Physical downlink control channel (PDCCH) demodulation reference signal (DMRS) transmission and reception

1. One or more non-transitory, computer-readable media having instructions that, when executed by one or more processors, cause a base station to:

embed a first even number of demodulation reference signals (DMRSs) in a corresponding first even number of resource elements (REs) in a first resource level of a pair of resource levels of a physical downlink control channel (PDCCH), wherein the first even number of DMRSs are associated with a first antenna pair;

embed a second even number of DMRSs in a corresponding second even number of REs in a second resource level of the pair of resource levels of the PDCCH, wherein the second even number of DMRSs are associated with a second antenna pair;

apply, to the first resource level and the second resource level, a transmit diversity scheme; and

identify, for transmission from the first antenna pair, the first resource level, and, for transmission from the second antenna pair, the second resource level, wherein the instructions, when executed, further cause the base station to:

number sequentially the first resource level and the second resource level, wherein the first resource level has an even number and the second resource level has an odd number;

identify, for transmission by the first antenna pair, the first resource level, based on the even number; and

identify, for transmission from the second antenna pair, the second resource level, based on the odd number.

2. The one or more non-transitory, computer-readable media of claim 1 , wherein the first or second resource level is a resource element group (REG), a REG cluster, or a resource block.

3. The one or more non-transitory, computer-readable media of claim 1 , wherein the transmit diversity scheme is a space frequency block coding (SFBC) transmit diversity scheme.

4. The one or more non-transitory, computer-readable media of claim 1 , wherein the transmit diversity scheme is per-RE precoder cycling transmit diversity scheme.

5. The one or more non-transitory, computer-readable media of claim 4 , wherein the first antenna pair is a first pre-coded antenna pair, and wherein the second antenna pair is a second pre-coded antenna pair.

6. The one or more non-transitory, computer-readable media of claim 1 , wherein the instructions, when executed, further cause the base station to:

provide, for transmission from the first antenna pair and the second antenna pair, a quasi-colocation reference signal (QCL-RS) for the first resource level and the second resource level.

7. The one or more non-transitory, computer-readable media of claim 6 , wherein the QCL-RS is one of a channel state indicator RS (CSI-RS) or a mobility RS (MRS).

8. A base station, comprising:

memory to store transmit diversity scheme information; and

processor circuitry, coupled with the memory, to:

embed a first even number of demodulation reference signals (DMRSs) in a corresponding first even number of resource elements (REs) in a first resource level of a pair of resource levels of a physical downlink control channel PDCCH, wherein the first even number of DMRSs are associated with a first antenna pair;

embed a second even number of DMRSs in a corresponding second even number of REs in a second resource level of the pair of resource levels of the PDCCH, wherein the second even number of DMRSs are associated with a second antenna pair;

apply, to the first resource level and the second resource level, a transmit diversity scheme based on the transmit diversity scheme information; and

identify, for transmission from the first antenna pair, the first resource level and, for transmission from the second antenna pair, the second resource level, wherein the processor circuitry is further configured to:

number sequentially the first resource level and the second resource level, wherein the first resource level has an even number and the second resource level has an odd number;

identify, for transmission by the first antenna pair, the first resource level, based on the even number; and

identify, for transmission from the second antenna pair, the second resource level, based on the odd number.

9. The base station of claim 8 , wherein the first resource level or the second resource level is a resource element group (REG).

10. The base station of claim 8 , wherein the first resource level or the second resource level is a REG cluster, wherein REs of a first REG of the REG cluster include DMRSs, and wherein REs of a second REG of the REG cluster are without the DMRSs.

11. The base station of claim 8 , wherein the first resource level or the second resource level is a resource block (RB), wherein REs of a first REG of the RB include DMRSs, and wherein REs of a second REG of the RB are without the DMRSs.

12. The base station of claim 8 , wherein the transmit diversity scheme is a space frequency block coding (SFBC) transmit diversity scheme.

13. The base station of claim 8 , wherein the transmit diversity scheme is per-RE precoder cycling transmit diversity scheme.

14. The base station of claim 13 , wherein the first antenna pair is a first pre-coded antenna pair, and wherein the second antenna pair is a second pre-coded antenna pair.

