1. A method for transmitting, by a user equipment (UE), channel state information (CSI) in a communication system, the method comprising: receiving a downlink control information (DCI) message, the DCI message including a CSI request field indicating a CSI transmission; obtaining, from the CSI request field included in the received DCI message, an indication indicating a CSI process set for the CSI transmission; and transmitting the CSI based on the indicated CSI process set on a physical uplink shared channel (PUSCH), wherein the CSI corresponding to one of CSI process sets respectively associated with measurements of respective reference signals, and the CSI request field includes 2 bits indicating each of a first set of interpretations, wherein, the first set of interpretations are a 2 bit value of ‘00’ indicates no CSI transmission, a 2 bit value of ‘01’ indicates CSI transmission for a CSI process set corresponding to a downlink (DL) cell, a 2 bit value of ‘10’ indicates CSI transmission for a first CSI process set, and a 2 bit value of ‘11’ indicates CSI transmission for a second CSI process set.