Channel state information reference signals in contention-based spectrum

1. A method of wireless communication, comprising:

receiving an indication of an offset for channel state information (CSI) reference signals within a transmission time interval (TTI) structure, the offset representing a relative location for the CSI reference signals within the TTI structure;

detecting, in a contention-based spectrum, after receiving the indication of the offset, signaling indicative of a transmission in the contention-based spectrum according to the TTI structure;

determining, based at least in part on detecting the signaling indicative of the transmission in the contention-based spectrum, to monitor for a CSI reference signal in the contention-based spectrum at the relative location within the TTI structure identified by the indicated offset;

receiving, based at least in part on the monitoring, the CSI reference signal in the contention-based spectrum at the relative location within the TTI structure identified by the indicated offset;

computing a channel quality indicator (CQI) based at least in part on the CSI reference signal; and

transmitting a report comprising the CQI and an indicator indicating that the CQI is based at least in part on the CSI reference signal received in the contention-based spectrum.

2. The method of claim 1 , further comprising:

receiving a cell-specific reference signal (CRS), wherein the CQI is based at least in part on the CSI reference signal and the CRS.

3. The method of claim 1 , wherein the signaling indicative of the transmission in the contention-based spectrum according to the TTI structure comprises a physical channel of the transmission in the contention-based spectrum according to the TTI structure.

4. The method of claim 3 , wherein the signaling indicative of the transmission in the contention-based spectrum according to the TTI structure comprises a portion of a physical control format indicator channel (PCFICH) of the transmission in the contention-based spectrum according to the TTI structure or a portion of a physical frame format indicator channel (PFFICH) of the transmission in the contention-based spectrum according to the TTI structure.

5. The method of claim 3 , wherein the signaling indicative of the transmission in the contention-based spectrum according to the TTI structure comprises a portion of a physical downlink control channel (PDCCH) of the transmission in the contention-based spectrum according to the TTI structure.

6. The method of claim 1 , wherein the CSI reference signal comprises a plurality of symbol periods.

7. The method of claim 6 , wherein a density of the CSI reference signal is based at least in part on an interference measurement gap.

8. The method of claim 1 , wherein receiving the CSI reference signal in the contention-based spectrum comprises:

receiving the CSI reference signal in a final transmission time interval (TTI) of a downlink (DL) burst.

9. The method of claim 1 , wherein receiving the CSI reference signal in the contention-based spectrum comprises:

receiving a downlink (DL) burst comprising a first CSI reference signal and a second CSI reference signal, wherein the CQI comprises a first CQI computed based at least in part on the first CSI reference signal and a second CQI computed based at least in part on the second CSI reference signal.

10. The method of claim 1 , wherein receiving the indication of the offset for CSI reference signals within the TTI structure comprises:

receiving the indication of the offset for CSI reference signals in radio resource control (RRC) signaling.

11. The method of claim 1 , wherein detecting the signaling indicative of the transmission in the contention-based spectrum according to the TTI structure comprises:

detecting, in the contention-based spectrum, a preamble of the transmission in the contention-based spectrum according to the TTI structure.

12. A method of wireless communication, comprising:

transmitting an indication of an offset for channel state information (CSI) reference signals within a transmission time interval (TTI) structure, the offset representing a relative location for the CSI reference signals within the TTI structure;

determining, after transmitting the indication of the offset, that a contention-based spectrum is available for transmission;

transmitting, based at least in part on the determining and after transmitting the indication of the offset, signaling indicative of a transmission according to the TTI structure in the contention-based spectrum;

transmitting, in the transmission according to the TTI structure, a CSI reference signal in the contention-based spectrum at the relative location within the TTI structure identified by the indicated offset; and

receiving a report comprising a channel quality indicator (CQI) computed based at least in part on the transmitted CSI reference signal and an indicator indicating that the CQI is based at least in part on the transmitted CSI reference signal.

13. The method of claim 12 , further comprising:

identifying a user equipment (UE) configured for CSI reference signal based CQI reporting, wherein the signaling is transmitted in the contention-based spectrum based at least in part on identifying the UE.

14. The method of claim 12 , further comprising:

determining that the CQI was computed using the CSI reference signal based at least in part on transmitting the CSI reference signal in the contention-based spectrum.

15. The method of claim 12 , further comprising:

determining that the CQI was computed using the CSI reference signal based at least in part on the indicator indicating that the CQI is based at least in part on the transmitted CSI reference signal.

