Method and apparatus for robust MIMO transmission

1. A user equipment (UE) comprising:

a transceiver configured to:

receive information about a downlink (DL) transmission transmitted from N_RRH>1 remote radio head (RRH), wherein:

N_RRH is a number of remote radio heads (RRHs),

RRH r comprises a group of antenna ports, and

r=1, . . . , N_RRH; and

receive the DL transmission; and

a processor operably coupled to the transceiver, the processor configured to decode the information about the DL transmission;

wherein the DL transmission is based on a precoding scheme and a diversity scheme,

wherein the precoding scheme corresponds to applying an intra-RRH precoder component to antenna ports within an RRH, and

wherein the diversity scheme corresponds to applying an inter-RRH diversity component to antenna ports across RRHs.

2. The UE of claim 1 , wherein:

the diversity scheme comprises RRH cycling,

in a given time-frequency resource, the DL transmission is transmitted from one RRH, and

the one RRH is cycled from RRH 1, . . . , RRH N_RRH through time-frequency resources that are allocated for the DL transmission.

3. The UE of claim 1 , wherein:

an RRH selection is performed based on a subset comprising n out of N_RRH RRHs,

the DL transmission is from the subset of n out of N_RRH RRHs, and

1<n<N_RRH.

4. The UE of claim 1 , wherein:

the diversity scheme comprises precoder cycling,

the inter-RRH diversity component corresponds to inter-RRH precoders, and

the inter-RRH precoders are cycled through time-frequency resources that are allocated for the DL transmission.

5. The UE of claim 4 , wherein the precoder cycling is based on a per frequency domain (FD) unit, where the FD unit is one of a physical resource block group (PRG), a physical resource block (PRB), a subband (SB), or a resource element (RE).

6. The UE of claim 1 , wherein:

the diversity scheme comprises delay diversity, and

a delay information from each RRH is used to obtain a corresponding inter-RRH diversity component.

7. The UE of claim 6 , wherein the delay information from each RRH is based on a round-trip delay or a one-way delay, where the round-trip delay is based on both a DL delay and an UL delay, and the one-way delay is based on one of either a DL delay or an UL delay.

8. A base station (BS) comprising:

a processor configured to generate information about a downlink (DL) transmission transmitted from N_RRH>1 remote radio head (RRH), wherein:

N_RRH is a number of remote radio heads (RRHs),

RRH r comprises a group of antenna ports, and

r=1, . . . , N_RRH; and

a transceiver operably coupled to the processor, the transceiver configured to:

transmit the information about the DL transmission, and

transmit the DL transmission;

wherein the DL transmission is based on a precoding scheme and a diversity scheme,

wherein the precoding scheme corresponds to applying an intra-RRH precoder component to antenna ports within an RRH, and

wherein the diversity scheme corresponds to applying an inter-RRH diversity component to antenna ports across RRHs.

9. The BS of claim 8 , wherein:

the diversity scheme comprises RRH cycling,

in a given time-frequency resource, the DL transmission is transmitted from one RRH, and

the one RRH is cycled from RRH 1, . . . , RRH N_RRH through time-frequency resources that are allocated for the DL transmission.

10. The BS of claim 8 , wherein:

an RRH selection is performed based on a subset comprising n out of N_RRH RRHs,

the DL transmission is from the subset of n out of N_RRH RRHs, and

1<n<N_RRH.

11. The BS of claim 8 , wherein:

the diversity scheme comprises precoder cycling,

the inter-RRH diversity component corresponds to inter-RRH precoders, and

the inter-RRH precoders are cycled through time-frequency resources that are allocated for the DL transmission.

12. The BS of claim 11 , wherein the precoder cycling is based on a per frequency domain (FD) unit, where the FD unit is one of a physical resource block group (PRG), a physical resource block (PRB), a subband (SB), or a resource element (RE).

13. The BS of claim 8 , wherein:

the diversity scheme comprises delay diversity, and

a delay information from each RRH is used to obtain a corresponding inter-RRH diversity component.

14. The BS of claim 13 , wherein the delay information from each RRH is based on a round-trip delay or a one-way delay, where the round-trip delay is based on both a DL delay and an UL delay, and the one-way delay is based on one of either a DL delay or an UL delay.

15. A method for operating a user equipment (UE), the method comprising:

receiving information about a downlink (DL) transmission transmitted from N_RRH>1 remote radio head (RRH), wherein:

N_RRH is a number of remote radio heads (RRHs),

RRH r comprises a group of antenna ports, and

r=1, . . . , N_RRH;

receiving the DL transmission; and

decoding the information about the DL transmission;

wherein the DL transmission is based on a precoding scheme and a diversity scheme,

wherein the precoding scheme corresponds to applying an intra-RRH precoder component to antenna ports within an RRH, and

wherein the diversity scheme corresponds to applying an inter-RRH diversity component to antenna ports across RRHs.

16. The method of claim 15 , wherein:

the diversity scheme comprises RRH cycling,

in a given time-frequency resource, the DL transmission is transmitted from one RRH, and

the one RRH is cycled from RRH 1, . . . , RRH N_RRH through time-frequency resources that are allocated for the DL transmission.

17. The method of claim 15 , wherein:

an RRH selection is performed based on a subset comprising n out of N_RRH RRHs,

the DL transmission is from the subset of n out of N_RRH RRHs, and

1<n<N_RRH.

18. The method of claim 15 , wherein:

the diversity scheme comprises precoder cycling,

the inter-RRH diversity component corresponds to inter-RRH precoders, and

the inter-RRH precoders are cycled through time-frequency resources that are allocated for the DL transmission.

19. The method of claim 18 , wherein the precoder cycling is based on a per frequency domain (FD) unit, where the FD unit is one of a physical resource block group (PRG), a physical resource block (PRB), a subband (SB), or a resource element (RE).

20. The method of claim 15 , wherein:

the diversity scheme comprises delay diversity, and

a delay information from each RRH is used to obtain a corresponding inter-RRH diversity component.