Channel quality predictor and method of estimating a channel condition in a wireless communications network
View Patent ↗In one embodiment of the method, a channel quality metric for a first subframe is estimated based at least in part on a channel quality metric for a previous subframe, and a channel quality metric for a second subframe is estimated based at least in part on the channel quality metric for the previous subframe. Here, the second subframe is later in time than the first subframe. Then, a channel quality metric for a time slot located between the first and second subframes is estimated based on the channel quality metrics for the first and second subframes.
1. A method of estimating a channel condition, comprising:
first estimating a channel quality metric for a first subframe based at least in part on a channel quality metric for a previous subframe, wherein the first estimating step filters the channel quality metric for the previous subframe to generate the estimated channel quality metric for the first sub frame;
second estimating a channel quality metric for a second subframe based at least in part on the channel quality metric for the previous subframe, the second subframe being later in time than the first subframe, wherein the second estimating step filters the channel quality metric for the previous subframe to generate the estimated channel quality metric for the second subframe; and
third estimating a channel quality metric for a time slot located between the first and second subframes based on the channel quality metrics for the first and second subframes.
2. The method of claim 1 , wherein at least one of the first and second estimating steps performs infinite impulse response filtering.
3. The method of claim 1 , wherein at least one of the first and second estimating steps performs finite impulse response filtering.
4. The method of claim 1 , wherein the first estimating step determines at least one first filter coefficient using one of a least-mean-square algorithm and a recursive-least-square algorithm based on the channel quality metric of the previous subframe and the estimated channel quality metric of the first sub frame.
5. The method of claim 1 , wherein the second estimating step determines at least one filter coefficient using one of a least-mean-square algorithm and a recursive-least-square algorithm based on the channel quality metric of the previous subframe and the estimated channel quality metric of the second subframe.
6. The method of claim 1 , wherein the third estimating step estimates the channel quality metric for the time slot by interpolation using the channel quality metrics for the first and second subframes.
7. The method of claim 6 , wherein the interpolating is performed by a linear interpolator.
8. The method of claim 1 , wherein the first and second subframes are separated by at least one subframe.
9. The method of claim 1 , further comprising:
receiving a channel quality indicator for the previous subframe; and
converting the channel quality indicator into the channel quality metric for the previous subframe.
10. The method of claim 9 , wherein the channel quality indicator is received on an uplink channel.
11. The method of claim 10 , wherein the uplink channel is a High Speed Dedicated Physical Control Channel in accordance with 3GPP-UMTS.
12. The method of claim 1 , wherein the first and second subframes are separated by at least one of a subframe interval and a multiple of the subframe interval.
13. The method of claim 1 , further comprising:
adjusting a downlink transmission parameter on a downlink channel based on the estimated channel quality metric for the time slot.
14. The method of claim 13 , wherein the downlink transmission parameter includes a downlink transmission power and the adjusting step increases or decreases the downlink transmission power on the downlink channel.
15. The method of claim 13 , wherein the downlink transmission parameter includes a data encoding/modulation parameter and the adjustment step increases or decreases a level of encoding/modulation on the downlink channel.
16. A channel quality predictor, comprising:
a first filter coefficient generating unit generating at least one first filter coefficient, wherein the first filter coefficient generating unit generates the at least one first filter coefficient based on the channel quality metric for the previous subframe and output from the first filter;
a second filter coefficient generating unit generating at least one second filter coefficient, wherein the second filter coefficient generating unit generates the at least one second filter coefficient based on the channel quality metric for the previous subframe and output from the second filter;
a first filter unit filtering a channel quality metric for a previous subframe based on the at least one first filter coefficient to generate a channel quality metric estimate for a first subframe;
a second filter unit filtering the channel quality metric for the previous subframe based on the at least one second filter coefficient to generate a channel quality metric estimate for a second subframe, later in time than the first subframe; and
an interpolator unit estimating a channel quality metric for a time slot located between the first and second subframes based on the channel quality metric estimates for the first and second subframes.
17. The channel quality predictor of claim 16 , wherein at least one of the first and second filters is an infinite impulse response filter.
18. The channel quality predictor of claim 16 , wherein at least one of the first and second filters is a finite impulse response filter.