15. One or more non-transitory, computer-readable media having instructions that, when executed by one or more processors, cause a user equipment (UE) to:

derive, based on physical downlink control channel (PDCCH) demodulation reference signal (DMRS) information of the UE, a DMRS sequence of a PDCCH of the UE, wherein one or more control channel resource blocks include the PDCCH of the UE;

determine, based on PDCCH DMRS information of one or more multi-user multiple-input multiple-output (MU-MIMO) UEs, DMRS sequences of MU-MIMO PDCCHs of the one or more MU-MIMO UEs, wherein the one or more control channel resource blocks include the MU-MIMO PDCCHs;

estimate, based on the DMRS sequences of the MU-MIMO PDCCHs, channels for the MU-MIMO PDCCHs;

estimate, based on the channels for the one or more MU-MIMO PDCCHs, one or more channel powers of the MU-MIMO PDCCHs;

determine whether a channel power of the one or more channel powers exceeds a threshold; and

suppress, if the channel power exceeds the threshold, MU-MIMO PDCCH interference, wherein the instructions, when executed, further cause the UE to:

estimate a soft symbol of the PDCCH of the UE; and

estimate a soft symbol of the MU-MIMO PDCCH interference, to generate an estimated MU-MIMO PDCCH symbol.

16. The one more non-transitory, computer-readable media of claim 15 , wherein the PDCCH DMRS information is a PDCCH DMRS scrambling ID, and wherein the DMRS sequences are non-orthogonal DMRS sequences.

17. The one more non-transitory, computer-readable media of claim 15 , wherein the PDCCH DMRS information is an antenna port that includes an orthogonal cover code (OCC), and wherein the DMRS sequences are orthogonal DMRS sequences.

18. The one more non-transitory, computer-readable media of claim 15 , wherein, the instructions, when executed, further cause the UE to:

map to a quadrature phase shift keying (QPSK) symbol, based on a detector criteria, the estimated MU-MIMO PDCCH symbol;

refine the soft symbol of the PDCCH of the UE, to generate a refined UE PDCCH symbol estimate; and

provide, based on the refined UE PDCCH symbol estimate, downlink control information (DCI) bit recovery.

19. The one more non-transitory, computer-readable media of claim 15 , wherein the instructions, when executed, further cause the UE to:

estimate, based on the DMRS sequence of the PDCCH of the UE, a channel for the PDCCH of the UE; and

decode the PDCCH of the UE.

20. A user equipment (UE), comprising:

memory to store physical downlink control channel (PDCCH) demodulation reference signal (DMRS) information; and

processor circuitry, coupled with the memory, to:

derive, based on the PDCCH DMRS information, a DMRS sequence of a PDCCH of the UE, wherein one or more control channel resource blocks include the PDCCH;

determine, based on PDCCH DMRS information of a multi-user multiple-input (MU-MIMO) UE, a DMRS sequence of MU-MIMO PDCCH of the MU-MIMO UE, wherein the one or more control channel resource blocks include the MU-MIMO PDCCH;

estimate, based on the DMRS sequence of the MU-MIMO PDCCH of the MU-MIMO UE, a channel for the MU-MIMO PDCCH;

estimate, based on the channel for the MU-MIMO PDCCH, a channel power of the MU-MIMO PDCCH;

determine whether the channel power exceeds a threshold; and

suppress, if the channel power exceeds the threshold, MU-MIMO PDCCH interference, wherein the processor circuitry is further configured to:

estimate a soft symbol of the PDCCH of the UE; and

estimate a soft symbol of the MU-MIMO PDCCH interference, to generate an estimated MU-MIMO PDCCH symbol.

21. The UE of claim 20 , wherein the PDCCH DMRS information is a PDCCH DMRS scrambling ID, and wherein the DMRS sequences are non-orthogonal DMRS sequences.

22. The UE of claim 20 , wherein the PDCCH DMRS information is an antenna port that includes an orthogonal cover code (OCC), and wherein the DMRS sequences are orthogonal DMRS sequences.

23. The UE of claim 20 , wherein the processor circuitry is further configured to:

estimate, based on the DMRS sequence of the PDCCH of the UE, a channel for the PDCCH of the UE; and

decode the PDCCH of the UE.