Methods, architectures, apparatuses and systems for enabling fast beam switching

A method implemented by a wireless transmit/receive unit (WTRU), the method comprising:

• receiving configuration information including quasi co-location (QCL) relation information for one or more transmission configuration indicator (TCI) states, wherein the one or more TCI states include a first TCI state associated with a first source reference signal (RS) beam as a QCL source for a first set of variable RS beams;
• determining one or more measurements using the first source RS beam;
• receiving beam switching information that includes information indicating a first replacement RS beam is associated with a first variable RS beam, wherein the first variable RS beam is included in the first set of variable RS beams;
• determining one or more measurements using the first replacement RS beam;
• and
• sending, in response to the beam switching information, information indicating that the first TCI state is updated to be associated with the first replacement RS beam as the QCL source for the first set of variable RS beams based on the one or more measurements using the first source RS beam, the one or more measurements using the first replacement RS beam, and threshold information.

A base station comprising:

• a processor, memory, and a transceiver which are configured to:
• send configuration information including quasi co-location (QCL) relation information for one or more transmission configuration indicator (TCI) states, wherein the one or more TCI states include a first TCI state associated with a first source reference signal (RS) beam as a QCL source for a first set of variable RS beams,
• send one or more transmissions using the first source RS beam,
• send beam switching information that includes information indicating a first replacement RS beam is associated with a first variable RS beam, wherein the first variable RS beam is included in the first set of variable RS beams,
• send one or more transmissions using the first replacement RS beam, and
• receive, in response to the beam switching information, information indicating that the first TCI state is updated to be associated with the first replacement RS beam as the QCL source for the first set of variable RS beams.