Methods, apparatus and computer programs for controlling feedback about channel conditions
A user equipment (UE) provides feedback about channel conditions. From a set of primary sub-bands subject to channel state information reporting by the UE, there is identified one or more of the primary sub-bands for reporting channel quality with a finer frequency-domain granularity than other primary sub-bands of the set ( 202 ). The one or more is less than all primary sub-bands in the set. In various embodiments, either the UE or the network can select which are the primary sub-bands to be identified for the finer granularity reporting, and the selection can be for example the best primary sub-bands or those with the highest variance in a measure of channel quality or random ( 206 ). Then for each of the identified primary sub-bands, the UE measures and reports the channel quality with the finer frequency-domain granularity for each secondary sub-band whose frequency lay within the respective identified primary sub-band.
1. A method for controlling a user equipment (UE) to provide feedback about channel conditions, comprising:
identifying a subset of a plurality of primary sub-bands for reporting channel quality using a finer frequency-domain granularity than a frequency-domain granularity used to report channel quality in other primary sub-bands of the plurality of primary sub-bands, wherein prior to the subset being identified, measuring and reporting channel quality with the frequency-domain granularity other than the finer frequency-domain granularity of the primary sub-bands;
measuring and reporting channel quality with the finer frequency-domain granularity for each secondary sub-band included in a corresponding primary sub-band in the subset identified, a frequency range of each secondary sub-band being smaller than a frequency range of the corresponding primary sub-band; and
further measuring and reporting channel quality with the frequency-domain granularity other than the finer frequency-domain granularity for each secondary sub-band included in a corresponding primary sub-band in the subset identified,
wherein the subset of the plurality of primary sub-bands for reporting channel quality with the finer frequency-domain granularity include at least primary sub-bands having highest channel quality based on a signal-to-interference-plus-noise ratio (SINR), and
the channel quality reported for each secondary sub-band is reported as a difference value relative to a channel quality reported for a corresponding primary sub-band.
2. The method according to claim 1 , further comprising selecting, by the UE, the subset of the plurality of primary sub-bands.
3. The method according to claim 2 , wherein the subset of the plurality of primary sub-bands for reporting channel quality with the finer frequency-domain granularity include at least sub-bands having highest variance in a measure of channel quality.
4. The method according to claim 2 , wherein the reporting comprises:
reporting a channel quality indicator for each of the other primary sub-bands not in the subset identified; and
reporting only a channel quality indicator for each secondary sub-band of a corresponding primary sub-band in the subset identified.
5. The method according to claim 1 , wherein the reporting comprises:
reporting a channel quality indicator for each primary sub-band in the subset identified.
6. The method according to claim 1 , wherein the UE identifies the subset of primary sub-bands from a message wirelessly received from a network access node.
7. The method according to claim 6 , wherein the message is wirelessly received at the UE in response to the UE reporting a channel quality indicator for each of the plurality of primary sub-bands; and
after receiving the message, reporting the channel quality with the finer frequency-domain granularity comprises reporting a channel quality indicator for each secondary sub-band of a corresponding one of the subset of primary sub-bands identified.
8. The method according to claim 1 , wherein the method is performed by the UE which is a mobile phone.
9. An apparatus for controlling a user equipment (UE) to provide feedback about channel conditions, comprising:
circuitry configured to:
identify a subset of primary sub-bands from a plurality of primary sub-bands for reporting channel quality with a finer frequency-domain granularity than a frequency-domain granularity used to report channel quality in other primary sub-bands of the plurality of primary sub-bands, wherein prior to the subset being identified, measuring and reporting channel quality with the frequency-domain granularity other than the finer frequency-domain granularity of the primary sub-bands;
measure and report channel quality with the finer frequency-domain granularity for each secondary sub-band included in a corresponding primary sub-band in the subset identified, a frequency range of each secondary sub-band being smaller than a frequency range of the corresponding primary sub-band; and
further measure and report channel quality with the frequency-domain granularity other than the finer frequency-domain granularity for each secondary sub-band included in a corresponding primary sub-band in the subset identified,
wherein the subset of the plurality of primary sub-bands for reporting channel quality with the finer frequency-domain granularity include at least primary sub-bands having highest channel quality based on a signal-to-interference-plus-noise ratio (SINR), and
the channel quality reported for each secondary sub-band is reported as a difference value relative to a channel quality reported for a corresponding primary sub-band.
10. The apparatus according to claim 9 , wherein circuitry is further configured to cause the UE to select the one or more primary sub-bands.
11. The apparatus according to claim 10 , wherein the circuitry is further configured to report the channel quality by:
reporting a channel quality indicator for each of the other primary sub-bands not in the subset identified; and
reporting only a channel quality indicator for each of the secondary sub-bands corresponding to primary sub-bands in the subset identified.
12. The apparatus according to claim 9 , wherein the circuitry is further configured to cause the UE to identify the subset of the plurality of primary sub-bands from a message wirelessly received from a network access node.
13. The apparatus according to claim 12 , wherein the message is wirelessly received at the UE in response to the UE reporting a channel quality indicator for each of the plurality of primary sub-bands; and
the circuitry is configured to cause the UE to report, after receiving the message, the channel quality with the finer frequency-domain granularity as a channel quality indicator for each secondary sub-band corresponding to primary sub-bands in the subset.
14. A method for controlling a network access node, comprising:
selecting a subset of primary sub-bands from a plurality of primary sub-bands for the reporting of channel quality using a finer frequency-domain granularity than a frequency-domain granularity used to report channel quality in other primary sub-bands not in the subset selected, wherein prior to the subset being identified, measuring and reporting channel quality with the frequency-domain granularity other than the finer frequency-domain granularity of the primary sub-bands;
notifying the user equipment of the subset of primary sub-bands selected;
receiving from the user equipment, for each secondary sub-band included in a primary sub-band included in the subset selected, an indication of channel quality with the finer frequency-domain granularity, a frequency range of each secondary sub-band being smaller than a frequency range of the corresponding primary sub-band; and
further receiving from the user equipment, for each secondary sub-band included in a primary sub-band included in the subset selected, an indication of channel quality with the frequency-domain granularity other than the finer frequency-domain granularity,
wherein the subset of the plurality of primary sub-bands for reporting channel quality with the finer frequency-domain granularity include at least primary sub-bands having highest channel quality based on a signal-to-interference-plus-noise ratio (SINR), and
the indication of channel quality received for each secondary sub-band is received as a difference value that is relative to a corresponding indication of channel quality of a corresponding primary sub-band.
15. The method according to claim 14 , wherein the network access node selects the one or more primary sub-bands randomly, as primary sub-bands having best channel quality, or both.
16. The method according to claim 14 , wherein the indications of channel quality with the finer frequency-domain granularity are received with sub-band indices indicating a corresponding indication of channel quality.
17. The method according to claim 14 , wherein the method is performed by the network access node and the network access node is an eNB operating in an LTE or LTE A system.