Method and apparatus of beam determination in a wireless communication system

A method for a network node, comprising:

• configuring, by the network node, a UE (User Equipment) with at least two serving cells, including a PCell (Primary Cell) which is activated and an SCell (Secondary Cell) which is deactivated;
• transmitting, by the network node, an SCell activation/deactivation MAC (Medium Access Control) control element to activate the SCell;
• transmitting, by the network node, a beam indication by a MAC control element via the PCell, wherein the beam indication includes an indicator of SSB (SS Block) or CSI-RS (Channel State Information Reference Signal) and a cell index indicating that the beam indication is for the SCell, and the beam indication is used by the UE to derive at least one beam to be used in the SCell for PDCCH (Physical Downlink Control Channel) or for an UL (Uplink) transmission on PUCCH (Physical Uplink Control Channel) or PUSCH (Physical Uplink Shared Channel), wherein the network node determines whether the at least one beam is used for the PDCCH or for the UL transmission;
• and
• using, by the network node, the at least one beam for the PDCCH or for the UL transmission in the SCell.

A User Equipment (UE) configured with at least two serving cells, including a PCell (Primary Cell) which is activated and an SCell (Secondary Cell) which is deactivated, comprising:

• a processor;
• and
• a memory operatively coupled to the processor, wherein the processor is configured to execute a program code to:
• receive, by the UE from a network node, an SCell activation/deactivation MAC (Medium Access Control) control element to activate the SCell;
• activate, by the UE, the SCell based on the SCell activation/deactivation MAC control element;
• receive, by the UE from the network node, a beam indication by a MAC control element via the PCell, wherein the beam indication includes an indicator of SSB (SS Block) or CSI-RS (Channel State Information Reference Signal) and a cell index indicating that the beam indication is for the SCell, and the beam indication is used to derive at least one beam to be used in the SCell for monitoring PDCCH (Physical Downlink Control Channel) or for an UL (Uplink) transmission on PUCCH (Physical Uplink Control Channel) or PUSCH (Physical Uplink Shared Channel), wherein whether the at least one beam is used for monitoring the PDCCH or for the UL transmission is determined by the network node;
• and
• use, by the UE, the at least one beam for monitoring the PDCCH or for the UL transmission in the SCell.

A network node, comprising:

• a processor;
• and
• a memory operatively coupled to the processor, wherein the processor is configured to execute a program code to:
• configure, by the network node, a UE (User Equipment) with at least two serving cells, including a PCell (Primary Cell) which is activated and an SCell (Secondary Cell) which is deactivated;
• transmit, by the network node, an SCell activation/deactivation MAC (Medium Access Control) control element to activate the SCell;
• transmit, by the network node, a beam indication by a MAC control element via the PCell, wherein the beam indication includes an indicator of SSB (SS Block) or CSI-RS (Channel State Information Reference Signal) and a cell index indicating that the beam indication is for the SCell, and the beam indication is used by the UE to derive at least one beam to be used in the SCell for PDCCH (Physical Downlink Control Channel) or for an UL (Uplink) transmission on PUCCH (Physical Uplink Control Channel) or PUSCH (Physical Uplink Shared Channel), wherein the network node determines whether the at least one beam is used for the PDCCH or for the UL transmission;
• and
• use, by the network node, the at least one beam for the PDCCH or for the transmission in the SCell.