Reference signal for receive beam refinement in cellular systems
User Equipment (UE) and base station (eNB) apparatus and methodology for adjusting receive beamforming. A beam refinement reference signal (BRRS) is transmitted with the same transmit beam direction on which data is to be transmitted. While receiving the BRRS, the receiver varies its receive beam direction and measures a signal characteristic of reception of the BRRS to determine a refined receive beam direction. The refined receive beam direction is used to receive the data.
1. An apparatus, comprising:
a processor configured to cause a base station to:
encode a downlink control information (DCI) for transmission to a user equipment (UE), the DCI indicating one or more beam refinement reference signal (BRRS) symbols and data symbols of a physical downlink shared channel (PDSCH);
encode BRRS for transmission in the one or more BRRS symbols; and
encode the data symbols for transmission, wherein the data symbols follow the one or more BRRS symbols in the PDSCH, wherein the one or more BRRS symbols are demodulation reference symbols (DMRS) and wherein there are no other DMRS symbols associated with the data symbols after the one or more BRRS symbols.
2. The apparatus of claim 1 , wherein a beam used for the data symbols is based on the one or more BRRS symbols and a previously determined beam.
3. The apparatus of claim 1 , wherein the data symbols are transmitted using a plurality of multiple-input, multiple-output (MIMO) layers.
4. The apparatus of claim 1 , wherein the processor is further configured to cause the base station to transmit channel state information reference signal (CSI-RS) in the PDSCH, wherein the base station receives feedback based on the CSI-RS.
5. The apparatus of claim 4 , wherein the feedback received is based on a receive beam used by the UE to receive the BRRS and the CSI-RS.
6. The apparatus of claim 1 , wherein the processor is further configured to cause the base station to receive a sounding reference signal (SRS) from the UE based on a receive beam used by the UE to receive the BRRS.
7. The apparatus of claim 1 , wherein the BRRS is a quadrature phase shaft keying (QPSK) based sequence.
8. The apparatus of claim 1 , wherein the one or more BRRS symbols comprise two symbols.
9. An apparatus, comprising:
a processor, configured to cause a user equipment device (UE) to:
receive a downlink control information (DCI) from a base station, the DCI indicating one or more beam refinement reference signal (BRRS) symbols and data symbols of a physical downlink shared channel (PDSCH);
receive BRRS in the one or more BRRS symbols; and
receive the data symbols, wherein the data symbols follow the one or more BRRS symbols in the PDSCH, wherein the one or more BRRS symbols are demodulation reference symbols (DMRS) and wherein there are no other DMRS symbols associated with the data symbols after the one or more BRRS symbols.
10. The apparatus of claim 9 , wherein a beam used for the data symbols is based on the one or more BRRS symbols and a previously determined beam.
11. The apparatus of claim 9 , wherein the data symbols are received using a plurality of multiple-input, multiple-output (MIMO) layers.
12. The apparatus of claim 9 , wherein the processor is further configured to cause the UE to:
receive channel state information reference signal (CSI-RS) in the PDSCH; and
transmit, to the base station, feedback based on the CSI-RS.
13. The apparatus of claim 12 , wherein the feedback received is based on a receive beam used by the UE to receive the BRRS and the CSI-RS.
14. The apparatus of claim 9 , wherein the processor is further configured to cause the UE to transmit a sounding reference signal (SRS) to the base station based on a receive beam used to receive the BRRS.
15. The apparatus of claim 9 , wherein the BRRS is a quadrature phase shaft keying (QPSK) based sequence.
16. The apparatus of claim 9 , wherein the one or more BRRS symbols comprise two symbols.
17. A user equipment device (UE), the UE comprising:
a radio; and
a processor operably connected to the radio and configured to cause the UE to:
receive a downlink control information (DCI) from a base station, the DCI indicating one or more beam refinement reference signal (BRRS) symbols and data symbols of a physical downlink shared channel (PDSCH);
receive BRRS in the one or more BRRS symbols; and
receive the data symbols, wherein the data symbols follow the one or more BRRS symbols in the PDSCH, wherein the one or more BRRS symbols are demodulation reference symbols (DMRS) and wherein there are no other DMRS symbols associated with the data symbols after the one or more BRRS symbols.
18. The UE of claim 17 , wherein the data symbols are received using a plurality of multiple-input, multiple-output (MIMO) layers.
19. The UE of claim 17 , wherein the processor is further configured to cause the UE to:
receive channel state information reference signal (CSI-RS) in the PDSCH; and
transmit, to the base station, feedback based on the CSI-RS.
20. The UE of claim 17 , wherein the processor is further configured to cause the UE to transmit a sounding reference signal (SRS) to the base station based on a receive beam used to receive the BRRS.