Beam reference signal based narrowband channel measurement and CQI reporting
When beamforming (e.g., via a millimeter wave system (mmW)) is used for wireless communication, a base station may transmit beams that are directed to certain directions. Due to the directional nature of the beams in the mmW system, an approach to determine a beam that provides a desirable gain is studied. The apparatus may be a user equipment (UE). The apparatus receives, from a base station, a plurality of signals through a plurality of beams of the base station, each of the plurality of beams corresponding to a respective antenna port of a plurality of antenna ports of the base station, where the plurality of signals include a plurality of beam reference signals, a plurality of beam refinement reference signals, a plurality of channel state information reference signals (CSI-RSs), or a combination thereof. The apparatus performs channel estimation for each beam of the plurality of beams from the plurality of antenna ports based on the plurality of signals.
1. A method of wireless communication by a user equipment (UE), comprising:
receiving, from a base station, a plurality of signals through a plurality of beams of the base station, each of the plurality of beams corresponding to a respective antenna port of a plurality of antenna ports of the base station, wherein the plurality of signals include a plurality of beam reference signals, a plurality of beam refinement reference signals, a plurality of channel state information reference signals (CSI-RSs), or a combination thereof,
wherein each of the plurality of signals includes an extended synchronization signal that is cyclically shifted to indicate a particular symbol index within a subframe;
receiving, from the base station, a number N, wherein N is a number of beams to be reported;
performing wideband channel estimation on each beam of the plurality of beams from the plurality of antenna ports based on the plurality of signals, then performing narrowband channel estimation on selected one or more beams and selecting one or more resource blocks based on the narrowband channel estimation;
ranking the plurality of beams based on the wideband and narrowband channel estimation; and
transmitting, to the base station, a feedback signal including information about N beams of the one or more beams selected from the plurality of beams.
2. The method of claim 1 , wherein a millimeter wave (mmW) band is used for the wireless communications.
3. The method of claim 1 , wherein the plurality of beam reference signals are received during a synchronization subframe.
4. The method of claim 1 , wherein at least one beam of the selected one or more beams comprises a high measurement for each of a plurality of symbols, the high measurement being greater than a threshold measurement for at least one of the wideband channel estimation or the narrowband channel estimation.
5. The method of claim 4 , wherein the selected one or more beams are selected within one or more frequency bands based on the narrowband channel estimation.
6. The method of claim 1 , wherein the feedback signal is transmitted to the base station via at least one of a physical uplink control channel (PUCCH) or in uplink control information (UCI) conveyed via a physical uplink shared channel (PUSCH).
7. The method of claim 1 , wherein the feedback signal is transmitted to the base station through a random access channel (RACH) subframe.
8. The method of claim 1 , wherein the narrowband channel estimation is based on a measurement of at least one of a signal-to-noise ratio, an antenna gain, or a reference signal measurement of each of the plurality of beams.
9. A method of wireless communication by a base station, comprising:
transmitting, to a user equipment (UE), a plurality of signals through a plurality of beams of the base station, each of the plurality of beams corresponding to a respective antenna port of a plurality of antenna ports of the base station,
wherein the plurality of signals include a plurality of beam reference signal, a plurality of beam refinement reference signals, a plurality of channel state information reference signals (CSI-RSs), or a combination thereof,
wherein each of the plurality of signals includes an extended synchronization signal that is cyclically shifted to indicate a particular symbol index within a subframe;
transmitting, to the UE, a number N, wherein N is a number of beams to be reported; and
receiving, from the UE, a feedback signal including information about N beams of one or more beams selected from the plurality of beams, wherein the one or more beams are selected based on a ranking of the plurality of beams, the ranking being based on a wideband channel estimate and wherein the feedback signal is received on resource blocks based on a subsequent narrowband channel estimation for each beam of the plurality of beams.
10. The method of claim 9 , wherein a millimeter wave (mmW) band is used for the wireless communication.
11. The method of claim 9 , where the plurality of beam reference signals are transmitted during a synchronization subframe.
12. The method of claim 9 , wherein the transmitting the plurality of signals includes:
sweeping through a plurality of directions in different symbols to transmit the plurality of signals.
13. The method of claim 9 , wherein the feedback signal is received from the UE via at least one of a physical uplink control channel (PUCCH) or in uplink control information (UCI) conveyed via a physical uplink shared channel (PUSCH).
14. The method of claim 9 , wherein the feedback signal is received from the UE through a random access channel (RACH) subframe.
15. The method of claim 9 , further comprising:
performing communication with the UE based on the feedback signal.
16. The method of claim 15 , further comprising:
choosing a beam among the one or more beams based on the feedback signal,
wherein the communication with the UE is performed via the chosen beam.
17. A user equipment (UE) for wireless communication, comprising:
a memory; and at least one processor coupled to the memory and configured to:
receive, from a base station, a plurality of signals through a plurality of beams of the base station, each of the plurality of beams corresponding to a respective antenna port of a plurality of antenna ports of the base station,
wherein the plurality of signals include a plurality of beam reference signals, a plurality of beam refinement reference signals, a plurality of channel state information reference signals (CSI-RSs), or a combination thereof,
wherein each of the plurality of signals includes an extended synchronization signal that is cyclically shifted to indicate a particular symbol index within a subframe;
receive, from the base station, a number N, wherein N is a number of beams to be reported;
perform wideband channel estimation and select one or more beams based on the wideband channel estimation for each beam of the plurality of beams from the plurality of antenna ports based on the plurality of signals, then perform narrowband channel estimation on selected one or more beams and select one or more resource blocks based on the narrowband channel estimation;
rank the plurality of beams based on the wideband and narrowband channel estimation; and
transmit, to the base station, a feedback signal including information about N beams of the one or more beams selected from the plurality of beams.
18. The UE of claim 17 , wherein at least one beam of the selected one or more beams comprises a high measurement for each of a plurality of symbols, the high measurement being greater than a threshold measurement for at least one of the wideband channel estimation or the narrowband channel estimation.
19. A base station for wireless communication, comprising:
a memory; and
at least one processor coupled to the memory and configured to:
transmit, to a user equipment (UE), a plurality of signals through a plurality of beams of the base station, each of the plurality of beams corresponding to a respective antenna port of a plurality of antenna ports of the base station, wherein the plurality of signals include a plurality of beam reference signal, a plurality of beam refinement reference signals, a plurality of channel state information reference signals (CSI-RSs), or a combination thereof, wherein each of the plurality of signals includes an extended synchronization signal that is cyclically shifted to indicate a particular symbol index within a subframe;
transmit, to the UE, a number N, wherein N is a number of beams to be reported; and
receive, from the UE, a feedback signal including information about N beams of one or more beams selected from the plurality of beams, wherein the one or more beams are selected based on a ranking of the plurality of beams, the ranking being based on a wideband channel estimation, and wherein the feedback signal is received on resource blocks selected based on a subsequent narrowband channel estimation for each beam of the plurality of beams.
20. The base station of claim 19 , wherein the at least one processor is further configured to:
perform communication with the UE based on the feedback signal.
21. The base station of claim 20 , wherein the at least one processor is further configured to:
choose a beam among the one or more beams based on the feedback signal,
wherein the communication with the UE is performed via the chosen beam.