Transmit power control in a radio communication system

• US 6,259,927 B1
• Filed: 06/06/1997
• Issued: 07/10/2001
• Est. Priority Date: 06/06/1997
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Persson, Magnus, Butovitsch, Peter, Sandin, Tomas
• Primary Examiner(s): Kincaid, Lester G.
• Application Number:
  US08/870,867
• Time in Patent Office: 1,495 Days
• Field of Search: 455/67.3, 455/69, 455/70, 455/436, 455/450, 455/453, 455/522, 455/524, 455/442, 455/67.1
• US Class Current: 455/522
• CPC Class Codes: H04B 7/022 Site diversity; Macro-diversity using two or more spaced independent antennas H04B7/04
• CPC Class Codes: H04W 52/36 with a discrete range or set of values, e.g. step size, ramping or offsets
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff

Abstract

Methods of controlling the power levels of transmitted signals in telecommunication systems are described. For example, a remote terminal measures the quality of a received signal, either by determining the frame error rate or the bit error rate, and reports its quality measurement to a network by sending a quality message. The network causes the signal transmitters to adjust their transmit power levels appropriately. Faster power control methods may be combined with slower power control methods for downlink (network to remote terminal) transmissions in various communications scenarios, such as soft hand-overs.

Claims

1. A method of controlling power levels of signals transmitted by base stations in a communication system having base stations and remote stations, comprising the steps of:

determining in a remote station whether the remote station is simultaneously receiving a first signal transmitted by a first base station and at least one second signal transmitted by at least one second base station that include substantially identical message information;

transmitting to a controller from the first base station a first report of a power level of the first signal;

transmitting to the controller from the at least one second base station at least one second report of a power level of the at least one second signal;

comparing in the controller the first report and the at least one second report;

transmitting from the controller to the first base station a first command for controlling the power level of the first signal; and

transmitting from the controller to the at least one second base station at least one second command for controlling the power level of the at least one second signal;

or

when the first and at least one second signal do not include substantially identical message information or when only one of the first signal and at least one second signal is received at the remote station;

determining a signal to interference ratio of the received signal;

transmitting from the remote station a report of the determined signal to interference ratio; and

substantially simultaneously controlling the power level of the signal based on the report as received at the first base station.

2. The method of claim 1, wherein the first and second commands cause the first and second base stations to adjust the power levels of their transmitted signals such that the power levels have a predetermined relation.

3. The method of claim 2, wherein the predetermined relation is substantial equality to an arithmetic mean of the power levels of the signals transmitted by the first and second base stations.

4. The method of claim 1, wherein reports are sent periodically.

5. The method of claim 1, wherein a report is sent upon occurrence of a predetermined event.

6. A method of controlling power levels of signals transmitted by base stations in a communication system having base stations and remote stations, comprising in a remote station the steps of:

determining whether the remote station is simultaneously receiving a first signal transmitted by a first base station and at least one second signal transmitted by at least one second base station that include substantially identical message information;

when the first and at least one second signal include substantially identical message information, determining at the remote station a quality of at least one of the received first signal and the at least one second signal;

transmitting from the remote station a report of the determined quality;

substantially simultaneously controlling the power level of the first signal and the power level of the at least one second signal based on the report as received at the first base station and the report as received at the at least one second base station;

when the first signal and at least one second signal do not include substantially identical message information, determining a signal to interference ratio of the received first signal;

transmitting from the remote station a report of the determined signal to interference ratio; and

substantially simultaneously controlling the power level of the first signal based on the report as received at the first base station; and

when only one of the first signal and at least one second signal is received at the remote station, determining a signal to interference ratio of the one received signal;

transmitting from the remote station a report of the determined signal to interference ratio; and

substantially simultaneously controlling the power level of the one received signal based on the report as received at the first base station.

7. The method of claim 6, wherein the determined quality is a frame error rate.

8. The method of claim 6, wherein the determined quality is a bit error rate.

9. The method of claim 6, wherein reports are sent periodically.

10. The method of claim 6, wherein a report is sent upon occurrence of a predetermined event.

11. A method of controlling power levels of signals transmitted by base stations in a communication system having base stations and remote stations comprising the steps of:

determining whether the remote station is simultaneously receiving a first signal transmitted by a first base station and at least one second signal transmitted by at least one second base station that include substantially identical message information;

when the first signal and at least one second signal include substantially identical message information identifying at the remote station the signal having a highest power level;

transmitting from the remote station a report of the identified base station;

controlling a power level of the first signal and a power level of the at least one second signal based on the report such that the power level of the at least one second signal is controlled to be substantially less than the power level of the first signal when the report indicates the power level of the first signal is higher than the power level of the at least one second signal;

when the first signal and at least one second signal do not include substantially identical message information, determining a signal to interference ratio of the received first signal, transmitting from the remote station a report of the determined signal to interference ratio, and substantially simultaneously controlling the power level of the first signal based on the report as received at the first base station; and

when only one of the first signal and at least one second signal is received at the remote station determining a signal to interference ratio of the one received signal;

transmitting from the remote station a report of the determined signal to interference ratio; and

substantially simultaneously controlling the power level of the one received signal based on the report as received at the first base station;

wherein the controlling step includes determining a signal to interference ratio of the received first signal, transmitting from the remote station a report of the determined signal to interference ratio, and controlling the power level of the first signal based on the report as received at the first base station.

12. The method of claim 11, wherein reports are sent periodically.

13. The method of claim 11, wherein a report is sent upon occurrence of a predetermined event.

14. The method of claim 11, wherein the power level of the at least one second signal is controlled to be substantially zero.

15. A method of controlling power levels of signals transmitted by base stations in a communication system having base stations and remote stations, comprising the steps of:

determining whether the remote station is simultaneously receiving a first signal transmitted by a first base station and at least one second signal transmitted by at least one second base station that include substantially identical message information;

when the first signal and at least one second signal include substantially identical message information, estimating at the first base station a signal to interference ratio of the first signal received at the remote station;

estimating at the at least one second base station a signal to interference ratio of the at least one second signal received at the remote station;

transmitting to a controller from the first base station and from the at least one second base station respective reports of the estimated signal to interference ratios;

comparing in the controller the respective reports;

transmitting from the controller to the first base station a first command for controlling the power level of the first signals;

transmitting from the controller to the at least one second base station at least one second command for controlling the power level of the at least one second signal;

when the first signal and at least one second signal do not include substantially identical message information, determining a signal to interference ratio of the received first signal, transmitting from the remote station a report of the determined signal to interference ratio, and substantially simultaneously controlling the power level of the first signal based on the report as received at the first base station; and

when only one of the first signal and at least one second signal is received at the remote station, determining a signal to interference ratio of the one received signal;

transmitting from the remote station a report of the determined signal to interference ratio; and

substantially simultaneously controlling the power level of the one received signal based on the report as received at the first base station;

wherein the at least one second command causes the at least one second base station to reduce the power level of the at least one second signal to substantially zero when the controller determines that the estimated signal to interference ratio of the first signal is larger than the estimated signal to interference ratio of the at least one second signal.

16. The method of claim 15, wherein reports are sent periodically.

17. The method of claim 15, wherein a report is sent upon occurrence of a predetermined event.