Wireless Oom

What is AN (Access Network, UTRAN)’s role ?
Provide simple connectivity to the core network (CN) – whether it is a CS or PS.
Remember that UE wishes to make a call or data connection to do some useful and helpful thing.
AN just helps it in the middle between UE and CN.

In connected mode, the GTP-U can be established between GGSN and AN (without SGSN), which is more efficient.