· Standalone (SA) – When only one radio access technology is used. For 5G SA deployment, Independent 5G network (Radio & Core) is used and it is known as Option 2. This option is widely used in Greenfield 5G Networks. Similarly, 4G SA is known as Option 1.
· Non-Standalone (NSA) – When both 5G radio and 4G radio access networks are used in Network. Two access networks inter work using dual connectivity to provide a combined radio access to UEs. Core Network can either belong to 4G (EPC) or 5G (5GC).
Initially in NSA, option 3 is widely used (EPC present), then in later stages option 7 & option 4 (5GC present) can be used by telcos before shifting to 5G SA. NSA deployment is used by most of the network operators with existing 4G infrastructure today.
Note: In NSA, two access nodes are known as master and secondary node. Control Plane must route through Master node whereas User Plane can route through either master node or secondary node. Option 3a and 3x are the evolved version of option 3 basis flexibility of routing of user plane.
There are two more SA options - 5 & 6. These options are not used for deployment generally.
Migration to 5G needs to be carefully planned and evaluated by telcos from business as well as from current network architecture prospective.
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