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. Apparatus of user equipment (UE) configured for receive beamforming, the apparatus comprising:
memory; and
processing circuitry to:
decode downlink control information (DCI) received from a generation Node B (gNB), the DCI indicating a subframe and first beam refinement reference signal (BRRS) symbols within the subframe of a physical downlink shared channel (PDSCH) for (BRRS);
decode the BRRS received in the first BRRS symbols of the subframe of the PDSCH to determine refined receive beam directional information for a previously determined receive beam; and
decode second data symbols, using the refined receive beam directional information, the second data symbols received in the subframe of the PDSCH that included the BRRS, the second data symbols following the first BRRS symbols in the subframe,
wherein the memory is configured to store the DCI.
2. The apparatus of claim 1 , wherein the processing circuitry is further configured to:
decode a channel state information reference signal (CSI-RS) using the refined receive beam directional information, the CSI-RS being received in the subframe,
wherein the processing circuitry is configured to determine a channel estimate based on the CSI-RS for use in decoding the second data symbols, wherein the receive beam directional information is dynamically adjusted based on the channel estimate.
3. The apparatus of claim 2 , wherein the CSI-RS is received on a same transmit beam direction on which the BRRS is transmitted.
4. The apparatus of claim 2 , wherein the CSI-RS is received on a different transmit beam direction than the transmit beam direction on which the BRRS is transmitted.
5. The apparatus of claim 1 , wherein the BRRS includes a plurality of BRRS sequences in a set of contiguous subcarriers.
6. The apparatus of claim 1 , wherein the BRRS includes a plurality of BRRS sequences in a set of non-contiguous interleaved subcarriers.
7. The apparatus of claim 1 , wherein the refined receive beam directional information is determined based on a maximization algorithm that varies the receive beam direction in response to a signal characteristic measurement.
8. The apparatus of claim 1 , wherein the BRRS is used as a demodulation reference sequence (DMRS) to demodulate the second data symbols.
9. The apparatus of claim 1 , wherein the processing circuitry is configured to identify reception of the BRRS based on a signal correlation of the BRRS.
10. The apparatus of claim 1 , wherein the processing circuitry is to identify reception of the BRRS based on a priori knowledge of resource elements on which the BRRS is to be transmitted.
11. The apparatus of claim 1 , wherein the processing circuitry comprises a baseband processor.
12. The apparatus of claim 1 , wherein the apparatus further comprises transceiver circuitry electrically coupled to a plurality of antenna elements.
13. A non-transitory computer-readable medium comprising instructions that, when executed by processing circuitry of an apparatus of user equipment (UE), cause the apparatus to:
decode downlink control information (DCI) received from a generation Node B (gNB), the DCI indicating a subframe and first beam refinement reference signal (BRRS) symbols within the subframe of a physical downlink shared channel (PDSCH) for (BRRS);
decode the BRRS received in the first BRRS symbols of the subframe of the PDSCH to determine refined receive beam directional information for a previously determined receive beam; and
decode second data symbols, using the refined receive beam directional information, the second data symbols received in the subframe of the PDSCH that included the BRRS, the second data symbols following the first BRRS symbols in the subframe.
14. The non-transitory computer-readable medium of claim 13 , wherein the instructions are to further cause the apparatus to:
decode a channel state information reference signal (CSI-RS) using the refined receive beam directional information, the CSI-RS being received in the subframe; and
determine a channel estimate based on the CSI-RS for use in decoding the second data symbols, wherein the receive beam directional information is dynamically adjusted based on the channel estimate.
15. The non-transitory computer-readable medium of claim 14 , wherein the instructions are to further cause the apparatus to receive the CSI-RS on a same transmit beam direction on which the BRRS is transmitted.
16. The non-transitory computer-readable medium of claim 14 , wherein the instructions are to further cause the apparatus to receive the CSI-RS on a different transmit beam direction than the transmit beam direction on which the BRRS is transmitted.
17. The non-transitory computer-readable medium of claim 13 , wherein the BRRS includes a plurality of BRRS sequences in a set of contiguous subcarriers.
18. The non-transitory computer-readable medium of claim 13 , wherein the BRRS includes a plurality of BRRS sequences in a set of non-contiguous interleaved subcarriers.
19. The non-transitory computer-readable medium of claim 13 , wherein the refined receive beam directional information is determined based on a maximization algorithm that varies the receive beam direction in response to a signal characteristic measurement.
20. The non-transitory computer-readable medium of claim 13 , wherein the BRRS is used as a demodulation reference sequence (DMRS) to demodulate the second data symbols.
21. The non-transitory computer-readable medium of claim 13 , wherein the instructions are to further cause the apparatus to identify reception of the BRRS based on a signal correlation of the BRRS.
22. The non-transitory computer-readable medium of claim 13 , wherein the instructions are to further cause the apparatus to identify reception of the BRRS based on a priori knowledge of resource elements on which the BRRS is to be transmitted.
23. Apparatus of a generation node-B (gNB) configured for transmit beamforming, the apparatus comprising:
memory; and
processing circuitry to:
encode a downlink control information (DCI) for transmission to a user equipment (UE), the DCI indicating a subframe and first beam refinement reference signal (BRRS) symbols within the subframe of a physical downlink shared channel (PDSCH) for (BRRS);
encode the BRRS for transmission in the first BRRS symbols of the subframe of the PDSCH for use by the UE to determine refined receive beam directional information for a previously determined receive beam; and
encode second data symbols for transmission in the subframe of the PDSCH that included the BRRS, the second data symbols following the first BRRS symbols in the subframe.
24. The apparatus of claim 23 , wherein the processing circuitry is further configured to:
encode a channel state information reference signal (CSI-RS) to be transmitted in the subframe that included the BRRS.
25. The apparatus of claim 24 , wherein the processing circuitry is to encode the CSI-RS to be transmitted on a same transmit beam direction on which the BRRS is to be transmitted.
26. The apparatus of claim 24 , wherein the processing circuitry is to encode the CSI-RS to be transmitted on a different transmit beam direction than the transmit beam direction on which the BRRS is to be transmitted.
27. The apparatus of claim 24 , wherein the processing circuitry is to encode the CSI-RS to be transmitted in the subframe after the BRRS and before the second data symbols.
28. The apparatus of claim 24 , wherein the processing circuitry is to encode the CSI-RS to be transmitted in the subframe after the second data symbols.
29. The apparatus of claim 23 , wherein the BRRS includes a sequence based on a Zadoff-Chu sequence based on at least one parameter selected from the group consisting of: cell ID, virtual cell ID, Beamformed Reference Signal (BRS) ID, BRS group ID, or any combination thereof.
30. The apparatus of claim 23 , wherein the BRRS includes a sequence based on a quadrature phase shift keying sequence based on at least one parameter selected from the group consisting of: cell ID, virtual cell ID, Beamformed Reference Signal (BRS) ID, BRS group ID, or any combination thereof.