Control of transmission power in a radio system

• US 20020045460A1
• Filed: 07/19/2001
• Published: 04/18/2002
• Est. Priority Date: 01/19/1999
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Nokia Corporation
• Inventors: Rahkala, Jari, Makinen, Jarmo
• Granted Patent: US 7,647,062 B2
• Time in Patent Office: Days
• US Class Current: 455/522
• CPC Class Codes: H04W 52/10 Open loop power control
• CPC Class Codes: H04W 52/20 using error rate
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters

Abstract

The invention relates to a method for controlling transmission power in a radio system, preferably in a radio link system. To establish a power control mechanism which is capable of taking into account the various phenomena affecting the performance of the radio connection and which can also respond to degrading signal quality before bit errors begin to occur, pseudo errors, i.e. decision-making instants at which a symbol error nearly occurred, are monitored at the receiving end. The transmission power is then decreased when the rate of the pseudo errors is below a predetermined threshold and increased when pseudo errors occur so that a predetermined criterion is fulfilled.

Claims

1. A method for controlling transmission power in a radio system having a transmitting end and a receiving end, the method comprising the steps of

transmitting a digital signal from the transmitting end to the receiving end,

receiving said digital signal at the receiving end,

monitoring signal quality at the receiving end, and

adjusting the transmission power at the transmission end in accordance with the monitored signal quality, said monitoring and adjusting being characterized by the further steps of

monitoring pseudo error occurrence at the receiving end,

decreasing the transmission power when the rate of the pseudo errors is below a predetermined threshold, and

increasing the transmission power when pseudo errors occur so that a predetermined condition is fulfilled.

2. A method as claimed in claim 1, characterized in that the transmission power is increased immediately when a pseudo error is detected.

3. A method as claimed in claim 1, characterized in that the transmission power is decreased in small steps for a predetermined time period at each step.

4. A method as claimed in claim 2 or 3, characterized by

(a) adjusting the transmission power after the set-up of the radio system to a value high enough so that no pseudo errors are detected at the receiving end,

(b) decreasing the transmission power until the first pseudo error is detected,

(c) increasing the transmission power in response to the pseudo error detected, and

(d) jumping to phase (b) if no pseudo errors are detected during a predetermined time period after the transmission power has been increased in phase (c).

5. A method as claimed in claim 1, characterized in that the transmission power is increased by a small predetermined amount when said pseudo errors are detected.

6. A method as claimed in claim 1, characterized by

using forward error correction (FEC) in the transmitted signal,

decoding the signal at the receiving end by means of a FEC decoder, and

interpreting the corrections made by the decoder as pseudo errors.

7. A method as claimed in claim 1, characterized by using at the receiving end a demodulator provided with a first set of thresholds for making a decision on a received symbol and a second set of thresholds for making a decision on whether a pseudo error has occurred.

8. A method as claimed in claim 1, characterized by the further steps of monitoring the rate of actual errors at the receiving end, and

increasing the transmission power temporarily to the maximum transmission power when a predetermined error rate threshold is exceeded.

9. A radio system including

at a receiving end first means (SMa, SMb, 15a, 15b) for monitoring signal quality and for producing a control signal on the basis of the monitored signal quality, and

at a transmitting end second means (15a, 15b) for adjusting the transmission power in response to said control signal,

characterized by

said first means being adapted to monitor the occurrence of pseudo errors and to produce a control signal indicating when the pseudo errors are detected and when the rate of the pseudo errors is below a predetermined threshold, whereby said second means are responsive to said control signal by increasing the transmission power when the pseudo errors are detected and by decreasing the transmission power when the rate of the pseudo errors is below a predetermined threshold.

10. A radio system as claimed in claim 9, characterized in that said first means include a FEC decoder (45) for decoding a FEC coded signal and for detecting pseudo errors.

11. A radio system as claimed in claim 9, characterized in that said first means include a demodulator provided with a first set of thresholds for making a decision on a received symbol and a second set of thresholds for making a decision on whether a pseudo error has occurred.