M.1 Dual Connectivity operation

36.3003GPPEvolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN)Overall descriptionRelease 17Stage 2TS

For Dual Connectivity, the UE is configured with two cell groups (CGs). A CG may only include cells that are associated to the same eNB and those cells are synchronized at the eNB level similar as for carrier aggregation. Two operations are defined: synchronous and asynchronous DC. In synchronous DC operation, the UE can cope with a maximum reception timing difference up to at least 33µs and maximum transmission timing difference up to at least 35.21µs between CGs. In asynchronous DC operation, the UE can cope with a maximum reception/transmission timing difference up to 500µs between CGs.

When DC is deployed, frame timing and SFN are aligned among the component carriers to be aggregated within a CG, and may or may not be aligned between different CGs.