Secondary timing advance groups with only license assisted access secondary cells

A method for wireless communication at a user equipment (UE), comprising:

• connecting to a base station in a license assisted access (LAA) mode using a primary cell (PCell) and an LAA secondary cell (SCell) associated with a shared radio frequency spectrum band;
• receiving timing advance information associated with a secondary timing advance group (sTAG) dedicated to LAA SCells, wherein the LAA SCell is a member of the sTAG;
• identifying a downlink timing reference for an uplink transmission over the LAA SCell;
• and
• transmitting the uplink transmission over the LAA SCell based at least in part on the identified downlink timing reference and the received timing advance information.

An apparatus for wireless communication at a base station, comprising:

• a processor;
• memory in electronic communication with the processor;
• and
• instructions stored in the memory, wherein the instructions are executable by the processor to:
• connect to a user equipment (UE) in a license assisted access (LAA) mode using a primary cell (PCell) and a secondary cell (SCell) associated with a shared radio frequency spectrum band;
• determine a scheduling carrier over which scheduling information is provided to the UE for uplink transmissions from the UE over the SCell;
• add the SCell to a secondary timing advance group (sTAG) based at least in part on the shared radio frequency spectrum band of the SCell and the determination of the scheduling carrier;
• and
• transmit timing advance information associated with the sTAG to the UE for uplink transmissions over the SCell.

An apparatus for wireless communication at a user equipment (UE), comprising:

• a processor;
• memory in electronic communication with the processor;
• and
• instructions stored in the memory, wherein the instructions are executable by the processor to:
• connect to a base station in a license assisted access (LAA) mode using a primary cell (PCell) and an LAA secondary cell (SCell) associated with a shared radio frequency spectrum band;
• receive timing advance information associated with a secondary timing advance group (sTAG) dedicated to LAA SCells, wherein the LAA SCell is a member of the sTAG;
• identify a downlink timing reference for an uplink transmission over the LAA SCell;
• and
• transmit the uplink transmission over the LAA SCell based at least in part on the identified downlink timing reference and the received timing advance information.