Radio communication base station apparatus and method for controlling transmission power of sounding reference signal
A radio terminal is provided that can provide a flexible transmission power control for an SRS without restrictions due to the transmission power control of a PUSCH, for the purpose of enabling use of an SRS for various purposes in a HetNet CoMP environment. The radio terminal receives a control signal including a transmission power control command (TPC command) to be applied to an aperiodic sounding reference signal (A-SRS), through a physical downlink control channel (PDCCH), updates a transmission power value of the A-SRS using the TPC command, and transmits the A-SRS using the updated transmission power value in accordance with a transmission request included in a control signal indicating assignment of a physical downlink data channel (PDSCH) or assignment of a physical uplink data channel (PUSCH).
1. A radio communication base station apparatus, comprising:
a transmitter, which, in operation, transmits control information including a transmission request for an aperiodic sounding reference signal (A-SRS) and including a transmission power control command (TPC command) for transmission of the A-SRS; and
a receiver, which, in operation, receives the A-SRS at a controlled transmission power value, wherein
the controlled transmission power value of the A-SRS is based on a first accumulation value of the TPC command updated with the transmitted TPC command, wherein
an initial value of the first accumulation value is set to zero, in a first case in which a radio resource control (RRC) control signal more frequently updates a transmission power parameter associated with the TPC command than a defined frequency threshold, and
the initial value of the first accumulation value is set to a PUSCH (Physical Uplink Shared Channel) TPC command accumulation value, in a second case in which the RRC control signal less frequently updates the transmission power parameter associated with the TPC command than the defined frequency threshold.
2. The radio communication base station apparatus according to claim 1 , wherein the TPC command is included in a downlink control information (DCI) format 3/3A.
3. The radio communication base station apparatus according to claim 1 , wherein the first accumulation value is updated with the TPC command received from two or more nodes in one cell.
4. The radio communication base station apparatus according to claim 1 , wherein
the controlled transmission power value of the A-SRS is based on either the first accumulation value or a second accumulation value, the second accumulation value is different from the first accumulation value and independent of the first accumulation value, and the second accumulation value is updated with a TPC command transmitted in a specific subframe in a specific downlink control information (DCI) format.
5. The radio communication base station apparatus according to claim 1 , wherein
the control information including the TPC command is different from control information indicative of PUSCH allocation, and includes one or a plurality of TPC commands targeted at one or a plurality of radio communication terminal apparatuses.
6. The radio communication base station apparatus according to claim 1 , wherein
the receiver, in operation, receives the A-SRS in response to a specific combination of a type of the control information and a bit value of the transmission request.
7. A radio communication method implemented in a radio communication base station apparatus, the method comprising:
transmitting control information including a transmission request for an aperiodic sounding reference signal (A-SRS) and including a transmission power control command (TPC command) for transmission of the A-SRS; and
receiving the A-SRS at a controlled transmission power value, wherein
the controlled a transmission power value of the A-SRS is based on a first accumulation value of the TPC command updated with the transmitted TPC command, wherein
an initial value of the first accumulation value is set to zero, in a first case in which a radio resource control (RRC) control signal more frequently updates a transmission power parameter associated with the TPC command than a defined frequency threshold, and
the initial value of the first accumulation value is set to a PUSCH (Physical Uplink Shared Channel) TPC command accumulation value, in a second case in which the RRC control signal less frequently updates the transmission power parameter associated with the TPC command than the defined frequency threshold.
8. The radio communication method according to claim 7 , wherein the TPC command is included in a downlink control information (DCI) format 3/3A.
9. The radio communication method according to claim 7 , wherein the first accumulation value is updated with the TPC command received from two or more nodes in one cell.
10. The radio communication method according to claim 7 , wherein
the controlled the transmission power value of the A-SRS is based on either the first accumulation value or a second accumulation value, the second accumulation value is different from the first accumulation value and independent of the first accumulation value, and the second accumulation value is updated with a TPC command transmitted in a specific subframe in a specific downlink control information (DCI) format.
11. The radio communication method according to claim 7 , wherein
the control information including the TPC command is different from control information indicative of PUSCH allocation, and includes one or a plurality of TPC commands targeted at one or a plurality of radio communication terminal apparatuses.
12. The radio communication method according to claim 7 , wherein
the A-SRS is received in response to a specific combination of a type of the control information and a bit value of the transmission request.