UE, network node and methods therein for beam reporting in a wireless communication system
A method performed by a User Equipment (UE) is performed. The UE obtains ( 202 ) a beam reporting configuration. The beam reporting configuration defines a beam reporting procedure for determining an optimal beam for each of different sub-bands of a system bandwidth. The UE measures ( 204 ) different reference signals transmitted by the network node. The measured different reference signals correspond to each of the different sub-bands according to the beam reporting configuration. The UE then determines ( 206 ) a preferred beam for each of the different sub-bands based on the corresponding received reference signals.
1. A method performed by a User Equipment (UE), the method comprising:
obtaining a beam reporting configuration defining a beam reporting procedure for determining an optimal beam for each of different sub-bands of a system bandwidth;
measuring, according to the beam reporting configuration, different reference signals transmitted by a network node corresponding to each of the different sub-bands; and
determining a preferred beam for each of the different sub-bands based on the corresponding received reference signals.
2. The method of claim 1 , further comprising receiving a triggering signal for starting the beam reporting procedure at the UE.
3. The method of claim 2 , wherein the receiving the triggering signal is based on a data requirement of the UE and an available portion of the system bandwidth.
4. The method of claim 2 , wherein the triggering signal is transmitted to the UE in Downlink Control Information (DCI).
5. The method of claim 1 , wherein the beam reporting configuration is signaled to the UE via Radio Resource Control (RRC) signaling.
6. The method of claim 1 , wherein the beam reporting configuration comprises one or more parameters corresponding to one or more of: frequency granularity of the different sub-bands, a number of beams usable by the network node, Reference Signal Received Power (RSRP), and/or Channel Quality Indicator (CQI) reporting.
7. The method of claim 1 , further comprising transmitting a beam reporting message to the network node, the beam reporting message indicating the preferred beam for each of the different sub-bands.
8. The method of claim 7 , wherein the beam reporting message further indicates a wideband preferred beam for the system bandwidth as a whole.
9. The method of claim 7 , wherein the beam reporting message further indicates one or more Reference Signal Received Power (RSRP) values and/or Channel Quality Indicator (CQI) values associated with the measured reference signals.
10. The method of claim 1 , wherein the different reference signals comprise different Channel State Information Reference Signals (CSI-RS).
11. A User Equipment (UE), comprising:
processing circuitry;
memory containing instructions executable by the processing circuitry whereby the UE is operative to:
obtain a beam reporting configuration defining a beam reporting procedure for determining an optimal beam for each of different sub-bands of a system bandwidth;
measure, according to the beam reporting configuration, different reference signals transmitted by the network node corresponding to each of the different sub-bands; and
determine a preferred beam for each of the different sub-bands based on the corresponding received reference signals.
12. A method performed by a network node, the method comprising:
determining a beam reporting configuration defining a beam reporting procedure to be utilized by a User Equipment (UE) for determining an optimal beam for each of different sub-bands of a system bandwidth;
signaling the beam reporting configuration to the UE;
transmitting different reference signals to the UE according to the beam reporting configuration, the different reference signals corresponding to each of the different sub-bands; and
receiving a beam reporting message from the UE, the beam reporting message indicating a preferred beam for each of the different sub-bands.
13. The method of claim 12 , further comprising transmitting, to the UE, a triggering signal for initializing the beam reporting procedure at the UE.
14. The method of claim 13 , wherein the triggering signal is transmitted in Downlink Control Information (DCI).
15. The method of claim 13 , wherein the triggering signal is transmitted based on a data requirement of the UE and an available portion of the system bandwidth.
16. The method of claim 12 , wherein the beam reporting configuration is signaled to the UE via Radio Resource Control (RRC) signaling.
17. The method of claim 12 , wherein the beam reporting configuration comprises one or more parameters corresponding to one or more of: frequency granularity of the different sub-bands, a number of beams usable by the network node, Reference Signal Received Power (RSRP), and/or Channel Quality Indicator (CQI) reporting.
18. The method of claim 14 , wherein the different reference signals comprise different Channel State Information Reference Signals (CSI-RS).
19. The method of claim 12 , wherein the determining the beam reporting configuration comprises:
estimating a frequency selectivity associated with the system bandwidth; and
determining a frequency granularity defining the sub-bands within the system bandwidth based on the estimated frequency selectivity.
20. The method of claim 19 , wherein the estimating the frequency selectivity comprises obtaining a measured coherence bandwidth and/or reciprocal of delay spread.
21. The method of claim 19 , wherein the frequency granularity defining the sub-bands is UE-specific, cell-specific, or common for a group of UEs with similar channel properties.
22. The method of claim 12 , wherein the beam reporting message further indicates one or more Reference Signal Received Power (RSRP) values and/or Channel Quality Indicator (CQI) values associated with the reference signals measured at the UE.
23. The method of claim 12 , wherein the beam reporting message further indicates a wideband preferred beam for the system bandwidth as a whole.
24. A network node, comprising:
processing circuitry;
memory containing instructions executable by the processing circuitry whereby the network node is operative to:
determine a beam reporting configuration defining a beam reporting procedure to be utilized by a User Equipment (UE) for determining an optimal beam for each of different sub-bands of a system bandwidth;
signal the beam reporting configuration to the UE;
transmit different reference signals to the UE according to the beam reporting configuration, the different reference signals corresponding to each of the different sub-bands; and
receive a beam reporting message from the UE, the beam reporting message indicating a preferred beam for each of the different sub-bands.