Method for transmitting uplink and wireless device using same
A method is described for uplink transmission in a wireless communication system. A user equipment determines whether to transmit or drop a sounding reference signal (SRS) on a last symbol in an i th subframe. The determination is performed if multiple timing advance groups (TAGs) are configured and if a portion of the last symbol of the i th subframe for the SRS transmission toward the a serving cell in a first TAG is overlapped with an (i+1) th subframe for transmitting an uplink channel toward a second serving cell in a second TAG.
1. A method for uplink transmission in a wireless communication system, the method comprising:
transmitting, by a user equipment, a random access preamble,
after receiving a random access response including a timing advance command (TAC), adjusting, by the user equipment, an uplink transmission timing based on the TAC;
determining, by the user equipment, a sounding reference signal (SRS) symbol in an i th subframe of an SRS transmission for a first serving cell in a first timing advance group (TAG); and
dropping, by the user equipment, the SRS transmission on the SRS symbol in the ith subframe if:
multiple TAGs are configured,
a portion of a last symbol of the i th subframe for the SRS transmission toward the first serving cell in the first TAG is overlapped with an (i+1) th subframe for transmitting an uplink channel toward a second serving cell in a second TAG, and
a total uplink transmission power exceeds a maximum value on the overlapped portion of the last symbol.
2. The method of claim 1 , further comprising
starting, by the user equipment, a first time alignment timer for the first TAG; and
starting, by the user equipment, a second time alignment timer for the second TAG.
3. The method of claim 1 , wherein an uplink channel for the uplink channel transmission includes at least one of a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH) and a random access channel.
4. The method of claim 1 , further comprising:
receiving a periodic configuration indicating an SRS periodicity and an SRS subframe offset,
wherein the i th subframe for the SRS symbol is determined based on the periodic configuration.
5. The method of claim 1 , further comprising:
receiving a request for the SRS transmission.
6. A user equipment for uplink transmission in a wireless communication system, the user equipment comprising:
a radio frequency (RF) unit configured to transmit and receive radio signals; and
a processor operatively coupled with the RF unit and configured to:
transmit a random access preamble,
after receiving a random access response including a timing advance command (TAC), adjust an uplink transmission timing based on the TAC,
determine a sounding reference signal (SRS) symbol in an i th subframe of an SRS transmission for a first serving cell in a first timing advance group (TAG), and
drop the SRS transmission on the SRS symbol in the i th subframe if:
multiple TAGs are configured,
a portion of a last symbol of the i th subframe for the SRS transmission toward the first serving cell in the first TAG is overlapped with an (i+1) th subframe for transmitting an uplink channel toward a second serving cell in a second TAG, and
a total uplink transmission power exceeds a maximum value on the overlapped portion of the last symbol.
7. The user equipment of claim 6 , wherein the processor is further configured to:
start a first time alignment timer for the first TAG; and
start a second time alignment timer for the second TAG.
8. The user equipment of claim 6 , wherein an uplink channel for the uplink channel transmission includes at least one of a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH) and a random access channel.
9. The user equipment of claim 6 , wherein the processor is further configured to receive a periodic configuration indicating an SRS periodicity and an SRS subframe offset, and
wherein the i th subframe for the SRS symbol is determined based on the periodic configuration.
10. The user equipment of claim 9 , wherein the processor is further configured to receive a request for the SRS transmission.