Method for adjusting transmit power during call set-up, and a cellular radio system

• US 6,272,354 B1
• Filed: 02/17/1998
• Issued: 08/07/2001
• Est. Priority Date: 08/18/1995
• Status: Expired due to Fees

• Current Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Original Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Inventors: Saario, Eija
• Primary Examiner(s): Hunter, Daniel
• Assistant Examiner(s): CHOW, CHARLES CHIANG
• Application Number:
  US09/011,804
• Time in Patent Office: 1,267 Days
• Field of Search: 455/422, 455/69, 455/95, 455/522, 455/68
• US Class Current: 455/522
• CPC Class Codes: H04W 52/50 at the moment of starting communication in a multiple access environment

Abstract

A cellular radio system and a method for adjusting transmit power during call set-up. The system comprises at least one base station and a group of subscriber equipment communicating with one or more of the base stations. The signal-to-noise ratio between the subscriber equipment and a base station is estimated before an actual connection is set up. In order that the new connection not interfere with the existing connections, a desired power transmit value with which the desired signal-to-noise ratio is obtained is calculated for the transmit power of the transmitter. An initial value for the transmit power is calculated by means of the power-control parameters of the system and a given time constant and the transmission is started with the initial value. The transmit power in increased from the initial value to the desired power transmit value during a given time constant.

Claims

1. A method for adjusting a transmit power of a communication over a communication channel in a cellular radio system comprising the steps of:

estimating a desired signal-to-noise ratio of the communication over the communication channel between a base station and a subscriber equipment before the communication channel is established;

calculating, during a call set-up period, a desired transmit power value for transmitting the communication over the communication channel from a transmitter in the system, wherein the desired signal-to-noise ratio is obtained;

calculating, during the call set-up period, an initial transmit power value for transmitting the communication over the communication channel using at least one power control parameter of the system and a predetermined time constant, wherein the initial power value is smaller than the desired power value;

initiating a transmission of the communication over the communication channel using the initial transmit power level; and

increasing a transmission power of the communication from the initial transmit power level to the desired transmit power value over a predetermined time period.

2. A method according to claim 1, wherein the step of estimating the signal-to-noise ratio between the subscriber equipment and the base station comprises the step of estimating the signal-to-noise ratio in an uplink direction, and the initial transmit power is adjusted in the subscriber equipment.

3. A method according to claim 2, further comprising the steps of:

measuring in the base stations (100) the total interference of a prior signal received from the subscriber equipment (108-112);

transmitting a pilot signal from the base station with a predetermined transmit power over a control channel;

measuring at the subscriber equipment a power level of the pilot signal from each base station that is on a list of nearby base stations maintained by the subscriber equipment;

estimating the attenuations over the connections between the subscriber equipment and the base stations by means of the pilot signals; and

estimating the signal-to-noise ratio between the subscriber equipment and the base station in the uplink direction on the basis of the total interference measured in the base station, the attenuation over the connection, and an assumed transmit power of the subscriber equipment.

4. A method according to claim 3, wherein the step of estimating the signal-to-noise ratio further comprises the steps of dividing the assumed transmit power of the subscriber equipment by the estimated attenuation over the connection and calculating the ratio of a value obtained by the dividing step to the total interference measured in the base station.

5. A method according to claim 4, further comprising the step of subtracting the ratio of the value obtained by the dividing step to the total interference from the total interference before the estimate for the signal-to-noise ratio has been calculated.

6. A method according to claim 1, wherein the step of estimating the signal-to-noise ratio between the subscriber equipment and the base station comprises the step of estimating the signal to noise ratio in a downlink direction, and the initial transmit power is adjusted in the base station.

7. A method according to claim 1, further comprising the step of increasing the transmit power from the initial power to the calculated desired power level in a time period corresponding to the power control updating rate of the system.

8. A method according to claim 1, further comprising the step of updating the calculated desired power level to which the transmit power is increased according to the power control updating rate of the system.

9. A method according to claim 1, further comprising the step of calculating an initial value for the transmit power by multiplying the ratio between the power control updating rate of the system and the given time constant by a final desired value of the transmit power.

