Transmission power control method and apparatus

• US 20060003789A1
• Filed: 07/22/2005
• Published: 01/05/2006
• Est. Priority Date: 06/19/2003
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Kobayashi, Yutaka, Murata, Shuuichi
• Granted Patent: US 7,778,656 B2
• Time in Patent Office: Days
• US Class Current: 455/522
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04W 52/12 Outer and inner loops
• CPC Class Codes: H04W 52/241 taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo

Abstract

Disclosed is a transmission power control method for controlling a target SIR which is a target ratio of signal to interference upon comparing error rate and target error rate of receive data on a receiving side, and causing transmission power control to be performed on a transmitting side in such a manner that measured SIR will agree with the target SIR. The method includes previously measuring and storing a correspondence characteristic between error rate and SIR; finding, from the correspondence characteristic, a first SIR with respect to a target error rate and a second SIR with respect to a measured error rate; and updating the target SIR by increasing or decreasing the target SIR by the difference between the first SIR and the second SIR.

Claims

1. A transmission power control method for controlling a target SIR which is a target ratio of signal to interference upon comparing error rate and target error rate of receive data on a receiving side, and causing transmission power control to be performed on a transmitting side so that measured SIR will agree with said target SIR, comprising:

first step of previously measuring and storing a correspondence characteristic between error rate and SIR;

second step of fining a first SIR with respect to a target error rate and a second SIR with respect to a measured error rate from said correspondence characteristic; and

third step of updating said target SIR by increasing or decreasing said target SIR by the difference between said first SIR and the second SIR.

2. A transmission power control method according to claim 1, wherein:

in the first step, previously measuring and storing a correspondence characteristic between error rate and SIR, for each service in every combination of services multiplexed, in a case where a plurality of services are multiplexed and transmitted;

in the second step, in a case where a plurality of services of a prescribed combination are multiplexed and transmitted, finding, from said characteristic, the first SIR with respect to said target error rate and the second SIR with respect to said measured error rate of each service in said combination; and

in the third step, updating said target SIR by increasing or decreasing said target SIR based upon the difference between said first SIR and second SIR of every service.

3. A transmission power control method according to claim 1, wherein the third step includes:

updating said target SIR at a first period in order to pull error rate into a stipulated range of required error rates within a first stipulated time, and

updating said target SIR at a second period, which is longer than the first period, after pull-in in order to make the error rate converge to within said stipulated range within a second stipulated time.

4. A transmission power control method according to claim 3, the third step further includes:

deciding said first period t1 upon comparing a time, which is required to acquire said measured error rate, with said first stipulated time, and

updating the target SIR when pull-in is performed at the first period t1.

5. A transmission power control method according to claim 3, the third step further includes:

setting target SIR of an initial setting sufficiently higher than a SIR that satisfies the required error rate in a case where the time required to acquire said measured error rate is greater than said first stipulated time;

adopting said first period as a decision period for deciding whether or not an error is present;

investigating occurrence of error at said period;

reducing the target SIR a prescribed amount if an error does not occur; and

deciding that pull-in has been completed when an error occurs.

6. A transmission power control method according to claim 4, wherein previously storing said second time t2 (>

t1), or α

(>

1) that prevails when t2=α

·

t1 holds, and updating the target SIR at this second period t2 after pull-in.

7. A transmission power control method according to claim 1, wherein in the first step, storing said correspondence characteristic in accordance with service quality and in the third step, updating said target SIR using a characteristic that conforms to a service of a transport channel.

8. A transmission power control method according to claim 1, wherein linearly approximating and storing said characteristic.

9. A transmission power control method according to claim 3, wherein the third step further includes:

previously storing range of fluctuation of SIR of said second period in a static environment; and

shortening said second period if the actual range of fluctuation of SIR is greater then said stored range of fluctuation by more than a set value.

10. A transmission power control method according to claim 3, wherein the third step further includes:

providing an error-rate measurement interval that is longer than said second period;

increasing the target SIR a prescribed amount if the error rate in this interval is inferior to the required error rate by more than a set value; and

decreasing the target SIR a prescribed amount if the error rate in this interval is superior to the required error rate by more than a set value.

