A method of a User Equipment, UE, in a mobile communication system, the method comprising: receiving, from a base station, a physical uplink control channel, PUCCH, configuration indicating whether a simultaneous PUCCH-physical uplink shared channel, PUSCH, transmission is configured; identifying whether a power headroom report, PHR, is triggered; when the PHR is triggered, determining a first maximum uplink transmission power for a Type 1 power headroom, PH, for a primary cell, a second maximum uplink transmission power for a Type 2 PH for the primary cell, and a third maximum uplink transmission power for a Type 1 PH for a secondary cell based on at least one of cell specific maximum allowed transmission power and UE specific maximum allowed transmission power, wherein the first maximum uplink transmission power is determined based on a reference maximum uplink transmission power with back-off parameters being zero when the UE does not transmit the PUSCH on the primary cell, and the first maximum uplink transmission power is determined based on a real maximum uplink transmission power when the UE transmits the PUSCH on the primary cell, wherein the third maximum uplink transmission power is determined based on the reference maximum uplink transmission power with back-off parameters being zero when the UE does not transmit the PUSCH on the secondary cell, and the third maximum uplink transmission power is determined based on a real maximum uplink transmission power when the UE transmits the PUSCH on the secondary cell, and wherein the second maximum uplink transmission power is determined based on the real maximum uplink transmission power when the UE transmits one of the PUSCH or the PUCCH, and the second maximum uplink transmission power is determined based on the reference uplink transmission power when the UE does not transmits both the PUSCH and the PUCCH; calculating the Type 1 PH for the primary cell based on the first maximum uplink transmission power, the Type 2 PH for the primary cell based on the second maximum uplink transmission power, and the Type 1 PH for the secondary cell based on the third maximum uplink transmission power; and transmitting, to the base station, the PHR including the type 1 PH for the primary cell, the type 2 PH for the primary cell and the type 1 PH for the secondary cell, wherein the Type 2 PH for the primary cell is calculated when the information indicating the simultaneous PUCCH-PUSCH transmission is configured, and wherein the back-off parameters include Maximum Power Reduction, MPR, Additional-MPR, A-MPR, and an operating band edge transmission power relaxation value. receiving, from a base station, a physical uplink control channel, PUCCH, configuration indicating whether a simultaneous PUCCH-physical uplink shared channel, PUSCH, transmission is configured; identifying whether a power headroom report, PHR, is triggered; when the PHR is triggered, determining a first maximum uplink transmission power for a Type 1 power headroom, PH, for a primary cell, a second maximum uplink transmission power for a Type 2 PH for the primary cell, and a third maximum uplink transmission power for a Type 1 PH for a secondary cell based on at least one of cell specific maximum allowed transmission power and UE specific maximum allowed transmission power, wherein the first maximum uplink transmission power is determined based on a reference maximum uplink transmission power with back-off parameters being zero when the UE does not transmit the PUSCH on the primary cell, and the first maximum uplink transmission power is determined based on a real maximum uplink transmission power when the UE transmits the PUSCH on the primary cell, wherein the third maximum uplink transmission power is determined based on the reference maximum uplink transmission power with back-off parameters being zero when the UE does not transmit the PUSCH on the secondary cell, and the third maximum uplink transmission power is determined based on a real maximum uplink transmission power when the UE transmits the PUSCH on the secondary cell, and wherein the second maximum uplink transmission power is determined based on the real maximum uplink transmission power when the UE transmits one of the PUSCH or the PUCCH, and the second maximum uplink transmission power is determined based on the reference uplink transmission power when the UE does not transmits both the PUSCH and the PUCCH; calculating the Type 1 PH for the primary cell based on the first maximum uplink transmission power, the Type 2 PH for the primary cell based on the second maximum uplink transmission power, and the Type 1 PH for the secondary cell based on the third maximum uplink transmission power; and transmitting, to the base station, the PHR including the type 1 PH for the primary cell, the type 2 PH for the primary cell and the type 1 PH for the secondary cell, wherein the Type 2 PH for the primary cell is calculated when the information indicating the simultaneous PUCCH-PUSCH transmission is configured, and wherein the back-off parameters include Maximum Power Reduction, MPR, Additional-MPR, A-MPR, and an operating band edge transmission power relaxation value.