Method and apparatus for transmitting sounding reference signal in radio communication system

A method for transmitting sounding reference signals by a user equipment in a radio communication system, comprising:

• receiving downlink control information defined in a legacy system along with downlink control information for uplink multiple input multiple output (MIMO) transmission from a base station;
• performing transmission of an uplink shared channel in an uplink MIMO mode;
• checking a flag bit included in the downlink control information defined in the legacy system;
• checking an interpretation bit included in the downlink control information defined in the legacy system if the flag bit indicates uplink;
• and
• performing transmission of an additional sounding reference signal based on the interpretation bit.

A user equipment in a radio communication system, comprising:

• a reception module configured to receive downlink control information from a base station;
• a processor configured to check a flag bit included in the downlink control information and to check an interpretation bit included in the downlink control information if the flag bit indicates uplink;
• and
• a transmission module configured to perform at least one of transmission of an additional sounding reference signal or transmission of an uplink shared channel based on the interpretation bit.

A user equipment in a radio communication system, comprising:

• a reception module configured to receive downlink control information defined in a legacy system along with downlink control information for uplink multiple input multiple output (MIMO) transmission from a base station;
• a transmission module configured to perform transmission of an uplink shared channel in an uplink MIMO mode;
• and
• a processor configured to check a flag bit included in the downlink control information defined in the legacy system and to check an interpretation bit included in the downlink control information defined in the legacy system if the flag bit indicates uplink,
• wherein the transmission module performs transmission of an additional sounding reference signal based on the interpretation bit.