11. A transmission power control method according to claim 2, wherein in the third step, updating the target SIR so as to satisfy a required error rate of a service for which a higher quality is required if, in a case where a plurality of services of a prescribed combination are multiplexed and transmitted, required error-rate ranges of respective ones of the services in said combination do not overlap.

12. A transmission power control method according to claim 2, wherein in the third step, updating the target SIR so as to satisfy a required error rate of a service for which a lower quality is required if, in a case where a plurality of services of a prescribed combination are multiplexed and transmitted, required error-rate ranges of respective ones of the services in said combination do not overlap.

13. A transmission power control apparatus for controlling a target SIR which is a target ratio of signal to interference upon comparing error rate and target error rate of receive data on a receiving side, and causing transmission power control to be performed on a transmitting side in such a manner that measured SIR will agree with said target SIR, comprising:

means for storing a previously measured correspondence characteristic between error rate and SIR;

means for finding a first SIR with respect to a target error rate and a second SIR with respect to a measured error rate from said correspondence characteristic; and

target SIR updating means for updating said target SIR by increasing or decreasing said target SIR by the difference between said first SIR and the second SIR.

15. A transmission power control apparatus according to claim 13, further comprising means for storing either t2 or α

(>

1) that prevails when t2=α

·

t1 holds, where t1 represents a first updating period of said target SIR for pulling error rate into a stipulated range of required error rates within a first stipulated time, and t2 represents a second updating period, which is longer than said first updating period, for making the error rate converge to within said stipulated range within a second stipulated time after pull-in;

wherein when pull-in is performed, said target SIR updating means updates the target SIR at said first updating period t1 and updates the target SIR at said second updating period t2 after pull-in.

16. A transmission power control apparatus according to claim 15, further comprising means for storing, as an initial target SIR, a SIR that is sufficiently higher than a SIR that satisfies the required error rate in a case where the time required to acquire said measured error rate is greater than said first stipulated time;

wherein when pull-in is performed, said target SIR updating means adopts the target SIR as said initial target SIR, adopts said first updating period t1 as a period for investigating whether there is an error, investigates occurrence of error at said period, reduces the target SIR a prescribed amount if an error does not occur, and decides that pull-in has been completed when an error occurs.

17. A transmission power control apparatus according to claim 15, further comprising:

storing means for previously storing range of fluctuation of SIR in said second period in a static environment; and

period changing means for comparing actual range of fluctuation of SIR and said stored range of fluctuation and shortening said second updating period if the difference is greater than a set value.

18. A transmission power control apparatus according to claim 15, further comprising second target SIR updating means for providing an error-rate measurement interval that is longer than said second updating period, increasing the target SIR a prescribed amount if the error rate in this interval is inferior to the required error rate by more than a set value, and decreasing the target SIR a prescribed amount if the error rate in this interval is superior to the required error rate by more than a set value.

19. A transmission power control apparatus according to claim 15, wherein if, in a case where a plurality of services of a prescribed combination are multiplexed and transmitted, required error-rate ranges of respective ones of the services in said combination do not overlap, then said SIR acquisition means uses a required error rate of a service for which a higher quality is required as said required error rate.

14. A transmission power control apparatus for controlling a target SIR which is a target ratio of signal to interference upon comparing error rate and target error rate of receive data on a receiving side, and causing transmission power control to be performed on a transmitting side in such a manner that measured SIR will agree with said target SIR, comprising:

means for previously measuring and storing a correspondence characteristic between error rate and SIR, for each service in every combination of services multiplexed, in a case where a plurality of services are multiplexed and transmitted;

SIR acquisition means, in a case where a plurality of services of a prescribed combination are multiplexed and transmitted, for acquiring, from said characteristic, a first SIR with respect to a target error rate and a second SIR with respect to a measured error rate of each service in said combination; and

target SIR updating means for updating said target SIR by increasing or decreasing said target SIR based upon the difference between said first SIR and second SIR of every service.

20. A transmission power control apparatus according to claim 14, wherein if, in a case where a plurality of services of a prescribed combination are multiplexed and transmitted, required error-rate ranges of respective ones of the services in said combination do not overlap, then said SIR acquisition means uses a required error rate of a service for which a lower quality is required as said required error rate.