Channel station information reporting and transmission mode for enhanced machine type communication
Methods, systems, and devices for wireless communication are described. A wireless device may identify a transmission mode that specifies a rank indicator (RI) feedback parameter for channel state indicator (CSI) reporting, and may determine that the appropriate CSI configuration excludes an RI. The device may then send CSI reports with a precoding matrix indicator (PMI) and without the RI, and it may communicate using the transmission mode. In some cases, the PMI may be based on a default rank (e.g., rank of 1 for device with single antenna). In some cases, a category or capability of the device may be identified, and the determination that the CSI configuration excludes the RI may be based on the category or capability. In other cases, the CSI configuration may be based on channel conditions. In some cases, a reference signal (e.g., a CRS) may be used as feedback depending on the device's capabilities.
1. A method of wireless communication at a user equipment (UE), comprising:
identifying a transmission mode that specifies a rank indicator (RI) feedback parameter for channel state information (CSI) reporting;
communicating an indication of a UE category of the UE, wherein the indication of the UE category is indicative of rank;
transmitting a CSI report that includes a precoding matrix indicator (PMI) and excludes an RI based at least in part on the UE category; and
communicating using the transmission mode.
2. The method of claim 1 , wherein the PMI is based at least in part on the RI.
3. The method of claim 1 , further comprising:
estimating a matrix representative of a channel for the communicating;
identifying, when a CSI configuration excludes an RI, a PMI based at least in part on a default rank for the UE category; and
determining a channel quality indicator (CQI) that corresponds to the identified PMI, wherein the CQI and the PMI are transmitted in the CSI report.
4. The method of claim 1 , further comprising:
transmitting at least one of a PMI, an RI, or a CQI using a control channel if the PMI, RI, or CQI are available for transmission; and
refraining from transmitting the control channel if the PMI, RI or CQI are unavailable for transmission.
5. The method of claim 1 , further comprising:
identifying a reference signal type to use for channel estimation based at least in part on the UE category of the UE;
determining at least one of a PMI or a CQI using a reference signal of the identified reference signal type; and
transmitting the PMI or the CQI.
6. The method of claim 5 , wherein the identified reference signal type comprises a cell-specific reference signals (CRS).
7. An apparatus for wireless communication, comprising:
means for identifying a transmission mode that specifies a rank indicator (RI) feedback parameter for channel state information (CSI) reporting;
means for communicating an indication of a user equipment (UE) category of a UE, wherein the indication of the UE category is indicative of rank;
means for transmitting a CSI report that includes a precoding matrix indicator (PMI) and excludes an RI based at least in part on the UE category; and
means for communicating using the transmission mode.
8. The apparatus of claim 7 , further comprising:
means for estimating a matrix representative of a channel for the communicating;
means for identifying, when a CSI configuration excludes an RI, a PMI based at least in part on a default rank for the UE category; and
means for determining a channel quality indicator (CQI) that corresponds to the identified PMI, wherein the CQI and the PMI are transmitted in the CSI report.
9. The apparatus of claim 7 , further comprising:
means for transmitting at least one of a PMI, an RI, or a CQI using a control channel if the PMI, RI or CQI are available for transmission and refraining from transmitting the control channel if the PMI, RI or CQI are unavailable for transmission.
10. The apparatus of claim 7 , further comprising:
means for identifying a reference signal type to use for channel estimation based at least in part on the UE category of the UE;
means for determining at least one of a PMI or a CQI using a reference signal of the identified reference signal type; and
means for transmitting the PMI or the CQI.
11. The apparatus of claim 7 , wherein the identified reference signal type comprises a cell-specific reference signals (CRS).
12. An apparatus for wireless communication, comprising:
a processor;
memory in electronic communication with the processor; and
instructions stored in the memory and operable, when executed by the processor, to cause the apparatus to:
identify a transmission mode that specifies a rank indicator (RI) feedback parameter for channel state information (CSI) reporting;
communicate an indication of a user equipment (UE) category of a UE, wherein the indication of the UE category is indicative of rank;
transmit a CSI report that includes a precoding matrix indicator (PMI) and excludes an RI based at least in part on the UE category; and
communicate using the transmission mode.
13. The apparatus of claim 12 , wherein the PMI is based at least in part on the RI.
14. The apparatus of claim 12 , wherein the instructions are operable to cause the apparatus to:
estimate a matrix representative of a channel for the communicating;
identify, when a CSI configuration excludes an RI, a PMI based at least in part on a default rank for the UE category;
determine a channel quality indicator (CQI) that corresponds to the identified PMI; and
transmit the CQI and the PMI in the CSI report.
15. The apparatus of claim 12 , wherein the instructions are operable to cause the apparatus to:
transmit at least one of a PMI, an RI, or a CQI using a control channel if the PMI, RI or CQI are available for transmission; and
refrain from transmitting the control channel if the PMI, RI or CQI are unavailable for transmission.
16. The apparatus of claim 12 , wherein the instructions are operable to cause the processor to:
identify a reference signal type to use for channel estimation based at least in part on the UE category of the UE;
determine at least one of a PMI or a CQI using a reference signal of the identified reference signal type; and
transmitting the PMI or the CQI.
17. The apparatus of claim 16 , wherein the identified reference signal type comprises a cell-specific reference signals (CRS).
18. A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable to:
identify a transmission mode that specifies a rank indicator (RI) feedback parameter for channel state information (CSI) reporting;
communicate an indication of a user equipment (UE) category of a UE, wherein the indication of the UE category is indicative of rank;
transmit a CSI report that includes a precoding matrix indicator (PMI) and excludes an RI based at least in part on the UE category; and
communicate using the transmission mode.