Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Patent
1996-01-11
1998-09-08
Le, Thanh Cong
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
455 69, 370337, H04B 726
Patent
active
058060030
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/F194/00321 filed Jul. 12, 1994.
BACKGROUND OF THE INVENTION
The invention relates to a method for adjusting transmission power of a subscriber mobile station in a cellular radio system when a call is established, the system comprising at least one base station in each cell, communicating with the mobile stations located in the cell. In the system, the base station sends data about itself on at least one control channel common to all mobile stations. The system comprises at least one common control channel for transmitting Channel Requests from mobile stations to the base station to establish an actual connection on a traffic channel. In the system, the mobile stations can adjust their transmission power on the basis of the data transmitted from the base station on a control channel.
In a cellular network system, when a subscriber mobile station wants to contact a base station, it sends a Channel Request on a control channel of the cellular radio network allocated for the purpose. On the basis of the request, the base station allocates an actual channel to the mobile station for communication. The base stations, on the other hand, regularly send on common control channels data which allows the mobile stations to synchronize themselves with the base station. On the channels, the base stations identify the network, the frequencies on which the traffic and control channels are, and the mobile station to which an incoming call is addressed. In the idle mode (connected to the network, but not busy with a call), the mobile stations continuously listen to the base stations on the control channels.
It is previously known that the power level at which a mobile station sends a Channel Request and the first few messages on the actual traffic channel is the same with all the mobile stations located within the area covered by the base station. The base station sends data about this initial power level on common control channels with other data about the base station. When a connection has been established, the base station or base station controller starts to adjust the power of the mobile station, connection by connection, on the basis of the measuring results and the quality of the connection.
Although all the mobile stations located within the base station area send a Channel Request at the same power, the base station receiver detects great differences in the levels of signals from different mobile stations. This is due to the fact that the radio waves propagate differently on different connections. The mobile stations are usually divided at random over the base station area. Since the cells may be up to 30 km in diameter, the differences in the distances of the mobile stations from the base stations may be great. Since attenuation of radio waves is, on average, relative to the square of the travel distance of the waves, signals transmitted at the same power are received at very different power levels in the base station.
As the base station receives Channel Requests on the control channel, a great difference in the levels of successive signals causes problems in the receiver. The base station attempts to adjust the power levels when a connection has been established, but this is usually slow and interference cannot be avoided. For example in the GSM, when the base station receives a Channel Request from a nearby mobile station at a great power, the base station receiver may be saturated, and the following time slot is lost due to jitter of the receiver. This may happen even when the base station operates in compliance with the GSM recommendations. When a connection has been established, the base station adjusts the power of the mobile station, but if the desired power significantly differs from the power at which Channel Requests are transmitted, the adjustment may take several seconds, during which the mobile station interferes with the system.
SUMMARY OF THE INVENTION
The object of the present invention is to avoid great differences in the lev
REFERENCES:
patent: 5212823 (1993-05-01), Fujii et al.
patent: 5278992 (1994-01-01), Su et al.
patent: 5455964 (1995-10-01), Roos et al.
patent: 5487180 (1996-01-01), Ohtake
Jolma Petri
Keskitalo Ilkka
Kiema Arto
Savusalo Jari
Cong Le Thanh
Nokia Telecommunications Oy
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