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Some of the definitions gathered with short description.

Location Area
Location Area is one or more cells. Location Area is controlled by VLR. Each time MS changes LA it needs to inform VLR about this with Location Update Procedure.
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Master Node
In Dual Connectivity, the node which provides signalling connection (control plane) between UE and CN.
Master Cell Group
Cells within Master Node configured for the connection.
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NAS - Non-Access Stratum
Set of protocols (i.e. MM, GMM, SM, CC, SS, SMS) and functions for communication between Ms (or Ue) and Core Network (both CS and PS domain).
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Primary Cell
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Secondary Cell.
Secondary Cell Group
Cells within Secondary Node configured for the connection.
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