Mechanisms for reduced density CSI-RS
According to some embodiments, a method for use in a network node of transmitting channel state information reference signals (CSI-RS) comprises: transmitting, to the wireless device, an indication of the subset of PRBs that the wireless device should use to measure CSI-RS; and transmitting CSI-RS on the indicated subset of PRBs. According to some embodiments, a method for use in a wireless device of receiving CSI-RS comprises: receiving an indication of a subset of PRBs that the wireless device should use to measure CSI-RS associated with an antenna port; and receiving CSI-RS on the indicated subset of PRBs. In some embodiments, the indication of the subset of PRBs that the wireless device should use to measure CSI-RS comprises a density value and a comb offset.
1. A method for use in a network node of transmitting channel state information reference signals (CSI-RS), the method comprising:
transmitting, to a wireless device, an indication of a subset of physical resource blocks (PRBs) that are available for the wireless device to measure CSI-RS, each CSI-RS associated with an antenna port; and
transmitting CSI-RS on the indicated subset of PRBs.
2. The method of claim 1 , further comprising obtaining the indication of the subset of PRBs that are available for the wireless device to measure CSI-RS.
3. The method of claim 1 , wherein the indication of the subset of PRBs that are available for the wireless device to measure CSI-RS ports comprises a density value and a comb offset.
4. The method of claim 3 , wherein:
the density value comprises a density of ½;
a first comb offset indicates that the wireless device should use the PRBs in a set m1 to measure CSI-RS, wherein the set m1 comprises {0, 2, . . . , N RB DL −2}; and
a second comb offset indicates that the wireless device should use the PRBs in a set m2 to measure CSI-RS, wherein the set m2 comprises {1, 3, . . . , N RB DL −1}.
5. The method of claim 3 , wherein:
the density value comprises a density of ⅓;
a first comb offset indicates that the wireless device should use the PRBs in a set m1 to measure CSI-RS, wherein the set m1 comprises {N RB DL −3};
a second comb offset indicates that the wireless device should use the PRBs in a set m2 to measure CSI-RS, wherein the set m2 comprises {N RB DL −2}; and
a third comb offset indicates that the wireless device should use the PRBs in a set m3 to measure CSI-RS, wherein the set m3 comprises {N RB DL −1}.
6. The method of claim 1 , wherein the indication of the subset of PRBs that are available for the wireless device to measure CSI-RS comprises an index value k, the index value k referring to one of a plurality of indications stored at the wireless device.
7. The method of claim 1 , wherein the indication of the subset of PRBs that are available for the wireless device to measure CSI-RS further comprises a number of successive CSI-RS subframes in which the wireless device should measure CSI-RS.
8. The method of claim 1 , wherein the network node transmits CSI-RS on a total number of antenna ports, and each PRB of the subset of PRBs includes a CSI-RS mapping for the total number of antenna ports.
9. A method for use in a wireless device of receiving channel state information reference signals (CSI-RS), the method comprising:
receiving an indication of a subset of physical resource blocks (PRBs) that are available for the wireless device to measure CSI-RS, each of the CSI-RS associated with an antenna port; and
receiving CSI-RS on the indicated subset of PRBs.
10. The method of claim 9 , further comprising:
determining a channel state information (CSI) based on the received CSI-RS; and
transmitting the CSI to a network node.
11. The method of claim 9 , wherein the indication of the subset of PRBs that are available for the wireless device to measure CSI-RS comprises a density value and a comb offset.
12. The method of claim 11 , wherein:
the density value comprises a density of ½;
a first comb offset indicates that the wireless device should use the PRBs in a set m1 to measure CSI-RS, wherein the set m1 comprises {N RB DL −2}; and
a second comb offset indicates that the wireless device should use the PRBs in a set m2 to measure CSI-RS, wherein the set m2 comprises {N RB DL −1}.
13. The method of claim 11 , wherein:
the density value comprises a density of ⅓;
a first comb offset indicates that the wireless device should use the PRBs in a set m1 to measure CSI-RS, wherein the set m1 comprises {N RB DL −3};
a second comb offset indicates that the wireless device should use the PRBs in a set m2 to measure CSI-RS, wherein the set m2 comprises {N RB DL −2}; and
a third comb offset indicates that the wireless device should use the PRBs in a set m3 to measure CSI-RS, wherein the set m3 comprises {N RB DL −1}.
14. The method of claim 9 , wherein the indication of the subset of PRBs that are available for the wireless device to measure CSI-RS comprises an index value k, the index value k referring to one of a plurality of indications stored at the wireless device.
15. The method of claim 9 , wherein the indication of the subset of PRBs that are available for the wireless device to measure CSI-RS further comprises a number of successive CSI-RS subframes in which the wireless device should measure CSI-RS.
16. The method of claim 15 , further comprising determining a channel state information (CSI) based on the received CSI-RS over the number of successive CSI-RS subframes.
17. The method of claim 9 , wherein the wireless device receives CSI-RS transmitted on a total number of antenna ports from a network node, and each PRB of the subset of PRBs includes a CSI-RS mapping for the total number of antenna ports.
18. The method of claim 9 , wherein the subset of PRBs comprises even numbered PRBs or the subset of PRBs comprises odd numbered PRBs.
19. A network node operable to transmit channel state information reference signals (CSI-RS), the network node comprising processing circuitry, the processing circuitry operable to:
transmit, to a wireless device, an indication of a subset of physical resource blocks (PRBs) that are available for the wireless device to measure CSI-RS, each CSI-RS associated with an antenna port; and
transmit CSI-RS on the indicated subset of PRBs.
20. The network node of claim 19 , the processing circuitry further operable to obtain the indication of the subset of PRBs that are available for the wireless device to measure CSI-RS.
21. The network node of claim 19 , wherein the indication of the subset of PRBs that are available for the wireless device to measure CSI-RS comprises a density value and a comb offset.
22. The network node of claim 19 , wherein the processing circuitry is further operable to transmit CSI-RS on a total number of antenna ports, and each PRB of the subset of PRBs includes a CSI-RS mapping for the total number of antenna ports.
23. A wireless device operable to receive channel state information reference signals (CSI-RS), the wireless device comprising processing circuitry, the processing circuitry operable to:
receive an indication of a subset of physical resource blocks (PRBs) that are available for the wireless device to measure CSI-RS, each of the CSI-RS associated with an antenna port; and
receive CSI-RS on the indicated subset of PRBs.
24. The wireless device of claim 23 , wherein the indication of the subset of PRBs that are available for the wireless device to measure CSI-RS ports comprises a density value and a comb offset.
25. The wireless device of claim 23 , wherein the processing circuitry is further operable to receive CSI-RS transmitted on a total number of antenna ports from a network node, and each PRB of the subset of PRBs includes a CSI-RS mapping for the total number of antenna ports.
26. The wireless device of claim 23 , wherein the subset of PRBs comprises even numbered PRBs or the subset of PRBs comprises odd numbered PRBs.