standard telephone network from anywhere within the service area, regardless of being in a stationary or a moving position.
In order to minimize the transmitter bandwidth of the cellular base stations within the cellular telephone communications network, typically, an identical range of radio frequencies is utilized repeatedly by each of the cells. Under this arrangement, even though each cell is located adjacent to another, there should not be a concern about interference from the neighboring cells, so long as the neighboring cells do not utilize precisely the same radio channels.
Furthermore, the one key in reducing interference within the cellular telephone communications network is to keep the transmitter power levels of each cellular base station low. Current algorithms for accomplishing this utilizes either a Received Signal Strength Indicator (RSSI) or Carrier/interference (C/I) Indicator as a determinant of whether the current power level of a cellular base station and/or a cellular telephone is too high or too low. The RSSI-based approach of setting transmitter power level is static however, and does not allow for the changing of C/I conditions at any time. In other words, if the transmitter power level of a cellular telephone within the RSSI window has achieved a C/I of 24 dB, the transmitter power level may be reduced while maintaining an acceptable signal. On the other hand, although the C/I-based approach of setting the transmitter power level is more responsive to these conditions, a constant settling to the minimum C/I tends to be the problem for this approach. In other words, if a first cellular telephone is experiencing a drop in C/I caused by a second cellular telephone on the same channel, the first cellular telephone would increase its transmitter power level. This may, in turn, cause the second cellular telephone to experience a drop in C/I such that the second cellular telephone would react by increasing its transmitter power level also. As a result, both cellular telephones will reach the maximum transmitter power eventually, and no in the C/I condition of either of the two cellular telephones can be further achieved.
Consequently, it would be desirable to provide an improved method and system to minimize transmitter power levels within a cellular telephone communications network such that the transmitter power-competing situation as described above may be avoided.
SUMMARY OF THE INVENTION
In view of the foregoing, it is therefore an object of the present invention to provide an improved method and system for a telephone communications network.
It is another object of the present invention to provide an improved method and system for a cellular telephone communications network.
It is yet another object of the present invention to provide an improved method and system for minimizing transmitter power levels within a cellular telephone communications network.
In accordance with the method and system of the present invention, a cellular communications network is provided which includes a cellular base station and a cellular telephone. A signal strength measurement is performed between the cellular base station and the cellular telephone. A determination is made periodically as to whether or not the measured signal strength is higher than a first threshold. In response to each determination that the measured signal strength is higher than the first threshold, the transmitter power at the cellular base station is reduced by one step such that the transmitter power levels within the cellular communications network are minimized.
All objects, features, and advantages of the present invention will become apparent in the following detailed written description.
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patent: 5448750 (1995-09-01), Eriksson et al.
patent: 5491837 (1996-02-01), Haartsen
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patent: 5697056 (1997-12-01), Tayloe
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Bracewell & Patterson L.L.P.
Crane John D.
Nguyen Simon
Nortel Networks Limited
Urban Edward F.
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