Method for triggering aperiodic sounding reference symbol, base station and user equipment

1. A method for triggering an aperiodic sounding reference symbol, comprising:

receiving a Downlink Control Information (DCI) indicating a transmission of an aperiodic Sounding Reference Symbol (SRS) from a base station which configures a resource used for transmission of the aperiodic SRS;

maintaining, by not releasing, the resource for transmitting the aperiodic SRS when there is at least one of a loss of uplink synchronization when a timer relating to the uplink synchronization expires and a failure in transmission of a scheduling request transmitted more than a predetermined number of times, wherein

if there is the loss of uplink synchronization, detecting the loss of uplink synchronization, wherein the resource for transmitting the aperiodic SRS is maintained when the loss is detected, or

if there is the failure in transmission, detecting the failure in transmission, wherein the resource for transmitting the aperiodic SRS is maintained when the failure is detected; and

executing a random access procedure.

2. The method according to claim 1 , further comprising transmitting a random access preamble.

3. The method according to claim 2 , further comprising determining whether to transmit the aperiodic SRS based on a type of the indication information contained in a Random Access Response (RAR) message received in response to the transmitted random access preamble.

4. The method according to claim 3 , further comprising: transmitting the aperiodic SRS on the resource configured by the base station when determining to transmit the aperiodic SRS.

5. The method according to claim 3 , wherein the indication information contained in the RAR message is carried by one of a reserved bit in the RAR message or a newly added bit in the RAR message, wherein the newly added bit in the RAR message is added in an uplink bandwidth grant field.

6. The method according to claim 5 , wherein a format of the RAR message corresponds to a mode carrying the indication information.

7. The method according to claim 1 , wherein maintaining, by not releasing, the resource for transmitting the aperiodic SRS does not modify the resource configured by the DCI received from the base station.

8. A user equipment comprising:

a receiver configured for receiving a Downlink Control Information (DCI) indicating a transmission of an aperiodic Sounding Reference Symbol (SRS) which configures a resource used for transmission of the aperiodic SRS;

a processor circuit configured to:

detect a loss of an uplink synchronization when a timer relating to the uplink synchronization expires,

detect a failure in transmission of a scheduling request when the scheduling request is transmitted more than a predetermined number of times,

maintain, by not releasing, the resource used for transmission of the aperiodic SRS when detecting the loss of the uplink synchronization, and

maintain, by not releasing, the resource used for transmission of the aperiodic SRS when detecting the failure in transmission of the scheduling request,

execute a random access procedure; and

a transmitter configured to transmit a random access preamble.

9. The user equipment according to claim 8 , wherein:

the receiver is further configured to receive a Random Access Response (RAR) message in response to the transmitted random access preamble, the RAR message including a type of indication information; and

the processor circuit further configured to determine whether to transmit the aperiodic SRS based on the type of indication information.

10. The user equipment according to claim 9 , wherein the transmitter is further configured to transmit the aperiodic SRS using the configured resource when determining to transmit the aperiodic SRS.

11. The user equipment according to claim 9 , wherein the DCI is transmitted on a Physical Downlink Control Channel (PDCCH).

12. The user equipment according to claim 9 , wherein the user equipment is triggered to transmit the aperiodic SRS based on a format of the DCI.

13. The user equipment according to claim 8 , wherein the processor circuit configured to maintain, by not releasing, the resource used for transmission of the aperiodic SRS does not modify the resource configured by the DCI.

14. A user equipment comprising:

a processor circuit coupled to a memory and configured to:

maintain, by not releasing, a resource for transmitting an aperiodic SRS when there is at least one of a loss of uplink synchronization when a timer relating to the uplink synchronization expires and a failure in transmission of a scheduling request transmitted more than a predetermined number of times, wherein

if there is the loss of uplink synchronization, detecting the loss of uplink synchronization, wherein the resource for transmitting the aperiodic SRS is maintained when the loss is detected, or

if there is the failure in transmission, detecting the failure in transmission, wherein the resource for transmitting the aperiodic SRS is maintained when the failure is detected;

executing a random access procedure; and

a transmitter configured to transmit a random access preamble.

15. The user equipment according to claim 14 , further comprising a receiver configured to receive a Random Access Response (RAR) message in response to the transmitted random access preamble, the RAR message including a type of indication information.

16. The user equipment according to claim 15 , wherein the transmitter is configured to transmit the aperiodic SRS using the configured resource based on a type of information included in a Random Access Response (RAR) message.