Downstream power control in point-to-multipoint systems

Details Downstream power control in point-to-multipoint systems Downstream power control in point-to-multipoint systems

1998-05-15

2001-06-26

Maung, Nay (Department: 2681)

Telecommunications

Radiotelephone system

Zoned or cellular telephone system

C455S522000, C455S067150

Reexamination Certificate

active

06253077

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
This invention relates to point-to-multipoint systems and more particularly to downstream power control of these systems.
BACKGROUND OF THE INVENTION
Point-to-multipoint communication systems provide service to a large number of subscribers or remote stations from a central base station (or central base station) at each node. To maximize the number of subscribers serviced by the base station, the node may be sectorized into several sectors with a separate transceiver (transmitter and receiver) and antenna system for each sector. This provides for 100% frequency reuse on each sector. The polarization of transmitted and received signal may alternate about the node as disclosed in J. Leland Langston application Ser. No. 08/345,183, filed Nov. 28, 1994 entitled “Low Power, Short Range Point-to-Multipoint Communications System ” incorporated herein by reference. This provides for 100% frequency reuse but creates sector to sector interference possibilities.
Previous 2-way point-to-multipoint systems include cellular telephony systems, wireless local loop systems, and satellite communication systems. Cellular telephone systems and wireless local loop systems incorporate a method of power control to minimize subscriber transmitted power. The power control system maintains each subscriber at threshold. In addition, both cellular telephone systems and wireless local loop systems do not re-use the same frequency at a base station. This does not eliminate the interference problems associated with systems like that in the Langston application that reuse frequencies at a base station to maximize capacity.
Other fixed wireless systems are known to use a measurement of signal to noise ratio to perform power control. The disadvantage of using signal to noise as a criteria for power control is that the power setting at the subscriber is performed on system interference as well as receiver noise. This is because the signal to noise measurement includes interference and actually measures signal to noise plus interference ratio. If subscriber power is increased when high interference is measured, the result is a further increase in interference.
The interference increase caused by increasing subscriber power may occur elsewhere in the system on a common frequency channel (frequency reuse between sectors and between nodes) and would be difficult to detect. It could further cause an increase in subscriber power elsewhere in the system resulting in or snowball effect, or system instability.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the present invention a point-to-multipoint power control system is provided for one or more base station transmitters by an off-the-air monitor and pick up antenna located in a given coverage area of the base station for detecting power transmitted by the one or more base station transmitters. The system includes a generator for generating power level control signals based on the detected power level at the remote monitor and coupling these power control signal to the basestation to adjust the power levels from the one or more transmitters.
These and other features of the invention that will be apparent to those skilled in the art from the following detailed description of the invention, taken together with the accompanying drawings.


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