Methods and systems of wireless communication with remote radio heads
View Patent ↗A method for transmitting control information in a telecommunications cell is provided. The method includes a transmission point in the cell transmitting a unicast PDCCH intended only for a specific UE in the cell. The unicast PDCCH contains at least one resource element in each resource element group. The at least one resource element contains a UE-specific DMRS that can be used for decoding the unicast PDCCH without the cell-specific reference signal.
1. A method for transmitting control information in a telecommunications cell, comprising:
a subset of transmission points of a set of transmission points associated with an eNodeB (eNB) in the cell transmitting a unicast physical downlink control channel (PDCCH) intended only for a specific user equipment (UE) in the cell,
wherein the unicast PDCCH contains at least one resource element in each resource element group, and
wherein at least one resource element contains a UE-specific demodulation reference signal (DMRS) that can be used for decoding the unicast PDCCH, and
wherein the decoding occurs without the use of a cell-specific reference signal broadcast by the eNB, and
wherein a remainder of the set of transmission points does not transmit the unicast PDCCH.
2. The method of claim 1 , wherein the at least one resource element is not allocated for the cell-specific reference signal being broadcast in the cell.
3. The method of claim 1 , wherein the UE-specific DMRS is a sequence of symbols carrying a bit sequence that allows the specific UE to decode the unicast PDCCH correctly.
4. The method of claim 1 , wherein the UE-specific DMRS is derived from at least one of:
a radio network temporary identifier assigned to the specific UE;
an identifier for the cell; and
a subframe index.
5. The method of claim 1 , wherein a beam forming type of precoded transmission is used for the unicast PDCCH, and wherein the PDCCH is weighted and transmitted from a plurality of antenna ports such that signals from the plurality of antenna ports are coherently combined at the specific UE.
6. The method of claim 5 , wherein a precoding vector for the precoded transmission is obtained from at least one of:
feedback from the specific UE regarding at least one downlink wideband channel;
and an uplink channel measurement based on channel reciprocity.
7. The method of claim 6 , wherein a set of precoding vectors is predefined, and wherein each resource element group of the unicast PDCCH is precoded with one of the precoding vectors.
8. The method of claim 7 , wherein a mapping from precoding vector to resource element group is performed in a cyclic manner.
9. A transmission point (TP) in a telecommunications cell, comprising:
a processor configured such that a subset of transmission points of a set of transmission points associated with an eNodeB (eNB) transmits a unicast physical downlink control channel (PDCCH) intended only for a specific user equipment (UE) in the cell,
wherein the unicast PDCCH contains at least one resource element in each resource element group, and
wherein at least one resource element containing a UE-specific demodulation reference signal (DMRS) that can be used for decoding the unicast PDCCH, and
wherein the decoding occurs without the use of a cell-specific reference signal broadcast by the eNB, and
wherein a remainder of the set of transmission points does not transmit the unicast PDCCH.
10. The TP of claim 9 , wherein the at least one resource element is not allocated for the cell-specific reference signal being broadcast in the cell.
11. The TP of claim 9 , wherein the UE-specific DMRS is a sequence of symbols carrying a bit sequence that allows the specific UE to decode the unicast PDCCH correctly.
12. The TP of claim 9 , wherein the UE-specific DMRS is derived from at least one of:
a radio network temporary identifier assigned to the specific UE;
an identifier for the cell; and
a subframe index.
13. The TP of claim 9 , wherein a beamforming type of precoded transmission is used for the unicast PDCCH, and wherein the PDCCH is weighted and transmitted from a plurality of antenna ports such that signals from the plurality of antenna ports are coherently combined at the specific UE.
14. The TP of claim 13 , wherein a precoding vector for the precoded transmission is obtained from at least one of:
feedback from the specific UE regarding at least one downlink wideband channel;
and an uplink channel measurement based on channel reciprocity.
15. The TP of claim 14 , wherein a set of precoding vectors is predefined, and wherein each resource element group of the unicast PDCCH is precoded with one of the precoding vectors.
16. The TP of claim 15 , wherein a mapping from precoding vector to resource element group is performed in a cyclic manner.
17. A user equipment (UE), comprising:
a processor configured such that:
the UE receives a unicast physical downlink control channel (PDCCH) from a subset of transmission points of a set of transmission points associated with an eNodeB (eNB) that contains at least one resource element in each resource element group,
wherein the at least one resource element contains a UE-specific demodulation reference signal (DMRS) that the UE can use to decode the unicast PDCCH, and
wherein the UE performs the decoding without the use of a cell-specific reference signal broadcast by the eNB, and
wherein the UE does not receive the unicast PDCCH from a remainder of the set of transmission points.
18. The UE of claim 17 , wherein the at least one resource element is not allocated for the cell-specific reference signal.
19. The UE of claim 17 , wherein the UE-specific DMRS is a sequence of symbols carrying a bit sequence that allows the specific UE to decode the unicast PDCCH correctly.
20. The UE of claim 17 , wherein the UE-specific DMRS is derived from at least one of:
a radio network temporary identifier assigned to the specific UE;
an identifier for the cell; and
a subframe index.