Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1999-11-22
2001-05-08
Hunter, Daniel (Department: 2684)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S422100, C455S432300, C455S526000, C455S067150, C455S069000
Reexamination Certificate
active
06230023
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method and a device for a transmit power control for connections between a base station and mobile stations of a radio communications system, for example a digital mobile radio network.
Radio communications systems serve to transmit subscriber signals via an air interface or radio interface using radio-frequency oscillations. Such radio communications systems are, for example, mobile radio networks or devices for wirelessly linking subscribers to a landline network or fixed network. The subscriber signals of various subscribers, that is to say mobile stations, are transmitted via a common radio interface. The term multiuser telecommunication system is used in this case. Time division multiplex, frequency division multiplex or code division multiplex methods can be used to separate the subscribers, that is to say the different connections between mobile stations and a base station. It is also possible to combine these methods.
In the following, a radio communications system is described in which information is transmitted to a plurality of mobile stations simultaneously in one frequency channel. These connections therefore cannot be separated by time division multiplex methods, nor by frequency division multiplex methods. The transmission from the mobile stations to the base station is designated as the upward direction, and the transmission from the base station to the mobile stations is designated as the downward direction.
The receivers of the base station or the mobile stations need to evaluate the information from a plurality of connections which is transmitted simultaneously in one frequency channel. The problem arises in this case that the received powers of the various connections vary greatly in the case of a constant transmit power due to the different distances between receiving and transmitting radio stations. In particular, the receivers, in which the received power of their connection is low compared to the rest of the received powers, have difficulties detecting data.
It is known to introduce a transmit power control into radio communications systems in order to overcome this problem. Thus, for example, it is known from the GSM mobile radio network (Global System for Mobile Communication) to set the transmit power both in the upward direction and in the downward direction in such a way that an adequate received power is available for the respective connection in the receiver. However, in the case of the GSM mobile radio network only information of a single connection is transmitted in one frequency channel and at one instant. The problem of jointly correcting or controlling the transmit powers for a plurality of connections therefore does not arise.
Published European patent application EP 0 565 505 A2 discloses a transmit power control in a CDMA (Code Division Multiple Access) system, the signal strength received by the base station being used to increase or reduce the transmit power of signals from the mobile station to the base station, and the transmit power of the signals from the base station to the respective mobile station.
Transmit power control is also carried out in the case of CDMA (Code Division Multiple Access) mobile radio systems, for example in accordance with the Mobile Radio Standard IS-95. In this case, the transmit powers for mobile stations for transmitting in the upward direction are set in such a way that constant received powers are present for the information of all connections in the case of the receiver of the base station. For this purpose, the signal
oise ratio is determined for each connection in the base station. The measurement results are signaled to the mobile stations, whereupon the latter set their transmit powers.
The receivers of the mobile stations need to evaluate the information only for their own connection. For this reason, the requirements placed on the quality of resolution or discrimination during a reception are less stringent. However, if the number of mobile stations in the radio cell of a base station increases, the number of connections between mobile stations and the base station also increases, with the result that the sum of the influences of the remaining connections increases compared to the received power of the own dedicated connection at the receiver of a mobile station. The mobile station becomes increasingly sensitive to received power fluctuations of its own connection.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method and a device for controlling a transmit power for connections from a base station to mobile stations which overcome the above-mentioned disadvantages of the heretofore-known methods and devices of this general type.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for controlling transmit power for connections between a base station and mobile stations of a radio communications system. The method includes the steps of designating a direction of transmissions from mobile stations to a base station as an upward direction, and designating a direction of transmissions from the base station to the mobile stations as a downward direction; transmitting information to the mobile stations in the downward direction simultaneously in a frequency channel; determining received powers at at least two of the mobile stations in the downward direction; setting a dynamic range of transmit powers for the frequency channel; and determining transmit powers for the base station, the transmit powers being mobile-station-specific by taking into account the received powers, a minimum transmit power being at least equal to a maximum transmit power reduced by the dynamic range.
With the objects of the invention in view there is also provided, a device for controlling transmit power for connections between a base station and mobile stations of a radio communications system, including a storage device for storing a dynamic range and for storing received powers determined at at least two mobile stations; and an evaluation device for determining transmit powers for a base station, the evaluation device determining mobile-station-specific transmit powers by taking into account the received powers, and determining a minimum transmit power at least equal to a maximum transmit power reduced by the dynamic range.
According to the invention, a dynamic range or control range is fixed or allocated for the corresponding frequency channel for the method for a transmit power control for connections between mobile stations and a base station of a radio communications system. Furthermore, receiver powers or received powers are determined in the downward direction for at least two mobile stations. Subsequently, transmit powers or transmitter powers specific to the individual mobile stations are determined for the base station by taking into account the determined received powers. The minimum transmit power is in this case at least equal to the maximum transmit power reduced by the dynamic range or control range.
The transmit power control in the downward direction reduces the interference level in the radio cell and improves the general transmission performance in the radio communications system. With the setting of the minimum transmit power, the difference between the maximum and minimum transmit power for connections which simultaneously transmit in one frequency channel is never greater than the dynamic range. Even if the dynamic range is selected to be very large, for example amounting to the difference between the maximum and minimum provided transmit powers, and thus scarcely has any influence on the lower boundary of the transmit powers, it is possible to ensure a transmit power control in the downward direction by taking the influences of the remaining connections into account.
In accordance with a preferred embodiment of the invention, the minimum received power is identified from the received powers, which have been determined, and a correspondi
Greenberg Laurence A.
Hunter Daniel
Lerer Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
LandOfFree
Method and device for a transmit power control for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for a transmit power control for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for a transmit power control for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2449638