16. The method of claim 12 , further comprising:

determining a transmission pattern for serving a UE in coordinated multiple point (CoMP) scheme; and

transmitting the CSI reference signal in the contention-based spectrum and the signaling based at least in part on the transmission pattern.

17. The method of claim 12 , wherein:

transmitting the CSI reference signal in the contention-based spectrum comprises transmitting a downlink (DL) burst in the contention-based spectrum comprising a first CSI reference signal directed to a first user equipment (UE) and a second CSI reference signal directed to a second UE according to the signaling; and

receiving the report comprising the CQI comprises receiving a first report comprising first CQI computed by the first UE based at least in part on the first CSI reference signal and receiving a second report comprising second CQI computed by the second UE based at least in part on the second CSI reference signal.

18. 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:

receive an indication of an offset for channel state information (CSI) reference signals within a transmission time interval (TTI) structure, the offset representing a relative location for the CSI reference signals within the TTI structure;

detect, in a contention-based spectrum, after receiving the indication of the offset, signaling indicative of a transmission in the contention-based spectrum according to the TTI structure;

determine, based at least in part on receiving the signaling indicative of the transmission in the contention-based spectrum, to monitor for a CSI reference signal in the contention-based spectrum at the relative location within the TTI structure identified by the indicated offset;

receive, based at least in part on the monitoring, the CSI reference signal in the contention-based spectrum at the relative location within the TTI structure identified by the indicated offset;

compute a channel quality indicator (CQI) based at least in part on the CSI reference signal; and

transmitting a report comprising the CQI and an indicator indicating that the CQI is based at least in part on the CSI reference signal received in the contention-based spectrum.

19. The apparatus of claim 18 , wherein the instructions are operable to cause the apparatus to:

receive a cell-specific reference signal (CRS), wherein the CQI is based at least in part on the CSI reference signal and the CRS.

20. The apparatus of claim 18 , wherein the signaling indicative of the transmission in the contention-based spectrum according to the TTI structure comprises a physical channel of the transmission in the contention-based spectrum according to the TTI structure.

21. The apparatus of claim 18 , wherein the CSI reference signal comprises a plurality of symbol periods.

22. The apparatus of claim 21 , wherein a density of the CSI reference signal is based at least in part on an interference measurement gap.

23. The apparatus of claim 18 , wherein the instructions are operable to cause the apparatus to:

receive the CSI reference signal in a final transmission time interval (TTI) of a downlink (DL) burst.

24. The apparatus of claim 18 , wherein the instructions are operable to cause the apparatus to:

receive the indication of the offset for CSI reference signals in radio resource control (RRC) signaling.

25. The apparatus of claim 18 , wherein, to detect the signaling indicative of the transmission in the contention-based spectrum according to the TTI structure, the instructions are operable to cause the apparatus to:

detect, in the contention-based spectrum, a preamble of the transmission in the contention-based spectrum according to the TTI structure.

26. 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:

transmit an indication of an offset for channel state information (CSI) reference signals within a transmission time interval (TTI) structure, the offset representing a relative location for the CSI reference signals within the TTI structure;

determine, after transmitting the indication of the offset, that a contention-based spectrum is available for transmission;

transmit, based at least in part on the determining and after transmitting the indication of the offset, signaling indicative of a transmission according to the TTI structure in the contention-based spectrum;

transmit, in the transmission according to the TTI structure, a CSI reference signal in the contention-based spectrum at the relative location within the TTI structure identified by the indicated offset; and

receive a report comprising a channel quality indicator (CQI) computed based at least in part on the transmitted CSI reference signal and an indicator indicating that the CQI is based at least in part on the transmitted CSI reference signal.

27. The apparatus of claim 26 , wherein the instructions are operable to cause the apparatus to:

identify a user equipment (UE) configured for CSI reference signal based CQI reporting, wherein the signaling is transmitted in the contention-based spectrum based at least in part on identifying the UE.

28. The apparatus of claim 26 , wherein the instructions are operable to cause the apparatus to:

determine that the CQI was computed using the CSI reference signal based at least in part on transmitting the CSI reference signal in the contention-based spectrum.

29. The apparatus of claim 26 , wherein the instructions are operable to cause the apparatus to:

determine that the CQI was computed using the CSI reference signal based at least in part on the indicator indicating that the CQI is based at least in part on the transmitted CSI reference signal.