10. The method of claim 1 wherein the step of estimating the desired signal-to-noise ratio further comprises the steps of:

transmitting a pilot signal with a known transmit power level from the base station to the subscriber equipment over a control channel;

measuring a received power level of the pilot signal received from the base station at the subscriber equipment; and

estimating an attenuation of the transmission over the communication channel by comparing the known transmit power level with the received power value.

11. The method of claim 1 wherein the call set-up period is a period of time occurring before an actual connection between the base station and the subscriber equipment is established.

12. A cellular radio system comprising:

at least one base station;

at least one subscriber equipment, each subscriber equipment adapted to communicate with one of the base stations;

a transceiver in the base station adapted to estimate a signal-to-noise ratio between the subscriber equipment and the base station in an uplink direction before an actual connection between the subscriber equipment and the base station is established, wherein the transceiver is further adapted to;

calculate a desired transmit power for a transmitter in the subscriber equipment corresponding to the estimated signal-to-noise ratio;

calculate an initial transmit power value for the transmitter using at least one power control parameter of the system and a time constant, the initial transmit power value being used to start a transmission between the subscriber equipment and the base station after the connection is established; and

increase the transmission power of the transmission from the initial transmit power value to the desired transmit power during a period of time corresponding to the time constant.

13. A cellular radio system according to claim 12 wherein the transceiver (108-112) is situated in the base station (100).

14. A cellular radio system according to claim 12 wherein the transceiver (108-112) is situated in the subscriber equipment.

15. A cellular radio system according to claim 14, wherein the base station comprises:

means (320, 326) for measuring the total interference of at least one signal received from the subscriber equipment, and

means (310) for transmitting a pilot signal with a predetermined transmit power; and

wherein the subscriber equipment (108-112) comprises;

means (320-326) for measuring the power levels of the pilot signal received from the base station, and wherein the transceiver comprises;

means (320, 326) for estimating an attenuation over the connection between the subscriber equipment and the base station by means of the pilot signals and means (320, 326) for estimating the signal-to-noise ratio between the subscriber equipment and the base station in the uplink direction on the basis of a total interference measured in the base station (100), the attenuation over the connection, and an assumed transmit power of the subscriber equipment (108-112).

16. A cellular radio system according to claim 14, p wherein the means (320, 326) for estimating the signal-to-noise ratio between the subscriber equipment and the base station are situated in the subscriber equipment (108-112).

17. A cellular radio system according to claim 14, wherein the means (320, 326) for estimating the signal-to-noise ratio between the subscriber equipment and the base station are situated in the base station.

18. A cellular radio system according to claim 14, wherein the transmitter is adapted to increase its transmit power from the initial power to the desired power level according to the power control updating rate of the system.

19. A cellular radio system according to claim 14, wherein the transmitter comprises means (310, 326) for updating the desired power level to which the transmit power of the subscriber equipment is increased according to the power control updating rate of the system.

20. A system for determining a transmit power level for a communication channel in a cellular radio system comprising:

at least one base station;

at least one terminal device adapted to communicate with the base station over the communication channel; and

a transceiver adapted to establish the communication pathway between the base station and the terminal device, wherein before the communication pathway is established, the transceiver is adapted to estimate a desired power transmit value for a transmission over the communication pathway and an initial power transmit level, wherein the initial power level is calculated to provide a low quality signal-to-noise ratio, the desired power transmit level being determined by estimating a signal-to-noise ratio of the communication pathway in an uplink direction by monitoring an attenuation of a pilot signal transmitted by the base station to the terminal device over a control channel, and wherein the transceiver initiates the transmission over the communication pathway using the initial power level with the low quality signal-to-noise ratio and increases a transmission power level of the communication to the desired power level having a good quality signal-to-noise ratio over a time period.

21. The system of claim 20 wherein the transceiver is located in the terminal device and is adapted to measure a received power level of the pilot signal transmitted by the base station over the control channel and determine the attenuation of the pilot signal based on a known transmit power of the pilot signal and the received power level.