Telecommunications – Transmitter – Power control – power supply – or bias voltage supply
Patent
1993-10-20
1996-01-23
Pham, Chi H.
Telecommunications
Transmitter
Power control, power supply, or bias voltage supply
455 8, 455 331, 455 531, 455 671, 455115, H04B 104, H04Q 730
Patent
active
054871859
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method for controlling base station transmitters in a cellular system, the base station comprising at least two transmitters transmitting on at least one control carrier and at least one traffic carrier, wherein the power transmitted on the traffic carrier is, on the average, lower than the power transmitted on the control carrier.
In the GSM radio system (like in any other similar cellular system, such as the PCN system), the channels to be used can be divided into two different classes: traffic channels (TCH) and control channels.
Traffic channels, which transmit either speech or subscriber data, employ a dynamic control of transmission power both at the base station and at the mobile station. The power control word comprises four bits, so that 16 power levels are available. The spacing between two successive power levels is 2 dB, the entire power control range being 30 dB. In the so-called TX-on time slot, in which the transmission takes place, the transmission power (on the traffic channel) is adjusted in each time slot of a frame in accordance with the above-mentioned power control word, to one of the sixteen different power levels.
The control channels are used for signalling and synchronization. The GSM control channels include a broadcast control channel (BCCH) which is a one-way channel from the base station to the mobile stations. The BCCH channel transmits cell-specific data (concerning power levels, frequencies, etc.) to the mobile stations. The power control of the mobile station is based on measurements performed by the base station, and vice versa. Because the measurements performed by the mobile station need a reference level, the power transmitted on the BCCH channel is constant in each cell. At the same time, this constant power is the maximum power of the cell, in order that the signal strength of the channel can be maintained so as to be acceptably strong even within the edge areas of the cell.
At present, the same base station transmitter is used for transmitting the BCCH carrier all of the time, and so this transmitter has to transmit at a power considerably higher than the average transmission power of the base-station transmitters transmitting the traffic carrier. As a result, the mean time between failure (MTBF) of the BCCH transmitter is considerably shorter than that of the transmitters transmitting the traffic carrier, which, in turn, negatively affects the lifetime of the entire transmitter unit of the base station.
SUMMARY OF THE INVENTION
The object of the present invention is to improve the overall life expectancy of the transmitters of the base station. This is achieved by means of a method according to the invention, which is characterized in that which one of the transmitters is transmitting the control carrier is changed frequently.
The basic idea of the invention is to increase the lifetime of the transmitter unit by dividing the transmission of the control channels having an average transmission power which is clearly higher than the average transmission power of the traffic channels, between different transmitters.
The arrangement according to the invention improves significantly the overall life expectancy of the base station transmitters, as appears from the calculation example which is provided hereinbelow.
BRIEF DESCRIPTION OF THE DRAWING
In the following, the invention and its preferred embodiments will be described in more detail with reference to the examples of the attached drawings, in which:
FIG. 1 is a block diagram illustrating the transmitter arrangement of a base station in a cellular system at a first time instant;
FIG. 2 illustrates the transmitter arrangement of FIG. 1 at a second time instant; and
FIG. 3 is a block diagram illustrating a base station transmitter arrangement in a cellular system when applying a preferred embodiment of the invention.
DETAILED DESCRIPTION
FIGS. 1 and 2 are block diagrams of a base station transmitter unit in a cellular system, such as a GSM system,
REFERENCES:
patent: 4940984 (1990-07-01), Kleiber
Nokia Telecommunications Oy
Pham Chi H.
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