Signal transmission method and apparatus

1. A method comprising:

receiving, by a user equipment from a base station, first information in a physical downlink control channel, wherein the first information is used for determining precoding information of a sounding reference signal (SRS);

determining, by the user equipment, the precoding information of the SRS based on the first information;

performing, by the user equipment based on the precoding information of the SRS, precoding on the SRS to generate a precoded SRS;

sending, by the user equipment, the precoded SRS to the base station; and

sending, by the user equipment, the SRS to the base station at a time other than a sending time of the precoded SRS,

wherein the first information is based on a demodulation reference signal (DMRS) or uplink service data.

2. The method according to claim 1 , wherein the first information triggers the user equipment to determine the precoding information of the SRS.

3. The method according to claim 2 , wherein determining, by the user equipment, the precoding information of the SRS based on the first information comprises, when the user equipment is triggered to determine the precoding information of the SRS in a wireless communication system using a time division duplex mode, determining, by the user equipment based on a downlink reference signal from the base station, the precoding information of the SRS.

4. The method according to claim 3 , wherein the downlink reference signal is a channel state information reference signal (CSI-RS).

5. The method according to claim 1 , further comprising receiving, by the user equipment, second information sent by the base station, wherein the second information indicates the sending time of the precoded SRS.

6. The method according to claim 1 , wherein the first information is based on the demodulation reference signal (DMRS).

7. The method according to claim 1 , wherein the first information is based on the uplink service data.

8. A method comprising:

sending, by a base station to a user equipment served by the base station, first information in a physical downlink control channel, wherein the first information is used to determine precoding information of a sounding reference signal (SRS);

receiving, by the base station, a precoded SRS from the user equipment, wherein the precoded SRS is generated by precoding the SRS using the precoding information; and

receiving, by the base station, the SRS from the user equipment at a time other than a sending time of the precoded SRS,

wherein the first information is based on the SRS, a demodulation reference signal (DMRS) or uplink service data.

9. The method according to claim 8 , wherein the first information triggers the user equipment to determine the precoding information of the SRS.

10. The method according to claim 9 , further comprising:

sending, by the base station, a downlink reference signal in a wireless communication system using a time division duplex mode, wherein the downlink reference signal is used to determine the precoding information of the SRS, and wherein the downlink reference signal is a channel state information reference signal (CSI-RS).

11. The method according to claim 8 , further comprising determining, by the base station, uplink channel information based on the SRS.

12. The method according to claim 8 , further comprising sending, by the base station, second information to the user equipment, wherein the second information indicates the sending time of the precoded SRS.

13. The method according to claim 8 , wherein the first information is based on the demodulation reference signal (DMRS).

14. A user equipment comprising:

a receiver;

a processor; and

a transmitter,

wherein the receiver is configured to receive first information in a physical downlink control channel from a base station, wherein the first information is used for determining precoding information of a sounding reference signal (SRS),

wherein the processor is configured to determine precoding information of SRS and perform precoding on the SRS based on the precoding information, to generate a precoded SRS,

wherein the transmitter is configured to send the precoded SRS to the base station,

wherein the transmitter is further configured to send the SRS to the base station at a time other than a sending time of the precoded SRS, and

wherein the first information is based on a demodulation reference signal (DMRS) or uplink service data.

15. The user equipment according to claim 14 , wherein the first information triggers the user equipment to determine the precoding information of the SRS.

16. The user equipment according to claim 15 , wherein the processor is configured to, when the user equipment is triggered to determine the precoding information of the SRS in a wireless communication system using a time division duplex mode, determine, based on a downlink reference signal from the base station, the precoding information of the SRS.

17. The user equipment according to claim 16 , wherein the downlink reference signal is a channel state information reference signal (CSI-RS).

18. The user equipment according to claim 14 , wherein the SRS is used by the base station to determine uplink channel information.

19. The user equipment according to claim 14 , wherein the receiver is further configured to receive second information from the base station, and wherein the second information indicates the sending time of the precoded SRS.

20. A base station comprising:

a transmitter; and

a receiver;

wherein the transmitter is configured to send first information in a physical downlink control channel to a user equipment served by the base station, wherein the first information is used by the user equipment to determine precoding information of a sounding reference signal (SRS),

wherein the receiver is configured to:

receive a precoded SRS from the user equipment, wherein the precoded SRS is generated by precoding the SRS using the precoding information; and

receive the SRS from the user equipment at a time other than a sending time of the precoded SRS, and

wherein the first information is based on a demodulation reference signal (DMRS) or uplink service data.

21. The base station according to claim 20 , wherein the first information triggers the user equipment to determine the precoding information of the SRS.

22. The base station according to claim 21 , wherein the transmitter is further configured to send a downlink reference signal in a wireless communication system using a time division duplex mode, wherein the downlink reference signal is used to determine the precoding information of the SRS, and wherein the downlink reference signal is a channel state information reference signal (CSI-RS).

23. The base station according to claim 20 , wherein the transmitter is further configured to send second information to the user equipment, wherein the second information indicates the sending time of a precoded signal.