Adjusting channel quality report in a wireless communication network

1. A method performed in a first communication node for adjusting a channel quality report transmitted between the first communication node and a second communication node, wherein the first communication node and the second communication node are in a wireless communication network and are configured to communicate with each other via a radio link, the method comprising:

receiving, from the second communication node, a channel quality report established by the second communication node;

obtaining, at the first communication node, at least one channel characteristic parameter responsive to receiving the channel quality report;

determining, at the first communication node, a channel quality offset based on the obtained channel characteristic parameter, wherein determining a channel quality offset comprises:

establishing a channel quality report delay, the delay being the time between establishment of the report in the second communication node and adjustment of the report in the first communication node; and

estimating a channel coherence time; and

adjusting, at the first communication node, the channel quality report based on the channel quality offset.

2. The method of claim 1 wherein the channel quality offset is based on

CQI offset =ƒ( x )· g ( y ),

where:

CQI offset is the channel quality offset;

ƒ(x) is a weight function; and

g(y) is a channel quality report parameter.

3. The method of claim 2 wherein ƒ(x) comprises a weight function based on the channel characteristic parameter, and on channel-coding rates or absolute level of a filtered channel quality report.

4. The method of claim 1

wherein the step of determining the channel quality offset is based on

CQI offset =ƒ( T CQI rx ,T c )·( CQI filt −CQI rx ),

where:

CQI offset is the channel quality offset;

ƒ(T CQI rx ,T c ) is the weight function;

T CQI rx is a channel quality report delay;

T C is a channel coherence time;

CQI filt is an output from a filtering of previously received channel quality reports; and

CQI rx is a newly received channel quality report.

5. The method of claim 1 wherein the channel quality report comprises a channel quality indicator (CQI) value.

6. The method of claim 1 wherein the at least one channel characteristic parameter is one of a Doppler spread, a channel coherence time, a root means square delay spread, a channel tap correlation, a number of channel taps, and a channel impulse response.

7. The method of claim 1 further comprising using the channel quality report after said adjusting in link adaptation or scheduling decisions.

8. The method of claim 1 :

wherein the first communication node comprises a user equipment and the second communication node comprises a base station; or

wherein the first communication node comprises a base station and the second communication node comprises a user equipment.

9. An arrangement in a first communication node for adjusting a channel quality report transmitted between the first communication node and a second communication node, wherein the first communication node and the second communication node are in a wireless communication network and configured to communicate with each other via a radio link, the first communication node comprising:

a receiver configured to receive, from the second communication node, a channel quality report established by the second communication node; and

a processing circuit configured to:

obtain at least one channel characteristic parameter responsive to receiving the channel quality report;

determine a channel quality offset based on the obtained channel characteristic parameter, wherein to determine the channel quality offset, the processing circuit is configured to:

establish a channel quality report delay, the delay comprising a time between the establishment of the report in the second communication node and the adjustment of the report in the first communication node; and

estimate a channel coherence time; and

adjust the channel quality report based on the channel quality offset.

10. The arrangement of claim 9 wherein the channel quality offset is based on

CQI offset =ƒ( x )· g ( y ),

where:

CQI offset is the channel quality offset;

ƒ(x) is a weight function; and

g(y) is a channel quality report parameter.

11. The arrangement of claim 10 wherein ƒ(x) comprises a weight function based on the channel characteristic parameter, and on channel-coding rates or absolute level of a filtered channel quality report.

12. The arrangement of claim 9 wherein the processing circuit is further configured to:

determine the channel quality offset based on

CQI offset =ƒ( T CQI rx ,T c )·( CQI filt −CQI rx ),

where:

CQI offset is the channel quality offset;

ƒ(T CQI rx ,T c ) is the weight function;

T CQI rx is a channel quality report delay;

T C is a channel coherence time;

CQI filt is an output from a filtering of previously received channel quality reports; and

CQI rx is a newly received channel quality report.

13. The arrangement of claim 9 wherein the channel quality report comprises a channel quality indicator (CQI) value.

14. The arrangement of claim 9 wherein the at least one channel characteristic parameter is one of a Doppler spread, a channel coherence time, a root means square delay spread, a channel tap correlation, a number of channel taps, and a channel impulse response.

15. The arrangement of claim 9 wherein the processing circuit is further configured to adjust the channel quality report based on the channel quality offset so as to be suitable for use in link adaptation or scheduling decisions.

16. The arrangement of claim 9 :

wherein the first communication node comprises a user equipment and the second communication node comprises a base station; or

wherein the first communication node comprises a base station and the second communication node comprises a user equipment.