초록 ▼

The present invention relates to methods of controlling transmitting power in a cellular radio communication system comprising one or several base stations each communicating with mobile terminals located within its respective area of coverage in which method the desired power change is calculated b

The present invention relates to methods of controlling transmitting power in a cellular radio communication system comprising one or several base stations each communicating with mobile terminals located within its respective area of coverage in which method the desired power change is calculated by means of an adaptive algorithm. Power drift between the desired output power and actually used output power is reduced by making the algorithm reduce the influence of the previously used output power by multiplying it with a “forgetting function” λ with values between 0 and 1. At the receiving end is a decision made whether the received power order commands are reliable or not by checking the soft value of the power order commands. This proposed power control algorithm provides a delta-modulated fast power control method which is robust to errors in the signalling channel and at the same time reacts quickly to fast fading variations.

대표청구항 ▼

1. A method of controlling transmitting power in a cellular radio communication system comprising one or several transmitters each communicating with receivers located within its respective area of coveragethe method characterised by the following stepsdetermining in the receiver the quality (Q) of

1. A method of controlling transmitting power in a cellular radio communication system comprising one or several transmitters each communicating with receivers located within its respective area of coveragethe method characterised by the following stepsdetermining in the receiver the quality (Q) of signals received from the transmitter;calculating in the receiver a desired output power level ({tilde over (P)} n ) from the transmitter as a function of estimated previously used output power ({circumflex over (P)} n−1 ) from the transmitter in relation to channel quality (Q n−1 ) from the transmitter to the receiver;delta-modulating in the receiver the desired output power ({tilde over (P)} n ) by comparing it with the estimated previously used output power ({circumflex over (P)}n− 1 ) from the transmitter to determine a power order command;transmitting the power order command to the transmitter ordering it to either raise or lower its output power; andcalculating in the transmitter its new output power dependent on the received power order command, a power step size function (Δp), previously used output power (P n−1 ) and a forgetting function (λ). 2. The method of claim 1 further characterised inmaking the average power step size function (Δp) a function of time correlation of the channel quality (Q) from the transmitter to the receiver. 3. The method of claim 1 further characterised indetermining in the transmitter the reliability of the power order command;making the average power step size function (Δp) a function of the reliability of the received power order command. 4. The method of claim 1 further characterised indetermining the difference P diff ={tilde over (P)} n −P mean where P mean is a long term mean value of the desired output power {tilde over (P)} n ; andmaking the maximum of P diff a function of channel quality (Q) from the transmitter to the receiver. 5. The method of claim 1 further characterised inmaking the forgetting function (λ) a function of time correlation of the channel quality (Q) from the transmitter to the receiver. 6. The method of claim 1 further characterised inmaking the forgetting function (λ) a function of the reliability of the received power order command. 7. The method of claim 1 further characterised incalculating the desired output power ({tilde over (P)} n ) in accordance with the relationship {tilde over (P)} n =α−β·( Q n−1 −{circumflex over (P)} n−1 )(dB)where α sets an average power level in the system and β is a function which determines a feedback of estimated previously used output power ({circumflex over (P)}n− 1 ) from the receiver in relation to channel quality (Q n−1 ) from the transmitter to the receiver. 8. The method of claim 1 further characterised indelta-modulating the desired output power ({tilde over (P)} n ) in accordance with the relationship TPC =sign( {tilde over (P)} n −{circumflex over (P)} n−1 )where {circumflex over (P)} n−1 is estimated previously used output power from the transmitter. 9. The method of claim 1 further characterised incalculating the new output power in accordance with the relationship P n =Δp·{overscore (TPC)}+λ·P n−1 +(1−λ)· P 0 (dB)where {overscore (TPC)} is the received power order command and λ is a forgetting function reducing the influence of previously used output power P n−1 and Δp is an adaptable power step size function. 10. The method of claim 1 further characterised indetermining the reliability of the power order command by checking the soft value of the power order command as it is received in the transmitter.