Method and system for controlling transmission power

• US 20040253929A1
• Filed: 03/09/2004
• Published: 12/16/2004
• Est. Priority Date: 06/16/2003
• Status: Active Grant

• Current Assignee: Oki Semiconductor Company Limited (ROHM Co., Ltd.)
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Akahori, Hiroji
• Granted Patent: US 7,486,935 B2
• Time in Patent Office: Days
• US Class Current: 455/68
• CPC Class Codes: H04W 52/04 TPC
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/228 using past power values or information
• CPC Class Codes: H04W 52/241 taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo

Abstract

A transmission power control system includes a control and a controlled station. In the control station, an SIR (Signal-to-interference Ratio) estimator calculates two different kinds of estimated SIRs having a long and a short mean processing time, respectively. A subtractor subtracts a target SIR from the estimated SIR with the long mean processing time while an error decider compares the resulting difference with a threshold to thereby output a result of decision. A comparison value updater updates, based on the result of decision, a comparison SIR held in a comparison value holder. Another subtractor subtracts the comparison SIR from the estimated SIR with the short mean processing time. A control information converter generates power control information in accordance with the output of the another subtractor. The controlled station selectively increases or decreases transmission power in accordance with the power control information received from the control station.

Claims

1. A method of controlling a transmission power of a transmission-power controlled station from a transmission-power control station, said method comprising:

an SIR (Signal-to-Interference Ratio) estimating step of calculating an estimated SIR having a long mean processing time and an estimated SIR having a short mean processing time on the basis of a received signal demodulated by said transmission-power control station;

a comparison value updating step of updating an SIR comparison value, which is held in a comparison value holder, in accordance with a difference between said estimated SIR having the long mean processing time and a desired target SIR; and

a transmission power controlling step of controlling the transmission power of the transmission-power controlled station such that said estimated SIR having the short mean processing time converges to said comparison SIR.

2. The method in accordance with claim 1, wherein said comparison value updating step comprises a step of storing said comparison SIR in said comparison value holder, a step of subtracting said target SIR from said estimated SIR having the long mean processing time to thereby produce a difference, and a step of subtracting said difference from said comparison SIR stored in said comparison value holder to thereby update said comparison SIR;

and

wherein said transmission power controlling step comprises a step of comparing said estimated SIR having the short mean processing time with said comparison SIR held in said comparison value holder, a step of generating power control information that indicates lowering of the transmission power if said estimated SIR having said short mean processing time is greater than said comparison SIR or indicates raising of said transmission power if said estimated SIR is smaller than said comparison SIR, and a step of controlling said transmission power in accordance with said power control information.

3. A transmission power control system comprising:

a transmission-power control station; and

a transmission-power controlled station;

said transmission-power control station comprising;

an SIR estimator for calculating an estimated SIR having a long mean processing time and an estimated SIR having a short mean processing time in accordance with a received signal demodulated;

a comparison value holder for holding a comparison SIR;

a subtractor for subtracting a desired target SIR from said estimated SIR having the long mean processing time to thereby produce a difference;

a comparison value updater for subtracting the difference output from said subtractor from said comparison SIR held in said comparison value holder to thereby update said comparison SIR;

a power control information generator for comparing said estimated SIR having the short mean processing time with said comparison SIR held in said comparison value holder to thereby generate power control information that indicates lowering of said transmission power if said estimated SIR is greater than said comparison SIR or indicates raising of said transmission power if said estimated SIR is smaller than said comparison SIR; and

a transmitter for transmitting said power control information;

said transmission-power controlled station comprising;

a receiver for receiving said power control information from said transmission-power control station; and

a transmission power controller for controlling transmission power in accordance with said power control information fed from said receiver.

4. The system in accordance with claim 3, wherein said SIR estimator comprises:

a mean power calculator for calculating mean powers of received signals;

a mean value calculator for calculating a mean value of the mean powers output from said mean power calculator;

another mean power calculator for calculating mean powers of signal wave components of the received signals;

another mean value calculator for calculating a mean value of said mean powers output from said another mean power calculator;

an estimated SIR calculator for calculating an estimated SIR having a short mean processing time on the basis of the mean powers output from said mean power calculator and the mean powers output from said another mean power calculator; and

another estimated SIR calculator for calculating an estimated SIR having a long mean processing time on the basis of the mean value output from said mean value calculator and the mean value output from said another mean value calculator.

5. The system in accordance with claim 3, wherein said comparison value updater updates said comparison SIR stored in said comparison value holder when an absolute value of a difference between said estimated SIR having the long mean processing time and a desired target SIR is greater than a preselected threshold value.

6. The system in accordance with claim 4, wherein said SIR estimator calculates said estimated SIR having a short mean processing time and said estimated SIR having a long mean processing time on the basis of pilot signals each being contained in a particular one of a plurality of slots, which constitute a frame of the received signals.